Hi to all!!

This was a circuit obtained by google image .

1)the doubt is first circuit , how does the current control knob operates that is 1Kohm 10 turns potentiometer in the first circuit?

2)the second circuit contain potentiometer of 500ohm which control the current in output of regulator Circuit?

3)the third circuit contain potentiometer accross a Diode, How does it make Current variable regulator?

Please help me in such way i could understand Variable current control circuit LM723 Voltage regulator.Particularly Variable current limiting with Potentiometer not constant current limiting.



So i am totally confused with these circuit. Please make me to understand the Technique behind Current control transistor in LM723 for Variable current control in power supplies..

Suggest me better technique to design Variable current Limiting power Supply using LM723..

Help me in this regard.. I think i have conveyed my thoughts.if any thing is incomplete . Correct me if i am wrong..

 

If you want to know how it works, read the Datasheet......


https://www.google.co.uk/url?sa=t&s...gggMAA&usg=AFQjCNFjJyOyuBUcVcx3DiNZuHBiCa_lWg

 

If you want to know how it works, read the Datasheet......


https://www.google.co.uk/url?sa=t&s...gggMAA&usg=AFQjCNFjJyOyuBUcVcx3DiNZuHBiCa_lWg

I limit=Vsense/Rsense , it is constant current limiting.

I want to design a knob which control current from minimum value to maximum value. Kindly do the needfull.

 

I limit=Vsense/Rsense , it is constant current limiting.

I want to design a knob which control current from minimum value to maximum value. Kindly do the needfull.

It's not constant current, it can be variable by use of a resistor as shown in your circuits, it senses a difference of 0.7V between pins 2,3.

This is a very old chip, there are several much better new designs available.

 

It's not constant current, it can be variable by use of a resistor as shown in your circuits, it senses a difference of 0.7V between pins 2,3.

How resistance is varied? from the three circuit. Kindly explain because all three cases ,the voltage developed accross is 0.65V. How(potentiometer) it is varied and current is adjustable?

 

Hi,

If i remember right it's not easy to do with this particular IC chip. That's because it uses a transistor base emitter voltage as the sense voltage, and since the voltage must be developed from the output current, that means you need very small resistor values to sense currents that are say on the order of 1 amp. For example, for 1 amp you'd need roughly a 0.65 ohm resistor, and for 2 amps you'd need 0.33 roughly. You might get a power pot if you really want to do this, but it's a very old style way of doing things.

If i were you i'd look for a better circuit.

 

Hi,

If i remember right it's not easy to do with this particular IC chip. That's because it uses a transistor base emitter voltage as the sense voltage, and since the voltage must be developed from the output current, that means you need very small resistor values to sense currents that are say on the order of 1 amp. For example, for 1 amp you'd need roughly a 0.65 ohm resistor, and for 2 amps you'd need 0.33 roughly. You might get a power pot if you really want to do this, but it's a very old style way of doing things.

If i were you i'd look for a better circuit.

What are the modern ways of current sensing?

because in IC723, the voltage developed across the resistor is reaches more than 0.7V. it reaches up to 5V or so and the current control transistor base emitter junction have went to break down. I have lost up to 6 IC's.

Give me some tips or literature survey to do current sensing in voltage regulators..

 

Hi,

There are a lot of ways to sense current, but what is your application?

Note that there are even IC's made just for current sensing.
Current sensing can also be done with an op amp and current sense resistor.

 

Hi,

There are a lot of ways to sense current, but what is your application?

Note that there are even IC's made just for current sensing.
Current sensing can also be done with an op amp and current sense resistor.

Hi sir,
I want to construct Linear regulated Power Supply(0-30V @0-5Ampere).kindly help me.

 

Hi sir,
I want to construct Linear regulated Power Supply(0-30V @0-5Ampere).kindly help me.

Hi,

I'd like to ask you why you want to build one rather than buy one. You can buy one already built with a switcher front end and everything. What do you think about that?

If you still want to build one, did you look around on the web for a schematic?

 

Hi,

I'd like to ask you why you want to build one rather than buy one. You can buy one already built with a switcher front end and everything. What do you think about that?

If you still want to build one, did you look around on the web for a schematic?

I am student, so I wanted to construct on my own.

 

Hi,

Ok good. What kinds of circuits have you worked on in the past, and have you used op amps?

 

He is a student and he wants to build with what he has.
Can we work on helping him rather than redirecting him ?

 

The attached PDF is s something I designed to use as a supply
It is 0-30V, 0-2A fully variable CV CC supply.
To make it handle current 0-5A, you need to change some components values and add some more components.

The control part is almost the same. It is designed to display VI via PIC on a LCD. You can leave out the OPAMPS used for VI ADC's.

The transformer and casing intended is from a satellite dish positional controller tht is sold in India couple of years back. The PSU PCB is designed to fit into that casing

 

The attached PDF is s something I designed to use as a supply
It is 0-30V, 0-2A fully variable CV CC supply.
To make it handle current 0-5A, you need to change some components values and add some more components.

The control part is almost the same. It is designed to display VI via PIC on a LCD. You can leave out the OPAMPS used for VI ADC's.

The transformer and casing intended is from a satellite dish positional controller tht is sold in India couple of years back. The PSU PCB is designed to fit into that casing

My college has been started from 23 june, So fully preoccupied. So i apologizes for poor reply. Sorry all. Thank You. I will Revert soon..

 

The attached PDF is s something I designed to use as a supply
It is 0-30V, 0-2A fully variable CV CC supply.
To make it handle current 0-5A, you need to change some components values and add some more components.

The control part is almost the same. It is designed to display VI via PIC on a LCD. You can leave out the OPAMPS used for VI ADC's.

The transformer and casing intended is from a satellite dish positional controller tht is sold in India couple of years back. The PSU PCB is designed to fit into that casing

I am aware that this thread is old, but I still want to make a reply.

Hi,
What is the IC type of IC2 and IC3 on this schematic ? I am building a variable current and voltage power supply.

BR

 

Hello,

Read the hole thread and you will see that the LM723 is used.

Bertus