A Royer oscillator with 2 IRF540 N-Channel mosfets, a 0.47uF Capacitor and a 1500uH inductor used for a simple DIY induction heater. The mosfets remain cool, even with such small heatsinks. An isolation transformer was used for the first test with a work coil of 20turns, then the transformer was removed and a work coil of 7+7 turns connected directly to the oscillator.
Construction is easy: small heatsinks for the mosfets and 12V regulator, capacitor close to mosfets and coil, tick wire in the work coil. For any other questions, use the comments form below.