JP2007085903A - Voltage measuring method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage measuring method and a device capable of improving the accuracy of voltage measurement. <P>SOLUTION: In this voltage measuring device, during a period of voltage measurement, a capacitor 3 is charged by a voltage of a voltage source to be measured, and the charge of the charged capacitor 3 is measured, and the voltage of the voltage source is calculated from an acquired measured value. Since the device includes a storage means 7 for storing a measured value measured at a complete discharge state time of the capacitor 3 as an offset value, and a voltage measuring means 7 for calculating the voltage of the voltage source by performing operation wherein the offset value stored in the storage means 7 is subtracted from the measured value determined during the period of voltage measurement, voltage detection accuracy can be improved without requiring addition of a component. Especially, detection accuracy of a small signal can be improved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a voltage measuring method and apparatus, and more particularly, to a voltage measuring method and apparatus for measuring a voltage of a voltage source using charging of a capacitor.

  As a device for measuring the voltage of each individual battery (voltage source) constituting a high-voltage power source in a high-voltage power source configured by connecting a large number of batteries (voltage source) in series like a power source of an electric vehicle, There is a flying capacitor type voltage measuring device.

  FIG. 1 is a configuration diagram of a conventional flying capacitor type voltage measuring apparatus. In FIG. 1, voltage sources V1 to V5 connected in series are connected to a first multiplexer 1 composed of switches S1, S3 and S5 and a second multiplexer 2 composed of switches S2, S4 and S6 from voltage detection terminals T1 to T6. The capacitor 3 is connected to a microcomputer 7 as voltage measuring means via a sample switch 4 comprising switches 4a and 4b and a polarity correction means 6. The microcomputer 7 includes an input port A / D1 to which a driving voltage is supplied from a power source + Vcc and a voltage to be measured is input to the power port Vcc.

  In the above-described configuration, after the desired voltage source is selected by the first and second multiplexers 1 and 2 while the sample switch 4 is open, the first and second multiplexers 1 and 2 are opened and the sample switch 4 is opened. Each voltage of the voltage sources V1 to V5 can be measured by repeating the operation of closing.

  For example, if the switches S1 and S2 are closed, the voltage of the voltage source V1 is charged in the capacitor 3, and then the switches S1 and S2 are opened, and then the sample switch 4 is closed. Charging voltage, that is, the voltage of the voltage source V1 is input. In this way, since the multiplexers 1 and 2 and the sample switch 4 are not closed at the same time, the voltage of the voltage source V1 is measured in an insulating manner.

  In addition, this apparatus includes polarity correcting means 6 for aligning the detected voltage polarities of the odd-numbered voltage source and the even-numbered voltage source. As the polarity correction means 6, for example, an absolute value circuit constituted by a differential amplifier is used.

Such a flying capacitor type voltage measuring device is disclosed in, for example, Japanese Patent Laid-Open No. 11-248755 (Patent Document 1).
Japanese Patent Laid-Open No. 11-248755

  However, in the above-described conventional device, when an offset voltage is generated at the input port A / D1 of the microcomputer 7 due to the stray capacitance and other influences, the offset amount directly causes a decrease in voltage detection accuracy. That is, unlike the design stage on the desktop, in the actual machine, in addition to the detection error factor due to the component accuracy, the error factor (A / D input level) other than the component accuracy error factor due to the surrounding circuit board routing and surrounding noise environment, etc. Fluctuations) and offsets due to these causes occur.

  In particular, when a small signal is handled, the ratio of the offset error to the actual voltage becomes large, and the voltage detection accuracy is significantly reduced.

  In view of the above-described problems, an object of the present invention is to provide a voltage measurement method and apparatus capable of improving the accuracy of voltage measurement.

  In the voltage measuring method according to the first aspect of the present invention, during the voltage measurement period, the voltage of the voltage source to be measured is charged in a capacitor, the charge of the charged capacitor is measured, and the voltage is calculated from the obtained measurement value. A voltage measurement method for calculating a voltage of a source, wherein a measurement value measured when the capacitor is completely discharged is stored as an offset value, and an operation of subtracting the offset value from the measurement value obtained during the voltage measurement period To calculate the voltage of the voltage source.

  According to a second aspect of the present invention, there is provided a voltage measuring apparatus that charges a capacitor with a voltage of a voltage source to be measured during a voltage measurement period, measures a charge of the charged capacitor, and calculates the voltage from the obtained measurement value. A voltage measurement device for calculating a voltage of a source, wherein a storage means for storing a measurement value measured when the capacitor is completely discharged as an offset value, and the storage means from the measurement value obtained during the voltage measurement period Voltage measuring means for calculating the voltage of the voltage source by performing an operation of subtracting the offset value stored in the voltage source.

  According to a third aspect of the present invention, there is provided a voltage measuring apparatus that selects a capacitor and an odd-numbered voltage detection terminal among the (N + 1) voltage detection terminals connected to the N voltage sources connected in series as the capacitor. A first multiplexer connected in series, a second multiplexer selectively connecting an even-numbered voltage detection terminal of the (N + 1) voltage detection terminals to the capacitor, and a voltage across the capacitor. Voltage measurement means to be charged, the voltage of the voltage source to be measured is charged to the capacitor, the charge of the charged capacitor is measured by the voltage measurement means during a predetermined voltage measurement period, and obtained. A voltage measuring device for calculating a voltage of the voltage source from a measured value, further comprising storage means for storing the measured value measured when the capacitor is completely discharged as an offset value. The voltage measuring means calculates the voltage of the voltage source by performing an operation of subtracting the offset value stored in the storage means from the measured value obtained during the voltage measurement period. And

  According to a fourth aspect of the present invention, in the voltage measuring device according to the second or third aspect, the determination means for determining whether or not a measured value measured when the capacitor is completely discharged is equal to or less than a preset set value. The storage means stores the measurement value as an offset value when the determination means determines that the measurement value measured when the capacitor is completely discharged is equal to or less than a preset set value. When the determination unit does not determine that the measured value measured when the capacitor is completely discharged is less than or equal to a preset set value, the set value is stored as an offset value. .

  According to the voltage measurement method of the first aspect of the present invention, during the voltage measurement period, the voltage of the voltage source to be measured is charged to the capacitor, the charge of the charged capacitor is measured, and the voltage is obtained from the obtained measurement value. This is a voltage measurement method for calculating the voltage of the source, storing the measured value measured when the capacitor is fully discharged as an offset value, and subtracting the offset value from the measured value obtained during the voltage measurement period. Since the voltage of the voltage source is calculated, the voltage detection accuracy can be improved without the need for additional components. In particular, the detection accuracy of small signals can be improved.

  According to the voltage measuring device of the second aspect of the present invention, during the voltage measurement period, the voltage of the voltage source to be measured is charged to the capacitor, the charge of the charged capacitor is measured, and the voltage is obtained from the obtained measurement value. A voltage measuring device for calculating a voltage of a source, storing a measured value measured when the capacitor is completely discharged as an offset value, and storing the measured value obtained during the voltage measurement period in the storing means. By performing an operation of subtracting the offset value, the voltage measurement means for calculating the voltage of the voltage source is provided, so that the voltage detection accuracy can be improved without requiring the addition of parts. In particular, the detection accuracy of small signals can be improved.

  According to the voltage measuring apparatus of the third aspect of the present invention, the capacitor and the odd-numbered voltage detection terminal among the (N + 1) voltage detection terminals connected to the N voltage sources connected in series are used as the capacitor. A first multiplexer that is selectively connected, a second multiplexer that selectively connects an even-numbered voltage detection terminal of (N + 1) voltage detection terminals to the capacitor, and a voltage across the capacitor are supplied. Voltage measuring means, charging a capacitor with the voltage of the voltage source to be measured, measuring the charge of the charged capacitor with a voltage measuring means during a predetermined voltage measurement period, and from the obtained measurement value, the voltage source A voltage measuring device for calculating the voltage of the capacitor, further comprising storage means for storing the measured value measured when the capacitor is completely discharged as an offset value, the voltage measuring means comprising a voltmeter Since the voltage of the voltage source is calculated by subtracting the offset value stored in the storage means from the measurement value obtained during the period, in the voltage measuring device having a flying capacitor type configuration with a multiplexer, The voltage detection accuracy can be improved without requiring the addition of parts. In particular, the detection accuracy of small signals can be improved.

  According to the voltage measuring device of the invention described in claim 4, in the voltage measuring device of claim 2 or 3, whether or not the measured value measured when the capacitor is completely discharged is equal to or less than a preset set value. The storage means further includes a determination means, and the storage means uses the measurement value as an offset value when the determination means determines that the measurement value measured when the capacitor is completely discharged is equal to or less than a preset set value. If it is not determined that the measured value measured by the determination means when the capacitor is completely discharged is less than or equal to a preset set value, the set value is stored as an offset value. A reduced voltage measuring device is obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a circuit diagram showing the configuration of a voltage measuring apparatus that implements the voltage measuring method of the present invention. The voltage measuring device is a flying capacitor type voltage measuring device, and includes a first multiplexer 1 and a second multiplexer 2 connected to voltage detection terminals T1 to T6 of the high-voltage power supply V, a bipolar capacitor 3, a sample switch 4, A polarity correction means 6 and a microcomputer (hereinafter referred to as a microcomputer) 7 are included.

  High-voltage power supply V includes N voltage sources (for example, single cells) V1-V5 connected in series (in this embodiment, for example, N = 5). Each of the voltage sources V1 to V5 is connected to (N + 1) (for example, six in this embodiment) voltage detection terminals T1 to T6.

  The first multiplexer 1 includes switches S1, S3, S5 connected to the voltage detection terminals T1, T3, T5, respectively. The second multiplexer 2 includes switches S2, S4, S6 connected to the voltage detection terminals T2, T4, T6, respectively.

  The switches S 1, S 3, S 5 of the first multiplexer 1 are connected to one terminal of the capacitor 3, and the switches S 2, S 4, S 6 of the second multiplexer 2 are connected to the other terminal of the capacitor 3.

  The sample switch 4 includes a switch 4 a connected to one terminal of the capacitor 3 and a switch 4 b connected to the other terminal of the capacitor 3.

  The polarity correction means 6 is for aligning the detected voltage polarities of the odd-numbered voltage source and the even-numbered voltage source, and an absolute value circuit constituted by, for example, a differential amplifier is used.

  The microcomputer 7 functions as a voltage measurement unit, a storage unit, and a determination unit, and has a power supply port Vcc to which a drive voltage from a power supply + Vcc is supplied and an input port A / D1. The microcomputer 7 performs A / D conversion and reads the voltage input to the input port A / D1.

  Next, voltage measurement processing of the flying capacitor type voltage measuring apparatus having the above-described configuration will be described. First, when the capacitor 3 is completely discharged without charge (when the charge is completely discharged), the switches 4a and 4b of the sample switch 4 are closed and the voltage across the capacitor 3 is measured by the microcomputer 7. The offset value representing the offset error of the voltage measurement device is stored in a built-in storage unit. Although this offset error is theoretically zero, it is measured in exactly the same measurement state as normal measurement, and can therefore be considered as a numerical value representing an inherent error factor such as a circuit in a real machine and the surrounding environment.

  Next, in the normal voltage measurement period, the switch corresponding to the voltage source to be measured among the switches of the first and second multiplexers 1 and 2 is closed, and the normal measurement cycle is started. For example, when measuring the voltage of the voltage source V1, if the switch S1 of the first multiplexer 1 and the switch S2 of the second multiplexer 2 are closed, the voltage source V1, the voltage detection terminal T1, the switch S1, the capacitor 3, the switch S2, and the voltage A closed circuit is formed by the detection terminal T2. Thereby, the voltage of the voltage source V1 is charged in the capacitor 3 so that the terminal side of the capacitor 3 connected to the switch S1 has a positive polarity.

  Next, the switches S1 and S2 are opened, the switches 4a and 4b of the sample switch 4 are closed for a predetermined period, and the charge of the charged capacitor 3, that is, the voltage of the voltage source V1 is passed through the sample switch 4 and the polarity correction means 6. , And supplied to the input port A / D1 of the microcomputer 7.

  The microcomputer 7 performs an operation of subtracting the offset value stored in the storage unit from the measured value of the voltage supplied to the input port A / D1, and reads the operation result as a value indicating the voltage of the voltage source V1. The voltage measurement of the voltage source V1 is thus completed, all the switches are opened, and the standby state before the measurement is returned.

  Next, prior to measuring the voltage of the voltage source V2, after confirming that the capacitor 3 is in a completely discharged state without charge, the switches 4a and 4b of the sample switch 4 are closed again, and the voltage across the capacitor 3 is set to the microcomputer 7 again. The measured value is stored in a built-in storage unit as an offset value representing an offset error of the voltage measuring device.

  Next, when the switches S2 and S3 are closed during the voltage measurement period of the voltage source V2, a closed circuit is formed by the voltage source V2, the voltage detection terminal T2, the switch S2, the capacitor 3, the switch S3, and the voltage detection terminal T3. Thereby, the voltage of the voltage source V2 is charged to the capacitor 3 so that the polarity is opposite to that at the time of measurement of the voltage source V1, that is, the terminal side of the capacitor 3 connected to the switch S2 has a positive polarity.

  Next, the switches S2 and S3 are opened, the switches 4a and 4b of the sample switch 4 are closed for a predetermined period, and the charged charge of the capacitor 3, that is, the voltage of the voltage source V2 is passed through the sample switch 4 and the polarity correction means 6. , And supplied to the input port A / D1 of the microcomputer 7.

  The microcomputer 7 performs a calculation of subtracting the offset value stored in the storage unit from the measured value of the voltage supplied to the input port A / D1, and reads the calculation result as a value indicating the voltage of the voltage source V2. The voltage measurement of the voltage source V2 is thus completed, all the switches are opened, and the standby state before the measurement is returned.

  Similarly, voltage measurements of the voltage sources V3, V4, and V5 are performed by combinations of the switches S3 and S4, S4 and S5, and S5 and S6, respectively.

  Next, the voltage measurement process described above will be described with reference to the flowchart shown in FIG.

  First, the voltage across the capacitor 3 is measured by the microcomputer 7 when the capacitor 3 is completely discharged (when the charge is completely discharged) (step S1; voltage measuring means). Next, it is determined whether or not the measured value is equal to or less than a preset set value Vt (step S2; determination means). This set value Vt sets an upper limit of the offset error, and is set to a voltage corresponding to several bits of A / D conversion at the input port A / D1 of the microcomputer 7, for example, 25 mV corresponding to 5 bits. Is done.

  If the measured value is less than or equal to the set value Vt (Y in step S2), then the microcomputer 7 stores the measured value as an offset value in its storage unit (step S3; storage means), and then proceeds to step S5.

  On the other hand, if the measured value is not less than or equal to the set value Vt (N in step S2), then the microcomputer 7 stores the set value Vt as an offset value in the storage unit (step S4; storage means), and then proceeds to step S5. move on.

  In step S5, a normal voltage measurement cycle for measuring the voltage of the voltage source is started. That is, among the switches of the first and second multiplexers 1 and 2, the switch corresponding to the voltage source to be measured is closed, the capacitor 3 is charged, and then the switches of the first and second multiplexers 1 and 2 are opened. Then, the sample switch 4 is closed for a predetermined period, and the charge of the charged capacitor is measured by the microcomputer 7 to obtain a measured value.

  Next, the microcomputer 7 performs an operation of subtracting the offset value stored in the storage unit from the obtained measurement value, and stores the calculation result in the storage unit as measurement data indicating the voltage of the voltage source to be measured (step) S6). Subsequent to step S6, the process returns to step S1, and voltage measurement of the voltage source to be measured next is executed.

  Thus, according to the present invention, the offset error of the voltage measuring apparatus immediately before measurement is monitored for each voltage measurement of the voltage source in consideration of the possibility of measurement failure due to noise, and the upper limit is set in advance. By setting the value as a value and subtracting the offset error grasped each time when actually measuring the voltage source voltage from the voltage detection value, the offset error due to the influence of the surroundings can be removed, and the detection accuracy can be improved.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various deformation | transformation and application are possible.

  For example, in the above-described embodiment, the switches S1 to S6 of the multiplexers 1 and 2 and the switches 4a and 4b of the sample switch 4 are automatically opened and closed by the microcomputer 7 at appropriate timing. Instead, it may be opened and closed manually.

  In each of the above-described embodiments, the case where the present invention is applied to a flying capacitor type voltage measuring device has been described. However, the present invention is not limited thereto, and a flying capacitor is used as long as the voltage measuring device uses charging of a capacitor. The present invention can be applied to other types of voltage measuring devices such as a voltage measuring device that does not directly measure voltage or a voltage measuring device without a multiplexer. Further, the present invention can also be applied to a ground fault detection device (for example, see Japanese Patent Application Laid-Open No. 2004-170103) that uses charging of a capacitor.

It is a circuit diagram which shows the structure of the voltage measuring apparatus which implements the voltage measuring method conventionally and this invention. It is a flowchart explaining the operation | movement in the voltage measuring device of FIG.

Explanation of symbols

V1 to V5 Voltage source 1 First multiplexer 2 Second multiplexer 3 Capacitor 4 Sample switch 7 Microcomputer (voltage measurement means, storage means, determination means)

Claims (4)

A voltage measurement method for charging a voltage of a voltage source to be measured to a capacitor during a voltage measurement period, measuring a charge of the charged capacitor, and calculating a voltage of the voltage source from an obtained measurement value. ,
Store the measured value measured when the capacitor is completely discharged as an offset value,
A voltage measurement method, wherein the voltage of the voltage source is calculated by performing an operation of subtracting the offset value from the measurement value obtained during the voltage measurement period. A voltage measuring device for charging a voltage of a voltage source to be measured to a capacitor during a voltage measurement period, measuring a charge of the charged capacitor, and calculating a voltage of the voltage source from an obtained measurement value. ,
Storage means for storing a measurement value measured when the capacitor is completely discharged as an offset value;
Voltage measurement means for calculating the voltage of the voltage source by performing an operation of subtracting the offset value stored in the storage means from the measurement value obtained during the voltage measurement period. Voltage measuring device. A capacitor and a first multiplexer that selectively connects an odd-numbered voltage detection terminal among (N + 1) voltage detection terminals connected to N voltage sources connected in series to the capacitor; A second multiplexer for selectively connecting an even-numbered voltage detection terminal among the (N + 1) voltage detection terminals to the capacitor, and a voltage measuring means to which the voltage across the capacitor is supplied, to be measured Voltage for charging the capacitor with the voltage of the voltage source, measuring the charged electric charge of the capacitor with the voltage measuring means during a predetermined voltage measurement period, and calculating the voltage of the voltage source from the obtained measurement value A measuring device,
Storage means for storing the measured value measured when the capacitor is completely discharged as an offset value;
The voltage measuring means calculates the voltage of the voltage source by performing an operation of subtracting the offset value stored in the storage means from the measured value obtained during the voltage measurement period. Voltage measuring device. In the voltage measuring device according to claim 2 or 3,
A determination means for determining whether or not a measured value measured when the capacitor is completely discharged is equal to or less than a preset set value;
The storage unit stores the measurement value as an offset value when the determination unit determines that the measurement value measured when the capacitor is completely discharged is equal to or less than a preset set value. The voltage measuring device is characterized by storing the set value as an offset value when it is not determined by the means that the measured value measured when the capacitor is completely discharged is equal to or less than a preset set value.

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