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3KW+ AC-DC converter Topology

Danny Andreev
Intellectual 310 points
Other Parts Discussed in Thread: UCC28950, UCC3895

Hey, 

I am currently developing a 3kW @120V and 10kW @ 240V AC-DC SMPS. My friend is helping out, and he is trying to convince me to use a forward converter, I see a few major issues with this. (thus far I have been going with a ZVT Full Bridge).

Can you help me explain to him why a forward converter is the not the right choice.

Also please let me know if you have any good ideas and reading material for making 3kW+ AC-DC converters and which topology you think I should be going with. 

Thank you!

  • 0
    Prodigy 5 points

    Hello Danny,

    A full bridge, ZVT or not, is a forward topology. You can only do kilowatts with some sort of forward topology.

  • 0 in reply to Ed Walker
    Prodigy 5 points
    Some more ideas on this Danny.
    In our TI DESIGNS landing page there are power designs.
    www.ti.com/.../refdesignsearch.tsp

    Sorting Output Power highest to lowest, you can see some designs.

    5KW Interleaved CCM Power Factor Correction Converter
    180-264Vinac, 400Vout 12Amps
    http://www.ti.com/tool/PMP4311

    Pre-Regulator for Air Conditioner 80Vdc Output with 3kW
    90-264Vinac, 390Vout 7.7Amps
    http://www.ti.com/tool/PMP4259

    These are PFC power factor front ends, necessary for pulling maximum power from an AC line.
    They DO NOT provide isolation, so an isolated stage usually follows.
    PFC is a boost topology.

    A boost must "boost" so at 120VACin (132Vrms at +10%, 186Vpeak) you can create an ~200VDC output.
    At 264VACin rms the Vpeak is 370Vpeak, so the Vout is ~390-400Vdc.

    Wide range PFC designs are common.
    However for a 390Vout at X watts, the currents are very high at the low line input, 120VAC.
    So the PFC must be designed to support those high currents, thus burdening the design at 240VAC.

    If your product will allow 2 different designs, 120VAC US and 240VAC Europe, then each can be made more cost effective.
    But you have 2 SKU's.

    What output voltage at what current do you need?

    The common topology that follows a high power PFC is a Phase Shifted Full Bridge (PSFB).
    This is an H bridge with ZVT, zero voltage switching, very high efficiency.
    UCC28950 is a PSFB controller that also drives synchronous rectifiers on the output.
    UCC3895 is another.


    I am interested in your thoughts on this.