How to keep a stable output voltage from changing input voltage

Question

I'm learning about solar panels and bought a 6V panel and a 3.7V Li-Ion battery as well as a solar battery charger, all from adafruit. I also got a boost converter thinking that the output of the circuit would be 3.7V but actually it outputs from 3.7 up to 6.8V depending on the sun. This was my mistake for not reading carefully. I need 5V at the output for a microcontroller and other components. I was looking around and found a 5V precision voltage reference REF02, but it takes a minimum of 8V input and upto 40V. So my question is, can I use a boost converter at the output of the solar charger set it up to where it won't go below 8V at the worst condition and use the REF02 to have the stable 5V? Is this a reasonable circuit or is there a better idea or better way of doing this? Thank you.

Answer 1

It sounds like what you need is a buck-boost converter. These are switching voltage regulators that can produce a stable output voltage from an input voltage that is above or below the desired output voltage.

If you want to keep things easy and just want something you can buy, Adafruit has exactly such a module. It can accept 3V-12V in and will output 5V at somewhere between 500mA and 1000mA depending on if it is in boost or buck mode.

However, more generally, if you look for 'buck-boost' converters, you will be able to find quite a few suitable modules.