Patent ID: 7402969

Claim:
A method for producing PWM voltage waveforms in a PWM motor controller of a PM DC brushless motor, wherein the motor has commutation states and first, second and third phases, wherein the voltage waveforms have a PWM period for each commutation state, wherein the motor controller has first, second and third half H-bridge transistor pairs to generate the voltage waveforms to electronically commutate the motor, and wherein the method comprises: a) always assigning the first transistor pair to the first phase for every commutation state requiring a voltage waveform from the first transistor pair; b) always assigning the second transistor pair to the second phase for every commutation state requiring a voltage waveform from the second transistor pair; c) always assigning the third transistor pair to the third phase for every commutation state requiring a voltage waveform from the third transistor pair; d) always starting a voltage waveform generated by the first transistor pair substantially at the beginning of the PWM period for a commutation state when the commutation state requires a voltage waveform from the first transistor pair; e) always delaying starting a voltage waveform generated by the second transistor pair by substantially ⅓ of the PWM period for the commutation state when the commutation state requires a voltage waveform from the second transistor pair; and f) always delaying starting a voltage waveform generated by the third transistor pair by substantially ⅔ of the PWM period for the commutation state when the commutation state requires a voltage waveform from the third transistor pair.