For example, injecting current into the feedback pin?Maybe some clever way to make the current limit adjustable?
Here's another TL431 current regulator. Unsure how it's different than the circuit above.TL431
Unless it's a switching regulator limit, they all will dissipate the same power (Ilimit * Vin-Vout).Which of these limiters will run cooler, all things being equal?
Unless it's an electronic-fuse type, it will just continuously limit the current.Will they all simply regulate the current, ie continuous limit? Or will they turn off current on overcurrent?
I believe you can do a parts count as well as I can.Which would have fewest parts in a real-world practical circuit?
Only those with a compensated reference, such as the LM317, and TL431 circuits.Are they all temperature-compensated?
You would have to see if the parts are available in SMD packages.Which would have the smallest PCB footprint, ie can they be implemented with all-SMD parts?
You can do that by looking at the supplier cost for the parts.How do costs compare, including external parts?
But these schematics may be simplified compared to real-world practical circuits. You may be as ignorant of that as i am.I believe you can do a parts count as well as I can.
I've been told they won't dissipate the same heat. For example, it may depend on the thermal characteristics of a selected transistor. Do you have hands-on experience with any of these circuits?Unless it's a switching regulator limit, they all will dissipate the same power (Ilimit * Vin-Vout).
In general the number of parts seem close to what the actual circuit would have.But these schematics may be simplified compared to real-world practical circuits.
Whoever told you that was wrong.I've been told they won't dissipate the same heat. For example, it may depend on the thermal characteristics of a selected transistor.
Great! Why might someone choose this design over any of the designs i posted above?Here's a simple current-limit circuit that requires only two transistors and two resistors.
Is that the same as saying it's not temperature compensated?The current limit value does increase about 0.3%/°C due to the change of Q1's base-emitter voltage with temperature.
The only thing the thermal characteristics will affect is how that heat will be dissipated to the ambient air.
Minimum number of parts.Why might someone choose this design over any of the designs i posted above?
Yes, if the power can be dissipated by the FET.Will it handle 4A?
Yes.That FET is marked -13.5A, –20 V. Will your circuit support positive V's?
If it's not in the current-limit mode, yes.Will the output V follow the input V?
Yes.s that the same as saying it's not temperature compensated?
No.as temp goes up, Vout goes down, correct?
The current limit would be more stable, but the sense resistor would be about 4 time larger, giving a higher voltage drop when operating normally with no current limit.Could a TL431 help here?
How what?"How"?
correct formula: Ptot = I_limit * (V_in - V-out)they all will dissipate the same power (Ilimit * Vin-Vout).
even if the MOSFET is in the saturated mode there will be a voltage drop:If it's not in the current-limit mode, yes.
The bjt determines the thermal behaviour. V_BE has negative temperature coefficient.No.
As temperature goes up, the current-limit goes up.
How what?
Do you understand what thermal resistance is and how power is dissipated from a transistor?
Thermal resistance is the temperature rise due to the transistor power dissipation.
The thermal resistance from the transistor die to ambient air must be low enough so the transistor does not overheat
Sorry for being pedantic. It seemed the word "how" might be misleading. "How" implies "manner", as in "the manner in which heat will be dissipated".The only thing the thermal characteristics will affect is how that heat will be dissipated to the ambient air.
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