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Need Voltage Doubler Circuit

D

Dave.H

Jan 1, 1970
0
I have a regen radio powered by two 23 volt wallwarts in series, but
would like to use a 24 VAC transformer with a voltage doubler to
provide the 45v B+, I've found circuits via Google, but they don't
give the values for 24 VAC. Also don't say what diode to use. I have
about 50 1N4004's lying around I could use. Transformer I'm planning
on using is M6672 @ www.dse.com.au

Thanks
Dave
 
M

Mike Silva

Jan 1, 1970
0
I have a regen radio powered by two 23 volt wallwarts in series, but
would like to use a 24 VAC transformer with a voltage doubler to
provide the 45v B+, I've found circuits via Google, but they don't
give the values for 24 VAC. Also don't say what diode to use.  I have
about 50 1N4004's lying around I could use. Transformer I'm planning
on using is M6672 @www.dse.com.au

Here is a standard voltage doubler circuit:
http://hyperphysics.phy-astr.gsu.edu/Hbase/electronic/voldoub.html

The 1N4004s will be fine. Use filter caps rated for 50V or more,
50-100uF, and consider adding a second stage of RC filtering by adding
a resistor (dropping, say, 10% of your voltage at your current draw)
followed by another filter cap (50-100uF again). For best results you
should also regulate the voltage going into the detector stage - a
simple resistor and zener will do. Many people also find that adding
bypass caps (0.01 to 0.001) across the diodes helps eliminate power-
supply radiated hum.

Mike
 
D

Dave.H

Jan 1, 1970
0
The diodes should work fine as long as the DC current load
is less than about a half amp. A simple doubles connects
two capacitors (negative side of one and positive side of
the other) to one side of the 24 supply and two diodes
(cathode or banded end of one and anode of the other) to the
other side of the 24 volt supply. Then connect the free
anode to the free negative capacitor end and the free
cathode to the free positive capacitor end. The output is
taken across those last two connections, so that the two
capacitors are acting as a pair of stacked half wave
supplies. Under no load, this will produce at least
24*sqrt(2) *2 minus two diode drops or about 66 volts. Keep
in mind that the 24 volts AC output may rise quite a bit
under no load, since it is rated for full load.

Any load will sag some the voltage, and add twice line
frequency ripple to the output. You may want to add an RC
low pass filter stage with the series R selected to lower
the voltage to closer to your desired 45 volts, and the
capacitor from that output to the other side of the supply
as an additional ripple filter. Or you may just lower the
voltage under load by adding some resistance in series with
the 24 volt AC output. This will not reduce the ripple as
much, but will make the 24 volt transformer run a little
cooler. I just looked up the transformer and it has several
taps, so you can try different combinations to get very
close to the desired output voltage.

For the two doubler capacitors, I would use something like
5,000 to 10,000 microfarads per amp of output load and rated
for at least 16 volts DC. Your diodes and transformer will
allow about 300 to 400 mA load current. If your load
current is at or below 400 mA, that implies something around
2,200 to 4,700 uF 16 or 25 volt capacitors for the doubler.

Of course, if you use the full 30 volt winding, you can get
pretty close to 45 volts output with a bridge rectifier made
with 4 of your diodes and a single capacitor, say, 2,200 to
4,700 uF, rated for 50 volts. This will give you a voltage
around 40 to 45 volts, depending on load current that can be
up to about 0.7 amps.

I might go with that bridge rectifier option. Sounds simpler, and I
believe I have a 2,200 MFD, 50 volt cap lying around.
 
D

Dave.H

Jan 1, 1970
0
I might go with that bridge rectifier option. Sounds simpler, and I
believe I have a 2,200 MFD, 50 volt cap lying around.

I found a 30 volt, 500 mA transformer I'll use with the bridge
rectifier, Smaller and cheaper than the one amp unit. I think the
current draw of the radio is only about 8-10 mA. Transformer is M2860
@ www.dse.com.au.
 
M

Mike Silva

Jan 1, 1970
0
I found a 30 volt, 500 mA transformer I'll use with the bridge
rectifier, Smaller and cheaper than the one amp unit.  I think the
current draw of the radio is only about 8-10 mA.  Transformer is M2860
@www.dse.com.au.- Hide quoted text -

- Show quoted text -

Another option is to use the 30V transformer in the voltage doubler
circuit. Take your 40-45V off the lower filter cap (and add
regulation for the detector), and take 80V off the upper cap for the
power output stage that you talked about.

Mike
 
D

Dave.H

Jan 1, 1970
0
Another option is to use the 30V transformer in the voltage doubler
circuit. Take your 40-45V off the lower filter cap (and add
regulation for the detector), and take 80V off the upper cap for the
power output stage that you talked about.

Mike

Is this how I would hook it up?
http://s222.photobucket.com/albums/dd237/ozguy89/?action=view&current=FullWavePowerSupply.gif
Sorry for the large image file, this image was emailed to me to help
in building a power supply for a battery transistor radio.
 
D

Dave.H

Jan 1, 1970
0
Another option is to use the 30V transformer in the voltage doubler
circuit. Take your 40-45V off the lower filter cap (and add
regulation for the detector), and take 80V off the upper cap for the
power output stage that you talked about.

Mike

What value resistor would I need to run a 2 volt LED off the 30 volts?
 
D

Dave.H

Jan 1, 1970
0
What value resistor would I need to run a 2 volt LED off the 30 volts?

Would it be possible to run the tube filament (2 volts, 60 mA) off a
6.3 volt, 500 mA transformer, using something like resistors? I would
like to eliminate using "D" cells.
Thanks,
Dave
 
P

Paul E. Schoen

Jan 1, 1970
0
John Popelish said:
For the two doubler capacitors, I would use something like 5,000 to
10,000 microfarads per amp of output load and rated for at least 16 volts
DC. Your diodes and transformer will allow about 300 to 400 mA load
current. If your load current is at or below 400 mA, that implies
something around 2,200 to 4,700 uF 16 or 25 volt capacitors for the
doubler.

Of course, if you use the full 30 volt winding, you can get pretty close
to 45 volts output with a bridge rectifier made with 4 of your diodes and
a single capacitor, say, 2,200 to 4,700 uF, rated for 50 volts. This
will give you a voltage around 40 to 45 volts, depending on load current
that can be up to about 0.7 amps.

You need to use capacitors rated at least as high as the maximum peak to
peak unloaded output voltage of the transformer, so for 24 VAC that would
be about 75 volts. Here is an LTspice ASCII showing a 24 VAC source boosted
to 68 VDC with two diodes and two capacitors. The first capacitor can be
rated at half the voltage of the second one. This circuit has poor
regulation, but is inherently current limiting, so you can just add a zener
(as shown) to the output for regulation. You need to adjust the value of C1
for the wattage of the zeners and load current. This is set for 45 VDC and
about 50 mA max.

Paul

=================================================================

Version 4
SHEET 1 880 680
WIRE 64 144 -48 144
WIRE 240 144 128 144
WIRE 288 144 240 144
WIRE 416 144 352 144
WIRE 512 144 416 144
WIRE 528 144 512 144
WIRE 640 144 528 144
WIRE 240 192 240 144
WIRE 416 192 416 144
WIRE -48 224 -48 144
WIRE 528 224 528 144
WIRE 640 224 640 208
WIRE 640 304 640 288
WIRE -48 384 -48 304
WIRE 240 384 240 256
WIRE 240 384 -48 384
WIRE 416 384 416 256
WIRE 416 384 240 384
WIRE 528 384 528 304
WIRE 528 384 416 384
WIRE 640 384 640 368
WIRE 640 384 528 384
WIRE 640 432 640 384
FLAG 640 432 0
FLAG 512 144 V+
SYMBOL diode 288 160 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D2
SYMATTR Value MUR460
SYMBOL polcap 400 192 R0
SYMATTR InstName C2
SYMATTR Value 1000µ
SYMATTR Description Capacitor
SYMATTR Type cap
SYMATTR SpiceLine V=63 Irms=2.51 Rser=0.025 MTBF=5000 Lser=0 ppPkg=1
SYMBOL voltage -48 208 R0
WINDOW 3 -14 227 Left 0
WINDOW 123 0 0 Left 0
WINDOW 39 24 44 Left 0
SYMATTR Value SINE(0 35 60 0 0 0 120)
SYMATTR SpiceLine Rser=.1
SYMATTR InstName V1
SYMBOL res 512 208 R0
SYMATTR InstName R1
SYMATTR Value 2000
SYMBOL polcap 128 128 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C1
SYMATTR Value 47µ
SYMATTR Description Capacitor
SYMATTR Type cap
SYMATTR SpiceLine V=63 Irms=2.51 Rser=0.025 MTBF=5000 Lser=0 ppPkg=1
SYMBOL diode 224 256 M180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D1
SYMATTR Value MUR460
SYMBOL zener 656 288 R180
WINDOW 0 40 32 Left 0
WINDOW 3 -137 34 Left 0
SYMATTR InstName D4
SYMATTR Value BZX84C15L
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL zener 656 208 R180
WINDOW 0 41 31 Left 0
WINDOW 3 -138 34 Left 0
SYMATTR InstName D3
SYMATTR Value BZX84C15L
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL zener 656 368 R180
WINDOW 0 41 47 Left 0
WINDOW 3 -144 33 Left 0
SYMATTR InstName D5
SYMATTR Value BZX84C15L
SYMATTR Description Diode
SYMATTR Type diode
TEXT 184 528 Left 0 !.tran 2
 
M

Mike Silva

Jan 1, 1970
0
Is this how I would hook it up?http://s222.photobucket.com/albums/dd237/ozguy89/?action=view¤t...
Sorry for the large image file, this image was emailed to me to help
in building a power supply for a battery transistor radio.- Hide quoted text -

- Show quoted text -

Not for my suggestion. I'm suggesting, if you also want a higher
voltage for a power output stage, that you use a voltage doubler like
so:http://www.amazon.com/Losing-Faith-Preacher-Atheist/dp/187773313X

The bottom of the two capacitors is your 0V or ground reference. The
top of the two capacitors will give you 80-90V with a 30V
transformer. The junction of the two capacitors will be at half that
voltage or 40-45V. Thus you have low voltage (suggest additional
filtering or regulation) for your detector and audio voltage
amplifier, and higher voltage for your power stage. Each capacitor
needs to be rated 50V or higher, since each one receives the full
secondary peak voltage.

Also, you asked about AC on the filaments. That's likely to lead to
hum. A good idea would be to turn the 6.3VAC into well-filtered DC
and drop that to 1.4V with a resistor. The resistor will help protect
your filaments from turn-on surge, which is why it's a better approach
than building a 1.4V regulated source.

Mike
 
P

Phil Allison

Jan 1, 1970
0
"Tim Wescott"
Voltage doublers give poor regulation,


** The standard voltage doubler has exactly the *same* ( load ) percentage
regulation as the same transformer would provide with a bridge rectifier and
capacitor filter.

http://hyperphysics.phy-astr.gsu.edu/Hbase/electronic/voldoub.html
and regenerative sets want a good, steady input voltage.


** Only way to get that is with a regulated supply.

You'll get better performance off of you pair of
wall warts, no matter how ugly things look.

** Not true.

Line voltage and load variations will affect them just like any unregulated
supply.

The actual percentage load regulation depends on the size of the transformer
and how much load is applied - ie light loads = good regulation.



...... Phil
 
D

Dave.H

Jan 1, 1970
0
"Tim Wescott"




** The standard voltage doubler has exactly the *same* ( load ) percentage
regulation as the same transformer would provide with a bridge rectifier and
capacitor filter.

http://hyperphysics.phy-astr.gsu.edu/Hbase/electronic/voldoub.html


** Only way to get that is with a regulated supply.


** Not true.

Line voltage and load variations will affect them just like any unregulated
supply.

The actual percentage load regulation depends on the size of the transformer
and how much load is applied - ie light loads = good regulation.

..... Phil

Actually the wallwarts are regulated, I think they're M9926 @ www.dse.com.au
 
D

Dave.H

Jan 1, 1970
0
Not for my suggestion. I'm suggesting, if you also want a higher
voltage for a power output stage, that you use a voltage doubler like
so:http://www.amazon.com/Losing-Faith-Preacher-Atheist/dp/187773313X

The bottom of the two capacitors is your 0V or ground reference. The
top of the two capacitors will give you 80-90V with a 30V
transformer. The junction of the two capacitors will be at half that
voltage or 40-45V. Thus you have low voltage (suggest additional
filtering or regulation) for your detector and audio voltage
amplifier, and higher voltage for your power stage. Each capacitor
needs to be rated 50V or higher, since each one receives the full
secondary peak voltage.

Also, you asked about AC on the filaments. That's likely to lead to
hum. A good idea would be to turn the 6.3VAC into well-filtered DC
and drop that to 1.4V with a resistor. The resistor will help protect
your filaments from turn-on surge, which is why it's a better approach
than building a 1.4V regulated source.

Mike

I see that I replied to your post by mistake. I meant to reply to
John Popelish 's message about using a bridge rectifier and cap to
boost the 30 Volts AC to 45 volts DC. Seems much more simpler to me.

Dave
 
M

Mike Silva

Jan 1, 1970
0
** The standard voltage doubler has exactly the *same* ( load ) percentage
regulation as the same transformer would provide with a bridge rectifier and
capacitor filter.

http://hyperphysics.phy-astr.gsu.edu/Hbase/electronic/voldoub.html

Are we sure about that? Only one-half of the capacitor stack is
charged each half cycle, but both capacitors are discharging each half
cycle.

Which brings up a circuit I ran across years ago and was able to find
again yesterday. This one claims to charge both capacitors each half
cycle, making it a true full-wave circuit. I haven't tried it or
analysed it - I just put it out for consideration.
http://www.kwarc.org/bulletin/99-04/tech_corner.htm

Mike
 
P

Phil Allison

Jan 1, 1970
0
"Mike Silva
"Phil Allison"

** The standard voltage doubler has exactly the *same* ( load ) percentage
regulation as the same transformer would provide with a bridge rectifier
and
capacitor filter.

http://hyperphysics.phy-astr.gsu.edu/Hbase/electronic/voldoub.html

Are we sure about that?


** Yes - so **** off.


Only one-half of the capacitor stack is
charged each half cycle, but both capacitors are discharging each half
cycle.


** So what - shithead ???

Ripple voltage depends on cap value, so can be made as small as you like.



Which brings up a circuit I ran across years ago and was able to find
again yesterday. This one claims to charge both capacitors each half
cycle, making it a true full-wave circuit. I haven't tried it or
analysed it - I just put it out for consideration.
http://www.kwarc.org/bulletin/99-04/tech_corner.htm


** The claims made are complete BOLLOCKS.

A "standard voltage doubler" generates 120 Hz ( or 100Hz ) ripple and
utilises the transformer just as fully as a bridge rectifier.

The page was written by a ham -

so you KNOW it is TOTAL SHIT !!!




........ Phil
 
M

Mike Silva

Jan 1, 1970
0
I knew you'd have one of your outbursts on this, but I thought the
question interesting enough to endure it. I hope others will weigh
in.
 
P

Phil Allison

Jan 1, 1970
0
"Mike Silva the fucking **** Head "



** Why don't you go eat a box of rat poison ???

Do the planet a favour by bleeding to death.




.... Phil
 
D

Dave.H

Jan 1, 1970
0
Sounds like a plan. The light load voltage may be something
like 33 volts, so the peak would be 33*sqrt(2)=47, but the
bridge will waste about 2 volts. so that might do very
nicely. At that low current, the 2,200 uF capacitor will
produce a low ripple output. If the voltage comes out a
little high, add a resistor in series with the either the 30
volt secondary, or in series with the primary.

Should I regulate the output? How about a voltage regulator IC like
the LM317?
 
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