Power supply system, DC / DC converter

Abstract

The invention relates to a power supply system (100) comprising: a first voltage subsystem including a first battery (130) connected to a load (140) via a relay (150); a second voltage subsystem including a second battery (110), the second battery (110) having a voltage lower than that of the first battery; and a DC / DC converter (160) disposed between the first voltage subsystem and the second voltage subsystem, in which before the switching of the closing of the relay, the DC / DC converter is configured to: supply a voltage lower than a voltage of the second battery to the first voltage subsystem; then supply the voltage of the second battery to the first voltage subsystem; and then increase the voltage of the second battery so that it is equal to a voltage of the first battery and supply the voltage of the second battery to the first voltage subsystem.Figure for the abridged version: Fig. 1.

Description

Title of the invention: Power supply system, DC / DC converter Technical field

[0001] The present invention relates to a power supply system provided with two subsystems having different voltages, and to a DC / DC converter for use in such a power supply system. Technological background

[0002] Usually, power supply systems are generally configured as 12 V power supply systems that supply power from a 12 V battery. However, in recent years, 48 ​​V power supply systems that supply power from a 48 V battery are increasingly being used. The use of a power supply system having a higher voltage than that of a conventional power supply system allows a supplied current to be reduced for the same power. This allows a reduction in vehicle weight, etc., to be expected due to a reduction in power loss during power transmission and / or a reduction in the thickness of electrical wires. It is expected that 48 V power supply systems will also be used in vehicles equipped with autonomous driving systems in the future.

[0003] It is assumed that even when using a 48 V power supply system, a 12 V power supply system is used with the 48 V power supply system in a vehicle for a certain period of time in order to operate, for example, the existing electrics and / or electronics in the vehicle. Combining the 12 V system with the 48 V system in a vehicle can provide a redundant power supply system that provides power supply redundancy. List of quotes

[0004] Patent Documentation

[0005] Patent document 1: JP 2021-29078 A Summary

[0006] [Fig.4] shows a block diagram illustrating a power supply system electric system 300 for an automobile that is equipped with both a 12 V subsystem and a 48 V subsystem. In the 12 V subsystem, a 12 V battery 310 powers a 12 V load 320, as shown in [Fig. 4]. In the 48 V subsystem, a 48 V battery 330 powers a 48 V load 340 via a main relay 350. As the main relay 350 is usually used a mechanical relay.

[0007] A DC / DC converter 360 is arranged between the 12 V subsystem and the 48 V subsystem, the DC / DC converter 360 being configured to be operated bidirectionally such that a mutual energy exchange is possible between the 12 V and 48 V subsystems.

[0008] The DC / DC converter 360 includes a step-up and step-down circuit 361, a 12V side isolation switch 362 for switching a connected state of the DC / DC converter 360 to the 12V battery 310, a 48V side isolation switch 363 for switching a connected state of the DC / DC converter 360 to the 48V battery 330, and a controller 364.

[0009] The 12V side isolation switch 362 and the 48V side isolation switch 363 are formed by MOSFETs, the 12V side isolation switch 362 being configured with a back-to-back connection to prevent current backflow. The control device 364 is formed, for example, by a CPU and configured to control the raising / lowering operation of the step-up and step-down circuit 361 as well as the opening / closing operation of the 12V side isolation switch 362 and / or the 48V side isolation switch 363.

[0010] In the 48 V subsystem, a capacitance C exists in parallel with the 48 V load 340. This is a capacitance that is generated, for example, by a capacitive component that is unique to the 48 V load 340, and / or by parasitic capacitance(s) existing in the 48 V subsystem. Typically, the capacitance C is discharged when the ignition is turned off and the main relay 350 is switched to open.

[0011] In the power supply system 300, when the main relay 350 is switched closed from its open state with the capacitance C not being charged, a high inrush current flows into the main relay 350 from the 48 V battery 330, which may result in welding of the main relay 350.

[0012] In the power supply system 300, the capacitor C is precharged using the 12 V battery 310 to prevent the main relay 350 from being welded due to such an inrush current. More specifically, before switching the closure of the main relay 350, the capacitor C is charged with a voltage of 12 V supplied by the 12 V battery 310, and the DC / DC converter 360 is then operated to increase the voltage from 12 to 48 V to charge the capacitor C. By using such a soft charge sequence, a voltage difference between the 48 V battery 330 and the capacitor C is eliminated before switching the closure of the main relay 350. In this way, welding, due to the inrush current, of the main relay 350 is avoided.

[0013] On the other hand, an inrush current is also generated during the precharging of the capacitor C using the 12 V battery 310, the inrush current flowing through the DC / DC converter 360 from the 12 V battery 310 into the capacitor C. This current inrush may result in a load being applied to the internal circuitry of the DC / DC converter 360, particularly the 12V side isolation switch 362. This problem can occur not only with power supply systems, but also with any power supply system that includes two different batteries with different voltages and a DC / DC converter.

[0014] Therefore, an object of the present invention is to provide a power supply system including a DC / DC converter and batteries in two subsystems having different voltages which allows an internal circuit of the DC / DC converter to be protected during pre-charging for high voltage side relay protection.

[0015] In order to achieve the objective as described above, a power supply system according to a first aspect of the present invention includes: a first voltage subsystem including a first battery connected to a load via a relay; a second voltage subsystem including a second battery, the second battery having a lower voltage than that of the first battery; and a DC / DC converter disposed between the first voltage subsystem and the second voltage subsystem, wherein before switching the closure of the relay, the DC / DC converter is configured to: supply a voltage lower than a voltage of the second battery to the first voltage subsystem; then supply the voltage of the second battery to the first voltage subsystem;and then increasing the voltage of the second battery to be equal to a voltage of the first battery and supplying the voltage of the second battery to the first voltage subsystem. ;

[0016] In order to achieve the objective as described above, a DC / DC converter according to a second aspect of the present invention is configured to be disposed between a first voltage subsystem and a second voltage subsystem, the first voltage subsystem including a first battery connected to a load via a relay and the second voltage subsystem including a second battery, the second battery having a lower voltage than the first battery, before switching the relay closure, the DC / DC converter being configured to: supply a voltage lower than a voltage of the second battery to the first voltage subsystem; then supply the voltage of the second battery to the first voltage subsystem; and then increase the voltage of the second battery to be equal to a voltage of the first battery and supply the voltage of the second battery to the first voltage subsystem. Brief description of the figures

[0017] [Fig.l] shows a configuration of a power supply system according to one embodiment;

[0018] [Fig.2] shows an example configuration of a step-up / step-down circuit;

[0019] [Fig.3] shows an illustration of the operation of the power supply system electrical according to the embodiment; and

[0020] [Fig.4] shows a configuration of a conventional power supply system equipped with batteries of two subsystems. Description of the embodiments

[0021] Embodiments of the present invention will be described in detail with reference to the drawings. [Fig. 1] shows a configuration of a power supply system according to one embodiment. The power supply system 100 is an automobile power supply system including two voltage subsystems together, in this example a 12 V voltage subsystem and a 48 V voltage subsystem. However, it should be noted that the present invention is not limited to automobile power supply systems having 12 V and 48 V subsystems, but can also be applied to a wide variety of power supply systems that have different batteries of different voltages.

[0022] As shown in this figure, the 12 V subsystem includes a 12 V battery 110 and a 12 V load 120, the 12 V battery 110 powering the 12 V load 120. The 48 V subsystem includes a 48 V battery 130 and a 48 V load 140, the 48 V battery 130 powering the 48 V load 140 via a main relay 150. In addition, an ISG (engine-function generator) may be provided to power the 48 V load 140. A mechanical relay is used as the main relay 150, the main relay 150 being configured to be switched to close, for example, via an ignition signal that is indicative of an ignition having been activated.

[0023] A DC / DC converter 160 is arranged between the 12 V subsystem and the 48 V subsystem, the DC / DC converter 360 being configured to be operated bidirectionally such that a mutual power exchange is possible between the 12 V and 48 V subsystems. For example, the DC / DC converter 160 may increase a voltage of 12 V in order to charge the 48 V battery 130, and / or decrease a voltage of 48 V in order to charge the 12 V battery 110. In addition, when, for example, a fault occurs in one battery, this can be compensated by the other battery. In addition, both batteries can supply a same load.

[0024] In the 48 V subsystem, a capacitance C exists in parallel to the 48 V load 140. This is a capacitance which is generated, for example, by a capacitive component which is specific to the 48 V load 140, and / or by a parasitic capacitance(s) existing in the 48 V subsystem.

[0025] The DC / DC converter 160 includes a step-up and step-down circuit 161, a com 12 V side isolation switch 162, a 48 V side isolation switch 163 and a control device 164. The 12 V side isolation switch 162 is arranged on a step-down output side of the step-up and step-down circuit 161, and is connected to the 12 V subsystem. The 12 V side isolation switch 162 is formed by two MOSFETs which are connected back-to-back. The 48 V side isolation switch 163 is arranged on a step-up output side of the step-up and step-down circuit 161, and is connected to the 48 V subsystem. The 48 V side isolation switch 163 is formed by a MOSFET, a body diode of the MOSFET being arranged with its forward direction facing the 48 V side.

[0026] The DC / DC converter 160 further includes a precharge switch 165 and a voltage sensor 166 between the step-up and step-down circuit 161 and the 12 V side isolation switch, the precharge switch 165 being configured to switch the connection / disconnection of a 10 V power supply. However, arranging the precharge switch 165 on a side of the DC / DC converter 160 that is closer to the 48 V subsystem than the 12 V side isolation switch 162 is sufficient.

[0027] As a 10 V power supply, one can, for example, apply one conventional, which is electrically powered by the 12 V battery 110 and is already provided, for example, to electrically power an electronic device 167, such as an IC included in the DC / DC converter 160. The use of such an existing power supply eliminates the need for a new additional power supply circuit for the 10 V power supply. Here, it should be noted that the power supply is not limited to a 10 V power supply, but can be any power supply which has a voltage for operating an electronic device included in the DC / DC converter 160 lower than the 12 V provided by the 12 V battery 110.

[0028] As the step-up and step-down circuit 161, an existing circuit can be applied. For example, the step-up and step-down circuit 161 can be configured as shown in [Fig. 2]. In the example of this figure, a coil 161a and a switching element 161c are connected in series between a pull-down output side and a pull-up output side of the step-up and step-down circuit 161, with a capacitor 161b connected between the pull-down output side and ground. Here, the switching element 161c is arranged such that its body diode has a forward direction oriented toward the pull-up output side.

[0029] Further, a switching element 161d is connected between ground and a node between the coil 161a and the switching element 161c. Here, the switching element 161d is arranged such that its body diode has a forward direction that is opposite to ground.

[0030] The drive section 161e is configured to drive the switching element 161c and the switching element 161d under the control of the control device 164. More specifically, for a lowering operation, the drive section 161e drives the switching element 161c to be turned on / off with the switching element 161d being in an off state. For a raising operation, the drive section 161e drives the switching element 161d to be turned on / off with the switching element 161c being in an off state.

[0031] The control device 164 is formed, for example, by a CPU and configured to control the raising and lowering operation of the step-up and step-down circuit 161 as well as an opening / closing operation of the 12V-side isolation switch 162, the 48V-side isolation switch 163, and the precharge switch 165 as described below, based on an ignition signal and a detection result of the voltage sensor 166, the ignition signal being indicative of the ignition being energized.

[0032] Next, the operation of the power supply system according to the present embodiment will be described with reference to [Fig. 3]. [Fig. 3] shows time sequences of the open / closed state of the main relay 150 controlled by a higher level system, the open / closed states of the 12V side isolation switch 162, the 48V side isolation switch 163 and the precharge switch 165 controlled by the controller 164, the operating state of the step-up and step-down circuit 161, and a charged voltage of the capacitor C.

[0033] First, in an initial state T0 of the ignition which is off, the first relay 150 is in an open state, the capacitor C being discharged and having a voltage of 0 V. The control device 164 controls the opening of the 12 V side isolation switch 162, the 48 V side isolation switch 163 and the precharge switch 165 and deactivates the step-up and step-down circuit 161.

[0034] When the ignition signal is supplied to the controller 164 at T1, wherein the ignition signal indicates that the ignition is on, the controller 164 performs the following control on T1 at T3 before the main relay 150 is switched to be closed by the higher level system at T4.

[0035] First, at T1, the controller 164 controls the closing of the precharge switch 165. In this way, a voltage of 10 V is applied between the step-up and step-down circuit 161 and the 12 V side isolation switch 162, and the capacitor C is charged to 10 V via the body diodes of the switching element 161c and the 48 V side isolation switch 163 in the step-up and step-down circuit 161 in the off state.

[0036] When based on an output signal from the voltage sensor 166, detects that capacitor C has been charged to 10 V, the controller 164 controls the 12 V side isolation switch 162 to close at T2. In this way, a voltage of 12 V is applied via the 12 V side isolation switch 162 from the 12 V battery 110, and capacitor C is charged to 12 V via the body diode of the switching element 161c and the body diode of the 48 V side isolation switch 163 in the step-up and step-down circuit 161 in the off state. In order to prevent backflow to the 10 V power supply during this process, the precharge switch 165 is switched to open at T2.

[0037] Just before initiating charging of capacitor C to 12 V, capacitor C is charged to 10 V by pre-charge switch 165. Therefore, only an inrush current corresponding to the difference of 2 V will flow into 12 V side isolation switch 162 in the closed state, which results in a sufficiently reduced load being applied to 12 V side isolation switch 162.

[0038] When based on the output signal from the voltage sensor 166, it is detected that the capacitor C has been charged to 12 V, the controller 164 controls the step-up and step-down circuit 161 to perform a step-up operation to increase the 12 V voltage supplied by the 12 V battery to 48 V at T4, with the controller 164 simultaneously controlling the 48 V-side isolation switch 163 to close. In this way, the capacitor C is charged to 48 V. The capacitor C can be charged to 48 V via the body diode of the 48 V-side isolation switch 163 with the 48 V-side isolation switch 163 remaining in an open state.

[0039] Then, the higher level system controls the main relay 150 to close at T4. Since the capacitance C is at 48 V in advance, no inrush current is generated, and the main relay 150 may not be welded. It should be noted that after T4, the controller 164 keeps the precharge switch 165 open, while the open / closed states of the 12 V side isolation switch 162, the 48 V side isolation switch 163, and the operating state of the step-up and step-down circuit 161 are adaptively controlled by the controller 164, for example, depending on a driving state of an automobile and / or a charging state of the batteries.

[0040] As described above, the power supply system 100 according to the present embodiment is configured to perform the soft precharge in which the capacitor C is charged with a voltage lower than the 12 V supplied by the 12 V battery 110, and after that charged with the voltage of 12 V. In this way, only an inrush current corresponding to a voltage difference between 12 V and the lower voltage will flow into the internal circuits of the DC / DC converter 160. Therefore, it is possible to protect the internal circuits of the DC / DC converter 160. of the inrush current during precharge.

[0041] Furthermore, for the voltage below 12 V, a voltage can be applied which is supplied by the 12 V battery 110 as a voltage source and is provided to supply the electronic device 167 included in the DC / DC converter 160. Therefore, it is not necessary to provide a new additional power supply for precharging with the voltage below 12 V, since the precharging can be carried out with a simplified configuration. List of reference signs

[0042] 100 Power supply system 110 12V Battery 120 Charge 12 V 130 Battery 48 V 140 Charge 48 V 150 Main Relay 160 DC / DC Converter 161 Step-up and Step-down Circuit 161a Coil 161b Capacitor 161c Switching element 16Id Switching element 161st Training Section 162 12V side isolation switch 163 48V side isolation switch 164 Control device 165 Precharge Switch 166 Voltage sensor 167 Electronic device.

Claims

Claims

1. A power supply system (100) comprising: a first voltage subsystem including a first battery (130) connected to a load (140) via a relay (150); a second voltage subsystem including a second battery (110), the second battery (110) having a voltage lower than that of the first battery (130); and a DC / DC converter (160) disposed between the first voltage subsystem and the second voltage subsystem, wherein before switching the closure of the relay (150), the DC / DC converter (160) is configured to: supply a voltage lower than a voltage of the second battery (110) to the first voltage subsystem; then supply the voltage of the second battery (110) to the first voltage subsystem;and then increasing the voltage of the second battery (110) to be equal to a voltage of the first battery (130) and supplying the voltage of the second battery (110) to the first voltage subsystem.;

2. The power supply system (100) of claim 1, wherein the DC / DC converter (160) includes an electronic device (167) configured to be operated with a voltage lower than the voltage of the second battery (110).

3. The power supply system (100) of claim 1 or 2, wherein the DC / DC converter (160) includes a switch (162) configured to switch a connected state of the DC / DC converter (160) to the second battery (110), and wherein the DC / DC converter (160) is configured to supply, from a side closer to the first voltage subsystem than the switch (162), the voltage lower than the voltage of the second battery (110) to the first voltage subsystem.

4. A DC / DC converter (160) configured to be disposed between a first voltage subsystem and a second voltage subsystem, wherein the first voltage subsystem includes a first battery (130) connected to a load (140) via a relay (150) and the second voltage subsystem includes a second battery (110), the second battery (110) having a lower voltage than the first battery (130), in which before switching the closing of the relay (150), the DC / DC converter (160) is configured to: providing a voltage lower than a voltage of the second battery (110) to the first voltage subsystem; then supplying the voltage of the second battery (110) to the first voltage subsystem; and then increasing the voltage of the second battery (110) to be equal to a voltage of the first battery (130) and supplying the voltage of the second battery (110) to the first voltage subsystem.

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