A capacitor is an electronic component that stores electrical charge and releases it when needed. It consists of two conductive plates separated by an insulating material called the dielectric. When the two plates of a capacitor are connected to the positive and negative poles of a power source, charges will accumulate on the plates, forming an electric field, thereby storing electrical energy, just like a container that can store charges. The size of the capacitor depends on the area of the plates, the distance between the plates, and the properties of the insulating medium. Capacitors are common components in switching power supplies. They can be used to reduce ripple noise and improve the stability and transient response of power supplies. However, there are many types of capacitors. How can we quickly select capacitors with high reliability and stable performance?
Knowledge of capacitor types
A general understanding of capacitor types will help you quickly screen the capacitor types when selecting capacitors. There are many types of capacitors. According to the package, there are chip capacitors and plug-in capacitors. According to the dielectric, there are ceramic capacitors, electrolytic capacitors, mica capacitors, etc. According to the structural form, there are fixed capacitors, semi-fixed capacitors, and variable capacitors. In switching power supplies, we use ceramic capacitors, electrolytic capacitors and tantalum capacitors the most.
The selection of capacitors in switching power supplies requires understanding of the characteristics of the capacitors themselves
Ceramic capacitors have smaller capacitance, good high-frequency characteristics, a wider operating temperature range, smaller ESR than electrolytic capacitors, smaller size.
Electrolytic capacitors can have larger capacitance, but have a narrower operating temperature range, larger ESR, and have polarity.
Tantalum capacitors have the smallest ESR, and can have a larger capacitance than ceramic capacitors, have polarity, poor safety performance, and are prone to fire.
After understanding the characteristics of the above three types of capacitors, you can use them with ease
The selection of capacitors in switching power supplies also requires understanding of the operating environment
The operating environment of capacitors is divided into internal circuit environment and external circuit environment. The internal circuit environment includes frequency, voltage value, current value, the main function of capacitor in the circuit, etc.; the type of capacitor can be determined according to the circuit frequency; the withstand voltage value of the selected capacitor can be determined according to the voltage value; the main function in the circuit can be used as a reference for the capacitance value of the selected capacitor, etc.; the capacitor can be selected according to the external circuit usage environment, the ambient temperature of the product, safety requirements, etc., which can be used to narrow the range of capacitor selection.
