Switching power supply is the use of modern power electronics technology, control the opening and closing of the switch tube time ratio, maintain a stable output voltage of a power supply, switching power supply generally by pulse width modulation (PWM) control IC and MOSFET composition. Compared with the linear power supply, the cost of both switches increases with the increase of output power, but the rate of growth is different. The linear power supply cost is higher than the switching power supply at an output power point, which is called the cost reversal point. With the development and innovation of power electronics technology, switching power supply technology is constantly innovating, this cost reversal point is increasingly moving to the low output power end, which provides a wide space for the switching power supply.
The high frequency of switching power supply is the direction of its development, which makes the switching power supply miniaturization and
Switching power supply into a wider range of applications, especially in the field of High-tech applications, promoting the miniaturization of High-tech products, portability. In addition, the development and application of switching power supply has important significance in saving energy, conserving resources and protecting environment. The power electronic devices used in switching power supply are mainly diode, IGBT and MOSFET. SCR in the switching power supply rectifier circuit and soft start circuit has a small number of applications, gtr drive difficult, low switching frequency, gradually replaced by IGBT and MOSFET.