This is one idea I have but I am not really sure about it.

Since I have very small ferrite transformers here I want to try it eventually.

The primary has a few turns. The secondary has much thinner wire.

Is it possible to build it as buck converter, with a PNP transistor, but then generate a higher voltage from the secondary winding?

What is the schematic for that? OK simple, I know buck converter, but isn't it correct it is used in continuous mode and no capacitor is charged from the primary inductance?

Would this be a proper circuit?

Or should I simply use a booster circuit + NPN?

I am just curious to do more experiments, using small transformers now or coils, even ringcores. To learn more about it, I do not need to build anything for a specific purpose.

Also a picture from the transformer. It is not a photo Flash transformer, but the secondary has much more windings than the primary.

Also want to try it with a LNK IC eventually. It is not a transformerless supply! Maybe the transformer will just explode, but maybe will work just fine.

 

Buck would not bee very useful, as the inductor feeds the output capacitor directly. Boost however is basically the same topology as a flyback. See smps.us/topologies.html for comparison.

 

Yes I know but what if I don't use a capacitor, short the inductor to ground, and remove energy via the secondary winding?

I was thinking as long as the pulses are short enough so the primary does not saturate, I could get away with that.

 

Yes I know but what if I don't use a capacitor, short the inductor to ground, and remove energy via the secondary winding?

I was thinking as long as the pulses are short enough so the primary does not saturate, I could get away with that.

That's basically a flyback converter, as kubeek stated.

 

That's basically a flyback converter, as kubeek stated.

Yes I understand that somehow, even if I am of course still learning about these circuits.

My question is if I could use a PNP for a flyback? Or does it even make any difference?

 

Yes I understand that somehow, even if I am of course still learning about these circuits.

My question is if I could use a PNP for a flyback? Or does it even make any difference?

It's not typically done but you could if you used it as a high side switch driving the grounded primary. Normally the low side is switched since NPN's or N-MOSFETS have higher gain, are somewhat faster, and it's easier to drive a low-side switch.