Research On Voltage Resonant Inverter Of High Frequency Induction Heating Power Supply

Compared with traditional heating, induction heating is a heating of new and advancedtechnologies. Basing on the working principle of coupled way, the heated materials willproduce induced eddy current, which can further produce heat energy for heating. Owing tothe induction heating technology has been used in more and more fields, the requirementstowards its heating process, intelligence, reliability and efficiency have become increasinglydemanding. Thus the research of high frequency induction heating is of great practicalsignificance.Some common adverse modulation circuits are analyzed in the first part. Their controldriving circuits are still relatively complex because they need to complete frequency trackingand power conditioning in the same inverter part. Therefore, they are not appropriate ininduction heating power supplies with a large range of power adjusting. After the advantagesand disadvantages of the two DC power have been analyzed, the method of usinguncontrolled rectification and chopper is determined. In the second part, in order to reducelosses caused by hard switching, soft switching chopper has been made and studied. Thentheoretical output result has been obtained after a series of simulation analysis. In the last part,comparative analysis of the characteristics of LC series load, LC parallel load and LLC seriesload have been made and it is determined to use the LLC series load which can reduce thecurrent flowing through the switch. Because energy storage components of the LLC seriesload have been increased, there is no need to use the equation used in the design parameters ofLC Series load. And an estimating the quality factor design method is proposed after a studyof load matching and maximum power transfer. In order to make the load can match themachine automatically, we need to track the resonance frequency of the LLC series circuit.Frequency tracking is done by the help of a phase-locked loop. The working principle andmathematical model of the phase-locked loop is introduced. After the analysis of theadvantages and disadvantages of frequency tracking by analog devices, it is studied much thatthe resonant frequency change of the LLC load is tracked by the digital phase-locked loopbased on TMS320F2812.It is verified by simulation that parameters obtained by the estimating the quality factordesign method meet the design requirements. It is verified that the soft switch reduces theswitching loss effectively by building simulation model of soft switch chopper circuit.Conclusion can be drawn that the output voltage, output current waveform and a good effectof frequency tracking can be obtained via the building of simple models based on frequencytracking.