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I am (re)learning electronics and I am currently playing around with "simple circuit" to practice a bit. For testing, I am doing a simple circuit that could have 2 different input voltage (not at the same time), one from a 12v and one from a simple Li-Po (3.7v). As I want 5v I use a simple step-down voltage regulator for the 12v. Regarding the battery, I know I could use a step-up voltage regulator, but I would like to know if it was "ok" and "safe" to use two (same) capacitors (non-polarized) to increase the voltage output voltage of the battery, and then use this "boosted" voltage inside my 5v voltage regulator. So I avoid to use 2 ICs for a "simple" tasks. Also, to learn a bit more, what would be the drawback of this solution even if it is "OK" to do it ?

N.B.: I know that step-up/step-down voltage regulator exists, but I do not own one and these ICs seems a bit more complex than "simple" fixed step-down voltage regulator. So for now if I can still use my step-down voltage regulator it would be great.

NB2: Li-Po have an integrated circuit to protect from overvoltage, so I suppose it's ok to boost the voltage

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No, you can't use just capacitors to do that. They will just sit there and do nothing unless you use the caps as part of a charge pump which can increase voltage.

But it would be a bad idea to boost the battery voltage and then use a 7805 as that would increase losses and reduce battery life.

If you don't want to bother designing a switching converter, you can buy cheap canned ones that will convert your battery voltage to 5V. For a one-off design, the choice is easy between spending lots of time selecting components for a DC-DC, and a canned solution...

Note it is often the case that you think you need 5V but you don't. Most "5V" microcontrollers like the Atmega in arduinos run just fine on one LiIon cell without voltage regulation.

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