Vehicle power supply device

Abstract

To provide a power supply device for a vehicle which obtains a stable low voltage power for driving an on-vehicle device in a low voltage by dropping-off a high voltage power supply if a voltage in high voltage storage means is changed.SOLUTION: In a construction that a power conversion is performed from a high voltage to a low voltage by selectively connecting a predetermined power storage element group to a low voltage electric power load from a high voltage power supply formed by serially connecting a power storage element in series, a voltage of each power storage element group, provides rectification means to an output side of switching means as well as setting the number of power storage elements so that the voltage of the power storage element slightly becomes higher than a static operation voltage of low voltage electric load means at the time when the voltage of them in the lowest, and a smooth circuit formed by an inductor and a capacitor. By controlling a ratio of an ON time and OFF time (a dead time) of the switching means, the low voltage power supply of a stable voltage can be constructed without an influence of the change of a voltage (SOC) of each power storage element.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power supply device mounted on a vehicle, which comprises a high-voltage storage means used particularly for driving the vehicle, and a low-voltage power supply for supplying to electrical loads other than those used for driving the vehicle, and is configured so that the low-voltage power supply is obtained from the high-voltage storage means via a step-down means. [Background technology]

[0002] As the above power supply device, a vehicle power supply device proposed by the present applicant is known (Patent Document 1). According to this, in a configuration in which a high voltage power supply formed by connecting storage elements in series is selectively connected to a low voltage electrical load to perform power conversion from high voltage to low voltage, the storage element groups are switched at high speed to reduce the switching loss of the switching means to approximately zero. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-26973 A Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, a lithium-ion secondary battery is used as the storage element of a high-voltage storage means for a vehicle. In this case, the usage range of the battery's SOC (State Of Charge) is about 30% to 80%. Accordingly, the unit cell voltage of the lithium-ion secondary battery varies from about 2.6V to about 3.6V, so that when the number of unit cells in the storage element group is four, the group voltage varies from 2.6V x 4 = 10.4V to 3.6V x 4 = 14.4V. In addition, it is known that a voltage drop occurs due to the multiplication of the current consumption of the low-voltage electric load and the internal resistance of the storage element.

[0005] Low-voltage electric loads for a vehicle include lighting devices using incandescent bulbs, or windshield wiper mechanisms driven by DC motors, and the operating states of these low-voltage electric loads change depending on the operating voltage, such as the brightness of the lights or the operating speed of the wipers. The vehicle power supply device of Patent Document 1 has a problem in that when the voltage of the high-voltage storage means and the current consumption of the low-voltage electric load change, the voltage of the low-voltage power supply changes in response, resulting in an unstable operating state of the low-voltage electric load.

[0006] The present invention has been made in consideration of the above-mentioned problems, and provides a vehicle power supply device that is mounted on a vehicle and obtains a low-voltage power supply from a high-voltage power supply via a step-down means, and that has a simple configuration and is capable of obtaining a stable low voltage even if the voltage of the storage element that constitutes the high-voltage power supply and the current consumption of the low-voltage electrical load change. [Means for solving the problem]

[0007] The vehicle power supply device according to the present invention comprises an electric load means that operates at a low voltage, and a plurality of Storage battery a high-voltage power supply which obtains a high-voltage DC power supply by connecting in series, and a step-down means which steps down the voltage of the high-voltage power supply to obtain a low-voltage DC power supply, wherein the voltage value of the low-voltage DC power supply is set to the rated operating voltage of the electrical load means.

[0008] The step-down means includes a switching means, and the plurality of serially connected Storage battery At each node, Storage battery When the voltage value of the first node is at the lowest value in the operating range, the single node or the plurality of nodes is selected by the switching means so that the voltage becomes substantially equal to the rated operating voltage of the electric load means.

[0009] The step-down means comprises a rectifying means connected to the switching means, and a known smoothing circuit consisting of an inductor and a capacitor connected in parallel to the rectifying means, and is configured so that both ends of the capacitor serve as a low-voltage DC power source to supply power to the electrical load means.

[0010] The plurality of Storage battery A high voltage power supply that obtains a high voltage DC power supply by connecting the above in series has a voltage that is N times (N is a natural number) the voltage of the low voltage DC power supply, Storage battery The number of is constructed as N×n (n is a natural number).

[0011] The step-down means includes a control means, and the control means controls the switching means to control the plurality of Storage battery The present invention operates by periodically varying the location of a single node or multiple nodes selected from among the above.

[0012] The control means acts to provide a so-called dead time during which the connections between all nodes and the rectifying means are cut off when the switching means changes the node position selected by the switching means.

[0013] The control means acts to change the ratio of the time during which the single or multiple nodes are selectively connected to the dead time.

[0014] In the vehicle power supply device according to the invention of claim 2, the control means acts to change the ratio of the time during which the node is selectively connected to the dead time depending on the voltage value of the single / or multiple nodes.

[0015] In the vehicle power supply device according to the invention of claim 3, the control means acts to change the ratio of the time during which the node is selectively connected to the dead time in accordance with the voltage value of the high voltage power supply.

[0016] In the vehicle power supply device according to the invention of claim 4, the control means is configured to feedback control the ratio of the time during which the nodes are selectively connected to the dead time so that the difference between the voltage value of the low-voltage DC power supply and the rated operating voltage of the electrical load means is minimized. Effect of the Invention

[0017] According to the invention of claim 1, Storage battery When the voltage value of the node is at the lowest level within the operating range, the voltage value of the single or multiple nodes selectively connected by the switching means is made substantially equal to the rated voltage value of the electrical load means. Storage battery Even when the voltage is at its lowest value, a low-voltage power supply voltage equal to or higher than the rated operating voltage of the electrical load means can be obtained.

[0018] Furthermore, according to the invention of claim 1, the control means is configured to change the ratio of the time during which the single node and / or the plurality of nodes are selectively connected to the dead time, and obtain a low-voltage DC power supply through a smoothing circuit consisting of a rectifying element, an inductor, and a capacitor. Storage battery It is possible to obtain a low-voltage DC power supply with an arbitrary voltage value regardless of the voltage of the power supply.

[0019] Furthermore, according to the invention of claim 1, Storage battery When the voltage value of the switching means is at the lowest level within the operating range, the voltage value of the single or multiple nodes selectively connected by the switching means is made approximately equal to the rated voltage value of the electrical load means, thereby minimizing the input / output potential difference of the switching means, thereby minimizing the known switching loss.

[0020] According to the invention of claim 2, the control means acts to change the ratio between the time when the node is selectively connected and the dead time depending on the voltage value of the single / or multiple nodes. Therefore, when the voltage value of the storage element becomes high, the switching means reduces the ratio between the time when the node is selectively connected and the time when it is not connected (dead time) to perform a step-down operation, thereby making it possible to keep the voltage value of the low-voltage DC power supply constant regardless of the voltage of the storage element.

[0021] According to the invention of claim 3, the control means acts to change the ratio between the time when the node is selectively connected and the dead time in accordance with the voltage value of the high-voltage power supply. Therefore, when the voltage value becomes high, the switching means reduces the ratio between the time when the node is selectively connected and the time when it is not connected (dead time) to perform a step-down operation, thereby making it possible to keep the voltage value of the low-voltage DC power supply constant regardless of the voltage value of the high-voltage power supply.

[0022] According to the invention of claim 4, the control means is configured to feedback control the ratio between the time during which the nodes are selectively connected and the dead time so that the difference between the voltage value of the low-voltage DC power supply and the rated operating voltage of the electrical load means is minimized, so that the voltage accuracy of the low-voltage DC power supply can be maintained high.

[0023] As described above, the vehicle power supply device of the present invention has the excellent effect of being able to stably operate various low-voltage electrical load means without causing changes in the illuminance of lights or changes in the operating force or speed of motor actuators, etc. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a diagram showing a basic configuration of a vehicle power supply device according to the present invention; [Diagram 2] 5 is a timing chart illustrating the operation of the vehicle power supply device of the present invention; [Diagram 3] FIG. 13 is a diagram showing the group voltage and the duty of the switching means. [Figure 4] FIG. 1 is a diagram showing a configuration of a general voltage reducing means; [Diagram 5] FIG. 1 is a diagram comparing the power loss of a general voltage step-down means with the power loss of the present invention. [Figure 6] FIG. 1 is a diagram showing another embodiment of a vehicle power supply device according to the present invention; EXAMPLES

[0025] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a vehicle power supply device of the present invention will be described with reference to the accompanying drawings.

[0026] FIG. 1 shows a basic embodiment of the present invention, in which a vehicle power supply device 1 comprises charging means 10 mounted on a vehicle and driven by the engine, power storage elements 20a-20o consisting of secondary batteries charged by the charging means 10, switching means 30-35, control means 40, electrical load means 50 operating at a rated voltage of 12V, rectifying means 60 having both ends connected to the switching means 30-35, and a smoothing circuit consisting of an inductor 70 and a capacitor 80 connected in parallel with the rectifying means 60, which acts as a low-voltage DC power source to supply a voltage Vo to the electrical load means 50.

[0027] The charging means 10 is driven by an engine (not shown) to supply the electric power required for the vehicle's electrical equipment, and when the vehicle decelerates, it acts to regenerate the kinetic energy generated during deceleration via the drive system to charge the storage elements 20a to 20o.

[0028] Each node of the storage elements 20a to 20o is, for example, a lithium ion battery with a nominal voltage of about 3V, and all the nodes of the storage elements 20a to 20o are connected in series to form a high-voltage power supply with a total of 36V or more, with a multiple N of 3 for the rated operating voltage of 12V of the electric load means 50. The high-voltage power supply is also supplied to an electric drive control system (not shown) that is comprised of an on-board motor, inverter, etc., and acts to assist the drive torque of the engine. As a result, when the vehicle accelerates, the energy regenerated during the deceleration can be reused to run, thereby improving the fuel efficiency of the vehicle.

[0029] The energy storage elements 20a to 20o are grouped into a first group including nodes 20a to 20e. The nodes from 20f to 20j are the second group, and the nodes from 20k to 20o are the third group. As a group, both ends of each group are connected to the switching means 30 to 35. The total number of storage elements 20a to 20o is the multiple N=3 multiplied by the number of elements in each group. Multiplying this by n=5 gives a total of N×n=15.

[0030] Generally, a lithium-ion secondary battery is used as the storage element of the high-voltage storage means for a vehicle. In this case, the usage range of the battery's SOC (State Of Charge) is about 30% to 80%. Accordingly, the single cell voltage of the lithium-ion secondary battery varies from about 2.6V to about 3.6V, so that when the number of single cells in each group is 5, the group voltage varies from 2.6V x 5 = 13V to 3.6V x 5 = 18V.

[0031] In addition, since the electric storage element has a certain internal resistance, the electric storage element also reduces the unit cell voltage due to the current flowing through the electric storage element. For example, if the internal resistance is 1 mΩ and the number of unit cells is 5, when the electric current flowing through the electric load means 50 is 100 A, the minimum value of the group voltage reduces to 13 V - 100 A x (1 mΩ x 5) = 12.5 V.

[0032] In FIG. 1, 40 is a control means for controlling the ON / OFF of the switching means 30 to 35. Acts to control the F state.

[0033] As shown in Fig. 1, the control means 40 turns on the switching means 30 and 32 to connect the rectifier means 60 and the first group of storage elements for a time Ton in Fig. 2. At this time, the switching means 31, 34, 33, and 35 are turned off. Since the switching means 30 is connected to the positive electrode side of the first group and the switching means 32 is connected to the negative electrode side of the first group, the DC voltage of each group is applied to the rectifier means 60 with the cathode side as + during the Ton period.

[0034] It is desirable that the time Ton be, for example, about 50 microseconds.

[0035] Next, the control means 40 maintains all of the switching means 30 to 35 OFF during a dead time Td shown in Fig. 2. The reason for providing the time Td is that, for example, if there is a period during which the switching means 30 and the switching means 31 are simultaneously ON, an excessive current will flow through a closed circuit formed by the switching means 30 and the switching means 31 and the storage elements 20a, 20b, 20c, 20d, and 20e, which may result in damage to the switching means or wasteful consumption of the charging power of each storage element.

[0036] In the first group, the control means 40 turns on the switching means 30, 32 for a period Ton, and supplies the voltage of the first group to the rectifier means 60, the inductor 70, and the capacitor 80. When all the switching means 30 to 35 are subsequently turned off during a period Td, the current of the inductor 70 flows in the forward direction through the capacitor 80 and the rectifier means 60. In the second group, the switching means 31 and 34 are turned ON for a period Ton, and the voltage of the second group is supplied to the rectifier means 60, the inductor 70, and the capacitor 80. When all the switching means 30 to 35 are subsequently turned OFF for a period Td, the current of the inductor 70 flows in the forward direction through the capacitor 80 and the rectifier means 60. In the third group, the switching means 33, 35 are turned ON for a period Ton, and the voltage of the third group is supplied to the rectifier means 60, the inductor 70, and the capacitor 80. When all the switching means 30 to 35 are subsequently turned OFF for a period Td, the current of the inductor 70 flows in the forward direction through the capacitor 80 and the rectifier means 60. The above operation is repeated with T in Fig. 2 being one cycle.

[0037] As a result, the output voltage Vo of the low-voltage DC power supply is Vo=voltage of each group×Ton / (Ton+Td), that is, Vo=group voltage×ON duty.

[0038] The rated operating voltage of the electrical load means 50 is generally 12 V. Therefore, according to the above configuration, even when the voltage of the storage element is at its minimum value, the voltage of each group is 12.5 V, so if the ON duty is set to 96%, the rated operating voltage of the electrical load means 50 can be 12 V or more.

[0039] When the voltage of the power storage elements 20a to 20o increases, the control means 40 reduces the ON duty and maintains the output voltage Vo as a low-voltage DC power supply at the rated operating voltage of the electric load means 50.

[0040] 3, when the group voltage is 12.5 V, the control means sets the ON duty to 96%, and when the group voltage is 18 V, the control means sets the ON duty to 66.7%, thereby maintaining the output voltage Vo as a low-voltage DC power supply at 12 V regardless of the value of the group voltage. In this way, the control means can keep the value of Vo constant by continuously changing the ON duty in response to changes in the group voltage.

[0041] Incidentally, the control means 40 monitors the voltage across the rectifying element 60 when the switching means 30 to 35 select any one of the groups, and measures the voltage of each group.

[0042] Alternatively, control means 40 may receive as input the series voltage of storage elements 20a to 20o, that is, the voltage value of a high voltage power supply, and vary the ON duty in response to this voltage.

[0043] As described above, the vehicle power supply device of the present invention is configured to convert power from high voltage to low voltage by selectively connecting a specified storage element group to a low voltage electrical load from a high voltage power supply formed by connecting storage elements in series, and the number of storage elements is set so that the voltage of each storage element group is slightly higher than the rated operating voltage of the low voltage electrical load means when the voltage of the storage elements is at its lowest.In addition, a rectifying means and a smoothing circuit consisting of an inductor and a capacitor are provided on the output side of the switching means, and the ratio of the ON time and OFF time (dead time) of the switching means is controlled, making it possible to make the voltage value of the low voltage power supply approximately match the rated value of the electrical load means without being affected by changes in the voltage of the storage elements.

[0044] Incidentally, a known step-down converter shown in FIG. 4 is generally used as a method for obtaining a low-voltage DC power supply from a high-voltage DC power supply.

[0045] FIG. 4 shows a high-voltage power supply consisting of storage elements 20a to 20o connected in series, which is switched on and off by switching means S30 and supplied to a rectifying and smoothing circuit consisting of rectifying means 60, inductor 70, and capacitor 80, while controlling the ON / OFF ratio of the switching means S30 to control the voltage Vo of the stepped-down low-voltage power supply.

[0046] When the operation of the step-down means of the present invention is compared with that of the above-mentioned step-down converter in FIG. 5, the voltage V applied to the switching means, the current I flowing through the switching means, and the loss V×I of the switching means result in a large power loss in the above-mentioned step-down converter as shown in (a), whereas the step-down means of the present invention minimizes the voltage value of the storage element group and therefore reduces the power loss as shown in (b), resulting in higher power conversion efficiency.

[0047] Next, another embodiment of the vehicle power supply device of the present invention will be described with reference to Fig. 6. Note that the components using the same reference numerals as those in Fig. 1 in the above embodiment have the same functions, so the description will be omitted.

[0048] FIG. 6-1 shows a power supply device for a vehicle in this embodiment, in which a control means 40 is provided with a differential amplifier 42, and the differential amplifier 42 compares the voltage Vo of a low-voltage DC power supply with a reference voltage 41, and controls the ON duty of the switching means 30-35 so that the difference between them becomes small.

[0049] Since the reference voltage 41 is set to 12 V, which is the constant operating rated voltage of the electrical load means 50, the voltage value Vo of the low-voltage power supply can be matched with a high degree of accuracy to the rated value of the electrical load means 50 without being affected by changes in the voltage of the storage elements 20a to 20o.

[0050] In this way, in a vehicle power supply device that is mounted on a vehicle and obtains a low-voltage power supply from a high-voltage power supply via a step-down means, it is possible to configure a vehicle power supply device that is capable of obtaining a stable low voltage even if the voltage of the storage element that constitutes the high-voltage power supply changes with a simple configuration.

[0051] In each embodiment of the present invention, limited configurations and functions are shown as examples. For example, the rectifying means has been described as being a diode, but the rectifying means may be a synchronous rectifying circuit using a known MOSFET. Furthermore, the number of series storage elements, the type of storage elements, the type and configuration of the switching means, the configuration of the smoothing circuit, and the operation timing of the control means can take any form. [Explanation of symbols]

[0052] 1 Vehicle power supply unit 10 Charging means 20a~20o Energy storage means 30~35 Switching means 40 Control Means 50 Electrical load means

Claims

1. an electrical load means operating at a low voltage; A high-voltage power supply that obtains high-voltage DC power by connecting a plurality of storage batteries in series; a step-down means for stepping down the voltage of a high-voltage power supply to obtain a low-voltage DC power supply; A vehicle power supply device comprising: the voltage value of the low voltage DC power source is the rated operating voltage of the electrical load means; The step-down means includes a switching means, the switching means operates to select one or more nodes so that a voltage at each node of the plurality of series-connected storage batteries becomes substantially equal to a rated operating voltage of the electrical load means when a voltage value of the storage battery is at the lowest value of an operating range; The step-down means includes a rectifier means connected to the switching means. The rectifier includes a known smoothing circuit including an inductor and a capacitor connected in parallel with the rectifier. The capacitor is configured to supply a low-voltage DC power supply to the electric load means; The voltage value of the high-voltage power supply is N times (N is a natural number) the voltage of the low-voltage DC power supply, and the number of the storage batteries is N×n (n is a natural number), The step-down means includes a control means, the control means operates to periodically vary the location of the node or nodes selected by the switching means from among the plurality of storage batteries; When changing the node portion selected by the switching means, a dead time is provided during which all the nodes are disconnected from the rectifying means; operative to vary a ratio of a time during which the node / s are selectively connected to the dead time; A vehicle power supply device comprising:

2. 2. The vehicle power supply device according to claim 1, wherein the control means acts to change a ratio of a time during which the node is selectively connected to the dead time in accordance with a voltage value of the single or multiple nodes.

3. 2. The vehicle power supply device according to claim 1, wherein the control means acts to change a ratio of a time during which the nodes are selectively connected to the dead time in accordance with a voltage value of the high voltage power supply.

4. 2. The vehicle power supply device according to claim 1, wherein the control means feedback controls a ratio of a time during which the nodes are selectively connected to the dead time so that a difference between a voltage value of the low-voltage DC power supply and a rated operating voltage of the electrical load means is minimized.

Images