What is the working principle of switching power supply? Schematic analysis of switching power supply

What is the working principle of switching power supply?

Switching power supply is to use the circuit to control the switch tube to pass and cut off at high speed.

Convert the direct current into high frequency alternating current to supply the transformer for transformation, so as to generate one or more groups of voltage required! The reason for switching to Huawei's high frequency AC is that the efficiency of high frequency AC in transformer transformer circuit is much higher than 50Hz. So the switching transformer can do very little, and the work is not very hot!! The cost is very low. If you don't change 50Hz to high frequency, then the switching power supply doesn't matter

The work flow of switching power supply is as follows:

Power supply → input filter → full bridge rectifier → DC filter → switch tube (oscillation inverter) → switch transformer → output rectifier and filter.

1. AC power input is rectified and filtered into DC

2. Control the switch tube with high frequency PWM (pulse width modulation) signal, and add that DC to the primary switch transformer

3. The secondary of the switch transformer senses high frequency voltage and supplies the load through rectification and filtering

4. The output part feeds back to the control circuit through a certain circuit to control the PWM duty cycle, so as to achieve the purpose of stable output

When the AC power is input, it usually passes through something like the current loop to filter out the interference on the power grid, and at the same time, it also filters out the interference of the power supply on the power grid;

When the power is the same, the higher the switching frequency is, the smaller the volume of the switching transformer is, but the higher the requirement of the switching tube is;

The secondary of the switching transformer can have multiple windings or one winding has multiple taps to obtain the required output;

Generally, some protection circuits should be added, such as no-load, short circuit protection, or the switching power supply may be burnt

Mainly used in industry and some household appliances, such as TV, computer, etc