![]() ![]() If the module power supplies are not shielded and they get very close, they might have mutual interference, so as to increase the output noise voltage. On the same PCB, there might be several module power supplies working together. In other words, the switching power supply adopts the frequency of the external synchronous input system, thus enabling the same frequency between the switching frequency and system frequency.Īvoiding the mutual interference among several module power supplies In order to reduce the output noise, the switching power frequency of the power supply should be synchronous with the system frequency. ![]() Its price is much lower than that of the high-molecular polymer solid electrolyte capacitance.Īdopting a switching power supply in synchronous frequency with the system Some powers with the switching frequency between 100 kHz to several hundreds of kHz also have good effects in adopting multilayer ceramic capacitance (MLCC) or Ta electrolytic capacitor as the output capacitance. It is still invalid if the capacitance is increased, because it has become the inductance characteristics when the frequency exceeds 10 kHz. It can only work under 10 kHz, but it is unable to work under high frequency (frequency above 100 kHz). If the ordinary aluminum electrolytic capacitor is used as the output capacitor with the rated voltage of 10V and the rated capacitance of 100μF, the equivalent series resistance in 20℃ and 120Hz is 5.0Ω, and the maximum ripple current is 70mA. Its size is 7.3mm (length) × 4.3mm (width) × 1.8mm (height). And the maximum allowed ripple current (in 100 kHz) is 2400mA (rms). Its maximum value of equivalent series resistance (ESR) is 25mΩ in 100kHz when the temperature is 20℃. It is most appropriate to high-efficiency, low-voltage, high-current decompression-type DC/DC converter and DC/DC module power source as the output capacitance.įor instance, a kind of high-molecular polymer Ta solid electrolytic capacitor is 68μF. ![]() Its characteristics include small size and big capacitance, low ESR resistance under high frequency, thus allowing high ripple current. It is the best to adopt aluminum or tantalum electrolytic capacitance of high-molecular polymer solid electrolyte as the output capacitance. This is also a method usually used to restrain the high-frequency noise.Īdopting capacitance with good high-frequency performance and low ESR on the output terminal In order to reduce the electromagnetic interference of the power line input, the power input terminal is equipped with the EMI power line filter, just as the below diagram shows (EMI filter is also named as the power line filter). The metal shell can be adopted as the shield which is used to reduce the radiated interference of the external electromagnetic field. Reducing EMI - diode back connection inductance Generally speaking, here are some approaches restraining or reducing it. As to the ripple wave of the switching power supply, it certainly exists both theoretically and practically.
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