Causes de Electromagnètic Compatibilitat Causat per Commutació Alimentació Font d'alimentació
The reason of Electromagnetic compatibilitat problem caused by 24V switching power supply working in the switching state of high voltage and high current is quite complex. From the perspective of Electromagnetic compatibility of the whole machine, there are mainly common impedància acoblament, línia a línia acoblament, elèctric camp acoblament, magnètic camp acoblament i electromagnètic ona acoblament. El tres elements de electromagnètic compatibilitat són: rascat font, Patogen transmissió i pertorbat cos. Comú resistència acoblament principalment refers a el comú impedància entre la pertorbació font i el pertorbat objecte elèctricament, a través el pertorbació senyal entra el pertorbat objecte. Línia a línia acoblament principalment es refereix a el mutual acoblament entre cables o PCB cables que generar ratllar voltatge i ratllar corrent degut a paral·lel cablejat.
Electric field coupling is mainly due to the presence of potential differences, resulting in the coupling of induced electric fields to the disturbed body. Magnetic field coupling mainly refers to the coupling of low-frequency magnetic fields generated near high current pulse power lines to the disturbance object. Electromagnetic field coupling is mainly caused by high-frequency electromagnetic waves generated by pulsating voltage or current, which radiate outward through space and couple the corresponding disturbed body. In fact, each coupling method cannot be strictly distinguished, only with different focuses.
In a 24V switching power supply, the main power switch operates in a high-frequency switching mode at a high voltage. The switching voltage and current are close to square waves. From spectrum analysis, it is known that the square wave signal contains rich high-order harmonics, that can reach a frequency spectrum of over 1000 times the square wave frequency. At the same time, because the Leakage inductance and distribuïd capacitance of the power transformer, as well as as the working state of the main power switching device, are not ideal, when the high frequency is turned on or off, high frequency and high voltage peak harmonic oscillation is sovint generated. El alt ordre harmònics generat per el harmònic oscil·lació són transmesos en el circuit intern a través de el distribuït capacitància entre el interruptor tub i el radiador oradiat en el espai a través de el radiador i el transformador.
Used for rectification and continuous current diodes, it is also an important reason for generating high-frequency disturbances. Because the rectifier and Flyback diode work in the high-frequency switching state, and because of the existence of the parasitic inductance of the diode's lead, the junction capacitance, and the influence of the reverse recovery current, they work at a molt high voltage and current change rate, and produeix alta freqüència oscil·lació. Ja que el rectificador i Flyback díode are generalment close to el power output line, the high-frequency interference generated by them is most likely to be transmitted through the DC output line.
In order to improve the power factor of 24V switching power supplies, active power factor correction circuits are adopted. At the same time, in order to improve the efficiency and reliability of the circuit and reduce the electrical stress of power devices, a large number of soft switching technologies have been adopted. Among them, zero voltage, zero current, or zero current switching technology is the most widely used. Aquesta tecnologia molt redueix el electromagnètic interferència generat per commutació dispositius. però, soft switching lossless absorció circuits mostly utilize L and C for energy transfer, utilizing the unidireccional conductivitat of díodes to achieve unidireccional energy conversion. 2c the diodes in this resonant circuit convertome a major source of electromagnetic disturbance.
In 24V commutació alimentació subministraments, energia emmagatzematge inductors i condensadors són generalment utilitzats a forma L i C filtratge circuits a filtre diferencial i comú mode pertorbació senyals, and to convert AC quadrat ona senyals into smooth DC signals. Due to the distribuïd capacitance of the inductance coil, the inductance coil
