Charger and integrated circuit having first and second charging currents

• US 7,554,298 B2
• Filed: 09/09/2005
• Issued: 06/30/2009
• Est. Priority Date: 09/28/2004
• Status: Active Grant

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Inventors: Okamoto, Manabu, Mori, Kiyoshi
• Primary Examiner(s): Ullah; Akm E
• Assistant Examiner(s): WILLIAMS, ARUN C
• Application Number:
  US11/221,894
• Publication Number:
  US 20060076928A1
• Time in Patent Office: 1,390 Days
• Field of Search: 320/137, 320/138, 320/158, 320/159, 320/163, 320/164, 320/170, 320/FOR.126, 320/101, 320/132, 307/46
• US Class Current: 320/138
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries

Abstract

A charger of the present invention includes a charging transistor and a charging integrated circuit. The charging transistor is series-connected with a secondary battery to supply a charging current to the secondary battery. The charging integrated circuit is incorporated into a package having a higher heat releasability than that of the charging transistor. The charging integrated circuit controls the charging transistor and besides, supplies a charging current to the secondary battery. For this purpose, the charging integrated circuit includes a current source supplying this charging current. The charging current from the current source is supplied to the secondary battery together with the charging current from the charging transistor to charge the secondary battery.

Claims

1. A charger, comprising:

a charging transistor series-connected with a secondary battery and supplying a first charging current from a first power source to the secondary battery; and

a charging integrated circuit controlling the charging transistor,

wherein the charging integrated circuit includes a current source supplying a second charging current to the secondary battery, and

the current source supplies the second charging current together with the first charging current to the secondary battery, wherein said current source supplying said second charging current comprises a second charging transistor that is series-connected between said secondary battery and a voltage terminal of said charging integrated circuit.

2. The charger according to claim 1, wherein the charging integrated circuit has a thermal resistance smaller than a thermal resistance of the charging transistor.

3. The charger according to claim 2, wherein the charging integrated circuit includes:

a current detection circuit detecting the first charging current and the second charging current; and

a control circuit controlling the charging transistor based on a detection result of the current detection circuit.

4. The charger according to claim 2, wherein the charging integrated circuit includes:

a current detection circuit detecting the first charging current and the second charging current; and

a control circuit controlling the charging transistor and the current source based on a detection result of the current detection circuit.

5. The charger according to claim 2, further comprising a control circuit controlling the current source based on a result of detecting a charging voltage of the secondary battery.

6. The charger according to claim 1, wherein the charging integrated circuit includes:

a current detection circuit detecting the first charging current and the second charging current; and

a control circuit controlling the charging transistor based on a detection result of the current detection circuit.

7. The charger according to claim 1, wherein the charging integrated circuit includes:

a current detection circuit detecting the first charging current and the second charging current; and

a control circuit controlling the charging transistor and the current source based on a detection result of the current detection circuit.

8. The charger according to claim 7, wherein the current source supplies a constant current in response to control of the control circuit.

9. The charger according to claim 7,

wherein a charging period for the secondary battery includes a constant-current charging period for charging the secondary battery with a constant current, and a constant-voltage charging period for charging the secondary battery at a constant voltage, and

the control circuit controls the charging transistor and the current source during at least the constant-current charging period.

10. The charger according to claim 1, further comprising a control circuit controlling the current source based on a result of detecting a charging voltage of the secondary battery.

11. The charger of claim 1, wherein said second charging transistor is controlled as a current mirror.

12. A charger, comprising:

a first charging current source supplying a first charging current to a secondary battery;

a second charging current source supplying a second charging current together with the first charging current to the secondary battery; and

a charging control circuit controlling the first charging current source and the second charging current source,

wherein the second charging current source and the charging control circuit are incorporated into one package, wherein said second charging current source comprises a transistor controlled as a current mirror.

13. The charger according to claim 12, wherein the package into which the second charging current source and the charging control circuit are incorporated, has a thermal resistance smaller than a thermal resistance of a package into which the first charging current source is incorporated.

14. An integrated circuit controlling a charging transistor series-connected with a secondary battery and supplying a first charging current to the secondary battery, comprising:

a control circuit controlling the charging transistor; and

a charging current source supplying a second charging current to the secondary battery,

wherein the second charging current is supplied together with the first charging current to the secondary battery, wherein said charging current source comprises a transistor controlled as a current mirror.

15. The integrated circuit according to claim 14, further comprising:

a detection circuit detecting the first charging current and the second charging current supplied to the secondary battery,

wherein the control circuit controlling the charging transistor and the charging current source based on a detection result of the detection circuit.

16. The integrated circuit according to claim 15, further comprising a monitoring circuit monitoring a charged state of the secondary battery.

17. The integrated circuit according to claim 14, further comprising a monitoring circuit monitoring a charged state of the secondary battery.