I am not able to understand the operation of CC CV using LM723 IC

[audio]

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.

[iMo]

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..

[dobsonr741]

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.

[xavier60]

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.

[iMo]

It could be the shunt has been made of a PCB trace, therefore the shunt is missing there in the schematics..

[audio]

Hi all,

Suggest me some circuit which could do regulation for 0-30v and 0-3ampere.

Thankyou all.

[xavier60]

Hi all,

Suggest me some circuit which could do regulation for 0-30v and 0-3ampere.

Thankyou all.

Not 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/#msg3582664
Even at 3A, tap changing should be included. With my build, I have the unregulated supply including relay on a separate PCB.

[StacyHaward]

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.

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