How to distinguish TVS from other diodes? 7 tips to pay attention to when choosing

How to distinguish TVS from other diodes? 7 tips to pay attention to when choosing

Transient interference of voltage and current is the main cause of damage to electronic circuits and equipment, often causing incalculable losses to people. These interferences usually come from the start stop operation of power equipment, instability of AC power grid, lightning interference, and electrostatic discharge. Transient interference is almost ubiquitous and always present, making people feel that it is difficult to prevent. Fortunately, the emergence of a high-performance circuit protection device TVS has effectively suppressed transient interference.

How to distinguish TVS from other diodes?

Transient Voltage Suppressor (TVS), abbreviated as TVS, is a high-performance protective device in the form of a diode.

Transient interference of voltage and current is the main cause of damage to electronic circuits and equipment, often causing incalculable losses to people. These interferences usually come from the start stop operations of power equipment, instability of AC power grids, lightning strikes, and electrostatic discharge. Transient interference is almost everywhere and always present, making people feel that it is difficult to prevent. Fortunately, the emergence of a high-performance circuit protection device TVS has effectively suppressed transient interference. TVS (Transient Voltage Suppressor), also known as Transient Suppressor Diode, is a new product developed on the basis of the voltage regulator process. Its circuit symbol is the same as that of a regular voltage regulator diode, and its appearance is no different from that of a regular diode. When the two ends of the TVS diode are subjected to instantaneous high-energy impact, it can rapidly reduce its impedance (up to 1/(10 ^ 12) second), absorb a large current, clamp the voltage between its two ends at a predetermined value, and ensure that the subsequent circuit components are not damaged by transient high-energy impact. If used, TVS has diode type and varistor type. I personally think that varistors have more advantages and are widely used in mobile phones, LCD modules, and some more precise handheld devices. Especially for products exported to Europe, they are generally added as one of the main means of electrostatic protection.

TVS and Zener voltage regulators can both be used for voltage regulation, but the Zener breakdown current is smaller, with only 1mA for voltage regulation greater than 10V, which is relatively larger than the breakdown current of Zener diodes. However, Zener diodes can achieve higher voltage regulation accuracy.

In a circuit, it generally operates in a reverse cutoff state, which does not affect any function of the circuit. Under the specified reverse application conditions, when there is a significant transient interference voltage or pulse current in the circuit due to lightning or various electrical interferences, TVS quickly switches to reverse conduction state in a very short time (up to 1 × 10-12 seconds) and clamps the voltage of the circuit at the required safe value, effectively protecting precision components in electronic circuits from damage. After the interference pulse passes, TVS enters the reverse cutoff state again. Due to its clamping voltage being lower than the maximum withstand voltage of other components in the circuit during reverse conduction, it plays a protective role for other components. The instantaneous pulse power that TVS can withstand can reach over kilowatts, with a clamping time of<1ns [1]. TVS can be divided into unidirectional and bidirectional TVS based on polarity. Unidirectional TVS is generally suitable for DC circuits, while bidirectional TVS is generally suitable for AC circuits. Due to its rapid action, long lifespan, and convenient use, TVS has a wide range of applications in the field of transient voltage protection.

Selection Techniques for TVS

(1) Determine the maximum DC or continuous operating voltage of the protected circuit, the rated standard voltage of the circuit, and the "high end" tolerance.

(2) The rated reverse turn off VWM of TVS should be greater than or equal to the maximum operating voltage of the protected circuit. If the VWM selected is too low, the device may enter avalanche or the normal operation of the circuit may be affected by excessive reverse leakage current. Series voltage divider, parallel current divider.

(3) The maximum clamping voltage VC of TVS should be less than the damage voltage of the protected circuit.

(4) Within the specified pulse duration, the maximum peak pulse power consumption PM of TVS must be greater than the peak pulse power that may occur in the protected circuit. After determining the maximum clamping voltage, its peak pulse current should be greater than the transient surge current.

(5) In order to protect the data interface circuit, it is also necessary to pay attention to selecting suitable TVS devices with capacitor C.

(6) Select the polarity and packaging structure of TVS according to the application. It is more reasonable to use bipolar TVS in the communication circuit; Using TVS arrays for multi line protection is more advantageous.

(7) Temperature considerations. The transient voltage suppressor can operate between -55 ℃ and+150 ℃. If TVS needs to operate at varying temperatures, as its reverse leakage current ID increases with an increase; The power consumption decreases linearly with the increase of TVS junction temperature, from+25 ° C to+175 ° C, by approximately 50%. As the temperature increases, the voltage VBR increases by a certain coefficient.

Therefore, it is necessary to consult relevant product information and consider the impact of temperature changes on its characteristics. The best way to deal with damage to components caused by transient pulses is to divert transient currents from inductive components. The TVS diode is connected in parallel with the protected circuit on the circuit board. When the instantaneous voltage exceeds the normal operating voltage of the circuit, the TVS diode generates an avalanche, providing an ultra-low resistance path for the instantaneous current.

As a result, instantaneous current is drawn through the diode. Avoid the protected components and keep the protected circuit at the cut-off voltage until the voltage returns to normal. When the instantaneous pulse ends, the TVS diode automatically returns to a high resistance state, and the entire circuit enters normal voltage. After multiple impacts, the parameters and performance of many components will decrease. As long as they operate within a limited range, the diode will not be damaged or degraded.