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UCC28070: What's the function of gate drive external circuit on EVM

Shaquille Chen
Intellectual 1770 points
Part Number: UCC28070

Dear Team,

What's the function of gate drive external circuit on EVM?

We want to know the function of C3, C4 and D7

Thanks

Shaq

  • 0
    TI__Mastermind 40520 points
    Hello Shaquille,

    C4 and D7 are part of the PWM ramp and offset network that is described on page 35 of the UCC28070 datasheet. This network is used to reduce THD when there is significant DCM in the boost inductor at light loads. The resonant ringing current from the DCM condition pre-biases the current transformer (CT) each cycle which distorts the CT output and increases THD as a consequence. The ramp and offset network can help reduce this effect and improve light load THD.

    If you type in "UCC28070 offset" into the E2E search box, some previous references to this issue will pop up.

    C3 (with R4) is one of the CT reset network options shown in Figure 26 on page 34 of the datasheet. A small capacitance can allow a high peak voltage to reset the CT, but be careful of the forward diode voltage rating.

    Regards,
    Ulrich