Power control equipment

Abstract

In the power supply control device, a control unit is configured to turn on a first switch and turn off a second switch when a backup power supply is to be charged, and to turn off the first switch and turn on the second switch when power is to be supplied from the backup power supply to the backup load. The control unit sets an upper limit value of a charging state of the backup power supply based on an output voltage to the backup load obtained by subtracting a voltage drop from an open circuit voltage of the backup power supply, the voltage drop being a voltage drop from the inside of the backup power supply to an output to the backup load side via the second switch.

Description

Technical Field

[0001] The invention relates to a power supply control device. Background Art

[0002] A vehicle power supply system is known, which includes a lead battery used as a main power supply and a lithium ion battery used as a backup power supply (see, for example, Patent Document 1). In the vehicle power supply system disclosed in Patent Document 1, the lithium ion battery is connected to the lead battery, the AC generator, the load, and the backup load via a DC / DC converter. The DC / DC converter is a bidirectional DC / DC converter that converts the voltage on the lead battery side and supplies the converted voltage to the lithium ion battery side, or converts the voltage on the lithium ion battery side and supplies the converted voltage to the lead battery side through a switching operation.

[0003] Patent document 1: JP-A-2017-063543. Summary of the invention

[0004] In the above-mentioned vehicle power supply system, when a ternary lithium-ion battery or the like having a higher voltage than a 12V battery when fully charged is used for a backup power supply, the voltage of the backup power supply when fully charged exceeds the upper limit value of the load voltage of the backup power supply system. Therefore, the voltage to be supplied from the backup power supply side to the backup load side must be reduced by a DC / DC converter.

[0005] However, when the required output of the DC / DC converter increases due to the increase in the load to be driven, the cost of the DC / DC converter increases, because, for example, the structure of the DC / DC converter needs to be significantly changed in order to improve the cooling performance of the DC / DC converter or the size of the components needs to be increased. Here, by releasing the power from the backup power supply side to the backup load side without using the DC / DC converter, the cost of the DC / DC converter can be reduced. However, in this case, the output voltage from the backup power supply to the backup load must be suppressed to an upper limit value equal to or less than the load voltage of the backup power supply system. For this purpose, the state of charge of the backup power supply must be kept low so that the open circuit voltage of the backup power supply is equal to or lower than the upper limit value of the load voltage of the backup power supply system. Therefore, the use range of the capacity of the backup power supply is narrowed, and the capacity of the backup power supply cannot be effectively used.

[0006] The present disclosure is made in consideration of the above circumstances, and an object of the present disclosure is to provide a power supply control device that can reduce the cost of a DC / DC converter and can effectively use the capacity of a backup power supply in a power supply system in which the voltage of the backup power supply when fully charged is higher than the voltage of a main power supply.

[0007] The present disclosure provides a power control device in a power system, the power system comprising a power supply unit, a main power supply, and a backup power supply whose voltage is higher than that of the main power supply when fully charged, the power control device connecting the power supply unit, the main power supply and the backup power supply, and configured to control the charging and discharging of the backup power supply, the power control device comprising: a power line, to which the power supply unit, the main power supply, the backup power supply and the backup load are connected; a first switch, which is arranged on the power line and configured to connect / disconnect the power supply unit and the connection between the main power supply and the backup power supply; a second switch, which is arranged on the power line and configured to connect / disconnect the connection between the backup power supply and the backup load; a charging DC / DC converter, connected to the power line in parallel with the second switch, and configured to convert the voltage supplied from the power supply unit side and supply the converted voltage to the backup power supply side; and a control unit, which is configured to turn on the first switch and turn off the second switch when the backup power supply is to be charged, and turn off the first switch and turn on the second switch when power is to be supplied from the backup power supply to the backup load, wherein the control unit is configured to set an upper limit value of the charging state of the backup power supply based on an output voltage to the backup load obtained by subtracting a voltage drop from an open-circuit voltage of the backup power supply, the voltage drop being a voltage drop from the inside of the backup power supply via the second switch to the output to the backup load side.

[0008] According to the present disclosure, by setting the upper limit value of the charging state of the backup power supply based on the output voltage to the backup load obtained by subtracting the voltage drop from the inside of the backup power supply via the second switch to the backup load side from the open-circuit voltage of the backup power supply, the cost of the DC / DC converter can be reduced, and the capacity of the backup power supply can be effectively used in a power supply system in which the voltage of the backup power supply when fully charged is higher than the voltage of the main power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a diagram showing a vehicle power supply system including a control module according to an embodiment of the present disclosure.

[0010] Figure 2 is a diagram showing a vehicle power supply system including a control module according to an embodiment of the present disclosure.

[0011] Figure 3 is a diagram showing a vehicle power supply system including a control module according to an embodiment of the present disclosure.

[0012] Figure 4 : is a graph showing the relationship between the voltage and the state of charge of the backup battery in the case where the backup battery is charged without performing an estimation process of estimating the upper limit value of the state of charge of the backup battery.

[0013] Figure 5: is a graph showing the relationship between the voltage and the state of charge of the backup battery after the estimation process of estimating the upper limit value of the state of charge of the backup battery is performed in the case of charging the backup battery. DETAILED DESCRIPTION

[0014] Hereinafter, the present disclosure will be described according to preferred embodiments. The present disclosure is not limited to the embodiments to be described below, and may be appropriately changed without departing from the scope of the present disclosure. Although some configurations are not shown or described in the embodiments to be described below, known or well-known technologies are appropriately applied to the details of the omitted technologies within the scope that the contents to be described below do not contradict each other.

[0015] Figures 1 to 3 is a diagram showing a vehicle-mounted power supply system 1 including a control module 10 according to an embodiment of the present disclosure. As shown in these figures, the vehicle-mounted power supply system 1, as an example of a power supply system, includes a main battery 2 as an example of a main power supply, a backup battery 3 as an example of a backup power supply, a high-voltage DC / DC converter 4 as an example of a power supply unit, and a control module 10 as an example of a power control device. In the vehicle-mounted power supply system 1 of the present embodiment, the main battery 2 is a conventional power supply that supplies power to a 12V main load 5, and the backup battery 3 is an emergency power supply that supplies power to a 12V backup load 6. In addition, the main battery 2 of the present embodiment is a 12V lead-acid battery. In contrast, the backup battery 3 of the present embodiment is a ternary lithium-ion secondary battery and has a higher voltage than the main battery 2.

[0016] The power supply unit includes, for example, a 48V high voltage power supply, a generator such as an AC generator, and a high voltage DC / DC converter 4. The high voltage DC / DC converter 4 reduces the high voltage output from the high voltage power supply and the generator, and outputs the reduced high voltage. The main battery 2, the main load 5, the standby load 6, and the standby battery 3 are connected to the power line PL1, which is connected to the output terminal of the high voltage DC / DC converter 4.

[0017] like Figure 1 As shown, in a normal state where no power failure occurs in the main power supply system, the power output from the high-voltage DC / DC converter 4 is supplied to the main load 5 and the main battery 2. When charging the backup battery 3, the power output from the high-voltage DC / DC converter 4 is supplied to the backup battery 3 via the control module 10. On the other hand, Figure 2 As shown in FIG. 1 , when a power failure occurs in the main power supply system, power is supplied from the backup battery 3 to the backup load 6. That is, the control module 10 controls the charging and discharging of the backup battery 3 so that: Figure 1As shown, in a normal state where no power failure occurs in the main power supply system, the backup battery 3 is charged by the power output by the high-voltage DC / DC converter 4, and when Figure 2 As shown, when a power failure occurs in the main power system, power is released from the backup battery 3 to the backup load 6.

[0018] Control module 10 includes first switch 11, second switch 12, charging DC / DC converter 13, discharge circuit 14, central processing unit (CPU) 20 as an example of a control unit, and power line PL1. First switch 11 and second switch 12 are provided on power line PL1.

[0019] The first switch 11 is provided on the power line PL1 between the connection point P1 of the main load 5 and the connection point P2 of the backup load 6. The first switch 11 is a transistor switch such as a metal oxide semiconductor field effect transistor (MOSFET), and is turned on in a normal state when no power failure occurs in the main power supply system to allow current to flow from the high voltage DC / DC converter 4 side to the backup battery 3 side, such as Figure 1 On the other hand, when a power failure occurs in the main power system, the first switch 11 is disconnected to cut off the current flowing from the backup battery 3 to the high-voltage DC / DC converter 4, as shown in FIG. Figure 2 shown.

[0020] The second switch 12 is provided on the power line PL1 between the connection point P2 of the backup load 6 and the VB2 terminal T1 as an example of the first terminal. The VB2 terminal T1 is a terminal of the control module 10 to which the power line PL5 connected to the backup battery 3 is connected. The second switch 12 is a transistor switch such as a MOSFET, and is turned off when no power failure occurs in the main power supply system (when charging the backup battery 3) to cut off the current flowing from the high-voltage DC / DC converter 4 side to the backup power supply 3 side, as shown in FIG. Figure 1 On the other hand, when Figure 2 As shown, when a power failure occurs in the main power supply system (when the backup battery 3 discharges power), the second switch 12 is turned on to allow current to flow from the backup battery 3 side to the backup load 6 side.

[0021] The charging DC / DC converter 13 is connected to the power line PL1 in parallel with the second switch 12. In other words, the charging DC / DC converter 13 is provided on the bypass line BL bypassing the second switch 12. The shunt resistor Rsh1 for the current sensor is provided on the bypass line BL.

[0022] When Figure 1As shown in FIG. 1 , when no power failure occurs in the main power supply system, the charging DC / DC converter 13 converts the voltage output from the high-voltage DC / DC converter 4 and outputs the converted voltage to the backup battery 3. Here, the current flowing through the charging DC / DC converter 13 when charging the backup battery 3 is a very small current of about 4A, and the output capacity required by the charging DC / DC converter 13 is small. On the other hand, when the backup battery 3 is charged as shown in FIG. Figure 2 As shown, when a power failure occurs in the main power supply system, the current output from the backup battery 3 to the backup load 6 is a relatively large current of about 80A.

[0023] The discharge circuit 14 is connected to the power line PL4 via the power line PL3, and the power line PL4 connects the power line PL1 and the Vout terminal T2 as an example of the second terminal. The Vout terminal T2 is a terminal to which the power line PL2 is connected, and the power line PL2 is connected to the standby load 6. The discharge circuit 14 includes a switch (not shown). When the backup battery 3 discharges power while the switch of the discharge circuit 14 is turned on, current flows from the power line PL3 to the discharge circuit 14, as shown in FIG. Figure 3 As shown. Shunt resistor Rsh2 for current sensor is provided on power line PL4, between connection point P2 and connection point P3 of power line PL3. In addition, shunt resistor Rsh3 for current sensor is provided on power line PL3.

[0024] The CPU 20 controls the first switch 11, the second switch 12, the charging DC / DC converter 13, and the discharging circuit 14. For example, in the event of a power failure in the main power system, such as when the output voltage of the main battery 2 decreases to a predetermined value or less, the CPU 20 turns off the first switch 11 and turns on the second switch 12, as shown in FIG. Figure 2 shown.

[0025] When no power failure occurs in the main power system, the CPU 20 turns on the first switch 11, turns off the second switch 12, and turns on the charging DC / DC converter 13, as shown in FIG. Figure 1 Here, when charging the backup battery 3 via the charging DC / DC converter 13, the CPU 20 sets the state of charge of the backup battery 3 to a value appropriate with respect to the allowable range of the load voltage of the backup power supply system. Further, the CPU 20 performs a process for estimating an upper limit value SOC2 of the state of charge of the backup battery 3, which is determined with respect to an upper limit value Vmax of the load voltage of the backup power supply system when the vehicle is stopped (when the ignition switch is turned off). This process will be described below.

[0026] Figure 4: is a graph showing the relationship between the voltage and the state of charge of the backup battery 3 in the case where the backup battery 3 is charged without performing the estimation process of estimating the upper limit value SOC2 of the state of charge SOC of the backup battery 3 .

[0027] The backup power supply system has an allowable range of load voltage, and the upper limit value Vmax is, for example, 16 V. On the other hand, the open circuit voltage OCV of the backup battery 3 (i.e., the ternary lithium ion secondary battery) of the present embodiment when fully charged is, for example, 16.8 V, which exceeds the upper limit value Vmax of the load voltage of the backup power supply system. Here, in the case where the estimation process of estimating the upper limit value SOC2 of the state of charge SOC of the backup battery 3 described later is not performed, since the upper limit value SOC2 cannot be calculated with high accuracy, the upper limit value SOC2 of the state of charge SOC of the backup battery 3 cannot be calculated with high accuracy. Figure 4 Therefore, the upper limit value SOC1 of the state of charge SOC of the backup battery 3 is set too low so that the output voltage Vout is equal to or less than the upper limit value Vmax of the load voltage of the backup power supply system. Therefore, the use range of the capacity of the backup battery 3 is narrowed.

[0028] Figure 5 1 is a graph showing the relationship between the voltage and the state of charge SOC of the backup battery 3 in the case of charging the backup battery 3 after the estimation process of estimating the upper limit value SOC2 of the state of charge SOC of the backup battery 3 is performed. As shown in the graph, in the present embodiment, the output voltage Vout from the backup battery 3 to the backup load 6 is appropriately calculated by the method to be described later, and the upper limit value SOC2 of the state of charge SOC is estimated based on the calculation result, and the upper limit value SOC2 is an appropriate value with respect to the upper limit value Vmax of the load voltage of the backup power supply system. Therefore, the state of charge SOC of the backup battery 3 can be appropriately set so that the use range of the capacity of the backup battery 3 is expanded, while the output voltage Vout does not exceed the upper limit value Vmax of the load voltage of the backup power supply system.

[0029] like Figure 3 As shown, the CPU 20 turns off the first switch 11, turns on the second switch 12, turns off the charging DC / DC converter 13, and turns on the discharge circuit 14. Therefore, the current flows from the backup battery 3 to the discharge circuit 14 and the backup load 6 via the second switch 12. At this time, the current value of the current flowing through the backup load 6 is Iout, and the current value of the current flowing through the discharge circuit 14 is I3.

[0030] The output voltage Vout is calculated using the following equation (1).

[0031] Vout=OCV-(Iout×Rout)…(1)

[0032] Rout is calculated using the following equation (2).

[0033] Rout=Rb+Rm…(2)

[0034] Rb is the internal resistance of the backup battery 3 , and Rm is the internal resistance of the control module 10 from the VB2 terminal T1 to the Vout terminal T2 .

[0035] Here, the current value Iout of the current output to the standby load 6 is set to the minimum value Ioutmin of the total current output to the loads that are continuously driven among the standby loads 6 .

[0036] The internal resistance Rb of the backup battery 3 is calculated using the following equation (3).

[0037] Rb=α(OCV-VB2) / I2…(3)

[0038] I2 is calculated using the following equation (4).

[0039] I2=Iout+I3…(4)

[0040] α is a conversion coefficient of the internal resistance Rb of the backup battery 3, which changes according to the discharge current and is obtained in advance by performing a characteristic evaluation test of the battery.

[0041] VB2 is the voltage of the backup battery 3 and is measured during execution of the estimation process.

[0042] I2 is a current value of a current flowing from the VB2 terminal T1 to the Vout terminal T2 in the control module 10 .

[0043] The internal resistance Rm of the control module 10 from the VB2 terminal T1 to the Vout terminal T2 via the second switch is calculated using the following equation (5).

[0044] Rm=(VB2-Vout) / I2…(5)

[0045] I2 is calculated by using the above equation (4).

[0046] The CPU 20 sets the upper limit value SOC2 of the state of charge SOC of the backup battery 3 to a value at which Vout=Vmax.

[0047] That is, in the estimation process of estimating the upper limit value SOC2 of the state of charge SOC of the backup battery 3, the output voltage Vout from the Vout terminal T2 to the backup load 6 is calculated by subtracting the voltage drop ΔV (=Iout×Rout) from the open circuit voltage OCV of the backup battery 3, which is the voltage drop from the inside of the backup battery 3 to the Vout terminal T2 of the control module 10. When calculating the output voltage Vout, the current value Iout of the current output from the Vout terminal T2 to the backup load 6 is set to the minimum value Ioutmin. Therefore, by setting the state of charge SOC of the backup battery 3 to the upper limit value SOC2 of the state of charge SOC with Vout=Vmax, the output voltage Vout can be reliably prevented from exceeding the upper limit value Vmax of the load voltage of the backup power supply system, and the use range of the capacity of the backup battery 3 can be extended from Figure 4 The SOC0 to SOC1 is expanded to Figure 5 SOC0 to SOC2 in.

[0048] Although the present disclosure has been described based on the embodiments, the present disclosure is not limited to the embodiments described above. The present disclosure may be appropriately modified without departing from the scope of the present disclosure, or known or publicly known technologies may be appropriately combined.

[0049] For example, in the above-described embodiment, the discharge circuit 14 is provided, and power is discharged from the backup battery 3 to the discharge circuit 14, and the voltage drop ΔV is calculated based on the current value I3 of the current flowing through the discharge circuit 14. Alternatively, the voltage drop ΔV may be calculated using other methods.

Claims

1. A power control device, wherein the power control device is in a power system, wherein the power system includes a power supply unit, a main power supply, and a backup power supply whose voltage is higher than that of the main power supply when fully charged, wherein the power control device is connected to the power supply unit, the main power supply, and the backup power supply, and is configured to control the charging and discharging of the backup power supply, wherein the power control device includes: a power line to which the power supply unit, the main power supply, the backup power supply and the backup load are connected; a first switch, which is provided on the power line and is configured to connect / disconnect the connection between the power supply unit and the backup power supply and between the main power supply and the backup power supply; a second switch, which is disposed on the power line and is configured to connect / disconnect the connection between the backup power source and the backup load; a charging DC / DC converter connected to the power line in parallel with the second switch and configured to convert a voltage supplied from the power supply unit side and supply the converted voltage to the backup power supply side; as well as a control unit configured to turn on the first switch and turn off the second switch when the backup power source is to be charged, and to turn off the first switch and turn on the second switch when power is to be supplied from the backup power source to the backup load, Wherein, the control unit is configured to set an upper limit value of the charging state of the backup power supply based on an output voltage to the backup load obtained by subtracting a voltage drop from an open-circuit voltage of the backup power supply, wherein the voltage drop is a voltage drop from the inside of the backup power supply via the second switch to the output to the backup load side when the second switch is turned on.

2. The power control device according to claim 1, further comprising: a discharge circuit provided between the second switch and the standby load, The control unit is configured to perform a discharge process of turning on the second switch to release power from the backup power supply through the discharge circuit, and calculate the voltage drop based on a current value of a current flowing through the discharge circuit during execution of the discharge process, a current value of a current output to the backup load, a current value of a current flowing from the backup power supply to the backup load via the second switch, a voltage of the backup power supply, and the open circuit voltage.

3. The power control device according to claim 1 or 2, in, The control unit is configured to set the upper limit value of the charging state of the standby power source so that the output voltage to the standby load is equal to an upper limit value of a predetermined load voltage.

4. The power control device according to claim 1 or 2, in, The control unit is configured to calculate the voltage drop based on a sum of an internal resistance of the backup power source and an internal resistance from a first terminal to a second terminal, the backup power source being connected to the first terminal and the backup load being connected to the second terminal.

5. The power control device according to claim 3, in, The control unit is configured to calculate the voltage drop based on a sum of an internal resistance of the backup power source and an internal resistance from a first terminal to a second terminal, the backup power source being connected to the first terminal and the backup load being connected to the second terminal.

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