JP2006284538A - Voltage-detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage-detecting device capable of inexpensively, precisely, and efficiently detecting a total voltage or the like of a battery pack. <P>SOLUTION: Voltages, converted at predetermined ratio from voltages outputted from the battery pack 1, are inputted to a differential amplifier circuit 13 for obtaining the difference between the voltages and a reference potential. The circuit 13 amplifies the differential voltage at a predetermined magnification to output the same to an A/D converter 16. A controller 17 of a CPU 3 calculates the voltage of the battery pack 1, based on data converted to digital data by the A/D converter 16, the predetermined ratio in magnification and the voltage value of the reference potential. At this time, the reference voltage value is made to corresponds to the voltage value such that the lower limit value of actual working voltage of the battery pack 1 is outputted from a voltage detector 11. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a voltage detection device that detects a voltage of an assembled battery or the like.

  An electric vehicle that travels using an electric motor, a hybrid vehicle that travels using an engine and an electric motor together, a fuel cell vehicle, and the like are known. In these automobiles, an assembled battery in which a plurality of secondary batteries such as nickel metal hydride batteries and lithium batteries are connected as a single cell and a large capacity capacitor are used as a power source for the electric motor.

  Battery packs and large-capacity capacitors supply power (discharge) to electric motors and other systems at the start of driving, during driving, and when stopping, etc., or use motor regeneration to store (charge) To do. It is known that an assembled battery is overcharged or overdischarged when a large amount of power is discharged or a large amount of power is charged. Such an overcharged state or an overdischarged state is not preferable, such as liquid leakage, abnormal heat generation, and shortened battery life. Therefore, a technique for accurately and safely detecting the voltage of the assembled battery is required.

  As an example of a technique for detecting the voltage of an assembled battery, a technique for measuring using a flying capacitor is known (see Patent Document 1). In this technique, a voltage is measured for each cell using a flying capacitor, and these are integrated to detect the total voltage of the assembled battery.

  However, since this flying capacitor method detects a voltage for each cell, a large amount of changeover switches such as the cell side and GND are required for each detection, resulting in high cost and complicated control. Furthermore, since it takes time due to the switch switching time, the charging time to the capacitor, etc., the measurement response is delayed, and the measurement accuracy during charging or discharging of the assembled battery is deteriorated. In a device that charges and discharges large power, there is a problem that an assembled battery falls into overdischarge or overvoltage due to poor response speed and measurement accuracy.

JP 2003-114243 A

  Therefore, a voltage detection device that measures the total voltage of the assembled voltage at once can be considered. However, the total voltage of the assembled battery is as high as 500 V, and a voltage detection device that can be used from 0 to 500 V is required in consideration of the upper limit value to be used. For example, when A / D conversion is performed by reducing the output of the assembled battery to 1/100, an A / D converter capable of A / D conversion in the range of 0 to 5 V is required. In order to obtain voltage measurement of a battery pack with higher accuracy, an expensive A / D converter capable of measuring with high accuracy in the range of 0 to 5V is required. In consideration of bit errors, an expensive A / D converter with a large number of bits is required.

  The present invention provides a voltage detection device that can accurately and efficiently detect the total voltage of an assembled battery at low cost.

  The present invention is applied to a voltage detection device, inputs a voltage output from a voltage detection target, outputs a voltage converted at a predetermined ratio, and a predetermined reference voltage from the voltage output from the conversion means. Subtracting means for subtracting, amplifying means for amplifying the voltage subtracted by the subtracting means with a predetermined amplification factor, and voltage value detecting means for obtaining a voltage value to be detected based on the voltage amplified by the amplifying means. It is characterized by.

  Since the present invention is configured as described above, the output voltage of the voltage detection target can be measured with high accuracy. In particular, the actual voltage range to be detected can be measured with high accuracy and high resolution.

  FIG. 1 is a diagram showing an assembled battery voltage detection system for a hybrid vehicle. The voltage of the assembled battery 1 is detected by the voltage detection function unit 2 and the CPU 3. The detected voltage of the assembled battery 1 is transmitted to the CPU 4 and used for various controls. The CPU 4 controls the connection between the assembled battery 1 and the load 5 by turning on and off the switches 6 and 7.

  The load 5 is an inverter circuit (not shown) or a motor (electric motor) (not shown) driven by the inverter circuit. The motor driven by the inverter circuit is a motor that drives the driving wheels of the hybrid vehicle. Various signals are exchanged between the CPU 3 and the CPU 4. The current detection sensor 8 detects a current that flows when the assembled battery 1 and the load 5 are connected, and transmits a detection signal to the CPU 3.

  FIG. 2 is a diagram showing details of the voltage detection function unit 2 and the CPU 3. The voltage detection function unit 2 includes a voltage detection unit 11, a reference potential generation unit 12, a differential amplifier circuit 13, switches 14 and 15, and the like. The CPU 3 includes a control unit (processor) 17, a memory (not shown), a peripheral circuit (not shown), and the like. The control unit 17 executes programs stored in the memory and performs various processes. The CPU 3 further includes an A / D converter 16, and the control unit 17 performs various processes using data from the A / D converter 16.

  The assembled battery 1 is an assembled battery in which a plurality of secondary batteries, such as nickel metal hydride batteries and lithium batteries, are connected in multiple as a single cell. Although the practical voltage range per single cell of the assembled battery 1 is around 2V to around 4.3V, the total voltage is several hundred volts. The assembled battery 1 of the present embodiment has a total voltage of a maximum of 500V. In such an assembled battery 1, the voltage at which discharge becomes impossible is not necessarily near 0V. For example, when the total voltage drops to around 200V, it becomes impossible to discharge even if the voltage remains. That is, the actual use voltage range of the assembled battery 1 is 200V to 500V.

  FIG. 3 is a diagram for explaining the principle of the present invention. In FIG. 3A, the horizontal axis represents the input voltage of the voltage detection unit 11, and the vertical axis represents the output voltage of the voltage detection unit 11. The voltage detector 11 converts the input voltage to 1/100. That is, an output voltage of 0 to 5V is output with respect to an input voltage of 0 to 500V. As shown in FIG. 3A, the above-described 0 to 200 V is a voltage range that is not actually used in the assembled battery 1. Thus, it is not necessary to measure the voltage accurately for the voltage range not used in actual applications.

  Therefore, in the present invention, as shown in FIG. 3B, only the range of 200 to 300 V, which is the actual use voltage range, is increased by amplifying the range of the output 2 V to 5 V of the voltage detection unit 11 to 0 to 5 V. Measure to accuracy.

  This will be described in more detail with reference to FIG. The CPU 3 turns on the switch 14 and the switch 15 during normal measurement. The voltage detection unit 11 converts the voltage range of 0 to 500 V of the assembled battery 1 at a ratio of 1/100, outputs 0 to 5 V, and inputs it to the differential amplifier circuit 13.

  The reference potential generator 12 generates and outputs a 2V reference potential. The reference potential is a value that is 1/100 of the lower limit value 200 V of the actual use voltage range of the assembled battery 1. In other words, the output value of the voltage detection unit 11 corresponds to the lower limit value of the actual use voltage range of the assembled battery 1. The lower limit value of the actual operating voltage range of the assembled battery 1 is also a voltage that does not drop further when the assembled battery 1 is operating normally (charging / discharging).

  The differential amplifier circuit 13 amplifies the difference between the voltage from the voltage detector 11 and the voltage from the reference potential generator 12 with a predetermined amplification factor and outputs the amplified difference. In the present embodiment, the predetermined amplification factor is 5/3 times. That is, the differential amplifier circuit 13 amplifies so that the maximum value of the difference between the voltage from the voltage detection unit 11 and the voltage from the reference potential generation unit 12 becomes a value of 5 V that is the full scale of the A / D converter 16. To do.

  The A / D converter 16 converts the analog voltage from the differential amplifier circuit 13 into a digital value and passes it to the control unit 17. The control unit 17 multiplies the output value from the A / D converter 16 by 3/5, adds the reference potential, and multiplies it by 100 to obtain the voltage of the assembled battery 1. That is, based on the voltage value amplified by the differential amplifier circuit 13, the amplification factor of the differential amplifier circuit 13, the conversion ratio of the voltage detector 11, and the reference voltage value, the voltage value of the assembled battery 1 is determined. Ask. It may be calculated so that the voltage of the assembled battery 1 corresponding to the reference potential is added last.

  Next, the measurement accuracy will be described. Assume that the A / D converter 16 is an A / D converter that measures a range of 0 to 5 V with a resolution of 8 bits (256 gradations). When the voltage 0 to 500 V of the assembled battery 1 is voltage-converted by the voltage detection unit 11 and directly input to the A / D converter 16, it is measured with a resolution of 500/256 = 1.95V.

  However, as shown in the circuit of FIG. 2, when the potential difference 300V of the assembled battery 1 of 200V to 500V is input at the full scale 5V of the A / D converter 16, it is measured with a resolution of 300/256 = 1.17V. The As a result, the resolution is improved and high-accuracy voltage measurement is possible.

  FIG. 4 is a diagram illustrating a flowchart of processing performed by the control unit 17 in the CPU 3. Start by turning on the vehicle ignition key. At this time, the switches 6 and 7 in FIG. 1 are not yet turned on by the CPU 4, and the assembled battery 1 and the load 5 are not connected. Therefore, the assembled battery 1 is in a non-charge / discharge state.

  First, in such a non-charge / discharge state, self-diagnosis and offset error setting are performed. In step S1, the switch 14 is turned off. When the ignition key is turned on, the switch 14 is not normally turned on, but is turned off just in case. In step S2, the switch 15 is connected to the GND side. In step S3, voltage measurement is performed. At this time, from the viewpoint of noise removal, sampling is performed a plurality of times and the read data is integrated to obtain a weighted average. A simple average may be taken.

  Normally, when the switch 14 is turned off, the output of the voltage detector 11 is 0V. However, a voltage of several mV may be output. Since this voltage becomes an error at the time of non-charging / discharging, it is measured as an offset voltage, and the offset voltage is subtracted from the measurement voltage at the subsequent charging / discharging, thereby realizing a high measurement without error. This offset voltage is on the order of several mV, but if this is measured as a voltage of several tens mV or more or several hundred mV or more, it can be self-diagnosed that some abnormality has occurred in the voltage detector 11 or the like.

  In step S4, it is determined whether or not the read voltage value is a predetermined value (for example, several hundred mV) or more. If it is determined that the value is not greater than the predetermined value, the process proceeds to step S5. If it is determined that the value is greater than the predetermined value, the process proceeds to step S8. In step S8, since it is equal to or greater than a predetermined value, it is determined that there is some abnormality in the voltage detection unit 11, an error is found as a result of self-diagnosis, and the result is transmitted to the CPU 4. The CPU 4 displays the result on the instrument panel or the like and warns the driver that there is an error in the voltage detection function unit 2 or the like.

  In step S5, the measured value is recorded in the internal memory of the CPU 3 as an error, that is, as an offset value. In step S6, the switch 14 is turned on. In step S7, the switch 15 is connected to the reference potential side. In step S8, a signal indicating that the self-diagnosis of the voltage detection function unit 2 has been normally completed is transmitted to the CPU 4. After receiving a signal indicating that the self-diagnosis has been completed normally, the CPU 4 turns on the switches 6 and 7 to connect the assembled battery 1 and the load 5.

  In step S9, the voltage of the assembled battery 1 is measured at a predetermined interval. That is, the switch 14 is turned on, the switch 15 is connected to the reference potential generation unit 12, and high-resolution voltage measurement using the differential amplifier circuit 13 is performed. This is a voltage measurement in a state where the load 5 is connected to the assembled battery 1 and charging / discharging is performed. Again, from the viewpoint of noise removal, sampling is performed a plurality of times and the read data from the A / D converter 16 is integrated to obtain a weighted average or simple average. The voltage measurement of the assembled battery 1 is repeatedly performed at predetermined intervals. The process is terminated when the ignition key is turned off, that is, when the use of the vehicle is stopped.

The assembled battery voltage detection system of the present embodiment configured as described above has the following effects.
(1) Since the voltage range of the assembled battery 1 is subtracted by the differential amplifier circuit 13 and the voltage of the assembled battery 1 is measured, in other words, only the actual used voltage range is set as the voltage measurement target range. Therefore, the resolution of voltage measurement can be improved, and voltage measurement with high accuracy can be realized. As a result, it is not necessary to use a high-resolution A / D converter, the cost is reduced, and the apparatus is not enlarged. Furthermore, overcharge and overdischarge of the assembled battery 1 due to measurement errors are eliminated.
(2) Since the offset error is measured when the battery pack 1 is not charged / discharged, that is, in a state where the load is not connected, it is possible to obtain an accurate offset error that is not affected by the load. As a result, voltage measurement with higher accuracy becomes possible.
(3) Since the self-diagnosis is performed when the assembled battery 1 is not charged / discharged, that is, in a state where the load is not connected, an accurate self-diagnosis can be performed. In addition, since an abnormality can be detected before the load is connected, troubles caused by connecting the load in a state where there is an abnormality can be prevented.
(4) Since the switch 4 is turned on and the switch 15 is connected to the reference potential generation unit 12 and the fact that the self-diagnosis has been completed is transmitted to the CPU 4, it is ensured that the accuracy is ensured when the load 5 is connected. High voltage measurements are made. As a result, charging / discharging control of the assembled battery 1 is performed based on highly accurate voltage measurement.

(Modification 1)
FIG. 5 is a diagram illustrating a detailed modification of the voltage detection function unit 2 and the CPU 3. This corresponds to FIG. 2 of the above embodiment. In FIG. 5, illustrations of the switch 14 and the switch 15 are omitted. The difference from the above embodiment is that the output of the new reference potential generation unit 21 is input to the A / D converter 16, and the control unit 17 of the CPU 3 adds correction calculation.

  The reference potential of the reference potential generating unit 21 detects an error of the A / D converter 16 when the operation power supply of the CPU 3 is shifted. For example, it is assumed that the power supply of the CPU 3 is shifted to 4.8V where it is normally 5V. In this case, an error also occurs in the measurement of the A / D converter 16 in the CPU 3 using the same power source. By inputting a predetermined reference potential to the A / D converter 16 and actually measuring it, it is possible to detect a measurement error due to the power supply being shifted.

  The error measured in this way is stored in a memory, and correction calculation is performed on the output data from the A / D converter 16 using the error during actual measurement. In this way, the measurement accuracy can be further improved.

(Modification 2)
FIG. 6 is a diagram illustrating another modification of details of the voltage detection function unit 2 and the CPU 3. This corresponds to FIG. 2 of the above embodiment. In FIG. 6, illustrations of the switch 14 and the switch 15 are omitted. The difference from the above embodiment is that a chopper unit 22 is inserted between the voltage detection unit 11 and the reference potential generation unit 12 and the differential amplifier circuit 13.

  The chopper unit 22 periodically disconnects the DC output of the voltage detection unit 11 and the DC output of the reference potential generation unit 12. Thereby, the influence of drift, distortion, etc. can be reduced and the measurement accuracy can be further improved.

  In FIG. 6, the new reference potential described in the first modification may be input to the A / D converter 16 and measured as in the first modification. Thereby, the measurement accuracy can be further improved.

(Modification 3)
In the above embodiment, as shown in FIG. 4, after performing the offset error and self-diagnosis, high-precision voltage measurement in the actual use voltage range using the differential function by the differential amplifier circuit 13 is performed. . However, such high-accuracy voltage measurement should be performed when the voltage exceeds a predetermined voltage, when a voltage change exceeds a predetermined value, when the voltage exceeds a predetermined current, or when a current change exceeds a predetermined value. Also good.

  FIG. 7 shows a high-accuracy voltage measurement (measurement based on a predetermined detection accuracy) when a voltage exceeds a predetermined voltage, when a voltage change exceeds a predetermined value, when a current exceeds a predetermined current, or when a current change exceeds a predetermined value. It is a figure explaining what to do. More than a predetermined voltage, more than a predetermined voltage change, more than a predetermined current, more than a predetermined current change is based on the voltage value of the battery pack 1 measured at a predetermined sampling time, the current value measured by the current sensor 8, etc. The control part 17 of CPU3 calculates | requires by a calculation.

  By doing in this way, since a highly accurate measurement is performed only when a truly highly accurate measurement value is required, the calculation load of the CPU 3 is reduced.

  In the said embodiment, although demonstrated in the example which measures the voltage of the assembled battery 1, it does not necessarily need to be limited to this content. It may be a case where the voltage of a single cell battery is measured. Moreover, the case where the voltage of a large capacity capacitor is measured may be sufficient. Furthermore, the present invention can be applied to all voltage measurements of an object that outputs a voltage.

  In the said embodiment, although demonstrated in the example which measures the direct current voltage of the assembled battery 1, it does not necessarily need to be limited to this content. The basic principle of the present invention can also be applied when measuring an alternating voltage.

  In the above embodiment, as an example of self-diagnosis, the switch 14 is turned off and the output of the voltage detection unit 11 is abnormal when the voltage is equal to or higher than a predetermined voltage. Further, when the switch 15 is connected to the GND side with the switch 14 turned on, a voltage equal to or higher than the reference potential is measured, and when the switch 15 is connected to the reference potential side, a voltage of 0 V is measured. Self-diagnosis may be performed if the detection unit 11 or the like is abnormal.

  Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

  Hereinafter, the correspondence between the constituent elements of the present invention and the constituent elements of the above embodiment will be described. The voltage detection device of the present invention corresponds to the voltage detection function unit 2 and the CPU 3, the voltage detection target corresponds to the assembled battery 1, the predetermined ratio corresponds to 1/100 times, and the conversion means corresponds to the voltage detection unit 11. The predetermined reference voltage corresponds to the output voltage from the reference potential generator 12, the subtracting means corresponds to the differential amplifier circuit 13, the amplification factor corresponds to 3/2, and the amplifying means corresponds to the differential amplifier circuit. 13 corresponds to the CPU 3 having the A / D converter 16 and the control unit 17. The voltage detection target is operating normally when the battery pack 1 is connected to the load and charging / discharging normally, and the voltage detected by the voltage detection target does not drop below that. Corresponds to the lower limit value 200 V of the actual operating voltage range of the assembled battery 1.

  The load connection determining means corresponds to the CPU 3 and corresponds to determining whether the self-diagnosis end signal is transmitted or not yet transmitted in step S8 of FIG. Further, the subtraction control means corresponds to the CPU 3 and the switch 15, the error detection means corresponds to the CPU 3, the input control means corresponds to the CPU 3 and the switch 14, and the self-diagnosis means corresponds to the CPU 3. The above description of the association is merely an example, and the present invention is not construed as being limited to this association.

It is a figure which shows the assembled battery voltage detection system of a hybrid vehicle. It is a figure which shows the detail of the voltage detection function part 2 and CPU3. It is a figure explaining the principle of this invention. It is a figure which shows the flowchart of the process which the control part 17 inside CPU3 performs. It is a figure which shows the modification of the detail of the voltage detection function part 2 and CPU3. It is a figure which shows the other modification of the detail of the voltage detection function part 2 and CPU3. It is a figure explaining performing a highly accurate voltage measurement when it is more than a predetermined voltage, when there is a voltage change more than a predetermined value, when it is more than a predetermined current, or when there is a current change more than a predetermined value.

Explanation of symbols

1 assembled battery 2 voltage detection function unit 3 and 4 CPU
5 Loads 6 and 7 Switch 8 Current detection sensor 11 Voltage detection unit 12 Reference potential generation unit 13 Differential amplification circuit 14 and 15 Switch 16 A / D converter 17 Control unit 21 Reference potential generation unit 22 Chopper unit

Claims (11)

A voltage detection device,
Conversion means for inputting a voltage output from a voltage detection target and outputting a voltage converted at a predetermined ratio;
Subtracting means for subtracting a predetermined reference voltage from the voltage output from the converting means;
Amplifying means for amplifying the voltage subtracted by the subtracting means at a predetermined gain;
A voltage detection device comprising: voltage value detection means for obtaining a voltage value of the voltage detection target based on the voltage amplified by the amplification means. The voltage detection device according to claim 1,
The voltage detection apparatus according to claim 1, wherein the reference voltage is a voltage corresponding to a voltage at which the voltage detection target voltage is assumed not to fall below that when the voltage detection target is operating normally. In the voltage detection apparatus in any one of Claim 1 to 2,
The voltage detecting device, wherein the subtracting means is constituted by a differential amplifier circuit. In the voltage detection apparatus in any one of Claim 1 to 3,
The voltage value detection means includes the voltage value amplified by the amplification means, the predetermined ratio, the reference voltage or the voltage detection target voltage value corresponding to the reference voltage, and the amplification factor. A voltage detection device that obtains a voltage value of the voltage detection target based on the voltage detection device. In the voltage detection apparatus in any one of Claim 1 to 4,
The voltage detection device includes an A / D conversion unit that inputs a voltage amplified by the amplification unit and outputs a digital value. In the voltage detection apparatus in any one of Claim 1 to 5,
Load connection determining means for determining whether or not the voltage detection target is connected to a load;
Subtraction control means for controlling whether or not to subtract a reference voltage from the voltage output from the conversion means in the subtraction means;
Error detection means for obtaining an error of the voltage detection device,
The error detection means determines that the load connection determination means determines that the voltage detection target is not connected to a load, and controls the subtraction control means not to subtract a reference voltage from the voltage output from the conversion means. The voltage detection device is characterized in that the error is obtained based on the voltage value of the voltage detection target obtained by the voltage value detection means. The voltage detection device according to claim 6,
An input control means for controlling on / off of the input to the conversion means of the voltage output from the voltage detection target;
The error detection means determines that the load connection determination means determines that the voltage detection target is not connected to a load, and controls the subtraction control means not to subtract a reference voltage from the voltage output from the conversion means. When the input control means controls to turn off the input of the voltage output from the voltage detection target to the conversion means, the error is offset based on the voltage value obtained by the voltage value detection means. As an error,
The voltage value detection means controls the subtraction control means to subtract a reference voltage from the voltage output from the conversion means, and the input control means supplies the voltage output from the voltage detection target to the conversion means. The voltage detection device obtains the voltage value of the voltage detection object in consideration of the offset error when the input is controlled to be turned on. In the voltage detection apparatus in any one of Claim 1 to 5,
Load connection determining means for determining whether or not the voltage detection target is connected to a load;
Subtraction control means for controlling whether or not to subtract a reference voltage from the voltage output from the conversion means in the subtraction means;
Self-diagnosis means for performing self-diagnosis of the voltage detection device,
The self-diagnosis unit determines that the load connection determination unit determines that the voltage detection target is not connected to a load, and controls so that the subtraction control unit does not subtract a reference voltage from the voltage output from the conversion unit. And a self-diagnosis based on the voltage value obtained by the voltage value detecting means. The voltage detection device according to claim 8,
An input control means for controlling on / off of the input to the conversion means of the voltage output from the voltage detection target;
The self-diagnosis unit determines that the load connection determination unit determines that the voltage detection target is not connected to a load, and controls so that the subtraction control unit does not subtract a reference voltage from the voltage output from the conversion unit. When the input control means controls to turn off the input of the voltage output from the voltage detection target to the conversion means, the voltage value obtained by the voltage value detection means is a predetermined value or more. A voltage detection device characterized by self-diagnosis that there is an abnormality when judged to be present. In the voltage detection apparatus in any one of Claim 1 to 5,
Subtracting control means for controlling whether or not to subtract a reference voltage from the voltage output from the converting means in the subtracting means,
When the voltage detection target voltage is equal to or higher than a predetermined voltage, and when the voltage change of the voltage detection target is equal to or higher than a predetermined voltage, the subtraction control means When it is above, when detecting whether any change in current flowing from the voltage detection target to the load is equal to or greater than a predetermined current, the subtracting means subtracts the reference voltage from the voltage output from the converting means. A voltage detecting device characterized by controlling. In the voltage detection apparatus in any one of Claim 1 to 10,
The voltage detection target is any one of an assembled battery, a large-capacity capacitor, and a single cell battery used for driving a motor of a vehicle.

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