Line Drive™ - 15A Linear Driver for Labbies

Re: Line Drive™ - 15A Linear Driver

Well, after some struggling with a board that
failed to produce any output (turned out to
be a resistor soldered in the wrong place) I
can now report some success!

The Line Drive Rev. 1.5a is happily pumping
15A into the test load. The dropout is about
500mV, at least within the granularity of the
diode stack. It could be even less. So in
the current test setup, it's disspiating about
7.5W @ 15A.

The thing that surprises the heck out of me
is that the thing acts like it WANTS to do
more. A quick calculation suggests that with
some modifications and enough heatsinking,
outputs in excess of 50A are theoretically
possible under the right conditions.

15A though is enough for now. Next up are
going to be some scope tests. Stay tuned
and hope for the best. :beer:

Well, the initial scope test results are
inconclusive until I can get a suitable
battery to test with, to the point where
they aren't even worth posting. It is
definitely picking up switching noise. A
battery is really the only way. So I'm still
not comfortable attaching a laser diode yet
at this point.

They do make a really great LED driver,
though. Here it is driving a PT-54 at the full
rated 8.1A continuous. These things are
insanely bright! Some changes still need to
be made if it is going to drive the red and IR
diodes with any efficiency. I feel like I am
getting very close. :bumpit:

Why not just build a suitable DC filtration board so you aren't reliant on batteries? I'm sure you've got some chokes or even large cores around, and some large electrolytics. A simple Pi filter of about 10H and ~8000uF should do I'd think, depending on switching frequency.

Then there is still the problem of isolating
the scope. I don't have/can't afford an
isolated probe. Floating the scope with an
inverter just introduces even more noise.
Ultracaps would also be real nice, but I can't
afford them, either! Batteries are cheap. I
may have found some that will work. We'll
see.

Is it a dual channel scope? Just do the poor-man's-differential method, add both channels and invert one channel, leave ground clips off. That's how I check my TC bridges when live.

Why yes it is, in fact. That not a bad
idea. I'll have to see if my scope will support
that. +2
:gj:

How are the high current CC regulators going? Finished with them yet? I'm interested in the design for something I need it for, I can have some built, if they work. Heat sinks are easy to find on ebay.

To tell the truth, I haven't been feeling
all that great the past couple weeks.
Everything is just sitting on the table,
but I can't do it. This happens from time
to time. Hopefully it will pass.

Understand, coasting for awhile. Thanks.

Well, after some more tweaking, I think I'm
finally satisfied with these. The total
dropout of the test setup is only about
500-600mV @ 15A, and almost half of that
was actually due to the wires and
connection points. You will find that
wiring is absolutely critical at higher
currents like this, and it only gets 'better'
as the current increases.

So here are the scope traces.


Startup @ 15A


Shutdown @ 15A

That is 143mA/mV for those fluent in
o'scope. There is a nice 2mS soft start up
to around 94%, and then a very long gentle
ramp up to the set current.

I plan to do these on a made-to-order basis.
If you're interested, just shoot me by a PM.
That is all.
:thanks: