Re: Another design

On 10/05/2024 7:57 pm, Edward Rawde wrote:

"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.
 

Ground referenced output is possible, rearrange the sense resistor and stand the reference on top of the LEDs. As in ...
Version 4
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piglet