JP2018064377A - Power supply monitoring system for vehicle using satellite board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine electrical short circuit between a high-voltage power supply and a thermistor, in a power supply monitoring system for a vehicle, in which a monitoring circuit is mounted on a satellite board.SOLUTION: A power supply monitoring system 10 for a vehicle using a satellite board 50 comprises: a monitoring circuit 52 mounted on the satellite board 50 independent of a main control board 12; a high-voltage power supply 30; and a plurality of thermistors 42. Further, the system comprises a path switching unit 60 provided among one end 46 and the other end 48 of the thermistor, a detection terminal of the monitoring circuit 52, and a negative electrode bus 34. The path switching unit 60 switches a path between a first path and a second path. The system comprises a short circuit determination unit 64 which determines that any one of the one end 46 and the other end 48 of the thermistor 42 is electrically short-circuited with a battery can 38, when a difference in voltages between terminals of the thermistor 42 before and after the path switching, exceeds a predetermined value.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a vehicle power supply monitoring system using a satellite substrate, and more particularly to a vehicle power supply monitoring system that uses a satellite substrate and monitors the temperature of a high-voltage power supply.

  The monitoring circuit for monitoring the state of each battery cell of a high voltage power source constituted by a plurality of battery cells includes a type mounted on a main board that operates with a low voltage power source such as 5 V, and a high voltage power source of several hundreds V, for example. There is a type that is mounted on the satellite substrate on the side.

  For example, Patent Document 1 describes an example in which power for driving a monitoring circuit mounted on a satellite substrate is supplied from a low-voltage power source via an insulated power source such as a transformer. It is pointed out that when the insulation power supply is provided on the main board in this way, the number of the insulation boards on the main board changes whenever the number of satellite boards changes, and it is disclosed that the insulation power supply is provided on the satellite board. doing.

  As a technique related to the present disclosure, Patent Document 2 discloses that the positive and negative buses of the high voltage power supply are floating with the vehicle body that is the circuit ground of the main board, and the positive and negative buses of the high voltage power supply and the vehicle body. An earth leakage detection circuit for detecting earth leakage during the period is disclosed.

Japanese Patent Application Laid-Open No. 2015-079585 JP 2004-347372 A

  If a thermistor as multiple temperature sensors is installed in a high-voltage power supply consisting of multiple battery cells and a monitoring circuit that monitors the battery temperature is mounted on the satellite board, the signal lines from multiple thermistors are mounted on the main board There is no need to route to the main controller.

  On the other hand, when the monitoring circuit is mounted on the main board, even if the high-voltage power supply and the thermistor are electrically short-circuited, (Patent Document 2). When a monitoring circuit is mounted on a satellite board, if the high-voltage power supply and the thermistor are electrically short-circuited, the insulation between the floating high-voltage power supply and the main board where the car body is at ground potential is maintained. Therefore, the leakage detection circuit disclosed in Patent Document 2 cannot be used.

  Therefore, in a vehicle power supply monitoring system in which a monitoring circuit is mounted on a satellite substrate, it is desired to determine an electrical short circuit between the high voltage power supply and the thermistor.

  A vehicle power supply monitoring system using a satellite substrate according to the present disclosure connects a predetermined plurality of battery cells housed in a battery can in series, and a positive bus and a negative bus are connected to a floating potential via an insulation resistance from a vehicle body. Mounted on a satellite board independent of the main control board, and a plurality of thermistors that are placed through insulators at the measurement positions defined for the high-voltage power supply and the battery cans, and one end and the other end are drawn out respectively. A monitoring circuit that monitors the battery temperature based on the voltage across the terminals between one end and the other end of the thermistor, with one end connected to a preset reference voltage and the other end monitored. Connected to the detection terminal of the circuit and provided between a predetermined series resistance provided for each thermistor and one end and the other end of the thermistor, the detection terminal of the monitoring circuit, and the negative bus A path switching unit, connecting one end of the thermistor to the detection terminal of the monitoring circuit and connecting the other end of the thermistor to the negative bus, connecting the other end of the thermistor to the detection terminal of the monitoring circuit; When the difference between the thermistor terminals exceeds a predetermined value before and after the path switching, the path switching unit that switches the path between the second path connecting one end of the thermistor to the negative electrode bus, and one end of the thermistor Alternatively, a short-circuit determining unit that determines that any one of the other ends is electrically short-circuited with the battery can.

  According to the above configuration, in the vehicle power supply monitoring system in which the monitoring circuit is mounted on the satellite substrate, it is possible to determine an electrical short circuit between the high voltage power supply and the thermistor.

1 is a configuration diagram of a vehicle power supply monitoring system using a satellite substrate according to an embodiment. (A) is a whole block diagram, (b) is an internal block diagram of the path | route switching part shown by B in (a). It is a block diagram of the vehicle power supply monitoring system using the satellite board | substrate when it switches to the 1st path | route which is a path | route of a prior art in a path | route switching part. FIG. 3 is a diagram showing a relationship between a terminal voltage of a thermistor detected by a monitoring circuit and a battery temperature in the vehicle power supply monitoring system using the satellite substrate of FIG. 2. FIG. 3 is a diagram showing a short-circuit current when the battery can and one end of the thermistor are electrically short-circuited in the vehicle power supply monitoring system using the satellite substrate of FIG. 2. In the case of FIG. 4, it is a figure which shows the relationship between the voltage between terminals of the thermistor which a monitoring circuit detects, and battery temperature. FIG. 5 is a diagram showing a short-circuit current when the battery can and the other end of the thermistor are electrically short-circuited as compared with FIG. 4. In the case of FIG. 6, it is a figure which shows the relationship between the voltage between terminals of the thermistor which a monitoring circuit detects, and battery temperature. 4 is a flowchart showing a procedure of a method for determining an electrical short circuit between a high voltage power supply and a thermistor in the vehicle power supply monitoring system using the satellite substrate according to the embodiment. In FIG. 8, it is a figure which shows a short circuit current when a path | route switch part switches to the 1st path | route. In FIG. 8, it is a figure which shows a short circuit current when a path | route switch part switches to the 2nd path | route. In the case of FIG.9 and FIG.10, it is a figure which shows the relationship between the voltage between terminals of the thermistor which a monitoring circuit detects, and battery temperature. It is a figure which shows the structure of the power supply monitoring system for vehicles which does not use a satellite board | substrate as a comparative example.

  Hereinafter, this embodiment will be described in detail with reference to the drawings. The number, voltage, resistance, and the like of the battery cells described below are illustrative examples, and can be appropriately changed according to the specifications of the vehicle power supply monitoring system using the satellite substrate. Below, the same code | symbol is attached | subjected to the same element in all the drawings, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a configuration diagram of a vehicle power supply monitoring system 10 using a satellite substrate according to an embodiment. Hereinafter, unless otherwise specified, the vehicle power supply monitoring system 10 using the satellite substrate is referred to as a power supply monitoring system 10. (A) is an overall configuration diagram, and (b) is a detailed diagram of the path switching unit 60.

  The power supply monitoring system 10 is a system that monitors the state of the high voltage power supply 30 mounted on the vehicle. The state of the high voltage power supply 30 to be monitored includes battery voltage and battery current. Here, the power supply monitoring system 10 that monitors the battery temperature of the high voltage power supply 30 using the thermistor 42 will be described. The vehicle equipped with the high voltage power supply 30 includes an electric vehicle driven by a rotating electrical machine and a hybrid vehicle equipped with an engine and a rotating electrical machine.

The power supply monitoring system 10 includes a part mounted on the main control board 12 and a part mounted on the satellite board 50. Hereinafter, the main control board 12 is referred to as a main board 12 unless otherwise specified. A plurality of circuits that are operated by a low voltage V _CC generated from a low voltage power source (not shown) are mounted on the main board 12 with the vehicle body 14 as a ground potential. The low voltage power source is a lead storage battery having a nominal terminal voltage of about 14.4V, and an example of the low voltage V _CC is about 5V. The circuit mounted on the main board 12 includes, for example, a vehicle lamp lighting circuit, a steering drive circuit, an air conditioning circuit, an audio circuit, and the like. FIG. 1 shows the main control device 16 and the leakage detection circuit 18.

  The main control device 16 communicates with the monitoring circuit 52 mounted on the satellite board 50 via the data communication line 70, acquires monitoring data of the state of the high voltage power supply 30 from the monitoring circuit 52, and monitors based on the result. This is an apparatus for instructing the circuit 52 and instructing other control elements of the vehicle. The main control device 16 is composed of a microcomputer suitable for in-vehicle use.

  The leakage detection circuit 18 is a circuit that detects a leakage between the positive electrode bus 32 and the negative electrode bus 34 of the high-voltage power supply 30 and the vehicle body 14. Hereinafter, unless otherwise specified, the positive electrode bus 32 of the high voltage power supply 30 and the negative electrode bus 34 of the high voltage power supply 30 are referred to as a positive electrode bus 32 and a negative electrode bus 34, respectively. Since the high voltage power supply 30 has a terminal voltage of about 100 V to about 300 V, the positive bus 32 and the negative bus 34 are at a floating potential with respect to the vehicle body 14 in order to prevent electric shock. The positive electrode bus 32 and the negative electrode bus 34 are insulated from the vehicle body 14 by an insulating material, space, or the like. If the insulation resistance is deteriorated or damaged for some reason, the positive electrode bus 32, the negative electrode bus 34 and the vehicle body 14 are insulated. Leakage occurs between the two. The leakage detection circuit 18 monitors the leakage between the vehicle body 14 and the high voltage power supply 30. When there is a possibility of electric leakage, the driving of the vehicle is stopped by the action of the vehicle control unit that controls the entire vehicle, and the high voltage power supply 30 and other components of the vehicle are electrically separated. Treatment is performed.

  The high-voltage power supply 30 is a high-current high-voltage DC power supply that serves as a driving power source for a rotating electrical machine of a vehicle. The high voltage power supply 30 connects a predetermined plurality of battery cells 36 in series and outputs a predetermined high voltage. In FIG. 1, a predetermined number n is 24, and each of the 24 battery cells 36 has a negative electrode terminal on the negative electrode bus 34 side and a positive electrode terminal on the positive electrode bus 32 side, and between adjacent battery cells 36. The positive terminal of one battery cell 36 is connected to the negative terminal of the other battery cell 36. In FIG. 1, 24 battery cells 36 are distinguished and numbered from n = 1 to n = 24 from the negative electrode bus 34 side toward the positive electrode bus 32 side. The potential of the negative electrode terminal of the battery cell 36 with n = 1 is the potential of the negative electrode bus 34, and the potential of the positive electrode terminal of the battery cell 36 with n = 24 is the potential of the positive electrode bus 32.

  As the type of the battery cell 36, a lithium ion battery having a nominal terminal voltage of about 3.6V or a nickel metal hydride battery having a nominal terminal voltage of about 1.2V is used. Here, the battery cell 36 is a lithium ion battery, and a nominal inter-terminal voltage of 3.6 V is used as the inter-terminal voltage. In FIG. 1, since 24 battery cells 36 are connected in series as the high voltage power supply 30, the voltage between the terminals of the high voltage power supply 30 is (3.6V × 24) = 86.4V. This is an illustrative example, and the number of series connections other than n = 24 may be used. For example, when n = 96, the voltage between the terminals of the high voltage power supply 30 is 345.6V. In the example of FIG. 1, each stage connected in series is one battery cell 36. However, a plurality of battery cells 36 may be connected in parallel to form one stage, and 24 stages may be connected in series. For example, a configuration in which 15 battery cells 36 are connected in parallel to each other may be one stage and 24 stages may be connected in series. The voltage between terminals of each stage is 3.6 V, but the output current is 15 times that of the case where one stage is one battery cell 36. Thus, the high-voltage power supply 30 can output a predetermined large current and high voltage by appropriately setting the number of stages connected in parallel and the number of stages connected in series. In the following, as shown in FIG. 1, it is assumed that the number of one stage = 1 and the number of stages connected in series = 24.

  The battery cell 36 of a lithium ion battery has a positive electrode active material layer and a negative electrode active material layer disposed via a separator. The separator is a porous sheet made of a polymer that holds or supports an electrolyte. A nonwoven fabric sheet may be used instead of the porous sheet. As the electrolytic solution, a liquid electrolytic solution in which a lithium salt is dissolved in an organic solvent is used. Examples of the organic solvent include carbonates, and examples of the lithium salt include inorganic acid anion salts and organic acid anion salts. Since these materials are known, further description is omitted.

  The battery cell 36 is housed inside a battery can 38, and the positive terminal and the negative terminal are insulated from the battery can 38 and project outside. Since the inside of the battery can 38 is filled with the electrolytic solution, the positive electrode terminal is electrically connected to the battery can 38 via the electrolytic solution resistor 40, and the negative electrode terminal is electrically connected to the battery can 38 via the electrolytic solution resistor 41. Connected. When the single battery cell 36 is taken out, the potential of the battery can 38 becomes a floating potential from the positive electrode terminal and the negative electrode terminal through the electrolytic solution resistors 40 and 41, and the electrolytic solution resistor 40 and the electrolytic solution resistor 41 are substantially the same. 3.6V / 2) = 1.8V. The outer surface of the battery can 38 is covered with an insulating film or an insulating tube.

The thermistor 42 is a resistor having a large electrical resistance change with respect to a temperature change, and is used as a temperature sensor for detecting the battery temperature by utilizing this phenomenon. The thermistor 42 decreases in resistance as the temperature rises. On the other hand, a positiver (registered trademark of Murata Manufacturing Co., Ltd.) whose resistance increases as the temperature rises is also known. In the following, a resistor whose resistance decreases with increasing temperature is used as the thermistor 42. If the resistance of the thermistor 42 at temperature θ ₀ is R (θ ₀ ), and the resistance of the thermistor 42 at temperature θ is R (θ), then R (θ) = R (θ ₀ ) × exp [B {(1 / θ ) − (1 / θ ₀ )}. B is a physical property value indicating the rate of change in resistance of the thermistor 42 with respect to temperature change, and is referred to as B constant. In the above equation, the unit of temperature is absolute temperature K, and the unit of B constant is also absolute temperature K.

  The thermistor 42 is disposed via an insulator 44 at a measurement position determined for the plurality of battery cans 38 of the high voltage power supply 30. The insulator 44 is a film that transmits temperature while electrically insulating the resistor, which is a conductor of the thermistor 42, and the battery can 38. As the insulator 44, an insulating film, an insulating tube, an insulating coating or the like covering the outer periphery of the thermistor 42 is used. An insulating film or the like that covers the outer peripheral surface of the battery can 38 may be used as the insulator 44.

  As a method for arranging the thermistor 42, a method can be used in which the thermistor 42 is fixed to a thermistor holder attached to a pack case that houses the entire high-voltage power supply 30 and brought into contact with the battery can 38. This is an example, and other methods may be used. In the example of FIG. 1, one thermistor 42 is assigned to each battery can 38 having an even number n, and a total of twelve thermistors 42 are arranged. This is also an illustrative example, and one thermistor 42 may be arranged for each battery can 38, or the thermistors 42 may be arranged at several appropriate positions of the high-voltage power supply 30.

  From each thermistor 42, a signal line is drawn out from one end 46 and the other end 48 of the resistor that senses temperature, and led to the satellite substrate 50.

  The satellite board 50 is a circuit board that is independent of the main board 12 and is arranged attached to the high voltage power supply 30. Being attached to the high voltage power supply 30 means being attached to the inside of the pack case of the high voltage power supply 30 or the outside of the pack case. The satellite substrate 50 is a temperature detection circuit substrate that detects the temperature of a predetermined battery can 38 of the high voltage power supply 30 using the thermistor 42. On the satellite substrate 50, a monitoring circuit 52, multiplexers 54 and 55, a series resistor 58 connected to the thermistor 42, a path switching unit 60, and the like are mounted and arranged.

The monitoring circuit 52 operates with a predetermined low voltage V _ref1 with the negative electrode bus 34 as a ground potential, monitors the battery temperature based on the voltage across the terminals between the one end 46 and the other end 48 of the thermistor 42, and performs main control. It is a circuit that communicates with the device 16 via the data communication line 70. Here, in particular, a short-circuit determining unit 64 that determines the presence or absence of an electrical short between the high-voltage power supply 30 and the thermistor 42 is included.

An example of the predetermined low voltage V _ref1 is about 5V, which is substantially the same as the predetermined low voltage V _cc of the main controller 16. The difference is that the reference potential of the predetermined low voltage V _cc in the main board 12 is the potential of the vehicle body 14, whereas the reference potential of the predetermined low voltage V _ref1 in the satellite board 50 is a floating negative electrode bus from the vehicle body 14. 34 potentials. As for the inter-terminal voltage between the one end 46 and the other end 48 of the thermistor 42, the detection data transmitted from the multiplexers 54 and 55 is acquired by the detection terminals 62 and 63. The detection data acquired by the detection terminals 62 and 63 is a voltage having the negative electrode bus 34 as a reference potential.

The multiplexers 54 and 55 are sequential selection circuits that sequentially select one of V _OUT as detection data transmitted from the twelve thermistors 42 and transmit it to the detection terminals 62 and 63 of the monitoring circuit 52. The multiplexer 54 sequentially selects one of V _OUT from the six thermistors 42 corresponding to the six battery cans 38 of n = 2, 4, 6, 8, 10, and 12 and detects the detection terminal of the monitoring circuit 52. 62. The multiplexer 55 sequentially selects one of V _OUT from the six thermistors 42 corresponding to the six battery cans 38 of n = 14, 16, 18, 20, 22, and 14 and detects the detection terminal of the monitoring circuit 52. 63.

FIG. 1 shows V _OUT (n = 2), V _OUT (n = 4), V _OUT (n = 20), V _OUT (n = 22), V _OUT (n = 24), and other illustrations. Omitted. By using the multiplexers 54 and 55, the number of detection terminals in the monitoring circuit 52 can be reduced. In the example of FIG. 1, only two detection terminals 62 and 63 are required to acquire 12 V _OUT data.

The multiplexers 54 and 55 are circuits that reduce the number of detection terminals of the monitoring circuit 52, and functionally, the V _OUT data from the thermistor 42 input to the multiplexers 54 and 55 is detected by the detection terminals of the monitoring circuit 52. 62 and 63 are the same as the acquired data. Therefore, hereinafter, unless otherwise specified, it is assumed that the sequential selection function of the multiplexers 54 and 55 is included in the broad monitoring circuit 52, and V _OUT from each thermistor 42 is input to the detection terminal of the monitoring circuit 52. .

The series resistor 58 is a resistor having one end connected to a preset reference voltage V _ref2 and the other end connected to the detection terminal of the monitoring circuit 52, and is provided for each of the twelve thermistors. The voltage value of the reference voltage V _ref2 and the resistance R ₀ of the series resistor 58 are set in consideration of the B constant indicating the sensitivity of the thermistor 42. Examples of these settings will be described later.

  One path switching unit 60 is provided for each thermistor 42, and is provided between one end 46 and the other end 48 of the thermistor 42, the detection terminal of the monitoring circuit 52, and the negative electrode bus 34, and switches the signal flow path. It is a switch group.

  FIG.1 (b) is an internal block diagram of the path | route switching part 60 shown as B in (a). The path switching unit 60 includes four switches SW1, SW2, SW3, SW4. The switches SW1, SW2, SW3, SW4 are constituted by switching transistors that operate under the control of the monitoring circuit 52.

  The path switching unit 60 turns on both SW1 and SW2 and turns off both SW3 and SW4, and turns off both SW1 and SW2 and turns on both SW3 and SW4. The route is changed with the second route to be performed. The first path is a path that connects one end 46 of the thermistor 42 to the detection terminal of the monitoring circuit 52 and connects the other end 48 of the thermistor 42 to the negative electrode bus 34. The second path is a path for connecting the other end 48 of the thermistor 42 to the detection terminal of the monitoring circuit 52 and connecting one end 46 of the thermistor 42 to the negative electrode bus 34.

When the path switching unit 60 switches from the first path to the second path, the short-circuit determination unit 64 uses a high-voltage power supply based on the change in _VOUT detected by the detection terminal of the monitoring circuit 52 before and after the path switching. The presence or absence of a short circuit between 30 and the thermistor 42 is determined. Since the path switching unit 60 is provided for each thermistor 42, V _OUT detected by the detection terminal of the monitoring circuit 52 is an inter-terminal voltage of one thermistor 42 whose path is switched by the path switching unit 60. Therefore, the short circuit determination unit 64 determines whether one thermistor 42 corresponding to the path switching unit 60 is electrically short-circuited to the high voltage power supply 30.

As an example in FIG. 1A, V _OUT (n = 20) when the path switching unit 60 corresponding to the thermistor 42 with n = 20 is switched to the first path under the control of the monitoring circuit 52. Obtained by the monitoring circuit 52. This is the first V _OUT (n = 20). Next, the path switching unit 60 corresponding to the n = 20 thermistor 42 is switched to the second path under the control of the monitoring circuit 52. At that time, it is acquired by the monitoring circuit 52. Let V _OUT (n = 20) be the second V _OUT (n = 20). When the absolute value of the voltage difference between the first V _OUT (n = 20) and the second V _OUT (n = 20) is less than a predetermined value, the short circuit determination unit 64 determines that n = 20 It is determined that there is no electrical short circuit between the thermistor 42 and the n = 20 battery can 38 of the high voltage power supply 30. In other words, when the absolute value of the voltage difference between the first V _OUT (n = 20) and the second V _OUT (n = 20) is equal to or less than a predetermined value, the short circuit determination unit 64 determines that n = 20 It is determined that an electrical short circuit has occurred between the thermistor 42 and the n = 20 battery can 38 of the high voltage power supply 30. Thus, the short circuit determination unit 64 determines the presence or absence of an electrical short circuit between each thermistor 42 and the corresponding battery can 38 in the high voltage power supply 30. The necessity of performing route switching will be described later.

FIG. 2 is a diagram illustrating a configuration of the power supply monitoring system 10 when each path switching unit 60 switches to the first path. When switching to the first path, one end 46 of the thermistor 42 is connected to the detection terminal of the monitoring circuit 52, and the other end 48 of the thermistor 42 is connected to the negative electrode bus 34. This state is the same as that of the conventional power supply monitoring system without the path switching unit 60, and the detection terminal of the monitoring circuit 52 uses the potential of the negative electrode bus 34, which is the potential of the other end 48 of the thermistor 42, as a reference potential. The potential at one end of the thermistor 42 is acquired as V _OUT .

FIG. 3 shows an example of the relationship between V _OUT acquired by the monitoring circuit 52 in FIG. 2 and the detected temperature of the thermistor 42 when the high voltage power supply 30 and each thermistor 42 are electrically insulated. FIG. The horizontal axis in FIG. 3 is the temperature of the thermistor 42, and the vertical axis is V _OUT . V _OUT is the voltage across the thermistor 42 when the series resistor 58 and the thermistor 42 are connected in series between the reference voltage V _ref2 and the negative electrode bus 34.

FIG. 3 corresponds to a temperature characteristic diagram of the thermistor 42 when the series resistor 58 and the thermistor 42 are connected in series between the reference voltage V _ref2 and the negative electrode bus 34. As the thermistor 42, a thermistor having a general characteristic of a resistance of 10 kΩ at 25 ° C. and a B constant of 3435 (K) is used. At this time, the resistance becomes several hundreds kΩ at a very low temperature, and becomes several Ω at a high temperature. By appropriately setting the resistance R ₀ of the series resistor 58, for example, a change in V _OUT with respect to a change in temperature can be made a linear change around 25 ° C., for example. According to the calculation, in order to make the range of the linear change as wide as possible, the reference voltage V _ref2 is set to 5.0 V which is standard as a measurement circuit, and the resistance R ₀ of the series resistor 58 is the thermistor 42 at 25 ° C. It can be seen that 10 kΩ, which is the same as the resistance, is good. The calculation result of this setting is shown in FIG. In this example, a change in _VOUT with respect to a change in temperature can be a substantially linear change in a range from about 0 ° C. to about 50 ° C. with 25 ° C. as the center. In the following, it is assumed that V _ref2 = 5.0 V and the resistance R ₀ of the series resistor 58 is 10 kΩ.

As shown in FIG. 3, when the electrical insulation between the high voltage power supply 30 and each thermistor 42 is maintained at normal time, the temperature characteristics of the respective _VOUT of each thermistor 42 are all the same. Become. That is, at an extremely low temperature of −50 ° C., V _OUT is almost the same value as V _ref2 , at 25 ° C., V _OUT is about 2.3 V, and at a high temperature of 300 ° C., V _OUT is almost 0 V.

Next, the necessity of the path switching unit 60 in the power supply monitoring system 10 using a satellite substrate will be described with reference to FIGS. 4 and 6 show that the electrical insulation between the n = n-th battery can 38 and the corresponding thermistor 42 is deteriorated or damaged, and the battery can 38 and the thermistor 42 are electrically connected. It is a figure which shows how the short circuit current flows when short-circuited. 4 shows a case where one end 46 of the thermistor 42 is electrically short-circuited with the battery can 38, and FIG. 6 shows a case where the other end 48 of the thermistor 42 is electrically short-circuited with the battery can 38. Note that Z _D shown in FIGS. 4 and 6 is a Zener diode provided for preventing overvoltage of the monitoring circuit 52 and the like.

In FIG. 4, a short-circuit current 74 when the one end 46 of the thermistor 42 and the battery can 38 are electrically short-circuited by the short-circuit path 72 is indicated by a thick line with an arrow. The short-circuit current 74 passes from the battery cell 36 to the negative electrode bus 34 through the electrolyte resistor 40 indicated by r, the battery can 38 and the short-circuit path 72, the one end 46 of the thermistor 42, the other end 48 of the thermistor 42. Flowing. V _OUT which is a voltage across the thermistor 42 is a value obtained by multiplying the sum of the short-circuit current 74 flowing through the thermistor 42 and the reference voltage V _ref2 and the current flowing through the series resistor 58 by the resistance of the thermistor 42. FIG. 5 shows the result of calculation using Kirchhoff's law and superposition principle used in electrical circuit analysis.

The vertical and horizontal axes in FIG. 5 are the same as those in FIG. The characteristic at normal time described in FIG. 3 is indicated by a broken line. When the position of the battery can 38 and the thermistor 42 which are electrically short-circuited by the short circuit 72 is indicated by n, the solid line indicates the voltage characteristic between the terminals of the thermistor 42 at the position n as V _OUT , and its temperature characteristic is n = It is the result of calculation for n = 24 from 2. For example, when the battery can 38 and one end 46 of the thermistor 42 are electrically short-circuited by the short circuit 72 at the position n = 2, the temperature characteristic of _VOUT of the thermistor 42 at the position n = 2 is shown in FIG. It is shown by the characteristic of n = 2. V _OUT of the thermistor 42 at the position of n = 2 is about 5.2 V at a very low temperature of −50 ° C., about 5.0 V at 25 ° C., and about 0.1 V at a high temperature of 300 ° C. At this time, V _OUT of the thermistor 42 at a position other than n = 2 indicates a normal characteristic indicated by a broken line if there is no electrical short circuit with the battery can 38 at that position. As described above, when the temperature of the V _OUT of the thermistor 42 is electrically short-circuited between the one end 46 of the thermistor 42 and the battery can 38 by the short circuit 72, the normal V V indicated by the broken line is used. The voltage is larger than _OUT .

Next, in FIG. 6, the short-circuit current 78 when the other end 48 of the thermistor 42 and the battery can 38 are electrically short-circuited by the short circuit 76 at the position of n = n is indicated by a thick line with an arrow. The short-circuit current 78 flows from the battery cell 36 through the electrolytic solution resistor 41, the battery can 38 and the short-circuit path 76, and the other end 48 of the thermistor 42 toward the negative electrode bus 34. At this time, at the same time as the short circuit current 78 flows, a current 79 flows through the short circuit 76 toward one end 46 of the thermistor 42. A current 79 flows from one end 46 of the thermistor through the series resistor 58 toward the monitoring circuit 52. Since the current 79 is a current flowing through the thermistor 42 and the series resistor 58, it does not affect V _OUT detected by the monitoring circuit 52. Therefore, the short-circuit current 78 is not reflected in V _OUT , which is the voltage across the thermistor 42, and it has the same temperature characteristics as when normal when there is no short circuit. Figure 7 shows a temperature characteristic of V _OUT of the thermistor 42 when the electrically short-circuited by a short circuit path 76 between the second end 48 and the battery can 38 of the thermistor 42, which is the temperature of V _OUT in the normal This is the same as FIG. 3 showing the characteristics. FIG. 3 shows normal _VOUT temperature characteristics without electrical short-circuit in the prior art, whereas FIG. 7 shows that the other end 48 of the thermistor 42 and the battery can 38 are electrically short-circuited. This is a temperature characteristic of V _OUT of the thermistor 42 when there is an abnormality. V _OUT of the thermistor 42 at a position other than the position of n = n also exhibits the temperature characteristics shown in FIG. 7 if there is no electrical short circuit with the battery can 38 at that position. Thus, V _OUT of the thermistor 42 shows the same temperature characteristics as in FIG. 3, whether or not the other end 48 of the thermistor 42 and the battery can 38 are electrically short-circuited by the short circuit 76. A short circuit cannot be detected.

  When the short-circuit current 74 in FIG. 4 or the short-circuit current 78 in FIG. 6 occurs, the high-voltage power supply 30 discharges toward the negative electrode bus 34 via the short circuit 72 or the short circuit 76 and is left in an overdischarge state if left as it is. . Since the short-circuit currents 74 and 78 do not flow toward the vehicle body 14 that is the ground potential in the main board 12, it cannot be detected by the leakage detection circuit 18.

When the battery can 38 and the one end 46 of the thermistor 42 are electrically short-circuited, the monitoring circuit 52 in the satellite substrate 50 has a temperature of V _OUT of the thermistor 42 when the short-circuit current 74 flows as described in FIG. It can be used that the characteristic is different from the temperature characteristic of V _OUT during normal operation. However, when the battery can 38 and the other end 48 of the thermistor 42 are electrically short-circuited, as described in FIG. 7, the temperature characteristic of _VOUT of the thermistor 42 when the short-circuit current 78 flows is normal. Since it is the same as the temperature characteristic of V _OUT , the occurrence of the short circuit 76 cannot be detected.

  FIG. 8 is a flowchart showing a procedure for detecting that one of the battery can 38 and one end 46 or the other end 48 of the thermistor 42 is electrically short-circuited by switching the path through which the short-circuit current flows by the path switching unit 60. is there. This procedure can be realized by the monitoring circuit 52 executing software, and specifically, can be realized by the monitoring circuit 52 executing a short-circuit determination program for the high-voltage power supply. Each procedure in FIG. 8 corresponds to each processing procedure of the short-circuit determination program for the high-voltage power supply. A part of the procedure of FIG. 8 may be realized by hardware.

  Since each procedure in FIG. 8 is sequentially executed for each thermistor 42, the procedure starts with the thermistor 42 having the smallest n. In the example of FIG. 1, twelve thermistors 42 are n = 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, so that n = 2 is initially set. (S10). In the following, the thermistor 42 at each position is simply indicated as the thermistor 42 unless otherwise specified until the procedure from the thermistor 42 at the n = 2 position to the thermistor 42 at the n = 24 position proceeds to S26.

Here, the path switching unit 60 corresponding to the thermistor 42 is set as the first path. Specifically, SW1 and SW2 are turned on, and SW3 and SW4 are turned off (S12). Then, V _OUT of the thermistor 42 at that time is acquired as the first V _OUT (n = n) (S14). Here, (n = n) is generally indicated, and n = 2 in the present case. The same applies to the following.

The V _OUT of the thermistor 42 in S14 has the normal temperature characteristics described with reference to FIG. 3 when there is no electrical short circuit between the high voltage power supply 30 and the thermistor 42. Because when the one end 46 of the battery can 38 and the thermistor 42 of the high voltage power supply 30 is electrically short-circuited by the short-circuit path 72 is in a state described in Fig. 4, V _OUT of the thermistor 42, the temperature as described in FIG. 5 It becomes a characteristic. In this case, since n = 2, the temperature characteristic of the solid line of n = 2 in FIG. 5 is obtained. When the battery can 38 of the high-voltage power supply 30 and the one end 46 of the thermistor 42 are electrically short-circuited by the short circuit 76, the state described in FIG. 6 is in effect, so that V _OUT of the thermistor 42 is normal as described in FIG. It becomes the temperature characteristic of the hour.

When the first V _OUT (n = n) is acquired, the path switching unit 60 corresponding to the thermistor 42 is set to the second path. Specifically, SW1 and SW2 are turned off, and SW3 and SW4 are turned on (S16). Then, V _OUT of the thermistor 42 at that time is acquired as the second V _OUT (n = n) (S18).

The V _OUT of the thermistor 42 in S18 has the normal temperature characteristics described with reference to FIG. 3 when there is no electrical short circuit between the high voltage power supply 30 and the thermistor 42. When there is an electrical short circuit between the high voltage power supply 30 and the thermistor 42, the battery can 38 and one end 46 of the thermistor 42 are short-circuited by the short circuit 72, and the other end of the battery can 38 and the thermistor 42. 48 will be described separately when they are short-circuited by the short circuit 76.

FIG. 9 is a diagram illustrating a case where one end 46 of the thermistor 42 is electrically short-circuited with the battery can 38. In FIG. 9, the short circuit current 80 when the one end 46 of the thermistor 42 and the battery can 38 are electrically short-circuited by the short circuit 72 at the position of n = n is indicated by a thick line with an arrow. The short-circuit current 80 passes from the battery cell 36 through the electrolytic solution resistor 40, through the battery can 38 and the short-circuit path 72, through the second path in the path switching unit 60 from the one end 46 of the thermistor 42 to the negative electrode bus 34. Flowing. At this time, the short-circuit current 80 does not flow toward the other end 48 of the thermistor 42. Between the other end 48 and one end 46 of the thermistor 42, only a current directed to the negative electrode bus 34 flows through the reference voltage V _ref2 and the series resistor 58. Therefore, the short-circuit current 80 is not reflected in the second V _OUT (n = n), which is V _OUT of the thermistor 42 in the second path, and shows the normal temperature characteristics described in FIG.

FIG. 10 is a diagram showing a case where the other end 48 of the thermistor 42 is electrically short-circuited with the battery can 38. In FIG. 10, the short circuit current 82 when the other end 48 of the thermistor 42 and the battery can 38 are electrically short-circuited by the short circuit 76 at the position of n = n is indicated by a thick line with an arrow. The short-circuit current 82 flows from the battery cell 36 through the electrolyte resistor 41, the battery can 38 and the short-circuit path 76 to the other end 48 of the thermistor 42 to the one end 46, and passes through the second path of the path switching unit 60. Flows toward the negative electrode bus 34. V _OUT which is a voltage across the thermistor 42 is a value obtained by multiplying the sum of the short-circuit current 82 flowing through the thermistor 42 and the reference voltage V _ref2 and the current flowing through the series resistor 58 by the resistance of the thermistor 42. FIG. 11 shows the result of calculation using Kirchhoff's law and superposition principle used in electric circuit analysis. The contents of FIG. 11 are the same as those of FIG. Thus, the second V _OUT (n = n), which is the V _OUT of the thermistor 42 in the second path, shows the temperature characteristic of the solid line in FIG. In this case, since n = 2, the temperature characteristic of the solid line of n = 2 in FIG. 11 is obtained.

Once the second V _OUT (n = n) is obtained, the absolute value of the voltage difference between the first V _OUT (n = n) and the second V _OUT (n = n) is then obtained in advance. It is determined whether it is less than a predetermined value ΔV _th (S20). This processing procedure is executed by the function of the short circuit determination unit 64 of the monitoring circuit 52.

The determination of S20 will be described in three cases. The first case is a case where there is no electrical short circuit between the high voltage power supply 30 and the thermistor 42. At this time, the first V _OUT (n = n) in the first route of the route switching unit 60 is the normal temperature characteristic described with reference to FIG. 3, and the second V _OUT in the second route of the route switching unit 60. V _OUT (n = n) is also a normal temperature characteristic described in FIG. These are the same temperature conditions because V _OUT for the same thermistor 42 is simply the difference between the first path and the second path. Therefore, the absolute value of the voltage difference between the first V _OUT (n = n) and the second V _OUT (n = n) is zero in the measurement error range, and ΔV _{th is set} to 0. By setting it to 1V, the determination of S20 is affirmed.

In the second case, the battery can 38 and the one end 46 of the thermistor 42 are electrically short-circuited by the short circuit 72. At this time, the first V _OUT (n = n) in the first route of the route switching unit 60 becomes the temperature characteristic of the solid line in FIG. On the other hand, the second V _OUT (n = n) in the second route of the route switching unit 60 has the normal temperature characteristic of FIG. 3 as described in FIG. 11 is used instead of FIGS. 3 and 5, and when n = 2, the first V _OUT (n = 2) is the temperature characteristic of the solid line of n = 2 in FIG. 11, and the second V _OUT (N = 2) is the temperature characteristic of the broken line in FIG. If the temperature of the thermistor 42 with n = 2 is 50 ° C., for example, the first V _OUT (n = 2) is about 4.5 V and the second V _OUT (n = 2) at the point (a) in FIG. 2) is about 1.5 V at the point (b) in FIG. Therefore, the absolute value of the voltage difference between the first V _OUT (n = n) and the second V _OUT (n = n) is about 3.0 V, which is a value that greatly exceeds the measurement error range. . If ΔV _th is 0.1 V which is the upper limit of measurement error, the determination in S20 is negative. Setting ΔV _th to 0.1 V is an example for explanation, and other numerical values may be used.

The third case is a case where the battery can 38 and the other end 48 of the thermistor 42 are electrically short-circuited by a short circuit 76. At this time, the first V _OUT (n = n) in the first path of the path switching unit 60 becomes the normal temperature characteristic of FIG. On the other hand, the second V _OUT (n = n) in the second route of the route switching unit 60 becomes the temperature characteristic of the solid line in FIG. 11, as described in FIG. If n = 2, the first V _OUT (n = 2) is the temperature characteristic of the broken line in FIG. 11, and the second V _OUT (n = 2) is the temperature of the solid line of n = 2 in FIG. It is a characteristic. If the temperature of the thermistor 42 with n = 2 is, for example, 50 ° C., the first V _OUT (n = 2) is about 1.5 V and the second V _OUT (n = 2) at the point (b) in FIG. 2) is about 4.5 V at the point (a) in FIG. Therefore, the absolute value of the voltage difference between the first V _OUT (n = n) and the second V _OUT (n = n) is about 3.0 V, which is a value that greatly exceeds the measurement error range. . If ΔV _th is 0.1 V which is the upper limit of measurement error, the determination in S20 is negative.

  Thus, even when the battery can 38 is electrically short-circuited with the one end 46 of the thermistor 42 and the short-circuit path 72 by the action of the path switching unit 60, the battery can 38 is electrically connected with the other end 48 of the thermistor 42 and the short-circuit path 76. Even if a short circuit occurs, the determination of S20 is denied. Thereby, it is possible to detect that the battery can 38 and the other end 48 of the thermistor 42 which are not detected by the power supply monitoring system 10 of FIG. 2 corresponding to the case where the path switching unit 60 is not provided are electrically short-circuited.

In S20, the first V _OUT (n = n) and the second V _OUT (n = n) for the same thermistor 42 were compared. Instead, V _OUT between different thermistors 42 is compared, and when the voltage difference exceeds ΔV _th , the thermistor 42 showing a large V _OUT is electrically short-circuited with the battery can 38. It is also possible to determine that it is present. As shown in FIG. 5, this proposal shows the temperature characteristic of the solid line V _OUT when the thermistor 42 is electrically short-circuited to the battery can 38, and the thermistor 42 is connected to the battery can 38. In this case, it is used that V _OUT when not electrically short-circuited shows a temperature characteristic indicated by a broken line. Since this scheme compares V _{OUT of} different thermistors 42, it can be used when the temperatures of the thermistors 42 to be compared are the same.

For example, in FIG. 11 having the same contents as FIG. 5, V _OUT of the thermistor 42 with n = 2 is a solid temperature characteristic, and V _{OUT of the} thermistor 42 indicating other normal conditions is a broken line temperature characteristic. If the temperature is both 50 ° C., V _OUT of n = 2 of the thermistor 42 is about 4.5V in point (a), V _OUT of the thermistor 42 in the normal is about 1.5V in point (b) The voltage difference exceeds ΔV _th . Therefore, it can be determined that the n = 2 thermistor 42 showing a large value of V _OUT is electrically short-circuited with the battery can 38. Even if the common temperature is not 50 ° C., the same determination can be made. For example, when the common temperature is 150 ° C., V _OUT of the thermistor 42 with n = 2 is about 1.5 V at the point (c), and V _OUT of the thermistor 42 at normal time is about 0. 1V, and the voltage difference exceeds ΔV _th .

However, the temperature of each battery can 38 of the high voltage power supply 30 is not necessarily the same, and in some cases, there may be a large temperature difference. In the example of FIG. 11, if the temperature of the thermistor 42 with n = 2 is 150 ° C. and the temperature of the thermistor 42 under normal conditions is 50 ° C., V _OUT of the thermistor 42 with n = 2 is about 1.5 V at the point (c). The V _OUT of the thermistor 42 in a normal state is about 1.5 V at the point (b). In this example, the voltage difference is almost zero and less than ΔV _th, and it cannot be determined that the n = 2 thermistor 42 is electrically short-circuited with the battery can 38. On the other hand, in S20, since the absolute value of the voltage difference of V _OUT when the path switching unit 60 switches the path in the same thermistor 42, the accurate determination can be made without being influenced by the temperature.

  Returning to FIG. 8, if the determination in S20 is affirmative, there is no electrical short circuit between the n = n thermistor 42 and the high voltage power supply 30 (S22). If the determination in S22 is negative, it is determined that there is an electrical short between the n = n thermistor 42 and the high voltage power supply 30 (S24). In the case of S24, since a short-circuit current is currently generated between the n = 2 thermistor 42 and the high voltage power supply 30, all the switches of the path switching unit 60 corresponding to the n = 2 thermistor 42 are turned on. Turn off (S26). As a result, it is possible to prevent a short-circuit current from flowing from the high voltage power supply 30 to the negative electrode bus 34 via the n = n thermistor 42 and to prevent overdischarge of the high voltage power supply 30. Thus, the path switching unit 60 also has a function of interrupting a short-circuit current between the high voltage power supply 30 and the thermistor 42.

  Since the short-circuit determination in the n = 2 thermistor 42 is completed in the processing procedure up to S22 and S26, the process proceeds to S28, and it is determined whether or not the short-circuit determination for all the thermistors 42 has been completed. That is, it is determined whether n has reached 24. In this case, there are twelve thermistors 42, and the determination is denied because the short-circuit determination in the n = 2 thermistor 42 has only been completed. It is determined whether n has reached 24. If the determination in S28 is negative, n is increased by (+2) (S30), the process returns to S12, and the above process is repeated. If the determination in S28 is affirmed, the short-circuit determination for all the thermistors 42 has been completed, and all processing procedures are ended.

  FIG. 12 is a diagram illustrating a configuration of a conventional power supply monitoring system 11 that does not use the satellite substrate 50 for comparison with the power supply monitoring system 10 of the embodiment. When the satellite substrate 50 is not used, the boundary between the high voltage side and the low voltage side is between each battery can 38 of the high voltage power supply 30 and each thermistor 42. Since the main board 12 is disposed away from the pack case in which the high-voltage power supply 30 is housed, the signal lines 49 drawn from one end 46 and the other end 48 of each thermistor 42 are routed to the main board. 12 is connected. The main board 12 is provided with a leakage detection circuit 18 that detects a leakage between the positive and negative buses 32 and 34 of the high-voltage power supply 30 and the vehicle body 14. When an electrical short circuit occurs between the high voltage power supply 30 and each thermistor 42, the short circuit current flows toward the vehicle body 14 and is detected by the leakage detection circuit 18.

  Thus, according to the power supply monitoring system 10 of the prior art, an electrical short circuit between the high voltage power supply 30 and each thermistor 42 can be detected by the leakage detection circuit 18. On the other hand, it is necessary to route a large number of signal lines 49 drawn from one end 46 and the other end 48 of each thermistor 42 to the main board 12. In the power supply monitoring system 10 of the present embodiment, since the satellite substrate 50 is used, it is not necessary to route a large number of signal lines 49 shown in FIG. When an electrical short circuit occurs between the high-voltage power supply 30 and each thermistor 42, the leakage detection circuit 18 cannot be used. However, due to the action of the path switching unit 60 and the short circuit determination unit 64, the electrical short circuit Detection is performed. According to the power monitoring system 10 of the present embodiment, the configuration is smaller and easier to handle than the power monitoring system 11 of the prior art.

In the vehicle power supply monitoring system 10 using the satellite substrate of the present embodiment, a predetermined plurality of battery cells 36 housed in a battery can 38 are connected in series, and the positive bus 32 and the negative bus 34 are connected from the vehicle body 14. It includes a high voltage power supply 30 that is at a floating potential through an insulation resistor. In addition, it includes a plurality of thermistors 42 which are arranged at the measurement positions determined for the plurality of battery cans 38 via the insulator 44 and from which one end 46 and the other end 48 are drawn out. The satellite board 50 is independent from the main control board 12. A monitoring circuit 52 that monitors the battery temperature based on the voltage across the terminals between one end 46 and the other end 48 of the thermistor 42 is mounted on the satellite substrate 50 with the negative electrode bus 34 as the ground potential. One end is connected to a preset reference voltage V _ref2 , the other end is connected to a detection terminal of the monitoring circuit 52, and a predetermined series resistor 58 provided for each thermistor 42 is included. Furthermore, a path switching unit 60 provided between one end 46 and the other end 48 of the thermistor 42, a detection terminal of the monitoring circuit 52, and the negative electrode bus 34 is included. The route switching unit 60 switches the route between the first route and the second route. In the first path, one end 46 of the thermistor 42 is connected to the detection terminals 62 and 63 of the monitoring circuit 52, and the other end 48 of the thermistor 42 is connected to the negative electrode bus 34. The second path connects the other end 48 of the thermistor 42 to the detection terminal of the monitoring circuit 52, and connects one end 46 of the thermistor 42 to the negative electrode bus 34. Then, before and after the path switching, when the difference between the terminals of the thermistor 42 exceeds a predetermined value, it is determined that one of the one end 46 and the other end 48 of the thermistor 42 is electrically short-circuited with the battery can 38. A short-circuit determining unit 64 is provided.

  According to the above configuration, in the vehicle power supply monitoring system 10 in which the monitoring circuit 52 is mounted on the satellite board 50, an electrical short circuit between the high voltage power supply 30 and the thermistor 42 can be determined.

  10 (for vehicle using satellite board) power supply monitoring system, 11 (prior art) power supply monitoring system, 12 main (control) board, 14 vehicle body, 16 main controller, 18 leakage detection circuit, 30 high voltage power supply, 32 (High voltage power supply) positive electrode bus, 34 (high voltage power supply) negative electrode bus, 36 battery cell, 38 battery can, 40, 41 electrolyte resistance, 42 thermistor, 44 insulator, 46 (thermistor) one end, 48 ( The other end of the thermistor, 49 signal line, 50 satellite board, 52 monitoring circuit, 54,55 multiplexer, 58 series resistance, 60 path switching unit, 62,63 detection terminal, 64 short circuit determination unit, 70 data communication line, 72, 76 Short circuit, 74, 78, 80, 82 Short circuit current, 79 Current.

Claims (1)

A high voltage power source in which a predetermined plurality of battery cells housed in a battery can are connected in series, and a positive bus and a negative bus are at a floating potential from the vehicle body via an insulation resistance;
A plurality of thermistors that are arranged via insulators at the measurement positions defined for the plurality of battery cans, and one end and the other end are each drawn out;
A monitoring circuit that is mounted on a satellite board independent of the main control board, sets the negative electrode bus to ground potential, and monitors the battery temperature based on the voltage between the terminals between the one end and the other end of the thermistor;
One end is connected to a preset reference voltage, the other end is connected to a detection terminal of the monitoring circuit, a predetermined series resistance provided in each of the thermistors,
A path switching unit provided between the one end of the thermistor, the other end, the detection terminal of the monitoring circuit, and the negative bus, and connecting the one end of the thermistor to the detection terminal of the monitoring circuit. A first path for connecting the other end of the thermistor to the negative electrode bus; connecting the other end of the thermistor to the detection terminal of the monitoring circuit; and connecting the one end of the thermistor to the negative electrode bus. A path switching unit that switches a path between the second path and
It is determined that one of the one end and the other end of the thermistor is electrically short-circuited with the battery can when the voltage difference between the terminals of the thermistor exceeds a predetermined value before and after path switching. A short circuit determination unit;
A vehicle power supply monitoring system using a satellite substrate.

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