Grid positive switching power knowledge sharing

Grid positive switching power knowledge sharing

The main circuit of the switching power supply is composed of an input electromagnetic interference filter (EMI), a rectification and filtering circuit, a power conversion circuit, a PWM controller circuit, and an output rectification and filtering circuit. The auxiliary circuit has an input over-voltage protection circuit, an output over-voltage protection circuit, an output over-current protection circuit, and an output short-circuit protection circuit.

AC input rectification and filtering circuit principle

1, the lightning protection circuit: when there is a lightning strike, when introduced into the power grid via a high pressure generated by MOV1, MOV2, MOV3: protection F1, F2, F3, FDG1 circuit thereof. When the voltage applied across the varistor exceeds its operating voltage, its resistance decreases, so that the high-voltage energy is consumed on the varistor. If the current is too large, F1, F2, and F3 will burn and protect the latter circuit.
2, input filter circuit: C1, L1, C2, C3 double π-type filter network is mainly to suppress the electromagnetic noise and clutter signals of the input power, to prevent interference to the power supply, but also prevent

The high frequency clutter generated by the power supply itself interferes with the power grid. When the power is turned on, the C5 should be charged. Because the instantaneous current is large, adding RT1 (thermistor) can effectively prevent the inrush current. Since the instantaneous energy is completely consumed on the RT1 resistor, the RT1 resistance decreases after the temperature rises after a certain time (RT1 is the negative temperature coefficient component), at which time the energy consumed is very small, and the latter circuit can work normally.
3. Rectification and filter circuit: After the AC voltage is rectified by BRG1, the C5 filter is used to obtain a relatively pure DC voltage. If C5 smaller capacity, large AC ripple output will increase.