Half-bridge resonance inverter for induction heating using digital-controlled pulse density modulation technique

This paper presents a half-bridge resonant inverter for induction heating using digital-controlled pulse density modulation technique to control output power. To obtain the maximum efficiency in all operating points, the phase difference between voltage and current is measured and controlled by the digital controller. The constant phase and power control algorithms are developed and implemented in the STM32F407, the high performance ARM-core microcontroller. The switching signal generator is controlled by the phase difference controller to generate the switching signal that has a frequency higher than the resonant frequency. The prototype is designed to operate at 1.2 kW and the test is performed on a 15 mm. diameter and 100 mm. long steel work-piece. The proposed system can heat the steel work-piece up to 1000 degree Celsius (°C) approximately.