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.
Circuit diagram:
Q1 = BD139
D1 = 1N4001
D2 = 4.7V - 1/2W
R1 = 560R - 1/2W
C1 = 16V - 100uF
Note:
- If the polarity is incorrect, it will destroy the mobile battery. So take extreme care.
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10 comments:
Help!
Strange to say that, The output is not 4.7volt but 2.8volt (RMS) just. I use Digital power supply for the input voltage. This can replaceable “A” type USB input. Sure, it set to 5.1volt (RMS). The output result was 3.3volt (RMS) without D1 diode. Why it is not 5volt around? How can I solve this? Would you tell me what is wrong? (P.S: I know as TR pin-number are 1(Emitter)-2(Collector)-3(Base).)
@yongsik
As you know that the circuits published here are from many sources like Magazines, Websites etc... I can not build and test all the circuits. So this time i am going to make this circuit because of you. Please wait max 7 days while i make the circuit and publish it's picture and bug fixing solutions here.
Thank You.
Have you checked the circuit?
Can any mobile battery can be used?
@Sjiv
Unfortunately i haven't built this circuit and can't suggest you to built it. If you have any kind of problem with this so please make another one available on this site.
@Samjay
What kind of software?
SORRY PAL I MEAN THE CIRCUT .. :)
I read this article and I question my self how you going to obtain 4.7v if you have a zener in the base with the same voltage and a diode in the end. The zener going to reduce the voltage in the base and in the reality the voltage in the output is going to be like 4.1v and the last diode to work needs 0.6v so the voltage is 3.5v Just remove the zener from the base and the diode from the output and you obtain 4.6v.
Replace D1 with 1N 4007 and try again my friend
Replace D1 with 1N 4007 and C1 with 25 V 100 uF and then try again
To younsik's post. Dated: 21 FEBRUARY, 2010
Dear friend, this circuit is designed with very limited components to save money & time. If u still want to use it, then replace R1 with a 1K potentiometer. Start lowering the resistant value and adjust it until u get 4.7V output.
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