At present, there are many types of power supplies on the market, ranging from tens of yuan to hundreds of yuan. How to choose a high-quality power supply depends mainly on its safety certification. Generally, the more certification items are obtained, the higher the reliability of the quality of the power supply is. When we buy, we should try our best to choose such a power supply.
Power supply certification project
1. CCC certification
CCC is the English abbreviation of China Electrical Product Safety Certification Committee, and it is the only electrical product safety certification body in my country. CCC certification is a compulsory certification standard for electrical products, that is, all electronic products sold on the Chinese market must be compulsory to pass this certification, otherwise they cannot be sold on the market. The CCC certification is a green pattern on a white background composed of symbols representing China and the Great Wall, so it is usually called the Great Wall certification.
2. FCC certification
FCC is a certification on electromagnetic interference. Strong electromagnetic interference will be generated internally when the power supply is working. If it is not shielded, it may affect the display, the motherboard and other electrical equipment, and even cause harm to the human body. Therefore, there are strict regulations on electromagnetic interference in the world. There are two general standards: FCC-A industrial standard and FCC-B civil standard. Only the power supply that meets the latter is safe and harmless.
3. UL certification
UL (Underwriters Laboratories) is the most authoritative and non-profit private safety testing organization in the United States. It mainly conducts safety tests and inspections on various equipment, systems and materials to confirm whether there is danger to life and property, and to The inspection results are announced. UL has published hundreds of standards, most of which have been adopted by ANSI (American National Standards Institute). Generally speaking, UL standards can be divided into: requirements for product structure, requirements for raw materials used in products, requirements for components used in products, requirements for test instruments and test methods, requirements for product marks and instructions, etc. . Now UL certification has become one of the most stringent certifications in the world.
4. CSA certification
CSA is the abbreviation of the Canadian Standards Association. It is Canada's first non-profit organization that specializes in formulating industrial standards and one of the most famous certification organizations in the world. Products such as electronics and electrical appliances sold in the North American market must obtain CSA safety certification. The standard mainly stipulates the testing methods of products, processes and materials, the safety of services and materials.
5. CE certification
CE is the Latin abbreviation of "European Union". It is a qualified product mark promoted by the European Union to prove that products meet its specified requirements. The CE mark is a mandatory pass and one of the basic certification standards for power supply manufacturing. It requires that power products must protect the health and safety of users and meet the basic requirements of environmental protection.
Indicators for evaluating power supply
Generally speaking, the safety certification of power supply is the most stringent in Germany based on the 1EC-380 standard VDE-0806 standard. my country's national standard is GB4943-1995 "Safety of Information Technology Equipment (Including Electrical Equipment)". Regardless of the standards formulated by any country, most of them have made strict regulations in terms of creepage distance, electric strength, leakage current, and temperature.
1. Requirements for creepage distance: The creepage distance refers to the shortest distance between two conductive devices or the interface between a conductive device and the equipment measured along an insulating surface. UL, CSA, and VDE safety standards emphasize the safety requirements for creepage distance, which is to prevent fire between devices or between devices and the ground, thereby threatening personal safety.
2. Requirement for electrical strength: when the zero voltage is applied between the AC input line or between the AC input and the chassis to AC 1500V or DC 2200V, it is qualified if it does not break down or draw an arc.
3. Requirements for leakage current: Both UL and CSA require that exposed, non-charged metal parts should be connected to the earth. The leakage current is measured by connecting a 1.5kΩ resistor between these parts and the earth to measure the leakage current. The leakage current of the switching power supply should not exceed 3.5mA under 260V AC input.
4. Temperature requirements: safety standards attach great importance to the temperature requirements of electrical appliances, and require materials to be flame retardant. For switching power supplies, the internal temperature rise should not exceed 65°C. If the ambient temperature is 25°C, the temperature of the components of the power supply should be less than 90°C. A power supply that does not meet the safety standards has no direct adverse effects on the user at the beginning, but after a long time, the high-voltage area may be short-circuited due to the influence of damp air and dust, which not only damages the power supply itself, but also serious Affect the power grid, thereby adversely affecting other electrical appliances.
5. Requirement for electromagnetic interference: The internationally accepted standards are FCC-A (industrial standard) and FCC-B (civilian standard), and the power supply should meet the civil standard. Electromagnetic interference is divided into conducted interference and radiated interference. Conducted interference propagates through the power line, the frequency is below 30MHz, and the main interference audio frequency band. Since the switching power supply for computers is shielded by a metal shell, power interference is more reflected as conduction interference. The magnitude of conducted interference is an important criterion for measuring the quality of computer power supply. It has two meanings: one is to prevent electromagnetic interference on the power grid from entering the power grid through the electromagnetic interference generated by the power supply itself, which affects the normal operation of the host system; the other is to prevent the host itself from generating The electromagnetic interference enters the power grid and affects other electrical appliances. We may have such experience in our daily work that when the computer is turned on, the nearby electrical appliances such as TVs and stereos cannot be used normally. This is caused by conduction interference.
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