Hay,
I need to drive an LED (actually three parallel led arrays each array at 15V,150mA ) at 15V ,1.05A. Also need to adjust the current with maximum precision. Does it possible with LM723 together with series pass transister ?How would be the circuit diagram? (I had seen the LM723 configuration for high voltage regulation and low voltage regulator with current booster. But not confident with a high voltage ,high current configuration.)
Is there any other better circuit for my requirement?
Can i use LM723 as voltage regulator and LM317 as a precise current regulator along with it for better accurate controlling of current ?
HELP me please...........

 

Can i use LM723 as voltage regulator and LM317 as a precise current regulator along with it for better accurate controlling of current ?

Please read something on Ohms law, you cannot control both voltage and current at the same time.
I think that a simple LM317 current regulator should be accurate enough. Or what accuracy do you require?

 

LM317 current source info:
http://forum.allaboutcircuits.com/showthread.php?t=30490

If using an LM317 constant current source you need about 3 volts extra to make up for the CCS voltage drop.
If your LED modules need 15vdc the 15vdc @1.05 amp supply would not provide the extra voltage needed.

Do you have options on the LED configuration or the power supply voltage ?
If the power supply is an un-regulated wall-wort they generally provide more voltage when operated at reduced current
it may possibly (barely) work.

 

I already answered your questions but the current was higher. Maybe from another kid in your classroom.
You DO NOT need a voltage regulator because LEDs set their own voltage. Instead you need a current regulator (an LM317 makes a good current regulator if you can find a suitable low ohms pot with a reverse logarithmic taper to adjust the current, or use switched resistors).

You DO NOT need an ancient LM723 voltage regulator.

 

A 723 will do the job but it's way more horsepower than you need. Nobody with good experience would bother wiring up such a complicated chip to do this simple job.

 

Maybe the teacher doesn't know anything about electronics so told the students to use an ancient LM723 voltage regulator instead of using a current regulator?
I think so.

In university I had a couple of professors who could barely "speeky zee Engrish" and knew very little about electronics. Me and other students got them OUT OF THERE!

 

Maybe the teacher doesn't know anything about electronics so told the students to use an ancient LM723 voltage regulator instead of using a current regulator?

A teacher may now and then create projects that may seem awkward in order to educate the students. Also the LM723 do have a current limiting built in. With some tuning it can be quite accurate

 

You can see the circuit as below, you also can search on google as : ua723 30v current adjustable
http://electroschematics.com/210/adjustable-power-supply-0-30v-1a/

 

The old LM723 voltage regulator has very simple current limiting (not current regulation). The amount of limited current changes when the voltage changes (like a simple resistor)and when the temperature changes. It is not suitable for powering LEDs.

An opamp, a power transistor and a current sensing resistor makes a much better current regulator.

 

Thank you for your personal message to me.
The other similar thread WAS from a classmate of yours!

 

Thank you for your personal message to me.

The PM was actually from me.
Unless he PM'ed you too

 

Hay,
I need to drive an LED (actually three parallel led arrays each array at 15V,150mA ) at 15V ,1.05A. Also need to adjust the current with maximum precision. Does it possible with LM723 together with series pass transister ?How would be the circuit diagram? (I had seen the LM723 configuration for high voltage regulation and low voltage regulator with current booster. But not confident with a high voltage ,high current configuration.)
Is there any other better circuit for my requirement?
Can i use LM723 as voltage regulator and LM317 as a precise current regulator along with it for better accurate controlling of current ?
HELP me please...........

 

@Ilyas anjum

Did you notice that this was a very old thread? The last post before yours was almost 10 years ago.

Management thinks we should have little reason to post anything on threads that are over a year old unless we have some significant contribution to make. Did you see the warning? Did you have something to add to this thread?

 

The older post above explained some of the shortfalls of the LM723 those interested why we should move on.
Since the thread will likely be closed because too much extranious material. The datasheet should help answer why the ancient magazine articles
published long ago could have given a false impression compared to regulators available today, which exceed the 723's performance.
https://electronicprojectsforfun.files.wordpress.com/2018/08/ua723_application_note.pdf