source:power supply Popular:adapter release time:2021-09-08 09:39:49 Article author:sznbone
What are the vulnerable components and faults of the switching power supply?
Nowadays, many faults in electronic circuits are caused by the failure of switching power supply, and most of the common faults of switching power supply are caused by damage to some parts.
For example, the switch tube in the switching power supply is habitually damaged, but the probability of damage to the switching transformer is very small! Basically it can be ignored.
Therefore, switching power supply manufacturers shared a summary of some easily damaged components in the switching power supply, and what failure conditions occurred after damage, and shared it with everyone.
1, fuse tube
The burning of commercial insurance is mostly caused by the large current of the back-end power circuit. In other words, the back power circuit has short-circuit fault conditions, such as switch tubes, current-limiting resistors, bridge stack burn-out and short-circuit faults, integrated IC damage, and large filter capacitor damage. All caused the commercial insurance to be burned out, and the failure status was not reflected when connected to the power supply. (Warm reminder: if you change the fuse, you don’t need to connect the power test lightly, you must find the fault or take certain countermeasures before connecting the power)
2, the filter capacitor is damaged (300V large capacitor)
The power of the filter capacitor or the decrease in volume will cause it to freeze or start without response. The damage of the filter capacitor can generally be seen from the appearance of the capacitor. (Naturally can't afford it)
3. Output filter capacitor: The fault condition is similar to that of the filter capacitor.
4, switch tube
As mentioned in the first point, commercial insurance is generally burned after the switch is damaged, and the current-limiting resistor is also damaged. In some cases, even the PWM integrated IC is burned (but this is rare).
Now that the fuse tubes are all burned, there is no doubt that the fault condition is not reflected when the power is connected.
5. Zener diode.
When the voltage in the reverse direction of the diode exceeds its tolerance voltage regulator tube value, the Zener tube will thermally break down in the opposite direction, but this type of thermal breakdown can be repaired, that is, after the voltage value is reduced, the Zener tube Will get rid of the thermal breakdown situation, which is equivalent to leading the way. If it is a short-circuit fault, the Zener tube has already been damaged, and the amount of current exceeds the current capacity of the Zener tube. It is a breakdown and cannot be repaired.
6, light lotus root and TL431
The damage of these two components will generally cause the output voltage to be unstable or no voltage output. How to check it has been introduced in detail in my previous article (damage of the sampling resistor will also cause similar problems).
7. Starting resistor:
The starting resistor is connected between the 300V switching power supply and the base of the switching tube. Damage to the starting resistor will cause 300V, but no voltage output, and the entire device has no response.
8. Current-limiting resistance:
To put it plainly, the resistor is damaged and the overcurrent protection circuit is working, and there is no output voltage of 300V like the starting resistor.
9, PWM control integrated ic:
PWM damage will result in 300V, but no output voltage will repeatedly burn the switch tube and commercial insurance. During the test, the resistance value to ground can be used to distinguish its advantages and disadvantages. All normal resistance values to ground except for the pair of feet, other The feet often have hundreds of euros.
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