JP2006288163A - Device for monitoring abnormality in load drive circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To monitor any abnormality in a voltage sensor in a load drive circuit. <P>SOLUTION: An ECU executes a program including a step in which, when a deviation between a VB sensor and a VL sensor during boosting is equal to or larger than a threshold value (1) (YES at S110) and a voltage value VL is lower than a threshold value (2) (YES at S120) or a voltage value VL is not lower than the threshold value (2) (NO at S120) but a voltage value VH does not agree with a boosting command value (YES at S150), it is determined that the VL sensor is abnormal (S160); and a step in which, when a voltage value VH agrees with the boosting command value (NO at S150), boosting control is stopped by feed forward control using only the voltage value VH (S170), and when the voltage value VH becomes substantially equal to a voltage value VB (YES at S180), the abnormality sensor is identified based on the combination of the deviations between two voltage values of the voltage values VB, VL, and VH detected by three sensors (S200, S210, and S230). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric circuit for driving a load mounted on a vehicle, and more particularly to an apparatus for monitoring an abnormality of a sensor in the load driving circuit.

  In recent years, hybrid vehicles and electric vehicles have attracted much attention as environmentally friendly vehicles. Some hybrid vehicles have already been put to practical use.

  This hybrid vehicle is a vehicle that uses a motor driven by a DC power source and an inverter as a power source in addition to a conventional engine. That is, power is obtained by driving the engine, and DC voltage from a DC power source is converted into AC voltage by an inverter, and power is obtained by rotating the motor by the converted AC voltage. An electric vehicle is a vehicle that uses a motor driven by a DC power source and an inverter as a power source.

  In such a hybrid vehicle or electric vehicle, there is a case where the voltage is boosted by a DC / DC converter from a low-voltage battery and electric power is supplied to the motor inverter. In this case, the rated voltage of the driving motor is high in order to reduce the current supplied to the motor for driving the vehicle to reduce the weight of the harness and to obtain a high driving force for driving the vehicle. There are many cases. On the other hand, in order to increase the voltage of the battery mounted on the vehicle, many battery cells of about 1.2V must be connected in series. If the rated voltage of the motor does not reach even when many are connected in series, the voltage of the battery is boosted by the DC / DC converter and supplied to the motor via the inverter. As described above, in the electric circuit mounted on the vehicle, it is necessary to step up / down the voltage of the battery. In such a case, a DC / DC converter is used. In such an electric circuit, the voltage at a plurality of locations is detected to control the step-up / step-down voltage of the DC / DC converter or to detect the voltage of the battery (power source).

  Japanese Patent Laying-Open No. 2004-364404 (Patent Document 1) includes a converter that performs at least one of a step-up operation and a step-down operation and a battery connected to the input side of the converter, and supplies power from the converter to a load. An abnormality monitoring device in a load drive circuit that performs first detection means (VB sensor) for detecting the voltage value of the battery and second detection means (VB sensor) for detecting the voltage value on the input side of the converter ( VL sensor), third detection means (VH sensor) for detecting the voltage value on the output side of the converter, calculation means for calculating the difference value of the voltage value detected by the detection means, and the difference value And monitoring means for monitoring the abnormality of the detecting means based on the predetermined threshold value and the converter is performing the step-up / step-down operation during the step-up / step-down operation of the converter. The monitoring means includes a control means for controlling the converter, and the monitoring means includes the voltage value detected by the first detection means and the second detection means when the converter is not performing the step-up operation and the step-down operation. The first difference value from the voltage value detected by the second detection value, the second difference value between the voltage value detected by the first detection means and the voltage value detected by the third detection means, and the second detection means Means for specifying an abnormal detection means in the detection means based on the third difference value between the voltage value detected by the third detection means and the voltage value detected by the third detection means.

According to the abnormality monitoring device in the load drive circuit, after the step-up / step-down operation is stopped, the first detection means (VB sensor), the second detection means (VL sensor), and the third detection means (VH sensor) The voltage value at the substantially equipotential position on the drive circuit is detected. Abnormalities of the first detection means, the second detection means, and the third detection means can be monitored by comparing the difference value with the threshold value by the monitoring means. That is, if the detection means is normal, the difference value does not exceed the threshold value. Therefore, if the difference value is greater than or equal to the threshold value, it can be determined that the detection means is abnormal. At this time, for example, the two detection means used when calculating the smallest difference value among the three difference values may be specified as normal and the other one as abnormal. As a result, in the load drive circuit, it is possible to provide an abnormality monitoring device that can monitor abnormality of a sensor that detects the voltage of each part and identify an abnormal detection means.
JP 2004-364404 A

  However, in the above-described abnormality monitoring device for the load drive circuit, after the step-up / step-down operation is stopped, the abnormality of the first detection means, the second detection means, and the third detection means is set as a difference value by the monitoring means. It can be monitored by comparing the value. When the step-up / step-down operation can be stopped in this way, the abnormality monitoring by the load drive circuit abnormality monitoring device is effective, but when the condition for stopping the step-up / step-down operation cannot be satisfied, Anomaly monitoring becomes difficult.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a sensor for detecting the voltage of each part in a load driving circuit having a converter and a battery for supplying power to a load. An object of the present invention is to provide an abnormality monitoring device in a load drive circuit for monitoring an abnormality.

  An abnormality monitoring device in a load drive circuit according to a first aspect of the present invention includes a converter that performs at least one of a step-up operation and a step-down operation and a battery connected to the input side of the converter, and supplies power from the converter to a load. An abnormality monitoring device in a load drive circuit to be supplied, comprising: a first detection means for detecting a voltage value of a battery; a second detection means for detecting a voltage value on the input side of the converter; Based on the deviation between the third detection means for detecting the voltage value on the output side and the two detection means for detecting the voltage value at the equipotential position, it is assumed that one of the two detection means is abnormal. By using the determination means for determination and the voltage value of the detection means tentatively determined to be abnormal, the abnormality of the detection means tentatively determined to be abnormal is determined, thereby detecting the difference in detection means. The and a monitoring means for monitoring.

  According to the first invention, when the converter is not performing the step-up / step-down operation, the first detection means and the second detection means, the first detection means and the third detection means, the second detection means and the third The detecting means detects an equipotential voltage value. When the converter is performing the step-up / step-down operation, the first detection means and the second detection means detect the equipotential voltage values, respectively. If the difference between the two detection means is large even though the voltage value is at the equipotential position, the determination means tentatively determines that one of the two detection means is abnormal. If the voltage value of the detection means tentatively determined to be abnormal is a voltage value that cannot be detected (abnormally high voltage value or abnormally low voltage value), the detection means tentatively determined to be abnormal is abnormal. Can be determined. As a result, in the load driving circuit having a converter and a battery for supplying power to the load, it is possible to provide an abnormality monitoring device in the load driving circuit that monitors the abnormality of the sensor that detects the voltage of each part.

  In the abnormality monitoring apparatus in the load drive circuit according to the second invention, in addition to the configuration of the first invention, the monitoring means has a predetermined threshold value for the voltage of the detection means tentatively determined to be abnormal. A means for determining that the temporarily determined detection means is abnormal when the value is lower than the value is included.

  According to the second aspect of the invention, for example, when the second detection means detects a voltage value far lower than the voltage value of the battery, it can be determined to be abnormal.

  In the abnormality monitoring device in the load drive circuit according to the third aspect of the invention, in addition to the configuration of the first or second aspect of the invention, the determination means includes the first detection means and the second detection means during the step-up / step-down operation by the converter. Means for temporarily determining that either one of the means is abnormal is included.

  According to the third aspect, even during the step-up / step-down operation by the converter, the potential at the position detected by the first detection means is equal to the potential at the position detected by the second detection means. For this reason, if the deviation of these two detection means is large, it can tentatively determine that either one is abnormal.

  In addition to the configuration of any one of the first to third aspects, the abnormality monitoring device in the load drive circuit according to the fourth aspect of the invention includes a target voltage command value and a voltage value of the third detection means during the step-up / step-down operation by the converter. And a means for monitoring the abnormality of the third detecting means.

  According to the fourth invention, during the step-up / step-down operation by the converter, when the target voltage command value to the converter greatly deviates from the voltage value of the third detecting means, the third detecting means or the second detecting means. It can be monitored that either the means or the converter itself is abnormal.

  In addition to the configuration of the fourth invention, the abnormality monitoring device in the load drive circuit according to the fifth invention uses the third detection means when the third detection means is not determined to be abnormal. And further includes means for controlling the converter to stop the buck-boost operation of the converter.

  According to the fifth invention, when it is determined that the third detection means is not abnormal (normal), the voltage step-up / down operation of the converter is stopped using the voltage value detected by the third detection means. Thus, an abnormal sensor can be identified based on the deviation between the sensors so that there is no voltage difference between the three sensors.

  In addition to the configuration of the fourth invention, the abnormality monitoring device in the load drive circuit according to the sixth invention uses the third detection means when the third detection means is not determined to be abnormal. The feed forward control further includes means for controlling the converter to stop the converter's step-up / step-down operation.

  According to the sixth aspect of the invention, when it is determined that the third detection means is not abnormal (normal), feed-forward control is performed using the voltage value detected by the third detection means to raise and lower the converter. By stopping the pressure operation so that there is no voltage difference between the three sensors, an abnormal sensor can be identified based on the deviation between the sensors.

  In addition to the configuration of the fifth or sixth invention, the abnormality monitoring device in the load drive circuit according to the seventh invention is a voltage detected by the first detection means in response to the converter stopping the step-up / step-down operation. A first difference value between the value and the voltage value detected by the second detection means, a second difference between the voltage value detected by the first detection means and the voltage value detected by the third detection means Based on the value and the third difference value between the voltage value detected by the second detection means and the voltage value detected by the third detection means, the abnormal detection means in the detection means is identified. Means are further included.

  According to the seventh aspect, after the step-up / step-down operation is stopped, the first detection unit and the second detection unit detect a voltage value at a substantially equipotential on the load drive circuit. The abnormality of the first detection means and the second detection means can be monitored by comparing the difference value with the threshold value. That is, if both detection means are normal, the difference value does not exceed the threshold value. Therefore, if the difference value is equal to or more than the threshold value, it can be determined that the detection means is abnormal. At this time, for example, the two detection means used when calculating the smallest difference value among the three difference values may be determined as normal and the other one as abnormal.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  With reference to FIG. 1, an entire circuit of a load drive circuit including an ECU (Electronic Control Unit) 1000 that realizes an abnormality detection device according to an embodiment of the present invention will be described. Such a load drive circuit is mounted on a hybrid vehicle or an electric vehicle. In the following description, the DC / DC converter is described as the step-up DC / DC converter 700, but may be a bidirectional (buck-boost) converter.

  This load drive circuit is a circuit that boosts the voltage of the main battery 100 by a boost DC / DC converter 700 and supplies electric power to the vehicle drive motor via an inverter. Between main battery 100 and step-up DC / DC converter 700, a system main relay (SMR) 500 and an electric load circuit 600 including auxiliary devices are connected.

  The main battery 100 is, for example, a secondary battery having a discharge voltage of 200 to 300 [V] in which nickel hydride batteries having a discharge voltage per cell of 1.2 [V] are connected in series. The step-up DC / DC converter 700 boosts the voltage of 200 to 300 [V] to about 500 to 600 [V], which is the rated voltage of the vehicle driving motor. The step-up DC / DC converter 700 is controlled by a control signal from the ECU 1000.

  The system main relay 500 is a relay (relay) that switches the main battery 100, the electric load circuit 600, and the step-up DC / DC converter 700 to either an electrically connected state or an electrically disconnected state. This system main relay 500 is controlled by a control signal from ECU 1000. For example, ECU 1000 outputs a control signal for switching the state of system main relay 500 in accordance with the state of the ignition switch of the vehicle.

  As an example of the auxiliary machines constituting the electric load circuit 600, an air conditioner 610 (more specifically, an electric compressor for an air conditioner and an electric motor for a blower fan) and a low-voltage battery 630 (for an auxiliary machine) A DC / DC converter 620 that steps down the voltage of the main battery 100 in order to charge a lead storage battery having a discharge voltage of about 12 [V] is shown. The DC / DC converter 620 steps down the discharge voltage of the main battery 100 from 200 to 300 [V] to about 14 [V] as the charging voltage of the low voltage battery 630. Similar to the system main relay 500 described above, the operation of these auxiliary machines is controlled by a control signal from the ECU 1000.

  In such a load driving circuit, a VB sensor 410 (first voltage detecting means) for detecting the voltage of the main battery 100 and a VL sensor 420 for detecting the voltage on the input side of the step-up DC / DC converter 700 are included. (Second voltage detection means) and a VH sensor 430 (third voltage detection means) for detecting the voltage on the output side of the step-up DC / DC converter 700. The voltage value VB detected by the VB sensor 410, the voltage value VL detected by the VL sensor 420, and the voltage value VH detected by the VH sensor 430 are respectively input to the ECU 1000.

  With reference to FIG. 2, a control structure of a program executed by ECU 1000 that realizes the abnormality detection device according to the present embodiment will be described.

  In step (hereinafter, step is abbreviated as S) 100, ECU 1000 determines that voltage value VB detected by VB sensor 410 and voltage value VL detected by VL sensor 420 while step-up DC / DC converter 700 is operating. A deviation ΔV (BL) is calculated as | VB−VL |.

  In S110, ECU 1000 determines whether or not deviation ΔV (BL) is equal to or greater than a predetermined threshold value (1). Regardless of whether the step-up DC / DC converter 700 is in operation or not, the voltage value VB detected by the VB sensor 410 and the voltage value VL detected by the VL sensor 420 are the same potential positions. Since the detection is such that the deviation ΔV (BL) is equal to or greater than the threshold value (1), at least one of the voltage value VB detected by the VB sensor 410 and the voltage value VL detected by the VL sensor 420 It can be tentatively determined that the above is over. If deviation ΔV (BL) is equal to or greater than a predetermined threshold value (1) (YES in S110), the process proceeds to S120. If not (NO in S110), the process proceeds to S130.

  In S120, ECU 1000 determines whether or not voltage value VL detected by VL sensor 420 is lower than threshold value (2). For example, when the VL sensor 420 is abnormal and the detected voltage value is so low as to be impossible. If voltage value VL detected by VL sensor 420 is lower than a predetermined threshold value (2) (YES in S120), the process proceeds to S160. If not (NO in S120), the process proceeds to S140.

  In S130, ECU 1000 determines that there is no sensor abnormality. Thereafter, the process ends.

  In S140, ECU 1000 controls step-up DC / DC converter 700 so as to perform further step-up operation, and VH sensor 430 detects voltage value VH.

  In S150, ECU 1000 determines whether or not voltage value VH detected by VH sensor 430 is in accordance with the boost command value from ECU 1000 to boost DC / DC converter 700. This is because in the boost feedback control of the boost DC / DC converter 700, even if at least one of the abnormality of the VL sensor 420, the abnormality of the VH sensor 430, and the abnormality of the booster circuit has occurred, the VL sensor 420, the VH sensor 430, Feedback control is executed assuming that the booster circuit is normal. Therefore, the integral term in the feedback control becomes large in order to set the steady deviation to 0, but the steady deviation does not disappear because an abnormality has occurred. For this reason, the voltage value VH detected by the VH sensor 430 is not boosted in accordance with the boost command value. If voltage value VH detected by VH sensor 430 is not boosted according to the boost command value (YES in S150), the process proceeds to S160. If not (NO in S150), the process proceeds to S170.

  In S160, ECU 1000 determines that VL sensor 420 is abnormal. At this time, in the step-up feedback control of the step-up DC / DC converter 700, if the boost is not performed normally, either the VL sensor 420 is abnormal, the VH sensor 430 is abnormal, or the boost circuit is abnormal. In FIG. 5, since it is determined that either the VB sensor 410 or the VL sensor 420 is abnormal, it is determined that the VL sensor 420 included in both of them is abnormal.

  In S170, ECU 1000 stops the pressure increase control (shifts to upper arm ON control). At this time, the feedforward control is performed based on the voltage value VH detected by the VH sensor 430 without using the voltage value VL detected by the VL sensor 420. The voltage value VH is lowered to the voltage value of the main battery 100 at a predetermined voltage drop rate per unit time. At this time, a voltage reduction rate that is gentler than the normal voltage reduction rate is used so that the voltage gradually decreases so as not to fall into a fatal state. At this time, it is assumed that the VH sensor 430 is normal. Further, feedforward control is performed based on voltage value VH detected by VH sensor 430 only when at least one of VB sensor 410 and VL sensor 420 determined to be YES in S110 is abnormal. is there.

  In S180, ECU 1000 determines whether or not voltage value VH detected by VH sensor 430 has decreased to approximately the same voltage value VB detected by VB sensor 410. When voltage value VH decreases to approximately the same as voltage value VB (YES in S180), the process proceeds to S190. If not (NO in S180), the process returns to S170, and the boost control stop process (feed forward control using only voltage value VH) is continued.

  In S190, ECU 1000 determines that the boost control stop has been completed. In S200, ECU 1000 detects voltage value VB using VB sensor 410, voltage value VL using VL sensor 420, and voltage value VH using VH sensor 430.

  In S210, ECU 1000 calculates VBL deviation = | VB−VL | as VBL deviation, VBH deviation = | VB−VH | as VBH deviation, and VHL deviation = | VH−VL | as VHL deviation. That is, the absolute value of three deviations consisting of a combination of two voltage values among the three voltage values detected by the three sensors is calculated.

  In S220, ECU 1000 determines whether or not all three deviations of VBL deviation, VBH deviation and VHL deviation calculated in S210 are equal to or smaller than threshold value (3). At this time, it is determined whether or not all three deviations are equal to or less than a threshold value for a certain time or more. If all three deviations are equal to or smaller than the threshold value (YES in S220), the process proceeds to S130. If not (NO in S220), the process proceeds to S230.

  In S230, ECU 1000 determines that the two voltage sensors used to calculate the smallest deviation among the three deviations (VBL deviation, VBH deviation, and VHL deviation) calculated in S210 are normal, and the remaining 1 One voltage sensor is judged abnormal. At this time, the boost control stop processing (feed forward control using only the voltage value VH) executed in S170 is based on the premise that the VH sensor 430 is normal. Specific voltage sensors are identified. Information regarding the sensor determined to be abnormal in this way is stored in a memory built in the ECU 1000 and used for diagnosis diagnosis and the like.

  The operation of the abnormality detection apparatus according to the present embodiment based on the above-described structure and flowchart will be described.

[During boost control]
When the boost control is executed by the boost DC / DC converter 700, the voltage value VB is detected by the VB sensor 410 and the voltage value VL is detected by the VL sensor 420, and the deviation ΔV (BL) is | VB−VL | is calculated (S100). If this deviation ΔV (BL) is not equal to or greater than a predetermined threshold value (1) (NO in S110), it is determined that there is no sensor abnormality (S130).

  However, if the deviation between voltage value VB that should be equipotential and voltage value VL is greater than or equal to a predetermined threshold value (1) (YES in S110), at least one of VB sensor 410 and VL sensor 420 Is temporarily determined to be abnormal. If voltage value VL detected by VL sensor 420 is lower than a predetermined threshold value (2) (YES in S120), it is determined that VL sensor 420 is abnormal (S160).

[Forced boost]
If voltage value VL detected by VL sensor 420 is not lower than predetermined threshold value (2) (NO in S120) and VL sensor 420 is not determined to be abnormal, the voltage is further increased. If voltage value VH detected by VH sensor 430 at that time does not match the boost command value (YES in S150), it is determined that VL sensor 420 is also abnormal (S160).

  As shown in FIG. 3, a boost stop command (upper arm ON request flag is set) to ECU 1000 from the boosted load (motor generator) side is set to boost command value ≦ voltage value VL + X. Here, X is a constant, 30 [V], and if the lower limit value of the boost command value is 204 [V], the voltage value VL detected by the VL sensor 420 is 174 [V] (= 204-30). ) If only the following is detected, the upper arm ON request flag is not set, so that the pressure increase cannot be stopped and the abnormal sensor cannot be specified.

[Forced pressurization canceled]
Therefore, even if the voltage is forcibly further boosted, if the voltage value VH detected by the VH sensor 430 at that time is in accordance with the boost command value (NO in S150), an abnormal sensor cannot be specified. The feedforward control is performed based on the voltage value VH, and the boost control is stopped. At this time, the voltage value VL detected by the VL sensor 420 is not used (that is, there is a possibility of abnormality) (that is, feedback control is not performed). When voltage value VH detected by VH sensor 430 is substantially equal to voltage value VB detected by VB sensor 410 (YES in S180), it is determined that the suspension of the boost control has been completed (S190).

  When the stop of the boost control is completed, the voltage value is detected by the three voltage sensors (S200). The voltage value VB detected by the VB sensor 410, the voltage value VL detected by the VL sensor 420, and the voltage value VH detected by the VH sensor 430 are all voltages at an equipotential or almost equipotential position. Therefore, the differences (deviations) of the three voltage values composed of combinations of two voltage values among the three voltage values detected by these three voltage sensors are all ideally 0.

  As the absolute value of the difference between the voltage value VB detected by the VB sensor 410 and the voltage value VL detected by the VL sensor 420, the VBH deviation is detected by the voltage value VB detected by the VB sensor 410 and the VH sensor 430. As the absolute value of the difference from the measured voltage value VH, the VHL deviation is calculated as the absolute value of the difference between the voltage value VH detected by the VH sensor 430 and the voltage value VL detected by the VL sensor 420 ( S210). If all three deviations are not less than the threshold value (NO in S220), the two voltage sensors used to calculate the smallest deviation among the three deviations are determined to be normal, and the remaining one voltage It is determined that the sensor is abnormal (S230).

  For example, assuming that the VBH deviation calculated in S210 is the smallest deviation, the VH sensor 430 used to calculate the VBH deviation is normal, and the VBH sensor 410 used to calculate the VBH deviation is also the same. Is determined to be normal. It is determined that the remaining VL sensor 420 is abnormal. In this way, the abnormal sensor is identified as the VL sensor 420 (S230).

  As described above, according to the ECU that realizes the abnormality monitoring device according to the present embodiment, when the step-up DC / DC converter is being stepped up, the deviation of the voltage values detected by the VB sensor and the VL sensor, respectively. The absolute value of ΔV (BL) is always monitored, the deviation is equal to or greater than the threshold value (1), and the voltage value detected by the VL sensor is lower than the threshold value (2) or forced If the voltage value detected by the VH sensor when the boost control is performed is not in accordance with the boost command value, it is determined that the VL sensor is abnormal. Further, if the voltage value detected by the VH sensor when the boost control is forcibly performed is in accordance with the boost command value, the boost control is forcibly stopped based only on the voltage value VH detected by the VH sensor. After the feedforward control is performed and the boost control is stopped, the absolute value of the difference between any two voltage values of the voltage value VB, the voltage value VL, and the voltage value VH is calculated. The abnormality of the voltage sensor can be monitored based on the deviation of the three voltage sensors that detect the location at the potential.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is an overall circuit diagram of a load drive circuit including an ECU that realizes an abnormality detection device according to an embodiment of the present invention. It is a flowchart which shows the control structure of the program performed with ECU of FIG. It is a figure which shows the operation state of a DC / DC converter.

Explanation of symbols

  100 main battery, 410 VB sensor, 420 VL sensor, 430 VH sensor, 500 system main relay (SMR), 600 electric load circuit, 610 air conditioner, 620 DC / DC converter, 630 low voltage battery, 700 step-up DC / DC converter 1000 ECU.

Claims (7)

An abnormality monitoring device in a load drive circuit that includes a converter that performs at least one of a step-up operation and a step-down operation, and a battery connected to an input side of the converter, and that supplies power to the load from the converter,
First detecting means for detecting the voltage value of the battery;
Second detection means for detecting a voltage value on the input side of the converter;
Third detection means for detecting a voltage value on the output side of the converter;
A determination means for temporarily determining that one of the two detection means is abnormal based on a deviation between the two detection means for detecting a voltage value at an equipotential position;
Monitoring means for monitoring the abnormality of the detection means by determining the abnormality of the detection means tentatively determined to be abnormal using the voltage value of the detection means tentatively determined to be abnormal. An abnormality monitoring device in a load driving circuit.   The monitoring means is means for determining that the detection means tentatively determined to be abnormal is abnormal when the voltage value of the provisionally determined detection means is lower than a predetermined threshold value. The abnormality monitoring apparatus in the load drive circuit according to claim 1, comprising:   The determination unit includes a unit for temporarily determining that one of the first detection unit and the second detection unit is abnormal during the step-up / step-down operation by the converter. 3. An abnormality monitoring device in the load drive circuit according to 2.   An abnormality monitoring device in the load drive circuit is for monitoring an abnormality of the third detection unit based on a target voltage command value during a step-up / step-down operation by the converter and a voltage value of the third detection unit. The abnormality monitoring apparatus in the load drive circuit according to claim 1, further comprising means.   The abnormality monitoring device in the load drive circuit uses the third detection unit to stop the step-up / step-down operation of the converter when the third detection unit is not determined to be abnormal. The abnormality monitoring device in the load driving circuit according to claim 4, further comprising means for controlling the converter.   The abnormality monitoring device in the load drive circuit stops the step-up / step-down operation of the converter by feedforward control using the third detection means when the third detection means is not determined to be abnormal. The abnormality monitoring device in a load drive circuit according to claim 4, further comprising means for controlling the converter to do so.   The abnormality monitoring device in the load drive circuit includes a voltage value detected by the first detection means and a voltage value detected by the second detection means in response to the converter stopping the step-up / step-down operation. The first difference value, the second difference value between the voltage value detected by the first detection means and the voltage value detected by the third detection means, and the second detection means 6. The apparatus according to claim 5, further comprising means for identifying an abnormal detection means in the detection means based on a third difference value between a voltage value and a voltage value detected by the third detection means. 6. An abnormality monitoring device in the load drive circuit according to 6.

Images