TVS diodes, also known as Transient Voltage Suppressors diodes, are a new class of high-efficiency circuit protection devices that have extremely fast response times (sub-nanoseconds) and high surge absorption. When its two ends are a high-energy Impact, the TVS can change the impedance between the two ends from high impedance to the low impedance at a very high speed to absorb a large instantaneous current and clamp the voltage across it. A predetermined value protects the subsequent circuit components from transient high voltage spikes.

TVS diode classification and features:
TVS diode classification:
TVS devices can be divided into unipolar and bipolar according to their polarities. According to their applications, they can be divided into general-purpose devices and special-purpose devices suitable for various circuits. Such as a variety of AC voltage protectors, 4 ~ 200mA Current environmental protection, data line protectors, coaxial cable protectors, telephone protectors. According to the package and internal structure can be divided into the axial lead diode, dual in-line TVS array (for multi-line protection), patch, component and high -power modular.
TVS diode features:
(1) Adding the TVS diode to the signal and power line can prevent the microprocessor or the microcontroller from malfunctioning due to the instantaneous fat impulse, such as the electrostatic discharge effect, the surge of the AC power supply, and the noise of the switching Power supply.
(2) The electrostatic discharge effect can release pulses exceeding 10000V and above 60A, and can last for 10ms; while the general TTL device will cause damage when it encounters a 10V pulse of more than 30ms. With the TVS diode, it can The pulse that will cause damage to the device and eliminate the interference caused by the switch between the buses (Crosstalk).
(3) Place the TVS diode between the signal line and the ground to avoid unnecessary noise from the data and control bus.



Does TVS diode have positive and negative poles? TVS diode positive and negative poles distinguishing method
Four applications for TVS diodes:
(1) Application of TVS diode in TN power system
Overvoltages caused by human error such as lightning overvoltage waves, load switches, etc., easily invade the inside of electrical and electronic equipment through the power supply line, causing failure or malfunction of the electrical and electronic equipment, and even cause permanent damage to the Two-stage protection is implemented by installing surge absorbers MOV and TVS on the power line, and common mode and differential mode protection are applied to the L and N lines. The specific method is to install MOV as the First-stage SPD protection at the front end of the line, to amplify part of the lightning current, and install a high-power TVS diode at the end of the line (the front end of the device) as the second-stage SPD protection, further weakening the over-voltage amplitude. Reduce the grid voltage to within the E/I safe withstand voltage range.
It should be noted that MOV and TVS should achieve voltage and energy coordination and coordination. The line length between AB should not be less than 5 M. Otherwise, the line length should be increased or decoupling devices should be installed.
( 2) Application of TVS diodes in network signal lines
The gas discharge tube GDT and TVS diodes are combined into a signal surge protector, which is characterized by fast response and small leakage. Almost no loss to the signal, it provides safe and reliable protection for high-speed network lines.
(3) Application of TVS diode in the DC power system
The power supply circuit of a common PC computer, the mains AC 220 V is stepped down to AC 20 V through the transformer, and then modulated and rectifier circuit, output DC 10 V DC power supply, and connected to the load. The bidirectional transient voltage suppressor TVS1 at the output of the transformer, the instantaneous impulse current of the L and N lines is absorbed, and the circuit voltage is clamped at a safe voltage level. The TVS1 can protect the transformer back-end rectifier and another circuit A unidirectional transient voltage suppressor TVS2 is installed at the DC power output of the rectifier to protect the DC load from overvoltage current surges.
(4) Application of TVS diode in a transistor circuit
As a current-controlled device, the transistor is an important part of electronic integrated circuits. It can be divided into NPN diode and PNP diode [5], which are used in switching circuits, amplifier circuits, and voltage regulator circuits.


Does the TVS diode have positive and negative poles? TVS diode positive and negative polarity differentiation method
The unidirectional TVS diode has the difference between positive and negative electrodes. The method of use is consistent with the method of the voltage regulator diode. The bidirectional TVS has no difference between positive and negative electrodes. The unidirectional TVS is similar to the ordinary diode when tested. It is also a single-pass, and the forward voltage is about 0.6V. When the direction is low, it is infinite. When the avalanche voltage is exceeded, the bidirectional TVS is equivalent to two identical characteristics. Composite to TVS, an ordinary meter test is not conductive. The following is the difference between the ratio of unidirectional TVS and bidirectional TVS:


First, use a multimeter to measure
Measuring the gear position of the diode, the unidirectional only one-way through, the bidirectional two sides have voltage;
DC measurement, two-way symmetry, the unidirectional only reverse is the avalanche breakdown characteristics, generally measured at 1 mA.
All TVS diodes will have a root cathode line after amplification, which is used to distinguish the positive and negative poles of the diode, regardless of the single bidirectional.

Second, the difference between unidirectional/bidirectional use
1. The unidirectional use in DC. The bidirectonal use in communication;
2. The TVS dopde has unidirectional and bidirectonal points. The characteristics of the unidirectional TVS diode are similar to those of the Zener diode. The characteristics of the bidirectonal TVS diode are equivalent to the reverse connection of two Zener diodes.
3. The inter-electrode capacitance Cj of the unidirection is larger than the bidirectional . Taking the LRC as an example, the unidirectional capacitor C has 65 PF, and the bidirectional has only 15 PF;
4. All the USB data line use Both sides;
5. The current curve is different. The circuit symbol of the unidirectional TVS diode is the same as that of the ordinary Zener diode. The voltage-current characteristic curve is shown in Figure 3. The forward characteristic is the same as that of the ordinary diode. The reverse characteristic is a typical PN junction avalanche device. Both forward and reverse are typical PN junction avalanche devices.


In the selection of TVS diodes, professional engineers are still required to guide them. After the analysis of the parameter fields, the targeted selection is safer.