Battery protection circuit and control method thereof and battery protection system

Abstract

The present invention discloses a battery protection circuit and a control method thereof and a battery protection system, wherein the battery protection circuit comprises a sub-protection module, a driving module, an overvoltage detection module and a first switch unit; the sub-protection module is used to control the driving module to output a shutdown signal to turn off the first switch unit when the battery voltage reaches a first preset voltage; the first end of the overvoltage detection module is connected to the first end of the battery protection circuit, the second end of the overvoltage detection module is connected to the second end of the battery protection circuit, the third end of the overvoltage detection module is connected to the second end of the driving module, and the overvoltage detection module is used to control the driving module to output a first conduction signal to turn on the first switch unit when the voltage difference between the first end and the second end of the battery protection circuit is detected to reach a second preset voltage; wherein the second preset voltage is greater than the first preset voltage. This solution can effectively improve the safety of the battery protection circuit when the battery is in a protection state.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of electronic technology, and in particular to a battery protection circuit and a control method thereof, and a battery protection system. Background Art

[0002] With the continuous development of electronic technology, handheld devices have become widely popular. Handheld devices usually use batteries as power supply, and lithium batteries account for a large proportion of the power supply of handheld devices. The safety of lithium batteries has always been the most important part of the safety of electronic equipment.

[0003] At present, as the capacity of lithium batteries becomes larger and larger, the charging current becomes larger and larger. Therefore, in order to have a greater transmission capacity, the voltage at the input end of the charger becomes higher and higher, which causes the output end of the charger to have a higher voltage when the lithium battery is in overvoltage protection. At the same time, high voltage will also be generated when using some equipment for testing, which can easily damage the battery protection circuit and make the battery protection function invalid. Summary of the invention

[0004] The embodiment of the present invention provides a battery protection circuit and a control method thereof and a battery protection system, so as to effectively improve the safety of the battery protection circuit when the battery is in a protection state.

[0005] According to one aspect of the present invention, a battery protection circuit is provided, comprising: a sub-protection module, a driving module, an overvoltage detection module and a first switch unit;

[0006] The first end of the sub-protection module is connected to a first power supply voltage, the second end of the sub-protection module is connected to the first end of the driving module, the second end of the driving module is connected to the control end of the first switch unit, the first end of the first switch unit is connected to the second pole of the battery, the second end of the first switch unit is connected to the second end of the battery protection circuit, the first pole of the battery is connected to the first end of the battery protection circuit, and the sub-protection module is used to control the driving module to output a shutdown signal to turn off the first switch unit when the battery voltage reaches a first preset voltage during the charging process of the battery;

[0007] A first end of the overvoltage detection module is connected to a first end of the battery protection circuit, a second end of the overvoltage detection module is connected to a second end of the battery protection circuit, and a third end of the overvoltage detection module is connected to a second end of the driving module, and the overvoltage detection module is used to control the driving module to output a first conduction signal to turn on the first switch unit when detecting that a voltage difference between the first end and the second end of the battery protection circuit reaches a second preset voltage;

[0008] Wherein, the second preset voltage is greater than the first preset voltage.

[0009] Optionally, during the charging process, the first end of the battery protection circuit is connected to the first end of the charger, the second end of the battery protection circuit is connected to the second end of the charger, and the driving module is further used to output a second conduction signal to turn on the first switch unit when the battery voltage does not reach a first preset voltage;

[0010] The conduction degree of the first switch unit under the control of the first conduction signal is smaller than the conduction degree under the control of the second conduction signal.

[0011] Optionally, the overvoltage detection module includes a first voltage dividing unit, a second voltage dividing unit and a second switch unit;

[0012] A first end of the first voltage dividing unit is connected to a first end of the battery protection circuit, a second end of the first voltage dividing unit is connected to a first end of the second voltage dividing unit, and a second end of the second voltage dividing unit is connected to a second end of the battery protection circuit;

[0013] The control end of the second switch unit is connected to the first end of the second voltage dividing unit, the first end of the second switch unit is connected to the first end of the battery protection circuit, and the second end of the second switch unit is connected to the second end of the driving module.

[0014] Optionally, the first voltage dividing unit includes a first resistor, the second voltage dividing unit includes a Zener diode, and the second switch unit includes a first transistor;

[0015] A first end of the first resistor is connected to a first end of the battery protection circuit, a second end of the first resistor is connected to a first electrode of the Zener diode, a second electrode of the Zener diode is connected to a second end of the battery protection circuit, a first electrode of the first transistor is connected to a first end of the battery protection circuit, a second electrode of the first transistor is connected to a second end of the driving module, and a gate of the first transistor is connected to a first electrode of the Zener diode.

[0016] Optionally, the first voltage dividing unit includes a first resistor, and the second switch unit includes a first transistor;

[0017] The second voltage dividing unit comprises a plurality of second transistors connected in series in sequence, the gate of each second transistor is connected to its own second electrode, the first electrode of each second transistor is connected to the second electrode of the previous second transistor, and the second electrode of each second transistor is connected to the first electrode of the next second transistor, wherein the first electrode of the first second transistor is connected to the second end of the first resistor, the second electrode of the last second transistor is connected to the second end of the battery protection circuit, and the first end of the first resistor is connected to the first end of the battery protection circuit;

[0018] The first electrode of the first transistor is connected to the first end of the battery protection circuit, the second electrode of the first transistor is connected to the second end of the driving module, and the gate of the first transistor is connected to the first electrode of the second transistor.

[0019] Optionally, the first switch unit includes a third transistor, a gate of the third transistor is connected to the second end of the driving module, a first electrode of the third transistor is connected to the second electrode of the battery, and a second electrode of the third transistor is connected to the second end of the battery protection circuit;

[0020] A width-to-length ratio of the first transistor is smaller than a width-to-length ratio of the third transistor.

[0021] Optionally, the driving module includes a driving unit and a second resistor;

[0022] The first end of the driving unit is connected to the second end of the sub-protection module, the second end of the driving unit is connected to the first end of the second resistor, the second end of the second resistor is connected to the control end of the first switching unit, and the third end of the overvoltage detection module is connected to the second end of the second resistor.

[0023] The driving unit includes m inverters, which are sequentially connected in series between the second end of the sub-protection module and the first end of the second resistor, wherein m is an integer greater than or equal to 1.

[0024] According to another aspect of the present invention, a control method for a battery protection circuit is provided, wherein the battery protection circuit comprises a sub-protection module, a driving module, an overvoltage detection module and a first switch unit, wherein a first end of the sub-protection module is connected to a first power supply voltage, a second end of the sub-protection module is connected to a first end of the driving module, a second end of the driving module is connected to a control end of the first switch unit, a first end of the first switch unit is connected to a second pole of a battery, a second end of the first switch unit is connected to a second end of the battery protection circuit, a first pole of the battery is connected to a first end of the battery protection circuit, a first end of the overvoltage detection module is connected to a first end of the battery protection circuit, a second end of the overvoltage detection module is connected to a second end of the battery protection circuit, and a third end of the overvoltage detection module is connected to the second end of the driving module;

[0025] The control method of the battery protection circuit comprises:

[0026] During the charging process, when the battery voltage reaches a first preset voltage, the sub-protection module controls the driving module to output a shutdown signal to shut down the first switch unit;

[0027] When the voltage difference between the first terminal and the second terminal of the battery protection circuit reaches a second preset voltage, the overvoltage detection module controls the driving module to output a first conduction signal to turn on the first switch unit; wherein the second preset voltage is greater than the first preset voltage.

[0028] According to another aspect of the present invention, a battery protection system is provided. The battery protection system includes the battery protection circuit provided by any embodiment of the present invention.

[0029] The technical solution provided by the embodiment of the present invention is that during the charging process of the battery connected to the charger, when the battery voltage is charged to a first preset voltage, the sub-protection module controls the driving module to turn off the first switch unit to cut off the charging path between the negative electrode of the battery and the second end of the battery protection circuit to achieve overvoltage protection. When the negative electrode of the battery and the second end of the battery protection circuit are in a high impedance state, due to the inherent characteristics of the charger, the voltage between the first end and the second end of the battery protection circuit will increase. When the overvoltage detection module detects that the voltage difference between the first end and the second end of the battery protection circuit reaches the second preset voltage, the overvoltage detection module controls the driving module to output a first conduction signal to turn on the first switch unit to achieve the continuous flow of the charger current. When the voltage difference between the first end and the second end of the battery protection circuit does not reach the second preset voltage, the driving module does not respond to the control signal output by the overvoltage detection module, thereby not affecting the normal operation of the battery protection circuit. Compared with the related technical solutions, the technical solution provided in this embodiment can limit the voltage difference between the first end and the second end of the battery protection circuit to a second preset voltage after the battery is fully charged, thereby avoiding irreversible damage to the battery protection circuit due to an excessively large voltage difference between the first end and the second end of the battery protection circuit, thereby greatly improving the safety and reliability of the battery protection circuit.

[0030] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 It is a structural schematic diagram of a battery protection circuit in the related art;

[0033] Figure 2 A schematic diagram of the structure of a battery protection circuit provided by an embodiment of the present invention;

[0034] Figure 3 A schematic diagram of the structure of another battery protection circuit provided by an embodiment of the present invention;

[0035] Figure 4 A schematic diagram of the structure of another battery protection circuit provided by an embodiment of the present invention;

[0036] Figure 5A schematic diagram of the structure of another battery protection circuit provided by an embodiment of the present invention;

[0037] Figure 6 A schematic diagram of the structure of another battery protection circuit provided by an embodiment of the present invention;

[0038] Figure 7 This is a schematic diagram of the structure of a driving module provided by an embodiment of the present invention;

[0039] Figure 8 A schematic diagram of the structure of another battery protection circuit provided by an embodiment of the present invention;

[0040] Fig. 9 A waveform diagram of a charging voltage and a charging current provided by an embodiment of the present invention;

[0041] Fig.10 The present invention provides a flow chart of a method for controlling a battery protection circuit. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme 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 only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0043] It should be noted that the terms "first", "second", etc. in the specification and claims 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. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0044] Figure 1 A schematic diagram of a battery protection circuit in the related art is shown in FIG. Figure 1In the related art, the output end of the charger is connected to the first end EB+ and the second end EB- of the battery protection circuit. In the constant current working mode, the charger is similar to an ideal current source, which continuously charges the battery U. When the battery voltage is charged too high, the protection module 200 controls the first switch unit 40 to be closed, so that the charging path between the negative electrode of the battery U and the second end EB- of the battery protection circuit is cut off. At this time, the negative electrode of the battery U and the second end EB- of the battery protection circuit are in a high impedance state. Since the charger is equivalent to an ideal current source, at the moment when the negative electrode of the battery U and the second end EB- of the battery protection circuit are in a high impedance state, a large voltage (the voltage value of the voltage depends on the characteristics of the charger) will be generated between the first end EB+ and the second end EB- of the battery protection circuit (i.e., the output end of the charger). If the voltage is too high, it will cause damage to the protection chip 100 in a very short time, for example, it can break through the first switch unit 40, causing irreversible damage to the first switch unit 40, thereby making the protection circuit ineffective.

[0045] In view of the above problems, an embodiment of the present invention provides a battery protection circuit. Figure 2 A schematic diagram of a battery protection circuit according to an embodiment of the present invention is provided. Figure 2 , the battery protection circuit provided by the embodiment of the present invention includes: a sub-protection module 10, a driving module 20, an overvoltage detection module 30 and a first switch unit 40;

[0046] The first end of the sub-protection module 10 is connected to the first power supply voltage VDD, the second end of the sub-protection module 10 is connected to the first end of the driving module 20, the second end of the driving module 20 is connected to the control end of the first switch unit 40, the first end of the first switch unit 40 is connected to the second pole of the battery U, the second end of the first switch unit 40 is connected to the second end EB- of the battery protection circuit, and the first pole of the battery U is connected to the first end EB+ of the battery protection circuit. During the charging process, the sub-protection module 10 is used to control the driving module 20 to output a shutdown signal to turn off the first switch unit 40 when the battery voltage reaches a first preset voltage;

[0047] A first end of the overvoltage detection module 30 is connected to a first end EB+ of the battery protection circuit, a second end of the overvoltage detection module 30 is connected to a second end EB- of the battery protection circuit, and a third end of the overvoltage detection module 30 is connected to a second end of the driving module 20. The overvoltage detection module 30 is used to control the driving module 20 to output a first conduction signal to turn on the first switch unit 40 when detecting that a voltage difference between the first end EB+ and the second end EB- of the battery protection circuit reaches a second preset voltage;

[0048] The second preset voltage is greater than the first preset voltage.

[0049] Specifically, the first pole of the battery U may be a positive pole, and the second pole may be a negative pole. The first pole of the battery U is connected to the first terminal EB+ of the battery protection circuit, and the second pole of the battery U is connected to the second terminal EB- of the battery protection circuit via the first switch unit 40. The first terminal EB+ and the second terminal EB- of the battery protection circuit are connected to the charger. During the charging process, the first switch unit 40 is in the on state, and the voltage at the output terminal of the charger (i.e., the voltage difference between the first terminal EB+ and the second terminal EB- of the battery protection circuit) is pulled to the battery voltage, so as to realize charging of the battery U.

[0050] As charging proceeds, when the sub-protection module 10 detects that the charging state of the battery U exceeds a preset condition, the sub-protection module 10 controls the first switch unit 40 to turn off. The charging state includes one or more of the charging voltage, the charging current, and the battery temperature, and the preset condition is one or more of the voltage preset value, the current preset value, and the temperature preset value. When the charging state of the battery U exceeds the preset condition, the battery voltage at this time may be the first preset voltage.

[0051] Exemplarily, the sub-protection module 10 is an overvoltage protection module. When the sub-protection module 10 detects that the battery voltage reaches the first preset voltage, the sub-protection module 10 may output an overvoltage protection signal to the driving module 20 to control the driving module 20 to output a shutdown signal to the first switch unit 40, turning off the first switch unit 40, thereby cutting off the charging path between the negative electrode of the battery U and the second terminal EB- of the battery protection circuit, so as to achieve overvoltage protection of the battery U. The first preset voltage may be a fully charged voltage. Optionally, the sub-protection module 10 may determine whether the battery voltage reaches the first preset voltage based on the first power supply voltage VDD, wherein the first power supply voltage VDD may be converted from the battery voltage.

[0052] When the negative electrode of the battery U and the second terminal EB- of the battery protection circuit are in a high impedance state, the voltage between the first terminal EB+ and the second terminal EB- of the battery protection circuit increases. When the voltage difference between the first terminal EB+ and the second terminal EB- of the battery protection circuit reaches the second preset voltage, the overvoltage detection module 30 outputs a control signal to the second terminal of the driving module 20, and the driving module 20 responds to the control signal and outputs a first conduction signal to the control terminal of the first switch unit 40. The first switch unit 40 is turned on under the action of the first conduction signal, thereby continuing the current in the charger, and then maintaining the voltage between the first terminal EB+ and the second terminal EB- of the battery protection circuit at the second preset voltage, so as to avoid damage to the battery protection circuit due to excessive voltage between the first terminal EB+ and the second terminal EB- of the battery protection circuit. Here, the second preset voltage is less than the breakdown voltage of the battery protection circuit.

[0053] The technical solution provided by the embodiment of the present invention is that during the charging process of the battery U connected to the charger, when the battery voltage is charged to a first preset voltage, the sub-protection module 10 controls the driving module 20 to turn off the first switch unit 40 to cut off the charging path between the negative electrode of the battery U and the second terminal EB- of the battery protection circuit to achieve overvoltage protection. When the negative electrode of the battery U and the second terminal EB- of the battery protection circuit are in a high impedance state, due to the inherent characteristics of the charger, the voltage between the first terminal EB+ and the second terminal EB- of the battery protection circuit will increase. When the overvoltage detection module 30 detects that the voltage difference between the first terminal EB+ and the second terminal EB- of the battery protection circuit reaches the second preset voltage, the overvoltage detection module 30 controls the driving module 20 to output a first conduction signal to turn on the first switch unit 40 to achieve the continuous flow of the charger current. When the voltage difference between the first terminal EB+ and the second terminal EB- of the battery protection circuit does not reach the second preset voltage, the driving module 20 does not respond to the control signal output by the overvoltage detection module 30, thereby not affecting the normal operation of the battery protection circuit. Compared with the related technical solutions, the technical solution provided in this embodiment can limit the voltage difference between the first terminal EB+ and the second terminal EB- of the battery protection circuit to a second preset voltage after the battery is fully charged, thereby avoiding irreversible damage to the battery protection circuit due to excessive voltage difference between the first terminal EB+ and the second terminal EB- of the battery protection circuit, thereby greatly improving the safety and reliability of the battery protection circuit.

[0054] Optionally, during the charging process, the first terminal EB+ of the battery protection circuit is connected to the first terminal of the charger, and the second terminal EB- of the battery protection circuit is connected to the second terminal of the charger. The driving module 20 is also used to output a second conduction signal when the battery voltage does not reach the first preset voltage to turn on the first switch unit 40, so that the battery U can be charged normally. The battery U can be a lithium battery or other types of batteries, which is not limited in this embodiment.

[0055] In this embodiment, the conduction degree of the first switch unit 40 under the control of the first conduction signal is less than the conduction degree under the control of the second conduction signal. That is, under the control of the first conduction signal, the first switch unit 40 is in a semi-conducting state.

[0056] Specifically, when the charger current is continued to flow, if the first switch unit 40 is in a fully on state, the charger will continue to charge the battery U, and the voltage at the charger output end will be pulled to the battery voltage again. The first switch unit 40 will be restored to the off state, so that the voltage between the first terminal EB+ and the second terminal EB- of the battery protection circuit will increase again, and the overvoltage detection module 30 will control the drive module 20 to turn on the first switch unit 40 again, and this cycle will be repeated, resulting in the first switch unit 40 being unable to be turned off.

[0057] In this embodiment, when the charger current is freewheeling, the first switch unit 40 is controlled to be in a semi-conducting state so that the first switch unit 40 has a larger on-resistance, thereby limiting the charging current, which is beneficial to reducing the impact of the charger continuing to charge the battery U, and can limit the voltage between the first terminal EB+ and the second terminal EB- of the battery protection circuit to a second preset voltage. Therefore, the first switch 40 can be more accurately controlled to be turned off after the freewheeling ends, thereby providing a protection function for the battery U.

[0058] Figure 3 A schematic diagram of another battery protection circuit provided by an embodiment of the present invention, referring to Figure 3 On the basis of the above embodiment, optionally, the overvoltage detection module 30 includes a first voltage dividing unit 301, a second voltage dividing unit 302 and a second switch unit 303, wherein the first end of the first voltage dividing unit 301 is connected to the first end EB+ of the battery protection circuit, the second end of the first voltage dividing unit 301 is connected to the first end of the second voltage dividing unit 302, and the second end of the second voltage dividing unit 302 is connected to the second end EB- of the battery protection circuit; the control end of the second switch unit 303 is connected to the first end of the second voltage dividing unit 302, the first end of the second switch unit 303 is connected to the first end EB+ of the battery protection circuit, and the second end of the second switch unit 303 is connected to the second end of the driving module 20.

[0059] The first voltage dividing unit 301 and the second voltage dividing unit 302 are used to divide the voltage between the first terminal EB+ and the second terminal EB- of the battery protection circuit. When the voltage between the first terminal EB+ and the second terminal EB- of the battery protection circuit reaches a second preset voltage, the voltage division of the first voltage dividing unit 301 and the second voltage dividing unit 302 causes the second switch unit 303 to be turned on, and the second switch unit 303 generates a control signal (such as a current signal). The driving module 20 controls the first switch unit 40 to be turned on under the action of the control signal. Here, the second preset voltage may be the sum of the voltage drops of the second voltage dividing unit 302 and the second switch unit 303.

[0060] The second voltage dividing unit 302 may have a variety of designs, and different circuit structures may be selected according to actual voltage requirements. Figure 4 A schematic diagram of another battery protection circuit provided by an embodiment of the present invention, referring to Figure 4On the basis of the above embodiment, optionally, the first voltage dividing unit 301 includes a first resistor R1, the second voltage dividing unit 302 includes a Zener diode D1, and the second switch unit 303 includes a first transistor Q1; the first end of the first resistor R1 is connected to the first end EB+ of the battery protection circuit, the second end of the first resistor R1 is connected to the first electrode of the Zener diode D1, the second electrode of the Zener diode D1 is connected to the second end EB- of the battery protection circuit, the first electrode of the first transistor Q1 is connected to the first end EB+ of the battery protection circuit, the second electrode of the first transistor Q1 is connected to the second end of the driving module 20, and the gate of the first transistor Q1 is connected to the first electrode of the Zener diode D1.

[0061] Optionally, the first switch unit 40 includes a third transistor Q3, a gate of the third transistor Q3 is connected to the second end of the driving module 20, a first electrode of the third transistor Q3 is connected to the second electrode of the battery U, and a second electrode of the third transistor Q3 is connected to the second end EB- of the battery protection circuit.

[0062] Specifically, the first electrode of the Zener diode D1 may be a cathode, and the second electrode may be an anode. The second preset voltage is equal to the sum of the breakdown voltage of the Zener diode D1 and the threshold voltage of the first transistor Q1.

[0063] When the voltage between the first terminal EB+ and the second terminal EB- of the battery protection circuit does not reach the second preset voltage, the first transistor Q1 is in the off state, the first transistor Q1 does not generate current, and the third transistor Q3 maintains the off state (overvoltage protection state).

[0064] When the voltage between the first terminal EB+ and the second terminal EB- of the battery protection circuit reaches a second preset voltage, the first transistor Q1 is turned on, and under the action of the gate voltage of the first transistor Q1 and the first electrode voltage, the first transistor Q1 generates a current. Under the action of the current output by the first transistor Q1, the driving module 20 changes the gate voltage of the third transistor Q3, so that the third transistor Q3 is turned on, thereby realizing the continuous flow of the charger current and avoiding the voltage at the charger output end being too high and damaging the third transistor Q3.

[0065] In another optional implementation provided by this embodiment, the second voltage dividing unit 302 may also be formed by a plurality of diodes connected in series. Figure 5 A schematic diagram of another battery protection circuit provided by an embodiment of the present invention, referring to Figure 5On the basis of the above embodiments, optionally, the first voltage dividing unit 301 includes a first resistor R1, the second switch unit 303 includes a first transistor Q1, and the second voltage dividing unit 302 includes a plurality of second transistors Q2 connected in series in sequence, the gate of each second transistor Q2 is connected to its own second electrode to form a diode connection structure, the first electrode of each second transistor Q2 is connected to the second electrode of the previous second transistor Q2, and the second electrode of each second transistor Q2 is connected to the first electrode of the next second transistor Q2, wherein the first electrode of the first second transistor Q2 is connected to the second end of the first resistor R1, the second electrode of the last second transistor Q2 is connected to the second end EB- of the battery protection circuit, and the first end of the first resistor R1 is connected to the first end EB+ of the battery protection circuit; the first electrode of the first transistor Q1 is connected to the first end EB+ of the battery protection circuit, the second electrode of the first transistor Q1 is connected to the second end of the driving module 20, and the gate of the first transistor Q1 is connected to the first electrode of the first second transistor Q2.

[0066] Specifically, the second voltage dividing unit 302 may include n second transistors Q2, where n is an integer greater than or equal to 2. Each second transistor Q2 is connected in a diode structure, and the second preset voltage is equal to the sum of the threshold voltage of the first transistor Q1 and the threshold voltages of the n second transistors Q2. Figure 5 The specific working process of the circuit structure shown is Figure 4 The working process of the circuit structure shown is the same and will not be repeated here.

[0067] Optionally, continue to refer to Figure 4 and Figure 5 In this embodiment, the width-to-length ratio of the first transistor Q1 is smaller than that of the third transistor Q3. Therefore, the driving capability of the first transistor Q1 is relatively weak, and the third transistor Q3 can be better placed in a semi-conducting state when continuing the voltage at the charger output end.

[0068] It should be noted that the above embodiments are described by taking the first transistor Q1 and the second transistor Q2 as P-type transistors and the third transistor Q3 as N-type transistors as examples, and are not intended to limit them. In other embodiments, by changing the signal type and / or connection method, the first transistor Q1 and the second transistor Q2 may also be N-type transistors, the third transistor Q3 may also be P-type transistors, or all three may be P-type transistors or N-type transistors.

[0069] Figure 6 A schematic diagram of another battery protection circuit provided by an embodiment of the present invention, referring to Figure 6On the basis of the above embodiments, optionally, the driving module 20 includes a driving unit 201 and a second resistor R2, a first end of the driving unit 201 is connected to a second end of the sub-protection module 10, a second end of the driving unit 201 is connected to a first end of the second resistor R2, a second end of the second resistor R2 is connected to a control end of the first switching unit 40, and a third end of the overvoltage detection module 30 is connected to a second end of the second resistor R2.

[0070] The driving unit 201 is used to generate a driving signal, and the second resistor R is used to limit current. When the voltage between the first terminal EB+ and the second terminal EB- of the battery protection circuit reaches the first preset voltage and does not reach the second preset voltage, the sub-protection module 10 outputs an overvoltage protection signal to the driving unit 201, and the driving unit 201 outputs a shutdown signal to the control end of the first switch unit 40 according to the received overvoltage protection signal, and controls the first switch unit 40 to shut down. When the voltage between the first terminal EB+ and the second terminal EB- of the battery protection circuit reaches the second preset voltage, the overvoltage detection module 30 outputs a current signal, which increases the voltage on the second resistor R2, thereby turning on the first switch unit 40, and continuing to flow the charger current to prevent the voltage between the first terminal EB+ and the second terminal EB- of the battery protection circuit from continuing to increase.

[0071] Figure 7 FIG. 1 is a schematic diagram of a driving module provided in an embodiment of the present invention, and specifically shows the structure of the driving unit 201. Figure 7 The driving unit 201 includes m inverters, which are sequentially connected in series between the second end of the sub-protection module 10 and the first end of the second resistor R2, where m is an integer greater than or equal to 1. Here, U- refers to the negative electrode of the battery U.

[0072] Specifically, the number of inverters can be determined according to the type of transistors included in the first switch unit 40 and the type of output signal of the sub-protection module 10. During overvoltage protection, the first switch unit 40 is turned off in response to a low-level signal. If the sub-protection module 10 also outputs a low-level signal, the number of inverters is an even number to ensure that the signal output by the drive unit 201 is still a low-level signal. If the sub-protection module 10 outputs a high-level signal, the number of inverters is an odd number to ensure that the signal output by the drive unit 201 is a low-level signal. In addition, through the action of multi-stage inverters, the driving capability of the output signal of the sub-protection module 10 can also be enhanced to ensure that the first switch unit 40 can be turned on or off quickly and reliably.

[0073] For example, the driving unit 201 includes four inverters, namely, a first inverter I1, a second inverter I2, a third inverter I3, and a fourth inverter I4. The sizes of the four inverters may not be equal. For example, the sizes of the four inverters are increased in sequence to continuously enhance the driving capability of the signal received by the driving unit 201. The size of the inverter may refer to the width-to-length ratio of the transistor inside the inverter. For example, the size of the first inverter I1 is 1:1, the size of the second inverter I2 is 1:4, the size of the third inverter I3 is 1:16, and the size of the fourth inverter I4 is 1:64.

[0074] Figure 8 A schematic diagram of the structure of another battery protection circuit provided by an embodiment of the present invention, Fig. 9 A waveform diagram of a charging voltage and a charging current provided by an embodiment of the present invention, referring to Figure 8 The battery protection circuit can be integrated on the protection chip 100. The battery protection circuit can also include a substrate control module 50. The substrate control module 50 is used to perform substrate switching on the third transistor Q3 according to the charging status of the battery U, so as to timely control the substrate voltage of the third transistor Q3. When the third transistor Q3 is turned off, the charging current is prevented from flowing into the battery U, thereby ensuring the charging safety of the battery U.

[0075] Combination Figure 8 and Fig. 9 The specific working process of the battery protection circuit provided in this embodiment is as follows:

[0076] The first terminal EB+ and the second terminal EB- of the battery protection circuit are connected to the charger. During the charging process, the driving module 20 controls the third transistor Q3 to be turned on, the battery U is connected to the charger, and the voltage at the output terminal of the charger (i.e., the voltage difference between the first terminal EB+ and the second terminal EB- of the battery protection circuit) is pulled to the battery voltage, thereby charging the battery U. Here, the battery voltage is the voltage at the first terminal EB+ of the battery protection circuit.

[0077] As charging proceeds, at time T1, when the sub-protection module 10 detects that the battery voltage reaches the first preset voltage VCU (specifically, it can be determined by detecting the first power supply voltage VDD, which can be obtained by filtering the battery voltage through the third resistor R3 and the first capacitor C1), the sub-protection module 10 can output an overvoltage protection signal to the driving module 20, and the overvoltage protection signal is amplified by the driving unit 201 to control the third transistor Q3 to turn off. At this time, under the action of the parasitic inductance inside the charger, the charging current Ichrg does not disappear immediately, and the substrate control module 50 controls the substrate of the third transistor Q3 to be connected to the second terminal EB- of the battery protection circuit to prevent the charging current from flowing into the battery U.

[0078] When the third transistor Q3 is turned off, since the charging current Ichrg still exists, under the action of the charging current Ichrg, the voltage of the second terminal EB- of the battery protection circuit starts to drop from 0V, and when the voltage of the second terminal EB- of the battery protection circuit drops to -VOV+VCU, where VOV is the second preset voltage, that is, when the voltage difference between the first terminal EB+ and the second terminal EB- of the battery protection circuit reaches the second preset voltage VOV, the first transistor Q1 is turned on. Here, -VOV+VCU is greater than -VHB, and VHB is the maximum withstand voltage value of the third transistor Q3.

[0079] The third transistor Q3 generates a current, under the action of which the voltage of the second resistor R2 increases, quickly turning on the third transistor Q3, and continuing the current of the charger, so that the charging current Ichrg drops to 0A (at time T2), and the voltage of the second terminal EB- of the battery protection circuit is fixed at VCU-VCH, where VCH is the voltage of the charger output terminal, and VCH is not greater than the second preset voltage VOV. Thus, the voltage between the first terminal EB+ and the second terminal EB- of the battery protection circuit is limited to the second preset voltage VOV, ensuring the safe operation of the entire battery protection circuit.

[0080] The technical solution provided in this embodiment is that when an over-high voltage appears between the first terminal EB+ and the second terminal EB- of the battery protection circuit, the overvoltage detection module 30 and the driving module 20 control the first switch unit 40 to be turned on, thereby providing an energy discharge path for the charger, thereby limiting the voltage between the first terminal EB+ and the second terminal EB- of the battery protection circuit to a safe voltage range, thereby preventing the battery protection circuit from being irreversibly damaged.

[0081] Optionally, an embodiment of the present invention further provides a method for controlling a battery protection circuit, which may be used to control the battery protection circuit provided by any embodiment of the present invention. Fig.10 A flowchart of a control method for a battery protection circuit provided by an embodiment of the present invention, referring to Fig.10 , the control method of the battery protection circuit includes:

[0082] S110. During the charging process, when the battery voltage reaches a first preset voltage, the sub-protection module controls the driving module to output a shutdown signal to shut down the first switch unit.

[0083] S120. When the voltage difference between the first terminal and the second terminal of the battery protection circuit reaches a second preset voltage, the overvoltage detection module controls the driving module to output a first conduction signal to turn on the first switch unit; wherein the second preset voltage is greater than the first preset voltage.

[0084] In this embodiment, the sub-protection module 10 may be an overvoltage protection module, an overcurrent protection module, or an overtemperature protection module. In other embodiments, the sub-protection module 10 may also include an overvoltage protection module, an overcurrent protection module, and an overtemperature protection module. Therefore, the technical solution provided in this embodiment is not only applicable to the charging overvoltage protection of the battery, but also to the charging overcurrent protection and charging overtemperature protection of the battery.

[0085] Optionally, in this embodiment, the overvoltage detection module 30 may be in a working state all the time, or may work only under set conditions, for example, starting to work after charging overvoltage protection, charging overcurrent protection, or charging overtemperature protection; or it may only work for a period of time, rather than being in a continuous working state, to reduce the power consumption of the battery protection circuit.

[0086] Since the control method of the battery protection circuit provided in this embodiment can control the battery protection circuit provided in any of the above embodiments, the control method also has the beneficial effects described in any of the above embodiments, which will not be described in detail.

[0087] Optionally, an embodiment of the present invention further provides a battery protection system, which includes the battery protection circuit provided by any embodiment of the present invention. Therefore, the battery protection system also has the beneficial effects described in any of the above embodiments, which will not be described in detail. The battery protection circuit may also include other protection modules, such as an overcurrent protection module, a short circuit protection module, etc.

[0088] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0089] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A battery protection circuit, characterized in that: include: A sub-protection module, a driving module, an overvoltage detection module and a first switch unit; The first end of the sub-protection module is connected to the first power supply voltage, the second end of the sub-protection module is connected to the first end of the driving module, the second end of the driving module is connected to the control end of the first switch unit, the first end of the first switch unit is connected to the second pole of the battery, the second end of the first switch unit is connected to the second end of the battery protection circuit, and the first pole of the battery is connected to the first end of the battery protection circuit. During the charging process, the sub-protection module is used to control the driving module to output a shutdown signal to turn off the first switch unit when the battery voltage reaches a first preset voltage; A first end of the overvoltage detection module is connected to a first end of the battery protection circuit, a second end of the overvoltage detection module is connected to a second end of the battery protection circuit, and a third end of the overvoltage detection module is connected to a second end of the driving module, and the overvoltage detection module is used to control the driving module to output a first conduction signal to turn on the first switch unit when detecting that a voltage difference between the first end and the second end of the battery protection circuit reaches a second preset voltage; Wherein, the second preset voltage is greater than the first preset voltage; During the charging process, the first end of the battery protection circuit is connected to the first end of the charger, and the second end of the battery protection circuit is connected to the second end of the charger, and the driving module is further used to output a second conduction signal to turn on the first switch unit when the battery voltage does not reach the first preset voltage; The conduction degree of the first switch unit under the control of the first conduction signal is smaller than the conduction degree under the control of the second conduction signal.

2. The battery protection circuit according to claim 1, characterized in that: The overvoltage detection module includes a first voltage dividing unit, a second voltage dividing unit and a second switch unit; A first end of the first voltage dividing unit is connected to a first end of the battery protection circuit, a second end of the first voltage dividing unit is connected to a first end of the second voltage dividing unit, and a second end of the second voltage dividing unit is connected to a second end of the battery protection circuit; The control end of the second switch unit is connected to the first end of the second voltage dividing unit, the first end of the second switch unit is connected to the first end of the battery protection circuit, and the second end of the second switch unit is connected to the second end of the driving module.

3. The battery protection circuit according to claim 2, characterized in that: The first voltage dividing unit includes a first resistor, the second voltage dividing unit includes a Zener diode, and the second switch unit includes a first transistor; A first end of the first resistor is connected to a first end of the battery protection circuit, a second end of the first resistor is connected to a first electrode of the Zener diode, a second electrode of the Zener diode is connected to a second end of the battery protection circuit, a first electrode of the first transistor is connected to a first end of the battery protection circuit, a second electrode of the first transistor is connected to a second end of the driving module, and a gate of the first transistor is connected to a first electrode of the Zener diode.

4. The battery protection circuit according to claim 2, characterized in that: The first voltage dividing unit includes a first resistor, and the second switch unit includes a first transistor; The second voltage dividing unit comprises a plurality of second transistors connected in series in sequence, the gate of each second transistor is connected to its own second electrode, the first electrode of each second transistor is connected to the second electrode of the previous second transistor, and the second electrode of each second transistor is connected to the first electrode of the next second transistor, wherein the first electrode of the first second transistor is connected to the second end of the first resistor, the second electrode of the last second transistor is connected to the second end of the battery protection circuit, and the first end of the first resistor is connected to the first end of the battery protection circuit; The first electrode of the first transistor is connected to the first end of the battery protection circuit, the second electrode of the first transistor is connected to the second end of the driving module, and the gate of the first transistor is connected to the first electrode of the second transistor.

5. The battery protection circuit according to claim 3 or 4, characterized in that: The first switch unit includes a third transistor, a gate of the third transistor is connected to the second end of the driving module, a first electrode of the third transistor is connected to the second electrode of the battery, and a second electrode of the third transistor is connected to the second end of the battery protection circuit; A width-to-length ratio of the first transistor is smaller than a width-to-length ratio of the third transistor.

6. The battery protection circuit according to claim 1, characterized in that: The driving module includes a driving unit and a second resistor; The first end of the driving unit is connected to the second end of the sub-protection module, the second end of the driving unit is connected to the first end of the second resistor, the second end of the second resistor is connected to the control end of the first switching unit, and the third end of the overvoltage detection module is connected to the second end of the second resistor.

7. The battery protection circuit according to claim 6, characterized in that: The driving unit includes m inverters, which are sequentially connected in series between the second end of the sub-protection module and the first end of the second resistor, wherein m is an integer greater than or equal to 1.

8. A control method for a battery protection circuit, characterized in that: The battery protection circuit comprises a sub-protection module, a driving module, an overvoltage detection module and a first switch unit, wherein a first end of the sub-protection module is connected to a first power supply voltage, a second end of the sub-protection module is connected to a first end of the driving module, a second end of the driving module is connected to a control end of the first switch unit, a first end of the first switch unit is connected to a second pole of a battery, a second end of the first switch unit is connected to a second end of the battery protection circuit, a first pole of the battery is connected to a first end of the battery protection circuit, a first end of the overvoltage detection module is connected to a first end of the battery protection circuit, a second end of the overvoltage detection module is connected to a second end of the battery protection circuit, and a third end of the overvoltage detection module is connected to a second end of the driving module; The control method of the battery protection circuit comprises: During the charging process, when the voltage of the battery does not reach the first preset voltage, the second on signal is output to turn on the first switch unit; when the voltage of the battery reaches the first preset voltage, the sub-protection module controls the driving module to output an off signal to turn off the first switch unit; When the voltage difference between the first terminal and the second terminal of the battery protection circuit reaches a second preset voltage, the overvoltage detection module controls the driving module to output a first conduction signal to turn on the first switch unit; wherein the second preset voltage is greater than the first preset voltage, and the conduction degree of the first switch unit under the control of the first conduction signal is less than the conduction degree under the control of the second conduction signal.

9. A battery protection system, characterized in that: The battery protection circuit comprises the battery protection circuit according to any one of claims 1 to 7.

Images