Systems and methods for high output, high color quality light

Abstract

Systems and methods for a high output, high color quality light are disclosed. In some embodiments, such a light may include a light fixture including one or more leds configured to output a cumulative light output; wherein the cumulative light output comprises an intensity of greater than or equal to 10,000 lumens; and wherein the cumulative light output comprises a CRI of at least 90.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to, and is a continuation of U.S. patent application Ser. No. 14/188,184 filed on Feb. 24, 2014,
ILED2=I*R1/(R1+R2)

Where:

• • ILED1=the current through the first string of LEDs, LED1;
  • ILED2=the current through the second string of LEDs, LED2; and
  • I=the total current shared by the two LED strings.

One drawback for a current sharing circuit according to this embodiment is that the voltage of the first string of LEDs (VLED1) needs to be no less than the string voltage of the second string of LEDS (VLED2). If this is not the case, then one of the transistors may enter saturation. When in saturation, the transistors may not control the current flowing through each string to the level set by the resistors, i.e., the current flowing through each string of LEDs may be different than the levels determined using the formulas above.

Another embodiment may comprise a third string of LEDs with a transistor connected in series with the third string and a common base with the other two transistors. Such an embodiment may further comprise a third sensing resistor in series with the third string of LEDs. In such an embodiment, the string voltage of the first string of LEDs (the string for which the transistor's base is connected to the collector) needs to be the highest among all the LED string voltages to ensure all the LED currents match the values set by the current sensing resistors.

In the embodiments described above, the constraint of maintaining the voltage drop across the first string of LEDs higher than the voltage drop across the other strings complicates the selection of LEDs. For example, the forward voltage drops of LED strings may vary with temperature and driving current. Thus, in one embodiment, desired operation may be ensured by selecting LEDs such that the minimum voltage of the first string of LEDs is no less than the maximum voltage of the other strings of LEDs. However, in some embodiments, this may increase power loss for the circuit. For example, in one embodiment, in a lighting fixture, if the voltage difference between the voltage of LED1 and the voltage of the other strings is 10V and the driving current is 0.35 A, the power loss will be 3.5 W. This may decrease the overall efficiency of the lighting fixture and also increase the thermal stress to the transistor and LEDs, thus shortening the operational life of the device.

Another embodiment may comprise using linear regulators to regulate the current to all but one of the strings of LEDs. However, such an embodiment may again suffer from the same deficiencies as the circuit described above.

Yet another embodiment for solving the problem discussed above may comprise current balancing transformers to equalize currents flowing through each of the LED strings. In one such embodiment, a magnetic balancer may be used to balance the current flowing through three strings of LEDs. In such an embodiment, two transformers with an equal number of turns of their primary and secondary windings may be connected between the output rectifier and the filter capacitor in three isolated outputs of a switch-mode power supply. Further, in such an embodiment, the current feedback from one output is used to set and regulate the current of the corresponding LED string. The 1:1 turn ratio of the transformer windings maintains the current flowing through each winding of the transformer at substantially the same value provided that the magnetizing current of the transformer is small compared to the winding current.

A deficiency of this embodiment is that it requires a switch-mode power supply. Thus, such an embodiment cannot be used independently, and lacks the flexibility to operate with an arbitrary DC source, for example, a DC current source. Furthermore, the addition of transformers for magnetic balancing into a switch-mode power supply increases the complexity and cost of the circuit. Furthermore, in some embodiments, separate output circuits may be detrimental if a large number of parallel LED strings are required. Furthermore, such an embodiment lacks the capability to individually change or tune the current flowing through each LED string once the turns-ratio of the transformer has been set. Thus, such an embodiment may not be effective for color mixing or control.

Another system for compensating for this problem without the above discussed deficiencies comprises a current control device such as a JFET or MOSFET in series with each string of LEDs. In this, embodiment, each current control device is controlled by a control device, such as a comparator and/or op-amp circuit. Each control device measures the voltage drop before and/or after the current control device, and based on this measurement, varies the impedance of the current control device, e.g., by varying a voltage to the base of the JFET, to increase or decrease the current flowing through each LED string. In some embodiments, the current measurement and control devices may be able to substantially balance the current flowing through each LED string in order to cause each LED string to have substantially the same light output.

Some embodiments may comprise sensing resistors placed in series with each LED string after the control circuit. Choosing resistors with different values may vary the voltage drop measured by each measurement device. Appropriate selection of the value of these sensing resistors enables the designer to vary the brightness of each string of LEDs to provide the desired light output. For example, the designer may comprise multiple strings of white LEDs kept at a substantially high brightness, but further comprise one string of red LEDs to provide a warmer light output. In such an embodiment, the designer may select sensing resistors configured to cause the string of red LEDs to receive a lower current, and therefore be dimmer than the string of white LEDs. In such an embodiment, the brightness of the red LEDs may be set to provide the desired warmth of the total light output.

These illustrative embodiments are mentioned not to limit or define the limits of the present subject matter, but to provide examples to aid understanding thereof. Illustrative embodiments are discussed in the Detailed Description, and further description is provided there. Advantages offered by various embodiments may be further understood by examining this specification and/or by practicing one or more embodiments of the claimed subject matter.

Illustrative System for High Output, High Color Quality Light

Turning now to the Figures, FIGS. 1-52 illustrate exemplary embodiments of LED light fixtures according to the present disclosure. As shown in FIGS. 1, 2 and 6, light fixture 10 comprises a housing 12 defining an enclosure 11 formed by a base 20 and a cover 30 movably secured with respect to base 20. FIGS. 3-7 show a power-circuitry unit 40 secured with respect to base 20 such that, when the cover 30 is closed, power-circuitry unit 40 is in thermal communication with cover 30.

As illustrated in FIGS. 2, 3 and 5, a light emitter, such as an LED, may be secured with respect to housing 12 within enclosure 11. FIGS. 3 and 5 show two alternative light emitters 50A and 50B, each of which comprises LED sources 51 on an LED-circuit board 52 which is secured with respect to base 20. As shown in FIGS. 3, 5 and 15-17, which illustrate alternative embodiments, the light emitter is in thermal communication with base 20. Base 20, as shown in FIGS. 2 and 3, is a single-piece metal casting. Cover 30, as shown in FIGS. 2 and 3, may comprise a metal casting supporting a light-transmitting lens member 31 over the light emitter.

In some embodiments, configurations in which the light sources are in thermal communication with base 20 while power-circuitry unit 40 is in thermal communication with cover 30, may be advantageous. In such embodiments, during operation of the light fixtures this arrangement provides primary heat transfer from the power-circuitry unit and primary heat transfer from the LED emitter(s) to separate major enclosure members, each of which serves as a heat sink.

As shown in FIG. 2, housing 12 has first and second housing members, base 20 being the first housing member and cover 30 being the second housing member and being movably secured with respect to base 20 between use and non-use positions. FIGS. 3-7 show power-circuitry unit 40 secured with respect to base 20. In some embodiments, which are not illustrated, the power-circuitry unit may be secured to the cover. Further, as shown in FIG. 2, some embodiments may comprise a cover 30, which is fully removable for access within enclosure 11.

As shown in FIGS. 6, 7, and 10-14, power-circuitry unit 40 may be constrained such that when cover 30 is in its use position, power-circuitry unit 40 is in thermal communication with cover 30. Power-circuitry unit 40 may be in a fully-fixed position for such primary thermal communication with cover 30, or it may be configured to be pressed against cover 30 when cover 30 is in its use position.

FIGS. 6 and 7 illustrate power-circuitry unit 40 in fixed orientation with respect to base 20 along a plane which comprises X and Y isometric axes of base 20. In the embodiments shown in FIGS. 6 and 7, power-circuitry unit 40 is movable along axis Z which is orthogonal to axes X and Y. In other embodiments, the power circuitry unit may have only one degree-of-freedom of movement with respect to base 20. In some embodiments, this degree-of-freedom of movement may comprise a linear freedom of movement.

FIG. 14 schematically illustrates an alternative embodiment in which the degree-of-freedom of movement is rotational about an axis R that is fixed with respect to base 20. In such an embodiment, power-circuitry unit 40 may be directionally biased toward cover 30 to facilitate thermal contact between power-circuitry unit 40 and cover 30.

As shown in FIGS. 2, 6, and 7, fixture 10 comprises a resilient member in the form of a compressible pad 14 situated between power-circuitry unit 40 and base 20. As shown in FIGS. 6 and 7, compressible pad 14 may be configured and positioned such that, when cover 30 is closed, pad 14 pushes power-circuitry unit 40 against cover 30. As shown in FIG. 2, pad 14 is sized to approximate the footprint of power-circuitry unit 40 on base 20, thereby to facilitate thermal isolation between power-circuitry unit 40 and base 20, and thus facilitate primary heat transfer from power-circuitry unit 40 to cover 30.

In FIG. 11, one embodiment of a resilient member is shown. In the embodiment shown in FIG. 11, the resilient member comprises springs 15. In some embodiments, springs 15 may comprise coil springs positioned between power-circuitry unit 40 and base 20 and serving to bias power-circuitry unit away from base 20 along axis Z into firm contact with cover 30 in its use position.

As shown in FIGS. 4, 6, and 7, light fixture 10 may comprise a first locator in the form of a post 43 and a second locator in the form of a hollow 44 defined by power-circuitry unit 40, such inter-engaged first and second locators serving to constrain power-circuitry unit 40 along the aforementioned X and Y axes. As shown in FIGS. 6 and 7, post 43 may extend onto the hollow 44 such that power-circuitry unit 40 is slidable on post 43 along axis Z to facilitate thermal contact between power-circuitry unit 40 and cover 30. The embodiment shown in FIG. 5 comprises two posts 43 and corresponding hollows 44, the post/hollow pairs being spaced from one another along the facing surfaces of base 20 and power-circuitry unit 40.

FIGS. 10-13 illustrate alternative embodiments of the first and second locators which allow back-and-forth movement of the power-circuitry unit along a direction substantially orthogonal to the aforementioned X-Y plane. In the embodiment shown in FIG. 10, the power-circuitry unit and the base define aligned hollows with a fastener such as a self-tapping screw being inserted through both hollows to secure the power-circuitry unit along the base while allowing back-and-forth movement of the power-circuitry unit orthogonally thereto. In the embodiment shown in FIG. 11, the power-circuitry unit has a post which extends into a hollow defined in the base, with springs 15 being positioned between the base and the power-circuitry unit. In the embodiment shown in FIG. 12, the power-circuitry unit is shown to comprise a protruding female portion defining a cavity which receives a post extending from the base. The embodiment shown in FIG. 13 illustrates an embodiment in which the power-circuitry unit is secured at a fixed distance from the base and is slidable along the base.

In the embodiments shown in FIGS. 1-7, power-circuitry unit 40 is shown to comprise a heat-conductive casing 45 which is in thermal contact with cover 45. As shown in FIGS. 4-6, casing 45 may comprise a flange portion 46 which defines hollow 44. In the embodiments shown in FIGS. 6 and 7, casing 45 is directionally biased toward cover 30 to facilitate thermal contact between casing 45 and cover 30.

The embodiments shown in FIGS. 8 and 9 illustrate the power-circuitry unit as a caseless LED driver 47. In some embodiments, such a caseless LED driver 47 can be removably secured with respect to base 20. In some embodiments, the power-circuitry components of caseless LED driver 47 are encapsulated (potted) in a protective polymeric material on a driver board prior to installation in the fixture such that driver 47 is readily replaceable and does not have any potting applied during or after installation in the fixture. Suitable examples of such protective polymeric encapsulating material comprise thermoplastic materials such as low-pressure injection-molded nylon, which amply protect caseless driver 47 from electrostatic discharge while conducting heat to facilitate cooling of the driver during operation.

In the embodiments shown in FIGS. 2-5, light fixture 10 comprises brackets 21 secured with respect to base 20 and holding power-circuitry unit 40 with respect to base 20 when enclosure 11 is open. As shown in FIGS. 4 and 7, each bracket 21 has an affixed end 22 secured with respect to base 20 and a free end 23 positioned to engage flange portion 46 of casing 45 of power-circuitry unit 40. FIG. 4 shows free end 23 defining an aperture 231 which receives distal post-end 430 with flange portion 46 of casing 45 being between base 20 and free end 23 of bracket 21.

The embodiments shown in FIGS. 2, 3, 5, 15-17, and 26 illustrate a heat-sink body 24 forming base 20 and having a circuit-board mounting surface 25. As shown in FIGS. 1, 2, 15-17, and 26, an aperture member may be supported over circuit-board mounting surface 25. In some embodiments, an LED circuit board 60 is affixed in thermal-contact relationship to circuit-board mounting surface 25. The LED circuit board, as later described herein, may be a metal-core board or other type of circuit board providing heat dissipation from LED emitters during operations.

In the embodiment shown in FIG. 5, circuit board 60 has an LED-populated area 61 with LED sources 51 concentrated in the middle region of the circuit board which has a non-LED-populated area 62 surrounding LED-populated area 61. FIG. 5 also shows that non-LED-populated area 62 is greater than LED-populated area 61.

The large non-LED-populated area surrounding the LED-populated area provides advantages, such as anisotropic heat conduction during operation. In particular, heat generated by the LED light sources on the LED-populated area spreads in lateral directions across the entire circuit board more than in directions orthogonal to the circuit board into the heat-sink body. That is, the circuit board, which comprises a good thermally-conductive material, such as copper or aluminum, spreads the heat laterally away from the LED-populated area and allows rapid heat transfer to the heat-sink body from across the entire circuit board—even in such “hidden” positions as are beyond the boundary of the optical aperture.

The embodiments shown in FIGS. 15-17 comprise circuit board 60 in thermal contact with circuit-board mounting surface 25 of heat-sink body 24 such that heat from the entire area of the circuit board is conducted to heat sink body 24 for heat dissipation. FIGS. 15-17 schematically illustrate that heat conduction laterally within circuit board 60 is greater than heat conduction from circuit board 60 to heat-sink body 24. This spreading of heat to non-LED-populated area 62 facilitates removal of heat from circuit board 60 and thus facilitates heat removal from LED-populated area 61 which increases the optical efficiency of the LEDs. The circuit board can be proximate heat-dissipating surfaces of the heat sink to provide a better thermal path to the heat dissipating surfaces of the heat sink.

As also schematically shown in FIGS. 15-17, the entire area of the circuit board, including the LED-populated and non-LED-populated areas, may approach being isothermal, i.e., with temperatures during operation being substantially isothermal thereacross. As such, the heat will tend to spread laterally away from the LED-populated area thus facilitating removal of heat from the LED-populated area to the non-LED-populated area and to the heat sink, which increases the optical efficiency of the LEDs.

In the embodiment shown in FIG. 5 the spacing between adjacent LED light sources 51 of LED-populated area 61 may comprise no more than approximately the cross-dimension of each of LED light sources 51. In some embodiments, tight spacing of the LED light sources on the LED-populated area tends to improve the substantially isothermal characteristic of the circuit board.

As shown in FIGS. 15-17, in some embodiments, LED circuit board 60 is in position between mounting surface 25 and the aperture member. The aperture member is shown to form a single optical aperture 33. Aspects of this disclosure are based on the recognition that the optical aperture need not be coextensive with the circuit board, but instead may be substantially coextensive with the LED-populated area—or at least be of a size such that it leaves much or substantially all of the non-LED-populated area beyond the boundary of the optical aperture.

The embodiments shown in FIGS. 16 and 17 schematically illustrate that the majority of non-LED-populated area 62 may extend beyond optical aperture 33. In the embodiments shown in both FIGS. 16 and 17, optical aperture 33 exposes all of LED-populated area 61. In some embodiments, at least 50% of the area of circuit board 60 extends beyond optical aperture 33.

Illustrative Heat Sink Structure for High Output, High Color Quality Light

The present disclosure provides efficient ways for addressing thermal challenges and extracting increased amounts of light from the LEDs of LED light fixtures. One such way, as described above, is increasing the surface area of the printed circuit board without changing the configuration of the LED array thereon. This takes advantage of the extra circuit-board material for heat-transfer purposes.

In some embodiments, the material used for the LED circuit board should be selected with particular regard to its thermal conductivity. In some embodiments, a simple metal-core circuit board is comprised of a solder mask, a copper circuit layer, a thermally-conducting thin dielectric layer, and a much thicker metal-core base layer. Such layers are laminated and bonded together, providing a path for heat dissipation from the LEDs. In some embodiments, the base layer is by far the thickest layer of the circuit board and may be aluminum, or in some cases copper, a copper alloy or another highly thermally-conductive alloy. A highly-conductive base layer facilitates lateral conduction of heat in the board from beneath the LED-populated area to and across the non-LED-populated area. And since board temperatures remain high even across the non-LED-populated area, the total area of substantial thermal transfer from the circuit board to the heat sink is beneficially large—substantially larger than just the LED-populated area.

In some embodiments, instead of sizing the circuit board to closely match the size of the LED array, the circuit board may be enlarged to have a non-LED-populated area around an LED-populated area such that the non-LED-populated area extends beyond the optical aperture. In one example, such circuit-board enlargement decreases the temperature of the LEDs by 2° C. without adding manufacturing costs allowing for an increase on total lumen output. Larger decrease in temperature and larger increase in total lumen output are possible depending on non-LED-populated area of such a circuit board.

The present disclosure provides a further way for addressing thermal challenges in LED light fixtures. In some embodiments, the thermal load of the driver (power-circuitry unit) is substantially removed from the fixture member (e.g., the base member), which is in primary thermal communication with the LED circuit board. In such an embodiment, the thermal load of the driver may instead be transferred to a separate fixture member such as the light-fixture cover. In one example, such thermal “repositioning” of the driver provides a decrease in the LED temperature of about 2° C. and the thermal separation of the driver from the LED circuit board also lowers the driver temp by 2° C. This permits drive current to be increased while still maintaining a 100,000 hour driver life rating and allowing an increase on total lumen output.

In some examples of light fixtures of this disclosure, enlargement of the non-LED-populated area is combined with separation of the primary thermal paths of the LEDs and the LED driver. In one example, this combination of thermal advantages decreases the LED temperature by 4° C. and allows a 15% increase in the drive current which resulted in 13% increase in total lumen output.

In the embodiments shown in FIGS. 15 and 16, the aperture member is a reflector 35 which extends from a first end 351 adjacent to and surrounding LED-populated area 61 to a second end 352 substantially aligned with cover opening 34. FIG. 2 shows LED-populated area 61 being substantially rectangular in shape and reflector 35 being frusto-pyramidal in shape. FIG. 17 shows cover 30 itself serving as the aperture member; cover opening 34 forms optical aperture 33A. In some embodiments, the opening in the cover defines the optical aperture. In other embodiments, a reflector or other optical element or lens defines the optical aperture. In some embodiments, the optical elements defining the optical aperture can be integral with or mounted to the cover and/or LED assembly.

In the embodiments shown in FIGS. 1 and 15-17, a light-transmissive member 31 is positioned in cover opening 34. Light-transmissive member 31 may comprise a phosphorescent material such that at least some of the light emitted by the fixture has a different wavelength than light emitted from the LED-populated area. For example, the LED-populated area may comprise LED sources of the type emitting light with wavelength of a blue color, and in order to achieve a customary white-color light, a so-called “remote phosphor” technique is used. The remote-phosphor technique typically utilizes blue LED(s). The phosphor that generates the white light is comprised on a lens or diffuser such as light-transmissive member 31 by coating or otherwise. In some embodiments, such “remote phosphor” technique delivers better efficacy than do phosphor-converted LEDs, since the phosphors are more efficient in conversion when operating at the lower phosphor temperatures made possible by such remote configurations. For example the LEDs can be blue LEDs where the blue light excites the phosphorescent material, such as yttrium aluminum garnet (“YAG”), to produce a secondary emission of light where the blue light and the secondary emission produce white light. In other embodiments, different color LEDs can be used together with individual white LEDs (blue LEDs plus phosphor) or with blue LEDs in a remote phosphor configuration where the light-transmissive element is coated and/or impregnated with the phosphorescent material.

Illustrative Low Profile LED Light Fixture for High Output, High Color Quality Light

The embodiments shown in FIGS. 1, 6, 15-21, 24 and 25 illustrate another aspect of the present disclosure, namely, LED light fixture 10 may comprise a low-profile LED light fixture with advantages, including, e.g., its serving as a surface-mount canopy light.

In the embodiments shown in FIGS. 3 and 5, light fixture 10 comprises a base plate 200 with LED circuit board 60 secured to a front surface 26 thereof and with LED power-circuitry unit 40 secured with respect to front surface 26 in a position adjacent to circuit board 60. In the embodiments shown in FIGS. 1-3 the heat-dissipating surfaces 27 extend from front surface 26 of base plate 200 with LED circuit board 60 being in position adjacent to heat-dissipating surfaces 27. In the embodiments shown in FIGS. 23-25, base plate 200 has a substantially planar back surface 28. In the embodiments shown in FIGS. 3, 6 and 15-17, LED power-circuitry unit 40, LED circuit board 60, and heat-dissipating surfaces positioned entirely in front of base plate 200, with no portion of the light fixture other than electrical connections extending behind back surface 28.

In some embodiments, heat-dissipating surfaces 27 extend substantially orthogonally to front surface 26 of base plate 200. In the embodiments shown in FIGS. 5 and 22, the base plate is rectangular and heat-dissipating surfaces 27 are in two regions 270 positioned beside LED circuit board 60 only on two opposite sides thereof.

In the embodiments shown in FIGS. 1, 2 and 22, cover 30 extends over LED power-circuitry unit 40 while leaving uncovered heat-dissipating surfaces 27. Cover 30 defines light-emitting opening 34 over LED circuit board 60.

In the embodiments shown in FIG. 5, base plate 200 comprises a rectangular base plate with heat-dissipating surfaces 27 being in two regions 270 positioned beside LED circuit board 60 only on two opposite lateral sides thereof. Regions 270 of heat-dissipating surfaces 27 are on two of the four lateral sides of base plate 200. As further shown in FIG. 5, in some embodiments, base plate 200 defines a pair of cavities 29 along front surface 26 thereof, one on either side of LED circuit board 60 in positions along the other two opposite lateral sides of base plate 200. In the embodiment shown in FIG. 5, LED power-circuitry unit 40 is positioned within one of two cavities 29. Light-fixture control circuitry 19 is shown positioned within the other of two cavities 29. In some embodiments, control circuitry 19, sensor 18 and/or communication circuitry may be positioned within cavities 29.

In the embodiments shown in FIGS. 15-21, 24 and 25, the cross-section of fixture 10 orthogonal to base plate 200 is such that the aspect ratio of such cross-section is greater than about 6. As used herein, the term “aspect ratio” means the ratio of a plan-view cross-dimension 16 of the base plate to the cross-dimension 17 of the fixture between back surface 28 of base plate 200 and a forwardmost surface 36 of cover 30. In some embodiments, the aspect ratio may be greater than about 7.5.

In the embodiments shown in FIGS. 15 and 16, thickness 17 of the cross-section between back surface 28 of base plate 200 and a forwardmost surface 36 of cover 30 may be no more than about 3 inches. In other embodiments, such as the fixture shown in FIG. 17.

In the embodiment shown in FIG. 21, light-emitting opening 34 in cover 30 defines a plane 340. In the embodiment shown in FIG. 21, lens 31 is substantially planar, in plane 340. In the embodiments shown in FIGS. 19 and 20 the lens comprises a drop-out lens 31A and 31B, which extends beyond plane 340 of opening 34. In some embodiments, this facilitates a portion of the light being directed laterally, which is useful for curb-side appeal.

In the embodiment shown in FIGS. 15-17, the LED light fixture is shown as a surface-mount LED light fixture for mounting on a surface 1 of a structure such that, when the fixture is installed, back surface 28 of base plate 200 is substantially against structure surface 1.

In the embodiment shown in FIG. 18, the LED fixture comprises a pendant light. The embodiments shown in FIGS. 1, 18, 24, and 25 also comprise an example of a sensor 18 at the exterior of enclosure 11 for control of the fixture. Sensor 18 is shown to extend forwardly from forwardmost surface 36 of cover 30. In some embodiments, the sensor 18 may have a non-metallic casing of various shapes, including a substantially flat configuration. In some embodiments, control of the fixture may require receipt of a wireless signal. In such embodiments, an antenna for receiving such wireless signal may be disposed within the non-metallic casing of the sensor and outside enclosure 11.

Illustrative System for High Output, High Color Quality Light

FIGS. 27-37 illustrate embodiments of LED light fixtures 10A and 10B according to the present disclosure. The embodiments shown in FIGS. 27-30 show that light fixture 10 comprises an LED assembly 60 which is open to air/water flow thereover. In the embodiments shown in FIGS. 28 and 30, LED assembly 60 has a plurality of LED-array modules 61 each secured to an individual LED heat sink 62 which has first and second heat-sink ends 63 and 64.

In the embodiments shown in FIGS. 28 and 30, LED light fixture 10 comprises a plurality of heat-sink-mounted LED-array modules 61. Each module 61 engages an LED-adjacent surface 680 of heat-sink base 68 for transfer of heat from module 61. The heat-sinks comprise fins 620 which extend away from modules 61, as shown in FIG. 39. Each heat-sink base 68 is wider than module 61 thereon such that heat-sink base 68 comprises a beyond-module portion 681.

In the embodiment shown in FIG. 33 each heat sink 62 has venting apertures 69 formed through heat-sink base 68 to provide cool-air ingress to and along heat-dissipating fins 620 by upward flow of heated air therefrom. FIGS. 30 and 33 also show venting apertures 69 through beyond-module portion 681 of heat-sink base 68.

In some embodiments, the heat-dissipating surfaces comprise the surfaces of edge-adjacent fins 621 extending transversely from beyond-module portion 681 of heat-sink base 68 at a position beyond venting apertures 69 therealong. As shown in FIG. 43, venting apertures 69 along beyond-module portion 681 are spaced along heat sink 62, which may be an extrusion. Beyond-module portion 681 of heat-sink base 68 has a non-apertured portion 682 extending thereacross to allow heat flow across beyond-module portion 681 toward edge-adjacent fin 621 extending therefrom.

In the embodiments shown in FIGS. 30 and 43, two venting apertures 69 along beyond-module portion 681 extending along heat sink 62 in spaced substantially end-to-end relationship. In such an embodiment, non-apertured portion 682 comprises a non-apertured portion which is between two elongated apertures 69 and is located substantially centrally along the length of heat sink 62. The combined length of apertures 69 along beyond-module portion 681 constitutes a majority of the length of heat sink 62, as shown in FIG. 43.

In some embodiments, heat-sink base 68 comprises a module-engaging portion 685 between beyond-module portions 681. Heat-sink heat-dissipating surfaces comprise the surfaces of a plurality of middle fins 622 extending transversely from module-engaging portion 685 of heat-sink base 68, as shown in FIG. 39.

In the embodiment shown in FIG. 39, edge-adjacent fins 621 extending from each one of beyond-module portions 681 of heat-sink base 68 are each a single edge-adjacent fin. Such two edge-adjacent fins 621 form opposite lateral sides 623 of heat sink 62. Heat-sink base 68 has a thickness at positions adjacent to edge-adjacent fins 621 that is greater than the thickness of base 68 at positions adjacent to some of middle fins 622, thereby to facilitate conduction of heat laterally away from module 61.

In the embodiment shown in FIG. 39, edge-adjacent fins 621 have a base-adjacent proximal portion 621A integrally joined to heat-sink base 68 and a distal edge 621B remote therefrom. Proximal portions 621A of edge-adjacent fins 621 are thicker than proximal portions 622A of at least some of middle fins 622, thereby to facilitate conduction of heat away from module 61. Fins 621 and 622 extend away from heat-sink base 68 in a first direction B. Edge-adjacent fins 621 also extend from heat-sink base 68 in a second direction A opposite to first direction B to provide additional heat-dissipating surface 624. Edge-adjacent fins 621 and heat-sink base 68 are shown to form an H-shaped structure shown in FIG. 39.

In the embodiments shown in FIGS. 29, 30, and 43 fixture 10 also has air gaps 18B defined between adjacent pairs of heat sinks 62 to provide heat removal along the entire length of each heat sink 62 by cool air drawn from below LED assembly 60 through air gaps 18B by rising heated air. FIGS. 29, 30, 43, and 44 show the plurality of heat sinks 62 beside one another in positions such that beyond-module portion 681 of each of heat sinks 62 is adjacent to but spaced from beyond-module portion 681 of another of heat sinks 62. As illustrated in FIG. 44, such arrangement further facilitates flow of cool air to the heat-dissipating surfaces of heat sinks 62 and thermal isolation of the heat sinks 62 from one another.

As shown in FIG. 43, in some embodiments, the spacing 181 between heat sinks 62 is at least as great as widths 690 of venting apertures 69 in beyond-module portions 681 of heat-sink bases 68. In some embodiments, light fixture 10 comprises a housing 23 with LED assembly 60 secured with respect thereto such that LED assembly 60 and housing 23 form a venting gap 18A therebetween to provide air ingress along heat-sink base 68 to the heat-dissipating surfaces. In the embodiments shown in FIGS. 37 and 40, air gaps 18A are along first and second heat sink ends 63 and 64 permitting air/water-flow to and from heat sinks 62 through heat sink ends 63 and 64.

FIG. 44 shows simulated velocity of air flow along LED assembly 60 according to one embodiment. The darker areas between heat sinks 62 and through venting apertures 69 illustrates increased air flow which facilitates heat removal from LED assembly 60. Modules 61 are shown as substantially rectangular elongated LED-array modules with a plurality of LEDs positioned on a circuit board which is secured to the heat sink.

Additional examples of LED-array modules are disclosed in co-pending U.S. patent application Ser. No. 11/774,422,
ILED2=((R1*R3)/Δ)*I
ILED3=((R1*R2)/Δ)*I

Where:

I=the total input current; and

Δ=R1*R2+R2*R3+R1*R3.

One of ordinary skill in the art will recognize that if R1=R2=R3, then ILED1=ILED2=ILED3. Thus, by setting each resistor to an equal value, each LED string may have substantially the same brightness. Alternatively, the resistor values may be varied in order to vary the brightness of each string. In some embodiments, this may be employed for color or lighting compensation. For example, in some embodiments, one or more of the LED strings may comprise different color LEDs, or LEDs with different light output characteristics, e.g., dominant wavelength (“DW”), peak wavelength (“PW”), uniform light output, total luminous flux (“TLF”), and light color rendering index (“CRI”). In some embodiments a designer may select values of resistors R1, R2, and R3 in order to compensate for these differences or provide a higher overall light quality. For example, in one embodiment, one of the LED strings may comprise LEDs of a different color than the other two strings. In such an embodiment, resistors R1, R2, and R3 may be selected such that this different color string has a different current level and thus a different brightness than the other two strings. This may be used to, for example, change the warmth of the light output or control the color of the light.

A person of ordinary skill in the art will recognize that the circuit shown in FIG. 57 may be used in combination with another circuit. For example, the current control system shown in FIG. 57 may be used in combination with components described with regard to FIGS. 54-56 and 58-62.

Turning now to FIG. 58, FIG. 58 shows yet another example system 600 for a current sharing driver for light emitting diodes according to one embodiment. The system 600 operates similarly to system 400 described with regard to FIG. 56. However, system 600 further comprises a third string of LEDs, LED3 (identified by reference no. 602), which is connected directly to the current source. In such an embodiment, the current provided to LED3, ILED3, maintains a constant value. However, the two remaining strings LED1 (identified by reference no. 604) and LED2 (identified by reference no. 606) are connected in parallel with each other but in series with LED3. Thus, the sum of the currents to LED1 and LED2 will equal the current supplied to LED3, i.e., ILED3=ILED1+ILED2. Thus, in some embodiments, the LED string LED3 may be substantially brighter than both LED1 and LED2.

In some embodiments, the designer may set the value of resistors R1 and R2 to set a balance between the current through LED strings LED1 and LED2. This will also set the brightness of each of these strings. A designer may set this brightness in order to compensate for color or other factors associated with the LEDs in each string.

Further, in the embodiment shown in FIG. 58, as with circuit 400 described with regard to FIG. 56, a pulse generating circuit, such as a PWM pulse is used to tune the impedance of the control switch QT. The components of this pulse generating circuit is shown within the dashed box identified by reference no. 608. This enables the current and the light intensity of string LED2 to be adjusted. In some embodiments, this variance in intensity may be useful for color mixing. For example, if LED1 is a BSY (blue- shifted-yellow) string and LED2 is a RED color string, the color temperature of the light fixture can be tuned to the desired value, for example, by increasing or decreasing the current flow to each string.

A person of ordinary skill in the art will recognize that the circuit shown in FIG. 58 may be used in combination with another circuit. For example, the current control system shown in FIG. 58 may be used in combination with components described with regard to FIGS. 54-57 and 59-62.

Turning now to FIG. 59, FIG. 59 shows yet another example system 700 for a current sharing driver for light emitting diodes according to one embodiment. As shown in FIG. 59, a plurality of current balancing circuits such as those described above with regard to FIGS. 53-58 are placed in series. In some embodiments, each module may contain two or more LED strings and a current sharing circuit. The embodiment shown in FIG. 59 allows a plurality of modules to be combined to obtain higher overall power and lumen output.

Each module shown in FIG. 59 comprises a current sharing driver circuit of the type described above with regard to FIGS. 54 and 55. As described above, a designer may adjust the value of sensing resistors in order to set the current balance between each string of LEDs in the module. In some embodiments, the designer may select resistors to adjust brightness such that it can create a more pleasing (e.g., warmer) light or to compensate for other factors associated with the each LED, string of LEDs, or module of LEDs.

Further, in some embodiments, other types of current balancing circuits, such as those described throughout this application may be comprised in a module form. Further, in some embodiments, a plurality of modules such as those shown in FIG. 59 may be grouped into a module, which may then be combined with other similar modules allowing an even larger number of modules to be combined to obtain higher overall power and lumen output.

A person of ordinary skill in the art will recognize that the circuit shown in FIG. 59 may be used in combination with another circuit. For example, the current control system shown in FIG. 59 may be used in combination with components described with regard to FIGS. 54-58 and 60-62.

Turning now to FIG. 60, FIG. 60 shows yet another example system 800 for a current sharing driver for light emitting diodes according to one embodiment. The embodiment shown in FIG. 8 differs from the other embodiments described above in that instead of a current sharing circuit with linear current regulators, a switching regulator is used. In some embodiments, a switching regulator, such as one or more of a boost, buck, or chop regulator, may rapidly switch a series device on and off. For example, as shown in FIG. 60, the switching regulator may rapidly switch the LEDs in LED string LED2 on and off in order to regulate the current flowing through that string.

In the embodiment shown in FIG. 60, the current flowing through the LED string LED2 is regulated by the switching regulator. Further, because the LED string LED1 is in parallel with the switching regulator, the switching regulator also controls the current flowing through LED1. In some embodiments, this design may be used to vary the brightness through each string of LEDs to improve the overall quality of light or compensate for other factors associated with each LED or string of LEDs, as discussed above.

In some embodiments, a benefit of using a switching regulator may be lower power loss. In some embodiments, this can improve the overall efficiency of the circuit, and reduce the amount of heat generated by the power loss. In some embodiments, this advantage may still be present even if the voltage difference between LED1 and LED2 is relatively high.

A person of ordinary skill in the art will recognize that the circuit shown in FIG. 60 may be used in combination with another circuit. For example, the current control system shown in FIG. 60 may be used in combination with components described with regard to FIGS. 54-59 and 61-62.

Turning now to FIG. 61, FIG. 61 shows yet another example system 900 for a current sharing driver for light emitting diodes according to one embodiment. The embodiment shown in FIG. 61, further comprises a buck switching regulator or any other type of switching regulator and dimming control.

In the embodiment shown in FIG. 61, the total current from the constant current source is sensed by resistor RS to generate a sense voltage. This sense voltage is then amplified by an operation amplifier circuit 902 with a gain equal to the value of RS11/RS10. The output of the operational amplifier, i.e., the amplified voltage VCTL is then passed into a switching regulator, shown in this example as a buck controller, which controls the current flowing through a MOSFET configured to control the current through LED2, ILED2. In the embodiment shown in FIG. 61, the higher the constant current I, the higher the control voltage VCTL, and thus the higher LED current ILED2.

In the embodiment shown in FIG. 61, the ratio for the current between each LED string, ILED1/ILED2, is kept constant, even when the current from constant current source I is reduced, e.g., during dimming. In some embodiment, this enables the circuit 900 to maintain the same overall color temperature even when the brightness of each string of LEDs is reduced.

A person of ordinary skill in the art will recognize that the circuit shown in FIG. 61 may be used in combination with another circuit. For example, the current control system shown in FIG. 61 may be used in combination with components described with regard to FIGS. 53-60 and 62.

Turning now to FIG. 62, FIG. 62 shows yet another example system 1000 for a current sharing driver for light emitting diodes according to one embodiment. The embodiment shown in FIG. 62 comprises a modular system comprising a plurality of current sharing drivers for light emitting diode circuits similar to those described above with regard to FIG. 61. This modular approach allows a plurality of modules to be combined to obtain higher overall power and lumen output. In some embodiments, a modular approach allows the total voltage across each module to be very low. Further, in some embodiments a modular approach allows for a high switching frequency, e.g., 500 kHz, to shrink the size of the switching regulators.

A person of ordinary skill in the art will recognize that the circuit shown in FIG. 62 may be used in combination with another circuit. For example, the current control system shown in FIG. 62 may be used in combination with components described with regard to FIGS. 54-61.

Advantages of Systems and Methods for High Output, High Color Quality Light

There are numerous advantages of the current sharing circuit of present disclosure.

The present disclosure provides efficient ways for addressing thermal challenges and extracting increased amounts of light from the LEDs of LED light fixtures. One such way, as described above, is increasing the surface area of the printed circuit board without changing the configuration of the LED array thereon. This takes advantage of the extra circuit-board material for heat-transfer purposes.

In some embodiments, the disclosed low-profile configuration of the light fixture permits installation against the structure with a relatively small aperture formed in structure surface 1 for electrical connections. This is beneficial in installations for outdoor canopies such as those used at gasoline stations. In particular, the small connection aperture minimizes access of water to the fixture. Another benefit provided by the light fixture according to the present disclosure is that all major components are accessible for servicing from the light-emitting front of the fixture, under the canopy.

Further, some embodiments of the present disclosure provide more flexibility when choosing LED strings. For example, embodiments of the present disclosure enable the designer to select different LEDs with different characteristics. In some embodiments, this enables the designer to comprise different numbers of LEDs in each string.

Further, embodiments of the present disclosure enable additional LED strings to be placed in the same package. Because these LED strings can be placed in parallel, the total voltage drop of the circuit can be reduced. This can allow the designer to build an LED circuit with a greater number of LEDs, and therefore a higher overall light output. Furthermore, as discussed above, an even larger number of LEDs may be incorporated by using a modular approach with a plurality of current sharing drivers of the types discussed above.

Embodiments described above also allow the designer to adjust brightness to create a more pleasing (e.g., warmer light) or to compensate for other factors associated with the each LED, string of LEDs, or module of LEDs. For example, in some embodiments the resistors may be selected to compensate for different light output characteristics, e.g., dominant wavelength (“DW”), peak wavelength (“PW”), uniform light output, total luminous flux (“TLF”), and light color rendering index (“CRI”). In some embodiments, this enables a broader range of LEDs to be used, reducing production cost, because marginal LEDs that would previously have been discarded may be used. Further, the current level can be set to maximize the life of each LED or string of LEDs.

Embodiments of the present disclosure may enable an LED to comprise advantageous light output characteristics. For example, in some embodiments, the cumulative light output of embodiments of the present disclosure may comprise an intensity of greater than or equal to 10,000 lumens. Further, in some embodiments, the cumulative light output may comprise a color temperature of greater than or equal to 4000° K. In some embodiments, the cumulative light output may comprise a Color Rendering Index (“CRI”) of at least 90. In some embodiments, the CRI may be 94 or greater. In some embodiments, the above characteristics may be achieved with a drive current of at least 700 mA. In some embodiments, the drive current may comprise 1,000 mA. In some embodiments, the cumulative light output comprises an intensity of greater than or equal to 13,000 lumens. In some embodiments, the chromaticity comprises within 0.2-0.225 u′ and 0.49-0.51 v′. Further in some embodiments, the total radiant flux is within the range of 30,900-41,600 mW.

Further, embodiments of the present disclosure may enable higher efficiency light, for example, in some embodiments the lumen efficiency may comprise at least 98 lumens per Watt. In some embodiments, the lumen efficiency may comprise at least 105 lumens per Watt.

The table below shows non-limiting example characteristics of LED lighting fixtures according to the embodiments disclosed herein.

	Input					LED	Total
Input	current/	1976	1976	General	Color	Intensity/	Radiant
Wattage/	mA	Chromaticity	Chromaticity	CRI/	Temp/	Lm	Flux/	Lm/
W	AC	u′	v′	Mean	° K	Mean	mW	W
93.42	781.7	0.2248	0.5003	93.92	4034	10265.00	30,920.0	109.88
119.66	1000.8	0.209	0.49	90.03	4945	12921.00	40,050.0	107.98
132.9	1112.5	0.2223	0.4978	94.32	4177	13124.00	40,190.0	98.75
132.07	1106	0.2231	0.4976	94.79	4147	13113.00	40,270.0	99.29
134.17	1123.9	0.2242	0.4979	95.01	4101	13512.00	41,590.0	100.71
132.64	1110.6	0.2209	0.4975	94.11	4239	13442.00	41,270.0	101.34

Embodiments of the present disclosure may enable an LED to comprise advantageous light output characteristics. For example, in some embodiments, the cumulative light output of embodiments of the present disclosure may comprise an intensity of at least 10,000 lumens and a lumen efficiency of at least 100 lumens per watt. Further in some embodiments, the cumulative light output may comprise a color temperature of greater than or equal to 4000° K and a Color Rendering Index (“CRI”) of at least 70. In some embodiments, the cumulative light output comprises a color temperature of greater than or equal to 5000° K and a CRI of at least 90. In some embodiments, the drive current comprises at least 1000 mA and the cumulative light output comprises an intensity of greater than or equal to 13,000 lumens. In other embodiments, the cumulative light output comprises an intensity of greater than or equal to 25,000 lumens. In other embodiments, the LED light fixture is configured to operate based on a drive current comprising at least 700 mA and the cumulative light output comprises an intensity of greater than or equal to 20,000 lumens

The table below shows non-limiting example characteristics of LED lighting fixtures according to the embodiments disclosed herein, in which the light temperature comprises at least 4000° K and the Color Rendering Index (“CRI”) comprises at least 70.

Input current/mA AC	Input Wattage/W	LED Intensity/Lm Mean
700	267	24,608
700	533	49,248
1000	421	33,045
1000	831	66,132
700	267	27,276
700	533	54,588
1000	421	36,628
1000	831	73,303
700	267	24,312
700	533	48,654
1000	421	32,647
1000	831	65,336
700	267	26,684
700	533	53,401
1000	421	35,832
1000	831	71,710

The table below shows non-limiting example characteristics of LED lighting fixtures according to the embodiments disclosed herein, in which the light temperature comprises at least 5700° K and the CRI comprises at least 70.

Input current/mA AC	Input Wattage/W	LED Intensity/Lm Mean
700	267	25,555
700	533	51,142
1000	421	34,316
1000	831	68,676
700	267	28,326
700	533	56,687
1000	421	38,037
1000	831	76,123
700	267	25,247
700	533	50,525
1000	421	33,903
1000	831	67,849
700	267	27,710
700	533	55,455
1000	421	37,210
1000	831	74,468

The table below shows non-limiting example characteristics of LED lighting fixtures according to the embodiments disclosed herein, in which the light temperature comprises at least 5000° K and the CRI comprises at least 90.

Input current/mA AC	Input Wattage/W	LED Intensity/Lm Mean
700	267	21,611
700	533	43,250
1000	421	29,021
1000	831	58,079
700	267	19,497
700	533	39,019
1000	421	26,182
1000	831	52,397
700	267	19,262
700	533	38,549
1000	421	25,867
1000	831	51,766
700	267	21,142
700	533	42,310
1000	421	28,390
1000	831	56,816

General Considerations

The methods, systems, and devices discussed above are examples. Various configurations may omit, substitute, or add various procedures or components as appropriate. For instance, in alternative configurations, the methods may be performed in an order different from that described, and/or various stages may be added, omitted, and/or combined. Also, features described with respect to certain configurations may be combined in various other configurations. Different aspects and elements of the configurations may be combined in a similar manner. Also, technology evolves and, thus, many of the elements are examples and do not limit the scope of the disclosure or claims.

Specific details are given in the description to provide a thorough understanding of example configurations (including implementations). However, configurations may be practiced without these specific details. For example, well-known circuits, processes, algorithms, structures, and techniques have been shown without unnecessary detail in order to avoid obscuring the configurations. This description provides example configurations only, and does not limit the scope, applicability, or configurations of the claims. Rather, the preceding description of the configurations will provide those skilled in the art with an enabling description for implementing described techniques. Various changes may be made in the function and arrangement of elements without departing from the spirit or scope of the disclosure.

Having described several example configurations, various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the disclosure. For example, the above elements may be components of a larger system, wherein other rules may take precedence over or otherwise modify the application of the invention. Also, a number of steps may be undertaken before, during, or after the above elements are considered. Accordingly, the above description does not bound the scope of the claims.

The use of “adapted to” or “configured to” herein is meant as open and inclusive language that does not foreclose devices adapted to or configured to perform additional tasks or steps. Additionally, the use of “based on” is meant to be open and inclusive, in that a process, step, calculation, or other action “based on” one or more recited conditions or values may, in practice, be based on additional conditions or values beyond those recited. Headings, lists, and numbering comprised herein are for ease of explanation only and are not meant to be limiting.

Embodiments in accordance with aspects of the present subject matter can be implemented in digital electronic circuitry, in computer hardware, firmware, software, or in combinations of the preceding. In one embodiment, a computer may comprise a processor or processors. The processor comprises or has access to a computer-readable medium, such as a random access memory (RAM) coupled to the processor. The processor executes computer-executable program instructions stored in memory, such as executing one or more computer programs including a sensor sampling routine, selection routines, and other routines to perform the methods described above.

While the present subject matter has been described in detail with respect to specific embodiments thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing may readily produce alterations to, variations of, and equivalents to such embodiments. Accordingly, it should be understood that the present disclosure has been presented for purposes of example rather than limitation, and does not preclude inclusion of such modifications, variations and/or additions to the present subject matter as would be readily apparent to one of ordinary skill in the art.

As used herein in referring to portions of the devices of this disclosure, the terms “upward,” “upwardly,” “upper,” “downward,” “downwardly,” “lower,” “upper,” “top,” “bottom” and other like terms assume that the light fixture is in its usual position of use and do not limit the invention to any particular orientation.

In descriptions of this disclosure, including in the claims below, the terms “comprising,” “including” and “having” (each in their various forms) and the term “with” are each to be understood as being open-ended, rather than limiting, terms.

Claims

1. A light fixture comprising:

a plurality of leds configured to output a cumulative light output, the plurality of leds comprising two or more strings of leds, at least two of the two or more strings of leds comprising different color leds, the two or more strings of leds comprising a first string of leds and a second string of leds connected in parallel with the first string of leds;

a first current control device connected in series with the first string of leds and configured to control a drive current provided to the plurality of leds, wherein the drive current comprises at least 700 mA; and

a second current control device connected in series with the second string of leds and configured to control the drive current provided to the plurality of leds;

a first voltage measurement device coupled to the first string of leds and the second string of leds, the first voltage measurement device coupled to the first current control device and configured to control the first current control device; and

a second voltage measurement device coupled to the first string of leds and the second string of leds, the second voltage measurement device coupled to the second current control device and configured to control the second current control device;

wherein the cumulative light output comprises an intensity of greater than or equal to 10,000 lumens and a color temperature of greater than or equal to 4000° K color rendering index (CRI) of at least 94.

2. The light fixture of claim 1, wherein the a plurality of leds comprise two or more strings of leds.

3. The light fixture of claim 2, wherein at least two of the two or more strings of leds comprise different color leds.

4. The light fixture of claim 3 1, wherein at least one of the strings comprises a Blue Shifted Yellow string and at least one of the strings comprises a Red string.

5. The light fixture of claim 3 1, wherein each of the strings comprises a Blue Shifted Yellow string with a different color temperature.

6. The light fixture of claim 3, wherein the two or more strings of leds comprise a first string of leds and a second string of leds connected in parallel with the first string of leds, and wherein the light fixture further comprises:

a first current control device connected in series with the first string of leds;

a second current control device connected in series with the second string of leds;

a first voltage measurement device coupled to the first string of leds and the second string of leds, the first voltage measurement device coupled to the first current control device and configured to control the first current control device; and

a second voltage measurement device coupled to the first string of leds and the second string of leds, the second voltage measurement device coupled to the second current control device and configured to control the second current control device.

7. The light fixture of claim 6 1, wherein each of the first and second current control devices comprise: a Bipolar Junction Transistor (BJT); a MOSFET; a junction gate field-effect transistor (JFET); or an insulated gate field effect transistor (IGFET).

8. The light fixture of claim 7, wherein each of the first and second voltage measurement devices comprise: a comparator and an op-amp.

9. The light fixture of claim 6 1, further comprising a third string of leds connected in series with the first and second string of leds.

10. The light fixture of claim 6 1, further comprising:

a pulse generator;

an RC circuit coupled to the pulse generator; and

a third current control device coupled to the RC circuit, the third current control device configured to vary the voltage measured by the second voltage measurement device.

11. The light fixture of claim 1, further comprising:

a plurality of heat-sink-mounted led array modules, each module engaging an led-adjacent surface of a heat-sink base for transfer of heat from the module;

a heat-sink heat-dissipating surface extending away from the modules;

at least one venting aperture through the heat-sink base to provide air ingress to the heat-dissipating surfaces adjacent to the aperture.

12. The light fixture of claim 1, further comprising:

a housing and an led assembly secured with respect thereto and open to permit air/water-flow over the led assembly, the led assembly comprising:

an led-array;

an extruded heat sink that has a base and heat-transfer surfaces extending from the base, wherein the heat-transfer surfaces are surfaces of a plurality of fins extending away from the base in a first direction, the fins including first and second fins along the opposite edges of the base, the first and second edge-adjacent fins also extending from the base in a second direction opposite to the first direction.

13. A light fixture comprising:

a plurality of leds configured to output a cumulative light output at an efficiency, the plurality of leds comprising two or more strings of leds, the two or more strings of leds comprising a first string of leds and a second string of leds connected in parallel with the first string of leds;

a first current control device connected in series with the first string of leds and configured to control a drive current provided to the plurality of leds, wherein the drive current comprises at least 700 mA; and

a second current control device connected in series with the second string of leds and configured to control the drive current provided to the plurality of leds;

a first voltage measurement device coupled to the first string of leds and the second string of leds, the first voltage measurement device coupled to the first current control device and configured to control the first current control device; and

a second voltage measurement device coupled to the first string of leds and the second string of leds, the second voltage measurement device coupled to the second current control device and configured to control the second current control device;

wherein the cumulative light output comprises an intensity of greater than or equal to 10,000 lumens and a color temperature of greater than or equal to 4000° K color rendering index (CRI) of at least 90.

14. The light fixture of claim 13, wherein the a plurality of leds comprise two or more strings of leds.

15. The light fixture of claim 14, wherein the two or more strings of leds comprise a first string of leds and a second string of leds connected in parallel with the first string of leds, and wherein the light fixture further comprises:

a first current control device connected in series with the first string of leds;

a second current control device connected in series with the second string of leds;

a first voltage measurement device coupled to the first string of leds and the second string of leds, the first voltage measurement device coupled to the first current control device and configured to control the first current control device; and

a second voltage measurement device coupled to the first string of leds and the second string of leds, the second voltage measurement device coupled to the second current control device and configured to control the second current control device.

16. The light fixture of claim 15 13, wherein each of the first and second current control devices comprise: a Bipolar Junction Transistor (BJT); a MOSFET; a junction gate field-effect transistor (JFET); or an insulated gate field effect transistor (IGFET).

17. The light fixture of claim 16, wherein each of the first and second voltage measurement devices comprise: a comparator and an op-amp.

18. The light fixture of claim 15 13, further comprising a third string of leds connected in series with the first and second string of leds.

19. The light fixture of claim 15 13, further comprising:

a pulse generator;

an RC circuit coupled to the pulse generator; and

a third current control device coupled to the RC circuit, the third current control device configured to vary the voltage measured by the second voltage measurement device.

20. The light fixture of claim 13, further comprising:

a plurality of heat-sink-mounted led array modules, each module engaging an led-adjacent surface of a heat-sink base for transfer of heat from the module;

a heat-sink heat-dissipating surfaces extending away from the modules;

at least one venting aperture through the heat-sink base to provide air ingress to the heat-dissipating surfaces adjacent to the aperture.

21. The light fixture of claim 13, further comprising:

a housing and an led assembly secured with respect thereto and open to permit air/water-flow over the led assembly, the led assembly comprising:

an led-array;

an extruded heat sink that has a base and heat-transfer surface extending from the base, wherein the heat-transfer surfaces are surfaces of a plurality of fins extending away from the base in a first direction, the fins including first and second fins along the opposite edges of the base, the first and second edge-adjacent fins also extending from the base in a second direction opposite to the first direction.

22. The light fixture of claim 1, wherein the cumulative light output comprises an intensity from 10,000 lumens to 74,468 lumens.

23. The light fixture of claim 1, wherein the light fixture is configured to operate based on a drive current comprising a current from 700 mA to 1000 mA.

24. The light fixture of claim 1, wherein the cumulative light output comprises a total radiant flux from 30,900 mW to 41,600 mW.

25. The light fixture of claim 1, wherein the cumulative light output comprises a color temperature from 4000° K to 5000° K.

26. The light fixture of claim 1, wherein the cumulative light output comprises an intensity from 10,000 lumens to 74,468 lumens, and wherein the light fixture is configured to operate based on a drive current comprising a current from 700 mA to 1000 mA.

27. The light fixture of claim 13, wherein, the cumulative light output comprises an intensity from 10,000 lumens to 74,468 lumens.

28. The light fixture of claim 13, wherein the light fixture is configured to operate based on a drive current comprising a current from 700 mA to 1000 mA.

29. The light fixture of claim 13, wherein the cumulative light output comprises a total radiant flux from 30,900 mW to 41,600 mW.

30. The light fixture of claim 13, wherein the cumulative light output comprises a color temperature from 4000° K to 5000° K.

31. The light fixture of claim 13, wherein the cumulative light output comprises an intensity from 10,000 lumens to 74,468 lumens, and wherein the light fixture is configured to operate based on a drive current comprising a current from 700 mA to 1000 mA.

32. A light fixture comprising:

a plurality of leds that provide a cumulative light output comprising an intensity of greater than or equal to 10,000 lumens and a color rendering index (CRI) of at least 94, the plurality of leds comprising two or more strings of leds, the two or more strings of leds comprising a first string of leds and a second string of leds connected in parallel with the first string of leds;

a first current control device connected in series with the first string of leds that provides a drive current comprising at least 700 mA to the plurality of leds;

a second current control device connected in series with the second string of leds and configured to control the drive current provided to the plurality of leds;

a first voltage measurement device coupled to the first string of leds and the second string of leds, the first voltage measurement device coupled to the first current control device and configured to control the first current control device; and

a second voltage measurement device coupled to the first string of leds and the second string of leds, the second voltage measurement device coupled to the second current control device and configured to control the second current control device.

33. The light fixture of claim 32, wherein the cumulative light output comprises an intensity from 10,000 lumens to 74,468 lumens.

34. The light fixture of claim 32, wherein the drive current comprises from 700 mA to 1000 mA.

35. The light fixture of claim 32, wherein the cumulative light output comprises a total radiant flux from 30,900 mW to 41,600 mW.

36. The light fixture of claim 32, wherein the cumulative light output comprises a color temperature of greater than or equal to 4000° K.

37. The light fixture of claim 32, wherein the cumulative light output comprises a color temperature of greater than or equal to 5000° K.

38. The light fixture of claim 32, wherein the cumulative light output comprises an intensity from 10,000 lumens to 74,468 lumens, and the drive current comprises a current from 700 mA to 1000 mA.

39. A light fixture comprising:

a plurality of leds configured to output a cumulative light output, the plurality of leds comprising two or more strings of leds, the two or more strings of leds comprising a first string of leds and a second string of leds connected in parallel with the first string of leds;

a first current control device connected in series with the first string of leds and configured to control a drive current provided to the plurality of leds, wherein the drive current comprises at least 700 mA;

a second current control device connected in series with the second string of leds and configured to control the drive current provided to the plurality of leds;

a first voltage measurement device coupled to the first string of leds and the second string of leds, the first voltage measurement device coupled to the first current control device and configured to control the first current control device; and

a second voltage measurement device coupled to the first string of leds and the second string of leds, the second voltage measurement device coupled to the second current control device and configured to control the second current control device, wherein the cumulative light output comprises an intensity of greater than or equal to 10,000 lumens and a color rendering index (CRI) of at least 90.

40. The light fixture of claim 39, wherein at least two of the two or more strings of leds comprise different color leds.

41. The light fixture of claim 40, wherein at least one of the strings comprises a Blue Shifted Yellow string and at least one of the strings comprises a Red string.

42. The light fixture of claim 40, wherein each of the strings comprises a Blue Shifted Yellow string with a different color temperature.

43. The light fixture of claim 39, wherein each of the first and second current control devices comprise: a Bipolar Junction Transistor (BJT); a MOSFET; a junction gate field-effect transistor (JFET); or an insulated gate field effect transistor (IGFET).

44. The light fixture of claim 43, wherein each of the first and second voltage measurement devices comprise: a comparator and an op-amp.

45. The light fixture of claim 39, further comprising a third string of leds connected in series with the first and second string of leds.

46. The light fixture of claim 39, further comprising:

a pulse generator;

an RC circuit coupled to the pulse generator; and

a third current control device coupled to the RC circuit, the third current control device configured to vary the voltage measured by the second voltage measurement device.

47. The light fixture of claim 39, further comprising:

a plurality of heat-sink-mounted led array modules, each module engaging an led-adjacent surface of a heat-sink base for transfer of heat from the module;

a heat-sink heat-dissipating surface extending away from the modules;

at least one venting aperture through the heat-sink base to provide air ingress to the heat-dissipating surfaces adjacent to the aperture.

48. The light fixture of claim 39, further comprising:

a housing and an led assembly secured with respect thereto and open to permit air/water-flow over the led assembly, the led assembly comprising:

an led-array;

an extruded heat sink that has a base and heat-transfer surfaces extending from the base, wherein the heat-transfer surfaces are surfaces of a plurality of fins extending away from the base in a first direction, the fins including first and second fins along the opposite edges of the base, the first and second edge-adjacent fins also extending from the base in a second direction opposite to the first direction.

49. The light fixture of claim 39, wherein the cumulative light output comprises an intensity from 10,000 lumens to 74,468 lumens.

50. The light fixture of claim 39, wherein the light fixture is configured to operate based on a drive current comprising a current from 700 mA to 1000 mA.

51. The light fixture of claim 39, wherein the cumulative light output comprises a total radiant flux from 30,900 mW to 41,600 mW.

52. The light fixture of claim 39, wherein the cumulative light output comprises a color temperature from 4000° K to 5000° K.

53. The light fixture of claim 39, wherein the cumulative light output comprises an intensity from 10,000 lumens to 74,468 lumens, and wherein the light fixture is configured to operate based on a drive current comprising a current from 700 mA to 1000 mA.

54. A light fixture comprising:

a plurality of leds configured to output a cumulative light output at an efficiency, the plurality of leds comprising two or more strings of leds, the two or more strings of leds comprising a first string of leds and a second string of leds connected in parallel with the first string of leds;

a first current control device connected in series with the first string of leds and configured to control a drive current provided to the plurality of leds, wherein the drive current comprises at least 700 mA;

a second current control device connected in series with the second string of leds and configured to control the drive current provided to the plurality of leds;

a first voltage measurement device coupled to the first string of leds and the second string of leds, the first voltage measurement device coupled to the first current control device and configured to control the first current control device; and

a second voltage measurement device coupled to the first string of leds and the second string of leds, the second voltage measurement device coupled to the second current control device and configured to control the second current control device, wherein the cumulative light output comprises an intensity of greater than or equal to 10,000 lumens and a color rendering index (CRI) of at least 90.

55. The light fixture of claim 54, wherein each of the first and second current control devices comprise: a Bipolar Junction Transistor (BJT); a MOSFET; a junction gate field-effect transistor (JFET); or an insulated gate field effect transistor (IGFET).

56. The light fixture of claim 55, wherein each of the first and second voltage measurement devices comprise: a comparator and an op-amp.

57. The light fixture of claim 54, further comprising a third string of leds connected in series with the first and second string of leds.

58. The light fixture of claim 54, further comprising:

a pulse generator;

an RC circuit coupled to the pulse generator; and

a third current control device coupled to the RC circuit, the third current control device configured to vary the voltage measured by the second voltage measurement device.

59. The light fixture of claim 54, further comprising:

a plurality of heat-sink-mounted led array modules, each module engaging an led-adjacent surface of a heat-sink base for transfer of heat from the module;

a heat-sink heat-dissipating surfaces extending away from the modules;

at least one venting aperture through the heat-sink base to provide air ingress to the heat-dissipating surfaces adjacent to the aperture.

60. The light fixture of claim 54, further comprising:

a housing and an led assembly secured with respect thereto and open to permit air/water-flow over the led assembly, the led assembly comprising:

an led-array;

an extruded heat sink that has a base and heat-transfer surface extending from the base, wherein the heat-transfer surfaces are surfaces of a plurality of fins extending away from the base in a first direction, the fins including first and second fins along the opposite edges of the base, the first and second edge-adjacent fins also extending from the base in a second direction opposite to the first direction.

61. The light fixture of claim 54, wherein, the cumulative light output comprises an intensity from 10,000 lumens to 74,468 lumens.

62. The light fixture of claim 54, wherein the light fixture is configured to operate based on a drive current comprising a current from 700 mA to 1000 mA.

63. The light fixture of claim 54, wherein the cumulative light output comprises a total radiant flux from 30,900 mW to 41,600 mW.

64. The light fixture of claim 54, wherein the cumulative light output comprises a color temperature from 4000° K to 5000° K.

65. The light fixture of claim 54, wherein the cumulative light output comprises an intensity from 10,000 lumens to 74,468 lumens, and wherein the light fixture is configured to operate based on a drive current comprising a current from 700 mA to 1000 mA.

66. A light fixture comprising:

a plurality of leds that provide a cumulative light output comprising an intensity of greater than or equal to 10,000 lumens and a color rendering index (CRI) of at least 90, the plurality of leds comprising two or more strings of leds, the two or more strings of leds comprising a first string of leds and a second string of leds connected in parallel with the first string of leds;

a current source that provides a drive current comprising at least 700 mA to the plurality of leds;

a first current control device connected in series with the first string of leds;

a second current control device connected in series with the second string of leds;

a first voltage measurement device coupled to the first string of leds and the second string of leds, the first voltage measurement device coupled to the first current control device and configured to control the first current control device; and

a second voltage measurement device coupled to the first string of leds and the second string of leds, the second voltage measurement device coupled to the second current control device and configured to control the second current control device.

67. The light fixture of claim 66, wherein the cumulative light output comprises an intensity from 10,000 lumens to 74,468 lumens.

68. The light fixture of claim 66, wherein the drive current comprises from 700 mA to 1000 mA.

69. The light fixture of claim 66, wherein the cumulative light output comprises a total radiant flux from 30,900 mW to 41,600 mW.

70. The light fixture of claim 66, wherein the cumulative light output comprises a color temperature of greater than or equal to 4000° K.

71. The light fixture of claim 66, wherein the cumulative light output comprises a color temperature of greater than or equal to 5000° K.

72. The light fixture of claim 66, wherein the cumulative light output comprises an intensity from 10,000 lumens to 74,468 lumens, and the drive current comprises a current from 700 mA to 1000 mA.