Adjustable active bleeder circuit for capacitor discharging application

Abstract

A battery disconnect unit includes: a switched high-voltage bus having a high-side conductor and a low-side conductor, a disconnect switch, and a semiconductor device. The disconnect switch is configured to selectively disconnect a terminal of a battery from one of the high-side conductor or the low-side conductor, and the semiconductor device is configured to operate in an ohmic region for selectively conducting current between the high-side conductor and the low-side conductor for selectively discharging a capacitor connected across the switched high- voltage bus. A high-voltage (HV) system includes a battery having a positive terminal and a negative terminal and defining a direct current (DC) voltage therebetween. The HV system also includes the battery disconnect unit for selectively disconnecting a terminal of the battery from a corresponding one of the high-side conductor or the low-side conductor, and for selectively discharging a capacitor connected across the switched high-voltage bus.

Description

Attorney Docket No. 25065-2236 (713455PCT)ADJUSTABLE ACTIVE BLEEDER CIRCUIT FOR CAPACITOR DISCHARGING APPLICATIONCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This PCT international patent application claims the benefit of U.S. Provisional Patent Application No. 63 / 733,529, filed December 13, 2024, the contents of which is incorporated herein by reference in its entirety.FIELD OF THE INVENTION

[0002] The present disclosure is related to bleeder circuits for discharging one or more capacitors in a high-voltage system.BACKGROUND OF THE INVENTION

[0003] This section provides background information related to the present disclosure which is not necessarily prior art.

[0004] Safety discharge circuits are crucial in electric vehicles (EVs) to ensure that high- voltage components are safely discharged when the vehicle is turned off or during maintenance or during vehicle accidents. A bleeder circuit, sometimes called safety discharge circuit, is required for any high voltage (HV) capacitor to discharge HV levels to a safe level (i.e., below 60 V) to prevent electric shocks in case of humans coming in touch with the vehicle or high voltage electrical components. High voltage capacitors are often used in power electronics systems, such as inverters and DC-DC converters, to smooth out and stabilize the direct current (DC) voltage by acting as a buffer, storing energy during fluctuations and releasing it when needed, effectively filtering out voltage ripples and protecting the system from sudden voltage spikes or surges. AAttorney Docket No. 25065-2236 (713455PCT) high voltage capacitor may be referred to as a DC link capacitor. The high voltage (HV) source, as an example a battery, is disconnected from the rest of the HV system via contactors / relays as part of the battery disconnect unit (BDU) before the discharging event occurs. In electric vehicles (EVs) there are different power converter units with HV capacitors. These converters typically contain a built-in bleeder circuit in passive and / or active discharge form connected in parallel to the capacitor. This is a critical functional safety feature that is required in EVs to prevent thermal events in accidents. Typical combined bleeder circuits within a HV circuit for discharging the system HV capacitor include an active discharge path and a passive discharge path. In the active discharge path, a bleeder resistor of tens to hundreds of watts and an electronic switch or relay connected in series with the bleeder resistor is provided. The switch is controlled by the vehicle’s control system to ensure the discharge process occurs only when it is safe and required. In the passive discharge path, a second resistor with larger resistance is provided in parallel to the bleeder resistor and the switch or the HV capacitor. This allows a redundant path to slowly discharge the HV capacitor in case of a failure of the active bleeder circuit or in any situation where a fast discharge is not required. Proper thermal management is necessary to ensure that the resistor does not overheat during the discharge process. This may include heat sinks or other cooling mechanisms. The bleeder resistor is usually bulky and when combined with an electronic switch or relay the components required occupy a large space in the system.

[0005] As an example, when a HV capacitor is placed in parallel with a bleeder resistor Rb, five time-constants (5T) are required for the bleeder resistor to discharge to near zero. The size of the discharging bleeder resistor, as well as the required peak power (Ppk) and average power (Pavg) based on the desired discharge time (tdischai-g^) and corresponding discharged energy, and can be calculated as follows:Attorney Docket No. 25065-2236 (713455PCT)T — Rbx CHV

[0006] As the functionality of the bleeder resistor is dictated by its physical and functional characteristics, universal usage across a variety of applications may not be possible and it must be appropriately designed for each application as indicated.

[0007] Therefore, there is a need to provide an improved bleeder circuit with a reduced number of components, a smaller overall package, and utilizes the ability provide adjustability to meet a range of applications and disconnect conditions.SUMMARY OF INVENTION

[0008] The present disclosure provides a battery disconnect unit. The battery disconnect unit includes: a switched high-voltage bus, a disconnect switch, and a semiconductor device. The switched high-voltage bus includes a high-side conductor and a low-side conductor. The disconnect switch is configured to selectively disconnect a terminal of a battery from one of the high-side conductor or the low-side conductor. The semiconductor device is configured to operate in an ohmic region for selectively conducting current between the high-side conductor and the low-side conductor for selectively discharging a capacitor connected across the switched high- voltage bus.Attorney Docket No. 25065-2236 (713455PCT)

[0009] The present disclosure also provides a high-voltage system. The high-voltage system includes a battery and a battery disconnect unit. The battery has a positive terminal and a negative terminal and defining a direct current (DC) voltage therebetween. The battery disconnect unit includes: a switched high-voltage bus, a disconnect switch, and a semiconductor device. The switched high-voltage bus includes a high-side conductor and a low-side conductor. The disconnect switch is configured to selectively disconnect one of the positive terminal or the negative terminal of the battery from a corresponding one of the high-side conductor or the low- side conductor, and the semiconductor device is configured to operate in an ohmic region for selectively conducting current between the high-side conductor and the low-side conductor for selectively discharging a capacitor connected across the switched high-voltage bus.

[0010] These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description and appending drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The drawings described herein are for illustrative purposes only of selected embodiments and are not intended to limit the scope of the present disclosure. The inventive concepts associated with the present disclosure will be more readily understood by reference to the following description in combination with the accompanying drawings wherein:

[0012] FIG. 1 provides a diagram of a high voltage system utilizing an adjustable bleeder circuit;

[0013] FIG. 2 provides an example MOSFET characteristic curve used in the adjustable bleeder circuit; andAttorney Docket No. 25065-2236 (713455PCT)

[0014] FIG. 3 includes the adjustable discharge bleeder circuit within a typical battery disconnect unit in a high voltage system.DESCRIPTION OF THE ENABLING EMBODIMENTS

[0015] The present disclosure is related to providing an active adjustable bleeder circuit for use in a high voltage system. More specifically, the active adjustable bleeder circuit utilizes a semiconductor that is controlled to operate in its ohmic range to provide an adjustable resistance to discharge a capacitor. The semiconductor of the adjustable bleeder circuit may be a MOSFET, which can be precisely controlled by adjusting the gate-to-source voltage to influence the equivalent drain-to-source resistance value to provide a configurable discharge time. The active adjustable bleeder circuit may be utilized in a battery disconnect unit of a high voltage system.

[0016] An adjustable active bleeder circuit, which may be utilized with or without a passive bleeder circuit, is proposed for capacitor discharge in high voltage applications utilized in EVs. The adjustable active bleeder principle is based on variable resistance control, which adjusts according to the required discharge rate for different conditions and depending on the size of the HV DC-link capacitors. These operational scenarios include but are not limited to when the vehicle is powered off, when the vehicle is involved in a collision that compromises the HV system, during vehicle servicing, or when someone inadvertently comes into contact with the HV system. The required discharge time in a crash condition differs from that in service mode, therefore it would be beneficial to adjust the discharge rate differently between the two scenarios. Additionally, the discharge time of the HV capacitor depends on the application and the total capacitance used. Larger capacitance is utilized in a large inverter HV DC-link capacitor when compared to the smaller capacitance output capacitor of an On-Board Charger (OBC) or the input capacitor of anAttorney Docket No. 25065-2236 (713455PCT)Auxiliary Power Module (APM). An auxiliary power module may be a DC-DC converter stepping down high voltage to low voltage. Power converters of different ratings require HV capacitors of varying sizes, which in turn necessitate different bleeder circuit designs. Active discharging usually occurs in power electronics to leverage integrated circuits (ICs) and control signals, as seen in inverters, OBCs, APMs, etc., while the more cost-effective passive circuit is typically placed in parallel and close to the HV capacitor. The typical discharge time required by the active discharge circuit ranges from tens to hundreds of milliseconds, whereas the typical discharge time for the passive circuit is conducted over a much longer time, often measured in minutes.

[0017] The present disclosure provides an active adjustable discharge circuit connected in parallel with a capacitor. The active discharge circuit comprises a semiconductor switch having a drain, a source, and a gate connection. The drain is connected to a positive terminal, the source is connected to a negative terminal, and an external trigger is connected to the gate connection of the semiconductor switch to operate the semiconductor switch in an ohmic region when a discharge of the capacitor is required.

[0018] The present disclosure also provides a high voltage system that includes: a battery, a battery disconnect unit, and an electrical subsystem connected together via an electrical circuit which includes a capacitor connected between the positive and negative terminals, a battery disconnect device including a pair of switches capable of disconnecting the positive terminal and negative terminals from the battery and an active adjustable discharge device provided by a semiconductor connected in parallel with said capacitor where the semiconductor is operated in an ohmic region providing a controllable discharge of the capacitor when required.

[0019] FIG. 1 provides a diagram of a high voltage system 10 including a high voltage (HV) battery 12, a battery disconnect unit (BDU) 14, and an HV circuit 16. The HV battery 12 hasAttorney Docket No. 25065-2236 (713455PCT) a positive terminal (+) and a negative terminal (-) and defines a direct current (DC) voltage therebetween. The HV battery 12 may operate at a nominal voltage that is greater than 50 volts direct current (VDC). For example, the HV battery 12 may define a nominal voltage of 100 VDC, 400 VDC or 800 VDC between the positive terminal (+) and the negative terminal (-). The BDU 14 defines a switched HV bus 26H, 26L with a high-side conductor 26H and a low-side conductor 26L for supplying power to the HV circuit 16. The switched HV bus 26H, 26L may define a direct current (DC) high-voltage, such as 400VDC or 800VDC. The HV circuit 16 includes one or more HV components or HV subsystems 18, such as an inverter, onboard charger (OBC), or auxiliary power module (APM), in conjunction with a HV capacitor CHV connected between the high-side conductor 26H and the low-side conductor 26L. Optionally, a passive resistor R1 may be provided in parallel to HV capacitor CHV. The passive resistor R1 may discharge the HV capacitor CHV over an extended period of time that is longer than the configurable discharge time tdischarge provided by the adjustable bleeder circuit 20.

[0020] The HV system 10 of the present disclosure includes an adjustable bleeder circuit 20 that is configured to selectively conduct current between the high-side conductor 26H and the low-side conductor 26L for discharging the HV capacitor CHV. The adjustable bleeder circuit 20 may be provided within the BDU 14. The adjustable bleeder circuit 20 utilizes a semiconductor device QI that has the ability to control a flow of electrical current between the high-side conductor 26H and the low-side conductor 26L by applying a control signal to a bleed control node 21. The adjustable bleeder circuit 20 may, thereby, conduct a regulated current between the high-side conductor 26H and the low-side conductor 26L for discharging the HV capacitor CHV over a given time period. The Semiconductor device QI may be a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET). The semiconductor device QI defines a drain terminal (D), a sourceAttorney Docket No. 25065-2236 (713455PCT) terminal (S), and a gate terminal (G). The drain terminal (D) is connected to the high-side conductor 26H, the source terminal (S) is connected to the low-side conductor 26L, and the gate terminal (G) is connected to the bleed control node 21.

[0021] The BDU 14 may include a microcontroller unit (MCU) 22 which receives a trigger signal 23 from an external source to control the semiconductor device QI via the gate terminal (G). The BDU 14 also includes a first disconnect switch SI that is configured to selectively disconnect a positive terminal of the HV battery 12 from the high-side conductor 26H. The BDU 14 also includes a second disconnect switch S2 that is configured to selectively disconnect a negative terminal of the HV battery 12 from the low-side conductor 26L. The MCU 22 may also control operation of the first disconnect switch SI and the second disconnect switch S2 for selectively disconnecting the HV battery 12 from the switched HV bus 26H, 26L. The disconnect switches SI, S2 may be called line contactors and may be implemented using contactor devices that physically connect and disconnect an electrical path for selectively conducting electrical current therethrough. The disconnect switches SI, S2 may be electrically actuated, such as by an electromagnetic coil that uses AC or DC current for selectively disconnecting the HV battery 12 from the switched HV bus 26H, 26L.

[0022] A configurable discharge time tdischarge for discharging the HV capacitor CHI / may be controlled by the semiconductor device QI in an on-demand manner. The semiconductor device QI may be, for example, a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET). A configurable discharge time tdischarge may be implemented solely through software control adjustments by the MCU 22, without hardware modifications. This provides a scalable solution which is preferred to take advantage of the economy of scale for volume production scenarios for cost reduction, meaning the ability to use one design for multiple applications.Attorney Docket No. 25065-2236 (713455PCT)

[0023] The implementation of a configurable discharge time tdischarge can be achieved using a Digital-to-Analog Converter (DAC) pin of the MCU 22, based on predefined discharge scenarios. Alternatively, a hybrid analog-digital approach can be used, where the voltage is adjusted using analog circuits while the control command is provided by the MCU 22. An example of this hybrid method involves using a PWM signal from the MCU 22, combined with analog filtering, to convert the PWM signal into DC for VGS (Gate-to- Source Voltage) control. Alternatively, a sole analog implementation may be used where an analog control signal 24 is directly supplied to the bleed control node 21. VGS control is the process of using a voltage signal between the gate and source of a metal-oxide semiconductor field-effect transistor (MOSFET) to control the flow of electricity between the drain (D) and source (S) terminals. In all cases, the trigger signal 23 and / or the analog control signal 24 can originate from an external source, such as a Vehicle Control Unit (VCU) or any other vehicle control module. The bleed control node 21 can also be connected to a secondary signal, such as a safety disconnect switch, for emergency situations. It is worth noting that the requirement to discharge the HV capacitor CHV to below the safe level, such as 60V, is typically defined by functional safety standards and / or OEM-specific requirements.

[0024] FIG. 2 is an example MOSFET characteristic curve 30, graphically explaining how current (IDS) changes with gate-to-source voltage (VGS) and drain-to-source voltage (VDS). Characteristic curve 30 shows three regions of operation, the ohmic region 32, the non-linear region 34, and the linear region 36. In the initial portion of the curve the MOSFET is operating in the ohmic region 32 and will behave like a resistor with a relatively linear relationship between drain current (ID) and drain-source voltage (VDS). As VDS increases further, the MOSFET will enter a non-linear region 34 where the current starts to deviate from a linear relationship and curvesAttorney Docket No. 25065-2236 (713455PCT) upwards due to the "pinch-off effect, where the channel starts to narrow near the drain. Once pinch-off is fully established, the current becomes nearly constant with increasing VDS in a linear region 36, signifying the saturation region where the MOSFET acts like a current source.

[0025] The variable discharge path resistance of the MOSFET is achieved based on operation in the ohmic region 32 as shown. Operating in the ohmic region 32 can be precisely controlled by adjusting the gate-to-source voltage VGS to change the equivalent drain-to-source resistance value for a configurable discharge pattern. Typical current-voltage (IV) characteristics curves for a MOSFET with respect to different gate-to-source voltages (i.e., VGSI, VGS2, VGS3, etc.) are demonstrated in FIG. 2. It should be noted that for typical applications, MOSFETs are used in the linear or saturation region where the conduction channel is fully open and there is minimal resistance between the drain and the source, known as the ON drain-to-source resistance (i.e., R- DS(ON)). The MOSFET remains in the saturation region until close to the drain-to-source breakdown voltage (i.e., BVDSS).

[0026] The present disclosure provides a MOSFET as the semiconductor device QI, for its wide application and well known ohmic behavior. However, the semiconductor device QI may include a different semiconductor device with ohmic operation, where a current through the semiconductor device QI increases linearly with increasing voltage. However the semiconductor device QI must have a blocking voltage rating that is sufficient for the desired application. Some alternatives for the semiconductor device QI include Junction Field-Effect Transistors (JFETs) and High Electron Mobility Transistors (HEMTs), which also demonstrate ohmic operation. Bipolar Junction Transistors (BJTs) which have a forward-active mode where the collector current is controlled linearly by the base current has a somewhat-analogous ohmic behavior as found in Field-Effect Transistors (FETs). However, the analogy isn't perfect because BJTs do not have aAttorney Docket No. 25065-2236 (713455PCT) clear ohmic region in the same sense as FETs. In each of these cases, the ohmic or linear region refers to a part of the device's operation where the output current is linearly dependent on the input signal (voltage or current), and the device behaves similar to a resistor.

[0027] FIG. 3 illustrates the proposed HV system 10 with an adjustable bleeder circuit 20 within a battery disconnect unit (BDU) 14 of an electric vehicle 8. The HV system 10 uses a single BDU 14 to disconnect several HV subsystems 18A, 18B, 18C, 19A, 19B, 19C. In some embodiments, and as shown on FIG. 3, the HV system 10 also includes a plurality of the HV subsystems 18A, 18B, 18C, 19A, 19B, 19C are each connected to the switched HV bus 26H, 26L via a corresponding one of a plurality of parallel branches. In some embodiments, and as also shown on FIG. 3, the HV capacitor is formed by a plurality of branch capacitors C 1 , C2, C3, which are each connected across a corresponding branch of the plurality of parallel branches.

[0028] As shown on FIG. 3, the HV circuit 16 includes a first HV subsystem 18A, 19A with an auxiliary power module (APM) 18A configured to supply power to one or more auxiliary low-voltage (LV) loads 19A, such as 12VDC loads from the switched HV bus 26H, 26L. The APM 18A may include a DC / DC converter for generating low-voltage DC power using HV DC power from the switched HV bus 26H, 26L. A first fuse 50A limits current between the high-side conductor 26H of the switched HV bus 26H, 26L and a first HV supply node 51 A connected to the APM 18 A. A first HV capacitor Cl is connected between the first HV supply node 51A and the low-side conductor 26L of the switched HV bus 26H, 26L.

[0029] The HV circuit 16 also includes a second HV subsystem 18B, 19B with an onboard charger (OBC) 18B configured to generate HV DC power using alternating current (AC) power received from an AC wallbox 19B, such single-phase (IP) or 3-Phase (3P) AC power. The OBC 18B may include a rectifier for supplying a regulated HV DC to the switched HV bus 26H, 26L,Attorney Docket No. 25065-2236 (713455PCT) via a second HV supply node 5 IB. A second fuse 50B limits current between the second HV supply node 5 IB and the high-side conductor 26H of the switched HV bus 26H, 26L. A second HV capacitor C2 is connected between the second HV supply node 5 IB and the low-side conductor 26L of the switched HV bus 26H, 26L.

[0030] The HV circuit 16 also includes a third HV subsystem 18C, 19C with an inverter 18C configured to supply power to a motor 19C, using power from the switched HV bus 26H, 26L. The inverter 18C may generate AC power at a variable voltage and / or frequency for controlling speed and / or torque produced by the motor 19C, using HV DC power from the switched HV bus 26H, 26L. A third fuse 50C limits current between the high-side conductor 26H of the switched HV bus 26H, 26L and a third HV supply node 51C connected to the inverter 18C. A third HV capacitor C3 is connected between the third HV supply node 51C and the low-side conductor 26L of the switched HV bus 26H, 26L.

[0031] In the embodiment of FIG. 3, the first HV capacitor Cl, the second HV capacitor C2, and the third HV capacitor C3, each function as the HV capacitor CHV. However, other arrangements may include one or more other HV capacitors CHV connected directly across the switched HV bus 26H, 26L and / or to branch circuits powered by the switched HV bus 26H, 26L.

[0032] The BDU 14 includes protection circuits for short circuit and overcurrent protection, such as a fourth fuse 50D, which may be a melting fuse, and / or a pyro-mechanical fuse 52, to prevent battery thermal events. Additionally, a pre-charge circuit S3, R2 is included to charge the HV capacitors Cl , C2, C3 to a desired voltage before closing the first disconnect switch S 1. The pre-charge circuit S3, R2 includes a third switch S3 in series with a second resistor R2 for limiting current therethrough.Attorney Docket No. 25065-2236 (713455PCT)

[0033] As previously mentioned, integrating the adjustable bleeder circuit 20 within the BDU 14 enables the active discharge of all HV capacitors Cl, C2, C3 across various units (e.g., inverter, OBC, APM) during emergency safety-critical situations. This discharge process can be adjusted to the total DC-link capacitance size for different vehicles via software control from MCU 22.

[0034] As previously indicated, the MCU 22 may be eliminated and an analog control signal 24 may directly influence the discharge process in an optional arrangement. It is important to note that the disclosed adjustable bleeder circuit 20 is not limited to automotive applications as it can also be utilized in other HV applications for discharging HV capacitors inside or outside any Power Distribution Unit (PDU) with HV disconnects. Alternatively, the adjustable bleeder circuit 20 of the invention may be used in conjunction with standalone systems utilizing HV capacitors. As an example, the adjustable bleeder circuit 20 may be utilized with an on-board charger (OBC) powered by an AC power source where the adjustable bleeder circuit 20 would be located between the OBC and the high voltage DC battery parallel to the C-HV. The adjustable bleeder circuit 20 proposed may also be used in a standalone DC-DC converter, inverter or in a combined X-in-1 solution where an inverter, OBC, or APM / DC-DC are combined. In the X-in-1 solution only one adjustable bleeder circuit 20 would be needed as a single C-HV is shared in a similar arrangement, as previous described for usage in a BDU 14.

[0035] The present disclosure provides a battery disconnect unit. The battery disconnect unit includes: a switched high-voltage bus, a disconnect switch, and a semiconductor device. The switched high-voltage bus includes a high-side conductor and a low-side conductor. The disconnect switch is configured to selectively disconnect a terminal of a battery from one of the high-side conductor or the low-side conductor. The semiconductor device is configured to operateAttorney Docket No. 25065-2236 (713455PCT) in an ohmic region for selectively conducting current between the high-side conductor and the low-side conductor for selectively discharging a capacitor connected across the switched high- voltage bus.

[0036] In some embodiments, the semiconductor device includes a metal-oxide- semiconductor field-effect transistor (MOSFET) device.

[0037] In some embodiments, the battery disconnect unit defines a bleed control node connected to a terminal of the semiconductor device, and wherein the semiconductor device is configured operate in the ohmic region in response to a control signal on the bleed control node.

[0038] In some embodiments, the battery disconnect unit further includes a second disconnect switch configured to selectively disconnect a second terminal of the battery from another one of the high-side conductor or the low-side conductor.

[0039] In some embodiments, the battery disconnect unit further includes a pre-charge circuit for pre-charging the capacitor connected across the switched high-voltage bus. The pre-charge circuit may include a switch and a resistor in a series arrangement and which is disposed in parallel with the disconnect switch for conducting a limited current therethrough.

[0040] In some embodiments, a vehicle, such as an electrified vehicle, includes the battery disconnect unit of the present disclosure.

[0041] The present disclosure also provides a high-voltage system. The high-voltage system includes a battery and a battery disconnect unit. The battery has a positive terminal and a negative terminal and defining a direct current (DC) voltage therebetween. The battery disconnect unit includes: a switched high-voltage bus, a disconnect switch, and a semiconductor device. The switched high-voltage bus includes a high-side conductor and a low-side conductor. The disconnect switch is configured to selectively disconnect one of the positive terminal or theAttorney Docket No. 25065-2236 (713455PCT) negative terminal of the battery from a corresponding one of the high-side conductor or the low- side conductor, and the semiconductor device is configured to operate in an ohmic region for selectively conducting current between the high-side conductor and the low-side conductor for selectively discharging a capacitor connected across the switched high-voltage bus.

[0042] In some embodiments, the semiconductor device includes a metal-oxide- semiconductor field-effect transistor (MOSFET) device.

[0043] In some embodiments, the battery disconnect unit defines a bleed control node connected to a terminal of the semiconductor device, the semiconductor device is configured operate in the ohmic region in response to a control signal on the bleed control node, and the high- voltage system further includes a microcontroller unit configured to apply the control signal to the bleed control node in response to an external trigger.

[0044] In some embodiments, the battery disconnect unit defines a bleed control node connected to a terminal of the semiconductor device, the semiconductor device is configured operate in the ohmic region in response to a control signal on the bleed control node, and the high- voltage system further includes an analog control signal directly supplied to the bleed control node for controlling a current conducted by the semiconductor device between the high-side conductor and the low-side conductor.

[0045] In some embodiments, the battery disconnect unit further includes: a pre-charge circuit for pre-charging the capacitor connected across the switched high-voltage bus, and the pre-charge circuit includes a switch and a resistor in a series arrangement and which is disposed in parallel with the disconnect switch for conducting a limited current therethrough.

[0046] In some embodiments, the high-voltage system further includes a plurality of subsystems each connected to the switched high-voltage bus via a corresponding one of a pluralityAttorney Docket No. 25065-2236 (713455PCT) of parallel branches, and the capacitor connected across the switched high-voltage bus includes a plurality of branch capacitors each connected across a corresponding branch of the plurality of parallel branches.

[0047] In some embodiments, the plurality of subsystems include at least one of: an inverter for supplying power to a motor, an auxiliary power module (APM) configured to supply power to one or more auxiliary low-voltage loads, and a charger configured to supply power to the switched high-voltage bus for charging the battery.

[0048] In some embodiments, the plurality of subsystems include a first load and a second load connected across two branches of the plurality of parallel branches, respectively.

[0049] In some embodiments, the plurality of subsystems include a charger connected to a branch of the plurality of parallel branches, and wherein the charger is configured to supply power to the switched high-voltage bus for charging the battery.

[0050] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of disclosure.

Claims

Attorney Docket No. 25065-2236 (713455PCT)CLAIMSWhat is claimed is:

1. A battery disconnect unit, comprising: a switched high-voltage bus including a high-side conductor and a low-side conductor; a disconnect switch configured to selectively disconnect a terminal of a battery from one of the high-side conductor or the low-side conductor; and a semiconductor device configured to operate in an ohmic region for selectively conducting current between the high-side conductor and the low-side conductor for selectively discharging a capacitor connected across the switched high-voltage bus.

2. The battery disconnect unit of Claim 1, wherein the semiconductor device includes a metal-oxide-semiconductor field-effect transistor (MOSFET) device.

3. The battery disconnect unit of Claim 1, wherein the battery disconnect unit defines a bleed control node connected to a terminal of the semiconductor device, and wherein the semiconductor device is configured operate in the ohmic region in response to a control signal on the bleed control node.

4. The battery disconnect unit of Claim 1, further including a second disconnect switch configured to selectively disconnect a second terminal of the battery from another one of the high-side conductor or the low-side conductor.Attorney Docket No. 25065-2236 (713455PCT)5. The battery disconnect unit of Claim 1 , further including a pre-charge circuit for precharging the capacitor connected across the switched high-voltage bus, wherein the pre-charge circuit includes a switch and a resistor in a series arrangement and which is disposed in parallel with the disconnect switch for conducting a limited current therethrough.

6. A vehicle including the battery disconnect unit of Claim 1.

7. A high-voltage system, comprising: a battery having a positive terminal and a negative terminal and defining a direct current (DC) voltage therebetween; and a battery disconnect unit including: a switched high-voltage bus including a high-side conductor and a low-side conductor; a disconnect switch configured to selectively disconnect one of the positive terminal or the negative terminal of the battery from a corresponding one of the high-side conductor or the low- si de conductor; and a semiconductor device configured to operate in an ohmic region for selectively conducting current between the high-side conductor and the low-side conductor for selectively discharging a capacitor connected across the switched high-voltage bus.

8. The high-voltage system of Claim 7, wherein the semiconductor device includes a metal - oxide-semiconductor field-effect transistor (MOSFET) device.Attorney Docket No. 25065-2236 (713455PCT)9. The high-voltage system of Claim 7, wherein the battery disconnect unit defines a bleed control node connected to a terminal of the semiconductor device, wherein the semiconductor device is configured operate in the ohmic region in response to a control signal on the bleed control node, and wherein the high-voltage system further includes a microcontroller unit configured to apply the control signal to the bleed control node in response to an external trigger.

10. The high-voltage system of Claim 7, wherein the battery disconnect unit defines a bleed control node connected to a terminal of the semiconductor device, wherein the semiconductor device is configured operate in the ohmic region in response to a control signal on the bleed control node, and wherein the high-voltage system further includes an analog control signal directly supplied to the bleed control node for controlling a current conducted by the semiconductor device between the high-side conductor and the low-side conductor.

11. The high-voltage system of Claim 7, wherein the battery disconnect unit further includes: a pre-charge circuit for pre-charging the capacitor connected across the switched high-voltage bus, wherein the pre-charge circuit includes a switch and a resistor in a series arrangement and which is disposed in parallel with the disconnect switch for conducting a limited current therethrough.Attorney Docket No. 25065-2236 (713455PCT)12. The high-voltage system of Claim 7, further including: a plurality of subsystems each connected to the switched high-voltage bus via a corresponding one of a plurality of parallel branches, wherein the capacitor connected across the switched high-voltage bus includes a plurality of branch capacitors each connected across a corresponding branch of the plurality of parallel branches.

13. The high-voltage system of Claim 12, wherein the plurality of subsystems include at least one of: an inverter for supplying power to a motor, an auxiliary power module (APM) configured to supply power to one or more auxiliary low-voltage loads, and a charger configured to supply power to the switched high-voltage bus for charging the battery.

14. The high-voltage system of Claim 12, wherein the plurality of subsystems include a first load and a second load connected across two branches of the plurality of parallel branches, respectively.

15. The high-voltage system of Claim 12, wherein the plurality of subsystems include a charger connected to a branch of the plurality of parallel branches, and wherein the charger is configured to supply power to the switched high-voltage bus for charging the battery.

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