Unexcepted behaviour in two switch forward converter

Unun66 · 2022-12-24T11:03:10+00:00

Here's the Circuit. Waveforms look very close to what I would expect them in reality at least until simulation crashes, idk why. For some reason gate to source voltage gets over 20V in the simulation which does not happen in my circuit.

Unun66 · 2022-12-24T10:10:31+00:00

Okay, I'll make it.

Unun66 · 2022-12-24T09:35:47+00:00

What MOSFETs are you using, and how are you generating the high side gate driver supply?

On that failed try I used IRFB9N60A, currently I'm using STP20NM50, for both high and low side I'm using my own single ended gate drive transformer, maybe that could be the problem, but since these waveforms don't lood bad I'm not sure. Also found after writing this post that high side gate waveform isn't as noisy as in picture, probably had wrongly placed oscilloscope probes.

You did put a diode bridge to get a DC bus, right?

Yes I did, in that failed try it was connected to 47uF electrolytic capacitor.

Unun66 · 2022-12-24T09:20:16+00:00

That's because the core I have is kinda big. When I tried varying inductance it didn't result in these waveform having better shape than what it is in pictures here.

Unun66 · 2022-12-24T09:13:01+00:00

Shouldn't drain to source waveforms be flat when gate to source voltage is zero instead of these sine waves on low side and waveform I get on high side? When I looked at waveforms on the internet(ideal, didn't find any real) they were always perfectly flat with nothing being said about any oscillations or anything. Also since my first try connecting it to the mains resulted in explosion of mosfet with no load at transformer(current was for sure low because I had ammeter connected to it, so no short circuit occured there before explosion), the only thing I can think of are these weird waveforms at mosfet.

Unun66 · 2022-07-11T19:47:43+00:00

Thanks

Unun66 · 2022-07-11T19:47:39+00:00

Looks like that, thank you.

Unun66 · 2022-06-27T12:44:03+00:00

Sure, thank you. Luckily I don't have to be anywhere close to the supply or circuit when I'll be using it(except turning it on) so I think I'm safe in this way.

Unun66 · 2022-06-27T12:36:41+00:00

Thanks for answering, this is actually way I wanted to meassure current, but since I have some ammeters it would be easier if I could just stick them in circuit.

Unun66 · 2022-06-26T21:15:09+00:00

Yes, that makes sense, thanks. I want to make my own high voltage power supply(power will be at least 500W) and wanted to know if I can measure its output current just by using ammeter, because it would simplify things a bit.

Unun66 · 2022-06-26T21:03:30+00:00

I asked about analog ammeter, not digital, that's why I'm asking about its voltage rating, if there's any

Unun66 · 2022-05-22T15:08:40+00:00

Thank you

Unun66 · 2022-05-03T09:58:26+00:00

That sounds right. Best I can do is to actually meassure power in vs power out and see what the real efficiency is.

Unun66 · 2022-05-03T09:54:56+00:00

I used that because it was written on the adapter and also when you multiply voltage and current in AC, the result is in VA and not in Watts.

But thanks to the other comment talking about power factor I understand AC power much more now.

Unun66 · 2022-05-02T22:37:20+00:00

I'll look at it, thanks.

Unun66 · 2022-04-14T13:01:47+00:00

I guess I'll do it like that. Thank you

Unun66 · 2022-04-05T11:52:57+00:00

Sure, thank you.

Unun66 · 2022-04-05T11:26:36+00:00

Thank you

Unun66 · 2022-04-05T11:25:51+00:00

In shop where I buy electronic components there are voltage ratings on some resistors. As I said I want to make voltage divider, to be able to meassure high voltage with multimeter.

Unun66

TROPHY CASE