Resonant frequency tracking control by using one CT for high frequency inverter

This paper presents a novel resonant frequency tracking control method for the full bridge type high frequency inverter. The proposed method uses only one AC current transformer though a general PLL as a frequency control method uses 2 current or potential transformers. Furthermore, the high frequency inverter system does not need to employ an active converter to control the DC bus voltage for the output power regulation although the inverter system using PLL has to have an active converter. Accordingly, the inverter that installs the proposed control method can control the operation frequency adequate and regulate the output power by one converter system. Hence, the high frequency inverter that is used for changing reactance load like an induction heating load can be simplified by introducing the proposed frequency control method. The operation principle is illustrated with a sample of block diagram. Simulation is implemented to estimate the control method and its results show a good performance for tuning the operation frequency to the resonant frequency. In addition, the control method is installed in an actual inverter for high power induction heating application. Observed and measured results verify the performance of the proposed frequency control method.