Switching power supply is a kind of power supply that utilizes modern power electronic technology to control the ratio of switching tube turn-on and turn-off time to maintain a stable output voltage, switching power supply is generally composed of pulse width modulation (PWM) control IC and MOSFET. With the development and innovation of power electronics technology, it makes the switching power supply technology is also in constant innovation. At present, switching power supply with small, lightweight and high efficiency is widely used in almost all electronic equipment, is today's electronic information industry rapid development of an indispensable power supply method. Widely used in industrial automation control, military equipment, scientific research equipment, LED lighting, industrial control equipment, communications equipment, power equipment, instruments, medical equipment, semiconductor refrigeration and heating, air purifiers, electronic refrigerators, LCD monitors, LED lamps and lanterns, communications equipment, audio-visual products, security monitoring, LED light bags, computer chassis, digital products and instrumentation and other fields.