Is this voltage doubler different?
 

Regarding the circuit he
http://www.kwarc.org/bulletin/99-04/tech_corner.htm

Does this voltage doubler work any "better" (better regulation, better
transformer utilization, etc) than the classic 2-diode, 2-capacitor
doubler (as seen in e.g. the HP-23 supplies)? I know it uses more
parts; what I'm wondering is whether the extra parts actually provide
any benefits, and if so, under what circumstances.

Does anybody have any actual experience with this circuit?
73,
Mike, KK6GM

Mike Silva wrote:
Regarding the circuit he
http://www.kwarc.org/bulletin/99-04/tech_corner.htm

Does this voltage doubler work any "better" (better regulation, better
transformer utilization, etc) than the classic 2-diode, 2-capacitor
doubler (as seen in e.g. the HP-23 supplies)? I know it uses more
parts; what I'm wondering is whether the extra parts actually provide
any benefits, and if so, under what circumstances.

Does anybody have any actual experience with this circuit?
73,
Mike, KK6GM

If, as the author claims, it yeilds 120hz ripple, it will need
smaller filter caps than a regular doubler and provide less ripple
(lower hum). Diodes are cheap, caps are not (at least not HV high
capacitance ones!) though.

Hmmm, never seen that configuration before. I'll have to try it.

--
Gregg "t3h g33k"
http://geek.scorpiorising.ca
*Ratings are for transistors, tubes have guidelines*

I don't see any difference from a regular voltage doubler with an
added filter cap at the output. C1 and C2 are still charged with 1/2
wave power.

73
Gary K4FMX


On 31 Jan 2005 12:53:51 -0800, "Mike Silva"
wrote:

Regarding the circuit he
http://www.kwarc.org/bulletin/99-04/tech_corner.htm

Does this voltage doubler work any "better" (better regulation, better
transformer utilization, etc) than the classic 2-diode, 2-capacitor
doubler (as seen in e.g. the HP-23 supplies)? I know it uses more
parts; what I'm wondering is whether the extra parts actually provide
any benefits, and if so, under what circumstances.

Does anybody have any actual experience with this circuit?
73,
Mike, KK6GM

Mike Silva wrote:

Regarding the circuit he
http://www.kwarc.org/bulletin/99-04/tech_corner.htm

Does this voltage doubler work any "better" (better regulation, better
transformer utilization, etc) than the classic 2-diode, 2-capacitor
doubler (as seen in e.g. the HP-23 supplies)? I know it uses more
parts; what I'm wondering is whether the extra parts actually provide
any benefits, and if so, under what circumstances.

Does anybody have any actual experience with this circuit?
73,
Mike, KK6GM

It is more complicated than the normal full wave doubler,
http://hyperphysics.phy-astr.gsu.edu...oldoub.html#c1
but I can't see that it has any advantages.

--
John Popelish

Build s test ckt with a filament xfmr and *small* caps and a "heavy" load,
and look at the oupt ripple with a scope. Or build it virtually.

OT: Which are the other good, (affordable!?) ckt sims?
Anyone have a transferable version of Electronics Workbench he'd like to
sell?

73, Dave, N3HE
Cincinnati OH

"Mike Silva" wrote in message
ups.com...
Regarding the circuit he
http://www.kwarc.org/bulletin/99-04/tech_corner.htm

Does this voltage doubler work any "better" (better regulation, better
transformer utilization, etc) than the classic 2-diode, 2-capacitor
doubler (as seen in e.g. the HP-23 supplies)? I know it uses more
parts; what I'm wondering is whether the extra parts actually provide
any benefits, and if so, under what circumstances.

Does anybody have any actual experience with this circuit?
73,
Mike, KK6GM

Yes, both C1 and C2 are charged with 1/2 wave power (one pulse every
full cycle). However, it appears to me that the difference is that
they only discharge during one half-cycle of every full cycle. On the
charging half-cycle they are not also discharging, but they only
discharge on the opposite half-cycle. This is different from the 2x2
doubler, where both caps are charged on alternate half-cycles, but both
caps discharge during the entire full cycle. If I've analysed this
correctly, it seems that there should be some improvement in voltage
regulation over the 2x2. But I wanted others to look at the circuit
and offer their ideas on it as well.

73,
Mike, KK6GM

With regard to circuit simulation: have a look for LTSpice on the
Linear Technology website. Or if you don't mind text-based netlists
and classical Spice, see
http://www.rfglobalnet.com/IndustryS...hResults.aspx?
keyword=Spice&TabIndex=4&image1.x=0&image1.y=0 for some other sources.

With regards the circuit, it's fairly easy to do some mental arithmetic
to see if there is an advantage or not over the two-diode, two-caps,
floating-transformer "full wave voltage doubler" circuit.

In the old circuit, there are, if you will, four distinct time periods
in each cycle (though two of them are electrically equivalent, and the
other two are symmetrical). One is where the upper cap is charging,
and the load current may be considered to be through the two caps in
series -- or may be considered to be through the lower cap and the
transformer and upper diode. Following that is a period where the
transformer voltage is too low to charge the upper cap and too high
(not negative enough) to charge the lower cap. Then the load current
flows through the two caps in series. Following that, the transformer
charges the lower cap, and after that the transformer voltage is again
too low to forward bias either diode. So the net voltage across the
two caps increases twice each cycle, once when the upper cap is
charging and once when the lower cap is charging. The output (load)
ripple fundamental frequency is twice the line frequency. You can get
a reasonable idea of the ripple voltage if you assume the charging
takes place in a tiny fraction of the total cycle time; in fact, that
will be an upper bound on the ripple voltage. For simple analysis,
assume a 1Hz input so there are two charging pulses per second (one per
cap), and assume two 1-farad caps and a 1-amp load. Then the voltage
across each cap between the charging pulses sags at 1 volt per second,
and the output sags at 2 volts per second, but resets twice per second,
so the ripple is 1 volt peak to peak.

In the new circuit, you need to say something about the capacitor
values. Presumably the two "input" caps are the same value, but may
differ from the output cap. But what happens if you say that you are
going to use the same total energy-storage ability as you had in the
simpler circuit? Then the output cap might be, say, 0.25 farads, and
the two input caps might be 0.5 farads each, since the output cap must
be rated at twice the voltage of the caps in the original circuit.
Now...can you figure out an allocation of the caps that gives you even
the same performance as the original circuit, let alone a better one?
And is it worth using more caps and more diodes? Especially for low
voltage use, the original circuit has a distinct advantage of having
only one diode drop during charging.

You can also analyze transformer utilization and I think you'll find
that the "improved" circuit doesn't really offer any advantage, if you
set it up to give the same output ripple.

Any other viewpoints, backed by some analysis or simulation?

Cheers,
Tom

David J Windisch wrote:
Build s test ckt with a filament xfmr and *small* caps and a "heavy"
load,
and look at the oupt ripple with a scope. Or build it virtually.

OT: Which are the other good, (affordable!?) ckt sims?
Anyone have a transferable version of Electronics Workbench he'd like
to
sell?

73, Dave, N3HE
Cincinnati OH

"Mike Silva" wrote in message
ups.com...
Regarding the circuit he
http://www.kwarc.org/bulletin/99-04/tech_corner.htm

Does this voltage doubler work any "better" (better regulation,
better
transformer utilization, etc) than the classic 2-diode, 2-capacitor
doubler (as seen in e.g. the HP-23 supplies)? I know it uses more
parts; what I'm wondering is whether the extra parts actually
provide
any benefits, and if so, under what circumstances.

Does anybody have any actual experience with this circuit?
73,
Mike, KK6GM

K7ITM wrote:

With regard to circuit simulation: have a look for LTSpice on the
Linear Technology website. Or if you don't mind text-based netlists
and classical Spice, see
http://www.rfglobalnet.com/IndustryS...hResults.aspx?
keyword=Spice&TabIndex=4&image1.x=0&image1.y=0 for some other sources.

With regards the circuit, it's fairly easy to do some mental arithmetic
to see if there is an advantage or not over the two-diode, two-caps,
floating-transformer "full wave voltage doubler" circuit.

In the old circuit, there are, if you will, four distinct time periods
in each cycle (though two of them are electrically equivalent, and the
other two are symmetrical). One is where the upper cap is charging,
and the load current may be considered to be through the two caps in
series -- or may be considered to be through the lower cap and the
transformer and upper diode. Following that is a period where the
transformer voltage is too low to charge the upper cap and too high
(not negative enough) to charge the lower cap. Then the load current
flows through the two caps in series. Following that, the transformer
charges the lower cap, and after that the transformer voltage is again
too low to forward bias either diode. So the net voltage across the
two caps increases twice each cycle, once when the upper cap is
charging and once when the lower cap is charging. The output (load)
ripple fundamental frequency is twice the line frequency. You can get
a reasonable idea of the ripple voltage if you assume the charging
takes place in a tiny fraction of the total cycle time; in fact, that
will be an upper bound on the ripple voltage. For simple analysis,
assume a 1Hz input so there are two charging pulses per second (one per
cap), and assume two 1-farad caps and a 1-amp load. Then the voltage
across each cap between the charging pulses sags at 1 volt per second,
and the output sags at 2 volts per second, but resets twice per second,
so the ripple is 1 volt peak to peak.

In the new circuit, you need to say something about the capacitor
values. Presumably the two "input" caps are the same value, but may
differ from the output cap. But what happens if you say that you are
going to use the same total energy-storage ability as you had in the
simpler circuit? Then the output cap might be, say, 0.25 farads, and
the two input caps might be 0.5 farads each, since the output cap must
be rated at twice the voltage of the caps in the original circuit.
Now...can you figure out an allocation of the caps that gives you even
the same performance as the original circuit, let alone a better one?
And is it worth using more caps and more diodes? Especially for low
voltage use, the original circuit has a distinct advantage of having
only one diode drop during charging.

You can also analyze transformer utilization and I think you'll find
that the "improved" circuit doesn't really offer any advantage, if you
set it up to give the same output ripple.

Any other viewpoints, backed by some analysis or simulation?

Be sure to load each side of the AC source that represents the
transformer winding with a small capacitor to ground (something like
..01 uF) or the simulation will run slow. The source is constrained
only by the diode reverse bias capacitance during most of the swing,
so it takes a while for the simulation to scale up and down between
what is happening when the diodes are on and when they are off.

--
John Popelish

Behold, David J Windisch scribed on tube chassis:

OT: Which are the other good, (affordable!?) ckt sims? Anyone have a
transferable version of Electronics Workbench he'd like to sell?

73, Dave, N3HE
Cincinnati OH

Look for Circuit Maker Student - it's freeware and uses the Berkeley 3f4
spice models.

If you use tubes, Robert Casey, WA2ISE has made a bunch of 3f4 tube models
:-)

--
Gregg "t3h g33k"
http://geek.scorpiorising.ca
*Ratings are for transistors, tubes have guidelines*