Circuit of decoupling filter of circuit board proofing manufacturer

Circuit of decoupling filter of circuit board proofing manufacturer

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In order to reduce the noise coupled by the power supply system, it is usually necessary to provide decoupling for each circuit or group of circuits. The use of resistance capacitance (RC) decoupling filter or inductance capacitance (LC) decoupling filter can effectively isolate the circuit from the power supply, eliminate the coupling between the electrical circuits and prevent the noise of the power supply system from entering the circuit. The circuit using RC decoupling filter and LC decoupling filter.

For] RC filter, because the voltage drop on the resistance will reduce the power supply voltage provided to the circuit, it is usually necessary to consider the impact of the voltage drop on the resistance.

LC filter can reduce the drop of power supply voltage caused by resistance, especially can provide better filtering for high-frequency noise. However, it should be noted that for an LC filter, there is a resonant frequency. At this resonant frequency point, the high-frequency noise signal transmitted by the filter may be larger than the high-frequency noise signal when the filter is not used. During design, it is required to ensure that the resonant frequency of LC filter is outside the passband of the connected circuit. If necessary, add a resistance in series with the inductor to improve the damping. The inductor used must always be able to pass the DC current required by the circuit without saturation.

The dotted line capacitor can be added to each part of the circuit, so the decoupling filter circuit becomes a 71 type filter circuit, which can enhance the filtering of noise fed back from the circuit to the power supply.

When considering noise reduction, RC decoupling filter is better than LC decoupling filter. RC decoupling filter is in the form of absorption filter, and the noise voltage is converted into heat and dissipated. The LC decoupling filter is a reflective filter. At this time, the noise voltage does not appear on the load, but on the inductance, so it may be radiated and bring down disturbance to other parts of the circuit. Therefore, shielding measures may be required to eliminate its radiation.

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