Electronic – Change voltage without consumption


Is it possible to change voltage without consuming power?

I have a 5V Arduino circuit that makes use of a wireless chip (NRF24L01) that runs on 3.3V.
My current approach to get 3.3V out of a 5V source is a voltage divider using a two resistors. It is cheap and very easy to setup. The disadvantage is that the consumption over the remaining 5V – 3.3V = 1.7V is lost / wasted. I run the circuit on an AA battery so power consumption has to be as low as possible.

Now I am looking for a way to not loose any power in the process of getting a 3.3V out of 5V. One approach would be to use a DC buck step down converter. It uses very little power to do so, but it also is more expensive than the voltage divider using resistors. There is also the possiblity to use an AMS1117, but I have no experience with that.

Is there a cheap and power saving solution for getting 3.3V out of 5V?

Best Answer

a resistive divider is never an appropriate voltage regulator. It's dangerous – the voltage seen by the low voltage side depends 100% on the current it draws

The disadvantage is that the consumption over the remaining 5V - 3.3V = 1.7V is lost / wasted.

That's not even the point. You say this works, which means your resistors are using significantly more power than your 3.3V circuitry. This is a terrible design choice!

The voltage can be much higher or lower than the target current, unless you waste a lot of power through much too strong resistors; I hope you remember Ohm's law and how a loaded resistor divider is not the same as an unloaded one.

So, drop that really bad idea that everyone should tell you is a bad idea and use a linear voltage regulator. Done.

You get an actually regulated voltage, and don't waste as much power.

You could use a more expensive but more efficient buck converter instead of a linear voltage regulator, but "5V arduino" kind of implies "not power efficient" to begin with, so my guess (!) is that this won't save a significant amount of energy.

If you want to be more energy efficient, re-base your digital logic to run on a microcontroller off the same 3.3V (or lower) rail as your NRF chip, and supply both from a switch-mode power supply.