• Register
  • Login
  • Search 4 million + Products
    this message might be for you!

    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.

    attentionThe author D Mohankumar is not an active member anymore. Please take into consideration that the presented information might not be correct.
    ask a question

    51 Responses to "USB Cellphone Charger Circuit"

    1. Iftikhar Ahmad says: on March 23, 2010 at 5:58 am

      T1 & D1 will drop approx 0.7 volts each, so 5V (usb) min 1.4 volts will drop too much volts. More over it is mentioned if input polarity is wrong then battery will be damaged. In presence of D1 reverse volts will be blocked then how it can damage battery. Clarification of these facts required please

    2. Most Mobile battery is rated between 3.2 to 3.6 volts. Even if T1 and D1 drops voltage, sufficient voltage will be available to charge the battery. If required, ZD can be eliminated.But there will not be any regulation. D1 act as the polarity protector.But if the mobile battery terminal is connected in reverse,positive terminal of the battery goes to the negative of USB.This may harm the battery

      • Dear Mr. Mohankumar,

        I like your learned comments on the site. I am an electronics hobbyist (just begun). I want to make a dual power source cellphone charger. Source 1. 240 V AC supply
        Source 2. 1.5 V pencil cell that can be used in emergency.

        Sir, can you please send me a schematic


      • Dear Mr. Mohankumar,

        I like your learned comments on the site. I am an electronics hobbyist (just begun). I want to make a dual power source cellphone charger. Source 1. 240 V AC supply
        Source 2. 1.5 V pencil cell that can be used in emergency.

        Sir, can you please send me a schematic


      • Chinmoy Mitra says: on September 4, 2012 at 12:16 pm

        Dear Mohankumar,
        1. Your answer to Iftikar Ahmad is not convincing at all. The base emitter junction of T1 together with the diode D1 will drop 1.2V, so the final voltage at the output will be 3.2V, which is definitely not enough to charge a Li-On cellphone battery. And the output voltage shown in the schematic is 4.7V, such a blatant mistake!
        2. You mention that removing the zener diode will result in no regulation! I hope you are aware that the USB socket of any PC gives out REGULATED 5V DC. SO removal of the zener will not affect the regulation at all.
        3. Lastly, the whole circuit just does not serve any purpose at all, since the easiest way to charge a mobile phone battery is to directly connect it to the USB socket of a PC, the regulated 5V DC will charge the battery. Cool, isn’t it?

      • 1. If it were the base emitter then your current flow would also need to go through R1 which would really drop the voltage. Unless I am mistaken (it has been 5 year since I was into this type of stuff) the collector/emitter is the real voltage drop that we are concerned with as far as the voltage drop is concerned. This voltage drop is actually around 0.2V. So that raises it to a respectable 4.1V output if you have a 5V supply. Still not the 4.7 he was going for but it might work for some phones.
        If your going to talk about blatant mistakes you should at least get your own math right. 5 – 1.2 = 3.2? didn’t know that.
        2. Well it is true that it’s probably not needed and pretty sure it would need to be moved to have the right effect.
        3. I recently (the reason I’m even looking this stuff up)had my charge port on my phone go out and wanted a quick, and cheap alternative to buying a new phone or wall charging dock. This wont work for me but it was a fun mental exercise.

      • Chinmoy Mitra says: on October 27, 2012 at 8:46 pm

        Well Vox, it was good to see you respond to my post! You have been into this type of stuff for the past 5 years, and I have been into this kind of stuff for the past 35-40 years…but lets not blow our own trumpets. We are here, I believe, to help and guide others in this fascinating field of electronics.
        I would gracefully admit that I did make a silly mistake in my calculations. Actually, the base-emitter drop (0.7V) added to the diode D1 drop (again 0.7V) amounts to 1.4V; this when deducted from the zener voltage of 4.7V amounts to 3.3V so I was off by 0.1V! (Any book on basic electronics will tell you that the emitter of any transistor is always 0.7V lower than the base voltage).
        The current flow through R1 has nothing to do with this calculation, since the voltage across the zener diode is supposed to be regulated to 4.7V, and that is exactly what a zener is supposed to do, isn’t it?
        I would like to remind you once again that the “blatant” mistake is still there in the circuit diagram-the output can not be 4.7V under ANY circumstances, so PLEASE correct the schematic.
        Finally, I still believe that this circuit cannot serve the purpose it is designed to serve, and I feel really disturbed to see that even electrical engineering students think that “The USB mobile charger circuit is a good & useful ckt for me and others”…..!!
        I would also like to bring one more interesting fact to your notice, that a standard USB socket can supply 500mA current, which is enough to charge most mobile phone batteries.
        What it all boils down to is this: if you want to charge a mobile phone from a USB socket then simply connect your phone to the USB port, there is no need for any fancy circuit to do the job. And in case you don’t have access to a USB port, simply connect three ‘D’ size batteries (UM-1)in series and connect the output to the cellphone, the 4.5V will be sufficient to charge up the cellphone battery.
        We should refrain from publishing circuits just for filling up space and getting ‘thank you’ comments, the circuits should also be theoretically correct and practically viable. I am sorry if my comments seem harsh, I just wanted to be helpful. I am sure you are a learned person, and will take my comments with a sporting spirit. We all make mistakes, even I did it, and you pointed it out to me and I am happy for that. Wish you all the best.

      • prashant pal says: on July 24, 2014 at 1:05 pm

        i want to make solar charger so recommend me …what type of solar panel or dimension???

      • sir i want a solar mobile charger which can charge my mobile and solar panel is of 6v,
        please help me out

    3. this is a realy great and helpful site but D.Mohitkumar your doing a great job keep it up i am praying for your success.

    4. Hi Mohankumar, thanks for this schematic (USB mobile charger).

    5. Thanks for your interest in my circuit

    6. Hi Mohankumar, I have made one but no success charging for my old Nokia (6230i), displayed message on phone “Not charging”,
      I checked out voltage around 4.3V maybe current not enough.
      I use BD139. Same problem when I connected directly from USB port. Can you make another schematic with more high current output (maybe 300mA).

    7. USB out gives 5 volt regulated output, but not high current. This design is not for frequent charging but only for slow charging when we are doing work in PC. Some mobile phones require high current around 350 mA. Check the output from the circuit.Also check whether the pin is making contact with the phone socket.Also try with a new brand phone

      • Respected sir,
        can there be any alternative for the I/P ….
        As I am a student I need to submit this and it requires I/P from PC…

    8. Hi Mohankumar, maybe someone facing same problem with me, so I want to share this circuit, I’m not yet test this circuit.

    9. sir,
      i designed a rather very simple circuit for usb mobile charger having
      USB source : 5V
      2 resistance
      R1 = 5 ohm
      R2 = 20 ohm (R2||load)
      so my question is, what problems i might be facing and how each of those problems can be corrected…. and pls do explain me your circuit……..i a just a novice (no exp in designing )…
      waitin for your reply


      • D.Mohankumar says: on November 19, 2010 at 2:06 pm

        R1 is Resistor1.It is 560 Ohms.Since Ohm symbol is difficult to add in circuit diagrams, letter R or E is usually used to represent Ohm value.
        C1 is 100 Microfarad 25 volt capacitor and ZD is 4.7 volt 400 milli watt zener diode for regulating the output voltage to 4.7 volts.

    11. sir,
      I have so much of interest on your circuit.I want to implement your circuit for real purpose applications.Can you please give precautions to implement this circuit and where it is going to be implemented i.e.either PCB or Bread Board.

      • D.Mohankumar says: on December 16, 2010 at 8:44 am

        Dear Pandu

        You can assemble the circuit on a small piece of common PCB.This can be enclosed in a small box like one used in mobile charger.Use the ordinary USB pin and cord. In the USB cord, 4 wire are present. Red( +ve), Black(-ve), Green and White for data transmission. Use only Red and Black with correct polarity.Trim Green and White wires.

    12. Sir,
      How to check polarity and output i.e through which devices we are going to check these features.How to connect the o/p of the circuit to the mobile phone i.e through which data cable(can you specify it’s name).

      • D.Mohankumar says: on December 16, 2010 at 8:37 am

        Dear Pandu
        One simple way to check polarity of battery or output is using an LED. Connect 1K resistor in the Anode(long lead) of LED and use it.Touch the end of the resistor connected to the LED to one point and the other lead of the LED to the second point. LED glows only if the polarity is correct. If not, reverse the test.

        You can use the cord of a damaged mobile charger( with same type pin). Cut the cord below the charger box and use it. Usually a red or blue wire will be positive. Check the polarity and connect.

    13. Is there a way to include an antenna to get Rf to power the usb to charge a phone using a chip and amplifier? Im working on a RF charger for the cell phone. any ideas?

    14. CHANDRA PRAKASH MEENA says: on April 29, 2011 at 4:09 am

      I am an electrical engg. student.The USB mobile charger circuit is a good & useful ckt for me and others.

    15. vijaya lakshmi says: on June 2, 2011 at 4:03 pm


      shall we use a solarpanel in place of USB?

    16. dear sir i am intrested to start manu of mobile charger unit so u can send same helfull informashion regarding how to manu… of mobile charger

    17. can this circuit be used with 6 volt dc supply and if not than what changes are needed.i want to design the mobile charger circuit with 6 volt dc INPUT supply and 4.7V output AND current around 200-300mA.PLZ PROVIDE THE CHANGES NEED TO BE DONE.

    18. can this circuit be used with 6 volt dc supply and if not than what changes are needed.i want to design the mobile charger circuit with 6 volt dc INPUT supply and 4.7V output AND current around 200-300mA.PLZ PROVIDE THE CHANGES NEED TO BE DONE.

    19. hi
      i was trying to test this circuit using cicuit maker but i didnt find the same transistor type , what can be replaced instead of this transistor.

    20. Sir can you say that,the short circuiting in the circuit needed or not(which is shown in the diagram)between the resister r1 and t1?

    21. hi i am maria plz help me i am the student of 2nd year electronics i want to make a unnique electronic project pls guied me what should i do

    22. pls i am writing a project on mobile cell phone solar charger i dont know if you help me with some write up use it in chapter 2,3 and 4


    23. (i)What is the function of capacitor in this circuit?
      (ii)Can I replace the USB port by a 6V solar cell?
      Please sir answer me immediately because this is my college’s project.

    24. Dear Sir,

      I want to create a compact cellphone charger that will be able to charge multiple cellphones at once. I want this charger to be able to charge mobiles with different types of chargers.

      This charger aims at charging the cellphones while on long distance journeys(typically more than 5 hours), especially in trains. Can you please help me?

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

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

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

    28. 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.

    29. 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.

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

    31. 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?

      • 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.

      • C.Mitra says: on July 1, 2015 at 10:18 am

        Hello Anurag, you can try Awagatam Majumdar’s blog http://www.homemade-circuits.com/ 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.

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

    33. 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.

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

    You need to log in if you need to post comments on ElectroSchematics.com or register if you do not have an account.