The power supply module is a power supply that can be directly mounted on the printed circuit board, and it is characterized by providing power for application specific integrated circuits (ASIC), digital signal processors (DSP), microprocessors, memories, field programmable gate arrays (FPGA) and other digital or analog loads. Generally speaking, such modules are called load (POL) power supply system or point-of-use power supply system (PUPS). Because of the advantages of modular structure, modular power supply is widely used in communication fields such as switching equipment, access equipment, mobile communication, microwave communication, optical transmission, routers, automotive electronics, aerospace and so on.