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 group of storage elements is selectively connected to a low voltage load from a high voltage power supply formed by connecting storage elements in series, thereby performing power conversion from high voltage to low voltage, and in this structure, during cutting off of a high voltage circuit by a cutting unit provided between the high voltage power supply and a high voltage load, a leakage resistance from the high voltage circuit to ground is measured, and when the value is below a prescribed value, power supply from the high voltage power supply to the high voltage load device is cut off, 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, which is a low-voltage circuit, is usually grounded to the vehicle body as the body earth of the 12-volt power supply, when any one or more of the switch units 30-35 are closed, a certain point of the connection point of the series-connected energy storage units 20a-20L on the high-voltage side is directly connected to the vehicle body. Therefore, when a person comes into contact with the high-voltage circuit, they will be electrocuted. Specifically, assuming that the total voltage of the series-connected energy storage units 20a-20L is 480 volts, if the positive potential side of the energy storage unit 20a comes into contact with the vehicle body at the moment the switch unit 35 is closed, there is a possibility of applying a high voltage of 480 volts to the human body and causing an electric shock accident.

[0010] The present invention was made in view of the above-mentioned problems and provides a power supply device for a vehicle that is mounted on a vehicle and obtains a low-voltage power supply from a high-voltage power supply via a step-down unit. In the case of a system where the voltage on the high-voltage side exceeds 60 volts, which is the limit of electric shock to the human body, electric shock accidents can be prevented without the use of insulation units such as transformers, and approximately 100% power conversion efficiency can be easily obtained in the power conversion function to the low-voltage side.

[0011] Methods for solving problems

[0012] The vehicle power supply device of the first aspect of the invention comprises: an electrical load that operates at a specified low voltage; a high-voltage power supply that connects multiple energy storage elements, constituting nodes (groups of nodes) providing the specified low voltage, in series to obtain a high-voltage DC power supply; a high-voltage load device connected to the high-voltage power supply via a wiring harness; multiple switching units corresponding to nodes that provide the specified low voltage to the electrical load; and a control unit that sequentially and repeatedly performs the following control to supply voltage to all energy storage elements: by providing voltage from at least one node through the switching unit. The system provides voltage by turning on the switching unit 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 disconnected, it then turns on the switching unit of the node providing voltage and turns off the switching unit that provides voltage from other nodes; a disconnection unit that periodically disconnects the circuit between the high-voltage power supply and the high-voltage load device via a control unit; and a leakage current detection unit that detects the leakage resistance between the circuit portion formed by the high-voltage power supply and the high-voltage load device and the ground potential, and sends a signal to the control unit. Furthermore, the control unit determines the signal sent from the leakage current detection unit during the period when the disconnection unit is disconnected, and if the leakage resistance is below a predetermined value, maintains the disconnection state of the disconnection unit for a predetermined period.

[0013] In the vehicle power supply device of the second aspect of the invention, the high-voltage power supply is configured with n energy storage elements forming the specified low-voltage node, and multiple energy storage elements are connected 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.

[0014] In the vehicle power supply device of the third aspect of the invention, the control unit controls the switching unit by periodically changing the selected plurality of nodes.

[0015] In the vehicle power supply device of the fourth aspect of the invention, the control unit determines the selected node in a manner that makes the charging and discharging states of the plurality of energy storage elements substantially uniform.

[0016] In the vehicle power supply device of the fifth aspect of the invention, the control unit determines the selection and holding time of each node in a manner that makes the charging and discharging states of the plurality of energy storage elements substantially uniform.

[0017] In the vehicle power supply device of the sixth aspect of the invention, the time for connecting the high-voltage power supply to the high-voltage load device by the disconnection unit is set such that the duration of the current flowing from the high-voltage power supply to the human body is less than the time that would cause an electric shock accident.

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

[0019] In the vehicle power supply device of the invention in the eighth aspect, when the leakage resistance detection value of the leakage detection unit is below a predetermined value, the control unit fixes the cut-off unit in an open state.

[0020] In the vehicle power supply device of the ninth aspect of the invention, when the leakage resistance detection value of the leakage detection unit is below a predetermined value, the control unit repeatedly performs the following action: after maintaining the disconnected state of the disconnecting unit for a predetermined time, the disconnecting unit is reconnected.

[0021] In the vehicle power supply device of the tenth aspect of the invention, when the resistance value detected by the leakage detection unit is below a first threshold, the control unit repeatedly performs the following actions: disconnecting the cut-off unit, and when the resistance value becomes above a second threshold greater than the first threshold, reconnecting the cut-off unit.

[0022] In the vehicle power supply device of the eleventh aspect of the invention, the control unit controls the disconnection unit such that the product of the period during which the disconnection unit connects the high-voltage power supply to the high-voltage load device and the current flowing from the high-voltage power supply to the human body is less than 0.003 amperes × 1 second.

[0023] In the vehicle power supply device of the twelfth aspect of the invention, 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.

[0024] In the vehicle power supply device of the invention in the thirteenth aspect, a low-voltage capacitor is connected in parallel with the electrical load.

[0025] In the vehicle power supply device of the fourteenth aspect of the invention, a high-voltage capacitor is connected in parallel with the high-voltage load device.

[0026] In the vehicle power supply device of the invention in the fifteenth aspect, the no-load time period or the capacitance value of the low-voltage capacitor is set such that the voltage drop applied to the electrical load during the no-load time period is below a predetermined value.

[0027] In the vehicle power supply device of the invention in the sixteenth aspect, the disconnection period of the disconnection unit or the capacitance value of the high-voltage capacitor is set such that the voltage drop applied to the high-voltage load device during the disconnection period of the disconnection unit is below a predetermined value.

[0028] In the vehicle power supply device of the invention of the seventeenth aspect, capacitors are provided in parallel with each node of the energy storage element.

[0029] In the vehicle power supply device of the invention in the eighteenth aspect, each node of the high-voltage power supply from which a high-voltage DC power supply is obtained by connecting the plurality of energy storage elements in series is alternately reversed at predetermined intervals between the polarities of the high-potential side and the low-potential side when connected to the electrical load via the switching unit, thereby providing AC power to the electrical load.

[0030] Invention Effects

[0031] According to the invention of the first and second aspects, if the voltage of the low-voltage power supply is set to VL, the voltage VH of the high-voltage power supply obtained by connecting the energy storage elements in series is VL×N (N is a natural number). Since the number of energy storage elements is N×n (n is a natural number), for example, when VL is 12 volts and N = 40, VH is 480 volts. If n = 4, a high-voltage power supply is formed by a total of N×n = 160 series-connected energy storage elements, and the voltage of each energy storage element is 3 volts.

[0032] Therefore, to obtain a low-voltage power supply of 12 volts, it is sufficient to select four series-connected energy storage elements and connect them to the electrical load.

[0033] However, in order to obtain a low voltage 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, etc. Instead, a simple switching unit can be used to selectively connect each node (group of nodes) of a series-connected energy storage element to the electrical load to achieve voltage reduction.

[0034] Therefore, the structure of the switching unit can be simplified, and the known switching losses and losses generated from the inductor can be significantly reduced. As a result, the power loss for step-down can be reduced and the heat dissipation structure can be simplified. Consequently, the weight and cost of the power supply unit containing the device for step-down can be reduced.

[0035] Here, a portion of the node of the series-connected energy storage element of the high-voltage power supply is connected to the low-voltage circuit, i.e., the metal part of the vehicle body, via a switching unit. Therefore, when in contact with the high-voltage power supply circuit, an electric shock current flows through the human body.

[0036] However, the control unit periodically disconnects the cut-off unit and detects the leakage resistance value of the leakage current detection unit by using the grounding current flowing from the high-voltage circuit part connected to the external power supply of the vehicle as the leakage resistance value. If the value is below the specified value, it is determined that the human body is in contact with the high-voltage circuit. The cut-off unit disconnects and maintains the connection between the high-voltage power supply and the external environment, thus preventing electric shock accidents.

[0037] According to the second aspect of the invention, a high-voltage power supply uses n energy storage elements to form a node representing a specified low voltage. Multiple energy storage elements are connected in series (n×N), thereby obtaining a DC power supply with a high voltage N times that of the specified low voltage, where n and N are natural numbers. Therefore, all energy storage elements can be used to efficiently provide both high voltage and the specified low voltage.

[0038] According to the invention in the third aspect, by using a control unit to periodically change the node selected from multiple energy storage elements, it is possible to prevent the adverse situation where only a portion of the energy storage elements connected in series discharges while the other energy storage elements are overcharged.

[0039] According to the fourth aspect of the invention, the control unit determines the selected node in a manner that makes the charging and discharging states of the multiple energy storage elements approximately uniform, thus enabling it to also have the known battery cell balancing function required when charging and discharging multiple energy storage elements in series.

[0040] According to the invention in the fifth aspect, the control unit determines the selection and holding time of each node in a manner that makes the charge and discharge states of the multiple energy storage elements approximately uniform. The selection and holding time of each node is determined in such a manner that the discharge time is longer for nodes selected from energy storage elements with larger charge levels, and conversely, the discharge time is shorter for nodes selected from energy storage elements with smaller charge levels. This also incorporates the known battery cell balancing function required for charging and discharging multiple energy storage elements in series.

[0041] When a high voltage is applied to the human body, if the current value is below 5 mA, it has no effect on the human body. It is known that in the current range above 5 mA, the human body's response varies depending on the duration of the current. As the current value increases, the human body can be damaged due to short-term electric shock.

[0042] Therefore, a leakage current detection sensitivity of 30 mA × 0.1 sec is set in the residual current circuit breaker typically used in commercial power supplies.

[0043] Therefore, according to the invention of the sixth aspect, during the period when the high-voltage power supply is connected to the high-voltage load device by the disconnection unit, the control unit ensures that the duration of the leakage current flowing from the high-voltage power supply to the human body is less than the time that would cause an electric shock accident to the human body, so that even if a person comes into contact with a high-voltage part, the harm to the human body can be eliminated.

[0044] According to the seventh aspect of the invention, the control unit is configured such that the period during which the high-voltage power supply is connected to the high-voltage load device via the disconnection unit is a duration inversely proportional to the voltage value of the high-voltage power supply or a duration proportional to the resistance value detected by the leakage current detection unit. When the voltage value of the high-voltage power supply or the resistance value generated between the human body and ground decreases, and the electric shock current to the human body increases, the duration of electric shock to the human body can be shortened, thus further improving safety.

[0045] According to the invention in the eighth aspect, when the detection resistance value of the leakage current detection unit is below a predetermined value, the control unit fixes the cut-off unit in an open state. This disconnects the circuit from the high-voltage power supply to the outside, thus further improving safety.

[0046] According to the invention in the ninth aspect, when the detection resistance value of the leakage current detection unit is below a predetermined value, the control unit repeatedly performs the following action: after maintaining the disconnected state of the disconnection unit for a predetermined time such as 0.5 seconds or more, the disconnection unit is reconnected. This provides sufficient respite time for electric shock to the human body to ensure safety, and even if a temporary leakage current occurs due to a malfunction in any part of the vehicle body, power supply from the high-voltage power source to the high-voltage load device is resumed, thus maintaining vehicle functionality.

[0047] According to the tenth aspect of the invention, when the detection resistance value of the leakage current detection unit is below a first threshold of, for example, 10 kΩ, the following operation is repeatedly performed: after disconnecting the disconnection unit, the disconnection unit is reconnected when the detection resistance value becomes above a second threshold of, for example, 100 kΩ. Because the high-voltage power supply is disconnected in dangerous areas where the detection resistance value is low and the electric shock current to the human body is high, and then reconnected when the detection resistance value is high and the electric shock current decreases to a safe value, human safety is ensured. Furthermore, even if a temporary leakage current occurs due to a malfunction in any part of the vehicle body, power supply from the high-voltage power supply to the high-voltage load device is resumed, thus maintaining vehicle functionality.

[0048] According to the eleventh aspect of the invention, the control unit controls the switching unit so that the product of the period during which the disconnecting unit connects the high-voltage power supply to the high-voltage load device and the electric shock current value to the human body is less than 0.003 amps × 1 second. This ensures a safety level equivalent to that of residual current circuit breakers used in typical commercial power supplies, which have a safety rating of less than 0.03 amps × 0.1 seconds.

[0049] According to the twelfth aspect of the invention, the control unit sets the switching period of the selected node of 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. This minimizes the reduction in the lifespan of the energy storage element caused by excessive depth of charge and discharge of each element.

[0050] According to the thirteenth aspect of the invention, during the so-called no-load time when the control unit disconnects all nodes from the electrical load, the voltage drop supplied to the electrical load due to power supplied from the low-voltage capacitor can be suppressed. The voltage supplied to the electrical load can be maintained stably.

[0051] According to the fourteenth aspect of the invention, during the period when the control unit disconnects the cutting-off unit, power is supplied from the high-voltage capacitor to the high-voltage load device, thereby suppressing the voltage drop supplied to the high-voltage load device and stably maintaining the voltage supplied to the load device.

[0052] According to the invention of the fifteenth aspect, the voltage of the electrical load applied before and after the switching unit is switched can be maintained, thus having the effect of eliminating the potential difference between the two ends of the switching unit before the switching unit is about to be turned on, thereby eliminating switching losses.

[0053] According to the invention of the sixteenth aspect, the voltage of the high-voltage load device applied before and after the switching of the cutting unit can be maintained, thus having the effect of eliminating the potential difference between the two ends of the cutting unit before and after the cutting unit is turned on (or off) and eliminating switching losses.

[0054] Next, after the switching unit has just switched the connection of any node, given the high internal resistance of the energy storage element, it takes a considerable amount of time to charge the low-voltage capacitor connected in parallel with the electrical load.

[0055] Therefore, it is unavoidable that the voltage supplied to the electrical load decreases at the moment the switching unit switches.

[0056] Therefore, according to the invention of the seventeenth aspect, a capacitor with a small internal impedance is provided in parallel with the series node of the energy storage element. Thus, after the switching unit has just switched the connection of any node, the low-voltage capacitor can be charged with a sufficiently small power supply impedance, i.e., a large current, thereby suppressing the decrease in voltage supplied to the electrical load.

[0057] Similarly, when the disconnection unit is turned on, the charging current for the high-voltage capacitor can be increased, thereby suppressing the decrease in voltage supplied to the high-voltage load device.

[0058] According to the invention of the eighteenth aspect, AC power is supplied to an electrical load by alternately reversing the polarity of the high-potential side and the low-potential side when connected to the electrical load via a switching unit at predetermined intervals from each node of a high-voltage DC power supply obtained by connecting multiple energy storage elements in series. This enables the provision of AC power in a vehicle for use with household electrical products that require commercial power. Attached Figure Description

[0059] Figure 1 This is a diagram showing the basic structure of a typical vehicle power supply device.

[0060] Figure 2 This is a diagram illustrating the basic structure of a vehicle power supply device according to an embodiment of the present invention.

[0061] Figure 3 This is a timing diagram illustrating the basic operation of a vehicle power supply device according to an embodiment of the present invention.

[0062] Figure 4 This is a diagram illustrating the leakage resistance detection of a vehicle power supply device according to an embodiment of the present invention.

[0063] Figure 5 This is a diagram illustrating the leakage resistance detection of a vehicle power supply device according to an embodiment of the present invention.

[0064] Figure 6 This is a diagram illustrating the leakage resistance detection of a vehicle power supply device according to an embodiment of the present invention.

[0065] Figure 7This is a diagram showing the structure for measuring the voltage at each node of the energy storage element.

[0066] Figure 8 This is a graph showing the selection and retention time of each node.

[0067] Figure 9 This is a diagram illustrating one embodiment of a vehicle power supply device according to an embodiment of the present invention.

[0068] Figure 10 This is a diagram illustrating the power loss of a switching element.

[0069] Figure 11 This is a diagram illustrating the power loss of a switching element.

[0070] Figure 12 It is a diagram illustrating the depth of charge and discharge of energy storage components.

[0071] Figure 13 This is a diagram illustrating another embodiment of the vehicle power supply device according to an embodiment of the present invention.

[0072] Figure 14 This is a diagram illustrating a method of supplying AC power to an electrical load.

[0073] Figure 15 This is a diagram illustrating an embodiment of a structure that boosts the voltage of an energy storage element. Detailed Implementation

[0074] Hereinafter, embodiments of the vehicle power supply device of the present invention will be described with reference to the figures.

[0075] Figure 2 This is a basic embodiment of the present invention. The vehicle power supply unit 1 consists of energy storage elements 1a to 40d, switching units S1a to S40b, a control unit 200, a leakage current detection unit 100, and disconnection units 500 and 501. The energy storage elements 1a to 40d are charged by a power generation unit, which is composed of a secondary battery. The power generation unit is mechanically connected to a drive mechanism mounted on a vehicle (not shown) and driven by an engine and an electric motor. Furthermore, the vehicle power supply unit 1 is connected to an electrical load 300 operating at 12 volts with one end electrically connected to the vehicle body at the negative potential side. It also supplies high-voltage power from the energy storage elements 1a to 40d to a high-voltage load device 400 via externally extending wiring harnesses W1 and W2.

[0076] In addition, Figure 2 The diagram omits the energy storage elements 3b to 39d and the switching units S3b to S39a connected to these energy storage elements, and further omits the part where the switching unit is connected to the control unit 200.

[0077] The power generation unit (not shown) functions in order to provide the required power to the vehicle's electrical components in the following way: it is driven by the engine and charges the energy storage elements 1a to 40d by regenerating the kinetic energy during deceleration via the drive mechanism when the vehicle decelerates.

[0078] Each node of the energy storage elements 1a to 40d is, for example, a lithium-ion battery with a charging voltage of 3V. All nodes of these elements are connected in series, so that N, a multiple of 12 volts relative to the required voltage of the electrical load 300, is 40, thereby forming a high-voltage power supply of 480 volts. This high-voltage power supply functions to assist the engine's drive torque by providing power to a high-voltage load device 400, which consists of an onboard electric motor, inverter, etc. Therefore, during vehicle operation, energy regenerated during deceleration can be reused for propulsion, thus improving the vehicle's fuel efficiency.

[0079] The energy storage elements 1a to 40d take nodes 1a to 1d as the first group of nodes, nodes 2a to 2d as the second group of nodes, nodes 3a to 3d as the third group of nodes, and finally nodes 40a to 40d as the 40th group of nodes, and connect switching units S1a to S40b to both ends of each group of nodes respectively.

[0080] Furthermore, the total number of nodes in the energy storage elements 1a to 40d is calculated by multiplying the multiple N = 40 by the number of nodes in each group n = 4, resulting in N × n = 160. In the claims, there are instances where a group of nodes is simply referred to as a node.

[0081] Here, the total voltage of the series-connected energy storage elements in the 1st to 40th groups of nodes is 3 volts × 4 = 12 volts.

[0082] exist Figure 2 In this context, 200 is a control unit that functions to control the on / off states of switch units S1a to S40b and the on / off states of cut-off units 500 and 501.

[0083] like Figure 3 As shown, the control unit 200 turns on switching units S1a and S2a, thereby connecting the electrical load 300 to the first group of nodes of the energy storage element for a period of, for example, a Ton time set to 10 milliseconds. During this time, switching units other than S1a and S2a are disconnected. Switching unit S2a is connected to the positive side of the first group of nodes, and switching unit S1a is connected to the negative side of the first group of nodes; therefore, during the Ton period, a DC voltage of 12 volts is applied to the electrical load 300.

[0084] Next, in Figure 3During the time Td shown, the control unit 200 keeps all the aforementioned switch units S1a to S40b open. The reason for setting this time Td is that, for example, if there is a period during which switch units S1a and S1b are simultaneously turned on, excessive current will flow in the closed circuit formed by the switch units S1a, S1b, and nodes 1a, 1b, 1c, and 1d of the energy storage elements, which could lead to damage to the switch units or waste of the charging power of each energy storage element.

[0085] As for the switching units S1a to S40b, it is known that, for example, when using a known MOSFET, a time delay occurs before the switching unit S1a to S40b actually responds after the control unit 200 sends a signal to control the on / off state of each switching unit. Therefore, the control unit 200 needs a sufficient waiting time Td from turning off the desired switching unit to turning on other switching units. This Td is called the idle time, and in the case of a typical MOSFET, it requires tens of nanoseconds to several microseconds.

[0086] 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 The T (Ton time 10 milliseconds × number of nodes 40 = 0.4 seconds) 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 each energy storage element group node from the 1st to the 40th in a roughly uniform manner.

[0087] Next, refer to Figure 2 , Figure 4 as well as Figure 5 The function of the leakage current detection unit 100 is explained.

[0088] The leakage current detection unit 100 is connected to the high-voltage circuit portion of the wiring harnesses W1 and W2 extending to the outside of the vehicle power supply unit via terminals T102 and T101, and is grounded to the vehicle body via terminal T103. Here, the leakage current detection unit 100 is configured to have a voltage source (not shown) inside, measure the resistance value between terminal T101 and ground, and the resistance value between terminal T103 and ground, based on the values ​​of the current flowing between terminal T101 and ground terminal T103 and the current flowing between terminal T102 and ground terminal T103, and output the smaller resistance value to the control unit 200.

[0089] During the period when the disconnection units 500 and 501 are disconnected, terminals T101 and T102 of the leakage current detection unit 100 are floating relative to the vehicle body, so the leakage current resistance value is approximately infinite. However, when a human body comes into contact with the high-voltage circuit part on the wiring harness W1 side, since the resistance of the human body is about 5KΩ, a relatively small resistance value is detected between terminal T101 and ground terminal T103.

[0090] like Figure 4 As shown, the control unit 200 repeatedly performs the operation of turning on the cutting units 500 and 501 during the TN period and turning them off during the TF1 period according to the cycle TS. During the period when the cutting units 500 and 501 are turned on, the high voltage power supply from the energy storage element 1a to 40d is supplied to the high voltage load device 400. During the period when the cutting units 500 and 501 are turned off, the high voltage circuit parts of the wiring harnesses W1 and W2 connected to the external parts of the vehicle power supply device 1 are cut off and become floating.

[0091] therefore, Figure 4 During period TF1, the leakage resistance value Rleak of the leakage detection unit 100 is infinitely large. However, during period TF2, because the human body comes into contact with the high-voltage circuit part outside the vehicle power supply device, the leakage resistance value Rleak detected by the leakage detection unit 100 becomes a relatively small value.

[0092] The control unit 200 obtains the leakage resistance value Rleak from the terminal T100 of the aforementioned leakage detection unit 100 to the terminal T200 of the control unit 200. If Rleak is detected to be below a predetermined value RLth, then... Figure 4 As shown, the cutting unit 500 and the cutting unit 501 are fixed to be disconnected.

[0093] As another implementation, the control unit 200 can also be as follows: Figure 5 As shown, the period Thold during which the cutting units 500 and 501 are disconnected is set to, for example, about 0.5 seconds, and then the cutting units 500 and 501 are reconnected.

[0094] exist Figure 5 In the process, after the disconnection period Thold of disconnection units 500 and 501, the control unit 200 reconnects disconnection units 500 and 501. After the connection period TNn, if the leakage resistance value Rleak of leakage detection unit 100 in the next disconnection cycle TFn is below RLth, it is determined that the human body is still in contact with the high voltage circuit. The disconnection units 500 and 501 are then continuously disconnected during the Thold period. Thus, the above connection and disconnection are repeated at a cycle of approximately 0.5 seconds.

[0095] If the leakage resistance value Rleak of the leakage detection unit 100 in TFn is above RLth during the disconnection period of the disconnection units 500 and 501, it is determined that the human body is not in contact with the high voltage circuit, and the disconnection units 500 and 501 switch to the on state and resume power supply to the high voltage load device 400.

[0096] As another implementation method, such as Figure 6 As shown, it is also possible that when the control unit 200 detects that the leakage resistance value Rleak is below the first threshold RLth1, the cut-off unit 500 and the cut-off unit 501 remain in the off state. Then, when it detects that Rleak becomes above the second threshold RLth2, which is greater than the first threshold RLth1, the cut-off units 500 and 501 are turned on again.

[0097] In addition, preferably, the first threshold RLth1 is set to approximately 100 kilohms, which is obtained by dividing the voltage value of the high-voltage power supply 480V by the current value of 5 mA, which has no effect on the human body, and the second threshold RLth2 is set to approximately 1 megahms, which is the resistance value near the midpoint between RLth1 and the approximately infinite insulation resistance value between the floating high-voltage circuit and ground.

[0098] With the configuration described above, the high-voltage power supply provided to the external source from the energy storage elements 1a to 40d is cut off by the cutting-off units 500 and 501, thus preventing the high-voltage current from flowing through the human body and preventing electric shock. Furthermore, the vehicle power supply unit 1 is enclosed by a housing (not shown), thereby preventing direct contact between the human body and the interior of the vehicle power supply unit 1, thus preventing electric shock.

[0099] 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.

[0100] 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.

[0101] However, the control unit 200 via one side Figure 7 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.

[0102] As another implementation method, such as Figure 8 As shown, it can also be that the control unit 200 is connected via one side through Figure 7 The terminals T201, T202, T203 to T239, and T240 shown are used 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. The system calculates and controls the switching based on the charging amount of the energy storage element group (node) and the current flowing to the electrical load 300. Figure 8 The figures Ton1 to Ton40 are shown. This allows for a roughly uniform maintenance of the charging state of each energy storage element group (group node).

[0103] As described above, the function of the leakage current detection unit 100 is to detect whether the leakage resistance value of the leakage current detection unit 100 is below RLth during the period when the disconnection units 500 and 501 are disconnected. Figure 4 During the period when the disconnection units 500 and 501 are connected, whether there is electric shock between TN caused by human contact with high-voltage circuit parts. If human contact exists, disconnection units 500 and 501 are disconnected. Therefore, the actual time for electric shock current to flow to the human body is the maximum of TN.

[0104] However, the TN time needs to be within the range of human body reaction assumed to be harmless based on the electric shock current and its duration determined by the voltage value of the high-voltage power supply based on the energy storage element 1a to 40d and the resistance value of the human body. Generally speaking, at a current value of 30 mA, if the electric shock time is less than 0.1 seconds, there is no fatal human reaction.

[0105] That is, in order to suppress a safe human reaction, the maximum value of the product of electric shock current and electric shock time is 0.003 ampere-seconds.

[0106] Therefore, in this embodiment, assuming that the voltage value of the high-voltage power supply is 480 volts and the human body resistance is 5 kΩ, the maximum electric shock current is about 100 mA. Since the electric shock time that is not harmful to the human body is calculated to be less than 0.03 seconds, the maximum value of TN during the period when the cutting-off units 500 and 501 are connected is set to a small value of 0.001 seconds with sufficient margin.

[0107] On the other hand, since the leakage current detection unit 100 needs to measure the leakage current resistance Rleak during the disconnection period TF1 and TF2 when the control unit 200 disconnects the disconnection units 500 and 501, the disconnection period is preferably about 10 microseconds, considering the responsiveness of the known operational amplifier circuit (not shown) that forms the leakage current detection unit 100.

[0108] Vehicle systems with high-voltage power supplies not only present the possibility of human contact with high-voltage circuitry, but also the possibility of temporary leakage current flowing due to leaks in the electronic components, malfunctions in the insulation, or vibrations during driving. In such cases, if the power supply from the high-voltage power source to the high-voltage load device 400 is completely stopped by the control unit 200, there is a risk that the vehicle may lose all functions while in motion, posing a danger.

[0109] Therefore, according to Figure 5 and Figure 6 In the implementation described above, the control unit 200 is configured to periodically repeat the following actions when the leakage resistance value Rleak detected by the leakage detection unit 100 is below a predetermined threshold RLth: after holding the disconnected state of the disconnection units 500 and 501 for more than 0.5 seconds (Thold), the disconnection units 500 and 501 are turned on again, or when the leakage resistance value Rleak increases to more than a predetermined second threshold RLth2, the disconnection units 500 and 501 are turned on again.

[0110] Therefore, even if a temporary leakage current occurs due to a malfunction in any part of the vehicle, the vehicle function is restored and driving safety is maintained because power supply from the high-voltage power source to the high-voltage load device 400 is resumed. Furthermore, if the disconnection units 500 and 501 are in the off state for more than 0.5 seconds, the leakage current will not accompany the vehicle malfunction, and even in the event of electric shock, the potentially fatal impact on the human body can be eliminated.

[0111] Here, as Figure 5 and Figure 6As shown, preferably, when the control unit 200 restarts the operation of reconnecting the disconnection units 500 and 501, the energization time TNn after restarting is shortened inversely proportional to the voltage value of the high-voltage power supply of the aforementioned energy storage elements 1a to 40d, and / or proportionally shortened to the minimum value of the leakage resistance value Rleak detected by the leakage detection unit 100. Therefore, in cases where the leakage is caused by electric shock to a human body rather than a vehicle, the higher the voltage of the high-voltage power supply, the shorter the energization time to the human body, and / or the larger the electric shock current, the shorter the energization time to the human body, thus further improving safety.

[0112] Next, in the vehicle power supply device 1 according to the embodiment of the present invention, the control unit 200 switches the switching units S1a to S40b, and regarding the period of switching the nodes of each group of energy storage elements 1a to 40d, according to... Figure 12 Please provide an explanation.

[0113] In addition, the control unit 200 switches each group of nodes at a period T to provide a specified low voltage power supply to the electrical load 300. Furthermore, the power generation unit (not shown) is always charged in such a way that the total voltage of the series-connected energy storage elements 1a to 40d is a specified value.

[0114] Here, the group node of the energy storage element selected by the control unit 200 is, for example, as... Figure 12 Taking the first group of nodes as an example, by allowing a current of 300 to flow through the electrical load during the turn-on period, the nodes in this group are put into a discharging state, causing the charging voltage to drop. Simultaneously, in the non-selective group of nodes, charging current is supplied from the power generation unit in a manner that keeps the total voltage of all energy storage elements 1a to 40d constant, thus causing the voltage to increase. The difference between the maximum and minimum voltage in a specific group of nodes at this time is called the depth of charge / discharge; if this difference increases, the lifespan of the energy storage elements decreases.

[0115] However, from the perspective of the lifespan of the energy storage components, it is known that the time Ton for selectively connecting the energy storage component group (group node) to the electrical load 300 through the control unit 200 should be shortened, and the control cycle T for selecting all energy storage component groups (group nodes) once should also be shortened.

[0116] However, in this embodiment, such as Figure 10 As shown, during the switching transition of each switching unit S1a to S40b, the switching loss occurs because the voltage V across the switching unit when it is in the off state decreases with the switching action, and the current I increases accordingly. For example, when the voltage of each group of nodes of the energy storage element is 12 volts and the current of the electrical load 300 is 200 amperes, the peak loss I×V is 12×1 / 2×200×1 / 2=600 watts. Furthermore, this switching loss also occurs during the off-state transition of the switching unit.

[0117] Furthermore, since the switching loss occurs during the aforementioned no-load time Td, the average value of the switching loss relative to the control cycle T of the control unit 200 is Td / T. Therefore, as mentioned earlier, there is a problem that the switching loss becomes too large due to the shortening of the control cycle T.

[0118] Furthermore, according to this embodiment, Figure 3 During the no-load time Td shown, the applied voltage VL to the electrical load 300 is 0 volts during the period when all switching units S1a to S40b are open. Therefore, the power supply to the electrical load 300 is momentarily interrupted, resulting in a problem of a momentary stoppage of the low-voltage vehicle electrical load.

[0119] Therefore, as Figure 9 As shown, a low-voltage capacitor 310 is connected in parallel with the electrical load 300. Therefore, the voltage charged to the low-voltage capacitor 310 continuously supplies voltage to the electrical load 300, and thus the aforementioned voltage VL will not drop to 0 volts. Figure 3 As shown by the dashed line VLa, the voltage drop can be maintained from the peak voltage with a slight decrease. The amount of voltage drop in this case is determined by the current flowing to the electrical load 300, the capacitance of the low-voltage capacitor 310, and the no-load time Td. With the no-load time Td and the current flowing to the electrical load 300 fixed, the larger the capacitance of the low-voltage capacitor 310, the smaller the drop in VLa.

[0120] Furthermore, since the decrease in VLa is determined based on the capacitance of the low-voltage capacitor 310, the no-load time Td, and the current flowing to the electrical load 300, when the capacitance of the low-voltage capacitor 310 is specified, the decrease in VLa can certainly be reduced by shortening the no-load time Td.

[0121] Therefore, it is possible to prevent momentary interruptions in the voltage supplied to the electrical load 300. Furthermore, during the transition of any one of the switching units S1a to S40b to the on state, since the total voltage of the series-connected energy storage elements in the group node of the energy storage element connected by any switching unit is 12 volts, and the voltage of the low-voltage capacitor 310 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. Therefore, as... Figure 11 As shown, in this case, the switching loss I×V is minimal because the current I increases while the voltage V remains approximately 0 volts.

[0122] In other words, the voltage of one group node of the energy storage element is output as the voltage supplied to the electrical load 300. If the voltage of each group node is kept the same by using the low-voltage capacitor 310, then when all the group nodes are switched, the voltage of each group node is the same as the voltage of the electrical load 300 (low-voltage capacitor 310). Therefore, the operation of the switching unit becomes the so-called ZVS (known zero-volt switch) and theoretically no switching loss is generated.

[0123] According to this embodiment, since no switching losses are generated when stepping down from a high-voltage power supply to a low-voltage power supply, the heat loss generated by the switching element used for step-down is minimal. In the inventor's experiment, when a step-down device with an output of 2.5KW was manufactured, the power conversion efficiency was 99.5%, which can significantly reduce the system cost that does not require a heat sink.

[0124] In addition, in this embodiment, as described above, the control unit 200 measures the insulation resistance value between the high voltage part and the ground through the leakage current detection unit 100 during the period when the disconnection units 500 and 501 are disconnected.

[0125] In addition, to prevent the power supply to the high-voltage load device 400 from decreasing due to the vehicle-induced reduction in leakage resistance, and to avoid the danger caused by electric shock current flowing to the human body, the control unit 200 repeats the following action when the leakage resistance value Rleak of the leakage detection unit 100 is below the specified threshold RLth: after holding the disconnected state of the disconnection units 500 and 501 for a period of Thold, the disconnection units 500 and 501 are reconnected.

[0126] In this case, the power supply from the high-voltage power source to the high-voltage load device 400 is stopped for a specified period, therefore it is preferable to... Figure 2 A high-voltage capacitor 700 with a desired capacitance is provided in parallel with the high-voltage load device 400 as shown, so that the voltage supplied to the high-voltage load device 400 can be maintained even during the shutdown period.

[0127] Furthermore, by equipping the high-voltage capacitor 700, the switching losses of the periodically intermittently switching units 500 and 501 can be reduced. The reason for this is the same as the reason mentioned above for reducing the switching losses generated by the switching unit by adding the low-voltage capacitor 310, so a detailed explanation is omitted.

[0128] Next, as another implementation method, such as Figure 13 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 601, 602 to 640 is constructed by connecting capacitors 601, 602 to 640 at both ends.

[0129] 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.

[0130] 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 310 and the internal resistance mentioned above.

[0131] Therefore, the rising waveform of VL when the capacitor 310 is charged through the internal resistance of the energy storage element is as follows: Figure 3 As shown in VLb, a larger time constant results in a longer period of lower voltage. Furthermore, since this condition 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 to have a time constant as small as possible.

[0132] 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 601, 602-640 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 310 is charged through its internal resistance is as follows: Figure 3 As shown in VLc, the time constant is smaller, and the period of lower voltage is shortened. Since this situation is repeated with a period T, the average value of the voltage supplied to the electrical load 300 decreases less, and the accuracy of the voltage supplied to the electrical load 300 is improved.

[0133] The following uses Figure 14 A method for supplying AC power to equipment operating on commercial power supplies by outputting multiple energy storage elements from a high-voltage power supply formed by series connection is described. Furthermore, the basic structure is similar to the embodiment described above, therefore, figures showing the structure in this embodiment are omitted.

[0134] First, 180 lithium-ion batteries with a cell voltage of 3 volts are connected in series, resulting in an overall voltage of 540 volts. Next, 60 energy storage elements are grouped into one node, dividing the entire system into three groups (G1 to G3). A switching unit switches the voltage of each group every 1 millisecond to supply power to the commercial power load. After 10 milliseconds, the selected group becomes G1. When G2 is selected to supply power to the commercial power load, the switching unit operates by reversing the polarity of the energy storage element group (group node) connected to that commercial power load. Then, while maintaining the same polarity, the system switches to G3 and G1. In the next cycle after G2 is finally selected, when G3 is selected, the polarity of the energy storage element group (group node) connected to the commercial power load is reversed again.

[0135] By repeating the above operations, a rectangular AC voltage of 50Hz and ±90V can be applied to a commercial power load.

[0136] As described above, the vehicle power supply device according to the embodiments of the present invention selectively connects a predetermined group of energy storage elements (group nodes) to a low-voltage electrical load by means of a high-voltage power supply formed from energy storage elements connected in series, and can perform power conversion from high voltage to low voltage. At this time, by switching the group of energy storage elements (group nodes) at high speed, the depth of charge and discharge of the energy storage elements can be reduced and the lifespan can be improved. Furthermore, the switching loss of the switching unit that performs the switching can be made approximately zero. Therefore, it has excellent features such as significantly improving the weight and cost of components involved in the heat dissipation of the switching elements.

[0137] Furthermore, when the high-voltage circuit is temporarily disconnected by the disconnection unit, the leakage resistance value is measured. If the resistance value decreases, it is considered that the human body is in contact with the high-voltage circuit. The high-voltage circuit is continuously disconnected or disconnected within a specified period. Therefore, dangerous human reactions to electric shock can be suppressed without using units such as insulated DC-DC converters.

[0138] In addition, as another implementation method, such as Figure 15 As shown, by replacing the energy storage element and the electrical load unit in the above embodiments, the voltage of the energy storage element can be boosted and supplied to the electrical load unit, which is something that those skilled in the art to which this invention pertains will readily realize. Figure 14 In the embodiment shown, the configuration is such that the capacitor is a node, the voltage of the energy storage element is charged to each node, thereby extracting the boosted power from the series-connected capacitor.

[0139] In addition, in this embodiment, a cut-off unit is also added to the high-voltage side connected to the electrical load unit. Similar to the above embodiment, the ground resistance value of the high-voltage side is measured by the leakage current detection unit. If an electric shock to the human body is detected, the cut-off unit can be operated to cut off the high-voltage circuit.

[0140] Industrial availability

[0141] In the embodiments of the present invention, only the limited structure and function are shown as examples. It should be easily understood that the number of series-connected energy storage elements, the types of energy storage elements, the types and structures of the switching unit elements, the types of the cutting-off unit elements, the placement and number of the cutting-off unit, and the timing of the control unit operation can be adopted in any manner. At the same time, various known technologies exist as the structure of the leakage current detection unit, and various fault detection units and fault protection functions in case of faults can also be added.

[0142] Label Explanation

[0143] 1a~40d: Energy storage element (node); S1a~S40b: Switching unit; 100: Leakage detection unit; 200: Control unit; 300: Electrical load; 400: High voltage load device; 500, 501: Cut-off unit.

Claims

1. A power supply device for a vehicle, comprising: Low-voltage 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. A high-voltage load device that is connected to a high-voltage power supply via a pair of wire harnesses; Multiple switching units are provided, corresponding to nodes that provide the specified low voltage to the low-voltage 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. The disconnection unit disconnects the circuit between the high-voltage power supply and the high-voltage load device, causing a pair of wire harnesses to become floating. as well as A leakage current detection unit, having a grounding terminal, detects the leakage resistance between the grounding terminal and a pair of floating wire harnesses, and sends a signal to the control unit. Its features are, The control unit determines the signal sent from the leakage detection unit during the period when the disconnection unit is disconnected. If the leakage resistance value detected by the leakage detection unit is below a predetermined value, the control unit periodically repeats the following actions: after maintaining the disconnection unit in a disconnected state for a predetermined time, the disconnection unit is reconnected; or, if the leakage resistance value detected by the leakage detection unit is below a first threshold, the control unit periodically repeats the following actions: disconnecting the disconnection unit, and if the leakage resistance value becomes above a second threshold that is greater than the first threshold, the disconnection 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 any one of claims 1 to 5, characterized in that, The time for connecting the high-voltage power supply to the high-voltage load device via the disconnection unit is set such that the duration of the current flowing from the high-voltage power supply to the human body is less than the time that causes an electric shock accident, which is 0.1 seconds.

7. The vehicle power supply device according to claim 6, characterized in that, The time during which the high-voltage power supply is connected to the high-voltage load device by the disconnection unit is either inversely proportional to the voltage value of the high-voltage power supply or proportional to the leakage resistance value detected by the leakage detection unit.

8. The vehicle power supply device according to any one of claims 1 to 5, characterized in that, The control unit controls the disconnection unit so that the product of the period during which the disconnection unit connects the high-voltage power supply to the high-voltage load device and the current flowing from the high-voltage power supply to the human body is less than 0.003 amperes × 1 second.

9. The vehicle power supply device according to any one of claims 1 to 5, 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.

10. The vehicle power supply device according to any one of claims 1 to 5, characterized in that, A low-voltage capacitor is connected in parallel with the low-voltage electrical load.

11. The vehicle power supply device according to any one of claims 1 to 5, characterized in that, A high-voltage capacitor is connected in parallel with the high-voltage load device.

12. The vehicle power supply device according to claim 10, characterized in that, During the no-load period, or the capacitance value of the low-voltage capacitor, is set such that the voltage drop applied to the low-voltage 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, During the disconnection period of the cutting-off unit or the capacitance value of the high-voltage capacitor, the voltage drop applied to the high-voltage load device during the disconnection period of the cutting-off unit is set to be below a predetermined value.

14. The vehicle power supply device according to claim 10, characterized in that, Capacitors are provided in parallel with each node of the energy storage element.

15. The vehicle power supply device according to any one of claims 1 to 5, characterized in that, In each node of the high-voltage power supply that obtains a high-voltage DC power supply by connecting the plurality of energy storage elements in series, the polarities of the high-potential side and the low-potential side when connected to the low-voltage electrical load through the switching unit are alternately reversed at predetermined intervals, thereby providing AC power to the low-voltage electrical load.

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