Post by thread:[EE]: voltage regulator

I need some help choosing some components for my application. Power will be supplied by automotive battery (12V - car or motorcycle) AND a 9v battery. Logically, when 12v battery is connected, I don't need to draw energy from the 9v battery. I've seen a few (quite a few) models from national semi., ti and seiko, but I'm now sure if only one regulator will do the job or what kind of switching (between the 9v and 12v bats) components do I need to consider? The desired output voltage is 3.3 (I'm using the "LF" series of PICs) Thanks Padu ___________________________________________

At 04:59 PM 11/3/2004, Padu wrote: >I need some help choosing some components for my application. > >Power will be supplied by automotive battery (12V - car or motorcycle) AND >a 9v battery. Logically, when 12v battery is connected, I don't need to >draw energy from the 9v battery. All you need here is a couple of diodes. ____________________________________________

Just wondering if anyone has run across a working schematic for a DC voltage regulator. Input range is 20-48 and required output is 12vdc @ 10Amps with a max of say 15-20A. I'm looking at one schematic that has the required output but is too narrow in the input voltage range. So if you know of a good one please let me know. Tia Dave

Dave King wrote: {Quote hidden}> > Just wondering if anyone has run across a working schematic > for a DC voltage regulator. Input range is 20-48 and required > output is 12vdc @ 10Amps with a max of say 15-20A. > > I'm looking at one schematic that has the required output but > is too narrow in the input voltage range. So if you know of a good > one please let me know. > > Tia > > Dave Are you looking for a switching or linear regulator? A classic Linear regulator is the multi 2N3055 pass transistors feed by a single 3055 driven by a 723. Most ARRL handbooks have the design including the transformer and rectifier/filter section. There are better transistors and FETs that can be substituted. You will need a MASSIVE heat sink, or forced cooled sink. I have designed and built linear supplies with transistor and FET bricks for 100 amp+ performance. Tom -- * | __O Thomas C. Sefranek spam_OUTWA1RHPTakeThisOuTARRL.net |_-\<,_ Amateur Radio Operator: WA1RHP (*)/ (*) Bicycle mobile on 145.41, 448.625 MHz hamradio.cmcorp.com/inventory/Inventory.html http://www.harvardrepeater.org

Google for "IBA 48V 12V supply" and you will get the first hit from Maxim. 48V bus (telecom) or 42V bus (electric vehicle) will be very popular for IBA converters. VRM (eg: pentium 4/AMD64 power supply on the motherboard) is drawing power from the 12V bus (used to be from 5V bus in the Pentium 1 era). It is not what you exactly want. Still you may want to look at the forward converter design and adapt it to your design. www.maxim-ic.com/appnotes.cfm/appnote_number/3539/ln/en "A 50 Watt Internal Bus Architecture (IBA) Power Supply". Regards, Xiaofan

Tom Sefranek wrote: > Are you looking for a switching or linear regulator? > > A classic Linear regulator is the multi 2N3055 pass transistors feed > by a single 3055 driven by a 723. > Most ARRL handbooks have the design including the transformer and > rectifier/filter section. > There are better transistors and FETs that can be substituted. > You will need a MASSIVE heat sink, or forced cooled sink. > I have designed and built linear supplies with transistor and FET > bricks for 100 amp+ performance. > > Tom > I have a massive copper heatsink that came from a Sorensen linear power supply. It has room for 6 TO-3 devices [has 5 2n3055s on it right now], air cooled. If anyone wants it, I'd let it go for $15. It's 5+ pounds of copper. I'd give it away but I bought the non-working Sorensen supply on eBay for $60. I also have the transformer from the supply. It's really a monster. -- Martin Klingensmith http://wwia.org/ http://nnytech.net/

Dave King wrote: > > Just wondering if anyone has run across a working schematic > for a DC voltage regulator. Input range is 20-48 and required > output is 12vdc @ 10Amps with a max of say 15-20A. > > I'm looking at one schematic that has the required output but > is too narrow in the input voltage range. So if you know of a good > one please let me know. > > Tia > > Dave > You can make a relatively simple push-pull half bridge design with an LM/SG3525. The core selection is very important as it determines if your FETs will explode [core saturation]. I assume you have done some searching and have seen the car audio folk's SMPS. These are usually unregulated with poor design. If you don't need an isolated output [it seems you have an input transformer already] you can do this with some careful experimentation. Always check everything twice and power it up through a 1 ohm resistor the first time. It can be done but I'd be very skeptical of a first SMPS of that power working the first time. If you want me to check your schematic I'd be glad to [if you use the '3525 or '3846] I've been fiddling around with those for a few years. If you want design assistance I could help you there too. -- Martin Klingensmith http://wwia.org/ http://nnytech.net/