A method for charging temperature compensation of a charging battery using NTC

Abstract

The application provides a method for charging temperature compensation of a charging battery by using NTC, which comprises the following steps: setting the maximum charging voltage at high temperature, normal temperature and low temperature, combining the feedback voltage and current of a charging control IC, and calculating the target resistance value of an upper voltage dividing network at each temperature; selecting NTC with a specific temperature coefficient and a nominal resistance value, constructing a composite network in parallel with a fixed resistance and then in series, determining the resistance values of R2 and R3 through iterative calculation so that the equivalent resistance of the network at a characteristic temperature approaches the target value, and connecting the network to a feedback loop to realize automatic temperature compensation of the charging voltage. The application can realize automatic adjustment of the charging voltage of the charging battery at different temperatures, improve the charging precision and safety, and prolong the service life of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery charging technology, and more specifically, to a method for using NTC as a charging temperature compensation for rechargeable batteries. Background Technology

[0002] Rechargeable batteries are widely used in modern electronic devices, and their performance directly affects the device's battery life and operating range. To ensure safe and efficient charging of batteries under different temperature conditions, temperature compensation of the charging voltage is usually required. Existing rechargeable battery temperature compensation methods mostly rely on complex sensor networks or built-in temperature compensation functions. These methods either increase the complexity and cost of the system or cannot be effectively applied to charging control ICs that do not have built-in compensation functions. In addition, some simple compensation schemes often fail to accurately match the charging needs of batteries at different temperatures, leading to problems such as low charging efficiency or overcharging.

[0003] In implementing the embodiments of the present invention, the prior art has at least the following problems or defects: on the one hand, the use of complex sensor networks increases the cost and maintenance difficulty of the system; on the other hand, for charging control ICs that do not have built-in temperature compensation functions, there is a lack of effective external compensation schemes, making it difficult to achieve accurate charging voltage regulation, thereby affecting the charging efficiency and service life of the battery. Summary of the Invention

[0004] This invention provides a method for using NTC as a charging temperature compensation for rechargeable batteries, comprising:

[0005] S1. According to the rechargeable battery's specifications, determine the high temperature... , normal temperature and low temperature The maximum allowable charging voltage of the rechargeable battery at three characteristic temperatures are as follows: and ;

[0006] S2. Determine the value of the lower voltage divider resistor Rbase based on the feedback reference voltage Vref of the charging control IC and the input current Ifb of its feedback detection pin.

[0007] S3, based on the above , , And Vref and Rbase, respectively calculated in , and At that time, the target resistance value required by the upper voltage divider feedback network and ;

[0008] S4. Select an NTC thermistor with a specific temperature coefficient Beta and a nominal resistance of R25 at 25°C.

[0009] S5. Construct a composite network consisting of the NTC thermistor connected in parallel with a fixed resistor R3, and then connected in series with another fixed resistor R2; determine the resistance values ​​of R2 and R3 through iterative calculation methods, so that the composite network... , and The equivalent resistance values ​​at the three temperature points respectively approximate the target resistance value. and ;

[0010] S6. The composite network is connected to the feedback loop of the charging control IC. By utilizing the characteristic that its equivalent resistance changes with temperature, the charging voltage is automatically adjusted to achieve temperature compensation for the charging battery.

[0011] Furthermore, in step S2, the resistance value of the lower voltage divider resistor Rbase is determined according to the following constraint: the voltage drop generated by Ifb flowing through Rbase must be much smaller than Vref to ensure the accuracy of the feedback voltage.

[0012] Further, in step S3, the target resistance value and Calculated using the following set of formulas:

[0013] ;

[0014] ;

[0015] .

[0016] Furthermore, in step S4, the NTC thermistor is at any temperature The resistance value below Calculated using the following formula:

[0017] ,in, The current ambient temperature is expressed in degrees Celsius.

[0018] Furthermore, in step S5, the composite network is at any temperature The equivalent resistance below Calculated using the following formula:

[0019] .

[0020] Furthermore, in step S5, the iterative calculation method specifically includes the following sub-steps:

[0021] S51. Define the required change in the equivalent resistance of the composite network in the high-temperature and low-temperature ranges, wherein the change in the high-temperature range... Changes in the low-temperature range ;

[0022] S52. Within a predefined resistance range, iterate through the candidate R3 values ​​and, for each candidate R3, calculate its resistance value within the range specified by the given condition. and The equivalent resistance difference at temperature and its and The equivalent resistance difference at temperature ;

[0023] S53. From all candidate R3s, select the one that can make near And can make near The value of R3 is used as a feasible range of R3 values. ;

[0024] S54. Based on the selected R3 values, use the formula Calculate the corresponding resistance value of R2.

[0025] Further, in step S53, the and Calculated using the following formula:

[0026] ;

[0027] .

[0028] Furthermore, in step S5, after determining the resistance values ​​of R2 and R3, a parameter verification and correction step is also included: calculating the equivalent resistance curve of the composite network over the entire operating temperature range and comparing it with the ideal charging voltage-temperature characteristic curve of the rechargeable battery. If the matching degree does not meet the predetermined requirements, the process returns to step S4, reselects the R25 or Beta value of the NTC thermistor, and re-executes step S5.

[0029] Furthermore, the charging control IC is a constant voltage charging IC without built-in temperature compensation function; the method provides the required temperature compensation characteristics through the external NTC composite network.

[0030] Furthermore, in the iterative calculation of step S53, a segmented processing strategy is adopted for the low-temperature segment: when the ambient temperature is below 0℃, priority is given to ensuring that the charging voltage does not exceed the absolute maximum value allowed by the battery, while relaxing the requirements for charging accuracy; the feasible range of R3 values... The determination of the value is mainly based on fitting the temperature characteristics above 0℃.

[0031] The embodiments of the present invention have at least the following beneficial effects:

[0032] 1. Automatic compensation through the temperature characteristics of NTC thermistors: By utilizing the resistance of NTC thermistors to change with temperature, a composite network can be constructed to automatically sense changes in ambient temperature and adjust the charging voltage. No additional temperature sensor is required, which simplifies circuit design, reduces system complexity and cost, and improves the automation and reliability of the charging process.

[0033] 2. Precisely Matching Battery Charging Needs: Based on the maximum charging voltage characteristics of the rechargeable battery at different temperatures, the resistance value of the upper voltage divider feedback network is precisely calculated and iteratively optimized to ensure that the charging voltage can accurately compensate for temperature changes. This effectively avoids the problem of overcharging or undercharging the battery under high or low temperature conditions, improves charging efficiency, and extends the battery's lifespan.

[0034] 3. Applicable to a variety of charging control ICs: This method is specifically designed for constant voltage charging ICs that do not have built-in temperature compensation functions. By using an external composite network, it provides the necessary temperature compensation characteristics, which broadens the application range of existing charging control ICs and enables them to charge batteries safely and efficiently under a wider range of temperature conditions, thereby enhancing the versatility and flexibility of the system. Attached Figure Description

[0035] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of the invention are illustrated in the drawings by way of example and not limitation, wherein:

[0036] Figure 1 This is a flowchart illustrating a method for using NTC as a charging temperature compensation mechanism for rechargeable batteries according to an embodiment of the present invention.

[0037] Figure 2 This is a schematic diagram of a temperature compensation circuit provided in an embodiment of the present invention. Detailed Implementation

[0038] The principles and spirit of the invention will now be described with reference to several exemplary embodiments. It should be understood that these embodiments are provided merely to enable those skilled in the art to better understand and implement the invention, and are not intended to limit the scope of the invention in any way. Rather, these embodiments are provided to make the invention more thorough and complete, and to fully convey the scope of the invention to those skilled in the art.

[0039] Those skilled in the art will recognize that embodiments of the present invention can be implemented as a system, apparatus, device, method, or computer program product. Therefore, the present invention can be specifically implemented in the following forms: entirely hardware, entirely software (including firmware, resident software, microcode, etc.), or a combination of hardware and software.

[0040] It should be noted that the number of any elements in the accompanying drawings is for illustrative purposes only and not as a limitation, and any naming is for distinction only and has no limiting meaning.

[0041] The following is for reference. Figure 1 , Figure 1 This is a schematic flowchart illustrating a method for using NTC as a charging temperature compensation mechanism for rechargeable batteries, according to an embodiment of the present invention. Figure 1 As shown, a method for using NTC as a charging temperature compensation for rechargeable batteries includes:

[0042] S1. According to the rechargeable battery's specifications, determine the high temperature... , normal temperature and low temperature The maximum allowable charging voltage of the rechargeable battery at three characteristic temperatures are as follows: and ;

[0043] S2. Determine the value of the lower voltage divider resistor Rbase based on the feedback reference voltage Vref of the charging control IC and the input current Ifb of its feedback detection pin.

[0044] S3, based on the above , , And Vref and Rbase, respectively calculated in , and At that time, the target resistance value required by the upper voltage divider feedback network and ;

[0045] S4. Select an NTC thermistor with a specific temperature coefficient Beta and a nominal resistance of R25 at 25°C.

[0046] like Figure 2 As shown, in step S5, a composite network is constructed consisting of the NTC thermistor connected in parallel with a fixed resistor R3, and then connected in series with another fixed resistor R2; the resistance values ​​of R2 and R3 are determined through iterative calculation, such that the composite network... , and The equivalent resistance values ​​at the three temperature points respectively approximate the target resistance value. and ;

[0047] S6. The composite network is connected to the feedback loop of the charging control IC. By utilizing the characteristic that its equivalent resistance changes with temperature, the charging voltage is automatically adjusted to achieve temperature compensation for the charging battery.

[0048] This invention proposes a method for temperature compensation of rechargeable batteries using NTC (Negative Temperature Coefficient) thermistors. The core of this method lies in leveraging the temperature characteristics of the NTC thermistor, combined with the feedback mechanism of a charging control IC, to achieve automatic adjustment of the charging voltage. An NTC thermistor is a component whose resistance decreases with increasing temperature, and its characteristic can be used to detect changes in ambient temperature. A charging control IC is an integrated circuit used to control the charging process, adjusting the charging voltage through a feedback mechanism. This invention constructs a composite resistor network, combining the NTC thermistor with a fixed resistor, so that its equivalent resistance changes with temperature, thereby achieving temperature compensation of the charging voltage and ensuring that the battery can be charged safely and efficiently at different temperatures.

[0049] The rechargeable battery in this invention refers to a battery that requires temperature compensation, such as a nickel-metal hydride battery or a lithium battery. In implementation, it is first necessary to determine the battery's maximum charging voltage at different temperatures, such as high temperature, according to the battery's specifications. , normal temperature and low temperature The charging voltages are respectively , and These parameters are key indicators for safe battery charging, ensuring the battery is not damaged by overcharging or undercharging. Secondly, the charging control IC is an integrated circuit used to control the charging process. Its feedback reference voltage Vref and the input current Ifb of the feedback detection pin are crucial for calculating the voltage divider resistor Rbase. The value of Rbase needs to be determined based on the fact that the voltage drop generated when Ifb flows is much smaller than Vref, to ensure the accuracy of the feedback voltage. Furthermore, the NTC thermistor in the composite network has a specific temperature coefficient Beta and a nominal resistance R25 at 25°C. These parameters determine the resistance variation of the NTC at different temperatures, forming the basis for temperature compensation.

[0050] Preferably, the operation can be refined through the following steps during implementation: First, based on the three characteristic temperatures determined in the battery specifications... , , and the corresponding charging voltage , , By combining the feedback reference voltage Vref of the charging control IC and the input current Ifb of the feedback detection pin, the resistance value of the lower voltage divider resistor Rbase is calculated. Next, based on these parameters, the target resistance value required for the upper voltage divider feedback network at different temperatures is calculated. and Next, a suitable NTC thermistor is selected, with its temperature coefficient Beta and nominal resistance R25 being key parameters. The resistance Rtc(Tx) of the NTC at any temperature is calculated using a formula. Finally, a composite network is constructed, and the resistance values ​​of fixed resistors R2 and R3 are determined through iterative calculations, ensuring that the equivalent resistance of the composite network at different temperatures approximates the target resistance value. In the iterative calculations, the changes in equivalent resistance in the high-temperature and low-temperature ranges need to be defined. and The system iterates through candidate R3 values, filters out the range of R3 values ​​that meet the conditions, and then calculates the corresponding R2 value. In this way, the composite network can automatically adjust its equivalent resistance according to temperature changes, thereby achieving precise compensation for the charging voltage.

[0051] In some embodiments, in step S2, the resistance value of the lower voltage divider resistor Rbase is determined according to the following constraint: the voltage drop generated by Ifb flowing through Rbase must be much smaller than Vref to ensure the accuracy of the feedback voltage.

[0052] It should be noted that, in determining the value of the voltage divider resistor Rbase, this invention emphasizes that its voltage drop must be much smaller than the feedback reference voltage Vref to ensure the accuracy of the feedback voltage. Here, the feedback reference voltage Vref refers to the reference voltage used by the charging control IC to compare and adjust the charging voltage, while the input current Ifb refers to the input current of the feedback detection pin. If the voltage drop of Rbase is too large, it will cause the feedback voltage to deviate from the actual value, thus affecting the precise control of the charging voltage. Therefore, by limiting the voltage drop of Rbase, the accuracy of charging control can be effectively improved.

[0053] The feedback reference voltage Vref is a fixed voltage value set internally by the charging control IC. It is used to compare with the feedback voltage to adjust the charging voltage. The input current Ifb refers to the current flowing through the feedback detection pin, and its magnitude directly affects the voltage drop across Rbase. In practice, the specific values ​​of Vref and Ifb need to be determined based on the specifications of the charging control IC and the battery charging requirements. For example, if Vref is set to 0.8V and Ifb is 50nA, the resistance of Rbase should be much larger than Vref divided by Ifb to ensure that the voltage drop is much smaller than Vref. This design ensures the accuracy of the feedback voltage, allowing the charging control IC to accurately adjust the charging voltage according to the feedback voltage, avoiding overcharging or undercharging problems caused by feedback errors.

[0054] In some embodiments, in step S3, the target resistance value and Calculated using the following set of formulas:

[0055] ;

[0056] ;

[0057] .

[0058] It should be noted that the target resistance value mentioned in this invention... and The calculations are based on the relationship between the maximum charging voltage of the rechargeable battery at different temperatures and the feedback reference voltage Vref. These target resistance values ​​determine the resistive characteristics that the upper voltage divider feedback network should possess under different temperature conditions, thereby achieving precise regulation of the charging voltage. Specifically, the formulas for calculating these resistance values ​​reflect the proportional relationship between the charging voltage and the feedback reference voltage, and are adjusted through the lower voltage divider resistor Rbase to ensure that the charging control IC can accurately regulate the charging voltage according to the feedback voltage.

[0059] Target resistance value and These correspond to the voltage divider feedback network resistors under low temperature, normal temperature, and high temperature conditions, respectively. The formulas for calculating these resistor values ​​are based on the maximum charging voltage of the rechargeable battery at different temperatures. , , The proportional relationship between the voltage and the feedback reference voltage Vref of the charging control IC. (In the formula...) / Vref-1、 / Vref-1 and / Vref-1 represents the proportional difference between the charging voltage and the feedback reference voltage under low temperature, normal temperature, and high temperature conditions, respectively. Multiplying this by the following voltage divider resistor Rbase yields the target resistance value. The calculation of these target resistance values ​​ensures that the charging control IC can accurately adjust the charging voltage through a feedback mechanism under different temperature conditions, preventing overcharging or undercharging of the battery.

[0060] In some embodiments, in step S4, the NTC thermistor is at any temperature The resistance value below Calculated using the following formula:

[0061] ,in, The current ambient temperature is expressed in degrees Celsius.

[0062] It should be noted that the resistance calculation formula for the NTC thermistor mentioned in this invention is based on its temperature characteristics. An NTC thermistor is a special type of resistive element whose resistance changes significantly with temperature, making it ideal for use in temperature compensation circuits. In the formula, Beta is a temperature coefficient describing the rate of change of the NTC resistance with temperature, while R25 represents the nominal resistance of the NTC at 25°C, a standard parameter provided by the manufacturer. This formula allows for the calculation of the NTC's resistance at any temperature, providing accurate resistance data for temperature compensation of rechargeable batteries and ensuring dynamic adjustments during charging based on temperature changes.

[0063] The temperature characteristic formula for NTC thermistors reflects the non-linear relationship between their resistance and temperature. In the formula, Beta is a temperature coefficient used to describe the rate at which the NTC resistance changes with temperature; R25 is the nominal resistance of the NTC at a standard temperature of 25°C, usually provided by the manufacturer; and Tx is the current ambient temperature in degrees Celsius. The formula calculates the exponent part... This is used to reflect the effect of temperature changes on the resistance value, where 273 is the conversion constant between Celsius and absolute temperature, and 298 is the absolute temperature corresponding to 25°C. By multiplying R25 by this exponent, the resistance value Rtc(Tx) of the NTC at any temperature Tx can be obtained. This calculation method can accurately describe the resistance change of the NTC thermistor at different temperatures, providing a theoretical basis for temperature compensation of rechargeable batteries.

[0064] In some embodiments, in step S5, the composite network is at any temperature The equivalent resistance below Calculated using the following formula:

[0065] .

[0066] It should be noted that the equivalent resistance calculation of the composite network mentioned in this invention is based on the combined characteristics of an NTC thermistor and a fixed resistor. The composite network consists of an NTC thermistor connected in parallel with a fixed resistor R3, and then connected in series with another fixed resistor R2. The purpose of this structure is to combine the temperature sensitivity of the NTC with the stability of the fixed resistor to achieve the characteristic that the equivalent resistance changes with temperature, thereby meeting the charging voltage compensation requirements of the rechargeable battery at different temperatures. By calculating the equivalent resistance of the composite network at any temperature, it can be ensured that the charging control IC can automatically adjust the charging voltage according to temperature changes, achieving accurate temperature compensation.

[0067] The formula for calculating the equivalent resistance of the composite network reflects the electrical connection between the NTC thermistor and the fixed resistor. R2 is a fixed resistor connected in series between the NTC thermistor and the charging control IC feedback loop, used to adjust the overall network resistance range. R3 is a fixed resistor connected in parallel with the NTC thermistor, used to adjust the NTC's resistance variation characteristics to make it closer to the target resistance value. Rtc(Tx) in the formula represents the resistance of the NTC thermistor at the current temperature Tx, calculated using the NTC's temperature characteristic formula. The formula for calculating the equivalent resistance Req(Tx) combines the parallel resistance of the NTC and R3 with the series resistance of R2, thus obtaining the equivalent resistance of the composite network at any temperature. This calculation method can accurately describe the resistance variation characteristics of the composite network, providing a theoretical basis for temperature compensation of rechargeable batteries.

[0068] In practical applications, the calculation process of the equivalent resistance of the composite network can be refined through the following steps: First, calculate the resistance value Rtc(Tx) at the current temperature Tx using the temperature characteristic formula of the NTC thermistor. Then, select appropriate fixed resistors R2 and R3, and determine their resistance values ​​through iterative calculations, so that the equivalent resistance of the composite network at different temperatures approximates the target resistance value. For example, assuming R2 is 510kΩ, R3 is 100kΩ, and the resistance value Rtc(Tx) of the NTC at a certain temperature is 60kΩ, then the calculation process of the equivalent resistance Req(Tx) is: Req(Tx) = R2 + (Rtc(Tx) × R3) / (Rtc(Tx) + R3). In this way, the equivalent resistance of the composite network at different temperatures can be accurately calculated, thereby achieving dynamic adjustment of the charging voltage and ensuring that the battery can be charged safely and efficiently under different temperature conditions.

[0069] In some embodiments, step S5 specifically includes the following sub-steps:

[0070] S51. Define the required change in the equivalent resistance of the composite network in the high-temperature and low-temperature ranges, wherein the change in the high-temperature range... Changes in the low-temperature range ;

[0071] S52. Within a predefined resistance range, iterate through the candidate R3 values ​​and, for each candidate R3, calculate its resistance value within the range specified by the given condition. and The equivalent resistance difference at temperature and its and The equivalent resistance difference at temperature ;

[0072] S53. From all candidate R3s, select the one that can make near And can make near The value of R3 is used as a feasible range of R3 values. ;

[0073] S54. Based on the selected R3 values, use the formula Calculate the corresponding resistance value of R2.

[0074] It should be noted that the iterative calculation method mentioned in this invention is used to determine the resistance values ​​of fixed resistors R2 and R3 in the composite network, ensuring that the equivalent resistance of the composite network at different temperatures can approximate the target resistance value. This method defines the resistance changes in high-temperature and low-temperature ranges, selects a suitable R3 value within a predefined resistance range, and then calculates the corresponding R2 value. This iterative calculation method can accurately match the resistance characteristics of the composite network with the battery charging temperature compensation requirements, thereby achieving dynamic adjustment of the charging voltage.

[0075] Change in high temperature range and changes in the low temperature range These represent the required resistance variation ranges of the composite network under high and low temperature conditions, respectively. These variations are calculated based on the target resistance value. The calculation process involves iterating through candidate R3 values ​​and calculating their equivalent resistance differences ΔRm1 and ΔRm2 at different temperatures. ΔRm1 represents the change in the equivalent resistance of the composite network under high temperature conditions; ΔRm2 represents the change in the equivalent resistance of the composite network under low temperature conditions. By selecting values ​​that allow ΔRm1 to approach... And ΔRm2 is close to By determining the value of R3, we can ascertain the feasible range of values ​​for R3. Then, we use the formula to calculate the corresponding value of R2, thus completing the resistance matching of the composite network.

[0076] Calculate the changes in high-temperature and low-temperature ranges based on the target resistance value. and For example, suppose the change in the target resistance value at high and low temperatures is 9.1 × 10⁻⁶. 4 Ω and 2.275×10 4 Within a predefined resistance range, such as 1000Ω to 100kΩ, iterate through candidate values ​​for R3 and calculate the equivalent resistance difference ΔRm1 and ΔRm2 for each R3 value at different temperatures. For example, for a specific R3 value, calculate its equivalent resistance difference ΔRm1 at a high temperature of 70℃ and a normal temperature of 25℃, and its equivalent resistance difference ΔRm2 at a low temperature of -40℃ and a normal temperature. Then, select R3 values ​​that meet the condition that ΔRm1 is close to 9.1 × 10⁻⁶. 4 Ω and ΔRm2 is close to 2.275×104 The value of R3 (Ω) is determined to identify a feasible range of values ​​for R3. Based on the selected R3 values, the corresponding R2 value is calculated using a formula to complete the resistance matching of the composite network. This method allows for precise determination of the resistance values ​​of R2 and R3, thereby achieving the matching of the equivalent resistance of the composite network with the target resistance value at different temperatures, ensuring the temperature compensation effect of the rechargeable battery.

[0077] In some embodiments, in step S53, the and Calculated using the following formula:

[0078] ;

[0079] .

[0080] It should be noted that the calculation of ΔRm1 and ΔRm2 mentioned in this invention is a key step in the iterative calculation method, used to evaluate whether the change in equivalent resistance of the composite network under different R3 values ​​meets the target requirements. ΔRm1 represents the change in equivalent resistance of the composite network under high temperature conditions; ΔRm2 represents the change in equivalent resistance of the composite network under low temperature conditions. By calculating these two parameters, R3 values ​​that meet the target resistance change can be selected, thereby ensuring that the equivalent resistance of the composite network at different temperatures can accurately match the target resistance value, achieving temperature compensation for the charging voltage.

[0081] The formulas for calculating ΔRm1 and ΔRm2 reflect the changes in the equivalent resistance of the composite network at different temperatures. ΔRm1 is calculated at room temperature. and high temperature The difference in equivalent resistance of the composite network under certain conditions is used to obtain ΔRm2. ΔRm2 is calculated by considering the difference in equivalent resistance of the composite network under low temperature conditions. and room temperature The value is obtained by considering the difference in the equivalent resistance of the composite network under certain conditions. The formula contains... , and These represent the resistance values ​​of the NTC thermistor at room temperature, high temperature, and low temperature, respectively. These resistance values ​​can be calculated using the temperature characteristic formula of the NTC. R3 is a fixed resistor connected in parallel with the NTC, and its resistance value is a variable in the iterative calculation. By calculating these differences, it is possible to evaluate whether the change in equivalent resistance of the composite network under different R3 values ​​conforms to the target resistance change. and Requirements.

[0082] After determining the resistance values ​​of R2 and R3, the equivalent resistance curve of the composite network needs to be calculated and compared with the ideal charging voltage-temperature characteristic curve of the battery. The purpose of this process is to verify whether the actual performance of the composite network meets the predetermined temperature compensation requirements. If the matching degree does not meet the predetermined requirements, the parameters of the NTC thermistor, such as R25 or Beta value, need to be reselected, and iterative calculations need to be performed again to optimize the performance of the composite network.

[0083] The parameter verification and calibration steps involve the following key concepts: The equivalent resistance curve of the composite network refers to the relationship between the equivalent resistance of the composite network and temperature at different temperatures. This curve is obtained by calculating the equivalent resistance Req(Tx) at different temperatures, where Req(Tx) is the total resistance of the NTC thermistor combined with fixed resistors R2 and R3. The ideal charging voltage-temperature characteristic curve of the battery refers to the optimal charging voltage required by the battery at different temperatures, usually provided in the battery's datasheet. Matching degree refers to the degree of similarity between the equivalent resistance curve of the composite network and the ideal characteristic curve of the battery, usually evaluated through error analysis or goodness-of-fit. If the matching degree does not meet the predetermined requirements, it indicates a deviation between the resistance characteristics of the composite network and the battery's needs, requiring adjustment of the NTC parameters to optimize performance.

[0084] Preferably, in practical applications, the parameter verification and calibration process can be refined through the following steps: First, calculate the equivalent resistance curve of the composite network over the entire operating temperature range. This requires calculating the equivalent resistance Req(Tx) at multiple temperature points, such as -40℃, 25℃, and 70℃, and plotting the curve. Then, obtain the battery's ideal charging voltage-temperature characteristic curve, typically extracted from the battery specifications or obtained by fitting experimental data. Next, compare the equivalent resistance curve of the composite network with the battery's ideal characteristic curve to evaluate the matching degree. If the matching degree does not meet the predetermined requirements, for example, if the error exceeds 5%, the parameters of the NTC thermistor need to be reselected, such as R25, the nominal resistance value at 25℃, or the Beta temperature coefficient. After reselecting the parameters, repeat the previous iterative calculation steps, redetermining the resistance values ​​of R2 and R3, until the matching degree between the composite network's equivalent resistance curve and the battery's ideal characteristic curve meets the requirements. In this way, it can be ensured that the composite network can effectively achieve temperature compensation of the charging voltage over the entire operating temperature range, thereby improving the safety and efficiency of battery charging.

[0085] In some embodiments, the charging control IC is a constant voltage charging IC without built-in temperature compensation; the method provides the required temperature compensation characteristics through the external NTC composite network.

[0086] This invention provides the necessary temperature compensation characteristics through an external NTC composite network, enabling precise voltage regulation of the rechargeable battery under different temperature conditions. This method effectively expands the application range of the charging control IC, making it suitable for charging scenarios requiring temperature compensation, while reducing system complexity and cost.

[0087] A constant voltage charging IC is an integrated circuit used to control the charging process. Its main function is to provide a stable charging voltage, but it lacks the ability to automatically adjust the charging voltage according to temperature changes. An NTC composite network refers to a network composed of NTC thermistors and fixed resistors. Its equivalent resistance changes with temperature, enabling it to automatically adjust the charging voltage based on ambient temperature. By integrating the NTC composite network into the feedback loop of the charging control IC, the temperature sensitivity of the NTC and the stability of the fixed resistor are utilized to achieve dynamic adjustment of the charging voltage. The core of this method lies in using the change in the equivalent resistance of the NTC composite network to compensate for the insufficient temperature characteristics of the charging control IC, thereby achieving temperature compensation for the rechargeable battery.

[0088] For example, firstly, a suitable constant voltage charging IC is selected, ensuring its compatibility with the NTC composite network. Then, based on the battery specifications and charging requirements, the NTC composite network is designed, including selecting appropriate NTC thermistors and fixed resistors. Next, the NTC composite network is integrated into the feedback loop of the charging control IC to ensure its proper functioning. During implementation, the performance of the composite network needs to be verified to ensure effective temperature compensation across the entire operating temperature range. For example, the charging voltage at different temperatures can be experimentally tested to verify whether it meets the battery's charging requirements. If the compensation effect of the composite network is found to be unsatisfactory, the NTC parameters can be adjusted or the composite network redesigned until a satisfactory compensation effect is achieved. In this way, it can be ensured that the charging control IC can safely and efficiently charge the battery under different temperature conditions.

[0089] In some embodiments, during the iterative calculation in step S53, a segmented processing strategy is adopted for the low-temperature segment: when the ambient temperature is below 0°C, priority is given to ensuring that the charging voltage does not exceed the battery's allowable absolute maximum value, while relaxing the requirements for charging accuracy; the feasible range of R3 values... The determination of the value is mainly based on fitting the temperature characteristics above 0℃.

[0090] It should be noted that the low-temperature segmented processing strategy mentioned in this invention is to address the issue of significant differences between the characteristics of NTC thermistors and their nominal temperature coefficients at low temperatures. In such cases, directly using the nominal temperature coefficient for compensation may cause the charging voltage to exceed the battery's safe range. Therefore, this invention proposes prioritizing ensuring that the charging voltage does not exceed the battery's maximum allowable value under low-temperature conditions, while appropriately relaxing the requirements for charging accuracy. This method, by optimizing the compensation strategy in the low-temperature segment, ensures that the battery can be safely charged even at extremely low temperatures, while avoiding the risk of overcharging due to NTC characteristic deviations.

[0091] The low-temperature range refers to conditions where the ambient temperature is below 0℃. Within this temperature range, the resistance change of the NTC thermistor deviates significantly from its nominal temperature coefficient. The compensation objective in the low-temperature range is to ensure that the charging voltage does not exceed the battery's maximum allowable value. The feasible range of R3 values ​​was obtained by fitting the characteristics at temperatures above 0℃. This indicates that the compensation strategy in the low-temperature range is primarily based on parameters determined within the temperature range above 0℃ to ensure consistency between the compensation effect in the low-temperature range and the overall compensation strategy.

[0092] Preferably, in practical applications, the implementation process of the segmented processing strategy for the low-temperature segment can be refined through the following steps: First, determine the temperature range of the low-temperature segment, for example, an ambient temperature below 0°C. Then, based on the characteristics of the NTC thermistor in the temperature range above 0°C, calculate the feasible value range of R3. For example, by fitting within a temperature range of 0°C to 25°C, determine the minimum and maximum values ​​of R3. Next, in the low-temperature segment, below 0°C, prioritize ensuring that the charging voltage does not exceed the maximum allowable value of the battery, and appropriately relax the requirements for charging accuracy. In specific implementation, the compensation effect in the low-temperature segment can be optimized by adjusting the value range of R3. For example, when the ambient temperature is below 0°C, select a value for R3 that can limit the charging voltage to not exceed the maximum allowable value of the battery at low temperatures. In this way, the battery can be effectively protected under low-temperature conditions, avoiding the risk of overcharging due to NTC characteristic deviations, while ensuring the safety and reliability of the charging process.

[0093] The above embodiments of the present invention have the following beneficial effects:

[0094] 1. Automatic compensation through the temperature characteristics of NTC thermistors: By utilizing the resistance of NTC thermistors to change with temperature, a composite network can be constructed to automatically sense changes in ambient temperature and adjust the charging voltage. No additional temperature sensor is required, which simplifies circuit design, reduces system complexity and cost, and improves the automation and reliability of the charging process.

[0095] 2. Precisely Matching Battery Charging Needs: Based on the maximum charging voltage characteristics of the rechargeable battery at different temperatures, the resistance value of the upper voltage divider feedback network is precisely calculated and iteratively optimized to ensure that the charging voltage can accurately compensate for temperature changes. This effectively avoids the problem of overcharging or undercharging the battery under high or low temperature conditions, improves charging efficiency, and extends the battery's lifespan.

[0096] 3. Applicable to a variety of charging control ICs: This method is specifically designed for constant voltage charging ICs that do not have built-in temperature compensation functions. By using an external composite network, it provides the necessary temperature compensation characteristics, which broadens the application range of existing charging control ICs and enables them to charge batteries safely and efficiently under a wider range of temperature conditions, thereby enhancing the versatility and flexibility of the system.

[0097] Furthermore, the storage medium in the embodiments of this application stores program instructions capable of implementing all the above methods. These program instructions can be stored in the storage medium in the form of a software product, including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks, or terminal devices such as computers, servers, mobile phones, and tablets.

[0098] The above description is merely an explanation of some preferred embodiments of the present invention and the technical principles employed. Those skilled in the art should understand that the scope of the invention as described in the embodiments of the present invention is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in the embodiments of the present invention.

Claims

1. A method for using NTC as a charging temperature compensation for rechargeable batteries, characterized in that, Includes the following steps: S1. According to the rechargeable battery's specifications, determine the high temperature... , normal temperature and low temperature The maximum allowable charging voltage of the rechargeable battery at the three characteristic temperatures are as follows: and ; S2. Determine the value of the lower voltage divider resistor Rbase based on the feedback reference voltage Vref of the charging control IC and the input current Ifb of its feedback detection pin. S3, based on the above , , And Vref and Rbase, respectively calculated in , and At that time, the target resistance value required by the upper voltage divider feedback network and ; S4. Select an NTC thermistor with a specific temperature coefficient Beta and a nominal resistance of R25 at 25°C. S5. Construct a composite network consisting of the NTC thermistor connected in parallel with a fixed resistor R3, and then connected in series with another fixed resistor R2; determine the resistance values ​​of R2 and R3 through iterative calculation methods, so that the composite network... , and The equivalent resistance values ​​at the three temperature points respectively approximate the target resistance value. and ; S6. The composite network is connected to the feedback loop of the charging control IC. By utilizing the characteristic that its equivalent resistance changes with temperature, the charging voltage is automatically adjusted to achieve temperature compensation for the charging battery.

2. The method according to claim 1, characterized in that, In step S2, the resistance value of the lower voltage divider resistor Rbase is determined according to the following constraint: the voltage drop generated by Ifb flowing through Rbase must be much smaller than Vref to ensure the accuracy of the feedback voltage.

3. The method according to claim 2, characterized in that, In step S3, the target resistance value and Calculated using the following set of formulas: ； ； 。 4. The method according to claim 3, characterized in that, In step S4, the NTC thermistor is at any temperature The resistance value below Calculated using the following formula: ,in, The current ambient temperature is expressed in degrees Celsius.

5. The method according to claim 4, characterized in that, In step S5, the composite network is at any temperature The equivalent resistance below Calculated using the following formula: 。 6. The method according to claim 5, characterized in that, In step S5, the iterative calculation method specifically includes the following sub-steps: S51. Define the required change in the equivalent resistance of the composite network in the high-temperature and low-temperature ranges, wherein the change in the high-temperature range... Changes in the low-temperature range ; S52. Within a predefined resistance range, iterate through the candidate R3 values ​​and for each candidate R3, calculate its resistance value within the range specified in the original text. and The equivalent resistance difference at temperature and its and The equivalent resistance difference at temperature ; S53. From all candidate R3s, select the one that can make near And can make near The value of R3 is used as a feasible range of R3 values. ; S54. Based on the selected R3 values, use the formula Calculate the corresponding resistance value of R2.

7. The method according to claim 6, characterized in that, In step S53, the and Calculated using the following formula: ； 。 8. The method according to claim 1, characterized in that, In step S5, after determining the resistance values ​​of R2 and R3, a parameter verification and correction step is also included: calculate the equivalent resistance curve of the composite network over the entire operating temperature range and compare it with the ideal charging voltage-temperature characteristic curve of the rechargeable battery. If the matching degree does not meet the predetermined requirements, return to step S4, reselect the R25 or Beta value of the NTC thermistor, and repeat step S5.

9. The method according to claim 1, characterized in that, The charging control IC is a constant voltage charging IC without built-in temperature compensation function; the method provides the required temperature compensation characteristics through the external NTC composite network.

10. The method according to claim 6, characterized in that, In the iterative calculation of step S53, a segmented processing strategy is adopted for the low-temperature range: when the ambient temperature is below 0℃, priority is given to ensuring that the charging voltage does not exceed the absolute maximum value allowed by the battery, while relaxing the requirements for charging accuracy; the feasible range of R3 values... The determination of the value is mainly based on fitting the temperature characteristics above 0℃.

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