Path: Xl.tags.giganews.com!local-1.nntp.ord.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail
NNTP-Posting-Date: Sat, 11 May 2024 14:31:15 +0000
From: John Larkin <jjSNIPlarkin@highNONOlandtechnology.com>
Newsgroups: sci.electronics.design
Subject: Re: Another design
Date: Sat, 11 May 2024 07:29:26 -0700
Organization: Highland Tech
Reply-To: xx@yy.com
Message-ID: <frvu3jh6lj91hpd0u5ifsl57aifkeshi7k@4ax.com>
References: <v1ho21$4ps$1@nnrp.usenet.blueworldhosting.com> <v1k389$pcn$1@nnrp.usenet.blueworldhosting.com> <gnps3j99nl7t4dkdt22k7oe5tr0e6dh60i@4ax.com> <v1m22s$2qof$1@nnrp.usenet.blueworldhosting.com> <v1m48d$1j1bc$1@dont-email.me> <v1m6ed$28af$1@nnrp.usenet.blueworldhosting.com>
X-Newsreader: Forte Agent 3.1/32.783
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Lines: 92
X-Trace: sv3-H8VkQUlYFFb3Zg0IIIn43EPfE7bJOgSKc5yXkt9xnj7Qgh4I8YEYvfrG4xfbvbxqQtt1ge3RRMjM9zP!/j3ELOer3g5IgPLx9AeWExFN3GSlGmw4B6YVwUsShPOlbiXURD5IIzb8SoHs3LS4ezyavIqMzTXl!Bv1UGw==
X-Complaints-To: www.supernews.com/docs/abuse.html
X-DMCA-Complaints-To: www.supernews.com/docs/dmca.html
X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers
X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly
X-Postfilter: 1.3.40
Bytes: 4367

On Fri, 10 May 2024 18:17:47 -0400, "Edward Rawde"
<invalid@invalid.invalid> wrote:

>"piglet" <erichpwagner@hotmail.com> wrote in message 
>news:v1m48d$1j1bc$1@dont-email.me...
>> Edward Rawde <invalid@invalid.invalid> wrote:
>>> "John Larkin" <jjSNIPlarkin@highNONOlandtechnology.com> wrote in message
>>> news:gnps3j99nl7t4dkdt22k7oe5tr0e6dh60i@4ax.com...
>>>> On Thu, 9 May 2024 23:11:03 -0400, "Edward Rawde"
>>>> <invalid@invalid.invalid> 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.
>>>>
>>>> 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.