JP2012060723A - Dc-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promptly detect failure which occurs during droop control of output voltage of a DC-DC converter.SOLUTION: In a case where droop control of a voltage transformation unit 21 is performed by an output voltage control unit 53 controlling output voltage of the voltage transformation unit 21 of the DC-DC converter, when increased amount of output current of the voltage transformation unit 21 per predetermined time exceeds a predetermined threshold value, a failure detection unit 54 determines that failure occurs in the DC-DC converter or a section around the DC-DC converter. This invention is applicable to, for example, a DC-DC converter for an electric vehicle.

Description

  The present invention relates to a DCDC converter, and more particularly to a DCDC converter capable of executing droop control of an output voltage.

  Conventionally, in a DCDC converter, the total load resistance (hereinafter also simply referred to as load resistance) decreases due to an increase in the load amount or a short-circuit failure in which the electrodes on the output side of the DCDC converter are short-circuited in the circuit or on the load side. When the output current increases, so-called drooping control is performed in which the output voltage is lowered in order to prevent the occurrence of overcurrent.

  Also, some conventional DCDC converters can switch the pace at which the output voltage is lowered in the drooping control due to an increase in the output current. Specifically, for example, when the output current is greater than or equal to a predetermined first threshold, it is determined that the output current has increased due to a short circuit failure, the output voltage is instantaneously reduced, and the output of the DCDC converter is quickly Stopped. On the other hand, if the output current is smaller than the first threshold and greater than or equal to the predetermined second threshold, it is determined that the output current has increased due to an increase in the load, and the output is performed so as not to burden the hardware. The voltage is lowered step by step.

  Further, conventionally, there has been proposed a DCDC converter that determines that an internal converter has failed when a state where a difference between a command voltage and an actual output voltage is equal to or greater than a predetermined threshold continues for a specified time or longer (for example, , See Patent Document 1).

  However, in the DCDC converter described in Patent Document 1, in order to prevent erroneous detection of converter failure, determination of converter failure is prohibited during drooping control. Therefore, the DCDC converter described in Patent Document 1 cannot cope with, for example, a case where a short circuit failure occurs during the drooping control, and may cause a more serious failure.

JP 2006-50799 A

  The present invention is intended to make it possible to quickly detect a failure that has occurred during droop control of the output voltage of a DCDC converter.

  The DCDC converter according to the first aspect of the present invention is a DCDC converter including a transforming means for transforming and outputting an input voltage, the output voltage control means controlling the output voltage of the transforming means, and the output voltage When the output voltage drooping control is performed by the control means, when the amount of increase of the output current of the transformer means per predetermined time exceeds a predetermined threshold value, there is a failure in the DCDC converter or its surroundings. A failure detection means for determining that it has occurred.

  In the DCDC converter according to the first aspect of the present invention, when the drooping control of the output voltage of the transforming means is performed by the output voltage control means, the increase amount per predetermined time of the output current of the transforming means is predetermined. It is determined that a failure has occurred in or around the DCDC converter.

  Therefore, it is possible to quickly detect a short circuit failure that occurs during droop control of the output voltage of the DCDC converter.

  This transformer means is constituted by, for example, a power conversion circuit such as a half bridge method or a full bridge method using a switching element. The output voltage control means and the failure detection means are constituted by, for example, a microcomputer or a processor.

  When the output voltage drooping control is started when the increase amount per unit time of the output current is already equal to or greater than the threshold before the drooping control of the output voltage starts, It can be determined that a failure has occurred in the DCDC converter or in the vicinity thereof.

  As a result, it is possible to detect the short circuit failure when the drooping control of the output voltage of the DCDC converter is started due to the short circuit failure.

  The DCDC converter according to the second aspect of the present invention is a DCDC converter including a transformation means for transforming and outputting an input voltage, the output voltage control means for controlling the output voltage of the transformation means, and the output voltage When the output voltage drooping control is performed by the control means, when the amount of decrease in the output current of the transformer means per predetermined time exceeds a predetermined threshold value, there is a failure in the DCDC converter or its surroundings. A failure detection means for determining that it has occurred.

  In the DCDC converter according to the second aspect of the present invention, when the drooping control of the output voltage of the transforming means is performed by the output voltage control means, the reduction amount per predetermined time of the output current of the transforming means is predetermined. It is determined that a failure has occurred in or around the DCDC converter.

  Therefore, it is possible to quickly detect an open failure that occurs during droop control of the output voltage of the DCDC converter.

  This transformer means is constituted by, for example, a power conversion circuit such as a half bridge method or a full bridge method using a switching element. The output voltage control means and the failure detection means are constituted by, for example, a microcomputer or a processor.

  The DCDC converter according to the third aspect of the present invention is a DCDC converter including a transforming means for transforming and outputting an input voltage, the output voltage control means controlling the output voltage of the transforming means, and the output When the output voltage drooping control is performed by the voltage control means, the difference between the output voltage command value given from the output voltage control means to the transformer means and the actual output voltage is a predetermined first value. And a failure detection means for determining that a failure has occurred in the DCDC converter or its surroundings.

  In the DCDC converter according to the third aspect of the present invention, when the drooping control of the output voltage of the transformation means is performed by the output voltage control means, the output voltage applied from the output voltage control means to the transformation means When the difference between the command value and the actual output voltage is equal to or greater than a predetermined first threshold value, it is determined that a failure has occurred in the DCDC converter or its surroundings.

  Therefore, it is possible to quickly detect a short circuit failure that occurs during droop control of the output voltage of the DCDC converter.

  This transformer means is constituted by, for example, a power conversion circuit such as a half bridge method or a full bridge method using a switching element. The output voltage control means and the failure detection means are constituted by, for example, a microcomputer or a processor.

  The failure detection means starts the drooping control of the output voltage when the increase amount per predetermined time of the output current is not less than a predetermined second threshold before the drooping control of the output voltage is started. At this point, it can be determined that a failure has occurred in or around the DCDC converter.

  As a result, it is possible to detect the short circuit failure when the drooping control of the output voltage of the DCDC converter is started due to the short circuit failure.

  ADVANTAGE OF THE INVENTION According to this invention, the failure which generate | occur | produced during droop control of the output voltage of a DCDC converter can be detected rapidly.

It is a circuit diagram showing one embodiment of a DCDC converter to which the present invention is applied. It is a block diagram which shows the structural example of the function of a control part. It is a flowchart for demonstrating 1st Embodiment of the drooping control process performed by a DCDC converter. It is a graph which shows the example of the drooping characteristic of the DCDC converter at the time of normal and a short fault occurrence. It is a graph which shows the example of the drooping characteristic of the DCDC converter at the time of normal and an open failure occurrence. It is a flowchart for demonstrating 2nd Embodiment of the drooping control process performed by a DCDC converter. It is a graph which shows an example of a time-sequential change of output current Iout when droop control is performed normally. It is a graph which shows an example of a time-sequential change of output voltage Vout when droop control is performed normally. It is a graph which shows an example of a time-sequential change of output current Iout when a short circuit failure occurs during drooping control. It is a graph which shows an example of the time-sequential change of output voltage Vout when a short circuit failure occurs during drooping control. It is a block diagram which shows the structural example of a computer.

Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described. The description will be given in the following order.
1. Embodiment 2. FIG. Modified example

<1. Embodiment>
[Configuration Example of DCDC Converter 12]
FIG. 1 is a block diagram showing a configuration example of a DCDC converter circuit to which the present invention is applied. The DCDC converter 12 is provided in an electric vehicle such as an EV (Electric Vehicle), an HEV (Hybrid Electric Vehicle), or a PHEV (Plug-in Hybrid Electric Vehicle). The DCDC converter 12 is configured to include a transformer 21, a current sensor 22, a voltage sensor 23, and a controller 24.

  The transformer unit 21 is configured by a power conversion circuit using a switching element such as a FET (Field Effect Transistor), and the voltage of the DC power supplied from the high voltage battery 11 is used as the output voltage command value Vc supplied from the control unit 24. Converted to a voltage based on the output. The DC power output from the transformer 21 is supplied to the low voltage battery 13 and the load 14. The low voltage battery 13 is charged by the DC power supplied from the DCDC converter 12 and supplies DC power to the load 14.

  Note that the power conversion method of the transformer 21 is not limited to a specific method, and for example, a half-bridge method, a full-bridge method, or the like can be employed.

  The current sensor 22 detects the output current Iout of the transformer 21 and supplies a signal indicating the detection result to the controller 24.

  The voltage sensor 23 detects the output voltage Vout of the transformer 21 and supplies a signal indicating the detection result to the controller 24.

  The control unit 24 is constituted by, for example, a microcomputer, and sets the output voltage command value Vc based on the output current Iout and the output voltage Vout of the transformer unit 21 and supplies the output voltage command value Vc to the transformer unit 21. . Moreover, the control part 24 performs drooping control of the transformation part 21, as will be described later. Further, as will be described later, the control unit 24 detects a failure in the DCDC converter 12 or its surroundings and notifies the outside (for example, another ECU (Electronic Control Unit) or the like).

[Configuration Example of Function of Control Unit 24]
FIG. 2 is a block diagram illustrating a configuration example of functions of the control unit 24. The control unit 24 is configured to include a current detection unit 51, a voltage detection unit 52, an output voltage control unit 53, a failure detection unit 54, and a memory 55.

  The current detection unit 51 detects the output current Iout of the transformation unit 21 based on the signal supplied from the current sensor 22 and supplies the detected value of the output current Iout to the output voltage control unit 53 and the failure detection unit 54.

  The voltage detection unit 52 detects the output voltage Vout of the transformation unit 21 based on the signal supplied from the voltage sensor 23 and supplies the detected value of the output voltage Vout to the output voltage control unit 53 and the failure detection unit 54.

  The output voltage control unit 53 sets the output voltage command value Vc based on the output current Iout and the output voltage Vout of the transformer unit 21 and supplies the set output voltage command value Vc to the transformer unit 21. The output voltage Vout of 21 is controlled. Moreover, the output voltage control part 53 records the output voltage command value Vc in the memory 55 as needed.

  The failure detector 54 detects a failure in the DCDC converter 12 or its surroundings based on the output current Iout and output voltage Vout of the transformer 21 and the output voltage command value Vc set by the output voltage controller 53. The failure detection unit 54 notifies the detected failure to the output voltage control unit 53 and the outside. Further, the failure detection unit 54 records the detection value of the output current Iout in the memory 55 as necessary.

[First embodiment of drooping control processing]
Next, a first embodiment of the drooping control process executed by the DCDC converter 12 will be described with reference to the flowchart of FIG. In the first embodiment, failure detection is performed based on the output current Iout of the transformer 21.

  In the drooping control process, the total resistance component R of the load 14 (hereinafter also simply referred to as load resistance R) decreases due to an increase in the load amount or occurrence of a short circuit failure, and the output current Iout becomes equal to or greater than a predetermined threshold It0. Will start. The threshold value It0 is a threshold value that is set in advance to determine whether to start drooping control.

  In step S1, the DCDC converter 12 starts the drooping control. Specifically, the output voltage control unit 53 decreases the output voltage command value Vc by a predetermined voltage ΔV every predetermined time Δt and supplies it to the transformer unit 21. The transformer 21 controls the internal switching elements and the like so as to decrease the output voltage Vout step by step by the voltage ΔV every time Δt according to the output voltage command value Vc.

  In step S <b> 2, the output current detection unit 51 detects the output current Iout based on the signal supplied from the current sensor 22, and supplies the detected value of the output current Iout to the failure detection unit 54.

  In step S3, the failure detection unit 54 reads the detection value of the previous output current Iout from the memory 55, and calculates the difference ΔI between the detection value of the current output and the previous output current Iout.

  In step S <b> 4, the failure detection unit 54 records the detected value of the current output current Iout in the memory 55.

  In step S5, the failure detection unit 54 determines whether or not the difference ΔI between the detected values of the current and previous output currents Iout exceeds a predetermined threshold ΔIt2. The threshold value ΔIt2 is used for determining a failure, and is set in advance to a value larger than zero. If it is determined that the difference ΔI between the detected value of the current output and the previous output current Iout exceeds the threshold value ΔIt2, the process proceeds to step S6.

  In step S <b> 6, the failure detection unit 54 determines that a short failure has occurred between the current sensor 22 and the low voltage battery 13.

  In step S7, the DCDC converter 12 executes the failure handling process 1.

  Here, the failure handling process 1 will be described with reference to FIG. FIG. 4 is a graph showing an example of drooping characteristics of the DCDC converter 12 at the normal time and when the short fault occurs. The horizontal axis indicates the output current Iout, and the vertical axis indicates the output voltage Vout. The alternate long and short dash line indicates the drooping characteristic when the drooping control is normally performed, and the solid line indicates the drooping characteristic when the abnormal drooping occurs due to a short circuit failure.

  In this example, the normal drooping characteristic indicates a so-called inverted L-shaped drooping characteristic. That is, at the normal time, as the output voltage Vout decreases, the increase rate of the output current Iout gradually decreases, finally becomes substantially zero, and the output current Iout becomes substantially constant. The output voltage Vout is substantially equal to the voltage Vb of the low voltage battery 13.

  On the other hand, when a short circuit failure occurs, the load resistance R becomes almost zero, so the output current Iout increases rapidly and becomes larger than the assumed value. If this overcurrent state is left as it is, the DCDC converter 12, the low voltage battery 13 and the load 14 may be destroyed.

  Therefore, in the failure handling process 1 of step S7, the failure detection unit 54 notifies the output voltage control unit 53 and the outside of the occurrence of the short failure. Then, the output voltage controller 53 sets the output voltage command value Vc supplied to the transformer 21 to zero, stops the switching operation of the transformer 21, and quickly reduces the output voltage Vout to zero. Thereby, an overcurrent due to a short circuit failure is prevented from continuously flowing to the DCDC converter 12, the low voltage battery 13 and the load 14.

  Thereafter, the process proceeds to step S15. In step S15, the DCDC converter 12 stops the drooping control, and the drooping control process ends.

  On the other hand, if it is determined in step S5 that the difference ΔI between the current and previous output current Iout detection values does not exceed the threshold value ΔIt2, the process proceeds to step S8.

  In step S8, the failure detection unit 54 determines whether or not the difference ΔI between the detected values of the current and previous output currents Iout is less than a predetermined threshold value ΔIt1. The threshold value ΔIt1 is used for determining a failure, and is set in advance to a value smaller than zero. If it is determined that the difference ΔI between the current and previous output currents Iout is less than the threshold value ΔIt1, the process proceeds to step S9.

  In step S <b> 9, the failure detector 54 determines that a short failure has occurred between the transformer 21 and the current sensor 22.

  In step S10, the failure handling process 1 is executed as in the process of step S7.

  Thereafter, the process proceeds to step S15. In step S15, the drooping control is stopped, and the drooping control process ends.

  On the other hand, if it is determined in step S8 that the difference ΔI between the current and previous output currents Iout is not less than the threshold value ΔIt1, the process proceeds to step S11.

  In step S11, the failure detection unit 54 determines whether or not the difference ΔI between the detected values of the current and previous output currents Iout is greater than or equal to a threshold value ΔIt1 and less than or equal to zero. If it is determined that the difference ΔI between the current and previous output current Iout detection values is greater than or equal to the threshold ΔIt1 and less than or equal to zero, the process proceeds to step S12.

  In step S12, the failure detection unit 54 determines that an open failure has occurred. Here, the open failure is a failure in which the electrodes on the output side of the DCDC converter 12 are opened.

  FIG. 5 is a graph showing an example of drooping characteristics of the DCDC converter 12 at the normal time and when an open failure occurs. The horizontal axis indicates the output current Iout, and the vertical axis indicates the output voltage Vout. The alternate long and short dash line indicates the drooping characteristic when the drooping control is normally performed, and the solid line indicates the drooping characteristic when the abnormal drooping occurs due to the open failure. The normal graph is the same as FIG.

  When an open failure occurs, the output current Iout decreases rapidly and becomes zero, and the output voltage Vout becomes substantially equal to the voltage Vb of the low-voltage battery 13.

  Therefore, the failure detection unit 54 has an open failure when the decrease rate of the output current Iout (the decrease amount of the output current Iout per predetermined time) is larger than the threshold value ΔIt1 (<0) and smaller than zero. Is determined.

  In step S13, the DCDC converter 12 executes the failure handling process 2. Specifically, the failure detection unit 54 notifies the output voltage control unit 53 and the outside that an open failure has occurred. Since the output current Iout is almost zero at this time, it is not always necessary to stop the operation of the transformer 21. Therefore, the operation of the transformer 21 may be continued as it is without stopping the operation of the transformer 21 as in the failure handling process 1. Alternatively, as in the failure handling process 1, the operation of the transformer 21 may be stopped.

  Thereafter, the process proceeds to step S15, and the drooping control is stopped. When the operation of the transformer 21 is continued in the failure handling process 2, normal control is started as the drooping control is stopped. Then, the drooping control process ends.

  On the other hand, when it is determined in step S11 that the difference ΔI between the detected value of the current and the previous output current Iout is not less than the threshold ΔIt1 and not less than zero, the process proceeds to step S14.

  In step S14, the failure detection unit 54 determines whether or not the load 14 has returned to a normal state. For example, the failure detection unit 54 compares the output current Iout with a predetermined threshold value It3, and determines that the load 14 has not returned to a normal state when the output current Iout is equal to or greater than the threshold value It3. Return to. Then, drooping control is performed in which the output voltage Vout of the transformer 21 is lowered step by step by the voltage ΔV every time Δt.

  On the other hand, in step S14, when the output current Iout is smaller than the threshold value It3, the failure detection unit 54 determines that the load 14 has returned to a normal state, and the process proceeds to step S15. At this time, the failure detection unit 54 notifies the output voltage control unit 53 that the load 14 has returned to a normal state.

  When the state where the output current Iout is smaller than the threshold value It3 continues for a predetermined time, it may be determined that the load 14 has returned to the normal state.

  In step S15, the DCDC converter 12 stops the drooping control and starts normal control because the output current Iout has become sufficiently small. Then, the drooping control process ends.

  In this manner, during the drooping control of the output voltage of the DCDC converter 12, it is possible to quickly detect a short-circuit failure and an open failure based on the output current Iout and appropriately deal with it. As a result, the failure can be prevented from expanding.

[Second embodiment of drooping control processing]
Next, a second embodiment of the drooping control process executed by the DCDC converter 12 will be described with reference to the flowchart of FIG. In the second embodiment, failure detection is performed based on the output voltage Vout of the transformer 21.

  This process is started when the load resistance R of the load 14 decreases and the output current Iout becomes equal to or greater than a predetermined threshold It0 due to an increase in load amount or occurrence of a short circuit failure.

  In step S51, the drooping control is started in the same manner as in step S1 of FIG.

  In step S <b> 52, the voltage detection unit 52 detects the output voltage Vout based on the signal supplied from the voltage sensor 23 and supplies the detected value of the output voltage Vout to the output voltage control unit 53.

  In step 53, the output voltage control unit 53 obtains the output voltage command value Vc by subtracting the voltage ΔV from the detected output voltage Vout.

  In step S <b> 54, the output voltage controller 53 records the output voltage command value Vc in the memory 55 and supplies it to the transformer 21. The transformer 21 controls internal switching elements and the like so that the output voltage Vout becomes the output voltage command value Vc.

  In step S55, the voltage detection unit 52 is based on the signal supplied from the voltage sensor 23 when a predetermined time Δt has elapsed since the output voltage command value Vc was supplied to the transformation unit 21 in the process of step S53. The output voltage Vout is detected. The voltage detector 52 supplies the detected value of the output voltage Vout to the output voltage controller 53 and the failure detector 54.

  In step S56, the failure detection unit 54 determines whether or not the output voltage Vout is equal to the output voltage command value Vc. Specifically, the failure detection unit 54 reads the latest output voltage command value Vc from the memory 55 and compares it with the output voltage Vout detected in the process of step S54. If the difference between the output voltage Vout and the output voltage command value Vc is within a predetermined allowable range, the failure detection unit 54 determines that the output voltage Vout is equal to the output voltage command value Vc, and the process proceeds to step S57.

  In step S57, the failure detection unit 54 determines whether or not the load 14 has returned to a normal state. Specifically, the current detection unit 51 detects the output current Iout based on the signal supplied from the current sensor 22 and supplies the detected value of the output current Iout to the failure detection unit 54.

  The failure detection unit 54 determines whether or not the load 14 has returned to a normal state in the same manner as in step S14 in FIG. That is, it is determined whether or not the output current Iout has become smaller than the predetermined threshold It3. If it is determined that the load 14 has not returned to the normal state, that is, if it is determined that the output current Iout is greater than or equal to the threshold value It3, the process returns to step S53. Then, drooping control is performed in which the output voltage Vout of the transformer 21 is lowered step by step by the voltage ΔV every time Δt.

  On the other hand, if it is determined in step S57 that the load 14 has returned to a normal state, that is, if it is determined that the output current Iout is smaller than the threshold value It3, the process proceeds to step S66. At this time, the failure detection unit 54 notifies the output voltage control unit 53 that the load 14 has returned to a normal state.

  In step S66, the DCDC converter 12 stops the drooping control and starts normal control because the load 14 has returned to the normal state. Then, the drooping control process ends.

  On the other hand, in step S56, the failure detection unit 54 determines that the output voltage Vout is not equal to the output voltage command value Vc when the difference between the output voltage Vout and the output voltage command value Vc exceeds a predetermined allowable range. The process proceeds to step S58.

  In step S58, the failure detection unit 54 determines whether or not the absolute value of the difference between the output voltage Vout and the output voltage command value Vc is equal to or less than a predetermined threshold value ΔVth1. Note that the threshold value ΔVth1 is a threshold value set in advance for performing failure determination. When it is determined that the absolute value of the difference between the output voltage Vout and the output voltage command value Vc is equal to or less than the threshold value ΔVth1, the process proceeds to step S59.

  In step S59, as in the process of step S57, it is determined whether or not the load 14 has returned to a normal state. If it is determined that the load 14 has not returned to a normal state, the process proceeds to step S60.

  In step S60, the output voltage control unit 53 sets the output voltage command value Vc to the output voltage Vout− (ΔV + correction voltage). At this time, for example, the difference between the output voltage Vout and the output voltage command value Vc is set as the correction voltage.

  Thereafter, the process returns to step S54, and the drooping control is continued.

  On the other hand, if it is determined in step S59 that the load 14 has returned to the normal state, the process proceeds to S66.

  In step S66, the DCDC converter 12 stops the drooping control and starts normal control because the load 14 has returned to the normal state. Then, the drooping control process ends.

  On the other hand, if it is determined in step S58 that the absolute value of the difference between the output voltage Vout and the output voltage command value Vc is greater than the threshold value ΔVth1, the process proceeds to step S61.

  In step S61, the failure detection unit 54 determines whether or not the absolute value of the difference between the output voltage Vout and the output voltage command value Vc is larger than the threshold value ΔVth1 and smaller than the predetermined threshold value ΔVth2. Note that the threshold value ΔVth2 is a threshold value set in advance for performing failure determination. If it is determined that the absolute value of the difference between the output voltage Vout and the output voltage command value Vc is larger than the threshold value ΔVth1 and smaller than the threshold value ΔVth2, the process proceeds to step S62.

  In step S62, it is determined that an open failure has occurred, similarly to the process in step S12 in FIG. 3, and in step S63, the failure handling process 2 is executed in the same manner as the process in step S13 in FIG. Thereafter, the process proceeds to step S66.

  In step S66, the DCDC converter 12 stops the drooping control. Then, the drooping control process ends.

  On the other hand, if it is determined in step S61 that the absolute value of the difference between the output voltage Vout and the output voltage command value Vc is greater than or equal to the threshold value ΔVth2, the process proceeds to step S64.

  In step S64, the failure detection unit 54 determines that a short failure has occurred.

  In step S65, the failure handling process 1 is executed in the same manner as the process in step S7 of FIG. Thereafter, the process proceeds to step S66.

  In step S66, the DCDC converter 12 stops the drooping control. Then, the drooping control process ends.

  In this manner, during the drooping control of the output voltage of the DCDC converter 12, it is possible to quickly detect a short-circuit failure and an open failure based on the output voltage Vout and appropriately deal with it. As a result, the failure can be prevented from expanding.

<2. Modification>
[Modification of failure detection method]
In the above description, an example in which a failure during drooping control is detected using either the output current Iout or the output voltage Vout has been described, but both may be used. By using both, as described below, it becomes possible to further improve the accuracy of failure detection. In addition, it is possible to narrow down the location of failure occurrence to some extent.

  7 and 8 show time series of detected values of the output current Iout and the output voltage Vout when an abnormality occurs at time t1, reverse L-shaped drooping control is started, and drooping control is normally performed as it is. It is a graph which shows an example of a change of. In FIG. 7, the horizontal axis represents time, and the vertical axis represents the detected value of the output current Iout by the current sensor 22. Further, the horizontal axis of FIG. 8 indicates time, and the vertical axis indicates the detected value of the output voltage Vout by the voltage sensor 23.

  The output voltage Vout is lowered at substantially the same rate of change from the time t1 when the drooping control is started until the voltage Vb of the low voltage battery 13 is reached, and then is maintained at the voltage Vb. For reference, when the low voltage battery 13 is not provided, the output voltage Vout may be lowered to zero.

  On the other hand, the output current Iout rises for a while after time t1, reaches a short-circuit current determined by the design value, and then remains substantially constant. When the output voltage Vout decreases to zero, the output current Iout decreases to zero.

  FIG. 9 and FIG. 10 show examples of time-series changes in the detected values of the output current Iout and the output voltage Vout when an abnormality occurs at time t11, drooping control is started, and a short-circuit failure occurs at time t12. It is a graph to show. In FIG. 9, the horizontal axis represents time, and the vertical axis represents the detected value of the output current Iout by the current sensor 22. Further, the horizontal axis of FIG. 10 indicates time, and the vertical axis indicates the detected value of the output voltage Vout by the voltage sensor 23.

  In the example of FIG. 9, the output current Iout increases rapidly at time t12 when a short circuit failure occurs. As a result, it can be seen that a short circuit failure has occurred at least in the subsequent stage of the current sensor 22. Note that when a short circuit failure occurs in the previous stage of the current sensor 22, the output current Iout drops rapidly and becomes approximately −∞.

  In the example of FIG. 10, the output voltage Vout suddenly drops to 0 at time t12. Thereby, it is understood that a short circuit failure has occurred.

  In addition, when an open failure occurs after the output side of the transformer 21, the detected value of the output current Iout by the current sensor 22 is almost 0 regardless of the occurrence location. In the example of the drooping control process in FIG. 3, when this is used, it is determined that an open failure has occurred when the output current Iout decreases rapidly.

  However, depending on the installation position of the current sensor 22, there may be a short circuit failure after the output side of the transformer 21 and before the current sensor 22. In this case, as in the case where an open failure occurs, The detected value of the output current Iout is almost zero. Therefore, there is a possibility that the determination of the short fault and the open fault may be mistaken only with the output current Iout.

  On the other hand, when an open failure occurs after the output side of the transformer 21, the detected value of the output voltage Vout by the voltage sensor 23 is substantially equal to the voltage Vb of the low-voltage battery 13 when the occurrence location is the front stage of the voltage sensor 23. When the generation point is the latter stage of the voltage sensor 23, the output voltage of the transformer 21 is substantially equal. In addition, when a short circuit failure occurs after the output side of the transformer 21, the detected value of the output voltage Vout by the voltage sensor 23 is almost 0 regardless of the location of the short circuit failure.

  Therefore, when the detected value of the output current Iout is substantially 0, it is possible to more accurately identify whether an open fault or a short fault has occurred based on the detected value of the output voltage Vout. Further, based on the detected value of the output voltage Vout, it is possible to narrow down whether an open failure has occurred at the front stage or the rear stage of the voltage sensor 23.

[Other variations]
In the above description, the present invention is applied to a step-down DCDC converter. However, the present invention can also be applied to a step-up DCDC converter.

  Furthermore, in any of the droop control processes of FIG. 3 and FIG. 6, before the droop control is started, when the increase amount per time Δt of the output current Iout is already equal to or greater than the threshold ΔIt1, in other words, droop When the short failure determination condition is already established before the control is started, it may be determined that a short failure has occurred when the drooping control is started.

  The series of processes described above can be executed by hardware or can be executed by software. When a series of processing is executed by software, a program constituting the software is installed in the computer. Here, the computer includes, for example, a general-purpose personal computer capable of executing various functions by installing various programs by installing a computer incorporated in dedicated hardware.

  FIG. 10 is a block diagram illustrating an example of a hardware configuration of a computer that executes the above-described series of processing by a program.

  In a computer, a central processing unit (CPU) 201, a read only memory (ROM) 202, and a random access memory (RAM) 203 are connected to each other by a bus 204.

  An input / output interface 205 is further connected to the bus 204. An input unit 206, an output unit 207, a storage unit 208, a communication unit 209, and a drive 210 are connected to the input / output interface 205.

  The input unit 206 includes a keyboard, a mouse, a microphone, and the like. The output unit 207 includes a display, a speaker, and the like. The storage unit 208 includes a hard disk, a nonvolatile memory, and the like. The communication unit 209 includes a network interface and the like. The drive 210 drives a removable medium 211 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory.

  In the computer configured as described above, the CPU 201 loads, for example, the program stored in the storage unit 208 to the RAM 203 via the input / output interface 205 and the bus 204 and executes the program. Is performed.

  The program executed by the computer (CPU 201) can be provided by being recorded on the removable medium 211 as a package medium or the like, for example. The program can be provided via a wired or wireless transmission medium such as a local area network, the Internet, or digital satellite broadcasting.

  In the computer, the program can be installed in the storage unit 208 via the input / output interface 205 by attaching the removable medium 211 to the drive 210. The program can be received by the communication unit 209 via a wired or wireless transmission medium and installed in the storage unit 208. In addition, the program can be installed in the ROM 202 or the storage unit 208 in advance.

  The program executed by the computer may be a program that is processed in time series in the order described in this specification, or in parallel or at a necessary timing such as when a call is made. It may be a program for processing.

  Further, in this specification, the system represents the entire apparatus constituted by a plurality of apparatuses.

  Furthermore, the embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 11 High voltage battery 12 DCDC converter 13 Low voltage battery 14 Load 21 Transformer part 22 Current sensor 23 Voltage sensor 24 Control part 51 Current detection part 52 Voltage detection part 53 Output voltage control part 54 Fault detection part

Claims (5)

In a DCDC converter provided with a transforming means for transforming and outputting an input voltage,
Output voltage control means for controlling the output voltage of the transformer means;
When the output voltage drooping control is performed by the output voltage control means, when the amount of increase in the output current of the transformer means per predetermined time exceeds a predetermined threshold value, the DCDC converter or its surroundings A DCDC converter comprising: failure detection means for determining that a failure has occurred. The failure detection means, when the increase in the output current per predetermined time is already greater than or equal to the threshold before the start of the output voltage droop control, when the output voltage droop control is started, The DCDC converter according to claim 1, wherein it is determined that a failure has occurred in or around the DCDC converter. In a DCDC converter provided with a transforming means for transforming and outputting an input voltage,
Output voltage control means for controlling the output voltage of the transformer means;
When the output voltage drooping control is performed by the output voltage control means, when the amount of decrease of the output current of the transformer means per predetermined time exceeds a predetermined threshold, the DCDC converter or its surroundings A DCDC converter comprising: failure detection means for determining that a failure has occurred. In a DCDC converter provided with a transforming means for transforming and outputting an input voltage,
Output voltage control means for controlling the output voltage of the transformer means;
When the output voltage drooping control is performed by the output voltage control means, the difference between the output voltage command value given from the output voltage control means to the transformer means and the actual output voltage is a predetermined value. A DCDC converter, comprising: a failure detection unit that determines that a failure has occurred in the DCDC converter or its surroundings when the first threshold value or more is reached. The failure detection unit is configured to start the droop control of the output voltage when the increase amount of the output current per predetermined time is equal to or greater than a predetermined second threshold before the droop control of the output voltage is started. The DCDC converter according to claim 4, wherein it is determined that a failure has occurred in or around the DCDC converter.

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