VOLTAGE POLARITY DETERMINATION CIRCUIT AND CHARGE AMOUNT MEASUREMENT CIRCUIT

• US 20110313698A1
• Filed: 08/25/2011
• Published: 12/22/2011
• Est. Priority Date: 02/25/2009
• Status: Active Grant

• Current Assignee: Panasonic Semiconductor Solutions Co., Ltd. (Winbond Electronics Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Inoue, Atsuo, Matsuno, Noriaki
• Granted Patent: US 8,901,891 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: G01R 19/14 Indicating direction of current; Indicating polarity of voltage
• CPC Class Codes: G01R 31/3832 without measurement of battery voltage

Abstract

A voltage polarity determination circuit includes an integration circuit, a switch, and a time measurement circuit. The integration circuit includes an operational amplifier circuit having an input offset voltage which is larger than the maximum value of a voltage input to the integration circuit or smaller than the minimum value of the input voltage of the integration circuit. The switch switches the input voltage of the integration circuit between a voltage whose polarity is to be determined and a reference voltage. The time measurement circuit measures a time interval which it takes for the output voltage of the integration circuit to reach a set voltage, and based on the result of the measurement, determines the polarity of the input voltage of the integration circuit.

Claims

1. A voltage polarity determination circuit comprising:

an integration circuit;

a switch configured to switch a voltage input to the integration circuit between a voltage whose polarity is to be determined and a reference voltage; and

a time measurement circuit configured to measure a time interval which it takes an output voltage of the integration circuit to reach a set voltage, and based on a result of the measurement, determine the polarity of the input voltage of the integration circuit, wherein

the integration circuit includes an operational amplifier circuit having an input offset voltage which is larger than a maximum value of the input voltage of the integration circuit or smaller than a minimum value of the input voltage of the integration circuit.

2. The voltage polarity determination circuit of claim 1, wherein

the time measurement circuit includes

a comparison circuit configured to compare the output voltage of the integration circuit with a first reference voltage, and output a result of the comparison, and

a determination circuit configured to measure a time interval between when the input voltage of the integration circuit is switched by the switch and when the output voltage of the comparison circuit is inverted, and based on a result of the measurement, determine the polarity of the input voltage of the integration circuit.

3. The voltage polarity determination circuit of claim 1, wherein

the time measurement circuit determines the polarity of the input voltage of the integration circuit by comparing a time interval between when the input voltage of the integration circuit is switched to the reference voltage by the switch and when the output voltage of the integration circuit reaches a first reference voltage with a time interval between when the input voltage of the integration circuit is switched to the voltage whose polarity is to be determined by the switch and when the output voltage of the integration circuit reaches the first reference voltage.

4. The voltage polarity determination circuit of claim 1, wherein

the time measurement circuit includes

a first comparison circuit configured to compare the output voltage of the integration circuit with a first reference voltage, and output a result of the comparison,

a second comparison circuit configured to compare the output voltage of the integration circuit with a second reference voltage, and output a result of the comparison,

a logic circuit configured to output a voltage which is set or reset in response to inversion of an output voltage of the first comparison circuit or inversion of an output voltage of the second comparison circuit,

a counter configured to measure an output of the logic circuit until a set value, and

a determination circuit configured to measure a time interval between when the input voltage of the integration circuit is switched by the switch and when a value measured by the counter reaches the set value, and based on a result of the measurement, determine the polarity of the input voltage of the integration circuit, and

the voltage polarity determination circuit further includes an initialization circuit configured to initialize the output voltage of the integration circuit in response to an output of the logic circuit.

5. The voltage polarity determination circuit of claim 4, wherein

the determination circuit compares the time interval between when the input voltage of the integration circuit is switched to the reference voltage by the switch and when the value measured by the counter reaches the set value with a time interval between when the input voltage of the integration circuit is switched to the voltage whose polarity is to be determined by the switch and when the value measured by the counter reaches the set value, to determine the polarity of the input voltage of the integration circuit.

6. A charge amount measurement circuit comprising:

a voltage-to-charge conversion circuit configured to convert an input voltage into pulses corresponding to a charge amount;

a charging measurement circuit and a discharging measurement circuit each configured to count the output pulses of the voltage-to-charge conversion circuit; and

a storage circuit configured to store a count value of the charging measurement circuit which is obtained when the input voltage is 0 V, and set the count value into the charging measurement circuit,

wherein

when the count value of the charging measurement circuit reaches overflow, a count value of the discharging measurement circuit is subtracted, and when the count value of the discharging measurement circuit reaches overflow, the count value of the charging measurement circuit is subtracted, and

the voltage-to-charge conversion circuit includes an integration circuit including an operational amplifier circuit having an input offset voltage which is larger than a maximum value of the input voltage or smaller than a minimum value of the input voltage.

7. The charge amount measurement circuit of claim 6, wherein

the voltage-to-charge conversion circuit includes

a first switch configured to switch the input voltage of the integration circuit between a voltage to be measured and a reference voltage,

a first comparison circuit configured to compare an output voltage of the integration circuit with a first reference voltage, and output a result of the comparison,

a second comparison circuit configured to compare the output voltage of the integration circuit with a second reference voltage, and output a result of the comparison,

a logic circuit configured to output a voltage which is set or reset in response to inversion of an output voltage of the first comparison circuit or inversion of an output voltage of the second comparison circuit, and

a second switch configured to be controlled based on an output voltage of the logic circuit to be in a conductive state and a non-conductive state, thereby initializing the integration circuit.

8. The charge amount measurement circuit of claim 6, wherein

the charging measurement circuit includes a measurement counter and a charging counter, and the discharging measurement circuit includes a charge counter and a discharging counter,

the measurement counter, when the first switch is switched to the reference voltage, measures a time interval which it takes for the charge counter to reach overflow, and when the first switch is connected to the voltage to be measured, indicates the lapse of a measurement time, and

the charging counter increments by one when the measurement counter overflows, and decrements by one when the charge counter overflows.

9. The charge amount measurement circuit of claim 8, wherein

the charge counter counts the number of times of inversion of an output voltage of the first comparison circuit or an output voltage of the second comparison circuit, and

the discharging counter increments by one when the charge counter overflows, and decrements by one when the measurement counter overflows.

10. The charge amount measurement circuit of claim 8, wherein

the storage circuit is a register configured to stores a value which is measured by the measurement counter when the input voltage is 0 V, and set the measured value into the measurement counter.

11. A mobile electronic device comprising:

a sensing resistor connected in series to a secondary battery;

the charge amount measurement circuit of claim 6 configured to receive a voltage generated by a current flowing through the sensing resistor, and output a charge amount corresponding to the current flowing through the sensing resistor;

a calculation circuit configured to calculate a remaining capacity of the secondary battery from the charge amount measured by the charge amount measurement circuit; and

a display circuit configured to indicate a result of the calculation by the calculation circuit.

12. A charge amount measurement circuit comprising:

a voltage-to-charge conversion circuit configured to convert an input voltage into pulses corresponding to a charge amount;

a charge measurement circuit configured to count the output pulses of the voltage-to-charge conversion circuit; and

a time measurement circuit configured to measure a time interval which it takes for the charge measurement circuit to overflow when the input voltage is 0 V using a clock, and indicate the lapse of a measurement time during measurement of a charge amount;

a charge integration circuit configured to count the number of clocks corresponding to a difference in overflow time between the charge measurement circuit and the time measurement circuit; and

a storage circuit configured to store a count value of the time measurement circuit which is obtained when the input voltage is 0 V, and set the count value into the time measurement circuit,

wherein

the voltage-to-charge conversion circuit includes an integration circuit including an operational amplifier circuit having an input offset voltage which is larger than a maximum value of the input voltage or smaller than a minimum value of the input voltage.

13. The charge amount measurement circuit of claim 12, wherein

the voltage-to-charge conversion circuit includes

a first switch configured to switch the input voltage of the integration circuit between a voltage to be measured and a reference voltage,

a first comparison circuit configured to compare an output voltage of the integration circuit with a first reference voltage, and output a result of the comparison,

a second comparison circuit configured to compare the output voltage of the integration circuit with a second reference voltage, and output a result of the comparison,

a logic circuit configured to output a voltage which is set or reset in response to inversion of an output voltage of the first comparison circuit or inversion of an output voltage of the second comparison circuit, and

a second switch configured to be controlled based on an output voltage of the logic circuit to be in a conductive state and a non-conductive state, thereby initializing the integration circuit.

14. The charge amount measurement circuit of claim 13, wherein

the charge measurement circuit includes a charge counter configured to count the number of times of inversion of the output voltage of the first comparison circuit or the output voltage of the second comparison circuit.

15. The charge amount measurement circuit of claim 13, wherein

the time measurement circuit includes a measurement counter configured to, when the first switch is switched to the reference voltage, measure a time interval which it takes for the charge counter to reach overflow, and when the first switch is connected to the voltage to be measured, indicate the lapse of a measurement time.

16. The charge amount measurement circuit of claim 12, wherein

the charge integration circuit includes

a start/stop control circuit configured to generate an enable signal indicating a time interval between when one of an overflow signal of the charge measurement circuit and an overflow signal of the time measurement circuit is input earlier and when the other overflow signal is input later, and

an integration counter configured to be controlled to count or stop counting based on the enable signal of the start/stop control circuit.

17. The charge amount measurement circuit of claim 12, wherein

the storage circuit stores a value which is measured by the time measurement counter when the input voltage is 0 V, and sets the measured value into the time measurement counter.

18. A mobile electronic device comprising:

a sensing resistor connected in series to a secondary battery;

the charge amount measurement circuit of claim 12 configured to receive a voltage generated by a current flowing through the sensing resistor, and output a charge amount corresponding to the current flowing through the sensing resistor;

a calculation circuit configured to calculate a remaining capacity of the secondary battery from the charge amount measured by the charge amount measurement circuit; and

a display circuit configured to indicate a result of the calculation by the calculation circuit.