Switching power supply is the use of modern power electronics technology to control the switch on and off the time ratio, to maintain a stable output voltage of a power supply, switching power supply is generally composed of pulse width modulation (PWM) control IC and MOSFET. Switching power and linear power compared to the cost of both the output power increases with the growth, but the growth rate of the two different. Linear power costs at an output power point, but higher than the switching power supply, which is called the cost of reversal point. With the development and innovation of power electronics technology, the switching power supply technology is also constantly innovating, and this cost reversal point is moving toward the low output power end, which provides a broad space for the switching power supply.
High-frequency switching power supply is the direction of its development, high-frequency switching power supply to miniaturization, and the switching power supply into a wider range of applications, especially in the field of high-tech applications to promote the high-tech products, The In addition, the development and application of switching power supply in the conservation of energy, conservation of resources and the protection of the environment are of great significance. The power electronics used in switching power supplies are mainly diodes, IGBTs and MOSFETs. SCR in the switching power supply input rectifier circuit and a soft start circuit in a small amount of application, GTR drive difficult, low switching frequency, and gradually replaced by IGBT and MOSFET.