Output capacitance effect on the voltage gain in the high step-up series resonant converter

For the series resonant converter (SRC), the voltage gain defined as voltage conversion ratio is one when the switching frequency is equal to resonant frequency. However, it can be greater than one at light load condition especially in the high step-up SRC, which is caused by the high voltage side devices output capacitance. Also the current through the resonant tank is no longer the sinusoidal waveform. The steady-state analysis of this phenomenon based on the state trajectories is presented in this paper. The relationship between voltage gain and device output capacitance is given. The experimental results of 300-W hardware prototype with 30-V normal input and 380-V output validated the derived voltage gain under the effect of devices output capacitance.