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From: "Edward Rawde" <invalid@invalid.invalid>
Newsgroups: sci.electronics.design
Subject: Re: Another design
Date: Fri, 10 May 2024 14:57:03 -0400
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"piglet" <erichpwagner@hotmail.com> wrote in message 
news:v1li00$1eir3$1@dont-email.me...
> On 10/05/2024 4:11 am, Edward Rawde 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.
>>
....
>
>
> The venerable LM311 is still a good value comparator, if you want to penny 
> pinch omit the gate driver buffers and lower the pullup resistor but 
> efficiency will drop a lot from 85% to ca 72%.
>

Thanks, that works but I was hoping for a smaller inductor at about 1MHz and 
filtered LED feed referenced to ground for up to three LEDs.

I'm probably done with my circuit unless there's a cheaper comparator which 
can do the same job or a cheaper op amp which can run on lead acid voltage. 
Or preferably up to 15V.
Also a cheaper fet.