Summary of switching power supply maintenance experience
1, the switching power supply does not start vibration, generally check whether the switching frequency is correct, whether the protection circuit is blocked, the voltage feedback circuit and the current feedback circuit are no problem, whether the switch tube is broken down, etc.
2. When the transformer is hot or makes a "Zi Zi" sound, the switching frequency is generally wrong;
3, the output voltage power supply indicator light flashing is generally short-circuited on the secondary side.
Generally, switch tubes, charging resistors and rectifier diodes are easy to break down ... So generally, measure them with a digital multimeter first, and if there is no break, they will be tested on power. It would be easier to check if you could see the burnt place on the surface.
Internal interference and external interference of switching power supply
The interference of switching power supply is generally divided into two categories: one is the interference formed by internal components of switching power supply; The second is the interference caused by external factors. Both involve human factors and natural factors.
Internal interference of switching power supply:
EMI generated by switching power supply is mainly caused by high-order harmonic current interference generated by basic rectifier and peak voltage interference generated by power conversion circuit.
Basic rectifier: The rectification process of basic rectifier is a common cause of EMI*. This is because the power frequency AC sine wave is no longer a current with a single frequency after rectification, but becomes a direct current component and a series of harmonic components with different frequencies. Harmonics (especially higher harmonics) will cause conduction interference and radiation interference along the transmission line, which will distort the front-end current, on the one hand, distort the current waveform connected to its front-end power line, and on the other hand, generate radio frequency interference through the power line.
