VARIABLE PULSE WIDTH MODULATION FOR REDUCED ZERO-CROSSING GRANULARITY IN SENSORLESS BRUSHLESS DIRECT CURRENT MOTORS

摘要

Zero-crossing detection accuracy is enhanced in a sensorless brushless direct current (BLDC) motor by increasing the PWM drive frequency in anticipation of a zero-crossing event in any one or more commutation periods. Once a zero-crossing event is detected, the PWM frequency can go back to a lower normal operating frequency. Switching losses of the power drive transistors are thereby minimized while maintaining accurate zero-crossing detection for stable operation of the BLDC motor.