Patent ID: 7638966

Claim:
A power factor corrector for an AC induction motor, comprising: a) an input filter configured to receive AC voltage from an AC voltage source and attenuate the AC voltage to produce a filtered AC voltage; b) a current phase sampler configured to receive the filtered AC voltage from the input filter and output a current phase signal related to a phase of an AC current associated with the AC voltage; c) a signal conditioning circuit configured to derive voltage phase information from the AC voltage and receive the current phase signal from the current phase sampler, and generate a phase signal having a magnitude proportional to a phase dislocation between the AC voltage and the current associated with the AC voltage as well as a voltage polarity signal that depends on a polarity of the AC voltage; d) a first switch controller configured to receive the phase signal and the voltage polarity signal from the signal conditioning circuit and generate one or more polarity control signals and first and second pulse-width modulated polarity controlled chopping control signals; e) a first voltage control circuit configured to receive the filtered AC voltage and to receive the first and second polarity control signals and the first and second chopping signals from the control amplifier and output an AC output voltage having an amplitude proportional to a duty cycle of the pulse first or second chopping signal, wherein the switch controller is configured to adjust a duty cycle of the chopping signals in response to the phase signal in a way that changes the amplitude of the AC output voltage to reduce a phase dislocation between the AC voltage and the AC current; and f) a capacitor configured to prevent the voltage control circuit from interfering with the current phase sampler.