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High frequency switching power supply principle
Sep 19, 2018


    1. The AC power input is rectified and filtered into DC;

    2. The switching tube is controlled by a high frequency PWM (pulse width modulation) signal, and that DC is applied to the primary of the switching transformer;

    3. The secondary of the switching transformer induces a high-frequency voltage, which is supplied to the load through rectification and filtering;

    4. The output part feeds back to the control circuit through a certain circuit, and controls the PWM duty cycle to achieve the purpose of stable output. When the AC power input is input, it generally passes through something like the Ericshosphere to filter out the interference on the power grid. Filter out the interference of the power supply to the grid; when the power is the same, the higher the switching frequency, the smaller the volume of the switching transformer, but the higher the requirements for the switching tube;

    The secondary of the switching transformer can have multiple windings or one winding with multiple taps to get the required output; generally, some protection circuits should be added, such as no-load, short-circuit, etc., otherwise the switching power supply may be burned. Mainly used for Industrial and some household appliances, such as televisions.

    Four basic types of single-chip switching power supply feedback circuits such as computers

   1. Basic feedback circuit;

   2. Improved basic feedback circuit;

   3. The optocoupler feedback circuit with the voltage regulator tube;

   4. Optocoupler feedback circuit with TL431.


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