The introduction of micro-converter is effective in order to extract maximum energy from solar power. Boost and buck-boost type dc-dc converters generally consist of the micro converter. Downsizing the micro-converter is required because it is installed to each solar cell. The operation in the high frequency is required for downsize the power converter. Soft switching technology is effective in such situation. Active clamp circuit is used in order to reduce the peak value of the switch voltage caused by soft switching. In this paper, a consideration of active clamp circuit and resonant circuit affect the Single Ended Primary Inductor Converter (SEPIC) circuit is presented.