Battery state monitoring circuit and battery device

• US 6,265,848 B1
• Filed: 04/20/1999
• Issued: 07/24/2001
• Est. Priority Date: 04/21/1998
• Status: Expired due to Term

• Current Assignee: Ablic Inc. (Minebea Mitsumi, Inc.)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Mukainakano, Hiroshi
• Primary Examiner(s): Riley, Shawn
• Assistant Examiner(s): Toatley, Gregory J.
• Application Number:
  US09/294,467
• Time in Patent Office: 826 Days
• Field of Search: 320/132, 307/43, 307/66, 307/125, 307/130
• US Class Current: 320/132
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0047 with monitoring or indicating devices or circuits
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

In a battery state monitoring circuit including a voltage regulator therein, power supply of the voltage regulator is applied from a higher voltage either of a battery or a charger. Also, when the output voltage of the voltage regulator becomes lower, there is structured such as to provide a voltage detecting circuit that sends a signal to the micro-computer.

Claims

1. A battery state monitoring circuit for a portable electronic device, comprising:

an external connection terminal connectable to a secondary battery, to an external load driveable by the secondary battery, to an external charger for charging the secondary battery, and to at least one switch element connected between the secondary battery and the external connection terminal;

a control circuit for controlling the charge/discharge state of the secondary battery by controlling the on/off state of the at least one switch element;

a monitoring circuit for monitoring at least one of a voltage and a discharge current of the secondary battery;

a voltage change-over circuit connectable to the secondary battery, the external connection terminal, and the monitoring circuit for supplying a power supply voltage to at least the monitoring circuit by selecting the higher voltage of a voltage at the external connection terminal and the secondary battery voltage;

a voltage regulator connected to an output of the voltage change-over circuit for supplying a regulated voltage to at least the monitoring circuit; and

a circuit for suspending operation of the monitoring circuit when an output voltage of the voltage regulator is below a predetermined level adequate to ensure stable operation of the monitoring circuit so that the monitoring circuit is operative only when the selected power supply voltage supplied thereto is higher than the predetermined level;

wherein the monitoring circuit controls the at least one switch element so that the secondary battery is disconnected from the external connection terminal when the selected power supply voltage is lower than the predetermined level.

2. A battery state monitoring circuit according to claim 1;

wherein the voltage change-over circuit comprises a first diode having an anode connected to the external connection terminal and a cathode connected to at least the monitoring circuit, and a second diode having an anode connected to the secondary battery and a cathode connected tc a power input terminal of the monitoring circuit, so that cathodes of the first and second diodes are connected to each other and the higher voltage of a voltage applied to the external connection terminal by the charger and the voltage of the secondary battery is supplied to the power input terminal of the monitoring circuit.

3. A battery state monitoring circuit according to claim 1;

wherein the voltage change-over circuit comprises a comparing circuit for comparing a voltage at the external connection terminal with a voltage of the secondary battery and producing an output signal in accordance with the comparison result, and a switch element for connecting one of the voltage at the external connection terminal and the voltage of the secondary battery as a supply voltage to at least the monitoring circuit in accordance with the output signal of the comparing circuit.

4. A battery state monitoring circuit according to claim 1;

wherein the monitoring circuit comprises a processing circuit for processing at least one of the voltage and the charge/discharge current of the secondary battery and controlling the switch in accordance therewith.

5. A battery state monitoring circuit according to claim 4;

wherein the monitoring circuit further comprises a sense resistor connected to the secondary battery for converting a current output by the secondary battery into a voltage, and an amplifier for amplifying the voltage across the resistor to a desired level, an output of the amplifier being supplied to the processing circuit to monitor the charge/discharge current of the secondary battery.

6. A battery state monitoring circuit according to claim 4;

wherein the monitoring circuit further comprises an amplifier for amplifying the secondary battery voltage to a desired level and supplying an amplified output voltage to the processing circuit for monitoring the voltage of the secondary battery.

7. A battery state monitoring circuit according to claim 6;

wherein the secondary battery comprises a plurality of secondary batteries connected in series, and the monitoring circuit further comprises a multiplexer connected to the amplifier for selectively monitoring the voltage of the respective secondary batteries.

8. A battery state monitoring circuit according to claim 1;

wherein the monitoring circuit comprises a battery voltage detecting circuit for detecting a voltage of the secondary battery, a current detecting circuit for detecting a current of the secondary battery, and a processing circuit receptive of outputs of the voltage detecting circuit and the current detecting circuit for outputting a signal for controlling the at least one switch element for controlling the charge/discharge state of the secondary battery in accordance with the detected voltage and current.

9. A battery device for a portable electronic device, comprising:

external connection terminals;

a secondary battery connected in series with at least one of the external connection terminals, the external connection terminals comprising a plus terminal and a minus terminal of the battery device;

at least one switch element connected between the secondary battery and at least one of the external connection terminals, the on/off state of the at least one switch element controlling a voltage and a charge/discharge current of the secondary battery;

a monitoring circuit for monitoring at least one of the voltage and the charge/discharge current of the secondary battery;

a voltage change-over circuit for providing a power supply voltage to at least the monitoring circuit by selecting the higher voltage of the voltage between the plus terminal of the battery device and the switch element and the secondary battery voltage;

a voltage regulator connected to an output of the voltage change-over circuit for supplying a regulated voltage to at least the monitoring circuit;

and a circuit for suspending operation of the monitoring circuit when an output voltage of the voltage regulator is too low to ensure stable operation of the monitoring circuit so that the monitoring circuit is operative only when the selected power supply voltage supplied thereto is higher than the predetermined level;

wherein the monitoring circuit controls the at least one switch element so that the secondary battery is disconnected from the external connection terminal when the selected power supply voltage is lower than the predetermined level.

10. A battery device according to claim 9;

wherein the voltage change-over circuit comprises a first diode having an anode connected to one of the external connection terminals and a cathode connected to at least the monitoring circuit, and a second diode having an anode connected to the secondary battery and a cathode connected to a power input terminal of the monitoring circuit, so that cathodes of the first and second diodes are connected to each other and the higher voltage of a voltage applied to the one external connection terminal by a charger and the voltage of the secondary battery is supplied to the power input terminal of the monitoring circuit.

11. A battery device according to claim 9;

wherein the voltage change-over circuit comprises a comparing circuit for comparing a voltage at one of the external connection terminals with a voltage of the secondary battery and producing an output signal in accordance with the comparison result, and a switch element for connecting one of the voltage at the one external connection terminal and the voltage of the secondary battery as a supply voltage to at least the monitoring circuit in accordance with the output signal of the comparing circuit.

12. A battery device according to claim 9;

wherein the monitoring circuit comprises a processing circuit for processing at least one of the voltage and the charge/discharge current of the secondary battery and controlling the switch in accordance therewith.

13. A battery device according to claim 12;

wherein the monitoring circuit further comprises a sense resistor connected to the secondary battery for converting a current output by the secondary battery into a voltage, and an amplifier for amplifying the voltage across the resistor to a desired level, an output of the amplifier being supplied to the processing circuit to monitor the charge/discharge current of the secondary battery.

14. A battery device according to claim 12;

wherein the monitoring circuit further comprises an amplifier for amplifying the secondary battery voltage to a desired level and supplying an amplified output voltage to the processing circuit for monitoring the voltage of the secondary battery.

15. A battery device according to claim 14;

wherein the secondary battery comprises a plurality of secondary batteries connected in series, and the monitoring circuit further comprises a multiplexer connected to the second amplifier for selectively monitoring the voltage of the respective secondary batteries.

16. A battery device according to claim 9;

wherein the monitoring circuit comprises a battery voltage detecting circuit for detecting a voltage of the secondary battery, a current detecting circuit for detecting a current of the secondary battery, and a processing circuit receptive of outputs of the voltage detecting circuit and the current detecting circuit for outputting a signal for controlling the at least one switch element for controlling the charge/discharge state of the secondary battery in accordance with the detected voltage and current.

17. A battery state monitoring circuit for a portable electronic device, comprising:

a secondary battery voltage monitoring circuit for detecting a voltage of a secondary battery;

a monitoring circuit having a microcomputer for receiving an output of the secondary battery voltage monitoring circuit and calculating a battery state, a switch element connected between the secondary battery and an external connection load/charge terminal for controlling the charge/discharge state of the secondary battery under control of the microcomputer, and a regulator for supplying a regulated voltage to the microcomputer and the secondary battery voltage monitoring circuit;

a voltage change-over circuit connected between the secondary battery and the external connection load/charge terminal for supplying a voltage to the regulator selected by selecting the higher voltage of a voltage at the external connection terminal and the secondary battery voltage; and

a voltage detecting circuit for detecting the output voltage of the regulator and suspending operation of the microcomputer if the output voltage of the regulator is smaller than a predetermined voltage.