Is the power adapter whistling normally?

Issue Time:2006-11-23
Anyone who has worked on power supply design knows that during the test of the power adapter power supply, some whistling sounds are often heard, similar to the leakage sound emitted when the high voltage is bad, or the sound like a high voltage arc. Why is there a howling? Generally speaking, there are usually the following incentives.

1. Transformer dip paint is not good
Includes not impregnated with varnish. Howling and causing the waveform to have spikes, but the general loading capacity is normal, especially the description: the greater the output power, the stronger the howling, and the performance of the small power is not necessarily obvious. When the design of the transformer is poor, it is also possible that the vibration will be abnormal during operation.

2.PWM IC grounding line error
Usually, the product shows that some of the products can work normally, but some products cannot be loaded and may not be able to start the vibration. Especially when applying some low-power ICs, it is more likely that it will not work properly.

3. Optocoupler working current point routing error.
When the position of the optocoupler's operating current resistor is connected before the secondary filter capacitor, there is also the possibility of howling, especially when the load is more. In addition, when there is no load or the load is light, whistling will occur. If you encounter a power adapter whistling, you can find the reason according to the above points, and then go to the corresponding solution.

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