Abstract: A cell phone charging circuit of a USB interface. The charging circuit is supplied with a DC power of 5V via the USB interface and split into two, one has a first resister R1 connected to an emitter of a PNP transistor Q1 in series, and the other has two serially connected diodes D1 and D2. The diodes D1 and D2 have a negative thermal coefficient. The negative electrode of the diode D1 is connected to the base of the transistor, the collector of the transistor serves as a charging output terminal, such that the emitter voltage VEB of the transistor Q1 is the same as the voltage VD2 of the diode D2. Therefore, the current flowing through the resistor is VD1/R1, and the voltage and current limiting function is obtained. When the temperature of the battery increases for charging, the voltage VD1 is reduced to decrease the output current, such that temperature compensation is achieved.

Abstract: The invention discloses a connecting device installed on an external peripheral device for connecting the external peripheral device with mobile phones or PDAs that have different connection port specifications. The invention provides a connection base and a connector. The connection base is disposed on the external peripheral device and the connector is selected according to the connection port specifications of the accompanying electronic device. The connector connects the connection ports of the connection base and the electronic device, forming electrical communication between the connection base and the electronic device. This provides a wide variety of applications for external peripheral devices.