I am not able to understand the operation of CC CV using LM723 IC - Page 1
Forum section: electronics / beginners

author: audio
author_rank: Regular Contributor
timestamp: July 10, 2023, 12:56:58 pm
content: Hi all,we have LM723IC in our curriculum. When it comes to practical design of CC CV power suppy using LM723, I cant understand how it current limitation are designed. there are two IC in the circuit.There is voltage divider feeding it to the opamp inside IC723. I have attached the schematic for reference.Thank you all.

author: iMo
author_rank: Super Contributor
timestamp: July 10, 2023, 02:05:29 pm
content: The only way how the current limit might work in that schematics (provided nothing is missing there) is the U2 is sensing a voltage drop at the Vcc of the U2 - with the load the Vcc starts to drop and the U2 works like a comparator.The voltage of U2's Vref is divided to something around 0.9V what is too low for normal 723 operation, imho, thus they may leverage some nonstandard 723 behavior..PS: there could be some hysteresis introduced by the dividers around U2 such the U2's output will not oscillate around the set current limit..

author: dobsonr741
author_rank: Frequent Contributor
timestamp: July 10, 2023, 05:07:13 pm
content: Something is missing from the schematics. Perhaps the subject of the homework is to add the missing components?This is how I would go about doing it:First, I would figure out the acceptable input range of the error amplifier.Then add a probably high side current sensing shunt.

author: xavier60
author_rank: Super Contributor
timestamp: July 10, 2023, 07:08:36 pm
content: The low-side CS resistor would be between the bottom end of R31 and the bottom end of R32.The mess connected to REF, IN- and IN+ is to apply some voltage to both inputs to satisfy the common mode input range for the internal opamp and also a variable offset difference to set the CC threshold.

author: iMo
author_rank: Super Contributor
timestamp: July 10, 2023, 08:05:40 pm
content: It could be the shunt has been made of a PCB trace, therefore the shunt is missing there in the schematics..

author: audio
author_rank: Regular Contributor
timestamp: July 11, 2023, 12:59:04 pm
content: Hi all,Suggest me some circuit which could do regulation for 0-30v and 0-3ampere.Thankyou all.

author: xavier60
author_rank: Super Contributor
timestamp: July 11, 2023, 04:03:23 pm
content: Quote from: audio on July 11, 2023, 12:59:04 pmNot certain what your skill level is. A few members and myself have built very similar versions of this,https://www.eevblog.com/forum/beginners/lm324-power-supply-with-variable-voltage-and-current/msg3582664/#msg3582664Even at 3A, tap changing should be included. With my build, I have the unregulated supply including relay on a separate PCB.

author: StacyHaward
author_rank: Newbie
timestamp: August 22, 2023, 09:10:44 am
content: A voltage divider is often used to provide voltage feedback to the non-inverting input of the internal operational amplifier of the LM723. This allows for comparing the actual output voltage with a fixed reference voltage, enabling the regulator to maintain the desired output voltage.cv assistant juridique