Leakage current detection circuit and battery status detection circuit

Abstract

This invention provides a leakage current detection circuit that can use zero potential as the positive electrode reference for a battery. [Solution] A leakage current detection circuit 10 for detecting leakage current from a battery having a first electrode and a second electrode of opposite polarity to a chassis, comprising a detection circuit 5a having a reference voltage source terminal VR, a first detection terminal In1, and a ground terminal GND connected to the first electrode, a first resistor 21 (or 28) connected between the second electrode and the chassis, a second resistor 22 (or 27) connected between the chassis and the first detection terminal In1, and a third resistor 23 (or 26) connected between the first detection terminal In1 and a predetermined terminal, wherein when the polarity of the first electrode is positive, the predetermined terminal is the reference voltage source terminal VR, and the detection circuit 5a detects the presence or absence of leakage current based on the voltage of the first detection terminal In1.

Description

Technical Field

[0001] The present disclosure relates to a leakage detection circuit and a battery state detection circuit.

Background Art

[0002] In electric vehicles such as electric cars, a high-voltage and large-capacity battery that supplies DC power to a motor is mounted. Such a high-voltage battery is composed of a plurality of battery cells such as lithium-ion batteries connected in series, and is insulated from the vehicle body chassis as a ground for safety.

[0003] A leakage detection circuit for detecting the presence or absence of leakage between the high-voltage battery and the vehicle body chassis is disclosed in, for example, Patent Document 1.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Generally, since the leakage detection circuit connects a detection resistor to the vehicle body chassis, the leakage detection circuit is configured based on the vehicle body chassis potential that sets the vehicle body chassis to zero potential. On the other hand, the battery state detection circuit may be configured based on the positive electrode potential of the battery in order to monitor the battery voltage and charge / discharge current. When providing a leakage detection circuit as one of the functions of the battery state detection circuit to detect the presence or absence of battery leakage, it is also useful to configure the leakage detection circuit based on the positive electrode potential of the battery. Patent Document 1 is an example of a leakage detection circuit configured based on the battery potential, but is configured with the negative electrode of the battery as the zero potential of the leakage detection circuit. Therefore, it cannot be applied when the battery state detection circuit detects current on the positive electrode side of the battery and is configured with the positive electrode as the zero potential.

[0006] This disclosure provides a leakage current detection circuit that can reference the positive electrode of a battery to the zero potential of the leakage current detection circuit. [Means for solving the problem]

[0007] To solve the above problems, a leakage current detection circuit according to one aspect of the present disclosure is a leakage current detection circuit for detecting leakage current from a battery to a chassis, having a first electrode having positive or negative polarity and a second electrode having the opposite polarity to the first electrode, comprising: a reference voltage source terminal for outputting a reference voltage; a detection circuit having a first detection terminal and a ground terminal connected to the first electrode; a first resistor connected between the second electrode and the chassis; a second resistor connected between the chassis and the first detection terminal; and a third resistor connected between the first detection terminal and a predetermined terminal, wherein when the polarity of the first electrode is positive, the predetermined terminal is the reference voltage source terminal, and the detection circuit detects the voltage of the first detection terminal and detects the presence or absence of leakage current based on the detected voltage.

[0008] Furthermore, a battery state detection circuit according to one aspect of the present disclosure includes the above-mentioned leakage current detection circuit, a current detection resistor connected between the first electrode and the load, and an amplification circuit that detects the voltage across the current detection resistor as a signal indicating the current value of the battery. [Effects of the Invention]

[0009] According to the leakage current detection circuit of this disclosure, it is possible to set the zero potential of the leakage current detection circuit to the positive terminal of the battery. [Brief explanation of the drawing]

[0010] [Figure 1A] Figure 1A shows an example of a circuit configuration when the leakage current detection circuit according to the first embodiment is configured on the battery positive electrode side. [Figure 1B] Figure 1B shows a modified version of the leakage current detection circuit shown in Figure 1A. [Figure 1C] Figure 1C shows another modified example of the leakage current detection circuit shown in Figure 1A. [Figure 2] Figure 2 shows an example of the characteristics of a leakage current detection circuit according to the first embodiment. [Figure 3A] Figure 3A shows an example of a circuit configuration when the leakage current detection circuit according to the first embodiment is configured on the battery negative electrode side. [Figure 3B] Figure 3B shows a modified version of the leakage current detection circuit shown in Figure 3A. [Figure 3C] Figure 3C shows another modified example of the leakage current detection circuit shown in Figure 3A. [Figure 4] Figure 4 shows an example of the characteristics of the leakage current detection circuit shown in Figure 3A. [Figure 5] Figure 5 shows an example of a circuit configuration when the leakage current detection circuit according to the second embodiment is configured on the battery positive electrode side. [Figure 6] Figure 6 shows an example of the characteristics of a leakage current detection circuit according to the second embodiment. [Figure 7] Figure 7 shows an example of a circuit configuration when the leakage current detection circuit according to the second embodiment is configured on the battery negative electrode side. [Figure 8] Figure 8 shows an example of the characteristics of the leakage current detection circuit shown in Figure 7. [Figure 9] Figure 9 shows an example of a circuit configuration of a battery state detection circuit in which the leakage current detection circuit according to the third embodiment is installed on the positive terminal side of the battery. [Figure 10] Figure 10 shows an example of a circuit configuration of a battery state detection circuit in which the leakage current detection circuit according to the third embodiment is installed on the negative terminal side of the battery. [Modes for carrying out the invention]

[0011] Hereinafter, a leakage current detection circuit and a battery state detection circuit according to one aspect of this disclosure will be specifically described with reference to the drawings.

[0012] Note that all the embodiments described below show comprehensive or specific examples of the present disclosure. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, steps, order of steps, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. In addition, among the components in the following embodiments, the components not described in the independent claims indicating the most general concept are described as optional components.

[0013] (First Embodiment) The leakage detection circuit according to the first embodiment is configured such that the zero potential of the leakage detection circuit can be based on either the positive electrode or the negative electrode of the battery. First, the leakage detection circuit configured with the positive electrode of the battery as the zero potential will be described using FIGS. 1A to 1C and FIG. 2.

[0014] [1.1 Configuration Example of Leakage Detection Circuit with Battery Positive Electrode as Reference] FIG. 1A is a diagram showing a circuit configuration example when the leakage detection circuit of the first embodiment is configured on the positive electrode side of the battery. FIG. 1A also shows the battery 1. The battery 1 has a configuration in which a plurality of battery cells are connected in series, for example, to supply a voltage of several hundred volts to a motor when mounted on an electric vehicle. Since it is a high voltage, it is insulated from the vehicle body ground for safety, and usually, its insulation resistance is a high resistance of several MΩ or more. In FIG. 1A, it is equivalently considered to have insulation resistances R1 and R2 between the negative electrode - vehicle body ground and the positive electrode - vehicle body ground, respectively. Note that the battery 1 and the leakage detection circuit 10 may be mounted on something other than an electric vehicle. The battery 1 and the leakage detection circuit 10 may be mounted on, for example, an automobile, a power storage system, an aircraft, a ship, a server device, an AGV (also called an Automatic Guided Vehicle, unmanned transport vehicle), etc. The leakage detection circuit 10 is applied to detect the leakage of the battery 1 in devices and apparatuses where insulation between the chassis ground of the device or apparatus mounting the battery 1 and the battery 1 is required.

[0015] In FIG. 1A, the leakage detection circuit 10 includes resistors 21 to 25 and a detection circuit 5a. The detection circuit 5a has a reference voltage source terminal VR, a detection terminal In1, a detection terminal In2, a ground terminal GND, a reference voltage source 50, an AD converter 51, an AD converter 52, and a control circuit 53. Hereinafter, for each of the resistors 21 to 25, the terminal on the negative electrode side of the two terminals is referred to as one end, and the terminal on the positive electrode side is referred to as the other end.

[0016] The resistor 21 is a resistor connected between the negative electrode of the battery 1 and the chassis 11 as the vehicle body ground. That is, one end of the resistor 21 is connected to the negative electrode of the battery 1. The other end of the resistor 21 is connected to the chassis 11. Let the resistance value of the resistor 21 be r1.

[0017] The resistor 22 is a resistor connected between the detection terminal In1 and the chassis 11 as the vehicle body ground. That is, one end of the resistor 22 is connected to the chassis 11. The other end of the resistor 22 is connected to one end of the resistor 23 and the detection terminal In1. Let the resistance value of the resistor 22 be r2.

[0018] The resistor 23 is a resistor connected between the reference voltage source terminal VR and the detection terminal In1. That is, one end of the resistor 23 is connected to the other end of the resistor 22 and the detection terminal In1. The other end of the resistor 23 is connected to the reference voltage source terminal VR. Let the resistance value of the resistor 23 be r3.

[0019] The resistor 24 is a resistor connected between the negative electrode of the battery 1 and the detection terminal In2. That is, one end of the resistor 24 is connected to the negative electrode of the battery 1. The other end of the resistor 24 is connected to one end of the resistor 25 and the detection terminal In2. Let the resistance value of the resistor 24 be r4.

[0020] The resistor 25 is a resistor connected between the reference voltage source terminal VR and the detection terminal In2. That is, one end of the resistor 25 is connected to the other end of the resistor 24 and the detection terminal In2. Let the resistance value of the resistor 25 be r5.

[0021] The detection circuit 5a is configured with the positive terminal of battery 1 at zero potential. In other words, the ground terminal GND of the detection circuit 5a is connected to the positive terminal of battery 1. The detection circuit 5a detects the voltage at the detection terminal In1 as the detection voltage Vx and detects the presence or absence of a leakage current based on the detection voltage Vx.

[0022] The reference voltage source terminal VR is connected to the other end of resistor 23 and the other end of resistor 25.

[0023] The detection terminal In1 is connected to the connection point between resistor 22 and resistor 23.

[0024] The detection terminal In2 is connected to the connection point between resistor 24 and resistor 25.

[0025] The reference voltage source 50 is a voltage source that outputs a reference voltage Vr. The reference voltage source 50 is, for example, a regulator circuit that stabilizes a DC power supply voltage supplied from an external power supply to a constant voltage and outputs it as a reference voltage Vr. The reference voltage Vr is supplied from the reference voltage source 50 to the other end of resistor 23 and the other end of resistor 25 via the reference voltage source terminal VR. The reference voltage Vr is also used as the power supply for AD converter 51, AD converter 52, and control circuit 53.

[0026] The AD converter 51 converts the voltage applied to the detection terminal In1 from analog to digital.

[0027] The AD converter 52 converts the voltage applied to the detection terminal In2 from analog to digital.

[0028] The control circuit 53 determines whether there is a leakage current based on the output of the AD converter 51 and detects the voltage of the battery 1 based on the output of the AD converter 52. The control circuit 53 is composed of, for example, a microcontroller.

[0029] In the configuration described above, let Vx be the detection voltage applied to detection terminal In1, and Vy be the detection voltage applied to detection terminal In2. Also, let Vb be the voltage of battery 1, and Vgnd be the potential of the vehicle ground as seen from the negative terminal of battery 1. The detection voltage Vy applied to detection terminal In2 corresponds to the battery voltage Vb. The relationship between the detection voltage Vy and the battery voltage Vb is expressed by (Equation 1a) and (Equation 1b). Also, the detection voltage Vx corresponds to the potential of the vehicle ground Vgnd. The relationship between the detection voltage Vx and the potential of the vehicle ground Vgnd is expressed by (Equation 2a) and (Equation 2b).

[0030]

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[0031] On the other hand, the potential Vgnd of the vehicle body ground can also be expressed using each resistance value as shown in (Equation 3).

[0032]

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[0033] Figure 2 shows an example of the characteristics of the leakage current detection circuit in Figure 1A. In Figure 2, Vb = 400V, Vr = 5V, r1 = 1MΩ, r2 = 0.9875MΩ, and r3 = 0.0125MΩ. Figure 2 shows the calculation results of (a) the vehicle chassis potential Vgnd using (Equation 3) and (b) the detection voltage Vx using (Equation 2a) and (Equation 2b) for the case where R1 = 10MΩ is fixed and R2 is varied from 0.1MΩ to 10MΩ, and for the case where R2 = 10MΩ is fixed and R1 is varied from 0.1MΩ to 10MΩ.

[0034] If both insulation resistances R1 and R2 are high resistances of 10 MΩ, the potential Vgnd of the vehicle body ground is almost determined by the voltage division by resistors 21 to 23. As shown above, if r1 = r2 + r3, then Vgnd = (Vb + Vr) / 2, and the detection voltage Vx can be set to around 2.5V. However, if insulation failure, i.e., leakage current occurs for some reason, and for example the insulation resistance R1 decreases, the potential Vgnd of the vehicle body ground decreases, and the detection voltage Vx decreases accordingly. Conversely, if the insulation resistance R2 decreases, the potential Vgnd of the vehicle body ground increases, and the detection voltage Vx increases accordingly. Therefore, the control circuit 53 can detect insulation failure by determining whether the detection voltage Vx has fallen outside a predetermined range. Alternatively, the control circuit 53 may calculate the battery voltage Vb from the detection voltage Vy using (Equation 1b).

[0035] [1.11 Modified example of a leakage current detection circuit based on the positive electrode of a battery] Next, a modified example of the leakage current detection circuit 10 will be described.

[0036] Figure 1B shows a modified version of the leakage current detection circuit in Figure 1A. The leakage current detection circuit 10 in Figure 1B differs from that in Figure 1A in that switches 41 and 42 have been added, and detection circuit 5a1 has been replaced with detection circuit 5a. The following explanation will focus on the differences, avoiding repetition.

[0037] Switch 41 is connected in series with resistor 21 and is connected between resistor 21 and the negative terminal of battery 1. In other words, one end of switch 41 is connected to the negative terminal of battery 1. The other end of switch 41 is connected to one end of resistor 21. Switch 41 has a control terminal to which the control signal Con from control circuit 53 is input.

[0038] Switch 42 is connected between resistor 22 and the first detection terminal In1. That is, one end of switch 42 is connected to the other end of resistor 22, and the other end of switch 42 is connected to detection terminal In1 and one end of resistor 23. Switch 42 has a control terminal to which a control signal Con from control circuit 53 is input.

[0039] The control circuit 53 within the detection circuit 5a1 has an added function to generate a control signal Con for controlling the on and off states of switches 41 and 42. The control circuit 53 turns on switches 41 and 42 during periods when a ground fault is detected, and turns off switches 41 and 42 during periods when a ground fault is not detected.

[0040] According to this, for example, the current flowing through the voltage divider resistor of the leakage detection circuit 10 can be set to zero during periods other than the period in which leakage current is detected.

[0041] [1.12 Other variations of leakage current detection circuits based on the positive electrode of a battery] Figure 1C shows another modified example of the leakage current detection circuit in Figure 1A. The leakage current detection circuit 10 in Figure 1C differs from Figure 1A in that resistors 24 and 25, the AD converter 52, and the detection terminal In2 are removed, and detection circuit 5a2 is provided instead of detection circuit 5a. The following will focus on explaining the differences.

[0042] The removed resistors 24 and 25, AD converter 52, and detection terminal In2 are part of the circuit for calculating the battery voltage Vb based on the voltage Vy. Therefore, the detection circuit 5a2 in Figure 1C shows a minimal configuration example that detects the presence or absence of leakage current without calculating the battery voltage Vb.

[0043] [1.2 Example of a leakage current detection circuit configuration based on the negative terminal of the battery] Next, we will explain a leakage current detection circuit configured with the battery's negative terminal at zero potential, using Figures 3A, 3C, and 4.

[0044] Figure 3A shows an example of a circuit configuration of a leakage current detection circuit in which the detection circuit 5a of Figure 1A is configured with the negative terminal of battery 1 at zero potential. In Figure 3A, the ground terminal GND of the detection circuit 5a is connected to the negative terminal of battery 1.

[0045] The leakage current detection circuit 10 in Figure 3A comprises resistors 26 to 30 and a detection circuit 5a.

[0046] Resistor 26 is connected between the negative terminal of battery 1 and the detection terminal In1. That is, one end of resistor 26 is connected to the negative terminal of battery 1. The other end of resistor 26 is connected to the detection terminal In1 and one end of resistor 27. The resistance value of resistor 26 is r6.

[0047] Resistor 27 is connected between the detection terminal In1 and the chassis 11, which is the vehicle ground. In other words, one end of resistor 27 is connected to the detection terminal In1 and the other end of resistor 26. The other end of resistor 27 is connected to the chassis 11 and one end of resistor 28. The resistance value of resistor 27 is r7.

[0048] Resistor 28 is connected between the positive terminal of battery 1 and the vehicle ground. In other words, one end of resistor 28 is connected to the chassis 11 and the other end of resistor 27. The resistance value of resistor 28 is r8.

[0049] Resistor 29 is connected between the negative terminal of battery 1 and the detection terminal In2. That is, one end of resistor 29 is connected to the negative terminal of battery 1. The other end of resistor 29 is connected to the detection terminal In2 and one end of resistor 30. The resistance value of resistor 29 is r9.

[0050] Resistor 30 is connected between the positive terminal of battery 1 and the detection terminal In2. That is, one end of resistor 30 is connected to the detection terminal In2 and the other end of resistor 29. The other end of resistor 30 is connected to the positive terminal of battery 1. The resistance value of resistor 30 is r10.

[0051] The configuration of the detection circuit 5a is the same as in Figure 1A. However, the reference voltage source terminal VR of the detection circuit 5a is not connected to the voltage divider resistor. In Figure 1A, the zero potential of the detection circuit 5a is the positive terminal of battery 1, so the reference voltage source terminal VR is connected to the other end of resistor 23 in order to detect the voltage divided between resistor 21 and resistor 23. In contrast, in Figure 3A, the zero potential of the detection circuit 5a is the negative terminal of battery 1, so the detection circuit 5a can detect the voltage divided between resistors 26 and 28 without raising the potential of the other end of resistor 28.

[0052] In the configuration described above, the detected voltage Vy corresponds to the battery voltage Vb. The relationship between the detected voltage Vy and the battery voltage Vb is expressed by (Equation 4a) and (Equation 4b). Furthermore, the detected voltage Vx corresponds to the potential Vgnd of the vehicle ground. The relationship between the detected voltage Vx and the potential Vgnd of the vehicle ground is expressed by (Equation 5a) and (Equation 5b).

[0053]

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[0054] On the other hand, the potential Vgnd of the vehicle body ground can also be expressed using the respective resistance values ​​as shown in (Equation 6).

[0055]

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[0056] Figure 4 shows an example of the characteristics of the leakage current detection circuit in Figure 3A. In Figure 4, Vb=400V, Vr=5V, r6=0.0125MΩ, r7=0.9875MΩ, and r8=1MΩ are set. Figure 4 shows (a) the vehicle chassis potential Vgnd and (b) the detected voltage Vx when R1=10MΩ is fixed and R2 is varied from 0.1MΩ to 10MΩ, and when R2=10MΩ is fixed and R1 is varied from 0.1MΩ to 10MΩ. If both insulation resistances R1 and R2 are high resistances of 10MΩ, the potential Vgnd of the vehicle ground is almost determined by the voltage division by resistors 26 to 28. As described above, when r6+r7=r8, Vgnd=Vb / 2, and the detected voltage Vx can also be set to around 2.5V. However, if insulation failure, i.e., leakage current occurs for some reason, and for example the insulation resistance R1 decreases, the potential Vgnd of the vehicle body ground decreases, and the detected voltage Vx also decreases accordingly. Conversely, if insulation resistance R2 decreases, the potential Vgnd of the vehicle body ground increases, and the detected voltage Vx also increases accordingly. Therefore, the control circuit 53 can detect insulation failure by determining whether or not the detected voltage Vx has fallen outside a predetermined range. Alternatively, the control circuit 53 may calculate the battery voltage Vb from the detected voltage Vy using (Equation 4b).

[0057] As described above, the leakage current detection circuit can detect insulation failure in battery 1 whether the same detection circuit 5a is set as the positive terminal reference or the negative terminal reference of battery 1.

[0058] [1.21 Modified version of the leakage current detection circuit using the battery's negative terminal as the baseline] Next, a modified example of the leakage current detection circuit 10 shown in Figure 3A will be described.

[0059] Figure 3B shows a modified version of the leakage current detection circuit in Figure 3A. The leakage current detection circuit 10 in Figure 3B differs from that in Figure 3A in that switches 47 and 48 have been added, and detection circuit 5a1 has been replaced with detection circuit 5a. The following explanation will focus on the differences, avoiding repetition.

[0060] Switch 47 is connected between resistor 27 and the first detection terminal In1. That is, one end of switch 47 is connected to detection terminal In1 and the other end of resistor 26. The other end of switch 47 is connected to one end of resistor 27. Switch 47 has a control terminal to which a control signal Con from control circuit 53 is input.

[0061] Switch 48 is connected in series with resistor 28 and is connected between resistor 28 and the positive terminal of battery 1. In other words, one end of switch 48 is connected to the other end of resistor 28, and the other end of switch 48 is connected to the positive terminal of battery 1. Switch 48 has a control terminal to which the control signal Con from control circuit 53 is input.

[0062] The control circuit 53 within the detection circuit 5a1 has an added function to generate a control signal Con for controlling the on and off states of switches 47 and 48. The control circuit 53 turns on switches 47 and 48 during periods when a ground fault is detected, and turns off switches 47 and 48 during periods when a ground fault is not detected.

[0063] According to this, for example, the current flowing through the voltage divider resistor of the leakage detection circuit 10 can be set to zero during periods other than the period in which leakage current is detected.

[0064] [1.22 Other variations of leakage current detection circuits based on the negative terminal of a battery] Figure 3C shows another modified example of the leakage current detection circuit in Figure 3A. The leakage current detection circuit 10 in Figure 3C differs from Figure 3A in that resistors 29 and 30, the AD converter 52 and the detection terminal In2 are removed, and detection circuit 5a2 is provided instead of detection circuit 5a. The differences will be explained below.

[0065] The removed resistors 29 and 30, AD converter 52, and detection terminal In2 are part of the circuit for calculating the battery voltage Vb based on the voltage Vy. Therefore, the detection circuit 5a2 in Figure 3C shows a minimal configuration example that detects the presence or absence of leakage current without calculating the battery voltage Vb.

[0066] Each of the switches 41, 42, 47, and 48 described above may be a normally-off switch, and may be composed of, for example, an NMOS transistor, a PMOS transistor, a bipolar transistor, a relay, or a combination thereof.

[0067] As described above, the leakage current detection circuit 10 according to the first embodiment is a leakage current detection circuit 10 that detects leakage current from a battery 1 to a chassis, having a first electrode having positive or negative polarity and a second electrode having the opposite polarity to the first electrode, and comprises a reference voltage source terminal VR for outputting a reference voltage Vr, a detection circuit 5 having a first detection terminal In1 and a ground terminal GND connected to the first electrode, a first resistor (21 / 28) connected between the second electrode and the chassis, a second resistor (22 / 27) connected between the chassis and the first detection terminal In1, and a third resistor (23 / 26) connected between the first detection terminal In1 and a predetermined terminal, wherein when the polarity of the first electrode is positive, the predetermined terminal is the reference voltage source terminal VR, and when the polarity of the first electrode is negative, the predetermined terminal is the first electrode, and the detection circuit 5 detects the voltage of the first detection terminal In1 and detects the presence or absence of leakage current based on the detected voltage.

[0068] Here, when the polarity of the first electrode is positive, the leakage detection circuit 10 corresponds to Figures 1A to 1C. When the polarity of the first electrode is negative, the leakage detection circuit 10 corresponds to Figures 3A to 3C. Also, the first resistor corresponds to resistor 21 in Figures 1A to 1C and to resistor 28 in Figures 3A to 3C. The second resistor corresponds to resistor 22 in Figures 1A to 1C and to resistor 27 in Figures 3A to 3C. The third resistor corresponds to resistor 23 in Figures 1A to 1C and to resistor 26 in Figures 3A to 3C. The detection circuit 5 is any of the detection circuits 5a, 5a1, and 5a2 in Figures 1A to 1C and Figures 3A to 3C, or a general term for them.

[0069] According to this, the zero potential of the leakage current detection circuit 10 can be based on either the positive or negative terminal of the battery 1.

[0070] Here, the detection circuit 5 may determine that there is a ground fault if the voltage at the first detection terminal In1 falls outside a predetermined range.

[0071] According to this method, it is possible to easily determine the occurrence of insulation failure, that is, the occurrence of electrical leakage.

[0072] Here, the detection circuit 5 has a second detection terminal In2, a fourth resistor (24 / 30) connected between the second electrode and the second detection terminal In2, a fifth resistor (25 / 29) connected between the second detection terminal In2 and a predetermined terminal, and the detection circuit 5 may detect the voltage at the second detection terminal In2 and calculate the voltage Vb of the battery 1 based on the detected voltage.

[0073] Here, the fourth resistor corresponds to resistor 24 in Figures 1A to 1C and to resistor 30 in Figures 3A to 3C. The fifth resistor corresponds to resistor 25 in Figures 1A to 1C and to resistor 29 in Figures 3A to 3C.

[0074] According to this method, in addition to determining whether or not there is a short circuit, the voltage of battery 1 can also be calculated as one of the indicators showing the state of battery 1.

[0075] Here, the detection circuit 5 may include a first switch (41 / 48) connected in series with the first resistor (21 / 28) and connected between the first resistor (21 / 28) and the second electrode, and a second switch (42 / 47) connected in series with the second resistor (22 / 27) and connected between the second resistor (22 / 27) and the first detection terminal In1, and the detection circuit 5 may control the on and off states of the first and second switches.

[0076] Here, the first switch corresponds to switch 41 in Figure 1B and to switch 48 in Figure 3B. The second switch corresponds to switch 42 in Figure 1B and to switch 47 in Figure 3B.

[0077] According to this, for example, the first and second switches are turned on during the period when leakage current is detected, and the first and second switches are turned off during periods other than the period when leakage current is detected. During periods other than the period when leakage current is detected, the current flowing through the voltage divider resistor of the leakage current detection circuit 10 can be set to zero.

[0078] Here, the detection circuit 5 may include a first AD converter 51 connected to a first detection terminal In1, and a control circuit 53 that determines whether or not there is a leakage current based on the first data output from the first AD converter.

[0079] According to this, the voltage value of the first detection terminal In1 can be acquired as the first digital data, making it suitable for leakage current detection using digital processing with a microcontroller.

[0080] Here, the detection circuit 5 may include a first AD converter 51 connected to a first detection terminal In1, a second AD converter 52 connected to a second detection terminal In2, and a control circuit 53 that determines whether or not there is a leakage current and calculates the voltage value of the battery 1 based on first data output from the first AD converter and second data output from the second AD converter.

[0081] According to this, in addition to determining the presence or absence of a ground fault based on the first data, the voltage of battery 1 can be detected based on the second data.

[0082] (Second embodiment) [2.1 Example of a leakage current detection circuit configuration based on the positive electrode of the battery] Figure 5 shows an example of the circuit configuration of the leakage current detection circuit according to the second embodiment. In Figure 5, the difference from Figure 1A, which is the leakage current detection circuit of the first embodiment, is that a series circuit of resistor 31 and PMOS transistor 32 is provided between the vehicle body ground and the reference voltage source terminal VR, and the detection circuit is designated as 5b to distinguish it from Figure 1A. The following will explain the differences in detail.

[0083] Resistor 31 is connected between the chassis 11 and the PMOS transistor 32. That is, one end of resistor 31 is connected to the chassis 11, and the other end of resistor 31 is connected to one end of the PMOS transistor 32. The resistance value of resistor 31 is r11.

[0084] The PMOS transistor 32 is connected between the resistor 31 and the reference voltage source terminal VR. In other words, one end of the PMOS transistor 32 (i.e., the drain) is connected to the other end of the resistor 31. The other end of the PMOS transistor 32 (i.e., the source) is connected to the reference voltage source terminal VR. The gate of the PMOS transistor 32 is connected to the drive terminal Out1.

[0085] The detection circuit 5b differs from the detection circuit 5a in Figure 1A in that it has a drive terminal Out1 that outputs a drive signal to the PMOS transistor 32 based on a command from the internal control circuit 53. This drive signal controls the on and off states of the PMOS transistor 32.

[0086] First, when the drive terminal Out1 outputs a high-level drive signal equivalent to the reference voltage Vr, turning off the PMOS transistor 32, the circuit configuration is equivalent to that of Figure 1A. Therefore, the voltages at each part are the same as in (Equation 1a) to (Equation 3), and are as shown in (Equation 7a) to (Equation 9). To distinguish this from the case where the PMOS transistor 32 is turned on, the potential Vgnd of the vehicle ground when the PMOS transistor 32 is turned off is denoted as Vg1, and the detected voltage Vx is denoted as Vx1.

[0087]

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[0088] Next, when the drive terminal Out1 outputs a low-level drive signal equivalent to zero potential, turning on the PMOS transistor 32, a resistor 31 is connected in parallel between the vehicle ground and the reference voltage source terminal VR. As a result, the potential of the vehicle ground rises compared to when the PMOS transistor 32 is off. In this case, if the potential of the vehicle ground Vgnd is Vg2 and the detected voltage Vx is Vx2, then Vg2 and Vx2 are expressed by (Equation 10a) to (Equation 11).

[0089]

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[0090] Figure 6 shows an example of the characteristics of the leakage current detection circuit in Figure 5. In Figure 6, Vb=400V, Vr=5V, r2=r10=1MΩ, r3=0.9875MΩ, and r4=0.0125MΩ are set. Figure 6 shows (a) the vehicle chassis potential Vgnd and (b) the detection voltage Vx for the following cases: when R1=10MΩ is fixed and R2 is varied from 0.1MΩ to 10MΩ, when R2=10MΩ is fixed and R1 is varied from 0.1MΩ to 10MΩ, and when R1=R2 is varied from 0.1MΩ to 10MΩ. The case where the PMOS transistor 32 is off is shown by a solid line, and the case where the PMOS transistor 32 is on is shown by a dashed line.

[0091] When the PMOS transistor 32 is in the off state, the situation is the same as in Figure 2. However, if the equivalent insulation resistances of the positive and negative terminals are similarly small, such as when R1=R2, the changes in the ground potential Vgnd and the detected voltage Vx also become small, making leakage current detection difficult. On the other hand, when the PMOS transistor 32 is in the on state, under normal conditions where insulation resistances R1 and R2 are high, the ground potential Vgnd is biased towards the battery positive terminal side by resistor 31 and changes as the insulation resistance decreases. The way it changes does not change whether the PMOS transistor 32 is on or off. For example, if the insulation resistance R1 decreases, the potential Vgnd of the vehicle ground decreases, and the detected voltage Vx decreases accordingly. Conversely, if the insulation resistance R2 decreases, the potential Vgnd of the vehicle ground increases, and the detected voltage Vx increases accordingly. When R1=R2, the potential Vgnd of the vehicle ground asymptotically approaches Vb / 2. As described above, under normal conditions, the detection voltage of the PMOS transistor 32 in the off state is determined by resistors 21, 22, and 23, and in the on state, the detection voltage increases due to the influence of resistor 31. However, if an insulation failure occurs for some reason and the insulation resistance R1 or R2 decreases, the difference between the detection voltage in the on state and the detection voltage in the off state becomes smaller. When this difference in detection voltage falls below a predetermined value, the insulation failure can be detected. Of course, this can also be used in conjunction with determining an insulation failure when the detection voltage Vx falls outside a predetermined range, as in the first embodiment.

[0092] In the above explanation, leakage current was detected by comparing the detected voltage Vx with a predetermined threshold. However, if the detection circuit has a calculation function, it is also possible to calculate the insulation resistances R1 and R2. First, the potentials Vg1 and Vg2 of the vehicle body ground are determined from the detected voltages Vx1 and Vx2 using (Equation 8b) and (Equation 10b). Using these and (Equation 9) and (Equation 11), a system of equations for R1 and R2 is set up and solved, and the insulation resistances R1 and R2 can be calculated as shown in (Equation 12) and (Equation 13).

[0093]

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[0094] Furthermore, when calculating the insulation resistances R1 and R2 from (Equation 12) and (Equation 13), the voltage Vb of battery 1 may be calculated from (Equation 4b) or (Equation 7b), or it may be obtained from an external source. For example, if there is an external measurement circuit that measures the voltage Vb of battery 1, the voltage Vb may be obtained from that measurement circuit.

[0095] [2.2 Example of a leakage current detection circuit configuration based on the negative terminal of the battery] In this embodiment as well, the detection circuit can be configured as a leakage current detection circuit with the negative terminal of the battery 1 at zero potential. Figure 7 shows an example of the circuit configuration of a leakage current detection circuit in which the detection circuit 5b of Figure 5 is configured with the negative terminal of the battery 1 at zero potential. In Figure 7, the differences from Figure 3A are that a series circuit of an NMOS transistor 33 and a resistor 34 is provided between the vehicle ground and the negative terminal of the battery 1, and the detection circuit is designated as 5b to distinguish it from Figure 1A. The following will explain the differences in detail.

[0096] Resistor 34 is connected between the chassis 11 and the NMOS transistor 33. That is, one end of resistor 34 is connected to the other end of the NMOS transistor 33, and the other end of resistor 34 is connected to the chassis 11. The resistance value of resistor 34 is r14.

[0097] The NMOS transistor 33 is connected between the negative terminal of battery 1 and resistor 34. That is, one end of the NMOS transistor 33 (i.e., the source) is connected to the negative terminal of battery 1. The other end of the NMOS transistor 33 (i.e., the drain) is connected to one end of resistor 34. The gate of the NMOS transistor 33 is connected to the drive terminal Out1.

[0098] The ground terminal GND of the detection circuit 5b is connected to the negative terminal of battery 1. The drive terminal Out1 outputs a drive signal to drive the NMOS transistor 33. This drive signal controls the on and off states of the NMOS transistor 33.

[0099] First, when the drive terminal Out1 outputs a low-level drive signal at zero potential, turning off the NMOS transistor 33, the circuit configuration is equivalent to that of Figure 3A. Therefore, the voltages at each part are the same as those in (Equations 4a) to (Equation 6), and are as shown in (Equations 14a) and (Equation 17). To distinguish this from the case where the NMOS transistor 33 is turned on, let Vg3 be the potential of the vehicle ground Vgnd and Vx3 be the detected voltage Vx when the NMOS transistor 33 is turned off. Then Vx3 and Vg3 are expressed by (Equations 14a), (Equation 14b), and (Equation 15).

[0100]

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[0101] Next, when the drive terminal Out1 outputs a high-level drive signal equivalent to the reference voltage Vr, turning on the NMOS transistor 33, a resistor 34 is connected in parallel between the vehicle ground and the ground terminal GND. As a result, the potential of the vehicle ground is lower than when the NMOS transistor 33 is off. In this case, if the potential of the vehicle ground Vgnd is Vg4 and the detected voltage Vx is Vx4, then Vx4 and Vg4 are expressed by (Equation 16a) and (Equation 16b).

[0102]

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[0103] Figure 8 shows an example of the characteristics of the leakage current detection circuit in Figure 7. In Figure 8, Vb=400V, Vr=5V, r6=0.0125MΩ, r7=0.9875MΩ, and r8=r14=1MΩ are set. Figure 8 shows (a) the vehicle chassis potential Vgnd and (b) the detected voltage Vx for the following cases: when R1=10MΩ is fixed and R2 is varied from 0.1MΩ to 10MΩ, when R2=10MΩ is fixed and R1 is varied from 0.1MΩ to 10MΩ, and when R1=R2 is varied from 0.1MΩ to 10MΩ. The solid line indicates the off state of the NMOS transistor 33, and the dashed line indicates the on state of the NMOS transistor 33.

[0104] When the NMOS transistor 33 is in the ON state, under normal conditions where insulation resistances R1 and R2 are high, the ground potential Vgnd is biased towards the battery negative terminal side due to resistor 11. Except for this point, the way in which the vehicle ground potential Vgnd and the detected voltage Vx change due to insulation resistances R1 and R2 is the same as in Figure 6. That is, under normal conditions, the detected voltage when the NMOS transistor 33 is OFF is determined by resistors 26, 27, and 28, and when it is ON, the detected voltage decreases due to the influence of resistor 34. However, if an insulation failure occurs for some reason and insulation resistance R1 or R2 decreases, the difference between the detected voltage in the ON state and the detected voltage in the OFF state becomes smaller. When this difference in detected voltage falls below a predetermined value, the insulation failure can be detected. Of course, this can also be used in combination with determining an insulation failure when the detected voltage falls outside a predetermined range, as in the first embodiment.

[0105] In the above explanation, leakage current was detected by comparing the detected voltage Vx with a predetermined threshold. However, in this embodiment as well, if the detection circuit has a calculation function, the insulation resistances R1 and R2 can also be calculated, similar to the explanation in Figures 3A and 4. From (Equation 14b) and (Equation 16b), the potentials Vg3 and Vg4 of the vehicle body ground are determined from the detected voltages Vx3 and Vx4. Using these and (Equation 15) and (Equation 17), a system of equations relating to R1 and R2 is set up and solved, and the insulation resistances R1 and R2 can be calculated as shown in (Equation 18) and (Equation 19).

[0106]

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[0107] As described above, the leakage current detection circuit 10 according to this embodiment allows the same detection circuit 5b to be set on both the positive and negative terminal sides of the battery 1. Furthermore, the leakage current detection circuit 10 can calculate the resistance values ​​of insulation resistances R1 and R2 by connecting different resistive loads between the battery and the vehicle body ground using a switch element.

[0108] In this embodiment, multiple conditions were created using a switching element to obtain a system of equations for calculating insulation resistance, but the method is not limited to this.

[0109] As described above, the leakage current detection circuit 10 according to the second embodiment has a series circuit of a resistive element (31 / 34) and a switch element (32 / 33) connected between the chassis and a predetermined terminal, and the detection circuit 5 has a drive terminal Out1 that drives the switching between the open state and the closed state of the switch element (32 / 33).

[0110] Here, the resistive element corresponds to resistor 31 in Figure 5 and resistor 34 in Figure 7. The switching element corresponds to PMOS transistor 32 in Figure 5 and NMOS transistor 33 in Figure 7.

[0111] According to this method, the occurrence of an electrical leak can be easily determined.

[0112] Here, the detection circuit 5 may detect the voltage at the first detection terminal when the switch element (32 / 33) is open as the first voltage, and the voltage at the first detection terminal when the switch element (32 / 33) is closed as the second voltage, and determine that there is a leakage current if the difference between the first voltage and the second voltage is less than or equal to a predetermined value.

[0113] Here, the first voltage corresponds to the voltage Vx in equations 8a and 8b relating to Figure 5, and the voltage Vx2 in equations 10a and 10b relating to Figure 7. The second voltage corresponds to the voltage Vx3 in equations 14a and 14b relating to Figure 5, and the voltage Vx4 in equations 16a and 16b relating to Figure 7.

[0114] According to this method, the occurrence of an electrical leak can be easily determined.

[0115] Here, the detection circuit may detect the voltage at the first detection terminal when the switch element is in the open state as the first voltage, and the voltage at the first detection terminal when the switch element is in the closed state as the second voltage, and calculate the resistance value between the positive terminal of battery 1 and the chassis and the resistance value between the negative terminal of battery 1 and the chassis based on the first voltage and the second voltage.

[0116] According to this method, two insulation resistance values ​​R1 and R2 are calculated, namely the resistance between the positive electrode of battery 1 and the chassis, and the resistance between the negative electrode of battery 1 and the chassis. Therefore, even if the equivalent insulation resistances R1 and R2 happen to decrease in the same way, leakage current can be quantitatively determined. Furthermore, it is possible to determine whether the leakage current is occurring on the positive electrode side or the negative electrode side.

[0117] Here, the detection circuit includes a second detection terminal In2, a fourth resistor (24 / 30) connected between the second electrode and the second detection terminal In2, and a fifth resistor (25 / 29) connected between the second detection terminal In2 and a predetermined terminal. The detection circuit detects the voltage at the second detection terminal In2, calculates the battery voltage (Vb) based on the detected voltage, detects the voltage at the first detection terminal when the switch element is open as the first voltage, detects the voltage at the first detection terminal when the switch element is closed as the second voltage, and calculates the resistance value R2 between the positive electrode of battery 1 and the chassis and the resistance value R1 between the negative electrode of battery 1 and the chassis based on the battery voltage Vb, the first voltage, and the second voltage.

[0118] This allows for the quantitative determination of leakage current even if the equivalent insulation resistances R1 and R2 happen to decrease in the same way. Furthermore, it allows for the determination of whether the leakage current is occurring on the positive or negative electrode side.

[0119] (Third embodiment) [3.1 Example of a leakage current detection circuit configuration based on the positive electrode of the battery] Figure 9 shows an example of the circuit configuration of a battery state detection circuit 100, which is a third embodiment, in which a battery current detection circuit is added to the leakage current detection circuit of the second embodiment. In Figure 9, the difference from Figure 5, which is the leakage current detection circuit of the second embodiment, is that a resistor 35 is provided between the positive terminal of the battery and the load (not shown), and the detection circuit has an amplifier 54 that detects the voltage across its terminals, amplifies it, and outputs it to the control circuit 53. The detection circuit is named detection circuit 5c to distinguish it from the detection circuit in Figures 1 and 5.

[0120] Resistor 35 is a current-sensing resistor connected between the positive terminal of battery 1 and the load.

[0121] Amplifier 54 detects the voltage across resistor 35 as a signal indicating the current value of battery 1.

[0122] [3.2 Example of a leakage current detection circuit configuration based on the negative terminal of the battery] Figure 10 also shows the configuration of the battery state detection circuit 100, in which the detection circuit 5c is provided on the battery negative terminal side. In Figure 10, the differences from Figure 7 of the second embodiment are that a resistor 36 is provided between the battery negative terminal and the load (not shown), and the amplifier 54 of the detection circuit 5c detects and amplifies the voltage across its terminals and outputs it to the control circuit 53.

[0123] Resistor 36 is a current sensing resistor connected between the negative terminal of battery 1 and the load.

[0124] Amplifier 54 detects the voltage across resistor 36 as a signal indicating the current value of battery 1. This current value indicates the magnitude of the discharge current or charge current of battery 1.

[0125] As described above, the leakage current detection circuit can be configured to be on either the positive or negative side of the battery, depending on the installation location of the current detection circuit. This allows for the simplification of the overall system, such as by integrating it as a battery state detection circuit that detects battery voltage, current, presence or absence of leakage current, etc.

[0126] As described above, the battery state detection circuit 100 according to the third embodiment includes the leakage current detection circuit 10, a current detection resistor 35 / 36 connected between the first electrode and the load, and an amplification circuit 54 that detects the voltage across the current detection resistor 35 / 36 as a signal indicating the current value of the battery 1.

[0127] According to this, the battery state detection circuit can use either the positive or negative terminal of battery 1 as the reference for zero potential. Furthermore, the battery state detection circuit can detect the current value at which battery 1 is charging or discharging, and the presence or absence of leakage current, as indicators of the battery state.

[0128] Furthermore, the battery state detection circuit 100 according to the third embodiment includes the above-mentioned leakage current detection circuit 10, current detection resistors 35 / 36 connected between the first electrode and the load, and an amplification circuit 54 that detects the voltage across the current detection resistors 35 / 36 as a signal indicating the current value of the battery 1. The detection circuit includes a first AD converter 51 connected to a first detection terminal In1, a second AD converter 52 connected to a second detection terminal In2, and a control circuit 53 that determines the presence or absence of leakage current and calculates the battery voltage value and current value based on first data output from the first AD converter 51 and second data output from the second AD converter 52.

[0129] Here, the current sensing resistor corresponds to resistor 35 in Figure 9 and resistor 36 in Figure 10.

[0130] According to this, the battery state detection circuit can use either the positive or negative terminal of the battery as the reference point for zero potential. Furthermore, the battery state detection circuit can detect indicators of the battery state, such as the battery voltage, the current value at which the battery charges or discharges, and the presence or absence of leakage current.

[0131] Here, the amplification circuit 54 may be included in the detection circuit.

[0132] According to this, the detection circuit's function is not only to determine the presence or absence of a leakage current, but also to detect the current value at which the battery is charging or discharging.

[0133] Here, the detection circuit may be implemented as an integrated circuit.

[0134] According to this, the detection circuit can be miniaturized as an IC chip, reducing costs and improving usability.

[0135] In addition, in the leakage current detection circuit 10 of Figure 5, an NMOS transistor may be provided instead of the PMOS transistor 32. In that case, the control circuit 53 only needs to invert the logic level of the drive signal. Furthermore, in the leakage current detection circuit 10 of Figure 5, a switch circuit combining a PMOS transistor and an NMOS transistor in parallel may be provided instead of the PMOS transistor 32.

[0136] Furthermore, in the leakage current detection circuit 10 of Figure 5, switches 41 and 42 may be added, similar to Figure 1B, and the control circuit 53 may be configured to control switches 41 and 42. Alternatively, in the leakage current detection circuit 10 of Figure 5, resistors 24 and 25 and detection terminal In2 may be removed, similar to Figure 1C.

[0137] In addition, the leakage current detection circuit 10 in Figure 7 may be provided with a PMOS transistor instead of the NMOS transistor 33. In that case, the control circuit 53 only needs to invert the logic level of the drive signal. Furthermore, in the leakage current detection circuit 10 in Figure 7, the NMOS transistor 33 may be replaced with a switch circuit consisting of a PMOS transistor and an NMOS transistor connected in parallel.

[0138] Furthermore, in the leakage current detection circuit 10 of Figure 7, switches 47 and 48 may be added, similar to Figure 3B, and the control circuit 53 may be configured to control switches 47 and 48. Alternatively, the leakage current detection circuit 10 of Figure 7 may be configured by removing resistors 29 and 30 and detection terminal In2, similar to Figure 3C.

[0139] In addition, in the battery state detection circuit 100 shown in Figure 9, switches 41 and 42 may be added, similar to Figure 1B, and the control circuit 53 may be configured to control switches 41 and 42.

[0140] Furthermore, in the battery state detection circuit 100 shown in Figure 10, switches 47 and 48 may be added, similar to Figure 3B, and the control circuit 53 may be configured to control switches 47 and 48.

[0141] While several embodiments of this disclosure have been described, these embodiments are presented as examples only and are not intended to limit the scope of this disclosure. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of this disclosure, as well as in the claims and their equivalents. [Explanation of symbols]

[0142] 1 Battery 21-31 Resistors 32 PMOS transistors 33 NMOS transistors 34-36 resistors 5a, 5b, 5c detection circuits 50 Reference voltage source 51, 52 AD converters 53 Control circuits 54 Amplifier

Claims

1. A leakage detection circuit for detecting leakage current from a battery to a chassis, having a first electrode having positive or negative polarity and a second electrode having the opposite polarity to the first electrode, A detection circuit having a reference voltage source terminal for outputting a reference voltage, a first detection terminal, and a ground terminal connected to the first electrode, A first resistor connected between the second electrode and the chassis, A second resistor connected between the chassis and the first detection terminal, The device comprises a third resistor connected between the first detection terminal and a predetermined terminal, When the polarity of the first electrode is positive, the predetermined terminal is the reference voltage source terminal. The detection circuit detects the voltage at the first detection terminal and detects the presence or absence of a ground fault based on the detected voltage. Leakage current detection circuit.

2. When the polarity of the first electrode is negative, the predetermined terminal is the first electrode. The leakage current detection circuit according to claim 1.

3. The detection circuit determines that there is a ground fault when the voltage at the first detection terminal falls outside a predetermined range. The leakage current detection circuit according to claim 1 or 2.

4. It has a series circuit of a resistive element and a switching element connected between the chassis and the predetermined terminal, The detection circuit has a drive terminal that drives the switching between the open and closed states of the switch element. A leakage current detection circuit according to any one of claims 1 to 3.

5. The detection circuit detects the voltage at the first detection terminal when the switch element is open as the first voltage, and the voltage at the first detection terminal when the switch element is closed as the second voltage. If the difference between the first voltage and the second voltage is less than or equal to a predetermined value, it determines that there is a leakage current. The leakage current detection circuit according to claim 4.

6. The detection circuit detects the voltage at the first detection terminal when the switch element is in the open state as the first voltage. The voltage at the first detection terminal when the switch element is in the closed state is detected as the second voltage. Based on the first voltage and the second voltage, the resistance value between the positive electrode of the battery and the chassis and the resistance value between the negative electrode of the battery and the chassis are calculated. The leakage current detection circuit according to claim 4.

7. The aforementioned detection circuit includes a second detection terminal, A fourth resistor connected between the second electrode and the second detection terminal, The device includes a fifth resistor connected between the second detection terminal and the predetermined terminal, The detection circuit detects the voltage at the second detection terminal and calculates the battery voltage based on the detected voltage. A leakage current detection circuit according to any one of claims 1 to 6.

8. The aforementioned detection circuit includes a second detection terminal, A fourth resistor connected between the second electrode and the second detection terminal, The device includes a fifth resistor connected between the second detection terminal and the predetermined terminal, The aforementioned detection circuit is The voltage of the second detection terminal is detected, and the voltage of the battery is calculated based on the detected voltage. The voltage at the first detection terminal when the switch element is in the open state is detected as the first voltage. The voltage at the first detection terminal when the switch element is in the closed state is detected as the second voltage. Based on the battery voltage, the first voltage, and the second voltage, the resistance value between the positive electrode of the battery and the chassis and the resistance value between the negative electrode of the battery and the chassis are calculated. The leakage current detection circuit according to claim 4.

9. A first switch is connected in series with the first resistor and between the first resistor and the second electrode, The system comprises a second switch connected in series with the second resistor and connected between the second resistor and the first detection terminal, The detection circuit controls the on and off states of the first switch and the second switch. A leakage current detection circuit according to any one of claims 1 to 8.

10. The aforementioned detection circuit is A first AD converter connected to the first detection terminal, The system includes a control circuit that determines whether or not there is a ground fault based on the first data output from the first AD converter. A leakage current detection circuit according to any one of claims 1 to 9.

11. The aforementioned detection circuit is A first AD converter connected to the first detection terminal, A second AD converter connected to the second detection terminal, The system includes a control circuit that determines whether or not there is a leakage current and calculates the voltage value of the battery based on the first data output from the first AD converter and the second data output from the second AD converter. The leakage current detection circuit according to claim 7 or 8.

12. A leakage current detection circuit according to any one of claims 1 to 11, A current sensing resistor connected between the first electrode and the load, The circuit includes an amplification circuit that detects the voltage across the current sensing resistor as a signal indicating the current value of the battery. Battery status detection circuit.

13. A leakage current detection circuit according to claim 7 or 8, A current sensing resistor connected between the first electrode and the load, The circuit includes an amplification circuit that detects the voltage across the current sensing resistor as a signal indicating the current value of the battery, The aforementioned detection circuit is A first AD converter connected to the first detection terminal, A second AD converter connected to the second detection terminal, The system includes a control circuit that determines whether or not there is a leakage current based on the first data output from the first AD converter and the second data output from the second AD converter, and calculates the voltage and current values ​​of the battery. Battery status detection circuit.

14. The amplification circuit is included in the detection circuit The battery state detection circuit according to claim 12 or 13.

15. The aforementioned detection circuit is implemented as an integrated circuit. The battery state detection circuit according to claim 14.

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