High frequency switching power supply (also known as switching rectifier SMR) is a power supply operating at high frequency through MOSFET or IGBT. The switching frequency is generally controlled in the range of 50-100 KHZ to achieve high efficiency and miniaturization.

The switch K is repeatedly on and off at a certain time interval. When the switch K is on, the input power supply E is supplied to the load RL through the switch K and the filter circuit. During all the switch is on, the power supply E supplies energy to the load; When the switch K is off, the energy supply is interrupted by the input of power supply E. It can be seen that the input power supply to the load of energy is intermittent, in order to make the load can get continuous energy supply, the switch regulated power supply is necessary to have a set of energy storage equipment, when the switch on will be a part of the energy stored, in the switch off, release to the load. The output end is separately connected with a voltage regulator, current limiting and stable current, voltage limiting reaction circuit. When placed in the voltage stability condition, the voltage and current limiting circuit, when the output voltage increase or decrease sampling voltage regulating circuit with an inner voltage contrast comparison with reference voltage, the voltage error signal to the PWM control circuit, the PWM output pulse width accordingly change, then stable output voltage, such as high load current, current limiting circuit operation, Constrain the output current within the current limiting setting.