1. Principle of electromagnetic interference
Power Adapter may generate electromagnetic interference (EMI) during operation. This is mainly due to its internal circuit structure and working principle. Power Adapter usually contains circuit links such as rectification, filtering, inversion (in some types) and voltage regulation. When these circuits are working, the rapid changes of current and voltage will generate high-frequency signals. For example, when the switch tube in the switching power supply is turned on and off at high speed, it will produce instantaneous current mutations. This mutation current is like a small electromagnetic radiation source. According to the principle of electromagnetics, the changing current will generate a magnetic field, thereby radiating electromagnetic waves outward, which is one of the sources of electromagnetic interference. At the same time, components such as inductors and capacitors in the circuit may also generate electromagnetic noise during the charging and discharging process. These noises will interfere with surrounding electronic equipment to a certain extent.
2. Factors affecting the generation of electromagnetic interference
The degree of electromagnetic interference generated by the power adapter is affected by many factors. The first is the circuit design. Different topologies generate different levels of electromagnetic interference. For example, the use of advanced resonant switching power supply topology can reduce voltage and current mutations during the switching process compared to the traditional hard switching topology, thereby reducing the generation of electromagnetic interference. Secondly, the quality and performance of components are also critical. High-quality switching tubes, inductors, capacitors and other components have more stable characteristics and can reduce electromagnetic interference caused by fluctuations in component performance. In addition, the operating frequency is also an influencing factor. Higher operating frequencies are often accompanied by higher electromagnetic interference risks because current and voltage change more frequently at high frequencies.
3. Suppression measures taken
In order to reduce electromagnetic interference, Power Adapter manufacturers usually take a series of measures. In terms of circuit design, filtering circuits will be added, such as EMI filters at the input and output ends. These filters are composed of components such as inductors and capacitors, which can effectively filter out high-frequency noise in the circuit. At the same time, shielding technology is used, such as encapsulating the internal circuit of the Power Adapter in a metal shielding cover, which can reflect and absorb electromagnetic waves and prevent the electromagnetic interference generated inside from radiating outward. In terms of component layout, certain rules will also be followed to minimize electromagnetic coupling and keep components that are prone to electromagnetic interference away from sensitive circuit parts.
