Abstract: An AC power amplifier (50) with a pair of push-pull transistors (Q1, Q2) driving opposite sides (36, 38) of the primary winding of an output transformer (T1) controlled by a pair of variable duty cycle, pulse width modulated width trains (A, B) generated on the output of a pulse width modulator (26) controlled, in turn, through means of a wave shaping feedback system to cause the AC output at the secondary winding (20) to track the output of a precision reference sine wave oscillator (12) and through means of another feedback system for automatic DC compensation including a pair of CMOS analog switches respectively driven by the two pulse width modulated pulse trains (A on 28, B on 30) to produce a pair of feedback signals.

Abstract: A pulse-width ac voltage regulator that provides a precisely ac output voltage without the need for any inefficient protective circuitry for ensuring proper operation when it repeatedly switches between its two alternative operating modes. A transformer is arranged with a first winding connected between an input terminal and an output terminal and a second winding connected between one end of the first winding and a control terminal. A special switch assembly including four separate circuits, each having a series connected transistor and diode, is controllably switched such that the second winding is alternatively shorted or excited, to provide a stepped-up (or stepped-down) voltage out of the first winding. The transistors are controllably switched at a frequency substantially greater than that of the ac input signal and at a duty cycle selected to provide the desired ac output voltage.