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UCC28065: Calculating f_min given output wattage and AC input voltage

Kian Fotouhi
Prodigy 10 points
Part Number: UCC28065
Other Parts Discussed in Thread: UCC28070

Hi there, my name is Kian Fotouhi. I'm an electrical engineering student working on a high-power audio amplifier that will need a transition-mode boost PFC. The specifications will be:

-AC input: 85V to 265V for universal compatibility (the device will primarily be connected to 120V nominal North American grids)

-Power output: 1200W (this will not be a constant output given that the amplifier will present a dynamic load to the power supply)

-Voltage output: 390V nominal

For context, my goals are high switching frequencies and small component size. I'll be using GaN FETs for switching.

I've utilized the UCC28065 datasheet and Excel design tool to determine component values, but I'm unsure of what frequency to select for f_min. I want to capitalize on the benefits of high switching frequencies but I'm unaware of the consequences of allowing the IC to clamp the switching frequency to its upper limit of 800 kHz.

Thanks and kind regards,

Kian Fotouhi

  • 0
    TI__Guru 71385 points

    Hello,

    I am reviewing your inquiry and will get back to you shortly.

    Regards,

  • 0 in reply to Mike O'
    TI__Guru 71385 points

    Hello,

    Generally for transition mode PFC pre-regulators the UCC28065 is recommended for 800 W or less.  This would be two interleaved transition mode PFC boost stages at 400 W each.  In cases of designs greater than 800 W I would recommend using a UCC28070 in an interleaved CCM PFC application with a fixed frequency. 

    The transition mode PFC will have higher RMS and peak currents compared to CCM PFC.  At high power levels it is beneficial to design CCM PFC boost stages over transition mode PFC to reduce conduction losses.  In the case of the 1200 W design I would recommend the UCC28070 over the UCC28065.

    Regards,