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 18:27:33 +0100 Organization: A noisesome patent Spinner Lines: 137 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 19:27:34 +0200 (CEST) Injection-Info: dont-email.me; posting-host="59778dfed4dae8e0069ef6e07fccdba4"; logging-data="2270414"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19iKlIh4sqfm7DUfguSqQEH" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:OFEOOIclIqHOibnYBUT9WudmB4I= Content-Language: en-GB In-Reply-To: Bytes: 6353 On 11/05/2024 5:42 pm, John Larkin wrote: > On Sat, 11 May 2024 16:04:15 +0100, piglet > wrote: > >> 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. > > That's nice. It's only an LED, so it probably doesn't need +12v > compensation. > > LEDs lose light as temperature rises, so it probably doesn't need Vbe > temp compensation either. I'm glad that you saw the hysteresis trick, > and that you drew a decent looking schematic with a title, date, and > author. > > We have one project here that has had three or four project engineers > so far, and the project folder contains 175 (yes, 175!) .asc files, > most of which are hideous uncommented messes. > > My sim will be # 176. > > https://www.dropbox.com/scl/fi/i1rmnne2j2f2nhetfg1dn/P941C_May11.jpg?rlkey=9by4bmkzo6iim763468y21ko2&raw=1 > > It's a dual isolated programmable DC power supply, but it has remote > sense and a paralleling relay, which complicate life. We don't know > what bizarre loads the user will have, or if they will connect the > remote sense right. > > Sims run super slow and there are many cases to test, so we set up > three monster PCs in the conference room as a simulator farm, to > supplement the two we will use in engineers offices. > > Thanks. Compensating feedback systems to cope with wide ranging capacitive loads is awkward. I have good results with Phil Perkins stacked RC 3dB/octave method. piglet