[SOLVED] high current regulated power supply

[shreyas_patel21]

hello everyone,

I am designing a regulatead power supply from 1 to 15V with 8A load.

I used LM338 for this purpose but it was not giving voltage below 1.2V

If I give negative feedback then it cant give sufficient current.

I also tried LM3150 but it gives very high noise.

any suggestion will be acceptable..

thank you!
Regards
Shreyas

 

[DXNewcastle]

The very first sentence in the National Semiconductor datasheet for the LM338 says:
" . . regulators capable of supplying in excess of 5A over a 1.2V to 32V output range."

Perhaps you didn't notice that?

 

[Satish Nasik]

Dear Shreyas_Patel21,
You have not stated why you have used LM338 as voltage regulator.
Why not a standered LM723 circuit with pass transistors.
Elector has published a circuit under a name of Laboratory Power supply
using LM723 which is 0 to 30 v. The PCB for the same are available with Visha Electronics or Vega
Electronics in Mumbai. This circuit uses SL100 and 2N3055 in a Darligton
pair.Now even if you want to continue using the existing LM338 circuit
you can use a darligton transistor like TIP124 in the outpt of LM338 in
feedback mode to achive the required current gain to feed the pass transistors.
Satish
VU2SNK

 

[shreyas_patel21]

Hi DXNewcastle,

I have read it but we can use it for high current with pass transistor,

and for 1V we can use negative feedback to it.

---------- Post added at 09:54 ---------- Previous post was at 09:52 ----------

hi Satish Nasik,

I have done it using LM338 but the problem is for 1V i am not achieving sufficient current.

thank you

 

[hotwaterwizard]

Here is the one I made and it works great!

 

[shreyas_patel21]

hi hotwaterwizard

will this power supply work for 1V?
can it give 8A load?

thanks

 

[hotwaterwizard]

It goes from zero to 30 volts with no problem.
The transistors are well heatsinked and are capable of double that amp draw.
Mine is 8 amps and I used all 4 of the 2N3055 transistors in the diagram.

Here is the original Diagram and project page.

**broken link removed**

---------- Post added at 07:51 ---------- Previous post was at 07:31 ----------

Seen the NEW diagram for the Project?

http://users.belgacom.net/hamradio/schemas/20ampere_regulatable_powersupply_on6mu.gif

 

[Satish Nasik]

Dear Shreyas_patel,
I do agree with the circuit given by hotwatervizard.
I have built such kind of circuit using LM315T and was using it for my Yeasu FT757GX tranciver.
Though in my application the voltage was fixed to 13.8v the pass transistors do supply required
current.(in my case 20amp with 6 Nos of 2N3055) on a hefty heatsink. So you need not worry
about the output current that can be boosted by adding more no of pass transistors.
Please note I have not built the exact circuit.
Satish
VU2SNK

 

[shreyas_patel21]

thank you,

can I use this circuit attached by me?

I found it in datasheet

 

[DXNewcastle]

I think you have already told us that you require an output voltage which goes below the 1.2volts minimum from the LM338, so I don't understand why you are asking again if you can use the LM338.
" . . regulators capable of supplying in excess of 5A over a 1.2V to 32V output range."

I stronly recommend the excellent design presented by hotwaterwizard. I'm sure it will give you exactly the output you need. (I would be a little anxious about the current-sharing abilities of the multiple output transistors' base resistors of just 0.1R but I'm sure it works very reliably).

 

[Awarapunshee]

Here is the a Controller based PSU. Downloaded many years ago (so can't remember). It contains all Schematic, PCB, code, hex file etc

Regards

 

[shreyas_patel21]

I think you have already told us that you require an output voltage which goes below the 1.2volts minimum from the LM338, so I don't understand why you are asking again if you can use the LM338.
" . . regulators capable of supplying in excess of 5A over a 1.2V to 32V output range."

I stronly recommend the excellent design presented by hotwaterwizard. I'm sure it will give you exactly the output you need. (I would be a little anxious about the current-sharing abilities of the multiple output transistors' base resistors of just 0.1R but I'm sure it works very reliably).

thanks DXNewcastle,

LM 317 in hotwaterwizard design also stands for 1.2 to 37V
LM 338 stands for 1.2 to 32V

I have used the design similar to hotwaterwizard's design using LM338.

In that design I have problem of 1V output.
If we use diodes to achieve 1V it will require minimum load.
in absent of load the output goes higher than we set.

so I gave negative reference voltage to LM338 so 1V is achieved but it cant take high loads.


so I was asking for that design.
thank you

 

[shreyas_patel21]

another problem I had in hotwaterwizard's similar design is that the drop in output voltage is very large when I connect load with it.

 

[shreyas_patel21]

thank you all,

I have done it using lm138 using similar design of hotwaterwizard...