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, and the current increases in this low resistance region. 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.
TVS (Transient Voltage Suppresser) 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.
The TVS tube, like the voltage regulator tube, is also applied in the reverse direction. Among them, VR is called the maximum turning voltage, which is the critical voltage before reverse breakdown. VB is the breakdown voltage, and its corresponding reverse current IT is generally 1mA. VC is the maximum clamping voltage. When the peak current flowing in the TVS tube is a large current of IPP, the voltage at both ends of the tube no longer rises. Therefore, the TVS tube can always limit the port voltage of the protected device or equipment within the effective range of VB to VC. Different from the voltage regulator tube, the value of IPP can reach hundreds of amperes, and the clamp response time is only 1×10-12s. The maximum allowable pulse power of TVS is PM=VC*IPP, and under a given maximum clamping voltage, the greater the power consumption PM, the greater the surge current tolerance.
The similarities and differences between Zener tube and TVS tube. In the application of electronic systems, the transient interference of voltage and current will often cause damage to electronic equipment. The remarkable feature of transient interference is that the action time is extremely short, but the voltage amplitude is high and the transient energy is large. , So it is very destructive. In order to prevent this damage, TVS tube has been widely used. TVS (Transient Voltage Suppressor) is a high-efficiency circuit protection device developed on the basis of Zener tube technology. Its circuit symbol is the same as that of ordinary Zener diode. , The shape is no different from ordinary diodes. When the two ends of the TVS tube are subjected to instantaneous high-energy impact, it can suddenly reduce its impedance at a very high speed (up to 1*10-12 seconds) and absorb a large current at the same time , The voltage between its two ends is clamped to a predetermined value, so as to ensure that the following circuit components are not damaged by transient high-energy impacts. We can often see TVS diodes as one of the main means of ESD protection in some precision electronic equipment.
As the common point of the two, they can both be used for voltage stabilization, and both work in the reverse cut-off state, and their forward characteristics are the same as ordinary diodes, and the reverse characteristics are typical PN junction avalanche devices. However, the Zener breakdown current of TVS tube is smaller. The voltage regulation of more than 10V is only 1mA. Relatively speaking, the Zener diode breakdown current is much larger, but the Zener diode voltage regulation accuracy can be made relatively high. Moreover, the TVS tube emphasizes the transient response, so its time parameter is very important, that is to say, the response time of the Zener diode is usually slower than that of the TVS tube. At the same time, the power of the TVS tube is larger, and the power of the voltage regulator tube is smaller. Secondly, from a conceptual understanding, the TVS tube is mainly to prevent the effect of instantaneous large voltages, and finally can achieve the purpose of voltage stabilization, which is different from the role of the voltage regulator tube.