Double sampled phase detector circuit

摘要

A motor drive circuit for a three-phase motor includes a commutator that provides a driving voltage to the motor from a DC voltage source. A sequencer operates the commutator to pulse width modulate the source voltage so that the driving current has a continuously variable waveform, such as a sinusoidal waveform. The sequencer is responsive to an error signal from a phase detector to align the driving voltage waveform with a motor current waveform. The phase detector includes a sensor that senses the motor current and provides a voltage input to first and second sample circuits. The first sample circuit provides a plurality of samples of respective instantaneous values of the sensed voltage, and the second sample circuit provides a sample of a selected instantaneous value of the sensed voltage. An error generation circuit provides an error signal based on a difference between the second sample and each of the plurality of first samples.