DIY Induction Heater Build

Induction heaters are one of those builds where you learn a lot of power electronics in a small package. Mine heats a bolt red-hot in about 8 seconds.

The core circuit is a zero-voltage switching (ZVS) oscillator — two MOSFETs alternately drive a resonant tank circuit formed by the work coil and a capacitor bank. The oscillation frequency is determined by L and C: f = 1 / (2π√(LC)). For a 5μH work coil and 2μF cap bank, that's about 50kHz, well above audio frequency.

Safety considerations: this circuit draws 10-20A from a 12-30V supply and the work coil gets extremely hot from eddy current losses in the mounted piece. The MOSFETs will fail if the heat sink is inadequate — use TO-247 package devices with a large finned heatsink and a fan. Do not use near implanted medical devices (pacemakers, etc.). The AC magnetic field is strong enough to erase magnetic stripe cards within 30cm.