Charge/discharge type power supply

• US 20020018329A1
• Filed: 06/01/2001
• Published: 02/14/2002
• Est. Priority Date: 06/02/2000
• Status: Active Grant

• Current Assignee: Ablic Inc. (MinebeaMitsumi Inc.)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Yoshida, Shinichi
• Granted Patent: US 6,690,559 B2
• Time in Patent Office: Days
• US Class Current: 361/93.1
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/00306 Overdischarge protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence

Abstract

There is provided a charge/discharge type power supply that includes a MOS transistor (normally called “four-terminal MOS transistor”) of which a source, a drain, a gate and a body are separated from each other as a switching element that controls both of the charge operation and the discharge operation, and provides a charge/discharge control circuit with a function of controlling the charge/discharge operation in accordance with a voltage of a secondary battery, a function of detecting a voltage that varies in accordance with a current that flows in the switching elements to control the charge/discharge operation, and a function of recognizing whether a charger or a load is connected to an external connection terminal to control the charge/discharge operation; wherein one signal line is used for controlling the on/off operation of the switching element, and both of the charge operation and the discharge operation can be controlled without any diode.

Claims

1. A charge/discharge type power supply, comprising:

a chargeable and dischargeable secondary battery;

a switching element connected in series to said secondary battery;

an external connection positive terminal and an external connection negative terminal which are connected to a charger or a load; and

a charge/discharge control circuit that monitors a voltage across said secondary battery, a voltage across said switching element and a voltage between said external connection positive terminal and said external connection negative terminal to control the on/off operation of said switching element;

wherein a positive terminal of said secondary battery is connected to said external connection positive terminal, a negative terminal of said secondary battery is connected to said external connection negative terminal through said switching element, said charge/discharge control circuit is connected in parallel with said secondary battery, an over-current detection terminal of said charge/discharge control circuit is connected to said external connection negative terminal, and the charge/discharge control terminal of said charge/discharge control circuit is connected to an input terminal that controls the on/off operation of said switching element.

3. A charge/discharge type power supply as claimed in claim 1, wherein said switching element is a MOS transistor, and the source, the drain, the gate and the body of said MOS transistor are separated from each other, and diodes are inserted between the body and the source of said MOS transistor and between the body and drain thereof so as to be oppositely directed.

5. A charge/discharge type power supply as claimed in claim 1, wherein said charge/discharge control circuit comprises:

an over-charge detecting circuit for detecting a state in which the voltage of said secondary battery is higher than a predetermined voltage value (an over-charge detection voltage);

an over-discharge detecting circuit for detecting a state in which the voltage of said secondary battery is lower than a predetermined voltage value (an over-discharge detection voltage);

an over-current detecting circuit for detecting a state in which the voltage across said switching element is higher than a predetermined voltage value (an over-current detection voltage);

a charger detecting circuit for detecting a state in which a voltage between said external connection positive terminal and said external connection negative terminal is higher than a predetermined voltage value (a charger detection voltage); and

a control circuit for controlling the on/off operation of said switching element that controls the charge/discharge operation of said secondary battery upon receiving an output from said over-charge detecting circuit, an output from said over-discharge detecting circuit, an output from said over-current detecting circuit and an output from said charger detecting circuit.

7. A charge/discharge type power supply as claimed in claim 1, wherein said charge/discharge control circuit controls said switching element so as to be turned on in the case where the voltage of said secondary battery is the over-discharge detection voltage or more and the over-charge detection voltage or less, and the voltage across said switching element is the over-current detection voltage or less.

9. A charge/discharge type power supply as claimed in claim 1, wherein said charge/discharge control circuit controls said switching element so as to be turned off in the case where the voltage across said switching element is higher than the over-current detection voltage.

11. A charge/discharge type power supply as claimed in claim 1, wherein said charge/discharge control circuit controls said switching element so as to be turned off when the voltage between said external positive connection terminal and said external connection negative terminal is the charger detection voltage or less and so as to be turned on when the voltage between said external positive connection terminal and said external connection negative terminal is higher than the charger detection voltage, in the case where the voltage of said secondary battery is lower than the over-discharge detection voltage.

13. A charge/discharge type power supply as claimed in claim 1, wherein said charge/discharge control circuit controls said switching element so as to be turned on when the voltage between said external positive connection terminal and said external connection negative terminal is the charger detection voltage or less and when the voltage across said switching element is the over-current detection voltage or less, and so as to be turned off when the voltage between said external positive connection terminal and said external connection negative terminal is higher than the charger detection voltage or when the voltage across said switching element is higher than the over-current detection voltage, in the case where the voltage of said secondary battery is higher than the over-charge detection voltage.

15. A charge/discharge type power supply as claimed in claim 1, wherein said charge/discharge control circuit controls said switching element so as to be turned off when two or more secondary batteries are connected in series, in which one secondary battery whose voltage is higher than the over-charge detection voltage and another secondary battery whose voltage is lower than the over-discharger detection voltage coexist.

17. A charge/discharge type power supply as claimed in claim 1, wherein the gate and the body of said MOS transistor are connected to each other through a resistor.

19. A charge/discharge type power supply as claimed in claim 1, wherein said switching element comprises a plurality of MOS transistors.

21. A charge/discharge type power supply as claimed in claim 1, wherein the output of said over-current detecting circuit has a delay time.

2. A charge/discharge type power supply, comprising:

a chargeable and dischargeable secondary battery;

a switching element connected in series to said secondary battery;

an external connection positive terminal and an external connection negative terminal which are connected to a charger or a load; and

a charge/discharge control circuit that monitors a voltage across said secondary battery, a voltage across said switching element and a voltage between said external connection positive terminal and said external connection negative terminal to control the on/off operation of said switching element;

wherein a negative terminal of said secondary battery is connected to said external connection negative terminal, a positive terminal of said secondary battery is connected to said external connection positive terminal through said switching element, said charge/discharge control circuit is connected in parallel with said secondary battery, an over-current detection terminal of said charge/discharge control circuit is connected to said external connection positive terminal, and the charge/discharge, control terminal of said charge/discharge control circuit is connected to an input terminal that controls the on/off operation of said switching element.

4. A charge/discharge type power supply as claimed in claim 2, wherein said switching element is a MOS transistor, and the source, the drain, the gate and the body of said MOS transistor are separated from each other, and diodes are inserted between the body and the source of said MOS transistor and between the body and drain thereof so as to be oppositely directed.

6. A charge/discharge type power supply as claimed in claim 2, wherein said charge/discharge control circuit comprises:

an over-charge detecting circuit for detecting a state in which the voltage of said secondary battery is higher than a predetermined voltage value (in over-charge detection voltage);

an over-discharge detecting circuit for detecting a state in which the voltage of said secondary battery is lower than a predetermined voltage value (an over-discharge detection voltage);

an over-current detecting circuit for detecting a state in which the voltage across said switching element is higher than a predetermined voltage value (an over-current detection voltage);

a charger detecting circuit for detecting a state in which a voltage between said external connection positive terminal and said external connection negative terminal is higher than a predetermined voltage value (a charger detection voltage); and

a control circuit for controlling the on/off operation of said switching element that controls the charge/discharge operation of said secondary battery upon receiving an output from said over-charge detecting circuit, an output from said over-discharge detecting circuit, an output from said over-current detecting circuit and an output from said charger detecting circuit.

8. A charge/discharge type power supply as claimed in claim 2, wherein said charge/discharge control circuit controls said switching element so as to be turned on in the case where the voltage of said secondary battery is the over-discharge detection voltage or more and the over-charge detection voltage or less, and the voltage across said switching element is the over-current detection voltage or less.

10. A charge/discharge type power supply as claimed in claim 2, wherein said charge/discharge control circuit controls said switching element so as to be turned off in the case where the voltage across said switching element is higher than the over-current detection voltage.

12. A charge/discharge type power supply as claimed in claim 2, wherein said charge/discharge control circuit controls said switching element so as to be turned off when the voltage between said external positive connection terminal and said external connection negative terminal is the charger detection voltage or less and so as to be turned on when the voltage between said external positive connection terminal and said external connection negative terminal is higher than the charger detection voltage, in the case where the voltage of said secondary battery is lower than the over-discharge detection voltage.

14. A charge/discharge type power supply as claimed in claim 2, wherein said charge/discharge control circuit controls said switching element so as to be turned on when the voltage between said external positive connection terminal and said external connection negative terminal is the charger detection voltage or less and when the voltage across said switching element is the over-current detection voltage or less, and so as to be turned off when the voltage between said external positive connection terminal and said external connection negative terminal is higher than the charger detection voltage or when the voltage across said switching element is higher than the over-current detection voltage, in the case where the voltage of said secondary battery is higher than the over-charge detection voltage.

16. A charge/discharge type power supply as claimed in claim 2, wherein said charge/discharge control circuit controls said switching element so as to be turned off when two or more secondary batteries are connected in series, in which one secondary battery whose voltage is higher than the over-charge detection voltage and another secondary battery whose voltage is lower than the over-discharger detection voltage coexist.

18. A charge/discharge type power supply as claimed in claim 2, wherein the gate and the body of said MOS transistor are connected to each other through a resistor.

20. A charge/discharge type power supply as claimed in claim 2, wherein said switching element comprises a plurality of MOS transistors.

22. A charge/discharge type power supply as claimed in claim 2, wherein the output of said over-current detecting circuit has a delay time.