Abstract: A switched-mode power supply for producing a DC voltage output from a unidirectional-current or alternating-current input uses amplitude modulation of current through and inductor. Input terminals joined to the inductor receive the input. A switch in series connection with the inductor responds to a switching signal for controlling the inductor current. A capacitor and diode store energy received from the inductor. A computation circuit is joined to a switch control circuit for sensing the inductor current and producing a switching signal for opening the switch when the inductor current reaches a desired maximum. A reference voltage generator, which produces a signal indicative of the maximum inductor current, includes an adjustment circuit for modulating an error signal, derived from an integral of the difference between a desired output voltage and the actual output voltage, by the input voltage. Inductor current is thereby modulated in phase with input voltage.