How to improve regulation of a power supply

[lastdance]

I am still pleasantly surprised this thing worked using a LM339, which is a comparator. Could someone explain how does it work to regulate the current?
A comparator has way too much gain for this purpose.
I guess what you wanted to do is not current regulation, but an electronic circuit breaker when current limit is exceeded. If that's what you want, and you built in enough hysteresis in your comparator, or you put a latch there, your circuit could work.
Use sub-logic FET like Si4864 from Vishay, otherwise, you do not get the kind of Ron. Ron is a function of gate overdrive. Go to the website and search for FETs with low threshold.
Your GND terminal of the system has to be the output of your power supply, so that you could refer your 5V generator, LM339 and its potential divider to GND.
This way you could totally shut off your FET by pulling its gate down by LM339.

 

[smartsarath2003]

Use sub-logic FET like Si4864 from Vishay, otherwise, you do not get the kind of Ron. Ron is a function of gate overdrive. Go to the website and search for FETs with low threshold.
Your GND terminal of the system has to be the output of your power supply, so that you could refer your 5V generator, LM339 and its potential divider to GND.

So You are saying I can't turn ON the Mosfet completely at Vgs(th)

 

[lastdance]

check datasheet, it tells u how much Ron u get for different Vgs.
If u have the datasheet, the first thing u do is ,READ IT..no simpler way

 

[smartsarath2003]

If u have the datasheet, the first thing u do is ,READ IT..no simpler way

I can't find any such information from datasheet
The only related graphs are Rds Vs Id and Rds Vs Temp
I'll be great if you can find that for me
Thanks

 

[ME]

If u have the datasheet, the first thing u do is ,READ IT..no simpler way

I can't find any such information from datasheet
The only related graphs are Rds Vs Id and Rds Vs Temp
I'll be great if you can find that for me
Thanks

Have you looked at fig 6 in the IRF540 datasheet?
**broken link removed**
How hard can it be?
It seem you want somenone else to design the whole circuit for you.
Maybe you should hire an electronics engineer to design it for you.
Sorry if I sound a bit harsh, but you should try to do and effort yourself before asking about everything. We don't want to design the circuit for you, but we can help you design it by answering some question, if you do an effort yourself. Otherwise nobody cares to help you unless you hire someone to design it for you.
You still haven't answered the questions I asked in my last post. What are the circuits specs. for example?
And please don't attach schematics as .doc files, it's a waste of time and not all can read it. Please just upload a .png file as I asked you to do in an earlier post, what's the purpose of pasting the schematic inside a .doc file? It's much faster to read a .png file than first to open Word.

I agree with "lastdance" that using a comparator to shut down the output completely. This will just make the output oscillate. First in turnes off thw output and then the current falls, then the output turns on again which makes the current rise again, which again makes the output turn off, it oscillates like this forever until the current load goes uner the limit again.

 

[smartsarath2003]

How hard can it be?
It seem you want somenone else to design the whole circuit for you.
Maybe you should hire an electronics engineer to design it for you.

I am sorry If I mean like that,But I have a datasheet from IR, where is there ia same graph, but no Vgs mentioned. What I requested Latsdance is wether Rds is independent of Vgs.

Any way leaving that I dkidn't understand why he is saying GND terminal of the system has to be the output of power supply. The 5V supply is for internal operation.I don't need to use 5V output

Coming to specs I mentioned some here already

The basic spec's for this design are 5-30V output, upto 3A adjustable output current, 1% load regulation at max output ,short circuit protection,Digital Voltmeter and ammeter for voltage and current display

This is my first project with analogue electronics and I am designing for my personal use.Thats whysome of my designs may looks strange. Also I have free access to most/all of the components i used here. So I have to check to add new components, weather they are avilable or not?

Finally, to reference Vgs with ground, i wan't to move the Mosfet before Rsense. this way I can also eliminate drop across Ron as well. So it looks finally arriving at borber's idea of moving series elements before the regulator

Can any one see any problems with this change?
Thanks

 

[pokemon]

you can improve regulation throught adding bypass capacitor ,but you have to sure that your circuit is stable