What are the common protection components in the circuit, and what do these components protect respectively?

In circuit protection, the commonly used protection components are: TVS diode, ESD electrostatic protection diode, ceramic gas discharge tube, glass discharge tube, self-recovery fuse, semiconductor discharge tube, varistor and so on.

Transient TVS suppression diode

TVS diode is a transient suppressor, which is widely used in the protection of semiconductors and sensitive devices. It is usually used for secondary protection, secondary protection behind ceramic gas discharge tubes and direct primary protection of products. Its characteristics are fast reaction speed (ps level), small volume, high pulse power and low clamping voltage. The pulse power of 10/ 1000μs wave ranges from 200 W to 30 kW, the pulse peak current ranges from 0.52A to 544A, and the breakdown voltage ranges from 6.8V to 550 V, which is convenient for various circuits with different voltages.

voltage dependent resistor

The response time of varistor is ns, which is faster than air discharge tube and slightly slower than TVS tube. It is generally used for overvoltage protection of electronic circuits. The junction capacitance of varistor is generally in the order of hundreds to thousands of pf, which is not suitable for direct protection of high frequency signal lines. When it is used for AC circuit protection, due to the large junction capacitance, it needs to be fully considered when designing the protection circuit. The current capacity of varistor is larger, but smaller than that of gas discharge tube. Patch varistor is mainly used to protect components and circuits from ESD generated by power supply, control and signal lines.

Ceramic gas discharge tube

Ceramic gas discharge tube is the most widely used lightning protection device, which can protect both DC power supply and various signals. Its biggest characteristics are large flux, small interstage capacitance, high insulation resistance and wide optional range of breakdown voltage.

Semiconductor discharge tube

Semiconductor discharge tube is an overvoltage protection device, which is made by using the principle of thyristor. Depending on the breakdown current of PN junction to trigger the device to conduct and discharge, excessive surge current or pulse current can flow. The range of its breakdown voltage constitutes the range of overvoltage protection. When in use, the solid discharge tube can be directly connected across the two ends of the protected circuit. It has the characteristics of accurate conduction, fast response speed (response time ns level), strong surge absorption ability, bidirectional symmetry and high reliability.

Glass discharge tube

Glass discharge tube (high-power discharge tube and lightning protection tube) is a new type of lightning protection device introduced at the end of the 20th century. It has the advantages of ceramic gas discharge tube and semiconductor overvoltage protector: high insulation resistance (≥108 Ω), small interelectrode capacitance (≤0.8pF), large discharge current (up to 3 kA), bidirectional symmetry and fast response (no impact breakdown lag phenomenon). Its disadvantage is that the DC breakdown voltage is dispersed (20%).

Resettable fuse

Self-healing fuse PPTC is a kind of overcurrent electronic protection element, which is made of high molecular organic polymer under high pressure, high temperature and vulcanization reaction conditions, and then doped with conductive particle materials, and processed by special technology. When the circuit works normally, its resistance is very small (voltage drop is very small). When the temperature in the circuit rises due to overcurrent, the resistance increases by several orders of magnitude, which reduces the current in the circuit to below the safe value, thus protecting the subsequent circuit and automatically returning to low resistance after overcurrent disappears.

ESD electrostatic discharge diode

ESD diode is an overvoltage and antistatic protection device, which is designed for I/O port protection in high-speed data transmission applications. Electrostatic discharge diode (ESD) is used to prevent sensitive circuits in electronic equipment from being affected by ESD. It can provide extremely low capacitance, excellent transmission line pulse (TLP) test and IEC6 100-4-2 test capability, especially after the number of multiple sampling is as high as 1000, thus improving the protection of sensitive electronic components.

Circuit protection device