Overcurrent protection

[Rajinder1268]

Hi all,
I need some advice. I have a circuit that has a 3A fuse, this is to protect a supply line of 14V.
The 14V is then supplying power to a IC. The IC has a current rating of 1A. This device is being damaged, presumably by over current. The 3A fuse does not blow.

I have looked at using a TVS diode for over current protection. However, looking at a datasheet the clamping voltage current Ipp is usually greater than 3A. Do I need to add a resistor to manage the current to an acceptable level before the TVS diode?
Also is the TVS diode a good option for this application?
Best regards

 

[KlausST]

Hi,

It's not that simple.
It's a problem of current waveform and timing.

An IC rated with 1A maybe could be protected by a superfast blowing 1A fuse.

Why did you use 3A?
A 1A fuse will "hold" 1A RMS ... and will "trip" at (much) higher current. The higher the current the faster it trips.

Klaus

 

[betwixt]

TVS is for over voltage not over current, unless your 14V is too high and that's what causes too much current.

What is the IC and what supplies the 14V?

Brian.

 

[crutschow]

What might cause this "overcurrent"?
It could be damaged by overvoltage.
Is the 14V from a vehicle battery?

 

[Rajinder1268]

Hi
It is from a battery. Other devices are not getting damaged, so it is probably not a over voltage issue. I think it's overcurrent, probably due to low battery. Not sure.
I need a protection for this that does not blow a fuse but restricts the current when the fault is there.
Any ideas?

 

[barry]

Overcurrent from low battery? According to Ohm's Law, the lower the voltage, the lower the current.

(Actually, that's not totally true. If you've got a switching regulator and the input voltage drops, it will draw more instantaneous current).

You need to provide us more information about your application.

 

[crutschow]

Other devices are not getting damaged,

That may be because they have better protection against the high voltage spikes that can occur in a vehicle's power system.
I still believe the failure is likely from overvoltage, not current.

I need a protection for this that does not blow a fuse but restricts the current when the fault is there.

What "fault"?

 

[KlausST]

Hi,

There are many types of "overcurrent pritection". Every type can/should be characterized by: current value, trip time, I2t ...)
* trip on overcurrent .. and needs to be replaced (fuse)
* trip on overcurrent .. with push button to reactivate
* trip on overcurrent ... and needs a power cycling (thermal polyfuse)
* trip on overcurrent with automatic retry (how many cycles, delay)
* analog current limit (limiter getting hot)
* SMPS with current limit (load may get hot)
* SMPS with power down and auto retry mode
* I guess there are even more...

Which one do you prefer? Each has it's benefits and drawbacks.

*******
A battery has a "nominal voltage" (maybe 14V) but it will vary a lot depending on charging state (maybe 10.5V .... 14.4V).
Additionally there may be spikes in both directions, noise ....
But this all is "voltage" and is a differrent thing than "current" and thus needs different protection systems.


Klaus

 

[ƎLECTRON]

The Fuses are usually low speed elements to protection of electronic components. You can use the current limiter/switcher circuits to protect your circuit.