In the field of circuit protection, which types of products are currently mainstream products? do you know? If you don’t know, let’s follow our Ruilongyuan Electronics engineers to give everyone a popular science!
1. TVS tube
TVS tube (TransientVoltageSuppresser transient voltage suppressor) is a new type of high-efficiency circuit protection device commonly used, it has extremely fast response time (sub-nanosecond level) and quite high surge absorption capacity. When its two ends are subjected to an instantaneous high-energy impact, the TVS can change the impedance between the two ends from high impedance to low impedance at a very high speed, so as to absorb an instantaneous large current, thereby clamping the voltage at both ends of it. At a predetermined value, so as to protect the following circuit components from the impact of transient high-voltage spikes. Because of this, TVS can be used to protect equipment or circuits from static electricity, transient voltages generated by inductive load switching, and overvoltages generated by induced lightning.
TVS tube is the abbreviation of Transient Voltage Suppressor. Its characteristics are: extremely fast response speed (ps level); surge resistance is worse than discharge tubes and varistors, its 10/1000μs wave pulse power is from 400W to 30KW, and the pulse peak current is from 0.52A to 544A; The breakdown voltage has a series of values from 6.8V to 550V, which is convenient for circuits with different voltages.
TVS tube is divided into one-way and two-way (the letter behind the one-way model is "A", and the two-way one is "CA"). When the characteristics of the one-way TVS tube and the Zener diode TVS tube are used, they are generally connected in parallel to be protected On the circuit. In order to limit the current flowing through the TVS tube not to exceed the peak current IPP allowed by the tube, current-limiting components, such as resistors, resettable fuses, and inductors, should be connected in series on the line. Similarly, the characteristics of the bidirectional TVS tube is equivalent to two zener diodes connected in reverse series.
2. Varistor
Varistor is a voltage-limiting protection device. Using the non-linear characteristics of the varistor, when an overvoltage appears between the two poles of the varistor, the varistor can clamp the voltage to a relatively fixed voltage value, thereby realizing the protection of the subsequent circuit. The main parameters of varistor are: varistor voltage, current capacity, junction capacitance, response time, etc.
The response time of the varistor is ns, which is faster than the air discharge tube and slightly slower than the TVS tube. Under normal circumstances, the response speed of the overvoltage protection for electronic circuits can meet the requirements.
Varistors are mainly used for DC power supplies, AC power supplies, low-frequency signal lines, and antenna feeder lines with feeders.
The failure mode of the varistor is mainly a short circuit. When the passing overcurrent is too large, it may also cause the valve plate to burst and open the circuit. Varistor has a short service life, and its performance will decrease after repeated shocks. Therefore, the lightning arrester composed of varistor has maintenance and replacement problems after long-term use.
Three, Zener diode
Zener diode (also called Zener diode) is a semiconductor device with high resistance until the critical reverse breakdown voltage. At this critical breakdown point, the reverse resistance is reduced to a very small value. In this low resistance region, the current increases while the voltage remains constant. Zener diodes are classified according to breakdown voltage. Because of this characteristic, Zener diodes are mainly used as regulators or voltage reference components. Zener diodes can be connected in series for use at higher voltages, and more stable voltages can be obtained by connecting them in series.
Four, self-recovery fuse
Self-recovery fuse is a kind of over-current electronic protection component. Self-recovery fuse is made of high-tech polymer resin and nano-conductive crystal particles through special processing. Under normal circumstances, nano-conductive crystals are linked with the resin base to form a chain-shaped conductive path. The fuse works normally; when the circuit is short-circuited or overloaded, the large current flowing through the fuse increases the temperature. When it reaches the Curie temperature, its density of states decreases rapidly, the phase change increases, and the internal conductive link becomes When the avalanche state changes or breaks, the fuse transitions to a high resistance state in a stepwise manner, and the current is quickly pinched off, thereby quickly and accurately limiting and protecting the circuit. Its tiny current keeps the fuse in a protective state. After the fault is eliminated, the concentration temperature is reduced, the density of states is increased, the phase change is restored, the nanocrystals are reduced to a chain-like conductive path, and the self-recovery fuse returns to the normal state without manual replacement.
For more knowledge about electronic circuit protection, please follow the official website of Ruilongyuan Electronics: www.ruilon.com
