The types and main applications of thin film capacitors are described
Thin film capacitor is a kind of capacitor made of metal foil as electrode, which is overlapped with plastic film such as polyethyl ester, polypropylene, polystyrene or polycarbonate from two ends and wound into a cylinder.
Thin film capacitors can be classified by electrolyte, by the arrangement of thin film (medium) and foil (electrode plate), or by wire end, which is detailed below.
The main types of film capacitors
1. Classification by electrolyte
Thin film capacitors can be divided into three types according to the electrolyte:
(1) T-type: PET - Polyethylene(polyethylene p-phthalate (ester));
(2) P type: namely PP-Polypropylene (polypropylene);
(3) Type N: PEN-Polyethylene Naphthalate (PE).
2, according to the type of film classification
According to the type of plastic film, film capacitors can be divided into polyethyl ester capacitors (also known as Mylar capacitors), polypropylene capacitors (also known as PP capacitors), polystyrene capacitors (also known as PS capacitors) and polycarbonate capacitors.
The structure of the film capacitor is the same as that of the paper capacitor. The medium is polyester or polystyrene. Polyester film capacitor has high dielectric constant, small volume, large capacity and good stability, so it is suitable for bypass capacitor. Polystyrene film capacitor, dielectric loss is small, high insulation resistance, but the temperature coefficient is large, generally used in high frequency circuit.
Among all plastic film capacitors, polypropylene (PP) capacitors 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 uses PP capacitors and PS capacitors.
3. Classification by line end
Film capacitors are divided into DC film capacitors and AC film capacitors:
(1) DC film capacitor refers to the film capacitor working in the circuit powered by DC power supply, which is mainly divided into general class, electromagnetic interference suppression class, pulse class and precision class;
(2) AC film capacitor refers to the film capacitor working in the circuit powered by AC power supply, according to the function of motor start-up operation, power factor compensation and so on.
Applications of film capacitors
Film capacitors are also known as plastic film capacitors in the domestic environment. It mainly uses plastic film as dielectric. There are many kinds of capacitors because of their different charge quality. For example, electrolytic capacitors, air capacitors, paper capacitors and film capacitors. In application, we pursued it and made great contributions to our respective fields of discovery. At the same time, it also brings many benefits to people's life.
It mainly uses metal foil as an electrode and then works through electrical energy. Due to its own many excellent characteristics, it is an excellent capacitor, as are common knowledge characteristics in science and engineering, no polarity, good insulation impedance, etc. Therefore, many analog circuits will choose it, safe and reliable, can reduce the harm to people themselves.
In addition to circuits, film capacitors have many uses, such as electronics, home appliances, telephone, electrical and other industries. The use of film capacitors is very wide range, such as air conditioning, refrigerator, washing machine, fan, power supply and so on. Film capacitors are also involved in the transportation industry, we are familiar with the bullet trains also have film capacitors. Applications in power electronic circuits. Thin-film capacitors are used here, mainly to play a buffer and clamp power current, resonant bypass and suppress the electromagnetic interference of the source and so on.
When the thin-film capacitor is used as bypass, it mainly reduces the impedance of the DC bus, absorbs the ripple current of the load, and effectively inhibits the voltage fluctuation of the DC bus caused by the load mutation. When the device is used in a resonant converter, it can achieve resonance with an inductor.
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