Что есть Электромагнитный Совместимость Из Переключение Питание Источник питания
The reasons for the electromagnetic compatibility problems caused by switching power supplies are quite complicated because they work under high-voltage and high-current switching conditions. In terms of the electromagnetic properties of the whole machine, there are mainly common impedance coupling, line-to-line coupling, electric field coupling, magnetic field coupling and electromagnetic wave coupling. The common impedance coupling is mainly the electrical common impedance between the disturbance source and the disturbed body, through which the disturbance signal enters the disturbed body. Line-to-line coupling is mainly the mutual coupling of wires or PCB lines that generate disturbance voltage and current due to parallel wiring. The electric field coupling is mainly due to the existence of the potential difference, which generates the field coupling of the induced electric field to the disturbed body. Magnetic field coupling mainly refers to the coupling of the low-frequency magnetic field generated near the high-current pulse power line to the disturbing object. Electromagnetic field coupling is mainly due to the high-frequency electromagnetic waves generated by pulsating voltage or current radiating outward through space, and coupling to the corresponding disturbed body. In fact, each coupling method cannot be strictly distinguished, but the emphasis is different.
In the switching power supply, the main power switching tube works in a high-frequency switching mode at a very high voltage. The switching voltage and switching current are close to square waves. From the spectrum analysis, the square wave signal contains rich high-order harmonics. The frequency spectrum of the higher harmonic can reach more than 1000 times of the square wave frequency. At the same time, due to the leakage inductance and distributed capacitance of the power transformer and the non-ideal working state of the main power switching device, high frequency and high voltage peak harmonic oscillations are often generated when high frequency is turned on or off. The higher harmonics generated by the harmonic oscillation are transmitted to the internal circuit through the distributed capacitance between the switch tube and the radiator or radiated to the space through the radiator and the transformer. Switching diodes used for rectification and freewheeling are also an important cause of high-frequency disturbances. Because the rectification and freewheeling diodes work in a high-frequency switching state, the existence of the parasitic inductance of the diode's lead, the existence of the junction capacitance, and the influence of the reverse recovery current make it work at a very high voltage and current change rate, and produce high-frequency oscillations . The rectification and freewheeling diodes are generally closer to the output line of the power supply, and the high-frequency disturbances generated by them are most likely to be transmitted through the DC output line. In order to improve the power factor, the switching power supply adopts an active power factor correction circuit. At the same time, in order to improve the efficiency and reliability of the circuit and reduce the electrical stress of the power device, a large number of soft switching technologies are used. Among them, zero voltage, zero current or zero voltage/zero current switching technology is the most widely used. This technology greatly reduces the electromagnetic disturbance generated by switching devices. However, most of the soft-switching non-destructive absorption circuits use L and C for energy transfer, and use the unidirectional conductivity of diodes to realize unidirectional energy conversion. Therefore, the diodes in the resonant circuit become a major source of electromagnetic disturbance.
Коммутация питание источники питания в целом использование энергия хранение катушки индуктивности и конденсаторы к форме L и C фильтр цепи к фильтр дифференциал и общий режим возмущение сигналы. Из к Распределенный Емкость Емкость Из Индуктивность Катушка, The Self-Resonant частота Of The Inductance катушка IS Уменьшенный, so that a large number of high-frequency помехи сигналы pass through the inductance катушка and spreadless along the AC power line or the DC выход линия. Как частота возмущение сигнал увеличение, эффект ведущий индуктивность фильтр конденсатор провода к a непрерывный спад в емкость и фильтрация эффект % 2c и даже провода к изменениям в конденсатор параметры % 2c который есть также a причина электромагнитное возмущение.
