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Voltage multiplier

I need a small, low-current, very low noise high voltage supply to bias an exotic and expensive photodiode, measuring the energy of a

13.5 nm light source. I have +12 or maybe +15 to start with, and I want around +100 at less than a mA average. I looked at all the conventional approaches, flyback inverters and such, and didn't like them much: too big, too noisy, custom magnetics, snubbers, loop stability issues, simulation, too much hard thinking.

I was reminded of my previous concept, making a C-W multiplier chain using switched SSRs instead of AC drive and diodes. Phil Hobbs, certainly in a spirit of friendliness and good cheer, called this idea the Groucho Marx Generator.

OK, how about this:

ftp://jjlarkin.lmi.net/Harpo_Marx.JPG

This is the Harpo Marx Generator. A C-W/Groucho increases voltage linearly with the number of stages. This one doubles voltage every stage, sort of like the octaves on a harp. The dual diodes would, ideally, be more SSRs, but the diodes are small and cheap and I can tolerate the drop here.

Both Marx circuits can use big caps and switch at low frequencies, 500 Hz maybe, so they will be very quiet. The caps can be biggish ceramics or aluminums.

Each SPDT switch is a dual SSR. If I do three stages and drive each SSR control input from an FPGA pin - I have tons available - I can gate the clocks and select +24, +48, or +96 volts out, minus some diode drops. Good enough. Or build a hybrid, a true Marx Brothers Circuit, that does 24, 48, 72, or 96.

John

Reply to
John Larkin
Loading thread data ...

Well, Harpo _was_ pretty quiet. Of course Chico was a problem, especially with that ridiculous hat he insisted on wearing.....

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net
Reply to
Phil Hobbs

Well, maybe it's not ready for prime time. This is a little less whacko:

ftp://jjlarkin.lmi.net/HV_Sine.jpg

It uses a stock dual-winding inductor, aka transformer. Realistically,

75 volts would be plenty for this photodiode.

It wouldn't be hard to add a dac and some stuff to get regulated output.

I do plan to use one of those spiffy Hobbsonian bootstrap things, sort of.

John

Reply to
John Larkin

On Sep 25, 11:32=A0pm, John Larkin wrote:

The Baxandall class-D oscillator needs a centre-tapped transformer, an inductor and two switching transistors - Baxandall didn't have access to MOSFET's but he would have liked them.

formatting link

Peak voltage at either end of the centre-tapped winding is pi times the supply voltage, which is 47V from a 15V supply. A doubler would push that up to 90V.

Here's an example from my files. L5 can probably be a lot bigger with MOSFET switches - with bipolar switches higher values of L5 will give you squegging - as mentioned in the note at the bottom of page 752 of the paper.

Version 4 SHEET 1 1316 736 WIRE -464 336 -464 256 WIRE -464 624 -464 416 WIRE -464 656 -464 624 WIRE -368 256 -464 256 WIRE -208 256 -288 256 WIRE -160 96 -160 0 WIRE -160 400 -160 192 WIRE -160 448 -160 400 WIRE -160 496 -160 448 WIRE -160 624 -464 624 WIRE -160 624 -160 592 WIRE -112 96 -160 96 WIRE -112 192 -160 192 WIRE -80 0 -160 0 WIRE -80 400 -160 400 WIRE -48 576 -112 576 WIRE -48 576 -48 480 WIRE -16 448 -160 448 WIRE -16 576 -16 448 WIRE 0 400 -80 400 WIRE 16 192 -32 192 WIRE 16 256 -208 256 WIRE 16 256 16 192 WIRE 64 0 -80 0 WIRE 96 96 -32 96 WIRE 96 624 -160 624 WIRE 96 624 96 96 WIRE 144 480 -48 480 WIRE 176 576 -16 576 WIRE 256 96 96 96 WIRE 256 192 16 192 WIRE 288 0 144 0 WIRE 288 400 64 400 WIRE 320 576 256 576 WIRE 368 0 288 0 WIRE 368 96 336 96 WIRE 368 96 368 0 WIRE 368 192 336 192 WIRE 368 400 288 400 WIRE 368 400 368 192 WIRE 368 480 224 480 WIRE 368 480 368 400 WIRE 368 496 368 480 WIRE 368 624 96 624 WIRE 368 624 368 592 FLAG -464 656 0 FLAG -208 256 Vct FLAG 288 0 Vout+ FLAG -80 0 Vout- FLAG -80 400 tank- FLAG 288 400 tank+ SYMBOL ind2 -128 208 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 4 56 VBottom 0 SYMATTR InstName L1 SYMATTR Value 0.00025 SYMATTR Type ind SYMATTR SpiceLine Rser=3D0.022 SYMBOL ind2 240 208 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 4 56 VBottom 0 SYMATTR InstName L2 SYMATTR Value 0.00025 SYMATTR Type ind SYMATTR SpiceLine Rser=3D0.022 SYMBOL nmos 320 496 R0 SYMATTR InstName M1 SYMATTR Value FDS6680A SYMBOL nmos -112 496 M0 SYMATTR InstName M2 SYMATTR Value FDS6680A SYMBOL cap 64 384 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 46 32 VTop 0 SYMATTR InstName C1 SYMATTR Value 100n SYMBOL ind -384 272 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 5 56 VBottom 0 SYMATTR InstName L3 SYMATTR Value 0.001 SYMATTR SpiceLine Rser=3D0.044 Cpar=3D100p SYMBOL voltage -464 320 R0 WINDOW 123 0 0 Left 0 WINDOW 39 24 132 Left 0 SYMATTR SpiceLine Rser=3D0.001 SYMATTR InstName V1 SYMATTR Value 5 SYMBOL res 272 560 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R1 SYMATTR Value 10 SYMBOL res 240 464 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R2 SYMATTR Value 10 SYMBOL ind2 -128 112 R270 WINDOW 0 44 45 VTop 0 WINDOW 3 5 56 VBottom 0 SYMATTR InstName L4 SYMATTR Value 0.0000253 SYMATTR Type ind SYMATTR SpiceLine Rser=3D0.004 Cpar=3D100pF SYMBOL ind2 240 112 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 5 56 VBottom 0 SYMATTR InstName L5 SYMATTR Value 0.0000253 SYMATTR Type ind SYMATTR SpiceLine Rser=3D0.004 SYMBOL res 160 -16 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R3 SYMATTR Value 10k TEXT -402 664 Left 0 !.tran 0 10m 5m 10n TEXT -448 8 Left 0 !K1 L1 L2 0.99 TEXT -448 40 Left 0 !K2 L1 L4 0.99 TEXT -448 72 Left 0 !K3 L1 L5 0.99 TEXT -448 104 Left 0 !K4 L2 L4 0.99 TEXT -448 136 Left 0 !K5 L2 L5 0.99 TEXT -448 168 Left 0 !K6 L4 L5 0.99 TEXT -472 704 Left 0 !.ic V(tank-)=3D0 V(Vct)=3D7.8 V(tank+)=3D15.6 V(Vout

+)=3D2.5 V(Vout-)=3D-2.5 I(L3)=3D0.1 I(L1)=3D0 I(L2)=3D0

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

I tried running that, but I only see about 3 volts peak at TANK+, hardly anything at TANK-, and supply current is running about 30 amps. I think it's ringing and not oscillating.

47 volts peak wouldn't be healthy for the fet gates anyhow.

John

Reply to
John Larkin

Yeah, well, M1 is doing nothing and M2 is sucking the current.

Where'd you get that? I'm showing gates are below ground by a about a volt.

John S

Reply to
John S

Actually, now that I look more carefully, I notice that you cannot see

47 volts at the gates. You already said you only see a max of 3 volts at TANK+ and that is what the gate sees, thanks to the 10 ohm resistor.

Nevertheless, something is wrong with the circuit.

John S

Reply to
John S

Same here.

Bill predicted the 47 volts peak. Let's give him another 5 or 10 years to work the bugs out.

The Baxandall is potentially interesting, but has biasing problems, especially if I don't want a custom multi-winding transformer. Maybe I'll play with that a little.

My little 1-transistor thing is looking pretty good. I can tweak it to about 90 volts out at 30% efficiency, which is OK.

John

Reply to
John Larkin

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Wierd. I just re-ran without the .save line and I(V1) swung between

+15.28mA and -16.19mA, while tank+ swung between +5V and -10.73V.

It's fairly slow starting, which is why I let it settle down for

13.9msec before recording the last 100usec.

Are you sure your LTSpice is up-to-date?

Sure. You could tap the primary windings to provide a lower voltage swing for the MOSFET gates, or use a resistive divider (which wastes a bit of energy, but not much).

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

Nice. Three inductors, though--do you actually need L3 for anything?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net
Reply to
Phil Hobbs

On Sep 26, 2:04=A0am, John Larkin wrote:

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47V is what you'd get from a 15V power supply. The example circuit runs from a +5V rail, and the tank+ point swings from +5V down to

-10.7V, which is to say 15.7V or 47.1/3V.

Sorry. The circuit I thought that I was posting is not the circuit that I actually posted. That circuit seems to have a bad initial condition line

Swapping in ".ic V(tank-)=3D0 V(Vct)=3D0.8 V(tank+)=3D1.6" lets it settle down in a few milliseconds,

I've posted what should be the correct version below.

Baxandall comes in closer to 90%, which is better.

Here's the .asc file again

Version 4 SHEET 1 1316 872 WIRE -160 -192 -336 -192 WIRE 128 -192 -160 -192 WIRE 336 -192 128 -192 WIRE -160 -160 -160 -192 WIRE 336 -160 336 -192 WIRE -80 -144 -112 -144 WIRE 32 -144 0 -144 WIRE 160 -144 112 -144 WIRE 288 -144 240 -144 WIRE -160 -32 -160 -64 WIRE 112 -32 112 -144 WIRE 112 -32 -160 -32 WIRE 32 0 32 -144 WIRE 336 0 336 -64 WIRE 336 0 32 0 WIRE -160 80 -160 -32 WIRE -80 80 -160 80 WIRE 0 80 -80 80 WIRE 256 80 64 80 WIRE 336 80 336 0 WIRE 336 80 256 80 WIRE -336 160 -336 -192 WIRE -160 192 -160 80 WIRE -112 192 -160 192 WIRE 16 192 -32 192 WIRE 64 192 16 192 WIRE 224 192 64 192 WIRE 336 192 336 80 WIRE 336 192 304 192 WIRE 16 272 16 192 WIRE -80 400 -160 400 WIRE 64 400 -80 400 WIRE 256 400 144 400 WIRE 336 400 256 400 WIRE -160 496 -160 400 WIRE -112 496 -160 496 WIRE 96 496 -32 496 WIRE 224 496 96 496 WIRE 336 496 336 400 WIRE 336 496 304 496 WIRE -336 544 -336 240 WIRE 16 544 16 352 WIRE 16 544 -336 544 WIRE 96 544 96 496 WIRE 96 544 16 544 WIRE 336 544 96 544 WIRE -336 576 -336 544 FLAG -336 576 0 FLAG 64 192 Vct FLAG 256 400 Vout+ FLAG -80 400 Vout- FLAG -80 80 tank- FLAG 256 80 tank+ FLAG 128 -192 +5V SYMBOL ind2 -128 208 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 4 56 VBottom 0 SYMATTR InstName L1 SYMATTR Value 250=B5 SYMATTR Type ind SYMATTR SpiceLine Rser=3D0.022 Cpar=3D1p SYMBOL ind2 208 208 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 4 56 VBottom 0 SYMATTR InstName L2 SYMATTR Value 250=B5 SYMATTR Type ind SYMATTR SpiceLine Rser=3D0.022 Cpar=3D1p SYMBOL cap 64 64 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 46 32 VTop 0 SYMATTR InstName C1 SYMATTR Value 100n SYMBOL ind2 32 368 R180 WINDOW 0 36 80 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName L5 SYMATTR Value 1m SYMATTR SpiceLine Rser=3D0.044 Cpar=3D1p SYMATTR Type ind SYMBOL voltage -336 144 R0 WINDOW 123 0 0 Left 0 WINDOW 39 24 132 Left 0 SYMATTR SpiceLine Rser=3D0.001 SYMATTR InstName V1 SYMATTR Value 5 SYMBOL ind2 -128 512 R270 WINDOW 0 44 45 VTop 0 WINDOW 3 5 56 VBottom 0 SYMATTR InstName L3 SYMATTR Value 22.5=B5 SYMATTR Type ind SYMATTR SpiceLine Rser=3D0.004 Cpar=3D1p SYMBOL ind2 208 512 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 5 56 VBottom 0 SYMATTR InstName L4 SYMATTR Value 22.5=B5 SYMATTR Type ind SYMATTR SpiceLine Rser=3D0.004 Cpar=3D1p SYMBOL res 160 384 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R3 SYMATTR Value 10k SYMBOL pmos -112 -64 R180 SYMATTR InstName M1 SYMATTR Value BSS84 SYMBOL pmos 288 -64 M180 SYMATTR InstName M2 SYMATTR Value BSS84 SYMBOL res 16 -160 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R1 SYMATTR Value 330 SYMBOL res 256 -160 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R2 SYMATTR Value 330 TEXT -304 584 Left 0 !.tran 0 14m 13.9m 10n TEXT -376 624 Left 0 !.ic V(tank-)=3D0 V(Vct)=3D4.9995 V(tank+)=3D-4.999 V(Vout+)=3D0.00167 V(Vout-)=3D-0.000167 TEXT -376 656 Left 0 !K1 L1 L2 L3 L4 0.99 TEXT -104 656 Left 0 !.save V(Vct) V(Vout+) I(L5) time

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

L2:L3 is a double-winding inductor, or a 1:1 transformer if you will. It doubles the p-p swing into the diode things.

I'm trying to make this from parts we have in stock, and we have a few cute little Coiltronics DRQ-series dual-winding inductors.

It's looking like I may let the dc-dc run open-loop, making about 90 volts or so, and add a linear regulator afterwards. I can use a Supertex depletion fet and an NPN and do a classic toob type regulator with inherent current limiting. Looks like I can even do the DAC with two or three resistors off FPGA pins, for a 100% IC-free design. A few voltage steps on the photodiode HV would be plenty.

John

Reply to
John Larkin

Not since they bought my last employer.

--
You can't have a sense of humor, if you have no sense.
Reply to
Michael A. Terrell

On Sun, 25 Sep 2011 18:36:53 -0700 (PDT), Bill Sloman wrote:

....

I had to delete the Spice directive lines to get that to run.

This is actually pretty nice:

Version 4 SHEET 1 1040 772 WIRE 128 16 -208 16 WIRE 256 16 208 16 WIRE -208 64 -208 16 WIRE 128 128 96 128 WIRE 256 128 256 16 WIRE 256 128 208 128 WIRE 320 128 256 128 WIRE 432 128 400 128 WIRE -208 176 -208 144 WIRE 96 192 96 128 WIRE 224 192 96 192 WIRE 432 192 432 128 WIRE 432 192 288 192 WIRE 512 192 432 192 WIRE 640 192 576 192 WIRE 672 192 640 192 WIRE 784 192 736 192 WIRE 928 192 784 192 WIRE 928 224 928 192 WIRE 640 240 640 192 WIRE 784 240 784 192 WIRE 96 336 96 192 WIRE 640 336 640 304 WIRE 640 336 96 336 WIRE 784 368 784 304 WIRE 928 368 928 304 WIRE 96 416 96 336 WIRE 144 416 96 416 WIRE 256 416 224 416 WIRE 304 416 288 416 WIRE 432 416 432 192 WIRE 432 416 384 416 WIRE 96 464 96 416 WIRE 432 464 432 416 WIRE 288 496 288 416 WIRE 288 496 208 496 WIRE 208 544 208 496 WIRE 208 544 144 544 WIRE 256 544 256 416 WIRE 384 544 256 544 WIRE 96 608 96 560 WIRE 208 608 208 544 WIRE 256 608 256 544 WIRE 432 608 432 560 WIRE 208 752 208 688 WIRE 256 752 256 688 FLAG 96 608 0 FLAG 432 608 0 FLAG -208 176 0 FLAG 208 752 0 FLAG 256 752 0 FLAG 784 368 0 FLAG 928 368 0 SYMBOL ind2 112 144 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 4 56 VBottom 2 SYMATTR InstName L1 SYMATTR Value 33µ SYMBOL ind2 304 144 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 4 56 VBottom 2 SYMATTR InstName L2 SYMATTR Value 33µ SYMBOL ind 112 32 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L3 SYMATTR Value 130µ SYMBOL nmos 384 464 R0 WINDOW 0 133 16 Left 2 WINDOW 3 109 51 Left 2 SYMATTR InstName M1 SYMATTR Value 2N7002 SYMBOL nmos 144 464 M0 WINDOW 0 117 14 Left 2 WINDOW 3 95 50 Left 2 SYMATTR InstName M2 SYMATTR Value 2N7002 SYMBOL cap 288 176 R90 WINDOW 0 72 35 VBottom 2 WINDOW 3 79 32 VTop 2 SYMATTR InstName C1 SYMATTR Value 330n SYMBOL res 240 400 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 3.1K SYMBOL res 400 400 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R2 SYMATTR Value 3K SYMBOL voltage -208 48 R0 WINDOW 0 64 35 Left 2 WINDOW 3 64 71 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 15 SYMBOL res 240 592 R0 WINDOW 0 64 58 Left 2 WINDOW 3 62 95 Left 2 SYMATTR InstName R3 SYMATTR Value 1K SYMBOL res 192 592 R0 WINDOW 0 -65 57 Left 2 WINDOW 3 -69 94 Left 2 SYMATTR InstName R4 SYMATTR Value 1K SYMBOL cap 576 176 R90 WINDOW 0 -50 32 VBottom 2 WINDOW 3 -40 32 VTop 2 SYMATTR InstName C2 SYMATTR Value 330n SYMBOL cap 800 304 R180 WINDOW 0 -49 44 Left 2 WINDOW 3 -45 7 Left 2 SYMATTR InstName C3 SYMATTR Value 1µ SYMBOL diode 656 304 R180 WINDOW 0 72 52 Left 2 WINDOW 3 53 13 Left 2 SYMATTR InstName D1 SYMATTR Value GSD2004W-V SYMBOL diode 672 208 R270 WINDOW 0 84 18 VTop 2 WINDOW 3 70 30 VBottom 2 SYMATTR InstName D2 SYMATTR Value GSD2004W-V SYMBOL res 912 208 R0 WINDOW 0 67 53 Left 2 WINDOW 3 59 88 Left 2 SYMATTR InstName R5 SYMATTR Value 100K TEXT 288 48 Left 2 !K1 L1 L2 1 TEXT -88 200 Left 2 !.tran 5m

It makes 89 volts into 100K and seems pretty well behaved. It does need the biggish L3 inductor, but that's just the same part as the dual-winding L1:L2 thing, and I have room for two.

Gate drive starts at about 3.75 DC, and peaks about +11 when it's running.

The gate divider ratio is a little tricky. You need enough gate voltage to be sure it starts over temperature, but you don't want a huge startup current. This pulls about 1.1 amps peak at startup, probably too much for my application. That could be fixed, for more parts.

John

Reply to
John Larkin

On Sep 26, 5:44=A0am, John Larkin wrote:

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The doubling capacitors directly connected to the ends of the cente- tapped windings made a horrible mess of the waveforms when I tried to simulate your circuit; 1k of current-limiting resistor in series with each of the doubling capacitors (R6 and R7) killed that problem. You may not need as much, and ferrite bead/chips might be enough.

Version 4 SHEET 1 1416 772 WIRE 128 16 -208 16 WIRE 256 16 208 16 WIRE -208 64 -208 16 WIRE 128 128 96 128 WIRE 256 128 256 16 WIRE 256 128 208 128 WIRE 320 128 256 128 WIRE 432 128 400 128 WIRE -208 176 -208 144 WIRE 96 192 96 128 WIRE 224 192 96 192 WIRE 432 192 432 128 WIRE 432 192 288 192 WIRE 512 192 432 192 WIRE 704 192 592 192 WIRE 832 192 768 192 WIRE 864 192 832 192 WIRE 976 192 928 192 WIRE 1104 192 976 192 WIRE 1104 224 1104 192 WIRE 96 240 96 192 WIRE 832 240 832 192 WIRE 976 240 976 192 WIRE 432 272 432 192 WIRE 96 336 96 240 WIRE 512 336 96 336 WIRE 832 336 832 304 WIRE 832 336 592 336 WIRE 976 368 976 304 WIRE 1104 368 1104 304 WIRE 96 416 96 336 WIRE 144 416 96 416 WIRE 256 416 224 416 WIRE 304 416 288 416 WIRE 432 416 432 272 WIRE 432 416 384 416 WIRE 96 464 96 416 WIRE 432 464 432 416 WIRE 288 496 288 416 WIRE 288 496 208 496 WIRE 176 544 144 544 WIRE 208 544 208 496 WIRE 208 544 176 544 WIRE 256 544 256 416 WIRE 336 544 256 544 WIRE 384 544 336 544 WIRE 96 608 96 560 WIRE 208 608 208 544 WIRE 256 608 256 544 WIRE 432 608 432 560 WIRE 208 752 208 688 WIRE 256 752 256 688 FLAG 96 608 0 FLAG 432 608 0 FLAG -208 176 0 FLAG 208 752 0 FLAG 256 752 0 FLAG 976 368 0 FLAG 1104 368 0 FLAG 96 240 n003 FLAG 432 272 n004 FLAG 256 16 n002 FLAG 336 544 n007 FLAG 176 544 n008 SYMBOL ind2 112 144 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 4 56 VBottom 2 SYMATTR InstName L1 SYMATTR Value 33=B5 SYMBOL ind2 304 144 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 4 56 VBottom 2 SYMATTR InstName L2 SYMATTR Value 33=B5 SYMBOL ind 112 32 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L3 SYMATTR Value 130=B5 SYMBOL nmos 384 464 R0 WINDOW 0 133 16 Left 2 WINDOW 3 109 51 Left 2 SYMATTR InstName M1 SYMATTR Value 2N7002 SYMBOL nmos 144 464 M0 WINDOW 0 117 14 Left 2 WINDOW 3 95 50 Left 2 SYMATTR InstName M2 SYMATTR Value 2N7002 SYMBOL cap 288 176 R90 WINDOW 0 72 35 VBottom 2 WINDOW 3 79 32 VTop 2 SYMATTR InstName C1 SYMATTR Value 330n SYMBOL res 240 400 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 3.0K SYMBOL res 400 400 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R2 SYMATTR Value 3K SYMBOL voltage -208 48 R0 WINDOW 0 64 35 Left 2 WINDOW 3 64 71 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 15 SYMBOL res 240 592 R0 WINDOW 0 64 58 Left 2 WINDOW 3 62 95 Left 2 SYMATTR InstName R3 SYMATTR Value 1K SYMBOL res 192 592 R0 WINDOW 0 -65 57 Left 2 WINDOW 3 -69 94 Left 2 SYMATTR InstName R4 SYMATTR Value 1K SYMBOL cap 768 176 R90 WINDOW 0 -50 32 VBottom 2 WINDOW 3 -40 32 VTop 2 SYMATTR InstName C2 SYMATTR Value 330n SYMBOL cap 992 304 R180 WINDOW 0 -49 44 Left 2 WINDOW 3 -45 7 Left 2 SYMATTR InstName C3 SYMATTR Value 1 SYMBOL diode 848 304 R180 WINDOW 0 72 52 Left 2 WINDOW 3 53 13 Left 2 SYMATTR InstName D1 SYMATTR Value GSD2004W-V SYMBOL diode 864 208 R270 WINDOW 0 84 18 VTop 2 WINDOW 3 70 30 VBottom 2 SYMATTR InstName D2 SYMATTR Value GSD2004W-V SYMBOL res 1088 208 R0 WINDOW 0 67 53 Left 2 WINDOW 3 59 88 Left 2 SYMATTR InstName R5 SYMATTR Value 100K SYMBOL res 608 176 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value 1k SYMBOL res 608 320 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R7 SYMATTR Value 1k TEXT 288 48 Left 2 !K1 L1 L2 1 TEXT -88 200 Left 2 !.tran 50m TEXT 648 480 Left 2 !.ic V(n008)=3D5 I(L3)=3D-0.001

The huge start-up current is an artifact of the simulation process. In real life the circuit starts oscillating on thermal noise and is much better behaved.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

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My gut says an r.f.-style impedance-matching network at the output rather than the doubler could give a much larger multiple.

-- Cheers, James Arthur

Reply to
dagmargoodboat

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So patent the idea. It's clearly not been obvious to those skilled in the art for the last fifty-odd years.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

idea

500

ceramics

volt.

No, ferrites won't help. The loading of R6 and R7 are supressing the startup oscillation. See below.

Real life? Have you built it, and instrumented startup?

The mosfet Bax circuit has an inherent problem: both fets are on at turnon, and the oscillations take a while to get going. The high surge current us real, and fudging the Spice initial conditions is cheating.

It is not realistic to have Spice start it up after an initial a DC analysis, with cherry-picked initial conditions. Actually, it's more realistic to ramp up V1, since it will come from some real power supply. With a reasonable, 1 millisec, ramp on V1, this pulls about

0.6 amps at startup, still too much for me. For 10 millisec ramp time, it's down to 250 mA or so. I might be able to arrange that, but it's ugly.

The bipolar Baxandall started up beta limited, which helps a lot. The mosfet one has a tradeoff between surge current and starting reliably over temperature. In the real world, that tradeoff is untenable.

John

Reply to
John Larkin

How could you beat a smallish few VA 60HZ rectifier transformer turned backwards for low noise?

Reply to
Fred Bloggs

One idea is a push-pull driver, like a mosfet driver chip, feeding a series resonant L-C to give a big voltage boost. It could self-oscillate (somehow) to stay on the resonant peak.

I *do* have an FPGA available, so all sorts of clever drive schemes are possible. Turns out, on this project, all the FPGA programming will be paid for by the customer, so I can go wild.

I really should buy an HV power brick from VMI or Pico, and be done, but this is fun. And, long term, I could save $40 a unit maybe, which could matter if we eventually sell numbers of these things.

John

Reply to
John Larkin

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