What is the working principle of switching power supply?
The working process of switching power supply is quite easy to understand. In linear power supply, let the power transistor work in linear mode. Unlike linear power supply, PWM switching power supply is to let the power transistor work in the state of on and off. In these two states, the volts added to the power transistor-The product of an is very small (When on, the voltage is low and the current is large; When off, the voltage is high and the current is small)
/The volt-ampere product on the power device is the loss generated on the power semiconductor device.
Compared with linear power supply, PWM switching power supply is more effective in its working process through'Chopping'
, That is, the input DC voltage is cut into a pulse voltage with an amplitude equal to the amplitude of the input voltage.
The duty cycle of the pulse is adjusted by the controller of the switching power supply.
Once the input voltage is cut into an AC square wave, its amplitude can be raised or lowered by the transformer.
The output voltage value can be increased by increasing the number of secondary windings of the transformer.
Finally, these AC waveforms are rectified and filtered to obtain DC output voltage.
The main purpose of the controller is to keep the output voltage stable, and its working process is very similar to that of the linear controller.
That is to say, the function block, voltage reference and error amplifier of the controller can be designed to be the same as the linear regulator.
The difference between them is that the output of the error amplifier (Error voltage)
Before driving the Power Tube, it needs to go through a voltage/pulse width Conversion Unit.
Switching Power Supply has two main working modes: forward excitation conversion and boost conversion.
Although the arrangement difference of their parts is very small, the working process is very different and each has its own advantages in specific applications.