Charging device

• US 4,792,743 A
• Filed: 11/14/1986
• Issued: 12/20/1988
• Est. Priority Date: 11/15/1985
• Status: Expired due to Term

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Tsujino, Kazuhiro, Koyabu, Seiji
• Primary Examiner(s): HICKEY, ROBERT
• Application Number:
  US06/930,490
• Time in Patent Office: 767 Days
• Field of Search: 320/13, 320/14, 320/15-17, 320/22-24, 320/39, 320/40
• US Class Current: 320/124
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/00714 in response to battery charging or discharging current
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: Y10S 320/13 Fault detection
• CPC Class Codes: Y10S 320/19 Charger status, e.g. voltmeter

Abstract

A battery charging device including a series transistor inserted between a source circuit and a battery, and a comparison circuit which compares the voltage at the terminal of the battery and the voltage of an output of the source circuit so as to turn off the series transistor when the terminal voltage is higher than the output voltage, whereby, when the terminal voltage of the battery becomes higher than the output voltage of the source circuit at the time of an interruption of supply of power, the series transistor is brought into the off-state to prevent the battery from being discharged. The charging device further includes circuits for connecting a plurality of batteries successively to the source circuit for charging, switching control circuit means for operating said connecting circuits sequentially upon detection of a battery fully-charged state or short-circuited battery condition, and timing circuits for controlling the time of connection of short-circuit detection circuits and for temporarily prohibiting operation of the switching control circuit so that each of a total short-circuited condition, a partial short-circuited condition, and an over-discharged condition of a battery can be identified and the switching control circuit can be caused to appropriately operate or not operate in response to each condition.

Claims

1. A battery charging device comprising:

a constant current source;

a plurality of battery circuit lines for connecting each of a plurality of batteries, respectively, to the constant current source to be charged thereby;

a plurality of switch circuits for controlling the supply of current from the constant current source to each of the respective battery circuit lines;

a full-charge detection means of detecting upon connection to a battery a fully charged state of the battery;

a short-circuit detection circuit for determining whether a battery is short-circuited by measuring voltage level at a connection terminal of the battery at a selected time after said constant current source is connected thereto;

a switching control circuit means for switching said battery circuit line switch circuits one after another to successively connect each of said plurality of batteries to said constant current source to be charged, said switching control circuit means operating upon detection of one of a battery fully charged state and a short-circuited battery condition; and

a source voltage control circuit means for maintaining source voltage of the switching control circuit means when a battery connection terminal is short-circuited, including a series transistor connected in circuit between the constant current source and the battery circuit lines and a circuit including a control transistor connected to the series transistor and a Zener diode connected between the base of the control transistor and the constant current source to control the conducting condition of the series transistor in response to output voltage of the constant current source such that said source voltage control circuit means operates to drive said control transistor to a non-conducting condition to disconnect said constant current source from said battery circuit lines upon a drop in voltage due to connection of a short-circuited battery, said short-circuit detection circuit and said switching control circuit means being connected to said constant current source at a side of said control transistor connected to said constant current source so as to maintain connection of source voltage thereto and sustain operation of said short-circuit detection circuit and said switching control circuit means to disconnect said short-circuited battery from said constant current source and connect another battery to be charged.

2. A battery charging device as defined in claim 1, further including a short-circuit detection prohibiting circuit for prohibiting the switching operation of said switching control circuit, even when it is determined by the short-circuit detection circuit that the battery is in a short-circuited state, until terminal voltage of the battery being charged reaches a near steady state.

3. A battery charging device as defined in claim 1, further including a switch means which is turned on when each battery is connected to the constant current source, a rising detection circuit which detects the rising of an output from said switch means, and a signal forming circuit which forms an initially set signal on the basis of an output generated by said rising detection circuit, the switching control circuit means being set in an initial state by said initially set signal.

4. A battery charging device as defined in claim 1, further including an abnormal-charging condition detection circuit which detects whether a connected battery is charged in an abnormal condition, and a display means which identifies whether the condition of the battery is abnormally charged or fully charged.

5. A battery charging device as defined in claim 1, further including a battery and constant current source detection circuit for turning said series transistor on only when said constant current source is connected at a given position.

6. A battery charging device comprising:

a constant current source;

a plurality of battery circuit lines for connecting each of a plurality of batteries, respectively, to the constant current source to be charged thereby;

a plurality of switch circuits for controlling the supply of current from the constant current source to each of the respective battery circuit lines;

a full-charge detection means for detecting upon connection to a battery a fully charged state of the battery;

a short-circuit detection circuit for determining whether a battery is short-circuited by measuring voltage level at a connection terminal of the battery at a selected time after said constant current source is connected thereto;

an over-discharged battery discrimination means for determining whether a battery is over-discharged on the basis of measurement of an initial voltage of the output of the constant current source immediately after connection of the battery thereto, a charging voltage below a preset threshold being recognized as determining that an over-discharged battery has been connected for charging; and

means operated in accordance with said determination for setting a time of connection of said full-charge detection means to said battery to start detection of a fully-charged state of the battery to begin at a time later than a time at which said full-charge detection means is connected for detection of full-charge of a normally discharged battery, such that false detection of a charging condition of said over-discharged battery as a full-charge condition will be prevented; and

a switching control circuit means for switching said battery circuit line switch circuits one after another to successively connect each of said plurality of batteries to said constant current source to be charged, said switching control circuit means operating upon detection of one of a battery fully charged state and a short-circuited battery condition.

7. A battery charging device as defined in claim 6, further including a short-circuit detection prohibiting circuit for prohibiting the switching operation of said switching control circuit, even when it is determined by the short-circuit detection circuit that the battery is in a short-circuited state, until terminal voltage of the battery being charged reaches a near steady state.

8. A battery charging device as defined in claim 6, further including a switch means which is turned on when each battery is connected to the constant current source, a rising detection circuit which detects the rising of an output from said switch means, and a signal forming circuit which forms an initially set signal on the basis of an output generated by said rising detection circuit, the switching control circuit means being set in an initial state by said initially set signal.

9. A battery charging device as defined in claim 6, further including an abnormal-charging condition detection circuit which detects whether a connected battery is charged in an abnormal condition, and a display means which identifies whether the condition, and a display means which identifies whether the condition of the battery is abnormally charged or fully charged.

10. A battery charging device as defined in claim 6 further including a series transistor connected in circuit between the constant current source and the battery circuit lines, and a battery and constant current source detection circuit for turning said series transistor on only when said constant current source is connected at a given position.

11. A battery charging device comprising:

a constant current source;

a plurality of battery circuit lines for connecting each of a plurality of batteries, respectively, to the constant current source to be charged thereby;

a plurality of switch circuits for controlling the supply of current from the constant current source to each of the respective battery circuit lines;

a full-charge detection means for detecting upon connection to a battery a fully charged state of the battery;

a short-circuit detection circuit for determining whether a battery is short-circuited by measuring voltage level at a connection terminal of the battery at a selected time after said constant current source is connected thereto;

a series transistor connected in circuit between the constant current source and the battery circuit lines, and a reverse current detection circuit including a comparison circuit which compares terminal voltage of a battery with output voltage of the constant current source and operates to turn the series transistor to an off state when the terminal voltage of the battery is higher than the output voltage of the constant current source; and

a switching control circuit means for switching said battery circuit line switch circuits one after another to successively connect each of said plurality of batteries to said constant current source to be charged, said switching control circuit means operating upon detection of one of a battery fully charged state and a short-circuited battery condition;

wherein said short-circuit detection circuit includes a first short-circuit detection circuit which detects if the charging voltage reaches a first reference voltage within a first predetermined period of time, and a second short-circuit detection circuit which detects if the charging voltage reaches a second reference voltage, which is higher than said first reference voltage, within a second predetermined period of time which is longer than said first predetermined period of time.

12. A battery charging device comprising:

a constant current source;

a plurality of battery circuit lines for connecting each of a plurality of batteries, respectively, to the constant current source to be charged thereby;

a plurality of switch circuits for controlling the supply of current from the constant current source to each of the respective battery circuit lines;

a full-charge detection means for detecting upon connection to a battery a fully charged state of the battery;

a short-circuit detection circuit for determining whether a battery is short-circuited by measuring voltage level at a connection terminal of the battery at a selected time after said constant current source is connected thereto;

a switching control circuit means for switching said battery circuit line switch circuits one after another to successively connect each of said plurality of batteries to said constant current source to be charged, said switching control circuit means operating upon detection one of a battery fully charged state and a short-circuited battery condition; and

a source voltage control circuit means for maintaining source voltage of the switching control circuit means when a battery connection terminal is short-circuited, including a series transistor connected in circuit between the constant current source and the battery circuit lines and a circuit including a control transistor connected to the series transistor and a Zener diode connected between the base of the control transistor and the constant current source to control the conducting condition of the series transistor in response to output voltage of the constant current source;

wherein said short-circuit detection circuit includes a first short-circuit detection circuit which detects if the charging voltage reaches a first reference voltage within a first predetermined period of time, and a second short-circuit detection circuit which detects if the charging voltage reaches a second reference voltage, which is higher than said first reference voltage, within a second predetermined period of time which is longer than said first predetermined period of time.

13. A battery charging device comprising:

a constant current source;

a plurality of battery circuit lines for connecting each of a plurality of batteries, respectively, to the constant current source to be charged thereby;

a plurality of switch circuits for controlling the supply of current from the constant current source to each of the respective battery circuit lines;

a full-charge detection means for detecting upon connection to a battery a fully charged state of the battery;

a short-circuit detection circuit for determining whether a battery is short-circuited by measuring voltage level at a connection terminal of the battery at a selected time after said constant current source is connected thereto;

an over-discharged battery discrimination means for determining whether a battery is over-discharged on the basis of measurement of an initial voltage of the output of the constant current source immediately after connection of the battery thereto, and means operated in accordance with said determination for setting a time of connection of said full-charge detection means to said battery to start detection of a fully-charged state of the battery; and

a switching control circuit means for switching said battery circuit line switch circuits one after another to successively connect each of said plurality of batteries to said constant current source to be charged, said switching control circuit means operating upon detection of one of a battery fully charged state and a short-circuited battery condition;

wherein said short-circuit detection circuit includes a first short-circuit detection circuit which detects if the charging voltage reaches a first reference voltage within a first predetermined period of time, and a second short-circuit detection circuit which detects if the charging voltage reaches a second reference voltage, which is higher than said first reference voltage, within a second predetermined period of time which is long than said first predetermined period of time.