ShenZhen Yinghuiyuan Electronics Co.,Ltd
Switching power supply is a common equipment in the family, if there is a failure, we can simply repair and continue to use. The following is the common faults and maintenance of the switching power supply!
1. No output, safety tube general
This phenomenon indicates that the switching power supply is not working or in the mode. The first measurement of the power control chip starting pin can have starting voltage, if no starting voltage or starting voltage is too low, to check the starting resistance and starting foot external components can leak, such as power control chip, then the above check can quickly find the fault. If there is a starting voltage, measure whether the output end of the control chip can have a jump of high or low level immediately when it is started. If there is no jump, it is said that the control chip is bad, the peripheral oscillating electrical element or the electrical problem, you can replace the control chip first, and then check the peripheral element; If there is a jump, generally bad or damaged switch tube.
2. Safely burn or fry
Secondary inspection on 300V large filter capacitor, rectifier bridge diode and switch tube and other parts, anti-interference electrical problems will also lead to safety burning, black. It is important to note that safety burning caused by the breakdown of the switching tube will generally burn the current detection resistor and power control chip. Negative temperature coefficient thermistors are also easily and safely burned out along the way.
3. There is an output voltage, but the output voltage is too high
This problem generally comes from the stable voltage sampling and the stable voltage control. In the DC output, sampling resistance, error sampling amplifier such as TL431, optical coupler, power control chip and other electrical coordination to form a closed control loop, any problem will lead to the output voltage rise.
4 output voltage is too low in addition to voltage control will cause the output voltage low, and the following reasons will cause the output voltage low:
a. If there is a short fault in the switching power supply load (especially if the DC/DC converter is short or malfunctioning, etc.), at this time, it should disconnect all the loads of the switching power supply to distinguish whether the switching power supply is faulty or the load power supply is faulty. If the load voltage output is disconnected, it is stated that the load is too heavy; Or still say that the switch power supply is faulty.
b. Failure of rectifier diode and filter capacitor at output voltage end can be judged by substitution method.
c. The function of the switch tube declines, which will inevitably lead to the switch tube can not be generally switched on, so that the internal resistance of the power supply is added, and the load capacity is decreased.
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October 09, 2024
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