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I tried to make it with an automatic delatch, but it didn't go so well :D it starts oscillating when you go above the load rating. Typically that's how these circuits test if the short circuit is fixed, but it did so at a frequency that no relay could handle it, and slowing it down meant to slow the response time of the fuse so i abandoned it. It would need maybe another schmitt trigger to make it automatic and I've ran out of space.
Okay I've dug up this circuit from my archive and there was something i didn't like. The constant current source i used to drop the voltage, so that the trigger can detect a short circuit had a large voltage drop when close to the tripping point, up to 15V!!! So i devised a way to have the lowest voltage drop possible and still have a very accurate response with an op amp as a comparator. The 100mOhm resistor has only 0.5V voltage drop at 5A so it's a perfect substitute for a regular fuse, which also has low voltage drop , but this thing responds a lot faster for some sensitive circuitry, some 250 times faster or so, than a regular fuse. So when the output consumption rises above 5A, the op amp senses the voltage difference from the drop and amplifies it, thus triggering the Schmitt Trigger, which cuts off the supply for the circuit, via a relay. A red LED indicates short circuit at the output. When you've attended to it, you press the most left switch momentarily and the trigger restores the connection to the output, and a green LED indicates everything is OK. Basically this works like a bistable latch. I've placed a slight hysteresis loop on the op amp, for more stability from erratic behaviour when the output is close to the tripping point of the op amp. Just a quick note, use the fastest switching components you can get your hands on, because even though the circuit works a lot faster than a regular fuse, there is a given lag of around 400uS before everything triggers, and during that time the short circuit is at maximum (just like a normal fuse operates). That's usually not long enough time to destroy anything, and you need a high current peak level in order to charge some capacitors at the output for instance, but still make it as fast as you can. The drawback of this thing is that unlike a regular fuse it's constant load dependent and requires readjustment when used at different voltages from the one shown here. Basically it doesn't control the current versus the load like a normal fuse does, but controls the voltage drop over a load no matter the current through the load. For example no matter the current or voltage the trigger is set to always trigger when the load goes below 8ohms. At 40V that's 200W, but at 20V that's 50W, and you need to readjust the circuit, mostly the tripping point of the op amp. For instance to get 200W at 20V you need to readjust the 78k resistor to 19.7k, or substitute the 100mOhm resistor for 25mOhm.
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