Digital Inverter Control Of Simultaneous Dual-Frequency Induction Heating Power Supply Based On Single Inverter

Based on electromagnetic induction principle, induction heating is heating metallic workpiece technology by eddy current induction heating effect. Since its first application in industry in the early 20 th century, induction heating has been widely used in various areas due to its advantages of low cost, high efficiency, environmental friendliness and high automation.With rapid development of power semiconductor device, circuit topology and microprocessor technology, induction heating has been developing towards the trend of large capacity, high efficiency and intelligence. At present, induction heating devices mostly use analog control and the system has disadvantages of low reliability and poor expansion. So simple and reliable full digital control becomes an important research direction for induction heating. Based on single inverter dual-frequency induction heating power supply, this paper studies the strategy and method of digital inverter control.This paper first introduces basic principles and application fields of induction heating and describes the current development and future trends of induction heating power supply. It later analyzes working principles and characteristics of single inverter dual-frequency induction heating and describes the contents and purposes of synchronous dual-frequency induction heating using digital inverter.To overcome the disadvantaged of traditional analog circuit control, this paper designs full digital inverter control based on FPGA, as well as inverter control circuits containing digital phase-locked loop and digital SPWM. It also analyzes the structure of digital phase-locked loop and principles of each module. After researches of digital waveform generator, comparator and dead zone time delay in sine pulse modulation, this paper designs dual-frequency tracking control strategy based on complicated resonant circuits.Based on theoretical analysis, this paper designs bottom layer modules of digital phase-locked loop and digital SPWM in Quartus II using Verilog HDL. Simulation results proves the validity of the design. Open-loop and close-loop circuits of synchronous dual-frequency induction heating is established on the MOSFET high frequency induction heating power supply platform. Experiment results proves the feasibility of digital inverter control.Eventually, this paper summarizes digital inverter control strategy of single inverter synchronous dual-frequency induction heating power supply from the aspects of theoretical researches, simulation analysis and experiment. It also discusses inverter frequency accuracy of digital inverter control modules and aspects to be improved in future studies.