Safe to make switching regulator operate at maximum rated current?

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zenniz

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My switching regulator is a TL2575 buck booster rated at 1A with an input of 12V and output of 5V.
It is equipped with a 2cm by 2cm heat sink.

What will happen to my regulator if force it to operate at 1A for long period of time?
What is the suitable fuse rating to prevent my switching regulator from breaking down?
 

Well if its rated as !A, then you can use it to draw 1A for long time, its just that your IC will get heated up, and after come time it will reach a temperature equilibrium. If you want to draw 1A for long time, you need to consider all the testing parameters with which IC was tested for rating as 1A. Rule of thumb is provide a proper heat sink and cooling to your IC and you can have rated performace.
If you want to use fuse for prevention, i would say you need a very less current fuse. For instance lets do some calculations. on output you are getting 5V and 1A, so that comes out to be 5W power output. Generally these regulators have an efficiency of 85-90%,( you can check the datasheet for exact value), but lets say efficiency is 85%. so you have 0.85*Vi*Ii = Vo*Io = 5W. so Ii = 5/(12*.85)≈ 0.5 A. So it will be a good idea to put a fuse of rating 0.8-1.2A. Its a good idea to put a fuse of rating 2-3 times the nominal current.
 

You want to be very careful in looking at how that rating
is specified; there are certain to be assumptions you must
meet (case temp, use model (1A forever, 1A 10% of the
time).

You need to understand your environment - is there a
credible fault scenario that could put you at (say) 2A for
some period, and you need a 50% derating for confidence?
Some difference in your peak & average temp, from the
ratings basis?

Fuses will prevent sustained overcurrent but they will
not prevent breakdown - an overvoltage event - only
act sometime after, possibly preventing overtemp /
overcurrent damage but perhaps failing to prevent a
lower-level drift or damage that may still be unacceptable
in some aspect of regulation quality.

Heat sink area is nice, and all, but airflow is king.
 


Do you have any source that i can study for the formula that you stated above? Thanks.
 

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