What is Electrolytic Capacitor and Why It's Essential in Your Electronics?

The article introduces capacitors, vital electronic components composed of conductor plates separated by a dielectric layer. Emphasizing their importance in various functions like energy storage and filtering, it details their structure, types (electrolytic, ceramic, tantalum, film, and supercapacitors), and capacitance principles. The significance of adhering to rated voltage specifications for s

 

**I. Introduction**

A. Definition of Capacitors

Capacitors are electronic components composed of two conductor plates separated by a layer of insulating material, also known as a dielectric. There are thousands of capacitors in a single vehicle. Capacitors are electronic components consisting of two conductive plates sandwiching an insulating layer.

Capacitors, as one of the three basic components, primarily function in energy storage, filtering, DC isolation, bypassing, coupling, rectification, tuning, and energy conversion. When a voltage is applied across the terminals of a capacitor, an electric field is formed within the dielectric, storing charges. The capacitance of a capacitor depends on the dielectric constant of the dielectric, the area of the capacitor plates, and the distance between the plates.

B. Importance of Capacitors in Electronic Circuits

Why are capacitors essential?

Capacitors possess various characteristics, such as:

- They can store energy and dissipate it into the circuit when needed.

- They can block DC while allowing AC to pass, coupling one part of the circuit to another.

- Circuits with capacitors depend on frequency, thus can be used to amplify certain frequencies.

- Capacitors lead current ahead of voltage in AC applications, increasing effective load power and making it more economical in power supply applications.

- They permit high frequencies, hence can be used as filters to remove low frequencies or collect high frequencies.

Capacitors exhibit many properties when used in AC or DC circuits, thus playing a significant role in electrical and electronic circuits.

 

**II. Understanding Capacitors**

A. Basic Components and Structure

Capacitors are components that store charge and electrical energy (potential energy). The basic structure of a capacitor consists of two electrodes (metal plates) placed at a distance. When a DC voltage (V) is applied to the two electrodes, electrons gather momentarily on one electrode, making it negatively charged, while the other electrode is in a state of electron deficiency, making it positively charged.

This state persists even after the DC voltage is removed. That is, charge (Q) accumulates between the two electrodes. By inserting a dielectric (ceramic, plastic film, etc.) between the electrodes, the accumulated charge increases through polarization of the dielectric. The measure indicating how much charge a capacitor can store is called capacitance (C).

 

B. Types of Capacitors

1. Electrolytic Capacitors

electrolytic capacitor are polarized capacitors, and their polarity is crucial, requiring correct connection for proper operation.

They are commonly used in DC circuits, such as power supply filtering capacitors.

2. Ceramic Capacitors

Ceramic capacitors are non-polarized capacitors. Their dielectric is a ceramic material, and while they have relatively small capacitance, they exhibit good frequency response. Ceramic capacitors are often used in low-frequency circuits, such as coupling capacitors in filtering circuits.

3. Tantalum Capacitors

Key features: Lower loss, leakage compared to aluminum electrolytic capacitors. Applications: Substituting aluminum electrolytic capacitors in circuits with high demands. The anode is made of tantalum, the small yellow or black grains seen on graphics cards.

4. Film Capacitors

Structured similarly to paper dielectric capacitors, the dielectric is made of polyester or polystyrene. Polyester film capacitors have a high dielectric constant, small size, large capacity, and good stability, suitable for bypass capacitors. Polystyrene film capacitors have low dielectric loss and high insulation resistance but a large temperature coefficient, suitable for high-frequency circuits.

5. Supercapacitors

Supercapacitors are a new type of energy storage device between traditional capacitors and rechargeable batteries. Their capacity can range from several hundred to thousands of farads. Compared to traditional capacitors, they have larger capacity, energy or power density, a wider operating temperature range, and a much longer service life. Compared to batteries, they have higher power density and are environmentally friendly.

 

C. Capacitance and Rated Voltage

1. Capacitance: As shown in Figure 4-2. when the charge on the capacitor plate increases or decreases, the voltage between the two plates also increases or decreases, but the ratio of Q to U is a constant, different for different capacitors.

Capacitance is a measure of the ability of a capacitor to store charge, and it depends only on the properties of the capacitor itself, not on the charge it carries or the voltage between the capacitor plates.

2. Rated Voltage: The rated operating voltage of a capacitor typically refers to the DC voltage and is the maximum "safe voltage" applied to the capacitor. Capacitors exceeding the rated voltage are prone to breakdown, heating, and cracking; therefore, it is recommended to use a working voltage 1.5 to 2 times the rated voltage.

Typical capacitor rated voltages include: 6.3V, 10V, 16V, 25V, 35V, 50V, 63V, 100V, 160V, 250V, 400V, 450V, 500V, 630V, 1000V, 1200V, 1500V, 1600V, 1800V, 2000V, etc.