How to deal with failures by symptom of switching power supply


Is it a malfunction even if the switching power supply is output? I may think.

The sound is different from usual, what does it smell like, it’s hot, maybe it’s because of my mind?
Please refer to the causes and countermeasures for each of the common symptoms.


Abnormal noise


As the grease in the fan bearing deteriorates (hardens), it loses its function as a lubricant. Therefore, as the fan rotates, a larger force (torque) is required and the fan rotation noise becomes louder.

If the fan makes a strange noise, replace the fan.
The life of the fan at an ambient temperature of 40 ° C is about 4 to 5 years. It will last faster in a dusty environment.

* The fan manufacturer’s definition of life is when the rotation speed reaches 70% of the rated rotation speed. The time when the fan stops is not the life of the fan.



Since the core of the transformer vibrates, it makes a “boom” or “keen” sound, but it is usually not noticeable. There is no problem with the power supply itself.
However, if it is too large, it will be returned to the manufacturer.

Harmonic current suppression circuit

A power supply with a harmonic current suppression circuit may make a humming noise when the input is turned on. It is temporary until the internal voltage stabilizes and is not a malfunction.



Offensive odor (white smoke rises)

If the pressure inside the electrolytic capacitor rises for some reason, the “explosion-proof valve” of the electrolytic capacitor will open to release the pressure. At that time, a “shoe” sound is heard and white smoke rises and gives off a strange odor, so people who see it for the first time mistake it for smoke.

The power supply is out of order, so replace it with a new one.
Since it is a phenomenon that does not occur normally, ask the manufacturer to analyze it.

If an overvoltage is applied to the electrolytic capacitor, the internal pressure may increase. The explosion-proof valve opens to reduce the internal pressure before the electrolytic capacitor explodes. The explosion-proof valve has a slit (notch) in the head of the electrolytic capacitor, and the shape of the slit differs depending on the manufacturer. When the explosion-proof valve is opened, the gas inside is released, so smoke is emitted and there is a strange odor, so many people mistakenly think that it has “smoke”. The opening of the explosion-proof valve is proof that the safety device worked normally.





The power supply heats up because it transfers heat to the housing (chassis, cover) for heat dissipation.
If the temperature inside the power supply rises too high, overheat protection will work and the output will stop.

To lower the temperature of the power supply, change the power supply to one with a larger capacity (lower the load factor), change the location and orientation of the power supply, and open a slit in the housing to allow heat to escape.



Smoke / ignition


Since the parts used in switching power supplies are flame-retardant, they are unlikely to ignite due to smoke.
By the time it has protection, it is designed to stop safely.

However, usage outside the warranty, usage environment, and some adverse conditions may overlap.

In the unlikely event that smoke or fire occurs, immediately turn off the input and return it to the manufacturer as it is without touching anything.