New output voltage control techniques taking resonant capacitor voltage as variable for series resonant converters

Abstract

There have been a great deal of researches on the resonant power conversion due to the increasing demand for the high power density converters. Among them, a new class of resonant converter called a quantum series resonant converter (QSRC) has been recently introduced. This kind of converter can provide many advantages such as the zero current switching condition and linear characteristics like the conventional PWM converter. However, the quantized output voltage level and the relatively large ripple magnitude of the output voltage due to the integral cycle mode control are the major obstacles for the practical use. In this thesis, new output voltage control techniques taking the resonant capacitor voltage instead of the resonant current as a state are proposed to overcome the inherent disadvantages of a QSRC. Firstly, to do this work, the dynamic modeling of the full bridge series resonant converter (SRC) including the winding ratio of an isolation transformer is derived taking the rectified peak resonant capacitor voltage (RPRCV) as a state variable instead of the rectified peak resonant inductor current (RPRIC). Using this model, two kinds of the output voltage control techniques are suggested. One is an output voltage controller employing the deadbeat control action to overcome the disadvantages of the output voltage control employing the bang-bang control using only the output voltage information. With this technique, it is expected that the ripple magnitude is remarkably reduced and the start-up transient response becomes as fast as the bang-bang control technique using only the output voltage, because the fast state is directly controlled and the deadbeat action is employed. As a more improved output voltage control technique, a sliding mode control in the discrete time domain is suggested to control the resonant capacitor voltage in the inner feedback-loop. With this technique, the first-order reduced model representing the average motion between the RP...