Small signal model and control of a series resonant inverter with an auxiliary switched capacitor cell using describing function

The modeling and control of a soft-switched inverter with a switched capacitor cell is a challenging task, since the capacitor operates for a short time. This paper presents a unique technique to model the voltage fed high frequency series load resonant inverter with an auxiliary switched capacitor cell. The main objective of this paper is to demonstrate the dynamic characteristics of the switched capacitor type inverter and to control the capacitor-clamped ZVS high frequency inverter circuit using the PWM control scheme. There are various types of modeling methods applied to converters, such as average modeling, phasor transformation modeling, all of them however cannot be applied in resonant type inverters due to the variables of resonant inverter vary incessantly. Thus, an extended describing function method is utilized to model the resonant inverter circuit. The model of the series inverter circuit has been performed based on an asymmetrical PWM control scheme. The control performances of the high frequency inverter with the soft-switching operation ranges are verified through a cogency process.