Control device power circuit

Abstract

To provide a power source circuit for stepping down a battery voltage and supplying DC voltage to a control device including a microcomputer such that, even if output voltage from a step-down circuit increases due to a failure in the step-down circuit, operation of the microcomputer can be continued.SOLUTION: A power source circuit includes a step-down circuit 20, sensor power source circuits 30A, 30B and a microcomputer power source circuit 40 that generate power source voltage by receiving a power supply from the step-down circuit 20, switching circuits 32A, 32B, 42, and a failure detection circuit 50. When the step-down power source voltage stepped down by the step-down circuit exceeds a prescribed allowable voltage, the failure detection circuit determines that the step-down circuit has a failure, and drives the switching circuits to switch a power supply source for the microcomputer power source circuit, to the sensor power source circuits.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a power supply circuit for a control device. [Background technology]

[0002] As described in Patent Document 1, a power supply circuit is known in which a switching element and a coil are connected in sequence on a supply path of DC power to a control device, and a free-wheel circuit is connected to the connection point between the switching element and the coil. This power supply circuit is a step-down circuit that turns the switching element on and off to pass a current through the coil, step down the battery voltage, and output it to the control device. In this power supply circuit, the free-wheel circuit returns a current to the coil during the off period of the switching element, suppressing the generation of a high voltage due to the energy stored in the coil.

[0003] Furthermore, the power supply circuit described in Patent Document 1 is provided with a fault detection circuit that detects an open circuit fault in the free-wheel circuit. When the fault detection circuit detects an open circuit fault in the free-wheel circuit, the on / off state of the switching element is controlled so that the output voltage from the coil becomes a third voltage that is higher than a second voltage under normal conditions and lower than a first voltage that is the battery voltage. Therefore, even if an open circuit fault occurs in the free-wheel circuit, power supply from the step-down circuit to the control device continues, and the control device can safely stop operating during that period. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6539201 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the control device described in Patent Document 1 includes a sensor that detects the state of the controlled object, and a microcomputer (hereinafter, referred to as a microcomputer) that calculates the control amount based on the detection signal from the sensor. If the power supply voltage falls outside the specified voltage range, the protection circuit of the microcomputer is activated and the microcomputer stops operating. Therefore, if power is supplied to the microcomputer from the power supply circuit, i.e., the step-down circuit, the microcomputer may stop operating when the return circuit is disconnected.

[0006] In other words, the microcomputer operates by receiving power from a microcomputer power supply circuit that generates a constant microcomputer power supply voltage, but if the return circuit breaks and the DC voltage supplied from the step-down circuit rises, the microcomputer power supply circuit is unable to properly control the output voltage. Therefore, if the return circuit breaks, the microcomputer power supply voltage rises above the specified voltage range, causing the microcomputer to stop operating. Also, if a switching element in the step-down power supply circuit shorts out, the battery voltage is output, causing the microcomputer power supply voltage to rise above the specified voltage range and causing the microcomputer to stop operating. If the microcomputer stops operating in this way, it will no longer be able to continue control and safely stop the control device.

[0007] One aspect of the present disclosure aims to provide a power supply circuit that steps down battery voltage and supplies DC voltage to a control device including a microcontroller, which enables the microcontroller to continue operating even if the output voltage from the step-down circuit rises due to a failure of the step-down circuit. [Means for solving the problem]

[0008] A power supply circuit of a control device according to one embodiment of the present disclosure includes a step-down circuit (20), a sensor power supply circuit (30A, 30B), a microcomputer power supply circuit (40), a switching circuit (32A, 32B, 42), and a fault detection circuit (50).

[0009] Here, the step-down circuit is provided on a power supply path from the battery (12) to the control device (2) and configured to step down and output the battery voltage. The sensor power supply circuit is configured to receive power from the step-down circuit and generate a sensor power supply voltage for driving the sensors (6A, 6B, ...) provided in the control device.

[0010] The microcomputer power supply circuit is configured to receive power from the step-down circuit and generate a microcomputer power supply voltage for driving a microcomputer (8) provided in the control device. The switching circuit is configured to be able to switch the power supply source to the microcomputer power supply circuit from the step-down circuit to the sensor power supply circuit.

[0011] The fault detection circuit is configured to determine that the step-down circuit has failed when the stepped-down power supply voltage stepped down by the step-down circuit exceeds a predetermined allowable voltage, and to drive the switching circuit to switch the power supply source to the microcontroller power supply circuit to the sensor power supply circuit.

[0012] Therefore, if the step-down circuit fails and outputs a voltage higher than the allowable voltage, such as the battery voltage, the failure detection circuit detects this and drives the switching circuit to output the sensor power supply voltage generated in the sensor power supply circuit to the microcontroller power supply circuit.

[0013] Therefore, if the step-down circuit fails, the input voltage to the microcontroller power supply circuit is quickly switched from the high voltage output from the step-down circuit to the sensor power supply voltage generated by the sensor power supply circuit, allowing the microcontroller power supply circuit to continue generating the microcontroller power supply voltage.

[0014] Therefore, according to the power supply circuit of the control device disclosed herein, even if the step-down circuit fails, the control operation by the microcomputer can be continued and fail-safe control, etc. can be implemented in the event of a failure. [Brief description of the drawings]

[0015] [Figure 1] 1 is a block diagram showing an overall configuration of a power supply circuit of a control device according to an embodiment. [Diagram 2] 5 is a time chart showing a fault determination of a step-down circuit and a switching operation of a changeover switch. [Diagram 3] FIG. 13 is a block diagram illustrating a configuration of a power supply circuit according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. [Embodiment] As shown in FIG. 1, a control device 2 of this embodiment controls, for example, an engine mounted on a vehicle as a controlled object 4, and includes a plurality of sensors 6A, 6B . . . that detect the operating state of the controlled object 4.

[0017] The multiple sensors 6A, 6B... are sensors for detecting the condition of the engine and vehicle, which are the object of control 4, such as a crank angle sensor and a cam sensor that detect the rotation angle of the engine, an accelerator sensor that detects the amount of depression of the accelerator pedal, and a temperature sensor that detects the coolant temperature.

[0018] The control device 2 also includes a microcomputer 8, as the microcomputer of the present disclosure, that calculates a control amount for the controlled object 4 based on detection signals from the multiple sensors 6A, 6B, ..., and outputs the control amount to a drive device for the controlled object 4. Examples of this drive device include an injection pump that injects fuel into each cylinder of the engine, an ignition device that ignites a spark plug provided in each cylinder of the engine, etc.

[0019] The microcomputer 8 includes a CPU, a ROM, a RAM, etc., and functions as a control circuit for the controlled object 4. The microcomputer 8 may malfunction if the power supply voltage falls outside a specified voltage range, so the microcomputer 8 is provided with a voltage monitoring unit 9 that monitors its own power supply voltage. If the power supply voltage falls outside the specified voltage range, the voltage monitoring unit 9 resets the microcomputer 8 to stop the control operation.

[0020] Next, the power supply circuit 10 generates a predetermined power supply voltage for operating the above-mentioned plurality of sensors 6A, 6B, etc. and the microcomputer 8, and similarly to the above-mentioned Patent Document 1, includes a step-down circuit 20 that steps down the supply voltage from the battery 12, i.e., the battery voltage VB. Note that the battery voltage VB is not constant, but fluctuates within a range of about 10V to 16V due to fluctuations in the load.

[0021] The step-down circuit 20 includes a switching circuit 22 and a coil 24 connected in series in this order from the battery 12 on a power supply path that supplies power from the battery 12 to the sensors 6A, 6B, . . . and the microcomputer 8.

[0022] In the step-down circuit 20 , a free-wheeling circuit 26 is connected to the connection point between the switching circuit 22 and the coil 24 , and a capacitor 28 is connected to the side of the coil 24 opposite to the switching circuit 22 .

[0023] The freewheel circuit 26 causes current to flow back to the coil 24 during the off period of the switching circuit 22, thereby preventing a high voltage from being generated due to the energy stored in the coil 24. For example, the freewheel circuit 26 is composed of a freewheel diode.

[0024] The capacitor 28 is a voltage smoothing capacitor that stabilizes the step-down power supply voltage V1 that is generated on the opposite side of the coil 24 from the switching circuit 22 when the switching circuit 22 is turned on and off.

[0025] In the step-down circuit 20, the step-down power supply voltage V1 generated by turning on and off the switching circuit 22 is set to DC 6V, which is about half the battery voltage VB.

[0026] The power supply circuit 10 also includes two sensor power supply circuits 30A, 30B which receive power from the step-down circuit 20 and generate a sensor power supply voltage V2 for driving the multiple sensors 6A, 6B . . .

[0027] These two sensor power supply circuits 30A, 30B are each configured with a series regulator such as a three-terminal regulator, and generate a constant DC voltage of, for example, 5V as sensor power supply voltage V2 which is lower than step-down power supply voltage V1.

[0028] The power supply circuit 10 also includes a microcomputer power supply circuit 40 that receives power from the step-down circuit 20 and generates a microcomputer power supply voltage V3 lower than the sensor power supply voltage V2, for example a constant DC voltage of 1.2V.

[0029] The microcomputer power supply circuit 40 is configured with a switching regulator so as to generate the microcomputer power supply voltage V3 with low loss from the stepped-down power supply voltage V1. The microcomputer power supply voltage V3 generated by the microcomputer power supply circuit 40 is supplied to the microcomputer 8.

[0030] Next, on the two power supply paths from the sensor power supply circuits 30A, 30B to the multiple sensors 6A, 6B..., first changeover switches 32A, 32B are provided which can switch the output destination of the sensor power supply voltage V2 from the sensors 6A, 6B... to the microcomputer power supply circuit 40 side.

[0031] The power supply circuit 10 is also provided with a second changeover switch 42 that switches the power supply path to the microcomputer power supply circuit 40. The second changeover switch 42 can switch the power supply path to the microcomputer power supply circuit 40 from a first path L1 that directly inputs the stepped-down power supply voltage V1 from the step-down circuit 20 to a second path L2 that inputs the sensor power supply voltage V2 via the first changeover switches 32A and 32B.

[0032] The first changeover switches 32A and 32B and the second changeover switch 42 correspond to the changeover circuits of the present disclosure, and in the present embodiment, are each configured by a semiconductor switch capable of switching the power supply path.

[0033] Specifically, for example, a switching element such as an FET is provided in each of the two branched power supply paths, and one of the switching elements is selectively turned on, and the switching elements are configured as semiconductor switches. The first changeover switches 32A, 32B and the second changeover switch 42 can also be configured using relays or the like.

[0034] The power supply circuit 10 is also provided with a failure detection circuit 50 that detects a failure of the step-down circuit 20 from the step-down power supply voltage V1. The failure detection circuit 50 includes a comparator 52 and a delay circuit .

[0035] 2, the comparator 52 compares the step-down power supply voltage V1 with a threshold voltage Vth1 for fault determination, and when the step-down power supply voltage V1 exceeds the threshold voltage Vth1, the output is inverted from low level to high level to generate a first switching signal TS1. Note that the threshold voltage Vth1 corresponds to the allowable voltage in the present disclosure.

[0036] In other words, when the free-wheel circuit 26 in the step-down circuit 20 has an open circuit failure and the free-wheel path is opened, or when the switching circuit 22 has a short circuit failure and is turned on, the stepped-down power supply voltage V1 output from the step-down circuit 20 rises to near the battery voltage VB. When the stepped-down power supply voltage V1 exceeds the threshold voltage Vth1, the comparator 52 determines that the step-down circuit 20 has failed, and generates a first switching signal TS1.

[0037] The first switching signal TS1 output from the comparator 52 is input to the first switches 32A and 32B. Then, the first switches 32A and 32B are switched from the sensor 6A, 6B side to the microcomputer power supply circuit 40 side at time t1 when the first switching signal TS1 rises from a low level to a high level.

[0038] Therefore, when the failure detection circuit 50 detects a failure in the step-down circuit 20, the sensor power supply voltage V2 generated by the sensor power supply circuits 30A, 30B is output to the second changeover switch .

[0039] On the other hand, the delay circuit 54 delays the rising edge of the first switch signal TS1 by a fixed delay time DT1. The delayed signal output from the delay circuit 54 is input to the second switch 42 as the second switch signal TS2.

[0040] Therefore, the second changeover switch 42 switches the power supply path to the microcomputer power supply circuit 40 from the first path L1 to the second path L2 at time t2, which is delayed by the delay time DT1 from time t1 shown in FIG.

[0041] Therefore, in the power supply circuit 10, when the step-down circuit 20 fails and the step-down power supply voltage V1 exceeds the threshold voltage Vth1 for determining an abnormality, the first changeover switches 32A, 32B and the second changeover switch 42 will be switched in order from the initial state shown in FIG.

[0042] After each switch has been changed over, sensor power supply voltage V2 generated by sensor power supply circuits 30A, 30B is supplied to microcomputer power supply circuit 40, allowing microcomputer power supply circuit 40 to continue generating microcomputer power supply voltage V3.

[0043] In addition, since the second switch 42 is switched with a delay of the delay time DT1 after the first switches 32A and 32B are switched, the power supply to the microcomputer power supply circuit 40 is not interrupted when each switch is switched from its initial state.

[0044] Therefore, there is no momentary interruption in the microcomputer power supply voltage V3 output from the microcomputer power supply circuit 40, and the microcomputer 8 is not reset and does not stop operating due to a momentary interruption in the microcomputer power supply voltage V3.

[0045] In addition, the microcomputer 8 receives a first switching signal TS1 from the failure detection circuit 50. Therefore, the microcomputer 8 detects that the step-down circuit 20 has failed by the first switching signal TS1, and performs a control process when the step-down circuit 20 has failed.

[0046] Specifically, when the step-down circuit 20 fails, the power supply to the sensors 6A, 6B... is cut off, so that, for example, the detection results by the sensors 6A, 6B... are fixed to a predetermined value required to continue the operation of the controlled object 4, and the operation of the controlled object 4 is continued. Then, the control amount is gradually reduced so as to stop the operation of the controlled object 4.

[0047] In the control process when the step-down circuit 20 fails, for example, the driver of the vehicle may be notified of the failure of the step-down circuit 20 and engine control may be performed to drive the vehicle to an evacuation site at a low speed. If the vehicle is an autonomous vehicle, in addition to the engine control, the failure of the step-down circuit 20 may be notified to the vehicle's driving control device, so that autonomous driving control may be performed to move the vehicle to the shoulder at a low speed.

[0048] [Variations] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0049] For example, in the above embodiment, the fault detection circuit 50 has been described as being composed of an electronic circuit including an operational amplifier, a delay circuit, etc., but the function of the fault detection circuit 50 may be realized by a program executed in the microcomputer 8.

[0050] In the above embodiment, it has been described that when the step-down circuit 20 fails, all of the power supply paths from the sensor power supply circuits 30A, 30B to the multiple sensors 6A, 6B . . . are switched to the microcomputer power supply circuit 40 side.

[0051] However, as shown in FIG. 3, a first changeover switch 32B may be provided in the power supply path from the sensor power supply circuit 30B to the sensor 6B of the two sensor power supply circuits 30A, 30B, so that the power supply path from the sensor power supply circuit 30A to the sensor 6A cannot be interrupted.

[0052] In this way, when the step-down circuit 20 fails, the sensor power supply voltage V2 generated by the sensor power supply circuit 30B can be supplied to the microcontroller power supply circuit 40, allowing the microcontroller 8 to continue controlling the control object 4 while allowing the sensor 6A to operate.

[0053] Therefore, in the event of a failure of the step-down circuit 20, the microcontroller 8 can control the controlled object 4 using the detection results from the sensor 6A, and as described above, the operation of the controlled object 4 can be continued without stopping the operation of the controlled object 4.

[0054] In this case, it is preferable that the power supply paths from the two sensor power supply circuits 30A, 30B to the multiple sensors 6A, 6B, etc., are provided with dual-system sensors 6A, 6B that are provided in duplicate for the control object 4 in order to ensure control redundancy.

[0055] In this case, the sensors 6A and 6B do not necessarily have to be the same, and may be sensors capable of detecting the same type of physical quantities, such as the engine rotation angle or temperature, for example, a crank sensor and a cam sensor, or an intake air temperature and a cooling water temperature.

[0056] In this way, when the step-down circuit 20 fails, not only can the microcontroller 8 be prevented from ceasing operation, but the microcontroller 8 can continue to control the controlled object 4 more appropriately.

[0057] A plurality of functions possessed by one component in the above embodiments may be realized by a plurality of components, or a single function possessed by one component may be realized by a plurality of components. A plurality of functions possessed by a plurality of components may be realized by a single component, or a single function realized by a plurality of components may be realized by a single component. A part of the configuration of the above embodiments may be omitted. At least a part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0058] The power supply circuit of the present disclosure may be realized as a control system including a sensor and a microcomputer. The function of the fault detection circuit 50 may be stored in a computer-readable non-transient tangible recording medium. In other words, the present disclosure may be realized in various forms, such as a power supply circuit, a control system, a program, a non-transient tangible recording medium such as a semiconductor memory having a program recorded thereon, a power supply control method, and the like. [Explanation of symbols]

[0059] 2...control device, 6A, 6B...sensor, 8...microcontroller, 10...power supply circuit, 12...battery, 20...step-down circuit, 30A, 30B...sensor power supply circuit, 32A, 32B...first changeover switch, 40...microcontroller power supply circuit, 42...second changeover switch, 50...fault detection circuit.

Claims

1. a step-down circuit (20) provided on a power supply path from the battery (12) to the control device (2) and configured to step down the battery voltage and output the stepped-down voltage; a sensor power supply circuit (30A, 30B) configured to receive power from the step-down circuit and generate a sensor power supply voltage for driving a sensor (6A, 6B, ...) provided in the control device; a microcomputer power supply circuit (40) configured to receive power from the step-down circuit and generate a microcomputer power supply voltage for driving a microcomputer (8) provided in the control device; a switching circuit (32A, 32B, 42) configured to be able to switch a power supply source to the microcomputer power supply circuit from the step-down circuit to the sensor power supply circuit; a failure detection circuit (50) configured to determine that the step-down circuit has failed when the step-down power supply voltage stepped down by the step-down circuit exceeds a predetermined allowable voltage, and to drive the switching circuit to switch the power supply source for the microcomputer power supply circuit to the sensor power supply circuit; A power supply circuit for a control device comprising:

2. 2. A power supply circuit for a control device according to claim 1, A plurality of the sensor power supply circuits are provided, The power supply circuit of the control device, wherein the fault detection circuit is configured to switch the power supply source so that one of the plurality of sensor power supply circuits becomes the power supply source for the microcontroller power supply circuit when it determines that the step-down circuit has failed.

3. 3. A power supply circuit for a control device according to claim 1, The switching circuit includes: a first changeover switch (32A, 32B) provided on a power supply path from the sensor power supply circuit to the sensor, the first changeover switch being capable of switching an output destination of the sensor power supply voltage from the sensor to the microcomputer power supply circuit; a second changeover switch (42) capable of changing a power supply path to the microcomputer power supply circuit from a first path (L1) through which the stepped-down power supply voltage is directly input from the step-down circuit to a second path (L2) through which the sensor power supply voltage is input from the sensor power supply circuit via the first changeover switch; Equipped with the fault detection circuit is configured to switch the first changeover switch to the microcomputer power supply circuit side when the step-down power supply voltage exceeds a predetermined allowable voltage, and to switch the second changeover switch from the step-down circuit side to the sensor power supply circuit side simultaneously with or after the first changeover switch is switched.

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