In the complex electromagnetic environment of modern electronic devices, the power supply system serves not only as an energy carrier but also as a critical pathway for interference propagation. From transient surges and high-frequency harmonics introduced from the grid side to the high-frequency switching noise generated by switching power supplies themselves, these interferences act like invisible undercurrents, constantly threatening the stable operation of the entire system. In this critical domain, feedthrough capacitors have become core components in building the electromagnetic compatibility defense line of power supply systems, thanks to their unique structural design and high-frequency performance.
The value of feedthrough capacitors lies in their redefinition of the physical path for high-frequency filtering. Traditional capacitors, due to their leads and pads, introduce non-negligible parasitic inductance, leading to a sharp decline in filtering performance at high frequencies. In contrast, feedthrough capacitors adopt a “through-type” structure, allowing current to flow directly through the capacitor dielectric and minimizing the current loop to its limit. This reduces parasitic inductance to below 1nH. Such a design enables their self-resonant frequency to reach hundreds of MHz or even GHz levels, maintaining excellent impedance characteristics even in the challenging noise frequency bands of switching power supplies, ranging from several hundred kHz to tens of MHz.
In practical power supply system design, feedthrough capacitors often work in synergy with inductive components to form composite filtering networks. At the power supply input, they act as the system’s “gatekeeper,” effectively filtering out high-frequency interference and transient surges from the grid, providing a relatively clean input for subsequent rectification and conversion circuits. More importantly, they prevent these interferences from causing electromagnetic coupling within the power supply, avoiding impacts on power conversion efficiency and stability. At the power supply output, feedthrough capacitors play the role of a “purifier,” specifically suppressing the high-frequency noise generated by the switching power supply itself.
It is particularly worth emphasizing that the installation method of feedthrough capacitors in power supply systems directly affects their performance. Proper installation should ensure that their metal housing achieves a large-area, low-impedance connection with the power supply system’s grounding plane. Any poor grounding can severely hinder the conduction of high-frequency noise. In applications where space is extremely limited, feedthrough capacitors can even be installed directly on the metal housing of the power supply module, saving space while achieving ideal grounding effects.
As power supply technology advances toward higher frequencies and greater density, electromagnetic compatibility challenges are becoming increasingly severe. Feedthrough capacitors are evolving toward higher voltage resistance, wider temperature ranges, and lower equivalent series resistance to meet the demands of new-generation high-efficiency, high-reliability power supply systems. Although it is a small passive component, it plays an irreplaceable and crucial role in ensuring power purity and enhancing system reliability.
