Sonsivri
 
*
Welcome, Guest. Please login or register.
Did you miss your activation email?
December 04, 2016, 02:48:08 02:48


Login with username, password and session length


Pages: [1]
Print
Author Topic: 0-30V 0-3/5amp power supply  (Read 6979 times)
0 Members and 1 Guest are viewing this topic.
Wizpic
Global Moderator
Hero Member
*****
Offline Offline

Posts: 976

Thank You
-Given: 197
-Receive: 344



« on: October 23, 2010, 01:23:52 13:23 »

This is my vesrion of a power supply.
O-30V 0-3amps fully tested and fully working, You need to use a 28V ac transformer or if you use a 30V AC transformer then make sure that teh main voltage (open circuit dc voltage) does not go above 44V because that's the op-amps will take.
I had a 0-15V 0-15V transformer with 240V input but the mains is higher which give me an higher ouput.

Logged

When you think, "I can't do anymore. I need a break," that is the time to challenge yourself to keep going another five minutes. Those who persevere for even an extra five minutes will win in life..
Wizpic
Global Moderator
Hero Member
*****
Offline Offline

Posts: 976

Thank You
-Given: 197
-Receive: 344



« Reply #1 on: October 23, 2010, 08:55:52 20:55 »

So if you were to set the output voltage at 0.1 volts and draw three amps, the output resistors could dissipate nearly 100 watts? The output transistors are within their Safe Operating Area at all loads and conditions? At three amps output you might consider a "remote sense" connection as an additional feature.
I have not tired to set the PSU and drawed 3amps at 100mv. Which I doubt would be possible ever would. The PSU is well designed and thuoght of. This is the updated vesrion ofr the electronics lab PSU.
Small and simple to build and cheap. You can get free samples of the TL2141E like I did.

Logged

When you think, "I can't do anymore. I need a break," that is the time to challenge yourself to keep going another five minutes. Those who persevere for even an extra five minutes will win in life..
eSilviu
Newbie
*
Offline Offline

Posts: 34

Thank You
-Given: 4
-Receive: 7


« Reply #2 on: October 24, 2010, 11:13:14 11:13 »

So if you were to set the output voltage at 0.1 volts and draw three amps, the output resistors could dissipate nearly 100 watts? The output transistors are within their Safe Operating Area at all loads and conditions? At three amps output you might consider a "remote sense" connection as an additional feature.

this is the main problem of the linear power supply; not only this design, but all.
If you want to avoid this problem, then use a switching mode power supply, or a combination of switching+linear circuit.
Logged
oldvan
V.I.P
Senior Member
*****
Offline Offline

Posts: 375

Thank You
-Given: 152
-Receive: 106


If the van is a Rockin'...


WWW
« Reply #3 on: October 25, 2010, 01:46:01 01:46 »

Multiple taps on the secondary of the transformer and a few relays were used to improve
efficiency on the Mastech 0-30V 0-5A linear supply I picked up a couple years ago.
Logged

Give a man a fish and you feed him for a day.
Teach a man to fish and he will sit around in a boat drinking beer all day.
Sideshow Bob
Senior Member
****
Offline Offline

Posts: 457

Thank You
-Given: 160
-Receive: 494



« Reply #4 on: October 25, 2010, 10:24:49 10:24 »

So if you were to set the output voltage at 0.1 volts and draw three amps, the output resistors could dissipate nearly 100 watts?
Eh..... what do you mean by this statement. P=UxI=IxRxI. So if you refer to the 0.33 Ohm resistors this will not be correct
Logged

I really am ruggedly handsome, aren't I?
Old_but_Alive
V.I.P
Active Member
*****
Offline Offline

Posts: 211

Thank You
-Given: 152
-Receive: 56


« Reply #5 on: October 25, 2010, 10:57:15 10:57 »


if you have a look at the LT3080 datasheet or more specifically the LT3080-1 at www.linear.com

you will find an application circuit which is very economical on parts ( maybe not cost).

they show in the application part of the datasheet, a switch-mode pre-regulator, and the LT3080 used as the final linear output.

Mike
Logged
borberk
V.I.P
Senior Member
*****
Offline Offline

Posts: 298

Thank You
-Given: 309
-Receive: 598


« Reply #6 on: October 25, 2010, 12:07:54 12:07 »

Suitable heatsink for above project must have thermal resistance lower than 0.8K/W and such can be seen here:

http://www.farnell.com/datasheets/310891.pdf
Logged
Suky
Guest
« Reply #7 on: October 25, 2010, 03:42:07 15:42 »

Have you done a test of the power supply? What results obtained at idle and under load? (Ripple, stability, etc)
Logged
carbontracks
Junior Member
**
Offline Offline

Posts: 67

Thank You
-Given: 20
-Receive: 4


« Reply #8 on: October 29, 2010, 03:18:45 15:18 »

I have not tired to set the PSU and drawed 3amps at 100mv. Which I doubt would be possible ever would.
Well short circuit output conditions could easily give you that... has to be considered.

The design overall is good.  But a thermal shutdown on the pass transistors would be great from a robustness standpoint.  Or a variable transformer tap setup like Oldvan mentioned to improve efficiency.  Then you would want a separate transformer for the control circuitry.
Logged
Wizpic
Global Moderator
Hero Member
*****
Offline Offline

Posts: 976

Thank You
-Given: 197
-Receive: 344



« Reply #9 on: October 29, 2010, 05:56:43 17:56 »

Well short circuit output conditions could easily give you that... has to be considered.

The design overall is good.  But a thermal shutdown on the pass transistors would be great from a robustness standpoint.  Or a variable transformer tap setup like Oldvan mentioned to improve efficiency.  Then you would want a separate transformer for the control circuitry.
I have just tried this and I'm supprised to see at 100Mv you can draw 3amps but this falls down to 1.5amps, The ouput transsistors do not get warm, I take this is down to little voltage ?
This PSU deisgn has been in use many years(not my version but based on the same) and I've never heard about this before.

After all you don't have to build it if you don't think it's any good. Who would be stupid enough to leave it like that for long periods of time anyway, easyway round it is use a temp sensor if it gets to hot it turnd the mains supply off, My workshop isolater is only truned on when I'm in there so I won't have to worry about it Grin Grin
Logged

When you think, "I can't do anymore. I need a break," that is the time to challenge yourself to keep going another five minutes. Those who persevere for even an extra five minutes will win in life..
ahmed
Active Member
***
Offline Offline

Posts: 207

Thank You
-Given: 21
-Receive: 255


« Reply #10 on: October 30, 2010, 05:59:39 17:59 »

Is there a short circuit protection in this power supply
 
Logged
th_sak
Active Member
***
Offline Offline

Posts: 141

Thank You
-Given: 149
-Receive: 149



« Reply #11 on: November 15, 2010, 08:33:28 20:33 »

Hi, I have some questions about this PSU. First is the wattage of the shunt resistor. Should I use 0.47R 10w? Second question is the maximum output current of this PSU. Is it 5A and if yes can I use 240v/25v @5A transformer? And final question, is it possible to change power transistors with MOSFETs or some other equivalent bipolar transistor?

Thank's in advance.
Logged
Sideshow Bob
Senior Member
****
Offline Offline

Posts: 457

Thank You
-Given: 160
-Receive: 494



« Reply #12 on: November 15, 2010, 09:51:42 21:51 »

If you want 5 amps DC from this PSU you should chose a transformer with a current rating equal to
I D.C. = 0.62 X Sec. I A.C.
Logged

I really am ruggedly handsome, aren't I?
Wizpic
Global Moderator
Hero Member
*****
Offline Offline

Posts: 976

Thank You
-Given: 197
-Receive: 344



« Reply #13 on: November 15, 2010, 10:03:26 22:03 »

For the 5A version you have to use a .33R 10W or higher 0.47R will only give you 3A.
The circuit will work with a 25VAC transformer but the max output voltage at 3A will be about 28VDC and less for 5A. The unregulated positive supply will be about 35.7V.

This will not work with Mosfets has it is not desinged to. Tip3055 transisotrs are quite popular. It would be possible to use other transisitors but you would have to check there like for like on the spec sheet,

Wizpic
Logged

When you think, "I can't do anymore. I need a break," that is the time to challenge yourself to keep going another five minutes. Those who persevere for even an extra five minutes will win in life..
Sideshow Bob
Senior Member
****
Offline Offline

Posts: 457

Thank You
-Given: 160
-Receive: 494



« Reply #14 on: November 16, 2010, 11:57:53 11:57 »

For the 5A version you have to use a .33R 10W or higher 0.47R will only give you 3A.
The circuit will work with a 25VAC transformer but the max output voltage at 3A will be about 28VDC and less for 5A. The unregulated positive supply will be about 35.7V.
Then it come to specifying  the power transformer current ratings. Most people do NOT know how to do this correct. The transformer AC current rating will NEVER be equal to DC current rating then using a typical setup with rectifier and filter cap. This is due to how the current from the transformer flow then the filter cap is charging. I include some papers descibing this
 
Logged

I really am ruggedly handsome, aren't I?
gogo246
Newbie
*
Offline Offline

Posts: 19

Thank You
-Given: 71
-Receive: 7


« Reply #15 on: November 25, 2010, 11:05:09 11:05 »

Practically you can't use 28 / 30 V raw DC for 30VDC supply it should be at least 1.5 times higher ie 30 * 1.5 = 45 V raw DC .
Same for current ie for 3A o/p current x'mer current should be 3 * 1.5 = 4.5A AC.
And Filter cap should be at least 6000uF for 3A and 10,000 uF for 5A.
Transistor 2N3055 is 115W transistor. So if you set 0.1V and allow 3A to flow then power dissipation in transistor is
 (45 - 0.1 ) * 3.0 = 135W approx. Safe watts to operate should near 50 - 60% of max.  if you select three transistors then each will dissipate
135/3 = 45 W (approx. 50% of max). I prefer 1 to 1.2 A per transistor would be good for design. So 3 Transistor for 3A and 5 for 5A.
If you have problem that you can't increase raw DC voltage due to opamp's power supply then use zener diode for all opamp supply.
you can also introduce per-regulator as earlier stated. that will be good for transistor as Vce will not be as much high for 0.1mV output.
You can break entire voltage range in 3 ie 0-11V, 9-21V,19-31V.
For Output Board stage use 10 Ohms to 22 Ohms resistors at base of 2N3055 and BD139.
« Last Edit: November 25, 2010, 11:10:56 11:10 by gogo246 » Logged
Pages: [1]
Print
Jump to:  


DISCLAIMER
WE DONT HOST ANY ILLEGAL FILES ON THE SERVER
USE CONTACT US TO REPORT ILLEGAL FILES
ADMINISTRATORS CANNOT BE HELD RESPONSIBLE FOR USERS POSTS AND LINKS

... Copyright 2003-2999 Sonsivri.to ...
Powered by SMF 1.1.18 | SMF © 2006-2009, Simple Machines LLC | HarzeM Dilber MC