Onboard control device
The in-vehicle control device addresses overheating issues by using a control unit to detect and interrupt current flow through body diodes of FETs, ensuring they remain in an on state when necessary, thus preventing overheating.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- AUTONETWORKS TECH LTD
- Filing Date
- 2026-01-06
- Publication Date
- 2026-07-23
AI Technical Summary
Existing in-vehicle control devices using N-channel MOSFETs with body diodes risk overheating due to reverse current flow through the diode when the FET is erroneously controlled to an off state during necessary power supply to the load.
The in-vehicle control device includes a control unit that determines current flow through the body diodes of FETs and switches them to an on state when current is detected, interrupting the current flow through the diodes to prevent overheating.
This configuration effectively prevents FETs from overheating by switching them to an on state when current flows through their body diodes, thereby suppressing heat generation.
Smart Images
Figure JP2026000122_23072026_PF_FP_ABST
Abstract
Description
In-vehicle control device
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[0001] The present disclosure relates to an in-vehicle control device.
[0002] Patent Document 1 discloses a power supply system including a DC power supply and a reverse current prevention switching element. The reverse current prevention switching element is an N-channel MOSFET having a body diode and is provided on the positive power line. The body diode allows the output current of the DC power supply and blocks the reverse current in the opposite direction to this output current.
[0003] Japanese Patent Application Laid-Open No. 2022-187720 <00-00008> In the configuration of Patent Document 1, in a situation where power supply to the load is unnecessary, it is conceivable to control the reverse current prevention switching element to an off state in order to block the reverse current to the DC power supply. However, if the reverse current prevention switching element is erroneously controlled to an off state even in a situation where power supply to the load is necessary, the output current of the DC power supply may flow to the load through the body diode, and the FET may enter a heat generation state.
[0005] An object of the present disclosure is to provide a technology capable of suppressing the FET from entering a heat generation state.
[0006] The in-vehicle control device of the present disclosure includes a first FET provided in a first conductive path that supplies power from a first power supply unit to a first load, and a control unit that controls the first FET. The first FET has a first body diode. The anode of the first body diode is electrically connected to the conductive path on the first power supply unit side. The cathode of the first body diode is electrically connected to the conductive path on the first load side. The control unit determines whether a current is flowing through the first body diode in a state where the first FET is controlled to an off state, and controls the first FET to an on state when it is determined that a current is flowing through the first body diode.
[0007] According to the technology according to the present disclosure, it is possible to suppress the FET from entering a heat generation state.
[0008] Figure 1 is a schematic diagram showing an in-vehicle system equipped with an in-vehicle control device according to the first embodiment. Figure 2 is the first half of the flowchart of the processing performed by the first control unit in the first embodiment. Figure 3 is the second half of the flowchart of the processing performed by the first control unit in the first embodiment. Figure 4 is an explanatory diagram showing the state in which current flows through the first body diode when the first FET in the first embodiment is in the off state. Figure 5 is an explanatory diagram showing the state in which current flows through the second body diode when the second FET in the first embodiment is in the off state. Figure 6 is an explanatory diagram showing the state in which current flows through the third body diode when the third FET in the first embodiment is in the off state. Figure 7 is an explanatory diagram showing the state in which current flows through the fourth body diode when the fourth FET in the first embodiment is in the off state. Figure 8 is a schematic diagram showing an in-vehicle system equipped with an in-vehicle control device according to the second embodiment.
[0009] [Description of Embodiments of the Disclosure] First, embodiments of the Disclosure will be listed and described.
[0010] [1] An in-vehicle control device comprising: a first FET provided in a first conductive path that supplies power from a first power supply unit to a first load; and a control unit that controls the first FET, wherein the first FET has a first body diode, the anode of the first body diode is electrically connected to the conductive path on the first power supply unit side, and the cathode of the first body diode is electrically connected to the conductive path on the first load side; and the control unit determines whether or not current is flowing through the first body diode when the first FET is controlled to be in the off state, and controls the first FET to be in the on state when it is determined that current is flowing through the first body diode.
[0011] With this configuration, when current flows from the first power supply to the first load via the first body diode while the first FET is controlled to the off state, the first FET can be switched to the on state. This interrupts or suppresses the current flowing through the first body diode, thereby suppressing heat generation in the first FET. In other words, this configuration prevents the first FET from overheating.
[0012] [2] An intermediate conductive path is electrically connected to the conductive path on the first load side of the first FET in the first conductive path, and current from the second power supply can be supplied via the intermediate conductive path, as described in [1].
[0013] In a configuration where current from the second power supply unit can be supplied to the conduction path on the first load side of the first FET in the first conduction path, there is a risk that current from the second power supply unit may flow into the first power supply unit through the first FET. Therefore, the control unit needs to control the first FET to the off state as needed to prevent reverse current flow to the first power supply unit. However, if the first FET is mistakenly controlled to the off state when power supply to the first load is required, the output current from the first power supply unit may flow to the first load through the first body diode, potentially causing the first FET to overheat. In this configuration, however, if current flows from the first power supply unit to the first load through the first body diode while the first FET is controlled to the off state, the first FET can be switched to the on state. This interrupts or suppresses the current flowing through the first body diode, thereby suppressing heat generation in the first FET.
[0014] [3] The in-vehicle control device according to [2], further comprising a second FET provided in a second conductive path that supplies power from the second power supply unit to a second load, wherein the intermediate conductive path is provided between a conductive path in the first conductive path that is on the first load side of the first FET and a conductive path in the second conductive path that is on the second load side of the second FET, the second FET has a second body diode, the anode of the second body diode is electrically connected to a conductive path on the second power supply unit side, the cathode of the second body diode is electrically connected to a conductive path on the second load side, and the control unit determines whether or not current is flowing through the second body diode when the second FET is controlled to be in the off state, and controls the second FET to be in the on state when it is determined that current is flowing through the second body diode.
[0015] With this configuration, when the second FET is controlled to be in the off state and current flows from the second power supply to the second load via the second body diode, the second FET can be switched to the on state. This interrupts or suppresses the current flowing through the second body diode, thereby suppressing heat generation in the second FET. In other words, this configuration prevents the second FET from overheating.
[0016] [4] The in-vehicle control device according to [3], further comprising a third FET provided in the intermediate conductive path, wherein the third FET has a third body diode, the anode of the third body diode is electrically connected to the conductive path on the second conductive path side, and the cathode of the third body diode is electrically connected to the conductive path on the first conductive path side, and the control unit determines whether or not current is flowing through the third body diode when the third FET is controlled to be in the off state, and controls the third FET to be in the on state when it is determined that current is flowing through the third body diode.
[0017] With this configuration, when the third FET is controlled to be in the off state and current flows from the second power supply to the first load via the third body diode, the third FET can be switched to the on state. This interrupts or suppresses the current flowing through the third body diode, thereby suppressing heat generation in the third FET. In other words, this configuration prevents the third FET from overheating.
[0018] [5] An in-vehicle control device according to [3] or [4], further comprising a fourth FET provided in the intermediate conductive path, wherein the fourth FET has a fourth body diode, the anode of the fourth body diode is electrically connected to the conductive path on the first conductive path side, the cathode of the fourth body diode is electrically connected to the conductive path on the second conductive path side, and the control unit determines whether or not current is flowing through the fourth body diode when the fourth FET is controlled to be in the off state, and controls the fourth FET to be in the on state when it is determined that current is flowing through the fourth body diode.
[0019] With this configuration, when the fourth FET is controlled to be in the off state and current flows from the first power supply to the second load via the fourth body diode, the fourth FET can be switched to the on state. This interrupts or suppresses the current flowing through the fourth body diode, thereby suppressing heat generation in the fourth FET. In other words, this configuration prevents the fourth FET from overheating.
[0020] [6] The in-vehicle control device according to any one of [1] to [5], wherein the first load is controlled to be in an operating state and a stopped state, and the control unit determines whether or not current is flowing through the first body diode when it determines that the first load is in an operating state and the first FET is controlled to be in an off state, and determines whether or not current is flowing through the first body diode when it determines that the first FET is controlled to be in an off state, and controls the first FET to be in an on state when it determines that current is flowing through the first body diode.
[0021] When the first FET is turned off while the first load is operating, current flows from the first power supply to the first load via the first body diode. Therefore, as in the above-mentioned automotive control device, by determining whether or not current is flowing through the first body diode when the first FET is controlled to be off while the first load is operating, it is possible to more accurately determine whether or not current is flowing through the first body diode.
[0022] [Details of Embodiments of the Disclosure] 1. First Embodiment 1-1. Configuration of the In-Vehicle System 1 The in-vehicle system 1 shown in Figure 1 is a system mounted on a vehicle. The in-vehicle system 1 comprises a first power supply unit 10, a first load 11, a first conductive path 12, a second power supply unit 20, a second load 21, a second conductive path 22, an intermediate conductive path 23, a second control unit 24, and an in-vehicle control device 30.
[0023] The first power supply unit 10 is a DC power supply. The first power supply unit 10 is electrically connected to the first conductive path 12. In this embodiment, the first power supply unit 10 is configured as a DC-DC converter and applies the voltage input to it to the first conductive path 12 by boosting or stepping down the voltage. The first power supply unit 10 may also be configured as a battery. The output voltage of the first power supply unit 10 is applied to the first conductive path 12. The first power supply unit 10 supplies power to the first load 11 via the first conductive path 12. The first conductive path 12 supplies power from the first power supply unit 10 to the first load 11.
[0024] The second power supply unit 20 is a DC power supply. The second power supply unit 20 is electrically connected to the second conductive path 22. The second power supply unit 20 is configured, for example, by a battery. The output voltage of the second power supply unit 20 is applied to the second conductive path 22. In this embodiment, the output voltage of the second power supply unit 20 is smaller than the output voltage of the first power supply unit 10, but it may be the same as the output voltage of the first power supply unit 10, or it may be larger than the output voltage of the first power supply unit 10. The second power supply unit 20 supplies power to the second load 21 via the second conductive path 22. The second conductive path 22 supplies power from the second power supply unit 20 to the second load 21.
[0025] The intermediate conductive path 23 is provided between the first conductive path 12 and the second conductive path 22, and is electrically connected to the first conductive path 12 and the second conductive path 22.
[0026] The second control unit 24 is configured to include, for example, a microcomputer. The second control unit 24 includes, for example, a processor such as a CPU, memory such as ROM or RAM, and a communication interface for communicating with the first load 11 and the second load 21. The second control unit 24 controls the first load 11 and the second load 21. Each of the first load 11 and the second load 21 switches between an operating state and a stopped state by being controlled by the second control unit 24. The operating state is a state in which power is consumed, and the stopped state is a state in which less power is consumed than the operating state.
[0027] 1-2. Configuration of the In-Vehicle Control Device 30 The in-vehicle control device 30 comprises a first FET 31, a second FET 32, a third FET 33, a fourth FET 34, voltage detection units 41, 42, 43, 44, 45, and a first control unit 60. The first FET 31, second FET 32, third FET 33, and fourth FET 34 are Field Effect Transistors, and in this embodiment, they are N-channel type MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors).
[0028] The first FET 31 is provided in the first conductive path 12. The first FET 31 has a first body diode 31A. The first FET 31 is positioned on the first power supply unit 10 side of the connection portion between the first conductive path 12 and the intermediate conductive path 23. The source of the first FET 31 and the anode of the first body diode 31A are electrically connected to the conductive path on the first power supply unit 10 side. The drain of the first FET 31 and the cathode of the first body diode 31A are electrically connected to the conductive path on the first load 11 side and electrically connected to the conductive path on the intermediate conductive path 23 side. When the first FET 31 is ON, it allows current to flow bidirectionally through it. When the first FET 31 is OFF, it blocks current from flowing from the first load 11 side and the intermediate conductive path 23 side to the first power supply unit 10 side through it, and allows current to flow from the first power supply unit 10 side to the first load 11 side and the intermediate conductive path 23 side through its first body diode 31A.
[0029] The second FET 32 is provided in the second conductive path 22. The second FET 32 has a second body diode 32A. The second FET 32 is positioned on the second power supply unit 20 side of the connection portion between the second conductive path 22 and the intermediate conductive path 23. The source of the second FET 32 and the anode of the second body diode 32A are electrically connected to the conductive path on the second power supply unit 20 side. The drain of the second FET 32 and the cathode of the second body diode 32A are electrically connected to the conductive path on the second load 21 side and electrically connected to the conductive path on the intermediate conductive path 23 side. When the second FET 32 is ON, it allows current to flow bidirectionally through it. When the second FET 32 is OFF, it blocks current from flowing from the second load 21 side and the intermediate conductive path 23 side to the second power supply unit 20 side through it, and allows current to flow from the second power supply unit 20 side to the second load 21 side and the intermediate conductive path 23 side through its second body diode 32A.
[0030] The third FET 33 is provided in the intermediate conductive path 23. The third FET 33 has a third body diode 33A. The source of the third FET 33 and the anode of the third body diode 33A are electrically connected to the conductive path on the second conductive path 22 side. The drain of the third FET 33 and the cathode of the third body diode 33A are electrically connected to the conductive path on the first conductive path 12 side. When the third FET 33 is ON, it allows current to flow bidirectionally through it. When the third FET 33 is OFF, it blocks current from flowing from the first conductive path 12 side to the second conductive path 22 side through it, and allows current to flow from the second conductive path 22 side to the first conductive path 12 side through its third body diode 33A.
[0031] The fourth FET 34 is provided in the intermediate conductive path 23. The fourth FET 34 is arranged in series with the third FET 33 between the first conductive path 12 and the second conductive path 22. The fourth FET 34 is positioned on the second conductive path 22 side of the third FET 33. The fourth FET 34 has a fourth body diode 34A. The source of the fourth FET 34 and the anode of the fourth body diode 34A are electrically connected to the conductive path on the first conductive path 12 side. The drain of the fourth FET 34 and the cathode of the fourth body diode 34A are electrically connected to the conductive path on the second conductive path 22 side. When the fourth FET 34 is ON, it allows current to flow bidirectionally through it. When the fourth FET 34 is OFF, it blocks current flow from the second conductive path 22 side to the first conductive path 12 side through it, and allows current to flow from the first conductive path 12 side to the second conductive path 22 side through its fourth body diode 34A.
[0032] Voltage detection unit 41 detects the voltage at the source of the first FET 31 and the anode of the first body diode 31A. Voltage detection unit 42 detects the voltage at the source of the second FET 32 and the anode of the second body diode 32A. Voltage detection unit 43 detects the voltage at the drain of the first FET 31 and the cathode of the first body diode 31A. Voltage detection unit 43 detects the voltage at the drain of the third FET 33 and the cathode of the third body diode 33A. Voltage detection unit 44 detects the voltage at the drain of the second FET 32 and the cathode of the second body diode 32A. Voltage detection unit 44 detects the voltage at the drain of the fourth FET 34 and the cathode of the fourth body diode 34A. Voltage detection unit 45 detects the voltage at the source of the third FET 33 and the anode of the third body diode 33A. The voltage detection unit 45 detects the voltage at the source of the fourth FET 34 and the anode of the fourth body diode 34A.
[0033] The voltage detection units 41, 42, 43, 44, and 45 are configured, for example, by known voltage detection circuits. Signals indicating the detection results of the voltage detection units 41, 42, 43, 44, and 45 are input to the first control unit 60.
[0034] The first control unit 60 is an example of a control unit. The first control unit 60 is composed of, for example, a microcomputer. The first control unit 60 includes, for example, a processor such as a CPU, memory such as ROM or RAM, and drive circuits.
[0035] The first control unit 60 identifies the voltage across the first FET 31 (specifically, the drain-source voltage of the first FET 31) based on signals input from the voltage detection units 41 and 43. The first control unit 60 identifies the voltage across the second FET 32 (specifically, the drain-source voltage of the second FET 32) based on signals input from the voltage detection units 42 and 44. The first control unit 60 identifies the voltage across the third FET 33 (specifically, the drain-source voltage of the third FET 33) based on signals input from the voltage detection units 43 and 45. The first control unit 60 identifies the voltage across the fourth FET 34 (specifically, the drain-source voltage of the fourth FET 34) based on signals input from the voltage detection units 44 and 45.
[0036] The first control unit 60 controls the first FET 31 to the ON state by applying an ON signal to the gate of the first FET 31. The first control unit 60 controls the first FET 31 to the OFF state by applying an OFF signal to the gate of the first FET 31.
[0037] The first control unit 60 controls the second FET 32 to the ON state by applying an ON signal to the gate of the second FET 32. The first control unit 60 controls the second FET 32 to the OFF state by applying an OFF signal to the gate of the second FET 32.
[0038] The first control unit 60 controls the third FET 33 to an ON state by applying an ON signal to the gate of the third FET 33. The first control unit 60 controls the third FET 33 to an OFF state by applying an OFF signal to the gate of the third FET 33.
[0039] The first control unit 60 controls the fourth FET 34 to an ON state by applying an ON signal to the gate of the fourth FET 34. The first control unit 60 controls the fourth FET 34 to an OFF state by applying an OFF signal to the gate of the fourth FET 34.
[0040] 1-3. Example of operation of the in-vehicle control device 30 The first control unit 60 of the in-vehicle control device 30 controls the first FET 31 to the ON state when the first ON condition is met, controls the first FET 31 to the OFF state when the first OFF condition is met, controls the second FET 32 to the ON state when the second ON condition is met, controls the second FET 32 to the OFF state when the second OFF condition is met, controls the third FET 33 to the ON state when the third ON condition is met, controls the third FET 33 to the OFF state when the third OFF condition is met, controls the fourth FET 34 to the ON state when the fourth ON condition is met, and controls the fourth FET 34 to the OFF state when the fourth OFF condition is met.
[0041] The first control unit 60 performs the processing shown in Figures 2 and 3 in parallel with the basic operation described above. In step S10 of Figure 2, the first control unit 60 determines whether at least one of the first load 11 and the second load 21 is operating.
[0042] The first control unit 60 may determine whether the first load 11 and the second load 21 are operating based on information obtained, for example, from the second control unit 24. Furthermore, if the first load 11 and the second load 21 are operating when the vehicle's start switch is ON, and stopped when the start switch is OFF, the first control unit 60 may determine whether the first load 11 and the second load 21 are operating based on the ON / OFF state of the start switch. The start switch may be, for example, an ignition switch or a power switch.
[0043] When at least one of the first load 11 and the second load 21 is operating, power is supplied from at least one of the first power supply unit 10 and the second power supply unit 20, so that current can flow through the body diodes 31A, 32A, 33A, and 34A of the FETs 31, 32, 33, and 34.
[0044] When the first control unit 60 determines that both the first power supply unit 10 and the second power supply unit 20 are in the stopped state (No in step S10), it returns to step S10. That is, when the first control unit 60 determines that at least one of the first load 11 and the second load 21 is in the operating state (Yes in step S10), it determines whether the first FET 31 is controlled to be in the off state (step S11). The first control unit 60 determines whether the first FET 31 is controlled to be in the off state based on its own control state.
[0045] When the first control unit 60 determines that the first FET 31 is controlled to be in the off state (Yes in step S11), it determines whether a current is flowing through the first body diode 31A (step S12). In this embodiment, the first control unit 60 determines whether a current is flowing through the first body diode 31A based on the voltage across both ends of the first FET 31. For example, when the voltage across both ends of the first FET 31 is less than or equal to the threshold value, the first control unit 6 determines that a current is flowing through the first body diode 31A, and when the voltage across both ends of the first FET 31 is greater than the threshold value, it determines that no current is flowing through the first body diode 31A. The threshold value is a value of 0 or more.
[0046] When the first control unit 60 determines that a current is flowing through the first body diode 31A (Yes in step S12), it switches the first FET 31 to the on state (step S13).
[0047] For example, in the example shown in FIG. 4, the first FET 31 is erroneously controlled to be in the off state, the second FET 32 is normally controlled to be in the on state, and the third FET 33 and the fourth FET 34 are normally controlled to be in the off state. In this state, a current flows through the first body diode 31A of the first FET 31, and the first FET 3 is heated. In this state, the first control unit 60 determines that a current is flowing through the first body diode 31A and switches the first FET 31 to the on state. As a result, the current flowing through the first body diode 31A is interrupted or suppressed, and the heat generation of the first FET 31 is suppressed.
[0048] When the first control unit 60 determines No in step S11, determines No in step S12, or after step S13, it determines whether the second FET 32 is controlled to be in the off state (step S14). The first control unit 60 determines whether the second FET 32 is controlled to be in the off state based on its own control state.
[0049] When the first control unit 60 determines that the second FET 32 is controlled to be in the off state (Yes in step S14), it determines whether a current is flowing through the second body diode 32A (step S15). In this embodiment, the first control unit 60 determines whether a current is flowing through the second body diode 32A based on the voltage across the second FET 32. For example, when the voltage across the second FET 32 is less than or equal to a threshold value, the first control unit 60 determines that a current is flowing through the second body diode 32A, and when the voltage across the second FET 32 is greater than the threshold value, the first control unit 60 determines that no current is flowing through the second body diode 32A. The threshold value is a value of 0 or more.A
[0050] When the first control unit 60 determines that a current is flowing through the second body diode 32A (Yes in step S15), it switches the second FET 32 to the on state (step S16).
[0051] For example, in the example shown in FIG. 5, the second FET 32 is erroneously controlled to be in the off state, the first FET 31 is normally controlled to be in the on state, and the third FET 33 and the fourth FET 34 are normally controlled to be in the off state. In this state, a current flows through the second body diode 32A of the second FET 32, and the second FET 32 generates heat. In this state, the first control unit 60 determines that a current is flowing through the second body diode 32A and switches the second FET 32 to the on state. As a result, the current flowing through the second body diode 32A is blocked or suppressed, and the heat generation of the second FET 32 is suppressed.
[0052] The first control unit 60 determines whether or not it has controlled the third FET 33 to the off state if the result is No in step S14, if the result is No in step S15, or after step S16 (step S17). Based on its own control state, the first control unit 60 determines whether or not it has controlled the third FET 33 to the off state.
[0053] If the first control unit 60 determines that it has controlled the third FET 33 to the off state (Yes in step S17), it determines whether or not current is flowing through the third body diode 33A (step S18). In this embodiment, the first control unit 60 determines whether or not current is flowing through the third body diode 33A based on the voltage across the third FET 33. For example, the first control unit 60 determines that current is flowing through the third body diode 33A if the voltage across the third FET 33 is below a threshold value, and determines that no current is flowing through the third body diode 33A if the voltage across the third FET 33 is greater than the threshold value. The threshold value is 0 or greater.
[0054] If the first control unit 60 determines that current is flowing through the third body diode 33A (Yes in step S18), it switches the third FET 33 to the ON state (step S19).
[0055] For example, in the example shown in Figure 6, the third FET 33 is incorrectly controlled to the OFF state, while the first FET 31, second FET 32, and fourth FET 34 are correctly controlled to the ON state. In this state, current flows through the third body diode 33A of the third FET 33, causing the third FET 33 to heat up. In this state, the first control unit 60 determines that current is flowing through the third body diode 33A and switches the third FET 33 to the ON state. As a result, the current flowing through the third body diode 33A is interrupted or suppressed, and the heat generated by the third FET 33 is suppressed.
[0056] The first control unit 60 determines whether it has controlled the fourth FET 34 to the off state if the answer is No in step S17, if the answer is No in step S18, or after step S19 (step S20). Based on its own control state, the first control unit 60 determines whether it has controlled the fourth FET 34 to the off state.
[0057] If the first control unit 60 determines that it has controlled the fourth FET 34 to the off state (Yes in step S20), it determines whether or not current is flowing through the fourth body diode 34A (step S21). In this embodiment, the first control unit 60 determines whether or not current is flowing through the fourth body diode 34A based on the voltage across the fourth FET 34. For example, the first control unit 60 determines that current is flowing through the fourth body diode 34A if the voltage across the fourth FET 34 is below a threshold value, and determines that no current is flowing through the fourth body diode 34A if the voltage across the fourth FET 34 is greater than the threshold value. The threshold value is 0 or greater.
[0058] If the first control unit 60 determines that current is flowing through the fourth body diode 34A (Yes in step S21), it switches the fourth FET 34 to the ON state (step S22).
[0059] For example, in the example shown in Figure 7, the fourth FET 34 is incorrectly controlled to the OFF state, while the first FET 31, second FET 32, and third FET 33 are correctly controlled to the ON state. In this state, current flows through the fourth body diode 34A of the fourth FET 34, causing the fourth FET 34 to heat up. In this state, the first control unit 60 determines that current is flowing through the fourth body diode 34A and switches the fourth FET 34 to the ON state. As a result, the current flowing through the fourth body diode 34A is interrupted or suppressed, and the heat generated by the fourth FET 34 is suppressed.
[0060] If the result in step S20 is No, if the result in step S21 is No, or after step S22, the first control unit 60 returns to step S10.
[0061] 1-4. Effects of the First Embodiment In a configuration in which current from the second power supply unit 20 can be supplied to the conductive path on the first load 11 side of the first FET 31 in the first conductive path 12, there is a risk that current from the second power supply unit 20 may flow into the first power supply unit 10 via the first FET 31. Therefore, the first control unit 60 needs to control the first FET 31 to the off state as needed to prevent reverse current flow to the first power supply unit 10. However, if the first FET 31 is mistakenly controlled to the off state even though power supply to the first load 11 is required, the output current from the first power supply unit 10 may flow to the first load 11 via the first body diode 31A, potentially causing the first FET 31 to overheat. In this regard, the in-vehicle control device 30 can switch the first FET 31 to the on state when current flows from the first power supply unit 10 to the first load 11 via the first body diode 31A while the first FET 31 is controlled to the off state. As a result, the current flowing through the first body diode 31A is interrupted or suppressed, and the heat generation of the first FET 31 is suppressed. In other words, the in-vehicle control device 30 can prevent the first FET 31 from overheating.
[0062] According to the in-vehicle control device 30, when current flows from the second power supply unit 20 to the second load 21 via the second body diode 32A while the second FET 32 is controlled to the off state, the second FET 32 can be switched to the on state. As a result, the current flowing through the second body diode 32A is interrupted or suppressed, and the heat generation of the second FET 32 is suppressed. In other words, the in-vehicle control device 30 can prevent the second FET 32 from overheating.
[0063] According to the in-vehicle control device 30, when current flows from the second power supply unit 20 to the first load 11 via the third body diode 33A while the third FET 33 is controlled to the off state, the third FET 33 can be switched to the on state. As a result, the current flowing through the third body diode 33A is interrupted or suppressed, and the heat generation of the third FET 33 is suppressed. In other words, the in-vehicle control device 30 can prevent the third FET 33 from overheating.
[0064] According to the in-vehicle control device 30, when current flows from the first power supply unit 10 to the second load 21 via the fourth body diode 34A while the fourth FET 34 is controlled to the off state, the fourth FET 34 can be switched to the on state. As a result, the current flowing through the fourth body diode 34A is interrupted or suppressed, and the heat generation of the fourth FET 34 is suppressed. In other words, the in-vehicle control device 30 can prevent the fourth FET 34 from overheating.
[0065] When the first FET 31 is turned off while at least one of the first load 11 and the second load 21 is operating, current flows from the first power supply unit 10 to the first load 11 via the first body diode 31A. Therefore, in a state where the first FET 31 is controlled to be turned off when at least one of the first load 11 and the second load 21 is operating, such as in the in-vehicle control device 30, it is possible to more accurately determine whether current is flowing through the first body diode 31A by determining whether or not current is flowing through the first body diode 31A.
[0066] 2. Second Embodiment In the first embodiment, an example was described in which it is determined whether or not current is flowing through the body diode based on the detection result of the voltage detection unit. In contrast, in the second embodiment, an example will be described in which it is determined whether or not current is flowing through the body diode based on the detection result of the current detection unit. In the second embodiment, the same reference numerals are used for components that are the same as in the first embodiment, and detailed explanations are omitted.
[0067] The in-vehicle system 201 of the second embodiment shown in Figure 8 includes an in-vehicle control device 230 instead of the in-vehicle control device 30 described in the first embodiment. The in-vehicle control device 230 includes current detection units 241, 242, and 243 instead of the voltage detection units 41, 42, 43, 44, and 45 of the in-vehicle control device 30.
[0068] The current detection unit 241 detects the current flowing through the first FET 31. When the first FET 31 is in the off state, the current detection unit 241 detects the current flowing through the first body diode 31A. The current detection unit 242 detects the current flowing through the second FET 32. When the second FET 32 is in the off state, the current detection unit 242 detects the current flowing through the second body diode 32A. The current detection unit 243 detects the current flowing through the third FET 33 and the fourth FET 34. When the third FET 33 is in the off state, the current detection unit 243 detects the current flowing through the third body diode 33A, and when the fourth FET 34 is in the off state, the current detection unit 243 detects the current flowing through the fourth body diode 34A.
[0069] The current detection units 241, 242, and 243 are composed of, for example, known current sensors. Signals indicating the detection results from the current detection units 241, 242, and 243 are input to the first control unit 60.
[0070] The first control unit 60 determines the current value flowing through the first body diode 31A when the first FET 31 is controlled to the OFF state, based on the signal input from the current detection unit 241. The first control unit 60 determines that current is flowing through the first body diode 31A when the current value flowing through the first body diode 31A when the first FET 31 is controlled to the OFF state exceeds a threshold. The first control unit 60 determines that no current is flowing through the first body diode 31A when the current value flowing through the first body diode 31A when the first FET 31 is controlled to the OFF state is less than or equal to a threshold. The threshold is a value of 0 or greater.
[0071] The first control unit 60 determines the current value flowing through the second body diode 32A when the second FET 32 is controlled to the OFF state, based on the signal input from the current detection unit 242. The first control unit 60 determines that current is flowing through the second body diode 32A when the second FET 32 is controlled to the OFF state if it determines that the current value flowing through the second body diode 32A exceeds a threshold. The first control unit 60 determines that no current is flowing through the second body diode 32A when the second FET 32 is controlled to the OFF state if it determines that the current value flowing through the second body diode 32A is less than or equal to a threshold. The threshold is a value of 0 or greater.
[0072] The first control unit 60 determines the current value flowing through the third body diode 33A when the third FET 33 is controlled to the OFF state, based on the signal input from the current detection unit 243. The first control unit 60 determines that current is flowing through the third body diode 33A when the current value flowing through the third body diode 33A when the third FET 33 is controlled to the OFF state exceeds a threshold. The first control unit 60 determines that no current is flowing through the third body diode 33A when the current value flowing through the third body diode 33A when the third FET 33 is controlled to the OFF state is less than or equal to a threshold. The threshold is a value of 0 or greater.
[0073] The first control unit 60 determines the current value flowing through the fourth body diode 34A when the fourth FET 34 is controlled to the OFF state, based on the signal input from the current detection unit 243. The first control unit 60 determines that current is flowing through the fourth body diode 34A when the current value flowing through the fourth body diode 34A when the fourth FET 34 is controlled to the OFF state exceeds a threshold. The first control unit 60 determines that no current is flowing through the fourth body diode 34A when the current value flowing through the fourth body diode 34A when the fourth FET 34 is controlled to the OFF state is less than or equal to a threshold. The threshold is a value of 0 or greater.
[0074] As described above, the in-vehicle control device 230 of the second embodiment can determine whether or not current is flowing through the first body diode 31A, the second body diode 32A, the third body diode 33A, and the fourth body diode 34A based on the detection results of the current detection units 241, 242, and 243.
[0075] <Other Embodiments> This disclosure is not limited to the embodiments described above and in the drawings. For example, any combination of the features of the embodiments described above or below is possible as long as it does not contradict the original. Furthermore, any feature of the embodiments described above or below may be omitted unless explicitly stated as essential. In addition, the embodiments described above may be modified as follows.
[0076] In the embodiments described above, a second power supply unit 20 was provided, but a configuration without the second power supply unit 20 is also possible. Even in a configuration without the second power supply unit 20, it is assumed that the first FET 31 is switched to the off state in order to prevent current from flowing back from the first load 11 to the first power supply unit 10. In such a configuration as well, by controlling the first FET 31 to the on state when it is determined that current is flowing through the first body diode 31A, it is possible to suppress the first FET 31 from overheating.
[0077] In each of the above embodiments, the first load 11 was configured to switch between an operating state and a stopped state by being controlled by the second control unit 24. Alternatively, a switch unit may be provided that cuts off the power supplied from the first power supply unit 10 to the first load 11, and the first load 11 may switch between an operating state and a stopped state by switching the on / off state of the switch unit by the second control unit 24.
[0078] In each of the above embodiments, the second load 21 was configured to switch between an operating state and a stopped state by being controlled by the second control unit 24. Alternatively, a switch unit may be provided that cuts off the power supplied from the second power supply unit 20 to the second load 21, and the on / off state of the switch unit may be switched by the second control unit 24, thereby switching the second load 21 between an operating state and a stopped state.
[0079] In the first embodiment described above, the configuration determined whether or not current was flowing through the first body diode 31A when the first FET 31 was controlled to the off state while at least one of the first load 11 and the second load 21 was operating. In contrast, the configuration may determine whether or not current was flowing through the first body diode 31A when the first load 11 was operating and the first FET 31 was controlled to the off state.
[0080] In the first embodiment described above, the configuration determined whether or not current was flowing through the second body diode 32A when the second FET 32 was controlled to the off state while at least one of the first load 11 and the second load 21 was operating. In contrast, the configuration may determine whether or not current was flowing through the second body diode 32A when the second load 21 was operating and the second FET 32 was controlled to the off state.
[0081] In the first embodiment described above, the configuration determined whether or not current was flowing through the first body diode 31A when the first FET 31 was controlled to the off state while at least one of the first load 11 and the second load 21 was operating. In contrast, the configuration may determine whether or not current was flowing through the first body diode 31A when the first FET 31 was controlled to the off state without checking whether or not the first load 11 and the second load 21 were operating. The same applies to determining whether or not current was flowing through the second body diode 32A, the third body diode 33A, and the fourth body diode 34A.
[0082] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, but is indicated by the claims, and all modifications within the meaning and scope of the claims are intended to be included.
[0083] 1...In-vehicle system 10...First power supply unit 11...First load 12...First conductive path 20...Second power supply unit 21...Second load 22...Second conductive path 23...Intermediate conductive path 24...Second control unit 30...In-vehicle control device 31...First FET 31A...First body diode 32...Second FET 32A...Second body diode 33...Third FET 33A...Third body diode 34...Fourth FET 34A...Fourth body diode 41...Voltage detection unit 42...Voltage detection unit 43...Voltage detection unit 44...Voltage detection unit 45...Voltage detection unit 60...First control unit (control unit) 201...In-vehicle system 230...In-vehicle control device 241...Current detection unit 242...Current detection unit 243...Current detection unit
Claims
1. An in-vehicle control device comprising: a first FET provided in a first conductive path that supplies power from a first power supply unit to a first load; and a control unit that controls the first FET, wherein the first FET has a first body diode, the anode of the first body diode is electrically connected to the conductive path on the first power supply unit side, and the cathode of the first body diode is electrically connected to the conductive path on the first load side; and the control unit determines whether or not current is flowing through the first body diode when the first FET is controlled to be in the off state, and controls the first FET to be in the on state when it is determined that current is flowing through the first body diode.
2. An intermediate conductive path is electrically connected to the conductive path on the first load side of the first FET in the first conductive path, and current from the second power supply can be supplied via the intermediate conductive path, as described in claim 1.
3. An in-vehicle control device according to claim 2, further comprising a second FET provided in a second conductive path that supplies power from the second power supply unit to a second load, wherein the intermediate conductive path is provided between a conductive path on the first load side of the first FET in the first conductive path and a conductive path on the second load side of the second FET in the second conductive path, the second FET has a second body diode, the anode of the second body diode is electrically connected to a conductive path on the second power supply unit side, the cathode of the second body diode is electrically connected to a conductive path on the second load side, and the control unit determines whether or not current is flowing through the second body diode when the second FET is controlled to be in the off state, and controls the second FET to be in the on state when it is determined that current is flowing through the second body diode.
4. The in-vehicle control device according to claim 3, further comprising a third FET provided in the intermediate conductive path, wherein the third FET has a third body diode, the anode of the third body diode is electrically connected to the conductive path on the second conductive path side, and the cathode of the third body diode is electrically connected to the conductive path on the first conductive path side, and the control unit determines whether or not current is flowing through the third body diode when the third FET is controlled to be in the off state, and controls the third FET to be in the on state when it is determined that current is flowing through the third body diode.
5. An in-vehicle control device according to claim 3 or 4, further comprising a fourth FET provided in the intermediate conductive path, wherein the fourth FET has a fourth body diode, the anode of the fourth body diode is electrically connected to the conductive path on the first conductive path side, and the cathode of the fourth body diode is electrically connected to the conductive path on the second conductive path side, and the control unit determines whether or not current is flowing through the fourth body diode when the fourth FET is controlled to be in the off state, and controls the fourth FET to be in the on state when it is determined that current is flowing through the fourth body diode.
6. The in-vehicle control device according to any one of claims 1 to 4, wherein the first load is controlled to be in an operating state and a stopped state, and the control unit determines whether or not current is flowing through the first body diode when it determines that the first load is in an operating state and the first FET is controlled to be in an off state, determines whether or not current is flowing through the first body diode when it determines that the first FET is controlled to be in an off state, and controls the first FET to be in an on state when it determines that current is flowing through the first body diode.