With the rapid development of power electronics technology and the switch industry, the relationship between power electronic equipment and people's work and life is becoming increasingly close. Electronic equipment cannot do without reliable power sources. In the 1980s, computer power supplies fully realized the switch power supply, taking the lead in completing the power supply replacement of computers. In the 1990s, switch power supplies successively entered various electronic and electrical equipment fields. Switch power supplies have been widely used in programmable switches, communication, electronic detection equipment power supplies, control equipment power supplies, etc., which further promoted the rapid development of switch power supply technology. Switching power supply is a type of power supply that utilizes modern power electronics technology to control the time ratio of switching transistors on and off, and maintain a stable output voltage. Switching power supply is generally composed of pulse width modulation (PWM) control IC and MOSFET. Compared to linear power supplies, the cost of both increases with the increase of output power, but their growth rates vary. The cost of a linear power supply is actually higher than that of a switching power supply at a certain output power point, which is a cost reversal point. With the development and innovation of power electronics technology, switch mode power supply technology is constantly innovating, and this cost reversal point is increasingly moving towards the low output power end, providing a wide range of development space for switch mode power supplies.