PWM technique for acoustic noise reduction in power applications

As a consequence of PWM techniques, high frequency current ripple appears in power actuators generating acoustic noise at the corresponding frequency (switching noise). A PWM technique is presented for shaping the switching noise spectrum in such a way it can merge with the natural system noise. It consists of avoiding a discrete switching frequency spectrum by means of a pseudo-random PWM generator. Hence, the switching frequency is continuously and randomly variable over a given range. The switching noise is quasi-white in this range, and much less disturbing. Practical solution and results are presented for a motor drive application