Lithium battery protection system with NTC (Negative Temperature Coefficient)

Abstract

The invention discloses a lithium battery protection system with NTC (Negative Temperature Coefficient). The lithium battery protection system comprises a monitoring unit, an acquisition unit and an adjustment unit which are connected with one another, the acquisition unit acquires a voltage value of the NTC, and substitutes the voltage value into an NTC characteristic formula for calculation to obtain current temperature information, and transmits the temperature information to the monitoring unit; after the monitoring unit receives the temperature information, the temperature information is compared with a preset temperature interval, whether the temperature information falls into the temperature interval or not is judged, and a judgment result is transmitted into the adjusting unit; and after receiving the judgment result, the adjusting unit adjusts the working state of the lithium battery according to the judgment result, so that the temperature of the lithium battery is changed to reach a normal working level. The NTC is directly integrated in the lithium battery protection chip, fusion of temperature monitoring and battery protection functions is achieved, and therefore rapid monitoring and protection in the lithium battery charging process are achieved.

Description

Technical Field

[0001] The present invention relates to the field of battery management, and particularly to a lithium battery protection system with NTC. Background Art

[0002] In current battery management systems, especially for the protection of lithium-ion batteries, traditional lithium battery protection chip solutions are commonly adopted. These solutions usually include basic functions such as overcharge protection, over-discharge protection, and short-circuit protection to ensure that the battery operates within a safe range. However, with the widespread application of lithium-ion batteries in various fields such as portable electronic devices and electric vehicles, the requirements for battery safety and performance are increasing day by day.

[0003] In the existing technical solutions, although the lithium battery protection chip can achieve basic protection for the battery, there are obvious deficiencies in temperature monitoring. Traditional temperature monitoring usually relies on external temperature sensors, such as thermistors or digital temperature sensors. These sensors need to be connected to the lithium battery protection chip through an external circuit, which not only increases the complexity and cost of the system, but also lacks in the accuracy and response speed of temperature detection. Especially in extreme environments of high temperature or low temperature, the stability and reliability of external sensors are easily affected, thus affecting the overall performance and safety of the battery. Summary of the Invention

[0004] Aiming at the deficiencies in the above technologies, the present invention provides a lithium battery protection system with NTC, which directly integrates NTC inside the lithium battery protection chip to realize the integration of temperature monitoring and battery protection functions, so as to achieve rapid monitoring and protection during the charging process of lithium batteries.

[0005] To achieve the above object, the present invention provides a lithium battery protection system with NTC, including a monitoring unit, a collection unit, and an adjustment unit that are connected to each other; The collection unit collects the voltage value of the NTC, and substitutes the voltage value into the NTC characteristic formula for calculation to obtain the current temperature information, and transmits the temperature information into the monitoring unit; After receiving the temperature information, the monitoring unit compares the temperature information with a preset temperature range, determines whether the temperature information falls within the temperature range, and transmits the determination result into the adjustment unit; After receiving the determination result, the adjustment unit adjusts the working state of the lithium battery according to the determination result, so that the temperature of the lithium battery changes to reach the normal working level.

[0006] Preferably, the NTC characteristic formula is: 1 / T = A + B * ln(R) + C * (ln(R))3 , where T is the current temperature, R is the current resistance value of the NTC, and A, B, and C are the NTC material coefficients.

[0007] Preferably, the NTC characteristic formula is: 1 / T = 1 / T0 + 1 / B * ln(R / R0), where T0 = 298.15K, R0 is the nominal resistance of the NTC at 25 degrees Celsius, and B is the NTC material coefficient.

[0008] Preferably, there are multiple preset temperature intervals, and the multiple temperature intervals and their corresponding temperature ranges are respectively: Low temperature interval: -20°C - 0°C; Normal temperature interval: 0°C - 45°C; High temperature interval: 45°C - 60°C; Over-temperature interval: >60°C.

[0009] Preferably, within the low temperature interval, the battery is protected by increasing the charging voltage of the lithium battery and reducing the charging current. During normal charging within the normal temperature interval, within the high temperature interval, the battery is protected by reducing the charging current and shortening the charging time, and charging is stopped within the over-temperature interval.

[0010] Preferably, when the acquisition unit obtains the voltage value, the voltage signal of the voltage division circuit of the NTC temperature sensor is collected through the ADC module, and its output voltage is calculated. The calculation formula is: V OUT = (ADC value / (2 N - 1)) * V ref ; where ADC value is the ADC module sampling value, V ref is the ADC module reference voltage, and N is the ADC resolution number of bits.

[0011] Preferably, after obtaining the output voltage, the output voltage is substituted into the calculation formula to calculate the actual resistance value of the NTC. The calculation formula is: R NTC = R ref * V OUT / (V CC - V OUT ); where V CC is the power supply voltage, and R ref is the fixed reference resistance.

[0012] Preferably, a recording unit is further included. The recording unit records the temperature change of the lithium battery during the charging process, simultaneously records the corresponding current and voltage changes, and transmits all data information to the acquisition unit and the adjustment unit. The acquisition unit fits the acquisition information and data information within a period of time. When the fitting ratio of the two reaches the set threshold, the adjustment unit adjusts the current and voltage according to the data information.

[0013] The beneficial effects of the present invention are as follows: Compared with the prior art, through the highly integrated design and intelligent temperature monitoring and compensation functions, the safety of lithium-ion batteries during the charging process is significantly improved. The signal of the NTC temperature sensor is collected through the ADS module, and the relevant temperature value is calculated through a series of relevant formulas. According to the temperature range where the current temperature value is located, the charging process of the lithium battery is adjusted to ensure that the lithium battery is always in a safe charging environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a flowchart of the steps of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] In order to describe the present invention more clearly, the present invention will be further described below in conjunction with the drawings and embodiments. Of course, the protection scope of the present invention is not limited thereto. Any simple substitution that can be made by those skilled in the art without creative work belongs to the protection scope of the present invention.

[0016] Please refer to Figure 1 ; The present invention discloses a lithium battery protection system with NTC, including a monitoring unit, an acquisition unit, and an adjustment unit connected to each other; the acquisition unit acquires the voltage value of the NTC by the acquisition unit, and substitutes the voltage value into the NTC characteristic formula for calculation to obtain the current temperature information, and transmits the temperature information to the monitoring unit; after receiving the temperature information, the monitoring unit compares the temperature information with the preset temperature range to judge whether the temperature information falls within the temperature range, and transmits the judgment result to the adjustment unit; after receiving the judgment result, the adjustment unit adjusts the working state of the lithium battery according to the judgment result, so that the temperature of the lithium battery changes to reach the normal working level. In this embodiment, an NTC (Negative Temperature Coefficient) is set in the monitoring unit, which can sense the temperature change of the battery in real time and adjust the scheme according to the temperature change, so as to effectively protect the lithium battery and ensure that the battery operates under safer and more efficient conditions.

[0017] The NTC characteristic formula is: 1 / T =A+B*ln(R)+C*(ln(R))3 , Where T is the current temperature, R is the current resistance value of the NTC, and A, B, and C are NTC material coefficients. In this embodiment, NTC thermistors generally use metal oxides such as manganese, manganese, cobalt, nickel, and copper as the main materials, and these metal oxide materials all have semiconductor properties. Because in terms of the conduction mode, it is completely similar to semiconductor materials such as germanium and silicon. When the temperature is low, the number of carriers (electrons and holes) in these oxide materials is small, so the resistance value of its thermistor is relatively high; as the temperature rises, the number of carriers increases, so the resistance value of the thermistor decreases. And when using different materials to prepare NTC thermistors, the material coefficients are inconsistent. Therefore, a high-precision model can be used for relevant calculations to obtain the absolute temperature value.

[0018] However, in the actual use process, sometimes it is impossible to obtain the accurate values of A, B, and C from the manufacturer. At this time, when we need to calculate the temperature, we can use a simplified model for calculation. The relevant NTC characteristic formula is: 1 / T = 1 / T0 + 1 / B * ln(R / R0), where T0 = 298.15K, R0 is the nominal resistance of the NTC at 25 degrees Celsius, and B is the NTC material coefficient. Through this formula, the current temperature can be calculated based on the resistance value of the current NTC, so as to facilitate subsequent determination according to the temperature value.

[0019] There are multiple preset temperature intervals, and the multiple temperature intervals and their corresponding temperature ranges are respectively: low-temperature interval: -20°C - 0°C; normal-temperature interval: 0°C - 45°C; high-temperature interval: 45°C - 60°C; over-temperature interval: >60°C (the above temperature intervals do not include the right endpoint value. For example, the meaning of 0°C - 45°C is [0, 45)°C). In the low-temperature interval, the battery is protected by increasing the charging voltage of the lithium battery and reducing the charging current. Normal charging is carried out in the normal-temperature interval. In the high-temperature interval, the battery is protected by reducing the charging current and shortening the charging time. Charging is stopped in the over-temperature interval. In the specific implementation process, according to the conventional resistance heating calculation formulas Q = I²Rt and Q = U² / R, it can be known that the temperature can be increased by increasing the voltage or reducing the current. In the low-temperature interval, the temperature can be increased by increasing the voltage to make the charging temperature of the lithium battery reach the normal-temperature interval. If it is in the high-temperature interval, the temperature can be reduced by reducing the current and shortening the charging time. For the over-temperature interval, the temperature is already too high at this time. Therefore, it is necessary to cool down in the shortest time. And whether it is reducing the voltage or reducing the current, it is a slow decline process and cannot achieve a rapid change in temperature in a short time. To ensure the charging safety of the lithium battery, charging needs to be stopped in the over-temperature interval.

[0020] When the acquisition unit obtains the voltage value, it acquires the voltage signal of the voltage division circuit of the NTC temperature sensor through the ADC module and calculates its output voltage. The calculation formula is: V OUT = (ADC value / (2 N - 1)) * V ref ; where ADC value is the ADC module sampling value, V ref is the ADC module reference voltage, and N is the ADC resolution number of bits; after obtaining the output voltage, substitute the output voltage into the calculation formula to calculate the actual resistance value of the NTC. The calculation formula is: R NTC = R ref * V OUT / (V CC - V OUT ); where V CC is the power supply voltage, and R ref is the fixed reference resistance. In the specific implementation process, since the resistance value of the NTC thermistor is constantly changing and is not a constant value, in order to obtain the NTC resistance value in the current state, it is necessary to use the ADC module to collect the voltage. The ADC (Analog-to-digital converter) is a device used to convert the continuous signal of the analog voltage into a discrete digital signal. After collecting the voltage signal of the voltage division circuit of the NTC temperature sensor through the ADC module, its output voltage is obtained. More specifically, V ref is the reference voltage of the ADC module, generally 3.3V, N is the ADC module resolution number of bits. When it is 12-bit, N is 12; ADC value is the ADC sampling value (for example, the sampling value of a 12-bit ADC is 1500). Substituting it into the relevant formula for calculation, we can get V OUT = (ADC value / (2 N - 1)) * V ref = (1500 / (2 12 - 1)) * 3.3 = 1.21V; when the output voltage V OUT is obtained, substituting it into the formula to calculate the actual resistance value of the NTC. In the actual use process, the power supply voltage is generally 3.3V, the fixed reference resistance is 10000 ohms, and the material coefficient of the NTC is 3950. Substituting the relevant values into the formula to calculate, we can get R NTC = R ref * V OUT / (V CC - V OUT) = 10000 * (1.21 / (3.3 - 1.21)) = 5770 Ω; Finally, substitute this value into the NTC characteristic formula to calculate 1 / T = 1 / T0 + 1 / B * ln(R / R0) ⟹ 1 / T = (1 / 298.15) + (1 / 3950) * ln(5770 / 10000). Finally, after calculation and unit conversion, T = 38.4 °C.

[0021] It also includes a recording unit that records the temperature changes of the lithium battery during charging, simultaneously records the corresponding current and voltage changes, and transmits all data information to the acquisition unit and the adjustment unit. The acquisition unit fits the acquisition information and data information within a certain period of time. When the fitting ratio of the two reaches the set threshold, the adjustment unit adjusts the current and voltage according to the data information. In the specific implementation process, a recording unit is also set up to record the temperature changes experienced by the lithium battery during charging and the corresponding adjustment schemes, obtaining Scheme 1, Scheme 2, Scheme 3, etc.; when the same temperature changes occur during the subsequent charging of the lithium battery, first judge through simulation fitting, select the one with the highest fitting rate among multiple schemes and reach the set threshold. For example, the fitting rate with Scheme 2 reaches 93%, exceeding the specified threshold of 90%, it is judged that the subsequent temperature of the lithium battery will change according to the temperature trend of Scheme 2. Therefore, the current or voltage adjustment in Scheme 2 is adopted to ensure temperature prediction in a short time and ensure the safety of the lithium battery; of course, real-time monitoring is also required during the subsequent charging process, and quick adjustment can be made when other situations occur., The above discloses only several specific embodiments of the present invention, but the present invention is not limited thereto. Any changes that can be thought of by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A lithium battery protection system with NTC, characterized in that: It includes a monitoring unit, a collection unit and an adjustment unit which are interconnected; The acquisition unit acquires the voltage value of the NTC, substitutes the voltage value into the NTC characteristic formula for calculation, obtains the current temperature information, and transmits the temperature information to the monitoring unit; After receiving the temperature information, the monitoring unit compares the temperature information with a preset temperature range to determine whether the temperature information falls within the temperature range, and transmits the determination result to the adjustment unit; After receiving the judgment result, the adjustment unit adjusts the working state of the lithium battery according to the judgment result, so that the temperature of the lithium battery changes and reaches a normal working level.

2. The lithium battery protection system with NTC according to claim 1, characterized in that: The NTC characteristic formula is: 1 / T =A+B*ln(R)+C*(ln(R)) 3 , Where T is the current temperature, R is the current resistance value of the NTC, and A, B and C are the NTC material coefficients.

3. The lithium battery protection system with NTC according to claim 1, characterized in that: The NTC characteristic formula is: 1 / T=1 / T0+1 / B*ln(R / R0), Where T0=298.15K, R0 is the nominal resistance of NTC at 25 degrees Celsius, and B is the NTC material coefficient.

4. The lithium battery protection system with NTC according to claim 1, characterized in that: There are multiple preset temperature intervals, and the multiple temperature intervals and their corresponding temperature ranges are: Low temperature range: -20℃- 0℃; Normal temperature range: 0℃-45℃; High temperature range: 45℃-60℃; Over temperature range: >60℃.

5. The lithium battery protection system with NTC according to claim 4, characterized in that: In the low temperature range, the battery is protected by increasing the charging voltage of the lithium battery and reducing the charging current. Normal charging is performed in the normal temperature range. In the high temperature range, the battery is protected by reducing the charging current and shortening the charging time. Charging is stopped in the over-temperature range.

6. The lithium battery protection system with NTC according to claim 1, characterized in that: When the acquisition unit obtains the voltage value, the voltage signal of the voltage divider circuit of the NTC temperature sensor is collected through the ADC module to calculate its output voltage. The calculation formula is: In OUT =(ADC value / (2 N -1))*V ref ; Among them, ADC value is the sampling value of the ADC module, V ref is the reference voltage of the ADC module, and N is the number of bits of ADC resolution.

7. The lithium battery protection system with NTC according to claim 6, characterized in that: After obtaining the output voltage, substitute the output voltage into the calculation formula to calculate the actual resistance value of the NTC. The calculation formula is: R NTC =R ref *V OUT / (V CC -V OUT ); Where V CC is the power supply voltage, R ref is a fixed reference resistor.

8. The lithium battery protection system with NTC according to claim 1, characterized in that: It also includes a recording unit, which records the temperature changes of the lithium battery during the charging process, and records the corresponding current and voltage changes, and transmits all data information to the acquisition unit and the adjustment unit. The acquisition unit fits the acquisition information within a period of time with the data information. When the fitting ratio of the two reaches a set threshold, the adjustment unit adjusts the current and voltage according to the data information.

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