Power supply system

Abstract

To provide a power supply system capable of suppressing a load when charging a battery.SOLUTION: A power source system 10 includes an accessory battery 21 that supplies power to an accessory 23, a DC / DC converter 13 that charges the accessory battery 21, and a ECU15 that controls the DC / DC converter 13, wherein the ECU15 raises a voltage generated by the DC / DC converter 13 when a battery SOC, which is a charging ratio of the accessory battery 21, is low or when the accessory 23 is protected, and lowers the voltage generated by the DC / DC converter 13 when the battery SOC of the accessory battery 21 is high or when a load on the accessory 23 is low.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply system. [Background technology]

[0002] Patent Document 1 discloses a control method for charging an auxiliary battery from a main battery by intermittently operating a DC-DC converter. This control method determines whether the auxiliary battery has deteriorated based on the voltage drop of the auxiliary battery when charging is stopped during intermittent charging, and if it has deteriorated, stops the intermittent charging of the auxiliary battery and allows the auxiliary battery to be charged continuously. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-193598 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above control method, charging of the auxiliary battery is stopped during intermittent operation of the DC-DC converter, which causes the auxiliary battery to repeatedly discharge and place a load on it. For example, if the auxiliary battery is a lead battery, repeated discharge may cause deterioration such as softening, hardening, and shrinkage of the active material.

[0005] The present invention has been made in view of the above circumstances, and has as its object to provide a power supply system that can reduce the load when charging a battery. [Means for solving the problem]

[0006] In order to achieve the above object, the power supply system of the present invention comprises: an auxiliary battery for supplying power to the auxiliary; a charging unit that charges the auxiliary battery; a control unit that controls the charging unit; A power supply system comprising: The control unit When the charging rate of the auxiliary battery is low or when the auxiliary is to be protected, the power generation voltage of the charging unit is increased; When the charging rate of the auxiliary battery is high or when the load of the auxiliary device is low, the power generation voltage of the charging unit is reduced; The auxiliary battery lower limit voltage is set to be equal to or higher than the auxiliary battery OCV corresponding to when the auxiliary battery is at the target charging rate of the auxiliary battery, and the charging unit that charges the auxiliary battery is controlled so that the auxiliary battery voltage is equal to or higher than the auxiliary battery lower limit voltage, thereby maintaining the charging rate of the auxiliary battery at or above the target.

[0007] In this power supply system, the generated voltage is increased when the auxiliary battery's charging rate (battery SOC) is lower than the target charging rate (target SOC), and is decreased when the battery SOC is higher than the target SOC. Furthermore, the auxiliary battery's lower limit voltage is set to be equal to or higher than the battery SOC, so that even if the auxiliary battery reaches the lower limit voltage, it will still be above the target SOC and will not discharge. On the other hand, when the battery SOC is higher than the target SOC, the generated voltage is maintained at the lower limit voltage. This makes it possible, for example, to suppress discharge from the auxiliary battery while the vehicle is running, thereby reducing the burden on the auxiliary battery. Even if the auxiliary battery is a lead-acid battery, for example, it is possible to suppress deterioration such as softening, hardening, and shrinkage of the active material. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a power supply system that can reduce the load when charging the battery. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram illustrating the configuration of a power supply system according to this embodiment. [Figure 2] FIG. 2 is a diagram showing the SOC-OCV characteristic curve of the auxiliary battery. [Figure 3] FIG. 3 is a graph showing the state of the auxiliary battery. [Figure 4] FIG. 4 is a graph showing the state of the auxiliary battery when the generated voltage is feedback controlled within a range in which the battery voltage is lower than the lower limit battery voltage. [Figure 5] FIG. 5 is a graph showing the lower limit battery voltage feedback control. [Figure 6] FIG. 6 is a graph showing battery SOC feedback control. [Figure 7] FIG. 7 is a graph showing auxiliary charging and auxiliary device protection control. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram illustrating the configuration of a power supply system 10 according to this embodiment.

[0011] 1, a power supply system 10 according to this embodiment is a system equipped with a high-voltage battery 11, and is a suitable system for use in an electric vehicle that runs on the power of the high-voltage battery 11. Examples of electric vehicles include electric vehicles, hybrid vehicles, fuel cell vehicles, and other vehicles that run by driving a drive motor (not shown) with electric power.

[0012] The power supply system 10 includes a DC / DC converter (charging unit) 13 and an ECU (control unit) 15, and the ECU 15 controls the DC / DC converter 13. The ECU 15 controls the DC / DC converter 13, thereby controlling the charging and discharging of the high-voltage battery 11. For example, the ECU 15 controls the DC / DC converter 13 to control the supply of power from the high-voltage battery 11 to the drive motor and the charging of the high-voltage battery 11 with regenerative power from the drive motor.

[0013] This power supply system 10 includes an auxiliary battery (battery) 21 that is different from the high-voltage battery 11 that is the power source for running the vehicle. The auxiliary battery 21 is connected to auxiliary equipment 23 by a power line PL. The auxiliary equipment 23 to which the auxiliary battery 21 is connected is various electrical equipment equipped on the vehicle, such as a headlight, heater, horn, power window device, etc. The auxiliary battery 21 is a battery that supplies power to these various auxiliary equipment 23, and is mainly a 12 (V) secondary battery.

[0014] The auxiliary battery 21 is equipped with a battery sensor 25. This battery sensor 25 is a sensor that detects the state of charge (SOC), voltage, and current of the auxiliary battery 21. This battery sensor 25 is connected to the ECU 15, and each detection value of the auxiliary battery 21 detected by the battery sensor 25 is transmitted to the ECU 15.

[0015] The auxiliary battery 21 is connected to the DC / DC converter 13 by a power line PL, and is charged by power supplied from the DC / DC converter 13. The ECU 15 monitors the charge state of the auxiliary battery 21 based on a detection value from a battery sensor 25, and controls the DC / DC converter 13 to charge the auxiliary battery 21.

[0016] Next, the charging control of the auxiliary battery 21 by the ECU 15 in the power supply system 10 will be described.

[0017] The ECU 15 monitors the battery SOC (charging rate) of the auxiliary battery 21 based on the detected value from the battery sensor 25, and adjusts the voltage generated by the DC / DC converter 13 for the auxiliary battery 21.

[0018] Specifically, when the battery SOC of the auxiliary battery 21 is low or during auxiliary protection when the auxiliary device 23 requires protection, the DC / DC converter 13 increases the power generation voltage of the auxiliary battery 21, and when the battery SOC of the auxiliary battery 21 is high or during low auxiliary load when the load on the auxiliary device 23 is low, the DC / DC converter 13 decreases the power generation voltage of the auxiliary battery 21.

[0019] At this time, in the power supply system 10, a target SOC, which is a control target for the battery SOC of the auxiliary battery 21, is set in advance, and the ECU 15 controls the DC / DC converter 13 so that the battery SOC of the auxiliary battery 21 is maintained at the target SOC.

[0020] Furthermore, the ECU 15 controls the DC / DC converter 13 so that the battery voltage Vb of the auxiliary battery 21 does not fall below the lower limit battery voltage Vt.

[0021] FIG. 2 is a SOC-OCV characteristic curve showing the relationship between the battery SOC of the auxiliary battery 21 and the battery OCV of the auxiliary battery 21, and the battery SOC and the battery OCV have a substantially proportional relationship.

[0022] In this example, the battery OCV at a preset target SOC is set to a lower limit battery voltage Vt in the relationship between the battery SOC of the auxiliary battery 21 and the battery voltage Vb of the auxiliary battery 21. Then, the ECU 15 controls the DC / DC converter 13 within a region VA in which the battery OCV of the auxiliary battery 21 does not fall below the lower limit battery voltage Vt.

[0023] In this way, in this example, the ECU 15 controls the charging of the auxiliary battery 21 so that the battery voltage Vb of the auxiliary battery 21 does not fall below the lower limit battery voltage Vt, as shown in Figure 3. Therefore, the battery SOC of the auxiliary battery 21 is maintained higher than the target SOC, and discharge while the vehicle is running is suppressed.

[0024] 4 shows the state of the auxiliary battery 21 when the generated voltage is feedback-controlled within a range in which the battery voltage Vb is lower than the lower limit battery voltage Vt. For example, the DC / DC converter 13 is controlled within a range VB in which the battery voltage Vb is lower than the lower limit battery voltage Vt. As a result, the battery voltage Vb of the auxiliary battery 21 continues to be near the lower limit battery voltage Vt, causing the battery to be discharged until the battery SOC falls below the target SOC.

[0025] In contrast, in the power supply system 10 according to this embodiment, as described above, the battery voltage Vb of the auxiliary battery 21 is controlled so as not to fall below the lower limit battery voltage Vt. In other words, the battery voltage Vb of the auxiliary battery 21 can be maintained at or above the battery OCV at the target SOC, so that the battery SOC, which is the charging rate of the auxiliary battery 21, is maintained higher than the target SOC. This reduces the burden on the auxiliary battery 21, and, for example, even if the auxiliary battery 21 is a lead battery, it is possible to suppress deterioration such as softening, hardening, and shrinkage of the active material.

[0026] Hereinafter, each control of the auxiliary battery 21 will be described with reference to the drawings. (lower limit battery voltage feedback control) 5 is a graph showing the lower limit battery voltage feedback control. In this lower limit battery voltage feedback control, the ECU 15 controls the DC / DC converter 13 to feedback control the generated voltage of the auxiliary battery 21 so that the battery voltage Vb of the auxiliary battery 21 does not fall below the lower limit battery voltage Vt.

[0027] (Battery SOC feedback control) 6 is a graph showing battery SOC feedback control. In this battery SOC feedback control, the ECU 15 controls the DC / DC converter 13 to feedback control the power generation voltage of the auxiliary battery 21 so that the battery SOC of the auxiliary battery 21 is maintained at a target SOC.

[0028] (Auxiliary charging and auxiliary equipment protection control) 7 is a graph showing the auxiliary charging and auxiliary equipment protection control. In this auxiliary charging and auxiliary equipment protection control, ECU 15 executes auxiliary charging control when the battery SOC of auxiliary equipment battery 21 is low, and executes auxiliary equipment protection control when the load on auxiliary equipment 23 is heavy. As a result, during this auxiliary charging and auxiliary equipment protection control, ECU 15 controls DC / DC converter 13 to charge auxiliary equipment battery 21 at a constant high voltage. [Explanation of symbols]

[0029] 10 Power supply system. 13 DC / DC converter (charging section) 15 ECU (control unit) 21 Auxiliary battery 23 Auxiliary equipment

Claims

[Claim 1] an auxiliary battery for supplying power to the auxiliary; a charging unit that charges the auxiliary battery; a control unit that controls the charging unit; A power supply system comprising: The control unit When the charging rate of the auxiliary battery is low or when the auxiliary is to be protected, the power generation voltage of the charging unit is increased; When the charging rate of the auxiliary battery is high or when the load of the auxiliary device is low, the power generation voltage of the charging unit is reduced; an auxiliary battery lower limit voltage is set to an auxiliary battery OCV or higher corresponding to when the auxiliary battery is at a target charging rate for the auxiliary battery, and the charging unit that charges the auxiliary battery is controlled so that the auxiliary battery voltage is equal to or higher than the auxiliary battery lower limit voltage, thereby maintaining the charging rate of the auxiliary battery at or above the target; Power supply system.

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