Digital based interleaving control for GaN based MHz CRM totem pole PFC
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.
2016 IEEE Applied Power Electronics Conference and Exposition (APEC)