Path: ...!weretis.net!feeder9.news.weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: piglet Newsgroups: sci.electronics.design Subject: Re: Another design Date: Sat, 11 May 2024 16:04:15 +0100 Organization: A noisesome patent Spinner Lines: 219 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Sat, 11 May 2024 17:04:16 +0200 (CEST) Injection-Info: dont-email.me; posting-host="59778dfed4dae8e0069ef6e07fccdba4"; logging-data="2207475"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19MM2r938/dIsj0arslQpJq" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:gGALYOjg7TgoBJ4ifgxkopx1slo= In-Reply-To: Content-Language: en-GB Bytes: 7439 On 11/05/2024 3:29 pm, John Larkin wrote: > On Fri, 10 May 2024 18:17:47 -0400, "Edward Rawde" > wrote: > >> "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 :) >>> >>> 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. >> >> That makes me wonder whether the input could be made near enough DC by using >> two converters. >> One taking current when the other isn't. Perhaps two LEDs each. >> >> Thanks for all your input. I think I'm just about done with this unless John >> Larkin want to show his pfet and one npn circuit. >> >>> >>> Pay me for EMC compliance :) >>> >>> -- >>> piglet >> > > Something like this should work. > > https://www.dropbox.com/scl/fi/su03d8gaxbi67zhufz3th/LED_CC_Reg_1.jpg?rlkey=oh4ib9011ee1c74ih7hk7dzcb&raw=1 > > But I'd rather use a TPS562208, which would be cheaper and simpler and > has spread-spectrum to help the EMC thing by about 20 dB. > > Yes, my take is not too far distant but I tried to accomodate the OP's unexplained desire for ground referenced LED output. Version 4 SHEET 1 1044 708 WIRE -144 -112 -432 -112 WIRE 64 -112 -144 -112 WIRE 176 -112 64 -112 WIRE -144 -96 -144 -112 WIRE 64 -80 64 -112 WIRE -144 16 -144 -16 WIRE -144 16 -224 16 WIRE 176 16 176 -112 WIRE 64 32 64 0 WIRE 128 32 64 32 WIRE -144 48 -144 16 WIRE 176 144 176 112 WIRE 272 144 176 144 WIRE -224 176 -224 16 WIRE -144 176 -144 128 WIRE -64 176 -144 176 WIRE 176 176 176 144 WIRE 176 176 16 176 WIRE 176 208 176 176 WIRE 64 224 64 32 WIRE -144 272 -144 176 WIRE 0 272 -144 272 WIRE -432 320 -432 -112 WIRE -144 320 -144 272 WIRE 176 320 176 288 WIRE 176 320 64 320 WIRE 176 336 176 320 WIRE -144 432 -144 384 WIRE -48 432 -144 432 WIRE 176 432 176 416 WIRE 176 432 32 432 WIRE 352 432 176 432 WIRE 448 432 352 432 WIRE 352 480 352 432 WIRE 448 480 448 432 WIRE 272 496 272 144 WIRE -432 592 -432 400 WIRE -224 592 -224 240 WIRE -224 592 -432 592 WIRE 272 592 272 560 WIRE 272 592 -224 592 WIRE 352 592 352 544 WIRE 352 592 272 592 WIRE 448 592 448 544 WIRE 448 592 352 592 WIRE -432 640 -432 592 FLAG -432 640 0 FLAG 448 432 OUT SYMBOL schottky 288 560 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D3 SYMATTR Value 1N5817 SYMATTR Description Diode SYMATTR Type diode SYMBOL ind 160 192 R0 SYMATTR InstName L1 SYMATTR Value 0.068m SYMATTR SpiceLine Rser=50m SYMBOL LED 432 480 R0 SYMATTR InstName D4 SYMATTR Value LXK2-PW14 SYMATTR Description Diode SYMATTR Type diode SYMBOL voltage -432 304 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 12 SYMBOL res 160 320 R0 SYMATTR InstName R6 SYMATTR Value 0.15 SYMBOL cap 336 480 R0 SYMATTR InstName C1 ========== REMAINDER OF ARTICLE TRUNCATED ==========