Charging IC, charging apparatus and electronic device

A charging IC used for charging a rechargeable battery built into an electronic device, comprising:

• a power source unit that is fed with power from an external device connected to the electronic device to output constant currents;
• and
• a control unit that receives power-feeding information representative of a power feeding capacity of the external device by communicating with the external device and switches a magnitude of the constant currents applied from the power source unit to the rechargeable battery in accordance with the power-feeding capability of the external device,
• wherein the power source unit is fed with power from the external device connected to the electronic device and comprises a first power source circuit outputting a constant current and a second power source circuit outputting a constant current smaller than the constant current from the first power source circuit;
• and
• wherein the control unit is configured to apply the constant current from the second power source circuit to the rechargeable battery and switch output from the second power source circuit to the first power source circuit based on the power-feeding information provided from the external device to apply the constant current from the first power source circuit to the rechargeable battery.

A charging apparatus used for charging a rechargeable battery built into an electronic device, comprising:

• a first connector configured to connect to an external power source;
• a second connector configured to connect to an external device;
• a power source unit that is fed with power from an external power source having a drooping characteristic, the external power source being connected to the electronic device via the first connector, or an external device connected to the electronic device via the second connector;
• a switch that is disposed between the power source unit and the first and second connectors to switch connection of the external power source or the external device with the power source unit;
• a control unit;
• and
• an active element, disposed on a charging path of the rechargeable battery, the active element being constant-current controlled by the control unit, wherein
• the control unit, when the external power source is connected to the power source unit, applies a first constant current from the external power source to the rechargeable battery through the active element and applies a second constant current smaller than the first constant current from the power source unit to the rechargeable battery, without passing through the active element, after the rechargeable battery is charged with the first constant current to a predetermined voltage, and
• when the external device is connected to the power source unit, receives power-feeding information representative of a power feeding capacity of the external device from the external device and switches a magnitude of a constant current in accordance with the power-feeding capability of the external device to apply the constant current to the rechargeable battery.