Another design

"Edward Rawde" snipped-for-privacy@invalid.invalid wrote in message news:v1ho21$4ps$ snipped-for-privacy@nnrp.usenet.blueworldhosting.com...

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.

Version 4 SHEET 1 3044 680 WIRE 2032 -272 64 -272 WIRE 2192 -272 2032 -272 WIRE 2480 -272 2192 -272 WIRE 2192 -224 2192 -272 WIRE 2480 -224 2480 -272 WIRE 2336 -176 2256 -176 WIRE 2416 -176 2336 -176 WIRE 976 -128 160 -128 WIRE 1072 -128 1040 -128 WIRE 2032 -128 2032 -272 WIRE 2192 -80 2192 -128 WIRE 2336 -80 2336 -176 WIRE 2336 -80 2192 -80 WIRE 2480 -64 2480 -128 WIRE 2688 -64 2480 -64 WIRE 16 -48 -16 -48 WIRE 64 -48 64 -272 WIRE 64 -48 16 -48 WIRE 96 -48 64 -48 WIRE 240 -48 96 -48 WIRE 336 -48 240 -48 WIRE 448 -48 336 -48 WIRE 464 -48 448 -48 WIRE 528 -48 464 -48 WIRE 608 -48 528 -48 WIRE 672 -48 608 -48 WIRE 784 -48 768 -48 WIRE 816 -48 784 -48 WIRE 864 -48 816 -48 WIRE 992 -48 944 -48 WIRE 1024 -48 992 -48 WIRE 1072 -48 1072 -128 WIRE 1072 -48 1024 -48 WIRE 1264 -48 1072 -48 WIRE 1360 -48 1264 -48 WIRE 240 -16 240 -48 WIRE 336 -16 336 -48 WIRE 2192 -16 2192 -80 WIRE 2480 -16 2480 -64 WIRE 1264 0 1264 -48 WIRE 1360 0 1360 -48 WIRE -16 32 -16 -48 WIRE 2128 32 1872 32 WIRE 2592 32 2544 32 WIRE 448 64 448 -48 WIRE 464 64 464 -48 WIRE 96 80 96 -48 WIRE 160 80 160 -128 WIRE 240 80 240 64 WIRE 240 80 160 80 WIRE 336 80 336 64 WIRE 384 80 336 80 WIRE 416 80 384 80 WIRE 816 80 816 -48 WIRE 992 80 992 -48 WIRE 336 96 336 80 WIRE 336 96 288 96 WIRE 656 96 480 96 WIRE 688 96 688 0 WIRE 688 96 656 96 WIRE 1264 96 1264 64 WIRE 1312 96 1264 96 WIRE 1936 96 1312 96 WIRE 240 112 240 80 WIRE 384 112 240 112 WIRE 416 112 384 112 WIRE 528 112 528 -48 WIRE 608 112 608 -48 WIRE 240 128 240 112 WIRE 336 128 336 96 WIRE 1360 128 1360 80 WIRE 1424 128 1360 128 WIRE 1872 128 1872 32 WIRE 1872 128 1424 128 WIRE 2192 128 2192 80 WIRE 2352 128 2192 128 WIRE 2480 128 2480 80 WIRE 2480 128 2352 128 WIRE 2032 144 2032 -48 WIRE 2128 144 2032 144 WIRE 1360 160 1360 128 WIRE -16 176 -16 112 WIRE 2032 192 2032 144 WIRE 2352 192 2352 128 WIRE 240 240 240 208 WIRE 336 240 336 208 WIRE 336 240 240 240 WIRE 384 240 336 240 WIRE 432 240 432 128 WIRE 432 240 384 240 WIRE 448 240 448 128 WIRE 448 240 432 240 WIRE 464 240 464 128 WIRE 464 240 448 240 WIRE 528 240 528 176 WIRE 528 240 464 240 WIRE 544 240 528 240 WIRE 608 240 608 176 WIRE 608 240 544 240 WIRE 1360 240 1360 224 WIRE 1424 240 1360 240 WIRE 1536 240 1424 240 WIRE 1696 240 1600 240 WIRE 1872 240 1760 240 WIRE 2128 240 2128 144 WIRE 2128 240 2096 240 WIRE 2288 240 2128 240 WIRE 544 272 544 240 WIRE 1264 272 1264 96 WIRE 1360 272 1360 240 WIRE -16 368 -16 256 WIRE 96 368 96 144 WIRE 96 368 -16 368 WIRE 544 368 544 352 WIRE 544 368 96 368 WIRE 816 368 816 144 WIRE 816 368 544 368 WIRE 992 368 992 144 WIRE 992 368 816 368 WIRE 1264 368 1264 352 WIRE 1264 368 992 368 WIRE 1360 368 1360 336 WIRE 1360 368 1264 368 WIRE 1872 368 1872 240 WIRE 1872 368 1360 368 WIRE 2032 368 2032 288 WIRE 2032 368 1872 368 WIRE 2352 368 2352 288 WIRE 2352 368 2032 368 WIRE -16 384 -16 368 WIRE 1936 400 1936 96 WIRE 2592 400 2592 32 WIRE 2592 400 1936 400 WIRE 288 448 288 96 WIRE 992 448 288 448 WIRE 1328 448 1072 448 WIRE 2688 448 2688 -64 WIRE 2688 448 1328 448 FLAG -16 384 0 FLAG 16 -48 in FLAG 784 -48 sw FLAG 1024 -48 out FLAG 1424 128 isense FLAG 1312 96 iref FLAG 1328 448 ifb FLAG 384 80 cmp- FLAG 384 112 cmp+ FLAG 656 96 gate FLAG 384 240 cmpv- FLAG 1424 240 led SYMBOL Comparators\\LT1719 448 32 R0 WINDOW 0 27 27 Left 2 WINDOW 3 -92 6 Left 2 SYMATTR InstName U1 SYMBOL res 320 112 R0 WINDOW 0 41 34 Left 2 WINDOW 3 35 64 Left 2 SYMATTR InstName R4 SYMATTR Value 10K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL ind 960 -64 R90 WINDOW 0 63 51 VBottom 2 WINDOW 3 -27 53 VTop 2 SYMATTR InstName L1 SYMATTR Value 68µ SYMATTR SpiceLine Ipk=0.85 Rser=0.21 Rpar=0 Cpar=0 mfg="Sumida" pn="CDR105B-680" SYMBOL res 1376 -16 M0 WINDOW 0 -37 34 Left 2 WINDOW 3 -57 63 Left 2 SYMATTR InstName R8 SYMATTR Value 0.68 SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL res 224 -32 R0 WINDOW 0 -35 19 Left 2 WINDOW 3 -49 48 Left 2 SYMATTR InstName R1 SYMATTR Value 10K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL schottky 832 144 R180 WINDOW 0 -42 30 Left 2 WINDOW 3 -119 -3 Left 2 SYMATTR InstName D2 SYMATTR Value MBRS130L SYMATTR Description Diode SYMATTR Type diode SYMBOL pmos 768 0 M270 WINDOW 0 10 129 VLeft 2 WINDOW 3 -10 67 VLeft 2 SYMATTR InstName M1 SYMATTR Value AO6407 SYMBOL voltage -16 160 R0 WINDOW 0 -75 16 Left 2 WINDOW 3 -71 54 Left 2 WINDOW 123 0 0 Left 0 WINDOW 39 -185 81 Left 2 SYMATTR InstName V3 SYMATTR Value 12 SYMBOL res -32 16 R0 WINDOW 0 -39 29 Left 2 WINDOW 3 -63 65 Left 2 SYMATTR InstName R9 SYMATTR Value 0.001 SYMBOL zener 544 176 R180 WINDOW 0 37 29 Left 2 WINDOW 3 68 -5 Right 2 SYMATTR InstName D1 SYMATTR Value UMZ5_1N SYMBOL res 320 -32 R0 WINDOW 0 40 7 Left 2 WINDOW 3 37 33 Left 2 SYMATTR InstName R3 SYMATTR Value 10K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL res 528 368 M180 WINDOW 0 39 76 Left 2 WINDOW 3 38 42 Left 2 SYMATTR InstName R5 SYMATTR Value 220 SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL cap 592 176 M180 WINDOW 0 29 52 Left 2 WINDOW 3 30 13 Left 2 SYMATTR InstName C3 SYMATTR Value 0.1µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.0337 Lser=180p SYMBOL polcap 976 80 R0 WINDOW 3 24 56 Left 2 WINDOW 0 27 9 Left 2 SYMATTR Value 100µ SYMATTR InstName C1 SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.9 Lser=0 SYMBOL res 224 112 R0 WINDOW 0 -40 33 Left 2 WINDOW 3 -52 57 Left 2 SYMATTR InstName R2 SYMATTR Value 10K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL polcap 80 80 R0 WINDOW 3 -57 61 Left 2 WINDOW 0 -39 4 Left 2 SYMATTR Value 100µ SYMATTR InstName C2 SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.9 Lser=0 SYMBOL LED 1536 256 R270 WINDOW 0 72 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName LED1 SYMATTR Value LXZ1-PB01 SYMBOL res 976 432 M90 WINDOW 0 -2 59 VBottom 2 WINDOW 3 35 64 VTop 2 SYMATTR InstName R6 SYMATTR Value 220K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL cap 976 -144 M90 WINDOW 0 -3 31 VBottom 2 WINDOW 3 36 35 VTop 2 SYMATTR InstName C5 SYMATTR Value 0.01µ SYMATTR SpiceLine V=16 Irms=291m Rser=0.34258 Lser=0 SYMBOL res 1248 368 M180 WINDOW 0 -40 81 Left 2 WINDOW 3 -51 46 Left 2 SYMATTR InstName R7 SYMATTR Value 470 SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL schottky 1280 0 M0 WINDOW 0 43 24 Left 2 WINDOW 3 40 -8 Left 2 SYMATTR InstName D3 SYMATTR Value BAT54AHY SYMATTR Description Diode SYMATTR Type diode SYMBOL FerriteBead 1360 192 R0 SYMATTR InstName L2 SYMATTR Value 6µ SYMATTR SpiceLine Ipk=3 Rser=0.0102 Rpar=1220 Cpar=1.9p SYMBOL cap 1344 272 R0 SYMATTR InstName C4 SYMATTR Value 0.001µ SYMATTR SpiceLine V=10 Irms=0 Rser=0.1909 Lser=177p mfg="Würth Elektronik" pn="885012205006 WCAP-CSGP 0402" type="X7R" SYMBOL LED 1696 256 R270 WINDOW 0 72 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName LED2 SYMATTR Value LXZ1-PB01 SYMBOL pnp 2256 -128 R180 SYMATTR InstName Q2 SYMATTR Value 2N3906 SYMBOL pnp 2416 -128 M180 SYMATTR InstName Q3 SYMATTR Value 2N3906 SYMBOL npn 2128 -16 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL npn 2544 -16 M0 SYMATTR InstName Q4 SYMATTR Value 2N3904 SYMBOL npn 2288 192 R0 SYMATTR InstName Q5 SYMATTR Value 2N3904 SYMBOL npn 2096 192 M0 SYMATTR InstName Q6 SYMATTR Value 2N3904 SYMBOL res 2016 -144 R0 SYMATTR InstName R10 SYMATTR Value 100K TEXT 16 392 Left 2 !.tran 0.001 startup

On 10/05/2024 4:11 am, Edward Rawde wrote:

The venerable LM311 is still a good value comparator, if you want to penny pinch omit the gate driver buffers and lower the pullup resistor but efficiency will drop a lot from 85% to ca 72%.

Version 4 SHEET 1 996 708 WIRE -544 -112 -704 -112 WIRE -48 -112 -544 -112 WIRE 48 -112 -48 -112 WIRE 192 -112 48 -112 WIRE 336 -112 192 -112 WIRE 48 -96 48 -112 WIRE 192 -48 192 -112 WIRE -544 -16 -544 -112 WIRE 48 0 48 -16 WIRE 128 0 48 0 WIRE 336 64 336 -112 WIRE 192 80 192 48 WIRE 288 80 192 80 WIRE -544 176 -544 64 WIRE -448 176 -544 176 WIRE -240 224 -288 224 WIRE 336 224 336 160 WIRE 336 224 -160 224 WIRE -448 240 -448 176 WIRE 336 272 336 224 WIRE 416 272 336 272 WIRE 592 272 496 272 WIRE -704 320 -704 -112 WIRE 592 320 592 272 WIRE 592 320 416 320 WIRE -160 336 -192 336 WIRE -48 336 -48 -112 WIRE -48 336 -80 336 WIRE -544 352 -544 176 WIRE 592 352 592 320 WIRE 416 368 416 320 WIRE -48 384 -48 336 WIRE 192 384 192 80 WIRE -448 416 -448 320 WIRE -288 416 -288 224 WIRE -288 416 -448 416 WIRE -80 416 -288 416 WIRE 48 432 48 0 WIRE 48 432 0 432 WIRE 128 432 48 432 WIRE -192 448 -192 336 WIRE -80 448 -192 448 WIRE -448 464 -448 416 WIRE 336 464 336 272 WIRE 416 464 416 432 WIRE 592 464 592 416 WIRE 592 464 416 464 WIRE -192 496 -192 448 WIRE 592 496 592 464 WIRE -704 592 -704 400 WIRE -544 592 -544 416 WIRE -544 592 -704 592 WIRE -448 592 -448 544 WIRE -448 592 -544 592 WIRE -64 592 -64 480 WIRE -64 592 -448 592 WIRE -48 592 -48 480 WIRE -48 592 -64 592 WIRE 192 592 192 480 WIRE 192 592 -48 592 WIRE 336 592 336 528 WIRE 336 592 192 592 WIRE 592 592 592 576 WIRE 592 592 336 592 WIRE -704 640 -704 592 WIRE -192 672 -192 576 WIRE 416 672 416 464 WIRE 416 672 -192 672 FLAG -704 640 0 SYMBOL schottky 352 528 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D1 SYMATTR Value 1N5817 SYMATTR Description Diode SYMATTR Type diode SYMBOL ind 400 288 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L1 SYMATTR Value 0.22m SYMATTR SpiceLine Rser=50m SYMBOL LED 576 352 R0 SYMATTR InstName D2 SYMATTR Value LXK2-PW14 SYMATTR Description Diode SYMATTR Type diode SYMBOL voltage -704 304 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 12 SYMBOL res 576 480 R0 SYMATTR InstName R8 SYMATTR Value 0.15 SYMBOL zener -528 416 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D3 SYMATTR Value 1N750 SYMATTR Description Diode SYMATTR Type diode SYMBOL res -560 -32 R0 SYMATTR InstName R1 SYMATTR Value 2k SYMBOL res -464 448 R0 SYMATTR InstName R3 SYMATTR Value 100 SYMBOL res -464 224 R0 SYMATTR InstName R2 SYMATTR Value 4.3k SYMBOL res 32 -112 R0 SYMATTR InstName R7 SYMATTR Value 10k SYMBOL cap 400 368 R0 SYMATTR InstName C1 SYMATTR Value 0.1m SYMBOL res -144 208 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R4 SYMATTR Value 33k SYMBOL res -176 592 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R5 SYMATTR Value 100 SYMBOL npn 128 -48 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL pnp 128 480 M180 SYMATTR InstName Q2 SYMATTR Value 2N3906 SYMBOL pmos 288 160 M180 SYMATTR InstName M2 SYMATTR Value AO6407 SYMBOL res -64 320 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value 33k SYMBOL Comparators\\LT1011 -48 432 R0 SYMATTR InstName U2 TEXT -400 664 Left 2 !.tran 1m TEXT 496 -96 Left 2 ;EPW SED MAY 2024 TEXT 496 -48 Left 2 ;LED BUCK USING LM311 TEXT -152 616 Left 2 ;R6 IS OPT LINE REGULATION FEED FWD CORR TEXT -312 160 Left 2 ;R4 SETS HYSTERESIS TEXT 472 616 Left 2 ;C1 OPT EMI/RFI FILT FOR REMOTE LED TEXT -440 392 Left 2 ;VREF 100mV

piglet

(Sniiip)

I’m not following through all the spicery, but fwiw: The positive drive of an LM311 can be improved by 100x or more, by adding a

It pulls down to a diode drop above ground, but that can be a Schottky, and only has to handle the base bias, so it can be below 0.2 V, but you don’t care about 0.7 V in a gate driver anyway.

When the 311 goes low, the diode doesn’t start conducting till the transistor is off, and there’s no stored charge to worry about, since the NPN never saturates.

Cheers

Phil Hobbs

Oh, and take the output from the emitter.

Cheers

Phil Hobbs

I think the LED constant-current switcher can be done with a pfet and two NPN transistors.

...

Thanks, that works but I was hoping for a smaller inductor at about 1MHz and filtered LED feed referenced to ground for up to three LEDs.

I'm probably done with my circuit unless there's a cheaper comparator which can do the same job or a cheaper op amp which can run on lead acid voltage. Or preferably up to 15V. Also a cheaper fet.

Right , I actually did as you described in an earlier version but a PNP is practically the same cost as a diode and provides added beef.

On 10/05/2024 7:57 pm, Edward Rawde wrote:

Ground referenced output is possible, rearrange the sense resistor and stand the reference on top of the LEDs. As in ...

Version 4 SHEET 1 996 708 WIRE -544 -112 -704 -112 WIRE -48 -112 -544 -112 WIRE 48 -112 -48 -112 WIRE 192 -112 48 -112 WIRE 336 -112 192 -112 WIRE 48 -96 48 -112 WIRE 192 -48 192 -112 WIRE -544 -16 -544 -112 WIRE 48 0 48 -16 WIRE 128 0 48 0 WIRE 336 64 336 -112 WIRE 192 80 192 48 WIRE 288 80 192 80 WIRE -544 176 -544 64 WIRE -448 176 -544 176 WIRE -240 224 -288 224 WIRE 336 224 336 160 WIRE 336 224 -160 224 WIRE -448 240 -448 176 WIRE 336 272 336 224 WIRE 416 272 336 272 WIRE 528 272 496 272 WIRE 624 272 528 272 WIRE -704 320 -704 -112 WIRE 528 320 528 272 WIRE 528 320 400 320 WIRE 624 320 624 272 WIRE -160 336 -192 336 WIRE -48 336 -48 -112 WIRE -48 336 -80 336 WIRE -544 352 -544 176 WIRE -48 384 -48 336 WIRE 192 384 192 80 WIRE -448 416 -448 320 WIRE -288 416 -288 224 WIRE -288 416 -448 416 WIRE -80 416 -288 416 WIRE 48 432 48 0 WIRE 48 432 0 432 WIRE 128 432 48 432 WIRE -192 448 -192 336 WIRE -80 448 -192 448 WIRE 480 448 432 448 WIRE 624 448 624 400 WIRE 624 448 480 448 WIRE -448 464 -448 416 WIRE 336 464 336 272 WIRE 624 480 624 448 WIRE -192 496 -192 448 WIRE 480 496 480 448 WIRE -544 560 -544 416 WIRE -448 560 -448 544 WIRE -448 560 -544 560 WIRE -704 592 -704 400 WIRE -64 592 -64 480 WIRE -64 592 -704 592 WIRE -48 592 -48 480 WIRE -48 592 -64 592 WIRE 192 592 192 480 WIRE 192 592 -48 592 WIRE 336 592 336 528 WIRE 336 592 192 592 WIRE 480 592 480 560 WIRE 480 592 336 592 WIRE 624 592 624 544 WIRE 624 592 480 592 WIRE -704 640 -704 592 WIRE -192 672 -192 576 WIRE 400 672 400 320 WIRE 400 672 -192 672 WIRE -448 688 -448 560 WIRE 432 688 432 448 WIRE 432 688 -448 688 FLAG -704 640 0 SYMBOL schottky 352 528 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D1 SYMATTR Value 1N5817 SYMATTR Description Diode SYMATTR Type diode SYMBOL ind 400 288 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L1 SYMATTR Value 0.22m SYMATTR SpiceLine Rser=50m SYMBOL LED 608 480 R0 SYMATTR InstName D2 SYMATTR Value LXK2-PW14 SYMATTR Description Diode SYMATTR Type diode SYMBOL voltage -704 304 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 12 SYMBOL res 608 304 R0 SYMATTR InstName R8 SYMATTR Value 0.15 SYMBOL zener -528 416 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D3 SYMATTR Value 1N750 SYMATTR Description Diode SYMATTR Type diode SYMBOL res -560 -32 R0 SYMATTR InstName R1 SYMATTR Value 2k SYMBOL res -464 448 R0 SYMATTR InstName R3 SYMATTR Value 100 SYMBOL res -464 224 R0 SYMATTR InstName R2 SYMATTR Value 4.3k SYMBOL res 32 -112 R0 SYMATTR InstName R7 SYMATTR Value 10k SYMBOL cap 464 496 R0 SYMATTR InstName C1 SYMATTR Value 0.1m SYMBOL res -144 208 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R4 SYMATTR Value 33k SYMBOL res -176 592 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R5 SYMATTR Value 100 SYMBOL npn 128 -48 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL pnp 128 480 M180 SYMATTR InstName Q2 SYMATTR Value 2N3906 SYMBOL pmos 288 160 M180 SYMATTR InstName M2 SYMATTR Value AO6407 SYMBOL res -64 320 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value 33k SYMBOL Comparators\\LT1011 -48 432 R0 SYMATTR InstName U2 TEXT 664 672 Left 2 !.tran 1m TEXT 496 -96 Left 2 ;EPW SED MAY 2024 TEXT 496 -48 Left 2 ;LED BUCK USING LM311 TEXT -152 616 Left 2 ;R6 IS OPT LINE REGULATION FEED FWD CORR TEXT -312 160 Left 2 ;R4 SETS HYSTERESIS TEXT 472 616 Left 2 ;C1 OPT EMI/RFI FILT FOR REMOTE LED TEXT -440 392 Left 2 ;VREF 100mV

piglet

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.

That's overkill. A pfet and one NPN might work.

My LM311 based idea works ok with 68uH inductors too. Efficiency is above

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.

Pay me for EMC compliance :)

Ground is input negative.

Yes it crossed my mind that the input may need EMC filtering too.

As long as it doesn't go in circles with filter this, failed again, filter that, failed again, change the layout, failed again, etc

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.

Speaking of overkill, wrt our previous discussion you might be interested in this mixed-signal array that has 8(!) LDOs on board:

"Edward Rawde" snipped-for-privacy@invalid.invalid wrote in message news:v1m6ed$28af$ snipped-for-privacy@nnrp.usenet.blueworldhosting.com...

Simulation says that these synchronize in opposite phase. As expected there is overlap causing input current spikes and there's probably no way to fix that. I wonder what would happen in reality.

Version 4 SHEET 1 3044 680 WIRE 2032 -1056 64 -1056 WIRE 2192 -1056 2032 -1056 WIRE 2480 -1056 2192 -1056 WIRE 2192 -1008 2192 -1056 WIRE 2480 -1008 2480 -1056 WIRE 2336 -960 2256 -960 WIRE 2416 -960 2336 -960 WIRE 976 -912 160 -912 WIRE 1072 -912 1040 -912 WIRE 2032 -912 2032 -1056 WIRE 2192 -864 2192 -912 WIRE 2336 -864 2336 -960 WIRE 2336 -864 2192 -864 WIRE 2480 -848 2480 -912 WIRE 2688 -848 2480 -848 WIRE 64 -832 64 -1056 WIRE 64 -832 -16 -832 WIRE 96 -832 64 -832 WIRE 240 -832 96 -832 WIRE 336 -832 240 -832 WIRE 448 -832 336 -832 WIRE 464 -832 448 -832 WIRE 528 -832 464 -832 WIRE 608 -832 528 -832 WIRE 672 -832 608 -832 WIRE 816 -832 768 -832 WIRE 864 -832 816 -832 WIRE 992 -832 944 -832 WIRE 1072 -832 1072 -912 WIRE 1072 -832 992 -832 WIRE 1264 -832 1072 -832 WIRE 1360 -832 1264 -832 WIRE 240 -800 240 -832 WIRE 336 -800 336 -832 WIRE 2192 -800 2192 -864 WIRE 2480 -800 2480 -848 WIRE 1264 -784 1264 -832 WIRE 1360 -784 1360 -832 WIRE 2128 -752 1872 -752 WIRE 2592 -752 2544 -752 WIRE 448 -720 448 -832 WIRE 464 -720 464 -832 WIRE 96 -704 96 -832 WIRE 160 -704 160 -912 WIRE 240 -704 240 -720 WIRE 240 -704 160 -704 WIRE 336 -704 336 -720 WIRE 416 -704 336 -704 WIRE 816 -704 816 -832 WIRE 992 -704 992 -832 WIRE 336 -688 336 -704 WIRE 336 -688 288 -688 WIRE 688 -688 688 -784 WIRE 688 -688 480 -688 WIRE 1264 -688 1264 -720 WIRE 1936 -688 1264 -688 WIRE 240 -672 240 -704 WIRE 416 -672 240 -672 WIRE 528 -672 528 -832 WIRE 608 -672 608 -832 WIRE 240 -656 240 -672 WIRE 336 -656 336 -688 WIRE 1360 -656 1360 -704 WIRE 1872 -656 1872 -752 WIRE 1872 -656 1360 -656 WIRE 2192 -656 2192 -704 WIRE 2352 -656 2192 -656 WIRE 2480 -656 2480 -704 WIRE 2480 -656 2352 -656 WIRE 2032 -640 2032 -832 WIRE 2128 -640 2032 -640 WIRE 1360 -624 1360 -656 WIRE 2032 -592 2032 -640 WIRE 2352 -592 2352 -656 WIRE 240 -544 240 -576 WIRE 336 -544 336 -576 WIRE 336 -544 240 -544 WIRE 432 -544 432 -656 WIRE 432 -544 336 -544 WIRE 448 -544 448 -656 WIRE 448 -544 432 -544 WIRE 464 -544 464 -656 WIRE 464 -544 448 -544 WIRE 528 -544 528 -608 WIRE 528 -544 464 -544 WIRE 544 -544 528 -544 WIRE 608 -544 608 -608 WIRE 608 -544 544 -544 WIRE 1360 -544 1360 -560 WIRE 1536 -544 1360 -544 WIRE 1696 -544 1600 -544 WIRE 1872 -544 1760 -544 WIRE 2128 -544 2128 -640 WIRE 2128 -544 2096 -544 WIRE 2288 -544 2128 -544 WIRE 544 -512 544 -544 WIRE 1264 -512 1264 -688 WIRE 1360 -512 1360 -544 WIRE 96 -416 96 -640 WIRE 96 -416 -192 -416 WIRE 544 -416 544 -432 WIRE 544 -416 96 -416 WIRE 816 -416 816 -640 WIRE 816 -416 544 -416 WIRE 992 -416 992 -640 WIRE 992 -416 816 -416 WIRE 1264 -416 1264 -432 WIRE 1264 -416 992 -416 WIRE 1360 -416 1360 -448 WIRE 1360 -416 1264 -416 WIRE 1872 -416 1872 -544 WIRE 1872 -416 1360 -416 WIRE 2032 -416 2032 -496 WIRE 2032 -416 1872 -416 WIRE 2352 -416 2352 -496 WIRE 2352 -416 2032 -416 WIRE 1936 -384 1936 -688 WIRE 2592 -384 2592 -752 WIRE 2592 -384 1936 -384 WIRE 288 -336 288 -688 WIRE 992 -336 288 -336 WIRE 2688 -336 2688 -848 WIRE 2688 -336 1072 -336 WIRE 2032 -272 64 -272 WIRE 2192 -272 2032 -272 WIRE 2480 -272 2192 -272 WIRE 2192 -224 2192 -272 WIRE 2480 -224 2480 -272 WIRE 2336 -176 2256 -176 WIRE 2416 -176 2336 -176 WIRE 976 -128 160 -128 WIRE 1072 -128 1040 -128 WIRE 2032 -128 2032 -272 WIRE 2192 -80 2192 -128 WIRE 2336 -80 2336 -176 WIRE 2336 -80 2192 -80 WIRE 2480 -64 2480 -128 WIRE 2688 -64 2480 -64 WIRE -16 -48 -16 -832 WIRE 16 -48 -16 -48 WIRE 64 -48 64 -272 WIRE 64 -48 16 -48 WIRE 96 -48 64 -48 WIRE 240 -48 96 -48 WIRE 336 -48 240 -48 WIRE 448 -48 336 -48 WIRE 464 -48 448 -48 WIRE 528 -48 464 -48 WIRE 608 -48 528 -48 WIRE 672 -48 608 -48 WIRE 784 -48 768 -48 WIRE 816 -48 784 -48 WIRE 864 -48 816 -48 WIRE 992 -48 944 -48 WIRE 1024 -48 992 -48 WIRE 1072 -48 1072 -128 WIRE 1072 -48 1024 -48 WIRE 1264 -48 1072 -48 WIRE 1360 -48 1264 -48 WIRE 240 -16 240 -48 WIRE 336 -16 336 -48 WIRE 2192 -16 2192 -80 WIRE 2480 -16 2480 -64 WIRE 1264 0 1264 -48 WIRE 1360 0 1360 -48 WIRE -16 32 -16 -48 WIRE 2128 32 1872 32 WIRE 2592 32 2544 32 WIRE 448 64 448 -48 WIRE 464 64 464 -48 WIRE 96 80 96 -48 WIRE 160 80 160 -128 WIRE 240 80 240 64 WIRE 240 80 160 80 WIRE 336 80 336 64 WIRE 384 80 336 80 WIRE 416 80 384 80 WIRE 816 80 816 -48 WIRE 992 80 992 -48 WIRE 336 96 336 80 WIRE 336 96 288 96 WIRE 656 96 480 96 WIRE 688 96 688 0 WIRE 688 96 656 96 WIRE 1264 96 1264 64 WIRE 1312 96 1264 96 WIRE 1936 96 1312 96 WIRE 240 112 240 80 WIRE 384 112 240 112 WIRE 416 112 384 112 WIRE 528 112 528 -48 WIRE 608 112 608 -48 WIRE 240 128 240 112 WIRE 336 128 336 96 WIRE 1360 128 1360 80 WIRE 1424 128 1360 128 WIRE 1872 128 1872 32 WIRE 1872 128 1424 128 WIRE 2192 128 2192 80 WIRE 2352 128 2192 128 WIRE 2480 128 2480 80 WIRE 2480 128 2352 128 WIRE 2032 144 2032 -48 WIRE 2128 144 2032 144 WIRE 1360 160 1360 128 WIRE -16 176 -16 112 WIRE 2032 192 2032 144 WIRE 2352 192 2352 128 WIRE 240 240 240 208 WIRE 336 240 336 208 WIRE 336 240 240 240 WIRE 384 240 336 240 WIRE 432 240 432 128 WIRE 432 240 384 240 WIRE 448 240 448 128 WIRE 448 240 432 240 WIRE 464 240 464 128 WIRE 464 240 448 240 WIRE 528 240 528 176 WIRE 528 240 464 240 WIRE 544 240 528 240 WIRE 608 240 608 176 WIRE 608 240 544 240 WIRE 1360 240 1360 224 WIRE 1424 240 1360 240 WIRE 1536 240 1424 240 WIRE 1696 240 1600 240 WIRE 1872 240 1760 240 WIRE 2128 240 2128 144 WIRE 2128 240 2096 240 WIRE 2288 240 2128 240 WIRE 544 272 544 240 WIRE 1264 272 1264 96 WIRE 1360 272 1360 240 WIRE -192 368 -192 -416 WIRE -16 368 -16 256 WIRE -16 368 -192 368 WIRE 96 368 96 144 WIRE 96 368 -16 368 WIRE 544 368 544 352 WIRE 544 368 96 368 WIRE 816 368 816 144 WIRE 816 368 544 368 WIRE 992 368 992 144 WIRE 992 368 816 368 WIRE 1264 368 1264 352 WIRE 1264 368 992 368 WIRE 1360 368 1360 336 WIRE 1360 368 1264 368 WIRE 1872 368 1872 240 WIRE 1872 368 1360 368 WIRE 2032 368 2032 288 WIRE 2032 368 1872 368 WIRE 2352 368 2352 288 WIRE 2352 368 2032 368 WIRE -192 384 -192 368 WIRE 1936 400 1936 96 WIRE 2592 400 2592 32 WIRE 2592 400 1936 400 WIRE 288 448 288 96 WIRE 992 448 288 448 WIRE 1328 448 1072 448 WIRE 2688 448 2688 -64 WIRE 2688 448 1328 448 FLAG -192 384 0 FLAG 16 -48 in FLAG 784 -48 sw FLAG 1024 -48 out FLAG 1424 128 isense FLAG 1312 96 iref FLAG 1328 448 ifb FLAG 384 80 cmp- FLAG 384 112 cmp+ FLAG 656 96 gate FLAG 384 240 cmpv- FLAG 1424 240 led SYMBOL Comparators\\LT1719 448 32 R0 WINDOW 0 27 27 Left 2 WINDOW 3 -92 6 Left 2 SYMATTR InstName U1 SYMBOL res 320 112 R0 WINDOW 0 41 34 Left 2 WINDOW 3 35 64 Left 2 SYMATTR InstName R4 SYMATTR Value 10K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL ind 960 -64 R90 WINDOW 0 63 51 VBottom 2 WINDOW 3 -27 53 VTop 2 SYMATTR InstName L1 SYMATTR Value 68µ SYMATTR SpiceLine Ipk=0.85 Rser=0.21 Rpar=0 Cpar=0 mfg="Sumida" pn="CDR105B-680" SYMBOL res 1376 -16 M0 WINDOW 0 -37 34 Left 2 WINDOW 3 -57 63 Left 2 SYMATTR InstName R8 SYMATTR Value 0.68 SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL res 224 -32 R0 WINDOW 0 -35 19 Left 2 WINDOW 3 -49 48 Left 2 SYMATTR InstName R1 SYMATTR Value 10K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL schottky 832 144 R180 WINDOW 0 -42 30 Left 2 WINDOW 3 -119 -3 Left 2 SYMATTR InstName D2 SYMATTR Value MBRS130L SYMATTR Description Diode SYMATTR Type diode SYMBOL pmos 768 0 M270 WINDOW 0 10 129 VLeft 2 WINDOW 3 -10 67 VLeft 2 SYMATTR InstName M1 SYMATTR Value AO6407 SYMBOL voltage -16 160 R0 WINDOW 0 -75 16 Left 2 WINDOW 3 -71 54 Left 2 WINDOW 123 0 0 Left 0 WINDOW 39 -185 81 Left 2 SYMATTR InstName V3 SYMATTR Value 12 SYMBOL res -32 16 R0 WINDOW 0 -39 29 Left 2 WINDOW 3 -63 65 Left 2 SYMATTR InstName R9 SYMATTR Value 0.001 SYMBOL zener 544 176 R180 WINDOW 0 37 29 Left 2 WINDOW 3 68 -5 Right 2 SYMATTR InstName D1 SYMATTR Value UMZ5_1N SYMBOL res 320 -32 R0 WINDOW 0 40 7 Left 2 WINDOW 3 37 33 Left 2 SYMATTR InstName R3 SYMATTR Value 10K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL res 528 368 M180 WINDOW 0 39 76 Left 2 WINDOW 3 38 42 Left 2 SYMATTR InstName R5 SYMATTR Value 220 SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL cap 592 176 M180 WINDOW 0 29 52 Left 2 WINDOW 3 30 13 Left 2 SYMATTR InstName C3 SYMATTR Value 0.1µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.0337 Lser=180p SYMBOL polcap 976 80 R0 WINDOW 3 24 56 Left 2 WINDOW 0 27 9 Left 2 SYMATTR Value 100µ SYMATTR InstName C1 SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.9 Lser=0 SYMBOL res 224 112 R0 WINDOW 0 -40 33 Left 2 WINDOW 3 -52 57 Left 2 SYMATTR InstName R2 SYMATTR Value 10K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL polcap 80 80 R0 WINDOW 3 -57 61 Left 2 WINDOW 0 -39 4 Left 2 SYMATTR Value 100µ SYMATTR InstName C2 SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.9 Lser=0 SYMBOL LED 1536 256 R270 WINDOW 0 72 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName LED1 SYMATTR Value LXZ1-PB01 SYMBOL res 976 432 M90 WINDOW 0 -2 59 VBottom 2 WINDOW 3 35 64 VTop 2 SYMATTR InstName R6 SYMATTR Value 220K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL cap 976 -144 M90 WINDOW 0 -3 31 VBottom 2 WINDOW 3 36 35 VTop 2 SYMATTR InstName C5 SYMATTR Value 0.01µ SYMATTR SpiceLine V=16 Irms=291m Rser=0.34258 Lser=0 SYMBOL res 1248 368 M180 WINDOW 0 -40 81 Left 2 WINDOW 3 -51 46 Left 2 SYMATTR InstName R7 SYMATTR Value 470 SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL schottky 1280 0 M0 WINDOW 0 43 24 Left 2 WINDOW 3 40 -8 Left 2 SYMATTR InstName D3 SYMATTR Value BAT54AHY SYMATTR Description Diode SYMATTR Type diode SYMBOL FerriteBead 1360 192 R0 SYMATTR InstName L2 SYMATTR Value 6µ SYMATTR SpiceLine Ipk=3 Rser=0.0102 Rpar=1220 Cpar=1.9p SYMBOL cap 1344 272 R0 SYMATTR InstName C4 SYMATTR Value 0.001µ SYMATTR SpiceLine V=10 Irms=0 Rser=0.1909 Lser=177p mfg="Würth Elektronik" pn="885012205006 WCAP-CSGP 0402" type="X7R" SYMBOL LED 1696 256 R270 WINDOW 0 72 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName LED2 SYMATTR Value LXZ1-PB01 SYMBOL pnp 2256 -128 R180 SYMATTR InstName Q2 SYMATTR Value 2N3906 SYMBOL pnp 2416 -128 M180 SYMATTR InstName Q3 SYMATTR Value 2N3906 SYMBOL npn 2128 -16 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL npn 2544 -16 M0 SYMATTR InstName Q4 SYMATTR Value 2N3904 SYMBOL npn 2288 192 R0 SYMATTR InstName Q5 SYMATTR Value 2N3904 SYMBOL npn 2096 192 M0 SYMATTR InstName Q6 SYMATTR Value 2N3904 SYMBOL res 2016 -144 R0 SYMATTR InstName R10 SYMATTR Value 100K SYMBOL Comparators\\LT1719 448 -752 R0 WINDOW 0 27 27 Left 2 WINDOW 3 -92 6 Left 2 SYMATTR InstName U2 SYMBOL res 320 -672 R0 WINDOW 0 41 34 Left 2 WINDOW 3 35 64 Left 2 SYMATTR InstName R11 SYMATTR Value 10K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL ind 960 -848 R90 WINDOW 0 63 51 VBottom 2 WINDOW 3 -27 53 VTop 2 SYMATTR InstName L3 SYMATTR Value 68µ SYMATTR SpiceLine Ipk=0.85 Rser=0.21 Rpar=0 Cpar=0 mfg="Sumida" pn="CDR105B-680" SYMBOL res 1376 -800 M0 WINDOW 0 -37 34 Left 2 WINDOW 3 -57 63 Left 2 SYMATTR InstName R12 SYMATTR Value 0.68 SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL res 224 -816 R0 WINDOW 0 -35 19 Left 2 WINDOW 3 -49 48 Left 2 SYMATTR InstName R13 SYMATTR Value 10K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL schottky 832 -640 R180 WINDOW 0 -42 30 Left 2 WINDOW 3 -119 -3 Left 2 SYMATTR InstName D4 SYMATTR Value MBRS130L SYMATTR Description Diode SYMATTR Type diode SYMBOL pmos 768 -784 M270 WINDOW 0 10 129 VLeft 2 WINDOW 3 -10 67 VLeft 2 SYMATTR InstName M2 SYMATTR Value AO6407 SYMBOL zener 544 -608 R180 WINDOW 0 37 29 Left 2 WINDOW 3 68 -5 Right 2 SYMATTR InstName D5 SYMATTR Value UMZ5_1N SYMBOL res 320 -816 R0 WINDOW 0 40 7 Left 2 WINDOW 3 37 33 Left 2 SYMATTR InstName R15 SYMATTR Value 10K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL res 528 -416 M180 WINDOW 0 39 76 Left 2 WINDOW 3 38 42 Left 2 SYMATTR InstName R16 SYMATTR Value 220 SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL cap 592 -608 M180 WINDOW 0 29 52 Left 2 WINDOW 3 30 13 Left 2 SYMATTR InstName C6 SYMATTR Value 0.1µ SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.0337 Lser=180p SYMBOL polcap 976 -704 R0 WINDOW 3 24 56 Left 2 WINDOW 0 27 9 Left 2 SYMATTR Value 100µ SYMATTR InstName C7 SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.9 Lser=0 SYMBOL res 224 -672 R0 WINDOW 0 -40 33 Left 2 WINDOW 3 -52 57 Left 2 SYMATTR InstName R17 SYMATTR Value 10K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL polcap 80 -704 R0 WINDOW 3 -57 61 Left 2 WINDOW 0 -39 4 Left 2 SYMATTR Value 100µ SYMATTR InstName C8 SYMATTR Description Capacitor SYMATTR Type cap SYMATTR SpiceLine V=6.3 Irms=0 Rser=0.9 Lser=0 SYMBOL LED 1536 -528 R270 WINDOW 0 72 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName LED3 SYMATTR Value LXZ1-PB01 SYMBOL res 976 -352 M90 WINDOW 0 -2 59 VBottom 2 WINDOW 3 35 64 VTop 2 SYMATTR InstName R18 SYMATTR Value 220K SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL cap 976 -928 M90 WINDOW 0 -3 31 VBottom 2 WINDOW 3 36 35 VTop 2 SYMATTR InstName C9 SYMATTR Value 0.01µ SYMATTR SpiceLine V=16 Irms=291m Rser=0.34258 Lser=0 SYMBOL res 1248 -416 M180 WINDOW 0 -40 81 Left 2 WINDOW 3 -51 46 Left 2 SYMATTR InstName R19 SYMATTR Value 470 SYMATTR SpiceLine tol=1 pwr=0.1 SYMBOL schottky 1280 -784 M0 WINDOW 0 43 24 Left 2 WINDOW 3 40 -8 Left 2 SYMATTR InstName D6 SYMATTR Value BAT54AHY SYMATTR Description Diode SYMATTR Type diode SYMBOL FerriteBead 1360 -592 R0 SYMATTR InstName L4 SYMATTR Value 6µ SYMATTR SpiceLine Ipk=3 Rser=0.0102 Rpar=1220 Cpar=1.9p SYMBOL cap 1344 -512 R0 SYMATTR InstName C10 SYMATTR Value 0.001µ SYMATTR SpiceLine V=10 Irms=0 Rser=0.1909 Lser=177p mfg="Würth Elektronik" pn="885012205006 WCAP-CSGP 0402" type="X7R" SYMBOL LED 1696 -528 R270 WINDOW 0 72 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName LED4 SYMATTR Value LXZ1-PB01 SYMBOL pnp 2256 -912 R180 SYMATTR InstName Q7 SYMATTR Value 2N3906 SYMBOL pnp 2416 -912 M180 SYMATTR InstName Q8 SYMATTR Value 2N3906 SYMBOL npn 2128 -800 R0 SYMATTR InstName Q9 SYMATTR Value 2N3904 SYMBOL npn 2544 -800 M0 SYMATTR InstName Q10 SYMATTR Value 2N3904 SYMBOL npn 2288 -592 R0 SYMATTR InstName Q11 SYMATTR Value 2N3904 SYMBOL npn 2096 -592 M0 SYMATTR InstName Q12 SYMATTR Value 2N3904 SYMBOL res 2016 -928 R0 SYMATTR InstName R20 SYMATTR Value 100K TEXT -160 392 Left 2 !.tran 0.001 startup

Something like this should work.

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

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 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 SYMATTR InstName R4 SYMATTR Value 330 SYMBOL res 32 160 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R3 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

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.

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