I want to design a power supply for an RF doorbell. My requirement is this power supply should be operated on AC as well DC Power. Means It is Battery as well Mains Operated. So anybody know how is that design let me know?

 

One way is a simple diode from the output of each supply so that the one with the higher voltage provides the power. Design it so that this is the mains-derived output when both are available.

You can add in the ability for the mains-derived supply to float charge a suitable rechargeable battery so that you can get years of service before having to worry about the battery being dead when it is needed.

 

The easy way would be use a wall wart and put a diode to block the Battery when the ac is off it will
use the Battery
V1 you would hook wall wart there a v2 would be battery.


Sorry WBahn you posted the same idea while i made something up.
float charge would be good to the diode needs to be a Schottky diode.
float charge link
https://www.google.com/search?q=flo...AUICigB&biw=1067&bih=539#imgrc=5yct-cmC6v_ooM:

 

Better to put a diode in series with each supply. First, that allows the two supplies to be nominally the same voltage in order to get a largely source-independent voltage at the load. But even more so, some wall warts have pretty low impedance outputs when unplugged. The diode in series with it will prevent the battery from being drained into it. Without it, the TS has to be picky when they choose the wall wart -- and possibly later when they replace it long after they've forgotten about this point.

 

I added it i figured the wall wart would be higher voltages then battery. But your right it would probably
save problems later.

 

Can you tell me how rechargeable battery gets charged after discharging when AC mains is on & it supplies power to the load