Suppression of Quantization-Induced Limit Cycles in Digitally Controlled DC-DC Converters by Dyadic Digital Pulse Width Modulation

Quantization-induced limit cycle oscillations (LCOs) in digitally controlled DC-DC converters are addressed in this paper. The novel Dyadic Digital PWM (DDPWM) is proposed to increase the effective pulse-width-modulator (PWM) resolution, as required for LCO-free operation, at low cost, without sacrificing DC accuracy and with no detrimental effects on the ripple voltage. Experimental results on a synchronous buck validate the approach highlighting effective LCOs suppression and DC accuracy enhancement at 5x reduced output voltage ripple compared to thermometric dithering for the same resolution increase.