Overcharge and discharge protection device for energy storage batteries

Abstract

The application provides an overcharge and overdischarge protection device for an energy storage battery, comprising a signal collector, a differentiator electrically connected with the signal collector and configured to perform differential operation on received battery voltage and output a slope signal, a delay device comprising a controllable switch, a third capacitor, a third operational amplifier, a second resistor and a third resistor, a first end of the controllable switch being electrically connected with an output end of the differentiator, a second end being grounded through the third capacitor, the second end also being electrically connected with a non-inverting input end of the third operational amplifier, an output end of the third operational amplifier serving as a positive output end of the delay device, an inverting input end of the third operational amplifier being grounded through the second resistor and connected to the output end of the third operational amplifier through the third resistor, and a comparator, positive and negative input ends of the comparator being electrically connected with positive and negative output ends of the delay device respectively, the comparator being configured to output a pre-warning signal when a battery to be tested is in an overcharge or overdischarge stage.

Description

Technical Field

[0001] This invention relates to the field of battery safety warning, and more specifically to overcharge and discharge protection devices for energy storage batteries, particularly overcharge and discharge protection devices for lithium-ion energy storage batteries based on battery voltage slope. Background Technology

[0002] In response to climate change and to achieve a low-carbon transition in energy systems, countries around the world are actively promoting the development of renewable energy, and battery energy storage systems are gaining widespread adoption. Lithium-ion batteries, due to their advantages such as high energy density, long cycle life, low self-discharge rate, and low environmental pollution, have attracted extensive attention in battery energy storage systems and are one of the main energy carriers.

[0003] During prolonged charge-discharge cycles, the lithium molecules inside a lithium-ion energy storage battery lose their activity, leading to capacity degradation. If the battery experiences overcharging or over-discharging during cycling, the rate of capacity degradation increases significantly, resulting in performance loss. Therefore, limiting the battery from entering overcharge or over-discharge states during operation is extremely important. Summary of the Invention

[0004] The purpose of this invention is to provide an overcharge and discharge protection device for energy storage batteries.

[0005] To achieve the above objectives, embodiments of the present invention provide an overcharge and discharge protection device for an energy storage battery, comprising:

[0006] The signal acquisition unit is configured to acquire the battery voltage of the battery under test and filter the battery voltage.

[0007] The differentiator, electrically connected to the signal acquisition unit, is configured to receive the battery voltage, perform differential calculations, and output a slope signal reflecting the rate of change of the battery voltage.

[0008] The delay unit includes a controllable switch, a third capacitor, a third operational amplifier, a second resistor, and a third resistor. The first terminal of the controllable switch is electrically connected to the output terminal of the differentiator and serves as the positive input terminal of the delay unit. The second terminal of the controllable switch is grounded through the third capacitor. The second terminal of the controllable switch is also electrically connected to the non-inverting input terminal of the third operational amplifier. The output terminal of the third operational amplifier serves as the positive output terminal of the delay unit. The inverting input terminal of the third operational amplifier is grounded through the second resistor and connected to the output terminal of the third operational amplifier through the third resistor.

[0009] The comparator has its positive and negative input terminals electrically connected to the positive and negative output terminals of the delay unit, respectively. The comparator is configured to output a warning signal when the battery under test is in an overcharged or over-discharged state.

[0010] In this embodiment of the application, the overcharge and discharge protection device further includes:

[0011] A PWM signal generator is used to output PWM signals to a controllable switch.

[0012] In the embodiments of this application, the capacitance value of the third capacitor is positively correlated with the period of the PWM signal, and the duty cycle of the PWM signal is positively correlated with the capacitance value of the third capacitor.

[0013] In this embodiment, the resistance values ​​of the second resistor and the third resistor satisfy the following relationship:

[0014]

[0015] Where R2 is the resistance value of the second resistor and R3 is the resistance value of the third resistor.

[0016] In this embodiment of the application, the signal acquisition device includes:

[0017] The first operational amplifier and the first capacitor are used. The non-inverting input of the first operational amplifier is electrically connected to the positive terminal of the battery under test, and the inverting input of the first operational amplifier is electrically connected to the output of the first operational amplifier. The output of the operational amplifier is grounded through the first capacitor, which is used as a low-pass filter.

[0018] In this embodiment of the application, the differentiator includes:

[0019] The system comprises a second capacitor, a second operational amplifier, and a first resistor. The first terminal of the second capacitor is electrically connected to the output terminal of the first operational amplifier, and the second terminal of the second capacitor is electrically connected to the inverting input terminal of the second operational amplifier. The non-inverting input terminal of the second operational amplifier is electrically connected to the output terminal of the second operational amplifier through the first resistor. The output terminal of the second operational amplifier serves as the output terminal of a differentiator and is electrically connected to the first terminal of a controllable switch.

[0020] In this embodiment, the resistance value of the first resistor ranges from 1000 to 10000 ohms, and the capacitance value of the second capacitor ranges from 100nF to 1000nF.

[0021] In this embodiment, the differentiator further includes a low-pass filter, and the output of the differentiator is grounded through the low-pass filter.

[0022] In this embodiment, the controllable switch is an NMOS transistor, with the drain of the NMOS transistor being the first terminal of the controllable switch and the source being the second terminal of the controllable switch.

[0023] In this embodiment, the overcharge and discharge protection device is integrated on the circuit board.

[0024] The solution provided in this application involves real-time acquisition of battery voltage by a data acquisition device. The acquired battery voltage is then filtered and connected to a differentiator to obtain the slope of the battery voltage change. A delay unit retains historical battery voltage slopes, and the two slope values ​​are compared. When the real-time voltage slope is greater than the historical slope, the comparator outputs a high-level signal to generate an early warning. This solution is simple to implement and accurately provides early warnings based on the voltage change characteristics of lithium-ion energy storage batteries during overcharging and over-discharging.

[0025] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0026] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0027] Figure 1 This is a circuit diagram of an overcharge and discharge protection device for an energy storage battery provided according to an embodiment of this application;

[0028] Figure 2 This is a logic flowchart of an overcharge and discharge protection device for energy storage batteries that performs overcharge and discharge warning according to an embodiment of this application.

[0029] Explanation of reference numerals in the attached figures

[0030] A1 First operational amplifier; A2 Second operational amplifier

[0031] A3 Third operational amplifier, A4 comparator

[0032] C1 is the first capacitor, and C2 is the second capacitor.

[0033] C3 is the third capacitor, R1 is the first resistor.

[0034] R2 is the second resistor, and R3 is the third resistor.

[0035] SW1 Controllable Switch Detailed Implementation

[0036] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0037] It should be noted that the acquisition, transmission, storage, use, and processing of data in the technical solution of this application all comply with the relevant provisions of national laws and regulations. In the embodiments of this application, certain existing industry solutions such as software, components, and models may be mentioned. These should be considered exemplary, intended only to illustrate the feasibility of implementing the technical solution of this application, and do not imply that the applicant has already used or necessarily used such solutions.

[0038] At the end of the charge and discharge cycle, the voltage change rate of a lithium-ion energy storage battery increases significantly. Based on this characteristic, this application proposes an inventive concept that extracts the battery voltage slope and uses it to detect the charge and discharge state of the lithium battery, and issues a signal when the battery is about to enter an overcharge or over-discharge state.

[0039] Figure 1 This is a circuit diagram of an overcharge and discharge protection device for an energy storage battery provided according to an embodiment of this application. Figure 2 This is a logic flowchart illustrating the overcharge and discharge warning process of an overcharge and discharge protection device for energy storage batteries, according to an embodiment of this application. (See reference...) Figure 1 and Figure 2 In this embodiment of the application, the overcharge and discharge protection device may include:

[0040] The signal acquisition unit is configured to acquire the battery voltage of the battery under test and filter the battery voltage.

[0041] The differentiator, electrically connected to the signal acquisition unit, is configured to receive the battery voltage, perform differential calculations, and output a slope signal reflecting the rate of change of the battery voltage.

[0042] The delay circuit includes a controllable switch SW1, a third capacitor C3, a third operational amplifier A3, a second resistor R2, and a third resistor R3. The first terminal of the controllable switch SW1 is electrically connected to the output terminal of the differentiator and serves as the positive input terminal of the delay circuit. The second terminal of the controllable switch SW1 is grounded through the third capacitor C3. The second terminal of the controllable switch SW1 is also electrically connected to the non-inverting input terminal of the third operational amplifier A3. The output terminal of the third operational amplifier A3 serves as the positive output terminal of the delay circuit. The inverting input terminal of the third operational amplifier A3 is grounded through the second resistor R2 and connected to the output terminal of the third operational amplifier A3 through the third resistor R3.

[0043] Comparator A4, whose positive and negative input terminals are electrically connected to the positive and negative output terminals of the delay unit, is configured to output a warning signal when the battery under test is in an overcharged or over-discharged state.

[0044] Specifically, in the embodiments of this application, the overcharge and discharge protection device can be implemented as a circuit board structure, that is, the various components or electrical elements of the overcharge and discharge protection device can be integrated on the circuit board. The circuit board can be provided with a zero potential terminal.

[0045] The signal acquisition unit (hereinafter referred to as the acquisition unit) may include a first operational amplifier A1 and a filter (e.g., a first capacitor C1). The positive input terminal of the acquisition unit can be the non-inverting input terminal of the first operational amplifier A1, which can be electrically connected to the positive terminal of the battery under test during use. The negative input terminal of the acquisition unit can be the zero potential point of the first operational amplifier A1 (not shown in the figure), which can be electrically connected to the negative terminal of the battery under test during use. The first operational amplifier A1 can be selected with a sufficiently high input impedance and a small input current, so as not to affect the normal operation of the battery. The output terminal of the first operational amplifier A1 is shorted to its inverting input terminal, forming the positive output terminal of the acquisition unit. In this case, the ratio of the acquired output voltage to the input voltage is 1. The negative output terminal of the acquisition unit is electrically connected to the zero potential terminal of the overcharge / discharge protection device (e.g., a circuit board). The output terminal of the first operational amplifier A1 is grounded through the first capacitor C1, which forms a low-pass filter and can be used to filter out the voltage signal output from the output terminal of the first operational amplifier A1 (the positive output terminal of the acquisition unit). The capacitance value of the first capacitor C1 can be selected according to actual needs. Since the voltage change of the battery is small during charging and discharging, the capacitance value of the first capacitor C1 can be small enough to avoid eliminating the rate of change of the collected battery voltage.

[0046] In this embodiment, the differentiator may include a second capacitor C2, a second operational amplifier, and a first resistor R1. The positive and negative output terminals of the data acquisition unit are electrically connected to the positive and negative input terminals of the differentiator, respectively. Specifically, the first terminal of the second capacitor C2 is electrically connected to the output terminal of the first operational amplifier A1, and the second terminal is electrically connected to the inverting input terminal of the second operational amplifier A2. The first terminal of the second capacitor C2 can serve as the positive input terminal of the differentiator. The negative input terminal of the differentiator is electrically connected to the zero potential terminal. The first resistor R1 is connected in series in the feedback loop between the output terminal and the non-inverting input terminal of the second operational amplifier A2. The output terminal of the second operational amplifier A2 can serve as the positive output terminal of the differentiator, and the negative output terminal of the differentiator can be electrically connected to the negative power supply (not shown in the figure) and the zero potential terminal of the second operational amplifier A2. The ratio of the output voltage to the input voltage of the differentiator is:

[0047]

[0048] Among them, V o1 It is the output voltage of the differentiator, V i1R1 is the input voltage of the differentiator, R1 is the resistance value of the first resistor R1, and C2 is the capacitance value of the second capacitor C2.

[0049] Due to the differentiator input voltage V i1 This refers to the battery voltage value collected by the data acquisition unit. Its rate of change is extremely subtle before entering the overcharge or over-discharge phase; therefore, the gain (-R1C2) of the differentiator needs to be high to reflect battery voltage changes. The input current of the differentiator can be calculated using the following formula:

[0050]

[0051] Where I i1 ω is the input current of the differentiator, j is the complex unit, and ω is the angular frequency.

[0052] Therefore, given a fixed gain value for the differentiator, a higher resistance value R1 and a lower capacitance value C2 can be prioritized to reduce the input current of the differentiator and lower the overall power consumption of the device. However, leakage current exists at the input of the second operational amplifier A2, which can cause errors in the amplification factor. Therefore, the values ​​of R1 and C2 should be chosen such that the input current is much greater than the leakage current of the second operational amplifier A2. In this embodiment, the resistance value of the first resistor R1 ranges from 1000 to 10000 ohms, and the capacitance value of the second capacitor C2 ranges from 100nF to 1000nF.

[0053] Although Figure 1 In the illustrated embodiment, no filter is provided at the output of the differentiator. However, in practical applications, a filter can be added based on the specific debugging results. The positive output of the differentiator can be grounded (to zero potential) through the filter. The filter can be a low-pass filter used to filter out noise generated by the differentiator.

[0054] In this embodiment, the delay function of the delay unit can be implemented using a controllable switch SW1 and a third capacitor C3. Examples of controllable switches SW1 include MOSFETs, bipolar junction transistors (BJTs), etc. Since the differentiator gain is negative, the connection of the controllable switch SW1 requires attention to the device's unidirectional blocking capability. For example, the controllable switch SW1 can be an NMOS transistor, with its drain as the first terminal of the controllable switch SW1 (i.e., the positive input terminal of the delay unit) and its source as the second terminal of the controllable switch SW1, which can be grounded (zero potential terminal) through the third capacitor C3. The negative input terminal and negative output terminal of the delay unit (not shown in the figure) can be connected to the zero potential terminal.

[0055] The controllable switch SW1 can be turned on and off using a PWM signal. The overcharge / discharge protection device may include a PWM signal generator. In one example, the overcharge / discharge protection device may include a processor, such as a microcontroller, a programmable logic device (e.g., an FPGA), which can be used as a PWM signal generator to produce a PWM signal.

[0056] When the controllable switch SW1 is turned on, the voltage signal at the second terminal is updated to the voltage signal at the first terminal (the positive input terminal of the delay). When the controllable switch SW1 is turned off, the third capacitor C3 retains the most recent updated voltage value (the previous time the controllable switch SW1 was turned on), continuing until the next time the controllable switch SW1 is turned on. Therefore, the capacitance value of the third capacitor C3 should take into account the period of the control signal (PWM signal) of the controllable switch SW1. If the period of the PWM signal is relatively long, the third capacitor C3 should be selected with a large capacitance value to reduce the possible attenuation during voltage storage. The controllable switch SW1 should be selected such that the source-drain parasitic capacitance is much smaller than the capacitance value of the third capacitor C3 to reduce the impact of voltage changes at the delay input terminal on the stored voltage. Depending on the actual application, the period of the PWM signal can be set to the second or minute level (e.g., 10 seconds to 1 minute), but the duty cycle of the PWM signal can be adjusted according to the capacitance value of the third capacitor C3. If the capacitance of the third capacitor C3 is large, the duty cycle will increase accordingly, allowing sufficient time to update the voltage stored in the third capacitor C3. In other words, the capacitance value of the third capacitor C3 is positively correlated with the period of the PWM signal, and the duty cycle of the PWM signal is positively correlated with the capacitance value of the third capacitor C3.

[0057] The voltage stored in the third capacitor C3 needs to be amplified by a certain factor. This is because the rate of change (slope) of the battery voltage under normal operating conditions does not change much over time. Considering measurement errors, it is necessary to amplify the historical battery voltage slope by a certain factor to ensure that the current battery voltage slope changes significantly compared to the historical battery voltage slope. In this embodiment, the amplification of the historical battery voltage slope can be achieved by a non-inverting amplifier composed of the third operational amplifier A3. A second resistor R2 is connected in series between the inverting input terminal and the output terminal of the third operational amplifier A3, and the inverting input terminal is connected to the zero potential terminal through the third resistor R3. Therefore, the amplification factor can be calculated by the following formula:

[0058]

[0059] Where V o2 The output voltage of the non-inverting amplifier (third operational amplifier A3), V i2 It is the input voltage of the non-inverting amplifier (i.e., the storage voltage of the third capacitor C3). The value is the magnification factor. In one example, the magnification factor can be greater than 2.

[0060] The signal output from the positive output terminal of the differentiator is electrically connected to the non-inverting input terminal of comparator A4, representing the opposite of the current battery voltage change (slope) value; the signal output from the positive output terminal of the differentiator is also electrically connected to the positive input terminal of the delay unit (the first terminal of controllable switch SW1).

[0061] The output of the third operational amplifier A3 is connected to the inverting input of the comparator A4, representing the negative of the historical battery voltage change (slope) value.

[0062] When a battery enters an overcharge or over-discharge phase, the battery voltage change increases rapidly. At this point, the current battery voltage change (slope) will quickly exceed the historical battery voltage change (slope). At the input port of comparator A4, this manifests as the negative of the current battery voltage change rate (slope) being significantly lower than the negative of the historical battery voltage change (slope). In this situation, comparator A4 outputs a high-level signal, which serves as a warning signal. This warning signal can be output to a processor, which can then execute alarm actions upon receiving it, such as activating a buzzer or activating a light alarm.

[0063] The solution provided in this application involves real-time acquisition of battery voltage via a data acquisition device. The acquired battery voltage is then filtered and connected to a differentiator to obtain the slope of the battery voltage change. A delay unit retains historical battery voltage slopes, and the two slope values ​​are compared. When the real-time voltage slope is greater than the historical slope, comparator A4 outputs a high-level signal, generating an early warning. This solution is simple to implement and accurately provides early warnings based on the voltage change characteristics of lithium-ion energy storage batteries during overcharging and over-discharging.

[0064] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0065] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. An overcharge and discharge protection device for energy storage batteries, characterized in that, include: A signal acquisition unit is configured to acquire the battery voltage of the battery under test and filter the battery voltage. A differentiator, electrically connected to the signal acquisition unit, is configured to receive the battery voltage, perform differentiation on the battery voltage, and output a slope signal reflecting the rate of change of the battery voltage. The delay unit includes a controllable switch, a third capacitor, a third operational amplifier, a second resistor, and a third resistor. The first terminal of the controllable switch is electrically connected to the output terminal of the differentiator and serves as the positive input terminal of the delay unit. The second terminal of the controllable switch is grounded through the third capacitor. The second terminal of the controllable switch is also electrically connected to the non-inverting input terminal of the third operational amplifier. The output terminal of the third operational amplifier serves as the positive output terminal of the delay unit. The inverting input terminal of the third operational amplifier is grounded through the second resistor and connected to the output terminal of the third operational amplifier through the third resistor. A comparator, wherein the positive and negative input terminals of the comparator are electrically connected to the positive and negative output terminals of the delay unit, respectively, and the comparator is configured to output a warning signal when the battery under test is in an overcharge or over-discharge stage; The signal acquisition device includes: A first operational amplifier and a first capacitor, wherein the non-inverting input of the first operational amplifier is electrically connected to the positive terminal of the battery under test, the inverting input of the first operational amplifier is electrically connected to the output of the first operational amplifier, and the output of the operational amplifier is grounded through the first capacitor, which serves as a low-pass filter. The differentiator includes: The system comprises a second capacitor, a second operational amplifier, and a first resistor. The first terminal of the second capacitor is electrically connected to the output terminal of the first operational amplifier, and the second terminal of the second capacitor is electrically connected to the inverting input terminal of the second operational amplifier. The non-inverting input terminal of the second operational amplifier is electrically connected to the output terminal of the second operational amplifier through the first resistor. The output terminal of the second operational amplifier serves as the output terminal of the differentiator and is electrically connected to the first terminal of the controllable switch.

2. The overcharge and discharge protection device according to claim 1, characterized in that, Also includes: A PWM signal generator is used to output a PWM signal to the controllable switch.

3. The overcharge and discharge protection device according to claim 2, characterized in that, The capacitance value of the third capacitor is positively correlated with the period of the PWM signal, and the duty cycle of the PWM signal is positively correlated with the capacitance value of the third capacitor.

4. The overcharge and discharge protection device according to claim 1, characterized in that, The resistance values ​​of the second resistor and the third resistor satisfy the following relationship: ＞2 Wherein, R2 is the resistance value of the second resistor, and R3 is the resistance value of the third resistor.

5. The overcharge and discharge protection device according to claim 1, characterized in that, The resistance value of the first resistor ranges from 1000 to 10000 ohms, and the capacitance value of the second capacitor ranges from 100nF to 1000nF.

6. The overcharge and discharge protection device according to claim 1, characterized in that, The differentiator also includes a low-pass filter, and the output of the differentiator is grounded through the low-pass filter.

7. The overcharge and discharge protection device according to claim 1, characterized in that, The controllable switch is an NMOS transistor, with the drain of the NMOS transistor being the first terminal of the controllable switch and the source being the second terminal of the controllable switch.

8. The overcharge and discharge protection device according to claim 1, characterized in that, The overcharge and discharge protection device is integrated on the circuit board.

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