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- Newsgroups: sci.electronics
- Path: sparky!uunet!mcsun!chsun!bernina!schaerer
- From: schaerer@isi.ethz.ch (Thomas Schaerer)
- Subject: Re: 12 V -> 3V, 0.6 A
- Message-ID: <1992Nov9.185659.12877@bernina.ethz.ch>
- Sender: news@bernina.ethz.ch (USENET News System)
- Organization: Swiss Federal Institute of Technology (ETH), Zurich, CH
- X-Newsreader: TIN [version 1.1 PL6]
- References: <sehari.721325974@class1.iastate.edu>
- Date: Mon, 9 Nov 1992 18:56:59 GMT
- Lines: 44
-
- Babak Sehari (sehari@iastate.edu) wrote:
- : In <1992Nov9.114833.26094@bernina.ethz.ch> schaerer@isi.ethz.ch (Thomas Schaerer) writes:
- :
- : >Babak Sehari (sehari@iastate.edu) wrote:
- : >:
- : >: There are many ways to do this the cheapest way is to put:
- : ^^^^^^^^^
- :
- : >Sorry but all this is nonsense bcause of the high current. If you realise
- : >a linear regulator you will generate very high lostpower. In this example
- : >will be 0.6A * 9V = 5.4W. The better way is to build a switched regulator.
- : >The advandage is the high efficiency ang therefore less powerdissipation.
- : >There are many ic which can do this with a few additional components.
- : >Take the Switching-Regulator L296 from SGS-THOMSON. There is a kit with
- : >pcb-board and the needed components. Ask a SGS-THOMSON-Distributor.
- :
- : >So I hope I can help you. Greeting from Thomas
- :
- : You can spend 1000s of $s on a voltage transformer to make it as efficient as
- : possible. However, 5.4W in a car is not really that important. You
- : lose much more, just by not having a new battery in your car, or just
- : by turning on your lights. Here, the question is Engineering compromise.
- :
- : I guess you could use gold wire to wire up your car, too! -:) Even though,
- : it has less resistance than regular wire; the costs does not justify the
- : savings in this case.
- :
- : However, If you want to do this most efficient way, you should change it
- : to AC, using a Class B Amp, then send it through step down transformer
- : , with super conducting wires a ferrite core -:), than convert it back
- : to DC. The efficiency would be %85*%98*%85=%70. That is 0.7W Vs. 5.4W
- : loss. However, it costs more than $500 Vs. $5 of my design. This does not
- : justify 4.7W power saving in a car, which more power is consumed for
- : ornamental reasons. For example an extra stop light consumes 30W alone. -:)
- :
- : With highest regards,
- : Babak Sehari.
- : --
-
- I see you are right! I have forgotten to regard the car-powersystem. But
- one point is wrong. A selfmade switched power-supply doesn't cost $500.
- If you take L296 it's much cheaper, about $50 -$70.
-
- Greeting Thomas
-