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From: "Edward Rawde" <invalid@invalid.invalid>
Newsgroups: sci.electronics.design
Subject: Re: Another design
Date: Fri, 10 May 2024 17:03:23 -0400
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"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.
>>>
>>> Startup behaviour is not ideal but maybe that can be fixed if it needs
>>> fixing.
>>>
>>> What's the cheapest op amp I can use for U2 instead of OP07?
>>>
>>> Is there a cheaper comparator instead of LT1719 which will work?
>>> Also the fet is bigger than it needs to ne.
>>>
>>> Is there a better device for D4? Particularly if R4 can be reduced.
>>>
>>> Will it work at all? Except in simulation.
>>>
>>
>>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.
>
> I think the LED constant-current switcher can be done with a pfet and
> two NPN transistors.
>

Ok here's the spec.

Input voltage range 10.5V to 12.6 V. Preferably 10V to 15V.

Minimum efficiency. 80%

Inductor not bigger than 68uH 1A. Preferably smaller.

One, two or three LEDs at 500mA +/- 50mA

Filtered LED feed referenced to ground.

Maximum total LED wiring length. 12 inches.

EMC compliant in all countries.

Cost. Minimum which will meet spec.