Nowadays, the switching frequency of Switch-Mode Power Supply (SMPS) can be increased based on the development of the power semiconductor device. Increasing the switching frequency means decreasing the size of such the reactive component as transformer, inductor, and capacitor that SMPS consists of. Therefore, SMPS can be compact and light by the aid of the development of the power semiconductor device. However, the switching loss in the power semiconductor device increases at high frequency, so the efficiency of SMPS decreases. The soft switching technique is the solution to this problem. The soft switching technique consists of zero voltage switching technique and zero current switching technique. The former is turning on the switch when the voltage of switch becomes zero by the resonance, and the latter is turning off the switch when the current of switch becomes zero by the resonance. But, this switching technique deteriorates the performance of SMPS, because the resonance of voltage or current of switch increases the voltage stress or the current stress of the power semiconductor device. The soft switching technique that we are interested in, recently is switching at zero voltage condition or zero current condition using resonance phenomenon in the other components but switching device. Using the terminology, ‘transition’, we call these zero voltage transition (ZVT) and zero current transition (ZCT), respectively.
In this thesis, focusing the fact that the current of the switching device is larger at turning off the switch than at turning on the switch when the inductance of the DC/DC converter is finite value, I propose the ZCT circuit cell. The proposed ZCT circuit cell has higher performance than that of the existing ZCT circuit cell. The characteristics and analysis of the proposed ZCT circuit cell are described. And the operation of ZCT circuit cell is verified by the experiment for DC/DC boost converter and PFC (power factor correction) AC/DC boost converter integrated the proposed ZCT circuit cell.
