Hi,
In our interleaved PFC, there's one diode D3 as the attached picture.
What's it used for? Customer wants the details.
Thanks.
Br, Jordan
Hello Jordan,
This diode, D3, is a common addition to PFC circuits.
At startup when AC is applied, there is a straight path from Vs to the PFC bulk cap Cb.
This current can be very large depending on where on the AC waveform the Vs is applied.
This high current, if routed through the L1 L2 inductors, could cause core saturation.
When the PFC turns on it would start switching with saturated inductors, not good.
The boost diodes, D1 D2, are chosen for fast reverse recovery, while the added D3 is selected to withstand the peak inrush current and maximum AC line voltage.
The inrush diode is typically lower cost since it does not need to have fast recovery.
In the example for UCC28521 PFC Combo IC, Page 19:
-Boost diode is HFA08TB60, 8Amp 600V Ultrafast Soft Recovery
-Inrush bypass diode is GI756. 6Amp average, 400Amp surge, 600V
Good question.
