Fault detection device for a DC-DC converter

Abstract

To provide a failure detection device which can detect a disconnection failure of a diode in any of a plurality of DC / DC converter parts connected in parallel and detect a failure even without setting a determination value in consideration of a drive period of a switching element.SOLUTION: A microcomputer 14 measures generation time of flyback voltage to be generated at connection points (namely, a point A, a point B) between chalk coils 21a, 21b and switching elements 22a, 22b for each of two DC / DC converter parts 20a, 20b constituting a first booster circuit 11 (namely, the DC / DC converter). Then, the microcomputer 14 determines presence / absence of a failure of the first booster circuit 11 by comparing each piece of measured generation time.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a technique for detecting a failure of a DCDC converter.

Background Art

[0002] For example, Patent Document 1 below describes a DCDC converter configured such that a plurality of DCDC converter units of a chopper type are connected in parallel. In Patent Document 1, a diagnosis unit monitors the voltage between a choke coil and a switching element for each of the plurality of DCDC converter units, and when it is determined that the elapsed time during which the voltage to be monitored does not fluctuate is equal to or longer than a preset failure determination time, it is determined as a failure.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As a result of the inventors' detailed examination, the following problems were found in the technique of Patent Document 1. The DCDC converter unit includes a diode having one terminal connected between a choke coil and a switching element. In the DCDC converter unit, when this diode fails open, a voltage fluctuation synchronized with the drive signal of the switching element occurs between the choke coil and the switching element. Therefore, in the technique of Patent Document 1, even when an open failure of the diode in the DCDC converter unit occurs, this failure cannot be detected.

[0005] In addition, as a method for controlling the switching element in the DCDC converter section, there is a method (hereinafter referred to as the boundary current control method) of detecting that the current flowing through the circuit has reached a predetermined value and switching the on / off state of the switching element. Specifically, in the boundary current control method, when the current flowing through the switching element increases to a predetermined value, the switching element is switched off, or when the current released from the choke coil decreases to a predetermined value, the switching element is switched on. On the other hand, in the technique of Patent Document 1, it is necessary to set the above-mentioned fault determination time to a time longer than the driving period (i.e., the switching period) of the switching element. However, in the boundary current control method, the driving period of the switching element changes depending on the power supply voltage, the electrical characteristics of each element, etc. For this reason, in the case of the boundary current control method, it may be difficult to determine the above-mentioned fault determination time, or there may be a possibility of false detection of a fault.

[0006] Therefore, one aspect of the present disclosure provides a fault detection device that can detect an open-circuit fault of a diode in any of a plurality of DCDC converter sections connected in parallel, and can detect a fault without setting a determination value in consideration of the driving period of the switching element.

Means for Solving the Problems

[0007] A fault detection device according to one aspect of the present disclosure detects a fault in a DCDC converter (11). The DCDC converter to be the fault detection target includes a plurality of DCDC converter sections (20a, 20b) connected in parallel. Each of the plurality of DCDC converter sections includes a choke coil (21a, 21b), a switching element (22a, 22b), and a diode (23a, 23b).

[0008] And the fault detection device includes a measurement unit (14, S120) and a detection unit (14, S130, S140, S180 to S210). The measurement unit measures the occurrence time of the flyback voltage generated in each DCDC converter unit as each switching element is switched between on and off. The detection unit determines the presence or absence of a failure in the DCDC converter by comparing the occurrence times measured by the measurement unit.

[0009] In any of the plurality of DCDC converter units, for example, if any of the choke coil, switching element, and diode has an open-circuit failure or a short-circuit failure, the occurrence time of the flyback voltage will be different from that in the normal case. Therefore, when a failure occurs in any of the plurality of DCDC converter units, the occurrence time of the flyback voltage in the failed DCDC converter unit and the occurrence time of the flyback voltage in the normal DCDC converter unit are compared by the detection unit, and a failure is determined.

[0010] Therefore, according to the failure detection device according to one aspect of the present disclosure, it is possible to detect an open-circuit failure of a diode in any of the plurality of DCDC converter units. Also, it is possible to detect a failure without setting a determination value considering the driving cycle of the switching element.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. [1. First Embodiment] [1-1. Configuration] The control device 1 of the first embodiment shown in FIG. 1 controls the drive of an injector 15 that injects fuel into an internal combustion engine mounted on a vehicle. In FIG. 1, one injector 15 out of the injectors 15 for each of a plurality of cylinders provided in the internal combustion engine is shown. Further, the injector 15 is a solenoid type injector having a solenoid as an actuator for opening the valve, but is not limited thereto, and for example, an injector having a piezo actuator may be used.

[0013] The control device 1 includes a first boosting circuit 11 that boosts the power supply voltage VB, a second boosting circuit 12 that further boosts the output voltage Vbst1 of the first boosting circuit 11, a voltage detection circuit 13, a microcomputer (hereinafter referred to as a microcontroller) 14, and a drive circuit 16 for the injector 15. The power supply voltage VB is, for example, the voltage of an in-vehicle battery (i.e., the battery voltage).

[0014] The drive circuit 16 drives the injector 15 by switching and supplying the output voltage Vbst2 of the second boosting circuit 12 and the power supply voltage VB to the injector 15 in accordance with an injection command signal from the microcontroller 14, and injects fuel from the injector 15.

[0015] The microcontroller 14 calculates the fuel injection timing and the fuel injection amount based on the accelerator operation amount by the driver of the vehicle and the rotational speed of the internal combustion engine by performing fuel injection control processing, and outputs an injection command signal to the drive circuit 16 according to the calculation result.

[0016] The first boost circuit 11 includes two DCDC converter sections (hereinafter referred to as converter sections) 20a and 20b of the chopper type connected in parallel with each other, a capacitor 24 common to the two converter sections 20a and 20b, and a resistor 25 for current detection. The converter sections 20a and 20b are both step-up types.

[0017] The converter section 20a includes an inductor (hereinafter referred to as an inductor) 21a, a switching element 22a connected in series with the inductor 21a, and a diode 23a having an anode connected to a connection point (hereinafter referred to as point A) between the inductor 21a and the switching element 22a.

[0018] A power supply voltage VB is supplied to one end of the inductor 21a, and two output terminals of the switching element 22a are connected in series on a path between the other end of the inductor 21a and a reference potential lower than the power supply voltage VB.

[0019] In this embodiment, the reference potential is the ground potential (i.e., 0V). And the output terminal of the switching element 22a on the side opposite to the inductor 21a side is connected to the ground potential line (i.e., the ground line) via the resistor 25 for current detection. Also, the switching element 22a is an N-channel type MOSFET. And among the output terminals (i.e., the drain and the source) of the switching element 22a, the drain is connected to the side opposite to the power supply voltage VB side of the inductor 21a, and the source is connected to the ground line via the resistor 25. Note that the switching element 22a is not limited to a MOSFET, and may be other types of transistors such as bipolar transistors, and the same applies to other switching elements described later.

[0020] Furthermore, the converter section 20a includes a resistor 26a having one end connected to the gate of the switching element 22a. And a SW drive signal from the microcomputer 14 is supplied to the gate of the switching element 22a via the resistor 26a. Note that "SW" is an abbreviation for switch.

[0021] The converter section 20b also has the same configuration as the converter section 20a. Therefore, the converter section 20b also includes a coil 21b to which a power supply voltage VB is supplied at one end, and a switching element 22b having two output terminals connected in series on the path between the other end of the coil 21b and the ground line. The output terminal (i.e., the source) on the side opposite to the coil 21b side of the switching element 22b is connected to the ground line via a resistor 25. Further, the converter section 20b also includes a diode 23b having an anode connected to the connection point (hereinafter referred to as point B) between the coil 21b and the switching element 22b, and a resistor 26b having one end connected to the gate of the switching element 22b.

[0022] The side of the resistor 26b opposite to the switching element 22b side and the side of the resistor 26a opposite to the switching element 22a side are commonly connected. Therefore, the same SW drive signal from the microcomputer 14 is supplied to the gates of the two switching elements 22a and 22b via the respective resistors 26a and 26b.

[0023] The two converter sections 20a and 20b are connected in parallel to each other by commonly connecting the cathodes of the respective diodes 23a and 23b. One end of the capacitor 24 is connected to the ground line. The commonly connected cathodes of the diodes 23a and 23b are connected to the terminal (i.e., the plus terminal) on the side opposite to the ground line side of the capacitor 24. Note that the plus terminal of the capacitor 24 corresponds to a location having a potential different from that of points A and B.

[0024] The capacitor 24 is charged by the output voltage from the commonly connected cathodes of the diodes 23a and 23b. The commonly connected cathodes of the diodes 23a and 23b function as a common voltage output section of the DC-DC converter sections 20a and 20b. The voltage of the cathodes of the diodes 23a and 23b, which is the charging voltage of the capacitor 24, becomes the output voltage Vbst1 of the first boost circuit 11.

[0025] Since the configurations and operations of the converter units 20a and 20b are the same, the operation of the converter unit 20a will be described here. In the converter unit 20a, as shown in the (a) stage of FIG. 2, when the SW drive signal from the microcomputer 14 becomes high corresponding to the active level, the switching element 22a turns on, and when the SW drive signal becomes low, the switching element 22a turns off.

[0026] When the switching element 22a turns on, current flows through the switching element 22a and the resistor 25 to the coil 21a. Since the on-resistance of the switching element 22a and the resistance value of the resistor 25 are sufficiently smaller than the impedance of the coil 21a, when the switching element 22a turns on, as shown in the (b) stage of FIG. 2, the voltage at point A drops to approximately the ground potential.

[0027] Also, when the switching element 22a transitions from on to off, due to the back electromotive force from the coil 21a, a flyback voltage larger than the power supply voltage VB is generated at point A, as shown in the (b) stage of FIG. 2. In FIG. 2, the flyback voltage is simply represented as a rectangular wave. Then, due to this flyback voltage, the capacitor 24 is charged through the diode 23a. Therefore, as the on / off of the switching element 22a is repeated, the capacitor 24 is charged. Also, the diode 23a prevents discharge from the capacitor 24 to the switching element 22a side.

[0028] Also in the converter unit 20b, when the switching element 22b is turned on and off, as shown in the (c) stage of FIG. 2, the voltage at point B changes in the same manner as the voltage at point A in the converter unit 20a. And the capacitor 24 is also charged by the flyback voltage at point B.

[0029] The microcontroller 14 performs boost switching control on the switching elements 22a and 22b. Specifically, in the boost switching control, the microcontroller 14 first sets the SW drive signal high to turn on the switching elements 22a and 22b. Then, by monitoring the voltage generated across the resistor 25, the microcontroller 14 detects the current flowing through the switching elements 22a and 22b (hereinafter referred to as the SW conduction current). When the microcontroller 14 determines that the SW conduction current has increased to a predetermined off-switching threshold value, it sets the SW drive signal low to turn off the switching elements 22a and 22b from on. Then, when a predetermined on-switching time has elapsed since the SW drive signal was set low, the microcontroller 14 sets the SW drive signal high again to turn on the switching elements 22a and 22b. By repeatedly turning the switching elements 22a and 22b on and off, the capacitor 24 is gradually charged. Although not shown in FIG. 1, the microcontroller 14 monitors the output voltage Vbst1 of the first boost circuit 11, and when it determines that the output voltage Vbst1 has reached the first target voltage (for example, 53 V), it maintains the switching elements 22a and 22b in the off state. By such boost switching control for the switching elements 22a and 22b, the output voltage Vbst1 is maintained near the first target voltage.

[0030] Incidentally, as another example, a configuration may be adopted in which the side of the capacitor 24 opposite to the diodes 23a and 23b (i.e., the negative terminal) is connected to the ground line via, for example, a resistor 25. In this case, when the microcontroller 14 turns off the switching elements 22a and 22b, it can detect the charging current discharged from the coils 21a and 21b to the capacitor 24 by monitoring the voltage generated across the resistor 25. Therefore, the microcontroller 14 may be configured to turn on the switching elements 22a and 22b when it determines that the charging current of the capacitor 24 has decreased to a predetermined on-switching threshold value. A method of switching the on and off states of the switching elements 22a and 22b based on one or both of the detected values of the SW conduction current and the charging current from the coils 21a and 21b to the capacitor 24 is called a boundary current control method.

[0031] The second boost circuit 12 includes a converter section 30 having the same configuration as each of the converter sections 20a and 20b in the first boost circuit 11, a capacitor 34, and a resistor 35 for current detection.

[0032] The converter section 30 includes a coil 31 to which the output voltage Vbst1 of the first boost circuit 11 is supplied at one end, and a switching element 32 having two output terminals connected in series on the path between the other end of the coil 31 and the ground line. The output terminal (i.e., the source) on the side opposite to the coil 31 side of the switching element 32 is connected to the ground line via the resistor 35. Further, the converter section 30 includes a diode 33 having an anode connected to the connection point between the coil 31 and the switching element 32, and a resistor 36 having one end connected to the gate of the switching element 32.

[0033] To the gate of the switching element 32, a drive signal different from the SW drive signal to the first boost circuit 11 among the signals output from the microcomputer 14 is supplied via the resistor 36. One end of the capacitor 34 is connected to the ground line. And the cathode of the diode 33 is connected to the terminal (i.e., the plus terminal) on the side opposite to the ground line side of the capacitor 34. The voltage of the cathode of the diode 33, which is the charging voltage of the capacitor 34, becomes the output voltage Vbst2 of the second boost circuit 12.

[0034] The microcomputer 14 also performs the same boost switching control on the switching element 32 as the boost switching control on the switching elements 22a and 22b described above. And by the boost switching control on the switching element 32, the output voltage Vbst2 is maintained near a second target voltage (e.g., 240V) that is higher than the first target voltage.

[0035] The voltage detection circuit 13 is a circuit for outputting to the microcomputer 14 a signal indicating whether or not the aforementioned flyback voltage is generated at each of point A and point B. The voltage detection circuit 13 includes a buffer circuit 41a that divides the voltage at point A by a certain ratio and outputs it, a buffer circuit 41b that divides the voltage at point B by the above-mentioned certain ratio and outputs it, and comparators 42a and 42b to which the outputs of the buffer circuits 41a and 41b are respectively input. Further, the voltage detection circuit 13 includes two resistors 43 and 44 connected in series between a certain power supply voltage VD (for example, 5V) and the ground line. A reference voltage Vth obtained by dividing the power supply voltage VD is generated at the connection point between the resistors 43 and 44. The certain power supply voltage VD is generated, for example, by stepping down the power supply voltage VB with a regulator circuit.

[0036] When the output voltage of the buffer circuit 41a is greater than the reference voltage Vth, the comparator 42a outputs a high signal to the microcontroller 14, and when the output voltage of the buffer circuit 41a is not greater than the reference voltage Vth, the comparator 42a outputs a low signal to the microcontroller 14.

[0037] When the output voltage of the buffer circuit 41b is greater than the reference voltage Vth, the comparator 42b outputs a high signal to the microcontroller 14, and when the output voltage of the buffer circuit 41b is not greater than the reference voltage Vth, the comparator 42b outputs a low signal to the microcontroller 14.

[0038] The reference voltage Vth and the voltage division ratios in the buffer circuits 41a and 41b are set such that when the voltage at point A is equal to or higher than a predetermined determination voltage, the output signal of the comparator 42a becomes high, and when the voltage at point B is equal to or higher than the above-mentioned determination voltage, the output signal of the comparator 42b becomes high.

[0039] And the above-mentioned determination voltage may be set to a voltage value that is greater than the maximum value of the power supply voltage VB and smaller than the maximum value of the flyback voltages generated at points A and B. As the maximum value of the flyback voltages generated at points A and B, for example, it may be assumed that it is a value obtained by adding the forward voltage Vf (for example, 0.7V) of the diodes 23a and 23b to the first target voltage.

[0040] Therefore, when the output signal of the comparator 42a is high, it indicates that a flyback voltage is generated at point A, and when the output signal of the comparator 42b is high, it indicates that a flyback voltage is generated at point B.

[0041] The output signal of the comparator 42a is input to the port P1 of the microcomputer 14, and the output signal of the comparator 42b is input to the port P2 of the microcomputer 14. The ports P1 and P2 may be timer ports that can measure the time from the rising edge to the falling edge of the input signal (i.e., the high time) by the hardware in the microcomputer 14.

[0042] [1-2. Events at the time of failure occurrence] When the converter units 20a and 20b are normal (hereinafter, normal), as shown in the (b) and (c) stages of FIG. 2, the generation time Ta of the flyback voltage generated at point A and the generation time Tb of the flyback voltage generated at point B are both within a predetermined time range.

[0043] In addition, hereinafter, the generation time Ta of the flyback voltage generated at point A may be described as the flyback voltage generation time Ta at point A, or simply Ta. Similarly, the generation time Tb of the flyback voltage generated at point B may be described as the flyback voltage generation time Tb at point B, or simply Tb. Also, the generation time of the flyback voltage, or the flyback voltage generation time, in other words, is the time during which the flyback voltage continues to be generated.

[0044] Therefore, during normal operation, Ta and Tb are approximately equal, and the difference between Ta and Tb is approximately 0. On the other hand, when any of the switching elements 22a and 22b has an open-circuit fault, the difference between Ta and Tb becomes larger than that during normal operation.

[0045] For example, when the switching element 22b of the converter section 20b has an open-circuit fault, as shown in the (d) stage of FIG. 2, the voltage at point B remains the power supply voltage VB, and the flyback voltage generation time Tb at point B becomes 0. That is, no flyback voltage is generated at point B. Therefore, the difference between Ta and Tb becomes equal to the flyback voltage generation time Ta at point A in the normal converter section 20a. Incidentally, in FIG. 2, "when the B-system SW is open-circuited" means the case where the switching element 22b of the converter section 20b has an open-circuit fault.

[0046] Also, when any of the coils 21a and 21b has an open-circuit fault, the difference between Ta and Tb becomes larger than that in the normal state. For example, when the coil 21b of the converter section 20b has an open-circuit fault, as shown in the (e) stage of FIG. 2, the voltage at point B remains, for example, at the ground potential, and the flyback voltage generation time Tb at point B becomes 0. That is, even when the coil 21b has an open-circuit fault, no flyback voltage is generated at point B. Therefore, the difference between Ta and Tb becomes equal to the flyback voltage generation time Ta at point A in the normal converter section 20a. Incidentally, in FIG. 2, "when the B-system coil is open-circuited" means the case where the coil 21b of the converter section 20b has an open-circuit fault.

[0047] Also, when any of the diodes 23a and 23b has an open-circuit fault, the difference between Ta and Tb becomes larger than that in the normal state. For example, when the diode 23b of the converter section 20b has an open-circuit fault, as shown in the (f) stage of FIG. 2, the flyback voltage at point B becomes a predetermined high voltage greater than that in the normal state, and the energy stored in the coil 21b is consumed earlier than in the normal state. The above-mentioned predetermined high voltage is the breakdown voltage of the switching element 22b, and is greater than the flyback voltage at point B in the normal state (i.e., Vbst1 + Vf). Therefore, the flyback voltage generation time Tb at point B becomes significantly shorter compared to the flyback voltage generation time Ta at point A in the normal converter section 20a. For example, Tb becomes half or less of Ta. In FIG. 2, "when the B-system diode is open-circuited" means the case where the diode 23b of the converter section 20b has an open-circuit fault.

[0048] From the above, the difference between Ta and Tb increases in the order of the following 《1》→《2》→《3》. 《1》Normal state.

[0049] 《2》When any one of the diodes 23a and 23b has an open-circuit fault. 《3》When any one of the switching elements 22a and 22b or any one of the coils 21a and 21b has an open-circuit fault.

[0050] In addition, when any one of the switching elements 22a and 22b or any one of the coils 21a and 21b has a short-circuit fault, no flyback voltage is generated at point A or point B, so the difference between Ta and Tb is the same as in the case of 《3》.

[0051] Therefore, the microcomputer 14 determines the presence or absence of a fault in the first boost circuit 11 by comparing Ta and Tb. [1-3. Processing] Next, among the processes executed by the microcomputer 14, the boost-related process including the process of determining the presence or absence of a fault in the first boost circuit 11 will be described using the flowchart of FIG. 3.

[0052] When the ignition switch of the vehicle is turned on and the power supply voltage VB is supplied to the control device 1, for example, the boosting related process shown in FIG. 3 starts. Although not shown, the microcomputer 14 also executes the aforementioned fuel injection control process separately from the boosting related process shown in FIG. 3.

[0053] As shown in FIG. 3, when the microcomputer 14 starts the boosting related process, first, at S110, the two-stage boosting of the power supply voltage VB by the first boosting circuit 11 and the second boosting circuit 12 is started. Specifically, the boosting switching control for the switching elements 22a and 22b and the boosting switching control for the switching element 32 are started.

[0054] At the next S120, the microcomputer 14 measures the flyback voltage generation time Ta at point A and the flyback voltage generation time Tb at point B. Specifically, the microcomputer 14 monitors the output signals of the comparators 42a and 42b, measures the time when the output signal of the comparator 42a is high (i.e., the high time) as Ta, and measures the high time of the output signal of the comparator 42b as Tb. The microcomputer 14 may measure Ta and Tb by monitoring the output signals of the comparators 42a and 42b in synchronization with the falling timing of the SW drive signal for the switching elements 22a and 22b. Also, the microcomputer 14 may measure Ta and Tb by monitoring the output signals of the comparators 42a and 42b during a predetermined period.

[0055] At the next S130, the microcomputer 14 calculates the difference between Ta and Tb measured at S120, and determines whether the calculated difference is greater than a predetermined determination value Tth (for example, 2.6 μs). The difference between Ta and Tb mentioned here is the absolute value of the difference. Also, the determination value Tth is set to a value greater than the maximum value of the difference between Ta and Tb during normal operation and smaller than the minimum value of the difference between Ta and Tb when any of the diodes 23a and 23b has an open circuit fault.

[0056] Further, in S130, the difference between Ta and Tb during the same OFF period of the switching elements 22a and 22b may be calculated. Also, in S130, the difference between Ta and Tb during different OFF periods of the switching elements 22a and 22b may be calculated. Further, in S130, the difference between the average values of Ta and Tb during a plurality of OFF periods of the switching elements 22a and 22b may be calculated.

[0057] When the microcomputer 14 determines in S130 that the difference between Ta and Tb is greater than the determination value Tth, that is, when there is a difference greater than the determination value Tth between Ta and Tb, the process proceeds to S140. In this case, as described with reference to steps (d) to (f) of FIG. 2, it is considered that a failure has occurred in either the converter units 20a or 20b.

[0058] Therefore, in S140, the microcomputer 14 determines that there is a failure in the first boost circuit 11. That is, it is determined that a failure has occurred in the first boost circuit 11. More specifically, it is determined that a failure has occurred in either the converter units 20a or 20b. Then, further, the fact that a failure has occurred in the first boost circuit 11 is notified to, for example, a control circuit such as another microcomputer provided in the control device 1, or another control device connected to the control device 1 via a communication line.

[0059] In the next S150, the microcomputer 14 performs a suppression process for suppressing the energy consumption of the boost voltage. The boost voltage here refers to at least the output voltage Vbst1 of the first boost circuit 11 among the output voltage Vbst1 of the first boost circuit 11 and the output voltage Vbst2 of the second boost circuit 12.

[0060] Specifically, in S150, the microcomputer 14 suppresses the energy consumption of the boost voltage by performing a process of suppressing the driving frequency of the injector 15 as a suppression process. By suppressing the driving frequency of the injector 15, the energy consumption of the output voltage Vbst2 supplied from the drive circuit 16 to the injector 15 is suppressed. By suppressing the energy consumption of the output voltage Vbst2, the energy consumption of the output voltage Vbst1 is suppressed. That is, although the output voltage Vbst1 is further boosted by the second boost circuit 12, ultimately, since it is used to drive the injector 15, by suppressing the driving frequency of the injector 15, the energy consumption of the output voltage Vbst1 is suppressed.

[0061] And by suppressing the energy consumption of the output voltage Vbst1, it is possible to reduce the load applied to the non-failed one of the converter units 20a and 20b of the first boost circuit 11. For this reason, it is possible to reduce the possibility that even the non-failed one of the converter units 20a and 20b will fail.

[0062] Also, in S150, as a process for suppressing the driving frequency of the injector 15, for example, a process of restricting the rotational speed of the internal combustion engine (i.e., the engine rotational speed) to a predetermined rotational speed (e.g., 4000 rpm) may be performed. By restricting the engine rotational speed, the number of driving times (i.e., the driving frequency) of the injector 15 per unit time is restricted, and by extension, the driving frequency of the injector 15 is suppressed.

[0063] Also, in S150, as a process for suppressing the driving frequency of the injector 15, for example, a thinning-out process of prohibiting the driving of the injector 15 at a ratio of M times out of the calculated N fuel injection timings may be performed. Here, N is an integer of 2 or more, and M is an integer of 1 or more and less than N.

[0064] After performing the process of S150, the microcomputer 14 proceeds to S160. Also, when the microcomputer 14 determines in S130 that the difference between Ta and Tb is not greater than the determination value Tth, that is, when it does not determine that the first boost circuit 11 has failed, the microcomputer 14 also proceeds to S160.

[0065] Then, at S160, the microcomputer 14 determines whether a boost stop request has occurred. The boost stop request may be a request that occurs when the internal combustion engine is to be stopped. For example, it may be that the ignition switch of the vehicle has been turned off.

[0066] If the microcomputer 14 determines at S160 that the boost stop request has not occurred, it returns to S120. Also, if the microcomputer 14 determines at S160 that the boost stop request has occurred, it proceeds to S170 and ends the boosting by the first boost circuit 11 and the second boost circuit 12. Specifically, it ends the boost switching control and leaves the switching elements 22a, 22b and the switching element 32 off. Then, thereafter, it ends the boost-related process.

[0067] [1-4. Effects] According to the first embodiment described in detail above, the following effects are obtained. (1a) The microcomputer 14 measures the flyback voltage generation times Ta and Tb for each of the converter units 20a and 20b, and determines the presence or absence of a failure in the first boost circuit 11 by comparing the measured Ta and Tb.

[0068] For this reason, it is also possible to detect an open-circuit failure of the diodes 23a and 23b in either of the converter units 20a and 20b. Also, it is possible to detect a failure without setting a determination value considering the drive cycle of the switching elements 22a and 22b. In particular, when the on / off switching of the switching elements 22a and 22b is performed by the above-described boundary current control method, the drive cycle of the switching elements 22a and 22b changes depending on the electrical characteristics of elements such as the coils 21a and 21b and the power supply voltage VB. For this reason, this embodiment, in which it is not necessary to consider the drive cycle when setting the failure determination value, is considered advantageous.

[0069] (1b) The microcomputer 14 is configured to determine that there is a failure when there is a difference between Ta and Tb that is greater than the determination value Tth. For this reason, the presence or absence of a failure can be determined by a simple process.

[0070] (1c) When the microcomputer 14 determines a failure of the first boost circuit 11 at S140 in FIG. 3, at S150, it is configured to suppress the energy consumption of the output voltage Vbst1. Therefore, among the converter units 20a and 20b of the first boost circuit 11, the load applied to the non-failed one can be reduced. Thus, the possibility of the non-failed one among the converter units 20a and 20b also failing can be reduced.

[0071] (1d) At S150 in FIG. 3, the microcomputer 14 is configured to suppress the energy consumption of the output voltage Vbst1 by suppressing the driving frequency of the injector 15 for which the output voltage Vbst1 is used for driving. Therefore, the energy consumption of the output voltage Vbst1 can be easily suppressed.

[0072] (1e) At S150 in FIG. 3, the microcomputer 14 is configured to suppress the driving frequency of the injector 15 by restricting the rotational speed of the internal combustion engine to a predetermined rotational speed. Therefore, the driving frequency of the injector 15 can be easily suppressed. Also, for example, compared with the case of performing the above-described driving thinning process for the driving of the injector 15, it is difficult to deteriorate the drivability of the vehicle (i.e., driveability).

[0073] Note that in the first embodiment, the voltage detection circuit 13 and the microcomputer 14 function as a failure detection device. Also, the microcomputer 14 functions as a control unit, a measurement unit, a detection unit, and a suppression unit, respectively. Among the processes in FIG. 3, S120 corresponds to the process as the measurement unit, S130 and S140 correspond to the processes as the detection unit, and S150 corresponds to the process as the suppression unit.

[0074] [2. Second Embodiment] [2-1. Differences from the First Embodiment] Since the basic configuration of the second embodiment is the same as that of the first embodiment, the differences will be described below. Note that the same reference numerals as those in the first embodiment indicate the same configuration, and refer to the previous description.

[0075] In the second embodiment, compared with the first embodiment, the microcomputer 14 is different in that it executes the boost-related process of FIG. 4 instead of the boost-related process of FIG. 3. The boost-related process of FIG. 4 is different from the boost-related process of FIG. 3 in that the process of S180 is executed instead of S130.

[0076] As shown in FIG. 4, the microcomputer 14 proceeds to S180 after S120, and determines whether any of the following relationships 1 and 2 holds for Ta and Tb measured in S120. <Relationship 1>: Tb < Ta / 2 <Relationship 2>: Ta < Tb / 2 Then, when the microcomputer 14 determines that any of relationships 1 and 2 holds, that is, when there is a difference greater than twice between Ta and Tb, and more specifically, when the ratio of Ta to Tb is greater than 2, it proceeds from S180 to S140. In this case, as described with reference to steps (d) to (f) of FIG. 2, it is considered that a failure has occurred in either the converter units 20a or 20b. Incidentally, even when either Ta or Tb is 0, either of relationships 1 and 2 holds. That is, even when either Ta or Tb is 0, it is included in the case where there is a difference greater than twice between Ta and Tb.

[0077] Also, when the microcomputer 14 determines that neither of relationships 1 and 2 holds, it proceeds from S180 to S160. [2-2. Effect] Also according to the second embodiment described in detail above, the same effects as the effects (1a), (1c) to (1e) of the first embodiment described above are achieved. In addition, the microcomputer 14 is configured to determine that there is a failure when there is a difference greater than twice between Ta and Tb. Therefore, also according to the second embodiment, the presence or absence of a failure can be determined by a simple process.

[0078] Incidentally, in the second embodiment, in the process of FIG. 4, S180 and S140 correspond to the processes as the detection unit. [3. Third Embodiment] [Differences from the First Embodiment] Since the basic configuration of the third embodiment is the same as that of the first embodiment, the differences will be described below. The same reference numerals as those in the first embodiment denote the same components, and reference is made to the previous description.

[0079] In the third embodiment, compared with the first embodiment, the microcomputer 14 differs in that it executes the boost-related processing of FIG. 5 instead of the boost-related processing of FIG. 3. The boost-related processing of FIG. 5 differs from the boost-related processing of FIG. 3 in that the processing of S190 to S210 is executed instead of S140.

[0080] As shown in FIG. 5, when the microcomputer 14 determines at S130 that the difference between Ta and Tb is greater than the determination value Tth, it proceeds to S190. Hereinafter, the determination value Tth in this third embodiment will be referred to as the first determination value Tth.

[0081] Then, at S190, the microcomputer 14 determines whether the difference between Ta and Tb is greater than a second determination value Tth2 set to a value greater than the first determination value Tth. Note that the second determination value Tth2 is set to a value greater than the maximum value of the difference between Ta and Tb when any one of the diodes 23a and 23b has an open-circuit fault. Further, the second determination value Tth2 is set to a value smaller than the minimum value of the difference between Ta and Tb when any one of the switching elements 22a and 22b or any one of the coils 21a and 21b has a fault.

[0082] If the microcomputer 14 determines at S190 that the difference between Ta and Tb is greater than the second determination value Tth2, it proceeds to S200 and determines that any one of the switching elements 22a and 22b or any one of the coils 21a and 21b has a fault. Then, it proceeds to S160.

[0083] Also, when the microcomputer 14 determines at S190 that the difference between Ta and Tb is not greater than the second determination value Tth2, it proceeds to S210 and determines that one of the diodes 23a and 23b is faulty. Then, it proceeds to S160.

[0084] [3-2. Effect] Also, according to the third embodiment described in detail above, the same effect as the effect (1a) of the first embodiment described above is achieved.

[0085] Further, the microcomputer 14 is configured to determine at S210 that one of the diodes 23a and 23b is faulty when the difference between Ta and Tb is greater than the first determination value Tth and less than the second determination value Tth2 which is greater than the first determination value Tth. And the microcomputer 14 is configured to determine at S200 that one of the switching elements 22a and 22b or one of the coils 21a and 21b is faulty when the difference between Ta and Tb is greater than the second determination value Tth2. Therefore, the faulty part of the first boost circuit 11 can be identified and detected.

[0086] Note that in the third embodiment, among the processes of FIG. 5, S130, S190 to S210 correspond to the processes as the detection unit. Also, in the third embodiment as well, the microcomputer 14 may be configured to perform the same process as S150 in FIG. 3 when it determines a fault at either S200 or S210.

[0087] [4. Fourth Embodiment] [4-1. Differences from the First Embodiment] Since the basic configuration of the fourth embodiment is the same as that of the first embodiment, the differences will be described below. Note that the same reference numerals as those in the first embodiment indicate the same configurations, and refer to the previous description.

[0088] In the fourth embodiment, compared with the first embodiment, as shown in FIG. 6, the first boost circuit 11 includes a spare converter section 50. Note that in FIG. 6, the illustration of the second boost circuit 12, the injector 15, and the drive circuit 16 is omitted.

[0089] The spare converter section 50 also has the same configuration as each of the converter sections 20a and 20b, and includes a coil 51, a switching element 52, a diode 53, and a resistor 56. The cathode of the diode 53 of the converter section 50 is commonly connected to the cathodes of the diodes 23a and 23b of the converter sections 20a and 20b, so that the converter section 50 is connected in parallel with the converter sections 20a and 20b.

[0090] Similar to the switching elements 22a and 22b of the converter sections 20a and 20b, the output terminal (i.e., the source) on the side opposite to the coil 51 of the switching element 52 is connected to the ground line via a resistor 25.

[0091] On the other hand, a drive signal different from the SW drive signal to the switching elements 22a and 22b is supplied from the microcomputer 14 to the gate of the switching element 52 via a resistor 56.

[0092] The microcomputer 14 executes the boost-related process of FIG. 7 instead of the boost-related process of FIG. 3. The boost-related process of FIG. 7 is different from the boost-related process of FIG. 3 in that the process of S220 is executed instead of S150.

[0093] As shown in FIG. 7, the microcomputer 14 proceeds to S220 after S140 and activates the spare system. The spare system mentioned here refers to the spare converter section 50. Specifically, at S220, the microcomputer 14 sets the output value of the output port so that the same drive signal as the SW drive signal to the switching elements 22a and 22b is output to the gate of the switching element 52.

[0094] [4-2. Effect] Also according to the fourth embodiment described above in detail, the same effects as the effects (1a) and (1b) of the first embodiment described above are achieved. Further, when a failure occurs in either of the converter units 20a and 20b, the backup converter unit 50 operates, so that a decrease in the output of the first boost circuit 11 can be suppressed.

[0095] [5. Other Embodiments] As described above, the embodiments of the present disclosure have been described. However, the present disclosure is not limited to the above-described embodiments and can be implemented with various modifications.

[0096] For example, the use of the output voltage Vbst1 is not limited to driving the injector 15, and may be, for example, driving an electrical device different from the injector 15, such as a fuel pump. Also, for example, in the first to third embodiments, the number of the converter units 20a and 20b provided in the first boost circuit 11 may be three or more. In this case, the microcomputer 14 may be configured to compare the flyback voltage generation times for every two of the three or more converter units. And this also applies to the fourth embodiment.

[0097] Also, the converter units 20a, 20b, and 50 are not limited to the boost type and may be the buck type. For example, explaining with the components of the converter unit 20a, in the case of a buck-type circuit configuration, the output terminal on the side opposite to the coil 21a side of the switching element 22a is connected to the line of the power supply voltage VB. And the side opposite to the switching element 22a side of the coil 21a becomes the voltage output unit and is connected to the plus terminal of the capacitor 24. Further, the diode 23a is connected between point A and the ground line with the cathode on the point A side. In this case, the ground line corresponds to a location having a potential different from that of point A.

[0098] In addition, the control device 1 and its method described in the present disclosure may be realized by a dedicated computer configured by a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the control device 1 and its method may be realized by a dedicated computer configured by a processor constituted by one or more dedicated hardware logic circuits. Or, the control device 1 and its method may be realized by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor constituted by one or more hardware logic circuits. Further, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions to be executed by a computer. Also, the method for realizing the functions of each part included in the control device 1 does not necessarily have to include software, and all of its functions may be realized using one or a plurality of hardware.

[0099] Also, a plurality of functions of one component in the above embodiment may be realized by a plurality of components, or one function of one component may be realized by a plurality of components. Further, a plurality of functions of a plurality of components may be realized by one component, or one function realized by a plurality of components may be realized by one component. Also, a part of the configuration of the above embodiment may be omitted. Further, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of another above embodiment.

[0100] In addition to the control device 1 described above, the present disclosure can also be realized in various forms such as a system having the control device 1 as a component, a program for causing a computer to function as the control device 1, a non-transitory physical recording medium such as a semiconductor memory storing this program, a fault detection method, and the like.

Description of Reference Numerals

[0101] 1... Control device, 11... First boosting circuit, 14... Microcomputer, 20a, 20b, 50... Converter section, 21a, 21b, 51... Choke coil, 22a, 22b, 52... Switching element, 23a, 23b, 53... Diode.

Claims

1. A failure detection device for a DC-DC converter (11) comprising a plurality of step-up type DC-DC converter sections (20a, 20b) each having a choke coil (21a, 21b), a switching element (22a, 22b), and a diode (23a, 23b), and being connected in parallel with each other, the failure detection device comprising: Measuring units (14, S120) configured to measure, respectively, the generation times of flyback voltages greater than the power supply voltage that occur at the connection points between the choke coil and the switching element in each of the DC-DC converter sections as the switching elements are turned on and off; A detection unit (14, S130, S140, S180 to S210) configured to determine the presence or absence of a failure in the DC-DC converter by comparing the generation times measured by the measuring unit; A failure detection device comprising the above.

2. The failure detection device according to Claim 1, wherein: The detection unit (14, S130, S140) is configured to determine a failure when there is a difference greater than a predetermined determination value between any of the generation times. A failure detection device.

3. The failure detection device according to Claim 1 or Claim 2, wherein: The detection unit (14, S180, S140) sets the generation time measured by the measuring unit for one of the plurality of DC-DC converter sections as Ta, and the generation time measured by the measuring unit for another one of the plurality of DC-DC converter sections as Tb, and is configured to determine a failure when either Tb < Ta / 2 or Ta < Tb / 2 is satisfied. A failure detection device.

4. The failure detection device according to any one of Claims 1 to 3, further comprising: A suppression unit (14, S150) configured to suppress the energy consumption of the output voltage from a common voltage output unit of the plurality of DC-DC converter sections when a failure is determined by the detection unit. A failure detection device.

5. The failure detection device according to Claim 4, wherein: The output voltage is used at least to drive an electrical device (15), and The suppression unit is configured to suppress the energy consumption of the output voltage by suppressing the driving frequency of the electrical device. A failure detection device.

6. The failure detection device according to Claim 5, wherein: The electrical device is an injector (15) that injects fuel into an internal combustion engine. The suppression unit is configured to suppress the driving frequency of the injector, which is the electric device, by restricting the rotational speed of the internal combustion engine to a predetermined rotational speed. Fault detection device.

7. The fault detection device according to claim 1, when a difference between any two of the generation times is greater than a first determination value and smaller than a second determination value greater than the first determination value, the detection units (14, S130, S190 to S210) determine that the diode in any one of the plurality of DC-DC converter units is faulty; and when a difference between any two of the generation times is greater than the second determination value, the detection units are configured to determine that the choke coil or the switching element in any one of the plurality of DC-DC converter units is faulty. Fault detection device.

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