CN216016483U - Improved generation lithium iron phosphate battery charging line - Google Patents
Improved generation lithium iron phosphate battery charging line Download PDFInfo
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- CN216016483U CN216016483U CN202122045425.2U CN202122045425U CN216016483U CN 216016483 U CN216016483 U CN 216016483U CN 202122045425 U CN202122045425 U CN 202122045425U CN 216016483 U CN216016483 U CN 216016483U
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Abstract
The utility model discloses an improved lithium iron phosphate battery charging circuit, relates to the technical field of battery charging, and solves the technical problems that a recharging threshold value set by an existing charging management chip is generally lower than a floating charging voltage by 0.1-0.2V, the charging management chip is not suitable for charging management of a lithium iron phosphate battery, and the performance degradation and the service life of the battery are easily caused. The charging circuit comprises a recharging voltage regulating circuit, wherein two ends of the recharging voltage regulating circuit are respectively connected with an NSTDBY pin of an SLM6900 chip and a first resistor (R6), and the recharging voltage value of the lithium iron phosphate battery can be regulated. The utility model reduces the recharging voltage threshold value through the recharging voltage regulating circuit, and is used for the charging management of the lithium iron phosphate battery. When the lithium iron phosphate battery is charged, the high-capacity state can be maintained, and the service life and the performance of the battery cannot be reduced due to overcharge.
Description
Technical Field
The utility model relates to the technical field of battery charging, in particular to an improved lithium iron phosphate battery charging circuit.
Background
At present, a common charging management chip generally performs charging management based on the voltage characteristic of a ternary lithium battery, and the voltage characteristic of the lithium iron phosphate battery is not fully considered. The characteristics of lithium batteries made of different materials are different, for example, after the ternary lithium battery is fully charged, a charging power supply is disconnected, the voltage drop amplitude of the battery is very small, and the voltage drop of the battery after standing at room temperature is about 0.1V in one month. After the lithium iron phosphate battery is normally charged and stopped, the voltage drop is larger than that of a ternary lithium battery, and the voltage drop of a single battery exceeds 0.2V within 10 minutes.
At present, a switching step-down chip is generally adopted for charging management of the lithium iron phosphate battery, and brands of the chip mainly include rhyme, MPS, TI, pinnamo, south core and the like, such as an SLM6900 chip and a corresponding charging circuit shown in fig. 1. The SLM6900 is a charging circuit supporting various types of lithium batteries or lithium iron phosphate batteries, and has 14 pins in total, and is preset with three or four lithium battery charging modes, and also supports other output voltage modes regulated by peripheral voltage dividing resistors.
In the conventional lithium iron phosphate battery, during charging management, after charging is normally stopped, the voltage of the battery quickly falls below a recharging threshold value. If the battery is not removed, the battery is restarted for charging, the voltage rises rapidly to the cutoff voltage, the battery charging is cut off, and then the pulse charging is continuously maintained until the charging power supply is disconnected. Long-term pulse charging can affect the material structure in the battery core, degrade the performance of the battery and shorten the service life of the battery. Based on the full consideration of the voltage characteristics of the lithium iron phosphate battery, an improved charging circuit aiming at the characteristics of the lithium iron phosphate battery is urgently needed.
In the process of implementing the utility model, the utility model people find that at least the following problems exist in the prior art:
the recharging threshold value set by the existing charging management chip is generally lower than the floating charging voltage by 0.1-0.2V, so that the charging management chip is not suitable for charging management of the lithium iron phosphate battery, and the performance degradation and the service life shortening of the battery are easily caused.
SUMMERY OF THE UTILITY MODEL
The utility model aims to provide an improvement on a charging circuit of a lithium iron phosphate battery, which aims to solve the technical problems that in the prior art, continuous pulse charging causes overcharge and the service life of the battery is shortened. The technical effects that can be produced by the preferred technical scheme in the technical schemes provided by the utility model are described in detail in the following.
In order to achieve the purpose, the utility model provides the following technical scheme:
the utility model provides an improved lithium iron phosphate battery charging circuit which comprises a recharging voltage regulating circuit, wherein two ends of the recharging voltage regulating circuit are respectively connected with an NSTDBY pin and a first resistor of an SLM6900 chip, and the recharging voltage value of the lithium iron phosphate battery can be regulated.
Preferably, the recharging voltage regulating circuit comprises a second resistor, a third resistor and a first MOS transistor; the third resistor and the first MOS tube are connected in series, and the third resistor and the first MOS tube are connected in series and then connected in parallel with the second resistor.
Preferably, the gate of the first MOS transistor is connected to an NSTDBY pin of the SLM6900 chip; the drain electrode of the first MOS tube is connected with the first resistor; and the source electrode of the first MOS tube is grounded.
Preferably, the first MOS transistor is an N-channel MOS transistor, and the model is 2N 7002.
Preferably, the recharge voltage regulating circuit further comprises a fourth resistor, and two ends of the fourth resistor are respectively connected with the source and the gate of the first MOS transistor.
Preferably, the resistance value of the second resistor and the resistance value of the third resistor after being connected in parallel are the same as the resistance value of the fifth resistor.
Preferably, the resistances of the second resistor and the third resistor are 210K and 4.7M, respectively.
Preferably, when the lithium iron phosphate battery is charged, the NSTDBY pin of the SLM6900 chip is at a high level, the first MOS transistor is turned on, and the second resistor and the third resistor are connected in parallel; when the lithium iron phosphate battery is charged, the NSTDBY pin of the SLM6900 chip is converted into a low level, the first MOS tube is cut off, the second resistor participates in voltage division, and the third resistor is suspended.
Preferably, when the capacity of the lithium iron phosphate battery is reduced to 80% -90% of the full charge capacity, the lithium iron phosphate battery automatically starts recharging.
Preferably, the recharging voltage of the lithium iron phosphate battery is 6.6V.
The implementation of one of the technical schemes of the utility model has the following advantages or beneficial effects:
the utility model can adjust the floating charge voltage through the recharge voltage adjusting circuit, thereby reducing the threshold value of the recharge voltage, enabling the recharge voltage threshold value to be lower than the floating charge voltage value by more than 0.2V, and being more suitable for charging management of the lithium iron phosphate battery. When the recharging voltage is reduced to a set threshold value, the improved lithium iron phosphate battery restarts recharging, and the technical problem that the service life and the performance of the battery are influenced because the lithium iron phosphate battery is continuously charged when a power supply is not unplugged is solved. The battery can maintain a high-capacity state, and continuous pulse charging caused overcharge can be avoided.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without inventive efforts, wherein:
fig. 1 is a charging circuit diagram of a conventional lithium iron phosphate battery;
figure 2 is a charging circuit diagram of an embodiment of the present invention.
Detailed Description
In order that the objects, aspects and advantages of the present invention will become more apparent, various exemplary embodiments will be described below with reference to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration various exemplary embodiments in which the utility model may be practiced. The same numbers in different drawings identify the same or similar elements unless otherwise indicated. The implementations described in the exemplary embodiments below are not intended to represent all implementations consistent with the present disclosure. It is to be understood that they are merely examples of processes, methods, apparatus, etc. consistent with certain aspects of the present disclosure as detailed in the appended claims, and that other embodiments may be used or structural and functional modifications may be made to the embodiments set forth herein without departing from the scope and spirit of the present disclosure.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," and the like are used in the orientations and positional relationships illustrated in the accompanying drawings for the purpose of facilitating the description of the present invention and simplifying the description, and do not indicate or imply that the elements so referred to must have a particular orientation, be constructed in a particular orientation, and be operated. The terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. The term "plurality" means two or more. The terms "connected" and "coupled" are to be construed broadly and may include, for example, a fixed connection, a removable connection, an integral connection, a mechanical connection, an electrical connection, a communicative connection, a direct connection, an indirect connection via intermediate media, and may include, for example, a connection between two elements or an interaction between two elements. The term "and/or" includes any and all combinations of one or more of the associated listed items. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In order to explain the technical solution of the present invention, the following description is made by way of specific examples, which only show the relevant portions of the embodiments of the present invention.
The first embodiment is as follows:
as shown in fig. 2, the present invention provides an improved lithium iron phosphate battery charging circuit, which includes a recharging voltage adjusting circuit, and two ends of the recharging voltage adjusting circuit are respectively connected to the NSTDBY pin (i.e., pin 5 in fig. 2) and the first resistor R6 of the SLM6900 chip, so as to adjust a value of the recharging voltage of the lithium iron phosphate battery. Such as adjusting the recharge voltage value to 6.6V (0.5V lower than the float voltage value of 7.1V). The improved lithium iron phosphate battery charging circuit reduces the recharging voltage of the charging circuit through the recharging voltage adjusting circuit, so that the recharging voltage threshold value is lower than the floating charging voltage value by more than 0.2V, and the charging circuit is more suitable for charging management of the lithium iron phosphate battery. When the recharging voltage is reduced to a set threshold value, the improved lithium iron phosphate battery restarts recharging, and the technical problem that the service life and the performance of the battery are influenced because the lithium iron phosphate battery is continuously charged when a power supply is not unplugged is solved. The battery can maintain a high-capacity state, and continuous pulse charging caused overcharge can be avoided.
As an alternative embodiment, the recharge voltage regulating circuit comprises a second resistor R7, a third resistor R8 and a first MOS transistor Q2; the third resistor R8 and the first MOS transistor Q2 are connected in series, and the third resistor R8 and the first MOS transistor Q2 are connected in series and then connected in parallel with the second resistor R7. Specifically, the circuit can adjust the floating charge voltage by adjusting the connection relationship between the resistance values of the second resistor R7 and the third resistor R8 and the second resistor R7, the third resistor R8 and the first MOS transistor Q2, thereby adjusting the recharging voltage.
As an optional implementation, the gate of the first MOS transistor Q2 is connected to the NSTDBY pin of the SLM6900 chip; the drain electrode of the first MOS transistor Q2 is connected with a first resistor R6; the source of the first MOS transistor Q2 is grounded. Specifically, the first resistor R6, the second resistor R7 and the third resistor R8 are externally connected with the first MOS transistor Q2 to form a recharging voltage regulating circuit. The drain electrode of the first MOS transistor Q2 is connected with a first resistor R6; the source electrode of the first MOS transistor Q2 is grounded, so that the second resistor R7 and the third resistor R8 are connected in parallel under the condition that the first MOS transistor Q2 is conducted; the grid electrode of the first MOS tube is connected with an NSTDBY pin of the SLM6900 chip, the NSTDBY pin of the SLM6900 chip is used for indicating the completion of battery charging, the voltage of the grid electrode can be changed through the change of the voltage of the NSTDBY pin, the working state of the first MOS tube Q2 can be changed, the floating charge voltage is adjusted, and therefore the recharging voltage is adjusted. During normal charging, the first MOS transistor Q2 is in a conducting state, and the second resistor R7 and the third resistor R8 are connected in parallel, so that the voltage at the first resistor R6 can be adjusted; after the charging is stopped, the first MOS transistor Q2 is in a stop state, the third resistor R8 is suspended, and only the second resistor R7 adjusts the voltage at the first resistor R6, so that the recharging voltage of the lithium iron phosphate battery can be reduced.
As an alternative implementation, the first MOS transistor Q2 is an N-channel MOS transistor, model 2N 7002. In particular, the 2N7002 design reduces on-resistance and provides robust, reliable, fast switching performance. 2N7002 is particularly useful for low voltage, low current applications, such as for small servo motor control, power MOSFET gate drivers, and other switching applications. The model of the first MOS transistor Q2 has other schemes, and this embodiment is a preferable scheme for improving the circuit.
As an optional implementation, the recharge voltage regulating circuit further includes a fourth resistor R9, and two ends of the fourth resistor R9 are respectively connected to the source and the gate of the first MOS transistor Q2. Specifically, the fourth resistor R9 can protect the first MOS transistor Q2, so that the operating state of the first MOS transistor Q2 is stable, and the influence of other interferences is avoided.
As an alternative embodiment, the resistance value of the second resistor R7 and the third resistor R8 after being connected in parallel is the same as that of the fifth resistor R7'; the resistances of the second resistor R7 and the third resistor R8 are 210K and 4.7M respectively. The fifth resistor R7' shown in FIG. 1 and the second resistor R7 shown in FIG. 2 are both connected in series with the resistor R6 shown in the figure for voltage sampling. Specifically, the resistance value of the second resistor R7 and the third resistor R8 after being connected in parallel is the same as that of the fifth resistor R7', so that the recharging voltages before and after adjustment can be more conveniently compared. Therefore, the resistance RP after the second resistor R7 and the third resistor R8 are connected in parallel is: r7 × R8/R7+ R8 × 4700 × 210/4700+210 × 201K, in accordance with the preferred value 201K of the fifth resistor R7'. The resistance values of the second resistor R7 and the third resistor R8 are selected as well as other resistance values, and 210K and 4.7M are the optimal resistance values provided by the present embodiment.
As an optional implementation manner, when the lithium iron phosphate battery is charged, the NSTDBY pin of the SLM6900 chip is at a high level, the first MOS transistor Q2 is turned on, and the second resistor R7 and the third resistor R8 are connected in parallel; when the lithium iron phosphate battery is charged, the NSTDBY pin of the SLM6900 chip is converted into low level, the first MOS transistor Q2 is cut off, the second resistor R7 participates in voltage division, and the third resistor R8 is suspended. Specifically, when the pin NSTDBY is at a high level, it indicates that the battery is charging, and at this time, the first MOS transistor Q2 is in a conducting state, and the second resistor R7 and the third resistor R8 participate in voltage division simultaneously; when the NSTDBY pin is turned to low level, it indicates that the battery has been charged, and the current for continuous input is cut off, at this time, the first MOS transistor Q2 is in cut-off state, the third resistor R8 does not participate in voltage division, and only the second resistor R7 participates in voltage division.
As an alternative embodiment, the recharge voltage of the lithium iron phosphate battery is 6.6V. Specifically, parameters of the SLM6900 chip: feedback voltage threshold VFB1.205V and recharge voltage feedback voltage threshold VRECHARGE＝96.4％*VFBAll 1.16V are fixed. In the charging circuit of the lithium iron phosphate battery shown in fig. 1, the resistances of the first resistor R6, the fifth resistor R7' and the sixth resistor R5 are 3.3K, 201K and 1M, respectively. At this time, the float voltage of the circuit is (R5+ R6+ R7)/(R6+ R7) × VFB(1000+3.3+201)/(3.3+201) × 1.205 ═ 7.10V; recharging voltage ═ (R5+ R6+ R7)/(R6+ R7) × VRECHARGE(1000+3.3+201)/(3.3+201) × 1.16 — 6.84V. In this embodiment, as shown in fig. 2, in the charging circuit of the improved lithium iron phosphate battery, the resistances of the first resistor R6 and the sixth resistor R5 are not changed, the resistor RP after the second resistor R7 and the third resistor R8 are connected in parallel participates in voltage division, and at this time, the floating charge voltage of the circuit is (R5+ R6+ RP)/(R6+ RP) × VFB(1000+3.3+201)/(3.3+201) × 1.205 ═ 7.10V. Wherein, RP represents the resistance after R7 is connected with R8 in parallel; r5+ R6+ RP represents the total resistance of the voltage divider loop; r6+ RP represents the sampling resistance; voltage at R6+ RP is VFB. According to the voltage dividing circuit principle, the voltage ratio is equal to the corresponding resistance ratio. Float voltage/VFBAfter formula conversion, (R5+ R6+ RP)/R6+ RP, the float voltage (R5+ R6+ RP)/(R6+ RP) × V is obtainedFB. When the battery is in a full-charge state, the first MOS transistor Q2 is switched to a cut-off state, and the recharging voltage of the circuit is (R5+ R6+ R7)/(R6+ R7) × VRECHARGE＝(1000+3.3+210)/(3.3+210) × 1.16 ═ 6.6V. Wherein, R5+ R6+ R7 represents the total resistance of the voltage dividing loop; r6+ R7 is the sampling resistor; vRECHARGERepresenting the voltage at R5+ R7. According to the voltage dividing circuit principle, the voltage ratio is equal to the corresponding resistance ratio. After the formula conversion, the recharge voltage is obtained (R5+ R6+ R7)/(R6+ R7) × VRECHARGE. Therefore, the recharging voltage of the charging circuit of the original lithium iron phosphate battery is 6.84V, and the recharging voltage of the charging circuit of the improved lithium iron phosphate battery of the embodiment is reduced from 6.84V to 6.6V.
As an optional implementation, when the capacity of the lithium iron phosphate battery is reduced to 80% -90% of the full charge capacity, the lithium iron phosphate battery automatically starts recharging; specifically, the recharging voltage of the improved lithium iron phosphate battery is 6.6V, which is about 80% -90% of the full charging capacity of the original lithium iron phosphate battery, and when the recharging voltage of the lithium iron phosphate battery is reduced to 6.6V, the lithium iron phosphate battery starts to recharge.
The embodiment is only a specific example and does not indicate such an implementation of the utility model.
While the utility model has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the utility model. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the utility model without departing from the essential scope thereof. Therefore, it is intended that the utility model not be limited to the particular embodiment disclosed, but that the utility model will include all embodiments falling within the scope of the appended claims.
Claims (10)
1. The improved lithium iron phosphate battery charging circuit is characterized by comprising a recharging voltage regulating circuit, wherein two ends of the recharging voltage regulating circuit are respectively connected with an NSTDBY pin of an SLM6900 chip and a first resistor (R6), and the recharging voltage value of the lithium iron phosphate battery can be regulated.
2. The improved lithium iron phosphate battery charging circuit according to claim 1, wherein the recharging voltage regulating circuit comprises a second resistor (R7), a third resistor (R8) and a first MOS transistor (Q2); the third resistor (R8) and the first MOS tube (Q2) are connected in series, and the third resistor (R8) and the first MOS tube (Q2) are connected in series and then connected in parallel with the second resistor (R7).
3. The improved lithium iron phosphate battery charging circuit according to claim 2, wherein a gate of the first MOS transistor (Q2) is connected to the NSTDBY pin of the SLM6900 chip; the drain electrode of the first MOS transistor (Q2) is connected with the first resistor (R6); the source electrode of the first MOS tube (Q2) is grounded.
4. The improved lithium iron phosphate battery charging circuit according to claim 2, wherein the first MOS transistor (Q2) is an N-channel MOS transistor, model 2N 7002.
5. The improved lithium iron phosphate battery charging circuit according to claim 2, characterized in that said recharging voltage regulating circuit further comprises a fourth resistor (R9), and two ends of said fourth resistor (R9) are respectively connected to the source and the gate of the first MOS transistor (Q2).
6. The improved lithium iron phosphate battery charging circuit according to claim 2, wherein the resistance value of the second resistor (R7) and the third resistor (R8) after being connected in parallel is the same as the resistance value of the fifth resistor (R7').
7. The improved lithium iron phosphate battery charging circuit according to claim 6, wherein the resistances of the second resistor (R7) and the third resistor (R8) are 210K and 4.7M, respectively.
8. The improved lithium iron phosphate battery charging circuit according to claim 2, wherein when the lithium iron phosphate battery is charged, the NSTDBY pin of the SLM6900 chip is at a high level, the first MOS transistor (Q2) is turned on, and the second resistor (R7) and the third resistor (R8) are connected in parallel; when the lithium iron phosphate battery is charged and stopped, the NSTDBY pin of the SLM6900 chip is switched to be low level, the first MOS tube (Q2) is stopped, the second resistor (R7) participates in voltage division, and the third resistor (R8) is suspended.
9. The improved lithium iron phosphate battery charging line according to claim 1, wherein the lithium iron phosphate battery automatically starts recharging when the capacity of the lithium iron phosphate battery drops to 80% -90% of the full charging capacity.
10. The improved lithium iron phosphate battery charging circuit according to claim 1, wherein the recharging voltage of the lithium iron phosphate battery is 6.6V.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202122045425.2U CN216016483U (en) | 2021-08-27 | 2021-08-27 | Improved generation lithium iron phosphate battery charging line |
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| CN202122045425.2U CN216016483U (en) | 2021-08-27 | 2021-08-27 | Improved generation lithium iron phosphate battery charging line |
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| CN216016483U true CN216016483U (en) | 2022-03-11 |
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| CN202122045425.2U Active CN216016483U (en) | 2021-08-27 | 2021-08-27 | Improved generation lithium iron phosphate battery charging line |
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