JP-7857117-B2 - High-speed overcurrent detection in battery management systems

JP7857117B2JP 7857117 B2JP7857117 B2JP 7857117B2JP-7857117-B2

Inventors

ガウラヴ・シン
ウレージュ・バウミク

Assignees

アナログ・ディヴァイシス・インターナショナル・アンリミテッド・カンパニー

Dates

Publication Date: 20260512
Application Date: 20220304
Priority Date: 20210331

Claims (20)

A battery monitor for protecting a switching device used to supply power to a load, A converter circuit including an input for receiving the voltage across a shunt resistor connected to a switching device , An oscillator that generates a pulse sequence based on the aforementioned voltage, It is a digital circuit, A first detector for detecting the occurrence or non-occurrence of a first fault event for the switching device based on determined characteristics of the pulse sequence measured over at least two different time windows, and a second detector for detecting the occurrence or non-occurrence of a second fault event for the switching device by determining a modeled junction temperature of the switching device based on the pulse sequence. Digital circuits including, A battery monitor equipped with this feature.
The system further comprises a resettable counter for counting pulses in the pulse sequence, The battery monitor according to claim 1, wherein the digital circuit is configured to determine the count of pulses counted by the resettable counter and to determine the number of pulses received over a certain period of time.
The battery monitor according to claim 1, wherein the first and second fault events include an overcurrent condition.
The battery monitor according to claim 1, wherein the battery monitor is configured to disable the switching device in response to the detection of at least one of the first or second failure events.
The battery monitor according to claim 1, wherein the switching device is a metal-oxide-semiconductor field-effect transistor (MOSFET).
The first detector, Based on the pulse sequence, the power dissipated over the different time windows is determined. For each time window, compare the power dissipated during that time window with the respective power threshold for that time window. The battery monitor according to claim 1, configured to detect the first fault event in response to the power dissipated over at least one of the time windows exceeding the respective power thresholds for that window.
The second detector, The digital representation of the resistance and capacitance values of a linear network of resistors and capacitors representing the thermal characteristics of the switching device is obtained. The battery monitor according to claim 1, configured to determine the modeled junction temperature based on the resistance value, the capacitance value, and the pulse sequence.
The second detector, The resistors and capacitors are grouped into sets of binary pairs, A first computing element is assigned to the first set of the binary pairs. The battery monitor according to claim 7, further configured to assign a second computing element to the remaining set of binary pairs.
The aforementioned converter circuit The system further includes a voltage-to-power converter for converting the aforementioned voltage into a squared current signal, The monitor according to claim 1, wherein the oscillator is configured to convert the squared current signal into the pulse sequence.
A method for protecting a switching device used to supply power to a load, The device detects the input voltage across a shunt resistor connected to a switching device , The device generates a pulse sequence based on the input voltage, The apparatus determines whether a first fault event occurs or not for the switching device based on the determined characteristics of the pulse sequence measured over at least two different time windows. The apparatus determines whether a second fault event occurs or not for the switching device by determining the modeled junction temperature of the switching device based on the pulse sequence, A method comprising the apparatus disabling the operation of the switching device in response to determining the occurrence of the first or second fault event.
The device counts the pulses in the pulse sequence to generate a resettable count, The method according to claim 10, further comprising determining the number of pulses received within a certain period of time based on the resettable count.
The method according to claim 10, wherein the first and second fault events include an overcurrent condition.
The method according to claim 10, wherein the switching device is a metal-oxide-semiconductor field-effect transistor (MOSFET).
The device determines whether the first failure event occurs or not. The device determines, based on the pulse sequence, the power to be dissipated over the different time windows, For each time window, the device compares the power dissipated in that time window with the respective power threshold for that time window. The method according to claim 10, wherein the apparatus detects the first fault event in response to the power dissipated over at least one of the time windows exceeding the respective power thresholds for that window.
The device determines whether the second failure event occurs or not. The apparatus acquires a digital representation of the resistance and capacitance values of a linear network of resistors and capacitors representing the thermal characteristics of the switching device. The method according to claim 10, wherein the apparatus determines the modeled junction temperature based on the resistance value and the capacitance value and the pulse sequence.
The apparatus groups the resistor and the capacitor into sets of binary pairs, The device assigns a first computing element to a first set of binary pairs, The method according to claim 15, further comprising the device assigning a second computing element to the remaining set of binary pairs.
A device for protecting a switching device used to supply power to a load, A converter circuit including an input for receiving the voltage across a shunt resistor connected to a switching device , An oscillator that generates a pulse sequence based on the aforementioned voltage, A fault detector comprising multiple timing filters and comparators, Based on the pulse sequence, the power dissipated over multiple time windows is determined. For each of the aforementioned multiple time windows, the power dissipated in that time window is compared with the respective power threshold for that window. Based on the above comparison, an overcurrent event is detected. In response to the detection of the overcurrent event, the switching device is disabled. Fault detector and A device equipped with the following features.
The system further comprises a resettable counter for counting pulses in the pulse sequence, The apparatus according to claim 17, wherein the fault detector is configured to determine the count of pulses counted by the resettable counter and to determine the number of pulses received within a certain period of time.
The apparatus according to claim 17, wherein the switching device is a metal oxide semiconductor field-effect transistor (MOSFET).
The apparatus according to claim 17, further comprising a different fault detector for detecting the occurrence or non-occurrence of a second fault event with respect to the switching device by determining the modeled junction temperature of the switching device based on the pulse sequence.

Description

This disclosure generally relates to safety technologies and mechanisms for battery management systems (BMS), such as overcurrent detection. As smart grid and electric vehicle (EV) technologies rapidly evolve, rechargeable batteries have emerged as large-scale energy storage devices. A Battery Management System (BMS) monitors these batteries and provides relevant data, such as battery charge levels, to control systems. BMSs have a wide range of potential applications, from grid energy storage to other consumer products like electric vehicles, electric bicycles, and electric scooters. Rechargeable batteries are inherently electrochemical and can exhibit various undesirable operating characteristics, such as outgassing, electrolyte leakage, or thermal problems like overheating or heat dissipation reactions with oxygen. One such undesirable condition is an overcurrent state, where a current greater than intended is supplied or suppressed by individual cells or the battery cell stack. Overcurrent can even lead to overheating and thermal runaway. To selectively connect and disconnect the battery from its corresponding load (e.g., an electric vehicle (EV) towing motor or associated control circuit) when the battery malfunctions, a switching mechanism such as a mechanical relay may be provided. However, mechanical relays can be expensive, slow, and bulky. The various drawings attached to this disclosure are merely illustrative embodiments and should not be considered to limit its scope. This is a block diagram of an exemplary part of the BMS. An example of a current spike in the system is shown. An example of a current spike in the system is shown. An illustrative portion of the BMS monitor is shown. An example of a time window is shown. The thermal impedance profile of the sample MOSFET is shown. The circuit representation of the sample MOSFET in the Cowell model is shown. A sample binary R-C system is shown. This shows a graph of current flow in a binary R-C system. The circuit diagram of the Cowell model for the sample MOSFET is shown. This shows a set of binary R-C pairs. This shows a network with switched resistors. This shows the switch timing method. An illustrative portion of the BMS monitor is shown. Embodiments of this disclosure provide improved overcurrent detection and mitigation systems, methods, and techniques for use in battery management systems (BMS). The BMS may be provided for electric vehicles (EVs). The BMS monitor may use two different techniques to detect overcurrent, providing redundancy and improving reliability. The first technique may detect overcurrent based on average power over different, overlapping periods. The second technique may detect overcurrent based on determining a modeled junction temperature of a switching device, such as a semiconductor element, and coupling the battery to a load. Both techniques may consider historical information of circuit performance, such as past current glitches. If an overcurrent is detected by either technique, the switching device may be quickly disabled, preventing failure of the switching device. Therefore, the overcurrent detection techniques described herein improve the safety and reliability of the BMS while reducing costs. This document describes a battery monitor for protecting switching devices used to supply power to a load. The battery monitor may include a converter circuit having an input for receiving a voltage and an oscillator for generating a pulse sequence based on the voltage. The battery monitor may further include a digital circuit having a first detector for detecting the occurrence or non-occurrence of a first fault event with respect to the switching device based on determined characteristics of the pulse sequence measured over at least two different time windows, and a second detector for detecting the occurrence or non-occurrence of a second fault event with respect to the switching device by determining a modeled junction temperature of the switching device based on the pulse sequence. This document also describes a method for protecting switching devices used to supply power to a load. The method may include: detecting an input voltage; generating a pulse sequence based on the input voltage; determining whether a first fault event has occurred or not for the switching device based on determined characteristics of the pulse sequence measured over at least two different time windows; determining whether a second fault event has occurred or not for the switching device by determining a modeled junction temperature of the switching device based on the pulse sequence; and disabling the operation of the switching device in response to determining the occurrence of the first or second fault event. This document further describes a device for protecting a switching device used to supply power to a load. The device may include a converter circuit having a voltage input and an oscillator that generates a pulse sequence based on