This schematic diagram is used for charging lithium ion battery. The power source is from a computer's USB port. With this circuit, you do not need to build power supply circuits for charging your battery.
A USB port is a great power source for charging a single cell li-on battery. It is capable of supplying maximum 5.25V and 500 mA. The circuit above is a USB powered single cell li-on battery charger. LM3622 is used as the controller. This special purpose IC has a precise end-of-charge control and low battery leakage current about 200nA.