USB Cellphone Charger Circuit

Now you can charge your Mobile Phone from the USB outlet of PC. This simple usb cellphone charger circuit can give regulated 4.7 volts for charging the mobile phone. USB outlet can give 5 volts DC and 100 mA current which is sufficient for the slow charging of mobile phones.

USB Cell Phone Charger Circuit Schematic

usb mobile charger circuit diagram

Most of the Mobile Phone battery is 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 and 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 T1 is used to give the regulated output. Any medium power NPN transistor like CL100, BD139, TIP122 can be used. Zener diode ZD 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.

Note: If the polarity is incorrect, it will destroy the cellphone battery. So take extreme care.


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    i want 1amp 2amp mobile charger circuit in smps base .. isolated miminum cost

  • emax

    The circuit works fine without D1 diode to charge 3.7V Li-Ion battery.
    The transistor gets into partial saturation with sufficient base current with 4.7V at the base due to 1 Watt zener and R1 of 51 ohms. The base to collector voltage drop is around 0.8V for BD139 and for a fully charged battery voltage of 4.2V the current drops to the minimum level.

  • Name *nilesh

    how can i increas ampear of mobile charger from 700ma to 1000ma

  • C.Mitra

    I had last posted on this topic on October 27, 2012, nearly three years back. It is amazing that even after I had pointed out some serious mistakes in the circuit diagram, the schematic has not been corrected. Is is sad to see the moderator of this blog ignore the suggestions of a well wisher like me. The gullible people visiting this page are being fooled into thinking that this is a path-breaking invention of the 21st century! THIS CIRCUIT CAN NOT WORK! But who cares?

    • C.Mitra

      Hello Anurag, you can try Awagatam Majumdar’s blog for a huge archive of circuits and ideas.

      Most of the circuits are workable, some are tried out and some are experimental ideas needing more research. The best part of his blog is that he regularly answers to most of the queries put to him by his readers patiently, which is not commonly seen in other websites and blogs. Hope this will help.

    • Anurag

      Hello Mitra sir, really happy to know your concern for starters like us.

      Is there any websites or blogs similar which would be helpful for the beginners.

  • israfil

    hello sir how to upgrade output current eg 4.7 volt 300 ma to 4.7 1 amps

  • arxaios

    THIS DO NOT WORK… do not try it ..!! This is a simple 5Volt supply but it is not charging any mobile phone…maybe Chinese Phones probably…!

    The philosophy behind charging a iphone or a mobile phone is not with this circuit. The D+ and D- pins of an USB must be used for this to work.

    Thank you.

  • windrage

    debating not helpful, very counter productive in the case of new readers and new hobbyists. site needs venting area for vents and proper informational structure without the babble for people who just came to learn and not get confused thank you.

  • raj

    I require the circuit diagram of mobile charger from which we can charge mobile using AC supply(Ac mobile charger)


    I want to make a Emergency light using 4.5 volt battery please tell me ckt diagram .

  • boyet

    thankz… sir, I’m about to try this gadget…
    can I used this gadget to charge AAAX3 batteries?