The torque ripple caused by diode freewheeling of the inactive phase during non-commutation state of PM brushless DC motor(BLDCM)when using the PWM_ON type of pulse width modulation was analyzed.

The design method for hybrid waveforms utilizing ran-dom poly-cell code pulse position modulation (PPM) and pulse-to-pulse binary sequences phase modulation (PM) is introduced in this paper.

In this article several operation modes of the 555 timer applied to the pulse Modulation (PM) and their corresponding operation characteristics are expounded.