Hello everyone!

I am trying to learn more about electronics in general, and for this project I'm trying to better understand how power supplies work and how to design them. I am a simple hobbyist learning through doing, so forgive me if I'm missing some information that might generally be considered basic or something to be assumed.

What I'm trying to make is essentially a wireless controller with one button and one led. It will contain and ESP-01 wifi module, a simple momentary push button, and (ideally) a single AAA or AA cell battery. This project wasn't originally intended to be focused on power electronics, but when I started to search for my components I realized that it's amazingly difficult to find a boost converter that can operate below 1.5v (where most of the life of the battery will be). I did find this which seemed like it would be able to support my use case but I couldn't get it to handle the startup current the ESP tried to draw.

After much searching and the above failure I decided I would shift focus for this project and try to custom design the power electronics myself. I found the TPS613222A which from the summary appears to be designed for exactly my use case, and even has a nearly step-by-step how-to guide in the application section. After spending a couple hours reading through the datasheet and trying to follow their equations in section 9 I feel like I'm definitely missing some core assumed knowledge and hoping that some of you fine people can help. First, I would like to confirm that this chip is actually a good fit for my purpose. I found this post that points out that the efficiency of this chip drops off dramatically at a quite low current level, which may end up heavily impacting my ability to function on a single battery. Second, I would like to understand how I would go about choosing my inductor and capacitor (and Schottky diode) if this chip turns out to be suitable. If someone would take the time to lay out the equations from section 9.2.1 explaining where each value comes from I would greatly appreciate the time and effort!

Thanks for reading

 

I am puzzled by your choices. The first thing an engineer should do is refrain from constraining himself unnecessarily to something that makes the problem extra difficult.

I am talking about you choice of a single AA or AA cell, 1.5V new, 1.0V at end of life, to power an ESP32, which operates at 3.3V. There are 3.7V lithium batteries that are similar in size and can supply far more current at 3.3V than your single AAA cell can. Why would you rule these out?

And the board you linked, outputs a fixed 5V, which you then have to step down to 3.3V, wasting 33% more energy after the initial loss for boosting. It also contradicts itself on the input voltage requirement, so would not trust it to operate below 1.5V, which your battery will likely be after less than an hour.

If you just want this as an academic challenge, fine, the chip you have picked looks almost appropriate, but it looks like it is no good for more than 100mA, and I think the ESP32 uses up to 500mA when transmitting, so it is also probably not going to work. Realize that to get 500mA at 3.3V from a 1.0V source at 90% efficiency, it will need to supply 1.83A which even an AA cell could not come close to for more than a few minutes.

I think you have made a pretty close to impossible battery choice, which is not a good start. Think about it, how many commercial WIFI capable products have you seen that operate off a single AAA cell?

Sorry to be so harsh, but I really think you are setting yourself up for failure.

 

Hello Bob, thanks for your thorough reply! I'll give some context on why I made the decisions I made, but first I wholeheartedly agree that after your explanation I agree that they were not great decisions and I will be taking most of your advice.

The original inspiration for the project was my wireless mouse. It works on a single AA battery and seems to have terrific battery life, I've been using it over 6 months now and it is still going strong. Searching for how wireless mice work is also how I found the TPS613222A. Honestly it didn't even occur to me that other battery types should be a consideration, and on top of that I didn't know at all that 3.7v lithium batteries exist!

Would you mind recommending me an IC or ICs that I should look at assuming 3.7v nominal battery voltage?

 

Hello Bob, thanks for your thorough reply! I'll give some context on why I made the decisions I made, but first I wholeheartedly agree that after your explanation I agree that they were not great decisions and I will be taking most of your advice.

The original inspiration for the project was my wireless mouse. It works on a single AA battery and seems to have terrific battery life, I've been using it over 6 months now and it is still going strong. Searching for how wireless mice work is also how I found the TPS613222A. Honestly it didn't even occur to me that other battery types should be a consideration, and on top of that I didn't know at all that 3.7v lithium batteries exist!

Would you mind recommending me an IC or ICs that I should look at assuming 3.7v nominal battery voltage?

A buck boost converter would be best, but I have never made one. I would look for a pre-built module module.

Or you could get a low dropout 3.0V regulator, which would get you most of the battery life. This is just a 3-pin device that you add only input and output capacitors to. The ESP will work at 3V.