Well that makes more sense. What is the current requirement? If it does not need much all you need is a series resistor.
Dan
Current is 350mA@12V , but Resistance will blow off the moment the high voltage is met with?
Adi
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Well that makes more sense. What is the current requirement? If it does not need much all you need is a series resistor.
Dan
The is a lot for a remote to draw. The crowbar is certainly the simplest, though you will need to replace the fuse when it happens.Current is 350mA@12V , but Resistance will blow off the moment the high voltage is met with?
Adi
The is a lot for a remote to draw. The crowbar is certainly the simplest, though you will need to replace the fuse when it happens.
You would need to sense the sensor side of the protection for an active cutoff of the type you are talking about, otherwise you get a regulator.
Dan
trueYes crowbar May work in time , but i was thinking about a fuseless system as in the process this is pretty common and people dont like to change fuses .
Adi
true
you could divide the SMPS output by 6/12 with a filter cap and divide down the other side by 5/12 and put a base emitter junction between them. That way you can switch it off when the higher voltage comes in with out any complex electronics.
Dan
No, resistive voltage divider. You have a 12V regulator supplying power to a remote sensor. You are trying to put a power switch in line to protect the regulator.I didnt get you when you say "6/12" is this the turn ratio? , and "other side"? or do you mean capacitors in series but I am having DC?
Adi
Look at the arrow in the substrate diode in the spec sheet. The diode needs to block what you want to block. You are effectively creating a synchronous rectifier and if you can afford the loss of less than a volt, it would certainly be easier to just put a fast rectifier in there instead.I again run into the trap of how to put-on the P-chan mosfet . The Vgs seems to overshoot the moment the Gnd reference gets shifted with over voltage external, condition?
-Adi
Look at the arrow in the substrate diode in the spec sheet. The diode needs to block what you want to block. You are effectively creating a synchronous rectifier and if you can afford the loss of less than a volt, it would certainly be easier to just put a fast rectifier in there instead.
like that... as I said, it would be easier just putting a diode in line
Did you get the updated version? I crashed in between. The series diodes set up a current source with the transistor, one for the BE junction and one for 0.6V drop across the emitter resistor.I dont get you , this is a schematic I posted earlier please see previous page . The prob is protecting it when the supplies tend to be in series connection this diode will be 0f no use at all. Your potential divider schematic welcomed!
-Adi
Did you get the updated version? I crashed in between. The series diodes set up a current source with the transistor, one for the BE junction and one for 0.6V drop across the emitter resistor.
The other thing I was saying was that you could protect the regulator with just a series diode.
Dan
sorry same file... new version... three transistorsNo I didnt, which updated version?
Adi
sorry same file... new version... three transistors
Dan