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USB Powered Mobile Phone Battery Charger

Now you can charge your Mobile Phone from the USB outlet of PC

This simple circuit can give regulated 4.7 volts for charging a mobile phone. USB outlet can give 5 volts DC at 100mA current which is sufficient for the slow charging of mobile phones. Most of the Mobile Phone batteries are rated 3.6 volts at 1000 to 1300 mAh. These battery packs have 3 NiMh or Lithium cells having 1.2 volt rating. Usually the battery pack requires 4.5 volts at 300-500 mA current for fast charging.

But low current charging is better to increase the efficiency of the battery. The circuit described here provides 4.7 regulated voltage and sufficient current for the slow charging of the mobile phone. Transistor Q1 is used to give the regulated output. Any medium power NPN transistor like CL100, BD139, TIP122 can be used. Zener diode D2 controls the output voltage and D1 protects the polarity of the output supply. Front end of the circuit should be connected to a A type USB plug.

Connect a red wire to pin1 and black wire to pin 4 of the plug for easy polarity identification. Connect the output to a suitable charger pin to connect it with the mobile phone. After assembling the circuit, insert the USB plug into the socket and measure the output from the circuit. If the output is OK and polarity is correct, connect it with the mobile phone.

USB Powered Mobile Phone Charger Circuit Diagram

USB Powered Mobile Phone Charger Circuit Diagram


Q1 = BD139
D1 = 1N4001
D2 = 4.7V – 1/2W
R1 = 560R – 1/2W
C1 = 16V – 100uF


If the polarity is incorrect, it will destroy the mobile battery. So take extreme care.

Tags: usb feature, battery charger,

Comments on this post:

Milly Cammie
By Milly Cammie (0) 0Score: 

1 year ago:  Thanks for the great info. I agree with you. Can you please explain me that when the cell phone is open once time like External Battery i mean when we need to edit something in phone after damage its not work like the Mobile Power Pack. In these smart phone have great sale in the market and everybody need USB Battery Pack in the shape of backup to keep touch with peoples.

Sudheer Gupta

1 year ago:  Thanks for providing this great information along with circuit diagram. There is also another circuit diagram on USB Mobile Battery Charger in ElectronicsHub.Org website which is very simple and easy to understand.

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