Research On Symmetrical Pulse Density Induction Heating Power Based On FPGA

Firstly, this paper introduced the principle of induction heating, the main power adjustment methods at present, and proposed a symmetrical pulse distribution method for the shortage of traditional Pulse Density Modulation, which makes the control pulses more symmetrical distribution. The control pulses were generated by using the state machine approach and verified by further simulation and experiments. In addition, this paper analyzed the effect of quality factor Q to load current in detail and gave a formula, which can calculate the minimum pulse density under a certain Q value. In order to ensure the output power stability, PI control circuit based on current closed loop was designed. A phase-locked-loop simulation model in matlab/simulink was established, and frequency tracking circuit based on high-speed phase-locked-loop 74HC4046 was designed, which makes the load power factor close to 1, and reduces the switching losses. Furthermore, frequency, power display circuit and over-voltage, over-current protection circuit were designed. The final adoption of prototype experiments proves that the design and research methods are valid and achieves good experimental effect.