micropower boost circuit

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I need a DC to DC boost circuit with an output defined not with respect to  
ground, but with respect to the input, which is variable.  Output about 15  
volts above the input, over a wide range -- from less than a volt in, up to  
15 or 16 volts in.  But can be inefficient and only needs to put out a few  
milliamps.  I pasted an LTspice netlist of a possible solution.
R15 simulates a grain-of-wheat incandescent.  For Q6, if the Zetex is hard  
to find I might use a DSS416 or some such.
What's the consensus about the vulnerability of Q6 when Vin = 16 volts?

Version 4
SHEET 1 1388 680
WIRE 496 -160 -80 -160
WIRE 384 -144 352 -144
WIRE -80 -128 -80 -160
WIRE 352 -112 352 -144
WIRE 512 -112 352 -112
WIRE 560 -112 512 -112
WIRE 352 -80 352 -112
WIRE 448 -80 448 -144
WIRE 448 -80 416 -80
WIRE 512 -64 512 -112
WIRE -528 -16 -528 -48
WIRE -528 -16 -560 -16
WIRE -464 -16 -528 -16
WIRE -368 -16 -464 -16
WIRE -352 -16 -368 -16
WIRE -304 -16 -352 -16
WIRE -288 -16 -304 -16
WIRE -192 -16 -288 -16
WIRE -160 -16 -192 -16
WIRE 208 -16 -160 -16
WIRE 272 -16 208 -16
WIRE 288 -16 288 -112
WIRE 288 -16 272 -16
WIRE 304 -16 288 -16
WIRE 448 -16 448 -80
WIRE 448 -16 384 -16
WIRE -464 0 -464 -16
WIRE -192 0 -192 -16
WIRE 272 32 272 -16
WIRE 384 32 272 32
WIRE -368 48 -400 48
WIRE -256 48 -288 48
WIRE 272 48 272 32
WIRE 496 80 496 -160
WIRE 496 80 448 80
WIRE -464 96 -592 96
WIRE -448 96 -464 96
WIRE -384 96 -288 48
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WIRE 112 320 -16 320
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WIRE 272 320 208 320
FLAG 560 -32 0
FLAG -528 -48 Vin
FLAG 512 -64 Vout
FLAG -80 320 0
SYMBOL npn -256 208 R0
SYMATTR InstName Q1
SYMATTR Value 2N2222
SYMBOL npn -400 208 M0
SYMATTR InstName Q2
SYMATTR Value 2N2222
SYMBOL pnp -400 96 R180
WINDOW 0 51 37 Left 2
WINDOW 3 31 60 Left 2
SYMATTR InstName Q3
SYMATTR Value 2N2907
SYMBOL pnp -256 96 M180
WINDOW 0 36 42 Left 2
WINDOW 3 -10 95 Left 2
SYMATTR InstName Q4
SYMATTR Value 2N2907
SYMBOL cap -240 192 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 1n
SYMBOL cap -352 192 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C2
SYMATTR Value 1n
SYMBOL cap -384 80 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C3
SYMATTR Value 1n
SYMBOL cap -208 80 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 8 14 VTop 2
SYMATTR InstName C4
SYMATTR Value 1n
SYMBOL res -320 112 R0
WINDOW 0 1 -2 Left 2
WINDOW 3 -13 62 Left 2
SYMATTR InstName R1
SYMATTR Value 47k
SYMBOL res -400 80 R0
WINDOW 0 0 40 Left 2
WINDOW 3 -5 70 Left 2
SYMATTR InstName R3
SYMATTR Value 47k
SYMBOL res -288 80 R0
WINDOW 0 1 42 Left 2
WINDOW 3 -2 72 Left 2
SYMATTR InstName R4
SYMATTR Value 4k7
SYMBOL voltage -528 112 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
WINDOW 3 -42 -248 Left 2
WINDOW 0 -13 58 Left 2
SYMATTR Value PULSE(0 1 0 100n)
SYMATTR InstName V1
SYMBOL res -480 96 R0
WINDOW 0 3 55 Left 2
WINDOW 3 13 80 Left 2
SYMATTR InstName R5
SYMATTR Value 10
SYMBOL res -208 96 R0
WINDOW 0 -16 36 Left 2
WINDOW 3 -2 70 Left 2
SYMATTR InstName R6
SYMATTR Value 10
SYMBOL diode -288 320 R180
WINDOW 0 3 -13 Left 2
WINDOW 3 -84 -14 Left 2
SYMATTR InstName D1
SYMATTR Value 1N4148
SYMBOL diode -336 320 R180
WINDOW 0 88 -13 Left 2
WINDOW 3 -1 -12 Left 2
SYMATTR InstName D4
SYMATTR Value 1N4148
SYMBOL diode -272 48 R180
WINDOW 0 8 108 Left 2
WINDOW 3 -29 82 Left 2
SYMATTR InstName D2
SYMATTR Value 1N4148
SYMBOL diode -352 48 R180
WINDOW 0 31 45 Left 2
WINDOW 3 9 94 Left 2
SYMATTR InstName D3
SYMATTR Value 1N4148
SYMBOL res -368 80 R0
WINDOW 0 6 32 Left 2
WINDOW 3 9 71 Left 2
SYMATTR InstName R2
SYMATTR Value 4k7
SYMBOL res -608 80 R0
WINDOW 0 17 38 Left 2
WINDOW 3 2 88 Left 2
SYMATTR InstName R7
SYMATTR Value 4k7
SYMBOL res -576 -32 R0
WINDOW 0 -3 53 Left 2
WINDOW 3 -12 89 Left 2
SYMATTR InstName R8
SYMATTR Value 4k7
SYMBOL res -144 80 R0
WINDOW 0 15 38 Left 2
WINDOW 3 7 73 Left 2
SYMATTR InstName R9
SYMATTR Value 4k7
SYMBOL res -176 -32 R0
SYMATTR InstName R10
SYMATTR Value 4k7
SYMBOL npn 144 224 R0
SYMATTR InstName Q5
SYMATTR Value 2N2222
SYMBOL npn 208 160 R0
WINDOW 0 56 45 Left 2
SYMATTR InstName Q6
SYMATTR Value FZT849
SYMBOL ind 256 32 R0
WINDOW 3 64 53 Left 2
SYMATTR Value 100
SYMATTR InstName L1
SYMATTR SpiceLine Rser=.5
SYMBOL schottky 272 160 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName D5
SYMATTR Value 1N5819
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL pnp 384 80 M180
SYMATTR InstName Q8
SYMATTR Value 2N2907
SYMBOL zener 416 -96 R90
WINDOW 0 -4 32 VBottom 2
WINDOW 3 37 -14 VTop 2
SYMATTR InstName D6
SYMATTR Value BZX84C15L
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL cap 352 -128 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C6
SYMATTR Value 1
SYMBOL res 544 -128 R0
SYMATTR InstName R14
SYMATTR Value 4k7
SYMBOL res 192 80 R0
WINDOW 3 -254 -27 Left 2
WINDOW 0 -5 2 Left 2
SYMATTR Value R10%0+sqrt(54000*V(Vin))
SYMATTR InstName R15
SYMBOL res 128 80 R0
WINDOW 0 -2 40 Left 2
WINDOW 3 -2 83 Left 2
SYMATTR InstName R16
SYMATTR Value 1k
SYMBOL res 400 -32 R90
WINDOW 0 9 81 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R11
SYMATTR Value 1k
SYMBOL npn 48 208 R0
SYMATTR InstName Q7
SYMATTR Value 2N2222
SYMBOL res -96 -144 R0
SYMATTR InstName R12
SYMATTR Value 1k
SYMBOL res 112 128 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R13
SYMATTR Value 10k
SYMBOL cap -16 128 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C7
SYMATTR Value 100p
SYMBOL diode 0 320 R180
WINDOW 0 24 64 Left 2
WINDOW 3 -17 25 Left 2
SYMATTR InstName D7
SYMATTR Value 1N4148
SYMBOL cap 448 -160 R90
WINDOW 0 27 65 VBottom 2
WINDOW 3 5 -6 VTop 2
SYMATTR InstName C5
SYMATTR Value 1n
TEXT -320 -136 Left 2 !.tran 0 5m 0  



Re: micropower boost circuit
On Sun, 22 Sep 2013 12:01:32 -0400, "Michael Robinson"

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Yikes, that's unreadable!


--  

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

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Re: micropower boost circuit
On Sun, 22 Sep 2013 09:21:59 -0700, John Larkin

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But it's "compact" >:-}
        
                                        ...Jim Thompson
--  
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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Re: micropower boost circuit
On Sun, 22 Sep 2013 09:27:35 -0700, Jim Thompson

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All drawings should be clean, commented, titled and dated.

LT Spice should have a title block. There is a checkbox "show title block" but
it's "for internal use."






Version 4
SHEET 1 1920 968
WIRE 240 144 112 144
WIRE 320 144 240 144
WIRE 464 144 400 144
WIRE 528 144 464 144
WIRE 656 144 608 144
WIRE 816 144 768 144
WIRE 960 144 896 144
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WIRE 1184 144 1104 144
WIRE 1232 144 1184 144
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WIRE 96 416 48 416
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WIRE 240 416 176 416
WIRE 656 432 656 320
WIRE -32 448 -32 416
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WIRE 400 448 368 448
WIRE 768 480 768 448
WIRE 960 480 960 448
WIRE 240 512 240 448
WIRE 304 512 240 512
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WIRE -32 528 -32 512
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WIRE 400 576 368 576
WIRE 656 592 656 528
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WIRE 1408 592 1360 592
WIRE 1424 592 1408 592
WIRE 48 608 48 576
WIRE 1136 640 1136 592
WIRE 1360 656 1360 592
WIRE 240 688 96 688
WIRE 320 688 240 688
WIRE 448 688 384 688
WIRE 480 688 448 688
WIRE 240 720 240 688
WIRE 1136 800 1136 720
WIRE 1360 800 1360 720
WIRE 48 832 48 704
WIRE 240 832 240 800
FLAG 1424 144 VP
FLAG 656 592 0
FLAG 112 320 0
FLAG 720 320 DRAIN
FLAG 560 512 GATE
FLAG 768 208 0
FLAG 960 592 0
FLAG 1136 800 0
FLAG 1408 592 EFF
FLAG 768 592 0
FLAG 1360 800 0
FLAG -32 528 0
FLAG 80 576 rc
FLAG 48 832 0
FLAG 240 832 0
FLAG 448 688 VP
FLAG 1360 400 0
SYMBOL ind2 512 160 R270
WINDOW 0 -41 56 VTop 2
WINDOW 3 -53 53 VBottom 2
SYMATTR InstName L1
SYMATTR Value 10
SYMATTR Type ind
SYMATTR SpiceLine Rser=0.06
SYMBOL schottky 1040 160 R270
WINDOW 0 -41 30 VTop 2
WINDOW 3 -49 27 VBottom 2
SYMATTR InstName D1
SYMATTR Value 10MQ060N
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL voltage 112 160 R0
WINDOW 0 48 55 Left 2
WINDOW 3 54 83 Left 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value 9
SYMBOL nmos 608 432 R0
WINDOW 0 -48 -65 Left 2
WINDOW 3 -87 -29 Left 2
SYMATTR InstName M1
SYMATTR Value Si7218DN
SYMBOL ind2 800 160 R270
WINDOW 0 -32 56 VTop 2
WINDOW 3 -41 57 VBottom 2
SYMATTR InstName L2
SYMATTR Value 90
SYMATTR Type ind
SYMATTR SpiceLine Rser=0.06
SYMBOL res 528 496 R90
WINDOW 0 77 56 VBottom 2
WINDOW 3 84 57 VTop 2
SYMATTR InstName R3
SYMATTR Value 25
SYMBOL res 1216 160 R270
WINDOW 0 47 31 VTop 2
WINDOW 3 74 86 VBottom 2
SYMATTR InstName R6
SYMATTR Value 1m
SYMBOL cap 1296 224 R90
WINDOW 0 68 59 VBottom 2
WINDOW 3 42 -8 VTop 2
SYMATTR InstName C3
SYMATTR Value 100m
SYMBOL res 304 160 R270
WINDOW 0 48 28 VTop 2
WINDOW 3 76 86 VBottom 2
SYMATTR InstName R8
SYMATTR Value 1m
SYMBOL cap 384 224 R90
WINDOW 0 73 60 VBottom 2
WINDOW 3 47 -14 VTop 2
SYMATTR InstName C6
SYMATTR Value 100m
SYMBOL res 944 352 R0
WINDOW 0 -50 38 Left 2
WINDOW 3 -57 75 Left 2
SYMATTR InstName R9
SYMATTR Value 500
SYMBOL cap 944 480 R0
WINDOW 0 -46 35 Left 2
WINDOW 3 -50 68 Left 2
SYMATTR InstName C7
SYMATTR Value 30p
SYMBOL bv 1136 624 R0
WINDOW 3 -558 118 Left 2
WINDOW 0 -89 56 Left 2
SYMATTR Value V= LIMIT (0, 100 * I(R6) * V(VP)  /  ( I(R8) * 9 ), 100 )
SYMATTR InstName B1
SYMBOL res 1280 576 R90
WINDOW 0 70 60 VBottom 2
WINDOW 3 78 61 VTop 2
SYMATTR InstName R1
SYMATTR Value 1K
SYMBOL res 752 352 R0
WINDOW 0 57 39 Left 2
WINDOW 3 51 80 Left 2
SYMATTR InstName R2
SYMATTR Value 200
SYMBOL cap 752 480 R0
WINDOW 0 60 34 Left 2
WINDOW 3 56 72 Left 2
SYMATTR InstName C1
SYMATTR Value 50p
SYMBOL cap 1344 656 R0
WINDOW 0 -37 63 Left 2
WINDOW 3 -43 94 Left 2
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SYMATTR Value 50n
SYMBOL Digital\schmtinv 128 512 R0
SYMATTR InstName A1
SYMATTR Value2 Vhigh=5 Vt=2.5 Vh=1
SYMATTR SpiceLine Td=5n
SYMBOL cap -48 448 R0
WINDOW 0 42 14 Left 2
WINDOW 3 42 51 Left 2
SYMATTR InstName C4
SYMATTR Value 1n
SYMBOL res 80 432 R270
WINDOW 0 -36 57 VTop 2
WINDOW 3 -43 57 VBottom 2
SYMATTR InstName R4
SYMATTR Value 1K
SYMBOL Digital\schmtinv 304 448 R0
SYMATTR InstName A2
SYMATTR Value2 Vhigh=5 Vt=2.5 Vh=1
SYMATTR SpiceLine Td=5n
SYMBOL Digital\schmtinv 304 384 R0
SYMATTR InstName A3
SYMATTR Value2 Vhigh=5 Vt=2.5 Vh=1
SYMATTR SpiceLine Td=5n
SYMBOL Digital\schmtinv 304 512 R0
SYMATTR InstName A4
SYMATTR Value2 Vhigh=5 Vt=2.5 Vh=1
SYMATTR SpiceLine Td=5n
SYMBOL Digital\schmtinv 304 320 R0
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SYMATTR Value2 Vhigh=5 Vt=2.5 Vh=1
SYMATTR SpiceLine Td=5n
SYMBOL nmos 96 608 M0
WINDOW 0 100 28 Left 2
WINDOW 3 79 72 Left 2
SYMATTR InstName M2
SYMATTR Value 2N7002
SYMBOL res 224 704 R0
WINDOW 0 -55 50 Left 2
WINDOW 3 -63 91 Left 2
SYMATTR InstName R5
SYMATTR Value 10K
SYMBOL zener 320 704 R270
WINDOW 0 -47 34 VTop 2
WINDOW 3 -54 32 VBottom 2
SYMATTR InstName D2
SYMATTR Value ZNR48
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL cap 1344 288 R0
WINDOW 0 56 10 Left 2
WINDOW 3 56 55 Left 2
SYMATTR InstName C5
SYMATTR Value 5
TEXT 1032 488 Left 2 !.tran 0 5m 0 10n uic
TEXT 1064 392 Left 2 ;DUMB BOOST
TEXT 1048 440 Left 2 ;JL  June 28 2013
TEXT 648 104 Left 2 !K L1 L2 0.95
TEXT 144 624 Left 2 ;74HC14


--  

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

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Re: micropower boost circuit
On Sun, 22 Sep 2013 09:38:28 -0700, John Larkin

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How is it you say, "Net dumb"?
        
                                        ...Jim Thompson
--  
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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Re: micropower boost circuit
Michael Robinson wrote:
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Wow, did you knead it afterwards or compress it with vise grips?  :-)


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A 30V transistor is the wrong choice here, it'll like go *PHUT* and I'd
suggest looking at some with at least 50V rating. At 16V input it sees
around 32V and you need some margin. Also, mind ESD. There should be a
capacitor on the VIN side.

[...]

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: micropower boost circuit

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DSS416 has a 60 volt rating.   And thanks for reminding me, I forgot the  
bypass.  



Re: micropower boost circuit
On Sun, 22 Sep 2013 12:01:32 -0400, Michael Robinson wrote:

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Snarky comments about the layout of the schematic aside, why don't you  
want to use a chip for the switcher, or a chip + op-amp?  You're going to  
consume a lot of board space with what you have here.

--  
Tim Wescott
Control system and signal processing consulting
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Re: micropower boost circuit

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Can you suggest a chip which will work in a range from less than a volt to  
fifteen volts.  



Re: micropower boost circuit
On Sun, 22 Sep 2013 18:24:17 -0400, Michael Robinson wrote:

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Whoops -- I missed the "less than a volt in".  Sorry -- I took the "few"  
from "milliamps" and applied it to "volts" as well.

That's going to make your job tremendously difficult (and your bipolar  
transistors suddenly make more sense) -- not only do you need something  
that'll work down to the sub-volt level at all, but your switcher design  
needs to be able to pull lots-o-current at those levels.

You really need to specify _how_ much less than a volt -- 0.9V in vs.  
0.5V is a huge difference, and if you want it down to 0.1V then you're  
probably in a world of hurt.

--  

Tim Wescott
Wescott Design Services
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Re: micropower boost circuit
Tim Wescott wrote:

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A joule thief based on a decent JFET will do the trick.

    Best regards, Piotr




Re: micropower boost circuit

Below is something to begin with. One can add an additional
winding and get a flyback-like topology with an autotransformer
or to use this circuit to power/start a real switcher etc.
If "below one volt" means ~0.8V, then a BJT will be fine,
otherwise a JFET would be necessary. The high input voltage sector
is an exercise left to the reader. ;-)

    Best regards, Piotr

Version 4
SHEET 1 880 680
WIRE 128 48 -64 48
WIRE 192 48 128 48
WIRE 240 48 192 48
WIRE 192 80 192 48
WIRE 240 80 240 48
WIRE -64 112 -64 48
WIRE 192 176 192 160
WIRE 240 176 240 144
WIRE 240 176 192 176
WIRE 128 192 80 192
WIRE 80 208 80 192
WIRE 128 240 128 192
WIRE 144 240 128 240
WIRE 80 304 80 288
FLAG -64 192 0
FLAG 192 272 0
FLAG 128 112 0
FLAG 80 304 0
SYMBOL njf 144 176 R0
SYMATTR InstName J1
SYMATTR Value 2N4393
SYMBOL ind2 176 64 R0
SYMATTR InstName L1
SYMATTR Value 100
SYMATTR Type ind
SYMBOL Misc\battery -64 96 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value 0.6
SYMBOL cap 112 48 R0
SYMATTR InstName C1
SYMATTR Value 10
SYMBOL ind2 64 192 R0
SYMATTR InstName L2
SYMATTR Value 900
SYMATTR Type ind
SYMBOL cap 224 80 R0
SYMATTR InstName C2
SYMATTR Value 1n
TEXT -98 328 Left 2 !.tran 0.1
TEXT 240 328 Left 2 !K L1 L2 1.0


Re: micropower boost circuit

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The LTC3108 claims to operate at 20mV. It appears to use a depletion mode  
mosfet driving a step-up transformer. Very simple, but the following  
regulator is a nightmare:

"http://datasheet.octopart.com/LTC3108EGN%23PBF-Linear-Technology-
datasheet-8701600.pdf"

JK

Re: micropower boost circuit

The link did't work. Try it this way:
  
<http://datasheet.octopart.com/LTC3108EGN%23PBF-Linear-Technology-
datasheet-8701600.pdf>
  
  


Re: micropower boost circuit
On 9/25/2013 3:19 PM, John K wrote:
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Both links are truncated in my newsreader, but copying the text of the  
link and pasting it into the browser address bar works just fine.

--  

Rick

Re: micropower boost circuit
On Sun, 22 Sep 2013 12:01:32 -0400, Michael Robinson wrote:

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The LT8410 does what you want, if by "a few mA" you mean 5 or so, and if  
you can stand the difference between Vin and Vboost to be close to, but  
not exactly, your set value:

(What a waste of a Sunday -- but it was fun)

Version 4
SHEET 1 1136 680
WIRE 768 -32 304 -32
WIRE -144 -16 -192 -16
WIRE -32 -16 -144 -16
WIRE 16 -16 -32 -16
WIRE 176 -16 96 -16
WIRE 768 -16 768 -32
WIRE -144 16 -144 -16
WIRE 176 32 176 -16
WIRE 304 32 304 -32
WIRE -32 96 -32 -16
WIRE 96 96 -32 96
WIRE 816 96 384 96
WIRE 944 96 816 96
WIRE 976 96 944 96
WIRE -144 112 -144 80
WIRE 944 112 944 96
WIRE 816 128 816 96
WIRE 480 176 384 176
WIRE 672 176 480 176
WIRE 480 192 480 176
WIRE 672 240 672 176
WIRE -352 256 -432 256
WIRE -32 256 -32 96
WIRE 96 256 -32 256
WIRE 416 256 384 256
WIRE -432 272 -432 256
WIRE 416 304 416 256
WIRE 480 304 480 272
WIRE 480 304 416 304
WIRE 480 320 480 304
WIRE 560 320 480 320
WIRE 768 320 768 48
WIRE 768 320 640 320
WIRE 816 320 816 192
WIRE 816 320 768 320
WIRE 944 320 944 192
WIRE 944 320 816 320
WIRE 976 320 944 320
WIRE 480 336 480 320
WIRE -432 384 -432 352
WIRE 240 448 240 320
WIRE 480 448 480 416
WIRE 672 448 672 304
FLAG 240 448 0
FLAG 480 448 0
FLAG 672 448 0
FLAG -432 384 0
FLAG -144 112 0
FLAG -352 256 Vin
FLAG -192 -16 Vin
FLAG 976 320 Vin
FLAG 976 96 Vout
SYMBOL PowerProducts\LT8410 240 176 R0
SYMATTR InstName U1
SYMBOL ind 0 0 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 5 56 VBottom 2
SYMATTR InstName L1
SYMATTR Value 470
SYMBOL cap 752 -16 R0
SYMATTR InstName C1
SYMATTR Value 100n
SYMBOL cap 800 128 R0
SYMATTR InstName C2
SYMATTR Value 100n
SYMBOL cap 656 240 R0
SYMATTR InstName C3
SYMATTR Value 100n
SYMBOL res 464 176 R0
SYMATTR InstName R1
SYMATTR Value 772k
SYMBOL res 464 320 R0
SYMATTR InstName R2
SYMATTR Value 559k
SYMBOL cap -160 16 R0
SYMATTR InstName C4
SYMATTR Value 100n
SYMBOL voltage -432 256 R0
WINDOW 123 0 0 Left 2
WINDOW 39 24 124 Left 2
SYMATTR InstName V1
SYMATTR Value PWL(0 12 400u 12 500u 5 3000u 16 5000u 5)
SYMATTR SpiceLine Rser10%
SYMBOL res 928 96 R0
SYMATTR InstName R3
SYMATTR Value 3300
SYMBOL res 656 304 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R4
SYMATTR Value 10meg
TEXT -424 432 Left 2 !.tran 5m

--  

Tim Wescott
Wescott Design Services
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Re: micropower boost circuit
On Sun, 22 Sep 2013 16:52:07 -0500, Tim Wescott wrote:

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BTW:

To get perfect* tracking, set

1/R4 = (1/31.85) * (1/R1 + 1/R2 + 1/R4)

To get your desired offset voltage, Vd, set

R4/R1 = Vd / Vref

Where the 31.85 and Vref come from the LT8410 data sheet.

Or:

R4 = whatever, but make it big enough for the chip (I chose 10 meg --  
that's big).

Then calculate R1 from R4 and your desired Vd.

Then calculate R2 from R1, R4, and your desire for perfect tracking.

* You'll never really perfect tracking, because (a) the 31.85 comes from  
the chip design, and will vary from chip to chip and probably with  
temperature and aging, and (b) you'll need to set your resistor ratios  
perfectly, which you can't, and (anyway) the resistor ratios will change,  
and R4 needs to be big to keep the chip happy, meaning you'll have  
leakage issues.

--  

Tim Wescott
Wescott Design Services
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Re: micropower boost circuit

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Tim, my requirements are a lot more forgiving on the output side.  No need  
for accuracy, it can float up or down a volt without any ill effects at all.
The tough part is on the input.  I can't use a chip that requires 2.5 volts  
to run.
You went to a lot of trouble and the least I can do is explain why the  
circuit has to run on a volt.
Vcc (the armature voltage of an antique six volt generator) isn't going to  
start at some higher voltage and drop to a volt, which might allow  
bootstrapping.  Vcc starts at zero and comes up to about a volt because of  
residual magnetism in the soft iron pole shoes (possibly even a little less  
than a volt).  Whereupon, nothing more will happen:  unless the booster  
produces some output, generator output will remain flat at one volt.  The  
booster has to take that one volt and boost it enough to turn on a mosfet,  
and get some current going in the field coils around the pole shoes.  Then  
will Vcc (the generator output) rise.
The circuit I posted only needs two thirds of a volt to run, according to  
the simulator.  



Re: micropower boost circuit

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can't use a depletion mode mosfet or a Normally closed relay?

--  
?? 100% natural


Re: micropower boost circuit
On a sunny day (23 Sep 2013 08:17:34 GMT) it happened Jasen Betts

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Or a simple JFET, driving transformer, driving normal MOSFET:
 
http://panteltje.com/pub/lighting_a_LED_with_a_candle_circuit_diagram_with_added_power_MOSFET.gif
 http://panteltje.com/pub/lighting_a_LED_with_a_candle_IMG_3604.GIF
 http://panteltje.com/pub/lighting_a_LED_with_a_candle_hardware_IMG_3605.GIF
Or whatever :-)
 http://panteltje.com/pub/lighting_a_LED_with_daylight_IMG_3643.GIF

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