A capacitor is a chargeable component. The most basic function in the circuit is to communicate AC and DC, but the capacitor is one of the most common electronic components in a PCBA motherboard. Capacitors have many uses.

  1. Energy storage

The capacitor can store electrical energy in the charging circuit and can therefore be used like a temporary battery. Capacitors are commonly used in electronic devices to maintain power during battery replacement. Helps prevent loss of information in volatile memory.

In car audio systems, the energy of a large-capacity storage amplifier is used on demand. Also for flash tubes, capacitors can be used to maintain high voltages.

2, digital memory

In the 1930s, John Atanasoff applied the energy storage principle to capacitors to build dynamic digital memories for the first binary computer using tube logic.

3, pulse power and weapons

A large, specially constructed low-inductance, high-voltage capacitor (capacitor bank) can be used to provide large current pulses in many pulsed power applications. These include electromagnetic forming, marx engines, pulsed lasers (especially TEA lasers), pulse forming networks, radar, fusion studies and particle accelerators.

Large capacitor banks (reservoirs) are used as an energy source for explosive bridge detonators or detonators in nuclear weapons and other specialized weapons.

4, power regulation

Battery capacitors are used for power supplies, which smooth the output of full-wave or half-wave rectifiers. They can also be used as energy storage elements in charge pump circuits to generate higher voltages than the input voltage. Capacitors are connected in parallel with most electronic equipment and power circuits of larger systems such as factories to shunt and filter current fluctuations from the mains to provide a “clean” power to the signal or control circuitry.

In power distribution, capacitors are used for power factor correction. Such capacitors are typically used as three capacitors connected by a three-phase load. Typically, the values ​​of these capacitors are not in Farads but in reactive power expressed in volt-amps (var). The goal is to counteract the inductive loads of devices such as motors and transmission lines, making the load appear to be mostly resistive. Individual motor power factor corrected capacitors can be installed in the load center of a large utility substation.

5, suppression and coupling

(1) Signal coupling

Since capacitors block DC signals by alternating current, they are typically used to separate the AC and DC components of the signal. This method is called AC coupling or “capacitive coupling.”

(2) Decoupling

A decoupling capacitor is a capacitor used to protect a portion of a circuit from another circuit, such as suppressing noise or transients. Noise caused by other circuit components is shunted through the capacitor, reducing the effects on the rest of the circuit.

(3) Noise suppression, spikes and buffers

When the sensing circuit is turned on, the current through the inductor collapses rapidly, creating a large voltage on the open circuit of the switch or relay. If the inductance is large enough, energy can spark, causing the contact to oxidize. The snubber capacitor on the newly opened circuit creates a path for this pulse to bypass the contact point, thus maintaining its lifetime. Buffer capacitors are typically used with low resistance in series to dissipate energy and minimize RFI. This resistor and capacitor combination can be used in a single package.

6, motor starter

In a single phase squirrel cage motor, the primary winding within the motor housing cannot initiate a rotational motion on the rotor, but can maintain rotor motion. To start the motor, the secondary “start” winding has a series of non-polarized starting capacitors to introduce leads in the sinusoidal current. A rotating electric field is generated when the secondary winding is placed at an angle relative to the primary (winding) winding.

7, signal processing

The energy stored in the capacitor can be used to represent information in binary form, such as in DRAM, or in analog form, such as information in analog sampling filters and CCDs. Capacitors can be used as analog components as components of the integrator, or more complex filters and negative feedback loops. The signal processing circuit can also use capacitors to integrate the current signal.

8, sensing

Most capacitors are designed to maintain a fixed physical structure. However, various factors will change the structure of the capacitor, and the resulting change in capacitance can be used to sense these factors.

9, the oscillator

The capacitor can have spring-like characteristics in the oscillator circuit. In the image example, the capacitor can affect the bias voltage at the base of the npn transistor. The resistance value of the voltage dividing resistor and the capacitance value of the capacitor together control the oscillation frequency.

10, luminous

The light emitting capacitor is made of a dielectric that uses phosphorescence to generate light. If the conductive plate is made of a transparent material, visible light. Light-emitting capacitors are used in the construction of electroluminescent panels and can be used in applications such as backlighting of laptop computers. In this case, the entire panel is a capacitor for generating light.

Capacitors can play a huge role in addition to their own characteristics, and can be combined with other components such as resistors to play a huge role in the circuit.

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