Dpll-based Induction Heating Power Supply Developed

At the beginning of 20th century, the induction heating power supply has started to emerge. Its heating temperature is high and the induction heating power supply is Non-contact heating. It has very high efficiency. Meanwhile, this power supply is easy to control the heating temperature and it has good operating environment. Regardless of any shape, this power supply can heating the work piece. So the induction heating power supply is becoming the hot issues. In our country the most common circuit of induction heating power supply is parallel resonance circuit, so this circuit's power adjustment should be adjusted through the direct current side. This way will be polluted to the electrical network. In this paper, the power supply uses the series resonance circuit. The direct current side uses uncontrolled rectification, and the inverter side uses the PWM phase shift adjusting method, and in this way the problem mentioned above can be avoided.The structure of this article is arranged as follows: First, there is an introduction about the basic tenets and the development process of heating power supply. Second, analysis the merits and shortcomings of the two different circuits, and compares their convert process. Then some popular power modulation way is referred. At last, this paper applies series resonance type circuit structure, and adjusts the power supply in the method of the PWM phase shift adjusting.After the circuit plan is determined, this paper introduces the definition and classification and new development of soft-switching, then compare it with hard switch. Usually soft-switching is realized in the way of ZVS, but when the load is light, zero voltage is hard to satisfy. In the condition of non-zero condition, voltage stress is two big, and seriously disturbed, which influence the quality of power supply. So this paper applies PWM technique which bases on ZVZCS to realize the development of the power supply, and advance leg uses zero voltage switch, lag leg uses zero current switch, then the parameter of every part is determined.The main part of this article is the design of phase-locked loop. In the tradition heating power supply, simulation phase-locked loop CD4046 is widespread applied as control loop. But simulation phase-locked loop exist lots of shortcoming, so this article proposes a digital phase-locked loop design based on FPGA. Phase-locked loop exists in FPGA internal integration which is mainly used in high frequency. In view of the fact, this paper applies built phase-locked loop 74297, uses VHDL language design corresponding auxiliary circuit, which guarantees the request of phase-locked in the wide range frequency. Also PWM circuit is designed in the chip, which generates four group IGBT actuation pulse and also retains certain dead time.In addition, according to the monolithic integrated circuit, the man-machine contact surface interactive has realized. According to the function of hardware PI regulator, the power of power supply and the adjusting of current are satisfied.According to MATLAB simulation, the accuracy of this design is proved, and corresponding simulation profile is provided. Then real circuit is built, the power of this circuit is 40KW, when the circuit is debugged, actual phase-lock scope is between 10 kHz and 200 kHz. From the effect of debugging, the goal is mainly achieved.