A lithium battery charging voltage control method and device

Abstract

The present invention relates to the field of lithium battery charging protection technology, and in particular to a lithium battery charging voltage control method and device. Compared with the prior art, the present invention charges the lithium battery with a constant current to obtain the charging protection voltage of the charging protection board of the lithium battery when it is fully charged; when the lithium battery is charged again, constant current charging is first performed, and then constant voltage charging is performed at a voltage value lower than the charging protection voltage. The present invention does not need to use a high-cost dedicated charging management chip to control the charging of the lithium battery. By using constant current charging during the first charging until the protection function of the charging protection board is triggered, a voltage value close to the protection voltage value is recorded. When the lithium battery is charged again, constant current charging can be used for fast charging first. When it is close to being fully charged, constant voltage charging is used and the recorded voltage value is used as the full condition. The high triggering accuracy of the charging protection board is used to improve the precise control of the charging voltage to prevent overcharging or undercharging.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery charging protection, and in particular to a lithium battery charging voltage control method and device. Background Art

[0002] During normal use, a positive chemical reaction occurs inside a lithium battery, where electrical energy and chemical energy are converted into each other. Under certain conditions, if a lithium battery is overcharged, over-discharged, or over-currented, a chemical side reaction will occur inside the battery. Once the chemical side reaction occurs, it will seriously affect the performance and service life of the battery. Even worse, a large amount of gas may be generated, causing the internal pressure of the battery to increase rapidly and then explode, leading to safety problems. Therefore, lithium batteries need to be equipped with a charging protection circuit to effectively monitor and control the charging of the battery, so as to protect the battery under certain conditions to prevent damage to the battery.

[0003] At present, the charging voltage control of lithium batteries usually adopts the following two methods: the most common one is the lithium battery charging protection method and charging protection circuit disclosed in the publication number CN103354349A (publication date October 16, 2013). This type of solution generally uses the MCU's internal 1 / 4VDD channel to sample the battery voltage to directly determine whether the lithium battery is full. This method is affected by the individual differences of the MCU and its own sampling accuracy, resulting in excessive deviation of the sampling voltage. However, the internal reference of the MCU has an error of ±1%, and the 1 / 4VDD obtained by stepping down the internal VDD of the MCU also has an error of ±3%, resulting in a sampling voltage error of up to ±4%. Therefore, the sampled battery voltage cannot be used as a voltage value for judging fullness. When dual protection is required, it will result in only one side working or not being fully charged; when dual protection is not required, it will also cause overcharging and damage the battery. The other is like Figure 1 As shown, a dedicated charging management chip is used to control the charging of lithium batteries. This method has high control accuracy, but the cost of this solution is also high.

[0004] In summary, the existing methods for protecting lithium battery charging have the problems of high cost or inaccurate detection and protection, which may easily lead to undercharging or overcharging. Summary of the invention

[0005] In order to solve the above-mentioned deficiencies in the prior art, the present invention provides a lithium battery charging voltage control method and device, wherein the lithium battery charging voltage control method comprises:

[0006] Performing constant current charging on the lithium battery, and obtaining a charging protection voltage of the charging protection board of the lithium battery when the battery is fully charged as a first voltage;

[0007] When charging the lithium battery again, firstly perform constant current charging, then perform constant voltage charging with the second voltage as the constant voltage value, and stop charging when the charging current is less than the preset cut-off current value;

[0008] The second voltage is the first voltage minus a preset protection difference.

[0009] In one embodiment, the method for obtaining the first voltage comprises the following steps:

[0010] S10: charging the lithium battery with a constant current and sampling the battery voltage of the lithium battery, wherein the lithium battery has a calibrated full charge voltage;

[0011] S20: When the battery voltage reaches 90-98% of the rated full voltage, memorizing the battery voltage every 0.5-5 seconds;

[0012] S30: When the charging protection board of the lithium battery performs charging protection, the battery voltage memorized last time is read as the first voltage.

[0013] In one embodiment, in the step S20 to the step S30, if the charging protection board is not in charging protection, charging is stopped and the memory value of the battery voltage is cleared.

[0014] In one embodiment, the first voltage is obtained when the lithium battery is fully charged for the first time.

[0015] In one embodiment, the preset cut-off current value is 20-150 mA.

[0016] In one embodiment, the preset protection difference is 10-50 mV.

[0017] In one embodiment, when the lithium battery is charged again, the constant voltage charging is performed when the charging voltage of the lithium battery reaches a second voltage through constant current charging.

[0018] In one embodiment, when the lithium battery is charged again, the constant voltage charging is performed when the charging voltage of the lithium battery reaches a third voltage through constant current charging, and the third voltage is lower than the second voltage.

[0019] In one embodiment, the constant current value of the constant current charging is 0.5-1.5A.

[0020] The present invention also provides a lithium battery device, which adopts the lithium battery charging voltage control method as described in any one of the above items.

[0021] Based on the above, compared with the prior art, the present invention charges the lithium battery with a constant current to obtain the charging protection voltage of the charging protection board of the lithium battery when it is fully charged; when the lithium battery is charged again, constant current charging is first performed, and then constant voltage charging is performed at a voltage value lower than the charging protection voltage. The present invention does not need to use a high-cost dedicated charging management chip to control the charging of the lithium battery. By using constant current charging during the first charging until the protection function of the charging protection board is triggered, a voltage value close to the protection voltage value is recorded. When the lithium battery is charged again, it can be fast charged by constant current charging first, and constant voltage charging is used when it is close to being fully charged, and the recorded voltage value is used as the full condition. The high triggering accuracy of the charging protection board is used to improve the precise control of the charging voltage to prevent overcharging or undercharging.

[0022] Other features and beneficial effects of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other beneficial effects of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. The positional relationships described in the drawings in the following description are based on the directions in which the components are drawn in the diagrams, unless otherwise specified.

[0024] Figure 1 A schematic diagram of a circuit for controlling the charging of a lithium battery using a dedicated charging management chip in the prior art;

[0025] Figure 2 A schematic diagram of the flow chart of the lithium battery charging voltage control method provided by the present invention;

[0026] Figure 3 A schematic diagram of a lithium battery charging circuit according to an embodiment of the present invention;

[0027] Figure 4 The present invention is a flow chart of a method for obtaining a first voltage according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; the technical features designed in different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be noted that all terms used in the present invention (including technical terms and scientific terms) have the same meanings as those generally understood by ordinary technicians in the field to which the present invention belongs, and cannot be understood as limiting the present invention; it should be further understood that the terms used in the present invention should be understood to have the same meanings as these terms in the context of this specification and in the relevant fields, and should not be understood in an idealized or overly formal sense, unless explicitly defined in the present invention.

[0030] The following is an explanation through specific examples.

[0031] The present invention provides a lithium battery charging voltage control method, which can be applied to lithium battery power supply products such as electric clippers, razors, etc. Figure 2 As shown, including:

[0032] Performing constant current charging on the lithium battery, and obtaining a charging protection voltage of the charging protection board of the lithium battery when the battery is fully charged as a first voltage;

[0033] When charging the lithium battery again, firstly perform constant current charging, then perform constant voltage charging with the second voltage as the constant voltage value, and stop charging when the charging current is less than the preset cut-off current value;

[0034] The second voltage is the first voltage minus a preset protection difference.

[0035] In the specific implementation, this embodiment takes the charging voltage control of a 3.7V 18650 battery as an example for explanation. The rated full voltage of the battery is 4.2V. It should be noted that the present invention is not limited to batteries with a full voltage of 4.2V. Figure 3 The figure shows a schematic diagram of the lithium battery charging circuit of this embodiment. The adapter charges the battery through the MOS tube, the MCU controls the MOS tube to charge the battery through PWM, and monitors the battery charging voltage by sampling the voltage of R10\R11.

[0036] Specifically, Figure 4 As shown, the method for obtaining the first voltage includes the following steps:

[0037] First, S10 performs constant current charging of the lithium battery with a constant current value of 0.5 to 1.5A and samples the battery voltage of the lithium battery. The lithium battery has a calibrated full charge voltage; the calibrated full charge voltage in this embodiment is 4.2V. Preferably, the constant current value of the constant current charging is 1A.

[0038] Then, in S20, when the battery voltage reaches 90-98% of the rated full voltage, the battery voltage is memorized every 0.5-5 seconds; in some embodiments, for a battery with a full voltage of 4.2V, when the battery voltage is greater than 4.05V and less than 4.3V during charging, the memory is memorized every 1S. Preferably, the memory cycle can take a relatively large value to reduce the number of record judgments and speed up the charging speed.

[0039] S30 When the charging protection board of the lithium battery is charging protection, the battery voltage memorized last time is read as the first voltage. It should be understood that when the first voltage is recorded, the design purpose is that the first voltage should be equal to the protection voltage of the charging protection board during charging protection, so as to have higher accuracy, but due to the memory cycle, the first voltage may be equal to the protection voltage, i.e., 4.2V, or it may be slightly less than the protection voltage but very close to the protection voltage, and the memory accuracy is within ±10mV. Preferably, the first voltage is obtained when the lithium battery is fully charged for the first time, and when charging is required subsequently, the full condition is determined based on the first voltage obtained when it is fully charged for the first time to improve the accuracy of voltage control.

[0040] Next, combine Figure 2 As shown, after the lithium battery is discharged, when charging the lithium battery again, first perform constant current charging with a constant current value of 1A, and then perform constant voltage charging with a second voltage as a constant voltage value until the charging current is less than the preset cut-off current value, and then stop charging; wherein the second voltage is the first voltage minus the preset protection difference. The preset cut-off current value is 20 to 150 mA, and preferably, the preset cut-off current value in this embodiment is 100 mA. And the preset protection difference is 10 to 50 mV, and the preset protection difference in this embodiment is not 20 mV.

[0041] Preferably, in some embodiments, when the lithium battery is subsequently charged again, when the charging voltage of the lithium battery reaches the second voltage through constant current charging, for example, the second voltage in the above embodiment is 4.18 volts, the constant voltage value during constant voltage charging is 4.18 volts. Or another way is to charge the lithium battery through constant current to a third voltage, and then perform constant voltage charging with the second voltage as the constant voltage value. For example, it can be set to enter the constant voltage charging mode when the constant current charging reaches the battery voltage of 4V, until the charging current is less than the preset cut-off current value of 100 mA. By setting constant current charging first and then constant voltage charging, it is possible to quickly charge the battery to almost full through constant current charging, and then accurately control the charging voltage through constant voltage charging to achieve efficient and high-quality charging control.

[0042] The present invention also provides a lithium battery device, such as a lithium battery product such as an electric hair clipper and an electric shaver, which adopts the lithium battery charging voltage control method as described in any of the above items.

[0043] In summary, compared with the prior art, the present invention charges the lithium battery with a constant current to obtain the charging protection voltage of the charging protection board of the lithium battery when it is fully charged; when the lithium battery is charged again, constant current charging is first performed, and then constant voltage charging is performed at a voltage value lower than the charging protection voltage. The present invention does not need to use a high-cost dedicated charging management chip to control the charging of the lithium battery. By using constant current charging during the first charging until the protection function of the charging protection board is triggered, a voltage value close to the protection voltage value is recorded. When the lithium battery is charged again, constant current charging can be used for fast charging first. When it is close to being fully charged, constant voltage charging is used and the recorded voltage value is used as the full condition. The high triggering accuracy of the charging protection board is used to improve the precise control of the charging voltage to prevent overcharging or undercharging.

[0044] In addition, those skilled in the art should understand that, although there are many problems in the prior art, each embodiment or technical solution of the present invention can be improved in only one or several aspects, without having to solve all the technical problems listed in the prior art or background technology at the same time. Those skilled in the art should understand that the content not mentioned in a claim should not be used as a limitation on the claim.

[0045] Although the terms such as constant current charging, constant voltage charging, first voltage, protection voltage, charging protection board, preset current value and preset are used more frequently in this article, the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional restrictions is contrary to the spirit of the present invention; the terms "first", "second", etc. (if any) in the description and claims of the embodiments of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium battery charging voltage control method, characterized in that: include: The MCU performs constant current charging on the lithium battery, and obtains the charging protection voltage of the charging protection board of the lithium battery when the battery is fully charged as the first voltage; When charging the lithium battery again, the MCU controls the lithium battery to first perform constant current charging, and then perform constant voltage charging with the second voltage as the constant voltage value, until the charging current is less than the preset cut-off current value, and the charging is stopped; The second voltage is the first voltage minus a preset protection difference; The method for obtaining the first voltage comprises the following steps: S10: charging the lithium battery with a constant current and sampling the battery voltage of the lithium battery, wherein the lithium battery has a calibrated full charge voltage; S20: When the battery voltage reaches 90-98% of the rated full voltage, memorizing the battery voltage every 0.5-5 seconds; S30: When the charging protection board of the lithium battery performs charging protection, the battery voltage memorized last time is read as the first voltage.

2. The lithium battery charging voltage control method according to claim 1, characterized in that: In the step S20: to the step S30, if the charging protection board is not in charging protection, charging is stopped and the memory value of the battery voltage is cleared.

3. The lithium battery charging voltage control method according to claim 2, characterized in that: The first voltage is obtained when the lithium battery is fully charged for the first time.

4. The lithium battery charging voltage control method according to claim 1, characterized in that: The preset cut-off current value is 20-150 mA.

5. The lithium battery charging voltage control method according to claim 1, characterized in that: The preset protection difference is 10 to 50 millivolts.

6. The lithium battery charging voltage control method according to claim 1, characterized in that: When the lithium battery is charged again, the constant voltage charging is performed when the charging voltage of the lithium battery reaches a second voltage through constant current charging.

7. The lithium battery charging voltage control method according to claim 1, characterized in that: When the lithium battery is charged again, the constant voltage charging is performed when the charging voltage of the lithium battery reaches a third voltage through constant current charging, and the third voltage is lower than the second voltage.

8. The lithium battery charging voltage control method according to any one of claims 1 to 7, characterized in that: The constant current value of the constant current charging is 0.5 to 1.5 amperes.

9. A lithium battery device, characterized in that: A lithium battery charging voltage control method as described in any one of claims 1 to 8 is adopted.

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