Battery connection detection circuit

• US 7,629,775 B2
• Filed: 03/01/2005
• Issued: 12/08/2009
• Est. Priority Date: 03/01/2004
• Status: Expired due to Fees

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Nishida, Junji
• Primary Examiner(s): Tso; Edward
• Assistant Examiner(s): Fantu; Yalkew
• Application Number:
  US10/589,682
• Publication Number:
  US 20080224669A1
• Time in Patent Office: 1,743 Days
• Field of Search: 320/165, 320/136, 429/150
• US Class Current: 320/165
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• 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 7/0036 using connection detecting circuits H02J7/0034 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery connection detection circuit is disclosed that is able to correctly determine an operation condition of a secondary battery and a connection condition between the secondary battery and a charging device. A determination circuit monitors both the voltage Vt1 on the battery connection terminal T1 and the current supplied to the secondary battery BAT, and therefore, the determination circuit can correctly determine the operation condition of the secondary battery and the connection condition between the secondary battery and the charging device even when high frequency noise is superposed on the power supply voltage Vdd, and when the power supply voltage decreases.

Claims

1. A battery connection detection circuit for detecting whether a secondary battery is operable and whether the secondary battery is reliably connected to a charging device, comprising:

a current supplying circuit configured to supply a current to the secondary battery;

a constant voltage circuit configured to control the current from the current supplying circuit so that a voltage on a connection terminal T1 for connecting the secondary battery is constant;

a constant current circuit configured to control the current from the current supplying circuit so that the current supplied to the secondary battery is constant; and

a determination circuit configured to concurrently determine operation states of both the constant voltage circuit and the constant current circuit, said determination circuit determining whether the secondary battery is operable and whether the secondary battery is reliably connected to the charging device according to the operation states of the constant voltage circuit and the constant current circuit,

wherein when it is determined that the current flowing through the secondary battery is higher than a predetermined value from the operation state of the constant current circuit, the determination circuit determines that the secondary battery is operable and the secondary battery is reliably connected to the connection terminal T1.

2. The battery connection detection circuit as claimed in claim 1, wherein the determination circuit determines an operation state of a load circuit that receives power supply from the secondary battery;

and

when it is detected that the load circuit does not consume a current, the determination circuit determines whether the secondary battery is operable and whether the secondary battery is reliably connected to the charging device according to the operation states of the constant voltage circuit and the constant current circuit.

3. The battery connection detection circuit as claimed in claim 1, wherein when it is determined that the voltage on the connection terminal T1 is lower than a predetermined value from the operation state of the constant current circuit, the determination circuit determines that the secondary battery is operable and the secondary battery is reliably connected to the connection terminal T1.

4. The battery connection detection circuit as claimed in claim 1, wherein the current supplying circuit includes a current control transistor that controls the current supplied to the secondary battery according to a control signal input to a control electrode thereof;

the constant voltage circuit includes

a voltage detection circuit that detects the voltage on the connection terminal T1 and outputs a voltage Vd1 proportional to the detected voltage,

a first calculation amplification circuit into which the output voltage Vd1 from the voltage detection circuit and a first reference voltage Vs1 are input, and

a first control transistor whose operation is controlled according to an output signal CV from the first calculation amplification circuit;

the constant current circuit includes

a current detection circuit that converts the current supplied by the current supplying circuit into a voltage and outputs the voltage,

a second calculation amplification circuit into which the output voltage from the current detection circuit and a second reference voltage Vs2 are input, and

a second control transistor whose operation is controlled according to an output signal CC from the second calculation amplification circuit; and

the current control transistor controls the current supplied to the secondary battery according to operations of the first control transistor and the second control transistor.

5. The battery connection detection circuit as claimed in claim 1, wherein the current supplying circuit includes a current control transistor that controls the current supplied to the secondary battery according to a control signal input to a control electrode thereof;

the constant voltage circuit includes

a voltage detection circuit that detects the voltage on the connection terminal T1 and outputs a voltage Vd1 proportional to the detected voltage,

a switching circuit that exclusively selects one of a plurality of input reference voltages Vr1 to Vrn according to an input control signal Sc1, and outputs the selected reference voltage as a first reference voltage Vs1,

a first calculation amplification circuit into which the output voltage Vd1 from the voltage detection circuit and the first reference voltage Vs1 are input, and

a first control transistor whose operation is controlled according to an output signal CV from the first calculation amplification circuit;

the constant current circuit includes

a current detection circuit that converts the current supplied by the current supplying circuit into a voltage and outputs the voltage,

a second calculation amplification circuit into which the output voltage from the current detection circuit and a second predetermined reference voltage Vs2 are input, and

a second control transistor whose operation is controlled according to an output signal CC from the second calculation amplification circuit; and

the current control transistor controls the current supplied to the secondary battery according to operations of the first control transistor and the second control transistor.

6. The battery connection detection circuit as claimed in claim 4, wherein the operation state of the constant voltage circuit corresponds to a state of the output signal CV from the first calculation amplification circuit;

and

the operation state of the constant current circuit corresponds to a state of the output signal CC from the second calculation amplification circuit.

7. The battery connection detection circuit as claimed in claim 4, wherein the current control transistor includes a MOS transistor.

8. The battery connection detection circuit as claimed in claim 4, wherein the current control transistor includes a bipolar transistor.

9. The battery connection detection circuit as claimed in claim 4, wherein the determination circuit determines the secondary battery is operable and the secondary battery is reliably connected to the connection terminal T1, when the output signal CV from the first calculation amplification circuit indicates that the output voltage Vd1 from the voltage detection circuit is lower than the first reference voltage Vs1, or when the output signal CC from the second calculation amplification circuit indicates that the output voltage from the current detection circuit is higher than or equal to the second reference voltage Vs2.

10. The battery connection detection circuit as claimed in claim 1, wherein the current supplying circuit, the constant voltage circuit, the constant current circuit, and the determination circuit are integrated in one Integrated Circuit (IC).

11. The battery connection detection circuit as claimed in claim 2, wherein the current supplying circuit, the constant voltage circuit, the constant current circuit, the determination circuit, and the load circuit are integrated in one Integrated Circuit (IC).

12. The battery connection detection circuit as claimed in claim 4, wherein the determination circuit determines the secondary battery is operable and the secondary battery is reliably connected to the connection terminal T1, when the output signal CV from the first calculation amplification circuit is higher than a first predetermined value, or when the output signal CC from the second calculation amplification circuit is lower than a second predetermined value.