There can be some misleading information on web sites. Take the www.lowESR.com web site it states the folowing:
The output capacitor (or capacitor bank) will have a ripple voltage (seen as noise on the supply voltage) proportional to the ESR of the capacitor (or capacitor bank).
V = I X R ... Ripple voltage = Current X ESR
If the current increases from 4A to 20A, within a circuit, the ripple voltage will increase by a factor of FIVE. This increased noise cannot be tolerated, so the ESR of the capacitors must be reduced.
This is very misleading in that it states that increasing ripple current through ESR will increase ripple voltage.
In any circuit it is the voltage source that determines the current through a resistor. It is not the reverse that the current determines the voltage. The only exception is the case of a current source developing and voltage across a resistor.
In a practical power supply the ripple voltage is developed in relation to the values of filter capacitor, the presence or not of a filter choke, the load and the frequency of ripple. The ripple appears as an AC voltage at the load and across the filter capacitor. The capacitor will bypass the AC ripple in proportion to the ESR, a high ESR will pass less current than a low ESR. The ESR is simple a resistance connected across and AC voltage source(neglecting the the capacitor reactance than is typically a very low value) . It cannot increase the ripple voltage, but a low ESR will decrease the ripple by virtue of the ripple voltage source resistance.
It was surprisng to find such a statement on a NIC site.
The output capacitor (or capacitor bank) will have a ripple voltage (seen as noise on the supply voltage) proportional to the ESR of the capacitor (or capacitor bank).
V = I X R ... Ripple voltage = Current X ESR
If the current increases from 4A to 20A, within a circuit, the ripple voltage will increase by a factor of FIVE. This increased noise cannot be tolerated, so the ESR of the capacitors must be reduced.
This is very misleading in that it states that increasing ripple current through ESR will increase ripple voltage.
In any circuit it is the voltage source that determines the current through a resistor. It is not the reverse that the current determines the voltage. The only exception is the case of a current source developing and voltage across a resistor.
In a practical power supply the ripple voltage is developed in relation to the values of filter capacitor, the presence or not of a filter choke, the load and the frequency of ripple. The ripple appears as an AC voltage at the load and across the filter capacitor. The capacitor will bypass the AC ripple in proportion to the ESR, a high ESR will pass less current than a low ESR. The ESR is simple a resistance connected across and AC voltage source(neglecting the the capacitor reactance than is typically a very low value) . It cannot increase the ripple voltage, but a low ESR will decrease the ripple by virtue of the ripple voltage source resistance.
It was surprisng to find such a statement on a NIC site.
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