Large-Signal based Design Approach in Boost PFC under Constant On-Time Digital CMC with Load Feedforward for Ultra-Fast Transient and Stability

The growing demand for high power-density power factor corrector (PFC) solutions for compact adaptors, electric vehicle chargers, light-emitting diode (LED) drivers, etc, necessitates high-performance energy-efficient control to achieve ultra-fast load transient with reduced output capacitor size. In this paper, a trajectory-based controller tuning approach is proposed in a boost PFC converter under digital constant on-time average current mode control (CMC) with normalized load current feedforward, which can achieve near-time-optimal recovery with reduced voltage undershoot/overshoot. Also, a CCM-DCM (continuous & discontinuous conduction mode) boundary detection technique is incorporated, which offers a natural transition with reduced switching/driving losses. Structural stability analysis is carried out using a discrete-time modeling framework, and the effect of parameter variations is discussed. The effectiveness of the proposed control technique and the performance improvement are demonstrated using simulation results.