Current Zero-Crossing Prediction-Based Critical Conduction Mode Control of Totem-Pole PFC Rectifiers

Critical conduction mode (CRM) is widely used in totem-pole Boost power factor correction converters due to its compatibility with soft-switching and high switching frequency. Conventionally, a current sensor or zero-current detector is required to realize CRM operation. The system performances highly rely on the behaviors of peripheral circuits. Additional power loss and delay are also introduced. Moreover, the inductor current contains obvious differential mode noise, which brings interferences to the sensing signals. To address this issue, a novel CRM realization method is proposed. It utilizes an inductor current estimator model to estimate the averaged current and to predict the current zero crossings. The noisy sensing signal is replaced by estimated values. Therefore, the zero-current detection circuit is removed, which simplifies the peripheral circuit design. Valley switching and zero-voltage switching can also be achieved. Operation principles, digital implementation, and error suppression of the proposed control are analyzed. The proposed concepts are validated on a 550-W,
$150 \mathrm{\text{k}}\text{Hz}-1.6 \mathrm{\text{M}}\text{Hz}$
, GaN-based prototype. Experimental results record 98.96% peak efficiency with a 0.9972 power factor.