DC to DC Voltage Doubler

[JohnC]

Good morning people.

I got this voltage doubler circuit from www.reconnsworld.com/power_voltdoubler.html.

I built this, but I only get the same voltage out as the voltage in.  The only thing that I see that I may have done wrong by his schematic is I joined Vcc,

V source and C4 together.  I circled the connection on the schematic.

Could someone please comment as what could be wrong.

http://www.otherpower.com/images/scimages/3724/voltdoubler.gif

THX

John E Cox

Ottawa, Canada

[Flux]

You have joined its output to its input so the volts have to be the same.

Vcc is the supply and v source is supposed to be the output and should be roughly 2 x vcc with respect to ground.

Don't expect it to supply more than a milliamp or two at twice volts.

Flux

[Opera House]

This is a constant problems with schematics.  They used to have a little hump over the wire it was crossing.  Others went to only connections having dots. Sometimes those dots are hard to see.  Remove the connection and the voltage will double up to about 50ma.  The same circuit can also be used to make a negative supply by reversinf the diodes and capacitors.  D1 would also have to connect to the ground.  Useful for powering those hall efect sensors with a +- supply.

[JohnC]

Thanks Flux it works.

Very greatfull.

[seanchan00]

Hi Flux,

If say 5 amps is put in Vcc at 12 Volts can't I expect 2.5 amps at 24 volts at V source?

SeanChan :>)

[veewee77]

Actually, yes, your thinking is correct (minus losses) however, the 555 IC is only capable of driving a load of about 50ma or the magic smoke starts to come out.

You could use the output from that circuit to drive some driver transistors and get higher current, but that is another ball of wax and a much more complicated circuit.

Doug

[commanda]

You don't control how many amps is put in. You can only control how many amps (milliamps, actually) you pull out. The input current will then be approx twice this.

You'll find the output voltage will collapse fairly quickly once you get past 50mA output current.

Amanda

[Flux]

These charge pump type voltage converters are really only suited to very low power.

If you want to deal with amps then you will be much better off using a conventional boost converter with an inductor as the energy store.

If you just want a 2:1 voltage change then a forward converter using a centre tapped choke and a pair of mosfets is likely to be the most efficient way.

I had a diagram on the old computer but it didn't get transfered to this one.

If you are not worried about the ultimate efficiency you can use a pair of bipolar transistors and a feedback winding and make it self oscillating.

Flux

[(unknown)]

Would it be possible to "externaly" power the 555 on pin 8 to use this same circuit to double lower voltages (1-2 volt range)?

[seanchan00]

Hi Flux,

I have since been reading with much interest but not so sucessful in really understanding your teachings in your post "Matching the load" where you talk about Buck and boost converter. Can I use this concept for my wind mill? Due to poor wind, my windmill is currently running at rpm capable of generating less than 12V worth of power 80% of the time, and i can't use this to charge my 12V batteries. I'm considering using your Boost converter circuit to boost my output voltage to above 13V. However, I do not know what Capacitor and Inductor values to use, or what type of Mosfet to use. I understand I need to include a timer of some sort to switch on and off at 30 KHz. 555 timer won't stand up to this function? Can you please advise?

Also, would it be necessary to put in a cut-off feature in my boost circuit when the wind picks up?

Regards,

SeanChan

[(unknown)]

If your windmill is AC then you could just use a stepup transformer.

[(unknown)]

Or even pulsating dc has a rise and fall should work on dc straight from the generator to raise the voltage above the 12 volts required. I have the same problem with a dc generator I'll let you know if it works. This is a very common problem with wind power that just has not been addressed as far as I can see.