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

A new 2-D random-switching pulsewidth modulation (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. Moreover, the controller parameters of a digitally controlled power converter are not required to change, which is quite essential to digitally controlled systems. Current random PWM methods are discussed and compared with the proposed method in this paper. It will be shown that the merits of the presented method include random-switching frequency, constant sampling frequency, and constant average inductor current. An field-programmable-gate-array-based digitally controlled buck converter experimental system has been set up. The specifications of the converter include 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.