From: "Edward Rawde" Newsgroups: sci.electronics.design Subject: Re: Another design Date: Fri, 10 May 2024 18:05:10 -0400 Organization: BWH Usenet Archive (https://usenet.blueworldhosting.com) Lines: 83 Message-ID: References: Injection-Date: Fri, 10 May 2024 22:05:13 -0000 (UTC) Injection-Info: nnrp.usenet.blueworldhosting.com; logging-data="37575"; mail-complaints-to="usenet@blueworldhosting.com" Cancel-Lock: sha1:y9Y6E78Km5hZ+P2b4WG0tfFij5E= sha256:jBYXH83BJc22sUhP+tjvsnpjGw4FBky3A4jcuzY2dMg= sha1:11/eAZemU4Wjq1JqrEZF9jVp8+E= sha256:aH7lsBVb7Jt7/W4aHJw5MUrqzy5S3yGeNxR/hra6iew= X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2900.5931 X-RFC2646: Format=Flowed; Original X-Priority: 3 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 Bytes: 3845 "piglet" wrote in message news:v1m48d$1j1bc$1@dont-email.me... > Edward Rawde wrote: >> "John Larkin" wrote in message >> news:gnps3j99nl7t4dkdt22k7oe5tr0e6dh60i@4ax.com... >>> On Thu, 9 May 2024 23:11:03 -0400, "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. >>> >>> 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. >> >> >> > > My LM311 based idea works ok with 68uH inductors too. Efficiency is above > 80% for supply 10 to 13V and still 77% at 16V > > Haven't explored 1, 2 or 3 LED outputs. > > 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. > > 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. > > 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 > > -- > piglet