Abstract: An inverter/converter power supply system that employs pulse-width modulation controlled by an absolute-value representation of a reference wave. A low-frequency wave, such as a 60 hertz sine wave, is precision-rectified which then is the reference input of a pulse-width modulation controller (PWM). The PWM then produces a high-frequency square-wave signal whose pulse width changes as the amplitude of the rectified reference wave changes. The high-frequency square-wave signal is further rectified at an inverter/converter transformer secondary, whose output is filtered through a low-pass filter that removes the high-frequency component while minimizing the stored charge in the filter capacitor(s) to an amount easily drained by a small constant-current load across it. Feedback from the constant-current load to the PWM further adjusts the pulse-width to compensate for load variations and circuit losses.