Research On Induction Heating Power Supply Of Time-sharing And Power-synthesis Based On IGBT

Nowadays, the domestic induction heating power supply whose frequency is higher than 100kHz almost adopts MOSFET. However, its inherent parasitic diode's reverse recovery characteristics is poor, must need fast recovery diodes in series. With the number of devices, reliability and efficiency will be reduced. Devices'series and parallel technology are often used for power supply's high capcity, but this method will bring the problem of unequal distribution of voltage and current, easy to damage the devices.Based on the induction heating power supply as the research object, this paper adopted the series resonant inverter which is more suitable for high frequency induction heating power supply, and chose the more flexible phase controlling on inverter side of its power regulating. For high-frequency and great-power requirements of welding and heat treatment fields, this paper put forward a new main circuit topology. IGBT parallel time-sharing control strategy was used, the strategy controlled the different cycle period of each IGBT switches to improve system's frequency, the working process and control stategy of the new topology was detailed analyzed; besides that, based on the problem of unequal distribution of voltage and current by devices'series and parallel, this paper chose the power synthetic method of transformer's primary parallel and second series. This method could realize high power through transformer secondary voltage's increase and the equal distribution of current in transformer primary side, eased the consistency of inverter in a certain extent, and improved the power effectively. What's more, the algorithm of PI digital power controlling based on DSP was also provided, which can ensure the system's stable operation.On the basis of theoretical analysis, this paper provided the simulation analysis on control strategy, including the simulation of time-sharing and phase-controlling strategy, the simulation of power synthesis, and the simulation of the whole system.The simulation result of power supply which is 350kW/400kHz is very good. Besides that, this paper set up the relative platform for experiment. In the control circuit, TMS320LF2407A DSP of TI corporation and EPM1270T144C5 CPLD of Altera corporation are adopted. The control module based on CPLD included phase angle locked circuit, pulse signal generator and dead time module, etc, generated trigger pulse by VHDL Programming in Quartus II; DSP microcontroller realized digital PI power control and sampling, protecting functions. Detailed design of hardware and software are given in this paper, as well as results of. the experiment.The overall control system not only simplified the structure, but improved the performance of the system.