If we want to understand the working principle and use of TVS tube, we first need to understand what is TVS tube? The name of the TVS tube is Transient Voltage Suppressor, which is also called a transient voltage suppressor in Chinese, or it can also be called an avalanche breakdown diode, which is a semiconductor used to protect electronic equipment from transient overvoltage and current shocks protection device. Its main function is to quickly respond and suppress transient voltages in the circuit to prevent damage to electronic equipment caused by voltage. figure 1Working principle of TVS tube:TVS tubes are usually made of silicon or other semiconductor materials and have nonlinear voltage-current characteristics. Under normal working conditions, the TVS tube is in a high-impedance state, which has little influence on the circuit. When a transient overvoltage occurs in the circuit, the impedance of the TVS tube decreases rapidly, so that the overvoltage passes through the TVS tube instead of sensitive components, thereby protecting electronic equipment from damage. figure 2TVS tube working curveUse of TVS tube:1. Select the appropriate TVS tube: When selecting a TVS tube, the following parameters need to be considered:a. Rated operating voltage: The rated operating voltage of the TVS tube should be slightly higher than the normal operating voltage of the circuit to avoid malfunction.b. Maximum transient voltage: The maximum transient voltage of the TVS tube should be higher than the possible maximum transient voltage to ensure effective suppression of overvoltage.c. Maximum transient current: The maximum transient current of the TVS tube should be higher than the possible maximum transient current to ensure that it can withstand the impact of overcurrent.d. Response time: The response time of the TVS tube should be as short as possible in order to respond quickly and suppress transient voltage.e. Polarity: TVS tubes are divided into two types: unidirectional and bidirectional. Unidirectional TVS tubes can only suppress positive or negative transient voltages and are suitable for unipolar power supply systems; bidirectional TVS tubes can suppress both positive and negative transient voltages and are suitable for bipolar power supply systems.f. Packaging type: TVS tubes have various packaging types, such as SOD, SMA, SMB, etc. Board space and layout requirements, as well as factors such as thermal dissipation and reliability need to be considered when selecting a package type.2. Connect the TVS tube correctly: The TVS tube should be connected in parallel with the protected electronic equipment. The specific connection method is as follows:a. For unidirectional TVS tubes, the positive pole is connected to the positive pole of the power supply, and the negative pole is connected to the negative pole of the power supply.b. For the bidirectional TVS tube, the two ends are connected to the positive and negative poles of the power supply respectively, and there is no need to distinguish the positive and negative poles. figure 33. Pay attention to heat dissipation: TVS tubes will generate heat when suppressing transient voltages, so attention should be paid to heat dissipation. When designing a circuit, the following methods can be considered:a. Select a TVS tube with higher heat resistance.b. Add radiators or fins to improve heat dissipation.c. Make sure the layout of the circuit board is reasonable to avoid heat accumulation.4. Avoid using in series: TVS tubes should not be used in series, because series connection may lead to uneven voltage distribution and affect the protection effect. If necessary, multiple TVS tubes can be used in parallel to improve the protection capability.5. Regular inspection and maintenance: In order to ensure the protective effect of the TVS tube, it is recommended to check the working status of the TVS tube regularly. If there is any damage or aging, it should be replaced in time.In general, when using a TVS tube, it is necessary to select a suitable TVS tube according to the specific application and performance requirements, and ensure proper connection, heat dissipation and maintenance to achieve effective transient voltage protection.
