There's not much I can do to increase the Dell power adapters, there fixed at 12 Volts at a rating of 18 Amps. I have a few of the HP adapters, there just over 11 Amps. I've tried both makes of PSU adapters in series and parallel. The HP 19 Volt adapter PSU's are happy in series or parallel, but the Dell will only play ball in parallel. The boost converter I was looking at was a 30 Amp unit off Amazon, I've got one configured to run a couple of my universal motor tools, drill etc up to 80 Volts from this converter for drill stand use, it works with that very well. The boost converter is in the picture below, it's only the Dell PSU adapters I was thinking of boosting first before then running that voltage through a linear regulator circuit. I might be able to close the 12 volt to 20 volt gap, so long as the linear regulator has enough overhead voltage to function.