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What caused the burning of the TVS at the power input terminal?

Hardware design
March 17, 2021 by Jacob 2840

We made a car instrument, the system is powered by 24V, and a 40V TVS tube (SMBJ40CA) is added to the power inlet. Recently, the TVS burned out during the test on the car, and the power supply was short-circuited.

     Ask the gods. Is the peak voltage energy too large when the machine is turned on, and the TVS tube is broken? Or is it caused by too much current generated by the engine when it is turned off?

       The following solutions will not work:

       1 Varistor plus inductance plus TVS, there is a problem with the varistor when testing at home, canceled! Directly add TVS to the inductor, and it is found that the TVS is burned and the inductor is open;

       2 Replace the inductor with a self-recovery fuse or burn the TVS;

       3 Change the power of the TVS tube to a 1500W (original 600W), and the 1500W is also burned.

       PS: Because the varistor uses the principle of physical absorption, the material will be physically damaged after an ESD event, forming an irrecoverable leakage path, so the previous varistor is not used!

The above is the circuit diagram, the varistor is removed, and L1 is replaced by a resettable fuse!

All Comments

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Joshua Posted on March 17, 2021

An electrolytic capacitor is added to the right side of the common-mode inductor to absorb the instantaneous overvoltage. Will F1 be damaged? Find the cause of the overvoltage.

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Emily Posted on March 17, 2021

In terms of ordinary TVS and varistor, in terms of surge current protection, TVS is much worse than varistor. For example, the main material of the current lightning arrester is a varistor, and TVS cannot be used. This is precisely because when the lightning surge is protected, the TVS flow rate (surge absorption capacity) is small, and the varistor flow rate is large.

Work hard on the quality of TVS diodes.

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William Posted on March 17, 2021

It's the ghost of peak voltage! It has nothing to do with the current size! To get a 60V TVS.


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