ANALOG SWITCH, BATTERY PACK INCLUDING THE SAME AND BATTERY VOLTAGE MEASURING METHOD

• US 20120139548A1
• Filed: 06/23/2011
• Published: 06/07/2012
• Est. Priority Date: 12/01/2010
• Status: Active Grant

• Current Assignee: Samsung SDI Company Limited
• Original Assignee: Samsung SDI Company Limited
• Inventors: Yang, Jongwoon, Segawa, Susumu
• Granted Patent: US 8,803,478 B2
• Time in Patent Office: Days
• US Class Current: 324/433
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]

Abstract

A battery pack is provided. The battery pack includes first battery cells, a second battery cell coupled to one of the first battery cells, a voltage sensing and balancing circuit for measuring voltages of the first battery cells and for maintaining voltage balance between the first battery cells, a controller that includes an analog-to-digital (A/D) converter, and an analog switch for measuring a voltage value of the second battery cell and for transferring the measured voltage value to the A/D converter. The controller is for controlling charging and discharging of the first and second battery cells. The analog switch includes a flying capacitor, a first switch unit for transferring a voltage between the second battery cell and the flying capacitor, a second switch unit for transferring a voltage of the flying capacitor to the A/D converter, and a first diode for protecting a voltage source from a surge current.

Claims

1. An analog switch comprising:

a flying capacitor comprising first and second terminals;

a first switch unit coupled to the first and second terminals of the flying capacitor, the first switch unit being configured to transfer a voltage between first and second terminals of a battery to the flying capacitor;

a second switch unit coupled to the first terminal of the flying capacitor, the second switch unit being configured to transfer a voltage of the flying capacitor to an analog-to-digital (A/D) converter; and

a first diode coupled between the second terminal of the flying capacitor and a first capacitor for storing a supply voltage, the first diode being configured to protect a voltage source from a surge current.

2. The analog switch as claimed in claim 1, further comprising a second diode coupled to the first diode in parallel.

3. The analog switch as claimed in claim 2, wherein the first and second diodes have a same temperature characteristic.

4. The analog switch as claimed in claim 2, wherein the first and second diodes are implemented in one package.

5. The analog switch as claimed in claim 1, wherein the first switch unit comprises:

a first transistor comprising a grounded first electrode, a second electrode, and a control electrode for receiving a first control signal for controlling voltage sensing of the battery;

a second transistor comprising a first electrode that is coupled to the first terminal of the battery, a second electrode that is coupled to the first terminal of the flying capacitor, and a control electrode that is coupled to the second electrode of the first transistor; and

a third transistor comprising a first electrode that is coupled to the second terminal of the battery, a second electrode that is coupled to the second terminal of the flying capacitor, and a control electrode that is coupled to the second electrode of the first transistor.

6. The analog switch as claimed in claim 1, wherein the second switch unit comprises:

a fourth transistor comprising a grounded first electrode, a second electrode, and a control electrode for receiving a second control signal for controlling a voltage that is transferred to the A/D converter; and

a fifth transistor comprising a first electrode that is coupled to the first terminal of the flying capacitor, a second electrode that is coupled to the A/D converter, and a control electrode that is coupled to the second electrode of the fourth transistor.

7. The analog switch as claimed in claim 6, further comprising a second diode coupled to the first diode in parallel, wherein the second diode comprises an anode coupled to the A/D converter and a cathode coupled to the control electrode of the fifth transistor.

8. A battery pack comprising:

a plurality of first battery cells;

a second battery cell coupled to one of the first battery cells;

a voltage sensing and balancing circuit for measuring voltages of the first battery cells, and for maintaining voltage balance between the first battery cells;

a controller comprising an analog-to-digital (A/D) converter, the controller for controlling charging and discharging of the first and second battery cells; and

an analog switch unit for measuring a voltage value of the second battery cell, and for transferring the measured voltage value of the second battery cell to the A/D converter, wherein the analog switch unit comprises;

a flying capacitor comprising first and second terminals;

a first switch unit coupled to the first and second terminals of the flying capacitor, the first switch unit being configured to transfer a voltage between first and second terminals of the second battery cell to the flying capacitor;

a second switch unit coupled to the first terminal of the flying capacitor, the second switch unit being configured to transfer a voltage of the flying capacitor to the A/D converter; and

a first diode coupled between the second terminal of the flying capacitor and a first capacitor for storing a supply voltage, the first diode being configured to protect a voltage source from a surge current.

9. The battery pack as claimed in claim 8, further comprising a voltage correction unit for correcting the measured voltage value of the second battery cell, wherein the voltage correction unit comprises a second diode coupled to the first diode in parallel.

10. The battery pack as claimed in claim 9, wherein

the voltage correction unit is configured to measure a first voltage value of the first diode when measuring the voltage value of the second battery cell, and to reflect a difference between the first voltage value and a second voltage value in the measured voltage value of the second battery cell to correct the measured voltage value, and

the second voltage value is a driving voltage value of the second diode that has been measured at room temperature.

11. The battery pack as claimed in claim 10, wherein the voltage correction unit is configured to measure the first voltage value using the equation

V_f1=(V_reg×

V_AD)÷

2^M,

where V_f1 denotes the first voltage value, V_reg denotes a reference voltage value of the A/D converter, V_AD denotes a driving voltage value of the second diode when measuring the voltage value of the second battery cell, and M denotes a number of bits of the A/D converter.

12. The battery pack as claimed in claim 10, wherein the voltage correction unit is configured to subtract the second voltage value from the first voltage value to produce a first difference, and to add the first difference to the measured voltage value of the second battery cell to correct the measured voltage value.

13. A method of measuring a battery voltage value using a flying capacitor for storing a voltage of a battery, a plurality of switches, and an analog switch comprising the flying capacitor and a first diode for protecting a voltage source from a surge current, the method comprising:

measuring a voltage value of the battery with the analog switch;

measuring a first voltage value of the first diode when measuring the voltage value of the battery, with a second diode that is coupled to the first diode in parallel; and

correcting the measured voltage value of the battery, comprising reflecting a difference between the first voltage value and a second voltage value in the measured voltage value of the battery to correct the measured voltage value,

wherein the second voltage value is a driving voltage value of the second diode that has been measured at room temperature.

14. The method as claimed in claim 13, wherein the measuring of the first voltage value uses the equation

V_f1=(V_reg×

V_AD)÷

2^M,

where V_f1 denotes the first voltage value, V_reg denotes a reference voltage value of an analog-to-digital (A/D) converter configured to receive the measured voltage value of the battery, V_AD denotes a driving voltage value of the second diode when measuring the voltage value of the battery, and M denotes a number of bits of the A/D converter.

15. The method as claimed in claim 13, wherein the correcting of the measured voltage value of the battery comprises subtracting the second voltage value from the first voltage value to produce a first difference, and adding the first difference to the measured voltage value of the battery to correct the measured voltage value.