Application of film capacitors and related requirements

Thin film capacitors have excellent electrical characteristics, high stability and long life, and are used in various industries, but even if the film capacitor performance is high enough, capacitor manufacturers continue to improve the manufacturing process to provide in a smaller package size. Larger capacitance. Capacitor manufacturers can optimize the characteristics of the film capacitor by selecting the appropriate dielectric for the specific application. For example, manufacturers use film capacitors made of polyester film, with high dielectric constant, high dielectric strength, self-healing, good temperature stability, etc., to meet customer needs, decoupling, blocking, bypassing and noise. It is a popular choice in suppressing DC applications, and the cost is not high.

Capacitors made of polypropylene film have low dielectric loss, high insulation resistance, low dielectric absorption, high dielectric strength, good stability, etc., can provide rated voltage of 400VAC or higher, and are AC input filters. Electronic ballasts, snubber circuits, switching power supplies, frequency discrimination and filter circuits, storage and other applications are popular choices.

The principle of selecting a film capacitor for product design is usually relatively simple. It is important that the capacitor meet the performance standards for components connected to the mains and have corresponding certification. For example, EMI filters in power line-powered products use common topologies to easily select capacitance values. The X capacitor placed between the mains and neutral phases has no theoretical upper limit, but is usually between 0.1 microfarad and 1.0 microfarad. Place the Y capacitor between the main or neutral line and the ground of the chassis. You need to select the smallest possible capacitance so that the leakage current to the ground is small. For most designs, the 4700pf is ideal. Capacitance stability includes sufficient self-recovery capacitance, which is a key performance criterion. After meeting these requirements, special requirements, supply and other issues will become issues to consider.