Working principle and basic composition of high-power switching power supply
Working principle of high-power switching power supply
1. AC power input is rectified and filtered into DC;
2. Control the switch tube by high frequency PWM (pulse width modulation) signal, and add that DC to the primary of the switching transformer;
3. The high-frequency voltage is induced by the secondary of the switching transformer and supplied to the load through rectification and filtering;
4. The output part is fed back to the control circuit through a certain circuit to control the PWM duty ratio, so as to achieve the purpose of stable output.
5. Generally, when AC power is input, it must pass through the loop and other things to filter out the interference on the power-off network, and at the same time, it also filters out the interference of power supply on the power grid;
6. At the same power, the higher the switching frequency, the smaller the volume of the switching transformer, but the higher the requirements for the switching tube;
7. The secondary of the switching transformer can have multiple windings or one winding can have multiple taps to get the required output;
8. Generally, some protection circuits should be added, such as no-load and short-circuit protection, otherwise the switching power supply may be burned.
Basic composition of high-power switching power supply
High-power power supply is composed of main power circuit, PWM control circuit, single-chip microcomputer control circuit and auxiliary power supply.
Main power circuit
Impulse current limiting: limit the impulse current at the input side at the moment when the power supply is turned on. Input filter: its function is to filter the clutter existing in the power grid and prevent the clutter generated by this machine from being fed back to the power grid.
Rectification and filtering: the AC power supply of the power grid is directly rectified into smoother DC power.
Inverter: Convert the rectified DC into high-frequency AC, which is the core part of high-frequency switching power supply.
Output rectification and filtering: provide stable and reliable DC power supply according to load requirements.
PWM control circuit
On the one hand, sampling from the output end, comparing with the set value, and then controlling the inverter, changing its pulse width or pulse frequency, so as to make the output stable; on the other hand, according to the data provided by the test circuit, the control circuit is provided to carry out various protection measures for the power supply after being identified by the protection circuit.
Single chip microcomputer control circuit
Single chip microcomputer uses ADC to sample the output voltage and current, and controls the change of output voltage and current through DAC output, and monitors the running state of the whole power supply, and is responsible for continuous communication with the computer.
auxiliary power supply
Realize the software (remote) startup of power supply, and supply power for the protection circuit, control circuit (PWM and other chips) and single chip microcomputer.
