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Original question:

TIDA-00961: A few question about High power density 1.6 kW Bridgeless ZVS Transition Mode GaN PFC introduction

TIDA-00961: A few question about High power density 1.6 kW Bridgeless ZVS Transition Mode GaN PFC introduction

Marcus Wu
Prodigy 30 points

Part Number: TIDA-00961

thank for your kindly answered.

I'm still confused and just wanna know in light load, is its duty fixed and changed the frequency?  or both be changed?

if I use MCU for digital control, how to make sure that can be achieved ZVS at full load or light load

Is it need to calculate the period in each cycle to determine switching frequency that makes the inductor current come to negative before the next cycle?

  • 0
    TI__Expert 3860 points
    Hi Marcus,

    As the load goes lighter, in CrM operation, the on time and off time both change to go higher in frequency. However, there is a frequency clamp at 1.2MHz, forcing the circuit to go into DCM operation. Currently burst mode or pulse skipping is not implemented in the software; but this will be required for very low power operation.

    This design is using digital control, and achieves ZVS at full and moderate load levels. At low loads, trying for full ZVS may not be efficient, as the extra negative current can increase losses. So DCM operation is implemented.

    Switching frequency is never directly determined. The on time and off time are calculated.

    Regards,

    Salil