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3Volt power supply - some advice needed

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Hishamsaleh

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3Volt power supply.

look at this circuit and tell me plz. what other regulators can I use instead of LM317? and what changs should i do?

it's just that i'm looking for mor effeciency! and good cost!

thanks
 

M!k

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You could use a low-drop-regulator, but it would help if you specify the maximum drawn current. Maximum current for LM317T is 1.5A. Do you really need that ?

Btw: 3V (topic) or 13.6V ?


Mik
 

bimbla

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3V Supply

For a voltage as low as 3V, and using LM317, I would not be very happy with the regulation of the prresent circuit.
I would use an external op-amp and employ -ve feedback fot much tighter voltage regulation.

bimbla.
 

Sebi

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Use a "Simple Switcher" buck converter from N*a*t*i*o*n*a*l.
 

leonqin

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Re: 3Volt power supply.

Hishamsaleh said:
look at this circuit and tell me plz. what other regulators can I use instead of LM317? and what changs should i do?

it's just that i'm looking for mor effeciency! and good cost!

thanks
it depent on your expect output current
 

Al Farouk

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LM317 is a cheep regulator. if you face any technical problems explain it and we may guide you to solve.
 

eYe

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I have made the same circuit for my external supply for Garmin Vista GPS.

The problem that I found is Resistor has an error itself. You may need to readjust value from calculation to match to the desired output voltage.

Especially, if your min and max operation voltage is very close.
 

Hishamsaleh

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yes i have problems... many!

sorry if i wasn't clear...

the problem is that the output is not sharp 3V... tolerance are small for my device and the error in this circuit is not controlled... some times E=30%... too much! the variable resistance solving the problem of R error... (100:140 is the ratio between R1 and R2)...

so do any one have alternative circuit to produce 500 mA (or highr) and have high effeciency?

thanks:)
 

Al Farouk

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I think you can try the following arranged to its cost

1- use metal film resistors to set the adjust pin voltage as carbon film resistors has big error compared to the precsion you need and the pot always cause high drift.

2- use some kind of feed back to monitor the output voltage.

3- Use current posting transistor, if your circuit draws high currnt that cause heeat dissipation in regulator that make its output drift (refer to data shhets).

8O Don not forget the heat sink.
 

algilsan

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there are many regulators that can do the task but it depends on wich amount of output current you need.
 

Sonic

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Many regulators indeed - don't overlook Linear tech they ahve a wide variety.
 

blankcd

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Re: 3Volt power supply.

Hishamsaleh said:
look at this circuit and tell me plz. what other regulators can I use instead of LM317? and what changs should i do?

it's just that i'm looking for mor effeciency! and good cost!

thanks

RC1117 3.3V is very good.

You can find it in http://www.fairchildsemiconductor.com/
 

jzaghal

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Use Lm317 switching mode !!

Hi,

You can use an LM317T as a switching regulator.
Simple and efficient.

Bye. :D
 

hcet

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ti bought burr&brown. go to www.ti.com and you can find many regulators.
 

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