Without any USB to phone battery charger circuit we can charging phone battery using port on USB computer , but it will quickly damage the phone battery, and the battery will bulge. Because the voltage which was issued on usb is 5 volts , while the average-voltage phone battery 3.5 - 3.7 volts. That's why this USB to phone battery charger circuit is required , this USB to phone battery charger circuit reduce votlage to 3.7 volt usb, but will not reduce currents and will make a durable phone battery.
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USB to phone battery charger circuit diagrams |
List of components :R1 : 1 KR2 : 330 RR3 : 4K7R4 : 300 RR5 : 27RD1 : 4.7 volt zener /1WC1 : 100uF/16VQ1 : BC548Q2 : BC558ALED1 : Green LedX1-1 : Vcc USBX1-4 : Ground USBX2-1 , X2-2 : To phone battery
See also this printed circuit board ( PCB ) of USB to phone battery charger :
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USB to phone battery charger printed circuit board |