boosting device

Abstract

In a boost device (301) mounted on an idling stop vehicle, an input voltage (VL) supplied from a storage battery (15) is boosted and output to an in-vehicle device (40), and a boost circuit (20) including a reactor (21) and a switching element (22) is provided. A boost circuit control unit (31) controls the operation of the switching element (22) so that the output voltage (VH) of the boost circuit (20) becomes a target voltage. A failure detection unit (32) determines that the switching element (22) has an open circuit failure when the output voltage is less than a predetermined failure detection threshold value in an initial check of the boost device (301). At least in a region where the input voltage (VL) is higher than a predetermined threshold value, the target voltage at the time of the initial check is set to a value higher than the target voltage at the time of operation other than the initial check, that is, at the time of normal control.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Japanese Patent Application No. 2020-009838, filed on January 24, 2020, which is hereby incorporated by reference herein in its entirety. Technical Field

[0003] The present disclosure relates to a voltage boosting device. Background Art

[0004] Conventionally, booster devices are known for use in vehicles with an idling stop function. These devices boost the input voltage supplied from a battery and output it to onboard equipment. For example, the controller of the booster device disclosed in Patent Document 1 switches the output voltage of the booster circuit to a higher value than the pre-restart value during restart after an idling stop and before starting the engine. This reduces the voltage drop that occurs during restart. This prevents resetting of onboard equipment caused by the voltage drop.

[0005] Patent Document 1: Japanese Patent No. 5561610.

[0006] The boost circuit disclosed in Patent Document 1 is a chopper-type boost circuit comprising a reactor, a switching element, and a diode. If a switching element such as a MOS fails, the boost circuit will not operate properly. Therefore, a voltage drop due to startup, for example, causes the on-board equipment to reset, resulting in reduced marketability. Therefore, it is necessary to detect open-circuit failures of the switching element during the initial inspection after startup. The fault detection unit can use a fault detection threshold set to a value lower than the normal output voltage. When the output voltage falls below the fault detection threshold, it detects an open-circuit failure of the switching element.

[0007] Furthermore, if the input voltage of the boost circuit rises due to fluctuations in the battery SOC, the output voltage during an open-circuit failure of the switching element becomes higher, making it difficult to distinguish it from the normal output voltage. If normal control is implemented while the open-circuit failure of the switching element is not detected, there is a risk that a voltage drop caused by starting after an idling stop could cause the boost circuit to fail and reset the vehicle's onboard equipment. Summary of the Invention

[0008] An object of the present disclosure is to provide a booster device capable of accurately detecting an open-circuit failure of a switching element even when the input voltage of the booster circuit is high.

[0009] The boost device disclosed herein is mounted on an idling stop vehicle and boosts the input voltage supplied from a battery and outputs the voltage to onboard equipment. The boost device includes a chopper-type boost circuit, an output voltage sensor, a boost circuit control unit, and a fault detection unit.

[0010] The boost circuit includes a reactor with one end connected to the battery and a switching element connected between the other end of the reactor and ground. An output voltage sensor detects the output voltage (VH) of the boost circuit. The boost circuit control unit controls the operation of the switching element so that the output voltage of the boost circuit reaches a target voltage. During the initial inspection of the boost device, the fault detection unit determines that an open-circuit fault has occurred in the switching element if the output voltage falls below a predetermined fault detection threshold.

[0011] At least in a region where the input voltage is higher than a predetermined threshold value, the target voltage during the initial check is set to a value higher than the target voltage during normal control, which is an operation other than the initial check.

[0012] From the perspective of withstand voltage and heat generation in components such as boost circuits, it's preferable to set the target voltage during normal control as low as possible. In the present disclosure, by setting the target voltage during initial inspection to a higher value than the target voltage during normal control, the input voltage range capable of distinguishing between the output voltage during an open-circuit fault of the switching element and normal operation is expanded to a higher voltage range. This protects the withstand voltage of the components during normal control, reduces heat generation, and increases the chances that the fault detection unit can accurately detect an open-circuit fault of the switching element. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above-mentioned object and other objects, features and advantages of the present disclosure will become more apparent through the following detailed description with reference to the accompanying drawings.

[0014] Figure 1 is a structural diagram of a booster device according to a first embodiment.

[0015] Figure 2A is a timing chart showing an operation image during normal operation of the first embodiment.

[0016] Figure 2B 1 is a timing chart showing an operation image when a MOS open-circuit fault occurs in the first embodiment.

[0017] Figure 3 is a diagram showing the relationship between the input voltage and the target voltage in the first embodiment.

[0018] Figure 4 is a flowchart of the initial inspection of the first embodiment,

[0019] Figure 5 is a structural diagram of a boosting device according to a second embodiment.

[0020] Figure 6 is a diagram showing the relationship between the input voltage and the target voltage in the second embodiment.

[0021] Figure 7Ais a timing chart showing an action image during normal operation of a comparative example.

[0022] Figure 7B is a timing chart showing an operation image of a MOS open circuit fault in a comparative example.

[0023] Figure 8 : is a graph showing the relationship between the input voltage and the target voltage in a comparative example. DETAILED DESCRIPTION

[0024] Hereinafter, multiple embodiments of the boost device will be described based on the accompanying drawings. In multiple embodiments, substantially identical structures are denoted by the same reference numerals and their descriptions are omitted. The boost device of this embodiment is mounted on an idling-stop vehicle, and boosts the input voltage supplied from the battery and outputs it to an onboard device. As an onboard device, for example, an electric power steering device is assumed. In addition, the onboard device may be any device that utilizes battery power to operate, such as brakes, blowers, electric windows, and wipers.

[0025] (First embodiment)

[0026] exist Figure 1 The overall configuration of the first embodiment is shown. A boost device 301 includes a boost circuit 20, a capacitor 24, an output voltage sensor 34, a boost circuit control unit 31, and a fault detection unit 32. The boost circuit 20 is a chopper-type boost circuit comprising a reactor 21, a MOS transistor 22 (a "switching element"), and a diode 23. MOSFETs are omitted in this specification and are simply referred to as "MOS." Furthermore, an "open-circuit failure of the MOS transistor 22" is referred to as an "open-circuit failure of the MOS transistor 22."

[0027] One end of the reactor 21 is connected to the battery 15. Alternatively, a diode or other element may be connected between the battery 15 and the reactor 21. The MOS transistor 22 is connected between the other end of the reactor 21 and the ground. Specifically, the drain terminal of the n-channel MOS transistor 22 is connected to the reactor 21, and the source terminal is grounded. The anode of the diode 23 is connected to the connection point N between the reactor 21 and the MOS transistor 22, and the cathode is connected to the in-vehicle device 40. The voltage drop across the diode 23 is denoted as Vf.

[0028] Figure 1The boost circuit 20, with its configuration, functions exclusively as a circuit for boosting the power from the battery 15 and supplying it to the in-vehicle device 40. It does not assume a usage scenario in which it steps down the power from the in-vehicle device 40 and regenerates it back into the battery 15. Therefore, the "input" of the boost circuit 20 refers to the input from the battery 15, and the "output" of the boost circuit 20 refers to the output to the in-vehicle device 40. The boost circuit 20 boosts the input voltage VL and outputs an output voltage VH by repeatedly accumulating and releasing inductive energy through the reactor 21 through the switching action of the MOS 22.

[0029] In the case where the in-vehicle device 40 is an electric power steering system, for example, the output voltage VH is used via a power supply IC to generate a microcomputer operating power supply (typically a 5V power supply). Furthermore, the voltage of the battery 15 is used as the power supply voltage for the inverter that supplies power to the assist motor, the so-called PIG voltage, via a separate path from the boost circuit 20. Therefore, the input voltage VL below can also be interpreted as the PIG voltage.

[0030] The input voltage VL does not necessarily match the battery voltage. For example, when a diode or other element is connected between the battery 15 and the reactor 21, the input voltage VL becomes the battery voltage minus the voltage drop of the diode or other element.

[0031] Capacitor 24 is provided on the output side of boost circuit 20 and is charged by output voltage VH. Output voltage sensor 34 detects output voltage VH and feeds it back to boost circuit control unit 31. Boost circuit control unit 31 typically controls the operation of MOS 22 through PWM control so that output voltage VH of boost circuit 20 reaches a target voltage.

[0032] Similar to the configuration disclosed in Patent Document 1 (Japanese Patent No. 5561610), a starter activation signal is input to the boost circuit control unit 31 from the idle stop system ("ISS" in the figure) 50 and the starter 55. However, as indicated by the dotted line, the starter activation signal is not limited to direct communication with the boost circuit control unit 31; for example, communication may be performed via a CAN or other control unit.

[0033] After the boost device 301 is activated, an initial check is performed. While the output voltage sensor 34 of the boost device 301 can also be subject to the initial check, this embodiment focuses specifically on MOS open-circuit faults. Furthermore, before detecting an open-circuit fault, it is assumed that the MOS 22 is not short-circuited. During this initial check, the fault detection unit 32 determines that the MOS 22 has an open-circuit fault if the output voltage VH is less than a predetermined fault detection threshold. If the fault detection unit 32 determines that the MOS 22 is normal, the system transitions to normal control. Hereinafter, operations other than those performed during the initial check are referred to as normal control.

[0034] During normal control, similar to the conventional technology of Patent Document 1, the boost circuit control unit 31 drives the boost circuit 20 to prevent a voltage drop and reset of the microcomputer operating power supply, etc., caused by the activation of the starter 55 during restart after an idling stop. Specifically, a minimum voltage of approximately 4V must be maintained. If normal control is performed while the MOS 22 is open-circuited and the boost circuit 20 is inoperable, a drop in input voltage VL, such as during restart, could cause a reset of the in-vehicle device 40, potentially reducing marketability.

[0035] Therefore, it is necessary to detect MOS open-circuit failures during the initial inspection to prevent a reset caused by a voltage drop. The fault detection unit 32 can use a fault detection threshold set to a value lower than the normal output voltage VH. When the output voltage VH falls below the fault detection threshold, it detects an MOS open-circuit failure. This function will be described in detail later.

[0036] If the fault detection unit 32 detects an open-circuit MOS fault, it transmits a fault signal to various components, as indicated by the short-dashed line. For example, the fault detection unit 32 instructs the boost circuit control unit 31 to stop the operation of the boost circuit 20. The idle stop system 50, having received the fault signal via the boost circuit control unit 31, can also prohibit the idle stop from restarting. Furthermore, the onboard equipment 40, having received the fault signal, can limit the output of the assist motor to a level that eliminates the need for boosting the PIG voltage. Alternatively, the warning light 60, etc., that has received the fault signal, can output an alert to the driver.

[0037] Next, the detection structure of the MOS open circuit failure of the first embodiment will be described in comparison with the comparative example. Figure 7A 、 Figure 7B 、 Figure 8 .exist Figure 7A 、 Figure 7BThe operation images in normal state and in the case of a MOS open fault are shown. When the boost device 301 is activated at time to, a constant input voltage VL indicated by a bold dashed line is input to the boost circuit 20. The fault detection threshold VHth is set to a value between the input voltage VL and the target voltage VH*_n.

[0038] like Figure 7A As shown, in normal operation, the output voltage VH is boosted to the target voltage VH*_n and then maintained constant during the initial check period from time ts to time te. At this time, the output voltage VH is above the fault detection threshold VHth, and the MOS 22 is determined to be normal. Figure 7B As shown, when the MOS 22 is open-circuited, the output voltage VH indicated by the thick solid line is the voltage obtained by subtracting the voltage drop Vf of the diode 23 from the input voltage VL. At this time, the output voltage VH is lower than the fault detection threshold VHth, and the MOS 22 is determined to be open-circuited.

[0039] In this way, when the input voltage VL is lower than the target voltage VH*_n, an open-circuit MOS failure can be accurately detected. However, due to fluctuations in the battery SOC, the input voltage VL may rise to the maximum value VLmax indicated by the thinner dashed line. Consequently, as indicated by the thin solid line, when the output voltage VH is above the failure detection threshold VHth, the MOS 22 may be mistakenly determined to be normal despite being an open-circuit failure.

[0040] exist Figure 8 The horizontal axis shows the maximum value VLmax of the input voltage and the minimum value VLmin which is the lower limit value that can be used in practice. In a 16V battery for a vehicle, the maximum value VLmax is about 18V and the minimum value VLmin is about 4V. Figure 8 The vertical axis shows the output voltage VH on the same scale as the horizontal axis. The double-dashed line corresponds to the output voltage VH (=VL) without the boost circuit 20. The dotted line, offset by a voltage drop of Vf below the double-dashed line, shows the output voltage VH during an open-circuit MOS failure. The target voltage VH*_n is set to a value higher than the input voltage VL, except in regions where the input voltage VL is relatively high. No boost is performed in regions where the input voltage VL is above the target voltage VH*_n. Therefore, the output voltage VH during normal operation and the output voltage VH during an open-circuit MOS failure become identical and indistinguishable.

[0041] For example, if the target voltage VH*_n is approximately 14V and the fault detection threshold VHth is approximately 12V, as indicated by the (X) mark, MOS open-circuit fault detection cannot be performed when the input voltage VL during initial testing is approximately 12V or above. In this case, it is also possible to set the target voltage VH*_n higher than the maximum value VLmax of the input voltage VL. However, setting the output voltage VH during normal control too high is not desirable from the perspective of withstand voltage and heat generation of components such as the boost circuit 20.

[0042] Alternatively, in configurations where other loads capable of consuming high power are connected to battery 15, forcibly discharging battery 15 during the initial check to lower input voltage VL is a possible solution. However, in reality, loads capable of consuming such high power do not exist, and even if such loads existed, the wasteful consumption of power would be a significant drawback. Therefore, a solution is required that achieves both voltage protection and heat reduction for components during normal control, as well as reliable detection of MOS open-circuit faults during the initial check.

[0043] Then refer to Figure 2A 、 Figure 2B 、 Figure 3 , a detection structure of a first embodiment for solving the above-mentioned problems is described. Figure 2A 、 Figure 2B 、 Figure 3 Compared with the comparative example Figure 7A 、 Figure 7B 、 Figure 8 Corresponding. Figure 2A As shown, in the first embodiment, two target voltages are set during normal control and initial inspection. Target voltage VH*_h during the initial inspection is set to a higher value than target voltage VH*_n during normal control. After startup at time to, target voltage VH*_n is applied except during the initial inspection, and target voltage VH*_h is applied only during the initial inspection from time ts to time te.

[0044] Here, while target voltage VH*_n during normal control is lower than the maximum input voltage value VLmax, target voltage VH*_h during the initial check is set to a value higher than the maximum input voltage value VLmax. Furthermore, fault detection threshold VHth is set to a value between maximum input voltage value VLmax and target voltage VH*_h during the initial check.

[0045] When the initial inspection is normal, the output voltage VH is further increased from the target voltage VH*_n during normal control to the target voltage VH*_h during the initial inspection. At this time, the output voltage VH is above the fault detection threshold VHth, and it is determined that the MOS 22 is normal. Figure 2BAs shown, in the case of an open-circuit fault of the MOS, the output voltage VH is lower than the fault detection threshold VHth even at the maximum value VLmax of the input voltage, and it is determined that the MOS 22 has an open-circuit fault.

[0046] like Figure 3 In the first embodiment shown, the target voltage VH*_h during the initial check is set to a value higher than the maximum input voltage VLmax over the entire range from the minimum input voltage VLmin to the maximum input voltage VLmax, regardless of the value of the input voltage VL. Furthermore, the fault detection threshold VHth is set to a constant value regardless of the value of the input voltage VL. This differs from the second embodiment described below.

[0047] Reference Figure 4 The initial check process of the first embodiment is described using the flowchart. In the flowchart, the symbol "S" indicates a step. In S1, the initial check begins upon startup of the boost device 301. In S2, the target voltage VH*_h during the initial check is set to a value higher than the target voltage VH*_n during normal control. Furthermore, the boost circuit control unit 31 controls the operation of the MOS 22 so that the output voltage VH of the boost circuit 20 reaches the target voltage VH*_h.

[0048] In S3, the fault detection unit 32 obtains the output voltage VH detected by the output voltage sensor 34. In S4, the fault detection unit 32 determines whether the obtained output voltage VH is above the fault detection voltage threshold VHth. If the answer in S4 is yes, the MOS 22 is determined to be normal in S5. When the initial check is completed in S6, the target voltage VH*_h during the initial check is changed to the target voltage VH*_n during normal control. If no abnormalities are found in the initial checks of other items, the system transitions to normal control.

[0049] On the other hand, if output voltage VH is less than fault detection threshold VHth and S4 is negative, fault detection unit 32 determines in S7 that a MOS open-circuit fault has occurred. In S8, fault detection unit 32 transmits a fault signal to various components, causes boost circuit control unit 31 to stop operation of boost circuit 20, and issues a warning to the driver via warning lamp 60.

[0050] As described above, in the boost device 301 of the first embodiment, the target voltage VH*_n during normal control is set as low as possible, while the target voltage VH*_h during the initial check is set to a value higher than the target voltage VH*_n during normal control. This expands the input voltage range, which allows for distinguishing between the output voltage during a MOS open-circuit failure and normal operation, to a higher voltage range. This ensures component withstand voltage protection and reduces heat generation during normal control, while also increasing the chances that the fault detection unit 32 can accurately detect an MOS open-circuit failure.

[0051] By accurately detecting MOS open-circuit failures during the initial inspection and taking necessary measures, it is possible to prevent the onboard device 40 from being reset prematurely due to failure of the boost circuit 20 during a voltage drop caused by, for example, starting after an idling stop. This can prevent degradation of the marketability of idling stop vehicles.

[0052] In particular, the target voltage VH*_h during the initial check is set to a value higher than the maximum input voltage value VLmax, and the fault detection threshold VHth is set to a value between the maximum input voltage value VLmax and the target voltage VH*_h during the initial check. This allows the fault detection unit 32 to accurately detect open-circuit MOS faults across the entire range of the input voltage VL. Furthermore, in the first embodiment, which does not include an input voltage sensor, the target voltage VH*_h during the initial check and the fault detection threshold VHth are set independently of the value of the input voltage VL. This eliminates the need for an input voltage sensor, simplifying the device configuration.

[0053] (Second embodiment)

[0054] Next, refer to Figure 5 、 Figure 6 , the second embodiment is described. Figure 5 As shown, the booster device 302 of the second embodiment includes an input voltage sensor 33 for detecting an input voltage VL in addition to the configuration of the booster device 301 of the first embodiment. The detected value of the input voltage VL is input to the booster circuit control unit 31 .

[0055] like Figure 6 As shown, the initial check target voltage VH*_h is set to a variable value higher than the input voltage VL based on the input voltage VL. For example, if the value obtained by adding the specified voltage difference ΔVH to the input voltage VL (VL + ΔVH) is higher than the target voltage VH*_n during normal control, the initial check target voltage VH*_h is set to "VL + ΔVH," that is, a value higher than the target voltage VH*_n during normal control. On the other hand, if the value obtained by adding the specified voltage difference ΔVH to the input voltage VL (VL + ΔVH) is lower than the target voltage VH*_n during normal control, the initial check target voltage VH*_h is set to the same value as the target voltage VH*_n during normal control.

[0056] Here, the input voltage of "VL + ΔVH = VH*_n" is represented as the threshold value VLc. In the second embodiment, in the region where the input voltage VL exceeds the threshold value VLc, the target voltage VH*_h during the initial check is set to a variable value higher than the target voltage VH*_n during normal control. Therefore, summarizing the first and second embodiments, it can be said that "at least in the region where the input voltage VL exceeds the threshold value VLc, the target voltage VH*_h during the initial check is set to a value higher than the target voltage VH*_n during normal control."

[0057] The fault detection unit 32 obtains the target voltage VH*_h for the initial check, which is set by the boost circuit control unit 31. The fault detection threshold VHth is set to a variable value between the input voltage VL and the target voltage VH*_h for the initial check. For example, the value (VL + ΔVth) obtained by adding a predetermined voltage difference ΔVth (< ΔVH) to the input voltage VL is set as the fault detection threshold VHth.

[0058] Thus, in the second embodiment, the minimum target voltage VH*_h is set based on the actual input voltage VL during the initial inspection, which allows for distinguishing between the output voltage during a MOS open-circuit failure and normal operation. This minimizes the voltage increase during the initial inspection, making it more preferable from the perspectives of device withstand voltage protection and heat reduction.

[0059] In addition, the relationship between the input voltage VL, the target voltage VH*_h, and the fault detection threshold VHth is Figure 6 In addition to the linear characteristic shown in the example, a characteristic in which the target voltage VH*_h and the fault detection threshold VHth change in a stepwise manner for each interval of the input voltage VL may also be employed. By limiting the possible values ​​of the target voltage VH*_h and the fault detection threshold VHth to a finite number, the computational load on the boost circuit control unit 31 and the fault detection unit 32 can be reduced.

[0060] (Other Embodiments)

[0061] (a) In the boost circuit 20 of the above embodiment, a second MOS may be provided in place of the diode 23 connected to the output side of the connection point N between the reactor 21 and the MOS 22, thereby using a "buck-boost circuit" capable of stepping down and regenerating the power from the onboard device 40. Even with this configuration, the present embodiment focuses solely on its function as a boost circuit.

[0062] (b) The switching element is not limited to MOSFET, and may be formed of other types of transistors or the like.

[0063] (c) In the above embodiment Figure 1 、 Figure 5In the figure, for convenience of explanation, the boost circuit control unit 31 and the fault detection unit 32 are shown as separate modules. However, the functions of the boost circuit control unit 31 and the fault detection unit 32 may be integrated. In this case, the transmission of the fault signal from the fault detection unit 32 to the boost circuit control unit 31 and the acquisition of the target voltage VH*_h in the second embodiment can be processed within a single module.

[0064] The present disclosure is not limited to the above-described embodiments, and can be implemented in various forms without departing from the spirit and scope of the present disclosure.

[0065] The control unit and method described in the present disclosure may also be implemented by a dedicated computer provided by a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the control unit and method described in the present disclosure may also be implemented by a dedicated computer provided by a processor composed of one or more dedicated hardware logic circuits. Alternatively, the control unit and method described in the present disclosure may also be implemented by one or more dedicated computers composed of a combination of a processor and a memory programmed to execute one or more functions and a processor composed of one or more hardware logic circuits. In addition, the computer program may also be stored as an instruction executed by a computer in a non-migratable tangible recording medium that can be read by a computer.

[0066] The present disclosure is described based on the embodiments. However, the present disclosure is not limited to the embodiments and configurations. The present disclosure also includes various modifications and variations within the same scope. In addition, various combinations and methods, even those containing only one element, more or fewer elements, are also included in the scope and scope of the present disclosure.

Claims

1. A boost device mounted on an idling stop vehicle, which boosts an input voltage supplied from a battery and outputs the voltage to an onboard device, wherein: have: A chopper-type boost circuit includes a reactor having one end connected to the battery side, and a switching element connected between the other end of the reactor and the ground; An output voltage sensor, detecting the output voltage of the boost circuit; a boost circuit control unit that controls the operation of the switching element so that the output voltage of the boost circuit reaches a target voltage; as well as a fault detection unit that determines that the switching element has an open-circuit fault when the output voltage is lower than a predetermined fault detection threshold value during an initial inspection of the boost device; At least in a region where the input voltage is higher than a predetermined threshold value, the target voltage during the initial check is set to a value higher than the target voltage during normal control, which is an operation other than the initial check.

2. The boosting device according to claim 1, wherein: The target voltage during the initial inspection is set to a value higher than the maximum value of the input voltage regardless of the value of the input voltage. The failure detection threshold is set to a constant value between the maximum value of the input voltage and the target voltage during the initial check.

3. The boosting device according to claim 1, wherein: It also includes an input voltage sensor for detecting the input voltage. The target voltage during the initial inspection is set to a variable value higher than the input voltage according to the input voltage. The failure detection threshold is set to a variable value between the input voltage and the target voltage during initial inspection.

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