Voltage Detector

Abstract

To enable the occurrence of a conversion state switching fault to be determined for even an input voltage whose output voltage agrees in a first and a second conversion state.SOLUTION: A voltage detection device (10) comprises: a conversion switching unit (60) for switching between a first conversion state in which an input voltage from a battery (Cn) in a first range is converted to an output voltage of a prescribed region and a second conversion state in which an input voltage in a second range that is included in the first range is converted to an output voltage of a prescribed region; an AD conversion unit (80) for converting the output voltage from analog to digital; a voltage conversion unit (92) for converting the AD converted value to a detection voltage of a first range and a detection voltage of a second range, in accordance with a switching command that switches between the first and the second conversion states; an input change unit (30) for causing the input voltage to the conversion switching unit to change in the first range to be wider than the width of the second range; and a determination unit (93) for determining a conversion state switching fault on the basis of the detection voltage that is converted before and after the input voltage is changed, respectively.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a voltage detection device that detects the voltage of a battery. [Background technology]

[0002] Conventionally, there is a voltage detection device that can detect the total voltage of a battery pack as well as the voltage of each cell by changing the gain of a differential amplifier circuit (see Patent Document 1). In the voltage detection device described in Patent Document 1, the gain of the differential amplifier circuit when detecting the total voltage of the battery pack is set smaller than the gain of the differential amplifier circuit when detecting the voltage of each cell. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-156353 A Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors of the present application have devised a voltage detection device that, when detecting the voltage of each cell, can be switched between a first conversion state in which an input voltage in a first range is converted into an output voltage in a predetermined range, and a second conversion state in which an input voltage in a second range included in the first range is converted into an output voltage in the predetermined range, and converts the output voltage into a detection voltage in the first range and a detection voltage in the second range according to the first conversion state and the second conversion state, respectively. The first range is the range of all cell voltages including abnormal states, and the second range is a range that expands the cell voltage in the normal use range, which has the effect of improving detection accuracy.

[0005] In the voltage detection device of the above invention, for an input voltage where the output voltage is the same in the first conversion state and the second conversion state, even if a conversion state switching fault occurs, the detection voltage does not change before and after the conversion state switching for the input voltage. Therefore, it may not be possible to determine that a conversion state switching fault has occurred based on the detection voltages before and after the conversion state switching. This problem is not limited to the case of detecting the voltage of each cell, but may also occur when detecting the total voltage of a battery pack or the voltage of a single cell.

[0006] The present invention has been made to solve the above-mentioned problems, and its main object is to make it possible to determine that a conversion state switching fault has occurred even for an input voltage where the output voltage is the same in the first conversion state and the second conversion state. [Means for solving the problem]

[0007] A first means for solving the above problem is a voltage detection device (10), a conversion switching unit (60) that switches between a first conversion state in which an input voltage from a battery (Cn) in a first range is converted into an output voltage in a predetermined range, and a second conversion state in which the input voltage in a second range included in the first range is converted into an output voltage in the predetermined range; an AD conversion unit (80) that performs AD conversion on the output voltage from the conversion switching unit and outputs the converted value; a switching command unit (91) that outputs a switching command to the conversion switching unit to switch between the first conversion state and the second conversion state; a voltage conversion unit (92) that converts the converted value input from the AD conversion unit into a detection voltage of the first range and a detection voltage of the second range in response to the switching command output by the switching command unit; an input change unit (30, 130, 230) that changes the input voltage to the conversion switching unit in the first range to a width wider than the width of the second range; a determination unit (93) that determines a switching failure of the conversion state by the conversion switching unit based on the detection voltage converted by the voltage conversion unit before and after the input voltage is changed by the input change unit; Equipped with.

[0008] According to the above configuration, when the conversion state is switched to the first conversion state, the input voltage from the battery can be obtained as a detected voltage in the first range that is wider than the second range, whereas when the conversion state is switched to the second conversion state, the input voltage from the battery can be obtained as a highly accurate detected voltage in the second range that is included in the first range.

[0009] Here, since the second range is included in the first range, at a given input voltage in the second range, the output voltage converted in the first conversion state may match the output voltage converted in the second conversion state. Therefore, even if a switching failure of the conversion state by the conversion switching unit occurs, when the converted value of the output voltage is converted into the detection voltage of the first range and the detection voltage of the second range in response to the switching command, the detection voltages may match. Therefore, it may not be possible to determine that a switching failure of the conversion state by the conversion switching unit has occurred based on the detection voltages before and after the switching of the conversion state.

[0010] In order to determine this switching failure, the input change unit changes the input voltage to the conversion change unit in the first range by a width wider than the width of the second range. At this time, the input voltages before and after the change are both included in the first range, whereas at least one of the input voltages before and after the change is an input voltage outside the second range.

[0011] Therefore, when the switching command unit outputs a switching command to switch to the first conversion state, if the conversion switching unit has normally switched to the first conversion state, both of the input voltages before and after being changed by the input changing unit are converted to output voltages in a predetermined range and then converted to detection voltages in the first range. In contrast, when the switching command unit outputs a switching command to switch to the first conversion state, it is assumed that a switching failure occurs in which the conversion switching unit switches to the second conversion state. In this case, at least one of the input voltages before and after being changed by the input changing unit is converted to an output voltage at the end of the predetermined range or an output voltage outside the predetermined range and then converted to a detection voltage at the end of the first range or a detection voltage outside the first range. Therefore, even for an input voltage whose output voltages are the same in the first conversion state and the second conversion state, a detection voltage different from the detection voltage in the normal state can be obtained.

[0012] In addition, when the switching command unit outputs a switching command to switch to the second conversion state, if the conversion switching unit has normally switched to the second conversion state, at least one of the input voltages before and after being changed by the input changing unit is converted to an output voltage at the end of the predetermined range or an output voltage outside the predetermined range, and then converted to a detection voltage at the end of the second range or a detection voltage outside the second range. In contrast, when the switching command unit outputs a switching command to switch to the second conversion state, it is assumed that a switching failure occurs in which the conversion switching unit switches to the first conversion state. In this case, both of the input voltages before and after being changed by the input changing unit are converted to an output voltage in the predetermined range, and then converted to a detection voltage in the second range. Therefore, even for an input voltage whose output voltage is the same in the first conversion state and the second conversion state, a detection voltage different from the detection voltage in the normal state can be obtained.

[0013] Therefore, the determination unit can determine that a switching failure has occurred due to the conversion switching unit based on the detected voltage before and after the input voltage is changed by the input change unit, and can therefore determine that a switching failure has occurred in the conversion state even for an input voltage for which the output voltages in the first conversion state and the second conversion state are the same.

[0014] In the second means, in the second conversion state, the conversion switching unit converts the input voltage in the second range to an output voltage in the predetermined range, and converts the input voltage outside the second range to an output voltage at the near end of the predetermined range. Here, it is assumed that a switching failure occurs in which the conversion switching unit switches to the second conversion state when the switching command unit outputs a switching command to switch to the first conversion state. In this case, at least one of the input voltages before and after being changed by the input changing unit is converted to an output voltage at the near end of the predetermined range and then converted to a detection voltage at the end of the first range.

[0015] In consideration of the above, when the switching command is a switching command to switch to the first conversion state, the determination unit determines that a switching failure has occurred in which the conversion switching unit has switched to the second conversion state, based on the fact that at least one of the detected voltages before and after the input voltage is changed by the input changing unit is the detected voltage at the end of the first range. Therefore, it is possible to determine that a switching failure has occurred in which the conversion switching unit has switched to the second conversion state, even for an input voltage whose output voltages in the first conversion state and the second conversion state are the same.

[0016] In the third means, in the first conversion state, the conversion switching unit converts the input voltage in the first range into an output voltage in the predetermined range in a proportional relationship. Therefore, when the input voltage is multiplied by a predetermined factor, the output voltage also becomes multiplied by a predetermined factor, and the converted value output by the AD conversion unit also becomes multiplied by a predetermined factor. When the switching command is a switching command for switching to the first conversion state, the voltage conversion unit converts the converted value input from the AD conversion unit into a detection voltage in the first range by a proportional function. Therefore, when the converted value is multiplied by a predetermined factor, the detection voltage also becomes multiplied by a predetermined factor. Then, the input change unit changes the input voltage to the conversion switching unit by a positive predetermined factor smaller than 1, thereby making the input voltage wider in the first range than the width of the second range. Therefore, when the input voltage is multiplied by a positive predetermined factor smaller than 1, the detection voltage also finally becomes multiplied by a predetermined factor.

[0017] As described above, when the switching command unit outputs a switching command to switch to the first conversion state, if the conversion switching unit has normally switched to the first conversion state, the detected voltage after the input voltage is changed by the input change unit becomes a predetermined multiple of the detected voltage before the input voltage is changed. Therefore, when the switching command is a switching command to switch to the first conversion state and the predetermined multiple of the detected voltage before the input voltage is changed by the input change unit and the detected voltage after the input voltage is changed by the input change unit can be considered to be equal, the determination unit can determine that a switching failure of the conversion state by the conversion switching unit has not occurred.

[0018] On the other hand, when the switching command unit outputs a switching command for switching to the first conversion state, and a switching failure occurs in which the conversion switching unit switches to the second conversion state, the operation is as follows. The conversion switching unit converts the input voltage in the second range to an output voltage in the predetermined range, and converts the input voltage outside the second range to an output voltage at the closer end of the predetermined range. Therefore, when the input voltage to the conversion switching unit is multiplied by a positive predetermined value smaller than 1, the input voltage after the change is converted by the input changing unit to an output voltage at the smaller end of the predetermined range. As a result, the output voltage is not multiplied by the predetermined value, the converted value output by the AD conversion unit is not multiplied by the predetermined value, and the detection voltage is not multiplied by the predetermined value. Therefore, when the switching command is a switching command for switching to the first conversion state, and the predetermined value of the detection voltage before the input voltage is changed by the input changing unit and the detection voltage after the input voltage is changed by the input changing unit cannot be regarded as being equal to each other, the determination unit can determine that a switching failure occurs in which the conversion switching unit switches to the second conversion state.

[0019] However, when the second range is one range selected from a plurality of ranges different from each other, the following problem may occur. When the switching command is a switching command to switch to the first conversion state, a switching failure may occur in which the conversion switching unit switches to the second conversion state in the second range different from the assumption. When a voltage obtained by multiplying the input voltage by a positive predetermined value smaller than 1 is included in the second range different from the assumption, the input voltage after the change by the input changing unit is not converted to an output voltage at the lower end of the predetermined range, but is converted to an output voltage in the predetermined range. In this case, the predetermined value multiplied by the detection voltage before the input changing unit changes the input voltage may be equal to the detection voltage after the input changing unit changes the input voltage. For this reason, when the switching command is a switching command to switch to the first conversion state, even though a switching failure occurs in which the conversion switching unit switches to the second conversion state in the second range different from the assumption, it may be erroneously determined that no switching failure of the conversion state by the conversion switching unit has occurred.

[0020] When the above switching failure occurs and the voltage obtained by multiplying the input voltage by a positive predetermined factor smaller than 1 is included in the second range different from the assumption, the input voltage before being changed wider than the width of the second range is outside the second range with respect to the second range different from the assumption. Therefore, in the fourth means, when the third means considers the input voltage to be equal and the detected voltage before the input voltage is changed by the input changing unit is the detected voltage at the end of the first range, the determining unit determines preferentially that an abnormality has occurred. Therefore, when the switching command is a switching command for switching to the first conversion state, it is possible to suppress erroneous determination that no switching failure of the conversion state by the conversion switching unit has occurred despite the occurrence of a switching failure in which the conversion switching unit has switched to the second conversion state in the second range different from the assumption.

[0021] In a fifth aspect, in the second conversion state, the conversion switching unit converts the input voltage in the second range to an output voltage in the predetermined range, and converts the input voltage outside the second range to an output voltage at the near end of the predetermined range. Here, when the switching command is a switching command to switch to the second conversion state, a switching failure occurs in which the conversion switching unit switches to the first conversion state. In this case, both of the input voltages before and after being changed by the input changing unit are converted to output voltages in the predetermined range and then converted to detection voltages other than the end of the second range.

[0022] In consideration of the above, when the switching command is a switching command to switch to the second conversion state, the determination unit determines that a switching failure has occurred in which the conversion switching unit has switched to the first conversion state, based on the fact that neither of the detected voltages before and after the input voltage is changed by the input changing unit is the detected voltage at the end of the second range. Therefore, it is possible to determine that a switching failure has occurred in which the conversion switching unit has switched to the first conversion state, even for an input voltage whose output voltages in the first conversion state and the second conversion state are the same.

[0023] In a sixth aspect, the input change unit changes the input voltage to the conversion switching unit by a positive predetermined multiple smaller than 1, thereby changing the input voltage in the first range to a width wider than the width of the second range. Therefore, when the switching command unit outputs a switching command to switch to the second conversion state, if the conversion switching unit has normally switched to the second conversion state, the detected voltage after the input voltage is changed by the input change unit becomes the detected voltage at the small end of the second range. Therefore, when the switching command is a switching command to switch to the second conversion state, and the detected voltage after the input voltage is changed by the input change unit and the detected voltage at the small end of the second range can be considered to be equal, the determination unit can determine that a switching failure of the conversion state by the conversion switching unit has not occurred.

[0024] On the other hand, when the switching command unit outputs a switching command to switch to the second conversion state and a switching fault occurs in which the conversion switching unit switches to the first conversion state, the operation is as follows. The conversion switching unit converts the input voltage in the first range into an output voltage in the predetermined range. Therefore, when the input voltage to the conversion switching unit is multiplied by a positive predetermined value smaller than 1, the input voltage after the change is converted by the input changing unit into an output voltage other than the terminal of the predetermined range, and then converted into a detection voltage other than the terminal of the second range. Therefore, when the switching command is a switching command to switch to the second conversion state and the detection voltage after the input voltage is changed by the input changing unit cannot be regarded as being equal to the detection voltage at the smaller terminal of the second range, the determination unit can determine that a switching fault occurs in which the conversion switching unit switches to the first conversion state.

[0025] In the sixth means, if the battery is overcharged and the input voltage from the battery becomes higher than the voltage at the higher end of the second range, the following problem may occur: When the switching command is a switching command to switch to the second conversion state, and the voltage obtained by multiplying the input voltage by a positive predetermined factor smaller than 1 is included in the second range, the input voltage may be converted to an output voltage other than the lower end of the predetermined range, and then converted to a detection voltage other than the lower end of the second range. For this reason, when the switching command is a switching command to switch to the second conversion state, there is a risk of erroneously determining that a switching failure has occurred in which the conversion switching unit has switched to the first conversion state, even though no switching failure has occurred in the conversion switching unit.

[0026] Here, when the voltage obtained by multiplying the input voltage by a positive predetermined factor smaller than 1 is included in the second range, the input voltage before being changed to a value wider than the width of the second range falls outside the second range. Therefore, in the seventh means, when the input voltage cannot be regarded as equal in the sixth means and the detected voltage before the input voltage is changed by the input changing unit is the detected voltage at the end of the first range, the determining unit determines preferentially that a switching failure of the conversion state caused by the conversion switching unit has not occurred. Therefore, when the switching command is a switching command for switching to the second conversion state, it is possible to suppress erroneous determination that a switching failure has occurred in which the conversion switching unit has switched to the first conversion state, even though a switching failure of the conversion switching unit has not occurred.

[0027] For batteries such as LFP (lithium iron phosphate) batteries, where the change in open circuit voltage (OCV) relative to the change in the battery's charging rate is small, it is necessary to detect the OCV with high accuracy when detecting the battery's charging rate. On the other hand, when monitoring the battery for overcharging or overdischarging, it is necessary to detect the battery voltage in a wide range.

[0028] In this regard, in the eighth means, the switching command unit sets the switching command to the first conversion state when monitoring overcharging or overdischarging of the battery, and sets the switching command to the second conversion state when detecting the charging rate of the battery. Therefore, it is possible to appropriately switch between the first conversion state and the second conversion state when monitoring overcharging or overdischarging of the battery and when detecting the charging rate of the battery.

[0029] In a ninth aspect, the battery is one cell selected from a plurality of cells included in a battery pack, and the input change unit is configured with a circuit that discharges each cell when equalizing the charging rates of the plurality of cells. With this configuration, the input voltage to the conversion switching unit can be changed in the first range to a width wider than the width of the second range by using a circuit that discharges each cell when equalizing the charging rates of the plurality of cells. Therefore, there is no need to add a new circuit to configure the input change unit. [Brief description of the drawings]

[0030] [Figure 1] FIG. [Diagram 2] Graph showing the relationship between SOC and normal range. [Diagram 3] Graph showing the relationship between SOC and extended range. [Figure 4] 1 is a table showing detection voltages in the normal range and each extended range. [Diagram 5] A graph showing the relationship between the input voltage and the AD conversion value for each range. [Figure 6] 11 is a graph showing points of agreement between AD conversion values ​​in the normal range and each expanded range. [Figure 7] 1 is a graph showing the principle of overcharging caused by a switching fault. [Figure 8] FIG. 4 is a partial circuit diagram showing the input voltage during fault diagnosis. [Figure 9] 5 is a graph showing the relationship between an input voltage and a detection voltage during normal detection. [Figure 10] 11 is a graph showing the relationship between an input voltage and a detection voltage during focus detection. [Figure 11] 4 is a graph showing the relationship between the input voltage and the AD conversion value under normal conditions. [Figure 12] 6 is a graph showing the relationship between an AD conversion value and a detection voltage under normal conditions. [Figure 13] 13 is a graph showing the relationship between the input voltage and the AD conversion value when a switching fault occurs in which the normal range is erroneously switched to the expanded range. [Figure 14]11 is a graph showing the relationship between the AD conversion value and the detection voltage when a switching fault occurs in which the normal range is erroneously switched to the expanded range. [Figure 15] 13 is a flowchart showing the procedure of ZZ' diagnosis. [Figure 16] 11 is a graph showing the relationship between the input voltage and the AD conversion value when a switching fault occurs in which the expanded range setting is erroneously switched to the normal range. [Figure 17] 11 is a graph showing the relationship between the AD conversion value and the detection voltage when a switching fault occurs in which the expanded range is erroneously switched to the normal range. [Figure 18] 4 is a flowchart showing a procedure for Z'V1 diagnosis. [Figure 19] Graph showing the ZZ' diagnosable range when switching to the expanded range R6. [Figure 20] 13 is a graph showing the ZZ' diagnosable range when a switching fault occurs due to erroneous switching to the expanded range R1 when the normal range is set. [Figure 21] 13 is a graph showing the ZZ' diagnosable range and the over-range diagnosable range when a switching fault occurs in which the normal range is erroneously switched to the expanded range R1. [Figure 22] FIG. 13 is a diagram showing the relationship between the ZZ' diagnosable range and the over-range diagnosable range. [Figure 23] 13 is a flowchart showing the procedure of a modified example of the ZZ' diagnosis. [Figure 24] 13 is a graph showing the Z'V1 diagnosable range when a switching fault occurs due to an erroneous switch to normal when the expanded range is set. [Diagram 25] 13 is a graph showing the Z'V1 diagnosable range and the V2Z diagnosable range when a switching fault occurs in which the expanded range setting is erroneously switched to normal. [Figure 26] FIG. 13 is a diagram showing the relationship between the Z'V1 diagnosable range and the V2Z diagnosable range. [Figure 27] 11 is a flowchart showing the procedure of a modified example of Z'V1 diagnosis. [Figure 28] FIG. 11 is a circuit diagram showing a modified example of the equalization circuit. [Figure 29] FIG. 13 is a circuit diagram showing a modified example of the input voltage changing unit. [Diagram 30]FIG. 13 is a circuit diagram showing another modified example of the input voltage changing unit. [Diagram 31] A timing chart showing the relationship between VG and input voltage. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a voltage detection device for detecting the voltage of each battery cell of a battery pack will be described below with reference to the drawings.

[0032] As shown in FIG. 1, the voltage detection device 10 includes an input voltage change section 30, a multiplexer 50, a differential amplifier circuit 60, an AD converter 80, a control section 90, and the like.

[0033] The battery pack 20 is configured by connecting a plurality of battery cells Cn (C1 to C6 are shown) which are secondary batteries in series.

[0034] The input voltage change section 30 (input change section) includes a plurality of RC filters each formed of a series circuit of a resistance element 31 and a capacitor 32, a plurality of discharge resistance elements 33, a plurality of discharge switches San (Sa1 to Sa6 are shown), and the like.

[0035] A series circuit of a resistance element 31 and a capacitor 32 is connected to the positive terminal and the negative terminal of each battery cell Cn (battery). Between the positive terminal and the negative terminal of each battery cell Cn, a series circuit of the resistance element 31 and the capacitor 32 and a series circuit of a discharge resistance element 33, a discharge switch San, and a discharge resistance element 33 are connected in parallel. The discharge switch San is connected between the two discharge resistance elements 33. The discharge switch San is composed of, for example, an N-channel MOSFET. As an example, the resistance value of the discharge resistance element 33 is 82 [Ω], the resistance value of the resistance element 31 is 320 [Ω], and the capacitance of the capacitor 32 is about 1 [μF].

[0036] When the discharge switch San is turned on, the battery cell Cn is discharged via the discharge resistance element 33 connected to the positive terminal and the discharge resistance element 33 connected to the negative terminal. The discharge switch San is controlled by the control unit 90.

[0037] The multiplexer 50 includes a plurality of switches Sbn (Sb1 to Sb12 are shown in the figure). The odd-numbered switches Sbn are connected to a connection point between the discharge resistive element 33 and the discharge switch San. The even-numbered switches Sbn are connected to a connection point between the resistive element 31 and the capacitor 32. The switches Sbn are controlled by a control unit 90.

[0038] The differential amplifier circuit 60 (conversion switching unit) includes an operational amplifier 61, input resistance elements 62, 63, a plurality of feedback resistance elements Ran (Ra0 to Ra7), a plurality of switches Scn (Sc0 to Sc7), a variable voltage power supply 65, a plurality of resistance elements Rbn (Rb0 to Rb7), a plurality of switches Sdn (Sd0 to Sd7), etc.

[0039] The odd-numbered switches Sbn of the multiplexer 50 are connected to the inverting input terminal (- terminal) of the operational amplifier 61 via an input resistor element 62. The even-numbered switches Sbn of the multiplexer 50 are connected to the non-inverting input terminal (+ terminal) of the operational amplifier 61 via an input resistor element 63. The voltage difference between the voltages input to the inverting input terminal and the non-inverting input terminal of the operational amplifier 61 is input to the AD converter 80.

[0040] The feedback resistance elements Ra0 to Ra7 are connected to the inverting input terminal and the output terminal of the operational amplifier 61 via the switches Sc0 to Sc7, respectively. The resistance elements Rb0 to Rb7 are connected to the positive terminal of the variable voltage power supply 65 and the non-inverting input terminal of the operational amplifier 61 via the switches Sd0 to Sd7, respectively. The variable voltage power supply 65 is a power supply capable of changing the output voltage. The gain of the differential amplifier circuit 60 is adjusted by selecting one of the switches Scn and Sdn to be turned on. The output voltage level of the differential amplifier circuit 60 is adjusted by changing the output voltage of the variable voltage power supply 65. The switches Scn and Sdn and the variable voltage power supply 65 are controlled by the control unit 90.

[0041] The AD converter 80 (AD conversion unit) converts the output voltage (analog signal) from the operational amplifier 61 (differential amplifier circuit 60) into an AD conversion value (digital signal). The AD converter 80 outputs the AD conversion value to the control unit 90.

[0042] The control unit 90 is configured by a microcomputer including a CPU, a ROM, a RAM, an input / output interface, etc. The control unit 90 realizes the functions of a switching command unit 91, a voltage conversion unit 92, and a determination unit 93, which will be described later.

[0043] The control unit 90 controls the switches Sbn to individually detect the voltage of each battery cell Cn. For example, when detecting the voltage of the battery cell C1, the control unit 90 turns on the switches Sb1 and Sb2.

[0044] The control unit 90 controls the discharge switch San of the input voltage change unit 30 to execute an equalization process for equalizing the charging rates (SOC: State Of Charge) [%] of each battery cell Cn. When executing the equalization process, for example, the odd-numbered battery cells Cn are discharged, and then the even-numbered battery cells Cn are discharged. For example, when discharging the battery cells C1 and C5, the discharge switches Sa1 and Sa5 are turned on. The input voltage change unit 30 is configured with a circuit that discharges each battery cell Cn when equalizing the SOC of the multiple battery cells Cn.

[0045] As shown in FIG. 2, the voltage detection device 10 performs normal detection to detect the open circuit voltage (OCV) of each battery cell Cn in a normal range R0 of 0 to 5 [V]. Since the relationship between SOC [%] and OCV [V] is determined according to the type of each battery, the SOC [%] can be calculated based on this relationship and the detected SOC [V]. When monitoring the overcharge or overdischarge of each battery cell Cn, it is required to detect the OCV of each battery cell Cn in a wide range. For this reason, the voltage detection device 10 performs normal detection.

[0046] In a battery such as an LFP (lithium iron phosphate) battery in which the change in OCV relative to the change in SOC of the battery cell is small, it is necessary to detect the OCV with high accuracy in order to accurately detect the SOC of the battery cell. Therefore, as shown in Fig. 3, the voltage detection device 10 performs focused detection in which the normal range of voltage of each battery cell Cn is expanded and detected. The expanded range R4 is the normal range of voltage in the battery cell of the LFP battery, for example, 2.5 to 3.75 [V].

[0047] 4 is a table showing the detection voltages for the normal range R0 and each of the expanded ranges R1 to R7. The remarks column lists examples of the types of batteries to which each expanded range applies.

[0048] Each range R0 to R7 is set by the switching command unit 91 outputting a switching command to the differential amplifier circuit 60 to control the switches Scn and Sdn. The differential amplifier circuit 60 switches between a first conversion state in which an input voltage from the battery in the normal range R0 (first range) is converted to an output voltage of 0 to 5 [V] (predetermined range) and a second conversion state in which an input voltage in the expanded ranges R1 to R7 (second range) included in the normal range R0 is converted to an output voltage of 0 to 5 [V] (predetermined range). When switching to the second conversion state, the switching command unit 91 selects one of the expanded ranges R1 to R7. When monitoring the overcharge or overdischarge of the battery cell Cn, the switching command unit 91 issues a switching command to the differential amplifier circuit 60 to switch to the first conversion state, and when detecting the SOC of each battery cell Cn, issues a switching command to the differential amplifier circuit 60 to switch to the second conversion state.

[0049] The AD converter 80 performs AD conversion on the output voltage from the differential amplifier circuit 60 and outputs the converted value to the control unit 90. In response to the switching command for switching between the first conversion state and the second conversion state, the voltage conversion unit 92 converts the AD converted value input from the AD converter 80 into a detection voltage of the normal range R0 and a detection voltage of any one of the expanded ranges R1 to R7.

[0050] 5 is a graph showing the relationship between the input voltage [V] and the AD converted value [V] in each range R0 to R7. The expanded ranges R1 to R7 are included in the normal range R0 (0 to 5 [V]). Therefore, the graphs showing the relationship between the input voltage and the AD converted value in the expanded ranges R1 to R7 each intersect with the graph showing the relationship between the input voltage and the AD converted value in the normal range R0.

[0051] 6 is a graph showing the points of agreement of AD converted values ​​between the normal range R0 and each of the expanded ranges R1 to R7. At the points of agreement of AD converted values ​​indicated by circles, the AD converted values ​​obtained by converting the output voltage of the differential amplifier circuit 60 by the AD converter 80 match between the normal range R0 and each of the expanded ranges R1 to R7. For this reason, it is not possible to determine that the expanded ranges R1 to R7 (second conversion state) have been erroneously switched to because the AD converted value for the input voltage is different from the AD converted value obtained by conversion in the normal range R0 (first conversion state). There are various other methods for determining a range (conversion state) switching failure by the differential amplifier circuit 60.

[0052] If it is not possible to distinguish between the normal range and the expanded range switching fault, overcharging of the battery cells may occur, as shown in Figure 7. This figure shows a case where the expanded range is mistakenly switched to the normal range when it is set.

[0053] Assume that the AD conversion values ​​match when the cell voltage (input voltage) is X1 [V], and it is erroneously determined that no switching failure has occurred. If the range has been switched to the expanded range, the detection voltage becomes Z2 [V] at cell voltage X2 [V], and charging is terminated. In contrast, if the range has been switched to the normal range, the detection voltage becomes Z1 [V] at cell voltage X2 [V], and charging continues. Then, charging continues until the detection voltage becomes Z2 [V] at cell voltage X3 [V], and the battery cell becomes overcharged.

[0054] Therefore, in this embodiment, the following diagnosis is performed to make it possible to determine that a range (conversion state) switching failure has occurred even for an input voltage whose AD conversion values ​​are the same in the normal range (first conversion state) and the expanded range (second conversion state).

[0055] The discrimination unit 93 changes the input voltage to the differential amplifier circuit 60 in the normal range R0 (first range) to a width wider than the width of the expanded ranges R1 to R7 (second range) by the input voltage change unit 30. The discrimination unit 93 discriminates a switching failure of the range (conversion state) by the differential amplifier circuit 60 based on the detection voltages converted by the voltage conversion unit 92 before and after the input voltage is changed by the input voltage change unit 30.

[0056] For example, when the voltage X of the battery cell C2 is used as the input voltage to the differential amplifier circuit 60, when the input voltage to the differential amplifier circuit 60 is changed by the input voltage change unit 30, the discharge switch Sa2 is turned on as shown in Fig. 8. As a result, the input voltage X' to the differential amplifier circuit 60 becomes 0.5X (X' = 0.5X).

[0057] FIG. 9 is a graph showing the relationship between input voltage X and detection voltage Z during normal detection. During normal detection, input voltage X is converted to detection voltage Z according to the solid line normal range graph. Under normal conditions, input voltage X and detection voltage Z are the same. For example, for input voltage X, detection voltage Z=X.

[0058] FIG. 10 is a graph showing the relationship between input voltage X and detection voltage Z during focus detection. During focus detection, the input voltage X is converted to detection voltage Z according to the expanded range graph of the solid line. Under normal conditions, the input voltage X and detection voltage Z are the same. For example, for an input voltage X, detection voltage Z=X.

[0059] FIG. 11 is a graph showing the relationship between the input voltage X and the AD conversion value Y in a normal state. The conversion from the input voltage X to the AD conversion value Y is performed by the differential amplifier circuit 60 and the AD converter 80. In the normal range, the input voltage X is converted to the AD conversion value Y by the formula Y=X. That is, when the normal range is set (first conversion state), the differential amplifier circuit 60 converts the input voltage X in the normal range (0 to 5 [V]) into an output voltage of 1 to 5 [V] (predetermined range) by a proportional relationship. In the expanded range, the input voltage X is converted to the AD conversion value Y by the formula Y=5(X-V1) / (V2-V1). That is, when the expanded range is set (second conversion state), the differential amplifier circuit 60 converts the input voltage X in the expanded range (V1 to V2) into an output voltage of 1 to 5 [V] (predetermined range), and converts the input voltage X outside the expanded range into an output voltage at the closer end of 1 to 5 [V]. Then, the AD converter 80 converts the output voltage into an AD conversion value Y.

[0060] FIG. 12 is a graph showing the relationship between the AD conversion value Y and the detection voltage Z in a normal state. Conversion from the AD conversion value Y to the detection voltage Z is executed by the voltage conversion unit 92. In the normal range, the AD conversion value Y is converted to the detection voltage Z by the formula Z=Y. That is, when a switching command to the differential amplifier circuit 60 is a switching command to switch to the normal range (first conversion state), the voltage conversion unit 92 converts the AD conversion value input from the AD converter 80 to the detection voltage Z of the normal range (first range) by a proportional function. In the expanded range, the AD conversion value Y is converted to the detection voltage Z by the formula Z=(V2-V1)Y / 5+V1.

[0061] In the normal range, the equation for converting the input voltage X to the AD-converted value Y and the equation for converting the AD-converted value Y to the detection voltage Z are inverse functions of each other. In the expanded range, the equation for converting the input voltage X to the AD-converted value Y and the equation for converting the AD-converted value Y to the detection voltage Z are inverse functions of each other. Therefore, in the normal range and the expanded range, the input voltage X and the detection voltage Z are the same.

[0062] Therefore, in the conversion shown in FIGS. 9 to 12, as an example of a method for determining a switching failure, if the detection voltage Z is the same before and after switching between the normal range and the expanded range for the input voltage X, it can be determined that the range has been switched normally.

[0063] Returning to FIG. 9, a case where a switching failure occurs in which the normal range is erroneously switched to the expanded range when the normal range is set will be described. In this case, the input voltage X is converted to a detection voltage Z by the dashed expanded range graph while the horizontal and vertical axes of FIG. 9 are maintained. Therefore, the detection voltage Z converted by the solid normal range graph for the input voltage X and the detection voltage Z converted by the dashed expanded range graph will generally have different values. However, when the input voltage X is at the AD conversion value match point, the detection voltage Z converted by the solid normal range graph for the input voltage X and the detection voltage Z converted by the dashed expanded range graph will have the same value. Therefore, even if the detection voltage Z is the same before and after switching between the expanded range and the normal range for the input voltage X, it may not be possible to determine that the range has been switched normally.

[0064] Therefore, the input voltage change unit 30 changes the input voltage X to the differential amplifier circuit 60 by a times, so that the normal range is wider than the expanded range (V1 to V2). a is a positive predetermined number smaller than 1, and a=0.5 in this embodiment. The detection voltage Z for the input voltage aX is Z'. In a normal state, the input voltage aX is converted to aX according to the graph of the normal range. On the other hand, in an abnormal state, the input voltage aX is converted to 0 [V] according to the graph of the expanded range. Therefore, the discrimination unit 93 discriminates that a switching failure has occurred in which the differential amplifier circuit 60 has switched to the expanded range, based on Z'=0 [V]. In other words, when the switching command to the voltage conversion unit 92 is a switching command to switch to the normal range (first conversion state), the discrimination unit 93 determines that a switching failure has occurred in which the differential amplifier circuit 60 (conversion switching unit) has switched to the expanded range (second conversion state), based on the fact that at least one of the detection voltages Z converted by the voltage conversion unit 92 before and after the input voltage X is changed by the input voltage change unit 30 is the detection voltage at the end of the normal range (first range).

[0065] Specifically, when aZ-Z'=0, it is determined to be normal, and when aZ-Z'≠0, it is determined that a switching failure has occurred in switching to the expanded range (hereinafter referred to as "ZZ' diagnosis"). aZ is a times the detection voltage Z for the input voltage X. Z' is the detection voltage Z for the input voltage aX. That is, when the switching command to the voltage conversion unit 92 is a switching command to switch to the normal range, and when it is deemed that a times (predetermined times) the detection voltage Z converted by the voltage conversion unit 92 before the input voltage X is changed by the input voltage change unit 30 is equal to the detection voltage Z' converted by the voltage conversion unit 92 after the input voltage X is changed by the input voltage change unit 30, the discrimination unit 93 determines that no switching failure of the range (conversion state) by the differential amplifier circuit 60 (conversion switching unit) has occurred, and when it is not deemed equal, it determines that a switching failure has occurred in switching to the expanded range by the differential amplifier circuit 60.

[0066] 13 is a graph showing the relationship between the input voltage X and the AD conversion value Y at the time of a switching fault in which the normal range is erroneously switched to the extended range. During normal operation, the input voltage X is converted to the AD conversion value Y (Y=X) and the input voltage aX is converted to the AD conversion value Y' (Y'=aX) according to the formula Y=X. Y' is the AD conversion value Y for the input voltage aX. In contrast, when the extended range is erroneously switched to, the input voltage X is converted to the AD conversion value Y {Y=5(X-V1) / (V2-V1)} according to the formula Y=5(X-V1) / (V2-V1), and the input voltage aX is converted to the AD conversion value Y' (Y'=0).

[0067] 14 is a graph showing the relationship between the AD conversion value Y and the detection voltage Z when a switching failure occurs in which the normal range is erroneously switched to the expanded range. In a normal state, the AD conversion value Y (Y=X) is converted to the detection voltage Z (Z=X) and the AD conversion value Y' (Y'=aX) is converted to the detection voltage Z' (Z'=aX) according to the formula Z=Y. In contrast, when the expanded range is erroneously switched to, the AD conversion value Y{Y=5(X-V1) / (V2-V1)} is converted to the detection voltage Z{Z=5(X-V1) / (V2-V1)} according to the formula Z=Y and the AD conversion value Y' (Y'=0) is converted to the detection voltage Z' (Z'=0).

[0068] Therefore, it can be explained by Figures 13 and 14 that when aZ-Z' = 0, it is determined to be normal, and when aZ-Z' ≠ 0, it is possible to determine that a switching failure has occurred in which the range is switched to the extended range.

[0069] 15 is a flow chart showing the procedure of the ZZ' diagnosis. This series of processes is executed by the control unit 90.

[0070] First, set it to the normal range (S101). Specifically, output a switching command to the differential amplifier circuit 60, and let the differential amplifier circuit 60 switch to the normal range, and set the equation for converting the AD conversion value Y to the detection voltage Z to Z = Y. Select the battery cell Ci (S102). i is an arbitrary natural number for selecting one battery cell Ci from a plurality of battery cells Cn. Specifically, turn on two switches Sbn (n = 2i - 1, n = 2i) corresponding to the battery cell Ci by the multiplexer 50.

[0071] Subsequently, turn off all the discharge switches San (S103). Obtain the detection voltage Z (S104). Specifically, convert the input voltage X into an AD conversion value Y by the differential amplifier circuit 60 and the AD converter 80, and convert the AD conversion value Y into the detection voltage Z according to the equation Z = Y.

[0072] Subsequently, turn on the discharge switch Sai corresponding to the battery cell Ci by the input voltage change section 30 (S105). Obtain the detection voltage Z' (S106). Specifically, convert the input voltage aX (a = 0.5) into an AD conversion value Y' by the differential amplifier circuit 60 and the AD converter 80, and convert the AD conversion value Y' into the detection voltage Z' according to the equation Z = Y.

[0073] Subsequently, determine whether |aZ - Z'| < Zth (S107). The threshold value Zth is a value for determining that |aZ - Z'| can be regarded as 0, and is set to a positive value close to 0 based on the error of the AD converter 80. In this determination, if it is determined that |aZ - Z'| < Zth (S107: YES), it is determined that the range switching by the differential amplifier circuit 60 is normal (S108). On the other hand, in this determination, if it is determined that |aZ - Z'| < Zth is not satisfied (S107: NO), it is determined that the differential amplifier circuit 60 has been erroneously switched to the enlarged range (S109). Then, end this series of processes (END).

[0074] The process of S101 corresponds to the process performed by the switching command unit 91, the processes of S104 and S106 correspond to the process performed by the voltage conversion unit 92, and the processes of S107 to S109 correspond to the process performed by the discrimination unit 93.

[0075] Returning to FIG. 10, a case where a switching failure occurs in which the normal range is mistakenly switched to when the expanded range is set will be described. In this case, while the horizontal and vertical axes of FIG. 10 are maintained, the input voltage X is converted to a detection voltage Z by the dashed normal range graph. For this reason, the detection voltage Z converted by the solid expanded range graph for the input voltage X and the detection voltage Z converted by the dashed normal range graph will generally have different values. However, when the input voltage X is at the AD conversion value match point, the detection voltage Z converted by the solid expanded range graph for the input voltage X and the detection voltage Z converted by the dashed normal range graph will have the same value. Therefore, even if the detection voltage Z is the same before and after switching between the normal range and the expanded range for the input voltage X, it may not be possible to determine that the range has been switched normally.

[0076] Therefore, the input voltage change unit 30 changes the input voltage X to the differential amplifier circuit 60 to a times, so that the normal range is wider than the expanded range (V1 to V2). a is a positive predetermined number smaller than 1, and a=0.5 in this embodiment. The detection voltage Z for the input voltage aX is Z'. In a normal state, the input voltage aX is converted to V1 according to the expanded range graph. On the other hand, in an abnormal state, the input voltage aX is converted to V3 [V] (>V1) according to the normal range graph. Therefore, the discrimination unit 93 discriminates that a switching failure has occurred in which the differential amplifier circuit 60 has switched to the normal range, based on the fact that Z'≠V1 [V]. In other words, when the switching command to the voltage conversion unit 92 is a switching command to switch to the expanded range (second conversion state), the discrimination unit 93 determines that a switching failure has occurred in which the differential amplifier circuit 60 (conversion switching unit) has switched to the normal range (first conversion state) based on the fact that neither of the detection voltages Z converted by the voltage conversion unit 92 before and after the input voltage X is changed by the input voltage change unit 30 is the detection voltage at the end of the expanded range (second range).

[0077] Specifically, if Z'-V1=0, it is determined to be normal, and if Z'-V1≠0, it is determined that a switching failure has occurred in which the range has been switched to the normal range (hereinafter referred to as "Z'V1 diagnosis"). Z' is the detection voltage Z for the input voltage aX. That is, if the switching command to the voltage conversion unit 92 is a switching command to switch to the expanded range, and the detection voltage Z' converted by the voltage conversion unit 92 after the input voltage X is changed by the input voltage change unit 30 is considered to be equal to the detection voltage (V1) at the small end of the expanded range, the discrimination unit 93 determines that a switching failure of the range (conversion state) by the differential amplifier circuit 60 (conversion switching unit) has not occurred, and if they cannot be considered to be equal, it determines that a switching failure has occurred in which the range has been switched to the normal range by the differential amplifier circuit 60.

[0078] FIG. 16 is a graph showing the relationship between the input voltage X and the AD conversion value Y at the time of a switching failure in which the expanded range is erroneously switched to the normal range. During normal operation, the input voltage X is converted to the AD conversion value Y {Y=5(X-V1) / (V2-V1)} by the formula Y=5(X-V1) / (V2-V1), and the input voltage aX is converted to the AD conversion value Y' (Y'=0). Y' is the AD conversion value Y for the input voltage aX. In contrast, when the range is erroneously switched to the normal range, the input voltage X is converted to the AD conversion value Y (Y=X) by the formula Y=X, and the input voltage aX is converted to the AD conversion value Y' (Y'=aX).

[0079] FIG. 17 is a graph showing the relationship between the AD conversion value Y and the detection voltage Z when a switching failure occurs in which the expanded range is erroneously switched to the normal range. In a normal state, the AD conversion value Y{Y=5(X-V1) / (V2-V1)} is converted to the detection voltage Z(Z=X) by the formula Z=(V2-V1)Y / 5+V1, and the AD conversion value Y'(Y'=0) is converted to the detection voltage Z'(Z'=V1). In contrast, when the normal range is erroneously switched to, the AD conversion value Y(Y=X) is converted to the detection voltage Z{Z=(V2-V1)X / 5+V1} by the formula Z=(V2-V1)Y / 5+V1, and the AD conversion value Y'(Y'=aX) is converted to the detection voltage Z'{Z'=(V2-V1)aX / 5+V1}.

[0080] Therefore, it can be understood from Figures 16 and 17 that when Z'-V1=0, it is determined to be normal, and when Z'-V1 ≠ 0, it is possible to determine that a switching failure has occurred in which the range is switched to the normal range.

[0081] 18 is a flowchart showing the procedure of Z'V1 diagnosis. This series of processes is executed by the control unit 90.

[0082] First, set it to the expansion range (S201). Specifically, output a switching command to the differential amplifier circuit 60, and cause the differential amplifier circuit 60 to switch to the expansion range, and set the equation for converting the AD conversion value Y into the detection voltage Z as Z = (V2 - V1)Y / 5 + V1. Select the battery cell Ci (S202). i is an arbitrary natural number for selecting one battery cell Ci from a plurality of battery cells Cn. Specifically, turn on two switches Sbn (n = 2i - 1, n = 2i) corresponding to the battery cell Ci by the multiplexer 50.

[0083] Subsequently, turn off all the discharge switches San (S203). Obtain the detection voltage Z (S204). Specifically, convert the input voltage X into the AD conversion value Y by the differential amplifier circuit 60 and the AD converter 80, and convert the AD conversion value Y into the detection voltage Z according to the equation Z = (V2 - V1)Y / 5 + V1.

[0084] Subsequently, turn on the discharge switch Sai corresponding to the battery cell Ci by the input voltage change unit 30 (S205). Obtain the detection voltage Z' (S206). Specifically, convert the input voltage aX (a = 0.5) into the AD conversion value Y' by the differential amplifier circuit 60 and the AD converter 80, and convert the AD conversion value Y' into the detection voltage Z' according to the equation Z = (V2 - V1)Y / 5 + V1.

[0085] Subsequently, determine whether |Z' - V1| < Zth (S207). The threshold value Zth is a value for determining that |Z' - V1| can be regarded as 0, and is set to a positive value close to 0 based on the error of the AD converter 80. In this determination, if it is determined that |Z' - V1| < Zth (S207: YES), it is determined that the range switching by the differential amplifier circuit 60 is normal (S208). On the other hand, in this determination, if it is determined that |Z' - V1| < Zth is not satisfied (S207: NO), it is determined that the differential amplifier circuit 60 has been erroneously switched to the normal range (S209). Then, end this series of processes (END).

[0086] The process of S201 corresponds to the process performed by the switching command unit 91, the processes of S204 and S206 correspond to the process performed by the voltage conversion unit 92, and the processes of S207 to S209 correspond to the process performed by the discrimination unit 93. The processes of S203 and S204 may be omitted.

[0087] The present embodiment described above in detail has the following advantages.

[0088] When switched to the first conversion state, in the normal range which is wider than the expanded range, the input voltage X from the battery cell Cn can be obtained as the detected voltage Z. On the other hand, when switched to the second conversion state, in the expanded range which is included in the normal range, the input voltage X from the battery cell Cn can be obtained as the highly accurate detected voltage Z.

[0089] When the switching command unit 91 outputs a switching command to switch to the first conversion state (normal range), if the differential amplifier circuit 60 has normally switched to the first conversion state, any input voltage aX changed by the input voltage change unit 30 is converted to an output voltage of 0 to 5 [V] and then converted to a detection voltage Z of the normal range. In contrast, when the switching command unit 91 outputs a switching command to switch to the first conversion state, a switching failure occurs in which the differential amplifier circuit 60 switches to the second conversion state (extended range). In this case, the input voltage aX changed by the differential amplifier circuit 60 is converted to an output voltage (0 [V]) at the end of 0 to 5 [V] and then converted to a detection voltage Z' (0 [V]) at the end of the normal range. Therefore, even for an input voltage X whose output voltages are the same in the first conversion state and the second conversion state, a detection voltage Z' different from the detection voltage Z' in normal conditions can be obtained.

[0090] When the switching command unit 91 outputs a switching command to switch to the second conversion state (expanded range), if the differential amplifier circuit 60 has normally switched to the second conversion state, the input voltage aX after being changed by the differential amplifier circuit 60 is converted to an output voltage (0 [V]) at the end of 0 to 5 [V] and then converted to a detection voltage Z' (0 [V]) at the end of the expanded range. In contrast, when the switching command unit 91 outputs a switching command to switch to the second conversion state, it is assumed that a switching failure occurs in which the differential amplifier circuit 60 switches to the first conversion state. In this case, the input voltage aX after being changed by the differential amplifier circuit 60 is converted to an output voltage of 0 to 5 [V] and then converted to a detection voltage Z' of the expanded range. Therefore, even for an input voltage X whose output voltages are the same in the first conversion state and the second conversion state, a detection voltage Z' different from the detection voltage Z' in the normal state can be obtained.

[0091] The discrimination unit 93 can discriminate a switching fault caused by the differential amplifier circuit 60 based on the detected voltages Z and Z' before and after the input voltage X is changed by the input voltage change unit 30. Therefore, it can discriminate that a switching fault in the conversion state (range) has occurred even for an input voltage X for which the output voltages in the first conversion state and the second conversion state are the same.

[0092] When the switching command is a switching command to switch to the first conversion state, the discrimination unit 93 determines that a switching fault has occurred in which the differential amplifier circuit 60 has switched to the second conversion state, based on the fact that the detected voltage Z' after the input voltage X is changed by the input voltage change unit 30 is the detected voltage Z' (0 [V]) at the end of the normal range. Therefore, even for an input voltage X whose output voltages match in the first conversion state and the second conversion state, it can be determined that a switching fault has occurred in which the differential amplifier circuit 60 has switched to the second conversion state.

[0093] · When the switching instruction unit 91 outputs a switching instruction to switch to the first conversion state, if the differential amplifier circuit 60 has been normally switched to the first conversion state, the detected voltage Z' after the input voltage changing unit 30 changes the input voltage X is a times (predetermined multiple) of the detected voltage Z before the input voltage X is changed. Therefore, when it can be considered that the switching instruction is a switching instruction to switch to the first conversion state, and a times the detected voltage Z before the input voltage changing unit 30 changes the input voltage X is equal to the detected voltage Z' after the input voltage changing unit 30 changes the input voltage X (|aZ - Z'| < Zth), the discrimination unit 93 can determine that no switching failure of the conversion state by the differential amplifier circuit 60 has occurred.

[0094] · When the switching instruction unit 91 outputs a switching instruction to switch to the first conversion state and a switching failure occurs in which the differential amplifier circuit 60 has been switched to the second conversion state, it operates as follows. The differential amplifier circuit 60 converts the input voltage X in the expansion range into an output voltage of 0 to 5 [V], and converts the input voltage X outside the expansion range into the output voltage (0 [V]) at the closer end of 0 to 5 [V]. Therefore, when the input voltage X to the differential amplifier circuit 60 is set to a positive predetermined multiple (a times) smaller than 1, the input voltage after the change in the differential amplifier circuit 60 is converted into the output voltage (0 [V]) at the smaller end of 0 to 5 [V]. As a result, the output voltage does not become a times, the AD conversion value Y output by the AD converter 80 does not become a times, and the detected voltage Z' does not become a times. Therefore, when it cannot be considered that the switching instruction is a switching instruction to switch to the first conversion state, and a times the detected voltage Z before the input voltage changing unit 30 changes the input voltage X is equal to the detected voltage Z' after the input voltage changing unit 30 changes the input voltage X (|aZ - Z'| ≥ Zth), the discrimination unit 93 can determine that a switching failure has occurred in which the differential amplifier circuit 60 has been switched to the second conversion state.

[0095] ·Assume that when the switching command causes a switch to the second conversion state, a switching failure occurs where the differential amplifier circuit 60 has been switched to the first conversion state. In this case, both the input voltages X and aX before and after being changed by the differential amplifier circuit 60 are converted to detection voltages Z and Z' other than the ends in the enlarged range after being converted to an output voltage of 0 to 5 [V]. Based on the above, when the switching command is a switching command that causes a switch to the second conversion state, since the detection voltage Z' after changing the input voltage X by the input voltage changing unit 30 is not the detection voltage (V1 [V]) at the end of the enlarged range, the discrimination unit 93 discriminates that a switching failure has occurred where the differential amplifier circuit 60 has been switched to the first conversion state. Therefore, even for the input voltage X for which the output voltages match between the first conversion state and the second conversion state, it is possible to discriminate that a switching failure has occurred where the differential amplifier circuit 60 has been switched to the first conversion state.

[0096] ·The input voltage changing unit 30 changes the input voltage X to the differential amplifier circuit 60 by a positive predetermined multiple (a times) smaller than 1, so as to change it wider than the width of the enlarged range in the normal range. Therefore, when the switching command unit 91 outputs a switching command that causes a switch to the second conversion state, if the differential amplifier circuit 60 has been normally switched to the second conversion state, the detection voltage Z' after changing the input voltage X by the input voltage changing unit 30 becomes the detection voltage (V1 [V]) at the smaller-side end in the enlarged range. Therefore, when the switching command is a switching command that causes a switch to the second conversion state, and it can be considered that the detection voltage Z' after changing the input voltage X by the input voltage changing unit 30 is equal to the detection voltage (V1 [V]) at the smaller-side end in the enlarged range (|Z' - V1| < Zth), the discrimination unit 93 can discriminate that no switching failure has occurred in the conversion state by the differential amplifier circuit 60.

[0097] When the switching command unit 91 outputs a switching command to switch to the second conversion state, and a switching failure occurs in which the differential amplifier circuit 60 switches to the first conversion state, the operation is as follows. The differential amplifier circuit 60 converts the input voltage X in the normal range to an output voltage of 0 to 5 [V]. Therefore, when the input voltage X to the differential amplifier circuit 60 is multiplied by a positive predetermined factor (a times) that is smaller than 1, the input voltage after the change is converted by the differential amplifier circuit 60 to an output voltage other than the terminal of 0 to 5 [V], and then converted to a detection voltage Z' other than the terminal (V1 [V]) of the expanded range. Therefore, when the above switching command is a switching command to switch to the second conversion state, and the detection voltage Z' after the input voltage X is changed by the input voltage change unit 30 cannot be considered to be equal to the detection voltage (V1 [V]) at the small terminal of the expanded range (|Z'-V1|≧Zth), the discrimination unit 93 can discriminate that a switching failure occurs in which the differential amplifier circuit 60 switches to the first conversion state.

[0098] The switching command unit 91 (control unit 90, voltage detection device 10) sets the above switching command as a switching command to switch to the first conversion state (normal range) when monitoring overcharging or overdischarging of the battery cell Cn, and sets the above switching command as a switching command to switch to the second conversion state (extended range) when detecting the SOC (charging rate) of the battery cell Cn. Therefore, it is possible to appropriately switch between the first conversion state and the second conversion state when monitoring overcharging or overdischarging of the battery cell Cn and when detecting the SOC of the battery cell Cn.

[0099] The input voltage change unit 30 is configured with a circuit that discharges each battery cell Cn when equalizing the SOC of the multiple battery cells Cn. With this configuration, the input voltage X to the differential amplifier circuit 60 can be changed to a wider range than the expanded range in the normal range by using the circuit that discharges each battery cell Cn when equalizing the SOC of the multiple battery cells Cn. Therefore, there is no need to add a new circuit to configure the input voltage change unit 30.

[0100] The above embodiment can be modified as follows: The same parts as those in the above embodiment are denoted by the same reference numerals and the description thereof will be omitted.

[0101] 19 is a graph showing the ZZ' diagnosable range when switching to the expanded range R6. The horizontal axis is the input voltage X of the battery cell Cn, and the vertical axis is aZ-Z' when a=1 / 2. When the voltage of the battery cell Cn is normally controlled, the voltage of the battery cell Cn is V1 to V2 [V]. As described above, when the switching command to the voltage conversion unit 92 is a switching command to switch to the normal range R0 (first conversion state) and a switching failure occurs in which the differential amplifier circuit 60 switches to the range R6 (second conversion state), Z / 2-Z'>0 is obtained when the input voltage X>V1, and ZZ' diagnosis is possible. Note that the figure also shows a graph of Z / 2-Z' when a switching failure occurs in which the ranges are erroneously switched to R1 to R5, R7.

[0102] Since the expanded range is one range selected from a plurality of ranges R1 to R7 that are different from each other, the following problem may occur. When a switching command to the voltage conversion unit 92 is a switching command to switch to the first conversion state (normal range R0), a switching failure may occur in which the differential amplifier circuit 60 switches to the second conversion state in an expanded range different from the expected range. For example, FIG. 20 shows a case where the expanded range R1 is mistakenly selected when switching to the expanded range R6. When a voltage obtained by multiplying the input voltage X by a positive predetermined multiple (a times) smaller than 1 is included in the expanded range R1 different from the expected range, the output voltage after the change is not converted to an output voltage at the small end of 0 to 5 [V], but is converted to an output voltage of 0 to 5 [V]. In this case, a times the detection voltage Z converted by the voltage conversion unit 92 before the input voltage X is changed by the input voltage change unit 30 may be equal to the detection voltage Z' converted by the voltage conversion unit 92 after the input voltage X is changed by the input voltage change unit 30. Specifically, when the input voltage X of the battery cell Cn is V1'+V2', Z / 2-Z'=0. V1' and V2' are terminal input voltages in the expanded range R1 different from the assumption. For this reason, when a switching command to the voltage conversion unit 92 is a switching command to switch to the first conversion state, there is a risk of erroneously determining that no switching failure of the conversion state by the differential amplifier circuit 60 has occurred, even though a switching failure has occurred in which the differential amplifier circuit 60 has switched to the second conversion state in the expanded range R1 different from the assumption.

[0103] As shown in FIG. 21, when the above switching failure occurs and the voltage obtained by setting the input voltage X to a positive predetermined multiple (a times) smaller than 1 is included in an extended range R1 different from the assumption, the input voltage X before being changed wider than the width of the extended range R1 is outside the extended range with respect to an extended range (V1' to V2') different from the assumption. Therefore, when it can be considered that aZ and Z' are equal (|aZ - Z'| < Zth), and when the detected voltage Z before changing the input voltage X by the input voltage changing unit 30 is the detected voltage (5 [V]) at the end of the normal range R0, the determination unit 93 preferentially determines that an abnormality has occurred (range over diagnosis). FIG. 22 is a diagram showing the relationship between the ZZ' diagnosis possible range and the range over diagnosis possible range. The outside of the ZZ' diagnosis possible range (ZZ' diagnosis impossible range) is the range over diagnosis possible range.

[0104] FIG. 23 is a flowchart showing the procedure of the above-described modification example of the ZZ' diagnosis. In FIG. 23, processes S301 and S302 are added to the flowchart of FIG. 15, and other processes are the same as those in the flowchart of FIG. 15. That is, when it is determined that |aZ - Z'| < Zth (S107: YES), instead of determining that the range switching by the differential amplifier circuit 60 is normal, it is determined whether Z < Vmax (S301). The threshold value Vmax is a value for determining that the detected voltage Z converted by the voltage conversion unit 92 before the input voltage change unit 30 changes the input voltage X is the detected voltage (5 [V]) at the larger end in the normal range R0, and is set to a value slightly smaller than the detected voltage at the larger end in the normal range R0, for example, 4.9 [V]. In this determination, when it is determined that Z < Vmax (S301: YES), it is determined whether Z > Vmin (S302). The threshold value Vmin is a value for determining that the detected voltage Z converted by the voltage conversion unit 92 before the input voltage change unit 30 changes the input voltage X is the detected voltage (0 [V]) at the smaller end in the normal range R0, and is set to a value slightly larger than the detected voltage at the smaller end in the normal range R0, for example, 0.1 [V]. In this determination, when it is determined that Z > Vmin (S302: YES), it is determined that the range switching by the differential amplifier circuit 60 is normal (S108). On the other hand, in the above determination, when it is determined that Z < Vmax is not satisfied (S301: NO), or when it is determined that Z > Vmin is not satisfied (S302: NO), it is determined that a range over abnormality has occurred (S303). Then, this series of processes is terminated (END).

[0105] Therefore, when the switching command is a switching command that causes the first conversion state to be switched, even if a switching failure occurs in which the differential amplifier circuit 60 is switched to the second conversion state in the enlarged range R1 different from the assumption, it is possible to suppress misjudgment that no switching failure of the conversion state by the differential amplifier circuit 60 has occurred.

[0106] When the battery cell Cn is overcharged and the input voltage X from the battery cell Cn becomes higher than the voltage (V2 [V]) at the higher end of the expanded range, the following problem may occur. For example, as shown in FIG. 24, when the input voltage X multiplied by a positive predetermined multiple (a times) smaller than 1 is included in the expanded range R2, the output voltage may be converted to an output voltage other than the lower end of 0 to 5 [V]. As a result, the detection voltage Z' obtained by converting the AD conversion value Y output by the AD converter 80 may become a detection voltage Z' other than the lower end (V1 [V]) of the expanded range R2. More specifically, when the input voltage X of the battery cell Cn>2V1, Z'-V1>0. For this reason, when the above-mentioned switching command is a switching command for switching to the second conversion state, it may be erroneously determined that a switching failure has occurred in which the differential amplifier circuit 60 has switched to the first conversion state, even though a switching failure in the conversion state by the differential amplifier circuit 60 has not occurred.

[0107] As shown in FIG. 25, when the above-mentioned overcharging occurs and the voltage obtained by multiplying the input voltage X by a positive predetermined factor (a times) smaller than 1 is included in the expanded range R2 (V1 to V2), the input voltage X before being changed wider than the width of the expanded range R2 falls outside the expanded range. In addition, as a general characteristic of the battery cell Cn, the voltage V2 at the larger end of the expanded range R2 is 2V1 or less. Therefore, when Z' and V1 cannot be considered to be equal (|Z'-V1|≧Zth), and the detected voltage Z before the input voltage change unit 30 changes the input voltage X is the detected voltage Z (5 [V]) at the end of the normal range R0, the discriminator 93 preferentially discriminates that a switching failure of the conversion state by the differential amplifier circuit 60 has not occurred (V2Z diagnosis). FIG. 26 is a diagram showing the relationship between the Z'V1 diagnosable range and the V2Z diagnosable range. The range outside the Z'V1 diagnosable range (Z'V1 non-diagnosable range) is the V2Z diagnosable range.

[0108] FIG. 27 is a flowchart showing the procedure of the above modification example of the Z’V1 diagnosis. In FIG. 27, the process of S401 is added to the flowchart of FIG. 18, and other processes are the same as those in the flowchart of FIG. 18. That is, when it is determined that |Z’-V1| < Zth is not satisfied (S207: NO), it is not determined that the differential amplifier circuit 60 has been erroneously switched to the normal range, but it is determined whether |V2-Z| < Zth (S401). The threshold value Zth is a value for determining that |V2-Z| can be regarded as 0, and is set to a positive value close to 0 based on the error of the AD converter 80. In this determination, when it is determined that |V2-Z| < Zth (S401: YES), it is determined that the range switching by the differential amplifier circuit 60 is normal (S208). On the other hand, in the above determination, when it is determined that |V2-Z| < Zth is not satisfied (S401: NO), it is determined that the differential amplifier circuit 60 has been erroneously switched to the normal range (S209). Then, this series of processes is terminated (END).

[0109] Therefore, when the switching command is a switching command that causes the second conversion state to be switched, it is possible to suppress misjudgment that a switching failure has occurred in which the differential amplifier circuit 60 has been switched to the first conversion state even though no switching failure has occurred in the conversion state by the differential amplifier circuit 60.

[0110] As shown in FIG. 28, the voltage detection device of the above embodiment can be applied to a circuit including a filter circuit 40 and an equalization circuit 45. The filter circuit 40 includes resistors 41 and 42, a capacitor 43, etc. The equalization circuit 45 includes a diode 46, a switch 47, etc. The lowest potential terminal and the highest potential terminal of the assembled battery 20 are connected by a capacitor 44. In this case, as shown in FIG. 29, the input voltage change unit 130 is connected to the multiplexer 50. Note that, although the filter circuit 40 and the equalization circuit 45 are not shown in FIG. 29, the filter circuit 40 and the equalization circuit 45 are connected between the assembled battery 20 and the multiplexer 50. The input voltage change unit 130 includes a resistor 133, a switch 134, etc. The resistor 133 and the switch 134 realize the same functions as the discharge resistance element 33 and the switch San in FIG. 8. With this configuration, even if the input voltage to the differential amplifier circuit 60 does not become a positive predetermined multiple (a times) smaller than 1 when the switch 47 of the equalization circuit 45 is turned on, the input voltage can be multiplied by a using the input voltage change unit 130. Since the input voltage change unit 130 is common to each battery cell Cn, the addition of new circuits can be minimized.

[0111] ·As shown in FIG. 30, the voltage detection device of the above embodiment can also be applied to a circuit including an input voltage changing unit 230. The input voltage changing unit 230 includes a filter circuit 40 (similar to FIG. 28), a switch 48, a gate voltage variable circuit 49, etc. The switch 48 is constituted by, for example, a MOSFET. The gate voltage variable circuit 49 makes the gate voltage VG applied to the gate of the switch 48 variable. As shown in FIG. 31, the input voltage to the differential amplifier circuit 60 becomes the voltage X of the battery cell Cn when the switch 48 is off (VG = 0), becomes 0 when the gate voltage VG increases (for example, 5 [V]) and the switch 48 is fully on. Also, the input voltage to the differential amplifier circuit 60 becomes aX (0 < a < 1) when the gate voltage VG is intermediate (for example, 2.5 [V]) and the switch 48 is half on. Therefore, in the circuit shown in FIG. 30, by adjusting the gate voltage VG by the gate voltage variable circuit 49, the input voltage to the differential amplifier circuit 60 can be multiplied by a.

[0112] ·It can also be determined based on the ratio of aZ to Z' that it can be regarded that a times (predetermined times) of the detected voltage Z converted by the voltage conversion unit 92 before the input voltage X is changed by the input voltage changing unit 30 is equal to the detected voltage Z' converted by the voltage conversion unit 92 after the input voltage X is changed by the input voltage changing unit 30. Specifically, the process of S107 in FIGS. 15 and 23 may be changed to k1 < aZ / Z' < k2?. k1 is a positive value slightly smaller than 1, and k2 is a positive value slightly larger than 1.

[0113] ·It can also be determined based on the ratio of Z' to V1 that it can be regarded that the detected voltage Z' converted by the voltage conversion unit 92 after the input voltage X is changed by the input voltage changing unit 30 is equal to the detected voltage (V1) at the smaller end in the enlarged range. Specifically, the process of S207 in FIGS. 18 and 27 may be changed to k1 < Z' / V1 < k2?. k1 is a positive value slightly smaller than 1, and k2 is a positive value slightly larger than 1.

[0114] · By setting the input voltage to the differential amplifier circuit 60 to a positive b times (predetermined multiple) greater than 1, it is also possible to vary it wider than the width of the extended range (second range) in the normal range (first range). b is, for example, 2. In this case, the process of S207 in FIGS. 18 and 27 may be changed to |Z’ - V2| < Zth?, and the process of S401 in FIG. 27 may be changed to |V1 - Z| < Zth.

[0115] · The switching command unit 91 (control unit 90) may switch to the normal range when a range over occurs during detection in the extended range, not limited to monitoring overcharge or overdischarge of the battery cell Cn. Further, the switching command unit 91 (control unit 90) may output a switching command for switching between the first conversion state (normal range) and the second conversion state (extended range) based on a command from the upper ECU (upper control device). Also, the upper ECU may implement the function of the switching command unit 91.

[0116] · If the SOC (state of charge) of the battery cell Cn is equalized, it is also possible to use the voltages of different battery cells Cn before and after multiplying the input voltage X by a. Further, the above-described embodiment can be applied not only to the voltage of the battery cell Cn of the battery pack 20, but also to the total voltage of the battery pack 20 or a voltage detection device that detects the voltage of a single cell.

[0117] Note that each of the above modification examples can be implemented in combination.

Description of Reference Numerals

[0118] 10... voltage detection device, 30... input voltage change unit (input change unit), 60... differential amplifier circuit (conversion switching unit), 80... AD converter (AD conversion unit), 90... control unit, 91... switching command unit, 92... voltage conversion unit, 93... determination unit, 130... input voltage change unit (input change unit), 230... input voltage change unit (input change unit), C1 to C6... battery cells (batteries).

Claims

1. a conversion switching unit (60) that switches between a first conversion state in which an input voltage from a battery (Cn) in a first range is converted into an output voltage in a predetermined range, and a second conversion state in which the input voltage in a second range included in the first range is converted into an output voltage in the predetermined range; an AD conversion unit (80) that AD converts the output voltage from the conversion switching unit and outputs it as a converted value; A switching command unit (91) that outputs a switching command to the conversion switching unit to switch between the first conversion state and the second conversion state; a voltage conversion unit (92) that converts the converted value input from the AD conversion unit into a detection voltage of the first range and a detection voltage of the second range in response to the switching command output from the switching command unit; an input change unit (30, 130, 230) that changes the input voltage to the conversion switching unit in the first range to a width wider than the width of the second range; a determination unit (93) that determines a switching failure of the conversion state by the conversion switching unit based on the detection voltage converted by the voltage conversion unit before and after the input voltage is changed by the input change unit; A voltage detection device (10) comprising:

2. the conversion switching unit, in the second conversion state, converts the input voltage in the second range into an output voltage in the predetermined range, and converts the input voltage outside the second range into an output voltage at a closer end of the predetermined range; 2. The voltage detection device according to claim 1, wherein when the switching command output by the switching command unit is a switching command to switch to the first conversion state, the discrimination unit determines that a switching failure has occurred in which the conversion switching unit has switched to the second conversion state, based on the fact that at least one of the detection voltages converted by the voltage conversion unit before and after the input voltage is changed by the input change unit is a detection voltage at the end of the first range.

3. the conversion switching unit converts the input voltage in the first range into an output voltage in the predetermined range in a proportional relationship in the first conversion state; the voltage conversion unit converts the converted value input from the AD conversion unit into a detection voltage of the first range by a proportional function when the switching command output by the switching command unit is a switching command for switching to the first conversion state; the input change unit changes the input voltage to the conversion switching unit by a positive predetermined multiple smaller than 1, so as to change the input voltage in the first range to a width wider than a width of the second range, 3. The voltage detection device according to claim 2, wherein the discrimination unit determines that a switching failure in the conversion state caused by the conversion switching unit has not occurred when the switching command output by the switching command unit is a switching command for switching to the first conversion state and when the predetermined multiple of the detection voltage converted by the voltage conversion unit before the input voltage is changed by the input change unit and the detection voltage converted by the voltage conversion unit after the input voltage is changed by the input change unit can be considered equal, and determines that a switching failure in switching to the second conversion state caused by the conversion switching unit has occurred when the switching command output by the switching command unit and the detection voltage converted by the voltage conversion unit after the input voltage is changed by the input change unit can be considered equal.

4. the second range is one range selected from a plurality of ranges different from each other, 4. The voltage detection device according to claim 3, wherein the discrimination unit preferentially determines that an abnormality has occurred when the input voltage can be considered to be equal and the detection voltage converted by the voltage conversion unit before the input voltage is changed by the input change unit is the detection voltage at the end of the first range.

5. the conversion switching unit, in the second conversion state, converts the input voltage in the second range into an output voltage in the predetermined range, and converts the input voltage outside the second range into an output voltage at a closer end of the predetermined range; 2. The voltage detection device according to claim 1, wherein when the switching command output by the switching command unit is a switching command to switch to the second conversion state, the discrimination unit determines that a switching failure has occurred in which the conversion switching unit has switched to the first conversion state, based on the fact that neither of the detection voltages converted by the voltage conversion unit before and after the input voltage is changed by the input change unit is a detection voltage at the end of the second range.

6. the input change unit changes the input voltage to the conversion switching unit by a positive predetermined multiple smaller than 1, so as to change the input voltage in the first range to a width wider than a width of the second range, 6. The voltage detection device according to claim 5, wherein the discrimination unit determines that a switching failure in the conversion state caused by the conversion switching unit has not occurred when the switching command output by the switching command unit is a switching command to switch to the second conversion state and when the detection voltage converted by the voltage conversion unit after the input voltage is changed by the input change unit and the detection voltage at the smaller end of the second range can be considered equal, and determines that a switching failure in switching to the first conversion state caused by the conversion switching unit has occurred when the detection voltages cannot be considered equal.

7. 7. The voltage detection device according to claim 6, wherein the discrimination unit preferentially determines that a conversion state switching failure by the conversion switching unit has not occurred when the input voltage cannot be deemed equal and the detection voltage converted by the voltage conversion unit before the input voltage is changed by the input change unit is a detection voltage at the end of the first range.

8. A voltage detection device as described in any one of claims 1 to 7, wherein the switching command unit sets the switching command to the first conversion state when monitoring overcharging or over-discharging of the battery, and sets the switching command to the second conversion state when detecting the charging rate of the battery.

9. The battery is one cell selected from a plurality of cells (Cn) included in a battery pack (20), The voltage detection device according to any one of claims 1 to 8, wherein the input change unit is configured by a circuit (30, 230) that discharges each cell when equalizing the charging rates of the multiple cells.

Images