How to build USB Powered Mobile Phone Battery Charger

Description

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:

Parts:

• 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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Infinite Thin Mobile Phone

n the United States 2012 consumer electronics show, Chinese manufacturers Huawei technologies released a body in the thin thickness is only 6.68 mm smart phone  Ascend P1 S, become the CES smart phone thin. A few days before the Spring Festival of Chinese the traditional Chinese calendar, Japanese manufacturers NEC the company unveiled a fuselage is only 6.7 mm thickness smart phone Medias ES N-05 D, and Huawei that style of Ascend P1 S counterparts. Not the thinnest, only a thin, the industry still can be in "thin splendid", "thin out selling point" on how far?We can see above the thickness of the claim, and not all the thickness of the fuselage, but the thinnest thickness of the place, because some of the devices and the thickness of the design challenge, to make mobile phone in the "unlimited thin" on road to meet very big obstacles.
When the phone screen diagonal size has a transparent, the thickness of the smart phone has become the cell phone manufacturers now than the important selling point. But, do big easy, sacrifice some cost choice, but to do "ultra-thin" is not easy, and not cost to do, the challenge of it too much.
Reliability and standby is huge challenge. "Three ability, two challenges, profound, and each is a difficult to conquer mountain. More important production, high cost need highly profitable to bear and China's brand of mobile phone price insurmountable RMB 3000 Yuan.
There is a kind of show/touch screen solutions can also be reduce thickness and bring down the cost of advantage. Although AMOLED patent was Samsung firmly to control, but Touch on lens (TOL) and on cell technology can dramatically reduce the thickness of the Touch screen.
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