Analog switch, battery pack including the same and battery voltage measuring method

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;
• 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 of the supply voltage from a surge current, the first diode comprising an anode coupled to a first terminal of the first capacitor and a cathode coupled to the second terminal of the flying capacitor;
• and
• a voltage correction unit for correcting the measured voltage value of the second battery cell, the voltage correction unit comprising a second diode coupled to the first diode in parallel, 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 of the second battery cell,
• the second voltage value is a driving voltage value of the second diode that has been measured at room temperature, and
• the voltage correction unit is further configured to measure the first voltage value using the equation
• Vf1=(Vreg×VAD)÷2M,
• where Vf1 denotes the first voltage value, Vreg denotes a reference voltage value of the A/D converter, VAD 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.

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 having first and second terminals, a first 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, the first diode comprising an anode coupled to a first terminal of the first capacitor and a cathode coupled to the second terminal of the flying capacitor;
• 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 of the battery,
• wherein the second voltage value is a driving voltage value of the second diode that has been measured at room temperature, and
• wherein the measuring of the first voltage value uses the equation
• Vf1=(Vreg×VAD)÷2M,
• where Vf1 denotes the first voltage value, Vreg denotes a reference voltage value of an analog-to-digital (A/D) converter configured to receive the measured voltage value of the battery, VAD 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.