Overcurrent protection

  • Thread starter gnurf
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  • #1
gnurf
370
8
I need to prevent a malfunctioning load from drawing too much current from a supply of around 3Vdc@2A(max). There is already a current sensor in series with the load which outputs a voltage, Vsense, proportional to the current drawn by the load.

I was thinking a PMOS switch with the gate tied to the output of a comparator that compares Vsense to a Vref, where Vref would represent the maximum allowed current draw for that load. When a over-current is detected the switch must shut down the load immediately and stay in that state until externally reset (by a microcontroller) or if the load resumes normal operation.

Some kind of hysteresis (or a flip-flop??) -- or something -- is missing from this picture, and I have a feeling there exists some standard way of doing this that I'm unaware of, so any ideas are welcomed. Thanks.


EDIT1: Oh, and btw -- high efficiency is a priority.

EDIT2: I've already found what I need (e.g., MAX869), but if you know of a circuit with discrete components that does the same job, I'm still interested for educational purposes.
 
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Answers and Replies

  • #2
stewartcs
Science Advisor
2,178
3
I need to prevent a malfunctioning load from drawing too much current from a supply of around 3Vdc@2A(max). There is already a current sensor in series with the load which outputs a voltage, Vsense, proportional to the current drawn by the load.

I was thinking a PMOS switch with the gate tied to the output of a comparator that compares Vsense to a Vref, where Vref would represent the maximum allowed current draw for that load. When a over-current is detected the switch must shut down the load immediately and stay in that state until externally reset (by a microcontroller) or if the load resumes normal operation.

Some kind of hysteresis (or a flip-flop??) -- or something -- is missing from this picture, and I have a feeling there exists some standard way of doing this that I'm unaware of, so any ideas are welcomed. Thanks.


EDIT1: Oh, and btw -- high efficiency is a priority.

EDIT2: I've already found what I need (e.g., MAX869), but if you know of a circuit with discrete components that does the same job, I'm still interested for educational purposes.

How about a circuit breaker or fuse?

CS
 
  • #3
Lancelot59
646
1
A circuit breaker or fuse as suggested are the simplest ways to go.

If you're looking to go fancy you can try something similar to a crowbar circuit.
 

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