Film capacitors are metal foil as electrodes, and polyethylenes, polypropylene, polystyrene or polycarbonate and other plastic films, from the two ends of the overlap, winding into a cylindrical structure of the capacitor. The working principle of a film capacitor is the same as that of a general capacitor, which is to store electrical energy by storing charge on the electrodes, and is usually used together with an inductor to form an LC oscillation circuit.