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UCC28070: 4-phase interleaved PFC with two paralleled UCC28070EVM

Jeong Sang Yoo
Prodigy 10 points
Part Number: UCC28070

Hello.

I am planning to use two UCC28070EVM to make a 4-phase interleaved PFC but even though I read UCC28070 datasheet I still don't get how to synchronize two modules together.

It will be very helpful if you answer the questions I have below.

 In the figure 18 (Simplified four-phase application diagram using two UCC28070 devivces) from UCC28070 datasheet, it says 'synchronized clocks with 180 degree phase shift' to parallel two UCC28070. 

1. Should I design a circuit to input synchronized clocks with 180 degree phase shift to RDM pin?

2. If so, since switching frequency of the UCC28070EVM is 200kHz per phase, is total frequency for RDM 800kHz (4 x fsw)?

3. It will be great if you let me know the details I have to consider other than the questions above for four-phase interleaved PFC with two paralleled UCC28080.

Thank you.

  • 0
    TI__Mastermind 34465 points

    Hello Jeong Sang Yoo,

    The block schematic of Figure 18 is a concept drawing of a four phase interleaved pfc and there is no reference design available with an actual design specification. However I can explain to you the concept behind Figure 18.

    The synchronized clock block has two outputs that are 180 degrees out of phase . These outputs go to the RDM input of the UCC28070.

    This sets the  sync frequency of the UCC28070. The sync frequency is twice the pwm frequency.

    A schematic for the synchronized clock is not available but obviously the oscillator for this clock is running at twice the synchronized output frequency.

    So if your require a pwm frequency of 200kHz then the signal on the RDM pin needs to be 400kHz and the synchronized clock needs an internal oscillator frequency of 800kHz.

    Regards

    John