hi,
Measure the current thru the TL431.?
E

Thanks !
Current through TL431 is 0mA untill 5.7V input supply !

 

Any reason for damaging the cell !

It's down to the cell chemistry. Have a read of this.

 

It's down to the cell chemistry. Have a read of this.

You may be correct with your points.
But if cell manufacture says it can be discharged upto 2.5V. Why do we bother.
lets leave this topic and come back in current regulator topics if you can suggest some solution as i am struggling past 5 hours and still do not have solutions for the same !

 

Thanks all for your participation. I think this thread will be ended without any logical conclusion.

I still can figure out reason !

Without TL431 current regulator works and if i use TL431 it does not work.

 

5.3V it has to work !

maybe not -- unless you use (perhaps multiple parallel) 2N3904 and 2N3906 . . . has to do with ICEO ICEX (i speculate !)
.
. looks the BC547/557 is better than 2N3904/06
.
.
.
—————————————————————————————————————————————————————
. . . donno -- your circuit does something

 

I still can figure out reason ! Without TL431 current regulator works and if i use TL431 it does not work.

When the supply voltage is only 5 volts, the 4 volts dropped by the TL431 leaves only 1 volt for your entire current regulator to operate on. This is not enough, largely because of the way you're biasing Q1 (see diagram, below).




The way you have the circuit right now, the minimum operating voltage for the current regulator is equal to the forward voltage of D1 plus the Vbe of Q2 plus the Vbe of Q1 plus the voltage across R2 needed to drive enough current through R2 to bias Q1 (roughly 15 mA divided by the gain of Q1).

Obviously, these voltages total more than 1 volt and therefore the circuit will not work on a 5 volt supply.

There is an easy fix for this problem: disconnect the upper end of R2 from Q1's collector and connect the upper end of R2 instead to your 5 volt supply. Thus, base current for Q1 will still be available even at the minimum supply voltage. This change will allow Q1 to almost saturate (in other words, with Vce almost zero) before the current goes out of regulation, allowing you to operate at a lower supply voltage.

Try this fix and see what happens.

 

Hi

See below.

 

Hi

See below.


View attachment 214174

Thanks !

Could you please share your .asc file?

Regards,

 

When the supply voltage is only 5 volts, the 4 volts dropped by the TL431 leaves only 1 volt for your entire current regulator to operate on. This is not enough, largely because of the way you're biasing Q1 (see diagram, below).


View attachment 214154

The way you have the circuit right now, the minimum operating voltage for the current regulator is equal to the forward voltage of D1 plus the Vbe of Q2 plus the Vbe of Q1 plus the voltage across R2 needed to drive enough current through R2 to bias Q1 (roughly 15 mA divided by the gain of Q1).

Obviously, these voltages total more than 1 volt and therefore the circuit will not work on a 5 volt supply.

There is an easy fix for this problem: disconnect the upper end of R2 from Q1's collector and connect the upper end of R2 instead to your 5 volt supply. Thus, base current for Q1 will still be available even at the minimum supply voltage. This change will allow Q1 to almost saturate (in other words, with Vce almost zero) before the current goes out of regulation, allowing you to operate at a lower supply voltage.

Try this fix and see what happens.

Thanks for your time.

I made changes as per your proposal.
I want let you know circuit design should be as per it was earlier because and load is on Vcc_ground and there ground level is above the input source ground level.
Current is stable in the span of 17mA - 22mA as per below.

It will draw the same current when load is not not connected i.e. 17-22mA. Is there any way to reduce this current ?

 

It will draw the same current when load is not not connected i.e. 17-22mA. Is there any way to reduce this current ?

No. You've designed this thing as a shunt voltage regulator (the TL431) driven by a constant current source, so constant current is what you're going to get whether the load is connected or not.

 

See

 

https://www.microchip.com/wwwproducts/en/MCP6001#additional-features
● Rail to Rail Input and Output ✓ (Should be Vss sensing = common mode should include neg. rail and a bit beyound . . . and it does)
● Supply voltage range: 1.8V to 6V ? (as i get 2x LiPo would give the Vs.TOT 8.4V = no problem to limit supply for op amp for presented design)
● no 4V regulation !
● Input Offset Voltage ±4.5mV ? (about -- will do . . . maybe)

otherwise excellent/elegant solution

 

( ? what is the purpose of this CC/CV regulator ? )
? a short description of the actual application example -- would help us to better suggest any adjustments for your design !

 

Thanks !

Could you please share your .asc file?

Regards,

Here ya go...

 

See

 

TL431 is treated as an (op amp with a Vref) You can see it's equivalent model on the data sheet.
Depending on the application, the circuit's thermal properties are often the limiting factor.

The concept.

Ltspice: voltage controlled resistor, voltage controlled current source.
precision current source page 8
https://www.analog.com/media/en/technical-documentation/data-sheets/LT1001.pdf
Many names for the variants (V - I converters) 11.3
https://wiki.analog.com/university/courses/electronics/text/chapter-11
Figure 11.12 the linear slope of a Wildlar current source