JP4624326B2 - Method for detecting charging / discharging current of vehicle - Google Patents

Description

  The present invention mainly relates to a method for detecting a charge / discharge current of a hybrid car.

  In a hybrid car, it is important to accurately detect the charge / discharge current of the battery and accurately calculate the remaining capacity of the battery. This is because an error in the remaining capacity of the battery limits the capacity with which the battery can be charged and discharged effectively, and also causes the battery to deteriorate and shorten its life. The hybrid car charges and discharges with the remaining capacity limited to a specific range so that the battery can be charged and discharged effectively and to reduce the deterioration of the battery and extend its life. The remaining capacity is calculated by integrating the charge / discharge of the battery. The detection error of the charge / discharge current increases the detection error of the remaining capacity as the discharge is repeated. This is because errors are accumulated as charging and discharging are repeated.

  The hybrid car detects the charge / discharge current of the battery with a current sensor. The current sensor linearly outputs a voltage corresponding to the detected charge / discharge current. The output of the current sensor is input to an electronic circuit and amplified. Furthermore, the output amplified by the electronic circuit is input to an A / D converter and converted into a digital signal. The digital signal is input to the arithmetic circuit. The arithmetic circuit calculates the charge / discharge current of the input digital signal to calculate the remaining battery capacity.

In the method of detecting the charge / discharge current of the battery with the above circuit, an error occurs in the detected current due to the offset error of the electronic circuit. Unfortunately, the offset error fluctuates due to temperature and also changes over time. For this reason, the offset error cannot be completely corrected in the manufacturing process. In order to solve this problem, a circuit for correcting an offset error has been developed. (See Patent Document 1)
JP-A-3-165245

  According to the offset error correction method described in Patent Document 1, an output voltage is detected in a state where a detected current is 0 A to obtain an offset voltage. The current detected by this offset voltage is corrected. However, in this method, the offset voltage is detected at one point where the current is 0 A, and correction is performed on the assumption that the linearity between the detected current and the output voltage does not change. Therefore, the deviation in linearity of the output characteristics cannot be corrected. The linearity of the output characteristics is not always constant and changes with temperature or the like. For this reason, the method of Patent Document 1 does not achieve an ideal correction accurately. The deviation in straightness can be reduced by correcting not only 0A but also a state in which a specific reference current flows, and correcting at two points of 0A and the reference current. However, this method requires a circuit for supplying a reference current. Furthermore, since the circuit for supplying the reference current also has a temperature characteristic in which the reference current varies depending on the temperature, the circuit for supplying the reference current with extremely high accuracy always uses high-precision parts and further complicates the circuit configuration. There are drawbacks.

  The present invention has been developed for the purpose of solving this drawback. An important object of the present invention is to provide a vehicle charge / discharge current detection method capable of accurately detecting charge / discharge current by correcting two points with a simple circuit configuration.

The vehicle charge / discharge current detection method of the present invention has the following configuration in order to achieve the above-described object.
The vehicle charge / discharge current detection method includes a current sensor 3 that outputs a voltage corresponding to the charge / discharge current of the battery 1 to be detected, an electronic circuit 4 connected to the output side of the current sensor 3, and the electronic circuit. 4 and an A / D converter 5 connected to the output side. The electronic circuit 4 outputs an intermediate set voltage in a state where the charge / discharge current is 0 A, and outputs a detection voltage higher than the intermediate set voltage in a state where the positive side charge / discharge current is detected. It outputs a low detection voltage than the medium Ma設 constant voltage in a state detected. Further, the charge / discharge current detection method starts from 0 V detected in the first correction state in which the voltage input from the electronic circuit 4 to the A / D converter 5 is 0 V while the power supply voltage of the electronic circuit 4 is cut off. In the state in which the power voltage is input to the electronic circuit 4 and the measurement point a of the output voltage of the shifted A / D converter (5) and the charge / discharge current is 0 A, the A / D was detected in a second compensation state to enter the middle Ma設 constant voltage to the converter 5, and a measurement point b of the output voltage of the a / D converter deviates from the intermediate setting voltage (5) by linear interpolation, a / The detected current of the D converter 5 is corrected.

  The method for detecting the charging / discharging current of the vehicle according to the present invention is characterized in that the charging / discharging current is corrected at two points and can be accurately detected with a very simple circuit configuration. In the detection method of the present invention, the first correction state in which the voltage input from the electronic circuit to the A / D converter is 0 V while the power supply voltage of the electronic circuit is cut off, and the state in which the power supply voltage is input to the electronic circuit This is because the detected current of the A / D converter is corrected in the second correction state in which the intermediate set voltage is input from the electronic circuit to the A / D converter in a state where the charge / discharge current is 0 A. . In particular, according to this method, a current can be detected with high accuracy without providing a high-accuracy reference current circuit or the like for supplying a specific reference current. This is because the method of the present invention corrects in two points: a state in which the supply of the power supply voltage is interrupted and a state in which the charge / discharge current is set to 0 A while the power supply voltage is supplied. The state in which the power supply voltage is not supplied and the state in which the current is set to 0 A have no cause for error and can be corrected with extremely high accuracy.

  Embodiments of the present invention will be described below with reference to the drawings. However, the embodiment shown below exemplifies a vehicle charging / discharging current detection method for embodying the technical idea of the present invention, and the present invention describes a vehicle charging / discharging current detection method as follows. Not specific.

  Further, in this specification, in order to facilitate understanding of the scope of claims, numbers corresponding to the members shown in the examples are indicated in the “claims” and “means for solving problems” sections. It is added to the members. However, the members shown in the claims are not limited to the members in the embodiments.

  A current detection circuit that uses the vehicle charge / discharge current detection method according to the present invention is mounted on a hybrid car and detects a battery charge / discharge current. FIG. 1 shows a block diagram of a hybrid car provided with a current detection circuit 2. In the hybrid car of this figure, the charge / discharge current of the battery 1 is detected by the current detection circuit 2, the remaining capacity is calculated, and the charge / discharge of the battery 1 is controlled. The battery 1 is discharged by supplying electric power to a motor 9 that runs the vehicle, and is charged by a generator (not shown) mounted on the vehicle. The current detection circuit 2 inputs the charge / discharge current to be detected to an arithmetic circuit (not shown) of the battery ECU 8. The arithmetic circuit of the battery ECU 8 calculates the charge / discharge current detected by the current detection circuit 2 to detect the remaining capacity of the battery 1. Further, the battery ECU 8 controls the charging / discharging of the battery 1 so that the remaining capacity of the battery 1 falls within a predetermined range, and causes the vehicle to travel.

  The current detection circuit 2 is shown in FIG. The current detection circuit 2 in this figure detects a charge / discharge current of the battery 1 and outputs a voltage corresponding to the charge / discharge current, and an electronic circuit 4 connected to the output side of the current sensor 3. The A / D converter 5 connected to the output side of the electronic circuit 4 is provided.

  The current sensor 3 detects a current on the plus side from the minus side, and increases the output voltage to the plus side as the charge / discharge current increases from the minus side to the plus side. FIG. 3 is a graph showing the input-output characteristics of the current sensor 3. The current sensor 3 increases the output voltage linearly with respect to the detected charge / discharge current. The current sensor 3 shown in the figure detects a current of −250 A to +250 A and linearly increases the output voltage in this current range.

  The electronic circuit 4 includes a differential amplifier 6. The output characteristics of the electronic circuit 4 are shown in FIG. The electronic circuit 4 outputs an intermediate set voltage in a state where the output voltage is 0 V at the maximum negative current, the maximum voltage is output at the maximum positive current, and the charge / discharge current is 0 A. In the electronic circuit 4 in the figure, the output voltage is 4V with the maximum current on the plus side, and the intermediate set voltage in the state where the charge / discharge current is 0A is 2V which is 1/2 of 4V. The electronic circuit 4 including the differential amplifier 6 has a reference voltage input to the negative input terminal and has an output characteristic shown in FIG. The positive input terminal of the differential amplifier 6 is connected to the output of the current sensor 3. The electronic circuit 4 having the output characteristics shown in FIG. 4 sets the output voltage to 0 V in a state where the charge / discharge current is −250 A, that is, the battery 1 is discharged at 250 A. Further, the output voltage is set to 4 V in a state where the charge / discharge current is +250 A, in other words, the battery 1 is charged at 250 A. In a state where the charge / discharge current is 0 A, the output voltage is 2 V. The electronic circuit 4 adjusts the amplification factor of the differential amplifier 6 and adjusts the negative input voltage so that the output characteristics of FIG. 4 are obtained. The differential amplifier 6 can adjust the slope of the output characteristic line with respect to the current, that is, the slope, with the amplification factor. Further, the entire output characteristic line can be shifted up and down by changing the negative input voltage. FIG. 4 shows an ideal output characteristic of the electronic circuit 4. In the actual electronic circuit 4, the output characteristic line is shifted up and down as indicated by an arrow A in the figure due to an offset of the differential amplifier 6, and the gradient is also deviated from the design value as indicated by an arrow B. . The deviation of the output characteristic line is corrected by a method described later. The electronic circuit 4 is in an operating state when a power supply voltage is input to the differential amplifier 6, and in an inoperative state when the supply of the power supply voltage is cut off, the output voltage is set to 0V.

  The output voltage of the electronic circuit 4 is input to the A / D converter 5. The electronic circuit 4 outputs an output voltage of an analog signal. The output voltage of the analog signal is input to the A / D converter 5 and converted into a digital signal. The voltage signal converted into the digital signal is input to the arithmetic circuit of the battery ECU 8. The digital voltage signal input from the A / D converter 5 to the arithmetic circuit corresponds to the charge / discharge current. Therefore, the arithmetic circuit specifies the charge / discharge current from the input digital voltage signal, calculates the remaining capacity of the battery 1, and controls the charge / discharge of the battery 1.

  The electronic circuit 4 and the A / D converter 5 do not always operate in an ideal state, and have an error such as an offset. Therefore, the voltage signal converted into a voltage signal by the A / D converter 5 includes an error. This error is corrected in the following first correction state and second correction state. In the first correction state, the power supply voltage of the electronic circuit 4 is cut off, and the voltage input from the electronic circuit 4 to the A / D converter 5 is set to 0V. The second correction state is a state in which a power supply voltage is input to the electronic circuit 4 and a charge / discharge current is set to 0 A, and an intermediate set voltage is input from the electronic circuit 4 to the A / D converter 5. FIG. 5 shows a state where the voltage signal output from the A / D converter 5 is corrected. As shown in this figure, the output characteristic line is in a state in which the supply of the power supply voltage in the first correction state is cut off, and in a state in which the charge / discharge current is set to 0 A while supplying the power supply voltage in the second correction state. The two points are corrected. In FIG. 5, the straight line A represents the corrected output characteristic line, and the straight line B represents the ideal output characteristic line.

  The first correction state is a state in which the output voltage of the electronic circuit 4 is 0V, that is, the input voltage of the A / D converter 5 is 0V. Therefore, the A / D converter 5 in an ideal operating state sets the output voltage to 0V. When the voltage actually output from the A / D converter 5 is not 0V but a minute voltage (Vr) is output, the output characteristic line is shifted and corrected so that the minute voltage (Vr) becomes 0V.

  Since the second correction state is a state in which the charge / discharge current is 0 A, the output voltage of the A / D converter 5 becomes an intermediate set voltage (2 V in FIG. 5) in the ideal operation state. When the voltage actually output from the A / D converter 5 is not the same as the intermediate set voltage and is deviated from the intermediate set voltage by the error voltage (Vo), the voltage including the error voltage (Vo) corresponds to the intermediate set voltage. As described above, the gradient of the output characteristic line is corrected.

  As shown by the straight line A in FIG. 5, the output characteristic line corrected at two points is the measurement point a detected in the first correction state and shifted from 0 V by a minute voltage (Vr), and the second It is obtained by linear interpolation between the measurement point b detected in the correction state and shifted from the intermediate set voltage by the error voltage (Vo). The voltage signal output from the A / D converter 5 detects the charge / discharge current based on the corrected output characteristic line. For example, in FIG. 5, when the output voltage from the A / D converter 5 is Vx, the current value Ix converted by the corrected output characteristic line is adopted as the charge / discharge current.

  FIG. 6 shows a current detection circuit 12 for detecting a ground-side disconnection of a signal line from the current sensor 13. When the ground side is disconnected, the current detection circuit 12 becomes unstable in output voltage and cannot accurately detect the current. In order to eliminate this problem, the current detection circuit 12 in this figure supplies a bias voltage to the negative side input terminal 16 a of the differential amplifier 16 of the electronic circuit 14. As shown in FIG. 7, the differential amplifier 16 is designed to have a normal output voltage while supplying a positive bias voltage. For this reason, the differential amplifier 16 is in a normal output state, that is, in a state where the detection current is set to −250 A, in a state where a positive bias voltage is supplied to the negative side input terminal 16a without disconnecting the negative side of the signal line. The output voltage is set to 0 V, and linear output characteristics are obtained so that the output voltage is increased as the current increases to the plus side. However, when the negative side of the signal line is disconnected and the positive bias voltage is not supplied to the negative side input terminal 16a of the differential amplifier 16, the output voltage of the differential amplifier 16 becomes negative side as shown in FIG. Shifted. From this, it is detected that the output voltage is shifted to the negative side, and the ground side disconnection of the signal line is determined. In this figure, reference numeral 15 denotes an A / D converter.

1 is a block diagram of a hybrid car including a current detection circuit that uses a charge / discharge current detection method according to an embodiment of the present invention. It is a block circuit diagram of the current detection circuit shown in FIG. It is a graph which shows the input-output characteristic of a current sensor. It is a graph which shows the output characteristic of an electronic circuit. It is a graph which shows the state which correct | amends the voltage signal output from an A / D converter. It is a block circuit diagram which shows another example of a current detection circuit. 7 is a graph showing output characteristics when the current detection circuit shown in FIG. 6 is normal. It is a graph which shows the output characteristic at the time of the minus side disconnection of the signal line of the current detection circuit shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Battery 2 ... Current detection circuit 3 ... Current sensor 4 ... Electronic circuit 5 ... A / D converter 6 ... Differential amplifier 8 ... Battery ECU
DESCRIPTION OF SYMBOLS 9 ... Motor 12 ... Current detection circuit 13 ... Current sensor 14 ... Electronic circuit 15 ... A / D converter 16 ... Differential amplifier 16a ... Negative side input terminal

Claims (1)

A current sensor (3) that outputs a voltage corresponding to the charge / discharge current of the battery (1) to be detected, an electronic circuit (4) connected to the output side of the current sensor (3), and this electronic circuit (4 A / D converter (5) connected to the output side of
The electronic circuit (4) outputs an intermediate set voltage in a state where the charge / discharge current is 0 A, outputs a detection voltage higher than the intermediate set voltage in a state where the positive charge / discharge current is detected, and the detection process of charge and discharge current of the vehicle is formed by outputs a low detection voltage than the medium Ma設 constant voltage in a state of detecting the discharge current,
A shifted from 0 V detected in the first correction state in which the voltage input from the electronic circuit (4) to the A / D converter (5) is 0 V while the power supply voltage of the electronic circuit (4) is cut off. In the state where the power supply voltage is inputted to the measurement point a of the output voltage of the / D converter (5) and the electronic circuit (4), and the charge / discharge current is set to 0 A, the A / D from the electronic circuit (4) was detected in a second compensation state to enter the middle Ma設 constant voltage to the converter (5), and a measurement point b of the output voltage of the a / D converter deviates from the intermediate setting voltage (5) by linear interpolation, A method for detecting a charging / discharging current of a vehicle for correcting a detection current of an A / D converter (5).

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