Patent Publication Number: US-11390167-B2

Title: Power supply system

Description:
INCORPORATION BY REFERENCE 
     This is a continuation application of U.S. patent application Ser. No. 15/882,403, filed Jan. 29, 2018, which claims the disclosure of Japanese Patent Application No. 2017-016056 filed on Jan. 31, 2017 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Technical Field 
     The disclosure relates to a power supply system. 
     2. Description of Related Art 
     There is known a vehicle power supply system including a converter connected between one power line and the other power line (see, for example, Japanese Patent Application Publication No. 2007-131134 (JP 2007-131134 A)). In this vehicle power supply system, an alternator, a lead-acid battery and a load, such as an audio device, are connected to the one power line, and a lithium-ion battery and a load, such as an electric power steering system, are connected to the other power line. 
     SUMMARY 
     As in the case of the above-described technique, there is a power supply system that is mounted on a vehicle and in which a first circuit including a first power supply line and a second circuit including a second power supply line are connected to each other via a direct current to direct current converter (hereinafter, referred to as a DC-DC converter). A first load, a power supply source and a first battery are connected to the first power supply line, and a second load and a second battery are connected to the second power supply line. In the thus configured power supply system, the second battery of the second circuit is charged with electric power that is supplied from the power supply source of the first circuit via the DC-DC converter. 
     In addition, with the above configuration, if the first load and the second load each have the function of backing up the other one, the function of the first load is backed up by the function of the second load even when the first load malfunctions because of an abnormality in the first circuit. 
     However, when the voltage of the first power supply line becomes lower than the voltage of the second battery, the electric charge of the second battery can migrate to the first power supply line via the DC-DC converter, and the amount of electric charge stored in the second battery can reduce. If there occurs an abnormality in the first circuit in a state where the amount of electric charge stored in the second battery has reduced in this way, there can be a case where electric power for actuating the second load cannot be ensured by the second battery in the event of an abnormality in the first circuit. In this case, for example, even when the first load malfunctions because of an abnormality in the first circuit, the function of the first load may not be backed up by the function of the second load. 
     An aspect of the disclosure provides a power supply system that is able to prevent a stop of supply of electric power for actuating a second load from a second battery in the event of an abnormality in a first circuit. 
     An aspect of the disclosure provides a power supply system. The power supply system includes a first circuit including a first power supply line connected to a first load, a power supply source connected to the first power supply line, and a first battery connected to the first power supply line; a second circuit including a second power supply line connected to a second load and a second battery connected to the second power supply line, the second load being configured to perform a function that substitutes for a function performed by the first load; and a voltage controller including a converter control unit and a DC-DC converter, the DC-DC converter being connected between the first power supply line and the second power supply line, the converter control unit being configured to control the DC-DC converter by using an input voltage from the first power supply line such that an output voltage higher than or equal to a voltage of the second battery is output to the second power supply line. 
     With the thus configured power supply system, the DC-DC converter is controlled by using the input voltage from the first power supply line such that the output voltage higher than or equal to the voltage of the second battery is output to the second power supply line. Therefore, even when the voltage of the first power supply line becomes lower than the voltage of the second battery, the voltage of the second power supply line is kept at a voltage higher than or equal to the voltage of the second battery through control over the DC-DC converter. For this reason, even when the voltage of the first power supply line becomes lower than the voltage of the second battery, it is possible to prevent migration of the electric charge of the second battery to the first power supply line via the DC-DC converter. Thus, it is possible to prevent a reduction in the amount of electric charge stored in the second battery before there occurs an abnormality in the first circuit, so electric power for actuating the second load at the time when there occurs an abnormality in the first circuit is ensured by the second battery. As a result, even when the first load malfunctions because of an abnormality in the first circuit, the function of the first load is backed up by the function of the second load. 
     In the power supply system according to the aspect of the disclosure, the voltage controller may include a first abnormality detection unit configured to detect an abnormality of the first circuit. The converter control unit may be configured to, when the abnormality of the first circuit has not been detected by the first abnormality detection unit, control the DC-DC converter by using the input voltage from the first power supply line such that the output voltage higher than or equal to the voltage of the second battery is output to the second power supply line from the DC-DC converter, and the converter control unit may be configured to, when the abnormality of the first circuit has been detected by the first abnormality detection unit, control the DC-DC converter such that the first power supply line is interrupted from the second power supply line. 
     Thus, when there is no abnormality in the first circuit, even when the voltage of the first power supply line becomes lower than the voltage of the second battery, the voltage of the second power supply line is kept at a voltage higher than or equal to the voltage of the second battery through control over the DC-DC converter. Therefore, as in the case of the above, it is possible to prevent a reduction in the amount of electric charge stored in the second battery before there occurs an abnormality in the first circuit, so electric power for actuating the second load at the time when there occurs an abnormality in the first circuit is ensured by the second battery. On the other hand, when there occurs an abnormality in the first circuit, the DC-DC converter is controlled such that the first power supply line is interrupted from the second power supply line. Thus, it is possible to stop flow of current between the first power supply line and the second power supply line via the DC-DC converter, so it is possible to prevent the influence of an abnormality of the first circuit on the second circuit. 
     In the power supply system according to the aspect of the disclosure, the converter control unit may be configured to, when a first under voltage fault in which a voltage of the first power supply line becomes lower than the voltage of the second battery has been detected by the first abnormality detection unit, control the DC-DC converter such that the first power supply line is interrupted from the second power supply line. 
     Thus, even when there occurs the first under voltage fault in which the voltage of the first power supply line becomes lower than the voltage of the second battery, it is possible to prevent migration of the electric charge of the second battery to the first power supply line via the DC-DC converter. Therefore, it is possible to reduce the degree to which the amount of electric charge stored in the second battery reduces after occurrence of the first under voltage fault. As a result, it is possible to extend a time during which electric power for actuating the second load at the time when there occurs an abnormality in the first circuit is ensured by the second battery. In addition, even when the first load malfunctions because of an abnormality in the first circuit, it is possible to extend a time during which the function of the first load is backed up by the function of the second load. 
     Specific examples of the first under voltage fault in which the voltage of the first power supply line becomes lower than the voltage of the second battery include a ground short circuit of the first power supply line, an internal short circuit of the first load, and the like. 
     The power supply system according to the aspect of the disclosure may include a third power supply line connected between a third load and a node located between the second battery and the second power supply line; and a first interrupting mechanism connected between the node and the second power supply line. The converter control unit may be configured to, when the abnormality of the first circuit has been detected by the first abnormality detection unit, control the first interrupting mechanism such that the node is interrupted from the second power supply line before electric power for actuating the third load from the second battery becomes empty. 
     Thus, when there is an abnormality in the first circuit, the first interrupting mechanism is controlled such that the node is interrupted from the second power supply line before electric power for actuating the third load from the second battery becomes empty. Therefore, before all the electric power of the second battery is consumed as electric power for actuating the second load, electric power for actuating the third load is ensured by the second battery. As a result, it is possible to extend the operating time of the third load as compared to the second operating time. This is particularly effective when the third load is more important than the second load. 
     In the power supply system according to the aspect of the disclosure, the power supply system may be mounted on a vehicle, and the third load may be include a steering controller configured to control a wheel steering angle of the vehicle by steer-by-wire. 
     Thus, even when there is an abnormality in the first circuit, it is possible to particularly extend the operating time of the steering controller, so it becomes easier to ensure a time for moving the vehicle to a safe place. 
     In the power supply system according to the aspect of the disclosure, the voltage controller may include a second abnormality detection unit configured to detect an abnormality of the second circuit, and the converter control unit may be configured to, when the abnormality of the second circuit has been detected by the second abnormality detection unit, control the DC-DC converter such that the first power supply line is interrupted from the second power supply line. 
     Thus, when there occurs an abnormality in the second circuit, the DC-DC converter is controlled such that the first power supply line is interrupted from the second power supply line. Therefore, it is possible to stop flow of current between the first power supply line and the second power supply line via the DC-DC converter, so it is possible to prevent the influence of an abnormality of the second circuit on the first circuit. 
     In the power supply system according to the aspect of the disclosure, the converter control unit may be configured to, when a second under voltage fault in which a voltage of the second power supply line becomes lower than a voltage of the first battery has been detected by the first abnormality detection unit, control the DC-DC converter such that the first power supply line is interrupted from the second power supply line. 
     Thus, even when there occurs the second under voltage fault in which the voltage of the second power supply line becomes lower than the voltage of the first battery, it is possible to prevent migration of electric power from the power supply source and the electric charge of the first battery to the second power supply line via the DC-DC converter. Therefore, it is possible to reduce the degree to which the amount of electric charge stored in the first battery reduces after occurrence of the second under voltage fault. As a result, it is possible to extend a time during which electric power for actuating the first load at the time when there occurs an abnormality in the second circuit is ensured by the first battery. In addition, even when the second load malfunctions because of an abnormality in the second circuit, it is possible to extend a time during which the function of the second load is backed up by the function of the first load. 
     Specific examples of the second under voltage fault in which the voltage of the second power supply line becomes lower than the voltage of the first battery include a ground short circuit of the second power supply line, an internal short circuit of the second load, and the like. 
     In the power supply system according to the aspect of the disclosure, the output voltage may be higher than or equal to the voltage of the second battery in a full charge state. 
     Thus, even when the voltage of the first power supply line becomes lower than the voltage of the second battery, the voltage of the second power supply line is kept at a voltage higher than or equal to the voltage of the second battery in a full charge state through control over the DC-DC converter. Therefore, the amount of electric charge stored in the second battery is allowed to be kept in a full charge state before there occurs an abnormality in the first circuit, so the second battery becomes easier to ensure electric power for actuating the second load at the time when there occurs an abnormality in the first circuit. 
     The power supply system according to the aspect of the disclosure may include a battery sensor configured to monitor the second battery; and a degradation detection unit configured to detect degradation of the second battery. The voltage controller may include a first internal resistance estimation unit configured to estimate an internal resistance of the second battery by stepping up and stepping down the voltage of the second battery. The battery sensor may include a second internal resistance estimation unit configured to estimate an internal resistance of the second battery by causing the second battery to perform pulse discharge. The degradation detection unit may be configured to detect degradation of the second battery based on the internal resistance estimated by the first internal resistance estimation unit and the internal resistance estimated by the second internal resistance estimation unit. 
     Thus, both the internal resistance estimated by the first internal resistance estimation unit and the internal resistance estimated by the second internal resistance estimation unit are considered in order to detect degradation of the second battery, so the accuracy of detecting degradation of the second battery improves. 
     In the power supply system according to the aspect of the disclosure, the first load and the second load each may be configured to back up the other one by performing the same function as a function that the other one performs. 
     Thus, even when a predetermined function of the first load malfunctions because of an abnormality in the first circuit, it is possible to back up the predetermined function of the first load by using the function of the second load, which is the same as the predetermined function. On the other hand, even when a predetermined function of the second load malfunctions because of an abnormality in the second circuit, it is possible to back up the predetermined function of the second load by using the function of the first load, which is the same as the predetermined function. 
     In the power supply system according to the aspect of the disclosure, the power supply system may be mounted on a vehicle, and the first load and the second load each may have a motion control function associated with control over a motion of the vehicle, and each may be configured to back up the motion control function that the other one performs. 
     Thus, even when the motion control function of the first load malfunctions because of an abnormality in the first circuit, it is possible to back up the motion control function of the first load by using the motion control function of the second load. On the other hand, even when the motion control function of the second load malfunctions because of an abnormality in the second circuit, it is possible to back up the motion control function of the second load by using the motion control function of the first load. 
     The motion of the vehicle may mean at least one motion of the vehicle among running, turning and stopping. 
     In the power supply system according to the aspect of the disclosure, the DC-DC converter may be configured to output the output voltage to the second power supply line in accordance with control that is executed by the converter control unit. 
     In the power supply system according to the aspect of the disclosure, the first load and the second load each may have a function of backing up a function of the other one. 
     According to the aspect of the disclosure, it is possible to prevent a stop of supply of electric power for actuating the second load from the second battery in the event of an abnormality in the first circuit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
         FIG. 1  is a view that shows an example of the configuration of a power supply system; 
         FIG. 2  is a view that shows an example of the functional configuration of a voltage controller; 
         FIG. 3  is a flowchart that shows an example of the operation of the voltage controller; 
         FIG. 4  is a view that shows an example of the hardware configuration of the voltage controller; and 
         FIG. 5  is a view that shows an example of the functional configuration of a battery sensor. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the disclosure will be described with reference to the accompanying drawings. 
       FIG. 1  is a view that shows an example of the configuration of a power supply system. The power supply system  1  shown in  FIG. 1  is an example of a power supply system that is mounted on a vehicle  50 . The power supply system  1  includes a circuit  100 , a circuit  200 , a voltage controller  10 , a load  310  and a power supply line  302 . 
     The circuit  100  is an example of a first circuit. The circuit  100  includes a load group  110 , a power supply line  102 , a power supply  103  and a battery  101 . The load group  110  includes a plurality of loads  111  to  127 . 
     The load  111  is an engine electronic control unit (ECU) that governs engine control over the vehicle  50 . When the vehicle  50  is a hybrid vehicle that uses both an engine and a motor, the load  111  includes both the engine ECU and an HVECU that governs hybrid control. 
     The load  112  is an airbag ECU that controls deployment of an airbag of the vehicle  50 . 
     The load  113  is a steering angle sensor that detects the steering angle of the wheels of the vehicle  50 . 
     The load  114  includes at least one of a sensor that detects a surrounding object located laterally forward of the vehicle  50  and a sensor that detects a surrounding object located laterally behind the vehicle  50 . 
     The load  115  includes at least one of a sensor that detects a surrounding object located behind the vehicle  50  and a sensor that detects a surrounding object located laterally to the vehicle  50 . 
     The load  116  is a head up display (HUD) that shows information in the field of view of a driver who drives the vehicle  50 . 
     The load  117  is a data communication module (DCM) that wirelessly communicates with a device outside of the vehicle  50 . 
     The load  118  is a driver monitoring device that monitors the driver of the vehicle  50 . 
     The load  119  is an automatic mode switch that switches between the on and off states of an automatic drive mode of the vehicle  50 . 
     The load  120  is a driver support ECU that controls a driver support system (DSS). The DSS supports driver&#39;s driving of the vehicle  50  with the use of an automatic brake, an alarm, and the like. 
     The load  121  is a brake control system that controls the brake force of the vehicle  50 . 
     The load  122  is a system (electronic power steering (EPS)) that supports the steering operation of the driver of the vehicle  50  with the use of a motor. 
     The load  123  is a sensor that detects a surrounding object located forward of the vehicle  50 . 
     The load  124  is a camera that captures a surrounding object located forward of the vehicle  50 . 
     The load  125  is an indicator that informs the driver of the vehicle  50  of a predetermined vehicle state of the vehicle  50  through a lamp, and, for example, includes a check engine lamp, a brake alarm lamp, and the like. 
     The load  126  is a speaker that outputs sound, such as alarm sound and voice, toward the driver of the vehicle  50 . 
     The load  127  is a headlamp installed at the front left side of the vehicle  50 . 
     The power supply line  102  is an example of a first power supply line, and is a current path connected to the loads  111  to  127 . The power supply line  102  is, for example, a 12V power supply line. 
     The power supply  103  is an example of a power supply source, and is connected to the power supply line  102 . The power supply  103  supplies electric power to the battery  101 , the load group  110  and the voltage controller  10 . The power supply  103  supplies electric power to the load  310  via the power supply line  102 . The power supply  103  is able to supply electric power to the circuit  200  and the load  310  via a converter  17  when the converter  17  is controlled. Specific examples of the power supply  103  include an alternator, a converter (another converter different from the converter  17 ), and the like. 
     The battery  101  is an example of a first battery, and is connected to the power supply line  102 . The battery  101  is a secondary battery that is rechargeable when supplied with electric power. A specific example of the battery  101  is a lead-acid battery. In a state where the output voltage of the power supply  103  is lower than the battery voltage of the battery  101 , the battery  101  serves as a power supply that supplies electric power to the load group  110 , the voltage controller  10  and the load  310 . In a state where the output voltage of the power supply  103  is lower than the battery voltage of the battery  101 , the battery  101  is able to supply electric power to the circuit  200  and the load  310  via the converter  17  when the converter  17  is controlled. 
     The circuit  200  is an example of a second circuit. The circuit  200  includes a load group  210 , a power supply line  202 , a battery  201  and a battery sensor  203 . The load group  210  includes a plurality of loads  211  to  220 . 
     The load  211  is an automatic drive ECU that controls an automatic drive system (ADS). The ADS controls the automatic drive of the vehicle  50  with the use of the automatic brake, an automatic steering, and the like. 
     The load  212  is a brake control system that controls the brake force of the vehicle  50 . 
     The load  213  is a system (electronic power steering (EPS)) that supports the steering operation of the driver of the vehicle  50  with the use of a motor. 
     The load  214  is a sensor that detects a surrounding object located forward of the vehicle  50 . 
     The load  215  is a camera that captures a surrounding object around the vehicle  50 . 
     The load  216  is a map data storage unit that stores map data. 
     The load  217  is a display (multi-information display (MID)) that informs the driver of the vehicle  50  of predetermined information of the vehicle  50  through screen display. 
     The load  218  is a buzzer that sounds an alarm sound for the driver of the vehicle  50 . 
     The load  219  is a headlamp installed at the front right side of the vehicle  50 . 
     The load  220  is a wiper that wipes the windshield of the vehicle. 
     The power supply line  202  is an example of a second power supply line, and is a current path connected to the loads  211  to  220 . The power supply line  202  is, for example, a 12V power supply line that carries the same voltage as the power supply line  102 . 
     The battery  201  is an example of a second battery, and is connected to the power supply line  202 . The battery  201  supplies electric power to the load group  210  and the voltage controller  10 . The battery  201  supplies electric power to the load  310  via the power supply line  302 . The battery  201  is a secondary battery that is rechargeable when supplied with electric power. A specific example of the battery  201  is a lead-acid battery. 
     The battery sensor  203  monitors the battery  201 , and outputs the monitored result to the voltage controller  10 . For example, the battery sensor  203  estimates the internal resistance of the battery  201  by measuring the battery voltage and battery current of the battery  201  at the time when the battery  201  is caused to perform pulse discharge, and outputs the estimated result to the voltage controller  10 . 
     The voltage controller  10  is an example of a device that controls voltage conversion between the power supply line  102  and the power supply line  202 . The voltage controller  10  includes the converter  17 , a relay  18  and a relay  19 . 
     The converter  17  is an example of a DC-DC converter. The converter  17  is connected between the power supply line  102  and the power supply line  202 , and carries out DC-DC voltage conversion between the power supply line  102  and the power supply line  202 . 
     The relay  18  is an example of a first interrupting mechanism connected between a node  207  and the power supply line  202 . The node  207  represents a connection point at which a battery line  204  and the power supply line  302  are connected to each other. The battery line  204  is a current path between the power supply line  202  and the battery  201 . The relay  18  is serially inserted in the battery line  204  so as to be able to interrupt the node  207  from the power supply line  202 . 
     The relay  19  is an example of a second interrupting mechanism connected between the node  207  and the battery  201 . The relay  19  is serially inserted in the battery line  204  so as to be able to interrupt the node  207  from the battery  201 . 
     The load  310  includes a steering controller that controls the wheel steering angle of the vehicle  50  by steer-by-wire. The steering controller is a system that controls the wheel steering angle of the vehicle  50  in a steer-by-wire system that performs not mechanical transmission but electrical transmission between the shaft of a steering wheel and a wheel steering shaft. The load  310  may include a load other than the steering controller. 
     The power supply line  302  is an example of a third power supply line, and is a current path connected between the node  207  and the load  310 . The power supply line  302  is, for example, a 12V power supply line that carries the same voltage as the power supply line  202 . 
     Each of the loads  120  to  127  is an example of a first load. Each of the loads  211  to  219  is an example of a second load. The load  310  is an example of a third load. 
     The load  120  and the load  211  each backs up the function of the other one by using a similar function to the function of the other one. The load  120  is an example of a load that backs up the function of the load  211  by using a similar function to the function of the load  211 . The load  211  is an example of a load that backs up the function of the load  120  by using a similar function to the function of the load  120 . The load  120  and the load  211  have a similarity in supporting the driver, but differ from each other in the manner of supporting. 
     The load  121  and the load  212  each back up the function of the other one by using the same function as the function of the other one. The load  121  is an example of a load that backs up the function of the load  212  by using the same function as the function of the load  212 . The load  212  is an example of a load that backs up the function of the load  121  by using the same function as the function of the load  121 . The load  121  and the load  212  have the same function of controlling the brake force of the vehicle  50  in the same manner. For example, the share of each of the load  121  and the load  212  is 50% of the total brake force that is required of the vehicle  50 . 
     The load  122  and the load  213  each back up the function of the other one by using the same function as the function of the other one. The load  122  is an example of a load that backs up the function of the load  213  by using the same function as the function of the load  213 . The load  213  is an example of a load that backs up the function of the load  122  by using the same function as the function of the load  122 . The load  122  and the load  213  have the same function of supporting the steering operation of the driver of the vehicle  50  with the use of the motor in the same manner. For example, the share of each of the load  122  and the load  213  is 50% of the total output that is required to support the steering operation. 
     The load  123  and the load  214  each back up the function of the other one by using the same function as the function of the other one. The load  123  is an example of a load that backs up the function of the load  214  by using the same function as the function of the load  214 . The load  214  is an example of a load that backs up the function of the load  123  by using the same function as the function of the load  123 . The load  123  and the load  214  have a commonality in detecting a surrounding object located forward of the vehicle  50 . 
     The load  124  and the load  215  each back up the function of the other one by using a similar function to the function of the other one. The load  124  is an example of a load that backs up the function of the load  215  by using a similar function to the function of the load  215 . The load  215  is an example of a load that backs up the function of the load  124  by using a similar function to the function of the load  124 . The load  124  and the load  215  have a similarity in capturing a surrounding object around the vehicle  50  but differ from each other in the manner of capturing. 
     The load  125  and the load  217  each back up the function of the other one by using a similar function to the function of the other one. The load  125  is an example of a load that backs up the function of the load  217  by using a similar function to the function of the load  217 . The load  217  is an example of a load that backs up the function of the load  125  by using a similar function to the function of the load  125 . The load  125  and the load  217  have a similarity in informing a vehicle state but differ from each other in the manner of informing. 
     The load  126  and the load  218  each back up the function of the other one by using a similar function to the function of the other one. The load  126  is an example of a load that backs up the function of the load  218  by using a similar function to the function of the load  218 . The load  218  is an example of a load that backs up the function of the load  126  by using a similar function to the function of the load  126 . The load  126  and the load  218  have a similarity in outputting sound but differ from each other in the manner of outputting sound. 
     The load  127  and the load  219  each back up the function of the other one by using the same function as the function of the other one. The load  127  is an example of a load that backs up the function of the load  219  by using the same function as the function of the load  219 . The load  219  is an example of a load that backs up the function of the load  127  by using the same function as the function of the load  127 . The load  127  and the load  219  have the same function of illuminating an area forward of the vehicle  50  in the same manner. For example, the load  127  illuminates an area on the left forward of the vehicle  50 , and the load  219  illuminates an area on the right forward of the vehicle  50 . 
     The “back up” means that, when one load malfunctions, the other load maintains the function of the one load. 
       FIG. 2  is a view that shows an example of the functional configuration of the voltage controller. The voltage controller  10  includes an abnormality detection unit  11 , an abnormality detection unit  12 , a converter control unit  13 , a step-up/step-down control unit  14 , an internal resistance estimation unit  15  and a degradation detection unit  16 . 
     As shown in  FIG. 4  (described later), the voltage controller  10  includes a central processing unit (CPU)  34  that is an example of a processor, a read only memory (ROM)  41  and a random access memory (RAM)  42 . The processing functions of the abnormality detection unit  11 , abnormality detection unit  12 , converter control unit  13 , step-up/step-down control unit  14 , internal resistance estimation unit  15  and degradation detection unit  16  are implemented by the CPU  34  when the CPU  34  executes programs stored in the ROM  41 . The programs include a program for causing the CPU  34  to execute the procedure of processes. The RAM  42  stores various data including intermediate data, and the like, in computation based on programs that the CPU  34  executes. 
     In  FIG. 2 , the abnormality detection unit  11  is an example of a first abnormality detection unit, and detects an abnormality (for example, first under voltage fault, or the like) of the voltage circuit  100 . The abnormality detection unit  12  is an example of a second abnormality detection unit, and detects an abnormality (for example, second under voltage fault, or the like) of the circuit  200 . 
     The converter control unit  13  is an example of a converter control unit. The converter control unit  13  controls the converter  17  by using an input voltage from the power supply line  102  such that an output voltage higher than or equal to the voltage of the battery  201  is output to the power supply line  202 . When an abnormality has been detected by at least one of the abnormality detection units  11 ,  12 , the converter control unit  13  controls the converter  17  such that the power supply line  102  is interrupted from the power supply line  202 . 
     When no abnormality has been detected by any of the abnormality detection units  11 ,  12 , the step-up/step-down control unit  14  controls stepping up and stepping down of the battery  201  in order to detect degradation of the battery  201 . The internal resistance estimation unit  15  is an example of a first internal resistance estimation unit. The internal resistance estimation unit  15  estimates the internal resistance of the battery  201  by using Ohm&#39;s law by causing the step-up/step-down control unit  14  to step up and step down the battery  201 . The degradation detection unit  16  detects degradation of the battery  201  on the basis of the estimated internal resistance of the battery  201 . 
       FIG. 3  is a flowchart that shows an example of the operation of the voltage controller. The CPU  34  (see  FIG. 4 ) executes the flow from START to END at predetermined intervals. 
     In step S 10 , the abnormality detection unit  11  determines whether an abnormality of the circuit  100  has been detected. In step S 20 , the abnormality detection unit  12  determines whether an abnormality of the circuit  200  has been detected. 
     When neither an abnormality of the circuit  100  nor an abnormality of the circuit  200  has been detected, the converter control unit  13  turns on the converter  17 , turns on the relay  18  and turns on the relay  19  (step S 30 ). In step S 30 , the converter control unit  13  controls the converter  17  by using the input voltage from the power supply line  102  such that the output voltage higher than or equal to the voltage of the battery  201  is output to the power supply line  202 . 
     As the converter  17  is controlled in this way, electric power is supplied from the power supply line  102  side to the power supply line  202  side, and the voltage of the power supply line  202  is kept at a voltage higher than or equal to the voltage of the battery  201 . For this reason, after that, even when the voltage of the power supply line  102  becomes lower than the voltage of the battery  201 , it is possible to prevent migration of the electric charge of the battery  201  to the power supply line  102  via the converter  17 . Thus, it is possible to prevent a reduction in the amount of electric charge stored in the battery  201  before there occurs an abnormality in the circuit  100 , so electric power for actuating the loads  211  to  219  at the time when there occurs an abnormality in the circuit  100  is ensured by the battery  201 . As a result, even when the loads  120  to  127  malfunction because of an abnormality in the circuit  100 , it is possible to back up the functions of the loads  120  to  127  by using the functions of the loads  211  to  219 . 
     In step  30 , for example, the output voltage higher than or equal to the voltage of the battery  201  (that is, the output voltage of the converter  17  to the power supply line  202 ) is higher than or equal to the voltage of the battery  201  in a full charge state. In step  30 , the converter control unit  13  may control the converter  17  such that the output voltage higher than the voltage of the battery  201  is output to the power supply line  202 . In this case, for example, the output voltage higher than the voltage of the battery  201  (that is, the output voltage of the converter  17  to the power supply line  202 ) may be higher than the voltage of the battery  201  in a full charge state. 
     Thus, even when the voltage of the power supply line  102  becomes lower than the voltage of the battery  201 , the voltage of the power supply line  202  is kept at a voltage higher than or equal to the voltage of the battery  201  in a full charge state through control over the converter  17 . Therefore, the amount of electric charge stored in the battery  201  is allowed to be kept in a full charge state before there occurs an abnormality in the circuit  100 , so electric power for actuating the loads  211  to  219  is more easily ensured by the battery  201  at the time when there occurs an abnormality in the circuit  100 . 
     When an abnormality of the circuit  100  has not been detected but an abnormality of the circuit  200  has been detected in step S 20 , the converter control unit  13  turns off the converter  17 , turns off the relay  18  and turns off the relay  19  (step S 40 ). In step S 40 , the converter control unit  13  controls the converter  17  such that the power supply line  102  is interrupted from the power supply line  202 . As the converter  17  is controlled in this way, the power supply line  102  is interrupted from the power supply line  202 , electric power of at least one of the power supply  103  and the battery  101  is supplied to the loads  111  to  127  in the load group  110  and the load  310 . 
     In this way, when there occurs an abnormality in the circuit  200 , the converter  17  is controlled such that the power supply line  102  is interrupted from the power supply line  202 . Therefore, it is possible to stop flow of current between the power supply line  102  and the power supply line  202  via the converter  17 , so it is possible to prevent the influence of an abnormality of the circuit  200  on the circuit  100 . 
     For example, when the second under voltage fault where the voltage of the power supply line  202  is lower than the voltage of the battery  101  has been detected by the abnormality detection unit  12 , the converter control unit  13  controls the converter  17  such that the power supply line  102  is interrupted from the power supply line  202 . For example, the abnormality detection unit  12  detects an under voltage fault of the circuit  200  when the voltage of the power supply line  202  becomes lower by a predetermined amount of decrease than the voltage of the battery  101 . In this case, the abnormality detection unit  12  estimates that there occurs a ground short circuit of the power supply line  202 , an internal short circuit of any of the loads  211  to  220 , or the like. 
     With step S 40 , even when there occurs the second under voltage fault in which the voltage of the power supply line  202  becomes lower than the voltage of the battery  101 , it is possible to prevent migration of electric power from the power supply  103  and the electric charge of the battery  101  to the power supply line  202  via the converter  17 . Therefore, it is possible to reduce the degree to which the amount of electric charge stored in the battery  101  reduces after the second under voltage fault has occurred in the circuit  200 . As a result, it is possible to extend a time during which electric power for actuating the loads  120  to  127  is ensured by the battery  101  at the time when there occurs an abnormality in the circuit  200 . In addition, even when the loads  211  to  219  malfunction because of an abnormality in the circuit  200 , it is possible to extend a time during which the functions of the loads  211  to  219  are backed up by using the functions of the loads  120  to  127 . 
     When an abnormality of the circuit  100  has been detected in step S 10 , the converter control unit  13  determines whether a predetermined delay time has elapsed from the detection of the abnormality of the circuit  100  (step S 50 ). When the converter control unit  13  determines that the predetermined delay time has not elapsed from the detection of the abnormality of the circuit  100 , the converter control unit  13  executes the process of step S 60 . When the converter control unit  13  determines that the predetermined delay time has elapsed from the detection of the abnormality of the circuit  100 , the converter control unit  13  executes the process of step S 70 . 
     In step S 60 , the converter control unit  13  turns off the converter  17 , turns on the relay  18  and turns on the relay  19  (step S 60 ). Thus, the power supply line  102  is interrupted from the power supply line  202 , and the electric power of the battery  201  is supplied to the loads  211  to  220  in the load group  210  and the load  310 . 
     In this way, when there occurs an abnormality in the circuit  100 , the converter  17  is controlled such that the power supply line  102  is interrupted from the power supply line  202 . Thus, it is possible to stop flow of current between the power supply line  102  and the power supply line  202  via the converter  17 , so it is possible to prevent the influence of an abnormality of the circuit  100  on the circuit  200 . 
     For example, when the first under voltage fault in which the voltage of the power supply line  102  becomes lower than the voltage of the battery  201  has been detected by the abnormality detection unit  11 , the converter control unit  13  controls the converter  17  such that the power supply line  102  is interrupted from the power supply line  202 . For example, when the voltage of the power supply line  102  becomes lower by a predetermined amount of decrease than the voltage of the battery  201 , the abnormality detection unit  11  detects an under voltage fault of the circuit  100 . In this case, the abnormality detection unit  11  estimates that there occurs a ground short circuit of the power supply line  102 , an internal short circuit of any of the loads  111  to  127 , or the like. 
     With step S 60 , even when there occurs the first under voltage fault in which the voltage of the power supply line  102  becomes lower than the voltage of the battery  201 , it is possible to prevent migration of the electric charge of the battery  201  to the power supply line  102  via the converter  17 . Therefore, it is possible to reduce the degree to which the amount of electric charge stored in the battery  201  reduces after the first under voltage fault has occurred in the circuit  100 . As a result, it is possible to extend a time during which electric power for actuating the loads  211  to  219  is ensured by the battery  201  at the time when there occurs an abnormality in the circuit  100 . In addition, even when the loads  120  to  127  malfunction because of an abnormality in the circuit  100 , it is possible to extend a time during which the functions of the loads  120  to  127  are backed up by using the functions of the loads  211  to  219 . 
     In step S 70 , the converter control unit  13  turns off the converter  17 , turns off the relay  18  and turns on the relay  19  (step S 70 ). Thus, the power supply line  102  is interrupted from the power supply line  202 , and the electric power of the battery  201  is supplied to the load  310  without being supplied to the loads  211  to  220  in the load group  210 . 
     In this way, when an abnormality of the circuit  100  has been detected by the abnormality detection unit  11 , the converter control unit  13  controls the relay  18  such that the node  207  is interrupted from the power supply line  202  before electric power for actuating the load  310  from the battery  201  becomes empty. 
     Thus, when there is an abnormality in the circuit  100 , the relay  18  is controlled such that the node  207  is interrupted from the power supply line  202  before electric power for actuating the load  310  from the battery  201  becomes empty. Therefore, electric power for actuating the load  310  is ensured by the battery  201  before all the electric power of the battery  201  is consumed as electric power for actuating the loads  211  to  219 . As a result, it is possible to extend the operating time of the load  310  as compared to a second operating time. This is particularly effective when the load  310  is more important than the loads  211  to  219 . 
     For example, the load  310  includes the steering controller that controls the wheel steering angle of the vehicle  50  by steer-by-wire. In this case, even when there is an abnormality in the circuit  100 , it is possible to particularly extend the operating time of the steering controller, so it is possible to ensure a time for moving the vehicle  50  to a safer place. 
     In this way, with the power supply system  1 , the same or similar function of each of the loads  120  to  127  and the loads  211  to  219  to the function of the other one is a motion control function for controlling the motion of the vehicle  50 . Thus, even when the motion control functions of the loads  120  to  127  malfunction because of an abnormality in the circuit  100 , it is possible to back up the motion control functions of the loads  120  to  127  by using the motion control functions of the loads  211  to  219 . On the other hand, even when the motion control functions of the loads  211  to  219  malfunction because of an abnormality in the circuit  200 , it is possible to back up the motion control functions of the loads  211  to  219  by using the motion control functions of the loads  120  to  127 . 
       FIG. 4  is a view that shows an example of the hardware configuration of the voltage controller. The voltage controller  10  includes the converter  17 , the relay  18 , the relay  19 , shunt resistors  31 ,  32 , an input circuit  33 , a CPU  34 , drivers  35 ,  36 , a current detection unit  37 , an overcurrent detection unit  38 , a voltage detection unit  39 , a signal input circuit  40 , a ROM  41  and a RAM  42 . 
     The converter  17  is a so-called H-bridge bidirectional regulator circuit including transistors  21  to  24  and an inductor  25 . The converter  17  selectively performs the operation of converting the voltage of input electric power from the power supply line  102  and supplying the power supply line  202  with the output electric power after voltage conversion and the operation of converting the voltage of input electric power from the power supply line  202  and supplying the power supply line  102  with output electric power after voltage conversion. 
     When the on state of an ignition signal IG has been detected via the input circuit  33 , the CPU  34  turns on the voltage conversion of the converter  17 . When the off state of the ignition signal IG has been detected via the input circuit  33 , the CPU  34  turns off the voltage conversion of the converter  17 . 
     The current detection unit  37  detects a current flowing through the power supply line  102  with the use of the shunt resistor  31 , and detects a current flowing through the power supply line  202  with the use of the shunt resistor  32 . The voltage detection unit  39  detects the voltage of the power supply line  102  and the voltage of the power supply line  202 , and detects the voltage of the battery  201  and the voltage of the load  310 . The CPU  34  supplies a pulse width modulation signal based on the current detected by the current detection unit  37  and the voltage detected by the voltage detection unit  39  to the driver  35 . Thus, the voltage conversion of the converter  17  is driven by the driver  35 . When the current detected by the current detection unit  37  is detected as an overcurrent by the overcurrent detection unit  38 , the CPU  34  turns off the converter  17 . The CPU  34  turns on or off the relays  18 ,  19  with the use of the driver  36 . 
       FIG. 5  is a view that shows an example of the functional configuration of the battery sensor. The battery sensor  203  includes a pulse discharge control unit  205  and an internal resistance estimation unit  206 . The pulse discharge control unit  205  controls pulse discharge of the battery  201 . The internal resistance estimation unit  206  is an example of a second internal resistance estimation unit. The internal resistance estimation unit  206  estimates the internal resistance of the battery  201  by using a voltage difference and a current difference at the time of step-up/step-down operation of the battery  201  during pulse discharge by causing the battery  201  to carry out pulse discharge with the use of the pulse discharge control unit  205 . Pulse discharge is to periodically repeat discharge of the battery  201  and stop of discharge. 
     The battery sensor  203 , as well as  FIG. 4 , includes a central processing unit (CPU) that is an example of a processor, a read only memory (ROM) and a random access memory (RAM). The processing functions of the pulse discharge control unit  205  and internal resistance estimation unit  206  are implemented by the CPU when the CPU executes programs stored in the ROM. The programs include a program for causing the CPU to execute the procedure of processes. The RAM stores various data including intermediate data, and the like, in computation based on programs that the CPU executes. 
     The internal resistance estimation unit  206  transmits the estimated internal resistance to the degradation detection unit  16  of the voltage controller  10 . The degradation detection unit  16  detects degradation of the battery  201  on the basis of the internal resistance estimated by the internal resistance estimation unit  15  and the internal resistance estimated by the internal resistance estimation unit  206 . Thus, both the internal resistance estimated by the internal resistance estimation unit  15  and the internal resistance estimated by the internal resistance estimation unit  206  are considered in order to detect degradation of the battery  201 , so the accuracy of detecting degradation of the battery  201  improves. 
     A degradation mode of the battery  201  includes a mode in which degradation is able to be detected on the basis of the internal resistance estimated by the internal resistance estimation unit  15  but degradation cannot be detected on the basis of the internal resistance estimated by the internal resistance estimation unit  206 . On the other hand, there is a mode in which degradation cannot be detected on the basis of the internal resistance estimated by the internal resistance estimation unit  15  but degradation is able to be detected on the basis of the internal resistance estimated by the internal resistance estimation unit  206 . Therefore, the degradation detection unit  16  is able to detect the degradation mode, which cannot be detected on the basis of the internal resistance estimated by the internal resistance estimation unit  15 , on the basis of the internal resistance estimated by the internal resistance estimation unit  206 . On the other hand, the degradation detection unit  16  is able to detect the degradation mode, which cannot be detected on the basis of the internal resistance estimated by the internal resistance estimation unit  206 , on the basis of the internal resistance estimated by the internal resistance estimation unit  15 . 
     The degradation mode of the battery  201  includes a mode in which degradation is able to be detected on the basis of the internal resistance estimated by the internal resistance estimation unit  15  and is also able to be detected on the basis of the internal resistance estimated by the internal resistance estimation unit  206 . Therefore, the degradation detection unit  16  is able to highly accurately determine that the detected degradation mode is a degradation mode that is detectable with the use of any of the internal resistance estimation manners when degradation has been detected with the use of any of the internal resistance estimation manners. 
     The power supply system is described on the basis of the embodiment; however, the disclosure is not limited to the above-described embodiment. Various modifications and improvements, such as combinations and replacements with part or all of another embodiment, are applicable within the scope of the disclosure.