One of the factors is the price filter size, usually at the time of purchase of the filter, the rated current is the same case usually choose small filter, the volume of the filter is mainly determined by the filter circuit inductance inductance the volume of the coil, the greater the volume of the filter. Small size filter has been used for small inductance element, its inductance why small? At the expense of current capacity, or at the expense of low-frequency characteristics? After paying these costs, whether it can meet the core requirements - suppression of electromagnetic interference? In addition, when a small volume of the filter, inside the device must be in close proximity, which reduces high frequency filtering performance of the filter, resulting in excessive radiation emitting devices. The following factors affect the volume of inductors:
 
1. Rated current: When the rated operating current filter is large, the inductor will use thicker wire around the system, which will naturally increase the volume; in addition, in order to prevent the occurrence of magnetic saturation of the core phenomenon, often use a larger volume The core, which will increase the volume;
2. The low-frequency characteristics: low interfering signal when the desired frequency filtering, common mode and differential mode inductance choke choke require large, resulting in an increase in the volume of the inductive element. For example, the lower frequency switching power supply, the greater the need to filter inductance;