What is the effect of power filter insertion loss
Insertion loss is an indicator of filter performance. It refers to the ability of EMI filters to attenuate interference signals under certain conditions. It is described by the logarithm of the power directly transmitted from the signal source to the load before insertion of the filter and the power transmitted to the load after insertion. When testing within a 50 Ω system, the following equation can be used to represent:
IL=20Lg(E0/E1)
Among them, IL insertion loss (unit: dB), EO load voltage directly connected to the signal source, E1 load voltage after inserting the filter
How to measure insertion loss?
The most common setting is to set the impedance of both the power supply and resistive load to 50 Ω. The most important point in measuring insertion loss is consistency, and the specific testing method is as follows:
Use a spectrum analyzer, FM receiver or tracking generator to establish a zero dB reference point without a filter. Then insert a filter and record the attenuation provided within the desired frequency range.
For power line filters, we are interested in two different modes of attenuation:
Common mode (CM) interference signal - the signal between the phase line (L) and ground (E) and the neutral line (N) and ground (E).
Differential Mode (DM) interference signal - the signal between the phase line (L) and the neutral line (N). Due to the fact that power filters can suppress both common mode EMI signals and differential mode EMI signals, insertion loss should also include common mode insertion loss and differential mode insertion loss.
When measuring common mode insertion loss, connect the L and N at the power supply end of the filter together, and connect the signal source between the power supply end and the ground end. At the same time, the L and N at the load end of the filter are also connected together, and the receiver is connected between the power and ground terminals.
When measuring differential insertion loss, unbalanced unbalanced and balanced unbalanced converters should be connected to the signal source and receiver ends respectively.
PS: The common mode and differential mode insertion losses provided in this manual are measured according to the above regulations. There are also other methods for measuring insertion losses, please refer to relevant materials.
It should be noted that the insertion loss of the EMI filter provided in this manual may not be equivalent to the attenuation of interference signals by the actual filter used, and sometimes may differ significantly. This is because the insertion loss given in this manual was measured within a 50 Ω system, while in practical applications, the impedance of the EMI filter terminal is not 50 Ω, which is the fundamental reason for the difference
What is the effect of insertion loss?
Standard insertion loss data cannot accurately determine the performance of filters in equipment, but it can serve as an important means of verifying product conformity during incoming inspection.
The judgment criterion is that the insertion loss measured in a standard manner must meet or exceed the data on the sample. That is to say, the "typical" insertion loss data is meaningless. The data you measured should be the minimum value. Most of the insertion loss data on the sample is the minimum value that it can guarantee, and this value can be tested to demonstrate the compliance of the component
