Novel Random Switching PWM Technique with Constant Sampling Frequency and Constant Inductor Average Current for Digital-Controlled Converter

A new two-dimensional random switching PWM technique is proposed to reduce the dominant harmonic clusters while retaining constant average inductor current and constant sampling frequency. The special feature of constant average inductor current can reduce the output voltage ripple. And the controller parameters of digital-controlled power converter are not required to change which is quite essential to digital-controlled system. Current random PWM methods are discussed and compared with the proposed method in this paper. It will be shown that the presented method is with the merits of randomly changes switching frequency while keeping constant sampling frequency and average inductor current. An FPGA-based digital-controlled buck converter experimental system has been set up. The specifications of the converter includes: input voltage = 5 V, output voltage = 1.5 V and switching frequency = 200 kHz. The proposed random switching pattern is implemented by software. Experimental results demonstrate the effectiveness of the proposed random switching pattern.