Patent Publication Number: US-2022224148-A1

Title: Backup power system

Description:
TECHNICAL FIELD 
     The present disclosure relates to backup power systems used in various vehicles. 
     BACKGROUND ART 
     Hereinafter, a conventional backup power device will be described. In a conventional backup power device that includes a vehicle battery, a charging circuit connected to the vehicle battery, and power storage, electric power to be output from a backup power supply in the event of an emergency is supplied from the vehicle battery to the power storage through the charging circuit at normal times. 
     Note that Patent Literature (PTL) 1, for example, is known as related art document information pertaining to the present disclosure. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: International Publication No. 2013-125170 
       
    
     SUMMARY OF THE INVENTION 
     A backup power system according to the present disclosure includes: a battery; a charging circuit electrically connected to the battery; power storage configured to be charged by the charging circuit; a first load electrically connected to the power storage; a second load electrically connected to the power storage; and a controller configured to control the charging circuit. The controller detects at least one of an input current at the charging circuit and a charging voltage at the power storage in response to a start signal input to the controller. The controller causes the input current at the charging circuit to increase at a first rate of change in response to the start signal. When the controller detects an increase in the charging voltage at the power storage up to a first voltage at which driving of the first load is possible, the controller causes the charging circuit to cause the input current at the charging circuit to increase at a second rate of change lower than the first rate of change. The charging circuit is controlled by the controller to cause the input current to increase at the second rate of change, and the charging voltage at the power storage increases up to a second voltage at which driving of both the first load and the second load is possible. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a circuit block diagram illustrating the configuration of a backup power system according to an exemplary embodiment of the present disclosure. 
         FIG. 2  is a circuit block diagram illustrating a vehicle in which a backup power system according to an exemplary embodiment of the present disclosure is disposed. 
         FIG. 3  is an operating characteristic diagram illustrating the operation of a backup power system according to an exemplary embodiment of the present disclosure. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     Hereinafter, an exemplary embodiment of the present disclosure will be described with reference to the drawings. 
     With a conventional backup power device such as that described above, in the case of storing a large amount of electric power into the power storage in a short time, the charging circuit needs to supply the electric power to the power storage using a large amount of electric power or electric current. This means that a device supporting a large amount of electric power or electric current needs to be used in the charging circuit. As a result, the backup power device is large in size. The backup power system according to the present disclosure enables miniaturization. 
     Exemplary Embodiment 
       FIG. 1  is a circuit block diagram illustrating the configuration of a backup power system according to an exemplary embodiment of the present disclosure. Backup power system  1  includes: backup power device  20  including power storage  4  and charging circuit  5 ; battery  2  connected to input terminal  3  of backup power device  20 ; loads  7  and  8  connected to output terminal  6  of backup power device  20 ; and controller  9 . 
     Note that controller  9  is included in backup power device  20  in the present exemplary embodiment, but this is not necessarily required; it is sufficient that controller  9  be included in backup power system  1 . 
     Battery  2  according to the present exemplary embodiment is a vehicle battery installed in vehicle  10 . One example of power storage  4  according to the present exemplary embodiment is a capacitor power storage device capable of charging and discharging with high electric current density, such as an electric double-layer capacitor and a lithium-ion capacitor. Furthermore, the use of a secondary battery including, but not limited to the capacitor power storage device, is possible. 
     Battery  2  is connected to input terminal  3 . Charging circuit  5  is connected between input terminal  3  and power storage  4 . Output terminal  6  is connected to power storage  4  and outputs electric power stored in power storage  4 . Output terminal  6  is connected to load  7  and load  8 . 
     [Outline of Backup Power System  1 ] 
     First, the outline of backup power system  1  will be described with reference to  FIG. 1  and  FIG. 3 . Note that details of backup power system  1  will be described later with reference to  FIG. 2  and  FIG. 3 . 
     Controller  9  is capable of detecting both of input current Iin at charging circuit  5  and a charging voltage at power storage  4  or at least one of input current Iin at charging circuit  5  and the charging voltage at power storage  4 . Furthermore, controller  9  is capable of receiving start signal SG 1 . Moreover, controller  9  is capable of controlling the operation of charging circuit  5 . 
     Controller  9  receives start signal SG 1  and thereby operates charging circuit  5 . Input current Iin is changed by controller  9  controlling the operation of charging circuit  5 . First, input current Iin is increased at the first rate of change. Subsequently, charging circuit  5  increases charging voltage Vc at power storage  4  up to first voltage V 1  at which driving of load  7  is enabled. After charging voltage Vc at power storage  4  is increased up to first voltage V 1 , input current Iin is increased at the second rate of change until charging voltage Vc at power storage  4  reaches second voltage V 2 . The second rate of change is smaller in value than the first rate of change. Second voltage V 2  is charging voltage Vc at power storage  4  at which driving of both load  7  and load  8  is enabled. 
     With the above configuration and operation, in the case where power storage  4  is charged using charging circuit  5 , the rate of increase of input current Iin at charging circuit  5  per unit time is reduced upon completion of charging of one load (load  7  in the present exemplary embodiment) among a plurality of loads (loads  7  and  8  in the present exemplary embodiment). Note that the completion of charging of a load herein indicates a point in time when electric power supply from the load becomes available. Thus, the maximum value of an electric current flowing to charging circuit  5  is reduced. In the present exemplary embodiment, the electric current capacity of a device used in charging circuit  5  can be reduced, making it possible to miniaturize backup power system  1 . 
     [Details of Backup Power System  1 ] 
     Next, details of backup power system  1  will be described with reference to the circuit block diagram in  FIG. 2  illustrating the configuration of vehicle  10  in which backup power system  1  according to an exemplary embodiment of the present disclosure is disposed and the operating characteristic diagram in  FIG. 3  illustrating the operation of backup power system  1  according to the exemplary embodiment. 
     Backup power system  1  is disposed in vehicle  10  (vehicle body  11 ). When an occupant operates start operator  12 , start signal SG 1  is transmitted from start operator  12  to controller  9 . 
     At time T 0  at which start signal SG 1  is transmitted from start operator  12  to controller  9 , vehicle  10  is activated. Furthermore, at time T 0 , charging circuit  5  starts operating according to an instruction from controller  9 . When charging circuit  5  starts operating, battery  2  starts charging power storage  4  with electric power. 
     Note that controller  9  may control input current Iin using an electric current output from charging circuit  5  (charging current Ic). Furthermore, controller  9  may control charging current Ic on the output side using input current Iin at charging circuit  5 . Moreover, controller  9  may directly control input current Iin at charging circuit  5 . Furthermore, controller  9  may control input current Iin using charging voltage Vc at power storage  4 . Moreover, controller  9  may control charging current Ic using charging voltage Vc at power storage  4 . 
     Controller  9  controls charging circuit  5  so as to cause input current Iin to increase from I 0  to I 1  between time T 0  and time T 1 . The first rate of change corresponding to the rate of increase of input current Iin between time T 0  and time T 1  is (I 1 −I 0 )/(T 1 −T 0 ). The voltage at power storage  4  reaches first voltage V 1  at time T 1 . When charging voltage Vc at power storage  4  is greater than or equal to first voltage V 1 , load  7  can be driven using the electric power stored in power storage  4 . Input current Iin at time T 0 , that is, I 0 , may have any value and may be zero. 
     In the present exemplary embodiment, load  7  has a function, the operation of which is given priority over load  8 . For example, vehicle  10  is propelled by electric power, and load  7  is a device that operates to protect occupants from electric power of vehicle propelling power storage (not illustrated in the drawings) if vehicle  10  has an accident. Examples of the device for protecting occupants from the electric power of the vehicle propelling power storage (not illustrated in the drawings) include a device for cutting off the electric power of the vehicle propelling power storage (not illustrated in the drawings) and a device for causing a propelling load (not illustrated in the drawings) to consume electric power temporarily stored in a propelling power converter (not illustrated in the drawings) to which the electric power of the vehicle propelling power storage (not illustrated in the drawings) is supplied. 
     Load  8 , which comes later than load  7  in the activation sequence in vehicle  10 , is a device that operates to protect occupants at the stage following the operation of load  7 . Alternatively, load  8  is a device that operates to allow occupants to safely escape out of vehicle  10  at said stage following the operation of load  7 . Examples of the device for protecting occupants at the stage following the operation of load  7  may include a device that operates to unlock the doors of vehicle body  11 . An alternative example may be a device that operates to open the door latches of vehicle body  11 . 
     Furthermore, as illustrated in  FIG. 2 , discharging circuit  13  may be disposed between power storage  4  and output terminal  6 . Electric power may be supplied from output terminal  6  to loads  7  and  8  after charging voltage Vc at power storage  4  is increased using discharging circuit  13 . This makes it possible to drive loads  7  and  8  having various functions. 
     As illustrated in  FIG. 3 , charging current Ic is a constant current between time T 0  and time T 1  in the present exemplary embodiment. Note that charging current Ic may be an electric current that is reduced over time between time T 0  and time T 1 . 
     Next, after the voltage at power storage  4  reaches first voltage V 1  at time T 1 , controller  9  performs control such that input current Iin continuously increases from I 1  to I 2  until time T 2 . The second rate of change corresponding to the rate of increase of input current Iin between time T 1  and time T 2  is (I 2 −I 1 )/(T 2 −T 1 ), which is smaller in value than the first rate of change mentioned earlier. Time T 2  is the time at which charging voltage Vc at power storage  4  reaches second voltage V 2 . When charging voltage Vc at power storage  4  is greater than or equal to second voltage V 2 , both load  7  and load  8  can be driven using the electric power stored in power storage  4 . 
     As illustrated in  FIG. 3 , charging current Ic is a constant current between time T 1  and time T 2  in the present exemplary embodiment. Note that charging current Ic may be an electric current that is reduced over time between time T 1  and time T 2 . 
     For the sake of comparison,  FIG. 3  indicates, by dashed lines, trajectories that input current Iin and charging voltage Vc at power storage  4  would take if input current Iin kept increasing at the first rate of change. In the case where input current Iin keeps increasing at the first rate of change, charging voltage Vc at power storage  4  reaches second voltage V 2  at time T 2 ′, which is earlier than time T 2 . Meanwhile, input current Iin at time T 2 ′ is I 2 ′ which is greater than I 2  mentioned earlier. Therefore, in the case of continuously increasing input current Iin at the first rate of change, it is necessary to increase the electric current capacity of charging circuit  5 , and in the case of disposing a protection circuit (not illustrated in the drawings), such as a fuse, between charging circuit  5  and battery  2 , it is necessary to increase the electric current capacity of the protection circuit (not illustrated in the drawings). 
     In this working example, load  7  and load  8  are ranked in priority order, and in the case where power storage  4  is charged using charging circuit  5 , the increase in the input current at charging circuit  5  per unit time is reduced upon completion of charging of one load given priority among the plurality of loads, namely, load  7  and load  8 , to a level at which electric power can be supplied. Thus, the maximum value of an electric current flowing to charging circuit  5  is reduced. Accordingly, the electric current capacity of a device used in charging circuit  5  can be reduced, making it possible to miniaturize backup power system  1 . 
     Furthermore, when the operation of electric power supply from backup power system  1  to load  7  is preferentially made available after the start of vehicle  10 , the operation of at least load  7  is possible even if an emergency occurs in vehicle  10  shortly after the start of vehicle  10 . This makes it possible to ensure the safety of vehicle  10  and occupants in vehicle  10 . 
     The switch of input current Iin from the first rate of change to the second rate of change at time T 1  may be a continuous change from the first rate of change at time T 1  to time T 1 ′ later than time T 1 . This makes it possible to shorten the required period between time T 1  and time T 2 . As a result, driving of both load  7  and load  8  with the electric power stored in power storage  4  is enabled at an early stage. 
     The present exemplary embodiment is described using a configuration in which backup power system  1  includes backup power device  20  and backup power device  20  includes power storage  4 , charging circuit  5 , and controller  9  in order to facilitate understanding. However, backup power device  20  is not essential; backup power system  1  may include power storage  4 , charging circuit  5 , controller  9 , battery  2 , load  7 , and load  8 . In the case where backup power device  20  is not provided, for example, a portion of a connection line between charging circuit  5  and battery  2  may be regarded as input terminal  3 , and a portion of a connection line between load  7  (or load  8 ) and power storage  4  may be regarded as output terminal  6 . Alternatively, the input terminal of charging circuit  5  may be regarded as input terminal  3 , and the output terminal of discharging circuit  13  may be regarded as output terminal  6 . 
     Note that there are cases where load  7  and power storage  4  are connected to each other via a circuit including, but not limited to discharging circuit  13 . This is also the case for load  8 . 
     In the present exemplary embodiment, two loads (loads  7  and  8 ) are described as the load connected to output terminal  6 , but three or more loads may be connected to output terminal  6 . 
     CLOSING 
     Backup power system  1  according to one aspect of the present disclosure includes: battery  2 ; charging circuit  5  electrically connected to battery  2 ; power storage  4  configured to be charged by charging circuit  5 ; load  7  electrically connected to power storage  4 ; load  8  electrically connected to power storage  4 ; and controller  9  configured to control charging circuit  5 . Controller  9  detects at least one of input current Iin at charging circuit  5  and charging voltage Vc at power storage  4  in response to start signal SG 1  input to controller  9 . Controller  9  causes input current Iin at charging circuit  5  to increase at a first rate of change in response to start signal SG 1 . When controller  9  detects an increase in charging voltage Vc at power storage  4  up to first voltage V 1  at which driving of load  7  is possible, controller  9  controls charging circuit  5  to cause input current Iin at charging circuit  5  to increase at a second rate of change lower than the first rate of change. Charging circuit  5  is controlled by controller  9  to cause input current Iin to increase at the second rate of change, and charging voltage Vc at power storage  4  increases up to second voltage V 2  at which driving of both the first load and the second load is possible. 
     In backup power system  1  according to another aspect of the present disclosure, input current Iin is switched to continuously change from the first rate of change to the second rate of change. 
     In backup power system  1  according to another aspect of the present disclosure, discharging circuit  13  is further included, and load  7  and load  8  are connected to power storage  4  via discharging circuit  13 . 
     INDUSTRIAL APPLICABILITY 
     The backup power system according to the present disclosure has the advantageous effect of enabling miniaturization and is useful in various vehicles. 
     REFERENCE MARKS IN THE DRAWINGS 
     
         
         
           
               1  backup power system 
               2  battery 
               3  input terminal 
               4  power storage 
               5  charging circuit 
               6  output terminal 
               7  load 
               8  load 
               9  controller 
               10  vehicle 
               11  vehicle body 
               12  start operator 
               13  discharging circuit 
               20  backup power device 
             Ic charging current 
             Iin input current 
             Vc charging voltage