# Low power DC voltage doubler question.

#### evo.motorsport

Joined Jun 20, 2007
21

Can anyone help me with the low power DC voltage doubler circuit?

Basically I need to double the DC voltage from (0V to 5V) to (0V to 10V). For example, if my input is 0.1 I need it to be 0.2, if the voltage is 2v I need it to be 4v, if is 2.5V I need it to be 5V

Any help is appreciated.

#### beenthere

Joined Apr 20, 2004
15,819
If it's really low power you can use an op amp set up as a voltage follower with a gain of 2. That will limit current to about 10 ma, though.

Your description of the circuit and application is too vague to do more than guess.

#### lightingman

Joined Apr 19, 2007
374
o.k.So it sounds like a control voltage you are talking about.....You could do it with an dual op-amp, driving up to about 20mA (depending on the device used)....If you need to drive at a higher current, you can use a complimentary pair of transistors after the op-amp output, but taking the feedbak from the output of the transistors, rather than the op-amp....You will need a -ve supply for the op-amp, and a +ve supply at least a couple of volts above the maximum output that you require.....I can post some schematics tomorow if you wish.....Daniel.

#### Papabravo

Joined Feb 24, 2006
20,621
And there is the ever popular Diode-Capacitor-Diode Doubler

#### recca02

Joined Apr 2, 2007
1,212
i was thinking about that too but isnt that ac to dc ?

#### Papabravo

Joined Feb 24, 2006
20,621
Not really. In a logic circuit you create an oscillator(square wave) and that goes to the DCD components. It is what a MAX 232 does to make RS-232 levels from +5V

#### recca02

Joined Apr 2, 2007
1,212
well thanks for the info MR P.B.

#### mrmeval

Joined Jun 30, 2006
833
If you only have +5 to work with you need a xbxuxckx boost regulator
This says 6V but I suspect it'll work with 5V

http://www.aaroncake.net/circuits/6-12conv.asp

This is a kit that looks interesting. Dunno what it needs to run at 5v
http://www.elexp.com/t_dc-dc.htm

This will do a switcher even though it's linear. I know there's a smaller TO92 version but I'm not seeing it.
http://cache.national.com/ds/LM/LM117HV.pdf

EEP you can use an ATTINY as a switcher! And Atmel is Linux friendly, this is the competing part to Ti's little mini chip for which they will not release some code for Linux other than a closed source binary so I'm getting one.

http://www.atmel.com/journal/documents/issue5/pg41_43_Atmel5_Tiny.pdf

#### lightingman

Joined Apr 19, 2007
374
Hi..

I think this is what you may be after....
The output will only serve as a control voltage...
There are acouple of ways to increase the output drive, but if you need to do this then just let me know, and I will post the schematics....

Good luck....

Daniel.

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#### Papabravo

Joined Feb 24, 2006
20,621
If you only have +5 to work with you need a buck regulator
...
Don't you mean a boost regulator? A buck regulator goes from a higher voltage to a lower voltage.

#### evo.motorsport

Joined Jun 20, 2007
21
Hi..

I think this is what you may be after....
The output will only serve as a control voltage...
There are acouple of ways to increase the output drive, but if you need to do this then just let me know, and I will post the schematics....

Good luck....

Daniel.
Thanks, this is what I'm after..... I'm using output voltage as control only. Is it any way to do that simpler way?

#### lightingman

Joined Apr 19, 2007
374
Hi..There is no simpler way if you wish it to be accurate.....You could do it leaving out the buffer (IC1b), and do it with a single op-amp (TLO61, TLO71, TLO81).....If you allready have a -ve supply, then you can leave out the ICL7660.....I built and tested this last night in about 15 mins, so it is not that complicated......Wish you luck.....Daniel.

#### lightingman

Joined Apr 19, 2007
374
Hi,You will still only get 0 to 5 volts from the circuit in that article.unless there is 10 volts accross the sensor....And that is only possible if the sensor is designed to operate at that voltage....The op-amp in the article is only used as a high impedence buffer, in that it has no gain in that configuration.....Daniel.

#### bloguetronica

Joined Apr 27, 2007
1,541
If you need to amplify a signal, a Op-amp will do (the LM324 might be ideal for a single power supply), but if you need voltage to supply to something, try a charge pump. MAX232 is an example of a chip that uses charge pumping to output signals to the RS232 level.
Maxim has a broad selection of charge pumps. The principle of such device is two capacitors that charge in parallel, and discharge in series.

#### lightingman

Joined Apr 19, 2007
374
Hi there cumesoftware, hope you are well....We have allready established what evo.motorsport are trying to do, and I have given a schematic....The problem is "I think", that they are trying to find a simple way to do it....But as you said, the op-amp is the answer.....What they are wanting to do is to double a 0 to 5 control voltage, so that if the input spans 0 to 5v, the output will give 0 to 10v, in proportion.....This as you will see is what my circuit does...I think you will aggree that this is the best way to do it....Oh yes.. the single rail option is no good, as it will not work correctly rite down to 0v.....Also "evo.motorsport" if you wish to reduce the component count further, you could swap the transistor, resistor, zener and capacitor for a 78L05 regulator......Daniel.

#### bloguetronica

Joined Apr 27, 2007
1,541
Hi there cumesoftware, hope you are well....We have allready established what evo.motorsport are trying to do, and I have given a schematic....The problem is "I think", that they are trying to find a simple way to do it....But as you said, the op-amp is the answer.....What they are wanting to do is to double a 0 to 5 control voltage, so that if the input spans 0 to 5v, the output will give 0 to 10v, in proportion.....This as you will see is what my circuit does...I think you will aggree that this is the best way to do it....Oh yes.. the single rail option is no good, as it will not work correctly rite down to 0v.....Also "evo.motorsport" if you wish to reduce the component count further, you could swap the transistor, resistor, zener and capacitor for a 78L05 regulator......Daniel.
Well, I see that you wanted precision in this circuit, but I really suggest a 78L05 regulator, since it is more precise than a zener. Nevertheless, a 78L05 needs at least 7V to regulate well. Also, why using a second op-amp of the same type as a voltage follower? The feedback network will not draw much power from the output (but I suggest a resistor closer to 10K and a variable resistor with a smaller resistance, for more precision).

#### lightingman

Joined Apr 19, 2007
374
Yes, O.K. The 78L05 wins.....Regulation on the -ve supply is not so important, the only reason that I used the reg, is to limit the input voltage to the ICL7660, as it has an absolute maximum of +10.5 volts, and +12.5 volts for the 7660A......The buffer was added as I was not sure of the sort of load they were driving into....O.K. lower values around the feedback circuit could slightly improve things, but 10K is the norm.....I had this tracking to within a couple of mV....All things said, If this was done in surface mount. It would be no bigger than a standard 24 pin DIL IC, and would cost only a few GBP / dollars.Cheers.... Daniel.

#### mrmeval

Joined Jun 30, 2006
833
Yes I meant a boost.

Don't you mean a boost regulator? A buck regulator goes from a higher voltage to a lower voltage.