Precharge Short Circuit Detection

Abstract

To provide a solid state battery disconnect and protection circuit, including a pre-charge control function.SOLUTION: An adaptive pre-charge control circuit 108 includes a high-voltage switch 207 coupled between an electric battery 102 and a DC link capacitor 106 of an electric vehicle, where the electric vehicle is powered by the electric battery. The control circuit 108 issues a pulse width modulated (PWM) signal to generate a current profile, where every other pulse exceeds a predefined limit, monitors the current profile during pre-charging, and determines that an overcurrent fault exists when two consecutive pulses exceed the predefined limit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION Embodiments of the present disclosure relate to a solid-state battery disconnect and protection circuit that includes a pre-charge control function. [Background technology]

[0002] Pre-charge circuits are used in high voltage DC applications with capacitive loads that can cause high inrush currents at power-on. Pre-charging the power line voltage is a standby mode that limits the inrush current. The pre-charge circuit thus prevents damage to system components by blocking high amperage current spikes.

[0003] High voltage systems with large capacitive loads can be exposed to high currents when first powered up, which, if not limited, can cause significant stress or damage to system components, including but not limited to, causing contactors to weld closed.

[0004] In electric vehicle applications, battery disconnect is implemented using a contactor, overcurrent protection is implemented with a combination of the same contactor and additional protection elements such as fuses or pyrofuses controlled by specific circuitry, and pre-charge control is implemented with additional dedicated circuitry.

[0005] In electric vehicle applications, a large capacitive load is the DC link in the electric motor. The "DC link capacitor" is actually the sum of several parallel capacitors in sub-units within the electric vehicle: one for the electric motor, one for the air conditioning compressor, one for window enabling, etc.

[0006] Pre-charging of the DC link capacitor occurs at each vehicle start. Battery voltage can vary at each vehicle start, depending on the battery's state of charge. Therefore, the battery voltage can be anywhere within the battery's operating range, for example, 550V to 800V in an 800V battery system. The pre-charging circuit limits inrush current and slowly charges the downstream DC link capacitor. When the DC link capacitor voltage approaches that of the battery, the main switch can be closed. Thus, the pre-charging circuit allows current to flow in a controlled manner during vehicle start-up.

[0007] A pre-charging circuit in an electric vehicle consists of an auxiliary switch in series with a large resistor and in parallel with the main switch to control the inrush current flowing into the vehicle during start-up. The main switch is open and the auxiliary switch is closed, allowing the DC link capacitor to charge at a slow rate as determined by the resistor. Once the DC link capacitor is sufficiently charged (so that its voltage approaches that of the battery), the main switch is fully closed and the battery can safely power the vehicle.

[0008] However, pre-charging systems based on pulse-width modulation (PWM) control typically operate above nominal current for fast pre-charging functionality, making it difficult to distinguish between actual over-current fault conditions in this use case.

[0009] The present improvements may be useful with regard to these and other considerations. Summary of the Invention

[0010] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to aid in determining the scope of the claimed subject matter.

[0011] In one approach, an adaptive pre-charge control circuit for use in a solid-state battery disconnection and protection system may include a high-voltage switch coupled between an electric battery and a DC link capacitor of an electric vehicle, where the electric vehicle is powered by the electric battery, and a control circuit. The control circuit may be operable to emit a pulse width modulated (PWM) signal to generate a current profile, where every other pulse exceeds a predefined limit. The control circuit may further monitor the current profile during pre-charge and determine that an overcurrent fault exists when two consecutive pulses exceed the predefined limit.

[0012] In another approach, an adaptive pre-charge control circuit for use in a solid-state battery disconnection and protection system may include a high voltage switch coupled between an electric battery and a DC link capacitor of an electric vehicle, where the electric vehicle is powered by the electric battery, and a control circuit. The control circuit emits a pulse width modulated (PWM) signal to generate a current profile to regulate a voltage V of the DC link capacitor during pre-charge. out and may be operable to determine that an overcurrent fault exists if the voltage increase is not positive after applying the pulse. [Brief explanation of the drawings]

[0013] The accompanying drawings illustrate exemplary approaches to the disclosed embodiments currently contemplated for practical application of the principles thereof.

[0014] [Figure 1] FIG. 1 illustrates an adaptive pre-charge control circuit for use in an electric vehicle system, according to an exemplary embodiment.

[0015] [Figure 2] 2 illustrates the operating principle of pulse width modulation used by the adaptive pre-charge control circuit of FIG. 1, according to an exemplary embodiment.

[0016] [Figure 3] 2 illustrates the operating principle of pulse width modulation used by the adaptive pre-charge control circuit of FIG. 1, according to an exemplary embodiment.

[0017] The drawings are not necessarily to scale. The drawings are merely representational and are not intended to portray specific parameters of the present disclosure. The drawings are intended to illustrate exemplary embodiments of the present disclosure and therefore should not be considered limiting in scope. In the drawings, like reference numerals represent like elements. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present disclosure will now proceed with reference to the accompanying drawings, in which various approaches are shown. It should be understood, however, that a reusable snap-in fitting may be embodied in many different forms and should not be construed as limited to the approaches set forth herein. Rather, these approaches are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0019] An adaptive pre-charge control circuit is disclosed for providing pre-charging capability in an electric vehicle. The adaptive pre-charge control circuit is disposed between an electric battery that supplies power to the electric vehicle and a load on the electric vehicle. The voltage of a DC link capacitor, which represents a capacitor of the vehicle load, can be modified by issuing a pulse-width modulated signal to a high-voltage switch. When the voltage of the DC link capacitor approaches that of the electric battery, the high-voltage switch turns on, allowing current to be safely delivered to the load. The adaptive pre-charge control circuit includes overvoltage protection and current limiting functions. As further described herein, embodiments of the present disclosure can reliably detect overcurrent fault conditions in a fast PWM-based pre-charge function using a defined current pattern (e.g., one current pulse above an overcurrent threshold, one current pulse below an overcurrent threshold) and / or output voltage measurements.

[0020] FIG. 1 is a representative diagram of an adaptive pre-charge control circuit 108 for providing pre-charge capability in a solid-state battery disconnection and protection system 100, according to an exemplary embodiment. The solid-state battery disconnection and protection system 100 is comprised of an electric vehicle (EV) battery 102, a load 104, and a DC link capacitor 106, with the adaptive pre-charge control circuit 108 disposed between the EV battery 102 and the load 104. Primarily, the load 104 is the EV motor of the electric vehicle, but the load also includes other powered components in the electric vehicle, such as an air conditioning compressor, window enabling motors, etc. Each subunit in the vehicle has an input capacitance, and the number of individual capacitors and subunits is unknown. The aggregate of the individual capacitors represents a DC link capacitance (C DC )

[0021] The adaptive pre-charge control circuit 108 is a solid-state battery disconnection and protection circuit featuring a high-voltage bidirectional switch circuit 116, or simply high-voltage switch 116, and a control block 124. The solid-state battery disconnection and protection circuit uses a microprocessor or microcontroller coupled to a current sensor to sample waveforms and detect any overcurrent scenarios. The solid-state battery disconnection and protection circuit has a very fast response time compared to traditional circuit breakers. The high-voltage switch 116 of the adaptive pre-charge control circuit 108 turns on (closed) or off (open) to control (allow or prevent) current flow between the EV battery 102 and the load 104. In an exemplary embodiment, the control block 124 issues a PWM signal 210 to the high-voltage switch 116, causing the switch 202 therein to turn on and off at a rate based on the duty cycle of the PWM signal. The on / off rate, or the number of switching events per time, is defined by the PWM switching frequency. The duty cycle defines the ratio between the on-time and the switching period.

[0022] Voltage V of EV battery 102 battand the voltage V of the DC link capacitor 106 out In an exemplary embodiment, the adaptive pre-charge control circuit 108 is designed to allow slow charging of the DC link capacitor 106 until the voltage of the DC link capacitor 106 approaches the voltage of the EV battery 102. V out and V batt V is the predefined difference between diff When V reaches V, the high voltage switch 116 turns on (closes), allowing current to flow freely between the EV battery 102 and the load 104. In this way, the EV battery 102 can safely power the load. Mathematically, V batt -V out ≦V diff If this occurs, the switch will remain closed until the electric vehicle is turned off.

[0023] The control block 124 features a microprocessor 208 and three analog-to-digital converters (ADCs) 204, 206, and 214. In other embodiments, the control block 214 may be an equivalent integrated circuit. The ADC 204 converts the battery voltage V batt while the ADC206 measures the output voltage V out Before any calculations can be made, the microprocessor 208 measures the battery voltage V batt and output voltage V out ADC 204 measures the voltage and converts it to a digital value, while ADC 206 measures the current. Microprocessor 208 then reads these results and calculates the voltage difference V diff Additionally, the microprocessor 208 generates a PWM pattern to turn the switch 202 on and off. The control block 124 also receives the input V batt current measurement 118 and voltage measurement 128 at the output V out1. In an exemplary embodiment, the logic and gate drives of the adaptive pre-charge control circuit 108 cause the issuance of a PWM signal 210 to the high-voltage switch 116. The PWM signal 210 enables the high-voltage switch 202 to turn on or off, thereby enabling or preventing current flow between the EV battery 102 and the DC link capacitor 106. The adaptive pre-charge control circuit 108 thus implements pre-charge control using the PWM control signal to control the pulse width profile to control the current. The logic and gate drives 122 of the control block 124 are connected to a control interface 126, which may be a wired or wireless connection.

[0024] In an exemplary embodiment, the PWM signal 210 of the adaptive pre-charge control circuit 108 uses a defined current pattern (e.g., one current pulse above the over-current threshold, one current pulse below the over-current threshold) and / or output voltage measurement to support more reliable pre-charging.

[0025] In an exemplary embodiment, the sensor used by current measurement 118 is a Hall effect sensor with a predefined threshold so that a logic signal is issued to logic and gate drive 122 when the current reaches the threshold. As an alternative to using a Hall sensor, in some embodiments, current measurement 118 may use a shunt resistor to sense overcurrent. It should be understood that in alternative embodiments, virtually any current sensor type may be used. In an exemplary embodiment, adaptive pre-charge control circuit 108 also includes a current limiting function. The current sensor in FIG. 1 is comprised of current measurement 118, with the circle representing the wire being measured. The magnetic flux generated by the flowing current is converted to a voltage via the Hall effect. The voltage is compared to a reference within the sensor representing a threshold voltage that indicates an overcurrent. If an overcurrent occurs, a single logic signal is generated and sent to logic and gate drive 122. In an exemplary embodiment, this occurs within a microsecond time frame.

[0026] If the current exceeds a certain limit (e.g., two consecutive times), the current limit function is triggered and the adaptive pre-charge control circuit 108 disconnects the battery and load (and stops charging). Without the current limit function, the current could rise without limit, causing stress or damage to components and interconnects.

[0027] In the exemplary embodiment, switch 202 of high-voltage switch 116 is a solid-state switching device such as a semiconductor, such as an insulated gate bipolar junction transistor (IGBT), a power metal-oxide semiconductor field-effect transistor (MOSFET), a thyristor, a silicon-controlled rectifier (SCR), a triode for alternating current (TRIAC), or any other suitable high-power controlled solid-state device. Switch 202 connects or disconnects EV battery 102 to the vehicle's high-voltage on-board system. In the exemplary embodiment, switch 202 is bidirectional to allow EV battery 102 to supply the vehicle (load 104) and allow a charger to supply the battery. In the exemplary embodiment, switch 202 is controlled by an incoming PWM signal 210 from control block 124.

[0028] Pre-charge circuits are typically part of high-voltage systems, such as electric vehicle systems, where downstream capacitance can be exposed to inrush current when the vehicle is turned on. These pre-charge circuits typically have a large-value resistor that switches on before the vehicle starts and slowly charges the DC link capacitor. Once the capacitor is fully charged, the switch is fully closed. Having a set pre-charge threshold does not account for battery discharge after vehicle use. Furthermore, prior art pre-charge circuits do not utilize pulse-width modulation to control charging, as does the adaptive pre-charge control circuit 108. The adaptive pre-charge control circuit 108 thus provides a novel method for detecting battery discharge and setting the pre-charge threshold based on the initial and final battery charge, while also using one or more defined current patterns (e.g., one current pulse above the over-current threshold, one current pulse below the over-current threshold) and / or output voltage measurements to more reliably detect over-current fault conditions.

[0029] 2 is a representative diagram of the operating principle of pulse width modulation used by the adaptive pre-charge control circuit 108, according to an exemplary embodiment. In this embodiment, a PWM pattern may be defined to generate a specific current profile, such as one current pulse above the overcurrent threshold, followed by one current pulse below the overcurrent threshold. For the adaptive pre-charge control circuit 108, after turning on the bidirectional switch 202, the charging current 301 (I charge ) is accumulated. In FIG. 2, pulse intervals 302 are shown, with a small amount of current 304 being delivered with each pulse. Because the DC link capacitor 106 is initially at zero volts, an uncontrolled charging current would be similar to a short circuit current and could be destructive. By delivering short pulses, the current stays within safe limits and the DC link capacitor 106 is nominally charged. The current is then applied to the battery voltage V batt and DC link voltage V DC_SYS 306 (V in Figure 1 out ) voltage difference V diff, an increase in DC link voltage results in a decrease in current for the next pulse. With each pulse, the DC link voltage 306 increases. As shown, the charging current 301 may be defined such that only every other second pulse exceeds limit 310. That is, the first pulse 304A is below limit 310, the second pulse 304B is above limit 310, the third pulse 304C is below limit 310, the fourth pulse 310D is above limit 310, and the fifth pulse 304E is also above limit 310. Because two consecutive pulses (304D, 304E) exceed limit 310, an actual overcurrent fault is detected.

[0030] In some embodiments, the overcurrent protection circuit is resettable. That is, when the circuit protection trips, the system can retry after a period of time to verify whether the overcurrent condition persists or whether it was caused by some other transient noise effect. Upon reconnection, a similar method (e.g., using a defined PWM pattern) can be used to detect an overcurrent event even if the device is not in pre-charge mode (so that the DC link voltage approaches the battery voltage).

[0031] 3 is a representative diagram of the operating principle of pulse width modulation used by adaptive pre-charge control circuit 108, according to another exemplary embodiment. In this embodiment, a PWM pattern is again defined to generate a specific current profile. In this example, the overcurrent threshold is disabled during pre-charge, and V DC_SYS The voltage increase at 306 is measured. If the voltage increase is not positive after applying the pulse, this indicates an actual overcurrent fault for the current 301.

[0032] The above discussion has been presented for purposes of illustration and description and is not intended to limit the present disclosure to the form or forms disclosed herein. For example, various features of the present disclosure may be grouped together in one or more aspects, embodiments, or configurations for the purpose of streamlining the disclosure. However, it should be understood that various features of specific aspects, embodiments, or configurations of the present disclosure may be combined in alternative aspects, embodiments, or configurations. Furthermore, the following claims are hereby incorporated by reference into the Detailed Description, with each claim standing on its own as a separate embodiment of the present disclosure.

[0033] As used herein, elements or steps described in the singular and preceded by the word "a" or "an" should be understood as not excluding a plurality of elements or steps, unless such exclusion is expressly stated. Furthermore, references to "one embodiment" of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[0034] The use of "including," "comprising," or "having," and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof, as well as additional items. Thus, the terms "including," "comprising," or "having," and variations thereof, are open-ended and can be used interchangeably herein.

[0035] The present disclosure is not limited in scope by the specific embodiments described herein. Indeed, various other embodiments and modifications of the present disclosure, in addition to those described herein, will be apparent to those skilled in the art from the foregoing description and the accompanying drawings. Accordingly, such other embodiments and modifications are intended to be within the scope of the present disclosure. Moreover, the present disclosure has been described herein in the context of particular implementations in particular environments for particular purposes. Those skilled in the art will recognize that the usefulness is not limited thereto; the present disclosure may be usefully implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in light of the full breadth and spirit of the present disclosure as described herein.

Claims

1. a high voltage switch coupled between an electric battery of an electric vehicle and a DC link capacitor, wherein the electric vehicle is powered by the electric battery; and 1. A control circuit comprising: emit a pulse width modulation (PWM) signal with a PWM pattern defined to generate a specific current profile, wherein the specific current profile exhibits every other pulse exceeding a predefined limit; monitoring the pre-charge current profile during pre-charge; and determining that an overcurrent fault exists when two consecutive pulses of the current profile of the pre-charge exceed the predefined limit; a control circuit operable to 1. An adaptive pre-charge control circuit for use in a solid state battery disconnection and protection system, comprising:

2. The adaptive pre-charge control circuit of claim 1 , wherein the control circuit is further operable to open the high voltage switch if the overcurrent fault is determined.

3. 3. The adaptive pre-charge control circuit of claim 1, further comprising the step of resetting said control circuit in response to said overcurrent fault.

4. a high voltage switch coupled between an electric battery of an electric vehicle and a DC link capacitor, wherein the electric vehicle is powered by the electric battery; and 1. A control circuit comprising: emit a pulse width modulation (PWM) signal with a PWM pattern defined to generate a specific current profile, wherein the specific current profile exhibits one current pulse above an overcurrent threshold and one current pulse below the overcurrent threshold following the one current pulse above the overcurrent threshold; monitoring a pre-charge current profile during the pre-charge; and determining that an overcurrent fault exists when two consecutive pulses of the current profile of the pre-charge exceed a predefined limit, and determining that an overcurrent fault does not exist when only a single pulse of the current profile of the pre-charge exceeds the predefined limit; a control circuit operable to 1. An adaptive pre-charge control circuit for use in a solid state battery disconnection and protection system, comprising:

5. The adaptive pre-charge control circuit of claim 4 , wherein the control circuit is further operable to open the high voltage switch if the overcurrent fault is determined.

6. 6. The adaptive pre-charge control circuit of claim 4 or 5, further comprising the step of resetting the control circuit in response to the overcurrent fault.

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