Theory behind voltage double/tripplers etc (dc)

In the circuits you see with the diodes and capacitors they require ac? to work?.

or can you have a voltage doubler that works purely with diodes and capacitors? it was not clear and unfortunately the picture is on my phone and i'm on my desktop.


Should the source be DC or a pulsed DC? (PWM)

cjdelphi:
In the circuits you see with the diodes and capacitors they require ac? to work?.

Yes.

cjdelphi:
Should the source be DC or a pulsed DC? (PWM)

They need a negative voltage at some point.

Yes the vin is infact ac voltage, stepped down .
you get multiplied dc voltage as output.

the source is AC not dc/pulsed dc.

if pulsed dc is not ac what is?

umm pulsed dc = rectified ac .there is no negative cycle in that .
you need negative cycles as well, at the input iirc.

cjdelphi:
if pulsed dc is not ac what is?

Doublers work by shifting the voltage up so the most negative value becomes 'ground'.

A pulsed DC doesn't have any negative values so there's no voltage shift.

OTOH you can feed a pulsed DC into an old-fashioned transformer and raise the voltage that way.

No folks, both circuits illustrated have capacitor-coupled inputs so any DC component is irrelevant
and pulsed DC will work just the same as DC-balanced AC (so long as the capacitor maximum voltage
isn't exceeded!)

The circuits do need push-pull drive though, you can't just switch the DC on-and-off with a high-side
switch, you have to drive the input alternately to each rail with a half-bridge circuit.

MarkT:
No folks, both circuits illustrated have capacitor-coupled inputs so any DC component is irrelevant
and pulsed DC will work just the same as DC-balanced AC (so long as the capacitor maximum voltage
isn't exceeded!)
...

agree.

A wide variety of alternating signal inputs are used with multiplier circuits. The most popular are sine and square wave inputs.

App note By Joseph M. Beck, Senior Applications Enginee of General Semiconductor.

http://www.eettaiwan.com/ARTICLES/2001JUN/2001JUN14_AMD_AN2009.PDF

Fourier Series - Square Wave

With a few discrete components and some creative thinking, spare microcontroller peripherals can be used to provide a low-current, regulated voltage boost, as Keith Curtis, Technical Staff Engineer, Microchip Technology Inc. explains. The right mix of spare peripherals can be used to boost a 5V supply voltage to a low-current, regulated 15V.

Couple of pics of a 2 cell driving a 5volt lcd. A lot of 5volt lcd's are able to be driven by 3.3V but the contrast must be driven by a voltage that is negative. So I'm using the circuit seen in the one pic (the 2 diodes and the 2 caps)to create a negative voltage fed to the contrast thru a pot to control it. The circuit is driven from one of the timer0 output pins which means it just runs without any need to be updated by software control, just the initial setup.

Can also use a chip like MAX1680/1681 to double the voltage and also invert, so 5V in creates +/-10V out, same as you'd find in a MAX232 for RS232 voltage swings.
http://datasheets.maximintegrated.com/en/ds/MAX1680-MAX1681.pdf

This datasheet shows the kind of switching that goes on in these chips
http://datasheets.maximintegrated.com/en/ds/MAX1682-MAX1683.pdf

100y old circuits :slight_smile: :slight_smile:

Dave of EEVBLOG recently did a set of tutorials on assorted voltage multipliers.
They start here: http://www.eevblog.com/2013/05/10/eevblog-469-cockcroft-walton-multiplier/