AC 220v-DC 5v10A switching power supply working principle
The working process of the switching power supply is quite easy to understand. In the linear power supply, the power transistor works in the linear mode. Unlike the linear power supply, the PWM switching power supply makes the power transistor work in the on and off states. In these two In the state, the volt-ampere product added to the power transistor is very small (when it is turned on, the voltage is low and the current is large; when it is turned off, the voltage is high and the current is small) / the volt-ampere product on the power device is the power semiconductor losses incurred on the device.
Compared with the linear power supply, the more effective working process of the PWM switching power supply is achieved by "chopping", that is, chopping the input DC voltage into a pulse voltage whose amplitude is equal to the input voltage amplitude.
The duty cycle of the pulse is adjusted by the controller of the switching power supply. Once the input voltage has been chopped into an AC square wave, its amplitude can be stepped up or down through a transformer. By increasing the number of secondary windings of the transformer, the output voltage value can be increased. Finally, these AC waveforms are rectified and filtered to obtain a DC output voltage.
The main purpose of the controller is to keep the output voltage stable, and its operation is very similar to the linear form of the controller. That is to say, the functional block, voltage reference and error amplifier of the controller can be designed to be the same as that of the linear regulator. Their difference is that the output of the error amplifier (error voltage) passes through a voltage/pulse width conversion unit before driving the power transistor.
There are two main working modes of switching power supply: forward conversion and boost conversion. Although the arrangement of their various parts is very small, the working process is very different, and each has its own advantages in specific applications.
