Use capacitor to reduce the countermeasure of noise
[introduction] noise divides a lot of kinds, property also is varied. So, noise countermeasure (the method that reduces noise namely) varied also. Basically talk about the noise related switch power source here, accordingly, n of the voltage in understanding the voltage that it is DC please the noise with inferior, louder frequency. Additional, outside eliminating electric capacity, still have neat accept diode and noise / surge / ESD is restrained implement etc fall component of a confusion of voices. Different noise property, what need fall component of a confusion of voices also each are not identical. If be DC/DC converter, most meeting is mixed according to its circuit voltage n, will reduce noise with LCR.
Use capacitor reduces noise
Noise divides a lot of kinds, property also is varied. So, noise countermeasure (the method that reduces noise namely) varied also. Basically talk about the noise related switch power source here, accordingly, n of the voltage in understanding the voltage that it is DC please the noise with inferior, louder frequency. Additional, outside eliminating electric capacity, still have neat accept diode and noise / surge / ESD is restrained implement etc fall component of a confusion of voices. Different noise property, what need fall component of a confusion of voices also each are not identical. If be DC/DC converter, most meeting is mixed according to its circuit voltage n, will reduce noise with LCR.
Use capacitor reduces the sketch map of noise
The give typical examples that outputs voltage noise through adding capacitor to reduce DC/DC converter is below.
When the capacitance that the weaveform above is filter of output end LC is 22µF, the noise that in the frequency range that restricts 200MHz existence 180mVp-p controls (ringing, reflex) . The weaveform below is to reduce this kind of noise and the result after adding 2200pF electric capacity. From weaveform the graph can see, the electric capacity that adds 2200pF makes noise reduced 100mV left and right sides.
Ask: What should think here is “ why be 2200pF” . Next graphs add the impedance frequency character of capacitor for place.
Answer: Choose the capacitance of 2200pF, because impedance is near 160MHz,be lowest, use character of this kind of impedance, can reduce noise extent to make an appointment with 2MHz.
This is the impedance that will reduce target noise frequency through adding capacitor, reduce the gimmick of noise extent thereby.
When resembling reduce noise so through adding capacitor, need holds noise (ringing, reflex) frequency, choose to have the capacitor of the frequency character of corresponding impedance.
The key wants a place:
? Will reduce noise scope through reducing the impedance of target noise frequency.
? Fall a confusion of voices needs to undertake according to the frequency character of impedance with the type selecting of capacitor (and rather than holds a cost) .