Induction heater short circuit

Question

I see a short circuit in a widely used induction heater diagram.

Why does this circuit work despite the short circuit?

This circuit is widely successfully tested on youtube and I want to make it too, but I am afraid a little due to this short circuit.

I [made a rough simulation](https://tinyurl.com/25xkduek) of this circuit, which might help you understand its behaviour a little better. — Polynomial, Oct 21 '22 at 14:43

score 4 · Accepted Answer · answered Oct 21 '22 at 14:30

It's not a short circuit; the path is from positive supply, through an inductor, then through a MOSFET and back to the negative terminal of the supply.

Only if the MOSFET was permanently enabled might it be regarded as a short circuit. However, for normal MOSFET operation, when activated, the current through the inductor ramps up storing magnetic energy then, when the MOSFET deactivates, that stored energy is released to the "work coil" which resonates and generates eddy currents in the work-piece (not shown).

Ditto the other MOSFET circuit (and its associated inductor) but, it operates alternately to the first MOSFET circuit due to the way D3 and D4 are cross-coupled.

Don't try and use it at powers more than a hundred watts or so until you are happy the MOSFETs are not getting too warm.

Thank you. Now it is clear why inductor ramps are need for. – Vadim Ostanin Oct 21 '22 at 15:15 — Vadim Ostanin, Oct 21 '22 at 15:15

Induction heater short circuit

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