One-switch and two-switch transition-mode ZVS inverters for cooker magnetron drives

This paper presents the one-switch and two-switch transition-mode zero-voltage-switching (ZVS) inverters for cooker magnetron drives. Both inverters utilize step-up leakage transformers to boost voltage and limit current. The transformer is magnetized with rectified DC voltage while the main transistor of inverters is conducted. While the main transistor is cut off, the transformer resonates with parallel capacitors and magnetron load to complete the AC cycle of transformers. For ZVS, the main transistor is turned on again after a half cycle of RLC resonance. The conduction time of main transistor is used to regulate the current and power of magnetron. And, the required off time depends on the conditions of magnetron load. A longer conduction time normally generates a larger resonant voltage. Therefore, to reduce the voltage stress applied on the main transistor, a two-switch resonant circuit is designed for AC220V applications. To demonstrate the analysis and design, simulation is performed and a 1kW transition-mode ZVS inverter is built and tested practically.