Microcontroller-based MHz totem-pole PFC with critical mode control

This paper focuses on how to implement critical conduction mode (CRM) control for GaN-based MHz totem-pole PFC with a commercial low-cost microcontroller (MCU), including basic CRM operation, programmed on-time control for achieving low current THD, off-time extension for achieving ZVS for whole line cycle operation, and two-phase interleaving control for input current ripple cancellation and EMI filter size reduction. A novel but simple improvement of zero-current-detection (ZCD) based CRM control method is proposed to solve signal processing delay issue to realize CRM operation for MHz totem-pole PFC. A simple but very accurate on-time calculation method is also proposed for implementing programmed on-time control at MHz high frequency. The result of aforementioned control function integration and implementation is demonstrated on a 1.2kW GaN-based MHz totem-pole PFC prototype.