Power supply system and method for converting power thereof

A power supply system includes an input stage converting circuit, a first energy storage component, and an output stage converting circuit. The first energy storage component is electrically coupled to the input stage converting circuit, and the output stage converting circuit is electrically coupled to the first energy storage component. The input stage converting circuit is configured to charge the first energy storage component, and the first energy storage component stores charging electricity. The output stage converting circuit is configured to convert the charging electricity into output electricity and provide the output electricity to a load. The input stage converting circuit has a first electric power, and the output stage converting circuit has a second electric power greater than the first electric power. A method for converting power of the power converter is also disclosed herein.