james wrote:
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?


No. I may be dumping these transformers.


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).


Just pulling a few amps with a 25 volt VCC generates a lot of heat.


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.


I know, I know...