Pay attention to the following points when selecting a filter for a switching power supply
(1) Specify the working frequency and the interference frequency to be suppressed. If the two are very close, you need to apply a filter with very steep frequency characteristics to separate the two frequencies;
(2) Ensure that the filter can work reliably under high pressure;
(3) When the filter is continuously supplied with the maximum rated current, its temperature rise should be low, so as to ensure that the working performance of the components in the filter will not be damaged when the rated current is continuously working;
(4) In order to make the frequency characteristics of the filter at work consistent with the design value, the value of the signal source impedance and load impedance connected to it is required to be equal to the specified value at the time of design:
(5) The filter must have a shielding structure, and the shielding box cover and the body must have good electrical contact. The capacitor lead of the filter should be as short as possible, and it is best to use a feedthrough capacitor with a short lead and low inductance;
(6) It must have high working reliability, because the faults of filters used to protect against electromagnetic interference are often more difficult to find than the faults of other components.
