Charging IC, charging apparatus and electronic device

• US 20070001646A1
• Filed: 10/28/2005
• Published: 01/04/2007
• Est. Priority Date: 07/01/2005
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Kojima, Masakazu
• Granted Patent: US 7,733,060 B2
• Time in Patent Office: Days
• US Class Current: 320/128
• CPC Class Codes: H02J 5/00 Circuit arrangements for transfer of electric power between ac networks and dc networks H02J3/36 takes precedence
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/00309 Overheat or overtemperature protection
• CPC Class Codes: H02J 7/0032 disconnection of loads if battery is not under charge, e.g. in vehicle if engine is not running
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: H02J 7/02 for charging batteries from ac mains by converters

Abstract

The present invention relates to charging of rechargeable batteries built into electronic devices and is configured to constrain heat generation during the charging. A charging IC used for charging a rechargeable battery built into an electronic device is disclosed that comprises a power source unit which can be fed with power from an external power source with a drooping characteristic to pick up a constant current; and a control unit which applies a first constant current from the external power source to the rechargeable battery through a circuit element installed on a charging path of the rechargeable battery, the control unit applying a second constant current smaller than the first constant current from the power source unit to the rechargeable battery after the rechargeable battery is charged with the first constant current to a predetermined voltage.

Claims

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

a power source unit which can be fed with power from an external power source with a drooping characteristic to pick up a constant current; and

a control unit which applies a first constant current from the external power source to the rechargeable battery through a circuit element disposed on a charging path of the rechargeable battery, the control unit applying a second constant current smaller than the first constant current from the power source unit to the rechargeable battery after the rechargeable battery is charged with the first constant current to a predetermined voltage.

2. The charging IC of claim 1,

wherein the power source unit is fed with power from an external device connected to the electronic device to output the constant current or a constant voltage, and

wherein the control unit is configured to apply a constant voltage from the power source unit to the rechargeable battery to switch over to constant-voltage charging after the charging with the second constant current.

3. The charging IC of claim 1,

wherein the external power source is an AC adaptor converting an alternate current received from an alternate-current power source into a direct current with a predetermined voltage to be picked up.

4. The charging IC of claim 1,

wherein the power source unit is a switching power source converting direct-current input to direct-current output.

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

a power source unit which is fed with power from an external device connected to the electronic device to output constant currents; and

a control unit which switches constant currents applied from the power source unit to the rechargeable battery based on power-feeding information provided from the external device.

6. The charging IC of claim 5,

wherein the power source unit is fed with power from an 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 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 power-feeding information provided from the external device to apply the constant current to the rechargeable battery.

7. The charging IC of claim 5,

wherein the external device is an electronic device connected by a USB cable.

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

a power source unit which is fed with power from an external power source having a drooping characteristic or an external device connected to the electronic device;

a switch which is disposed between the power source unit and the external power source or the external device to switch connection of the external power source or the external device with the power source unit;

a circuit element disposed on a charging path of the rechargeable battery; and

a control unit, if the external power source is connected to the power source unit, applying a first constant current from the external power source to the rechargeable battery through the circuit element and applying a second constant current smaller than the first constant current from the power source unit to the rechargeable battery after the rechargeable battery is charged with the first constant current to a predetermined voltage, the control unit, if the external device is connected to the power source unit, switching a constant current in accordance with a power-feeding capability of the external device based on power-feeding information provided from the external device to apply the constant current to the rechargeable battery.

9. The charging apparatus of claim 8,

wherein the switch is configured to select either the external power source or the external device or select the external power source to connect to the power source unit, if both of the external power source and the external device are connected.

10. The charging apparatus of claim 8,

wherein the control unit is configured to select either the external power source or the external device with the switch to connect to the power source unit, if both of the external power source and the external device are connected.

11. The charging apparatus of claim 8,

wherein the power source unit is fed with power from an external device connected to the electronic device to output a current or voltage in accordance with a power-feeding capability of the electronic device;

and

wherein the control unit is configured to switch over to constant-voltage charging after the charging with the second constant current.