How to Design a Linear Power Supply

[asabalon]

I want to design a Linear Power Supply with an output voltage of 80V and an output current of 2.5A. Is this possible? If it is possible, please tell me what circuit design to use. Thank You.

 

[Tahmid]

Hi,
Why wouldn't it be possible?

You can use an 80-0-80 3A transformer, 5A diodes and bulk capacitor (2000-5000uF).

Then you need to decide if it has to be regulated. This is where it gets tricky.

You can use a discrete regulator circuit built around BJTs. Works but inefficient.
Or you could use a buck regulator (efficient but since, you mentioned linear, maybe you won't want to do this).

Hope this helps.
Tahmid.

 

[srizbf]

whether it is linear or switched ,
first make it clear what is the input voltage variation expected ?

sriabf
24thjune2010

 

[asabalon]

Tahmid

What circuit design should i use to implement the Linear Power Supply? I have read about LPS and I found out that there are a lot of ways to implement it. Could you tell me the most efficient one? I also want its output to be regulated. Thanks.

 

[Tahmid]

Hi,
The transformer, rectifiers and capacitor are a must and must be used no matter how you configure your circuit. Here you have your unregulated DC.
If you have centre tapped transformer use a full wave rectifier method, if not, then use bridge rectifier.

For regulation, I think you have to use discrete circuitry, because I know of no 80V regulators. This will be based on zener-transistor or similar method. Since this is linear the circuit will work effectively and reliably, but not very efficiently. Your transistor will generate PLENTY of heat, along with the diodes. And these parts need to be mounted on heatsink. However, after this you can expect a reliable power supply.

Hope this helps.
Tahmid.

 

[karesz]

Hi asabalon,
Whats your input voltage pls, or is it trivialry 230V AC?
K.

Added after 4 hours 46 minutes:

Hi,
Did you seen thes parallel topic?: 50v to 120volt power supply 2A
#1286468
K.

 

[asabalon]

Sir sorry for the late reply.
The input voltage is 230Vac
the output current can either be 2A or 2.5A
I have seen a schematic of a 40V 2A circuit.
https://www.redcircuits.com/Page123.htm
How do I change/derive the 80V linear supply from the 40V supply in the link?

 

[karesz]

Hi,
No problem...
The LM 317 can not be your solution!
Its MAXIMUM Uin=40V!! :-(
http://www.datasheetcatalog.com/datasheets_pdf/L/M/3/1/LM317.shtml
Otherwiese refer pls to Fig.3 of National`s datasheet for Uout setting_but select less as 35V_others you will kill the regulator, & other question is that its only a 1-1.5A type. For higher Iload you need parallel transistor(s)!
Why is the from me linked "similar topic" not good for your applikation pls?
K.

 

[asabalon]

Sir i have commented on the link you posted. I just wanted to know if the circuit i referred to was working. I haven't had it simulated because i am still studying on how to use SIMetrix and LTspice. I badly need to make a linear power supply and the circuit i told you has a lower voltage. Can you tell any ways on how to redesign the circuit to be able for it to output 80V and 2.5A? Thank You.

 

[karesz]

OK,
I didnt much comment found, but as you know too, english isnt my mother language..
You see, the problem is the transistor dont have more as 40V!
You need some another, I belive, a discret built circuit for 80V output & ca. 2.5A_with really masive power block & cooling.
The regulator transistor must have =>5V/2.5A, will diisipate min. 12-13W.
Do you need a fix 80V output pls?
K.

 

[asabalon]

Yes i need an 80-Volt output. Thank You

Added after 45 seconds:

OK,
The regulator transistor must have =>5V/2.5A, will diisipate min. 12-13W.
Do you need a fix 80V output pls?
K.

And sir, what do you mean by this?

 

[karesz]

I mean, that the minimum needed input voltage is so at 85V or even 90V for some input tolerances (as reserve), so you need a regulator device(transistor or MOSFET) what is i.e. for 100V specified...
K.

 

[asabalon]

do i have to make my own regulator for the expected 80V output?

 

[karesz]

These was my opinion before too, here another basic idea (if you dont like FET circuits):...
**broken link removed**
K.