Boost Converter Efficiency Improvements

Shouldn't be a big problem but you can hang a diode in series with the zener.

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.

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.

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.

No more. It's fixed, costs one extra diode:

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 480 672 464 672 WIRE 560 672 544 672 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 3µ 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 27µ 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 5µ 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 0.33µ SYMBOL res 224 928 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R10 SYMATTR Value 10k SYMBOL diode 544 688 M270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D3 SYMATTR Value 1N4148 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

On Sun, 30 Jun 2013 13:22:27 -0700, Joerg wrote:

Try this one. Sweet startup current curve.

Version 4 SHEET 1 1920 1076 WIRE 224 96 96 96 WIRE 96 144 96 96 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 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 656 640 656 528 WIRE 656 640 400 640 WIRE 1152 672 1152 624 WIRE 96 688 96 576 WIRE 272 688 96 688 WIRE 656 688 656 640 WIRE 1360 688 1360 624 WIRE 272 704 272 688 WIRE 400 752 400 640 WIRE 400 752 336 752 WIRE 656 800 656 768 WIRE 272 832 272 800 WIRE 1152 832 1152 752 WIRE 1360 832 1360 752 WIRE 96 880 96 688 WIRE 160 880 96 880 WIRE 272 880 160 880 WIRE 464 880 400 880 WIRE 560 880 464 880 WIRE 688 880 624 880 WIRE 720 880 688 880 WIRE 272 912 272 880 WIRE 464 912 464 880 WIRE 96 928 96 880 WIRE 400 992 400 880 WIRE 400 992 320 992 WIRE 96 1040 96 992 WIRE 272 1040 272 1008 WIRE 464 1040 464 992 FLAG 1344 144 VP FLAG 656 800 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 1040 0 FLAG 160 880 rc FLAG 272 1040 0 FLAG 688 880 VP FLAG 1328 400 0 FLAG 224 96 9V FLAG 464 1040 0 FLAG 272 832 0 SYMBOL ind2 512 160 R270 WINDOW 0 -41 56 VTop 2 WINDOW 3 -53 53 VBottom 2 SYMATTR InstName L1 SYMATTR Value 3µ 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 27µ SYMATTR Type ind SYMATTR SpiceLine Rser=0.06 SYMBOL res 528 496 R90 WINDOW 0 -15 56 VBottom 2 WINDOW 3 46 56 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 -269 254 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 80 928 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 320 912 M0 WINDOW 0 77 0 Left 2 WINDOW 3 63 35 Left 2 SYMATTR InstName M2 SYMATTR Value 2N7002 SYMBOL res 448 896 R0 WINDOW 0 47 64 Left 2 WINDOW 3 40 94 Left 2 SYMATTR InstName R5 SYMATTR Value 10K SYMBOL zener 560 896 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 5µ 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 640 672 R0 WINDOW 0 70 52 Left 2 WINDOW 3 75 86 Left 2 SYMATTR InstName R10 SYMATTR Value 0.6 SYMBOL npn 336 704 M0 WINDOW 0 100 35 Left 2 WINDOW 3 76 73 Left 2 SYMATTR InstName Q1 SYMATTR Value 2N4401 TEXT 1040 416 Left 2 !.tran 0 5m 0 10n uic TEXT 1016 464 Left 2 ;PRETTY DUMB BOOST TEXT 1040 552 Left 2 ;JL June 30 2013 TEXT 648 104 Left 2 !K L1 L2 0.95 TEXT 192 624 Left 2 ;74HC14 TEXT 160 504 Left 2 ;OSC TEXT 696 168 Left 2 ;1:3 TEXT 1056 504 Left 2 ;(npn soft start)

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.

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.