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Switching power supply common breakdown maintenance skills
Add time:2019-08-30    Click:38
    Electric power failure in troubleshooting accounted for most of electronic device failure. So familiar with switching power supply common faults and maintenance skills, is beneficial to shorten the maintenance time of electronic equipment, improve equipment maintenance skills.

    One, common faults
    (1) blown fuse:
 
    Under normal circumstances, the blown fuse that power supply is a problem with the internal wiring. Due to the power supply work in high voltage, large current state, the power grid voltage fluctuations, surge current in the power supply will cause instant increase and make the blown fuse. Focus should check the power supply at the input rectifier diode, high pressure filter electrolytic capacitor, the inverter power switch tube and so on, check that the component breakdown, open circuit, damage, etc. If it was blown fuse, should first check the circuit boards of each element, see the appearance of all these components have to be burned, is there any electrolyte overflow, if did not find the above situation, the switch tube with or without breakdown short circuit is measured with a multimeter. Need to pay special attention to is: not in found to a certain element of damage, replace directly after boot, this is likely due to the high pressure components are defective and will replace the element damage, must all high voltage to the circuit components to conduct a comprehensive inspection measure, can completely eliminate the malfunction of blown fuse.

    (2) no dc voltage output or the output voltage is not stable

    If the fuse is intact, with the load cases, dc voltage no output at all levels. This situation is mainly due to the following reasons: short circuit fault, open circuit fault phenomenon occurring in a power supply, the overvoltage and overcurrent protection circuit malfunction, auxiliary power supply failure, oscillation circuit without work, the power load is overweight, high frequency rectification filter circuit in the rectifier diode is punctured, the filter capacitor leakage, etc. In secondary element is measured with a multimeter, ruled out high-frequency rectifier diode breakdown, load short circuit, if the output is zero at this moment, you can definitely is a fault in the power control circuit. If any part of the voltage output shows that the front-end circuit works well, failure in high-frequency rectifier filter circuit. High frequency filter circuit is mainly composed of rectifier diode and low pressure filter capacitor dc voltage output, including rectifier diode breakdown can make the circuit no voltage output, output filter capacitor leakage will cause the voltage instability of fault. Measured with a multimeter static corresponding components can check out the damaged components.

    (3) the power load ability is poor
 
    The power load capacity is a common fault, are generally appeared in the old or work long time power supply, the main reason is that the components ageing, switch tube is not stable, not in a timely manner heat dissipation, etc. Should check whether the zener diode is mainly fever leakage, rectifier diode damage, damage to the high pressure filter capacitance, etc.

    Second, the maintenance skills
 
    Switching power supply maintenance can be divided into two steps:
 
    (1) power case, "look, smell, ask,"
 
    (see: open the power supply of the enclosure, check whether the fuse fusing, then observe the power of the internal situation, if it is found that the power of burning or PCB components is broken, and should be focusing on the components and the related circuit components.
 
    (2) smell: the smell of the power supply inside to see if there is the smell of burnt food, check whether there is a burning in the components.
 
    (3) q: ask the power damage after, whether to violate compasses operation power supply.
 
    (4) : no electricity, the multimeter measure high voltage capacitor voltage at the ends of the first. If the vibration is can't afford to switch power supply or switch tube caused by open circuit fault, is in most cases, the high pressure at the ends of the filter capacitor voltage sites not discharge, the voltage is 300 v, need to be careful. With a multimeter to measure AC power cord on both ends of the positive and negative to the resistor and capacitor charging, resistance should not be too low, otherwise the power inside there may be a short circuit. Capacitors should be able to charge and discharge. Release load, measured each group the output to ground resistance, normal, whose hands should have capacitor charge and discharge, final instructions for the discharge of the chain of the resistance value.

    (2) add electrical detection
 
    After electrify observation power if there is a fire insurance and individual components the phenomenon such as smoking, if you have to cut off the power supply in time for maintenance.
 
    Presence of 300 FuShu on both ends of the measuring high pressure filter capacitance, without should focus on the rectifier diode, filter capacitance, etc.
 
    With or without measuring the high frequency transformer secondary coil output without should check whether the switch tube is damaged, mainly whether to start up, whether the protection circuit action, etc., if any should be focusing on the output side of the rectifier diode voltage regulator tube, filter capacitor, tee, etc.
 
    If the power start just stop, then the power protection conditions, can directly measure the voltage of PWM chip protection input feet, if the voltage beyond the specified value, shows the power protection conditions, should check mainly causes of protection.
 
Kim
                                                                                                                                                  2019-8-30
      Disclaimer: This article comes from individual, KRECO has the right of final interpretation.  
 
 

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