a power maximization circuit periodically samples the output power of a power supply to regulate output voltage or current toward that resulting in maximum output power . power increasing variations in voltage or current are continued until maximum power is reached and exceeded , at which time the direction of variation is reversed until operation becomes stabilized at maximum power conditions . the circuit includes a sampling means for periodically sampling the output power . the sampling means is connected to a comparison means providing an output signal , the condition of which is indicative of whether the power at any given sampling period is greater or less than the previous sampling period . means are provided for detecting on a coincidence basis , the condition of the comparison means output signal and for altering the magnitude of the current or voltage of the power supply toward that which obtains maximum power .