how to design a charge pump

I am learning how to design a charge pump and have read a lot of papers. Only theories are discussed in these papers. No one talks about how to set the parameters: W and L of transistors, f, capacitors and so on. Does anybody have some materials about this kind of information?
Regards,

To get the most from a charge pump, you normally want capacitor charges to rise to maximum voltage and stay at that level. Therefore you use a high enough Farad value so that they show slight voltage change during each cycle. Once you do that you do not gain anything from increasing Farad values further. 5 or 10 percent voltage change seems reasonable to aim for. Of course the output capacitors need to be sufficient to smooth ripple to your desired amount.

To reduce output voltage, you can do one or more of the following:

* Reduce capacitor values, which causes wide voltage swings on them.

* Reduce duty cycle.

* Turn on transistors to a lesser extent, to admit less current through the system. However this is the same as introducing resistive drop, and you lose efficiency.

This is an ideal candidate for simulation. The charge pumps work best when the load is constant (relatively speaking) and you can tolerate some amount of ripple. Many of the parameters interact and you will need to experiment. Usually it is simpler to keep the frequency constant and play with the ripple voltage and the capacitor value. There are free simulators you can search for in the web.

hello, thank you for your reply.
you said that There are free simulators I can search for on the web.
can you tell me how to search?
I don't know what kind of simulators you mean.
Regards,

If you are not familiar, please check first: https://en.wikipedia.org/wiki/Electronic_circuit_simulation

Next get some idea about spice - it is a old software originally developed for the military.

There are simulations that can be done online too (but I have not used them).

Also see the article: https://en.wikipedia.org/wiki/List_of_free_electronics_circuit_simulators

Most people here (I guess) use Verilog but that is not free. But clones, with some restrictions are free.

I use geda-project tools. But they are a work-in-progress. Perhaps you can try easyeda.com

Once you get some familiarity with a simulator, you will save some money, time and headache. They are here for that only.

what you are talking about are the capacitors and the frequency.
what about the transistors?

Please select any suitable transistor depending on the power (both voltage and current) and speed (frequency)- you are basically using any switching transistor that is consistent with the level of voltage and current.

In this case, the transistor is the least critical part and the output will depend on the load, frequency, output capacitor and duty cycle. If the input voltage is stable, you can easily get a stable output by changing the capacitor.

If you are fussy about the ripple, you need to adjust the duty cycle also. A simple charge pump (without feedback) will not have a great input or output regulation.

So you design your charge pump around the load in mind.