need high current regulator

[maapcs]

hello.
i need a high current regulator(about 5A&5V).
the 7805 regulator is very heating in high current.
i want a regulator with mosfets a minimom of matrials.
please help me.

 

[Gayan Soyza]

Use a high current pass transistor with 7805.

 

[maapcs]

i,m from iraq and i cant speek and write english very well,excuse me.
thanks dear Gayan Soyza ;but my problem is heating of regulator.
in the circuit that you drow it the transistor is heating Instead of regulator .
i want use this regulator on a Submarine and any Each heat is dangerous.

How can I creating a regulator with high current without make heat .

 

[ronv]

All regulators will generate some wasted heat. You can use a switching regulator to minimize this.

 

[maapcs]

thanks ronv
very monts ago i see a circuit in internet that make a regulator with p-mosfet and 2 bjt and som cap and resistor that have very low heating. But I forgot to save the circuit and now that I'm looking for. Who is this information?

 

[ronv]

Maybe it was this one? It is not very good.
http://www.simple-electronics.com/2011/10/12v-to-5v-converter-555ic-mosfet.html

Give us some more specification:

1- Input voltage range
2- Output current - minimum and maximum

There are many ICs for this but maybe not in Iraq?

 

[maapcs]

thanks dear ronv
i see the link that you Have proposed.but It is not.
i need min 2A and max 5a and input voltage is 12V.
It is important not to generate heat
i want a circuit with mosfet or bjt,i dont want ic.ic is not in iraq

 

[alec_t]

Any linear regulator will waste (12-5)V x 5A = 35W as heat. The only solution to avoid that is to use a switching regulator as suggested in post #4. You are unlikely to be able to make one just "with p-mosfet and 2 bjt and som cap and resistor".

 

[ronv]

Buck Regulator

Here is one that uses a 555 IC. I bet you can find one because they are very common.
This one "burns" about 4 watts as opposed to the 35 watts for the linear regulator. It is not nearly as good as a chip designed for the purpose, but maybe it will work for you.
Just to make sure the lowest load you will have is 2 amps? This is important because if the load is to low the voltage will go up.
The inductor will be a big one as it needs to be good for about 6 amps.
Let us know if you need to change components.

 

[kinarfi]

Take a look at this

 

[alec_t]

The sim shows the FET is dissipating 35W. Something the OP is hoping to avoid

 

[kinarfi]

I know, but when I ran it with 20v in and 12 out at 5 amps, it didn't seem that bad, I'll be playing with it again today and playing with this design also. It also sims at 35 watts.

 

[alec_t]

and playing with this design also.

That's fine as a linear regulator, but as with all linears it will be dissipating ~ 35W.

 

[kinarfi]

can you explain why the FET is dissipating 35 watts? It's on for a very short time and has a low rdson, so it shouldn't be dissipating that much, should it??

 

[ronv]

The circuit lacks an inductor to limit the current rise time so as soon as the FET starts to turn on the voltage reaches 4.5 volts so it turns back off. The net result is the current is very high and the FET never turns fully on so it is kind of in the twilight zone.