Publish:SHENZHEN ENXIC ELECTRONICS CO., LTD,Schottky diodes, rectifier diodes, fast recovery diodes, switching transistors, thermistors, MOS tube, TVS tube, Youze Electronics Time:2017-11-04 Views:2217
TVS or transient voltage suppression diode is a new product developed on the basis of the voltage regulator technology. Its circuit symbol is the same as ordinary voltage diode, and its shape is not the same as ordinary diode. When the two ends of the TVS tube are subjected to instantaneous high energy shock, it can make its impedance abruptly at a very high speed (up to 1*10^-12 seconds). At the same time, a large current is absorbed and the voltage between the two ends of the two ends is clamped on a predetermined value to ensure that the circuit elements behind the circuit are not damaged by the transient high energy impact.
Therefore, the precise components in electronic circuits can be effectively protected. It has many advantages, such as fast response time, high transient power, low leakage current, small breakdown voltage, easy control of clamping voltage, high damage limit and small volume.
In practical application circuits, the best way to deal with the damage of instantaneous pulses to devices is to remove transient currents from sensitive devices. To achieve this goal, the TVS diode is connected to the protected device on PCB. In this way, when the instantaneous voltage exceeds the normal operating voltage of the circuit, the TVS diode will have an avalanche breakdown, which provides an ultra low impedance path to the instantaneous current, and the result is that the instantaneous current is opened through the TVS diode to avoid the protected device, and the protected circuit is kept until the voltage is restored to the normal value. After holding the cut-off voltage, after that, the TVS diode is automatically restored to the high resistance state when the instantaneous pulse ends, and the whole circuit goes into the normal voltage state. The following are some typical examples of TVS diodes in circuit applications.
Application of TVS diode in AC circuit
Unidirectional TVS diode parallel rectifier side, in order to protect the rectifier is not instantaneous pulse breakdown.

TVS diode is applied to rectifying circuit
The application of the bidirectional TVS diode in the AC circuit can effectively suppress the overload pulses brought by the power grid, thus protecting the functions of all the components in the rectifier bridge and the load.

TVS diode is applied to AC circuit
Application of TVS diode to DC regulated power supply protection
The following diagram is a DC voltage regulated voltage with a TVS diode at its output. It can protect the instrument using the power supply, and can also absorb the peak voltage between the transistor‘s collector and the emitter in the circuit, thus protecting the transistor. It is suggested that a TVS diode be added to the output end of each regulator, which will greatly improve the reliability of the whole machine.

Application of TVS diode to DC regulated power supply protection
he application of TVS diode to the protection of transistor circuit
A variety of transient voltages can damage the EB junction or CE junction of a transistor. When the transistor collector has a load of inductive (relay coil, transformer, motor), it usually produces a high voltage back potential, which may damage the transistor. In practical applications, it is suggested that TVS diodes should be used as protection devices. Figure 4 shows the protection example of TVS diode used in transistor circuit.

TVS diode is used for the protection of transistor circuits
Application of TVS diode to integrated circuit operation and amplifier protection
The integrated operational amplifier is very sensitive to the external electric stress. Figure 6 shows the protection circuit that prevents overvoltage damage with TVS at the differential mode input terminal of the operational amplifier.
Application of TVS diode to integrated op amp protection
The protection of integrated circuits
Because the integration of modern IC is getting higher and higher, and its pressure resistance is getting lower and lower, so it is easily damaged by the impact of transient voltage, so it is necessary to take protective measures. Usually, there are protective networks in the input and output ports of CMOS circuits. In order to be reliable, various protection networks have been added to the external interfaces of all the machines. The relevant circuit measures for protecting CMOS devices with TVS diodes are given in Figure 5.

An example of TVS diode integrated circuit protection
TVS diode is an effective and low cost device to protect sensitive components from ESD and EMI surge pulses. With the rapid development and wide application of the TVS diode, this paper introduces the characteristics and key parameters of the TVS diode, the selection, typical application, performance optimization and the cautions in the circuit design, so as to make the TVS diode. In the application of circuit design, the best performance is achieved, which effectively solves the overvoltage problem caused by transient interference, and greatly improves the safety and reliability of electronic devices.