Any suggestions for regulators that will handle a max 48 volt
VCC?. I have 3 transformers that output 35 VAC at a few amps.
I'd like to build some 13.8 VDC supplies. Seems 723's and 317's
are maxxed at 40 volts. I see 317HV's that are good to a VCC
of 60 volts. The large pass transistors from PC power supplies
are good for 10 amps and the smaller ones make good buffers.
Each stage drops .7 volts, so maybe I can go back to the old
zener diode/resistor regulator trick. A buffer and output would
give a final 13.6 volts.

On a sunny day (Thu, 19 Jan 2006 02:12:09 -0500) it happened Scott in
Baltimore wrote in
:

Any suggestions for regulators that will handle a max 48 volt
VCC?. I have 3 transformers that output 35 VAC at a few amps.
I'd like to build some 13.8 VDC supplies. Seems 723's and 317's
are maxxed at 40 volts. I see 317HV's that are good to a VCC
of 60 volts. The large pass transistors from PC power supplies
are good for 10 amps and the smaller ones make good buffers.
Each stage drops .7 volts, so maybe I can go back to the old
zener diode/resistor regulator trick. A buffer and output would
give a final 13.6 volts.
I am using a AT computer power supply, this one can do 8A at +12 V.
Some of the newer ones can do 25 A @12V, but may be more difficult
to start.
There may be some hum or you would have to add some filter caps.
But switchmode is all that will be here in the future..
http://www.alternate.nl/html/shop/pr...el2=Voedingen&

For output voltages and current look up (clikc) each individual one.

How much current do you plan to draw from this 13.8V supply?

Professor
www.telstar-electronics

How much current do you plan to draw from this 13.8V supply?

Professor
www.telstar-electronics.com

How about an LM338?
http://cache.national.com/ds/LM/LM138.pdf

Professor
www.telstar-electronics.com

On Thu, 19 Jan 2006 02:12:09 -0500, Scott in Baltimore
wrote:

+Any suggestions for regulators that will handle a max 48 volt
+VCC?. I have 3 transformers that output 35 VAC at a few amps.
+I'd like to build some 13.8 VDC supplies. Seems 723's and 317's
+are maxxed at 40 volts. I see 317HV's that are good to a VCC
+of 60 volts. The large pass transistors from PC power supplies
+are good for 10 amps and the smaller ones make good buffers.
+Each stage drops .7 volts, so maybe I can go back to the old
+zener diode/resistor regulator trick. A buffer and output would
+give a final 13.6 volts.
****

Are any of them center tapped secondaries?

man dropping around 35 volts across any regualtor or pass transistor
is going to require a good size heat sink with any appreciable current
draw. Three amps and you are dropping about 100+ Watts across any
regulator or pass transistor(s).

With center tapped secondaries you can run a fullwave center tap
rectifier setup and are looking at upwards to 25 VDC out into a
capacitor input filter. About 16 VDC with a choke input filter. There
your regualtor or pass transistor wil not have as much voltage drop
across them. The heat sink size is reduce considerably.

james

James is certainly right... if you plan to draw much current from your
supply... you may have make other arrangements then just dropping all
that voltage. That thing will be a real furnace.

Professor
www.telstar-electronics.com

On 19 Jan 2006 13:39:54 -0800, "Professor"
wrote:

+James is certainly right... if you plan to draw much current from your
+supply... you may have make other arrangements then just dropping all
+that voltage. That thing will be a real furnace.
+
+Professor
+www.telstar-electronics.com
*****

I was once thinking of using a transformer that had a secondary
voltage of 36VAC and use pass transistors I had in my spare box. I
wanted to use a T0-220 case NPN and the design required the use of 8
of them in order to lower the heat dissapation per transistor. That
changed my mind and ended up usign a different transformer.

james

"james" wrote in message
...
On 19 Jan 2006 13:39:54 -0800, "Professor"
wrote:

+James is certainly right... if you plan to draw much current from your
+supply... you may have make other arrangements then just dropping all
+that voltage. That thing will be a real furnace.
+
+Professor
+www.telstar-electronics.com
*****

I was once thinking of using a transformer that had a secondary
voltage of 36VAC and use pass transistors I had in my spare box. I
wanted to use a T0-220 case NPN and the design required the use of 8
of them in order to lower the heat dissapation per transistor. That
changed my mind and ended up usign a different transformer.

james

Usually, transformers can be found more reasonably priced than
semiconductors of high current ratings, especially surplus!

Usually, transformers can be found more reasonably priced than
semiconductors of high current ratings, especially surplus!


I got a great center tapped 60 Amp xfmr on ebay of all places! Also
got some 100 Amp rectifiers so i'd suggest trying there...