Hello everyone,

I have a PCB design that is powered by mains electricity via an 9V adapter. When there is no electricity, I want it to switch to li-ion battery mode and provide energy. When there is electricity, the battery must not provide energy. At the same time, I want the battery to be charged from the circuit when not in use.
The battery will be embedded, it cannot be taken out and charged. How to split battery voltage and adaptor voltage?
I didn't know how to do this.
If you have any information, I would like your help.

Thanks in advance.

 

that really depends on how complex the system needs to be. Are you looking to figure out the stuff yourself or are you looking for a functional tested system?
A simple diode might be the simplest solution, but there are a lot of concerns with that. Battery chemistry, current ratings, charge rates. Lots of information thats needed to answer the question fully.
You said you wanted to use lithium ion batteries so a simple diode will not work for that, you need to charge them correctly and just wanging a diode in with a random power supply is going to start a fire.
You may have to design in a charge controller and a boost converter into your pcb to make the functionality you want. I did a cursory search on amazon and the only premade modules I found weren't for Lithium batteries, but would work for NiMH or lead acid. Like these

 

The Power-Supply is quite often the most important part of the project,
and it could be quite complex.

Why did You choose a 9-Volt Power-Supply ?
What is it's measured Output-Voltage and Current ?, and is it regulated ?
.
.
.

 

that really depends on how complex the system needs to be. Are you looking to figure out the stuff yourself or are you looking for a functional tested system?
A simple diode might be the simplest solution, but there are a lot of concerns with that. Battery chemistry, current ratings, charge rates. Lots of information thats needed to answer the question fully.
You said you wanted to use lithium ion batteries so a simple diode will not work for that, you need to charge them correctly and just wanging a diode in with a random power supply is going to start a fire.
You may have to design in a charge controller and a boost converter into your pcb to make the functionality you want. I did a cursory search on amazon and the only premade modules I found weren't for Lithium batteries, but would work for NiMH or lead acid. Like these

I added the flowchart of the system. I'm new for electronics and I'm confused.

I can say that it works like computers power system.
That is, if the system is working with the adapter, there must be no voltage coming from the battery to the system.
If there is no mains electiricity, the battery must be activated and the system must be operated.
The battery should only be activated automatically when there is no mains electricity.

 

Likely the best solution is to use an IC battery controller that performs the desired separation and charge function.

 

It makes a lot more sense now. The system running at 5v simplifies the problem. Like crutschow said there are chips that will handle all of that now. But from the sounds of it you may not want to go down that road of designing your own battery management system. You mentioned the TP5100 module in your flowchart so I'm guessing modules would fit just fine. I did some digging on amazon and found some step down modules to output 5vdc. These. I'm not saying these are the only option, but these seem to fit what you're looking for since you already are using the TP5100 module.
And as far as doing the backup a simple diode from battery and power supply to the step down 5vdc module will do what you want.

The diodes can be any really. Like these at digikey. i just picked a generic shottkey diode rated for double what I saw. The step down module I linked to above will accept 12vdc as well as battery voltage. So the diodes will ensure that the supply with the highest voltage is the one providing power to the 5v module. Hope this helps.

 

A very simple solution could be the use of a DPDT relay powered by the mains adapter. When it is energised, it cinnects the mains power source to the circuit and the battery to the charger. When it is de-energised, it will disconnect the charger and connect the battery to the circuit.