Limit Cycle-Free Digitally Controlled DC-DC Converters based on Dyadic Digital PWM

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 peak output voltage ripple and up to 16dB lower-frequency harmonic component reduction compared to thermometric dithering for the same resolution increase.