Battery voltage measurement system and method thereof

1. A battery voltage measurement system suitable for measuring a battery voltage of a battery, comprising:

a measurement unit for measuring the battery voltage;

a calibration unit coupled between the measurement unit and the battery, for providing a plurality of test voltages to the measurement unit; and

a control unit coupled to the measurement unit and the calibration unit, for controlling the calibration unit and receiving an output voltage of the measurement unit;

wherein the battery voltage measurement system has a calibration mode and a measurement mode, and under the calibration mode, the calibration unit outputs the test voltages to the measurement unit, and the control unit calculates a calibration value according to a relation between the test voltages and the output voltage of the measurement unit; and under the measurement mode, the calibration unit transmits the battery voltage to the measurement unit, and the control unit calibrates the output voltage of the measurement unit according to the calibration value for acquiring the battery voltage.

2. The battery voltage measurement system according to claim 1 , wherein the calibration unit includes:

an isolation unit coupled between the measurement unit and the battery; and

a voltage generation unit for generating the test voltages to the measurement unit;

wherein under the calibration mode, the isolation unit isolates the measurement unit from the battery; and under the measurement mode, the isolation unit transmits the battery voltage to the measurement unit.

3. The battery voltage measurement system according to claim 2 , wherein the isolation unit comprises:

a first isolation circuit coupled between a first input end of the measurement unit and a first end of the battery, for isolating the measurement unit from the battery; and

a second isolation circuit coupled between a second input end of the measurement unit and a second end of the battery, for isolating the measurement unit from the battery.

4. The battery voltage measurement system according to claim 3 , wherein the first isolation circuit comprises:

a PMOS transistor having a source node coupled to the first input end of the measurement unit, and a drain node coupled to the first end of the battery;

a first resistor coupled between the source node and a gate node of the PMOS transistor;

a second resistor having one end coupled to the gate node of the PMOS transistor; and

an NPN transistor having a collector node coupled to another end of the second resistor, an emitter node coupled to a ground, and a base node is coupled to the control unit.

5. The battery voltage measurement system according to claim 3 , wherein the second isolation circuit comprises:

a PMOS transistor having a source node coupled to the second input end of the measurement unit, and a drain node coupled to the second end of the battery;

a first resistor coupled between the source node and a gate node of the PMOS transistor;

a second resistor having one end coupled to the gate node of the PMOS transistor; and

an NPN transistor having a collector node coupled to another end of the second resistor, an emitter node coupled to a ground, and a base node coupled to the control unit.

6. The battery voltage measurement system according to claim 3 , wherein the first isolation circuit and the second isolation circuit are formed by using respective switches.

7. The battery voltage measurement system according to claim 2 , wherein the voltage generation unit comprises:

a voltage generation circuit for generating the test voltages;

an enabling circuit coupled between the voltage generation circuit and the battery, for transmitting electric power to the voltage generation circuit according to a determination enabling signal; and

an output isolation circuit coupled between the voltage generation circuit and the measurement unit;

wherein the output isolation circuit is controlled by an output voltage of the enabling circuit.

8. The battery voltage measurement system according to claim 7 , wherein the voltage generation circuit comprises:

a plurality of bias voltage generation circuits coupled in parallel between an output end of the enabling circuit and a ground, wherein the bias voltage generation circuits are in correspondence to different bias voltages; and

a voltage division circuit coupled between the bias voltage generation circuits and the output isolation circuit, for generating a first test voltage and a second test voltage to the output isolation circuit.

9. The battery voltage measurement system according to claim 8 , wherein each bias voltage generation circuit comprises:

a standard voltage component having a negative end coupled to the output end of the enabling circuit; and

an NPN transistor coupled between a positive end of the standard voltage component and the ground.

10. The battery voltage measurement system according to claim 8 , wherein the voltage division circuit is formed by a plurality of series-coupled resistors.

11. The battery voltage measurement system according to claim 7 , wherein the enabling circuit comprises:

a PNP transistor having an emitter node coupled to the battery, and a collector node coupled to the voltage generation circuit;

a first resistor coupled between the emitter node and a base node of the PNP transistor;

a second resistor having one end coupled to the base node of the PNP transistor; and

an NPN transistor having a collector node coupled to another end of the second resistor, an emitter node coupled to a ground, and a base node coupled to the control unit.

12. The battery voltage measurement system according to claim 1 , wherein the measurement unit comprises:

an operational amplifier having a non-inverted input end and an inverted input end which are coupled to the calibration unit;

a resistor coupled between an output end of the operational amplifier and the second end; and

an analog to digital converter coupled to the output end of the operational amplifier.

13. A battery voltage measurement method, comprising:

providing a plurality of test voltages to a measurement unit in sequence;

calculating a calibration value according to a relation between the test voltages and an output voltage of the measurement unit; and

transmitting a battery voltage to the measurement unit for measuring the battery voltage, and calibrating the output voltage of the measurement unit according to the calibration value.