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This post was last edited by yunrun on 2019-6-28 at 21:29. TVS stands for Transient Voltage Suppressors Devices; from this perspective, common devices such as silicon-based TVS, MOV, GDT, and TSS can all be classified under this category. It is simply because of the differences in materials and protection mechanisms that the industry uses different classification terms, which also helps with differentiation. TVS is designed to effectively suppress very high transient voltages, such as static electricity and surges. It enables these destructive energies to be kept at a certain level, thereby protecting the product. It can be seen, therefore, that the true purpose of TVS is to provide overvoltage protection for products during actual use and testing. Electrostatic discharge testing is essentially an EMC requirement that all instruments and equipment must meet, and it often becomes a major headache for electronic engineers. During regular electrostatic testing, design, and correction processes, many electronic engineers often ask a question: \"By adding TVS diodes to the ports and some sensitive circuits, can I solve the ESD problem?\" ”So I also often explain things to the person asking the question. Why do so many people have similar thoughts? As is known, the items that involve TVS transient voltage suppression diodes in EMC testing are generally ESD, surges, automotive 7637-2, and EFT. For example, when early electronic engineers were trying to solve the problem of ESD, someone recommended TVS to them, saying that it is a device for protecting against static electricity (a static discharge tube). Perhaps that’s how people began to call it: electrostatic tube, or simply ESD (actually, ESD stands for Electrostatic Discharge; it is not a type of device, but rather a testing criterion). Maybe something like this exists: surge tube. So many people who had not been exposed to this information before would think that a device called ESD actually exists; strictly speaking, it doesn’t, but we understand what he is talking about. It seems there’s nothing wrong with it in itself; it’s just that the issue mentioned in the first paragraph might arise. Many people think that TVS transient voltage suppression diodes can solve all problems related to electrostatic discharge testing. The nature of electrostatic discharge interference: What electrostatic discharge testing focuses on is not static electricity itself, but rather the interference experienced by the product during and after an electrostatic discharge event. So, what is studied is the phenomenon of electrostatic discharge. Electrostatic discharge is a phenomenon involving high voltage, high frequency, and strong electromagnetic fields. So, apart from causing the circuit to be damaged by breakdown, it is actually the characteristics of high frequency and strong electromagnetic fields that lead to poor common-mode interference in the product. This interference does not cause damage to the product, but it does lead to various minor issues such as restarts, freezes, and distorted screens. And this kind of interference is actually the most common in everyday life, as direct testing of signal wires rarely occurs (after all, who would expose signal wires to the outside?). These differential common-mode interferences are beyond the capability of TVS. These issues need to be addressed from aspects such as PCB, structure, filtering, shielding, and grounding. In practical applications, for ports such as TF cards and HDMI, TVS protection is provided for each of the signal lines of those ports in the actual design. In fact, when testing the HDMI port, whether it is air discharge or contact discharge, the static current always flows from the metal casing of the port to ground, and does not directly affect the signal lines. Therefore, the HDMI TVS protection shown in the above image is intended to address static electrical interference that may occur on the signal lines in actual use, and it is not meant for testing purposes. The testing for the TF card slot is a bit different, as the card in the TF slot is inserted into the memory card during testing. At this time, during discharge, the static current flows directly from the memory card to the signal pins; at this point we can consider the TVS to be used for testing purposes (since it is indeed subjected to direct impacts at this time). TVS transient voltage suppression diodes are a new type of efficient circuit protection component developed on the basis of the Zener diode technology. Their key advantages lie in their response time on the order of picoseconds and their high capacity to absorb surges. The working principle of TVS transient voltage suppression diodes is very similar to that of conventional Zener diodes; within a certain range, they can limit the voltage across a circuit, keeping the voltage between the two terminals at a safe level. This helps to protect the sensitive components in the circuit from damage caused by high voltages, high currents, or sudden surges. Currently, TVS transient voltage suppression diodes are widely used in household appliances, computer systems, communication equipment, automotive electronics, AC/DC power supplies, electronic ballasts, instruments, medicine, aviation, and other fields. What parameters are needed to select a TVS model? When selecting a TVS transient voltage suppression diode model, it is necessary to identify certain parameters. Changhui Instruments has summarized a few points for reference: ① Maximum operating voltage ； ②Transient voltage ③ Clamping voltage ； ④Leakage current ； ⑤junction capacitance ； ⑥Packaging format: How to determine the quality of TVS transient voltage suppression diodes? When purchasing TVS transient voltage suppression diodes, it is essential to choose reputable, professional, and reliable manufacturers/suppliers in order to minimize risks. Of course, if you are still worried, you can use a multimeter set to the 1k ohm range to check the quality of the TVS transient voltage suppression diode. How to distinguish the positive and negative poles of a TVS transient voltage suppression diode, as well as whether it is unidirectional or bidirectional? When you have a transient voltage suppression diode in your hands, the first thing to know is its positive and negative terminals, as well as whether it is unidirectional or bidirectional. ①Check the TVS transient voltage suppression diode markings. TVS transient voltage suppression diodes come in unidirectional and bidirectional types; unidirectional TVS diodes have a thin colored ring on one end, which is connected to the positive pole ； Bi-directional TVS transient voltage suppression diodes have two rings in the middle or no markings at all, and they have no polarity. ②Check the specification sheet to distinguish between the positive and negative terminals of TVS transient voltage suppression diodes, as well as whether they are unidirectional or bidirectional. ③Check the TVS transient voltage suppression diode model. The model naming of TVS transient voltage suppression diodes follows a pattern, and the parameters of most TVS transient voltage suppression diode models can be identified from their names. ④With the help of a multimeter: there is voltage on one side in unidirectional mode, and avalanche breakdown characteristics occur in the DC regime ； There is voltage in both directions; in terms of DC, it is symmetric in both directions. Changhui Instruments http://yunrun.com.cn/