Switching power supply repair methods which how to maintain the socket switch

Switching power supply repair methods which how to maintain the socket switch

Switching power supply troubleshooting methods, here to tell you about.

1, repair switching power supply, first of all, use a multimeter to detect whether the power components are short-circuit breakdown, switching power supply shell, such as power rectifier bridge stack, switching tubes, high-frequency high-power rectifier; inhibit the inrush current of the high-power resistor is not burned out. Then test the output voltage port resistance is abnormal, the above components need to be replaced if damaged.

2, after the completion of the first step, after turning on the power supply can not work properly, and then to test the power factor module (PFC) and pulse width modulation components (PWM), consult the relevant information, familiar with the function of each foot of the PFC and PWM module and its modules work properly necessary conditions.

3, then, for the power supply with PFC circuit is required to measure the filter capacitor voltage on both sides of the 380VDC or so, if there is a voltage of 380VDC or so, indicating that the PFC module is working properly, and then detect the PWM components of the working state, measure the power input VC, reference voltage output VR, start control Vstart/Vcontrol voltage is normal, and then the PWM components of the working state, measure its power input VC, reference voltage output VR, start control Vstart/Vcontrol voltage is normal. 220VAC/220VAC isolation transformer to the switching power supply, with an oscilloscope to observe the PWM module CT terminal to the ground waveform is a good linearity of the sawtooth wave or triangle, such as the TL494 CT terminal for the sawtooth wave, the FA5310 CT end of the triangle wave. Whether the waveform of output V0 is an orderly narrow pulse signal.

4, in the switching power supply maintenance practice, there are many switching power supply using UC38 × × series 8-pin PWM components, switching power adapter most of the power supply can not work because the power supply start-up resistor is damaged, or chip performance degradation. When R breaks no VC, PWM components can not work, need to replace the same resistance with the original power resistance. When the PWM component start-up current increases, you can reduce the value of R to PWM components can work normally. In the repair of a GE DR power supply, PWM module for the UC3843, testing did not find other abnormalities in the R (220K) and connected to a 220K resistor, PWM components work, the output voltage are normal. Sometimes due to peripheral circuit failures, resulting in the VR terminal 5V voltage of 0V, PWM components do not work in the repair of the Kodak 8900 camera power supply, encountered this situation, connected to the VR side of the external circuit to disconnect the VR from 0V to 5V, PWM components work normally, the output voltage is normal. Power supply repair methods and techniques

5, when the filter capacitor on the voltage of 380VDC or so, indicating that the PFC circuit does not work properly, switching power supply circuit schematic PFC module key detection feet for the power input feet VC, start feet Vstart/control, CT and RT feet and V0 feet. Repair a Fuji 3000 camera, test a board on the filter capacitor without 380VDC voltage. VC, Vstart/control, CT and RT waveforms as well as V0 waveforms are normal, measurement of the field effect power switching tube G-pole without V0 waveforms, due to the FA5331 (PFC) for the SMD components, the machine used for a long time to appear V0 end of the board and the virtual weld between the V0 signal did not sent to the field effect tube G pole. The V0 end and the board on the solder joints welded, using a multimeter to measure the filter capacitor has 380VDC voltage. When the Vstart/control terminal is low, PFC can not work, it is necessary to detect its endpoints and the periphery connected to the relevant circuits.