| Induction heating is a non-contact electromagnetic process that creates heat within metal parts that are placed in an intense alternating magnetic field. Induction heating has been a part of high power applications and widely used in industrial automation and electric home appliances. The studies of induction heating power in our country are focused on the control circuits of parallel resonant inverter and the series resonant inverter, but gave little attention to the analysis of realization of soft switching, inverter circuit modeling and the new circuit topology.This paper analyzes the asymmetrical voltage control (AVC), a generalized control technique for resonant inverters. It is applied to the popular full-bridge series resonant inverter. The proposed control technique achieves better efficiency performances than conventional fixed-frequency control strategies, on considering zero-voltage-switching (ZVS) operation, output power and load variations. Moreover, this paper presents the digital control module for optimum AVC control based on field programmable gate array (FPGA), which provides flexibility, short prototyping periods, parallel processing, simple user-friendly interfaces, and fast operation.Afterwards, a state-space model for arbitrary switching converters is presented, which uses the modeling of ideal lossless switches. Ideal switching action may produce impulsive voltages and currents (Dirac impulses). Therefore, that terminal variable is indeterminate at switching instant, and the next state for the switch is also indeterminate. So this model considers Dirac impulses at the switching instants. This model is valid as a circuit simulator.Finally, the model has been applied to a two-output series-resonant inverter, which allows the control of the two outputs simultaneously and independently. Meanwhile two-output series-resonant inverter can save component count compared with the two-converter solution and provide a higher utilization of electronics.
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