From: John Popelish
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Subject: Re: 12 vdc to 6vdc @ 30amps
References: <firstname.lastname@example.org> <3D8295F3.6B10E9CB@rica.net>
Date: Sat, 14 Sep 2002 03:07:35 GMT
NNTP-Posting-Date: Fri, 13 Sep 2002 23:07:35 EDT
Winfield Hill wrote:
> John Popelish wrote...
> > "Michael B. Williams" wrote:
> >> I have a need to convert 12vdc to 6vdc from a motorcycle battery
> >> to drive a electric motor which could pull up to 30 amps.
> > I once made a very compact 12 to 6 volt converter to run a 6 volt
> > trolling motor at half speed. I think it drew something like 10
> > amps. The converter fit in a match box and consisted of 7 parts.
> > It doesn't regulate, but it is very simple and rugged. I think a
> > 30 amp version would fit in a 4 cubic inch volume. Interested?
> That's simply a 50% PWM switch, right? perhaps with an LC filter?
> Hmm, what about short-circuit protection, voltage soar policy, etc,
> - Win
No, it is just a self oscillating autotransformer DC to DC converter.
It has no short circuit protection. A fuse should work, though.
Here is what I had in mind. I switched from junction transistors to
fets and reduced the parts count a bit.
| | |
A M A
|. |. |
|D \ / |D
-| / |-
(I picked parts from Digikey catalog)
Where A is one of two schottky diodes in an I.R. 47CTQ020 (40 amp 20
M is the motor load,
mmm+mmm is a toroidal core with a bifilar 14 ga. winding (as many
turns as will fit) on a shield bead like a Panasonic KR16TT281815 28
mm O.D., 18 mm I.D, 15 mm height,
And the two Mosfets are IRF1010E, 60 volt, 0.012 ohm,
The one I made with junction transistors was well over 90% efficient,
and I think this might beat it.