Variable width pulses with fast rise times are provided by Ul, and MC34060 operating at 120kHz, the optimum frequency for heating aluminum alloy containers. The pulse width is modulated by sensing the temperature of the target with a thermistor, using its negative temperature coefficient to change pulse duration. The MC34060 produces output pulses that are ac-coupled to push-pull MJE200 transistors Q1 and Q2.
This IC provides the current needed to ensure fast switching for MTM15N45 TMOS power FET Q3. The estimated efficiency is 80%, based on switching losses and an RoN of 0.4 0 (max). The MTM15N45, with maximum ratings of 15 A and 450 V, was chosen because the induction heater might be operated from either 115 or 220 V sources. A modest heatsink is required because 100 W is dissipated in the power FETs at a full output power of 500 W.