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about short-protection and overcurrent-protection

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lhlbluesky

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in LED driver,there is two protection-- short-protection and overcurrent-protection,pls tell me what's the diffrence of the two protection?what's the principle for both short-protection and overcurrent-protection?thanks all.
 

Short protection turns off the device...

overcurrent protection limits the current being supplied by the device.


in case of over current the load increases but its not a huge one... in this case u simply use a comparator to sense this increment and use its output to partially turn off (reduce the vgs) the passdevice(one that supplies current)

Hope this gives you the very basic idea of styff.
 

any more explanations?
which cause can lead to short-protection and overcurrent-protection in LED driver?
how to detect short-protection and overcurrent-protection from signal change?
 

Actually, short circuit protection is an extreme case of over-current protection. It has a much larger protection threshold current and a shorted dectection delay.
When LED driver works, a surge current may occurs. According to the level of current, these two protections are advised.
How to detect is your business as a chip designer. Just work on it!
 

when its a short... that particular terminal of LED will show a huge drop in voltage...
from its normal condition.
 

what's the reason of the huge drop in voltage from its normal condition?
 

Generaly these circuits are supplied by some chargepump and LDO...

when the current is huge it goes out of spec for the regulator... and consequently the voltgae drops ... which is reflected acrss LED also.
 

lhlbluesky said:
in LED driver,there is two protection-- short-protection and overcurrent-protection,pls tell me what's the diffrence of the two protection?what's the principle for both short-protection and overcurrent-protection?thanks all.
Click to expand...

I think the protection in LED driver you said are LED short protection and LED open protection. LED short protection: is used to protect device when one or more LEDs are shorted. LED open protection is used to prevent output voltage exceeding the maximum voltage. When one string or more strings are open or disconnected, the loading decreases, which leads to output voltage increase. Sometime we can call it overvoltage protection.
Overcurrent protection maybe the currentlimit, which senses inductor current or output current.
 

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