2023-03-02
What is a transient suppression diode? What are the selection techniques of transient suppression diodes? What is a transient suppression diode? What are the selection techniques of transient suppression diodes? TVS tube is a high-efficiency protection device, when the two ends are subjected to instantaneous high energy impact, TVS tube can instantly convert its own high resistance characteristics into low resistance characteristics, absorb large current so that the voltage at both ends of the TVS tube clamp on a certain value (TVS tube voltage value), so that the back circuit from the transient high energy impact, protect the circuit safety.
First, the working principle of transient suppression diode
When the circuit is working normally, it is in a cut-off state (high resistance state), which does not affect the normal operation of the line. When the circuit is abnormal overvoltage and reaches its breakdown voltage, it quickly changes from a high resistance state to a low resistance state, providing a low impedance conduction path for the instantaneous current, and clamping the abnormal high voltage within a safe level to protect the protected IC or line. When the abnormal overvoltage disappears, it returns to the high resistance state and the circuit works normally.
Second, the selection of transient suppression diode skills
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, TVS rated reverse turn-off VWM should be greater than or equal to the maximum operating voltage of the protected circuit. If the selected VWM is too low, the device may enter the avalanche or affect the normal operation of the circuit because the reverse leakage current is too large. Serial connection sub-voltage, parallel connection sub-current.
3, the maximum clamping voltage of TVS VC should be less than the damage voltage of the protected circuit.
4, in the specified pulse duration, the maximum peak pulse power of TVS PM must be greater than the peak pulse power that may occur in the protected circuit. After determining the maximum clamping voltage, the peak pulse current should be greater than the transient surge current.
5, for the protection of the data interface circuit, we must also pay attention to the selection of TVS devices with appropriate capacitance C.
6, according to the use of TVS polarity and packaging structure. It is reasonable to choose bipolar TVS for AC circuit. TVS array is more advantageous for multi-line protection.
7, temperature consideration. Transient voltage suppressors can operate between -55 and +150 ° C. If TVS is required to work at a changing temperature, its reverse leakage current ID increases with the increase; The power consumption decreases with the increase of TVS junction temperature, from +25℃ to +175℃, and the rain breakdown voltage VBR decreases linearly by 50% with the increase of temperature according to a certain coefficient. Therefore, it is necessary to consult the relevant product information and consider the impact of temperature changes on its characteristics.
