NEEDED: Simple, low power AC voltage doubler & rectifier

[flx]

Hi guys!

I will only describe my input and the desired output. I won't suggest any of the solutions I've been thinking of... just so as to preserve the "freshness" of your ideas

- NO POWER SOURCE IS AVAILABLE -

Input:
2.0V 20kHz Sine AC (~1.4V RMS), low power... some 50mA (approx 70mW). An audio signal, essentially.

Desired output:
4.0V 40kHz "DC". Lower than 4.0V is fine, if overall power loss is not significant. As the graph shows, I DO need the ripples, so please keep'em!

Entirely optional: If you could also "squarify" the output a little bit, again without losing too much power, even better!

As always, the ideal solution would have a minimal amount of components - OR - even better, would be an IC!

I sincerely appreciate your help... Thank You.

**broken link removed**

 

[ronv]

Rectifier with gain

Here is a circuit. Just remove the cap at the input to the last stage and set the gain.

Circuit - PRECISION FULLWAVE RECTIFIER - Circuits designed by David A. Johnson, P.E.

 

[flx]

Here is a circuit. Just remove the cap at the input to the last stage and set the gain.
Circuit - PRECISION FULLWAVE RECTIFIER - Circuits designed by David A. Johnson, P.E.

Oops, I forgot to mention... a power source is not available. Also, the output doesn't have to be "perfect". But thanks anyway!

 

[ronv]

Sorry didn't see that. Seems your back to the 1 to 2 transformer and bridge rectifier. Or actually I guess there would be less loss with a centertapped transformer and a full wave rectifier. Your probably not going to find a lossless system.

 

[flx]

Lossless is utopic; never wanted such. As for transformers, well, let's just leave them at the movie theater. No space - sorry.

NEEEEXT!

 

[MrAl]

Hello,


One way would be to build three bridge rectifiers out of higher speed diodes like 1N4148, and connect them all to the input as you would connect one, except using coupling capacitors of at least 1uf to do it. The outputs of the bridge rectifiers (the pulsing dc sides) are connected in series so that the outputs add. That gives you about 3.5v pulsing.
When coupling on the AC side of the bridge rectifiers, one capacitor goes in each AC line, so that means you'll need 6 capacitors to do all three bridges.

The following is a quick drawing showing the connections. A and B are the AC input lines, C is a capacitor and D is a diode and all diodes have their cathodes pointing up. All the A's connect together and all the B's connect together, and then any A goes to one AC line and any B goes to the other AC input line.
Note that it may take quite a few cycles to reach steady state (possibly 100 or more).
Also note that you will probably need to load the output with say 100k ohms, or possibly each bridge with 100k.

                +----+---o Output
                |    |
                D    D
                |    |
  A o-----C-----+    |
                |    |
  B o-----C----------+
                |    |
                D    D
                |    |
                +----+
                |
                +----+
                |    |
                D    D
                |    |
  A o-----C-----+    |
                |    |
  B o-----C----------+
                |    |
                D    D
                |    |
                +----+
                |
                +----+
                |    |
                D    D
                |    |
  A o-----C-----+    |
                |    |
  B o-----C----------+
                |    |
                D    D
                |    |
                +----+---o GND

 

[flx]

With each reply, I notice more and more stuff that I forgot to specify...

For example. Space is *very* limited. I can't afford more than a few tiny SMD caps, let alone 1uF ones...

 

[Ubergeek63]

Lossless is utopic; never wanted such. As for transformers, well, let's just leave them at the movie theater. No space - sorry.

NEEEEXT!

actually at 20KHz you probably do have space. go to radio shack and get a 8Ω/1KΩ CT audio transformer is is only about a 3/4" cube. put your 20KHz on half the center tapped winding and a full wave bridge across the whole thing. the whole set up will take the space of a packed 16 pin dip circuit.

 

[flx]

All the space / volume I have is 0.13" x 0.1" x 0.31" (3.5mm x 2.5mm x 8mm). Gulp.

 

[Ubergeek63]

tell us what you are trying to drive. this sounds suspiciously like an aircraft instrument i designed long ago.

a salesman asked me why we kept no bidding it. it had to be 1% accurate at frequency measurement with a low 2Hz 2V peak 3PH signal source. when i asked my boss why he said because it has no power source to which i replied "Tom, our SIGNAL source puts out over 100W full scale!" I could do better now since 20 years ago there was very little available that would do that sort of thing... the only commercially available F/V was the 2917 which would not run reliably below 5V so i had to roll my own.

At any rate a frequency counter is the only reason i can think of that you would "need the pulses", and i am here to tell you there is a better way than demanding that you need them.

 

[flx]

@übergeek - Check your PM.
If anyone else feels like brainstorming, please PM me. When a solution is found, we'll post it here.