foldback triggered timed trip/shutdown?

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jimmiegin

Joined Apr 4, 2014
49
Hello. I am currently researching psu design and am now onto short circuit protection. I have been looking at the foldback and am wondering what I would have to search for on google to get info/tutorials on trip switches set off by a foldback. I figure that instead of connecting emitter to Vout it would be much better to have some sort of set up where the emitter connects to a shut off circuit, maybe a trip or a shut off with a timer with led and buzzer to tell you when its not happy on overload. What is such a circuit called please? it may be a dumb question. I am looking for tutorials so I may learn principles of shut down devices and trip switches so a point in the right direction would be really helpful please. Thank you
 

AnalogKid

Joined Aug 1, 2013
10,986
"connecting emitter to Vout" sounds like a linear voltage regulator. If so, what are the output voltage, current, and adjustment ranges, and overcurrent trip value? Also, why are you going with foldback as opposed to constant current limiting? I'm not saying one is better than the other, just need some background to shape a response.

ak
 

#12

Joined Nov 30, 2010
18,224
I've done it both ways. I highly admire the foldback method but I had to do this in AC at one point. I guess I'm saying that I wouldn't bother to design something to assist the foldback method because it works like a charm.

If you do, it's a current detecting resistor to a bipolar transistor (or an op-amp or a comparator) that fires a load of current into a capacitor on a mosfet gate and the mosfet disables the driver of the power supply. You can put an adjust pot on the sensor and you can put a latch-out instead of a delay on the mosfet side.
 
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