HV Bias Supply Challenge
 

OK, here's a challenge to you guys ... I have been trying to ID a IC /
inductor combination to generate 150 to 200 VDC ... in the nano-microamp
range. I need to supply a bias voltage to an electrostatic microphone
element.

Any ideas ??

Wish list:

Very low current ... 2ma ;-)
Runs from 5 to 9 volt DC source
Minimal components

Most of the specs I find for HV units ( backlight supplies ) are too much
current. Most of the inductor type DC-DC converters seem geared towards low
voltage high current apps.

Will watch the discussion for tips and ideas ... all welcome.

Thanks

Tony, KD7TOG

( KD7TOG at earthlink dot net )

KD7TOG wrote:

OK, here's a challenge to you guys ... I have been trying to ID a IC /
inductor combination to generate 150 to 200 VDC ... in the nano-microamp
range. I need to supply a bias voltage to an electrostatic microphone
element.

Any ideas ??

Wish list:

Very low current ... 2ma ;-)
Runs from 5 to 9 volt DC source
Minimal components

Most of the specs I find for HV units ( backlight supplies ) are too much
current. Most of the inductor type DC-DC converters seem geared towards low
voltage high current apps.

Will watch the discussion for tips and ideas ... all welcome.
Nothing is likely to be very efficient at this low power level. I
think I would look into a step up transformer design, perhaps using
something like a MT4143:
http://www.tamuracorp.com/pdf/MET-01.pdf
driven by a two transistor half bridge at ultrasonic frequency. With
a 14 to 1 step up, it could produce 200 volts peak across the whole
secondary, with only 7 volts peak across half its primary. If the
secondary was connected to a voltage doubler, you could drive it with
half that. The transformer is rated for 10 mw, but at 20 kHz, I think
it could do a bit more than that or run fairly efficiently at much
less.

--
John Popelish

KD7TOG wrote:

OK, here's a challenge to you guys ... I have been trying to ID a IC /
inductor combination to generate 150 to 200 VDC ... in the nano-microamp
range. I need to supply a bias voltage to an electrostatic microphone
element.

Any ideas ??

Wish list:

Very low current ... 2ma ;-)
Runs from 5 to 9 volt DC source
Minimal components

Most of the specs I find for HV units ( backlight supplies ) are too much
current. Most of the inductor type DC-DC converters seem geared towards low
voltage high current apps.

Will watch the discussion for tips and ideas ... all welcome.
Nothing is likely to be very efficient at this low power level. I
think I would look into a step up transformer design, perhaps using
something like a MT4143:
http://www.tamuracorp.com/pdf/MET-01.pdf
driven by a two transistor half bridge at ultrasonic frequency. With
a 14 to 1 step up, it could produce 200 volts peak across the whole
secondary, with only 7 volts peak across half its primary. If the
secondary was connected to a voltage doubler, you could drive it with
half that. The transformer is rated for 10 mw, but at 20 kHz, I think
it could do a bit more than that or run fairly efficiently at much
less.

--
John Popelish

Tony,

To make it easy snag one of the surplus electronic flash units or
dismantle a disposable camera. Some of them are quite small.
An RC filter will clean up the DC and a simple resistor voltage
divider to cut the voltage to what you want. Regulation shouldn't be
a problem with a steady and low current draw.

To get the input current down it may help to swap the photoiflash
capacitor for something with very low leakage.

73,
Jim

On Wed, 10 Dec 2003 00:28:50 GMT, "KD7TOG"
wrote:

OK, here's a challenge to you guys ... I have been trying to ID a IC /
inductor combination to generate 150 to 200 VDC ... in the nano-microamp
range. I need to supply a bias voltage to an electrostatic microphone
element.

Any ideas ??

Wish list:

Very low current ... 2ma ;-)
Runs from 5 to 9 volt DC source
Minimal components

Most of the specs I find for HV units ( backlight supplies ) are too much
current. Most of the inductor type DC-DC converters seem geared towards low
voltage high current apps.

Will watch the discussion for tips and ideas ... all welcome.

Thanks

Tony, KD7TOG

( KD7TOG at earthlink dot net )

Tony,

To make it easy snag one of the surplus electronic flash units or
dismantle a disposable camera. Some of them are quite small.
An RC filter will clean up the DC and a simple resistor voltage
divider to cut the voltage to what you want. Regulation shouldn't be
a problem with a steady and low current draw.

To get the input current down it may help to swap the photoiflash
capacitor for something with very low leakage.

73,
Jim

On Wed, 10 Dec 2003 00:28:50 GMT, "KD7TOG"
wrote:

OK, here's a challenge to you guys ... I have been trying to ID a IC /
inductor combination to generate 150 to 200 VDC ... in the nano-microamp
range. I need to supply a bias voltage to an electrostatic microphone
element.

Any ideas ??

Wish list:

Very low current ... 2ma ;-)
Runs from 5 to 9 volt DC source
Minimal components

Most of the specs I find for HV units ( backlight supplies ) are too much
current. Most of the inductor type DC-DC converters seem geared towards low
voltage high current apps.

Will watch the discussion for tips and ideas ... all welcome.

Thanks

Tony, KD7TOG

( KD7TOG at earthlink dot net )

In article . net, "KD7TOG"
writes:

OK, here's a challenge to you guys ... I have been trying to ID a IC /
inductor combination to generate 150 to 200 VDC ... in the nano-microamp
range. I need to supply a bias voltage to an electrostatic microphone
element.

Any ideas ??

Wish list:

Very low current ... 2ma ;-)
Runs from 5 to 9 volt DC source
Minimal components

Most of the specs I find for HV units ( backlight supplies ) are too much
current. Most of the inductor type DC-DC converters seem geared towards low
voltage high current apps.

Will watch the discussion for tips and ideas ... all welcome.

A simple low-RF oscillator can do it with a small transformer having
an enormous turns ratio. I'd suggest a toroidal type with a ferrite
core rather than powdered-iron core to work around 50 to 100 KHz.
Something like a 1:30 turns ratio seems about right with the
secondary tuned, the primary driven by a single transistor emitter,
feedback to the base which will also load down the tuned secondary
some. Maybe a Darlington connection using two bipolars if too
much resistive loading.

Since a 2.5 mHy 4-pie RFC and 1000 pFd tune very close to 100 KHz,
you might use that as the "secondary." The "primary" could have
several turns wound in between the pie sections. Bulkier than a
toroid but a lot easier to handle on the first go-around for feasibility
checking. With 3900 pFd, the 2.5 mHy RFC will tune about 51 KHz.

Staying in the LF region allows most ordinary newer silicon diodes
to directly rectify the LF yet the harmonics don't interfere much with
AM radios nearby. It's well above the top frequency for human
hearing so a simple C-R-C filter ought to make the DC fairly clean
for the microphone without too much C value and bulk.

Len Anderson
retired (from regular hours) electronic engineer person

In article . net, "KD7TOG"
writes:

OK, here's a challenge to you guys ... I have been trying to ID a IC /
inductor combination to generate 150 to 200 VDC ... in the nano-microamp
range. I need to supply a bias voltage to an electrostatic microphone
element.

Any ideas ??

Wish list:

Very low current ... 2ma ;-)
Runs from 5 to 9 volt DC source
Minimal components

Most of the specs I find for HV units ( backlight supplies ) are too much
current. Most of the inductor type DC-DC converters seem geared towards low
voltage high current apps.

Will watch the discussion for tips and ideas ... all welcome.

A simple low-RF oscillator can do it with a small transformer having
an enormous turns ratio. I'd suggest a toroidal type with a ferrite
core rather than powdered-iron core to work around 50 to 100 KHz.
Something like a 1:30 turns ratio seems about right with the
secondary tuned, the primary driven by a single transistor emitter,
feedback to the base which will also load down the tuned secondary
some. Maybe a Darlington connection using two bipolars if too
much resistive loading.

Since a 2.5 mHy 4-pie RFC and 1000 pFd tune very close to 100 KHz,
you might use that as the "secondary." The "primary" could have
several turns wound in between the pie sections. Bulkier than a
toroid but a lot easier to handle on the first go-around for feasibility
checking. With 3900 pFd, the 2.5 mHy RFC will tune about 51 KHz.

Staying in the LF region allows most ordinary newer silicon diodes
to directly rectify the LF yet the harmonics don't interfere much with
AM radios nearby. It's well above the top frequency for human
hearing so a simple C-R-C filter ought to make the DC fairly clean
for the microphone without too much C value and bulk.

Len Anderson
retired (from regular hours) electronic engineer person

The guy with the flash camera idea is on track. Audio Express Magazine had
a writeup on them a few months ago, as did Nuts and Volts some years back.
I reverse engr'd a Fuji camera and it's just like the AE Mag circuit.

Circa 1976, I made a simple two transistor oscillator, which ran off a 1.5
volt battery that connected across a reversed filament transformer, lite a
neon bulb for weeks. I'm sure it would really honk with 9 volts DC chop
input.

cheers
skipp

http://sonic.ucdavis.edu

: KD7TOG wrote:
: OK, here's a challenge to you guys ... I have been trying to ID a IC /
: inductor combination to generate 150 to 200 VDC ... in the nano-microamp
: range. I need to supply a bias voltage to an electrostatic microphone
: element.

: Any ideas ??

: Wish list:

: Very low current ... 2ma ;-)
: Runs from 5 to 9 volt DC source
: Minimal components

: Most of the specs I find for HV units ( backlight supplies ) are too much
: current. Most of the inductor type DC-DC converters seem geared towards low
: voltage high current apps.

: Will watch the discussion for tips and ideas ... all welcome.

: Thanks

: Tony, KD7TOG

: ( KD7TOG at earthlink dot net )

The guy with the flash camera idea is on track. Audio Express Magazine had
a writeup on them a few months ago, as did Nuts and Volts some years back.
I reverse engr'd a Fuji camera and it's just like the AE Mag circuit.

Circa 1976, I made a simple two transistor oscillator, which ran off a 1.5
volt battery that connected across a reversed filament transformer, lite a
neon bulb for weeks. I'm sure it would really honk with 9 volts DC chop
input.

cheers
skipp

http://sonic.ucdavis.edu

: KD7TOG wrote:
: OK, here's a challenge to you guys ... I have been trying to ID a IC /
: inductor combination to generate 150 to 200 VDC ... in the nano-microamp
: range. I need to supply a bias voltage to an electrostatic microphone
: element.

: Any ideas ??

: Wish list:

: Very low current ... 2ma ;-)
: Runs from 5 to 9 volt DC source
: Minimal components

: Most of the specs I find for HV units ( backlight supplies ) are too much
: current. Most of the inductor type DC-DC converters seem geared towards low
: voltage high current apps.

: Will watch the discussion for tips and ideas ... all welcome.

: Thanks

: Tony, KD7TOG

: ( KD7TOG at earthlink dot net )

Thanks all for the ideas ... I have a couple of potential solutions.

Tony, KD7TOG