Due to the immature technology and the limitations of the device performance, some of the early switching power supplies did not seem to make EMC difficult to pass, large standby power consumption, and low efficiency. Electromagnetic compatibility EMC (ElectroMagnetic Compatibility) refers to the ability of a device or system to operate in accordance with requirements in its electromagnetic environment without generating unbearable electromagnetic interference to any equipment in its environment. Therefore, EMC includes two requirements: on the one hand, it means that the electromagnetic interference generated by the equipment in the environment during normal operation cannot exceed a certain limit; on the other hand, it means that the appliance has certain electromagnetic interference in the environment. Degree of immunity, ie electromagnetic sensitivity. Various operating power equipment are related to each other and affect each other in three ways: electromagnetic conduction, electromagnetic induction, and electromagnetic radiation. Under certain conditions, it will cause interference, impact and harm to the operating equipment and personnel. The EMC discipline that emerged in the 1980s is aimed at studying and solving this problem. It is mainly to study and solve the generation, propagation, reception, and suppression mechanisms of interference and their corresponding measurement and metrology technologies. Based on this, The most reasonable principle of technology and economy, make clear regulations on the interference level, anti-interference level and suppression measures, so that the equipment in the same electromagnetic environment are compatible, and it is not allowed to introduce to any entity in the environment. Electromagnetic disturbance.
With the development of modern science and technology, the performance of devices has improved, especially the emergence of energy-saving power chips, and the maturity of circuit design. Thing, the design of energy-saving switching power supply is exactly to meet the needs of energy saving and emission reduction.
I will now take the circuit diagram in Figure 1 as an example, and take the California Energy Star Act (Class IV) TableU-2 (implemented in January 2008) as the design basis to illustrate the main points of designing green switching power supplies. The requirements for TableU-2 of the California Energy Star Act (Class IV) are as follows:
Note 1: In the table, Pn is the standard output power of the external switching power supply, and Ln is the natural logarithm.
Note 2: California Energy Star is mandatory and is a California local regulation. Commercial switching power supplies entering California must comply with this regulation. Many manufacturers in China design and produce green switching power supplies in accordance with the California Energy Star Act.