Variable speed AC induction motor controller

A circuit for powering a two-phase AC induction motor. The circuit generates a first signal of the form Vdc+A sin(2 pi ft-0 DEG ) and a second signal of the form Vdc+A sin(2 pi ft-90 DEG ). The first signal is input to a first error amplifier along with a first sampled difference signal from the motor. The second signal is input to a second error amplifier along with a second sampled difference signal from the motor. The outputs from each of the first and second amplifiers is input into a first comparator and a second comparator along with a sawtooth waveform to create a first sinusoidally modulated square wave signal and a second sinusoidally modulated square wave signal. The first and second sinusoidally modulated square wave signals are fed to driver circuits which in turn control an H-bridge circuit for powering the motor from a DC bus.