Power System

Abstract

To provide a power supply system capable of suppressing a sub-battery from being overcharged when excessive regenerative power occurs in a load connected to the backup sub-battery.SOLUTION: The power supply system for controlling a power supply to a load capable of generating regenerative power includes: a first battery; a bidirectional DC-DC converter that converts the power of the first battery into an operating voltage of the load and supplies the same to the load; a second battery that is connected to the load to supply the power to the load when the first battery fails;and a control unit that controls the operation of the bidirectional DC-DC converter. The control unit is configured so as to, when detecting the generation of regenerative power due to load, control the bidirectional DCDC converter to supply the regeneration power of the load to the first battery through hardware.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power supply system mounted on a vehicle. [Background technology]

[0002] Patent Document 1 discloses a vehicle power supply system that can recover regenerative power generated by a motor generator with high power efficiency. This vehicle power supply system describes that, during deceleration regeneration, if the SOC of a second battery, which is a secondary power supply that supplements a first battery, which is a main power supply, is equal to or lower than a regeneration permission upper limit, the second battery is charged with regenerative power supplied from a second inverter to a second power line, and if the SOC of the second battery is higher than the regeneration permission upper limit, charging of the second battery is prohibited and at least a portion of the regenerative power is supplied (discharged) to the first battery via a power converter and the first power line. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-180210 Summary of the Invention [Problem to be solved by the invention]

[0004] In the vehicle power supply system described in Patent Document 1, if excessive regenerative power occurs, such as when the regenerative power increases suddenly, the software-based discharge control of the first battery by the power converter may not be able to keep up, and the second battery may end up being overcharged.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a power supply system that can prevent the sub-battery from being overcharged when excessive regenerative power is generated in a load connected to the backup sub-battery. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of the disclosed technology is a power supply system that controls power supply to a load that can generate regenerative power, and includes: a first battery; a bidirectional DCDC converter that converts the power of the first battery into an operating voltage for the load and supplies the operating voltage to the load; a second battery that is connected to the load and supplies power to the load when the first battery fails; and a control unit that controls the operation of the bidirectional DCDC converter; when the control unit detects generation of regenerative power by the load, it controls the bidirectional DCDC converter by hardware so that the regenerative power of the load is supplied to the first battery. [Effects of the Invention]

[0007] According to the power supply system of the present disclosure, when excessive regenerative power occurs in a load connected to the second backup battery, the bidirectional DC-DC converter is controlled by hardware, which allows power to be supplied to the first main battery as quickly as possible using the response speed of the hardware, thereby preventing the second battery from being overcharged. [Brief explanation of the drawings]

[0008] [Figure 1] A functional block diagram of a power supply system and its peripheral components according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a diagram showing an example of a detailed electrical circuit of an overvoltage detection unit. [Figure 3] 10 is a flowchart illustrating the power control executed by the control unit. [Figure 4] Diagram explaining the power flow in a bidirectional DC-DC converter during normal control [Figure 5] Diagram explaining the power flow of the bidirectional DC-DC converter during hardware control of regenerative power [Figure 6] Diagram explaining the power flow of the bidirectional DC-DC converter when regenerative power is controlled by software DETAILED DESCRIPTION OF THE INVENTION

[0009] The power supply system disclosed herein, which is redundantly configured with a main battery and a sub-battery, controls the exchange of power between the main battery and the sub-battery using both software and hardware. When a large amount of power is generated on the sub-battery that cannot be processed in time by software control, the hardware controls the discharge to the main battery quickly. This control prevents the sub-battery from being overcharged. Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0010] <Embodiment> [composition] Fig. 1 is a functional block diagram of a power supply system 1 and its peripheral components according to an embodiment of the present disclosure. The power supply system 1 illustrated in Fig. 1 includes a first battery 11, a second battery 12, a bidirectional DC-DC converter 30, and a control unit 40. In Fig. 1, solid lines indicate connection lines through which power flows, and dotted lines indicate connection lines through which detection signals, control signals, and the like flow. This power supply system 1 is mounted on a vehicle such as an automobile.

[0011] The first battery 11 is a secondary battery configured to be chargeable and dischargeable, such as a lead-acid battery. The first battery 11 is connected to the first load 21 and the bidirectional DC-DC converter 30, and supplies its stored power to the first load 21 and to the second load 22 via the bidirectional DC-DC converter 30. The first battery 11 can also store power generated by a generator (not shown) or power output from a high-voltage battery (not shown). The first battery 11 functions as a main battery that supplies power to the second load 22.

[0012] The second battery 12 is a secondary battery configured to be chargeable and dischargeable, such as a lithium-ion battery. The second battery 12 is connected to the second load 22 and the bidirectional DC-DC converter 30, and supplies its own stored power to the second load 22 and charges the power output from the first battery 11 via the bidirectional DC-DC converter 30. The second battery 12 functions as a sub-battery that supplies backup power to the second load 22 when the first battery 11 fails, for example.

[0013] The first load 21 is a device such as an electronic device or electrical component called an ECU (Electronic Control Unit) mounted on the vehicle. The first load 21 is configured to operate using power stored in the first battery 11. Examples of the first load 21 include lighting devices such as headlamps and interior lights, and air conditioning devices such as heaters and coolers.

[0014] The second load 22 is a device such as an electronic device called an ECU or an electrical component mounted on the vehicle. The second load 22 is a device having the same or equivalent function as a device among the first loads 21 that requires a redundant power supply configuration. More specifically, the second load 22 is an important load related to the safe running of the vehicle, requiring a power supply of a predetermined current for a predetermined period of time from the second battery 12 even if the first battery 11 fails. Examples of the second load 22 include an electric power steering (EPS), an electric brake (EBK), an autonomous driving (AD) system, an advanced driver assistance system (ADAS), and a shift-by-wire (SBW) system. In this embodiment, the second load 22 includes at least one load (e.g., an EPS) capable of generating regenerative power. The type of electronic device or electrical component to be mounted as the second load 22 is determined appropriately depending on the vehicle specifications, required performance, and the like.

[0015] The bidirectional DC-DC converter 30 is a power converter for converting input power into power of a predetermined voltage (for example, the operating voltage of the second load 22) and outputting it. This bidirectional DC-DC converter 30 can convert (for example, step up) power of voltage V1 input from a primary side terminal to which the first battery 11 is connected to power of voltage V2 and output it to a secondary side terminal to which the second battery 12 is connected. In addition, the bidirectional DC-DC converter 30 can convert (for example, step down) power of voltage V2 input from a secondary side terminal to power of voltage V1 and output it to the primary side terminal.

[0016] This bidirectional DC-DC converter 30 includes a switching element SW1 (a step-down upper arm element), an inductor L, and a switching element SW4 (a step-up upper arm element) connected in series between a primary side terminal and a secondary side terminal, a switching element SW2 (a step-down lower arm element) that grounds between the switching element SW1 and the inductor L, and a switching element SW3 (a step-up lower arm element) that grounds between the inductor L and the switching element SW4. This bidirectional DC-DC converter 30 operates based on instructions (such as a voltage command value) from a control unit 40, which will be described later.

[0017] The multiple switching elements SW1 to SW4 are active elements that can be switched between on and off by the control unit 40, and are, for example, metal oxide semiconductor field effect transistors (MOSFETs). These multiple switching elements SW1 to SW4 can pass current when in on operation (when an on voltage is applied to the gate). The switching element SW1 is provided with a parasitic diode (or body diode) oriented to rectify current from the second battery 12 side to the first battery 11 side. The switching element SW4 is provided with a parasitic diode oriented to rectify current from the first battery 11 side to the second battery 12 side. The inductor L is a passive element that can generate a magnetic field using a flowing current and store magnetic energy, and is, for example, a choke coil having a constant current characteristic that attempts to maintain a current.

[0018] The control unit 40 controls the operation (step-up / step-down, conversion direction) of the bidirectional DC-DC converter 30, thereby controlling the exchange of power between the first battery 11, the second battery 12, and the second load 22. The control unit 40 includes a DDC control unit 41 and an overvoltage detection unit 42.

[0019] The DDC control unit 41 is a configuration (first control unit) that controls the on / off operations of the multiple switching elements SW1 to SW4 that constitute the bidirectional DCDC converter 30 in a software manner according to a predetermined program, and supplies the power of the first battery 11 to the second battery 12 and the second load 22. Specifically, the DDC control unit 41 controls the on / off operations of the switching elements SW1 to SW4 independently by individually specifying the duty ratio of the signal to be applied to the gate of each of the switching elements SW1 to SW4 so that the output voltage of the bidirectional DCDC converter 30 becomes a predetermined target voltage.

[0020] The overvoltage detection unit 42 is a configuration (second control unit) for controlling, by hardware, the on / off operation of specific switching elements, which are part of the switching elements SW1 to SW4 constituting the bidirectional DC-DC converter 30, in accordance with the regenerative power generated in the second load 22, thereby supplying the regenerative power to the first battery 11 and / or the first load 21. Specifically, when the overvoltage detection unit 42 detects that the voltage V2, which is the terminal voltage of the second battery 12, has risen to exceed a predetermined threshold due to the influence of the regenerative power generated in the second load 22, the overvoltage detection unit 42 forcibly switches the state of the bidirectional DC-DC converter 30 by hardware operation so that the regenerative power is discharged (supplied) to the first battery 11 and the first load 21. An example of a state in which the voltage V2 rises is a state in which the second battery 12 has reached a fully charged state and is no longer able to charge any more power. Therefore, the predetermined threshold can be set to any value based on the rated voltage of the second battery 12.

[0021] 2 shows an example of a detailed electrical circuit configuration of the overvoltage detection unit 42. The overvoltage detection unit 42 shown in FIG. 2 has a configuration in which the output of a comparator, which receives as inputs a voltage V2, which is the terminal voltage of the second battery 12, and a threshold Vfef, is connected to the gates of switching elements SW1 and SW3 (specific switching elements) of the bidirectional DC-DC converter 30. The overvoltage detection unit 42 compares the voltage V2 with the threshold Vfef, and fixes the output of the comparator to a low level when the voltage V2 exceeds the threshold Vfef. In this way, when the voltage V2 exceeds the threshold Vfef, the gate voltages of the switching elements SW1 and SW3 are reduced. Therefore, the on-state operation of the switching elements SW1 and SW3, which has been software-controlled by the gate signal Gcont of the DDC control unit 41, is forcibly switched to an off-state operation by hardware control of the overvoltage detection unit 42.

[0022] Hereinafter, the power control executed by the control unit 40 (the DDC control unit 41 and the overvoltage detection unit 42) when regenerative power is generated in the second load 22 will be described in detail.

[0023] [control] Next, the control performed by power supply system 1 will be described with further reference to Fig. 3. Fig. 3 is a flowchart illustrating the procedure for power control executed by control unit 40. The power control illustrated in Fig. 3 is started, for example, when the ignition of the vehicle is turned on, and is repeatedly performed until the ignition is turned off.

[0024] (Step S301) The DDC control unit 41 of the control unit 40 performs software control (SW control) on the bidirectional DC-DC converter 30 to supply power from the first battery 11 to the second battery 12 and the second load 22 during normal operation when excessive regenerative power is not being generated. More specifically, when the voltage of the first battery 11 is lower than the rated voltage of the second battery 12, for example, the DDC control unit 41 turns on the switching elements SW1 and SW4, turns off the switching element SW2, and controls the duty ratio of the switching element SW3 to on / off, thereby causing the bidirectional DC-DC converter 30 to function as a boost circuit. Figure 4 shows the flow of power in the bidirectional DC-DC converter 30 functioning as a boost circuit during normal control.

[0025] When the DDC control unit 41 performs power supply (normal operation) from the first battery 11 to the second battery 12 and the second load 22 by software control, the process proceeds to step S302.

[0026] (Step S302) The overvoltage detection unit 42 of the control unit 40 determines whether the voltage V2, which is the terminal voltage of the second battery 12, exceeds the threshold Vfef. That is, the overvoltage detection unit 42 determines whether the second load 22 has generated regenerative power that exceeds the amount that the second battery 12 can tolerate. The threshold Vfef is, for example, the rated voltage of the second battery 12.

[0027] If the overvoltage detection unit 42 determines that the voltage V2 exceeds the threshold Vfef (step S302, Yes), the process proceeds to step S303. On the other hand, if the overvoltage detection unit 42 determines that the voltage V2 is less than the threshold Vfef (step S302, No), the process proceeds to step S301.

[0028] (Step S303) The overvoltage detection unit 42 of the control unit 40 performs hardware control (HW control) on the bidirectional DC-DC converter 30 so that the regenerative power generated in the second load 22 can be discharged to the first battery 11. More specifically, the overvoltage detection unit 42 latches the gate voltages of the switching elements SW1 and SW3 at a low level to turn off the switching elements SW1 and SW3. FIG. 5 shows the flow of power in the bidirectional DC-DC converter 30 during hardware control of the regenerative power. As shown in FIG. 5, by forcibly turning off the switching element SW1, the regenerative power generated in the second load 22 can be released to the first battery 11 and the first load 21 via a parasitic diode while preventing charge from leaking from the first battery 11 to the second battery 12.

[0029] When the overvoltage detection unit 42 performs a discharge from the second battery 12 and the second load 22 side to the first battery 11 and the first load 21 side by hardware control, the process proceeds to step S304.

[0030] (Step S304) The overvoltage detection unit 42 of the control unit 40 determines whether the voltage V2, which is the terminal voltage of the second battery 12, continues to exceed the threshold Vfef until a predetermined time has elapsed since the voltage V2 exceeded the threshold Vfef. If the voltage V2 remains high despite the discharge of regenerative power to the first battery 11 and the first load 21 in step S303, there is a concern that the switching element SW1 may be damaged. Therefore, this determination is made to avoid damage to the switching element SW1. The predetermined time is set appropriately based on the structure, performance, etc. of the switching element SW1.

[0031] If the overvoltage detection unit 42 determines that the predetermined time has elapsed while the voltage V2 has exceeded the threshold Vfef (YES in step S304), the process proceeds to step S305. On the other hand, if the overvoltage detection unit 42 determines that the voltage V2 has exceeded the threshold Vfef but the predetermined time has not yet elapsed (NO in step S304), the process proceeds to step S302.

[0032] (Step S305) The DDC control unit 41 of the control unit 40 performs software control (SW control) on the bidirectional DC-DC converter 30 so that more of the regenerative power generated in the second load 22 can be discharged to the first battery 11. More specifically, the DDC control unit 41 forcibly disconnects the connection between (the gate of) the switching element SW1 and the overvoltage detection unit 42 using a relay R, for example, to turn on the switching element SW1. FIG. 6 shows the flow of power in the bidirectional DC-DC converter 30 when the regenerative power is software controlled. As shown in FIG. 6, turning on the switching element SW1 allows a large amount of current to flow not only through the parasitic diode but also through the transistor, so that the regenerative power can be discharged to the first battery 11 and the first load 21 without damaging the switching element SW1.

[0033] When the DDC control unit 41 performs software-controlled discharge (special operation) from the second battery 12 and second load 22 side to the first battery 11 and first load 21 side, the process proceeds to step S306.

[0034] (Step S306) The overvoltage detection unit 42 of the control unit 40 determines whether the voltage V2, which is the terminal voltage of the second battery 12, has become less than the threshold Vfef. In other words, the overvoltage detection unit 42 determines whether the regenerative power generated by the second load 22 has disappeared or whether the regenerative power generated by the second load 22 has become equal to or less than the allowable amount of the second battery 12.

[0035] If the overvoltage detection unit 42 determines that the voltage V2 is less than the threshold Vfef (step S306, Yes), the process proceeds to step S301. On the other hand, if the overvoltage detection unit 42 determines that the voltage V2 is not less than the threshold Vfef (step S306, No), the process proceeds to step S305.

[0036] In the above embodiment, the generation of excessive regenerative power in the second load 22 is determined by monitoring the voltage V2, which is the terminal voltage of the second battery 12. However, the generation of excessive regenerative power in the second load 22 can also be determined by monitoring the current flowing through the switching element SW1, the current flowing into the second battery 12, and the like, in addition to the voltage V2.

[0037] <Actions and Effects> As described above, in the power supply system 1 according to an embodiment of the present disclosure, when excessive regenerative power that the second battery 12 cannot tolerate (handle) is generated in the second load 22 connected to the second battery 12 that serves as a backup for the first battery 11, the power supply system 1 forcibly controls the bidirectional DC-DC converter 30 by a hardware circuit so that the regenerative power can be discharged to the first battery 11 and the first load 21. This control makes it possible to prevent the second battery 12 from becoming overcharged due to the regenerative power.

[0038] Furthermore, in the power supply system 1 according to this embodiment, when excessive regenerative power continues to be generated for a long period of time, the DDC control unit 41 controls the bidirectional DC-DC converter 30 by software to maintain electrical continuity between the first battery 11 and the first load 21 side and the second battery 12 and the second load 22 side. This control can prevent breakdown of the switching element SW4 constituting the bidirectional DC-DC converter 30. [Industrial Applicability]

[0039] The power supply system of the present disclosure can be used in vehicles and the like that are equipped with a load capable of generating regenerative power. [Explanation of symbols]

[0040] 1 Power System 11 First Battery 12 Second Battery 21 1st load 22 2nd load 30 Bidirectional DC / DC converter 40 Control Unit 41 DDC control unit (first control unit) 42 Overvoltage detection unit (second control unit) SW1 to SW4 Switching elements (MOSFET) L inductor

Claims

1. A power supply system that controls power supply to a load capable of generating regenerative power, A first battery; a bidirectional DC-DC converter configured to be capable of step-up and step-down operation using a plurality of switching elements, converting the power of the first battery into an operating voltage of the load and supplying the operating voltage to the load; a second battery connected to the load and configured to supply power to the load when the first battery fails; a control unit that controls the operation of the bidirectional DC-DC converter, when generation of regenerative power by the load is detected in a state in which power is being supplied from the first battery to the load, the control unit controls, by hardware, to turn off a step-down upper arm switching element and a step-up lower arm switching element, among the plurality of switching elements constituting the bidirectional DC-DC converter, each having a parasitic diode that rectifies current from the load to the first battery, so that the regenerative power of the load is supplied to the first battery.

2. The control unit a first control unit that controls the on / off operations of the plurality of switching elements by software in accordance with a predetermined program; a second control unit that controls the on / off operations of the plurality of switching elements by hardware via a predetermined electric circuit, 2. The power supply system according to claim 1, wherein, when generation of regenerative power by the load is detected in a state in which power is being supplied from the first battery to the load, the electric circuit of the second control unit latches the step-down upper arm switching element and the step-up lower arm switching element, which have been turned on by the first control unit, to an off operation.

3. 3. The power supply system according to claim 2, wherein the second control unit latches the step-down upper arm switching element and the step-up lower arm switching element in an off state when the voltage of the second battery exceeds a predetermined threshold.

4. 4. The power supply system according to claim 3, wherein, when a state in which the voltage of the second battery exceeds the predetermined threshold continues for a predetermined time, the first control unit cuts off the electric circuit of the second control unit and controls the voltage-down upper arm switching element to an on operation.

5. A power supply system as described in claim 3 or 4, wherein the predetermined threshold is the rated voltage of the second battery.

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