Briefly describe the types and main application fields of thin film capacitors

Main types of film capacitors

1. Classification by electrolyte

Thin film capacitors can be divided into the following three types according to different electrolytes:

(1) Type T: i.e. PET – Polyethylene (polyethylene terephthalate (or ester));

(2) Type P: PP-Polypropylene (polypropylene);

(3) Type N: PEN-Polyethylene Naphthalate (polyethylene naphtha).

2. Classified by film type

According to the type of plastic film, the film capacitance can be divided into polyethylene capacitance (also called Mylar capacitance), polypropylene capacitance (also called PP capacitance), polystyrene capacitance (also called PS capacitance) and polycarbonate capacitance.

The structure of the film capacitor is the same as that of the paper capacitor, and the medium is polyester or polystyrene. The polyester film capacitor has high dielectric constant, small volume, large capacity and good stability, and is suitable for being a bypass capacitor. Polystyrene film capacitor, with low dielectric loss, high insulation resistance, but high temperature coefficient, is generally used in high-frequency circuits.

Among all plastic film capacitors, polypropylene (PP) and polystyrene (PS) capacitors have the most remarkable characteristics, but the price of these two capacitors is relatively high. In recent years, in order to improve the quality of sound, most of the audio equipment has used PP capacitors and PS capacitors.

3. Classification by line end mode

Film capacitors are divided into DC film capacitors and AC film capacitors:

(1) DC thin film capacitor refers to the thin film capacitor working in the circuit powered by DC power supply, which is mainly divided into four categories: general type, electromagnetic interference suppression type, pulse type and precision type;

(2) AC thin film capacitor refers to the thin film capacitor working in the circuit powered by AC power supply. It can be divided into motor starting operation, power factor compensation, etc. according to its function.

Application fields of thin film capacitors

Film capacitors are also called plastic film capacitors in living environment. It mainly uses plastic film as the dielectric. Due to the different electrical quality of capacitors, there are many kinds of capacitors. For example, electrolytic capacitor, air capacitor, paper capacitor and film capacitor. In terms of application, we pursue it and have made great contributions to their respective discovery fields. At the same time, it also brings many benefits to people's lives.

It mainly uses metal foil as electrode, and then works through electric energy. Because it has many excellent characteristics, it is an excellent capacitor, like common knowledge characteristics in science and engineering, non-polarity, good insulation resistance, etc. Therefore, many analog circuits will choose it, which is safe and reliable and can reduce the harm to people themselves.

In addition to circuits, film capacitors have many applications, such as electronics, household appliances, telephone, electrical and other industries. Film capacitors are widely used, such as air conditioners, refrigerators, washing machines, fans, power supplies, etc. Film capacitors are also involved in the transportation industry, and we are familiar with the film capacitors in motor cars. Application in power electronic circuits. Thin film capacitor is used here, mainly to buffer and clamp the power current, resonance bypass and suppress the electromagnetic interference of power supply.

When the film capacitor is used as a bypass, it mainly reduces the impedance of the DC bus, absorbs the ripple current of the load, and effectively suppresses the voltage fluctuation of the DC bus caused by the sudden change of the load. When the device is used for resonant converter, it can realize resonance together with inductance.