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UCC28070: Current path of PFC bridgeless circuit

Kaji@PAN
Mastermind 7280 points
Part Number: UCC28070
Other Parts Discussed in Thread: PMP9640,

Hello,

I am considering a bridgeless circuit for PFC.
In it, I'm examining the PMP9640 reference design and the UCC28070 interleave.

(question 1)
As shown in the attachment, I have shown the current path of the PMP9640 and UCC28070 interleaves.
Is the current path in the figure correct?

(Question 2)
Comparing the PMP9640 and UCC28070 interleaves, the PMP9640 follows a current path using a bridge diode and a FET body diode when the FET is off.
So is it less efficient than UCC28070 Interleave?

Best regards,

Current path of PFC bridgeless circuit.pptx

  • +1
    TI__Genius 9140 points

    hello Kaji,

    thanks for your interest in UCC28070 bridgeless solution.

    I saw you already create another post for the test of  bridgeless using UCC28070.

    for your question 1, it is not fully correct.

    once the mosfet in UCC28070 acted as the returned path, the RMS current still can flow through the mosfet because at this condition, the returned mosfet can not detect the CSA or CSB signal， so the current loop for this phase is saturation with controller output Dmax duty. And the bridge Diode only handle high frequency current.

    for your second question.

    it is hard to compare the two solution since PMP960 is working at CRM and UCC28070 is working CCM.

    CRM with has less system cost because of no need of SIC diode and higher switching off loss, but less switching on loss.

    CCM needs higher system cost but if GaN/SIC Mosfet, SIC diode can be used, the efficiency can be very high.