Tunable Self-Oscillating Switching Technique for Current Source Induction Heating Systems

This paper presents a tunable self-oscillating switching (TSOS) technique for current source parallel resonant inverters. Using this technique, the inverter has lower voltage stress in comparison with conventional methods such as phase-locked loop (PLL) circuits or integral controllers. The new switching technique instantly tracks the variation of resonant frequency. In addition, the TSOS has the capability of phase error tuning which is essential for parallel operation and zone control induction heating systems. The TSOS method has simple structure and operates in wide range of frequencies. Hence, the inverter can be utilized as a general-purpose inverter to supply different coils, loads and self-switched capacitor banks. The dynamics of the new tuning system is compared with the PLL method in transient conditions. A laboratory prototype with operating frequency of 25-100 kHz is implemented to verify the performance of the new tuning system.