EMC Design Classic Q & A III

Basic Principles of EMC Design

(1) At high frequencies, a core-piercing capacitor or a support capacitor with a small lead inductance should be preferred for filtering compared to a lead capacitor.

(2)The effect of lead inductance on filtering efficiency should be considered when lead capacitance must be used.

(3) Aluminum electrolytic capacitors may undergo a few microseconds of temporary dielectric breakdown, so solid capacitors should be used in circuits with large ripple or transient voltages.

(4) Use parasitic inductors and resistors with small capacitance. sheet resistor can be used in ultra-high frequency band.

(5) Large inductance has a large parasitic capacitance. In order to improve the insertion loss of the low frequency part, the single filter should not be used, but the multi-section filter composed of several small inductors should be used.

(6) The use of core inductors should pay attention to the saturation characteristics, especially the high level pulse will reduce the inductance of the core inductance and the insertion loss in the filter circuit.

(7) Use shielded relays to the maximum extent possible and ground the shield case.

(8) Select input transformers that are effectively shielded and isolated.

(9) Power transformers for sensitive circuits shall be provided with electrostatic shielding, and both the shielding case and the transformer case shall be grounded.

(10) Interconnect signal lines within the device must use shielded wires to prevent harassment and coupling between them.

(11) In order for each shield to be connected to its own pin, a sufficient number of plug seats should be selected.