Electromagnetic compatibility of communication switching power supply

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Electromagnetic compatibility of communication switching power supply

Abstract : This paper briefly introduces the electromagnetic compatibility requirements, domestic and foreign standards, causes of electromagnetic compatibility, research solutions and the current status of electromagnetic compatibility of domestic communication switching power supplies.
Keywords: communication switching power supply; electromagnetic compatibility; standard
Communication switching power supplies are widely used in program-controlled switching, optical data transmission, wireless base stations, cable TV systems and IP networks due to their advantages of small size, light weight, high efficiency, reliable operation and remote monitoring . They are the power core for the normal operation of information technology equipment.
With the development of information technology, information technology equipment is spread all over the country, from developed central cities to remote mountainous areas, providing great convenience for communication and information transmission between people. Due to the differences between urban and rural areas, the power supply network for communication equipment has both stable large power grid power supply and independent small hydropower power supply. Under the power supply mode of small hydropower stations, due to the changes in water volume, large changes in user power consumption and unstable operation of power generation equipment, the grid waveform is seriously distorted and the voltage fluctuates greatly. At the same time, due to the irregular wiring of the distribution system, it has formed a severe test for the communication switching power supply.
Railway communication and power communication are growing stronger. Because the electric locomotive passes by, a strong induced voltage is generated, which causes a large fluctuation in the ground line voltage, thereby causing a large fluctuation in the grid voltage. The strong electric field can easily cause instantaneous instability in the operation of the switching power supply equipment. Although the grid voltage of the communication switching power supply running near the high-voltage grid is stable, it is easily affected by the interference of the strong electromagnetic field caused by the change of the grid load. The
communication switching power supply used for base stations is more susceptible to lightning attacks because it is mostly installed on higher buildings or mountain tops.
Therefore, the communication switching power supply must have a strong ability to resist electromagnetic interference, especially the ability to adapt to lightning strikes, surges, and grid voltage fluctuations, and it must also have sufficient anti-interference ability for electrostatic interference, electric fields, magnetic fields, and electromagnetic waves to ensure that it can work normally and the stability of the power supply to the communication equipment.
On the other hand, because the power switch tube, rectifier or freewheeling diode and main power transformer inside the communication switching power supply work under high voltage, high current and high frequency switching, its voltage and current waveforms are mostly square waves. In the process of high voltage and high current square wave switching, serious harmonic voltage and current will be generated. On the one hand, these harmonic voltages and currents are transmitted through the power input line or the output line of the switching power supply, interfering with other equipment and the power grid powered by the communication power supply on the same power grid, and at the same time interfering with equipment powered by the communication power supply, such as program-controlled switching equipment, wireless base stations, optical transmission equipment, and cable TV equipment, so that the equipment cannot work normally; on the other hand, serious harmonic voltages and currents generate electromagnetic interference inside the switching power supply, which causes instability in the internal operation of the switching power supply and reduces the performance of the power supply. Some electromagnetic fields also radiate to the surrounding space through the gaps in the switching power supply housing, and together with the radiated electromagnetic fields generated by the power lines and DC output lines, they propagate through space, causing interference to other high-frequency equipment and equipment that is sensitive to electromagnetic fields, causing other equipment to work abnormally.
Therefore, for communication switching power supplies, it is necessary to limit the conducted interference generated by the load lines and power lines and the electromagnetic field interference propagated by radiation, so that telecommunication equipment in the same electromagnetic environment can work normally without interfering with each other.