JP2016161352A - Deterioration detector and method for detecting deterioration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a deterioration detector and a method for detecting deterioration that can increase the accuracy of detecting deterioration in insulation resistance of a power source if the detector has a voltage converter raising voltages output from the power source.SOLUTION: The deterioration detector according to an embodiment of the present application includes: a capacitor; a voltage detecting unit; and a deterioration detecting unit. The capacitor is connected to an insulated power source and conducts charge and discharge, and the voltage detecting unit detects voltages of the capacitor. The deterioration detecting unit detects deterioration in insulation resistance of a power source based on the capacitor voltage detected by the voltage detecting unit, and the voltage detecting unit can detect a negative voltage charged to the capacitor.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a deterioration detection apparatus and a deterioration detection method.

  Conventionally, for example, a vehicle such as a hybrid vehicle or an electric vehicle includes a power source that supplies electric power to a motor that is a power source. A power source is configured to be insulated from the vehicle body, and a device that monitors the insulation state of the power source, in other words, a device that detects deterioration of the insulation resistance of the power source is known (for example, a patent) Reference 1).

  In the above prior art, the deterioration of the insulation resistance of the power source is detected using the flying capacitor method. Specifically, in the prior art, the capacitor is charged by passing current from the power supply through the insulation resistance, and the deterioration of the insulation resistance of the power supply is detected based on the charged voltage of the capacitor. In recent years, a vehicle has been proposed in which a voltage output from a power source is boosted by a voltage converter and supplied to a motor.

JP 2014-20914 A

  However, when the voltage converter described above is provided, the body voltage may exceed the power supply voltage depending on the state of the insulation resistance, the operation timing of the voltage converter, etc., and the capacitor may be charged with a negative voltage. In such a case, the above-described conventional technology cannot accurately detect the voltage of the capacitor, and as a result, there is a possibility that the deterioration detection accuracy of the insulation resistance is lowered.

  The present invention has been made in view of the above, and it is possible to improve the degradation detection accuracy of the insulation resistance of the power supply even when the voltage converter that boosts the voltage output from the power supply is provided. An object of the present invention is to provide a detection device and a deterioration detection method.

  In order to solve the above problems and achieve the object, the present invention includes a capacitor, a voltage detector, and a deterioration detector in a deterioration detector. The capacitor is connected to an insulated power source to perform charging / discharging. The voltage detector detects the voltage of the capacitor. The deterioration detector detects deterioration of the insulation resistance of the power source based on the voltage of the capacitor detected by the voltage detector. The voltage detector can detect a negative voltage charged in the capacitor.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where the voltage converter which raises the voltage output from a power supply is provided, the degradation detection precision of the insulation resistance of a power supply can be improved.

FIG. 1 is a block diagram illustrating a configuration example of a charge / discharge system including a deterioration detection apparatus according to the first embodiment. FIG. 2 is a block diagram illustrating a configuration example of the deterioration detection apparatus. FIG. 3 is a diagram illustrating a configuration example of the voltage detection circuit unit. FIG. 4 is a diagram illustrating a charging path for charging the capacitor with the voltage of the first stack. FIG. 5 is a diagram illustrating a discharge path for discharging the charged capacitor. FIG. 6 is a diagram illustrating a charging path for charging the capacitor with the voltage of the second stack. FIG. 7 is a diagram illustrating a charging path when detecting deterioration of the insulation resistance on the positive electrode side of the assembled battery. FIG. 8 is a diagram illustrating a charging path when detecting deterioration of the insulation resistance on the negative electrode side of the assembled battery. FIG. 9 is a flowchart illustrating a part of a processing procedure of processing executed by the battery monitoring system. FIG. 10 is a block diagram illustrating a configuration example of a control unit of the deterioration detection apparatus according to the second embodiment. FIG. 11 is a graph for explaining stray capacitance estimation processing performed in the stray capacitance estimation unit. FIG. 12 is a graph for explaining the correction process performed by the deterioration detection unit. FIG. 13 is a flowchart illustrating a part of a processing procedure of processing executed by the battery monitoring system according to the second embodiment.

  Hereinafter, embodiments of a deterioration detection device and a deterioration detection method disclosed in the present application will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

(First embodiment)
<1. Configuration of charge / discharge system>
FIG. 1 is a block diagram illustrating a configuration example of a charge / discharge system including a deterioration detection apparatus according to the first embodiment. The charge / discharge system 1 is mounted on a vehicle such as a hybrid vehicle (HEV), an electric vehicle (EV), and a fuel cell vehicle (FCV) (not shown). The charge / discharge system 1 is a system that performs charge / discharge of a power source that supplies electric power to a motor that is a power source of a vehicle.

  Specifically, the charge / discharge system 1 includes an assembled battery 10, a battery monitoring system 20, a vehicle control device 30, a motor 40, a voltage converter 50, and a fail-safe relay 60. In addition, the battery monitoring system 20 includes a plurality of satellite substrates 22 having monitor ICs (Integrated Circuits) 21 and the like, and a deterioration detection device 23.

  The assembled battery 10 is a power source (battery) insulated from a vehicle body (not shown), and includes a plurality of blocks 11. One block 11 includes a plurality of, for example, two battery stacks 12 connected in series. Further, one battery stack 12 includes a plurality of battery cells 13 connected in series, for example.

  The numbers of blocks 11, battery stacks 12, and battery cells 13 are not limited to those described above or illustrated. Moreover, as the above-described assembled battery 10, for example, a lithium ion secondary battery, a nickel hydride secondary battery, or the like can be used, but the present invention is not limited to this.

  Each of the plurality of battery cells 13 is electrically connected to a monitor IC 21 provided on the satellite substrate 22. Then, the voltage of each battery cell 13 is detected by the monitor IC 21. The monitor IC 21 includes a plurality of first monitor ICs 21a and second monitor ICs 21b, and each of the first and second monitor ICs 21a and 21b detects the voltage of the battery cells 13 for one battery stack 12.

  The deterioration detection device 23 detects deterioration of an insulation resistance (described later) of the battery monitoring system 20, which will be described later. Here, the deterioration of the insulation resistance means that, for example, the resistance value of the insulation resistance is lowered and the battery pack 10 is leaked.

  The deterioration detection device 23 also has a function of monitoring the individual voltages of the plurality of battery cells 13 and monitoring the voltage of each battery stack 12. That is, the deterioration detection device 23 monitors the state of charge of the assembled battery 10.

  Specifically, the deterioration detection device 23 transmits a voltage detection request to the monitor IC 21 to detect each individual voltage of the plurality of battery cells 13 and receives the detection result via the communication line L1. The voltage of the battery cell 13 is monitored. In addition, the deterioration detection device 23 directly measures the stack voltage by charging the voltage of the battery stack 12 (hereinafter sometimes referred to as “stack voltage”) to a capacitor, which will be described later, via the lead L2, and sets The state of charge of the battery 10 is monitored.

  In addition, it is preferable that the deterioration detection device 23 also has a function of determining whether or not the monitor IC 21 is operating normally. Specifically, for example, the deterioration detection device 23 compares the stack voltage obtained by adding the individual voltages of the battery cells 13 received from the monitor IC 21 with the stack voltage directly detected, and the difference between the two is acceptable. When it is larger than the value, it is determined that the monitor IC 21 is abnormal. Then, when it is determined that the monitor IC 21 is abnormal, the deterioration detection device 23 may disconnect the fail-safe relay 60 so that the battery cell 13 is not charged / discharged.

  The voltage converter 50 includes a boost converter 51 (see FIG. 3) and an inverter (not shown). The voltage converter 50 boosts a voltage output from the assembled battery 10 as a power source and converts the voltage from a direct current to an alternating voltage. In FIG. 1, the deterioration detection device 23 and the voltage converter 50 are illustrated separately, but this is an example and is not limited. For example, the deterioration detection device 23 includes the voltage converter 50. It may be configured.

  The vehicle control device 30 performs vehicle control by charging / discharging the assembled battery 10 according to the state of charge of the assembled battery 10. Specifically, the vehicle control device 30 drives the motor 40 by supplying the voltage of the assembled battery 10 that has been boosted by the voltage converter 50 and converted into alternating current to the motor 40. Thereby, the assembled battery 10 is discharged.

  In the above description, the motor 40 is given as an electric load to which a voltage is supplied from the voltage converter 50. However, this is only an example and is not limited. For example, an air conditioner, an illumination lamp, an audio device, or a car navigation system Other electrical components such as a system may be used.

  The vehicle control device 30 converts the voltage generated by the regenerative braking of the motor 40 from an AC voltage to a DC voltage by the voltage converter 50 and supplies the voltage to the assembled battery 10. Thereby, the assembled battery 10 will be charged. Thus, the vehicle control device 30 monitors the voltage of the assembled battery 10 based on the state of charge of the assembled battery 10 acquired from the deterioration detection device 23, and executes control according to the monitoring result.

<2. Configuration of degradation detection device>
Next, the configuration of the deterioration detection device 23 will be described. FIG. 2 is a block diagram illustrating a configuration example of the deterioration detection device 23. In FIG. 2, the satellite substrate 22, the communication line L1, and the like are omitted. In FIG. 2, for convenience of understanding, one of the plurality of blocks 11 is shown. In the following, one of the two battery stacks 12 in the block 11 is referred to as “first stack 12a”, and the other. May be referred to as “second stack 12b”.

  The deterioration detection device 23 is, for example, an electronic control unit (ECU), and includes a voltage detection circuit unit 24, an A / D conversion unit 25, and a control unit 26 as shown in FIG.

  The voltage detection circuit unit 24 includes a circuit for detecting each stack voltage and detecting deterioration of insulation resistance. Here, the voltage detection circuit unit 24 will be described in detail with reference to FIG.

  FIG. 3 is a diagram illustrating a configuration example of the voltage detection circuit unit 24. As illustrated in FIG. 3, the voltage detection circuit unit 24 includes a capacitor C1, a first switch S1 to a sixth switch S6, and a first resistor R1 to a seventh resistor R7. The assembled battery 10 includes an insulation resistance Rp on the positive electrode side and an insulation resistance Rn on the negative electrode side.

  In this voltage detection circuit unit 24, a flying capacitor method is applied, and as described later, after charging the capacitor C1 with the voltage of each stack 12a, 12b, the voltage of the capacitor C1 is detected as the voltage of each stack 12a, 12b. ing.

  Specifically, the voltage detection circuit unit 24 is divided into a charge side circuit and a discharge side circuit via a capacitor C1. The charging side circuit is a part including a path in which the stacks 12a and 12b of the battery pack 10 and the capacitor C1 are connected and the voltage of the stacks 12a and 12b is charged to the capacitor C1. The discharge side circuit is a part including a path for discharging the voltage charged in the capacitor C1.

  Then, by controlling on / off of the switches S1 to S6, charging and discharging of the capacitor C1 are controlled. In addition, as each above-mentioned switch S1-S6, although a solid state relay (SSR: Solid State Relay) can be used, for example, it is not limited to this. The first resistor R1 to the seventh resistor R7 are resistors used for voltage detection of the capacitor C1.

  In the charging side circuit of the voltage detection circuit unit 24, each of the first stack 12a and the second stack 12b is connected in parallel to the capacitor C1. That is, both ends of the capacitor C1 are connected to the positive and negative electrodes of the first stack 12a, and are also connected to the positive and negative electrodes of the second stack 12b.

  Further, a first resistor R1, a first switch S1, and a fifth resistor R5 are provided in series between the positive electrode side of the first stack 12a and the capacitor C1, and the negative electrode side of the first stack 12a and the capacitor C1 are connected to each other. A second resistor R2 and a second switch S2 are provided in series between them.

  A third resistor R3, a third switch S3 and a fifth resistor R5 are provided in series between the positive side of the second stack 12b and the capacitor C1, and the negative side of the second stack 12b and the capacitor C1 are connected to each other. A fourth resistor R4 and a fourth switch S4 are provided in series between them.

  In the discharge side circuit of the voltage detection circuit unit 24, a fifth switch S5 is provided in the path on the positive electrode side of the first stack 12a and the second stack 12b, and a fifth switch S5 is provided between one end of the fifth switch S5 and the capacitor C1. A resistor R5 is provided. Further, a sixth switch S6 is provided on the negative-side path of the first and second stacks 12a and 12b, and one end of the sixth switch S6 is connected to the capacitor C1.

  The other end of the fifth switch S5 is connected to the A / D conversion unit 25 and is branched in the middle to be connected to the vehicle body GND via the sixth resistor R6. The other end of the sixth switch S6 is connected to the vehicle body GND via a seventh resistor R7. The vehicle body GND is an example of a grounding point, and the voltage at the grounding point may be referred to as “body voltage” below.

  The A / D conversion unit 25 converts an analog value indicating the voltage at the detection point A of the voltage detection circuit unit 24 into a digital value, and the converted digital value is a control unit 26 (more precisely, a voltage detection unit described later). Output to.

  Here, charging and discharging of the capacitor C1 performed to detect the voltages of the first and second stacks 12a and 12b will be described with reference to FIGS. FIG. 4 is a diagram illustrating a charging path for charging the capacitor C1 with the voltage of the first stack 12a. FIG. 5 is a diagram showing a discharge path for discharging the charged capacitor C1, and FIG. 6 is a diagram showing a charge path for charging the capacitor C1 with the voltage of the second stack 12b.

  In the deterioration detection device 23, the capacitor C1 is charged for each of the first and second stacks 12a and 12b. First, an example of charging the capacitor C1 with the voltage of the first stack 12a (hereinafter sometimes referred to as “first stack voltage”) will be described. As shown in FIG. 4, the first switch S1 and the second switch S2 Is turned on, and the other switches S3 to S6 are turned off.

  Thus, the positive side of the first stack 12a is connected to the negative side of the first stack 12a via the first resistor R1, the first switch S1, the fifth resistor R5, the capacitor C1, the second switch S2, and the second resistor R2. Connected. That is, a first path P1 connecting the first stack 12a and the capacitor C1 is formed, and the capacitor C1 is charged with the first stack voltage.

  Then, after a predetermined time has elapsed since the formation of the first path P1, the voltage of the capacitor C1 is discharged. Specifically, as shown in FIG. 5, the first switch S1 and the second switch S2 are turned off, and the fifth switch S5 and the sixth switch S6 are turned on.

  As a result, a second path P <b> 2 that is a discharge path is formed in the voltage detection circuit unit 24. Since the A / D converter 25 is connected to the other end of the fifth switch S5, when the second path P2 is formed, the voltage of the capacitor C1 (that is, the first stack voltage) is changed to the A / D converter 25. Is input. The A / D converter 25 converts an analog value input at the moment when the fifth and sixth switches S5 and S6 are turned on into a digital value and outputs the digital value to the controller 26. As a result, the first stack voltage is detected.

  Next, an example in which the capacitor C1 is charged with the voltage of the second stack 12b (hereinafter sometimes referred to as “second stack voltage”) will be described. As shown in FIG. 6, the third switch S3 and the fourth switch S4 are turned on, and the other switches S1, S2, S5, S6 are turned off.

  Thus, the positive side of the second stack 12b is connected to the negative side of the second stack 12b via the third resistor R3, the third switch S3, the fifth resistor R5, the capacitor C1, the fourth switch S4, and the fourth resistor R4. Connected. That is, a third path P3 connecting the second stack 12b and the capacitor C1 is formed, and the capacitor C1 is charged with the second stack voltage.

  Then, after a predetermined time has elapsed since the formation of the third path P3, the third and fourth switches S3 and S4 are turned off, and the fifth and sixth switches S5 and S6 are turned on. The voltage is discharged (see FIG. 5).

  As a result, a second path P <b> 2 is formed in the voltage detection circuit unit 24, and the voltage of the capacitor C <b> 1 (that is, the second stack voltage) is input to the A / D conversion unit 25. Then, the A / D converter 25 converts the analog value of the input voltage into a digital value and outputs it to the controller 26 in the same manner as described above. As a result, the second stack voltage is detected.

  In this way, the first stack voltage and the second stack voltage can be detected by switching between the discharge side path and the charge side path to charge and discharge the capacitor C1.

  Further, as shown in FIG. 3, the circuit of the voltage detection circuit unit 24 is provided with an insulation resistance Rp on the positive electrode side and an insulation resistance Rn on the negative electrode side of the assembled battery 10 described above. Each of the insulation resistances Rp and Rn indicates a combined resistance of the mounted resistance and a resistance that virtually represents the insulation with respect to the vehicle body GND. Here, the mounted resistance and the virtual resistance It doesn't matter which one.

  The resistance value of each of the insulation resistances Rp and Rn is set to a sufficiently large value, for example, several MΩ, so that almost no current is supplied in a normal state. However, when the insulation resistances Rp and Rn are deteriorated abnormally, for example, the assembled battery 10 is short-circuited to the vehicle body GND or the like, or the resistance value is reduced to such an extent that the battery is energized in a state close to a short circuit.

  Here, charging and discharging of the capacitor C1 performed for detecting deterioration of the insulation resistances Rp and Rn of the assembled battery 10 will be described with reference to FIGS. FIG. 7 is a diagram illustrating a charging path when detecting deterioration of the insulation resistance Rp on the positive electrode side of the assembled battery 10. FIG. 8 is a diagram illustrating a charging path when detecting the deterioration of the insulation resistance Rn on the negative electrode side of the assembled battery 10.

  First, when detecting the deterioration of the insulation resistance Rp on the positive electrode side, as shown in FIG. 7, the fourth switch S4 and the fifth switch S5 are turned on, and the other switches S1 to S3, S6 are turned off. As a result, the positive side of the first stack 12a passes through the insulation resistance Rp, the sixth resistance R6, the fifth switch S5, the fifth resistance R5, the capacitor C1, the fourth switch S4, the fourth resistance R4, and the second stack 12b. Are connected to the negative electrode side of the first stack 12a.

  That is, a fourth path P4 is formed that connects the first and second stacks 12a and 12b and the capacitor C1 via the positive-side insulation resistance Rp. At this time, when the resistance value of the insulation resistance Rp is normal, the fourth path P4 hardly conducts, and when the insulation resistance Rp deteriorates and the resistance value decreases, the fourth path P4 It will be conducted.

  Then, after a predetermined time has elapsed since the formation of the fourth path P4, the fourth switch S4 is turned off and the sixth switch S6 is turned on to discharge the voltage of the capacitor C1 (see FIG. 5). The voltage of the capacitor C1 detected at this time is set to “voltage VRp”, and the deterioration of the insulation resistance Rp is detected based on the voltage VRp, which will be described later.

  When detecting deterioration of the insulation resistance Rn on the negative electrode side, as shown in FIG. 8, the first switch S1 and the sixth switch S6 are turned on, and the other switches S2 to S5 are turned off. As a result, the positive side of the first stack 12a passes through the first resistor R1, the first switch S1, the fifth resistor R5, the capacitor C1, the sixth switch S6, the seventh resistor R7, the insulation resistor Rn, and the second stack 12b. Are connected to the negative electrode side of the first stack 12a.

  That is, a fifth path P5 is formed that connects the first and second stacks 12a and 12b and the capacitor C1 via the negative-side insulation resistance Rn. At this time, when the resistance value of the insulation resistance Rn is normal, the fifth path P5 hardly conducts, and when the insulation resistance Rn deteriorates and the resistance value decreases, the fifth path P5 It will be conducted.

  And after predetermined time passes since the 5th path | route P5 was formed, as shown in FIG. 5, the voltage of the capacitor C1 is discharged. The voltage of the capacitor C1 detected at this time is “voltage VRn”, and the deterioration of the insulation resistance Rn is detected based on the voltage VRn. This will be described later.

  In the deterioration detection process of the insulation resistances Rp and Rn, the battery is charged for a predetermined time shorter than the time required for full charge, and the charge voltage is used as the voltages VRp and VRn to detect the deterioration of the insulation resistances Rp and Rn. I do.

  In the charge / discharge system 1 described above, for example, the boost converter 51 may operate in a state where a charging path (fifth path P5) for detecting deterioration of the insulation resistance Rn is formed. In such a case, for example, depending on the state of the insulation resistance Rn, the operation timing of the boost converter 51, and the like, the body voltage may fluctuate and exceed the voltage of the power supply.

  When the body voltage exceeds the voltage of the power supply, the capacitor C1 is charged with a negative voltage. Specifically, as shown in FIG. 8, when a current flows from the boost converter 51 as in the charging path P5a and the current in the charging path P5a becomes larger than the current in the fifth path P5, the capacitor C1 is charged with a negative voltage. It becomes. In such a case, the conventional technique cannot accurately detect the voltage of the capacitor C1, and as a result, there is a possibility that the deterioration detection accuracy of the insulation resistance Rn is lowered.

  Also, as shown in FIG. 7, for example, when the boost converter 51 is operated in a state where a charging path (fourth path P4) for detecting the deterioration of the insulation resistance Rp is formed, the boosting converter 51 and the charging path P4a are operated. A current may flow like this. The charging path P4a and the charging path P5a shown in FIGS. 7 and 8 are both examples of current flow.

  In the above case, the capacitor C1 is charged with the voltage from the boost converter 51 in addition to the voltage from the first and second stacks 12a and 12b, so that the voltage of the capacitor C1 rises and the insulation resistance Rp It may be difficult to accurately detect deterioration.

  Therefore, the degradation detection device 23 according to the present embodiment is configured to improve the degradation detection accuracy of the insulation resistances Rp and Rn even when the boost converter 51 is provided. Hereinafter, the configuration of the deterioration detection device 23 will be described in more detail.

  As shown in FIG. 2, the control unit 26 of the deterioration detection device 23 is a microcomputer including a CPU, a RAM, a ROM, and the like, and includes a voltage detection circuit unit 24, an A / D conversion unit 25, and the like. Control the whole. Specifically, the control unit 26 includes a charging path forming unit 26a, a discharging path forming unit 26b, a voltage detecting unit 26c, a charging state monitoring unit 26d, and a deterioration detecting unit 26e.

  The charging path formation unit 26a controls the first to sixth switches S1 to S6 to form the first, third to fifth paths P1, P3 to P5, that is, forms the charging path (FIGS. 4 and 4). 6 to 8).

  Note that the switching patterns of the first to sixth switches S1 to S6 are stored in advance in a storage unit such as a RAM and a ROM. Then, the charging path forming unit 26a and the discharging path forming unit 26b form a charging path or a discharging path by reading the switching pattern from the storage unit at an appropriate timing.

  The discharge path forming unit 26b controls the first to sixth switches S1 to S6 to form the second path P2, that is, to form a discharge path (see FIG. 5).

  The voltage detection unit 26c detects the voltage of the charged capacitor C1 through the A / D conversion unit 25 when the discharge path is formed by the discharge path formation unit 26b. Specifically, the voltage detection unit 26c detects the first and second stack voltages and the voltages VRp and VRn.

  Moreover, the voltage detection part 26c is comprised so that the negative voltage charged by the capacitor C1 can be detected. As a result, for example, as described above, even when the capacitor C1 is charged with a negative voltage, the voltage of the capacitor C1 can be accurately detected, thereby improving the degradation detection accuracy of the insulation resistances Rp and Rn. be able to.

  Specifically, the A / D conversion unit 25 provided between the voltage detection unit 26c and the capacitor C1 is offset so that the input voltage range includes a positive voltage and a negative voltage. That is, for example, when the input voltage range of the A / D conversion unit 25 is 0V to 200V, this is offset so as to be −100V to 100V. Accordingly, the voltage detection unit 26c can detect the negative voltage of the capacitor C1 with a simple configuration.

  In the above description, in order to detect the negative voltage of the capacitor C1, the input voltage range of the A / D conversion unit 25 is offset. However, the present invention is not limited to this. That is, for example, the input voltage range of the A / D converter 25 is expanded to include a positive voltage and a negative voltage, or the A / D converter 25 used for detecting a positive voltage and the negative voltage are used for detection. An A / D conversion unit 25 may be provided.

  The voltage detection unit 26c outputs a signal indicating the detected voltage of the capacitor C1 to the charge state monitoring unit 26d and the deterioration detection unit 26e.

  The charge state monitoring unit 26d uses the first and second stacks based on the first and second stack voltages detected after charging the capacitor C1 through the first path P1 and the third path P3 (see FIGS. 4 and 6). The state of charge of 12a, 12b is monitored. And the charge condition monitoring part 26d outputs the information which shows the monitoring result of the charge condition of the assembled battery 10 containing the 1st, 2nd stack 12a, 12b to the vehicle control apparatus 30 (refer FIG. 1). In addition, the vehicle control apparatus 30 performs vehicle control according to the monitoring result of the charge condition of the assembled battery 10, as described above.

  The degradation detector 26e degrades the insulation resistances Rp and Rn based on the voltages VRp and VRn of the capacitor C1 detected after charging the capacitor C1 through the fourth path P4 and the fifth path P5 (see FIGS. 7 and 8). Is detected.

  Specifically, when the insulation resistances Rp and Rn deteriorate, the voltage charged in the capacitor C1 increases. Therefore, when the voltage of the charged capacitor C1 increases, the deterioration of the insulation resistances Rp and Rn is detected. To.

  Specifically, the deterioration detection unit 26e first adds the voltage VRp and the voltage VRn to calculate the voltage VRp + VRn. Thereby, it is possible to eliminate the influence of boost converter 51 in the detection of deterioration of insulation resistances Rp and Rn.

That is, as shown in FIGS. 7 and 8, the voltage VRp and the voltage VRn charged in the capacitor C1 include the voltage from the boost converter 51 in addition to the voltages from the first and second stacks 12a and 12b. . Specifically, the voltage VRp and the voltage VRn are expressed by the following two expressions.
Voltage VRp = (Voltage from stack) + (Voltage from boost converter)
Voltage VRn = (Voltage from stack) − (Voltage from boost converter)

  Therefore, for example, if the voltage VRp and the voltage VRn are used as they are for detecting the deterioration of the insulation resistances Rp and Rn, the deterioration may not be detected accurately depending on the magnitude of the voltage from the boost converter 51.

  Therefore, in this embodiment, the voltage VRp and the voltage VRn are added to cancel the voltage from the boost converter 51. Then, by using the added voltage VRp + VRn for detection of deterioration of the insulation resistances Rp and Rn, the influence of the boost converter 51 can be eliminated.

  Here, the time constants in charging paths P4 and P4a shown in FIG. 7 and the time constants in charging paths P5 and P5a shown in FIG. 8 are preferably set to be the same.

  More specifically, as shown in FIG. 7, the sixth resistor R6 is provided in the fourth path P4, which is a charging path for detecting the deterioration of the positive-side insulation resistance Rp, with one end side on the vehicle body GND and the other end side on the other side. Connected to capacitor C1. Further, as shown in FIG. 8, the seventh resistor R7 is provided in the fifth path P5 which is a charging path for detecting the deterioration of the negative-side insulation resistance Rn, one end side is connected to the vehicle body GND and the other end side is connected to the capacitor C1. Is done.

  For example, if the resistance value of the sixth resistor R6 and the resistance value of the seventh resistor R7 are set different from each other, the voltage component from the boost converter 51 at the voltage VRp is equal to the voltage from the boost converter 51 at the voltage VRn. It will be different from the voltage. Thereby, even if the voltage VRp and the voltage VRn are added as described above, there may be a case where the voltage from the boost converter cannot be offset.

  Therefore, in the present embodiment, for example, by setting the resistance value of the sixth resistor R6 and the resistance value of the seventh resistor R7 to the same value, the time constant in the charging paths P4 and P4a and the time in the charging paths P5 and P5a are set. Made constants the same. Thereby, when the voltage VRp and the voltage VRn are added, the voltage from the boost converter 51 can be surely canceled. In the present specification, “same” is used to mean a certain width including not only the case where they are exactly the same but also the case where they are almost the same.

  The deterioration detection unit 26e compares the added voltage VRp + VRn with a threshold value Va which is a preset voltage value, and detects deterioration of the insulation resistances Rp and Rn based on the comparison result. Here, in the present embodiment, since the threshold value Va is set to a voltage value, it is possible to shorten the time required for the process of detecting the deterioration of the insulation resistances Rp and Rn in the deterioration detection unit 26e.

  Specifically, in the prior art, for example, the resistance values of the insulation resistances Rp and Rn are calculated based on the voltage VRp or voltage VRn of the capacitor C1 and the stack voltage. In the prior art, when the calculated resistance value is equal to or lower than a threshold value that is a preset resistance value, the deterioration of the insulation resistances Rp and Rn is detected. Therefore, it takes time to calculate the resistance values of the insulation resistances Rp and Rn, and the processing time for detecting the deterioration of the insulation resistances Rp and Rn may be relatively long.

  When the insulation resistance Rp and the insulation resistance Rn described above are not deteriorated and the resistance value is not lowered, the capacitor C1 is hardly charged or a sufficiently small voltage is charged even if it is charged. Therefore, the deterioration detection unit 26e according to the present embodiment compares the voltage VRp + VRn with a threshold value Va preset to a relatively low voltage value.

  Then, when the voltage VRp + VRn of the capacitor C1 is equal to or higher than the threshold value Va, the deterioration detection unit 26e detects the deterioration of the insulation resistances Rp and Rn, in other words, the insulation resistances Rp and Rn are abnormal. judge. On the other hand, when the voltage VRp + VRn is less than the threshold value Va, the deterioration detection unit 26e determines that the insulation resistances Rp and Rn are not deteriorated, in other words, the insulation resistances Rp and Rn are normal.

  Thus, in this embodiment, since the threshold value Va is set to a voltage value, the deterioration of the insulation resistances Rp and Rn is equivalent to the processing time for calculating the resistance values of the insulation resistances Rp and Rn. The time required for the detection process can be shortened.

  In the above description, the voltage VRp + VRn is used for detecting the deterioration of the insulation resistances Rp and Rn. However, the present invention is not limited to this, and for example, the input voltage of the A / D converter 25 may be used.

  Further, the voltage VRp + VRn of the capacitor C1 described above varies depending on the increase / decrease of the stack voltage supplied to the capacitor C1. Therefore, the deterioration detection unit 26e switches the threshold value Va according to the stack voltage. Specifically, the deterioration detection unit 26e increases the threshold value Va as the stack voltage increases. Here, the stack voltage is a value obtained by adding the first stack voltage of the first stack 12a and the second stack voltage of the second stack 12b.

  As a result, in the deterioration detection unit 26e, the threshold value Va can be set to an appropriate voltage value corresponding to the increase / decrease of the stack voltage, thereby further improving the detection accuracy of the deterioration of the insulation resistances Rp and Rn. Can do.

  Moreover, it is preferable that the deterioration detection unit 26e switches the threshold value Va according to the stack voltage detected by the voltage detection unit 26c immediately before comparing the voltage VRp + VRn of the capacitor C1 with the threshold value Va. Thereby, the threshold value Va can be set to an appropriate voltage value corresponding to the current charging state of the power supply.

  In the above description, the stack voltage detected by the voltage detection unit 26c immediately before the comparison is used. However, the present invention is not limited to this. That is, for example, the deterioration detection unit 26e may calculate an average value of the stack voltages for a plurality of times detected by the voltage detection unit 26c, and switch the threshold value Va according to the average value.

  Thereby, for example, even when the stack voltage instantaneously increases or decreases, the threshold value Va does not change abruptly, so the threshold value Va is set to an appropriate voltage value corresponding to the state of charge of the power supply. It becomes possible. In addition, various average values, such as a simple average and a weighted average, can be applied to the above average value.

  The above-described threshold value Va is assumed to be stored in advance in the storage unit, for example. As a result, the deterioration detecting unit 26e only needs to read the threshold value Va corresponding to the stack voltage from the storage unit, and can further reduce the processing time for detecting the deterioration of the insulation resistances Rp and Rn. Can also be reduced.

  In this embodiment, for example, a reference resistance (not shown) for forcibly creating a leakage state is connected to the fourth path P4 and the fifth path P5, and the capacitor C1 is charged in the leakage state. The value of the voltage VRp + VRn is preferably set as the threshold value Va.

  In this way, by setting the threshold value Va based on the actually measured value, for example, even when there is an individual difference in the capacitor C1 or each of the resistors R1 to R7, the threshold value Va is absorbed. This can further improve the detection accuracy of the deterioration of the insulation resistances Rp and Rn.

  The deterioration detection unit 26e outputs information indicating the result of the deterioration state of the insulation resistances Rp and Rn to the vehicle control device 30 and the like. And the vehicle control apparatus 30 performs the vehicle control according to a degradation state, the alerting | reporting operation | movement to a user, etc.

<3. Specific operation of charge state monitoring process and deterioration detection process>
Next, specific operations of the charge state monitoring process and the deterioration detection process performed by the battery monitoring system 20 configured as described above will be described with reference to FIG. FIG. 9 is a flowchart showing a part of a processing procedure of processing executed by the battery monitoring system 20. Various processes shown in FIG. 9 are executed based on control by the control unit 26 of the deterioration detection device 23.

  As shown in FIG. 9, the control unit 26 detects the first stack voltage of the first stack 12a (step S1), and subsequently detects the voltage VRp of the capacitor C1 (step S2). Next, the control unit 26 detects the second stack voltage of the second stack 12b (step S3), and subsequently detects the voltage VRn of the capacitor C1 (step S4).

  Next, the control unit 26 calculates the voltage VRp + VRn (step S5), and then calculates the stack voltage (step S6). The stack voltage is a value obtained by adding the first stack voltage and the second stack voltage detected in steps S1 and S3, for example.

  Subsequently, the control unit 26 switches the threshold value Va according to the stack voltage (step S7). Note that the process of switching the threshold value Va is not necessarily performed every time the stack voltage is detected, and may be executed once every time the stack voltage is detected a predetermined number of times, for example.

  The control unit 26 compares the voltage VRp + VRn with the switched threshold value Va (step S8). Then, when the voltage VRp + VRn is equal to or higher than the threshold value Va (step S8, Yes), the control unit 26 detects deterioration of the insulation resistances Rp, Rn (step S9). On the other hand, when the voltage VRp + VRn is less than the threshold value Va (step S8, No), the control unit 26 determines that the insulation resistances Rp, Rn are not deteriorated (step S10).

  Next, the control unit 26 transmits information indicating the deterioration state of the insulation resistances Rp and Rn as the deterioration detection result, and information indicating the first and second stack voltages and the stack voltage as the monitoring result of the charge state of the assembled battery 10. It outputs to the control apparatus 30 (step S11).

  As described above, the deterioration detection device 23 according to the first embodiment includes the capacitor C1, the voltage detection unit 26c, and the deterioration detection unit 26e. When the vehicle includes the voltage converter 50, the voltage converter 50 boosts the voltage output from the power supply and supplies the boosted voltage to the motor 40.

  The capacitor C1 is connected to an insulated power source to perform charging / discharging. The voltage detector 26c detects the voltage of the capacitor C1. The deterioration detector 26e detects deterioration of the insulation resistances Rp and Rn based on the voltages VRp and VRn of the capacitor C1 detected by the voltage detector 26c. The voltage detector 26c can detect the negative voltage charged in the capacitor C1.

  Thereby, even if the deterioration detection device 23 includes the voltage converter 50 that boosts the voltage output from the power supply, the deterioration detection accuracy of the insulation resistances Rp and Rn can be improved.

  In the deterioration detection device 23, the voltage detection unit 26c uses the voltages VRp and VRn of the capacitor C1 charged through the charging paths (fourth and fifth paths P4 and P5) for detecting the deterioration of the insulation resistances Rp and Rn. To detect. The deterioration detection unit 26e compares the voltages VRp and VRn of the capacitor C1 with a threshold value Va that is a preset voltage value, and detects deterioration of the insulation resistances Rp and Rn based on the comparison result. As a result, it is possible to shorten the time required for the process of detecting the deterioration of the insulation resistances Rp and Rn.

<4. Configuration of Deterioration Detection Device According to Second Embodiment>
(Second Embodiment)
Next, the charge / discharge system 1 including the deterioration detection device 23 according to the second embodiment will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  Vehicles have stray capacitances that are not intended at the time of design. Under the influence of the stray capacitance, for example, the voltage VRp and the voltage VRn of the capacitor C1 may not be accurately detected, and the accuracy of detecting the deterioration of the insulation resistances Rp and Rn may be reduced.

  For this reason, for example, the stray capacitance is measured by adding a resistor or a switch used for measuring the stray capacitance to the circuit of the voltage detection circuit unit 24, and the insulation resistances Rp and Rn are deteriorated while taking the measured stray capacitance into consideration. A method of detection can be considered. However, the above-described technique may complicate the configuration of the deterioration detection device 23 due to the addition of an element such as a resistor, and may increase the cost.

  Therefore, in the second embodiment, in the deterioration detection device 23, the stray capacitance can be estimated with a simple configuration, and the deterioration of the insulation resistances Rp and Rn can be accurately detected by considering the stray capacitance. The configuration.

  FIG. 10 is a block diagram illustrating a configuration example of the control unit 26 of the deterioration detection device 23 according to the second embodiment. As shown in FIG. 10, the control unit 26 includes a stray capacitance estimation unit 26f in addition to the deterioration detection unit 26e and the like.

  The stray capacitance estimation unit 26f estimates the stray capacitance of the charging path based on the voltage at the detection point A (see FIG. 7). In FIGS. 7 and 8, the stray capacitance is virtually indicated by a broken line and is denoted by Cp.

  FIG. 11 is a graph for explaining the stray capacitance Cp estimation process performed by the stray capacitance estimation unit 26f. In the example shown in FIG. 11, the voltage change at the detection point A when the charging circuit (fourth path P4) for detecting the deterioration of the positive-side insulation resistance Rp is formed.

  In the example shown in FIG. 11, the voltage change when there is no stray capacitance Cp is indicated by the solid line e1, and the voltage when the stray capacitance Cp increases in the order of the broken line e2, the alternate long and short dash line e3, and the two-dot chain line e4. It shows a change.

  In the example shown in FIG. 11, the moment when the fourth and fifth switches S4 and S5 are turned on and the fourth path P4 is formed is defined as “time t0”, which is shorter than the time when the capacitor C1 is fully charged. The time point is “time t2”. A time point between time t0 and t2 and when a predetermined time has elapsed from time t0 is defined as “time t1”.

  Prior to the description of FIG. 11, the detection point A will be described with reference to FIG. As described above, the sixth resistor R6 is provided in the fourth path P4 for detecting deterioration of the insulation resistance Rp, and one end side thereof is connected to the vehicle body GND (grounding point). A detection point A is provided on the other end side of the sixth resistor R6.

  When the stray capacitance Cp exists, the voltage at the detection point A described above rapidly increases once to the negative voltage side because an inrush current due to the stray capacitance Cp flows at the moment when the fourth and fifth switches S4 and S5 are turned on. (See time t0 in FIG. 11). Thereafter, the voltage at the detection point A changes so as to gradually rise and return. When the stray capacitance Cp does not exist, the voltage at the detection point A is determined only by the resistance values of the insulation resistance Rp, the resistances R4 to R6, and so on, and is slightly reduced to the negative voltage side.

  For example, if the stray capacitance Cp is relatively small, the voltage changes when the stray capacitance Cp is present, and charges are likely to accumulate. Therefore, as shown by the broken line e2 in FIG. It becomes. On the other hand, for example, when the stray capacitance Cp is relatively large, charge accumulation is slow, so that the return of the voltage at the detection point A is slow as indicated by a two-dot chain line e4 in FIG.

  In the second embodiment, the stray capacitance Cp is estimated by paying attention to the relationship between the stray capacitance Cp and the voltage change at the detection point A.

  Specifically, the stray capacitance estimation unit 26f includes the voltage V0 at the detection point A immediately after the charging path is formed, and the voltage V1 at the detection point A after a predetermined time t1 has elapsed since the charging path is formed. Based on the above, the voltage change rate Vd at the detection point A is calculated. In FIG. 11, the voltage at the detection point A for the solid line e1 is indicated by V1e1, and the voltages at the detection point A for the lines e2, e3, and e4 are indicated by Ve2, Ve3, and Ve4, respectively.

Specifically, the voltage change rate Vd is a value obtained by subtracting the absolute value of the voltage V1 from the absolute value of the voltage V0 and dividing the subtracted value by the absolute value of the voltage V0, as shown in the following equation. It is.
Voltage change rate Vd = (| V0 | − | V1 |) / | V0 |

  Then, the stray capacitance estimation unit 26f estimates the stray capacitance Cp based on the calculated voltage change rate Vd. Specifically, the stray capacitance estimation unit 26f is set so that the estimated stray capacitance Cp decreases as the voltage change rate Vd increases.

  The voltage dropping to the negative voltage side at time t0 is substantially the same value (voltage V0) regardless of the size of the stray capacitance Cp if the stray capacitance Cp before the switches S4 and S5 are turned on is fully charged. It becomes. Therefore, the stray capacitance estimation unit 26f may estimate the stray capacitance Cp based on the voltage V1 at time t1, for example.

  As described above, the stray capacitance estimation unit 26f can easily estimate the stray capacitance Cp with a simple configuration. In addition, since the configuration is simple, the cost of the degradation detection device 23 can be reduced.

  The predetermined time from the time t0 to the time t1 can be set to an arbitrary value. For example, the time at which the voltage change (voltage change rate Vd) at the detection point A due to the magnitude of the stray capacitance Cp can be distinguished. It is preferable to set to.

  Moreover, since the voltage detection part 26c is comprised so that a negative voltage can be detected, even if it is a case where the voltage of the detection point A falls to the negative voltage side, it can detect a voltage.

  Moreover, although the voltage detection part 26c detects a negative voltage using the A / D conversion part 25, it is not limited to this. That is, for example, as indicated by an imaginary line in FIG. 3, an A / D converter 25a used for estimating the stray capacitance Cp may be newly provided.

  In addition, the stray capacitance estimation unit 26f estimates the stray capacitance Cp based on the voltage at the detection point A, but is not limited thereto. That is, for example, the stray capacitance Cp may be estimated based on the voltage at the detection point B shown in FIG.

  The detection point B will be described. First, the seventh resistor R7 is provided in the fifth path P5 for detecting the deterioration of the negative-side insulation resistance Rn, and one end side thereof is connected to the vehicle body GND (grounding point). A detection point B is provided on the other end side of the seventh resistor R7.

  Although not shown in the figure, when the stray capacitance Cp exists, the voltage at the detection point B is positive because the inrush current due to the stray capacitance Cp flows at the moment when the first and sixth switches S1 and S6 are turned on. The voltage changes so as to rise rapidly to the side and then gradually drop back. Therefore, the stray capacitance estimation unit 26f can also estimate the stray capacitance Cp based on the voltage at the detection point B. The sixth resistor R6 and the seventh resistor R7 are examples of voltage detection resistors.

  The deterioration detection unit 26e corrects the voltages VRp and VRn of the capacitor C1 based on the stray capacitance Cp estimated by the stray capacitance estimation unit 26f. FIG. 12 is a graph for explaining a correction process performed by the deterioration detection unit 26e.

  The example shown in FIG. 12 shows the change in the charging voltage of the capacitor C1 when the charging circuit (fourth path P4) for detecting the deterioration of the positive-side insulation resistance Rp is formed. In the example shown in FIG. 12, the change in the charging voltage when the stray capacitance Cp does not exist is indicated by a solid line, while the change in the charging voltage when the stray capacitance Cp exists is indicated by a one-dot chain line.

  When the stray capacitance Cp exists, the inrush current due to the stray capacitance Cp flows into the capacitor C1 at the moment (time t0) when the fourth and fifth switches S4 and S5 are turned on and the fourth path P4 is formed. Compared to the case where the capacitance Cp does not exist, the charging voltage increases rapidly. The increase Vf of the charging voltage increases as the stray capacitance Cp increases, in other words, as the inrush current increases.

  Therefore, the deterioration detection unit 26e calculates an increase Vf of the charging voltage of the capacitor C1 generated by the stray capacitance Cp based on the estimated stray capacitance Cp. Then, the deterioration detection unit 26e corrects the voltage VRp of the capacitor C1 detected by the voltage detection unit 26c with the increment Vf in the second path (discharge path) P2 after the formation of the fourth path P4. . That is, a value obtained by subtracting the increment Vf from the detected voltage VRp of the capacitor C1 is replaced with a new voltage VRp.

  Further, the deterioration detection unit 26e may correct the voltage VRn of the capacitor C1 detected by the voltage detection unit 26c in the second path P2 after the formation of the fifth path P5 with the increment Vf. .

  Then, the deterioration detection unit 26e can improve the accuracy of detecting the deterioration of the insulation resistances Rp and Rn by detecting the deterioration of the insulation resistances Rp and Rn based on the corrected voltages VRp and VRn of the capacitor C1. .

<5. Specific Operation of Charge State Monitoring Process and Deterioration Detection Process in Second Embodiment>
Next, specific operations of the charge state monitoring process and the deterioration detection process performed in the battery monitoring system 20 according to the second embodiment will be described with reference to FIG. FIG. 13 is a flowchart illustrating a part of a processing procedure of processing executed by the battery monitoring system 20 according to the second embodiment. In FIG. 13, the same steps as those in the first embodiment are denoted by the same step numbers.

  As shown in FIG. 13, after detecting the first stack voltage in step S1, the control unit 26 forms the fourth path P4 and detects the voltages V0 and V1 at the detection point A (step S1a). Then, the control unit 26 calculates the voltage change rate Vd (step S1b), and estimates the stray capacitance Cp based on the calculated voltage change rate Vd (step S1c).

  Subsequently, in Step S2 to Step S4, the control unit 26 detects the voltage VRp of the capacitor C1, the second stack voltage, and the voltage VRn of the capacitor C1, and then corrects the voltages VRp and VRn based on the stray capacitance Cp ( Step S4a).

  Accordingly, the control unit 26 uses the corrected voltages VRp and VRn in the processing after step S6, and as a result, it is possible to accurately detect the deterioration of the insulation resistances Rp and Rn.

  In addition, since the control unit 26 performs the process of estimating the stray capacitance Cp in a series of processes of detecting the voltages VRp and VRn and detecting the deterioration of the insulation resistances Rp and Rn, the processing unit is efficient and real time. It can be set as the process excellent in property.

  As described above, the degradation detection device 23 according to the second embodiment includes the capacitor C1, the voltage detection resistors (sixth and seventh resistors R6 and R7), the voltage detection unit 26c, and the stray capacitance estimation unit. 26f and a degradation detector 26e. The capacitor C1 is connected to an insulated power source to perform charging / discharging. The voltage detection resistor is provided in a charging path (fourth and fifth paths P4 and P5) for detecting deterioration of the insulation resistances Rp and Rn, and one end side is connected to a ground point. After the charging path for detecting the deterioration of the insulation resistances Rp and Rn is formed, the voltage detection unit 26c detects the voltages VRp and VRn of the capacitor C1 and the detection points A and B on the other end side of the voltage detection resistor. Detect voltage. The stray capacitance estimation unit 26f estimates the stray capacitance Cp of the charging path based on the voltages at the detection points A and B. The deterioration detection unit detects deterioration of the insulation resistances Rp and Rn based on the voltages VRp and VRn of the capacitor C1 and the stray capacitance Cp.

  Thereby, it is possible to estimate the stray capacitance Cp with a simple configuration, and by using the estimated stray capacitance Cp, it is possible to improve the accuracy of detecting the deterioration of the insulation resistances Rp and Rn.

  In the second embodiment described above, in the detection of deterioration of the insulation resistances Rp and Rn, the voltage VRp + VRn is calculated and compared with the threshold value Va. However, the present invention is not limited to this. That is, for example, the voltage VRp and the voltage VRn of the capacitor C1 may be compared with threshold values to detect the deterioration of the insulation resistances Rp and Rn. In such a case, the threshold values compared with the voltage VRp and the voltage VRn may be set to the same value or different values.

  In the first and second embodiments, the detection is performed in the order of the first stack voltage, the voltage VRp, the second stack voltage, and the voltage VRn. However, this is an example and is not limited. The order of detection can be set arbitrarily.

  In addition, the timing for executing the deterioration detection process in the first and second embodiments is not limited to the above. That is, for example, when the vehicle is started or stopped, the timing for executing the deterioration detection process may be changed, such as every predetermined time interval or every predetermined travel distance.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

DESCRIPTION OF SYMBOLS 1 Charging / discharging system 10 Assembly battery 12a 1st stack 12b 2nd stack 20 Battery monitoring system 23 Deterioration detection apparatus 24 Voltage detection circuit part 25 A / D conversion part 26 Control part 26a Charging path formation part 26b Discharge path formation part 26c Voltage detection Unit 26d charge state monitoring unit 26e deterioration detection unit 26f stray capacitance estimation unit 30 vehicle control device 40 motor 50 voltage converter 51 boost converter 60 fail-safe relay

Claims (6)

A capacitor that is connected to an isolated power source to charge and discharge;
A voltage detector for detecting the voltage of the capacitor;
A deterioration detector that detects deterioration of the insulation resistance of the power source based on the voltage of the capacitor detected by the voltage detector; and
The voltage detector is
A deterioration detection device characterized in that a negative voltage charged in the capacitor can be detected. An A / D conversion unit provided between the voltage detection unit and the capacitor, which converts an analog value indicating the voltage of the capacitor into a digital value and outputs the digital value to the voltage detection unit;
The A / D converter is
The deterioration detection apparatus according to claim 1, wherein the input voltage range is offset so as to include a positive voltage and a negative voltage. The insulation resistance of the power source is
Including the insulation resistance on the positive electrode side and the insulation resistance on the negative electrode side,
The deterioration detector
The voltage of the capacitor when charged by a charging path for detecting deterioration of the insulation resistance on the positive electrode side and the voltage of the capacitor when charged by a charging path for detecting deterioration of the insulation resistance on the negative electrode side The deterioration detection apparatus according to claim 1, wherein the deterioration is detected by adding and detecting deterioration of the insulation resistance of the power source based on the added voltage. Provided in a charging path for detecting deterioration of the insulation resistance on the positive electrode side, one end side is connected to the ground and the other end side is connected to the capacitor, and a charging path for detecting deterioration of the insulation resistance on the negative electrode side The deterioration detection device according to claim 3, wherein a resistance value of a resistor having one end side connected to a grounding point and the other end side connected to the capacitor is set to the same value. The deterioration detector
The voltage of the capacitor is compared with a threshold value that is a preset voltage value, and deterioration of the insulation resistance of the power supply is detected based on the comparison result. Deterioration detection device described in 1. A voltage detecting step of charging and discharging a capacitor connected to an insulated power source to detect a voltage of the capacitor;
A deterioration detecting step of detecting deterioration of the insulation resistance of the power source based on the voltage of the capacitor detected in the voltage detecting step,
The voltage detection step includes
A deterioration detection method characterized in that a negative voltage charged in the capacitor can be detected.

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