5 5V UPS Circuit

This UPS has a regulated and uninterrupted 5V output. This type of UPS is very useful to low power 5V devices, microcontrollers, and some memory modules. This UPS design has a very stable 5V output but the drawback is very low efficiency. 

5V UPS schematic
Part List:
R1 - 39 ohms 1/2W
D1, D3, D4 - 1N4001 or similar diode
D2 - 13V zener rated 1W
C1 - 220uF electrolytic capacitor rated 25V
C2 - 10uF electrolytic capacitor rated 10V
IC - 7805 or similar 5V regulator
BAT - 12V lead acid battery rated 1.2Ah minimum
DC INPUT - see AC-DC converter below
AC-DC converter
Part List:
D - 1N4001 or similar dioded
C - 2200uF electrolytic capacitor rated 25V
Transformer - Primary (220V or 110V), Secondary (12V-0V-12V) rated 12VA minimum

Similar UPS circuits:
Simple 12V UPS


  1. I like your circuit. I have a question though?
    Is it possible to use 5volt input from USB?
    Also lead acid battery, how can I integrate a Li-Ion charging circuit in there and possibly use 7.2volt batteries?

    The efficiency does not matter as long as when 5volts from USB gets unplugged the output still maintains an uninterrupted power supply of 5volts.

    Is it possible?

    1. ^ You can't use the 5v from USB ports, 7805 needs an input that's significantly greater than the regulated output.

  2. I love this! I am trying to implement this in my project. The 12 volts is coming from a wall adapter that is transforming the 120vac from a wall outlet to 12v. I see that this steps the voltage down and that disconnecting either the dc power supply or the battery still results in 5vdc coming out of the regulator. I have 2 questions though.

    1. Does the voltage come from the dc power supply and then is only drawn from the battery if the power goes out?
    2. Does this charge the batteries while the dc power supply is there?

  3. Hi, This looks like a great circuit and just what I'm looking for. I have a few questions if anyone could help me. I'm not an expert, I'm just interested in electronics to help with my hobbies.

    1) I'd like the input to come from a car battery, I know these output around 12v-14v at about 40amps, so my question is, will this circuit be able to handle the input, or do I require some mods, If so, which ones?

    2) I was thinking of using a rechargeable battery pack, like the ones used for mobile phones, but how would I mod it so the output charge and input for charging are separate?

    The theory is that while the car is on, the device is running from the 12v and the battery pack is also being charged. When the car turns off, the 12v flips to the battery pack (not being charged as car is off) and continues to power the device.

    the Device in question is a Apple TV. I believe this to run on 3.4v. It uses 1.5w when on and is use and .5w when in sleep/standby.

    I've got it to sleep after 2mins of inactivity, but this currently doesn't come into play as the device comes on and goes off with the car startup and shutoff.

    Any help would be much appreciated.

    Thank you,

  4. Sorry, I forgot to mention that I require the output to be 1 ~ 1.75 amps as the Apple TV is rated at 1.75 amps max.

    Thank you