JP2009244275A - Ground fault detection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fault detection system for detecting an unnecessary cable way between a reference electric potential and at least one of a floating power supply (a), a first power conductor (b) connecting to a first terminal of the floating power supply, and a second power conductor (c) connecting to a second terminal of the floating power supply. <P>SOLUTION: The system includes an impedance network electrically connected to the first and second power conductors and having an output terminal for supplying a first voltage signal to the reference electric potential, and an amplifier circuit generating an amplification signal showing presence of the unnecessary cable way when a difference between the first voltage signal and reference voltage exceeds a prescribed value in response to the first voltage signal and the reference voltage. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to ground fault protection, and more particularly to a DC ground fault sensor system for detecting ground fault conditions.

  An electric vehicle is a vehicle that relies on a relatively large electric traction battery rather than relying on an internal combustion engine for propulsion power. The traction battery of an electric vehicle is connected to an electric traction motor that propels the vehicle, and the traction battery can be recharged and used repeatedly.

  It will be appreciated that the traction battery must have a relatively large capacity and provide a relatively large amount of power as compared to a conventional 12 volt car storage battery. Since power is directly proportional to battery voltage and system current, the traction battery must meet the high power supply requirements that the voltage present in the electric vehicle is relatively low to power the auxiliary load when the internal combustion engine is not running It necessarily means that it will be higher than the voltage present in automobiles powered by fossil fuels that normally only require electric power and low voltage storage batteries.

  A hybrid electric vehicle (HEV) combines a conventional vehicle internal combustion engine with an electric vehicle battery and an electric motor. This increases fuel economy over conventional vehicles. This combination also extends the cruising range beyond what a user would expect from a conventional vehicle, provides quick refueling, and provides an important part of the energy and environmental benefits of an electric vehicle. The practical benefits of HEV include improved fuel economy and lower emissions compared to conventional vehicles. Because of its inherent flexibility, HEV has a wide range of applications and can be used from personal transportation to commercial transportation.

  Since electric or hybrid electric vehicles require little or no fossil fuel combustion, such vehicles produce little or no environmentally harmful emissions as opposed to vehicles that run on fossil fuels. Absent. Such vehicles are becoming increasingly attractive to replace passenger cars powered by fossil fuels. However, due to the high voltage requirements of traction batteries, there are concerns about the electrical safety of electric or hybrid electric vehicles.

  For example, undesired currents outside the desired electrical circuit (ie, ground fault conditions) can cause significant damage to electronic components in the system (such as HEV propulsion systems), disabling or destroying electronic devices. Or In addition, such ground fault conditions can result in electric shock and can have serious consequences when electric shock occurs in contact with a high voltage traction battery system as compared to conventional relatively low voltage automotive battery storage systems. . In order to reduce the possibility of such an electric shock, many traction battery systems are not grounded to the vehicle chassis, in contrast to conventional vehicle storage battery systems. Instead, many traction battery systems have a closed loop return that isolates the system's negative power conductor (ie, the current return) from the chassis of an electric or hybrid electric vehicle.

  FIG. 1 shows a detection circuit for detecting a DC ground fault. The high impedance network 700 is coupled between the first positive power conductor 200 and the second negative power conductor 300, and continues between positive and negative voltage values with respect to the ground reference potential (ie, chassis voltage) 540. Operates to balance equally high voltage batteries in line. The high-impedance network 700 includes resistors Ra, Rb,... Rn connected in series, a first terminal 710 coupled to the first power conductor 200, and a first power coupled to the second power conductor 300. And Rn having a second terminal 720 and a third terminal 730 coupled to the ground reference potential 540 via a resistor R168. Each of the resistors Ra, Rb,... Rn preferably has an equal resistance and is arranged so that the magnitude of the voltage is equally centered above and below the chassis. Sense resistor R168 operates to detect this centering shift due to undesired impedance faults by sensing the induced current through resistor R168.

  Such an insulated system can minimize the possibility of electric shock to a person if a short circuit or a low impedance connection between the positive or negative power conductor and the chassis occurs, but such a circuit may be It only provides for the detection of unwanted electrical paths between the (reference potential) and the positive or negative power conductor. It cannot provide for the detection of unwanted electrical paths between the chassis and a series of stored energy centers, nor can it provide any compensation to re-equalize the voltage potential between both power conductors and chassis. What is desired is a ground fault detection system that senses DC ground fault conditions within the high voltage stored energy and actively compensates to correct such conditions.

  The fault detection system is coupled to a reference potential and (a) a floating power source, (b) a first power conductor coupled to the first terminal of the floating power source, and (c) a second terminal of the floating power source. An unnecessary electrical path between at least one of the second power conductors is detected. The system includes an impedance network that is electrically coupled to the first and second power conductors and has an output terminal that provides a first voltage signal relative to a reference potential, and a first voltage signal and a reference voltage. In response, an amplifier circuit is included that generates an amplified signal indicating the presence of an unwanted electrical path when the difference between the first voltage signal and the reference voltage exceeds a predetermined value. In the case of an unwanted circuit between the chassis reference and the node in the floating power source, the system detects a signal indicating the impedance imbalance (vs. car body) from the center point and provides a compensation impedance between the first and second power conductors Operates to equalize the voltage (vs. car body).

  The fault detection system includes a reference potential and (a) a floating power source, (b) a first power conductor coupled to the first terminal of the power source, and (c) a second coupled to the second terminal of the power source. A system for detecting and compensating for an unwanted electrical path between at least one of the power conductors of the first and second power conductors, wherein the system is electrically coupled to the first and second power conductors, and a first voltage signal relative to a reference potential is provided. An impedance network having an output terminal to provide an amplified signal in response to the first voltage signal and the reference voltage, indicating an presence of an unnecessary electric circuit when a difference between the first voltage signal and the reference voltage exceeds a predetermined value; A high gain amplifier that generates, and an input that is electrically coupled to the output of the high gain amplifier, and a first and second output that are electrically coupled to the first and second power conductors, respectively, through a conductive path. Compensation circuit, first and second Providing at least one compensation signal of the power conductors, the compensation signal includes a compensation circuit for reducing the difference between the first voltage signal and the reference voltage according to the magnitude of the amplified signal.

  The fault monitoring apparatus includes a floating power source having a first terminal coupled to the first power conductor and a second terminal coupled to the second power conductor, and a first electrically coupled to the first power conductor. 1 terminal, a second terminal electrically coupled to the second power conductor, and a third terminal coupled to the reference potential, the voltage applied to the first and second power conductors (vs. reference) An impedance network that equally balances the potential), based on the occurrence of an accidental circuit between at least one of the first power conductor, the second power conductor, and the power source and a reference potential. An impedance network in which a voltage is generated at the third terminal of the impedance network, electrically coupled to the third terminal, to provide a control signal that is proportional to the difference between the accidental voltage at the third terminal and the reference potential. Amplifier that works And electrically coupled to the control signal, providing a compensation signal to at least one of the first and second power conductors via a feedback path, the compensation signal between the accidental voltage generated at the third terminal and the reference potential A compensation circuit that operates to reduce the difference.

  The fault detection system includes a reference potential and (a) a power source, (b) a first power conductor coupled to the first terminal of the power source, and (c) a second coupled to the second terminal of the power source. A system for detecting an unwanted electrical path between at least one of the power conductors, the system being electrically coupled to the first and second power conductors and referenced to a voltage across the first and second power conductors An impedance network that operates to center equally around a voltage, the impedance network having a tap that provides a center voltage signal relative to a reference voltage, a first input terminal electrically coupled to the tap, a first A transistor having a second terminal electrically coupled to the power conductor and a third terminal electrically coupled to the second power conductor, and a second electrically coupled to the third terminal of the transistor 1 An amplifier circuit having a terminal, a second terminal electrically coupled to a reference voltage, and an output terminal, wherein the amplifier circuit has a feedback loop between the first terminal and the output terminal and is connected to the third terminal of the transistor An amplifier circuit is provided that provides a compensation signal and modifies the amount of current flowing from the third terminal to the second power conductor.

  The fault detection compensation system is electrically coupled to a first power conductor, a floating power source having a first terminal coupled to the first power conductor and a second terminal coupled to the second power conductor. A first terminal; a second terminal electrically coupled to the second power conductor; and a third terminal coupled to the vehicle body; a voltage applied to the first and second power conductors (vs. the vehicle body) ) Are equally balanced, and based on the occurrence of an accidental electrical circuit between the vehicle body and a node in the floating power source, an accidental voltage signal is generated by the impedance imbalance between the first and second power conductors (vs. the vehicle body). ) Provides an impedance network generated at the third terminal of the impedance network, and a control signal indicating the impedance imbalance between the first and second power conductors (vs. car body) in response to an accidental voltage signal. And an amplifier electrically coupled to the amplifier and providing a compensation impedance path to at least one of the first and second power conductors to equalize the voltage between the first and second power conductors (vs. the vehicle body) Includes circuitry.

1 is a schematic diagram of a DC ground fault detection system. 1 is a schematic diagram of a DC ground fault detection system according to an embodiment of the present invention. 2B is a schematic diagram of the circuit shown in FIG. 2A showing a compensation signal that compensates for a small leakage current according to the present invention. 2B is a schematic diagram of the circuit shown in FIG. 2A showing a compensation signal applied to compensate for a large leakage current according to the present invention. 2B is a schematic diagram of the circuit shown in FIG. 2A showing a compensation signal applied to compensate for a large leakage current due to a failure occurring between batteries of a battery pack power source according to the present invention. 4 is a schematic diagram of a DC ground fault detection system according to another embodiment of the present invention. 3B is a schematic diagram of the circuit shown in FIG. 3A showing a compensation signal that compensates for a small leakage current according to the present invention. 3B is a schematic diagram of the circuit shown in FIG. 3A showing a compensation signal applied to compensate for a large leakage current according to the present invention. 4 is a schematic diagram of a DC ground fault detection system according to another embodiment of the present invention. 2 is a more detailed schematic diagram of a DC ground fault detection system according to another embodiment of the present invention. 4 is a schematic diagram of a DC ground fault detection system according to another embodiment of the present invention. 4 is a schematic diagram of a DC ground fault detection system according to another embodiment of the present invention.

  The benefits, properties, and various other features of the present invention will become more apparent from the embodiments described in detail below with reference to the drawings.

  FIG. 2A detects an accidental circuit such as a short circuit or ultra-low impedance connection between a load such as high power conductor 200 or low power conductor 300 or power source 100 and a reference potential 540 such as chassis or ground. 1 shows a simplified embodiment of a DC ground fault detector system 10 according to the present invention. The power source 100 includes a series of batteries 101A and 101B, provides a high voltage (eg, 600V) power source, and drives a load such as an electric traction motor (not shown). Alternatively, the power source 100 may comprise a series capacitor (eg, ultracapacitor), a fuel cell, or a mechanically stored energy source that provides a power or energy source to the system. The first power conductor 200 is electrically coupled to the terminal 110 of the power source 100 and provides a first power source (eg, a positive DC link) to the load or motor. The second power conductor 300 is electrically coupled to the terminal 150 of the power source 100 and provides a second power source (eg, a negative DC link) to the motor.

  A high impedance network 700 electrically coupled between the first and second power conductors equalizes a series of high voltage batteries of power between positive and negative voltage values with respect to a ground reference potential (ie, chassis voltage) 540. Works to balance. The high-impedance network 700 includes resistors Ra, Rb,... Rn connected in series, a first terminal 710 coupled to the first power conductor 200, and a first power coupled to the second power conductor 300. Rn having two terminals 720 and resistors Ra, Rb,... Rn having a third terminal or tap 730, and a central voltage signal (vs. reference voltage) that centers the floating power supply between the first and second power conductor voltages. I will provide a. Preferably, each of the resistors Ra, Rb,... Rn has equal resistance so that the voltage magnitude at node 710 relative to ground 540 is equal to the voltage magnitude at node 720 relative to ground 540. The center voltage at the terminal (node) 730 is equal to the reference or ground (ie chassis) voltage 540.

  Amplifier device 400 comprising a high gain amplifier has a non-inverting input 410 electrically coupled to tap 730 to receive voltage signal 732 and an inverting input 420 electrically coupled to reference voltage 540. The high gain amplifier device 400 is responsive to the voltage signal 732 and the reference (ie, chassis) voltage 540 and generates an amplified signal S1 at the output terminal 430. The amplified signal S1 corresponds to the difference between the voltage signal 732 and the reference potential 540. Under normal operating conditions (ie, when there is no short circuit or low impedance condition), the high voltage bus is equally balanced between the first power conductor 200 (+ DC link) and the second power conductor 300 (−DC link). Thus, the output signal at the voltage divider tap 730 is equal to the reference voltage (eg, 0V). The amplified signal S1 output from the amplifier device 400 is also 0V with respect to the reference voltage (0V). However, when a short circuit or low impedance connection occurs, the difference between the voltage signal 732 and the reference voltage 540 exceeds a predetermined value and the output signal S1 is: (a) a first power conductor, (b) a second power conductor, (C) Indicates the presence of an unwanted electrical path between one of the battery pack power sources and the reference or chassis voltage.

  Compensation circuit 500 comprising high power isolation amplifier 510 has an input 512 electrically coupled to the output of the high gain amplifier. First terminal 514 is electrically coupled to first power conductor 200 via electrical path 202, and second terminal 516 is electrically coupled to second power conductor 300 via electrical path 204. The sensor 530 including the sensing resistor Rs is electrically coupled between the output terminal 518 and the reference voltage 540, and senses the current flowing through the generated balance impedance by the voltage applied to the resistor Rs. As shown in the figure, the impedance obtained by Rs and R1 and the internal impedance between the terminals 514 and 518 are equal to the unnecessary circuit impedance as shown in FIGS. 2B, 2C and 2D. Act as a balance to provide between. Thus, the energy storage system remains “balanced” and the voltage between the positive conductor and the chassis is equal to the voltage between the negative conductor and the chassis. The voltage signal Vs can be returned to the system controller, for example. A compensation signal passes through a corresponding compensation path (202, 204) from the reference potential (chassis) to at least one of the first and second power conductors, or at least one of the first and second power conductors. To the reference potential (chassis). A compensation path is generated from the amplified signal S1 and reduces the difference between the first voltage signal and the reference voltage. In an embodiment, the compensation signal reduces this difference according to the magnitude of the amplified signal, thus rebalancing the circuit.

  FIG. 2B shows a compensation signal C1 applied to the second power conductor along path 204 to compensate for a small leakage current of about 1 mA due to fault F1 occurring between power conductor 200 and chassis 540. 2A is a schematic diagram of the circuit shown in 2A. In the embodiment, assuming that the gain of the power operational amplifier is 2 mA / Volt, the amplified signal S1 = −0.5 V is detected at the output of the amplifier device 400. 500 (Senses voltage drop across resistor Rs and sends 1 mA correction current C1 to power conductor 300 to compensate for leakage current due to fault F1.

  2C shows the compensation signal C1 applied to the second power conductor so as to compensate for a large leakage current of about 5 mA due to the major fault F2 occurring between the power conductor 200 and the chassis 540. The circuit shown in FIG. FIG. In this case, the voltage on the power conductor 200 is at the reference potential (ie 0V). Accordingly, the voltage on the power conductor 300 is the overall power supply voltage Vps (ie, -600V). Thus, the voltage at tap 730 is Vps / 2 or -300V. Therefore, the output of the operational amplifier 400 is saturated at -5V. 500 (Senses voltage drop across resistor Rs and sends 5 mA correction current C1 to power conductor 300 to compensate for leakage current due to major fault F2.

  FIG. 2D is applied to the first power conductor 200 to compensate for a large leakage current of about 5 mA due to a major fault F3 occurring in the power source 100, in the illustrated example, between the batteries 101A and 101B of the power source battery pack 100. 2B is a schematic diagram of the circuit shown in FIG. 2A showing the compensation signal C2. In this case, the voltage at tap 730 is about 1 mV and is supplied to amplifier circuit 400 for comparison with a reference voltage. The output S1 of the operational amplifier 400 is saturated at + 5V. A 5 mA current C2 flows through the sense resistor Rs through path 202.

  In an alternative embodiment shown in FIG. 3A, DC ground fault detection monitor system 30 includes a floating battery pack 100 having a battery 101A coupled to power conductor 200 at a first terminal and a battery 101B coupled to power conductor 300 at a second terminal. including. Impedance network 700 includes a series resistor having a first terminal 710 coupled to first power conductor 200, a second terminal 720 coupled to second power conductor 300, and a third terminal or tap 730. A center voltage signal (vs. a reference voltage) comprising Ra and Rb and centering the floating power supply between the first and second power conductor voltages. A transistor device 300, such as a field effect transistor (FET), includes a first terminal 300a coupled to the output of tap 730, a second terminal 300b coupled to power conductor 200, and a load element 310 and an amplifier at node A. A third terminal 300c coupled to 320's inverting input. The transistor device 300 is arranged as a source follower having a load element 310 that is a bias resistor coupled to the second power conductor 300. The non-inverting input of amplifier 320 is coupled to voltage V. The output signal S1 of the amplifier 320 is coupled to the inverting terminal via a negative feedback resistor Rn. When there is no ground fault, the operation of the monitor system 30 is as follows. For a power supply battery pack voltage V of 600V, the voltage drop VRa at the resistor Ra is 300V, which is equal to the voltage drop VRb at the resistor Rb (ie, VRb = 300V). There is a voltage drop of 3.5 V between the gate terminal 300a and the drain terminal 300b. Thus, the voltage at the power conductor 200 is + 303.5V, and the voltage at the power conductor 300 is -296.5V. The bias current I bias flowing from the power conductor 200 through the bias resistor 310 is about 10 mA. The voltage at the inverting input of the amplifier 320 is 0V, and the output S1 is also 0V.

  FIG. 3B shows a 2 mA compensation applied to the second power conductor 300 via the bias resistor 310 to compensate for a small leakage current of about 2 mA due to the fault F1 occurring between the power conductor 200 and the chassis 540. 3B is a schematic diagram of the circuit shown in FIG. 3A showing the signal C1. The 8 mA bias current I bias flowing from the conductor 200 is combined with the compensation current signal C1 that feeds back to the resistor 310 to compensate for the leakage current due to the fault F1.

  FIG. 3C shows a compensation signal C1 applied to the second power conductor 300 to compensate for a large leakage current of about 20 mA due to a major fault F2 occurring between the power conductor 200 and the chassis 540. 1 is a schematic diagram of a circuit. Further, FIG. 3C includes a limiter such as a clamp diode 312 coupled between node A and chassis 540. In this case, the voltage on the power conductor 200 is at the reference potential (ie 0V). The bias current I bias flowing from the conductor 200 is 0 mA. The diode 312 operates to clamp the voltage at the node A with the clamp voltage VCL of −0.7V, and the operational amplifier 320 is arranged in a saturated state so that the output signal S1 is at + 5V. A 10 mA compensation current C 1 flows through the feedback path of the amplifier 320 to the bias resistor 310 and a 10 mA compensation current C 2 flows through the diode 312 to the resistor 310. Thus, a current of C1 + C2 = 20 mA flows through the resistor 310 and is sent to the power conductor 300 to compensate for the leakage current due to the major fault F2.

  FIG. 4 is another alternative embodiment in which the current source 330 is arranged in place of the bias resistor 310 of FIG. 2A. The current source 330 can operate to limit the fault current to any or predetermined level, eg, 10 mA.

  FIG. 5 illustrates a more detailed embodiment of an active DC ground fault detection monitor system 500 according to the present invention. A high impedance network 700 electrically coupled between the first power conductor 200 and the second power conductor 300 is a power source (not shown) between positive and negative voltage values with respect to the ground reference potential (ie, chassis voltage) 540. I) works to balance a series of high voltage batteries equally. The high-impedance network 700 includes resistors Ra, Rb,... Rh connected in series, a first terminal 710 coupled to the first power conductor 200, and a first power coupled to the second power conductor 300. Rh, Rb,... Rh having two terminals 720 and a third terminal or tap 730, and a central voltage signal (vs. reference voltage) that centers the floating power supply between the first and second power conductor voltages I will provide a. Preferably, each of the resistors Ra, Rb,... Rh has equal resistance so that the voltage magnitude at node 710 relative to ground 540 is equal to the voltage magnitude at node 720 relative to ground 540. Is to be arranged. Amplifier device 400 comprising a high gain amplifier includes a non-inverting input 410 electrically coupled to tap 730 to receive voltage signal 732 and an inverting input 420 electrically coupled to reference voltage 540 via resistor R155. And have. An input protection circuit 740, illustrated as clamp diodes D21 and D23, operates to protect the input of the amplifier device. The high gain amplifier device 400 is responsive to the voltage signal 732 and the reference (ie, chassis) voltage and generates an amplified signal S1 at the output terminal. The amplified signal S1 corresponds to the difference between the voltage signal 732 (pack center) and the reference voltage. The output of the amplifier is coupled to the inverting input via a feedback loop compensation error compensation circuit 408 comprising resistors R129, R154, R155 and capacitors C37, C38, C40, C44. As shown in FIG. 5, the circuit uses a high gain amplifier to compare the voltage at the center of the high voltage bus to the chassis. If the high voltage side is centered with respect to the chassis, the voltages will be equal (within component tolerances). That is, under normal operating conditions (ie, when there is no short circuit or low impedance condition), the high voltage bus is between the first power conductor 200 (+ DC link) and the second power conductor 300 (−DC link). For example, the output signal at the voltage divider tap 730 corresponding to the high voltage side of the bus is equal to the reference voltage (eg, 0V) because it is balanced equally. The amplified signal S1 output from the amplifier device 400 is also 0V with respect to the reference voltage (0V). However, when a short circuit or low impedance connection occurs, the difference between the voltage signal 732 and the reference voltage 540 exceeds a predetermined value and the output signal S1 is: (a) a first power conductor, (b) a second power conductor, (C) Indicates the presence of an unwanted electrical path between one of the battery pack power sources and the reference or chassis voltage. In this case, if there is a sufficient voltage difference, amplifier device 400 operates to activate (ie, turn on) either FET switch Q8 or FET switch Q9 via conductive paths 80,90. This can be achieved by turning on one of the corresponding couplers 82, 92, illustrated as optocouplers U68, U57. The coupler activates the respective conductive path from the corresponding filter circuit 83, 93 to the switches Q8, Q9. Activating either the "high side" switch (FETQ8) or the "low side" switch (FETQ9) will produce an equal reverse impedance (vs. chassis) to rebalance the high voltage bus with respect to the chassis. Act on. Either of the switches Q8 and Q9 is turned on, and the current Is passing through the generated balance impedance (provided via the compensation path 202 for the switch Q8 and the compensation path 204 for the switch Q9) is caused by the voltage applied to the sense resistor R194. Sense. The sensed voltage can be returned to the system controller or other control device. The current limiting circuits 85 and 95 operate so as to limit the currents through the respective FETs Q8 and Q9 to a predetermined value (for example, +5 mA or −5 mA) to protect the circuits. Thus, due to leakage below a predetermined value, the circuit can still operate to center the pack voltage. The circuit described above is mounted on a printed circuit board using, for example, an automatic insertion device, and can be used in various applications such as a hybrid electric vehicle, an application including an electric vehicle, or a case where grounding failure detection correction is required. .

  Although the present invention has been described with reference to specific embodiments, the present invention is not limited to these embodiments. For example, while a ground fault detection monitor circuit and system has been shown based on a feedback loop, FIG. 6 provides an embodiment of an open loop system according to the present invention. In FIG. 6, a voltage divider 700 coupled between the first positive power conductor 200 and the second negative power conductor 300 has a center tap 730 coupled to the gate of the FET device 610. FET device 610 is configured as a source follower whose source is coupled to the gate through resistor R1 and diode ZD. Amplifier device 620 senses the voltage difference applied to the inverting and non-inverting terminals and provides an output signal indicative of this voltage difference. This output signal is applied to the inverting input via a negative feedback path through Rn. Thus, after detecting the maximum leakage current (IGF), a ground fault is determined and the battery pack tends to deviate from its center voltage. Further, as shown in FIG. 7, a plurality of FETs 710 and 715 may be coupled to each other in a source follower configuration in which the gate is clamped by a diode ZD. The output of the center tap 730 is coupled to the inverting input of the amplifier device 725 via the current protection circuit 750, and the non-inverting input is coupled to the reference potential. The output signal S1 corresponds to the difference between the center voltage signal and the reference potential, and indicates the presence of an unnecessary electric circuit or ground fault condition. These and all other such modifications and changes are intended to be within the scope of the claims.

Claims (22)

A reference potential; (a) a floating power source; (b) a first power conductor coupled to the first terminal of the power source; and (c) a second power coupled to the second terminal of the power source. A system for detecting an unwanted electrical path between at least one of the conductors,
An impedance network electrically coupled to the first and second power conductors and having an output terminal for providing a first voltage signal relative to the reference potential, wherein the output terminal is provided at a center point of impedance; and An amplifier that generates an amplified signal indicating the presence of the unnecessary electric circuit when a difference between the first voltage signal and the reference vehicle body voltage exceeds a predetermined value in response to the first voltage signal and the reference vehicle body voltage. A fault detection system comprising a circuit.   A compensation circuit having an input path coupled to the amplified signal and an output path coupled to the first and second power conductors for providing a compensation signal to at least one of the first and second power conductors; The failure detection system according to claim 1, further comprising the compensation circuit that reduces a difference between a first voltage signal and the reference vehicle body voltage.   The failure detection system according to claim 2, wherein the compensation signal changes according to the magnitude of the amplified signal.   3. The fault detection system according to claim 2, wherein the compensation circuit includes a load that senses a voltage, and the sensed voltage corresponds to a degree of compensation applied by the compensation signal.   3. The fault detection system of claim 2, wherein the compensation circuit includes a pair of switches that provide separate conductive paths to the first and second power conductors.   The failure detection system according to claim 5, wherein the pair of switches includes a pair of transistors.   The fault detection system according to claim 6, wherein each of the transistors is a field effect transistor (FET).   One of the pair of switches operates in response to the characteristics of the amplified signal, conducts to a corresponding one of the first and second power conductors along the associated conductive path, and cooperates with the conductive path The impedance imbalance between the reference potential and one of the first and second power conductors caused by the unnecessary electric circuit is sufficiently canceled by generating the generated impedance (vs. the reference potential). 5. The failure detection system according to 5.   The failure detection system according to claim 1, wherein the power source is a floating power source.   The failure detection system according to claim 9, wherein the floating power source includes one or more batteries connected to each other.   The failure detection system according to claim 9, wherein the floating power source includes one or more fuel cells connected to each other.   The fault detection system according to claim 9, wherein the floating power source includes one or more capacitors connected to each other.   9. The fault detection system according to claim 8, wherein the compensation circuit includes a pair of current limiters, and each limiter cooperates with a corresponding one of the conductive paths to limit the amount of current passing therethrough to a predetermined value. A reference potential; (a) a power source; (b) a first power conductor coupled to the first terminal of the power source; and (c) a second power conductor coupled to the second terminal of the power source. A system for detecting an unnecessary electrical circuit between at least one of the following:
An impedance network electrically coupled to the first and second power conductors and having an output terminal for providing a first voltage signal with respect to the reference potential; and responsive to the first voltage signal and the reference voltage. And a means for generating an amplified signal indicating the presence of the unnecessary electric circuit when a difference between the first voltage signal and the reference voltage exceeds a predetermined value.   Responsive to the amplified signal, providing a conductive path for the amplified signal to one of the first and second power conductors and generating a compensation signal to produce a difference between the first voltage signal and the reference voltage 15. The fault detection system of claim 14, further comprising means for reducing   The fault detection system according to claim 14, wherein the power source is a floating power source.   15. A fault detection system according to claim 14, wherein said means for generating an amplified signal comprises a high gain amplifier circuit including a feedback device. A reference potential; (a) a floating power source; (b) a first power conductor coupled to the first terminal of the power source; and (c) a second power coupled to the second terminal of the power source. A system for detecting and compensating for unwanted electrical paths between at least one of the conductors,
An impedance network having an output terminal electrically coupled to the first and second power conductors and providing a first voltage signal relative to the reference potential;
In response to the first voltage signal and the reference voltage, a high gain amplifier that generates an amplified signal indicating the presence of the unnecessary electric circuit when a difference between the first voltage signal and the reference voltage exceeds a predetermined value And a compensation circuit having an input electrically coupled to the output of the high gain amplifier and a first and second output electrically coupled to the first and second power conductors, respectively, through a conductive path. And providing a compensation signal to at least one of the first and second power conductors, the compensation signal reducing the difference between the first voltage signal and the reference voltage according to the magnitude of the amplified signal. A failure detection system comprising a compensation circuit.   The fault detection system according to claim 18, wherein the compensation circuit includes a load that senses a voltage corresponding to a degree of compensation applied by the compensation signal. A floating power source having a first terminal coupled to the first power conductor and a second terminal coupled to the second power conductor;
A first terminal electrically coupled to the first power conductor; a second terminal electrically coupled to the second power conductor; and a third terminal coupled to a reference potential. , An impedance network that equally balances the voltage across the first and second power conductors (vs. the reference potential), wherein the first power conductor, the second power conductor, and the power source The impedance network in which an accidental voltage is generated at the third terminal of the impedance network based on the occurrence of an accidental circuit between at least one and the reference potential;
An amplifier electrically coupled to the third terminal and operative to provide a control signal proportional to a difference between the incidental voltage at the third terminal and the reference potential; and to the control signal Electrically coupled and providing a compensation signal to at least one of the first and second power conductors via a feedback path, the accidental voltage generated at the third terminal and the reference potential A fault monitoring apparatus comprising a compensation circuit that operates to reduce a difference between the two. A reference potential; (a) a power source; (b) a first power conductor coupled to the first terminal of the power source; and (c) a second power conductor coupled to the second terminal of the power source. A system for detecting an unnecessary electrical circuit between at least one of the following:
An impedance network electrically coupled to the first and second power conductors and operative to equally center a voltage across the first and second power conductors around a reference voltage, the reference network The impedance network having a tap to provide a center voltage signal for the voltage;
A first input terminal electrically coupled to the tap, a second terminal electrically coupled to the first power conductor, and a third electrically coupled to the second power conductor A transistor having a terminal; a first terminal electrically coupled to the third terminal of the transistor; a second terminal electrically coupled to the reference voltage; and an amplifier circuit having an output terminal. A compensation loop is provided between the first terminal and the output terminal to provide a compensation signal to the third terminal of the transistor, and the amount of current flowing from the third terminal to the second power conductor is reduced. A fault detection system comprising the amplifier circuit to be corrected. A floating power source having a first terminal coupled to the first power conductor and a second terminal coupled to the second power conductor;
A first terminal electrically coupled to the first power conductor, a second terminal electrically coupled to the second power conductor, and a third terminal coupled to the vehicle body; An impedance network that equally balances the voltage (vs. vehicle body) applied to the first and second power conductors, and the accidental voltage based on the occurrence of an accidental electrical circuit between the vehicle body and the node in the floating power source The impedance network in which a signal is generated at the third terminal of the impedance network by an impedance imbalance (vs. vehicle body) between the first and second power conductors;
An amplifier for providing a control signal in response to the accidental voltage signal and indicating an impedance imbalance (to the vehicle body) between the first and second power conductors; and electrically coupled to the amplifier; A fault detection and compensation system comprising a compensation circuit that provides a compensation impedance path to at least one of the two power conductors and equalizes the voltage between the first and second power conductors (vs. the vehicle body).

Images