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Project Notes

#393 DicksonChargePump

Zener-regulated 12V Dickson Charge Pump driven with Arduino PWM.

Build

Notes

The Dickson Charge Pump is a very neat trick for multiplying an input voltage.

It is basically a capacitor bucket-brigade, with diodes for flow control, and a switching signal to make it go.

It is not the most efficient voltage booster, and cannot drive very high currents, but may be a convenient solution depending on the application.

Switching Signal

I’m using Timer2 Fast PWM to generate a pair of square-waves on Arduino pins 3 and 11 (OCR2B, OCR2A) at 62kHz. The duty cycle is set at 50%, and the waves are an inverted pair by setting OC2A to clear on Compare Match and OC2B to set on Compare Match.

Here’s a scope trace of the two waveforms (CH2 is offset -6V for clarity).

pwm_pump_control

Since we’re using the chip’s native PWM capabilities, it is not possible to change the pins that the PWM signals appear on.

Note: it is possible to use other pins by using one of the other timers. This sketch uses Timer2 as it is generally available and is not used by other standard libraries.

See LEAP#254 AvrHardwarePWM for more details on hardware PWM.

Zener Regulation

Without the zener diode in place, this 4-stage charge pump delivers about 16V at the output tap.

The 1N4742 has a nominal zener voltage of 12V. An (optional) 2.2kΩ resistor is in series to soak up some of the voltage drop.

I’ve included a 10kΩ resistor to simulate a load on the 12V supply.

Performance

Works great:

  • very little ripple, < 20mV
  • charge pump and load drawing under 2mA
  • Arduino, which is also powering the charge pump, is drawing around 20mA total

Code

The DicksonChargePump.ino sketch is about as simple as it gets:

  • sets up PWM
  • in the main loop, demonstrates how to turn on and off the PWM outputs by changing the pin mode (5 seconds on, 5 seconds off)

Construction

The capacitors used here are monolithic ceramics, 220nF for the pump stages and 1µF for the final. The ones I have are rated for at least 25V.

Breadboard

Schematic

Build

Credits and References

About LEAP#393 ArduinoPower
Project Source on GitHub Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is my personal collection of electronics projects, usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting (IMHO!).

The projects are usually inspired by things found wild on the net, or ideas from the sources such as:

Feel free to borrow liberally, and if you spot any issues do let me know. See the individual projects for credits where due. There are even now a few projects contributed by others - send your own over in a pull request if you would also like to add to this collection.