Digital-based interleaving control for GaN-based MHz CRM totem-pole PFC

Abstract

In this paper, the performance of different interleaving control methods for gallium-nitride (GaN) devices based MHz critical conduction mode (CRM) totem-pole power factor correction (PFC) circuit is compared. Both closed-loop interleaving and open-loop interleaving are good for low frequency CRM PFC; but for MHz very high frequency CRM PFC with microcontroller (MCU) implementation, open-loop interleaving outperforms closed-loop interleaving with small and non-amplified phase error. After software optimization, the phase error of open-loop interleaving is smaller than 3 degree at 1MHz, when the control is implemented by 60MHz low cost MCU. Significant ripple cancellation effect and differential-mode (DM) filter size reduction is achieved with good interleaving. For a 1.2kW MHz totem-pole PFC, the DM filter size is reduced to one quarter compared to the counterpart of a 100kHz PFC. Last but not least, the stability of open-loop interleaving is also analyzed indicating that the MHz CRM totem-pole PFC with voltage-mode control, open-loop interleaving, and turn-on instant synchronization can maintain critical mode operation with better stability compared to low frequency CRM PFC.