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  1. #1
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    USB PD Lab Power Supply, flyback- vs forward-converter, pro's vs con's?

    Hello.

    I have what I think is a pretty neat idea, the latest laptop I bought feature a USB Type-C port which supports USB Power Delivery(USB PD)(my port is actually a Thunderbolt 3 port but it is compatible with USB 3.1 Gen 2 & USB PD, but let's not get into all that stuff) which means the such a port is capable of supplying up to 20V @ 5A or 100W of power.

    I have made a picture to show what I have in mind:
    Click image for larger version. 

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    That is obviously a very simplified concept picture but it only shows my intention at large, I might go for using TI C2000 microcontrollers for the converters.

    In any case, I have been reading about flyback- vs forward-converters and it appears to me that a forward-converter is what is most suitable for me, a two-switch forward converter that is, due to the lower output ripple, but there are so many considerations that I can't remember them all.

    But I want to ask, is there any difference in the difficulties in successfully designing a flyback- vs forward-converter? Is the feedback compensation more difficult in a flyback converter?

    As far as I can understand the two-switch forward converter is limited to duty-cycles below 50%, though I don't really grasp the implications of that, I mean as long as I choose a suitable turns-ratio that shouldn't be a problem right?

    Regards
    (I feel as though I am forgetting to ask the main question motivating this thread but I can't recall it..)

    - - - Updated - - -

    I have lost the picture I intended to post, the two channels are isolated and they should each be able to handle 3A output in case only one is used. I shouldn't have posted right now, I feel as though I have forgotten all the main points I wanted to describe.

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  2. #2
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    Re: USB PD Lab Power Supply, flyback- vs forward-converter, pro's vs con's?

    Weigh the risk if you attach homebrew circuits to your computer's USB port. You could ruin it. Switched-coil supplies are the type that ought to have a snubber, due to indcutive spikes.

    Another question is how much current you can get immediately from your USB. There's a protocol called enumeration. If a device does not complete it, then the port only provides 130 mA. It was that way not so long ago, maybe it's changed.



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  3. #3
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    Re: USB PD Lab Power Supply, flyback- vs forward-converter, pro's vs con's?

    which means the such a port is capable of supplying up to 20V @ 5A or 100W of power.....

    I have to ask: an USB port is capable of providing 20 volts ?
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