The ornamental design for a powersupply pedal, as shown and described.
FIG. 1 is a top plan view of a power supply pedal showing our new design;
FIG. 2 is a top left perspective view thereof;
FIG. 3 is top right perspective view thereof;
FIG. 4 is a front elevational view thereof;
FIG. 5 is a rear elevational view thereof;
FIG. 6 is a left side elevational view thereof;
FIG. 7 is a right side elevational view thereof; and,
FIG. 8 is an alternate embodiment of FIG. 1. The front, rear, left and right sides of FIG. 8 are identical to FIGS. 4-7 of the FIG. 1 embodiment respectively.