Voltage-clamped soft switching PWM inverter-type DC-DC converter for microwave oven and its utility AC side harmonics evaluations

A single-ended quasi-resonant zero voltage soft-switching inverter type DC-DC converter is used to drive the magnetron for a microwave oven. This converter is simple, downsizing, high efficiency and low cost in addition to simple control scheme. However, this power conversion circuit has to control its input power under a condition of ZVS in accordance with the variable frequency regulation. The heater current variation of the magnetron becomes large when the power regulation of this inverter is implemented. The regulation range of input power is to be in order to achieve ZVS operation. For high power application, the peak voltage of IGBT in this inverter becomes large. This paper presents a new topology of the voltage-clamped ZVS-PWM high-frequency inverter-fed DC-DC converter for driving a microwave oven. This paper also describes how to improve line current distortion and power factor on the utility AC power side. Because the anode current of the magnetron must not exceed 1.2 A, because of the lifetime of the magnetron, the voltage-clamped ZVS-PWM high-frequency inverter-fed DC-DC converter is implemented and evaluated under suppression conditions of the anode peak current of the magnetron.