Vehicle power supply device

Abstract

In a vehicle power supply device mounted on a vehicle and obtaining a low voltage power supply from a high voltage power supply via a step-down unit, electric shock of a human body is prevented without using an insulation unit such as a transformer. A prescribed set of storage elements is selectively connected to a low voltage electric load from a high voltage power supply formed by connecting the storage elements in series, thereby performing power conversion from high voltage to low voltage. In this structure, a leakage current from the high voltage power supply is measured during an idle time when the set of storage elements is not connected to the low voltage electric load, and the connection of the set of storage elements to the low voltage electric load is interrupted when the leakage current is above a prescribed value, thereby preventing electric shock.

Description

Technical Field

[0001] The present invention is a power supply device mounted on a vehicle, particularly a power supply device configured to have a high-voltage energy storage unit for driving and the like, and a low-voltage power supply for electrical loads other than driving, and the low-voltage power supply is obtained from the high-voltage energy storage unit via a step-down unit. Background Technology

[0002] As the aforementioned power supply device, the power supply device for vehicles proposed by the applicant is well known (Patent Document 1). Thus, in a structure in which a predetermined group of energy storage elements is selectively connected to a low-voltage electrical load from a high-voltage power supply formed by connecting energy storage elements in series, thereby converting power from high voltage to low voltage, the switching loss of the switching unit is approximately zero by switching the group of energy storage elements at high speed.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-26973 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] The voltage of the electric storage unit for driving a vehicle varies from a low voltage system of about 48 volts to a high voltage system of about 600 volts. Generally, in the voltage range of more than 60 volts, it is necessary to consider the prevention of electric shock accidents when a person comes into contact with the circuit parts connected to the vehicle's storage unit.

[0008] Therefore, in the typical high-voltage systems of vehicles, such as Figure 1 As shown, a DC-DC converter with an insulating transformer is configured between the high-voltage and low-voltage sections, and the high-voltage circuit avoids direct connection to the vehicle body, thus floating both the negative and positive potential circuits, resulting in a structure that will not cause electric shock even if a person comes into contact with any part of the circuit containing the high-voltage energy storage unit.

[0009] Here, according to Patent Document 1, since the low potential side of the load unit 50 as a low voltage circuit is normally connected to the vehicle body as a body earth of the 12-volt power supply, in the case where any one or more of the switch units 30 to 35 are closed, somewhere of the connection points of the series-connected storage units 20a to 20L on the high voltage side is directly connected to the vehicle body, so that there is a possibility that an electric shock will occur when a human body comes into contact with the high voltage circuit. Specifically, assuming that the series connection voltage of the storage units 20a to 20L is 480 volts, if contact is made between the positive potential side of the storage unit 20a and the vehicle body at the instant when the switch unit 35 is closed, there is a possibility that an electric shock accident will occur in which 480 volts of high voltage is applied to the human body.

[0010] The present application has been achieved in view of the above-described problems, and provides a vehicle power supply device mounted on a vehicle, which obtains a low voltage power supply from a high voltage power supply via a step-down unit, wherein even in the case where a system is assumed in which the voltage on the high voltage side exceeds 60 volts, which is the electric shock limit of a human body, an electric shock accident can be prevented without using an insulation unit such as a transformer, and in a power conversion function to the low voltage side, a power conversion efficiency of substantially 100% can be easily obtained.

[0011] Means for solving the problems

[0012] The vehicle power supply device of the first aspect has: an electric load that operates at a prescribed low voltage; a high voltage power supply that obtains a high voltage direct current power supply by connecting a plurality of storage elements that constitute each node (group node) that provides the prescribed low voltage in series; a plurality of switch units that are provided in correspondence with each node that provides the prescribed low voltage to the electric load; a control unit that causes all of the storage elements to provide voltage by sequentially repeating control in which voltage is provided by turning on the switch unit that provides voltage from at least one node and turning off the switch unit that provides voltage from another node, and then turning on the switch unit that provides voltage from the node and turning off the switch unit that provides voltage from another node after a no-load time period in which all of the switch units are temporarily turned off; and a leakage detection unit that detects a leakage current between the high voltage power supply and a ground potential and sends a signal to the control unit. Moreover, the vehicle power supply device is characterized in that the control unit determines the signal sent from the leakage detection unit during the no-load time period in which all of the plurality of switch units are in an off state, and in the case where the leakage current is a prescribed current or more, maintains a state in which all of the switch units are turned off for a prescribed period.

[0013] In the vehicle power supply device of the invention of the second aspect, the high-voltage power supply is configured of n storage elements, and the plurality of storage elements are connected in series n x N times to obtain a direct-current power supply of a high voltage that is N times the prescribed low voltage, where n and N are natural numbers.

[0014] In the vehicle power supply device of the invention of the third aspect, the control unit controls the switching unit in such a manner that the selected plurality of nodes are periodically changed.

[0015] In the vehicle power supply device of the invention of the fourth aspect, the control unit determines the selected nodes in such a manner that the charge and discharge states of the plurality of storage elements are substantially uniform.

[0016] In the vehicle power supply device of the invention of the fifth aspect, the control unit determines the selection hold time of each node in such a manner that the charge and discharge states of the plurality of storage elements are substantially uniform.

[0017] In the vehicle power supply device of the invention of the sixth aspect, the time during which any one of the nodes is connected to the electric load by the switching unit is set to be a duration that is less than the time that causes an electric shock accident of a human body, for a leakage current flowing from the high-voltage power supply to the human body.

[0018] In the vehicle power supply device of the invention of the seventh aspect, the time during which each node is connected to the electric load by the switching unit is a duration that is inversely proportional to the voltage value of the high-voltage power supply or a duration that is inversely proportional to the current value detected by the leakage detection unit.

[0019] In the vehicle power supply device of the invention of the eighth aspect, when the leakage detection value of the leakage detection unit is equal to or greater than a prescribed current value, the control unit fixes the switching unit to a state in which all of the switching units are turned off.

[0020] In the vehicle power supply device of the invention of the ninth aspect, the control unit repeatedly performs the following operation: when the leakage detection value of the leakage detection unit is equal to or greater than a prescribed current value, the state in which all of the switching units are turned off is maintained for a prescribed time, and then the switching units are caused to selectively connect each node to the electric load again.

[0021] In the vehicle power supply device of the invention of the tenth aspect, the control unit repeatedly performs the following operation: when the leakage detection value of the leakage detection unit is equal to or greater than a prescribed first threshold value, the switching units are turned off, and when the leakage detection value is equal to or less than a prescribed second threshold value that is less than the first threshold value, the switching units are turned on again.

[0022] In the vehicle power supply device of the eleventh aspect, the control unit controls the switching unit so that the product of the period during which each node is connected to the electric load and the leakage detection value of the leakage detection unit is 0.003 ampere x 1 second or less.

[0023] In the vehicle power supply device of the twelfth aspect, the control unit sets the period during which the node selected by the switching unit is switched to a value or less, so that the magnitude of the charge and discharge depth in each node of the electric storage element is a value or less.

[0024] In the vehicle power supply device of the thirteenth aspect, a capacitor is connected in parallel to the electric load.

[0025] In the vehicle power supply device of the fourteenth aspect, the no-load time period or the capacitance value of the capacitor is set so that the drop in the voltage applied to the electric load during the no-load time period is a value or less.

[0026] In the vehicle power supply device of the fifteenth aspect, a capacitor is provided in parallel to each node of the electric storage element.

[0027] In the vehicle power supply device of the sixteenth aspect, the polarity of the high potential side and the low potential side when each node of a high-voltage power supply obtained by connecting a plurality of electric storage elements in series to obtain a high-voltage direct-current power supply is connected to the electric load by the switching unit is alternately reversed every prescribed period, thereby supplying alternating-current power to the electric load.

[0028] Effects of the Invention

[0029] According to the first and second aspects, if the voltage of the low-voltage power supply is VL, the voltage VH of the high-voltage power supply obtained by connecting the electric storage elements in series is VL x N (N is a natural number), and since the number of the electric storage elements is N x n (n is a natural number), for example, in the case where VL is 12 volts and N = 40, VH is 480 volts, and if n = 4, the high-voltage power supply is composed of a total of N x n = 160 series-connected electric storage elements, and the voltage of each of the electric storage elements is 3 volts.

[0030] Therefore, in order to obtain a low-voltage power supply of 12 volts, it is sufficient to select four series-connected electric storage elements in a group and connect them to the electric load.

[0031] However, in order to obtain a low-voltage power supply of 12 volts from a high-voltage power supply of 480 volts, it is not necessary to use a known DC-DC converter based on a switching power supply circuit or the like, and the voltage reduction can be achieved by a simple switching unit that selectively connects each node (group node) of the series-connected electric storage elements to the electric load.

[0032] Therefore, it is possible to simplify the structure of the switching unit and greatly reduce the known switching loss and loss generated from the inductor, so as to reduce the power loss for voltage reduction and simplify the heat dissipation structure, as a result, it is possible to reduce the weight and cost of the power supply device containing the device for the voltage reduction.

[0033] Here, a part of the node of the series-connected storage elements of the high-voltage power supply is connected to the low-voltage circuit, i.e. the metal part of the vehicle body, via the switching unit, so that when in contact with the high-voltage power supply circuit part, the electric shock current flows through the human body.

[0034] However, the control unit detects the current flowing from the high-voltage power supply via the human body as the measured current value of the electric shock detection unit during the idle time when all the switching units are turned off, and in the case where the value is above a specified value, the turned-off state of the switching unit is maintained, so as to prevent the electric shock accident.

[0035] According to the invention of the second aspect, the high-voltage power supply is configured with n storage elements to form a node of a specified low voltage, and a plurality of storage elements are connected in series n x N times, thereby obtaining a direct-current power supply of a high voltage N times of the specified low voltage, wherein n and N are natural numbers. Therefore, all the storage elements can be used to efficiently provide high voltage and specified low voltage.

[0036] According to the invention of the third aspect, the switching unit is periodically changed by the control unit to select the node from the plurality of storage elements, so as to prevent the undesirable situation that only a part of the series-connected storage elements is discharged and the other storage elements are overcharged.

[0037] According to the invention of the fourth aspect, the control unit determines the selected node in such a way that the charge and discharge states of the plurality of storage elements are substantially uniform, so as to have the known battery cell balancing function required when charging and discharging the plurality of storage elements in series.

[0038] According to the invention of the fifth aspect, the control unit determines the selection holding time of each node in such a way that the charge and discharge states of the plurality of storage elements are substantially uniform. The selection holding time of each node is determined in such a way that the charge and discharge states of the plurality of storage elements are substantially uniform: for the node selected from the storage element with a larger charge, the discharge time is made longer, and conversely, for the node selected from the storage element with a smaller charge, the discharge time is made shorter. It is possible to have the known battery cell balancing function required when charging and discharging the plurality of storage elements in series.

[0039] When a high voltage is applied to a human body, if the current value is 5 mA or less, there is no effect on the human body. It is known that in a current region larger than 5 mA, the human body reaction varies depending on the duration thereof, and as the current value becomes larger, the human body is damaged due to electric shock for a short time.

[0040] Therefore, in a conventional leakage circuit breaker for a commercial power source, a leakage detection sensitivity of 30 mA x 0.1 sec is set.

[0041] Therefore, according to the invention of the sixth aspect, the control unit makes the duration of the leakage current flowing to the human body from the high voltage power source less than the time to cause an electric shock accident of the human body during the period in which the respective nodes are connected to the low voltage electric load by the switching unit, and thus even in the case where a human body contacts a circuit portion of the high voltage power source, the damage to the human body can be eliminated.

[0042] According to the invention of the seventh aspect, the control unit is configured to make the time in which the respective nodes are connected to the electric load by the switching unit a duration inversely proportional to the voltage value of the high voltage power source or a duration inversely proportional to the leakage current value flowing to the human body. In the case where the voltage value of the high voltage power source or the leakage current value flowing to the human body is high and the electric shock current of the human body is large, the energization time to the human body, i.e., the electric shock time, can be shortened, and thus the safety is further improved.

[0043] According to the invention of the eighth aspect, when the leakage detection value of the leakage detection unit is above a prescribed current value, the control unit fixes the switching unit to a state in which all of the switching units are turned off. In the case where leakage from the high voltage power source is detected, the high voltage power source continues to be in a state in which the vehicle body is floated, and thus the safety is further improved.

[0044] According to the invention of the ninth aspect, the control unit repeatedly performs the following operation: when the leakage detection value of the leakage detection unit is above a prescribed current value, the state in which all of the switching units are turned off is maintained for a prescribed time or more, and then the switching unit is caused to selectively connect the respective nodes to the electric load again. The electric shock current flowing to the human body is given a sufficient rest time to ensure safety, and even if a temporary leakage current is generated due to a failure of each portion of the power supply device of the vehicle body, the power supply from the high voltage power source to the electric load is restarted, and thus the vehicle function can be maintained.

[0045] According to the invention of the tenth aspect, the following operation is repeatedly performed: when the leakage detection value of the leakage detection unit is equal to or greater than a first threshold value of, for example, 0.003 A, the switching unit is turned off, and then, when the leakage detection value is equal to or less than a second threshold value of, for example, 0.001 A, the switching unit is turned on again. The configuration is such that, in a dangerous area where the leakage detection value is large and the electric shock current flowing to the human body is large, the state in which the high-voltage power supply is floated from the vehicle body is continued, and, in a case where the leakage detection value is small and the electric shock current is reduced to a safe value, the connection is made again, so that the safety of the human body is ensured, and, even if a temporary leakage current is generated due to a failure of each part of the vehicle body, the power supply from the high-voltage power supply to the electric load is restarted, so that the vehicle function can be maintained.

[0046] According to the invention of the eleventh aspect, the control unit controls the switching unit so that the product of the period during which each node is connected to the electric load and the leakage detection value of the leakage detection unit is equal to or less than 0.003 A x 1 second. A safety level equivalent to that of a leakage circuit breaker used in a general commercial power supply, which is equal to or less than 0.03 A x 0.1 second, can be ensured.

[0047] According to the invention of the twelfth aspect, the control unit sets the period during which the switching unit switches the selected node to be equal to or less than a prescribed value, so that the magnitude of the charge / discharge depth in each node of the electric storage element is equal to or less than a prescribed value. The reduction in the life of each electric storage element due to an excessively large charge / discharge depth of the electric storage element can be minimized.

[0048] According to the invention of the thirteenth aspect, during a so-called no-load time during which the control unit cuts off the connection between all nodes and the electric load by the switching unit, the reduction in the voltage supplied to the electric load due to the supply of power from the capacitor can be suppressed. The voltage supplied to the electric load can be stably maintained.

[0049] According to the invention of the fourteenth aspect, the voltage applied to the electric load before and after the switching of the switching unit can be maintained, so that the effect of eliminating the switching loss due to the disappearance of the potential difference across the switching unit immediately before the switching unit is turned on can be obtained.

[0050] Next, after the switching of the switching unit immediately after the connection of an arbitrary node, in a case where the internal resistance of the electric storage element is large, a large amount of time is required to charge the capacitor connected in parallel to the electric load.

[0051] Therefore, the reduction in the voltage supplied to the electric load at the time of the switching of the switching unit cannot be avoided.

[0052] According to the fifteenth aspect, a capacitor having a small internal impedance is connected in parallel with a node of the series connection of the storage elements, and thus, after switching by the switching unit, the capacitor can be charged with a small power supply impedance, i.e., a large current, and a decrease in the voltage supplied to the electrical load can be suppressed.

[0053] According to the sixteenth aspect, the polarity of the high potential side and the low potential side when connected to the electrical load by the switching unit is alternately reversed at a predetermined period, and thus, alternating-current power can be supplied to the electrical load. This can provide an alternating-current power source for using household electrical products requiring a commercial power source in a vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 FIG. 1 is a diagram showing the basic structure of a conventional vehicle power supply device.

[0055] Figure 2 FIG. 2 is a diagram showing the basic structure of a vehicle power supply device according to an embodiment of the present application.

[0056] Figure 3 FIG. 3 is a timing chart showing the basic operation of the vehicle power supply device according to the embodiment of the present application.

[0057] Figure 4 FIG. 4 is a diagram explaining the leakage detection of the vehicle power supply device according to the embodiment of the present application.

[0058] Figure 5 FIG. 5 is a diagram explaining the leakage detection of the vehicle power supply device according to the embodiment of the present application.

[0059] Figure 6 FIG. 6 is a diagram showing a structure for measuring the voltage of each node of the storage elements.

[0060] Figure 7 FIG. 7 is a diagram showing the selection holding time of each node.

[0061] Figure 8 FIG. 8 is a diagram showing one embodiment of the vehicle power supply device according to the embodiment of the present application.

[0062] Figure 9 FIG. 9 is a diagram explaining the power loss of the switching element.

[0063] Figure 10 FIG. 10 is a diagram explaining the power loss of the switching element.

[0064] Figure 11 FIG. 11 is a diagram explaining the charge and discharge depth of the storage elements.

[0065] Figure 12Fig. 1 is a diagram showing another embodiment of the vehicle power supply device of the embodiment of the present application.

[0066] Figure 13 Fig. 1 is a diagram showing another embodiment of the vehicle power supply device of the embodiment of the present application.

[0067] Figure 14 Fig. 1 is a diagram showing another embodiment of the vehicle power supply device of the embodiment of the present application. DETAILED DESCRIPTION

[0068] EMBODIMENT

[0069] Hereinafter, an embodiment of the vehicle power supply device of the present application will be described with reference to the drawings.

[0070] Figure 2 Fig. 1 is a diagram showing another embodiment of the vehicle power supply device of the embodiment of the present application.

[0071] Further, in Fig. 1, the storage elements 3b to 39d and the switching units S3b to S39a connected to these storage elements are omitted, and further, a diagram of a portion where the switching units are connected to the control unit 200 is omitted. Figure 2

[0072] The power generation unit functions in such a manner that it is driven by an engine not shown, and at the time of deceleration of the vehicle, the kinetic energy at the time of deceleration is regenerated via the drive mechanism to charge the storage elements 1a to 40d.

[0073] Each node of the storage elements 1a to 40d is, for example, a lithium ion battery having a charging voltage of 3 V, and all the nodes of the storage elements 1a to 40d are connected in series, and the multiple N of the required voltage 12 V with respect to the electric load 300 is 40, so that a high voltage power source of 480 V in total is formed. Further, the high voltage power source functions in such a manner that it provides to an electric drive control system composed of a motor not shown, an inverter, and the like, to assist the driving torque of the engine. Thereby, at the time of motoring of the vehicle, it is possible to reuse the energy regenerated at the time of deceleration to travel, so that it is possible to achieve improvement of the motoring fuel efficiency of the vehicle.

[0074] ​The storage elements 1a to 40d connect the nodes 1a to 1d as the first group of nodes, the nodes 2a to 2d as the second group of nodes, the nodes 3a to 3d as the third group of nodes, and finally the nodes 40a to 40d as the 40th group of nodes, to both ends of each group of nodes, respectively, with the switch units Sla to S40b. In addition, the total number of nodes of the storage elements 1a to 40d is the number of multiples N = 40 multiplied by the number n = 4 in each group of nodes, which totals N x n = 160. In the claims, there are cases where a group of nodes is simply referred to as a node.

[0075] Here, the total voltage of the series-connected storage elements in each of the first to 40th groups of nodes is 3 volts x 4 = 12 volts.

[0076] In Figure 2 , 200 is a control unit that functions to control the on / off state of the switch units Sla to S40b.

[0077] As shown in Figure 3 , the control unit 200 turns on the switch units Sla and S2a, thereby connecting the electrical load 300 to the first group of nodes of the storage elements during the Ton period. At this time, the switch units other than Sla and S2a are turned off. The switch unit S2a is connected to the positive side of the first group of nodes, and the switch unit Sla is connected to the negative side of the first group of nodes, so that a direct current voltage of 12 volts is applied to the electrical load 300 during Ton.

[0078] Next, during the time Td shown in Figure 3 , the control unit 200 maintains all of the above-mentioned switch units Sla to S40b in an off state. The reason for setting this time Td is that, for example, if there is a period in which the switch unit Sla and the switch unit S1b are turned on at the same time, an excessive current flows in the closed circuit formed by the switch units Sla, S1b and the nodes 1a, 1b, 1c, 1d of the storage elements, thereby causing damage to the switch units or wasteful consumption of the charging power of each storage element.

[0079] As the switch units Sla to S40b, it is known that, for example, in the case of using a known MOSFET, a time delay occurs before the switch units Sla to S40b actually respond when a signal to control the on / off of each switch unit is sent from the control unit 200. Therefore, the control unit 200 needs a sufficient waiting time Td from when the desired switch unit is turned off until when another switch unit is turned on. This Td is called an idle time, and in the case of a typical MOSFET, several tens of nanoseconds to several microseconds are required.

[0080] As described above, the control unit 200 functions as follows: in the first group of nodes of the energy storage element, it connects to the electrical load 300 during the period when the switching units S1a and S2a are turned on (Ton), thereby providing the required voltage of 12 volts to the electrical load 300; then, in the second group of nodes, it connects to the electrical load 300 during the period when the switching units S1b and S3a are turned on (Ton); subsequently, in the third group of nodes, it connects to the electrical load 300 during the period when the switching units S2b and S4a are turned on (Ton); finally, in the 40th group of nodes, it connects to the electrical load 300 during the period when the switching units S39b and S40b are turned on (Ton), and so on. Figure 3 T is repeated in one cycle, continuously providing 12 volts of DC power to the electrical load 300, thus maintaining the charging and discharging state of the nodes of the first to 40 energy storage element groups in a roughly uniform manner.

[0081] Next, refer to Figure 2 and Figure 4 The function of the leakage current detection unit 100 is explained.

[0082] The leakage current detection unit 100 is connected to both ends of the energy storage elements 1a to 40d via terminals T102 and T101, and is grounded to the vehicle body via terminal T103. Here, the leakage current detection unit is configured to output the leakage current detection value, which is the greater of the current flowing between terminal T101 and the ground terminal T103 and the current flowing between terminal T102 and the ground terminal T103, from terminal T100 to the control unit 200.

[0083] During the period when all switching units S1a to S40b are open, terminals T101 and T102 are floating relative to the vehicle body, so the leakage current detection value is 0 amperes. However, if a human body comes into contact with the positive terminal side of the energy storage element 40d, i.e., the T101 side, a leakage current will be detected between terminal T102 and ground terminal T103 because the resistance of the human body is about 5KΩ.

[0084] Therefore, as Figure 4 As shown, when switch units S1a and S2a are open, the leakage current detection value ILeak of the leakage current detection unit 100 during the no-load period Td1, during which all switch units, including S1a and S2a, are open, is 0 amperes. However, when a human body comes into contact with a high-voltage part during the period when switch units S1b and S3a are closed, the leakage current detection value ILeak of the leakage current detection unit 100 during the no-load period Td2, during which all switch units, including S1b and S3a, are open, is greater than 0 amperes.

[0085] The control unit 200 receives the leakage current detection value ILeak from the terminal T100 of the aforementioned leakage current detection unit 100 to the terminal T200 of the control unit 200. If the detected ILeak is above a predetermined value ILth, then... Figure 4 As shown, the process then stops by turning all the switching units off.

[0086] As a result, all the energy storage components 1a to 40d are in a floating state relative to the vehicle body, and the path of high-voltage current flowing through the human body is cut off, thus preventing electric shock.

[0087] Next, a power generation unit (not shown) limits the charging voltage of the energy storage element so that the voltage after connecting the nodes of the energy storage elements 1a to 40d in series becomes a specified maximum value.

[0088] On the other hand, the current consumption of the electrical load 300 is not constant; for example, it can sometimes vary significantly in a short period of time depending on the driver's operating state, as is the case with electric power steering. In this situation, if the switching units S1a to S40b are controlled by the control unit 200 and switched from the first group of nodes to the 40th group of nodes of the energy storage element at equal intervals, the charging state of each group of nodes may sometimes differ.

[0089] However, the control unit 200 via one side Figure 6 The terminals T201, T202, T203 to T239, and T240 are shown to monitor the voltage of each group of nodes of the energy storage element. While preferentially connecting the group of nodes with higher voltage to the electrical load 300 and not connecting the group of nodes with lower voltage to the electrical load 300, the energy storage element group (group node) to be discharged is selectively switched, thereby maintaining the charging state of each energy storage element group (group node) approximately uniformly.

[0090] As another implementation method, such as Figure 7 As shown, it can also be that the control unit 200 is connected via one side through Figure 6 The terminals T201, T202, T203 to T239, and T240 are shown to monitor the voltage of each group of nodes of the energy storage element. The switching period is set longer for nodes with higher voltage and shorter for nodes with lower voltage. Ton1 to Ton40 are calculated and controlled based on the charging amount of each energy storage element group (node) and the current flowing to the electrical load 300. This allows for a relatively uniform charging state to be maintained for each energy storage element group (node).

[0091] As mentioned earlier, the function of the leakage current detection unit 100 is to, based on... Figure 4whether the leakage detection value of the leakage detection unit 100 during the dead time Td at the moment when the on state of any two of the switching units Sla to S40b is switched to the off state is ILth or more to detect whether or not electric shock due to contact of a human body with a high voltage portion during the Ton when the any two of the switching units are on has occurred, and thus the time during which the electric shock current actually flows to the human body is at most Ton.

[0092] However, the time of Ton needs to be within a range in which a human body reaction assumed from the electric shock current and the duration thereof determined from the voltage value of the high voltage power supply based on the storage elements 1a to 40d and the resistance value of the human body is harmless to the human body, and in general, if the electric shock time is 0.1 seconds or less when the current value is 30 milliamps, there is no fatal human body reaction.

[0093] That is, in order to suppress a human body reaction that is safe, the maximum value of the product of the electric shock current and the electric shock time is 0.003 ampere seconds.

[0094] Therefore, in the present embodiment, it is assumed that the maximum electric shock current is 100 milliamps according to the voltage value 480 volts of the high voltage power supply and the human body resistance 5 KΩ, and since the electric shock time that is harmless to the human body is calculated to be 0.03 seconds or less, the maximum value of the period Ton during which any two of the switching units Sla to S40b are on is set to a small value of 0.001 seconds with a sufficient margin.

[0095] The system of the vehicle having the high voltage power supply not only has a case where a human body contacts a high voltage circuit portion, but also has a case where a leakage current temporarily flows due to leakage of an electronic component mounted or malfunction of an insulation portion and vibration during running, and the like. In such a case, if the supply of electric power from the high voltage power supply to the electric load 300 is completely stopped by the action of the control unit 200, there is a dangerous case where the vehicle loses the functions of each portion during running.

[0096] Therefore, according to another embodiment, the control unit 200 is configured to repeatedly perform the following actions: when the leakage detection value ILeak of the leakage detection unit 100 is ILth or more, a state in which all of the switching units Sla to S40b are off is maintained for 0.5 seconds or more, and then the switching units are caused to selectively connect the 1st storage element group (group node) to the 40th storage element group (group node) to the electric load 300 again.

[0097] Thus, even if a temporary leakage current occurs due to a failure of each part of the power supply device of the vehicle body or the like, since the power supply to the electric load 300 from the high-voltage power supply is restarted, the vehicle function is restored and the running safety can be maintained. In addition, if the state in which all of the switching units Sla-S40b are turned off is maintained for 0.5 seconds or more, the leakage current does not accompany a failure of the vehicle, and even if the human body is actually electrified, the fatal influence on the human body can be eliminated.

[0098] Here, it is preferable that, after the control unit 200 repeatedly maintains the state in which all of the switching units Sla-S40b are turned off for 0.5 seconds or more when the leakage detection value ILeak of the leakage detection unit 100 is the prescribed current value ILth or more, and then causes the switching units to selectively connect the 1st storage element group (group node) to the 40th storage element group (group node) to the electric load 300 again, the electrification time Ton after the restart is shortened in inverse proportion to the voltage value of the high-voltage power supply based on the storage elements 1a-40d and / or is shortened in inverse proportion to the leakage current value detected by the leakage detection unit 100. Thus, in a case where the leakage is not due to the vehicle but electrification of the human body, the higher the voltage of the high-voltage power supply, the shorter the electrification time to the human body, and / or the larger the electrification current of the human body, the shorter the electrification time to the human body, and thus the safety is further improved.

[0099] According to Figure 5 the embodiment, as described above, the control unit 200 is configured to periodically repeat the following operation: when the leakage resistance value RLeak detected by the leakage detection unit 100 is the prescribed first threshold value RLthl or more, the state in which all of the switching units Sla-S40b are turned off is maintained for 0.5 seconds or more (Thold), and then the switching units Sla-S40b are turned on again, or the switching units Sla-S40b are turned on again in a case where the leakage resistance value RLeak decreases to the prescribed second threshold value RLth2 or less.

[0100] Next, in the vehicle power supply device 1 of the embodiment of the present application, the control unit 200 switches the switching units Sla-S40b, and with respect to the period of switching the group nodes of the storage elements 1a-40d, the operation according to Figure 11 will be described.

[0101] In addition, the control unit 200 switches each group node at a period T to supply the prescribed low-voltage power supply to the electric load 300, and in addition, a power generation unit not shown always charges in a manner such that the total voltage of the series-connected storage elements 1a-40d is a prescribed value.

[0102] Here, the group node of the storage element selected by the control unit 200 is, for example, selected in a manner such that the group node of the storage element having the largest voltage value among the group nodes of the storage elements 1a-40d is selected when the voltage value of the high-voltage power supply based on the storage elements 1a-40d is the highest, and the group node of the storage element having the smallest voltage value among the group nodes of the storage elements 1a-40d is selected when the voltage value of the high-voltage power supply based on the storage elements 1a-40d is the lowest. Figure 11The voltage of the first group of nodes is decreased by flowing the current through the electric load 300 during the on period, and the group of nodes becomes a discharged state. At the same time, in the non-selected group of nodes, the charging current is supplied from the power generating cell body in such a manner that the total voltage of all the power storage elements 1a to 40d is constant, and thus the voltage is changed in the increasing direction. The difference between the maximum voltage and the minimum voltage in the specific group of nodes at this time is the so-called charge and discharge depth, and if this amplitude becomes large, the life of the power storage elements is reduced.

[0103] However, in order to suppress the human body reaction at the time of the human body electric shock as described above, from the viewpoint of the life of the power storage elements, it is also known that the time Ton during which the power storage element group (group of nodes) is selectively connected to the electric load 300 by the control unit 200 should be shortened, and the control period T during which the selection of all the power storage element groups (groups of nodes) is repeated once should be shortened, as well as the shortening of Ton.

[0104] However, in the present embodiment, as shown in Figure 9 the switching loss in the switching units S1a to S40b is generated during the on transition of each switching unit, and the voltage V across the switching unit when the switching unit is in the off state is decreased by the on operation, and the current I is increased in conjunction therewith. The loss I x V at this time, for example, when the voltage of each group of nodes of the power storage elements is 12 volts and the current of the electric load 300 is 200 amperes, generates a peak loss of 12 x 1 / 2 x 200 x 1 / 2 = 600 watts. In addition, the switching loss is also generated during the off transition of the switching unit.

[0105] In addition, since the switching loss is generated during the no-load time Td, the average value of the switching loss with respect to the control period T of the control unit 200 is Td / T, and thus, as described above, there is a problem that the switching loss becomes too large due to the shortening of the control period T.

[0106] In addition, according to the present embodiment, Figure 3 the applied voltage VL to the electric load 300 during the no-load time Td is 0 volts during the period when all the switching units S1a to S40b are off. Therefore, the supply of power to the electric load 300 is momentarily interrupted, and thus there is a problem that the low-voltage vehicle load is momentarily stopped.

[0107] Therefore, as shown in Figure 8 a capacitor 400 is provided in parallel with the electric load 300.

[0108] Thus, the voltage charged to the capacitor 400 is continuously supplied to the electric load 300, and thus the voltage VL does not decrease to 0 volts, as shown in Figure 3As shown by the broken line VLa, the voltage can be held at a slight voltage drop from the peak voltage. The amount of voltage drop in this case is determined by the current flowing to the electric load 300, the capacitance of the capacitor 400, and the no-load time Td, and in the case where the no-load time Td and the current flowing to the electric load 300 are fixed, the greater the capacitance of the capacitor 400, the smaller the amount of drop of VLa.

[0109] In addition, since the amount of drop of VLa is determined in accordance with the capacitance of the capacitor 400, the no-load time Td, and the current value flowing to the electric load 300, when the capacitance of the capacitor 400 is specified, the amount of drop of VLa can of course be reduced by shortening the time of the no-load time Td.

[0110] Therefore, it is possible to prevent the voltage supplied to the electric load 300 from being momentarily interrupted. Furthermore, during the process in which any one of the switching units Sla to S40b turns to the on state, since the voltage of the series-connected storage elements in the group node of the storage elements connected by the on of any one of the switching units is 12 volts in total, and the voltage of the capacitor 400 is approximately 12 volts, it is possible to make the voltage across the switching unit when the switching unit is in the off state approximately 0 volts, and therefore, as shown in FIG. 6, the switching loss in this case is extremely small since the current I increases while the voltage V is held at approximately 0 volts. Figure 10

[0111] In other words, the voltage of one group node of the storage elements is output as the voltage supplied to the electric load 300, and if the voltages of the group nodes are made the same by this case of holding the voltage of the group node by the capacitor 400, the voltage of each group node when all of the group nodes are switched is the same as the voltage of the electric load 300 (the capacitor 400), and therefore the operation of the switching unit becomes so-called ZVS (zero voltage switching) and theoretically no switching loss is generated.

[0112] According to the present embodiment, since no switching loss is generated when stepping down from the high-voltage power supply to the low-voltage power supply, the heat loss generated by the switching element for stepping down is extremely small, and in the inventor's experiment, when a stepping-down device outputting 2.5 KW was fabricated, the power conversion efficiency was 99.5%, and it is possible to greatly reduce the system cost of not requiring a heat sink.

[0113] ​In addition, as mentioned above, in order to avoid stopping the power supply to the electrical load 300 due to leakage current detection caused by the vehicle, and to avoid the danger caused by electric shock current flowing to the human body, the control unit 200 repeatedly performs the following actions: when the leakage detection value ILeak of the leakage detection unit 100 is higher than the specified current value ILth, the state of all switching units S1a to S40b being disconnected is maintained for, for example, for more than 0.5 seconds (specified time), and then the switching units selectively connect the first energy storage element group (group node) to the 40th energy storage element group (group node) to the electrical load 300 again.

[0114] In this case, the power supply from the energy storage element group (group node) to the electrical load 300 stops for 0.5 seconds. Therefore, it is preferable that the capacitor 400 has sufficient electrostatic capacitance to provide a specified voltage from the capacitor 400 to the electrical load 300 even during this stop period.

[0115] Next, as another implementation method, such as Figure 12 As shown, each energy storage element group (group node) formed by connecting four nodes of energy storage elements 1a to 40d in series with capacitors 501, 502 to 540 is constructed by connecting capacitors 501, 502 to 540 at both ends.

[0116] It is known that energy storage elements, such as those using lithium-ion batteries, have an equivalent series resistance value of tens of mΩ as their internal resistance (not shown). Therefore, in the case of four series-connected energy storage elements in one group of nodes in this embodiment, each group of nodes of the energy storage elements has an internal resistance of approximately 100 mΩ.

[0117] At the end Figure 3 When the no-load time Td is reached and the voltage VL of the electrical load 300 rises due to the switching unit being turned on, the electrical time constant of the rising portion is represented by the product of the electrostatic capacitance of the capacitor 400 and the aforementioned internal resistance.

[0118] Therefore, when the capacitor 400 is charged through the internal resistance of the energy storage element, the rising waveform of VL, as shown in VLb, has a large time constant and the low voltage state lasts for a long time. Furthermore, since this situation repeats with a period T, it becomes a major cause of the decrease in the average voltage supplied to the electrical load 300; therefore, it is preferable that this time constant be as small as possible.

[0119] The equivalent series resistance of a capacitor, which is an electrostatic capacitor element, is typically less than a few mΩ. Therefore, as in this embodiment, when capacitors 501, 502 to 540 are connected in parallel with each group of nodes of the energy storage element, the internal resistance of the energy storage element appears to decrease. The rising waveform of VL when capacitor 400 is charged through its internal resistance is as follows: Figure 3As shown in the VLc, the state in which the time constant is small and the voltage is low is shortened. Since this situation is repeated with the period T, the decrease in the average value of the voltage supplied to the electric load 300 is small, and the precision of the voltage supplied to the electric load 300 is improved.

[0120] Hereinafter, the description will be given using Figure 13 A method of outputting an alternating current power for supplying to a device operating with a commercial power source from a plurality of power storage elements of a high voltage power source formed by connecting in series will be described. Also, the basic structure is similar to that of the above-described embodiment, and thus the drawing showing the structure in the present embodiment is omitted.

[0121] First, the power storage elements are connected in series with 180 lithium ion batteries having a cell voltage of 3 volts, and the overall voltage is 540 volts. Next, 60 power storage elements are taken as one group node, and the overall is divided into three group nodes of G1 to G3, and the voltage of each group node is switched by the switching unit every 1 msec to supply to the commercial power source load. At the time when 10 msec has elapsed, the selected group node becomes G1, and then when G2 is selected to supply to the commercial power source load, the switching unit is operated in such a manner that the polarity of the power storage element group (group node) at the time of connection to the commercial power source load is reversed. Next, the switching is performed to G3, G1 in the state of maintaining the same polarity, and when G3 is selected in the next cycle in which G2 is finally selected, the polarity of the power storage element group (group node) at the time of connection to the commercial power source load is reversed again.

[0122] By repeating the above operation, a rectangular alternating current voltage of 50 Hz, ±90 volts can be applied to the commercial power source load.

[0123] As described above, the vehicle power source device of the embodiment of the present application can perform power conversion from high voltage to low voltage by selectively connecting a prescribed power storage element group (group node) to a low voltage electric load from a high voltage power source formed by connecting power storage elements in series, and at this time, by switching the power storage element group (group node) at high speed, the depth of charge and discharge of the power storage element can be reduced to improve the life, and the switching loss of the switching unit performing the switching can be made substantially zero, and thus the device has excellent features of being able to greatly improve the weight and cost of the components involved in heat dissipation of the switching element.

[0124] Further, without using a unit such as an insulation type DC-DC converter, even when the human body is in contact with the high voltage power source circuit, the dangerous human body reaction can be suppressed.

[0125] Also, as another embodiment, as Figure 14As shown, it is an easy matter for a person having ordinary knowledge in the technical field to which the present application pertains to provide the voltage of the power storage unit to the electric load by switching the power storage unit and the electric load in the above-described embodiments. In Figure 14 In the above-described embodiments, the capacitor constitutes the node and the power storage unit.

[0126] Industrial Applicability

[0127] In the embodiments of the present application, only the limited structure and function are shown as examples, and it should be easily understood that the following matters can be adopted in an arbitrary manner: the number of series-connected power storage units, the kind of power storage units, the kind and structure of the switching unit, and the operation timing of the control unit, and there are various known technologies as the structure of the electric leakage detection unit, and various failure detection units and failure protection functions at the time of failure can be added.

[0128] Explanation of Reference Numerals

[0129] 1a to 1d: power storage units (nodes); S1a to S40b: switching units; 100: electric leakage detection unit; 200: control unit; 300: electric load; 400: capacitor.

Claims

1. A power supply device for a vehicle, comprising: Electrical loads that operate at a specified low voltage; A high-voltage power supply is obtained by connecting multiple energy storage elements in series at each node that constitute the specified low voltage to obtain a high-voltage DC power supply. Multiple switching units are provided corresponding to nodes that provide the specified low voltage to the electrical load; The control unit provides voltage to all the energy storage elements by sequentially repeating the following control: providing voltage by turning on the switching unit that provides voltage from at least one node and turning off the switching unit that provides voltage from other nodes, and after a set no-load period during which all switching units are temporarily turned off, turning on the switching unit of the node that provides voltage and turning off the switching unit that provides voltage from other nodes. as well as The leakage current detection unit detects the leakage current between the high-voltage power supply and the ground potential, and sends a signal to the control unit. This leakage current is the current flowing from the high-voltage power supply through the human body. Its features are, The control unit determines the signal sent from the leakage current detection unit during the no-load period when all the multiple switching units are in the off state. If the leakage current is above a specified current, the control unit maintains the state of all switching units being off for a specified period. The time for connecting any one of the nodes to the electrical load via the switching unit is set such that the duration of the leakage current flowing from the high-voltage power supply to the human body is less than the time required to cause an electric shock, which is 0.1 seconds. The control unit repeatedly performs the following actions: when the leakage current detection value of the leakage current detection unit is above a predetermined first threshold, the switch unit is disconnected; when the leakage current detection value is below a predetermined second threshold which is less than the first threshold, the switch unit is reconnected.

2. The vehicle power supply device according to claim 1, characterized in that, The high-voltage power supply uses n energy storage elements to form the specified low-voltage node, and connects multiple energy storage elements in series n×N to obtain a high-voltage DC power supply that is N times the specified low voltage, where n and N are natural numbers.

3. The vehicle power supply device according to claim 1, characterized in that, The control unit controls the switching unit by periodically changing the selected plurality of nodes.

4. The vehicle power supply device according to claim 3, characterized in that, The control unit determines the selected node in a manner that makes the charging and discharging states of the plurality of energy storage elements approximately uniform.

5. The vehicle power supply device according to claim 3, characterized in that, The control unit determines the selected hold time of each node in a manner that makes the charging and discharging states of the plurality of energy storage elements approximately uniform.

6. The vehicle power supply device according to claim 1, characterized in that, The duration for which each node is connected to the electrical load via the switching unit is inversely proportional to the voltage value of the high-voltage power supply or inversely proportional to the current value detected by the leakage current detection unit.

7. The vehicle power supply device according to any one of claims 1 to 6, characterized in that, When the leakage current detection value of the leakage current detection unit is above the specified current value, the control unit fixes the switching unit in a fully open state.

8. The vehicle power supply device according to any one of claims 1 to 6, characterized in that, The control unit repeatedly performs the following actions: when the leakage current detection value of the leakage current detection unit is above the specified current value, it keeps the state of all the switching units disconnected for a specified time, and then causes the switching units to selectively connect each node to the electrical load again.

9. The vehicle power supply device according to any one of claims 1 to 6, characterized in that, The control unit controls the switching unit so that the product of the period during which each node is connected to the electrical load and the leakage current detection value of the leakage current detection unit is less than 0.003 amperes × 1 second.

10. The vehicle power supply device according to any one of claims 1 to 6, characterized in that, The control unit sets the period for switching the selected node by the switching unit to a predetermined value or less, so that the depth of charge and discharge in each node of the energy storage element is a predetermined value or less.

11. The vehicle power supply device according to any one of claims 1 to 6, characterized in that, A capacitor is connected in parallel with the electrical load.

12. The vehicle power supply device according to claim 11, characterized in that, During the no-load period, or the capacitance value of the capacitor, is set such that the voltage drop applied to the electrical load during the no-load period is below a predetermined value.

13. The vehicle power supply device according to claim 11, characterized in that, Capacitors are provided in parallel with each node of the energy storage element.

14. The vehicle power supply device according to any one of claims 1 to 6, characterized in that, Each node of the high-voltage power supply, which is a high-voltage DC power supply obtained by connecting the plurality of energy storage elements in series, will alternately reverse the polarity of the high-potential side and the low-potential side when connected to the electrical load through the switching unit at predetermined intervals, thereby providing AC power to the electrical load.

Images