A Digital Control Method with Feedforward Reconstruction for Improved Sampling Interference Suppression in GaN HEMTs based Totem-pole PFC Converters

The duty-ratio feedforward is usually used in totem-pole power factor correction (PFC) converters with digital control to achieve high power factor. However, the sampling interference can affect the input current through the feedforward channel and reduce system performance. In this paper, an improved digital control method with feedforward reconstruction is presented. The proposed method reconstructs the input voltage feedforward in the control system using the input voltage root mean square (RMS) and phase-locked loop, and it can be applied in digitally controlled totem-pole PFC converters based on GaN high electron mobility transistors (HEMTs) to suppress sampling interference and achieve high power factor. Finally, the improved method is verified at a 3.6kW totem-pole PFC prototype with 99.26% peak efficiency. The measured power factor remains above 0.99 from half load to full load. The input current total harmonics distribution (THD) is 2.42% at full load and meet the IEC-61000-3-2 standard.