cm choke for blocking oscillator

[Michael Robinson]

I want to take 1.5 volts and boost it to 5 volts. Don't need a lot of
power, maybe 100mW.
Common mode chokes are cheap and readily available. Do people ever make
blocking oscillators out of them?
I'm looking at
http://www.murata-ps.com/data/magnetics/kmp_1200lr.pdf?sel=magnetics%2Fkmp_1200lr.pdf

 

[John Fields]

On Sun, 19 Jul 2009 14:04:35 -0400, "Michael Robinson"
<nospam@billburg.com> wrote:

I want to take 1.5 volts and boost it to 5 volts. Don't need a lot of
power, maybe 100mW.
Common mode chokes are cheap and readily available. Do people ever make
blocking oscillators out of them?
I'm looking at
http://www.murata-ps.com/data/magnetics/kmp_1200lr.pdf?sel=magnetics%2Fkmp_1200lr.pdf

---
That's not a common mode choke.

http://www.murata.com/emc/knowhow/pdfs/te04ea-1/26to28e.pdf

JF

 

[ian field]

"Michael Robinson" <nospam@billburg.com> wrote in message
news:GeJ8m.7136$0z7.627@newsfe07.iad...

I want to take 1.5 volts and boost it to 5 volts. Don't need a lot of
power, maybe 100mW.
Common mode chokes are cheap and readily available. Do people ever make
blocking oscillators out of them?

Have done on a number of occasions.

 

[Michael Robinson]

"John Fields" <jfields@austininstruments.com> wrote in message
news:k3p665tobh3i4bvjkebqq0htk3vjjl069h@4ax.com...

On Sun, 19 Jul 2009 14:04:35 -0400, "Michael Robinson"
nospam@billburg.com> wrote:


I want to take 1.5 volts and boost it to 5 volts. Don't need a lot of
power, maybe 100mW.
Common mode chokes are cheap and readily available. Do people ever make
blocking oscillators out of them?
I'm looking at
http://www.murata-ps.com/data/magnetics/kmp_1200lr.pdf?sel=magnetics%2Fkmp_1200lr.pdf

---
That's not a common mode choke.

http://www.murata.com/emc/knowhow/pdfs/te04ea-1/26to28e.pdf

JF
I was a little hasty with digikey's parametric search.

Anyway, would use a common mode choke or possibly
a pulse transformer. Something like
http://www.murata-ps.com/data/magnetics/kmp_5000c.pdf
Make a joule thief-type circuit -- just one transistor,
a coil with a feedback winding to the transistor base
and a diode to pick off the pulses at the collector.
Made one once the hobbyist way, winding it myself.
Looking for something off the shelf.

 

[Michael Robinson]

"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:czL8m.19126$7I6.3416@newsfe17.ams2...

"Michael Robinson" <nospam@billburg.com> wrote in message
news:GeJ8m.7136$0z7.627@newsfe07.iad...

I want to take 1.5 volts and boost it to 5 volts. Don't need a lot of
power, maybe 100mW.
Common mode chokes are cheap and readily available. Do people ever make
blocking oscillators out of them?

Have done on a number of occasions.

Got any part numbers or links to chokes that might be appropriate for

my power level?

 

[ian field]

"Michael Robinson" <nospam@billburg.com> wrote in message
news:dPO8m.15022$3m2.5819@newsfe06.iad...

"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:czL8m.19126$7I6.3416@newsfe17.ams2...

"Michael Robinson" <nospam@billburg.com> wrote in message
news:GeJ8m.7136$0z7.627@newsfe07.iad...

I want to take 1.5 volts and boost it to 5 volts. Don't need a lot of
power, maybe 100mW.
Common mode chokes are cheap and readily available. Do people ever make
blocking oscillators out of them?

Have done on a number of occasions.

Got any part numbers or links to chokes that might be appropriate for
my power level?

Just a random common mode choke I harvested from a scrap monitor - the
blocking oscillator is probably one of the simplest circuits you will ever
build, almost any CM choke will work (even if only, after a fashion) small
ones work best, aim for between 15 - 30 turns for each winding, so you might
improve results by unwinding a few turns, I've always favoured the small
toroid types.

Also aim for higher output voltage than you want and use a second transistor
to shunt the B/E of the oscillator, the base of the shunt transistor is fed
from the rectified O/P via a zener and small limiting resistor in series.

 

[Michael Robinson]

"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:A7%8m.58554$tU4.834@newsfe19.ams2...

"Michael Robinson" <nospam@billburg.com> wrote in message
news:dPO8m.15022$3m2.5819@newsfe06.iad...

"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:czL8m.19126$7I6.3416@newsfe17.ams2...

"Michael Robinson" <nospam@billburg.com> wrote in message
news:GeJ8m.7136$0z7.627@newsfe07.iad...

I want to take 1.5 volts and boost it to 5 volts. Don't need a lot of
power, maybe 100mW.
Common mode chokes are cheap and readily available. Do people ever
make blocking oscillators out of them?

Have done on a number of occasions.

Got any part numbers or links to chokes that might be appropriate for
my power level?

Just a random common mode choke I harvested from a scrap monitor - the
blocking oscillator is probably one of the simplest circuits you will ever
build, almost any CM choke will work (even if only, after a fashion) small
ones work best, aim for between 15 - 30 turns for each winding, so you
might improve results by unwinding a few turns, I've always favoured the
small toroid types.

Also aim for higher output voltage than you want and use a second
transistor to shunt the B/E of the oscillator, the base of the shunt
transistor is fed from the rectified O/P via a zener and small limiting
resistor in series.

Yes, I built a blocking oscillator a while back and closed the loop the same

way.
Output voltage was swinging all over the place but a 0.1 uF cap across the
base/collector junction of the second transistor stabilized everythng and
then the circuit worked very well.
I used it to double 12 volts to 24. Let the circuit run and it crapped
after a day or so. Maybe the feedback winding had too many turns and
resulted in excessive reverse voltage at the base of the blocking oscillator
transistor. I might clamp the blocking transistor's b/e junction with a
reverse parallel diode next time.

 

[Michael Robinson]

"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:A7%8m.58554$tU4.834@newsfe19.ams2...

"Michael Robinson" <nospam@billburg.com> wrote in message
news:dPO8m.15022$3m2.5819@newsfe06.iad...

"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:czL8m.19126$7I6.3416@newsfe17.ams2...

"Michael Robinson" <nospam@billburg.com> wrote in message
news:GeJ8m.7136$0z7.627@newsfe07.iad...

I want to take 1.5 volts and boost it to 5 volts. Don't need a lot of
power, maybe 100mW.
Common mode chokes are cheap and readily available. Do people ever
make blocking oscillators out of them?

Have done on a number of occasions.

Got any part numbers or links to chokes that might be appropriate for
my power level?

Just a random common mode choke I harvested from a scrap monitor - the
blocking oscillator is probably one of the simplest circuits you will ever
build, almost any CM choke will work (even if only, after a fashion) small
ones work best, aim for between 15 - 30 turns for each winding, so you
might improve results by unwinding a few turns, I've always favoured the
small toroid types.

Also aim for higher output voltage than you want and use a second
transistor to shunt the B/E of the oscillator, the base of the shunt
transistor is fed from the rectified O/P via a zener and small limiting
resistor in series.

Yes, I built a blocking oscillator a while back and closed the loop the same

way.
Output voltage was swinging all over the place but a 0.1 uF cap across the
base/collector junction of the second transistor stabilized everythng and
then the circuit worked very well.
I used it to double 12 volts to 24. Let the circuit run and it crapped
after a day or so. Maybe the feedback winding had too many turns and
resulted in excessive reverse voltage at the base of the blocking oscillator
transistor. I might clamp the blocking transistor's b/e junction with a
reverse parallel diode next time.