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Re: Boost Converter Efficiency Improvements
John Larkin wrote:
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But R10 for the current mode causes the efficiency to go to pots because
the supply is only 9V. What I did in one such situation was pre-bias the
BE junction to around 400mV so the current sense resistor would only
have to drop 200mV.

It'll also have a rough start because Q10 truncates pulses brutally in
the beginning. Causes needle pulses, and probably some EMI worries.

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: Boost Converter Efficiency Improvements
Fred Abse wrote:
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Didn't slow down much here. But yesterday the fan speed cranked itself
to the hilt. I took the PC apart and found an incredible amount of dog
hair and dust in the cooling fins for the processor. One of our
Labradors has a habit of curling himself up in the small space under my
PC workplace.


Quoted text here. Click to load it

Here is a version with a better soft-start:

Version 4
SHEET 1 1920 1076
WIRE 208 48 96 48
WIRE 96 144 96 48
WIRE 240 144 96 144
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
WIRE 1040 144 960 144
WIRE 1152 144 1104 144
WIRE 1200 144 1152 144
WIRE 1328 144 1280 144
WIRE 1344 144 1328 144
WIRE 1360 144 1344 144
WIRE 96 176 96 144
WIRE 768 208 768 144
WIRE 240 240 240 144
WIRE 320 240 240 240
WIRE 464 240 464 144
WIRE 464 240 384 240
WIRE 1152 240 1152 144
WIRE 1200 240 1152 240
WIRE 1328 240 1328 144
WIRE 1328 240 1264 240
WIRE 1328 288 1328 240
WIRE 656 304 656 144
WIRE 720 304 656 304
WIRE 768 304 720 304
WIRE 96 320 96 256
WIRE 656 336 656 304
WIRE 768 336 768 304
WIRE 960 336 960 144
WIRE 304 384 272 384
WIRE 400 384 368 384
WIRE 1328 400 1328 352
WIRE 656 432 656 416
WIRE 144 448 96 448
WIRE 272 448 272 384
WIRE 272 448 224 448
WIRE 304 448 272 448
WIRE 400 448 400 384
WIRE 400 448 368 448
WIRE 768 480 768 416
WIRE 960 480 960 416
WIRE 272 512 272 448
WIRE 304 512 272 512
WIRE 400 512 400 448
WIRE 400 512 368 512
WIRE 432 512 400 512
WIRE 560 512 512 512
WIRE 608 512 560 512
WIRE 96 576 96 448
WIRE 160 576 96 576
WIRE 272 576 272 512
WIRE 272 576 224 576
WIRE 304 576 272 576
WIRE 400 576 400 512
WIRE 400 576 368 576
WIRE 656 592 656 528
WIRE 768 592 768 544
WIRE 960 592 960 544
WIRE 1216 624 1152 624
WIRE 1344 624 1296 624
WIRE 1360 624 1344 624
WIRE 96 672 96 576
WIRE 160 672 96 672
WIRE 272 672 160 672
WIRE 464 672 400 672
WIRE 560 672 464 672
WIRE 688 672 624 672
WIRE 720 672 688 672
WIRE 1152 672 1152 624
WIRE 1360 688 1360 624
WIRE 272 704 272 672
WIRE 464 704 464 672
WIRE 96 720 96 672
WIRE 400 784 400 672
WIRE 400 784 320 784
WIRE 96 832 96 784
WIRE 272 832 272 800
WIRE 1152 832 1152 752
WIRE 1360 832 1360 752
WIRE 240 912 144 912
WIRE 368 912 320 912
WIRE 464 912 464 784
WIRE 464 912 432 912
WIRE 464 928 464 912
WIRE 464 1056 464 1008
FLAG 1344 144 VP
FLAG 656 592 0
FLAG 96 320 0
FLAG 720 304 DRAIN
FLAG 560 512 GATE
FLAG 768 208 0
FLAG 960 592 0
FLAG 1152 832 0
FLAG 1344 624 EFF
FLAG 768 592 0
FLAG 1360 832 0
FLAG 96 832 0
FLAG 160 672 rc
FLAG 272 832 0
FLAG 464 1056 0
FLAG 688 672 VP
FLAG 1328 400 0
FLAG 208 48 9V
FLAG 144 912 9V
SYMBOL ind2 512 160 R270
WINDOW 0 -41 56 VTop 2
WINDOW 3 -53 53 VBottom 2
SYMATTR InstName L1
SYMATTR Value 3
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 96 160 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 -55 -55 Left 2
WINDOW 3 -101 -22 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 27
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 10
SYMBOL res 1184 160 R270
WINDOW 0 -38 31 VTop 2
WINDOW 3 -11 86 VBottom 2
SYMATTR InstName R6
SYMATTR Value 1m
SYMBOL cap 1264 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 -37 24 VTop 2
WINDOW 3 -11 88 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 944 320 R0
WINDOW 0 -54 67 Left 2
WINDOW 3 -58 98 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 1152 656 R0
WINDOW 3 -557 141 Left 2
WINDOW 0 -83 97 Left 2
SYMATTR Value V= LIMIT (0, 100 * I(R6) * V(VP)  /  ( I(R8) * 9 ), 100 )
SYMATTR InstName B1
SYMBOL res 1312 608 R90
WINDOW 0 70 60 VBottom 2
WINDOW 3 78 61 VTop 2
SYMATTR InstName R1
SYMATTR Value 1K
SYMBOL res 752 320 R0
WINDOW 0 53 70 Left 2
WINDOW 3 51 100 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 200p
SYMBOL cap 1344 688 R0
WINDOW 0 -37 63 Left 2
WINDOW 3 -43 94 Left 2
SYMATTR InstName C2
SYMATTR Value 50n
SYMBOL Digital\schmtinv 160 512 R0
SYMATTR InstName A1
SYMATTR Value2 Vhigh=5 Vt=2.5 Vh=0.5
SYMATTR SpiceLine Td=5n
SYMBOL cap 80 720 R0
WINDOW 0 44 60 Left 2
WINDOW 3 37 92 Left 2
SYMATTR InstName C4
SYMATTR Value 500p
SYMBOL res 128 464 R270
WINDOW 0 88 58 VTop 2
WINDOW 3 74 57 VBottom 2
SYMATTR InstName R4
SYMATTR Value 2K
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
SYMATTR InstName A5
SYMATTR Value2 Vhigh=5 Vt=2.5 Vh=1
SYMATTR SpiceLine Td=5n
SYMBOL nmos 320 704 M0
WINDOW 0 77 0 Left 2
WINDOW 3 63 35 Left 2
SYMATTR InstName M2
SYMATTR Value 2N7002
SYMBOL res 448 688 R0
WINDOW 0 47 64 Left 2
WINDOW 3 40 94 Left 2
SYMATTR InstName R5
SYMATTR Value 10K
SYMBOL zener 560 688 R270
WINDOW 0 50 33 VTop 2
WINDOW 3 -13 35 VBottom 2
SYMATTR InstName D2
SYMATTR Value 1N5369B
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL cap 1312 288 R0
WINDOW 0 -61 48 Left 2
WINDOW 3 -59 81 Left 2
SYMATTR InstName C5
SYMATTR Value 5
SYMBOL res 640 320 R0
WINDOW 0 47 70 Left 2
WINDOW 3 41 102 Left 2
SYMATTR InstName R7
SYMATTR Value 1m
SYMBOL res 448 912 R0
WINDOW 0 47 64 Left 2
WINDOW 3 40 94 Left 2
SYMATTR InstName R11
SYMATTR Value 10K
SYMBOL cap 368 928 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName C9
SYMATTR Value 0.33
SYMBOL res 224 928 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R10
SYMATTR Value 10k
TEXT 1064 432 Left 2 !.tran 0 15m 0 10n uic
TEXT 1040 488 Left 2 ;PRETTY DUMB BOOST
TEXT 1072 544 Left 2 ;JL  June 29 2013
TEXT 648 104 Left 2 !K L1 L2 0.95
TEXT 192 624 Left 2 ;74HC14
TEXT 296 1016 Left 2 ;SOFT
TEXT 296 1040 Left 2 ;START
TEXT 160 504 Left 2 ;OSC
TEXT 696 168 Left 2 ;1:3


--  
Regards, Joerg

http://www.analogconsultants.com/

Re: Boost Converter Efficiency Improvements

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Cute, but the oscillator runs a bit at powerup. The zener forward conducts and
clamps the 2N7002 gate voltage to VP+0.6. Not lethal, since VP jumps up and
fixes things pretty quickly. With my 4000 uF load, it might be a problem.

With 4000 uF, my soft-start would have to be pretty slow. Maybe we'll do it
digitally after all.

I'm in a situation where the customer is in a frenzy to get this thing done. We
quoted 5 weeks ARO for a first article, so they waited a few weeks and then cut
a PO stating 4 weeks. Two weeks later, we have no spec hard enough to design
around, and no answers to basic questions, like how does this thing mount? How
big can it be? What's the orientation of the connector? What's the required
output, into what load?

So I play with the power inverter now and then, and rest up for the panic.


--  

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

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Re: Boost Converter Efficiency Improvements
John Larkin wrote:
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Shouldn't be a big problem but you can hang a diode in series with the
zener.


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This one lends itself to do it with a uC. If you don't need a fast loop
any old uC could do this. If it has an ADC you can have it keep track of
the cap voltage.


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My worst one was a doc, boss of a large research hospital department.
Behaved very uppity but I can deal with that. What turned me off was
when they took a whole month to reach the simple decision about finally
going ahead with the project and then told me I had to get it done in
three days. With board layout, fab, debug and all. I turned them down.

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: Boost Converter Efficiency Improvements
On Sun, 30 Jun 2013 13:11:05 -0700, Joerg wrote:

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We all get that.

They usually come back, months later, having exhausted every other avenue.
Then you really get to stick it to 'em :-)

I won't entertain dealing with medics.

--  
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled."
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Re: Boost Converter Efficiency Improvements
wrote:

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I have another customer who is an MD. And he's designing circuits.

He's taking our 5-volt delay generator pulse, driving a transistor base, pulling
the collector up to 15 volts with a 3.3K resistor, and going into the gate of a
megawatt-class IGBT.

I sent him some gate driver chips.



--  

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

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Re: Boost Converter Efficiency Improvements
On Sun, 30 Jun 2013 09:48:35 -0700, Joerg wrote:

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<Spice listing snipped>

That's better. Initial current draw at switch start down to ~1.2 amps.

Runs faster, too, similar to the original circuit.

I was playing with something similar, hold the switch off by pushing an
artificial feedback voltage, then let it ramp down to meet the real
feedback coming up.
Feedforward, overtaken by feedback.

--  
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled."
We've slightly trimmed the long signature. Click to see the full one.

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