For some just contact transient suppression diode and contact transient suppression diode not long for friends, they have a transient suppression diode working principle and selection is not known, or understanding is not deep enough. What shall I do? Small make up in this for everyone professional explain the transient suppression diode principle and the selection of the main points of analysis!
Transient suppression diode and its working principle:
Devices in parallel to the circuit, when the circuit is in normal operation. It is a cut-off state (high impedance state), does not affect the normal operation of the line, when the circuit abnormal overvoltage and reach the breakdown voltage, it quickly from a high resistance state variable for the low resistance state, to the current moment provides low impedance of the conduction path, at the same time, the abnormal high pressure clamping within a safe level, thereby protecting the protected IC or line; when the abnormal overvoltage vanishes, the restoration of the high resistance state, the circuit works normally.
The selection technique of TVS transient suppression diode:
1. Determine the maximum DC or continuous operating voltage of the protected circuit, the rated voltage of the circuit and the tolerance of the "high end".
2, TVS transient suppression diode rated reverse turn off VWM should be greater than or equal to the maximum operating voltage of the protected circuit. If you choose
With the VWM is too low, the device may enter the avalanche or the reverse leakage current is too large to affect the normal operation of the circuit. Serial connected sub voltage, parallel connection current.
3, TVS damage voltage transient suppression diode maximum clamping voltage of the protected circuit should be VC.
4, in the prescribed pulse duration, TVS transient suppression diode maximum peak pulse power consumption of PM must be greater than the protection circuit may occur within the peak pulse power. In 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 a suitable capacitor TVS C transient suppression diode device.
6, based on the use of TVS transient suppression diode polarity and encapsulation structure. AC circuit selection of bipolar TVS is more reasonable; multi line protection using TVS array is more favorable.
7, temperature considerations. Transient voltage suppressor can work in 55~+150 c.. If need to TVs transient suppression diode in a change of temperature, due to the reverse leakage current ID is decreased with the increase of increase; power with TVs junction temperature increases and decreased, from 25 DEG C to + 175 DEG C, approximately linearly decreased 50% rain breakdown voltage VBR with temperature increased by a certain coefficient increase. Therefore, it is necessary to consult the relevant product information, consider the impact of temperature changes on its characteristics.
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