The Control System Of Induction Heating Power Supply Based On FPGA

With the development of power semiconductor devices, advanced circuit topology and control technology, induction heating power supply develops towards high power capacity, high frequency and intelligent control as well as other directions, whose control system also changes gradually from analog to all digital circuit form. FPGA is becoming dominant product in control field depending on its superior design, rapid data processing and many other advantages. In the paper, the series resonant induction heating power supply is used as the research object, in which a novel PWM Buck soft chopper circuit is designed, and then frequency-tracking control circuit and PI control algorithm of power regulation are realized based on FPGA.A direct way to realize portable and lightweight induction heating equipments is to improve switching frequency, but simply improving frequency will increase losses and reduce heating efficiency. So a novel ZVZCS PWM Buck chopper is designed. Conventional PLL is vulnerable to grid voltage, temperature drift and other factors, making it difficult to realize simultaneous regulation of the system. In view of the problem, a digital PLL based on FPGA is proposed. In order to make sure that PLL embedded in FPGA can be used in induction heating field, an even and odd frequency divider is realized using Verilog HDL. In addition, power control is needed to ensure that both the output power and the temperature under a given power are constant, meeting the heating requirements. Through analyzing power control principle of the series resonant inverter, the issue is transformed into the output DC voltage control of Buck chopper. Then a PI control algorithm for induction heating is completed using Verilog HDL, ensuring the output power keeps pace with the given power.Simulation results verify the validity and rationality of the design. The proposed PWM soft chopper circuit realizes soft-switching of both the main and auxiliary devices, reducing turn-on and turn-off losses greatly. The phase-locked frequency of ADPLL based on FPGA is suitable for induction heating applications because of the external frequency divider programmed by Verilog HDL. The PI power control algorithm ensures the constant output power.