Quantization effects and limit cycling in digitally controlled single-phase PFC rectifiers

This paper examines quantization effects and limit cycling in the voltage control loop of digitally controlled single-phase power factor correction (PFC) rectifiers. Low-frequency limit cycling in the voltage loop can result in undesirable DC components, even harmonics in the AC line current and flicker. It is shown that two mechanisms can result in low-frequency limit-cycling: nonsynchronous sampling of the output voltage and quantization of the power command signal. Conditions for avoiding limit cycling are presented and verified in simulations and experiments on digital average current mode (DACM) and digital non-linear carrier (DNLC) [1] controlled PFCs.