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
news:gnps3j99nl7t4dkdt22k7oe5tr0e6dh60i@4ax.com...

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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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 :)

Ground is input negative.

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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.

Yes it crossed my mind that the input may need EMC filtering too.

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Pay me for EMC compliance :)

As long as it doesn't go in circles with filter this, failed again, filter
that, failed again, change the layout, failed again, etc

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--
piglet