Fly-back transformer with a low ringing ratio

Abstract

In a fly-back transformer, the tertiary winding for obtaining the secondary B power source is wound in a position where the coupling with the primary winding is weak and where it interlinks the leakage flux of the secondary winding with the primary winding, and the output of the tertiary winding is rectified during the scanning period of a horizontal deflection circuit of a television receiver. Accordingly, only the wave crest value of the ringing is made smaller, regardless of the shot pulse to be obtained within the secondary winding.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a fly-back transformer which is used for supplying a DC high-voltage for example, to a cathode ray tube of a TV receiver or the like, and relates more particularly to a fly-back transformer which is improved in having a small ringing ratio.

Generally, the fly-back transformer includes a primary winding as an input winding, a secondary winding as a high-voltage output winding, and a tertiary winding for drawing out signals such as AFC, AGC, etc., and a secondary B power source. The windings are wound for magnetic coupling therebetween, said primary winding and tertiary winding being particularly closely coupled with each other. In the fly-back transformer having the above construction, it is desirable to make the ringing ratio small for efficient operation. As shown in FIG. 1 illustrating a high voltage pulse induced at the secondary side of a fly-back transformer, when for example, a fifth tuning is taken, the ringing ratio Rr is the ratio of the first wave crest value B of the ringing, and the sum A of a shot pulse wave crest value and the ringing wave crest value B, expressed as a percentageof the high-voltage coil bobbin 17.

In FIG. 19, the tertiary winding 15 is located in channels 18 at each end of the low high-voltage coil bobbin 17, parallel to the secondary winding 19. In each of the above configurations, the ringing ratios can be improved for the same reasons as pertain to the configuration of FIG. 2, although some differences exist among the above embodiments.

In FIG. 20, at least one portion of the tertiary winding 15 is wound at both ends of the inner bobbin 17 12 but near the secondary coil 19, so that the coupling with the primary winding 14 is weak and the tertiary winding 15 interlinks the leakage flux of the secondary winding 19 to the primary winding 14, and the tertiary winding 15 is normally rectified during the scanning period. The part of the tertiary windings 15 at each end is wound through a thick insulating material 16 such as resin film or the like to weaken the coupling with the primary winding 14. The two parts are near the secondary winding 19 and are connected in series as shown in FIG. 21. The winding direction of the tertiary coil 15 is optional, since the tertiary winding 15 is used to allow a so-called scanning period rectification to be performed. The pulse waveform induced in the secondary winding of this embodiment has a ringing ratio value R of 11.5%. Also, in this embodiment, solenoidal or other suitable windings can be used for the tertiary coil 15, not only splitwindings.

Also, note that, as in FIG. 22, while at least one portion of the tertiary winding 15 is located near the secondary coil 19, where its coupling with the primary winding 14 is weak, and interlinks the leakage flux of the secondary winding 19 with respect to the primary winding 14, the remaining portion of the tertiary winding 15 can be wound near the primary coil 14 so that its coupling with the primary winding 14 is strong, and can be connected in series with the first portion. When the tertiary windings 15 are disposed as in FIG. 22, superior high voltage regulation results and does not deteriorate even with a large load connected to the tertiary winding 15. That is, when the entire tertiary coil 15 is near the secondary coil 19 and the tertiary winding 15 interlinks the leakage flux of the secondary winding 19 with respect to the primary winding 14, a downward distortion occurs in the right shoulder of the shot pulse waveform from the secondary winding 19 when the current flowing through the tertiary winding 15 increases with the load, with a bad effect on the high voltage regulation. When the tertiary winding 15 is positioned in FIG. 22, no distortion of such shot pulse waveform occurs even with a large load.

It should also be noted that the tertiary winding 15 of the present invention is provided at both ends of the transformer, where the leakage flux of the secondary winding 19 with respect to the primary winding 14 is highest. However, when the parts of the tertiary coil 15 located at the ends are connected in series as described in connection with FIG. 20, the tertiary winding 15 is adapted to interlink the leakage flux of the secondary winding 19 except at the ends. In this configuration, the leakage flux of the secondary winding 19 is a maximum if the wire connecting the end portions of the tertiary coil 15 is wound around the primary winding 14 several times in the middle portion of the transformer. Thus, more effective method is ensured.

The tertiary windings 15 at each end of the transformer need not be connected in series. Each can be provided with a separate rectifier circuit and a separate load, and operated independently of each other. Again, they can be connected in parallel.

In short, the output of the tertiary windings 15 must be rectified during the scanning period. The load connected through the rectifier circuit to the tertiary winding 15 can be an external electric circuit or it can be merely an impedance element such as a simple resistor. The load connected to the tertiary winding 15 can be used so that the tertiary winding 15 improves the ringing ratio, instead of drawing the secondary B power source as in the case of impedance element, etc.

Another embodiment (see FIG. 23) is a fly-back transformer of multi-singular type characterized in that at least one portion of tertiary winding 15 is so located that it interlinks the leakage flux with respect to the primary winding 14 of at least one of the secondary windings 19 divided in AC manner by diodes D₂, with weak coupling of the tertiary winding 15 with the primary winding 14, and that the tertiary winding 15 is rectified during the scanning period. The transformer of this embodiment includes the low-voltage coil bobbin 12 having a plurality of winding channels 13 in its outer surface, the low-voltage coil bobbin 12 being engaged with the core 11. The primary winding 14 is split-wound along each of the channels 13 of the low-voltage coil bobbin 12 and is divided into three portions connected in series. A plurality of tertiary windings 15, for drawing the secondary B power source, are wound one at one end of each of the three primary coils 14 and all three connected in parallel. The tertiary coils 15 are wound through thick insulating material 16 in order to make the coupling with the primary coils 14 weak and in order that the tertiary coils shall be near the secondary coil 19. The high-voltage coil bobbin 17 is engaged with the low voltage coil bobbin 12 and has a plurality of winding channels 18 in its outer surface, the secondary windings 19 being split-wound in each of the winding channels 18 and being divided into three portions, each of which is located outside of the corresponding portions of the primary and tertiary coils 14 and 15 (see FIG. 23). Each of the three sections of secondary coil 19 is connected at its high-voltage end to a diode D₂, which is located in a winding channel 18 of the high-voltage coil bobbin 17 and connected in series to both adjacent secondary coils 19 (see circuit diagram of FIG. 24). The diodes D₂ divide the secondary windings 19 in AC manner and are adapted to having the DC high voltage drawn from their respective cathode sides.

These tertiary windings 15 are used so that a so-called scanning period rectification may be performed, wherein the rectification is performed only during the scanning period when the load L is connected through the second rectifier circuit SR. Various constructions for the circuit that is to perform the scanning period rectification are possible with different winding directions for the tertiary coils 15 and with various connecting directions of the rectification elements of the rectifier circuits connected thereto. In short, the circuit must be constructed so that rectification elements such as diodes, etc., constituting the rectifier circuits connected to the tertiary windings 15 are not conductive during the fly-back line period, but only during the scanning period.

As shown in the circuit diagram of FIG. 24, the horizontal deflection circuit HD is connected onto the side of the primary winding 14 of the fly-back transformer. A capacitor C₂ is connected in parallel with the secondary windings 19 and diodes D₂. The second rectifier circuit SR is connected across each of the parallel-connected tertiary coil 15. As described above, the tertiary coils 15 are so connected that the rectifier circuit will perform the scanning period rectification. Rectangular wave pulse signals of 15.75 KHz are applied to the input of the primary-side horizontal output transistor Tr. The load L is connected to the output of the second rectifier circuit SR. The pulse waveforms induced in the three secondary coils 19, when a fifth tuning has been made on two of the secondary coils and a seventh tuning on the other secondary coil are shown in FIGS. 25(a), (b) and (c), corresponding to the three secondary coils respectively. The ringing ratio values R obtained from these waveforms are 12.5%, 9.5% and 12.0% respectively. To compare the fly-back transformer of the present invention with the conventional design in which all the tertiary windings 15 are near to the primary winding 14, the tertiary windings 15 in FIG. 23 are directly wound on the primary winding 14 through removal of the insulating material 16. The pulse waveforms now induced in the secondary coils are shown in FIGS. 25(d), (e) and (f). The ringing ratio values R obtained from the waveforms are 27.0%, 20.5% and 19.5%, inferior to the values for the present invention. In the observation of the above waveforms, the fifth and seventh hybrid tunings are made on the secondary winding in order to improve the output waveforms on the secondary, to improve the efficiency of the transformer. However, it is needless to say that the hybrid tuning is not restricted to the fifth and seventh combinations, but can be applied to other proper combinations as required.

The great improvement in ringing ratio as described hereinabove is due solely to reduction in ringing amplitude and not to any changes in shot pulse waveform, as is apparent from comparison of FIGS. 25(a), (b) and (c) with FIGS. 25(d), (e) and (f). The smaller ringing amplitude is due to the higher frequency. The reasons only the ringing waveform changes without any change in the shot pulse waveform are as follows. The rectifier circuit SR performs the scanning period rectification and the load L is connected to the tertiary coils 15. Thus, the AC component of the output of the tertiary windings 15 is short-circuited by the capacitor C₁ only during the scanning period, that is, when ringing is produced. Since the tertiary windings 15 operating as described above are near the secondary windings 19, the inevitable leakage flux of the each secondary winding 19 with respect to the primary winding 14 will interlink with the tertiary windings 15. However, since the AC component of the output of the tertiary windings 15 is short-circuited only during the scanning period, the current which opposes the interlinked magnetic flux flows in the tertiary windings 15 and so reduces substantially the flux only during the scanning period and the shot pulse waveform is therefore not affected. On the other hand, each of the secondary winding ringing frequencies of the scanning period is the resonance frequency of a series resonance circuit of the respective leakage inductances L1 and stray capacities Cs of the secondary windings 19. As is well known, it is determined by ##EQU2## thus the leakage flux of each secondary winding is reduced and the resonance frequency, i.e., the ringing frequency, raised.

Since, as a practical matter, the desirability of the optimum ringing ratio must be balanced against other design requirements of the fly-back transformer, the transformers shown in FIGS. 26 to 30 are more practical than that of FIG. 23. FIGS. 26 to 28 in particular are superior in effect to that of FIG. 23.

In FIG. 26, each tertiary coil 15 is formed, parallel to the primary winding 14, in a channel 13 at one end of one of the divided primary windings 14 of the low-voltage coil bobbin 12. No insulating material is used. The three secondary windings 19 respectively cover the primary and tertiary coils 14 and 15. In this embodiment, the tertiary windings 15 should be wound at the low-potential ends of the secondary coils 19, considering the withstand voltage as in FIG. 23.

In FIG. 27, the channels 13 along which the tertiary windings 15 are wound are shallow so that the tertiary windings 15 are near the secondary windings 19, in order to improve the interlink of the secondary winding with the leakage flux. In FIG. 27, the tertiary coils, wound at the low-potential ends of the primary windings 14, can instead be wound at the high-potential ends. In FIG. 28, the tertiary coils 15 are located at both the low-potential and the high-potential ends of each of the primary coils 14. This could also be done in FIG. 26.

In FIG. 29, the shallow winding channels in the middle portion of each of the three primary windings 14 contain the tertiary windings 15.

In FIG. 30, the tertiary windings 15 are located in winding channels 18 at low-potential end of each of the secondary windings 19 on the high-voltage coil bobbin 17.

These five configurations all tend to reduce the ringing ratio, although some differences exist among them.

Although in these embodiments, the number of tertiary windings 15 equals the number of the secondary windings 19, such need not be the case. For example, there may be only one tertiary winding even if several secondary windings 19 are provided; in this embodiment, needless to say, it is most effective to locate the tertiary coil directly above the secondary winding that has the largest distributed capacity with respect to ground, i.e., on the secondary winding that would have the largest ringing amplitude. In this embodiment, the secondary windings not provided with tertiary windings are not improved in ringing ratio R. In a fly-back transformer having a plurality of secondary windings 19 divided in AC manner, like the multi-singular type, the number of the remaining secondary windings 19 which interface interfere with each other is reduced correspondingly when only one secondary winding is improved in ringing ratio R. Thus, the ringing ratio R can easily be adjusted by means of a conventional turning system, thus allowing the ringing ratio R of the entire fly-back transformer to be reduced.

When a tertiary winding is thus located adjacent to only one secondary winding, additional tertiary windings may be located so as to be strongly coupled with the primary winding, as in conventional fly-back transformers all the tertiary windings being connected in series, although they should not be located where they would be coupled weakly with the primary coil 14 and would interlink the leakage flux of the secondary winding 19 with respect to the primary winding 14.

When one tertiary winding 15 is split into two or more sections physically separated from each other, the high-voltage regulation can be improved in such a way that it will not deteriorate even with a large load L. Each tertiary winding 15 can be split into two sections in this manner, even when a tertiary winding is provided to correspond to each of the secondary winding windings 19.

It should be noted that when a plurality of tertiary windings 15 is provided, as in FIG. 23, they may be connected either in parallel or in series.

The output of the tertiary windings 15 must be rectified during the scanning period. The load L connected through the second rectifier circuit SR to the tertiary coils 15 may be either an external electric circuit or merely a single impedance element such as a resistor, since the original object of the tertiary winding 15 is to serve as the secondary B power source. As the load L connected to the tertiary winding 15 is an impedance element or the like, the tertiary winding 15 may be used to improve the ringing ratio or to draw out the output signal in addition to being the secondary B power source. When the tertiary winding is used only to improve the ringing ratio, the rectifier circuit SR and the load L of the impedance elements may be integrated with the fly-back transformer.

Various elements of the fly-back transformer of the present invention have been described above. The present invention has the novel advantages that adjustments may be made extremely easily, and the ringing ratio can be reduced without any effect upon the shot pulse waveform induced in the secondary winding even when the load of the tertiary winding is large. In addition, the present invention has the advantage over the prior art that unnecessary radiation is minimized when a fly-back transformer such as is described is incorporated in the television image receiver.

Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it should be noted that various changes and modifications will be apparent to those skilled in the art. Applicants therefore prefer not to be limited to the preferred embodiments herein described.

Claims

1. A fly-back transformer for use in a horizontal deflection circuit of a television receiver, the operation of said deflector deflection circuit being cyclical, and each cycle of said circuit being divided into a scanning period and a retract retrace period, said transformer comprising:

a core member,

a first coil bobbin provided on said core member;

a primary winding for low voltage supply mounted on said first coil bobbin;

a second coil bobbin located on said first coil bobbin;

a secondary winding for producing a high-voltage output responsive to an electromagnetic field generated by said core and located on said second coil bobbin;

a tertiary winding for generating a low-voltage output responsive to an electromagnetic field generated by said core and located at a position wherein the magnetic coupling of said tertiary winding to said primary winding is small in comparison with the magnetic coupling of said tertiary to said secondary winding, and wherein the leakage flux of said secondary winding with respect to said primary winding interlinks with said tertiary winding; and

a commutating circuit connected to said tertiary winding so as to commutate the output of said tertiary winding only during said scanning period of said horizontal deflection circuit.

2. A fly-back transformer as claimed in claim 1, wherein said primary winding is formed of a plurality of solenoid windings connected in series, each of said solenoid windings comprising a plurality of turns and each of said solenoid windings being separated from the others by at least a small distance.

3. A fly-back transformer as claimed in claim 1, wherein said secondary winding is formed of a plurality of solenoid windings connected in series, each of said solenoid windings comprising a plurality of turns and each of said solenoid windings being separated from the others by at least a small distance.

4. A fly-back transformer as claimed in claim 1, wherein said tertiary winding is formed of a plurality of solenoid windings connected in series, each of said solenoid windings comprising a plurality of turns and each of said solenoid windings being separated from the others by at least a small distance.

5. A fly-back transformer as claimed in claim 1, wherein said first coil bobbin has a plurality of circular channels on the outer surface thereof, and said primary winding is split-wound into said channels.

6. A fly-back transformer as claimed in claim 1, wherein said first coil bobbin has a plurality of circular channels on the outer surface thereof, and said primary winding is split-wound into some of said channels and said tertiary winding is split-wound into the rest of said channels.

7. A fly-back transformer as claimed in claim 1, wherein said first coil bobbin has a plurality of circular channels on the outer surface thereof, said primary winding is split-wound into said channels, and said tertiary winding is split-wound over said primary winding over an insulating material which is located over said primary winding and within said channels.

8. A fly-back transformer as claimed in claim 1, wherein said second coil bobbin has a plurality of circular channels on the outer surface thereof, and said secondary winding is split-wound into said channels.

9. A fly-back transformer as claimed in claim 1, wherein said second coil bobbin has a plurality of circular channels on the outer surface thereof, and said secondary winding is split-wound into some of said channels and said tertiary winding is split-wound into the rest of said channels.

10. A fly-back transformer as claimed in claim 1, wherein said tertiary winding is located relatively close to said secondary winding and relatively far from said primary winding, whereby said tertiary winding is strongly coupled to said secondary and weakly coupled to said primary winding.

11. A fly-back transformer as claimed in claim 1, wherein said tertiary winding is wound in a winding direction opposite to that of said secondary winding.

12. A fly-back transformer as claimed in claim 1, wherein said tertiary winding is so located that the ratio of the leakage flux of said secondary winding under the influence of both said primary and tertiary windings to the leakage flux of said secondary winding under the influence of said primary winding alone is less than 90%.

13. A fly-back transformer as claimed in claim 1, wherein said tertiary winding is mounted on said first coil bobbin, at one end of said primary winding.

14. A fly-back transformer as claimed in claim 1, wherein said tertiary winding is mounted on said first coil bobbin, at the center of said primary winding.

15. A fly-back transformer as claimed in claim 1, wherein said tertiary winding is mounted on said second coil bobbin, at one end of said secondary winding.

16. A fly-back transformer as claimed in claim 1, wherein said commutating circuit comprises a diode and a capacitance means.

17. A fly-back transformer for use in a horizontal deflection circuit of a television receiver, the operation of said circuit being cyclical, each cycle of said circuit being divided into a scanning period and a retrace period, said transformer comprising:

a core member;

a first core coil bobbin located on said core member;

a primary winding for low voltage supply located on said first coil bobbin;

a second coil bobbin located on said first coil bobbin;

a secondary winding producing a high voltage output responsive to an electromagnetic field generated by said core and located on said second coil bobbin;

a tertiary winding producing an output responsive to an electromagnetic field generated by said core, and having a first and a second portion, said first portion of said tertiary winding being located in a position such that the magnetic coupling of said first portion with said primary winding is loose, strong, and said second portion of said tertiary winding being located in a position such that the magnetic coupling of said second portion with said primary winding is weak relative to the coupling between said first portion and said primary winding, and said second portion of said tertiary winding interlinking interlinks with leakage flux of said secondary winding with respect to said primary winding; and

commutating circuit means connected to said tertiary winding being operated so as to commutate the output of said tertiary winding only during said scanning period of said deflection circuit.

18. A fly-back transformer as claimed in claim 17, wherein said second portion of said tertiary winding is located over an insulating material located over said primary winding and said first portion is located directly on said primary winding.

19. A fly-back transformer as claimed in claim 17, wherein said second portion of said tertiary winding is located at one end of said primary winding and said first portion is located directly on said primary winding.

20. A fly-back transformer as claimed in claim 17, wherein said second portion of said tertiary winding is located at one end of said secondary winding and said first portion is located directly on said primary winding.

21. A fly-back transformer for use in a horizontal deflection circuit of a television receiver, the operation of said circuit being cyclical, and each cycle of said circuit being divided into a scanning period and a retrace period, said transformer comprising:

a core member;

a first coil bobbin located on said core member;

a primary winding for supplying low voltage located on said first coil bobbin;

a second coil bobbin located on said first coil bobbin;

a secondary winding for supplying high voltage output responsive to an electromagnetic field generated by said core, located on said second coil bobbin;

a tertiary winding supplying an output responsive to an electromagnetic field generated by said core, and having first and second portions, said first portion being located at one end and said second portion being located at the other end of said primary winding, whereby the magnetic coupling of said tertiary winding with said primary winding is loose and said tertiary winding interlinks with leakage flux of said secondary winding with respect to said primary winding; and

commutating circuit means connected to said tertiary winding so as to commutate the output of said tertiary winding only during said scanning period of said deflection circuit.

22. A fly-back transformer for use in a horizontal deflection circuit of a television receiver, the operation of said circuit being cyclical, and each cycle of said circuit being divided into a scanning period and a retrace period, said transformer comprising:

a core member;

a first coil bobbin located on said core member;

a primary winding for supplying low voltage located on said first coil bobbin;

a second coil bobbin located on said first coil bobbin;

a secondary winding for supplying a high voltage output responsive to an electromagnetic field generated by said core, located on said second coil bobbin;

a tertiary winding for supplying an output responsive to an electromagnetic field generated by said core, and having first and second portions, said first portion being located at one end of said secondary winding and said second portion being located at the other end thereof, whereby the magnetic coupling of said tertiary winding with said primary winding is loose and said tertiary winding interlinks with lenkage flux of said secondary winding with respect to said primary winding; and

commutating circuit means connected to said tertiary winding for commutating the output of said tertiary winding only during said scanning period of said deflection circuit.

23. A fly-back transformer for use in a horizontal deflection circuit of a television receiver, the operation of said circuit being cyclical, and each cycle of said circuit being divided into a scanning period and a retrace period, said transformer comprising:

a core member;

a first coil bobbin located on said core member;

a primary winding for supplying a low voltage located on said first coil bobbin;

a second coil bobbin located on said first coil bobbin;

a secondary winding for supplying a high voltage output responsive to an electromagnetic field generated by said core, located on said second coil bobbin, said secondary winding being divided into a plurality of portions alternately connected in series to a plurality of diodes;

a tertiary winding for supplying an output responsive to an electromagnetic field generated by said core, so located that the magnetic coupling of said tertiary winding with respect to said primary winding is loose and said tertiary winding interlinks with leakage flux of said secondary winding with respect to said primary winding; and

commutating circuit means connected to said tertiary winding so as to commutate the output of said tertiary winding only during said scanning period of said deflection circuit.