There's a few resources out there for indcutorless boost circuits, or charge-pump voltage doublers and triplers.
http://www.electroschematics.com/648/555-voltage-doubler/
But this circuit is only able to convert a meager 70mA and the conversion efficiency is not that great. What should be done to increase the amperage into the 2-3A range with efficiencies similar to the charge pump ICs out there
The reason I am looking at these is they are known for their potentially high efficiency, I think I've seen a few that claim voltage conversion efficiency of 99% and power conversion of ~94% such as the TC1240
It would be great to be able to convert DC from a single cell lithium battery to high voltage easily with low loss.
How do I get the max amperage up to 5A on this circuit? Is it possible without an inductor?
Best Answer
Get an inductor and do this right. Charge pumps are inherently inefficient, and limited to relatively low currents. This is in part due to the low efficiency, and in part due to the large capacitors that would be needed to pump high current. Stepping 12 V to 20 V at 5 A out (100 W) is waaaaaayyyyyy beyond practical charge pump range. Fahgeddaboudit!
The obvious answer is a boost converter, which, of course, will contain a inductor. You have given no justification for avoiding inductors, so this is a viable answer. There are boost converter ICs out there. At this power level, you will need one that manages a external switch.
At 80% efficiency, for example, the average draw from the 12 V supply will be 10.4 A. I would look into multi-phase architectures to split up that current. At this power, you will probably have to design significant parts of the booster yourself. There may not be any suitable off the shelf chips. I'd probably look into a microcontroller driving three PWM outputs 120° out of phase.
At 100 W, you have to wake up and do some real design, not just slap parts together according to a circuit you found in some questionable corner of the internet. This is certainly no place for silly religious convictions, like that inductors are somehow evil.