Dickson Voltage Doubler

Dickson Doubler Dave CADWhen designing a microcontroller circuit, you may need a source of higher voltage.  This is particularly true when using a 3.3 volt micro such as the PIC18F25K22 on the Amicus board or when using the new Firewing board..  A circuit might operate perfectly from a pair of AA batteries except for a few milliamps needed at a higher voltage for an LCD or to power a sensor.  The usual option is to use a battery pack with more cells and multiple voltage regulators, but Dave at EEVBlog shows us an easier way in a recent video:

EEVBlog #473 – Microcontroller Voltage Doubler

dickson doubler

The above illustration (courtesy Spinningspark at Wikipedia) shows how simple the circuit can be to generate a higher voltage.  A couple Schottky diodes and caps and a PWM output from the micro is all that's needed.  Dave explains how the circuit works and its limitations in his usual comprehensive and entertaining style in the video.  This is a great way to generate a few milliamps at a higher voltage.

Dave used the example of powering a 5 volt LCD display with this voltage doubler circuit.  Another approach was suggested by Burt sometime back.  The same parts of the voltage doubler can be re-arranged to create a voltage inverter that operates on the same principle.  After some initial confusion about the function of this inverter, it was shown that many 5-volt character LCDs will operate properly from as little as 3 volts – the problem is that when the supply voltage is reduced, the LCD Ve bias voltage for display will reach zero and then negative values as the supply voltage is decreased.  This inverter circuit can be used to supply a negative bias voltage.

dickson doubler inverter

For a description of using this circuit with an LCD, read this post in the Microchip forums by Mbedder.

There are other applications requiring a negative voltage for which this circuit can be used.  The same limitations apply. 

Posted: 6 years 4 months ago by Jon Chandler #13270
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The following comment was received on the Digital-DIY Facebook page:

Ya think? There's a link to the EEVBlog video, several comments about Dave (the EEVBlog guy) and even a picture showing "DaveCAD"... Sorry if there was any doubt about where it came from!

This looked like a great topic to share with Digital-DIY readers and a nice circuit idea that may solve some problems. I highly recommend the EEVBlog but not everyone reads that site.
Posted: 6 years 4 months ago by Graham Mitchell #13263
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I can't see the reply - maybe it was written in error and removed?

Thanks for sharing the EEV post either way!

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