nuckolls.bob(at)aeroelect
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 Posted: Mon Dec 22, 2008 7:52 am Post subject: AEC 9051 Filtered LED Driver Circuit Question |
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At 11:23 PM 12/21/2008, you wrote:
| Quote: |
This is probably a question for Bob . . . .
I am in the process of building an LED driver that has 4 of
the 3021-D-E-1000 Buck Pucks on the same board. I am attempting to
parrot the filter design that Bob used for the AEC 9051 to quiet
down the Buck Pucks but I have a couple of questions:
1. This board will use PWM (100 Hz) from a PIC to control the
intensity of the LEDs attached to it. The Buck Pucks can be
"flashed" at up to 10 kHz by toggling the control pin between 0 and
5V. I have tested this at 100 Hz and they work very well this way
"bare". If I add the the filter network a-la the AEC 9051 to the
LED+ and LED- lines, will it detrimentally affect the ability to
toggle the output of the Buck Puck on and off at 100 Hz? I suspect
that it won't but I'd like a second (more informed) opinion.
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No problem . . .
| Quote: | 2. Each of the 4 Buck Pucks will have to have it's own filter
network on LED+ and LED-. But I would really like to avoid having
to replicate the filters 4 times for the VIN+ and VIN- lines. If I
combined these into a single filter, would I need to change the
inductance and capacitance values of the components? Inductance and
capacitance values aside, it would seem that I would now have to
have an inductor rated for at least 4A to feed the 4 Buck Pucks.
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Yes . . .
| Quote: | Does that sound right? The problem there is that a 100uH
inductor rated for 4A is physically pretty large and I'm really
trying to keep the size of this thing down. Any other suggested solutions?
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The values were WAGGED . . . I didn't have access to
the DO160 lab at the time to refine the components. All
we know now is that the components cited reduced observed
interference to acceptable if not imperceptible levels.
The filter may be overkill, or even less than suggested
by DO160. There were no objective measurements made.
I have some other test programs coming up that may
give me an opportunity to check the AEC9051's real
noise numbers. In the mean time, the values cited
offer a good starting point for your own experiments.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
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