Special power supply manufacturers tell you how to suppress electromagnetic interference

Special power supplyThe manufacturer tells you that when electricity flows in the body, energy will escape into the air, which is the so-called electromagnetic wave. These complex electromagnetic waves, if their energy is large enough, will cause electromagnetic interference (EMI) and then affect product functions, environmental pollution and human health. Medical literature points out that regardless of the source of electromagnetic waves from electrical equipment, high-voltage wires or household appliances, as long as the background value of electromagnetic waves in the environment is greater than 2 milligauss, the incidence of blood cancer will increase. The American Journal of Science once reported that there is evidence that electromagnetic waves above 60MHZ can cause damage to the structure of human cells, especially the effects of mobile phones on the human brain, including memory loss and reduced behavioral ability.

Special power supply manufacturers tell you that in order to reduce the harm of electromagnetic waves, electromagnetic wave absorbing materials are increasingly used in various electronic products. Such as mobile phones, computers, microwave ovens, signal base stations, etc. What is electromagnetic absorption material? The radio wave absorbing material cuts the incident radio wave to weaken its energy, thus reducing the ability of radio wave to radiate to the outside. It can be attached to the surface of any electronic component without changing the characteristics of the circuit. It can directly block or reduce the radiation of the EMI signal source. It can cut the base shape according to the needs of the organization.

1. Coupling of external interference

The input terminal is the entrance of the power supply, and internal noise can also be transmitted from here to the outside, causing interference to the outside world. Commonly used suppression measures are to add X and Y capacitors, differential mode and common mode inductance to the input to filter noise and interference.

If the output terminal has a long lead, after the power module is matched with the system, some internal noise interference may be coupled to the outside through the output line, and interfere with other electrical equipment. Generally, common mode and differential mode filtering are added, and a magnetic bead ring can be set in the output line, twisted pair or shielded line can be used to suppress EMI interference.

2. Diode

The diodes will have spikes during the fast cut-off and conduction process, especially the rectifier diodes. During the reverse recovery process, the parasitic inductance and capacitance of the circuit will oscillate at a high frequency and cause electromagnetic interference.

Commonly used interference suppression methods include adding an RC absorption circuit to allow the energy of the diode to be discharged smoothly, or putting a magnetic bead ring on its cathode pin to prevent sudden changes in the current to reduce spikes.

3. Switch tube

Due to the existence of the junction capacitance of the switch tube, the power module will produce burrs and spikes after fast switching during operation. The junction capacitance of the switch tube and the winding leakage inductance of the transformer may also resonate and cause interference.

4. PCB layout and routing

The PCB is the coupling channel of the above-mentioned interference source, and the quality of the PCB directly corresponds to the quality of the above-mentioned EMI source suppression. At the same time, the unreasonable layout and wiring of the components on the board will cause interference.

5. Energy storage inductor

Commonly used methods of suppressing interference include shielding or adjusting its parameters to avoid oscillation with the capacitance of the loop.

6. Transformer

The special power supply manufacturer tells you that the transformer is the energy storage component of the power module, and noise interference may occur during the charging and discharging of energy. Leakage inductance can form an oscillating loop with the distributed capacitance in the circuit, causing the circuit to oscillate at a high frequency and radiate electromagnetic energy outward, thereby causing electromagnetic interference. The potential difference between the primary winding and the secondary winding will also produce high-frequency changes. Through the coupling of the parasitic capacitance, the common mode conducted EMI current interference flowing between the primary side and the secondary side is generated.