Re: Another design

"piglet" <erichpwagner@hotmail.com> wrote in message
news:v1m48d$1j1bc$1@dont-email.me...

Edward Rawde <invalid@invalid.invalid> wrote:

"John Larkin" <jjSNIPlarkin@highNONOlandtechnology.com> wrote in message
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On Thu, 9 May 2024 23:11:03 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:
>

"Edward Rawde" <invalid@invalid.invalid> wrote in message
news:v1ho21$4ps$1@nnrp.usenet.blueworldhosting.com...

Now with 9V to 15V input range, direct gate drive and 500mA LED
current.
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Startup behaviour is not ideal but maybe that can be fixed if it needs
fixing.
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What's the cheapest op amp I can use for U2 instead of OP07?
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Is there a cheaper comparator instead of LT1719 which will work?
Also the fet is bigger than it needs to ne.
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Is there a better device for D4? Particularly if R4 can be reduced.
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Will it work at all? Except in simulation.
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I think I've answered my own question for the current controller but I
don't
think it's feasible to attempt a discrete comparator on cost grounds.

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I think the LED constant-current switcher can be done with a pfet and
two NPN transistors.
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Ok here's the spec.
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Input voltage range 10.5V to 12.6 V. Preferably 10V to 15V.
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Minimum efficiency. 80%
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Inductor not bigger than 68uH 1A. Preferably smaller.
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One, two or three LEDs at 500mA +/- 50mA
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Filtered LED feed referenced to ground.
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Maximum total LED wiring length. 12 inches.
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EMC compliant in all countries.
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Cost. Minimum which will meet spec.
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>
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My LM311 based idea works ok with 68uH inductors too. Efficiency is above
80% for supply 10 to 13V and still 77% at 16V
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Haven't explored 1, 2 or 3 LED outputs.
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You didn't say if "ground" was input negative or positive but if positive
ground then flip the circuit over and use a cheaper N-channel FET :)
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The input to a buck converter is pulsed current - you have mentioned
output
leads but some, possibly extensive, filtering will be needed on the input.

That makes me wonder whether the input could be made near enough DC by using
two converters.
One taking current when the other isn't. Perhaps two LEDs each.

Thanks for all your input. I think I'm just about done with this unless John
Larkin want to show his pfet and one npn circuit.

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Pay me for EMC compliance :)
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--
piglet