Transient Voltage Suppressor Diode Working

[SACHIN C]

Dear All,
How TVS diode Works above certain voltage which we want to suppress?
What should be the limit of voltage thet we can apply across TVS?
At the time of clamping the required voltage,how we can calculate the amount of current that can flow through the TVS to suppress the excess transient voltage & current?
How we can dissipate the energy stored in TVS?




Thanks & waiting for support to enhance the knowledge,:smile:

- - - Updated - - -

Also how to identify TVS whether,faulty or not when it is opened due to high voltage?



Thanks & waiting for support to enhance the knowledge,:smile:

 

[chuckey]

See :- https://en.wikipedia.org/wiki/Transient-voltage-suppression_diode To test the diode feed it with a variable DC voltage via a current limiting resistor (100 K), this should then allow the diode voltage to be measured at below its trip level and what the trip level is (turn DC up).
Frank

 

[SACHIN C]

Hi chuckey,
What should be the maximum voltage that we can apply across the TVS,beyond which it will get open circuit because of voltage that is faulty,it is clamping voltage?

TVS diode suppress the excess voltage in the form of current,so how to identify the amount of current by the wattage?

Peak wattage for TVS available is 600W & 1.5KW ,so continuous wattage depend up on package?

Do we need to connect any fuse or 0ohm resistor in series of TVS for shorting detection of TVS?

Thanks & waiting for support to enhance the knowledge,:smile:

 

[chuckey]

These questions can be answered from the manufacturers data sheet. If you connect a fuse in series with a TVS,the TVS take a peak of 50A and blows the fuse, how will you know that the TVS is not in circuit?
Frank

 

[SACHIN C]

Hi chuckey,
But how can we select lower value fuse when we are known 50A is peak power?
Wattage is 600Wpeak or 1.5KWpeak, but what will be normal wattage so that we can connect rated fuse say 2A or 5A in series,whether it is depend up on package of TVS?
How can we detect TVS is faulty due to higher voltage as it will become open,but in normal state also it is open i.e high impedance upto clamping voltage?


Thanks & waiting for support to enhance the knowledge,:smile:

 

[chuckey]

If you have a 230 V mains supply supplying up to 1A to a piece of kit. Then when a 2 KV spike comes along the TVS conducts heavily (up to 50A?) and blows the fuse. The power the TVS has dissipated is I^2 T, so if the fuse blows in 1 second, the power in the TVS is 2500 X 1 = 2.5 kA/S.
If you put 600V via a 10K resistor across a 500 V TVS, then a good TVS will conduct and the voltage will fall, if the TVS is open circuit, the voltage will still be 600V.
Frank

 

[FvM]

The discussion is based on wrong assumptions, e.g. TVS would fail open circuit. It more likely fails with short circuit, at least at medium overload enery levels.

 

[SACHIN C]

FvM,
TVS never fails because of high voltage that is getting open circuit?
Since it is passing excess voltage in terms of current so getting short circit in over voltage condition?




Thanks & waiting for support to enhance the knowledge,:smile:

 

[FvM]

TVS can fail open circuit, if you manage to evaporate the diode chip or the metal contacs and terminal leads. It's a matter of applied energy and instantaneous power.

 

[GUMY]

Based on my experience, TVS fails to short-circuit in most cases. If selection of TVS and overall circuit protection design is done correctly, TVS should not fail easely at all.

 

[SACHIN C]

How can we identify the watt at clamping voltage because peak power TVS available is 600Wp & 1.5KWp,do we need to calculate on package rating power?


Thanks & waiting for support to enhance the knowledge,:smile:

 

[FvM]

What are you exactly asking for?

TVS pulse power ratings (e.g. 600 W) are based on standard test conditions. The power handling in your application may be higher or lower, depending on the pulse duration. Maximum continuous power capability isn't higher than for regular diodes in the same package, e.g. a few watts.

The actual pulse power in your application will be mostly defined by the characteristics of the transient source, not the diode.

 

[SACHIN C]

TVS can fail open circuit, if you manage to evaporate the diode chip or the metal contacs and terminal leads. It's a matter of applied energy and instantaneous power.

means if applied transient power exceeds then TVS will get open circuit.
But how to identify externally open circuit of TVS as it is high impedance device.


Thanks & waiting for support to enhance the knowledge,:smile:

 

[FvM]

means if applied transient power exceeds then TVS will get open circuit.

No, it will probably fail open circuit at hundred- or even thousandfold transient power.

 

[vikash23]

Hi,

Could you pease let me know how the TVS diode can be used on the power supply. Do I need to use it before the fuse or after the fuse.

https://obrazki.elektroda.pl/5560553000_1384770748.jpg

 

[SACHIN C]

Vikash23,
TVS Diode use to protect the device against high voltage.
So provide the details of your power supply & can you specify the reason why you want to use TVS in power supply?


Thanks & waiting for support to enhance the knowledge,:smile:

 

[vikash23]

Hi,

The power supply is a normal DC 12-24V. This circuit is used in my project used in resident and to avoid voltage spikes we are using 2 TVS in my circuit. Could you please let me know why TVS is used after schottky and not before.

 

[schmitt trigger]

One common mistake with respect to TVS diodes (or any clamping device, for that matter) is not to consider the applied voltage waveform and equivalent series impedance.

Since this is a daunting task for even seasoned engineers, different worldwide safety and regulatory agencies have developed waveforms and models that, based on extensive research, will yield in optimal results for similar applications.

An example of a normalized waveform, called the 10X1000 is shown in figure 1 of the following document:

**broken link removed**

 

[SACHIN C]

For 18V Gate to Source which TVS rated diode need to be select?
Presently using 600W / 18V TVS.Bi-directional.
Can we use TVS diode across Drain to Source of MOSFET?


Thanks & waiting for support to enhance the knowledge,:smile:

 

[GUMY]

If 18V is maximum rating for MOSFET's Ugs, then TVS with lower standoff voltage should be used. 18V should be clamping voltage of TVS.