Reasons why switching power supplies produce noise:

1. Internal reasons

(1) Noise generated during use of switching power supply. During the use of the switching power supply, factors such as current and resistance will instantly change, causing changes in the internal conditions of the switching power supply. This change is generally characterized by rapidity and is prone to producing noise and affecting the surrounding environment.

(2) Noise generated by the loss of internal components of the switching power supply. Since the switching power supply requires frequent operation, its internal components have certain losses. Therefore, when the internal components of the switching power supply are lost, noise will be directly generated.

2. External reasons

(1) Natural factors will affect noise. Electric current has strong physical properties and is easily affected by external natural factors during operation. For example, during thunderstorms, switching power supplies tend to produce a lot of noise during use.

(2) Noise caused by factors affecting the circuit. The switching power supply controls the entire circuit system. The circuit system will react to the switching power supply under certain conditions and affect the switching power supply. In actual operation, switching power supply noise is often caused by circuit system problems.

Solutions to switching power supply noise:

1. Adding a filter is a very common suppression method.

(1) Install a power filter at the input end to reduce interference

(2) Install the common mode noise filter at the output end of the power supply. A magnetic ring is installed on the output line to form a conjugate reactor, and a high-frequency capacitor is installed, which can effectively suppress common mode noise. Increasing the size of the output filter inductor and filter capacitor can suppress differential mode noise. The more parallel capacitors, the better.

2. Line filter

If the power supply is subject to external interference such as lightning strikes and man-made noise interference, malfunction will cause great interference to the system. If a filter is connected to the AC input end, the generation of this interference can be effectively reduced, as well as the occurrence of switches. Noise inside the power supply does not leak out from the input terminal.

3. Grounding measures

The purpose of grounding the power supply is for safety reasons, and after grounding the power supply, it can also effectively deal with electromagnetic compatibility issues. A good grounding system plays a vital role in reducing electromagnetic interference.

4. Other measures

In addition to the above measures that can effectively suppress the noise of the power supply, we can also reduce the noise impact of the switching power supply in terms of the location and direction of component installation, the overall layout of the system circuit, etc.

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