Switching power adapters and electronic devices have electromagnetic compatibility requirements and corresponding testing methods. When designing a switching power adapter or electronic device, it is necessary to ensure that its electromagnetic compatibility indicators meet the requirements. However, the means, methods, and indicator requirements of electromagnetic compatibility design do not have an explicit numerical relationship, which means that electromagnetic compatibility design has a certain degree of ambiguity. Through long-term exploration and practice, some specifications have been established that are very beneficial for improving electromagnetic compatibility indicators. In the electromagnetic compatibility design of switching power adapters, grounding technology, lightning protection, and anti-static technology play a significant role in ensuring the reliability of electronic equipment. Let’s first understand the grounding function of a switching power adapter: Grounding is an essential component of a switching power adapter or other electronic device, which not only directly affects the quality and normal operation of the switching power adapter but also plays a role in protecting equipment and personal safety. Grounding is the most important design content for electromagnetic compatibility. It has an obvious effect on suppressing conducted interference and has the advantage of being cost-effective.
The protective grounding of a switching power supply usually uses the earth’s potential as a reference and the earth as the zero potential. The circuit ground is a reference point for a certain potential in a circuit system. It can be assumed that the potential at this point is used as a relative zero potential, which is generally not the same as the earth ground. For example, electronic circuits often use the metal base, rack, chassis, etc. of the equipment as the zero potential or “ground” potential. They are not necessarily connected to the earth ground. At this time, the “ground” potential inside the equipment may not be the same as the earth potential, and there is a potential difference between them (called floating voltage or coupling voltage). However, in order to prevent lightning strikes and potential differences from endangering the equipment and operators, the metal structures such as racks and chassis of the equipment should be connected to the earth ground. For chargers or power adapters with two-phase (neutral and live wire) inputs and without an earth wire connected, and whose outer casing is made of plastic parts, it is impossible to connect to the earth ground through wires. At this time, the coupling voltage (also known as floating voltage) between the output terminal and the earth is related to the insulation resistance, distributed capacitance, and leakage resistance to the ground of the power adapter. Double insulation or reinforced insulation is relied upon for electrical protection. Strict requirements should be placed on the insulation materials and structures of Y capacitors, optocouplers, and high-frequency transformers, insulation resistance, electric strength, and leakage current.
Switching power supply circuit grounding is a wire connection set up to discharge charges or establish the reference voltage of the circuit. In a switching power supply, grounding is an important method to suppress electromagnetic noise and prevent interference. Grounding of the metal structure body is also a design content for shielding and safety, which plays an important role in the electromagnetic compatibility of electronic equipment.
The role of grounding of switching power adapter mainly includes the following aspects:
1. Improving the stability of switching power circuit system operation and beneficial to suppress interference. Connecting the ground of the switching power supply to the earth can improve the stability of the electronic equipment and circuit system operation. If the electronic equipment is not connected to the earth, it will present a certain potential relative to the earth. This potential will change under the action of external interference fields, leading to the unstable operation of the circuit system. By connecting the “ground” of the electronic equipment to the earth and keeping it at the true zero potential, interference can be effectively suppressed.
2. Switching power supply grounding can release the electric charge accumulated on the chassis due to electrostatic induction, avoiding interference caused by charge accumulation. Through grounding, the electric charge accumulated on the chassis and circuits due to electrostatic induction can be released to avoid interference and damage caused by high voltage generated by charge accumulation leading to internal discharge of the equipment. Grounding of the switching power supply chassis can achieve the purpose of electrostatic shielding and electromagnetic shielding.
3. Switching power supply grounding can provide security for electronic equipment and operators. The output end of the switching power adapter or the chassis of the electronic equipment to the earth has zero potential, no floating voltage, and will not produce static electricity or electric shock sensations.
Post time: Jun-14-2023