JP2011162147A - Vehicular power source supply device and vehicular control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of reducing an electric power loss generated in a vehicular power source supply device. <P>SOLUTION: The power source supply device 12 includes a plurality of step-down circuits 23a and 23b mutually different in a conversion efficiency characteristic to an output current value, and a control unit 28 switches the step-down circuits to be put in an electric continuous state with an ECU 13 in response to the output current value of the power source supply device 12. Practically, among the plurality of step-down circuits 23a and 23b, the circuit having the maximum conversion efficiency in the output current value then is selected and put in the electric continuous state with the ECU 13. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vehicle power supply device that steps down electric power supplied from a battery to a predetermined voltage level and supplies the electric load to an electric load, and a vehicle control device that includes the vehicle power supply device.

  In general, in a vehicle such as an automobile, various electric loads (in-vehicle devices such as various ECUs (electronic control units) and actuators) mounted on the vehicle are operated using electric power stored in a battery. However, since the electric power stored in the battery is limited, it is preferable to use this as efficiently as possible. Various techniques for realizing efficient power use have been proposed (see, for example, Patent Document 1).

JP 2004-161064 A

  When the power supplied from the battery is higher than the voltage required by the in-vehicle device, the power supplied from the battery is stepped down and supplied to the in-vehicle device. In order to eliminate the waste of battery power consumption, one of the important issues is how high power can be stepped down with this power supply device.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a technique capable of reducing power loss generated in a vehicle power supply device.

  The invention according to claim 1 is a vehicle power supply device that steps down the electric power supplied from the battery to a predetermined voltage level by a step-down circuit and supplies the electric load to an electric load, and has a plurality of conversion efficiency characteristics different from each other for an output current value. A step-down circuit, a switching unit that switches between each of the plurality of step-down circuits and the electric load to a conductive state or a non-conductive state, and any one of the plurality of step-down circuits selected, and the selected step-down circuit And a control means for controlling the switching means so as to make a conductive state between the electric load and the other voltage step-down circuit and the electric load, the control means, An output current value of the step-down circuit in conduction with the electric load is specified, and the step-down circuit having the maximum conversion efficiency at the output current value among the plurality of step-down circuits is brought into conduction with the electric load. Selecting as a step-down circuit to.

  The invention according to claim 2 is the vehicle power supply device according to claim 1, wherein the plurality of step-down circuits include a switching step-down circuit and a linear step-down circuit.

  The invention according to claim 3 is the vehicle power supply device according to claim 1 or 2, wherein the control means monitors whether or not an abnormality has occurred in the step-down circuit connected to the electric load, When an abnormality is detected, the step-down circuit in which the abnormality is detected and the electric load are brought into a non-conductive state, and one of the other step-down circuits and the electric load are brought into a conductive state. The step-down circuit that controls the switching means so that the conversion efficiency becomes maximum at the output current value among the remaining step-down circuits excluding the step-down circuit in which the abnormality is detected among the plurality of step-down circuits. Is selected as a step-down circuit to be brought into conduction with the electric load.

  A fourth aspect of the present invention is the vehicle power supply device according to any one of the first to third aspects, wherein the electric load is a plurality of ECUs.

  According to a fifth aspect of the present invention, there is provided a battery mounted on a vehicle, an electrical load mounted on the vehicle, and a vehicle that steps down power supplied from the battery to a predetermined voltage level by a step-down circuit and supplies the power to the electrical load A vehicle power supply device according to any one of claims 1 to 4, wherein the vehicle power supply device is a vehicle power supply device.

  According to the first to fifth aspects of the present invention, the plurality of step-down circuits having different conversion efficiency characteristics with respect to the output current value are provided, and the conversion efficiency in the output current value of the step-down circuit in conduction with the electric load among the plurality of step-down circuits Is selected as the step-down circuit to be brought into conduction with the electric load. Therefore, it is possible to always maintain high conversion efficiency even if the current consumption of the electric load changes, and it is possible to reduce power loss that occurs in the vehicle power supply device.

  In particular, according to the invention of claim 2, the plurality of step-down circuits include a switching step-down circuit and a linear step-down circuit. Although the switching step-down voltage circuit has a relatively high average conversion efficiency, the conversion efficiency changes depending on the output current value, and therefore the conversion efficiency is low in a part of the current value region. On the other hand, the linear step-down circuit has a relatively low average conversion efficiency, but realizes a stable conversion efficiency regardless of the output current value. Therefore, according to the configuration in which these two types of step-down circuits are switched, switching to a linear type step-down circuit is performed in a current value region where conversion efficiency is low in the switching type step-down circuit. Even if it fluctuates, high conversion efficiency can be maintained.

  In particular, according to the invention of claim 3, when an abnormality is detected in the step-down circuit that is in a conductive state with the electric load, the step-down circuit in which the abnormality is detected is not connected to the electric load. At the same time, the switching means is controlled so that any one of the other step-down circuits and the electrical load are in a conductive state, and thereafter, the remaining step-down circuits excluding the step-down circuits in which an abnormality is detected among the plurality of step-down circuits. Among the circuits, the step-down circuit having the maximum conversion efficiency at the output current value is selected as the step-down circuit to be brought into conduction with the electric load. According to this configuration, a fail-safe function is realized by a plurality of step-down circuits.

  In particular, according to the invention of claim 4, the vehicle power supply device supplies power to a plurality of ECUs. In other words, in a power supply apparatus shared by a plurality of ECUs, it is possible to always maintain a high conversion efficiency regardless of the total current consumption amount of the plurality of ECUs, so that a reduction in power loss can be effectively realized. .

It is a figure which shows the external appearance of the control apparatus for vehicles. It is a block diagram which shows the structure of the control apparatus for vehicles. It is a figure which shows typically the example of the conversion efficiency characteristic with respect to an output current value of the step-down circuit of a switching system. It is a figure which shows typically the example of the conversion efficiency characteristic with respect to an output current value of a linear step-down voltage circuit. It is a figure which shows typically the example of the conversion efficiency characteristic with respect to the output current value of a 1st step-down circuit and a 2nd step-down circuit. It is a figure which shows the flow of the switching control process which a control part performs.

<1. Vehicle Control Device>
A vehicle control device 1 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a diagram illustrating an appearance of the vehicle control device 1. FIG. 2 is a block diagram illustrating a configuration of the vehicle control device 1.

  The vehicle control device 1 includes a battery 11 serving as a power source and a plurality of ECUs 13 that operate by receiving power supply from the battery 11. The battery 11 is typically a lead storage battery, and is charged by an alternator (not shown) rotated by an engine of the vehicle and supplies electric power to an electric load such as an ECU 13 mounted on the vehicle. In addition, although the electromotive force of the battery 11 is not restrict | limited, suppose that the electromotive force of the battery 11 is 12V in the following description.

  In addition, the vehicle control device 1 supplies power supplied from the battery 11 to a predetermined voltage level (specifically, a supply object) by a step-down circuit (first step-down circuit 23a or second step-down circuit 23b). The power supply device (vehicle power supply device) 12 is supplied to a plurality of ECUs 13 by reducing the voltage level to a voltage level required by the ECU 13 and assuming that it is 5 V in the following description.

  The power supply device 12 supplies the electric power stepped down by the step-down circuit (the first step-down circuit 23a or the second step-down circuit 23b) to a plurality of (five in the example of FIG. 1) ECUs 13 via the branch circuit 25, respectively. Supply. That is, in the vehicle control device 1 according to this embodiment, the power supply device that supplies power to the ECU 13 is shared by the plurality of ECUs 13, and the power from the battery 11 is supplied as one power source. It is supplied to a plurality of ECUs 13 via the device 12.

  In principle, any combination of the plurality of ECUs 13 may be used. For example, an ECU (an engine control ECU, a body ECU (room lamp, door opening / closing, window opening / closing, etc.) mounted as standard It is preferable to combine ECUs to be controlled and air conditioner ECUs). This is because there is no waste if the standard ECUs are combined because they are always installed in vehicles of any grade.

  Further, as another combination method, it is also preferable to combine ECUs connected to a harness (instrument panel harness or the like) that is close in mounting position and used in the same part. According to this configuration, the length of the electric wire does not increase unnecessarily. For example, in the case of a vehicle in which three types of ECUs such as a suspension control ECU, a power management ECU, and a driving support ECU are mounted in close positions, the combination of these ECUs can simplify the configuration without extending the wire length. Realized.

<2. Power supply device>
The configuration of the power supply device 12 will be specifically described with continued reference to FIG.

  The power supply device 12 includes a branch circuit 21 having one end connected to the battery 11 and the other end branched into a plurality (in the example of FIG. 2, two branches).

  The first step-down circuit 23a is connected to one (first circuit 211a) of the branch destinations 211a and 211b of the branch circuit 21, and the second step-down circuit 23b is connected to the other (second circuit 211b). The voltage of the battery 11 is input as an input voltage to each step-down circuit 23a, 23b. An input protection circuit 22 that is a functional unit for preventing the step-down circuits 23a and 23b from being damaged by static electricity is connected in series between the battery 11 and the step-down circuits 23a and 23b.

  Each step-down circuit 23a, 23b steps down the 12V power supplied from the battery 11 to 5V, which is a voltage level required by the ECU 13. The step-down circuits 23a and 23b will be described in detail later.

  Each step-down circuit 23a, 23b is connected to a branch circuit 25 branched into a plurality through a switching circuit 24. The ECU 13 is connected to each of the plurality of branch destinations 251 of the branch circuit 25, and each branch destination 251 functions as a supply line that supplies power from the battery 11 to any of the plurality of ECUs 13.

  Each supply line 251 is provided with a switch circuit 26 and a current detection circuit 27. The switch circuit 26 is configured by, for example, a relay switch, and switches on / off the voltage to the ECU 13 in accordance with an instruction from a control unit 28 described later. The current detection circuit 27 is configured by, for example, a shunt resistor connected in series to the ECU 13, and a control unit 28 described later measures the current consumption amount of the ECU 13 by detecting a voltage drop amount of the shunt resistor. . The switch circuit 26 and the current detection circuit 27 may be configured by an intelligent power switch (IPS).

  The switching circuit 24 is in a conductive state or a non-conductive state between each of the plurality of step-down circuits 23a and 23b and the branch circuit 25 (that is, between each of the plurality of step-down circuits 23a and 23b and the plurality of ECUs 13). Switch. For example, when the switching circuit 24 is in a conducting state between the first step-down circuit 23a and the branch circuit 25 and is in a non-conducting state between the second step-down circuit 23b and the branch circuit 25, 12V output from the battery 11 is obtained. Is stepped down to 5 V by the first step-down circuit 23 a and supplied to the plurality of ECUs 13 through the branch circuit 25. On the other hand, when the switching circuit 24 is in a conductive state between the second step-down circuit 23b and the branch circuit 25 and is in a non-conductive state between the first step-down circuit 23a and the branch circuit 25, the 12V output from the battery 11 is obtained. Is stepped down to 5V by the second step-down circuit 23b and supplied to the plurality of ECUs 13 through the branch circuit 25.

  The control unit 28 controls the switch circuit 26 provided in each supply line 251. Specifically, a control signal is acquired from the CAN via the CAN / IF circuit 29, and the switch circuit 26 provided in each supply line 251 is independently controlled based on the acquired control signal. Specifically, the control signal is an IG signal (signal generated when the ignition key is turned to the position of IG-ON (ignition on)) or an ACC signal (ignition key is ACC (accessory)). The signal emitted when it is turned to the position of For each type of ECU 13, it is individually defined which control signal to receive power supply when received. For example, when the IG signal is acquired from CAN, the control unit 28 turns on the relay switch of the switch circuit 26 connected to the engine control ECU. As a result, power supply to the engine control ECU is started.

  Further, the control unit 28 controls the switching circuit 24 to switch the step-down circuit that is brought into conduction with the plurality of ECUs 13 among the plurality of step-down circuits 23 a and 23 b. Specifically, one of the plurality of step-down circuits 23a and 23b is selected, and the conductive state is established between the selected step-down circuit and the branch circuit 25 (that is, between the selected step-down circuit and the plurality of ECUs 13). Then, the switching circuit 24 is controlled so as to make a non-conducting state between the other step-down circuit and the branch circuit 25. This control mode will be described in more detail later.

<3. Buck circuit>
The plurality of step-down circuits 23a and 23b included in the power supply device 12 will be described.

  As a general step-down circuit, a switching step-down circuit (so-called “switching regulator”) that adjusts an output voltage by controlling the on time and off time using a switching element, a power source and an electric load A linear step-down circuit that adjusts an output voltage by consuming an input voltage using an on-resistance of the switching element using a voltage adjusting switching element provided in series between the two (so-called “linear regulator”) ")It has been known.

  Incidentally, the conversion efficiency characteristic for the output current value of the step-down circuit varies depending on the circuit configuration of the step-down circuit. FIGS. 3 and 4 schematically show changes in conversion efficiency with respect to output current values of various step-down circuits. FIG. 3A and FIG. 3B schematically show the conversion efficiency characteristics of the switching type step-down circuit. FIG. 4 schematically shows the conversion efficiency characteristics of a linear step-down circuit.

  The switching efficiency of the switching step-down circuit varies depending on the output current value. However, even if the switching method is the same, the conversion efficiency characteristics will be different if the devices used are different. For example, in the case of the switching step-down voltage circuit illustrated in FIG. 3A, although a relatively high conversion efficiency is realized in a wide current value region, the conversion efficiency rapidly increases in a region where the current value is small (near 0 A to 20 mA). It is falling. On the other hand, in the case of the switching type step-down circuit illustrated in FIG. 3B, the conversion efficiency is also reduced in a region where the current value is small, but the degree of decrease is lower than that of the step-down circuit illustrated in FIG. Is moderate.

  On the other hand, the linear step-down circuit achieves stable conversion efficiency regardless of the output current value. For example, in the case of the linear step-down circuit illustrated in FIG. 4, a constant (about 41.6%) conversion efficiency value is realized regardless of the output current value.

  As described above, the power supply device 12 according to this embodiment includes two step-down circuits 23a and 23b. These step-down circuits 23a and 23b are step-down circuits having different conversion efficiency characteristics with respect to the output current value. What kind of conversion efficiency characteristics the step-down circuit is combined is arbitrary. For example, a switching type step-down circuit having the conversion efficiency characteristic illustrated in FIG. 3A may be combined with a linear type step-down circuit having the conversion efficiency characteristic illustrated in FIG. Further, the switching step-down voltage circuit having the conversion efficiency characteristic illustrated in FIG. 3B and the linear step-down circuit having the conversion efficiency characteristic illustrated in FIG. 4 may be combined. Further, the switching type step-down circuit having the conversion efficiency characteristic illustrated in FIG. 3A and the switching type step-down circuit having the conversion efficiency characteristic illustrated in FIG. 3B may be combined.

<4. Step-down circuit switching control>
<4-1. Control mode>
As described above, the control unit 28 controls the switching circuit 24 to switch the step-down circuit that is brought into conduction with the branch circuit 25 among the plurality of step-down circuits 23a and 23b. This control mode will be specifically described.

  As will be described below, the control unit 28 controls the switching of the step-down circuit based on the total amount of current consumed by each of the plurality of ECUs 13 connected to the power supply device 12 (total current consumption), The switching circuit 24 is controlled while using two types of control modes together with the switching control of the step-down circuit based on the detection.

<A. Switching control of step-down circuit based on total current consumption>
The control unit 28 constantly measures the amount of current consumed by each ECU 13 (that is, the amount of output current to each ECU 13) by detecting the voltage drop amount of the shunt resistor of each current detection circuit 27. The switching circuit 24 is controlled based on the measured value.

  This control mode will be described more specifically. First, the control unit 28 sums up the measured values obtained from the current detection circuits 27 provided in the supply lines 251. The value obtained here is the total current consumption of the plurality of ECUs 13 receiving power from the power supply device 12, that is, the step-down circuit (first step-down circuit 23a or The amount of current output from the second step-down circuit 23b). The control unit 28 acquires the obtained value as “output current value P”. However, the control part 28 shall acquire the value of the output current value P regularly or irregularly.

  Subsequently, the control unit 28 is a step-down circuit (optimal step-down circuit) that should make the step-down circuit having the maximum conversion efficiency at the obtained output current value P among the plurality of step-down circuits 23a and 23b conductive with the branch circuit 25. Circuit). Then, the switching circuit 24 is controlled so that the step-down circuit selected as the optimum step-down circuit and the branch circuit 25 are in a conductive state and the other step-down circuit and the branch circuit 25 are in a non-conductive state.

<Control example 1>
For example, the first step-down circuit 23a is a switching type step-down circuit having the conversion efficiency characteristic illustrated in FIG. 3A, and the second step-down circuit 23b is a linear type having the conversion efficiency characteristic illustrated in FIG. Suppose that it is a step-down circuit.

  In this case, as shown in FIG. 5, the conversion efficiency of the first step-down circuit 23a is zero when the output current value is zero, and gradually increases as the output current value increases. On the other hand, the conversion efficiency of the second step-down circuit 23b is always a constant value regardless of the output current value. Accordingly, when the output current value P is small, the second step-down circuit 23b achieves higher conversion efficiency than the first step-down circuit 23a, and the output current is higher than a certain value (hereinafter referred to as “reverse current value Q”). Conversely, when the value P increases, the first step-down circuit 23a realizes higher conversion efficiency than the second step-down circuit 23b. In the example of FIG. 5, the reverse current value Q appears in the vicinity of 20 mA.

  The control unit 28 stores in advance a reverse current value Q calculated based on the conversion efficiency characteristics of the step-down circuits 23a and 23b, and the output current value P is defined based on the reverse current value Q. If it is greater than the first threshold, the first step-down circuit 23a is selected as the optimum step-down circuit. Therefore, in this case, the control unit 28 controls the switching circuit 24 so that the second step-down circuit 23b and the branch circuit 25 are turned off and the first step-down circuit 23a and the branch circuit 25 are turned on. However, the first threshold value is slightly larger than the reverse current value Q (for example, a value of the reverse current value Q + 2 mA).

  Further, when the output current value P is smaller than the second threshold defined based on the reverse current value Q, the control unit 28 selects the second step-down circuit 23b as the optimum step-down circuit. Therefore, in this case, the control unit 28 controls the switching circuit 24 so that the first step-down circuit 23a and the branch circuit 25 are turned off and the second step-down circuit 23b and the branch circuit 25 are turned on. However, the second threshold is a value slightly smaller than the reverse current value Q (for example, a value of about the reverse current value Q-2 mA).

<Control example 2>
Further, for example, the first step-down circuit 23a is a switching step-down circuit having the conversion efficiency characteristic illustrated in FIG. 3A, and the second step-down circuit 23b has the conversion efficiency characteristic illustrated in FIG. 3B. Suppose that the switching step-down voltage circuit shown in FIG.

  In this case, the conversion efficiency of the first step-down voltage circuit 23a rapidly decreases in a region where the current value is small (near 0 A to 20 mA). On the other hand, the conversion efficiency of the second step-down circuit 23b is also reduced in this region, but the degree of decrease is moderate compared to the first step-down circuit 23a. Therefore, when the output current value P is small, the second step-down circuit 23b achieves higher conversion efficiency than the first step-down circuit 23a, and conversely, when the output current value P becomes larger than a certain value, The first step-down circuit 23a realizes higher conversion efficiency than the second step-down circuit 23b. Referring to FIGS. 3A and 3B, when the output current value P is, for example, 0.5 A, the conversion efficiency of the first step-down circuit 23a is about 90%, and the conversion efficiency of the second step-down circuit 23b is It turns out that it becomes about 87%. It can also be seen that when the output current value P is 0.01 A, the conversion efficiency of the first step-down circuit 23a is about 30% and the conversion efficiency of the second step-down circuit 23b is about 72%. Therefore, it can be seen that the reverse current value appears between 0.01 A and 0.5 A.

  The control unit 28 stores in advance a reverse current value calculated based on the conversion efficiency characteristics of the step-down circuits 23a and 23b, and the output current value P is defined based on the reverse current value. When it is larger than the threshold (for example, when the output current value P is 0.5 A), the first step-down circuit 23a is selected as the optimum step-down circuit. Therefore, in this case, the control unit 28 controls the switching circuit 24 so that the second step-down circuit 23b and the branch circuit 25 are turned off and the first step-down circuit 23a and the branch circuit 25 are turned on. Here, however, the first threshold value is a value slightly larger than the reverse current value (for example, a value of the reverse current value + 2 mA).

  Further, when the output current value P is smaller than the second threshold defined based on the reverse current value (for example, when the output current value P is 0.01 A), the control unit 28 sets the second step-down circuit. 23b is selected as the optimum step-down circuit. Therefore, in this case, the control unit 28 controls the switching circuit 24 so that the first step-down circuit 23a and the branch circuit 25 are turned off and the second step-down circuit 23b and the branch circuit 25 are turned on. However, also here, the second threshold is a value slightly smaller than the reverse current value (for example, a value of about the reverse current value −2 mA).

<B. Switching control of step-down circuit based on abnormality detection>
The controller 28 constantly monitors whether each of the plurality of step-down circuits 23a and 23b mounted on the power supply device 12 is operating normally. Specifically, the output voltage of each step-down circuit 23a, 23b is always detected, and when the output voltage becomes + 10% or more or −10% or less of the target output voltage, there is an abnormality in the step-down circuit. Judge that it occurred. The control unit 28 controls the switching circuit 24 based on whether or not an abnormality has occurred in each step-down circuit 23a, 23b.

  Specifically, when an abnormality is detected in the step-down circuit that is in conduction with the branch circuit 25, the control unit 28 causes the step-down circuit and the branch circuit 25 in which abnormality is detected to be in a non-conduction state, The switching circuit 24 is controlled so that any one of the other step-down circuits and the branch circuit 25 are in a conductive state. In this embodiment, since the number of step-down circuits 23a and 23b mounted on the power supply device 12 is two, when an abnormality is detected in one step-down circuit, the other step-down circuit is automatically set. The circuit is brought into conduction with the branch circuit 25. When three or more step-down circuits are mounted on the power supply device 12 and an abnormality is detected in any one of the step-down circuits, an abnormality is detected among the plurality of step-down circuits mounted on the power supply device 12. Any of the remaining step-down circuits excluding the step-down circuit in which is detected (specifically, the step-down circuit having the maximum conversion efficiency at the output current value P at that time) is newly selected as the optimum step-down circuit, The selected step-down circuit is brought into conduction with the branch circuit 25.

  Note that the control unit 28 prohibits the selection of the step-down circuit in which the abnormality is detected as the optimum step-down circuit thereafter. In other words, the control unit 28 selects the optimum step-down circuit from the remaining step-down circuits excluding the step-down circuit in which an abnormality is detected among the plurality of step-down circuits. Specifically, among the remaining voltage step-down circuits, the voltage step-down circuit having the maximum conversion efficiency at the current output current value P is selected as the optimum voltage step-down circuit. However, in this embodiment, since the number of step-down circuits 23a and 23b mounted on the power supply device 12 is two, when an abnormality is detected in any one of the step-down circuits, The other step-down circuit is always kept in conduction with the branch circuit 25. That is, thereafter, switching control of the step-down circuit based on the total current consumption amount is not performed, and the step-down circuit in which no abnormality has occurred regardless of the total current consumption amount is always kept in conduction with the branch circuit 25. Become.

<4-2. Process flow>
The flow of the switching control process performed by the control unit 28 will be described with reference to FIG. FIG. 6 is a diagram showing the flow of the processing. In the following description, the first step-down circuit 23a is a switching step-down circuit having the conversion efficiency characteristic illustrated in FIG. 3A, and the second step-down circuit 23b is the conversion efficiency characteristic illustrated in FIG. (Refer to FIG. 5).

  As described above, the control unit 28 constantly monitors whether the step-down circuits 23a and 23b are operating normally. Here, when an abnormality is detected in the step-down circuit that is in conduction with the branch circuit 25 (YES in step S11), the control unit 28 brings the step-down circuit and the branch circuit 25 in which abnormality is detected into a non-conduction state, The switching circuit 24 is controlled so that the other step-down circuit is brought into conduction with the branch circuit 25 (step S12). For example, when an abnormality is detected in the first step-down circuit 23a, the control unit 28 makes the first step-down circuit 23a non-conductive with the branch circuit 25 and makes the second step-down circuit 23b conductive with the branch circuit 25. The switching circuit 24 is controlled.

  When an abnormality is detected in the step-down circuit, the control unit 28 thereafter prohibits selection of the step-down circuit in which the abnormality is detected as the optimum step-down circuit, and an abnormality is detected among the plurality of step-down circuits 23a and 23b. The optimum step-down circuit is selected from the remaining step-down circuits excluding the selected step-down circuit. However, in this embodiment, since the number of step-down circuits 23a and 23b mounted on the power supply device 12 is two, when an abnormality is detected in one step-down circuit, the subsequent steps are always performed. The other step-down circuit is kept in conduction with the branch circuit 25. That is, thereafter, the step-down circuit switching control based on the total current consumption (steps S13 to S17) is not performed, and the other step-down circuit is always kept in conduction with the branch circuit 25 regardless of the total current consumption. become.

  When no abnormality is detected in the step-down circuit that is in conduction with the branch circuit 25 (NO in step S11), the control unit 28 subsequently performs switching control of the step-down circuit based on the total current consumption (steps S13 to S13). Step S17).

  Switching control of the step-down circuit based on the total current consumption is performed as follows. First, it is determined whether the step-down circuit that is in conduction with the branch circuit 25 is the first step-down circuit 23a or the second step-down circuit 23b (step S13).

  When the step-down circuit in conduction with the branch circuit 25 is the second step-down circuit 23b (YES in step S13), the control unit 28 determines whether or not the output current value P is larger than the first threshold value (step S14). ). However, as described above, the first threshold is a value slightly larger than the reverse current value Q (for example, a value of the reverse current value Q + 2 mA).

  When the output current value P is not larger than the first threshold (NO in step S14), the control unit 28 selects the second step-down circuit 23b as the optimum step-down circuit. Therefore, in this case, the step-down circuit is not switched. The situation where the output current value P does not become larger than the first threshold value can be considered, for example, when all of the plurality of ECUs 13 connected to the power supply device 12 are in the sleep mode. In such a case, the second step-down circuit 23b is brought into conduction with the branch circuit 25, and the power from the battery 11 is stepped down with high conversion efficiency by the linear second step-down circuit 23b (see FIG. 5). ).

  On the other hand, when the output current value P is larger than the first threshold (YES in step S14), the control unit 28 selects the first step-down circuit 23a as the optimum step-down circuit and switches the step-down circuit (step S15). That is, the switching circuit 24 is controlled so that the second step-down circuit 23b is in a non-conducting state with the branch circuit 25 and the first step-down circuit 23a is in a conductive state with the branch circuit 25. The situation in which the output current value P is larger than the first threshold is, for example, that at least one ECU 13 has transitioned to the normal mode from the state in which all of the plurality of ECUs 13 connected to the power supply device 12 are in the sleep mode. There are cases. In such a case, the first step-down circuit 23a is brought into conduction with the branch circuit 25 in place of the second step-down circuit 23b, and the power from the battery 11 is stepped down with high conversion efficiency by the switching type first step-down circuit 23a. (See FIG. 5).

  For example, there may be a plurality of modes with different power consumption in the normal mode. The same applies to the sleep mode. Therefore, for example, when one ECU 13 transitions from the state where all of the plurality of ECUs 13 connected to the power supply device 12 are in the sleep mode to the first normal mode where the power consumption is relatively low, the output current It may be assumed that the value P is not less than the reverse current value Q and not more than the first threshold value. In this case, the control unit 28 keeps the second step-down circuit 23b in conduction with the branch circuit 25 and does not switch the step-down circuit. That is, only in such a case, the step-down circuit having the maximum conversion efficiency at the output current value P is not brought into conduction with the branch circuit 25. However, for example, the ECU 13 in the first normal mode with relatively low power consumption further shifts to the second normal mode with high power consumption (for example, other ECUs 13 in the sleep mode are in the first mode). When the output current value P becomes larger than the first threshold value after the transition to the normal mode, the control unit 28 switches the step-down circuit to bring the first step-down circuit 23a into a conductive state with the branch circuit 25. That is, the step-down circuit having the maximum conversion efficiency at the output current value P is brought into conduction with the branch circuit 25.

  When the step-down circuit connected to the branch circuit 25 is not the second step-down circuit 23b (NO in step S13), that is, when the step-down circuit connected to the branch circuit 25 is the first step-down circuit 23a, the control unit 28 determines whether or not the output current value P is smaller than the second threshold value (step S16). However, as described above, the second threshold value is slightly smaller than the reverse current value Q (for example, a value of about the reverse current value Q-2 mA).

  When the output current value P is not smaller than the second threshold (NO in step S16), the control unit 28 selects the first step-down circuit 23a as the optimum step-down circuit. Therefore, in this case, the step-down circuit is not switched. The situation where the output current value P does not become smaller than the second threshold value may be a case where at least one ECU 13 among the plurality of ECUs 13 connected to the power supply device 12 is in the normal mode. In such a case, the first step-down circuit 23a is brought into conduction with the branch circuit 25, and the power from the battery 11 is stepped down with high conversion efficiency by the switching-type first step-down circuit 23a (see FIG. 5). ).

  On the other hand, when the output current value P is smaller than the second threshold (YES in step S16), the control unit 28 selects the second step-down circuit 23b as the optimum step-down circuit and switches the step-down circuit (step S17). That is, the switching circuit 24 is controlled so that the first step-down voltage circuit 23a is in a non-conductive state with the branch circuit 25 and the second step-down circuit 23b is in a conductive state with the branch circuit 25. A situation in which the output current value P is smaller than the second threshold value may be, for example, a case where all of the plurality of ECUs 13 connected to the power supply device 12 transition to the sleep mode. In such a case, the second step-down circuit 23b is connected to the branch circuit 25 in place of the first step-down circuit 23a, and the power from the battery 11 is stepped down with high conversion efficiency by the linear second step-down circuit 23b. (See FIG. 5).

  As described above, a value slightly larger than the reverse current value Q is used as the first threshold, and a value slightly smaller than the reverse current value Q is used as the second threshold (having hysteresis). Thus, a stable switching operation can be performed without being affected by noise.

<5. effect>
The power supply device 12 according to the above embodiment includes a plurality of step-down circuits 23a and 23b having different conversion efficiency characteristics with respect to the output current value P, and the control unit 28 corresponds to the total current consumption amount of the plurality of ECUs 13. The step-down circuit to be brought into conduction with the branch circuit 25 is switched. Specifically, the control unit 28 specifies the output current value P of the step-down circuit that is in conduction with the branch circuit 25, and in the specified output current value P among the plurality of step-down circuits 23a and 23b. The step-down circuit that maximizes the conversion efficiency is selected as the step-down circuit to be brought into conduction with the branch circuit 25. Therefore, even if the total current consumption of the plurality of ECUs 13 changes, it is possible to always maintain high conversion efficiency, and to reduce power loss that occurs in the power supply device 12.

  In particular, the plurality of step-down circuits 23a and 23b included in the power supply device 12 according to the above-described embodiment may include step-down circuits of different types. For example, the first step-down circuit 23a can be a switching step-down circuit, and the second step-down circuit 23b can be a linear step-down circuit. Although the switching step-down voltage circuit has a relatively high average conversion efficiency, the conversion efficiency varies depending on the output current value, so that the conversion efficiency is low in some current value regions (see FIG. 3). On the other hand, the linear step-down circuit achieves stable conversion efficiency regardless of the output current value, although the average conversion efficiency is relatively low (see FIG. 4). Therefore, according to the configuration in which these two types of step-down circuits are switched, the region of the output current value P in which the conversion efficiency is low in the switching type step-down circuit (current value region of 0 ≦ P ≦ Q in the example of FIG. 5). Therefore, even if the total current consumption of the plurality of ECUs 13 fluctuates, high conversion efficiency can be maintained.

  Further, according to the power supply device 12 according to the above-described embodiment, when an abnormality is detected in the step-down circuit in conduction with the branch circuit 25, the control unit 28 branches the step-down circuit in which the abnormality is detected. The switching circuit 24 is controlled so as to make the other voltage-lowering circuit non-conductive with the branch circuit 25 while making the other voltage-lowering circuit conductive with the circuit 25, and the voltage-lowering circuit in which the abnormality is detected is thereafter selected as the optimum voltage-lowering circuit. Is prohibited. That is, the step-down circuit in which the abnormality is detected is not selected as the optimum step-down circuit thereafter. According to this configuration, a fail-safe function is realized by the plurality of step-down circuits 23a and 23b.

  The power supply device 12 according to the above embodiment is configured to supply power to the plurality of ECUs 13. That is, in the power supply device 12 that is shared by the plurality of ECUs 13, it is possible to always maintain high conversion efficiency regardless of the total current consumption of the plurality of ECUs 13, thereby effectively reducing power loss. it can.

  Further, according to the configuration in which the power supply devices that supply power to the plurality of ECUs 13 are shared, if the power supply device breaks down, all the ECUs 13 are stopped and have a great influence. In such a power supply device 12, since the fail-safe function is realized by the plurality of step-down circuits 23a and 23b, the occurrence of enormous damage is prevented in advance.

  When a plurality of step-down circuits are mounted just to realize the fail-safe function, the other step-down circuit remains unused unless one of the step-down circuits breaks down, but the power supply according to the above embodiment In the device 12, since the step-down circuits 23a and 23b are switched and used according to the output current value P, all the step-down circuits 23a and 23b mounted on the power supply device 12 can be used without waste. In addition, it is possible to obtain the effect of reducing the power loss generated in the power supply device 12.

<6. Modification>
In the above embodiment, the number of step-down circuits mounted on the power supply device 12 is two, but three or more step-down circuits may be mounted. When the control unit 28 detects an abnormality in any one of the step-down circuits when the power supply apparatus 12 has three or more step-down circuits, as described above, the control unit 28 thereafter supplies power. The optimum step-down circuit is selected from the remaining step-down circuits excluding the step-down circuit in which an abnormality is detected among the plurality of step-down circuits mounted on the device 12. Specifically, among the remaining voltage step-down circuits, the voltage step-down circuit having the maximum conversion efficiency at the current output current value P is selected as the optimum voltage step-down circuit. That is, switching control of the step-down circuit based on the total current consumption is performed among the remaining plurality of step-down circuits.

  In the above embodiment, a plurality of ECUs 13 are connected to the power supply device 12, but the number of connected ECUs 13 may be one. Further, the electric load that receives the power supply from the battery 11 via the power supply device 12 is not necessarily the ECU 13.

  In the above-described embodiment, the first threshold value that is slightly larger than the reverse current value Q and the reverse current value Q are used as threshold values when switching the plurality of step-down circuits 23a and 23b. Although the second threshold value, which is a slightly smaller value, is used, the reverse current value Q may be used as it is as a threshold value when switching.

1 vehicle control device 11 battery 12 power supply device 13 ECU
23a First step-down circuit 23b Second step-down circuit 24 Switching circuit 26 Switch circuit 27 Current detection circuit 28 Control unit

Claims (5)

A vehicle power supply device that steps down power supplied from a battery to a predetermined voltage level by a step-down circuit and supplies the electric load to an electric load
A plurality of step-down circuits having different conversion efficiency characteristics for output current values, and
Switching means for switching between each of the plurality of step-down circuits and the electric load to a conductive state or a non-conductive state;
Selecting any one of the plurality of step-down circuits, bringing the selected step-down circuit and the electric load into a conductive state, and bringing the other step-down circuits and the electric load into a non-conductive state; Control means for controlling the switching means;
With
The control means is
The output current value of the step-down circuit in conduction with the electrical load is specified, and the step-down circuit having the maximum conversion efficiency at the output current value among the plurality of step-down circuits is to be brought into conduction with the electric load. Vehicle power supply device selected as a circuit. The vehicle power supply device according to claim 1,
In the plurality of step-down circuits,
A vehicle power supply device including a switching step-down circuit and a linear step-down circuit. The vehicle power supply device according to claim 1 or 2,
The control means is
Monitoring the presence or absence of an abnormality in the step-down circuit in conduction with the electrical load;
When an abnormality is detected, the step-down circuit in which the abnormality is detected and the electric load are brought into a non-conductive state, and one of the other step-down circuits and the electric load are brought into a conductive state. The step-down circuit that controls the switching means so that the conversion efficiency becomes maximum at the output current value among the remaining step-down circuits excluding the step-down circuit in which the abnormality is detected among the plurality of step-down circuits. Is selected as a step-down circuit to be brought into conduction with the electric load. The vehicle power supply device according to any one of claims 1 to 3,
A vehicle power supply device in which the electrical load is a plurality of ECUs. A battery mounted on the vehicle;
An electrical load mounted on the vehicle;
A vehicular power supply device that steps down the power supplied from the battery to a predetermined voltage level by a step-down circuit and supplies the electric load
With
The vehicle power supply device according to any one of claims 1 to 4, wherein the vehicle power supply device is a vehicle power supply device.

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