Re: Another design

On 11/05/2024 3:29 pm, John Larkin wrote:

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.
 

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
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SYMATTR Value 12
SYMBOL res 160 320 R0
SYMATTR InstName R6
SYMATTR Value 0.15
SYMBOL cap 336 480 R0
SYMATTR InstName C1
SYMATTR Value 0.1m
SYMBOL npn 0 224 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL res -64 448 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
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SYMATTR Value 330
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WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
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SYMATTR Value 47k
SYMBOL pmos 128 112 M180
SYMATTR InstName M1
SYMATTR Value AO6407
SYMBOL res 48 -96 R0
SYMATTR InstName R5
SYMATTR Value 330
SYMBOL res -160 32 R0
SYMATTR InstName R2
SYMATTR Value 3.9k
SYMBOL diode -160 320 R0
SYMATTR InstName D2
SYMATTR Value 1N914
SYMBOL res -160 -112 R0
SYMATTR InstName R1
SYMATTR Value 330
SYMBOL zener -208 240 R180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName D1
SYMATTR Value BZX84B6V2L
SYMATTR Description Diode
SYMATTR Type diode
TEXT 544 664 Left 2 !.tran 1m
TEXT 368 -88 Left 2 ;EPW SED MAY 2024
TEXT 368 -32 Left 2 ;LED BUCK USING 1Q 1PFET
TEXT -312 624 Left 2 ;R1 D1 IMPROVE LINE REG
TEXT -312 664 Left 2 ;D2 APPROX TC COMP Q1
TEXT 368 24 Left 2 ;NON OPTIMISED BUT SHOWS IT CAN BE DONE
piglet