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Ultra-simple, low-power 3V->1000V converter

H

Haude Daniel

Jan 1, 1970
0
Hello folks,

Frequently I need to make sure that things are well isolated from one another
at voltages of 500V. We have an ultra old, clunky, heavy Rohgde & Schwarz
thing for that purpose in our lab, but unfortunately people tend to run off
with it without leaving note of where it is.

So I thought I'd build my own, small, battery-operated thingy. I'd like it to
run off 2 AA cells. So I need something that makes 500V out of, say, 2-3V.
Output current max. 1 microamp. The output need not be regulated, nor do I
care if it is 490 or 510 V, but I'd like it to have a fairly reproducible max
voltage on the unloaded output. So I'd run the primary side from a regulated
rail.

Of course the output will collapse under load. That's a desired feature. I
just need a qualitative reading.

My ideas so far: battery -> low-power 5V boost regulator (copied from a Maxim
or LT appnote) -> push-pull switcher to some intermediate voltage -> diode/cap
ladder to output terminal. To measure the current I'd hang some TIA with a
mechanical ammeter to the other terminal.

The thing I'm unsure about is the HV generator. Right now I'd tend to do a
1:30 step-up followed by a voltage doubler (5V push-pull makes 10V p-p input
swing, times 30 makes 300 V, * 2 makes 600 modulo losses -> 500). It's be
great if the whole thing wouldn't draw more than 10mA (I can see you
micropower guys spill coffee all over your keyboards here. You'd probably
design it without as much as a power switch).

Thanks,

--Daniel
 
D

daceo

Jan 1, 1970
0
Hello folks,

Frequently I need to make sure that things are well isolated from one another
at voltages of 500V. We have an ultra old, clunky, heavy Rohgde & Schwarz
thing for that purpose in our lab, but unfortunately people tend to run off
with it without leaving note of where it is.

So I thought I'd build my own, small, battery-operated thingy. I'd like it to
run off 2 AA cells. So I need something that makes 500V out of, say, 2-3V.
Output current max. 1 microamp. The output need not be regulated, nor do I
care if it is 490 or 510 V, but I'd like it to have a fairly reproducible max
voltage on the unloaded output. So I'd run the primary side from a regulated
rail.

Of course the output will collapse under load. That's a desired feature. I
just need a qualitative reading.

My ideas so far: battery -> low-power 5V boost regulator (copied from a Maxim
or LT appnote) -> push-pull switcher to some intermediate voltage -> diode/cap
ladder to output terminal. To measure the current I'd hang some TIA with a
mechanical ammeter to the other terminal.

The thing I'm unsure about is the HV generator. Right now I'd tend to do a
1:30 step-up followed by a voltage doubler (5V push-pull makes 10V p-p input
swing, times 30 makes 300 V, * 2 makes 600 modulo losses -> 500). It's be
great if the whole thing wouldn't draw more than 10mA (I can see you
micropower guys spill coffee all over your keyboards here. You'd probably
design it without as much as a power switch).

Thanks,

--Daniel

you may be able to do some thing with an old tv or monitor line output
flyback transformer?

daceo
 
M

Marte Schwarz

Jan 1, 1970
0
Hi Daniel,
So I thought I'd build my own, small, battery-operated thingy. I'd like it
to
run off 2 AA cells. So I need something that makes 500V out of, say, 2-3V.
Output current max. 1 microamp. The output need not be regulated, nor do I
care if it is 490 or 510 V, but I'd like it to have a fairly reproducible
max
voltage on the unloaded output. So I'd run the primary side from a
regulated
rail.

I took for a similar project a simple oneway camera with a flash and use
this one for such purposes. The final voltage in the capacitor is around 350
V but easy tuneable, it works from a simple AA cell with a batteryclip and
includes a simple discharge unit ;-)

Very easy to built, very cheap (go to the next photoshop and ask for thes
empty cameras or buy anew one, you may need a bill ;-)
My ideas so far: battery -> low-power 5V boost regulator (copied from a
Maxim
or LT appnote) -> push-pull switcher to some intermediate voltage ->
diode/cap
ladder to output terminal. To measure the current I'd hang some TIA with a
mechanical ammeter to the other terminal.

Viel zu kompliziert Daniel ;-)

Marte
 
T

Tony Williams

Jan 1, 1970
0
Haude Daniel said:
So I thought I'd build my own, small, battery-operated thingy.
I'd like it to run off 2 AA cells. So I need something that
makes 500V out of, say, 2-3V. Output current max. 1 microamp.
The output need not be regulated, nor do I care if it is 490 or
510 V, but I'd like it to have a fairly reproducible max voltage
on the unloaded output. So I'd run the primary side from a
regulated rail.

Sounds similar to a camera flash circuit. A visit
to <http://www.repairfaq.org> might give some ideas.
 
W

Winfield Hill

Jan 1, 1970
0
Haude said:
So I thought I'd build my own, small, battery-operated thingy.
I'd like it to run off 2 AA cells. So I need something that
makes 500V out of, say, 2-3V. Output current max. 1 microamp.
[ snip ]
The thing I'm unsure about is the HV generator. Right now I'd
tend to do a 1:30 step-up followed by a voltage doubler (5V
push-pull makes 10V p-p input swing, times 30 makes 300 V, * 2
makes 600 modulo losses -> 500).

Your proposed push-pull aspect rules out many simple single-IC
solutions, yet would be required for a 2x output-doubler scheme.
If you give up on both of those, a one-step flyback circuit can
be used. Thirteen years ago I made a little HV supply using an
LTC LT1172 and a small stepup transformer wound on an RM8 core
with an A160 gap. It had to provide about 900mW to the load,
which was a fast high-voltage opamp.* Other slower low-voltage
ICs would be better suited for your lower-power requirement.

BTW, the camera flash-bulb crowd has nice low-power circuits.
There're web sites describing converting a disposable camera's
HV generator for general-purpose use.

* The overall circuit was to synchronize a light-phase shifter
to the middle of the shutter-opening time of a video camera in
a specialized motion-sensing microscope. It showed a blank
field (from phase cancellation), except for any movement that
occurred during the shutter's open time in each video field.
The shutter could be open for 100us (1/10,000 shutter speed),
and we'd catch and highlight any motion during that time. To
change the phase of the light at mid-shutter, I used an LM1881
video sync chip to grab each video line's back-porch pulse,
and used complex cPLD circuit to calculate the right lines to
generate shutter-open and mid-shutter signals. An additional
voltage-programmed delay circuit allowed fine tuning to the
exact shutter midpoint. I programmed the cPLD to work for all
of the Sony camera's shutter times, from 100us to 8 and 16.7ms
(60 per sec). The phase-shift pulse was tuned in amplitude to
drive an optical modulator crystal via the HV opamp. They had
the microscope optics ready before I got the electronics done,
and a cry of "waiting for the RIS-177" became the focus of
several lectures during the Institute's annual review.
 
H

Haude Daniel

Jan 1, 1970
0
Winfield said:
Your proposed push-pull aspect rules out many simple single-IC
solutions, yet would be required for a 2x output-doubler scheme.

Oh I don't care about the circuit topology. This is just the first thing
that crossed my mind.
If you give up on both of those, a one-step flyback circuit can
be used. Thirteen years ago I made a little HV supply using an
LTC LT1172 and a small stepup transformer wound on an RM8 core
with an A160 gap.

Those are good points to start. I've got some RM's kicking around
somewhere. For this application an RM 6 would probably big enough.

Time to start up LTSpice. This ought to be a fun project.

Thanks,

--Daniel
 
H

Haude Daniel

Jan 1, 1970
0
Marte said:
I took for a similar project a simple oneway camera with a flash and use
this one for such purposes. The final voltage in the capacitor is around 350
V but easy tuneable, it works from a simple AA cell with a batteryclip and
includes a simple discharge unit ;-)

I've thought about that, too. I'll have to check no-load power
consumption.

--Daniel
 
J

John Larkin

Jan 1, 1970
0
Hello folks,

Frequently I need to make sure that things are well isolated from one another
at voltages of 500V. We have an ultra old, clunky, heavy Rohgde & Schwarz
thing for that purpose in our lab, but unfortunately people tend to run off
with it without leaving note of where it is.

So I thought I'd build my own, small, battery-operated thingy. I'd like it to
run off 2 AA cells. So I need something that makes 500V out of, say, 2-3V.
Output current max. 1 microamp. The output need not be regulated, nor do I
care if it is 490 or 510 V, but I'd like it to have a fairly reproducible max
voltage on the unloaded output. So I'd run the primary side from a regulated
rail.

Of course the output will collapse under load. That's a desired feature. I
just need a qualitative reading.

My ideas so far: battery -> low-power 5V boost regulator (copied from a Maxim
or LT appnote) -> push-pull switcher to some intermediate voltage -> diode/cap
ladder to output terminal. To measure the current I'd hang some TIA with a
mechanical ammeter to the other terminal.

The thing I'm unsure about is the HV generator. Right now I'd tend to do a
1:30 step-up followed by a voltage doubler (5V push-pull makes 10V p-p input
swing, times 30 makes 300 V, * 2 makes 600 modulo losses -> 500). It's be
great if the whole thing wouldn't draw more than 10mA (I can see you
micropower guys spill coffee all over your keyboards here. You'd probably
design it without as much as a power switch).

Thanks,

--Daniel

Somebody makes a fairly cheap handheld DVM/hipot tester that does all
this already. I think I've seen it in Mouser or Digikey or somewhere
like that. I'll look.

John
 
M

Marte Schwarz

Jan 1, 1970
0
Hi Daniel,
I've thought about that, too. I'll have to check no-load power
consumption.

Do you really think, your homebrew design will top a ready to use design?

Marte
 
C

colin

Jan 1, 1970
0
Haude Daniel said:
Hello folks,

Frequently I need to make sure that things are well isolated from one
another
at voltages of 500V. We have an ultra old, clunky, heavy Rohgde & Schwarz
thing for that purpose in our lab, but unfortunately people tend to run
off
with it without leaving note of where it is.

So I thought I'd build my own, small, battery-operated thingy. I'd like it
to
run off 2 AA cells. So I need something that makes 500V out of, say, 2-3V.
Output current max. 1 microamp. The output need not be regulated, nor do I
care if it is 490 or 510 V, but I'd like it to have a fairly reproducible
max
voltage on the unloaded output. So I'd run the primary side from a
regulated
rail.

Of course the output will collapse under load. That's a desired feature. I
just need a qualitative reading.

My ideas so far: battery -> low-power 5V boost regulator (copied from a
Maxim
or LT appnote) -> push-pull switcher to some intermediate voltage ->
diode/cap
ladder to output terminal. To measure the current I'd hang some TIA with a
mechanical ammeter to the other terminal.

The thing I'm unsure about is the HV generator. Right now I'd tend to do a
1:30 step-up followed by a voltage doubler (5V push-pull makes 10V p-p
input
swing, times 30 makes 300 V, * 2 makes 600 modulo losses -> 500). It's be
great if the whole thing wouldn't draw more than 10mA (I can see you
micropower guys spill coffee all over your keyboards here. You'd probably
design it without as much as a power switch).

Id use a mc33063 in flyback mode, this gives you 40v swing,
a 4:1 transformer will be very easy to make, giving you 200v swing,
too high ratio means problems with leakage inductance and capacitance,
a 5 * multiplier is easy to make with 200v diodes, wich will give you 1000v.
ofc you might want to make it a bit more than 1000v to allow for losses etc.
the chip will regulate it.
ive done similar thing several times and it works quite well, with very
small footprint.

Colin =^.^=
 
H

Homer J Simpson

Jan 1, 1970
0
My ideas so far: battery -> low-power 5V boost regulator (copied from a
Maxim
or LT appnote) -> push-pull switcher to some intermediate voltage ->
diode/cap
ladder to output terminal. To measure the current I'd hang some TIA with a
mechanical ammeter to the other terminal.

You are in Germany? Buy a kit from Kemo like the ion kit which comes with a
nice pi wound transformer.

http://www.kemo-electronic.de/en/bausaetze/b137/index.htm
 
J

James Arthur

Jan 1, 1970
0
Hello folks,

Frequently I need to make sure that things are well isolated from one another
at voltages of 500V. We have an ultra old, clunky, heavy Rohgde & Schwarz
thing for that purpose in our lab, but unfortunately people tend to run off
with it without leaving note of where it is.

So I thought I'd build my own, small, battery-operated thingy. I'd like it to
run off 2 AA cells. So I need something that makes 500V out of, say, 2-3V.
Output current max. 1 microamp. The output need not be regulated, nor do I
care if it is 490 or 510 V, but I'd like it to have a fairly reproducible max
voltage on the unloaded output. So I'd run the primary side from a regulated
rail.

Of course the output will collapse under load. That's a desired feature. I
just need a qualitative reading.

My ideas so far: battery -> low-power 5V boost regulator (copied from a Maxim
or LT appnote) -> push-pull switcher to some intermediate voltage -> diode/cap
ladder to output terminal. To measure the current I'd hang some TIA with a
mechanical ammeter to the other terminal.

The thing I'm unsure about is the HV generator. Right now I'd tend to do a
1:30 step-up followed by a voltage doubler (5V push-pull makes 10V p-p input
swing, times 30 makes 300 V, * 2 makes 600 modulo losses -> 500). It's be
great if the whole thing wouldn't draw more than 10mA (I can see you
micropower guys spill coffee all over your keyboards here. You'd probably
design it without as much as a power switch).

Thanks,

--Daniel

Charles Wenzel has a number of designs close to what you seek,
nicely laid out here:
http://www.techlib.com/electronics/highvolts.html

Best,
James Arthur
 
T

Terry Given

Jan 1, 1970
0
Haude said:
Hello folks,

Frequently I need to make sure that things are well isolated from one another
at voltages of 500V. We have an ultra old, clunky, heavy Rohgde & Schwarz
thing for that purpose in our lab, but unfortunately people tend to run off
with it without leaving note of where it is.

So I thought I'd build my own, small, battery-operated thingy. I'd like it to
run off 2 AA cells. So I need something that makes 500V out of, say, 2-3V.
Output current max. 1 microamp. The output need not be regulated, nor do I
care if it is 490 or 510 V, but I'd like it to have a fairly reproducible max
voltage on the unloaded output. So I'd run the primary side from a regulated
rail.

Of course the output will collapse under load. That's a desired feature. I
just need a qualitative reading.

My ideas so far: battery -> low-power 5V boost regulator (copied from a Maxim
or LT appnote) -> push-pull switcher to some intermediate voltage -> diode/cap
ladder to output terminal. To measure the current I'd hang some TIA with a
mechanical ammeter to the other terminal.

The thing I'm unsure about is the HV generator. Right now I'd tend to do a
1:30 step-up followed by a voltage doubler (5V push-pull makes 10V p-p input
swing, times 30 makes 300 V, * 2 makes 600 modulo losses -> 500). It's be
great if the whole thing wouldn't draw more than 10mA (I can see you
micropower guys spill coffee all over your keyboards here. You'd probably
design it without as much as a power switch).

Thanks,

--Daniel

Go buy one of those $10 bug-zapper tennis-racket style flyswats, and rip
out the electronics. and maybe change the quadrupler to a doubler, or a
singler :)

Cheers
Terry
 
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