ABSTRACT
The differential-mode components must be of the high-Q type. The individual component Q must be high, while the circuit Q must be lowered to the point where the filter circuit is able to provide effective damping of these parasitic oscillations. Electromagnetic interference (EMI) filters demand specific types of capacitors for different levels of implementation. Some filter companies use the large nonpolarized can-type filter capacitors. The main specification for the capacitors is MIL-STD-15573. Capacitors, like everything else, have improved over the years. Better materials and newer techniques have improved the self-resonant frequency of polyester, ceramic, and other dielectrics for capacitors. Although this technique has been around a long time, the new name for it is “veeing the capacitor.” Most new people in the EMI design arena are knowledgeable about power supply design, where the main concerns about the capacitors are their working voltage and capacitor value.
