Liquid leakage detection circuit and electric device

Abstract

The utility model provides a liquid leakage detection circuit and an electric device. The liquid leakage detection circuit comprises an excitation circuit, a liquid level acquisition circuit and a comparison circuit. The excitation circuit is used for outputting an electric excitation signal; the liquid level acquisition circuit is coupled with the excitation circuit and is used for converting the liquid level of the liquid into an electric signal; the comparison circuit is coupled with the liquid level acquisition circuit and outputs a feedback signal based on the electric signal output by the liquid level acquisition circuit; wherein the feedback signals comprise different combinations of level signals; and the external control unit judges the liquid level grade of the liquid based on the feedback signal. Specifically, due to the design, the external control unit can obtain different liquid level grades based on different combinations of level signals, the requirements of graded early warning and on-demand protection on battery leakage are met, user loss caused by overprotection or safety risks caused by protection lag are effectively improved, and the safety of the battery is improved. And the reliability of liquid leakage detection of the battery is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery liquid leakage detection, in particular to a liquid leakage detection circuit and an electric device. BACKGROUND

[0002] In the application scenarios of BMS (Battery Management System) such as new energy vehicles and energy storage systems, leakage of the cooling liquid or electrolyte of the battery can cause safety accidents.

[0003] However, the existing liquid leakage detection of the battery has low reliability. UTILITY MODEL CONTENT

[0004] In view of the above problems, the present application provides a liquid leakage detection circuit and an electric device, which can solve the problem of low reliability of the existing liquid leakage detection.

[0005] In a first aspect, the present application provides a liquid leakage detection circuit, comprising:

[0006] An excitation circuit configured to output an electrical excitation signal;

[0007] A liquid level acquisition circuit coupled to the excitation circuit, the liquid level acquisition circuit being configured to convert the liquid level of the liquid into an electrical signal;

[0008] A comparison circuit coupled to the liquid level acquisition circuit, the comparison circuit being configured to output a feedback signal based on the electrical signal;

[0009] The feedback signal comprises different combinations of level signals, and an external control unit determines the liquid level grade based on the feedback signal.

[0010] In the technical solution of the present application, the comparison circuit can output different combinations of level signals as feedback signals based on the electrical signal of the liquid level of the liquid converted by the liquid level acquisition circuit. This design enables the external control unit to obtain different liquid level grades based on different combinations of level signals, overcoming the problem of rigid protection strategy caused by the binary detection of "leakage / no leakage" in the traditional liquid leakage detection. The present application can achieve the demand of "graded early warning and on-demand protection" through graded detection of liquid leakage, effectively improving the user loss caused by excessive protection or the safety risk caused by protection lag, and significantly increasing the reliability of liquid leakage detection.

[0011] In some embodiments, the comparison circuit comprises N sub-comparison circuits, each of the sub-comparison circuits is coupled to the liquid level acquisition circuit, and each of the sub-comparison circuits generates a voltage signal based on the electrical signal and outputs a level signal based on the comparison result of the voltage signal and the reference voltage of the sub-comparison circuit;

[0012] wherein N is a positive integer greater than or equal to 2; the reference voltage of each of the sub-comparison circuits is different, N sub-comparison circuits output N level signals, and an external control unit determines the liquid level grade of the liquid based on the N level signals.

[0013] By setting the comparison circuit to include multiple sub-comparison circuits, each sub-comparison circuit divides the voltage of the electrical signal representing the liquid level and compares it with the reference voltage of the sub-comparison circuit to obtain a level signal, and N sub-comparison circuits output N level signals, which enables the external control unit to combine the N level signals to obtain different liquid level grades, thereby achieving graded detection of liquid leakage.

[0014] In some embodiments, the comparison circuit includes a first sub-comparison circuit and a second sub-comparison circuit.

[0015] The first sub-comparison circuit includes a first resistor and a first comparator; a first end of the first resistor is coupled to the liquid level acquisition circuit, a second end of the first resistor is coupled to a same direction input end of the first comparator, and the first resistor is used to divide the voltage of the electrical signal to obtain the first voltage signal; a reverse input end of the first comparator is coupled to a first reference voltage providing circuit, the first reference voltage providing circuit is used to provide the first reference voltage; and an output end of the first comparator is coupled to an external control unit.

[0016] The second sub-comparison circuit includes a second resistor and a second comparator; a first end of the second resistor is coupled to the liquid level acquisition circuit, a second end of the second resistor is coupled to a same direction input end of the second comparator, and the second resistor is used to divide the voltage of the electrical signal to obtain the second voltage signal; a reverse input end of the second comparator is coupled to a second reference voltage providing circuit, the second reference voltage providing circuit is used to provide the second reference voltage; and an output end of the second comparator is coupled to an external control unit.

[0017] Specifically, by using a dual-channel sub-comparison circuit structure and further combining the value of the electrical signal output by the liquid level acquisition circuit, the embodiments of the present application can upgrade the liquid leakage detection from binary judgment to four-level quantization detection, such as dividing the liquid leakage level into four-level quantization detection of no liquid leakage, trace liquid leakage, moderate liquid leakage, and severe liquid leakage, which adapts to the demand of "graded early warning and on-demand protection", effectively improves the user loss caused by excessive protection or the safety risk caused by protection lag, and significantly increases the reliability of liquid leakage detection.

[0018] In some embodiments, the liquid level acquisition circuit includes:

[0019] A liquid level sensor coupled to the excitation circuit, the liquid level sensor being configured to convert the liquid level of the liquid into a liquid level equivalent signal.

[0020] a protection circuit coupled to the liquid level sensor;

[0021] a signal conditioning circuit configured to filter the liquid level equivalent signal to transition the liquid level equivalent signal to the electrical signal.

[0022] Specifically, the protection circuit is configured to suppress interference of external or internal factors on the liquid level equivalent signal, and the signal conditioning circuit is configured to convert the liquid level equivalent signal to an electrical signal processable by a backend circuit and filter and process signal noise caused by liquid level fluctuation or environmental factors to improve the accuracy of liquid leakage detection.

[0023] In some embodiments, the protection circuit comprises:

[0024] an anti-interference protection sub-circuit, the anti-interference protection sub-circuit comprising a first magnetic bead and a second magnetic bead; the first magnetic bead being coupled between a first connection end of the liquid level sensor and the excitation circuit; and the second magnetic bead being coupled between a second connection end of the liquid level sensor and a ground voltage.

[0025] By configuring magnetic beads on the two connection ends of the liquid level sensor, high-frequency electromagnetic interference such as motor radiation commonly found in vehicle environments is effectively attenuated, thereby reducing false positives and false negatives caused by electromagnetic interference and ensuring the accuracy of liquid leakage detection, thereby ensuring the reliability of safe operation of the battery system.

[0026] In some embodiments, the protection circuit further comprises a surge clamping protection sub-circuit coupled between the first connection end and the second connection end of the liquid level sensor and grounded.

[0027] The surge clamping protection sub-circuit comprises a transient voltage suppression diode.

[0028] Specifically, the transient voltage suppression diode in the surge clamping protection sub-circuit can effectively suppress transient surges commonly found in vehicle systems, such as vehicle start-stop impact, thereby reducing the damage rate of core devices and eliminating the risk of detection failure or false positives caused by surges.

[0029] In some embodiments, the excitation circuit comprises:

[0030] a signal generation circuit configured to output the electrical excitation signal;

[0031] a self-diagnosis circuit configured to detect the state of the signal generation circuit.

[0032] Specifically, the self-diagnosis circuit verifies the effectiveness of the signal generation circuit output by detecting the output state of the signal generation circuit, thereby achieving the accuracy of liquid leakage detection.

[0033] In some embodiments, the signal generation circuit comprises a third resistor and a fourth resistor; a first end of the third resistor is connected to the external control unit, a second end of the third resistor is connected to a first end of the fourth resistor, and a second end of the fourth resistor is connected to the liquid level acquisition circuit.

[0034] The signal generation circuit outputs the periodic electric excitation signal based on a pulse width modulation signal output by the external control unit.

[0035] Specifically, the third resistor and the fourth resistor can convert the pulse width modulation signal output by the external control unit into a periodic electric excitation signal output to the liquid level acquisition circuit, so that the liquid level acquisition circuit can periodically acquire the liquid level of the liquid and realize the continuity of the liquid leakage detection.

[0036] In some embodiments, the self-diagnosis circuit comprises a fifth resistor, a first end of the fifth resistor is connected to the signal generation circuit or the liquid level acquisition circuit, and a second end of the fifth resistor is connected to the external control unit.

[0037] The external control unit determines the state of the signal generation circuit based on the voltage of the fifth resistor.

[0038] Through the voltage monitoring mechanism of the fifth resistor, the external control unit can verify the validity of the output signal of the signal generation circuit in real time, effectively prevent the detection failure caused by the disconnection of the sensor from being misjudged as the no-liquid leakage state, improve the risk of continuous accumulation and diffusion of slight liquid leakage, and improve the safety redundancy of the liquid leakage detection system.

[0039] In a second aspect, the present application provides a power utilization device, comprising:

[0040] a battery;

[0041] a liquid leakage detection circuit, the liquid leakage detection circuit comprising any one of the liquid leakage detection circuits described above; the liquid leakage detection circuit is used to monitor the state of the battery;

[0042] a battery management system, the battery management system being coupled to the battery and the liquid leakage detection circuit, the battery management system determining a liquid level grade based on the feedback signal of the liquid leakage detection circuit and performing corresponding operations based on the liquid level grade.

[0043] Specifically, by arranging the liquid leakage detection circuit coupled to the battery management system in the power utilization device, the battery management system can determine the liquid level grade of the battery based on the feedback signal of the liquid leakage detection circuit, and then perform corresponding operations. For example, for slight liquid leakage, the liquid leakage is reported, but the normal operation of the battery is not intervened; for moderate liquid leakage, the liquid leakage is prewarned, and the corresponding personnel is notified for maintenance and inspection; and for serious liquid leakage, the system circuit is cut off under a preset condition to suppress the further expansion of the safety risk.

[0044] The above description is only a summary of the technical solutions of the present application. In order to make the technical means of the present application more clearly understood and implemented according to the content of the specification, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0045] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not meant to limit the present application. Moreover, the same reference numerals in all the drawings represent the same or similar elements. In the drawings:

[0046] Figure 1 Structural schematic diagram of a vehicle provided for some embodiments of the present application;

[0047] Figure 2 Exploded view of a battery provided for some embodiments of the present application;

[0048] Figure 3 Module schematic diagram of a liquid leakage detection circuit provided for some embodiments of the present application;

[0049] Figure 4 Module schematic diagram of a liquid leakage detection circuit provided for some embodiments of the present application;

[0050] Figure 5 Module schematic diagram of a liquid leakage detection circuit provided for some embodiments of the present application;

[0051] Figure 6 Module schematic diagram of a liquid leakage detection circuit provided for some embodiments of the present application;

[0052] Figure 7 Circuit structure schematic diagram of a liquid leakage detection circuit provided for some embodiments of the present application.

[0053] The reference numerals in the detailed description are as follows:

[0054] Vehicle-1000; battery-100; box-10; first part-11; second part-12; battery cell-20; controller-200; motor-300;

[0055] Excitation circuit-410; signal generation circuit-411; third resistor-R3; fourth resistor-R4; sixth resistor-R6; self-diagnosis circuit-412; fifth resistor-R5;

[0056] Liquid level acquisition circuit - 420; liquid level sensor - 421; protection circuit - 422; anti-interference protection sub-circuit - 4221; first magnetic bead - FB1; second magnetic bead - FB2; surge clamping protection sub-circuit - 4222; signal conditioning circuit - 423; seventh resistor - R7; first capacitor - C1; second capacitor - C2; third capacitor - C3;

[0057] Comparison circuit - 430; first sub-comparison circuit - 431; first resistor - R1; first comparator - D1; eighth resistor - R8; ninth resistor - R9; tenth resistor - R10; eleventh resistor - R11; fourth capacitor - C4; second sub-comparison circuit - 432; second resistor - R2; second comparator - D2; twelfth resistor - R12; thirteenth resistor - R13; fourteenth resistor - R14; fifteenth resistor - R15; fifth capacitor - C5. DETAILED DESCRIPTION

[0058] The embodiments of the technical solutions of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion.

[0060] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise explicitly and specifically limited.

[0061] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily all refer to the same embodiment, nor is it necessarily independent or alternative embodiments to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0062] In the description of the embodiments of the present application, the term "and / or" is only to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the existence of A alone, the existence of A and B at the same time, and the existence of B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are in an "or" relationship.

[0063] In the description of the embodiments of the present application, the term "a plurality of" refers to two or more (including two), and similarly, "a plurality of groups" refers to two or more groups (including two groups), and "a plurality of pieces" refers to two or more pieces (including two pieces).

[0064] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "coupling", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0065] At present, from the development of market situation, the application of battery is more and more extensive. The battery is not only applied to the energy storage power supply system of hydropower, thermal power, wind power and solar power station, but also widely applied to electric bicycles, electric motorcycles, electric vehicles and other electric vehicles, as well as military equipment, aerospace and other fields. With the continuous expansion of the application field of battery, the demand of its market is also increasing.

[0066] As the core energy source of new energy vehicles and energy storage systems, the safety of the battery directly determines the reliability of the terminal product and the safety of the user's life and property. With the development of the new energy industry towards high voltage (800V and above), high power density and long cycle life, the energy density of the battery continues to increase, and the working environment becomes more and more severe (-40℃~85℃ wide temperature, high frequency vibration, high pressure stress, etc.), which leads to a substantial increase in the risk of battery leakage (such as electrolyte and cooling liquid leakage).

[0067] However, in the related art, the leakage detection of the battery can only achieve binary judgment of "leakage / no leakage", and does not have grading recognition capability, so it cannot distinguish between slight leakage, moderate leakage and serious leakage in the early stage of leakage. This leads to the stagnation of the protection strategy of the battery management system (BMS): either the slight leakage cuts off the charging and discharging circuit, resulting in excessive protection and causing user loss, or the serious leakage triggers an alarm, resulting in protection lag and missing the disposal opportunity, and increasing the safety risk. Therefore, the existing leakage detection of the battery has low reliability.

[0068] In order to alleviate the problem of low reliability of existing liquid leakage detection, the applicant finds that the liquid level detection of the leakage liquid can be processed in stages to realize accurate staged identification of the leakage degree, adapt to the BMS "staged early warning and on-demand protection" requirement, avoid user loss caused by excessive protection or safety risks caused by protection lag, and thus improve the reliability of the battery leakage detection.

[0069] To solve the above problems, the embodiment of the present application provides a liquid leakage detection circuit, which comprises an excitation circuit, a liquid level acquisition circuit and a comparison circuit. The excitation circuit is used to output an electrical excitation signal; the liquid level acquisition circuit is coupled to the excitation circuit, and is used to convert the liquid level of the liquid into an electrical signal; the comparison circuit is coupled to the liquid level acquisition circuit, and outputs a feedback signal based on the electrical signal output by the liquid level acquisition circuit; wherein the feedback signal comprises different combinations of level signals; and an external control unit judges the liquid level grade of the liquid based on the feedback signal.

[0070] Specifically, in the technical scheme of the embodiment of the present application, the comparison circuit can output different combinations of level signals as feedback signals based on the electrical signal of the liquid level converted by the liquid level acquisition circuit, so that the external control unit can obtain different liquid level grades based on the different combinations of level signals, overcoming the problem of rigid protection strategy caused by the binary detection of "leakage / no leakage" in the traditional liquid leakage detection. Through staged detection of liquid leakage, the "staged early warning and on-demand protection" requirement of battery liquid leakage can be realized, effectively improving the safety risks caused by user loss due to excessive protection or protection lag, and significantly increasing the reliability of the battery leakage detection.

[0071] It should be noted that the liquid leakage detection circuit disclosed in the embodiment of the present application can be used in a power consumption device using a battery as a power source or an energy storage element. The power consumption device includes but is not limited to mobile phones, tablets, notebook computers, electric toys, electric tools, electric vehicles, electric vehicles, ships, spacecraft, etc. The electric toy can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric plane toys, etc. The spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0072] The following embodiments take the power consumption device of an embodiment of the present application as a vehicle 1000 for example for convenient description.

[0073] Please refer to Figure 1 , Figure 1A structural schematic diagram of a vehicle is provided for some embodiments of the present application. The vehicle 1000 can be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid vehicle or a range extended vehicle, etc. The vehicle 1000 is internally provided with a battery 100, which can be arranged at the bottom, head or tail of the vehicle 1000. The battery 100 can be used for power supply of the vehicle 1000, for example, the battery 100 can be used as an operating power supply of the vehicle 1000. The vehicle 1000 can further include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the working power demand of the vehicle 1000 during starting, navigation and driving.

[0074] In some embodiments of the present application, the battery 100 can not only be used as an operating power supply of the vehicle 1000, but also be used as a driving power supply of the vehicle 1000, instead of or partially instead of fuel or natural gas to provide driving power for the vehicle 1000.

[0075] Please refer to Figure 2 , Figure 2 An exploded view of the battery is provided for some embodiments of the present application. The battery 100 includes a box body 10 and a battery cell 20, and the battery cell 20 is contained in the box body 10. Among them, the box body 10 is used to provide a containing space for the battery cell 20, and the box body 10 can adopt various structures. In some embodiments, the box body 10 can include a first part 11 and a second part 12, the first part 11 and the second part 12 are covered with each other, and the first part 11 and the second part 12 jointly define a containing space for containing the battery cell 20. The second part 12 can be a hollow structure with one end open, and the first part 11 can be a plate structure, the first part 11 covers the open side of the second part 12, so that the first part 11 and the second part 12 jointly define the containing space; the first part 11 and the second part 12 can also be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12. Of course, the box body 10 formed by the first part 11 and the second part 12 can have various shapes, such as a cylinder, a cuboid, etc.

[0076] In the battery 100, the battery cells 20 can be multiple, and the multiple battery cells 20 can be connected in series or in parallel or in a mixed manner. The mixed manner means that the multiple battery cells 20 are connected in series and in parallel. The multiple battery cells 20 can be directly connected in series or in parallel or in a mixed manner, and then the multiple battery cells 20 are accommodated in the box body 10 as a whole. Of course, the battery 100 can also be that the multiple battery cells 20 are connected in series or in parallel or in a mixed manner to form a battery module, and then the multiple battery modules are connected in series or in parallel or in a mixed manner to form a whole and are accommodated in the box body 10. The battery 100 can also include other structures, for example, the battery 100 can also include a current collection component for realizing the electrical connection between the multiple battery cells 20.

[0077] Each battery cell 20 can be a secondary battery or a primary battery, and can also be a lithium-sulfur battery, a sodium-ion battery or a magnesium-ion battery, but is not limited thereto. The battery cell 20 can be in the shape of a cylinder, a flat body, a cuboid or other shapes.

[0078] During driving, the vehicle 1000 will inevitably vibrate, and the mutual friction and extrusion between the battery cells 20 in the battery 100 and between the battery cells 20 and the box body 10 can easily cause the battery cells 20 to be damaged and cause the electrolyte to leak, and can also cause the cooling liquid of the cooling system for cooling the battery cells 20 to leak. The leakage of the electrolyte and / or the cooling liquid will affect the performance of the battery cells 20, and the leaked liquid will also corrode the box body 10 and other circuit components, which has great safety hazards.

[0079] Therefore, the vehicle 1000 in the embodiments of the present application also has a liquid leakage detection circuit, at least part of the circuit structure of the liquid leakage detection circuit can be arranged in the accommodation space of the box body 10, and is used for monitoring the state of the battery 100. The liquid leakage detection circuit is also coupled to the controller 200, for example, the controller 200 includes a battery management system (Battery Management System, BMS), and the battery management system is used for at least one of state monitoring, state analysis, charge and discharge control, safety protection, thermal management, high-voltage power distribution and information management of the battery cells 20. In addition, the battery management system in the present application can also realize the functions of a vehicle controller (Vehicle control unit, VCU) and a motor controller (Motor Control Unit, MCU), and the present application does not limit this. The BMS is also coupled to the liquid leakage detection circuit.

[0080] Referring to Figures 3-6 , Figure 3 A module schematic diagram of the liquid leakage detection circuit provided by some embodiments of the present application is shown in the following figure; Figure 4 A module schematic diagram of the liquid leakage detection circuit provided by some embodiments of the present application is shown in the following figure;Figure 5 A module schematic diagram of a leakage detection circuit provided for some embodiments of the present application; Figure 6 A module schematic diagram of a leakage detection circuit provided for some embodiments of the present application.

[0081] In some embodiments, the leakage detection circuit includes an excitation circuit 410, a liquid level acquisition circuit 420, and a comparison circuit 430. The excitation circuit 410 is configured to output an electrical excitation signal. The liquid level acquisition circuit 420 is coupled to the excitation circuit 410 and configured to convert the liquid level of the liquid into an electrical signal Vsig. The comparison circuit 430 is coupled to the liquid level acquisition circuit 420 and configured to output a feedback signal based on the electrical signal Vsig output by the liquid level acquisition circuit 420. The feedback signal includes different combinations of electrical level signals. An external control unit (e.g., the BMS described above) determines the liquid level grade of the liquid based on the feedback signal and performs corresponding operations accordingly.

[0082] The electrical excitation signal can be a continuous or periodic voltage signal or current signal output by the external control unit, which is used to provide the liquid level acquisition circuit 420 with the required electrical energy so that the liquid level acquisition circuit 420 operates under the control of the electrical excitation signal. That is, if the liquid level acquisition circuit 420 does not receive the electrical excitation signal, the liquid level acquisition circuit 420 cannot operate.

[0083] The liquid level acquisition circuit 420 is a “signal converter” for leakage detection, which includes a “sensing component” that directly contacts the leaked liquid. When the coolant and / or the electrolyte of the battery monomer 20 in the battery 100 leaks, the leaked liquid contacts the “sensing component”, causing the electrical characteristics (such as resistance, capacitance, etc.) of the “sensing component” to change. The liquid level acquisition circuit 420 converts the “liquid level change” (such as the amount of leakage, whether there is leakage) into a corresponding electrical signal Vsig (such as voltage level, current size, capacitance size, resistance size, etc.), and then transmits the converted electrical signal Vsig to the subsequent comparison circuit 430.

[0084] The comparison circuit 430 is a “signal judge” for leakage detection. It internally presets one or more “reference standards”. After receiving the electrical signal Vsig transmitted by the liquid level acquisition circuit 420, it compares the processed electrical signal Vsig with the preset “reference standards”, and then outputs at least two electrical level signals as feedback signals to the external control unit. The external control unit further combines the received multiple electrical level signals to quickly identify the leakage condition and the liquid level grade of the battery 100, and reacts to the leakage level based on the liquid level grade.

[0085] Specifically, in the technical scheme of the embodiment of the present application, the comparison circuit 430 can output different combinations of level signals as feedback signals based on the electrical signal Vsig of the liquid level of the liquid converted by the liquid level collection circuit 420, so that the external control unit can obtain different liquid level grades based on the different combinations of level signals, thereby overcoming the problem of rigid protection strategy caused by the binary detection of "leakage / no leakage" of the traditional leakage detection. Through the hierarchical detection of the leakage, the "hierarchical early warning and on-demand protection" requirement of the battery 100 leakage can be realized, which effectively improves the user loss caused by excessive protection or the safety risk caused by protection lag, and significantly increases the reliability of the battery leakage detection.

[0086] In some embodiments, the comparison circuit 430 includes N sub-comparison circuits, each of which is coupled to the liquid level collection circuit 420, and each of which generates a voltage signal based on the electrical signal Vsig output by the liquid level collection circuit 420, and the value of the reference voltage of each sub-comparison circuit is different, and each sub-comparison circuit outputs a level signal based on the comparison result of the generated voltage signal and the reference voltage of the sub-comparison circuit.

[0087] Among them, the sub-comparison circuit is a subdivision judgment unit of the comparison circuit 430, which is equivalent to splitting a multifunctional judge into N "single-function judges". Each sub-comparison circuit has an independent "reference voltage (reference scale)", and can directly compare and judge the generated voltage signal and the reference voltage, and finally output a level signal (high or low). In this way, the N sub-comparison circuits can output N level signals. And the N sub-comparison circuits can output at least 3 different combinations of level signals.

[0088] Among them, N is a positive integer greater than or equal to 2. For example, the value of N is 2; or the value of N is 3, or the value of N is 5, etc., which is not limited here.

[0089] Let "1" represent a high-level signal received by the external control unit, and "0" represent a low-level signal received by the external control unit, with N being 2 as an example. If the voltage signals generated by both sub-comparison circuits based on the electrical signal Vsig are both less than or equal to the reference voltage of the corresponding sub-comparison circuit, then both sub-comparison circuits output low-level signals, and the external control unit receives "00", indicating no leakage. If the voltage signal generated by the sub-comparison circuit with the smaller reference voltage based on the electrical signal Vsig is greater than the reference voltage of its own sub-comparison circuit, then that sub-comparison circuit outputs a high-level signal, while the voltage signal generated by the sub-comparison circuit with the larger reference voltage based on the electrical signal Vsig is less than or equal to the reference voltage of its own sub-comparison circuit, then that sub-comparison circuit outputs a low-level signal, and the external control unit receives "10", indicating a slight leakage. If the voltage signals generated by both sub-comparison circuits based on the electrical signal Vsig are both greater than the reference voltage of the corresponding sub-comparison circuit, then both sub-comparison circuits output high-level signals, and the external control unit receives "11", indicating a moderate or severe leakage.

[0090] Specifically, by setting the comparison circuit 430 to include a multi-channel sub-comparison circuit, each sub-comparison circuit divides the electrical signal Vsig that characterizes the liquid level and compares it with the reference voltage of the sub-comparison circuit to obtain a level signal. The N sub-comparison circuits output N level signals, thereby enabling the external control unit to combine the N level signals to determine different liquid level levels and realize graded detection of leakage.

[0091] Combined Figure 4 and Figure 7 , Figure 7 This is a schematic diagram of the circuit structure of a leakage detection circuit provided in some embodiments of this application. In some embodiments, the comparison circuit 430 includes two sub-comparison circuits, specifically a first sub-comparison circuit 431 and a second sub-comparison circuit 432.

[0092] The first sub-comparison circuit 431 comprises a first resistor R1 and a first comparator D1. The first end of the first resistor R1 is coupled to the liquid level acquisition circuit 420, and the second end of the first resistor R1 is coupled to the same input end of the first comparator D1. The first resistor R1 is used to divide the voltage of the electrical signal Vsig to obtain a first voltage signal U1. The opposite input end of the first comparator D1 is coupled to a first reference voltage providing circuit, which is used to provide a first reference voltage Vref1. The output end of the first comparator D1 is coupled to the external control unit. For example, the first comparator D1 outputs a high level signal based on the first voltage signal U1 input to the same input end being greater than the first reference voltage Vref1 input to the opposite input end, and outputs a low level signal based on the first voltage signal U1 input to the same input end being less than or equal to the first reference voltage Vref1 input to the opposite input end.

[0093] The second sub-comparison circuit 432 comprises a second resistor R2 and a second comparator D2. The first end of the second resistor R2 is coupled to the liquid level acquisition circuit 420, and the second end of the second resistor R2 is coupled to the same input end of the second comparator D2. The second resistor R2 is used to divide the voltage of the electrical signal Vsig to obtain a second voltage signal U2. The opposite input end of the second comparator D2 is coupled to a second reference voltage providing circuit, which is used to provide a second reference voltage Vref2. The output end of the second comparator D2 is coupled to the external control unit. For example, the second comparator D2 outputs a high level signal based on the second voltage signal U2 input to the same input end being greater than the second reference voltage Vref2 input to the opposite input end, and outputs a low level signal based on the second voltage signal U2 input to the same input end being less than or equal to the second reference voltage Vref2 input to the opposite input end.

[0094] The first voltage signal U1 and the second voltage signal U2 can be the same or different.

[0095] For example, the first reference voltage Vref1 is less than the second reference voltage Vref2. If the first voltage signal U1 is less than or equal to the first reference voltage Vref1, and the second voltage signal U2 is less than or equal to the second reference voltage Vref2, the output end of the first comparator D1 and the output end of the second comparator D2 both output low-level signals, and the external control unit receives "00", indicating no leakage; if the first voltage signal U1 is greater than the first reference voltage Vref1, and the second voltage signal U2 is less than or equal to the second reference voltage Vref2, the output end of the first comparator D1 outputs a high-level signal, and the output end of the second comparator D2 outputs a low-level signal, and the external control unit receives "10", indicating slight leakage; if the first voltage signal U1 is greater than the first reference voltage Vref1, and the second voltage signal U2 is greater than the second reference voltage Vref2, the output end of the first comparator D1 and the output end of the second comparator D2 both output high-level signals, and the external control unit receives "11", indicating moderate or severe leakage. In this case, further combined with the value of the electrical signal Vsig output by the liquid level acquisition circuit 420, if the value of the electrical signal Vsig is less than a preset threshold (for example, 3.0V), it indicates moderate leakage, and if the value of the electrical signal Vsig is greater than or equal to the preset threshold, it indicates severe leakage.

[0096] Specifically, by the dual-path sub-comparison circuit structure, and combined with the value of the electrical signal Vsig output by the liquid level acquisition circuit 420, the embodiments of the present application can upgrade the leakage detection from binary judgment to four-level quantization detection, such as dividing the leakage level into four-level quantization detection of no leakage, slight leakage, moderate leakage and severe leakage, adapting to the demand of "graded early warning and on-demand protection", effectively improving the user loss caused by excessive protection or the safety risk caused by protection lag, and significantly increasing the reliability of leakage detection.

[0097] Referring to Figure 5 In some embodiments, the liquid level acquisition circuit 420 includes a liquid level sensor 421, a protection circuit 422 and a signal conditioning circuit 423; the liquid level sensor 421 is coupled to the excitation circuit 410, and is configured to convert the liquid level of the liquid into a liquid level equivalent signal; the protection circuit 422 is coupled to the liquid level sensor 421; and the signal conditioning circuit 423 is configured to filter the liquid level equivalent signal to smoothly transition the liquid level equivalent signal to a direct current electrical signal Vsig.

[0098] The liquid level sensor 421 is a tactile probe directly sensing the presence of a liquid (e.g., leaked electrolyte, cooling liquid), the liquid level height, or the amount of leaked liquid, and is installed in a potential liquid leakage area (e.g., the bottom or corner of the accommodation space of the box body 10, the liquid cooling pipe interface, etc.) of the battery 100. When a liquid leaks and contacts the liquid level sensor 421, the liquid level sensor 421 converts the physical information such as "whether there is a liquid leakage" and "how much liquid is leaked" into an electrical signal Vsig (e.g., voltage, current, resistance, or capacitance change) that can be recognized by a circuit, and then transmits the electrical signal Vsig to the subsequent signal conditioning circuit 423 and comparison circuit 430, to finally provide a basis for the BMS to determine the liquid leakage.

[0099] The protection circuit 422 is a circuit that protects the liquid level sensor 421 and the subsequent circuit from external factors (surge, electromagnetic interference, etc.) to ensure the long-term stable operation of the acquisition circuit.

[0100] The signal conditioning circuit 423 is an "electronic signal processing circuit" that "purifies" and "standardizes" the liquid level equivalent signal output by the liquid level sensor 421. Specifically, the signal output by the liquid level sensor 421 usually contains a large amount of noise and may also be a non-standard signal (liquid level equivalent signal) such as resistance or capacitance. The core function of the signal conditioning circuit 423 is to filter out noise and convert the non-standard signal into a stable standard electrical signal, which is finally output to the comparison circuit 430 to ensure that the comparison circuit 430 can accurately determine the liquid leakage state.

[0101] Specifically, the protection circuit 422 can suppress the interference of external adverse factors on the liquid level equivalent signal, and the signal conditioning circuit 423 can convert the liquid level equivalent signal into an electrical signal Vsig that can be processed by the backend circuit, and can filter and process to eliminate signal noise caused by liquid level fluctuations or environmental factors, thereby improving the accuracy of liquid leakage detection.

[0102] In combination with Figure 5 and Figure 7 In some embodiments, the protection circuit 422 includes an anti-interference protection sub-circuit 4221, and the anti-interference protection sub-circuit 4221 includes a first magnetic bead FB1 and a second magnetic bead FB2. The first magnetic bead FB1 is coupled between a first connection end of the liquid level sensor 421 and the excitation circuit 410. The second magnetic bead FB2 is coupled between a second connection end of the liquid level sensor 421 and a ground voltage.

[0103] Among them, the anti-interference protection subcircuit 4221 is a signal filter specially for suppressing electromagnetic interference (EMI); the magnetic bead is a high-frequency choke device that can present high impedance in the signal frequency range, effectively attenuating electromagnetic interference and converting interference energy into heat energy for elimination. The first magnetic bead FB1 is an "input side protection door" that prevents interference signals (such as high-frequency noise) in the excitation circuit 410 from entering the sensor, while allowing stable electric excitation signals to pass smoothly; the second magnetic bead FB2 is a ground side protection door that prevents external interference signals from entering the liquid level sensor 421 through the ground, while also discharging a small amount of interference signals generated by the liquid level sensor 421 to the ground, avoiding interference accumulation.

[0104] Specifically, by configuring magnetic beads on the two connection ends of the liquid level sensor 421, the high-frequency electromagnetic interference such as motor radiation commonly found in vehicle environments is effectively attenuated, thereby reducing false negatives and false positives caused by electromagnetic interference and ensuring the accuracy of liquid leakage detection, thereby ensuring the reliability of safe operation of the battery system.

[0105] In some embodiments, the protection circuit 422 further includes a surge clamping protection subcircuit 4222 coupled between the first connection end and the second connection end of the liquid level sensor 421 and grounded; wherein the surge clamping protection subcircuit 4222 includes a transient voltage suppression diode (TVS tube).

[0106] Among them, the surge clamping protection subcircuit 4222 is a "voltage safety valve" specially for suppressing transient high-voltage surges, and its core function is "fast clamping overvoltage, protecting core devices", which is connected across the two connection ends of the liquid level sensor 421 and grounded. When a transient high-voltage surge occurs, the surge voltage is limited within a safe range through the fast response characteristics of the TVS tube, avoiding high-voltage breakdown of the liquid level sensor 421, the subsequent signal conditioning circuit 423, or the comparison circuit 430.

[0107] Among them, the transient voltage suppression diode is a semiconductor device with avalanche breakdown characteristics, and its core characteristic is "high resistance cutoff in normal state, low resistance conduction in transient overvoltage", which is equivalent to a "high-voltage fuse that can automatically reset".

[0108] Specifically, the transient voltage suppression diode in the surge clamping protection subcircuit 4222 can effectively suppress the transient surges commonly found in vehicle systems, such as vehicle start-stop impact and liquid level sensor 421, and eliminate the risk of detection failure or false positives caused by surges.

[0109] In this embodiment of the application, the protection circuit 422 includes an anti-interference protection sub-circuit 4221 and a surge clamping protection sub-circuit 4222, which can resist common instantaneous surges in vehicle systems (such as start-stop impacts), while attenuating more than 80% of high-frequency electromagnetic interference (such as motor radiation), significantly reducing the damage rate of core components (such as comparators and sensors), and improving the problems of detection function failure and false alarms.

[0110] See Figure 6 In some embodiments, the excitation circuit 410 includes a signal generation circuit 411 and a self-diagnostic circuit 412; the signal generation circuit 411 is used to output an electrical excitation signal; and the self-diagnostic circuit 412 is used to detect the state of the signal generation circuit 411.

[0111] The self-diagnostic circuit 412 ensures the reliability of the detection system by monitoring the output status of the signal generation circuit 411 in real time. For example, the self-diagnostic circuit 412 includes a current-limiting resistor. The validity of the electrical excitation signal is determined by collecting the voltage difference across the current-limiting resistor. When the electrical excitation signal is detected to have no fluctuation or abnormal amplitude, a fault prompt is automatically triggered.

[0112] Specifically, the self-diagnostic circuit 412 verifies the validity of the output of the signal generation circuit 411 by detecting the output status of the signal generation circuit 411, eliminating the system's misjudgment of hardware faults as no leakage, and achieving accurate leakage detection.

[0113] Combination Figure 6 and Figure 7 In some embodiments, the signal generation circuit 411 includes a third resistor R3 and a fourth resistor R4; the first end of the third resistor R3 is connected to an external control unit, the second end of the third resistor R3 is connected to the first end of the fourth resistor R4, and the second end of the fourth resistor R4 is connected to the liquid level acquisition circuit 420; wherein, the signal generation circuit 411 outputs a periodic electrical excitation signal based on the pulse width modulation signal output by the external control unit.

[0114] In the signal generation circuit 411, the third resistor R3 and the fourth resistor R4 form a series resistor network to regulate and stabilize the output of the pulse width modulation (PWM) signal. The PWM signal output by the external control unit is current-limited by the third resistor R3 and then drives the liquid level sensor 421 to achieve periodic charging and discharging through the fourth resistor R4.

[0115] Specifically, the third resistor R3 and the fourth resistor R4 can convert the pulse width modulation signal output by the external control unit into a periodic electrical excitation signal and output it to the liquid level acquisition circuit 420, so that the liquid level acquisition circuit 420 can periodically acquire the liquid level and realize the continuity of leakage detection.

[0116] In some embodiments, the self-diagnosis circuit 412 comprises a fifth resistor R5, a first end of the fifth resistor R5 being connected to the signal generation circuit 411 or the liquid level acquisition circuit 420, and a second end of the fifth resistor R5 being connected to the external control unit; wherein the external control unit determines the state of the signal generation circuit 411 based on the voltage of the fifth resistor R5.

[0117] The fifth resistor R5 is used as a monitoring element, a first end of the fifth resistor R5 being connected to the signal generation circuit 411 (such as a second end of the fourth resistor R4) or the liquid level acquisition circuit 420 (such as an output end of the signal conditioning circuit 423), and a second end of the fifth resistor R5 being connected to the external control unit. The external control unit determines the output state of the signal generation circuit 411 by collecting the voltage change between the two ends of the fifth resistor R5 in real time, for example, determining that the PWM signal is invalid when the voltage has no fluctuation or abnormal amplitude. Through the voltage monitoring mechanism of the fifth resistor R5, the external control unit can verify the validity of the output signal of the signal generation circuit 411 in real time, effectively prevent the detection failure caused by the disconnection of the sensor from being misjudged as the no-leakage state, improve the risk of continuous accumulation and diffusion of slight leakage, and improve the safety redundancy of the leakage detection system.

[0118] Please refer to Figure 7 According to some embodiments of the present application, a leakage detection circuit is provided, which integrates PWM signal output, combines multi-threshold amplitude comparison of double comparators, outputs digital signal combination to calculate the capacitance value change of the liquid level sensor 421, and synchronously integrates the self-diagnosis function of the circuit to realize the rapid grading detection and fault early warning of the BMS leakage.

[0119] Specifically, the leakage detection circuit comprises an excitation circuit 410, a liquid level acquisition circuit 420, and a comparison circuit 430.

[0120] The excitation circuit 410 comprises a signal generation circuit 411 and a self-diagnosis circuit 412.

[0121] The signal generation circuit 411 comprises a third resistor R3 and a fourth resistor R4; a first end of the third resistor R3 is connected to the external control unit, a second end of the third resistor R3 is connected to a first end of the fourth resistor R4, and a second end of the fourth resistor R4 is connected to the liquid level acquisition circuit 420. Further, the signal generation circuit 411 can further comprise a sixth resistor R6, a first end of the sixth resistor R6 being connected between the first end of the third resistor R3 and the external control unit, and a second end of the sixth resistor R6 being grounded. The signal generation circuit 411 outputs a periodic electric excitation signal based on a pulse width modulation signal (PWM) output by the external control unit.

[0122] The self-diagnosis circuit 412 comprises a fifth resistor R5, a first end of the fifth resistor R5 is connected between an output end of the liquid level acquisition circuit 420 and an input end of the comparison circuit 430, and a second end of the fifth resistor R5 is connected to an external control unit. The external control unit monitors the output state of the PWM signal in real time by acquiring the voltage difference between the two ends of the fifth resistor R5, and ensures the stability of the excitation source.

[0123] The liquid level acquisition circuit 420 comprises a liquid level sensor 421, a protection circuit 422, and a signal conditioning circuit 423.

[0124] The liquid level sensor 421 is a capacitive sensor, and the equivalent capacitance Cx between the electrodes of the liquid level sensor 421 changes with the liquid level height (the higher the liquid level, the larger the Cx).

[0125] The protection circuit 422 comprises an anti-interference protection sub-circuit 4221 and a surge clamping protection sub-circuit 4222. The anti-interference protection sub-circuit 4221 comprises a first magnetic bead FB1 and a second magnetic bead FB2. The first magnetic bead FB1 is coupled between a first connection end of the liquid level sensor 421 and the excitation circuit 410. The second magnetic bead FB2 is coupled between a second connection end of the liquid level sensor 421 and a ground voltage. The first magnetic bead FB1 and the second magnetic bead FB2 are used to suppress electromagnetic interference and discharge the interference signals generated by the liquid level sensor 421 itself.

[0126] The surge clamping protection sub-circuit 4222 comprises a transient voltage suppression diode, which is coupled between the first connection end and the second connection end of the liquid level sensor 421 and grounded, and is used to suppress the transient surge common in vehicle-mounted systems.

[0127] The signal conditioning circuit 423 comprises a seventh resistor R7 and a first capacitor C1. A first end of the seventh resistor R7 is coupled to a second end of the first magnetic bead FB1 and a second end of the fourth resistor R4. A second end of the seventh resistor R7 is coupled to the comparison circuit 430. A first end of the first capacitor C1 is coupled between the second end of the seventh resistor R7 and the comparison circuit 430. A second end of the first capacitor C1 is grounded. The seventh resistor R7 and the first capacitor C1 are used to convert the liquid level equivalent signal output by the liquid level sensor 421 into an electrical signal Vsig that can be processed by the backend circuit.

[0128] Further, the protection circuit 422 further comprises a second capacitor C2 and a third capacitor C3. The second capacitor C2 is coupled between the first magnetic bead FB1 and the signal conditioning circuit 423. The third capacitor C3 is coupled between the second magnetic bead FB2 and the ground. The second capacitor C2 and the third capacitor C3 are used to filter and reduce noise.

[0129] The comparison circuit 430 comprises a first sub-comparison circuit 431 and a second sub-comparison circuit 432.

[0130] The first sub-comparison circuit 431 comprises a first resistor R1, a first comparator D1, and a first reference voltage providing circuit; a first end of the first resistor R1 is coupled to a second end of the seventh resistor R7, a second end of the first resistor R1 is coupled to a same direction input end of the first comparator D1, and the first resistor R1 is configured to divide the voltage of the electrical signal Vsig to obtain a first voltage signal U1; a reverse input end of the first comparator D1 is coupled to the first reference voltage providing circuit (comprising an eighth resistor R8 and a ninth resistor R9), and the first reference voltage providing circuit is configured to provide a first reference voltage Vref1 (e.g., 1.25 V); and an output end of the first comparator D1 is coupled to the external control unit. Further, a tenth resistor R10, an eleventh resistor R11, and a fourth capacitor C4 are further coupled between the output end of the first comparator D1 and the external control unit, the tenth resistor R10 is connected in series between the output end of the first comparator D1 and the external control unit, a first end of the eleventh resistor R11 is connected between the output end of the first comparator D1 and the tenth resistor R10, a second end of the eleventh resistor R11 is grounded, a first end of the fourth capacitor C4 is connected between a second end of the tenth resistor R10 and the external control unit, and a second end of the fourth capacitor C4 is grounded. Specifically, the eighth resistor R8 and the tenth resistor R10 are used as current limiting resistors, the ninth resistor R9 and the eleventh resistor R11 are used as pull-down resistors, and the fourth capacitor C4 is used as a filter capacitor.

[0131] The second sub-comparison circuit 432 comprises a second resistor R2, a second comparator D2, and a second reference voltage providing circuit; a first end of the second resistor R2 is coupled to the second end of the seventh resistor R7, a second end of the second resistor R2 is coupled to a same direction input end of the second comparator D2, and the second resistor R2 is configured to divide the voltage of the electrical signal Vsig to obtain a second voltage signal U2; a reverse input end of the second comparator D2 is coupled to the second reference voltage providing circuit (comprising a twelfth resistor R12 and a thirteenth resistor R13), and the second reference voltage providing circuit is configured to provide a second reference voltage Vref2 (e.g., 2.5 V); and an output end of the second comparator D2 is coupled to the external control unit. Further, a fourteenth resistor R14, a fifteenth resistor R15, and a fifth capacitor C5 are further coupled between the output end of the second comparator D2 and the external control unit, the fourteenth resistor R14 is connected in series between the output end of the second comparator D2 and the external control unit, a first end of the fifteenth resistor R15 is connected between the output end of the second comparator D2 and the fourteenth resistor R14, a second end of the fifteenth resistor R15 is grounded, a first end of the fifth capacitor C5 is connected between a second end of the fourteenth resistor R14 and the external control unit, and a second end of the fifth capacitor C5 is grounded. Specifically, the twelfth resistor R12 and the fourteenth resistor R14 are used as current limiting resistors, the thirteenth resistor R13 and the fifteenth resistor R15 are used as pull-down resistors, and the fifth capacitor C5 is used as a filter capacitor.

[0132] The following is the whole link process from signal collection to result output:

[0133] 1. Excitation signal generation: The external control unit outputs a PWM signal, which is transmitted to the liquid level sensor 421 after passing through the current limiting resistors (third resistor R3 and fourth resistor R4), providing periodic charging and discharging excitation for the capacitor Cx of the liquid level sensor 421.

[0134] 2. Liquid level signal conversion and collection: The equivalent capacitance Cx between the electrodes of the liquid level sensor 421 changes with the liquid level height (the higher the liquid level, the larger the Cx). After the PWM signal charges and discharges Cx, it is smoothed by the signal conditioning circuit 423 (seventh resistor R7 and first capacitor C1) to become an electrical signal Vsig (direct current voltage signal), and then the electrical signal Vsig is divided by the first resistor R1 to become the first voltage signal U1, and the electrical signal Vsig is divided by the second resistor R2 to become the second voltage signal U2.

[0135] 3. ESD protection processing: During the transmission of the liquid level equivalent signal, the protection circuit 422 works, and the TVS tube clamps the transient surge of the vehicle-mounted system (such as sensor start-stop impact), and the magnetic bead attenuates high-frequency electromagnetic interference (such as motor radiation).

[0136] 4. Leakage grading determination: The capacitance Cx of the liquid level sensor 421 changes with the liquid level h. After being charged and discharged by the external control unit output PWM signal, Cx is converted into a direct current voltage (i.e. Vsig), and the corresponding relationship is:

[0137] h < 2mm (no leakage) → Vsig < 1.25V;

[0138] h = 2mm (trace threshold) → Vsig = 1.25V;

[0139] h = 4mm (moderate threshold) → Vsig = 2.5V;

[0140] h ≥ 4.8mm (serious threshold) → Vsig ≥ 3.0V (close to 3.3V power supply, liquid level sensor 421 saturation).

[0141] Where, Vsig = Vcc × [Cx / (Cx + C0)];

[0142] Vcc: BMS supply voltage (3.3V);

[0143] Cx: Sensor electrode capacitance;

[0144] C0: Circuit parasitic capacitance.

[0145] 5. Voltage comparison and output logic: The dual comparators output level signals according to the size relationship between U1, U2 after Vsig voltage division and the reference voltage of itself, following the rule of "same phase terminal > opposite phase terminal -> high level (1), vice versa -> low level (0)", and the specific output combination is shown in Table 1:

[0146]

[0147] Table 1

[0148] Four-stage hierarchical execution:

[0149] No leakage (combination 00): Determine h < 2mm, the external control unit records "normal" state, BMS has no action, only update the state log.

[0150] Micro-leakage (combination 10): Determine 2mm≤h<4mm, the external control unit triggers "first-level warning", sends "micro-leakage" message through CAN bus, and does not intervene in the normal work of the battery 100.

[0151] Moderate leakage (combination 11+Vsig<3.0V): If 2.5V≤Vsig<3.0V, determine 4mm≤h<4.8mm, trigger "second-level warning", and report "moderate leakage".

[0152] Severe leakage (combination 11+Vsig≥3.0V): If Vsig≥3.0V, determine h≥4.8mm, trigger "emergency protection", such as immediately cutting off the high-voltage relay, reporting fault code, and forcibly shutting down the battery system.

[0153] Full-link self-diagnosis: The external control unit synchronously executes two diagnostic logics: one is to monitor the voltage of the fifth resistor R5 to determine whether the PWM output signal is abnormal (such as no fluctuation or amplitude exceeding limit); the other is to trigger a detection pulse signal every certain period of time, to generate corresponding voltage at the comparator (first comparator D1, second comparator D2) and compare with Vref1, Vref2, if the output deviates from the reference voltage (such as injecting high signal but outputting low level), determine that the comparator is short-circuited / broken, and shield the fault channel and enable single-channel redundant detection.

[0154] Taking the power supply voltage of the BMS as 3.3V, the liquid level acquisition circuit 420 includes a capacitive leakage sensor, and the "signal saturation threshold" of the capacitive leakage sensor is 3.0V as an example. 3.0V is the voltage output stable value when the leakage height reaches "electrode completely filled", and is also the "determination reference voltage of severe leakage" in the present application, and its essence is:

[0155] (1) Physical property mapping: The application adopts a parallel plate capacitive sensor. When the liquid leakage fills the gap between the electrodes as a medium, the capacitance Cx increases linearly with the liquid leakage height h, and the corresponding output electrical signal Vsig rises synchronously. When h≥4.8 mm, the electrode gap is completely filled with liquid leakage, and the capacitance Cx reaches the hardware structure limit (about 1416 pF). After that, no matter how much the liquid leakage increases (such as h=5 mm, 6 mm), the capacitance Cx no longer changes, and Vsig stabilizes between 3.0 V and 3.3 V (the core is the saturation starting point of 3.0 V).

[0156] (2) Circuit design reference: The liquid leakage detection circuit in the application is powered by 3.3 V, and the reference threshold is set by resistance division. 3 V is the accurate judgment point after matching the "sensor saturation signal" and "circuit reference voltage" (in actual working conditions, considering -40℃ low temperature and 3.2 V power supply fluctuation, the minimum saturation Vsig is about 3.02 V, and 3 V just covers this lower limit to ensure no missed judgment).

[0157] (3) Core anchor point of hierarchical detection: 3 V is the dividing point of Vsig signal from "linear change" to "saturation stability" - below 3 V, Vsig linearly fluctuates with the amount of liquid leakage (quantifiable liquid leakage degree: no liquid leakage, trace liquid leakage, and moderate liquid leakage); higher than or equal to 3 V, Vsig no longer reflects the amount of liquid leakage (has exceeded the controllable detection range of the sensor, serious liquid leakage)

[0158] Further, the reason for not directly using the electrical signal Vsig as the liquid leakage grading standard is that the original Vsig signal has the following fatal defects:

[0159] (1) Small amplitude: The maximum output of the capacitive sensor is only about 3 V, while the noise interference can reach ±50 mV, the signal-to-noise ratio is low, and direct comparison is easy to misjudge.

[0160] (2) Extremely high impedance: The output impedance of the capacitive sensor can reach 10 6 ~10 12 Ω, poor load capacity, and small interference will cause signal distortion.

[0161] (3) Serious temperature drift: A change of ±10℃ in the environment temperature can cause an output fluctuation of ±20 mV, and direct comparison will cause a large number of false positives.

[0162] The above is only an embodiment of the application, and does not limit the patent scope of the application. Any equivalent structure or equivalent flow transformation using the contents of the application specification and drawings, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the application.

Claims

1. A leakage detection circuit, characterized by comprising: include: Excitation circuit, used to output electrical excitation signal; A liquid level acquisition circuit is coupled to the excitation circuit, and the liquid level acquisition circuit is used to convert the liquid level into an electrical signal; A comparison circuit is coupled to the liquid level acquisition circuit, and the comparison circuit outputs a feedback signal based on the electrical signal; The feedback signal includes different combinations of level signals; the external control unit determines the liquid level based on the feedback signal.

2. The liquid leakage detection circuit according to claim 1, characterized by, The comparison circuit includes N sub-comparison circuits, each of which is coupled to the liquid level acquisition circuit. Each sub-comparison circuit generates a voltage signal based on the electrical signal and outputs a level signal based on the comparison result of the voltage signal and the reference voltage of the sub-comparison circuit. Wherein, N is a positive integer greater than or equal to 2; the reference voltage value of each of the sub-comparison circuits is different, and the N sub-comparison circuits output N level signals. The external control unit determines the liquid level level based on the N level signals.

3. The liquid leakage detection circuit according to claim 2, characterized by The comparison circuit includes a first sub-comparison circuit and a second sub-comparison circuit; The first sub-comparison circuit includes a first resistor and a first comparator; a first end of the first resistor is coupled to the liquid level acquisition circuit, and a second end of the first resistor is coupled to the non-inverting input of the first comparator. The first resistor is used to divide the electrical signal to obtain a first voltage signal; the inverting input of the first comparator is coupled to a first reference voltage providing circuit, which is used to provide the first reference voltage; the output of the first comparator is coupled to an external control unit. The second sub-comparison circuit includes a second resistor and a second comparator; the first end of the second resistor is coupled to the liquid level acquisition circuit, and the second end of the second resistor is coupled to the non-inverting input of the second comparator. The second resistor is used to divide the electrical signal to obtain a second voltage signal; the inverting input of the second comparator is coupled to a second reference voltage providing circuit, which is used to provide the second reference voltage. The output of the second comparator is coupled to an external control unit.

4. The leakage detection circuit according to any one of claims 1 to 3, characterized by The liquid level acquisition circuit includes: A liquid level sensor, coupled to the excitation circuit, is used to convert the liquid level into a liquid level equivalent signal; A protection circuit is coupled to the liquid level sensor; A signal conditioning circuit is used to filter the liquid level equivalent signal to convert it into an electrical signal.

5. The liquid leakage detection circuit according to claim 4, characterized by The protection circuit includes: An anti-interference protection sub-circuit is provided, comprising a first magnetic bead and a second magnetic bead; the first magnetic bead is coupled between the first connection terminal of the liquid level sensor and the excitation circuit; the second magnetic bead is coupled between the second connection terminal of the liquid level sensor and the ground voltage.

6. The liquid leakage detection circuit according to claim 5, wherein The protection circuit also includes a surge clamping protection sub-circuit, which is coupled between the first connection terminal and the second connection terminal of the liquid level sensor and grounded. The surge clamping protection sub-circuit includes a transient voltage suppression diode.

7. The leakage detection circuit according to any one of claims 1 to 3, characterized by The excitation circuit includes: A signal generating circuit is used to output the electrical excitation signal; A self-diagnosis circuit is configured to detect a state of the signal generation circuit.

8. The liquid leakage detection circuit according to claim 7, characterized by The signal generation circuit comprises a third resistor and a fourth resistor; a first end of the third resistor is connected to an external control unit; a second end of the third resistor is connected to a first end of the fourth resistor; and a second end of the fourth resistor is connected to the liquid level acquisition circuit. The signal generation circuit outputs the periodic electric excitation signal based on a pulse width modulation signal output by the external control unit.

9. The liquid leakage detection circuit according to claim 7, characterized by The self-diagnosis circuit comprises a fifth resistor; a first end of the fifth resistor is connected to the signal generation circuit or the liquid level acquisition circuit; and a second end of the fifth resistor is connected to the external control unit. The external control unit determines the state of the signal generation circuit based on a voltage of the fifth resistor.

10. An electrical device, characterized by The battery management system is coupled to the battery and the liquid leakage detection circuit; the battery management system determines a liquid level grade based on a feedback signal of the liquid leakage detection circuit, and performs corresponding operations based on the liquid level grade. The battery management system is coupled to the battery and the liquid leakage detection circuit; the battery management system determines a liquid level grade based on a feedback signal of the liquid leakage detection circuit, and performs corresponding operations based on the liquid level grade. ​ ​ ​

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