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Assuming a differential input inductance of the power supply asymmetry (that is, there are some differences in the sense of a hypothetical 100uH, a 60uH) what will be the problem? Its ability to suppress the differential mode signal is reduced?

differential mode choke coil asymmetry will produce the following situation Assumption 1: The original circuit of the differential mode inductance value of 60uH, has to meet the requirements of the circuit. (Provided that the magnetic properties of the core used, the same size specifications)

While the actual one is 100uH,

1, according to impedance theory, Z = 2 * π * F * L

The higher the inductance, the higher the impedance, the stronger the ability to suppress clutter. A high inductance value is perfectly desirable for the filtering effect.

2, according to the anti-saturation capacity calculation, H = 0.4π * N * Ie / Le

Core magnetic properties of choke coils manufacturers , size specifications under the same conditions, the core of the anti-saturation capacity needs to be considered. If the actual application conditions in the circuit, assuming that the core saturation, magnetic permeability decays to very low inductance drop is very low. Then the impedance will drop very low. On the differential mode signal can not be suppressed, or inhibit the ability to drop a lot. So that EMI detection is unable to meet the requirements.

Assumption 2: The original value of the differential mode inductance of the circuit is 100uH, has already met the requirement of the circuit. (Provided that the magnetic properties of the core used, the same size specifications) While the actual one is 60uH,

1, according to impedance theory, Z = 2 * π * F * L

The lower the inductance, the lower the impedance and the poorer the ability to suppress clutter. Then the effect of filtering the noise of the differential mode signal is deteriorated. So EMI detection is unable to meet the requirements.

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