Research On LaB6High Frequency Induction Heating Power Supply With Series And Parallel Resonant Topology

The LaB6material is widely used in radar, aerospace, electronics, insrumention, medicalequipment, household electrical appliances, metallurgy, environmental protection and othermore than20military and high-tech fields. The current research of heating LaB6technologyis mainly concentrated in the heating technology in LaB6cathodes. The heating methods ofLaB6cathode is derect or indirect. Direct heating cathode is often influenced by cathodecurrent. The electron beam power is relatively small and the life of the cathode is shorter. Thecathode need be replaced frequently. The problems that electron beam power is small by usingdirect heating method can be solved by Induction heating method. The traditional LaB6induction heating power supply is in large volume. The power factor is lower. Harmonicpollution is serious. The switching loss is larger. Because of the long distance between thehost and sensors, it will bring the transmission loss greatly, decreased efficiency of the wholemachine. The power supply needs to be improved to solve the problems.The output power of the power supply is3.5kW. Inverter operates at90~150kHz. Thepower efficiency is85%. The LaB6induction heating power supply is designed according tothese technical indexes. The transmission current between the host and the inductor is muchsmaller than the load heating current by using the LLC series-parallel resonant load. It reducesthe transmission loss of system, improves the efficiency of the whole machine. Based on theanalysis of common power control mode of induction heating power supply, this paperproposed a new PDM&AVC control strategies for the power circuit topology that can changthe driving pulse density and phase angle signal to realize the power regulation, and makes adetailed analysis of each stages of inverse operation. Combining with the phase locked looptechnology, the inverter can realize all switches operate at zero voltage switching (ZVS) mode,and the minimum switching frequency is reduced greatly. It can reduce the switching lossesand improve power supply utilization efficiency.This paper gives a method for selecting corresponding circuit components. The controlsystem of power supply uses DSP as the control core. It designs the software of the systemand the partial modules. On the basis of theoretical analysis, the operation conditions of theseries-parallel resonant inverter and the whole system is sumulated by using Pspice. Anexperimental prototype of the system is designed. The repeatedly measured results verify thefeasibility and practicality of this research.