Switching power supply principle and maintenance

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Switching power supply principle and maintenance description:

Power supply is an indispensable component of various electronic devices. Its performance is directly related to the technical specifications of electronic devices and whether it can work safely and reliably. Since the key components inside the switching power supply work in the high-frequency switching state, the power consumption is small, the conversion rate is high, and the volume and weight are only 20%-30% of the linear power supply, so it has become the mainstream product of the regulated power supply. The maintenance of electrical faults in electronic equipment, in the principle of easy to difficult, basically starts with the power supply, after determining that the power supply is normal, and then repairing other parts, and the power failure accounts for most of the electrical failure of the electronic equipment. . Therefore, understand the basic working principle of the power supply at the beginning, familiar with its maintenance skills and common faults, which will help shorten the repair time of electronic equipment and improve the maintenance skills of personal equipment.

The switching power supply consists of four main parts: the main circuit, the control circuit, the detection circuit, and the auxiliary power supply. See Figure 1.

Main circuit

• Inrush current limiting: Limits the inrush current on the input side of the power supply. Input filter: Its function is to filter the clutter in the grid and to prevent the clutter generated by the machine from feeding back to the grid.
• Rectification and filtering: directly rectify the grid AC power to a smoother DC.
• Inverter: The rectified DC power is changed to high frequency AC, which is the core part of the high frequency switching power supply.
• Output rectification and filtering: Provides a stable and reliable DC power supply according to the load requirements.

2. Control circuit

On the one hand, sampling from the output, comparing with the set value, then controlling the inverter, changing its pulse width or pulse frequency to stabilize the output, on the other hand, according to the data provided by the test circuit, the protection circuit provides identification and provides The control circuit performs various protection measures on the power supply.

3. Detection circuit

Provides various parameters and various meter data in operation in the protection circuit.

4. Auxiliary power

Software (remote) booting of the power supply provides power for protection circuits and control circuits (chips such as PWM).

See the PDF document for details.