New fixed-frequency ZVS-PWM load-resonant half-bridge type IGBT inverter with power factor correction and sinewave line current shaping schemes for high-frequency electromagnetic induction-heating applications

A new prototype constant-frequency variable power (CFVP) high-frequency load-resonant half-bridge inverter operating at soft-switched PWM scheme and using the latest developed IGBTs for soft-switching, is described. This type of quasi-resonant soft-switched inverter is more suitable for small scale induction-heating cooking appliances, with two or more burners. The operating principle of this inverter circuit and its power regulation characteristics are presented on the basis of computer-aided simulation analysis and experimental results. The proposed quasi-resonant inverter system configuration has the significant advantage of being capable of suppressing the irritating acoustic noise generated from the cooking burners composed of multiple load-resonant inverters. Moreover, this quasi-resonant half-bridge type inverter using a reverse blocking power switch (IGBT) and a reverse conducting one has many attractive features including lowered switching losses, reduced electrical dynamic stresses, considerable reduction of EMI noise level, snubberless arrangement, high-efficiency, lighter, weight, lower cost, high-power capability, easy regulation of output power at a fixed operating frequency and harmful acoustic beat interference noise. The experimental verifications of the soft-switched PWM quasi-resonant half-bridge inverter with CFVP function operating under unity power factor correction and sinewave line current shaping, were carried out and evaluated from a practical point of view.