Path: ...!news.misty.com!weretis.net!feeder9.news.weretis.net!usenet.blueworldhosting.com!diablo1.usenet.blueworldhosting.com!nnrp.usenet.blueworldhosting.com!.POSTED!not-for-mail From: "Edward Rawde" Newsgroups: sci.electronics.design Subject: Re: Another design Date: Fri, 10 May 2024 14:57:03 -0400 Organization: BWH Usenet Archive (https://usenet.blueworldhosting.com) Lines: 41 Message-ID: References: Injection-Date: Fri, 10 May 2024 18:57:07 -0000 (UTC) Injection-Info: nnrp.usenet.blueworldhosting.com; logging-data="51395"; mail-complaints-to="usenet@blueworldhosting.com" Cancel-Lock: sha1:XSfzMZWZjTOVnL/mqqFR6UwYoEs= sha256:Mme0dHIs1w1KpQgKaJBxNAX8lgi9M7FLaUaTMaz/Esk= sha1:CpNOyvIhDnMR6N3UHyLL8dc4KSs= sha256:Q3MjF2atmEeZhhglOamfIxTNO0pktUY8dvEIy9JOmms= X-RFC2646: Format=Flowed; Response X-MSMail-Priority: Normal X-Priority: 3 X-Newsreader: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 Bytes: 2721 "piglet" wrote in message news:v1li00$1eir3$1@dont-email.me... > On 10/05/2024 4:11 am, Edward Rawde wrote: >> "Edward Rawde" 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.