Current limiter

I don't think so. But you might get close with active/synchronous (MOS) rectification. ...Jim Thompson

-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

Trivially, a protective relay does this, as does any standard circuit breaker.

Did you have something in the way of microsecond response in mind?

On a sunny day (Wed, 3 Oct 2012 12:15:40 -0500) it happened "Vladimir Vassilevsky" wrote in :

Resistor!

Do you want to limit the current (ie, dissipate power), or shut down on overload?

Use a photo-mos SSR (or a relay!) and some sort of current sensing circuit to shut it down, maybe with periodic retry. I've done that with Claire SSRs and software.

There are some bidirectional photo-mos SSRs that claim to be self-protecting.

For high current, make your own SSR (or continuous current limiter, if that's the function you want) from back-to-back mosfets.

PTC thermistors and polyfuses work, too.

--

John Larkin         Highland Technology, Inc 

jlarkin at highlandtechnology dot com 
http://www.highlandtechnology.com 

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom laser drivers and controllers 
Photonics and fiberoptic TTL data links 
VME thermocouple, LVDT, synchro   acquisition and simulation

conceptually something like this?

Version 4 SHEET 1 1056 680 WIRE 672 -144 32 -144 WIRE 32 -112 32 -144 WIRE 320 -64 144 -64 WIRE 416 -64 320 -64 WIRE 672 -64 672 -144 WIRE 144 -48 144 -64 WIRE 496 0 336 0 WIRE 32 16 32 -32 WIRE 224 32 144 32 WIRE 416 32 416 -64 WIRE 496 32 496 0 WIRE 672 32 496 32 WIRE 336 48 336 0 WIRE 384 48 336 48 WIRE 256 64 144 64 WIRE 288 64 256 64 WIRE 624 64 624 16 WIRE 624 64 448 64 WIRE 144 80 144 64 WIRE 288 80 288 64 WIRE 384 80 288 80 WIRE 224 112 224 32 WIRE 416 112 416 96 WIRE 416 112 224 112 WIRE 528 112 416 112 WIRE 672 112 528 112 WIRE 320 128 320 -64 WIRE 336 128 320 128 WIRE 576 144 288 144 WIRE 336 160 336 128 WIRE 288 176 288 144 WIRE 304 176 288 176 WIRE 576 176 576 144 WIRE 640 176 576 176 WIRE 144 192 144 160 WIRE 224 192 224 112 WIRE 224 192 144 192 WIRE 624 192 368 192 WIRE 640 192 640 176 WIRE 672 192 640 192 WIRE 256 208 256 64 WIRE 304 208 256 208 WIRE 624 208 624 192 WIRE 336 256 336 224 WIRE 528 256 528 112 WIRE 528 256 336 256 WIRE 672 448 672 288 FLAG 32 16 0 FLAG 672 528 0 SYMBOL voltage 32 -128 R0 WINDOW 3 -329 58 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value SINE(0 12 10 0 0 0 1000) SYMBOL nmos 624 -64 R0 SYMATTR InstName M1 SYMATTR Value AO6408 SYMBOL nmos 624 288 M180 SYMATTR InstName M2 SYMATTR Value AO6408 SYMBOL res 656 16 R0 SYMATTR InstName R2 SYMATTR Value .1 SYMBOL voltage 144 -64 R0 WINDOW 3 -56 55 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value 5 SYMBOL voltage 144 64 R0 WINDOW 3 -99 55 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V3 SYMATTR Value 100m SYMBOL res 656 96 R0 SYMATTR InstName R4 SYMATTR Value .1 SYMBOL Opamps\\LT1006 416 0 R0 SYMATTR InstName U1 SYMBOL Opamps\\LT1006 336 128 R0 SYMATTR InstName U2 SYMBOL res 656 432 R0 SYMATTR InstName R1 SYMATTR Value 10 TEXT -298 14 Left 2 !.tran 1

Yup. Jim said it couldn't be done!

--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com

Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation

You can do anything given enough auxiliary supplies...

...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| Phoenix, Arizona  85048    Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

if you're talking about the amount of voltage you have to work with with in that limiting stage? THen yes, use an comparator that has some gain and is not limited to that drop. The control component could be a Fet, since those don't have a drop out like that.

If you are referring to rail supply voltage dwindling down that low, then I don't know.

Jamie

Yes, one may use a primary coil of a transformer, with a voltage bumped secondary limiting via feedback. Ken