TVs full name: transient voltage suppression diode — SUNMATE

TVs is called transient voltage suppressors devices. From this point of view, the commonly used silicon-based TVs, MOV, GDT and TSS devices can be classified into this category. However, due to the different materials and protection mechanism, the industry will have different classification names, which is also convenient to distinguish. TVs is designed to effectively suppress those very high transient voltages, such as static electricity and surge. It can limit these destructive energy to a certain level, so as to protect the product. Therefore, it can be seen that the real meaning of TVs is to protect the product from overvoltage during actual use and test.

Electrostatic discharge test is basically an EMC project that all instruments and meters need to pass, and it often becomes a headache for electronic engineers. In the process of ordinary electrostatic test, design and rectification, many electronic engineers often ask the question "can I solve the ESD problem by designing the port and some sensitive lines on TVs?" So I often explain to the questioner.

Why do many people have such similar ideas. As we all know, the items that TVS transient voltage suppression diode will be used in EMC test are generally ESD, surge, automobile 7637-2 and EFT. For example, when early electronic engineers solved the problem of ESD, someone recommended TVs to them, saying it was an anti-static device (electrostatic tube). Maybe that's how people began to call it: electrostatic tube, and directly called ESD (in fact, ESD is not a device, but a test item). Maybe something like this: surge tube. Therefore, many people who have not been exposed to this information before will think that ESD is really a device. Strictly speaking, it is not, but we know what he is talking about. There seems to be nothing in itself, but there may be a problem in the first paragraph. Many people will think that TVS transient voltage suppression diode is to solve all the problems of electrostatic discharge test.

Essence of electrostatic discharge interference

Electrostatic discharge test items are not concerned with static electricity itself, but the interference of products during and after electrostatic discharge. Therefore, the phenomenon of electrostatic discharge is studied. Electrostatic discharge is a phenomenon of high voltage, high frequency and strong electromagnetic field. Therefore, in addition to the breakdown and damage of the circuit, it is actually more the differential common mode interference of the characteristics of high frequency and strong electromagnetic field to the product. This interference will not cause damage to the product, but it will cause a lot of soft interference, such as restart, jamming, flower screen, etc. However, this kind of interference is the most encountered in daily life. After all, there are few cases of directly testing the signal line (because who will expose the signal line to the outside). These differential common mode interferences are beyond the power of TVs. These problems need to be solved from the aspects of PCB, structure, filtering, shielding, grounding and so on.

Actual case

Similar to TF card and HDMI, these ports will carry out TVs protection for each signal line of the port in the actual design. In fact, when testing the HDMI port, whether it is air discharge or contact discharge, the electrostatic flow must reach the ground through the metal shell of the port, which will not directly impact the signal line. Therefore, the TVS protection of HDMI in the figure above is to solve the electrostatic interference that may appear on the signal line in practical use, not for testing. There are some differences in the test of TF card holder, because the TF card holder is inserted into the memory card during the test. At this time, when discharging, the static current will be directly to the signal pin through the memory card. At this time, we can think that TVS is for testing (because it is really under direct impact at this time).

TVs transient voltage suppression diode is a new high-efficiency circuit protection component invented on the basis of Zener diode technology. The response time of p-second level and high surge absorption capacity are the core advantages of TVs transient voltage suppression diode. The working principle of TVs transient voltage suppression diode is very similar to that of common zener diodes. Within a certain range, it can limit the voltage at both ends of the circuit and stabilize the voltage clamping between the two poles at a safe value, so as to effectively protect the precision elements in the circuit from high voltage, high current and high surge. At present, TVs transient voltage suppression diodes are widely used in household appliances, computer systems, communication equipment, automotive electronics, AC / DC power supplies, electronic ballasts, instruments and meters, medicine, aviation and so on.

① Look at the TVS transient voltage suppression diode flag. TVs transient voltage suppression diode can be divided into unidirectional and bidirectional. One end of unidirectional TVs transient voltage suppression diode has a fine color ring and is connected to the positive electrode; There are two rings in the middle of the bidirectional TVs transient voltage suppression diode, or there is no sign and no polarity.

② See the specification to distinguish the positive and negative poles of TVs transient voltage suppression diode and the single and bidirectional poles of TVs transient voltage suppression diode.

③ See TVs transient voltage suppression diode model. The model name of TVs transient voltage suppression diode is regular, and the parameters can be seen in most TVs transient voltage suppression diode models.

④ With the help of multimeter tools: there is voltage on one side and avalanche breakdown characteristics on the DC side; There is voltage in both directions. In terms of DC, it is symmetrical in both directions.