Re: current-fed push-pull dc/dc converter

Jul 20, 2024 Last reply: 2 years ago 2 Replies

On 7/19/2024 11:11 PM, john larkin wrote: \



> What do you find nasty about that topology, it works well , or does it
>> remind you too much of Baxandall?
>
> When a fet turns off, it will spike (to kilovolts in simulation) and
> ring like a churchbell. Now we need snubbers.
>
> Worse, if the fet turnons are slightly asymmetric, you get DC in the
> transformer primary and potential saturation. That can cause flux
> walking, The Devil's Staircase.
>
> Only half of the primary is used at a time, which uses the copper > inefficiently.
>
> It needs another inductor. The waveform at the transformer CT is > ghastly.
>
> Certain Parties want to replace my design with this horror. I'm using
> a 4-fet full bridge driving both ends of my primary, from the 48v bulk
> supply. Nothing goes hi-z, the copper is fully used, and I can add a
> series cap to keep DC out of the transformer primary.
>

It says in the text the transistors are supposed to be turned on simultaneously for a fraction of the cycle.

This is exactly true ! Current fed so that you can do that.

I think this topology is also called a Clarke Converter.

boB

There's still a huge fly-up spike when one turns off.

But I will sim the overlap case.

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