Leakage Current Monitoring System

Abstract

The present disclosure relates to a leakage current monitoring system. A battery connection unit includes: a first branch having a first branch switch, the first branch being adapted to connect a first battery to at least one of a second battery and a vehicle load; and a second branch having a second branch switch, the second branch being parallel to the first branch. A first measurement switch is connected between the first branch and a storage element to enable / disable charging. A second measurement switch is connected between the second branch and the storage element. A processor is programmed to: disable at least one of the first branch and the second branch; enable at least one of the first measurement switch and the second measurement switch to charge the storage element with leakage current; and generate an output signal indicating a switch failure in response to a voltage of the storage element associated with the leakage current exceeding a reference voltage within a predetermined time period.

Description

Technical Field

[0001] One or more embodiments relate to a vehicle power distribution system for monitoring leakage current. Background

[0002] A vehicle includes a power distribution system having a switch for connecting and disconnecting a power source (e.g., a battery) to and from the vehicle electrical system. The performance of such a switch degrades over time, causing current to conduct or leak through the switch when it is open. Leakage current in the power distribution system may be difficult to measure on a vehicle with traditional current measurement equipment because the leakage current is much lower than the operating current. Summary of the Invention

[0003] In one embodiment, a battery connection unit includes a first branch and a second branch. The first branch is adapted to connect a first battery to at least one of a second battery and a vehicle load, and includes at least one first branch switch to enable / disable current flow along the first branch. The second branch is connected in parallel with the first branch and includes at least one second branch switch to enable / disable current flow along the second branch. The system further includes a storage element; a first measurement switch connected between the first branch and the storage element to enable / disable charging of the storage element; a second measurement switch connected between the second branch and the storage element to enable / disable charging of the storage element; and a processor. The processor is programmed to: disable at least one of the first branch and the second branch; enable at least one of the first measurement switch and the second measurement switch to charge the storage element with leakage current from at least one disabled branch; and generate an output signal indicating a switch failure in response to a storage element voltage associated with the leakage current exceeding a reference voltage within a predetermined period of time.

[0004] In another embodiment, a battery connection unit includes at least one branch adapted to connect a first battery to at least one of a second battery and a vehicle load. The branch includes a first switch and a second switch connected in series along the branch to enable / disable bidirectional current flow. A first measurement switch is connected between the first switch and the second switch of the branch and the storage element to enable / disable charging of the storage element with first branch leakage current.

[0005] In yet another embodiment, a method of monitoring leakage current in a power distribution system is provided. A battery connection unit is provided that has: a first branch switch and a second branch switch, the first branch switch being configured to enable / disable bidirectional current flow between a first battery and at least one of a second battery and a vehicle load, and the second branch switch being configured to enable / disable bidirectional current flow between the first battery and at least one of the second battery and the vehicle load. A monitoring circuit is provided that has: a storage element, a first measurement switch, and a second measurement switch, the first measurement switch being connected between the first branch switch and the storage element to enable / disable charging of the storage element, and the second measurement switch being connected between the second branch switch and the storage element to enable / disable charging of the storage element. At least one of the first branch switch and the second branch switch is disabled. At least one of the first measurement switch and the second measurement switch is enabled to charge the storage element with leakage current from at least one disabled branch switch. An output signal indicating a switch failure is generated in response to a voltage of the storage element associated with the leakage current exceeding a reference voltage within a predetermined time period. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a schematic block diagram of a vehicle having two power sources and a power distribution system according to one or more embodiments, the power distribution system including a battery connection unit.

[0007] Figure 2 is Figure 1 a schematic diagram of the battery connection unit of

[0008] Figure 3 is a flowchart showing a method for monitoring Figure 2 leakage current of a switch unit of

[0009] Figure 4 is Figure 1 a circuit diagram of the power distribution system of Figure 3 showing the method for monitoring leakage current of

[0010] Figure 5 is a schematic block diagram of another vehicle having one power source and a power distribution system according to one or more embodiments, the power distribution system including a battery connection unit.

[0011] Figure 6 is a flowchart showing a method for monitoring Figure 5 leakage current of a switch unit implemented in the power distribution system of Figure 2 showing the method for monitoring

[0012] Figure 7A isFigure 5 The circuit diagram of the power distribution system in the first configuration shows Figure 6 the method for monitoring leakage current.

[0013] Figure 7B is Figure 5 The circuit diagram of the power distribution system in the second configuration further shows Figure 6 the method for monitoring leakage current. DETAILED DESCRIPTION

[0014] As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely examples of the present invention, which may be presented in various and alternative forms. The drawings are not necessarily to scale; some features may be enlarged or minimized to show details of particular components. Thus, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a representative basis for teaching those skilled in the art to employ the present invention in various ways.

[0015] Referring to Figure 1 , a vehicle power distribution system is shown in accordance with one or more embodiments and is generally referred to by the numeral 110. The power distribution system 110 is depicted within a vehicle 112 and electrically connects one or more power sources to a vehicle electrical system 114. According to the illustrated embodiment, the power distribution system 110 includes two power sources: a main battery 116 and a secondary battery 118. According to one or more embodiments, the power distribution system 110 further includes a battery connection unit 120 and a fuse box 122. The battery connection unit 120 includes a switch unit 124, and the switch unit 124 includes one or more switches for connecting / disconnecting the batteries 116, 118 to / from the vehicle electrical system 114. The battery connection unit 120 further includes a controller 126 for controlling the switch unit 124 ( Figure 2 shown in). In other embodiments, the power distribution system 110 is implemented in a vehicle having a single battery 116 ( Figures 5 - 7B shown in).

[0016] During operation of the vehicle, the controller 126 controls the switch unit 124 to supply electrical energy from the batteries 116, 118 to various loads of the vehicle electrical system 114, such as the powertrain, heating, and cooling systems. When the vehicle 112 is idle or not operating, the controller 126 controls the switch unit 124 to open and disconnect the batteries 116, 118 from the vehicle electrical system 114. The performance of the switch unit 124 may degrade over time, which may ultimately cause the switch to malfunction, such as opening or closing. Prior to such a loss of functionality, when the switch is open, the switch open impedance (i.e., the impedance when the switch is open) may decrease and allow current to conduct or leak through the switch. The battery connection unit 120 monitors this leakage current and, if the leakage current exceeds a predetermined leakage current threshold, notifies other vehicle systems so that the switch unit 124 can be serviced before a loss or degradation of functionality occurs.

[0017] The power distribution system 110 may supply high currents, such as over 100 amperes, to the vehicle electrical system 114 during operating conditions. However, the instantaneous leakage current may be relatively low compared to the operating current. For example, the leakage current may be in the microampere range. Current sensors that measure currents in the microampere range can be expensive and not practical for sensors on a vehicle. The battery connection unit 120 includes a monitoring circuit 128 having a storage element that is charged over time to monitor the leakage current without using such expensive sensors. The controller 126 and the monitoring circuit 128 may be collectively referred to as a leakage current monitoring system.

[0018] Reference Figure 2 Referring, the battery connection unit 120 includes the switch unit 124, the controller 126, and the monitoring circuit 128. According to one or more embodiments, the switch unit 124 includes a pair of switches connected in a back-to-back configuration. According to the illustrated embodiment, the switch unit 124 includes two complementary branches, a first branch 130 and a second branch 132, which perform a similar function, i.e., connecting the batteries 116, 118 to the vehicle electrical system 114. The branches 130, 132 share the power transfer such that for embodiments having two branches, each branch 130, 132 can handle approximately half of the total current, which may allow for less expensive switches. Although shown as a pair of parallel branches, other embodiments of the battery connection unit 120 include a single branch or more than two branches.

[0019] According to one or more embodiments, each branch 130, 132 includes two switches arranged in series. The first branch 130 includes a first switch 134 and a second switch 136, and the second branch 132 includes a third switch 138 and a fourth switch 140. According to the illustrated embodiment, each switch 134, 136, 138, 140 is an n-channel metal oxide semiconductor field effect transistor (nMOSFET). MOSFET is a three-terminal device with a source (S), a drain (D) and a gate (G). According to the illustrated embodiment, each branch 130, 132 includes two switches arranged in a common source back-to-back configuration. This configuration allows bidirectional current to flow and close through each branch. For example, the battery 116, 118 provides current to the vehicle electrical system 114; and the vehicle electrical system 114 may include a device that generates current, such as a generator (not shown), for charging the battery 116, 118.

[0020] The monitoring circuit 128 monitors the change of the leakage current over time. The monitoring circuit 128 includes a storage element (e.g., a capacitor 142) connected to the switching unit 124 and charged based on the leakage current received. The voltage (Vc) across the capacitor is measured by the controller 126. In the illustrated embodiment, the monitoring circuit 128 includes a comparator 144, which compares Vc with a reference voltage (Vref) provided by the controller 126, where Vref corresponds to a predetermined leakage current threshold. After a predetermined period of time, if Vc exceeds Vref, the comparator 144 provides an output signal (output) to the controller 126, and the controller 126 notifies other vehicle electrical systems 114.

[0021] The monitoring circuit 128 includes a first measurement switch (S1) and a second measurement switch (S2) for connecting to the first branch 130 and the second branch 132 of the switch unit, respectively. The monitoring circuit 128 also includes a discharge switch (S D ), the discharge switch (S D ) Combined with resistor R D The capacitor 142 is connected in parallel to release the current stored in the capacitor 142 .

[0022] The controller 126 provides control signals to enable / disable each switch. According to one or more embodiments, the switch unit 124 includes a first driver 146 that is connected to the gates of the first switch 134 and the second switch 136 of the first branch 130. The controller 126 provides a control signal (E1) to the first driver 146 to commonly enable / disable the first switch 134 and the second switch 136. According to one or more embodiments, the switch unit 124 further includes a second driver 148 that is connected to the gates of the third switch 138 and the fourth switch 140 of the second branch 132. The controller 126 provides a control signal (E2) to the second driver 148 to commonly enable / disable the third switch 138 and the fourth switch 140. In other embodiments, the battery connection unit 120 includes drivers (not shown) for driving each switch, and the controller 126 provides control signals, such as E1a, E1b, E2a, and E2b, to each driver. Although shown as separate components, the controller 126 may include driver functionality, and the controller 126 may directly provide control signals to the switches.

[0023] The controller 126 provides a control signal (M1) to the first measurement switch (S1) and a control signal (M2) to the second measurement switch (S2) to enable / disable portions of the monitoring circuit 128 through each switch. The controller 126 can control S1 and S2 independently of each other to produce different monitoring configurations, including: both switches are enabled; both switches are disabled; a monitoring circuit A configuration in which S1 is enabled and S2 is disabled; and a monitoring circuit B configuration in which S2 is enabled and S1 is disabled. The controller 126 also provides a control signal (R) to the discharge switch (S D ) to reset the monitoring circuit.

[0024] Reference Figure 3 , according to one or more embodiments, a method for monitoring the leakage current of a vehicle power distribution system 110 is shown, and the method is generally referred to by the numeral 300. According to one or more embodiments, the method is implemented using software code included with the controller 126. The controller 126 generally includes any number of processors, microprocessors, ASICs, ICs, memories (such as flash memory, ROM, RAM, EPROM, and / or EEPROM), and software code to cooperate with each other to perform a series of operations. According to one or more embodiments, the controller 126 further includes predetermined data or a "look-up table" stored in the memory. Although the method is described using a flowchart shown in a plurality of consecutive steps, one or more steps may be omitted and / or performed in a different manner in one or more other embodiments.

[0025] In step 302, the controller 126 determines that the vehicle 112 is at idle. When the vehicle 112 is at idle, the vehicle electrical system 114 does not draw high current from the batteries 116, 118. According to one or more embodiments, the controller 126 communicates with other vehicle controllers and / or systems (not shown), e.g., via a CAN bus, and determines in step 302 that the vehicle is at idle based on signals received from these other systems. For example, the controller 126 may determine that the vehicle is at idle based on signals indicative of vehicle speed, engine speed, key status, and / or gear selection. In step 306, the controller 126 disables both branches of the switch unit 124, namely the first branch 130 and the second branch 132.

[0026] Figure 4 is a circuit diagram of the power distribution system 110 implemented in the vehicle 112, which has two batteries, e.g., a main battery 116 and a secondary battery 118. According to the illustrated embodiment, the switches 134, 136, 138, 140 are active high nMOSFETs. The controller disables the first branch 130 of the switch unit 124 by providing a low voltage ("0") control signal (E1) to the first driver 146, and the first driver 146 in turn opens the first switch 134 and the second switch 136. The controller disables the second branch 132 of the switch unit 124 by providing a low voltage ("0") control signal (E2) to the second driver 148, and the second driver 148 in turn opens the third switch 138 and the fourth switch 140.

[0027] Reference Figure 3 and Figure 4 , in step 308, the controller 126 resets the monitoring circuit 128. The storage element 142 of the monitoring circuit 128 may accumulate energy over time. When enabled, the discharge switch S D releases any energy stored in the storage element 142 by providing a parallel path to ground with a lower impedance. According to the illustrated embodiment, the discharge switch S D is an active high nMOSFET. The controller enables (closes) the switch by providing a high voltage ("1") control signal (R) to the discharge switch (S D ) to reset the monitoring circuit 128. Then, after a predetermined time, the controller provides a low voltage ("0") control signal to the discharge switch (S D ) to disable (open) the switch.

[0028] At step 310, the controller 126 enables the monitoring circuit 128. According to the illustrated embodiment, the first measurement switch (S1) and the second measurement switch (S2) are active low p-channel MOSFETs (pMOSFETs). The controller enables monitoring of the first branch 130 of the switching unit 124 by providing a low voltage (“0”) control signal (M1) to the first measurement switch (S1), which in turn closes the switch. With the first measurement switch S1 closed, as depicted by the dashed line 150, the first branch leakage current (I L1 ) from the open first switch 134 and second switch 136 flows to the monitoring circuit 128 within a predetermined time.

[0029] According to one or more embodiments, the controller 126 also enables monitoring of the second branch 132 of the switching unit 124 by providing a low voltage (“0”) control signal (M2) to the second measurement switch (S2), which in turn closes the switch. With the second measurement switch S2 closed, as depicted by the dashed line 152, the second branch leakage current (I L2 ) from the open third switch 138 and fourth switch 140 will flow to the monitoring circuit 128.

[0030] At step 312, the controller 126 compares the voltage drop (Vc) across the storage element 142 with a reference voltage (Vref). According to Equation 1, due to the accumulation of the leakage current (I L1 ) from the first branch and the leakage current (I L2 ) from the second branch, Vc will increase over time:

[0031]

[0032] where C represents the capacitance of the capacitor storage element 142, and I L represents the sum of the first branch leakage current (I L1 ) and the second branch leakage current (I L2 ). Δt represents a predetermined time period for charging the capacitor. If the controller 126 determines at step 312 that Vc is greater than Vref, the controller 126 proceeds to step 314 and generates an output signal indicating an alarm or fault associated with the switching unit 124. However, if Vc is not greater than Vref, the controller 126 proceeds to step 316 to complete the analysis.

[0033] For example, in one embodiment, the reference voltage (Vref) associated with simultaneously monitoring all four switches 134, 136, 138, 140 is equal to 40 volts, the capacitance (C) is equal to 100 microfarads (μF), and the predetermined time period (Δt) is equal to 100 seconds. With 40V as the reference limit, the calculation is as follows: If the maximum current leakage of each switch (i.e., the datasheet leakage current of the MOSFET) is 10 uA, and the maximum leakage current of the four switches is 40 uA, then when the leakage current is less than the datasheet limit (i.e., not degraded), the maximum leakage charge (Q) is equal to 4.0 millicoulombs (Q = 40 uA * 100 s = 4 mQ), and the resulting capacitor voltage (Vc) is equal to 40V, (Vc = Q / C = 4.0 mQ / 100 uF = 40V). Therefore, if a capacitor voltage (Vc) higher than (Vref) is observed before the predetermined time period (Δt), this will indicate that the MOSFET leakage current exceeds the datasheet limit and degradation has started, and the controller generates an output signal indicating an alarm or fault associated with the switch unit 124.

[0034] In another embodiment, the reference voltage (Vref) associated with simultaneously monitoring all four switches 134, 136, 138, 140 is equal to 10 volts, the capacitance (C) is equal to 100 microfarads (μF), and the predetermined time period (Δt) is equal to 25 seconds. With 10V as the reference limit, the calculation is as follows: If the maximum current leakage of each switch (i.e., the datasheet leakage current of the MOSFET) is 10 uA, and the maximum leakage current of the four switches is 40 uA, then when the leakage current is less than the datasheet limit (i.e., not degraded), the maximum leakage charge (Q) is equal to 1.0 millicoulomb (Q = 40 uA * 25 s = 1 mQ), and the resulting capacitor voltage (Vc) is equal to 10V, (Vc = Q / C = 1.0 mQ / 100 uF = 10V).

[0035] Although the above steps describe analyzing two branches of the switch unit 124 simultaneously, in other embodiments of the battery connection unit 120, the controller 126 analyzes each branch of the switch unit 124 separately. Using this method, the controller 126 can provide different alarms, for example, one alarm associated with the switches of the first branch 130 and one alarm associated with the switches of the second branch 132. In other embodiments, the controller 126 can save Vc in its memory for future reference. For example, the controller 126 can compare Vc with one or more previously measured Vc values to observe the trend or rate of change of Vc. Using this method, the controller 126 can be able to compare the rate of change of Vc with a predetermined rate-of-change value and generate a fault before Vc reaches the Vref threshold.

[0036] In one embodiment, the controller 126 analyzes each branch of the switching unit 124 separately. After disabling two branches of the switching unit 124 in step 306, the controller 126 proceeds to step 318 and, if either the first measurement switch (S1) or the second measurement switch (S2) is currently enabled, disables the first measurement switch (S1) and the second measurement switch (S2), and then resets the monitoring circuit 128. Further, the controller enables (closes) the switch by providing a high voltage (“1”) control signal (R) to the discharge switch (S D ), thereby resetting the monitoring circuit 128. Then, after a predetermined time, the controller provides a low voltage (“0”) control signal (R) to the discharge switch (S D ) to disable (open) S D . Next, the controller 126 closes the switch by providing a low voltage (“0”) control signal (M1) to the first measurement switch (S1), thereby enabling the monitoring circuit A. With the first measurement switch S1 closed and the second measurement switch S2 open, the first branch leakage current (I L1 ) flows to the monitoring circuit A, but the second branch leakage current (I L2 ) does not flow to the monitoring circuit A.

[0037] In step 320, within a predetermined time (Δt), the controller 126 compares the voltage drop (Vc) across the storage element 142 with a second reference voltage (Vref_2). In one embodiment, Vref_2 is equal to half of Vref described above with reference to step 312. For example, as described above, Vref associated with simultaneously monitoring all four switches 134, 136, 138, 140 can be equal to 40 volts. The second reference voltage (Vref_2) associated with simultaneously monitoring one branch (two switches) can be equal to 20 volts, the capacitance (C) is equal to 100 microfarads (μF), and the predetermined time period (Δt) is equal to 100 seconds. Calculated with 20V as the reference limit: If the maximum current leakage of each switch (i.e., the datasheet leakage current of the MOSFET) is 10 uA, and the maximum leakage current of two switches is 20 uA, then when the leakage current is less than the datasheet limit (i.e., not degraded), the maximum leakage charge (Q) is equal to 2.0 millicoulombs (Q = 20 uA * 100 s = 2 mQ), and the resulting capacitor voltage (Vc) is equal to 20V, (Vc = Q / C = 2.0 mQ / 100 uF = 20V). According to Equation 1 (shown above), due to the accumulation of the leakage current (I L1 ) from the first branch, Vc will increase over time. Wherein, C represents the capacitance of the capacitor storage element 142, and I L represents the first branch leakage current (I L1 ). Δt represents the predetermined time period for charging the capacitor.

[0038] In another embodiment, within a second predetermined time (Δt_2), the controller 126 compares the voltage drop (Vc) across the storage element 142 with a reference voltage (Vref), where Δt_2 is equal to twice the Δt described in reference step 312 above. For example, in one embodiment, the predetermined time period (Δt) is equal to 100 seconds, and the second predetermined time period (Δt_2) is equal to 200 seconds, and the reference voltage (Vref) associated with monitoring one branch (two switches) is equal to 40 volts. The 40V is used as a reference limit and is calculated as follows: If the maximum current leakage of each switch (i.e., the datasheet leakage current of the MOSFET) is 10 uA, the maximum leakage current of two switches is 20 uA, then when the leakage current is less than the datasheet limit (i.e., not degraded), the maximum leakage charge (Q) is equal to 4.0 millicoulombs (Q = 20 uA * 200 s = 4 mQ), and the resulting capacitor voltage (Vc) is equal to 40V, (Vc = Q / C = 4.0 mQ / 100 uF = 40V).

[0039] If the controller 126 determines at step 320 that Vc is greater than Vref_2 at the predetermined time (or Vc is greater than Vref within the second predetermined time), then the controller 126 proceeds to step 322 and generates an output signal indicating an alarm or fault associated with the first branch 130 of the switch unit 124.

[0040] If the controller 126 determines at step 320 that Vc is not greater than Vref_2, then the controller 126 proceeds to step 324, disables the monitoring circuit A, resets the monitoring circuit, and then enables the monitoring circuit B. The controller 126 disables the monitoring circuit A by providing a high voltage ("1") control signal (M1) to the first measurement switch (S1) to open the switch. Then, the controller 126 resets the monitoring circuit 128 by providing a high voltage ("1") control signal (R) to the discharge switch (S D ) to enable (close) the switch, and then provides a low voltage ("0") control signal (R) to the discharge switch (S D ) to disable (open) the switch after a predetermined time. The controller 126 enables the monitoring circuit B by providing a low voltage ("0") control signal (M2) to the second measurement switch (S2) to close the switch. With the second measurement switch S2 closed and the first measurement switch S1 open, within the predetermined time, the leakage current of the second branch (I L2 ) flows to the monitoring circuit B, but the leakage current of the first branch (I L1 ) does not flow to the monitoring circuit B.

[0041] At step 326, within a second predetermined time (Δt_2), the controller 126 again compares the voltage drop (Vc) across the storage element 142 with a second reference voltage (Vref_2). According to Equation 1 (shown above), due to the accumulation of the leakage current (I L2 ) from the second branch, Vc will increase over time. Where C represents the capacitance of the capacitor storage element 142, and I L represents the second branch leakage current (I L2 ). Δt_2 represents the second predetermined time period for charging the capacitor. If the controller 126 determines at step 326 that Vc is greater than Vref_2, the controller 126 proceeds to step 328 and generates an output signal indicating an alarm or a fault associated with the second branch 132 of the switch unit 124. However, if Vc is not greater than Vref_2, the controller 126 proceeds to step 330 to complete the method.

[0042] In another embodiment, the controller 126 performs steps 318 - 330 after step 312 or step 314. In one embodiment, after identifying a fault in the switch unit 124, the controller 126 performs steps 318 - 330 to further diagnose the fault, i.e., whether the fault is associated with the first branch 130 and / or the second branch 132.

[0043] Reference Figure 5 , according to one or more embodiments, a vehicle power distribution system is shown and generally referred to by the numeral 510. The power distribution system 510 is depicted as being within a vehicle 512 and electrically connects a power source (e.g., a main battery 516) to the vehicle electrical system 514.

[0044] According to one or more embodiments, the power distribution system 510 includes a main battery 516, a battery connection unit 520, and a fuse box 522. Similar to the power distribution system 110, the power distribution system 510 may include elements 524, 526, 528, 530, 532, 534, 536, 538, 540, 542, 544, 546, 548, 550, 552 that operate in accordance with the above - mentioned elements 124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, 148, 150, 152 respectively. The battery connection unit 520 includes a switch unit 524, and the switch unit 524 includes one or more switches for connecting / disconnecting the battery 516 to / from the vehicle electrical system 514. The battery connection unit 520 also includes a controller 526 for controlling the switch unit 524 ( Figures 7A - 7B shown in).

[0045] Reference Figure 6, according to one or more embodiments, a method for monitoring the leakage current of a vehicle power distribution system 510 is shown, and this method is generally referred to by the numeral 600. According to one or more embodiments, this method is implemented using software code included with the controller 526. The controller 526 generally includes any number of processors, microprocessors, ASICs, ICs, memories (such as flash memory, ROM, RAM, EPROM, and / or EEPROM), and software code to cooperate with each other to perform a series of operations. According to one or more embodiments, the controller 526 also includes predetermined data or a "look-up table" stored in the memory. Although this method is described using a flowchart shown in a plurality of consecutive steps, one or more steps may be omitted and / or performed in another manner in one or more other embodiments.

[0046] In step 602, the controller 526 determines that the vehicle 512 is at idle. When the vehicle 512 is at idle, the vehicle electrical system 514 does not draw a high current from the main battery 516. In step 606, the controller 526 disables one branch of the switch unit 524 and enables another branch. The power distribution system 510 can be used in a vehicle having a single main battery 516. In such an application, the power distribution system 510 can disable one branch of the switch unit 524 at a time to ensure that there is still energy available to control various switches.

[0047] Figure 7A is a circuit diagram of the power distribution system 510 implemented in a vehicle 512 having one battery (the main battery 516), and shows that the first branch 530 is enabled and the second branch 532 is disabled. Also, according to the illustrated embodiment, the switches 534, 536, 538, 540 are active high nMOSFETs. The controller 526 enables the first branch 530 of the switch unit 524 by providing a high voltage ("1") control signal (E1) to the first driver 546 (the first driver 546 then closes the first switch 534 and the second switch 536). The controller 526 disables the second branch 532 of the switch unit 524 by providing a low voltage ("0") control signal (E2) to the second driver 548 (the second driver 548 then opens the third switch 538 and the fourth switch 540). The enabled first branch 530 provides a power supply path for the fourth switch 540 in the disabled second branch 532. Otherwise, there is no path for any leakage current to flow through the fourth switch 540 and S2 to charge the capacitor 542.

[0048] Reference Figure 6 and Figure 7A , in step 608, the controller 526 discharges the switch (S D)Provide a high voltage (“1”) control signal (R) to enable (close) the switch, thereby resetting the monitoring circuit 528. Then, after a predetermined time, the controller supplies a low voltage (“0”) control signal (R) to the discharge switch (S D ) to disable (open) the switch.

[0049] In step 610, the controller 526 enables the monitoring circuit 528 for the second branch 532. The controller 526 enables the monitoring of the second branch 532 of the switch unit 524 by supplying a low voltage (“0”) control signal (M2) to the second measurement switch (S2), which in turn closes the switch. With the second measurement switch S2 closed, as depicted by the dashed line 552, the second branch leakage current (I L2 ) from the open third switch 538 and fourth switch 540 will flow to the monitoring circuit 528.

[0050] In step 612, within a predetermined time (Δt), the controller 526 compares the voltage drop (Vc) across the storage element 542 with a second reference voltage (Vref_2). According to Equation 1 (shown above), Vc will increase over time based on the accumulation of the leakage current (I L2 ) from the second branch. Here, C represents the capacitance of the capacitor storage element 542, and I L represents the leakage current of one branch. In one or more embodiments, when the controller 526 evaluates the leakage current from a single branch, the controller 526 compares Vc with a second reference voltage (Vref_2) that is less than Vref. In another embodiment, in step 612, the controller 526 compares Vc with Vref within a second predetermined time (Δt_2).

[0051] If the controller 526 determines in step 612 that Vc is greater than Vref_2, the controller 526 proceeds to step 614 and generates an output signal indicating an alarm or fault associated with the second branch 532 of the switch unit 524. However, if Vc is not greater than Vref_2, the controller 526 proceeds to step 616 to determine whether all branches of the switch unit have been tested. If not all branches have been tested, the controller 526 proceeds to step 618, disables the untested branches, and enables the previously tested branches.

[0052] Figure 7BIt is a circuit diagram of a power distribution system 510 implemented in a vehicle 512 having a battery (main battery 516), and shows that the first branch 530 is disabled and the second branch 532 is enabled. Also, according to the illustrated embodiment, switches 534, 536, 538, 540 are active high nMOSFETs. The controller 526 disables the first branch 530 of the switch unit 524 by providing a low voltage ("0") control signal (E1) to the first driver 546 (the first driver 546 in turn opens the first switch 534 and the second switch 536). The controller 526 enables the second branch 532 of the switch unit 524 by providing a high voltage ("1") control signal (E2) to the second driver 548 (the second driver 548 in turn closes the third switch 538 and the fourth switch 540).

[0053] Reference Figure 6 and Figure 7B , at step 608, the controller 526 again enables (closes) the switch by providing a high voltage ("1") control signal (R) to the discharge switch (S D ), thereby resetting the monitoring circuit 528. Then, after a predetermined time, the controller provides a low voltage ("0") control signal (R) to the discharge switch (S D ) to disable (open) the switch.

[0054] At step 610, the controller 526 enables the monitoring circuit 528 for the first branch 530. The controller 526 enables the monitoring of the first branch 530 of the switch unit 524 by providing a low voltage ("0") control signal (M1) to the first measurement switch (S1) (the first measurement switch (S1) in turn closes the switch). As the first measurement switch S1 closes, as depicted by the dashed line 550, the first branch leakage current (I L1 ) from the open first switch 534 and second switch 536 will flow to the monitoring circuit 528.

[0055] At step 612, the controller 526 again compares the voltage drop (Vc) across the storage element 542 with the second reference voltage (Vref_2) within a predetermined time (Δt), or alternatively, within a second predetermined time (Δt_2), compares Vc with Vref. According to Equation 1 (shown above), due to the accumulation of the leakage current (I L1 ) from the first branch, Vc will increase with time. Where C represents the capacitance of the capacitor storage element 542, and I L represents the leakage current of one branch.

[0056] If the controller 526 determines at step 612 that Vc is greater than Vref_2, the controller 526 proceeds to step 614 and generates an output signal indicating an alarm or a fault associated with the first branch 530 of the switching unit 524. However, if Vc is not greater than Vref_2, the controller 526 proceeds to step 616 to determine again whether all branches of the switching unit have been tested. Once all branches have been tested, the controller 526 proceeds to step 620 to complete the method.

[0057] While the above describes exemplary embodiments, these embodiments are not intended to describe all possible forms of the invention. Rather, the words used in the specification are descriptive words rather than limiting words, and it is to be understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of the embodiments of various implementations may be combined to form additional embodiments of the invention.

[0058] Aspects of the present disclosure may be implemented in one or more of the embodiments described below:

[0059] 1) A battery connection unit, comprising:

[0060] A first branch adapted to connect a first battery to at least one of a second battery and a vehicle load, the first branch including at least one first branch switch to enable / disable current flow along the first branch;

[0061] A second branch connected in parallel with the first branch, the second branch including at least one second branch switch to enable / disable current flow along the second branch;

[0062] A storage element;

[0063] A first measurement switch connected between the first branch and the storage element to enable / disable charging of the storage element;

[0064] A second measurement switch connected between the second branch and the storage element to enable / disable charging of the storage element; and

[0065] A processor programmed to:

[0066] Disable at least one of the first branch and the second branch;

[0067] Enable at least one of the first measurement switch and the second measurement switch to charge the storage element with leakage current from at least one disabled branch; and

[0068] An output signal indicating a switch failure is generated in response to a storage element voltage associated with the leakage current exceeding a reference voltage within a predetermined period of time.

[0069] 2) The battery connection unit according to 1), wherein the at least one first branch switch includes a first switch and a second switch, and wherein the first measurement switch is connected between the first switch and the second switch.

[0070] 3) The battery connection unit according to 2), wherein the first switch and the second switch include metal oxide semiconductor field effect transistors (MOSFETs) arranged in a common-source back-to-back configuration.

[0071] 4) The battery connection unit according to 1), wherein the at least one second branch switch includes a third switch and a fourth switch, and wherein the second measurement switch is connected between the third switch and the fourth switch.

[0072] 5) The battery connection unit according to 4), wherein the third switch and the fourth switch include metal oxide semiconductor field effect transistors (MOSFETs) arranged in a common-source back-to-back configuration.

[0073] 6) The battery connection unit according to 1), further comprising a discharge switch configured to discharge the storage element when the discharge switch is enabled, wherein the processor is further programmed to enable the discharge switch to release the energy stored in the storage element before enabling at least one of the first measurement switch and the second measurement switch.

[0074] 7) The battery connection unit according to 1), wherein the first branch is adapted to connect the first battery to the second battery, and wherein the processor is further programmed to:

[0075] Disable both the first branch and the second branch;

[0076] Enable both the first measurement switch and the second measurement switch to charge the storage element with leakage currents from the disabled first branch and the disabled second branch; and

[0077] Generate the output signal indicating a switch failure in response to a storage element voltage associated with leakage currents from the disabled first branch and the disabled second branch exceeding the reference voltage within the predetermined period of time.

[0078] 8) The battery connection unit according to 7), wherein the processor is further programmed to:

[0079] In response to generating the output signal indicating a switch failure, disable the second measurement switch; and

[0080] In response to the voltage of the storage element exceeding a second reference voltage within the predetermined time period, generate a first output signal indicating a failure of the first branch switch.

[0081] 9) The battery connection unit according to 8), wherein the processor is further programmed to:[[]]

[0082] Disable the first measurement switch;

[0083] Enable the second measurement switch to charge the storage element with the leakage current from the disabled second branch; and

[0084] In response to the voltage of the storage element exceeding the second reference voltage within the predetermined time period, generate a second output signal indicating a failure of the second branch switch, wherein the second reference voltage is equal to half of the reference voltage.

[0085] 10) A battery connection unit, comprising:[[]]

[0086] At least one branch adapted to connect a first battery to at least one of a second battery and a vehicle load, the at least one branch comprising:[[]]

[0087] A first switch; and

[0088] A second switch connected in series with the first switch along the at least one branch to enable / disable bidirectional current flow;

[0089] A storage element; and

[0090] A first measurement switch connected between the first switch and the second switch of the at least one branch and the storage element to enable / disable charging of the storage element with the leakage current of the first branch.

[0091] 11) The battery connection unit according to 10), wherein the at least one branch comprises:[[]]

[0092] A first branch comprising the first switch and the second switch;

[0093] A second branch connected in parallel with the first branch, the second branch comprising a third switch and a fourth switch connected in series along the second branch to enable / disable bidirectional current flow; and

[0094] The battery connection unit further includes a second measurement switch connected between the third switch and the fourth switch in the second branch and the storage element to enable / disable charging of the storage element using the leakage current of the second branch.

[0095] 12) The battery connection unit according to 11) further includes:

[0096] A controller configured to:

[0097] Disable at least one of the first branch and the second branch;

[0098] Enable at least one of the first measurement switch and the second measurement switch to charge the storage element using the leakage current from at least one disabled branch; and

[0099] Generate an output signal indicating a switch failure in response to the voltage of the storage element associated with the leakage current exceeding a reference voltage within a predetermined time period.

[0100] 13) The battery connection unit according to 12), wherein the controller is further configured to:

[0101] Generate the output signal indicating a switch failure in response to the rate of change of the voltage of the storage element associated with the leakage current exceeding a predetermined rate of change value.

[0102] 14) The battery connection unit according to 11) further includes:

[0103] A controller configured to:

[0104] Disable both the first branch and the second branch;

[0105] Disable the second measurement switch;

[0106] Enable the first measurement switch to charge the storage element using the leakage current from the disabled first branch; and

[0107] Generate a first output signal indicating a failure of the first branch switch in response to the voltage of the storage element exceeding a second reference voltage within a predetermined time period.

[0108] 15) The battery connection unit according to 11) further includes:

[0109] A controller configured to:

[0110] Disable one of the first branch and the second branch;

[0111] Enable the other of the first branch and the second branch;

[0112] Enable one of the first measurement switch and the second measurement switch to charge the storage element with the leakage current from the disabled branch; and

[0113] In response to the storage element voltage exceeding a second reference voltage within a predetermined time period, generate an output signal indicating a switch fault in the disabled branch associated with the enabled measurement switch.

[0114] 16) The battery connection unit according to 15), wherein the controller is further configured to: disable the other one of the first branch and the second branch;

[0115] Enable the previously disabled first branch or second branch;

[0116] Enable the other one of the first measurement switch and the second measurement switch to charge the storage element with the leakage current from the disabled branch; and

[0117] In response to the storage element voltage exceeding the second reference voltage within the predetermined time period, generate the output signal indicating a switch fault in the disabled branch.

[0118] 17) A method for monitoring leakage current of a power distribution system, comprising:

[0119] Provide a battery connection unit having a first branch switch and a second branch switch, the first branch switch being configured to enable / disable bidirectional current flow between a first battery and at least one of a second battery and a vehicle load, and the second branch switch being configured to enable / disable bidirectional current flow between the first battery and at least one of the second battery and the vehicle load;

[0120] Provide a monitoring circuit having a storage element, a first measurement switch, and a second measurement switch, the first measurement switch being connected between the first branch switch and the storage element to enable / disable charging of the storage element, and the second measurement switch being connected between the second branch switch and the storage element to enable / disable charging of the storage element;

[0121] Disable at least one of the first branch switch and the second branch switch;

[0122] Enable at least one of the first measurement switch and the second measurement switch to charge the storage element with the leakage current from at least one disabled branch switch; and

[0123] In response to the storage element voltage associated with the leakage current exceeding a reference voltage within a predetermined time period, generate an output signal indicating a switch fault.

[0124] 18) The method according to 17) further includes:

[0125] Disabling the first branch switch and the second branch switch; and

[0126] Enabling both the first measurement switch and the second measurement switch to charge the storage element with leakage current from the disabled first branch switch and the disabled second branch switch; and

[0127] Generating an output signal indicating a switch fault in response to the voltage of the storage element associated with the leakage current from the disabled first branch switch and the disabled second branch switch exceeding the reference voltage within the predetermined time period.

[0128] 19) The method according to 17) further includes:

[0129] Disabling one of the first branch switch and the second branch switch;

[0130] Enabling the other of the first branch switch and the second branch switch;

[0131] Enabling one of the first measurement switch and the second measurement switch to charge the storage element with leakage current from the disabled branch switch; and

[0132] Generating the output signal indicating a switch fault in the disabled branch in response to the voltage of the storage element exceeding the reference voltage within a second predetermined time period.

[0133] 20) The method according to 19) further includes:

[0134] Disabling the other of the first branch switch and the second branch switch;

[0135] Enabling the previously disabled first branch switch or second branch switch;

[0136] Enabling the other of the first measurement switch and the second measurement switch to charge the storage element with leakage current from the disabled branch switch; and

[0137] Generating the output signal indicating a switch fault in the disabled branch switch in response to the voltage of the storage element exceeding the reference voltage within the second predetermined time period.

Claims

1. A battery connection unit, comprising: A first branch adapted to connect a first battery to at least one of a second battery and a vehicle load, the first branch including at least one first branch switch to enable / disable current flow along the first branch; A second branch connected in parallel with the first branch, the second branch including at least one second branch switch to enable / disable current flow along the second branch; A storage element; A first measurement switch connected between the first branch and the storage element to enable / disable charging of the storage element; A second measurement switch connected between the second branch and the storage element to enable / disable charging of the storage element; And A processor programmed to: Disable at least one of the first branch and the second branch; Enable at least one of the first measurement switch and the second measurement switch to charge the storage element with leakage current from at least one disabled branch; And Generate an output signal indicating a switch failure in response to the voltage of the storage element associated with the leakage current exceeding a reference voltage within a predetermined period of time.

2. The battery connection unit according to claim 1, wherein, The at least one first branch switch includes a first switch and a second switch, and wherein the first measurement switch is connected between the first switch and the second switch.

3. The battery connection unit according to claim 2, wherein, The first switch and the second switch include metal-oxide-semiconductor field-effect transistors (MOSFETs) arranged in a common-source back-to-back configuration.

4. The battery connection unit according to claim 1, wherein, The at least one second branch switch includes a third switch and a fourth switch, and wherein the second measurement switch is connected between the third switch and the fourth switch.

5. The battery connection unit according to claim 4, wherein, The third switch and the fourth switch include metal-oxide-semiconductor field-effect transistors (MOSFETs) arranged in a common-source back-to-back configuration.

6. The battery connection unit according to claim 1 further includes a discharge switch configured to discharge the storage element when the discharge switch is enabled, wherein, The processor is further programmed to enable a discharge switch to release the energy stored in the storage element before enabling at least one of the first measurement switch and the second measurement switch.

7. The battery connection unit according to claim 1, wherein, The first branch is adapted to connect the first battery to the second battery, wherein the processor is further programmed to: Disable both the first branch and the second branch; Enable both the first measurement switch and the second measurement switch to charge the storage element with leakage current from the disabled first branch and the disabled second branch; and Generate the output signal indicating a switch failure in response to the voltage of the storage element associated with the leakage current from the disabled first branch and the disabled second branch exceeding the reference voltage within the predetermined period of time.

8. The battery connection unit according to claim 7, wherein, The processor is further programmed to: Disable the second measurement switch in response to generating the output signal indicating a switch failure; And Generate a first output signal indicating a first branch switch failure in response to the voltage of the storage element exceeding a second reference voltage within the predetermined period of time.

9. The battery connection unit according to claim 8, wherein, The processor is further programmed to: Disable the first measurement switch; Enable the second measurement switch to charge the storage element with the leakage current from the disabled second branch; And In response to the storage element voltage exceeding the second reference voltage within the predetermined time period, generate a second output signal indicating a second branch switch failure, wherein the second reference voltage is equal to half of the reference voltage.

10. A battery connection unit, comprising: A first branch adapted to connect a first battery to at least one of a second battery and a vehicle load, the first branch including: A first switch; and A second switch connected in series with the first switch along the first branch to enable / disable bidirectional current flow; A second branch connected in parallel with the first branch, the second branch including a third switch and a fourth switch connected in series along the second branch to enable / disable bidirectional current flow; A storage element; A first measurement switch connected between the first switch and the second switch of the first branch and the storage element to enable / disable charging of the storage element with the first branch leakage current; A second measurement switch connected between the third switch and the fourth switch of the second branch and the storage element to enable / disable charging of the storage element with the second branch leakage current; and A controller configured to generate an output signal indicating a switch failure in response to a storage element voltage associated with a leakage current exceeding a reference voltage within a predetermined time period.

11. The battery connection unit according to claim 10, wherein, The controller is further configured to: Disable at least one of the first branch and the second branch; and Enable at least one of the first measurement switch and the second measurement switch to charge the storage element with the leakage current from at least one disabled branch.

12. The battery connection unit according to claim 11, wherein, The controller is further configured to: Generate the output signal indicating a switch failure in response to a rate of change of the storage element voltage associated with the leakage current exceeding a predetermined rate of change value.

13. The battery connection unit according to claim 10, wherein, The controller is further configured to: Disable both the first branch and the second branch; Disable the second measurement switch; Enable the first measurement switch to charge the storage element with the leakage current from the disabled first branch; And In response to the storage element voltage exceeding the second reference voltage within the predetermined time period, generate a first output signal indicating a first branch switch failure.

14. The battery connection unit according to claim 10, wherein, The controller is further configured to: Disable one of the first branch and the second branch; Enable the other of the first branch and the second branch; Enable one of the first measurement switch and the second measurement switch to charge the storage element with the leakage current from the disabled branch; And In response to the storage element voltage exceeding the second reference voltage within the predetermined time period, generate an output signal indicating a switch failure in the disabled branch associated with the enabled measurement switch.

15. The battery connection unit according to claim 14, wherein, The controller is further configured to: Disable the other of the first branch and the second branch; Enable the previously disabled first branch or second branch; Enable the other one of the first measurement switch and the second measurement switch to charge the storage element with the leakage current from the disabled branch; And Generate the output signal indicating a switch failure in the disabled branch in response to the storage element voltage exceeding the second reference voltage within the predetermined time period.

16. A method for monitoring the leakage current of a power distribution system, comprising: Providing a battery connection unit having a first branch and a second branch, the second branch being connected in parallel with the first branch, wherein the first branch includes a first branch switch for enabling / disabling bidirectional current flow between a first battery and at least one of a second battery and a vehicle load, and wherein the second branch includes a second branch switch for enabling / disabling bidirectional current flow between the first battery and at least one of the second battery and the vehicle load; Providing a monitoring circuit having a storage element, a first measurement switch, and a second measurement switch, the first measurement switch being connected between the first branch switch and the storage element to enable / disable charging of the storage element, and the second measurement switch being connected between the second branch switch and the storage element to enable / disable charging of the storage element; Disable at least one of the first branch switch and the second branch switch; Enable at least one of the first measurement switch and the second measurement switch to charge the storage element with the leakage current from at least one disabled branch switch; And Generate an output signal indicating a switch failure in response to the storage element voltage associated with the leakage current exceeding a reference voltage within a predetermined time period.

17. The method according to claim 16, further comprising: Disable the first branch switch and the second branch switch; And Enable both the first measurement switch and the second measurement switch to charge the storage element with the leakage current from the disabled first branch switch and the disabled second branch switch; And Generate the output signal indicating a switch failure in response to the storage element voltage associated with the leakage current from the disabled first branch switch and the disabled second branch switch exceeding the reference voltage within the predetermined time period.

18. The method according to claim 16, further comprising: Disable one of the first branch switch and the second branch switch; Enable the other one of the first branch switch and the second branch switch; Enable one of the first measurement switch and the second measurement switch to charge the storage element with the leakage current from the disabled branch switch; And Generate the output signal indicating a switch failure in the disabled branch in response to the storage element voltage exceeding the reference voltage within a second predetermined time period.

19. The method according to claim 18, further comprising: Disable the other one of the first branch switch and the second branch switch; Enable the previously disabled first branch switch or second branch switch; Enable the other one of the first measurement switch and the second measurement switch to charge the storage element with the leakage current from the disabled branch switch; And In response to the voltage of the storage element exceeding the reference voltage within the second predetermined time period, generate the output signal indicating a switch fault in the disabled branch switch.

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