What are the application characteristics of TVS transient voltage suppression diode principle?
Transient suppression diode (TVS), also known as clamp diode, is a kind of high-efficiency circuit protection device commonly used in the world. Its appearance is the same as that of ordinary diodes, but it can absorb surge power of up to thousands of watts. Its main feature is that under reverse application conditions, when subjected to a large pulse of high energy, its working impedance immediately drops to a very low conduction value, thereby allowing a large current to pass, while clamping the voltage at a predetermined level, its The response time is only 10-12 milliseconds, so it can effectively protect the precision components in electronic circuits. The forward surge current allowed by TVS can reach 50 ～ 200A under TA = 250C and T = 10ms. Bidirectional TVS can absorb instantaneous large pulse power in both forward and reverse directions and clamp the voltage to a predetermined level. Bidirectional TVS is suitable for AC circuits, and unidirectional TVS is generally used for DC circuits. It can be used for anti-lightning, anti-overvoltage, anti-interference, surge power absorption, etc. It is an ideal protection device. Tolerance is expressed in watts (W).
TVS (Transient Voltage Suppression) is a voltage-limiting protection device with a function similar to a varistor. It is also to use the nonlinear characteristics of the device to clamp the overvoltage to a lower voltage value to achieve protection of the subsequent circuit. The main parameters of the TVS tube are: reverse breakdown voltage, maximum clamping voltage, instantaneous power, junction capacitance, response time, etc.
The response time of TVS can reach ps level, which is the fastest among voltage-limiting surge protection devices. When used for overvoltage protection of electronic circuits, its response speed can meet the requirements. The junction capacitance of the TVS tube can be roughly divided into two types according to the manufacturing process. The high junction capacitance TVS is generally in the order of hundreds to thousands of pF, and the low junction capacitance TVS junction capacitance is generally in the range of several pF to tens of The magnitude of pF. Generally, the junction capacitance of discrete TVS is relatively high, and there are two types of surface-mount TVS. In the protection of high-frequency signal lines, TVS tubes with low junction capacitance should be mainly used.
The non-linear characteristics of the TVS tube are better than the varistor. When the overcurrent through the TVS tube increases, the clamping voltage of the TVS tube rises more slowly than the varistor, so it can obtain a more ideal residual voltage output than the varistor . In many electronic circuits that require fine protection, the application of TVS tubes is a better choice. The flow capacity of the TVS tube is the smallest in the voltage-limiting surge protector. It is generally used for the last stage of fine protection. Because of its small flow rate, it is generally not used for the protection of AC power lines and the lightning protection circuit of DC power supplies. When using a TVS tube, it is generally necessary to use it with a device such as a varistor with a large flow capacity. The TVS tube is easy to integrate and is suitable for use on a single board.
Another advantage of TVS is that it can flexibly choose unidirectional or bidirectional protection devices. In unipolar signal circuits and DC power circuits, unidirectional TVS tubes can be used to obtain relatively low residual voltage.
The reverse breakdown voltage and current capacity of the TVS are important considerations in circuit design. In the DC circuit, there should be: min (UBR) ≥ (1.3 ~ 1.6) Umax, where UBR is the reverse breakdown voltage of the DC TVS, Umax is the peak voltage in the DC circuit.
TVS tube is mainly used for lightning protection of DC power supply, signal line and antenna feeder line.
The failure mode of TVS tube is mainly short circuit. However, when the overcurrent passed is too large, it may also cause the TVS tube to burst and open. The service life of TVS tubes is relatively long.
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