The following figure is a simple mobile phone battery charger circuit. Simple in design, easy to build and inexpensive. It uses LM78xx regulators to keep the output voltage stable and stable.

The mobile phone chargers available in the market are very expensive. The circuit shown here is shown as a low cost option to charge a mobile phone or battery pack rated at 7.2 volts, such as the Nokia 6110/6150.

220-240V AC power is stepped down to 9V AC by transformer X1. The transformer output is rectified by bridge-connected diodes D1 to D4, the positive DC supply is connected directly to the output contacts of the charger, and the negative terminal is connected through a current limiting resistor R2.

LED2 acts as a power indicator, resistor R1 acts as a current limiter, and LED3 indicates charging status. During charging, a voltage drop of approximately 3 volts occurs across resistor R2, turning on LED3 through resistor R3.

An external DC source (for example, from a car battery) can also be used to power the charger, where resistor R4 limits the input current to a safe value after polarity protection diode D5. The 3-terminal positive voltage regulator LM7806 (IC1) provides a fixed voltage output of 7.8V DC as LED1 interconnected between IC1’s common terminal (pin 2) and ground rail increases the output voltage to 7.8V DC. LED1 is also used as a power indicator for the external DC power supply.

After building the circuit on the veroboard, it is enclosed in a suitable enclosure. It is highly recommended to use a little heat sink for IC1.

Leave a Reply

Your email address will not be published.