The ornamental design for a powersupply, as shown and described.
FIG. 1 is a perspective view of a power supply showing our new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is another perspective view thereof.
The dot dash dot lines represent bounds of the claimed design. The broken line showing in the figures are for the purpose of illustrating portions of the power supply and form no part of the claimed design.