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Thread: 2.5kW RF power supply

  1. #1
    diysmps Member
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    2.5kW RF power supply

    Hello guys and thank you all for your great info here, i have so much to read.

    I wanted to ask you if you can give me any guidelines on what to follow, i would like to make a psu for a RF transmitter (the amplifier part of it to me more specific) which requires 50-60V and 50A (around 2.5kW)
    It has to avoid inducing noise to the amplifier, have protections and maybe even fault reporting, i don't know if i need an active PFC or not.

    How do i choose a transformer core (size etc) ? Which way should i go? What topology is preferred in these situations?
    Which controller is suitable for an application like this??


    Thank you all again

  2. #2
    If you really need a super quiet power supply to avoid the noise getting into the amplifier and your radio, I'd recommend a giant mains transformer with lots of filtering and linear regulation. It's not efficient or small, but there is no RFI interference from high speed switching like in a SMPS.

    If you can tolerate a small amount of noise, a much more reasonable approach would be to look online for a used 48VDC power supply pulled from a telecoms system. These are very well built power supplies and have protection circuitry built into them and usually have output connections for fault conditions. Telecom systems have limits for RFI noise so these supplies are very quiet for a SMPS and they are very tough. These companies pull these supplies and replace them on a schedule, even if the supply is 100% working, similarly to the 12V supplies pulled from server farms. They can no longer be used in telecoms once they're past their usage limit and many get sold as surplus. I've bought a couple of them and they work great for powering LDMOS amplifiers. Just don't buy any of the knock-off type supplies, they are cheap junk.

    If you're really set on building your own supply, here is a design note for a 10kW 800V to 48V power supply. Obviously changes need to be made to operate from 240VAC power and it can be scaled down to your lower power requirements. I used this as a basis for my never ending SMPS welder project, but the interleaved 2-switch forward converter design is pretty low on noise if designed properly. Just some idea materials.
    10KW Power Supply

    - Brad

  3. #3
    diysmps Member
    Join Date
    Jan 2019
    Location
    London
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    Hi Brad thank's for your answer.

    I do have many eltek valere at 48V 2kW (telecom engineer) and it's a nice idea however i would like to build mine, i remember once i opened one flatpack and it has planar transformers inside, very nice psu's indeed.

    I think i will go with the UCC28951 on a quasiresonant full bridge topology with active PFC and filters which will be quite close to the flatpacks.

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