Voltage sensing circuits, battery packs, and battery systems

Abstract

Provided are a voltage sensing circuit, a battery pack, and a battery system. The voltage sensing circuit includes a first sub-sensing circuit that includes a light-emitting device and is electrically connected in parallel to a battery; and a second sub-sensing circuit that includes a light-receiving device optically coupled to the light-emitting device and electrically isolated from the first sub-sensing circuit. The light-emitting device is configured to generate a light signal in response to a voltage across the light-emitting device. The second sub-sensing circuit is configured to output a voltage sensing signal in response to the light signal, indicating the level of the voltage across the battery. When the voltage across the battery equals a first reference voltage, indicating an overvoltage condition in the battery, a second reference voltage, lower than the first reference voltage, is applied across the light-emitting device. The second reference voltage is lower than a threshold voltage of the light-emitting device.

Description

Technical Field

[0001] The present disclosure relates to techniques for sensing battery voltage.

[0002] This application claims the benefit of Korean Patent Application No. 10-2020-0046094, filed on April 16, 2020, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Background Art

[0003] Recently, demand for portable electronic products such as laptop computers, cameras, and mobile phones has rapidly increased, and with the widespread development of electric vehicles, accumulators for energy storage, robots, and satellites, much research is being made into high-performance batteries that can be repeatedly recharged.

[0004] Currently, commercially available batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium batteries, etc., and among them, lithium batteries have almost no memory effect, and therefore are gaining more attention than nickel-based batteries due to their advantages of being able to be recharged whenever convenient, having a very low self-discharge rate, and having a high energy density.

[0005] To ensure safe and efficient long-term battery use, it is necessary to accurately sense the battery voltage. The voltage across the battery is sensed by electrically connecting a pair of input pins of a single type of voltage sensing circuit, such as the AD8452, to the positive and negative terminals of the battery, respectively. However, if a fault occurs in the voltage sensing circuit or a component connected to the voltage sensing circuit, it can be difficult to properly sense the battery voltage. Summary of the Invention

[0006] Technical issues

[0007] The present disclosure is designed to solve the above-described problems, and thus the present disclosure aims to provide a voltage sensing circuit for detecting a voltage across a battery alone or in combination with another voltage sensing circuit, and a battery pack including the voltage sensing circuit.

[0008] These and other purposes and advantages of the present disclosure can be understood through the following description and will be clear from the embodiments of the present disclosure.In addition, it will be readily understood that the purposes and advantages of the present disclosure can be achieved by the means set forth in the appended claims and their combinations.

[0009] Technical Solution

[0010] According to an aspect of the present disclosure, a voltage sensing circuit for a battery includes: a first sub-sensing circuit including a light emitting device and electrically connected in parallel to the battery; and a second sub-sensing circuit including a light receiving device optically coupled to the light emitting device and electrically isolated from the first sub-sensing circuit. The light emitting device is configured to generate a light signal in response to a voltage across the light emitting device. The second sub-sensing circuit is configured to output a voltage sensing signal in response to the light signal, which indicates the level of the voltage across the battery. When the voltage across the battery is equal to a first reference voltage indicating an overvoltage state of the battery, a second reference voltage lower than the first reference voltage is applied across the light emitting device. The second reference voltage is lower than a threshold voltage of the light emitting device.

[0011] The light receiving device may include at least one of a photo register or a photo transistor.

[0012] The resistance of the light emitting device when the second reference voltage is applied across the light emitting device may be greater than the resistance of the light emitting device when the threshold voltage is applied across the light emitting device.

[0013] The first sub-sensing circuit may further include a diode string electrically connected in series to the light emitting device, wherein the diode string includes at least one diode.

[0014] When the first reference voltage is applied across the first sub-sensing circuit, a third reference voltage lower than the first reference voltage may be applied across the diode string.

[0015] When the first reference voltage is applied across the first sub-sensing circuit, a first ratio between the second reference voltage and the resistance of the light emitting device may be equal to a second ratio between the third reference voltage and the resistance of the diode string.

[0016] When a first reference voltage is applied across the first sub sensing circuit, a total parallel resistance between an equivalent resistance of an adjacent circuit electrically connected in parallel to the battery and the resistance of the first sub sensing circuit may be equal to or greater than a predetermined ratio of the equivalent resistance.

[0017] The second sub-sensing circuit may further include a resistor electrically connected in series to the light receiving device, and an analog-to-digital converter generating a voltage sensing signal according to a voltage across the resistor.

[0018] A battery pack according to another aspect of the present disclosure includes the voltage sensing circuit.

[0019] A battery system according to yet another aspect of the present disclosure includes the battery pack.

[0020] Beneficial effects

[0021] According to at least one of the embodiments of the present disclosure, a voltage sensing circuit includes a first sub-sensing circuit electrically connected in parallel to two terminals of a battery and a second sub-sensing circuit optically coupled to the first sub-sensing circuit to indirectly detect the voltage across the battery alone or in combination with another voltage sensing circuit.

[0022] In addition, the voltage sensing circuit according to at least one of the embodiments of the present disclosure can sense the voltage of the battery using the voltage-current-resistance characteristic within a sub-threshold voltage range of the light emitting device included in the voltage sensing circuit. Therefore, when the battery voltage is within a predetermined normal range, the resistance of the first sub-sensing circuit is equal to or greater than a predetermined resistance, thereby reducing the impact on the battery voltage sensing operation of another sensing circuit.

[0023] The effects of the present disclosure are not limited to the above-mentioned effects, and these and other effects will be clearly understood by those skilled in the art from the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings illustrate preferred embodiments of the present disclosure and, together with the detailed description of the present disclosure described below, serve to provide a further understanding of the technical aspects of the present disclosure, and thus the present disclosure should not be construed as limited to the accompanying drawings.

[0025] Figure 1 is a diagram exemplarily illustrating a battery system according to an embodiment of the present disclosure.

[0026] Figure 2 is a diagram exemplarily showing a configuration of a voltage sensing circuit according to an embodiment of the present disclosure.

[0027] Figure 3 It is shown as an example Figure 2 A graph showing the voltage-current characteristics of a light emitting device.

[0028] Figure 4 It is shown as an example Figure 2 A graph showing the voltage-resistance characteristics of a light emitting device.

[0029] Figure 5 It is shown as an example Figure 2 A graph showing the voltage-current characteristics of a diode string.

[0030] Figure 6 It is shown as an example Figure 2 A graph showing the voltage-resistance characteristics of a diode string. DETAILED DESCRIPTION

[0031] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms or words used in the specification and the appended claims should not be understood as limited to the general and dictionary meanings, but should be interpreted based on the meanings and concepts corresponding to the technical aspects of the present disclosure on the basis of the principle that allows the inventor to appropriately define the terms for the best interpretation.

[0032] Therefore, the embodiments described herein and the schematics shown in the accompanying drawings are merely the most preferred embodiments of the present disclosure, and are not intended to fully describe the technical aspects of the present disclosure, so it should be understood that various other equivalents and modifications may have been made thereto when the application is filed.

[0033] Terms including ordinal numbers such as “first,” “second,” etc. are used to distinguish one element from another among various elements and are not intended to limit the elements by the terms.

[0034] Unless the context clearly indicates otherwise, it will be understood that when used in this specification, the term "comprising" specifies the presence of stated elements, but does not exclude the presence or addition of one or more other elements.

[0035] Additionally, throughout this specification, it will be further understood that when an element is referred to as being “connected to” another element, it can be directly connected to the other element or intervening elements may be present.

[0036] Figure 1 is a diagram exemplarily showing a battery system 10 according to an embodiment of the present disclosure.

[0037] refer to Figure 1 , the battery system 10 includes a battery pack 20 and a charge / discharge control device 30. The battery system 10 refers to an electric device on which the battery pack 20 is mounted, such as, for example, an electric vehicle or an energy storage system.

[0038] The battery pack 20 includes a battery B and a sensing device 40. The battery B includes at least one rechargeable unit cell. When the battery B includes at least two unit cells, they are electrically connected in series or in parallel.

[0039] The sensing device 40 is configured to individually sense the current, temperature, and voltage of the battery B. The sensing device 40 may include a current sensing circuit 50 , a temperature sensing circuit 60 , and a voltage sensing circuit 70 .

[0040] The current sensing circuit 50 is provided to be electrically connected to the charge / discharge path of the battery B. The current sensing circuit 50 is configured to generate a signal indicating the magnitude and direction of the current flowing through the battery B. For example, a shunt resistor and / or a Hall effect device may be used as the current sensing circuit 50 .

[0041] The temperature sensing circuit 60 is located within a predetermined distance from the battery B and is configured to generate a signal indicating the temperature of the battery B. For example, a negative temperature coefficient (NTC) thermistor may be used as the temperature sensing circuit 60 .

[0042] The voltage sensing circuit 70 is electrically connected in parallel to the battery B through the positive terminal and the negative terminal of the battery B. The voltage sensing circuit 70 is configured to generate a signal indicative of the voltage across the battery B (hereinafter referred to as the "battery voltage"). Figure 2 The detailed configuration of the voltage sensing circuit 70 is described.

[0043] Sensing device 40 may further include an additional voltage sensing circuit 80. Like voltage sensing circuit 70, voltage sensing circuit 80 is electrically connected in parallel to battery B and senses the voltage of battery B. Voltage sensing circuit 70 may be an analog front end such as an AD8452. When sensing device 40 is provided with voltage sensing circuit 70 and voltage sensing circuit 80, the two voltage sensing circuits 70 and 80 complement each other.

[0044] The sensing device 40 transmits a sensing signal for each of the sensed current, temperature, and voltage of the battery B to the charge / discharge control device 30. The charge / discharge control device 30 is configured to control the charge / discharge of the battery B based on the sensing signal from the sensing device 40. The charge / discharge control device 30 may include at least one of a controller, a relay, a DC-DC converter, or a DC-AC converter. For example, when the sensing signal indicates an abnormal state of the battery B (e.g., an overvoltage), the controller of the charge / discharge control device 30 may stop the charge / discharge of the battery B by turning off at least one of the relay, the DC-DC converter, or the DC-AC converter.

[0045] Figure 2 : is a diagram exemplarily showing the configuration of the voltage sensing circuit 70 according to an embodiment of the present disclosure. To help understanding, Figure 2 Only battery B and voltage sensing circuit 70 are shown.

[0046] refer to Figure 1 and 2 , the voltage sensing circuit 70 includes a first sub-sensing circuit 110 and a second sub-sensing circuit 120 .

[0047] The first sub-sensing circuit 110 is electrically connected in parallel to the battery B. The first sub-sensing circuit 110 includes a light-emitting device 111. The light-emitting device 111 generally refers to any device, such as a light-emitting diode (LED), that changes the intensity of light emitted from the light-emitting device 111 according to the voltage level across the light-emitting device 111. The light-emitting device 111 is configured to generate a light signal in response to the voltage applied across the light-emitting device 111 by the battery B. The light intensity of the light signal has a unique corresponding relationship with the forward voltage of the light-emitting device 111.

[0048] The first sub-sensing circuit 110 further includes a diode string 112. In this case, the first sub-sensing circuit 110 can be considered a series circuit of the light emitting device 111 and the diode string 112. The diode string 112 is electrically connected in series to the light emitting device 111. The diode string 112 includes a single diode D or at least two diodes D electrically connected in series. The light emitting device 111 and each diode D are electrically connected in a direction in which the voltage of the battery B is applied in the forward direction.

[0049] Assume V BAT is the voltage of the battery B, V1 is the voltage of the light emitting device 111, and V2 is the voltage of the diode string 112. BAT >V1,V BAT >V2, and it can be simplified to V BAT =V1+V2. Accordingly, when the voltage of battery B is equal to the first reference voltage (e.g., 4.2V) indicating an overvoltage state of battery B, a second reference voltage (e.g., 1.674V) lower than the first reference voltage is applied across the light emitting device 111, and a third reference voltage lower than the first reference voltage is applied across the diode string 112. The second reference voltage (see Figure 3 V R2 ) is lower than the threshold voltage of the light emitting device 111 (see Figure 3 V TH1 ). The threshold voltage of the light emitting device 111 indicates a forward voltage drop of the light emitting device 111 when a predetermined level of current flows through the light emitting device 111 in a forward direction. A voltage range that is equal to or greater than the threshold voltage of the light emitting device 111 may be referred to as a "main threshold voltage range", and a voltage range that is less than the threshold voltage of the light emitting device 111 may be referred to as a "sub-threshold voltage range". The sub-threshold voltage range is a range in which a micro current (for example, at the level of several microamperes) is used, so that low power is feasible.

[0050] The second sub-sensing circuit 120 is configured to output a voltage sensing signal indicating a voltage level across the battery B in response to the optical signal from the first sub-sensing circuit 110 .

[0051] The second sub-sensing circuit 120 includes a light receiving device 121. The light receiving device 121 is optically coupled to the light emitting device 111. The light receiving device 121 collectively refers to any device whose resistance is changed by the intensity of light transmitted to the light receiving device 121. For example, a photo resistor and a photo transistor can be used as the light receiving device 121.

[0052] The second sub-sensing circuit 120 may further include a resistor 122 and an analog-to-digital converter 123. The resistor 122 is connected to the voltage source V CC and ground are electrically connected in series to the light receiving device 121. The resistor 122 has a single resistance. The series circuit of the light receiving device 121 and the resistor 122 can be used as a voltage divider to divide the voltage from the voltage source V CC The constant voltage is divided.

[0053] The signal input pin of analog-to-digital converter 123 is electrically connected to the connection node between light receiving device 121 and resistor 122. Analog-to-digital converter 123 converts the voltage across resistor 122, which serves as an analog input, into a digital output, which serves as a voltage sensing signal. As described above, the light intensity of the light signal emitted by light emitting device 111 changes depending on the voltage of light emitting device 111, and light receiving device 121 changes its resistance in response to the intensity of the light transmitted to light receiving device 121. Because the analog input changes depending on the resistance of light receiving device 121, the digital output indicates the voltage level of battery B.

[0054] Figure 3 It is shown as an example Figure 2 The voltage-current characteristic curve of the light emitting device 111 is Figure 1 ,and Figure 4 It is shown as an example Figure 2 FIG. 1 is a graph showing the voltage-resistance characteristics of the light emitting device 111. FIG.

[0055] refer to Figures 2 to 4 , it can be seen that the current of the light emitting device 111 increases when the voltage V1 of the light emitting device 111 exceeds the threshold voltage V TH1 In addition, the resistance of the light emitting device 111 increases very quickly from when the voltage V1 of the light emitting device 111 exceeds the threshold voltage V TH1 The time is decreasing rapidly.

[0056] When a second reference voltage V is applied across the light emitting device 111 R2 The resistance of the light emitting device 111 may be greater than the threshold voltage V applied across the light emitting device 111. TH1 The resistance of the light emitting device 111.

[0057] Figure 5It is shown as an example Figure 2 A graph showing the voltage-current relationship characteristics of the diode string 112 is shown, and Figure 6 It is shown as an example Figure 2 FIG. 1 is a graph showing the voltage-resistance characteristics of the diode string 112 .

[0058] refer to Figure 2 、 5 6, it can be seen that the current of the diode string 112 is from when the voltage V2 of the diode string 112 exceeds the threshold voltage V TH2 In addition, the resistance of the diode string 112 increases very quickly from when the voltage V1 of the diode string 112 exceeds the threshold voltage V TH2 The threshold voltage V of the diode string 112 decreases very quickly. TH2 Indicates the forward voltage drop of the diode string 112 when a predetermined level of current flows through the diode string 112 in the forward direction.

[0059] When a third reference voltage V is applied across the diode string 112 R3 The resistance of the diode string 112 may be greater than the threshold voltage V of the diode string 112 when the diode string 112 is applied across the diode string 112. TH2 The resistance of the diode string 112 is .

[0060] When the voltage of battery B is equal to or lower than the first reference voltage, the forward current flowing through the light emitting device 111 is equal to the forward current flowing through the diode string 112. For example, when the first reference voltage is applied across the first sub-sensing circuit 110, the first ratio between the second reference voltage and the resistance of the light emitting device 111 is equal to the second ratio between the third reference voltage and the resistance of the diode string 112.

[0061] Meanwhile, when the voltage sensing circuit 80 as an adjacent circuit is electrically connected in parallel to the battery B, an error may occur in the voltage sensing circuit 80 due to the voltage-current-resistance characteristics of the voltage sensing circuit 70. This is because the voltage sensing circuit 80 has a unique equivalent resistance and the resistance of the first sub-sensing circuit 110 changes depending on the voltage of the battery B. Figure 4 and 6 , it can be seen that as the voltage of the light emitting device 111 increases, the resistance of the light emitting device 111 decreases, and as the voltage of the diode string 112 increases, the resistance of the diode string 112 decreases.

[0062] Assume that the voltage of battery B is equal to or lower than the first reference voltage. When the voltage of light emitting device 111 is the second reference voltage, the resistance of light emitting device 111 can be minimized, and when the voltage of diode string 112 is the third reference voltage, the resistance of diode string 112 can be minimized. Therefore, when the voltage of battery B is the first reference voltage, the resistance of first sub-sensing circuit 110, which is the sum of the resistance of light emitting device 111 and the resistance of diode string 112, can be minimized.

[0063] According to the principle of parallel combination of resistors, when the resistance of the first sub-sensing circuit 110 is smaller, the impact on the equivalent resistance of the adjacent circuit is greater. Therefore, when the resistance of the first sub-sensing circuit 110 is minimized, it is necessary to make the total parallel resistance between the equivalent resistance of the adjacent circuit and the resistance of the first sub-sensing circuit 110 equal to or greater than a predetermined ratio (for example, 98%) of the equivalent resistance of the adjacent circuit. Here, this predetermined ratio is used to ensure the accuracy of the voltage sensing result of the voltage sensing circuit 80 and can be preset based on the voltage sensing offset of the voltage sensing circuit 80.

[0064] The embodiments of the present disclosure described above may be implemented not only by devices and methods, but may also be implemented by programs that execute functions corresponding to the configurations of the embodiments of the present disclosure or by recording media having the programs recorded thereon, and from the disclosure of the embodiments described above, those skilled in the art may easily implement such implementations.

[0065] While the present disclosure has been described above with respect to a limited number of embodiments and drawings, it is not limited thereto, and it will be apparent to those skilled in the art that various modifications and changes may be made thereto within the technical aspects of the present disclosure and the equivalent scope of the appended claims.

[0066] In addition, because those skilled in the art can make many substitutions, modifications and changes to the disclosure described above without departing from the technical aspects of the disclosure, the disclosure is not limited to the embodiments and drawings described above, and some or all of the embodiments may be selectively combined to allow various modifications.

Claims

1. A voltage sensing device for a battery, comprising a first voltage sensing circuit, wherein the first voltage sensing circuit comprises: a first sub-sensing circuit comprising a light emitting device and electrically connected in parallel to the battery; and a second sub-sensing circuit comprising a light receiving device optically coupled to the light emitting device and electrically isolated from the first sub-sensing circuit, wherein the light emitting device is configured to generate a light signal in response to a voltage across the light emitting device, The second sub-sensing circuit is configured to output a voltage sensing signal in response to the light signal, the voltage sensing signal indicating a level of voltage across the battery, When the voltage across the battery is equal to a first reference voltage indicating an overvoltage state of the battery, applying a second reference voltage lower than the first reference voltage across the light emitting device, and The second reference voltage is lower than the threshold voltage of the light emitting device, The first sub-sensing circuit further includes a diode string electrically connected in series to the light emitting device, and the diode string includes at least one diode. wherein, when the first reference voltage is applied across the first sub-sensing circuit, a third reference voltage lower than the first reference voltage is applied across the diode string, The third reference voltage is lower than the threshold voltage of the diode string. wherein a resistance of the light emitting device when the second reference voltage is applied across the light emitting device is greater than a resistance of the light emitting device when the threshold voltage of the light emitting device is applied across the light emitting device, wherein a resistance of the diode string when the third reference voltage is applied across the diode string is greater than a resistance of the diode string when the threshold voltage of the diode string is applied across the diode string, The voltage sensing device further includes a second voltage sensing circuit electrically connected in parallel to the battery and sensing the voltage of the battery, and Wherein, when the first reference voltage is applied across the first sub-sensing circuit, a total parallel resistance between an equivalent resistance of the second voltage sensing circuit and a resistance of the first sub-sensing circuit is equal to or greater than a predetermined ratio of the equivalent resistance.

2. The voltage sensing device according to claim 1, wherein: The light receiving device includes at least one of a photo register or a photo transistor.

3. The voltage sensing device according to claim 1, wherein: When the first reference voltage is applied across the first sub-sensing circuit, a first ratio between the second reference voltage and the resistance of the light emitting device is equal to a second ratio between the third reference voltage and the resistance of the diode string.

4. The voltage sensing device according to claim 1, wherein: The second sub-sensing circuit further comprises: a resistor electrically connected in series to the light receiving device; and An analog-to-digital converter is configured to generate the voltage sensing signal based on the voltage across the resistor.

5. A battery pack comprising the voltage sensing device according to any one of claims 1 to 4.

6. A battery system comprising the battery pack according to claim 5.

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