15A current limiter circuit operating at 3.6V

[Doctorbass]

Can someone have any circuit for a current limiter that can operate at 3.6V?
I already have some 0.01ohm 16W resistor for the sensing.. but i'm not the best for these circuits...

THAT'S WHAT IS BLOCKING MY DC-DC PROJECT.... :lol:

Doc

Safe, Bob, GGoodrum? others?

 

[fechter]

It's hard to get a FET that will turn on with 3.6v of gate drive.

You might be able to use an Allegro current sensor on the 3.6v side, and use that to control the input side of the dc-dc.

What voltage are you running on the input side?

 

[Doctorbass]

I already have that fet.. an IRF3706

On the input side i will use 48V (44 to 52V) from a 25A 48V power supply. it will supply all my 12 DC-DC.

The reason why i want to limit the current is that i only will have 2A at 48V for each DC-DC input for a total of 24A. if i dont limit the current, the main power supply will be not able to supply the 5-6A draw at full power of each dc-dc and they will all shutdown due to the power supply excessive current and voltage drop.

2A per DC-DC will be just fine .. but i can't limit the input current on the DC-DC.. because they will shutdown and pulse ON and OFF even if they recover to a input normal voltage range. (that's their input low voltage protection)


So i need to limit the output of them... i have no choice.

The easiest way would be to have an independent curreint limiter circuit for each DC-DC.

Have you any suggestion... ideally using a MOSFET.

Doc

 

[fechter]

Hmm... if you limit the 15A side with a FET, it will get hotter than crap when it's limiting unless you PWM it.

Can you pull the voltage trim on the dc-dc down below 3.6v? If you could pull it down to, say 3v, then the batteries won't be able to draw big amps.

 

[Doctorbass]

I tried that using a comparator, a Vref and a shunt with the IRF3706 with a very low vgs.. but it is inconstant... if i limit the current let say to 10A, as the battery voltage increase, the current increase :| ... it's like if the V ref or the rail that supply the comparator would affect the comparator job or would interfere with it... for sure it can goes below 3.6V.. and if i set it to 3.0V it's ok.. but the limiting current job with my circuit is not great..


Also, see below the voltage loss to hold the 15A at the end of the wires with the sensing input including the current sense resistor:


i would search for pwm current limiting.. that does not border me to built 12 circuit like that for a great current limiting job... have you idea for me?

 

[Doctorbass]

UPDATE !!

http://endless-sphere.com/forums/viewtopic.php?f=14&t=2824&p=56318#p56318

Doc

 

[fechter]

As usual, good work doc!

That will be much better than trying to throttle the output.