Voltage question

[9 volts]

Hi, just wondering if anyone could help me out. I need to get 21volts dc from 15volts dc. Could I make a voltage doubler circuit and put a trim pot on the end, and adjust to suit? Thanks again

[GGBB]

You can do it that way, but a lot depends on whether you need 21 volts *regulated* and/or at a certain amount of current.  The better way is a voltage doubler into an adjustable regulator like the LM117.

[R.G.]

Also notice that 15Vdc will require a circuit to do the doubling. Read the specifications carefully if you intend to use a charge-pump doubler. Some of them die at anything over 10V, some at 12. There may be some that go over 15, so do the homework to find them if you pick this route. Otherwise, you're going to have to use some kind of discrete circuit or power supply controller and inductive stepup. Not a big deal, but more complexity.

[9 volts]

Many thanks, I will start researching and probably be back with more questions. I'm trying to resurrect the ensemble effect from parts of an old eminent organ.

[rring]

I can recommend the LT1144 - I use this device for creating dual supplies and voltage doubling - it only require three parts or so and can source 50 ma. It works with inputs up to 18VDC. It also has good application info in the data sheet