Battery Charging Circuits and Systems

Abstract

Embodiments of the present invention disclose a battery charging circuit and system. The battery charging circuit includes at least one comparison module, a first selection module, at least one second selection module, a matching module, input transistors, and output transistors. The output transistors include a first transistor and at least one second transistor. The first end of the first selection module, the control electrode of the input transistor, and the control electrode of the first transistor are connected to a first node. The second electrode of the input transistor, the first end of the matching module, and the second end of the first selection module are connected to a second node. The first selection module is configured to transmit different voltages to the second node based on a control signal output by the comparison module to adjust the mirror current of the input transistor in different charging modes. The second transistor is connected in parallel with the first transistor, and the second selection module is configured to control whether the second transistor is conductive based on the control signal output by the comparison module. This solution can improve the accuracy of the charging current.

Description

Technical Field

[0001] Embodiments of the present invention relate to the technical field of battery charging, and in particular to a battery charging circuit and system. Background Art

[0002] With the continuous development of electronic technology, mobile devices have become increasingly popular. These devices are typically powered by lithium batteries. Due to the increasing capacity of lithium batteries and the emergence of fast-charging technology, higher charger voltages are often used. This has led to increasingly shorter charging times. Furthermore, with the increasing application of lithium batteries, charging conditions are becoming increasingly demanding. During the plug-in and unplug phase of charging, surge voltages can occur. Excessively high surge voltages can sometimes damage chips and cause safety incidents.

[0003] In order to be compatible with the existing high charger voltage and surge voltage, the charging system needs to use high-voltage devices as charging current mirrors. However, the accuracy of the charging current in the existing technology is poor, resulting in the actual charging current not meeting the requirements. Summary of the Invention

[0004] Embodiments of the present invention provide a battery charging circuit and system to improve the accuracy of charging current.

[0005] According to one aspect of the present invention, a battery charging circuit is provided, comprising: at least one comparison module, a first selection module, at least one second selection module, a matching module, an input transistor, and an output transistor, wherein the output transistor comprises a first transistor and at least one second transistor;

[0006] The comparison module is used to transmit corresponding control signals to the control end of the first selection module and the control end of the second selection module according to the charging mode of the battery, and the charging mode includes at least a trickle charging mode and a constant current charging mode;

[0007] A first terminal of the first selection module, a control terminal of the input transistor, and a control terminal of the first transistor are connected to a first node, the first terminal of the input transistor is connected to a charging voltage, a second terminal of the input transistor, a first terminal of the matching module, and a second terminal of the first selection module are connected to a second node, and a second terminal of the matching module is grounded, and the first selection module is configured to transmit different voltages to the second node according to a control signal output by the comparison module, so as to adjust the mirror current of the input transistor in different charging modes;

[0008] The first electrode of the first transistor is connected to the charging voltage, the second electrode of the first transistor is connected to the first electrode of the battery, the second transistor is connected in parallel with the first transistor, and each second transistor is correspondingly connected to a second selection module, and the second selection module is used to control whether the second transistor is turned on according to the control signal output by the comparison module.

[0009] Optionally, the aspect ratio of the first transistor is K times the aspect ratio of the input transistor, the sum of the aspect ratio of the first transistor and the aspect ratio of the at least one second transistor is N times the aspect ratio of the input transistor, N>K, and N and K are both positive numbers.

[0010] Optionally, K and the voltage Vtrick transmitted to the second node in the trickle charging mode satisfy the following relationship: ; Wherein, V0 is the voltage corresponding to the target charging current in the trickle charging mode.

[0011] Optionally, the second transistor is configured as follows: in the trickle charging mode, the second transistor is turned off; in the constant current charging mode, the second transistor is turned on.

[0012] Optionally, the number of the comparison module is one, the number of the second selection module is one, and the number of the second transistor is one;

[0013] A first terminal of the comparison module is connected to a first reference voltage, a second terminal of the comparison module is connected to a first terminal of the battery, and a second terminal of the battery is grounded. A third terminal of the comparison module is connected to a control terminal of the first selection module and a control terminal of the second selection module respectively. A first terminal of the second selection module is connected to the first node, a second terminal of the second selection module is connected to the charging voltage or the battery voltage, a third terminal of the second selection module is connected to a control terminal of the second transistor, a first terminal of the second transistor is connected to a first terminal of the first transistor, and a second terminal of the second transistor is connected to a first terminal of the battery.

[0014] In which, the comparison module includes a first comparator, the second selection module includes a first selector, the first selection module includes a third selector and an operational amplifier, the first input end of the first comparator is connected to the first reference voltage, the second input end of the first comparator is connected to the first electrode of the battery, the output end of the first comparator is connected to the control end of the third selector and the control end of the first selector, the first input end of the first selector is connected to the first node, the second input end of the first selector is connected to the charging voltage or the battery voltage, the output end of the first selector is connected to the control electrode of the second transistor, the first input end of the third selector is connected to the first voltage, the second input end of the third selector is connected to the first target voltage, the output end of the third selector is connected to the first input end of the operational amplifier, the second input end of the operational amplifier is connected to the second node, and the output end of the operational amplifier is connected to the first node.

[0015] The number of the comparison module is one, the number of the second selection module is one, and the number of the second transistor is one;

[0016] A first terminal of the comparison module is connected to a first reference voltage, a second terminal of the comparison module is connected to a first terminal of the battery, and the second terminal of the battery is grounded; a third terminal of the comparison module is connected to a control terminal of the first selection module and a control terminal of the second selection module respectively; a first terminal of the second selection module is connected to a second terminal of the second transistor, a second terminal of the second selection module is connected to a first terminal of the battery, a first terminal of the second transistor is connected to a first terminal of the first transistor, and a control terminal of the second transistor is connected to the first node;

[0017] In which, the comparison module includes a first comparator, the second selection module includes a first inverter and a first auxiliary transistor, the first selection module includes a third selector and an operational amplifier, the first input end of the first comparator is connected to the first reference voltage, the second input end of the first comparator is connected to the first pole of the battery, the output end of the first comparator is connected to the control end of the third selector and the input end of the first inverter, the output end of the first inverter is connected to the control pole of the first auxiliary transistor, the first pole of the first auxiliary transistor is connected to the second pole of the second transistor, the second pole of the first auxiliary transistor is connected to the first pole of the battery, the first input end of the third selector is connected to the first voltage, the second input end of the third selector is connected to the first target voltage, the output end of the third selector is connected to the first input end of the operational amplifier, the second input end of the operational amplifier is connected to the second node, and the output end of the operational amplifier is connected to the first node.

[0018] Optionally, the number of the comparison modules is two, the number of the second selection modules is two, and the number of the second transistors is two;

[0019] A first terminal of the first comparison module is connected to a first reference voltage, a second terminal of the first comparison module is connected to a first terminal of the battery, and a second terminal of the battery is grounded. A third terminal of the first comparison module is connected to a first control terminal of the first selection module and a control terminal of the first second selection module respectively. A first terminal of the first second selection module is connected to the first node. A second terminal of the first second selection module is connected to the charging voltage or the battery voltage. A third terminal of the first second selection module is connected to a control terminal of the first second transistor. A first terminal of the first second transistor is connected to a first terminal of the first transistor. A second terminal of the first second transistor is connected to the first terminal of the battery.

[0020] A first terminal of the second comparison module is connected to a second reference voltage, a second terminal of the second comparison module is connected to the first electrode of the battery, a third terminal of the second comparison module is connected to the second control terminal of the first selection module and the control terminal of the second second selection module respectively, a first terminal of the second second selection module is connected to the first node, a second terminal of the second second selection module is connected to the charging voltage or the battery voltage, a third terminal of the second second selection module is connected to the control electrode of the second second transistor, a first terminal of the second second transistor is connected to the first terminal of the first transistor, and a second terminal of the second second transistor is connected to the first electrode of the battery; the first reference voltage is greater than the second reference voltage;

[0021] Wherein, the first comparison module includes a first comparator, the second comparison module includes a second comparator, the first second selection module includes a first selector, the second second selection module includes a second selector, the first selection module includes a third selector and an operational amplifier, the first input end of the first comparator is connected to the first reference voltage, the second input end of the first comparator is connected to the first electrode of the battery, the output end of the first comparator is connected to the first control end of the third selector and the control end of the first selector, the first input end of the first selector is connected to the first node, the second input end of the first selector is connected to the charging voltage or the battery voltage, and the output end of the first selector is connected to the control electrode of the first second transistor;

[0022] A first input terminal of the second comparator is connected to the second reference voltage, a second input terminal of the second comparator is connected to the first terminal of the battery, an output terminal of the second comparator is connected to the second control terminal of the third selector and the control terminal of the second selector, a first input terminal of the second selector is connected to the first node, a second input terminal of the second selector is connected to the charging voltage or the battery voltage, and an output terminal of the second selector is connected to the control terminal of a second second transistor;

[0023] The first input terminal of the third selector is connected to the first voltage, the second input terminal of the third selector is connected to the first target voltage, the third input terminal of the third selector is connected to the second target voltage, the output terminal of the third selector is connected to the first input terminal of the operational amplifier, the second input terminal of the operational amplifier is connected to the second node, and the output terminal of the operational amplifier is connected to the first node.

[0024] Optionally, the at least one comparison module includes a first comparison module and a second comparison module, the number of the second selection modules is two, and the number of the second transistors is two;

[0025] A first terminal of the first comparison module is connected to a first reference voltage, a second terminal of the first comparison module is connected to a first terminal of the battery, and a second terminal of the battery is grounded. A third terminal of the first comparison module is respectively connected to a first control terminal of the first selection module and a control terminal of the first second selection module. A first terminal of the first second selection module is connected to a second terminal of the first second transistor, a second terminal of the first second selection module is connected to a first terminal of the battery, a first terminal of the first second transistor is connected to a first terminal of the first transistor, and a control terminal of the first second transistor is connected to the first node.

[0026] The first terminal of the second comparison module is connected to the second reference voltage, the second terminal of the second comparison module is connected to the first electrode of the battery, the third terminal of the second comparison module is connected to the second control terminal of the first selection module and the control terminal of the second second selection module respectively, the first terminal of the second second selection module is connected to the second electrode of the second second transistor, the second terminal of the second second selection module is connected to the first electrode of the battery, the first electrode of the second second transistor is connected to the first electrode of the first transistor, and the control electrode of the second second transistor is connected to the first node; the first reference voltage is greater than the second reference voltage;

[0027] Wherein, the first comparison module includes a first comparator, the second comparison module includes a second comparator, the first second selection module includes a first inverter and a first auxiliary transistor, the second second selection module includes a second inverter and a second auxiliary transistor, the first selection module includes a third selector and an operational amplifier, the first input end of the first comparator is connected to the first reference voltage, the second input end of the first comparator is connected to the first electrode of the battery, the output end of the first comparator is connected to the first control end of the third selector and the input end of the first inverter, the output end of the first inverter is connected to the control electrode of the first auxiliary transistor, the first electrode of the first auxiliary transistor is connected to the second electrode of the first second transistor, and the second electrode of the first auxiliary transistor is connected to the first electrode of the battery;

[0028] A first input terminal of the second comparator is connected to the second reference voltage, a second input terminal of the second comparator is connected to the first terminal of the battery, an output terminal of the second comparator is connected to the second control terminal of the third selector and the input terminal of the second inverter, an output terminal of the second inverter is connected to the control terminal of the second auxiliary transistor, a first terminal of the second auxiliary transistor is connected to the second terminal of the second second transistor, and a second terminal of the second auxiliary transistor is connected to the first terminal of the battery;

[0029] The first input terminal of the third selector is connected to the first voltage, the second input terminal of the third selector is connected to the first target voltage, the third input terminal of the third selector is connected to the second target voltage, the output terminal of the third selector is connected to the first input terminal of the operational amplifier, the second input terminal of the operational amplifier is connected to the second node, and the output terminal of the operational amplifier is connected to the first node.

[0030] Optionally, the matching module includes a preset resistor, a first end of the preset resistor is connected to the second node, and a second end of the preset resistor is grounded; and the resistance of the preset resistor is adjustable.

[0031] According to another aspect of the present invention, a battery charging system is provided, comprising the battery charging circuit provided by any embodiment of the present invention.

[0032] The technical solution provided by an embodiment of the present invention adjusts the mirror current flowing through the input transistor in different charging modes by adjusting the target voltage transmitted to the second node by the first selection module, thereby adjusting the operating range of the input transistor to the saturation region, reducing the matching deviation between the mirror current and the charging current, and thus improving the accuracy of the charging current. At the same time, the original output transistor is split into a first transistor and at least one second transistor, and the second selection module is used to control whether the corresponding second transistor is turned on. This allows the size of the output transistor to be adjusted, that is, the mirror ratio of the current can be changed, thereby limiting the charging current to a current value that meets the requirements.

[0033] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] 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.

[0035] Figure 1 A schematic structural diagram of a battery charging circuit provided by an embodiment of the present invention;

[0036] Figure 2 A schematic structural diagram of another battery charging circuit provided by an embodiment of the present invention;

[0037] Figure 3 A schematic structural diagram of another battery charging circuit provided by an embodiment of the present invention;

[0038] Figure 4 A schematic structural diagram of another battery charging circuit provided by an embodiment of the present invention;

[0039] Figure 5 A schematic structural diagram of another battery charging circuit provided by an embodiment of the present invention;

[0040] Figure 6 A schematic structural diagram of another battery charging circuit provided by an embodiment of the present invention;

[0041] Figure 7 A schematic structural diagram of another battery charging circuit provided by an embodiment of the present invention;

[0042] Figure 8 A schematic structural diagram of another battery charging circuit provided by an embodiment of the present invention;

[0043] Figure 9 A schematic structural diagram of another battery charging circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the solutions of the present invention, 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 embodiments described 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 making creative efforts should fall within the scope of protection of the present invention.

[0045] It should be noted that the terms "first", "second", etc. in the description 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 numbers 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 clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0046] Figure 1 A schematic diagram of a battery charging circuit according to an embodiment of the present invention is provided. Figure 1The battery charging circuit provided in this embodiment includes: at least one comparison module 10, a first selection module 20, at least one second selection module 30, a matching module 40, an input transistor Q1, and an output transistor Q2, wherein the output transistor Q2 includes a first transistor Q2-1 and at least one second transistor Q2-2; the comparison module 10 is used to transmit a corresponding control signal to the control terminal of the first selection module 20 and the control terminal of the second selection module 30 according to the charging mode of the battery U, and the charging mode includes a trickle charging mode and a constant current charging mode; the first terminal of the first selection module 20, the control electrode of the input transistor Q1, and the control electrode of the first transistor Q2-1 are connected to the first node N1, and the first electrode of the input transistor Q1 is connected to the charging voltage VCC (i.e., the charger voltage). Voltage), the second electrode of the input transistor Q1, the first end of the matching module 40, and the second end of the first selection module 20 are connected to the second node N2, the second end of the matching module 40 is grounded, and the first selection module 20 is used to transmit different voltages to the second node N2 according to the control signal output by the comparison module 10, so as to adjust the mirror current of the input transistor Q1 in different charging modes; the first electrode of the first transistor Q2-1 is connected to the charging voltage VCC, the second electrode of the first transistor Q2-1 is connected to the first electrode of the battery U, the second transistor Q2-2 is connected in parallel with the first transistor Q2-1, and each second transistor Q2-2 is correspondingly connected to a second selection module 30. The second selection module 30 is used to control whether the second transistor Q2-2 is turned on according to the control signal output by the comparison module 10.

[0047] The battery charging mode includes a trickle charging mode, a constant current charging mode, and a constant voltage charging mode (the constant voltage charging mode is not considered in this embodiment). Specifically, different charging modes can be used to charge the battery U by judging the battery voltage. For example, when the battery voltage is less than the reference voltage VREF, it is trickle charging. The first selection module 20 selects the first target voltage Vtrick1 to be output according to the control signal output by the comparison module 10, and transmits the first target voltage Vtrick to the second node N2. At this time, the mirror current of the input transistor Q1 is I1, and the charging current output by the output transistor Q2 is , where N is the ratio of the width to length of the output transistor Q2 to the input transistor Q1. When the battery voltage is greater than the reference voltage VREF, constant current charging is performed. The first selection module 20 selects the first voltage V1 for output according to the control signal output by the comparison module 10 and transmits the first voltage V1 to the second node N2. At this time, the mirror current of the input transistor Q1 is I2, and the charging current output by the output transistor Q2 is Taking N=1000, V1=1V, and Vtrick=0.1V as an example, when the impedance Rp of the matching module 40 is 50KΩ, 10KΩ, and 1KΩ respectively, the mirror current and the charging current are as follows:

[0048] Table 1

[0049]

[0050] Table 2

[0051]

[0052] Among them, Table 1 is the charging current, and Table 2 is the mirror current. According to Tables 1 and 2, the range of the mirror current is between 2uA and 1000uA, a difference of 500 times. In order to ensure that the chip can support a maximum charging current of 1A, the size of the output transistor Q2 cannot be made too small, otherwise the on-resistance of the output transistor Q2 will increase, causing problems with the chip's charging capacity; at the same time, considering cost factors, the output transistor Q2 cannot be made too large. In the prior art, in order to achieve cost and performance compatibility, the input transistor Q1 is generally designed in the linear region in the trickle charging mode. The input transistor Q1 operating in the linear region will increase the current matching deviation, thereby reducing the accuracy of the charging current.

[0053] In this embodiment, in trickle charge mode, the mirror current flowing through the input transistor Q1 is increased by adjusting the voltage transmitted to the second node N2, such as increasing the first target voltage Vtrick1, thereby causing the input transistor Q1 to operate in the saturation region. Simultaneously, the output transistor Q2 is split into a first transistor Q2-1 and at least one second transistor Q2-2, and the second selection module 30 controls whether the corresponding second transistor Q2-2 is turned on or off, thereby adjusting the size of the output transistor Q2, that is, changing the mirror ratio of the current, so that when the mirror current increases, the charging current in trickle charge mode remains unchanged. Of course, in other embodiments, the charging current in trickle charge mode can also be changed.

[0054] The technical solution provided by the embodiment of the present invention adjusts the mirror current flowing through the input transistor Q1 in different charging modes by adjusting the target voltage transmitted to the second node N2 by the first selection module 20, thereby adjusting the operating range of the input transistor Q1 to the saturation region, thereby reducing the matching deviation between the mirror current and the charging current, and thus improving the accuracy of the charging current. At the same time, the original output transistor Q2 is split into a first transistor Q2-1 and at least one second transistor Q2-2, and the second selection module 30 controls whether the corresponding second transistor Q2-2 is turned on, thereby adjusting the size of the output transistor Q2, that is, changing the mirror ratio of the current, and thus limiting the charging current to a current value that meets the requirements.

[0055] Optionally, in other embodiments, by adjusting the mirror current flowing through the input transistor Q1 , the operating range of the input transistor Q1 can be adjusted to other operating ranges, not limited to the saturation region, as long as it can better match the charging current.

[0056] Optionally, in this embodiment, the aspect ratio of the first transistor Q2-1 is K times the aspect ratio of the input transistor Q1, and the sum of the aspect ratio of the first transistor Q2-1 and the aspect ratio of the at least one second transistor Q2-2 is N times the aspect ratio of the input transistor Q1, where N>K, and both N and K are positive numbers. Exemplarily, if the current mirror ratio is 1:1000, then N=1000, and K is a positive number less than 1000.

[0057] In this embodiment, the second transistor Q2-2 is configured such that: in trickle charge mode, the second transistor Q2-2 is turned off; in constant current charge mode, the second transistor Q2-2 is turned on. In other words, in trickle charge mode, the width-to-length ratio of the output transistor Q2 is adjusted; in constant current charge mode, the width-to-length ratio of the output transistor Q2 is not adjusted, and the original width-to-length ratio remains unchanged.

[0058] Since the mirror current and the charging current in the constant current charging mode are not regulated, in order to be compatible with the design in the prior art, that is, to obtain the same charging current when using the same matching module 40, it is only necessary to ensure that the charging current in the trickle charging mode remains unchanged. Therefore, K and the voltage Vtrick transmitted to the second node N2 in the trickle charging mode satisfy the following relationship: Wherein, Vtrick includes a first target voltage Vtrick1, and V0 is the voltage corresponding to the target charging current in the trickle charging mode. For example, V0=0.1V, and Vtrick can be adjusted according to actual needs. Still taking N=1000, V1=1V, and Vtrick=1V (the voltage transmitted to the second node N2 in the trickle charging mode in the prior art is 0.1V, i.e., V0) as an example, K can be calculated according to the above formula. When the impedance Rp of the matching module 40 is 50KΩ, 10KΩ, and 1KΩ respectively, the mirror current and the charging current are as follows:

[0059] Table 3

[0060]

[0061] Table 4

[0062]

[0063] Table 3 shows the charging current, and Table 4 shows the mirror current. As can be seen from Tables 3 and 4, the mirror current ranges from 20uA to 1000uA, a difference of 50 times. Compared to the prior art, the technical solution provided in this embodiment increases the minimum mirror current by 10 times in the trickle charging mode. Therefore, the operating range of the input transistor Q1 can be effectively improved, for example, enabling the input transistor Q1 to operate in the saturation region.

[0064] In an optional implementation provided by this embodiment, the number of the comparison module 10 is one, the number of the second selection module 30 is one, and the number of the second transistor Q2 - 2 is one. Figure 2 A schematic diagram of another battery charging circuit provided by an embodiment of the present invention, referring to Figure 2 Based on the above embodiment, optionally, a first terminal of the comparison module 10 is connected to a first reference voltage VREF1, a second terminal of the comparison module 10 is connected to a first terminal of the battery U, and a second terminal of the battery U is grounded. A third terminal of the comparison module 10 is connected to a control terminal of the first selection module 20 and a control terminal of the second selection module 30, respectively. A third terminal and a fourth terminal of the first selection module 20 are connected to a first voltage V1 and a first target voltage Vtrick1, respectively. A first terminal of the second selection module 30 is connected to a first node N1, a second terminal of the second selection module 30 is connected to a charging voltage VCC or a battery voltage U+ (i.e., connected to a first terminal of the battery U), a third terminal of the second selection module 30 is connected to a control terminal of a second transistor Q2-2, a first terminal of the second transistor Q2-2 is connected to a first terminal of the first transistor Q2-1, and a second terminal of the second transistor Q2-2 is connected to a first terminal of the battery U. The first terminal of the battery U may be a positive terminal, and the second terminal may be a negative terminal.

[0065] Figure 3 A structural diagram of another battery charging circuit provided by an embodiment of the present invention, specifically Figure 2 The battery charging circuit shown is a structural diagram of the device, refer to Figure 2 and Figure 3The comparison module 10 includes a first comparator OC1, the second selection module 30 includes a first selector SE1, and the first selection module 20 includes a third selector SE3 and an operational amplifier OA. The first input terminal of the first comparator OC1 is connected to the first reference voltage VREF1, the second input terminal of the first comparator OC1 is connected to the first electrode of the battery U, the output terminal of the first comparator OC1 is connected to the control terminal of the third selector SE3 and the control terminal of the first selector SE1, the first input terminal of the first selector SE1 is connected to the first node N1, the second input terminal of the first selector SE1 is connected to the charging voltage VCC or the battery voltage U+, the output terminal of the first selector SE1 is connected to the control electrode of the second transistor Q2-2, the first input terminal of the third selector SE3 is connected to the first voltage V1, the second input terminal of the third selector SE3 is connected to the first target voltage Vtrick1, the output terminal of the third selector SE3 is connected to the first input terminal of the operational amplifier OA, the second input terminal of the operational amplifier OA is connected to the second node N2, and the output terminal of the operational amplifier OA is connected to the first node N1.

[0066] The matching module 40 includes a preset resistor R, a first end of the preset resistor R is connected to the second node N2, and a second end of the preset resistor R is grounded. The resistance of the preset resistor R is adjustable.

[0067] Specifically, when the battery voltage U+ is less than the first reference voltage VREF1 (the first reference voltage VREF1 can be 2.9V), it is in the trickle charging mode, the first comparator OC1 outputs a low-level control signal, and the first selector SE1 controls the second transistor Q2-2 to turn off in response to the low-level control signal. The third selector SE3 transmits the first target voltage Vtrick1 to the first input terminal of the operational amplifier OA in response to the low-level control signal. According to the virtual short principle of the operational amplifier, the voltage of the second input terminal of the operational amplifier OA is equal to the voltage of its first input terminal. At this time, the voltage of the second node N2 is the first target voltage Vtrick1. The mirror current flowing through the input transistor Q1 is Vtrick1 / Rp, where Rp is the resistance of the preset resistor R. Here, the first target voltage Vtrick1 is greater than 0.1V in the prior art to increase the mirror current, thereby controlling the input transistor Q1 to operate in the saturation region in the trickle charging mode. After being mirrored by the current mirror, the charging current flowing through the first transistor Q2-1 is By adjusting the value of K, the charging current can be kept consistent with the charging current in the prior art, thereby improving the compatibility of the charging circuit. In this embodiment, since the mirror current has a high precision, the charging current after matching also has a high precision.

[0068] When the battery voltage U+ is greater than or equal to the first reference voltage VREF1, it is in the constant current charging mode, the first comparator OC1 outputs a high-level control signal, and the first selector SE1 controls the second transistor Q2-2 to turn on in response to the high-level control signal. The third selector SE3 transmits the first voltage V1 to the first input terminal of the operational amplifier OA in response to the high-level control signal. According to the virtual short principle of the operational amplifier, the voltage of the second input terminal of the operational amplifier OA is equal to the voltage of its first input terminal. At this time, the voltage of the second node N2 is the first voltage V1. The mirror current flowing through the input transistor Q1 is V1 / Rp. Here, the first voltage V1 is the same as the voltage in the prior art to ensure that the mirror current in the constant current charging mode remains unchanged. At this time, the mirror current itself is relatively large, so that the input transistor Q1 can be controlled to operate in the saturation zone in the constant current charging mode. After being mirrored by the current mirror, the charging current flowing through the first transistor Q2-1 is , ensuring that the charging current remains unchanged in constant current charging mode.

[0069] The technical solution provided by this embodiment, in trickle charge mode, controls the second transistor Q2-2 to be turned off by the second selection module 30 to reduce the size of the output transistor, thereby reducing the mirror current ratio. By increasing the voltage of the second node N2, the mirror current flowing through the input transistor Q1 is increased, so that the input transistor Q1 operates in the saturation region, which is conducive to improving the matching degree between the mirror current and the charging current, and improving the accuracy of the charging current. In constant current charging mode, the original design remains unchanged.

[0070] Figure 4 A structural diagram of another battery charging circuit provided by an embodiment of the present invention, Figure 2 The battery charging circuit structure shown is different in that Figure 4 In the structure shown, the second selection module 30 is connected in series between the second transistor Q2-2 and the first electrode of the battery U. By controlling the on / off of the second selection module 30, the on / off of the path where the second transistor Q2-2 is located can be controlled, thereby selecting whether to connect the second transistor Q2-2 to the output transistor Q2. Figure 4 Based on the above embodiments, optionally, a first terminal of the comparison module 10 is connected to the first reference voltage VREF1, a second terminal of the comparison module 10 is connected to the first electrode of the battery U, and the second electrode of the battery U is grounded. A third terminal of the comparison module 10 is respectively connected to the control terminal of the first selection module 20 and the control terminal of the second selection module 30. A first terminal of the second selection module 30 is connected to the second electrode of the second transistor Q2-2, a second terminal of the second selection module 30 is connected to the first electrode of the battery U, a first electrode of the second transistor Q2-2 is connected to the first electrode of the first transistor Q2-1, and a control electrode of the second transistor Q2-2 is connected to the first node N1.

[0071] Figure 5 A structural diagram of another battery charging circuit provided by an embodiment of the present invention, specifically Figure 4 The battery charging circuit shown is a structural diagram of the device, refer to Figure 5 and Figure 4 The comparison module 10 includes a first comparator OC1, the second selection module 30 includes a first inverter INV1 and a first auxiliary transistor Q3, and the first selection module 20 includes a third selector SE3 and an operational amplifier OA. The first input terminal of the first comparator OC1 is connected to the first reference voltage VREF1, the second input terminal of the first comparator OC1 is connected to the first electrode of the battery U, the output terminal of the first comparator OC1 is connected to the control terminal of the third selector SE3 and the input terminal of the first inverter INV1, the output terminal of the first inverter INV1 is connected to the control terminal of the first auxiliary transistor Q3, the first electrode of the first auxiliary transistor Q3 is connected to the second electrode of the second transistor Q2-2, the second electrode of the first auxiliary transistor Q3 is connected to the first electrode of the battery U, the first input terminal of the third selector SE3 is connected to the first voltage V1, the second input terminal of the third selector SE3 is connected to the first target voltage Vtrick1, the output terminal of the third selector SE3 is connected to the first input terminal of the operational amplifier OA, the second input terminal of the operational amplifier OA is connected to the second node N2, and the output terminal of the operational amplifier OA is connected to the first node N1.

[0072] Specifically, when the battery voltage U+ is less than the first reference voltage VREF1, the battery is in trickle charge mode. The first comparator OC1 outputs a low-level control signal, the first inverter INV1 outputs a high-level control signal, and the first auxiliary transistor Q3 is turned off in response to the high-level control signal, thereby disconnecting the path of the second transistor Q2-2. In response to the low-level control signal, the third selector SE3 transmits the first target voltage Vtrick1 to the first input terminal of the operational amplifier OA, resulting in the voltage at the second node N2 being the first target voltage Vtrick1. The subsequent operation is the same as in the above embodiment and will not be further described.

[0073] When the battery voltage U+ is greater than or equal to the first reference voltage VREF1, the battery is in constant current charging mode. The first comparator OC1 outputs a high-level control signal, the first inverter INV1 outputs a low-level control signal, and the first auxiliary transistor Q3 turns on in response to the low-level control signal. In response to the high-level control signal, the third selector SE3 transmits the first voltage V1 to the first input terminal of the operational amplifier OA. According to the virtual short circuit principle of the operational amplifier, the voltage at the second input terminal of the operational amplifier OA is equal to the voltage at its first input terminal. At this point, the voltage at the second node N2 is the first voltage V1. The input transistor Q1, the first transistor Q2-1, and the second transistor Q2-2 are all turned on. The subsequent operation is the same as in the above embodiment and will not be further described.

[0074] In another optional implementation provided by this embodiment, the number of the comparison modules 10 is two, the number of the second selection modules 30 is two, and the number of the second transistors Q- 2 is two. Figure 6 A schematic diagram of another battery charging circuit provided by an embodiment of the present invention, referring to Figure 6 A first end of the first comparison module 101 is connected to a first reference voltage VREF1, a second end of the first comparison module 101 is connected to a first electrode of the battery U, and a second electrode of the battery U is grounded. A third end of the first comparison module 101 is connected to a first control end of the first selection module 20 and a control end of the first second selection module 301, respectively. A first end of the first second selection module 301 is connected to a first node N1, a second end of the first second selection module 301 is connected to a charging voltage VCC or a battery voltage U+, a third end of the first second selection module 301 is connected to a control electrode of a first second transistor Q2-2-1, a first electrode of the first second transistor Q2-2-1 is connected to a first electrode of the first transistor Q2-1, and a second electrode of the first second transistor Q2-2-1 is connected to a first electrode of the battery U.

[0075] A first terminal of the second comparison module 102 is connected to the second reference voltage VREF2, a second terminal of the second comparison module 102 is connected to the first electrode of the battery U, a third terminal of the second comparison module 102 is connected to the second control terminal of the first selection module 20 and the control terminal of the second second selection module 302, respectively, a first terminal of the second second selection module 302 is connected to the first node N1, a second terminal of the second second selection module 302 is connected to the charging voltage VCC or the battery voltage U+, a third terminal of the second second selection module 303 is connected to the control electrode of the second second transistor Q2-2-2, a first terminal of the second second transistor Q2-2-2 is connected to the first terminal of the first transistor Q2-1, and a second terminal of the second second transistor Q2-2-2 is connected to the first terminal of the battery U.

[0076] The first reference voltage VREF1 is greater than the second reference voltage VREF2. For example, the first reference voltage VREF1 is 2.9V, and the second reference voltage VREF2 is 2.4V. By setting multiple reference voltages, the charging current can be made more precise.

[0077] Figure 7 A structural diagram of another battery charging circuit provided by an embodiment of the present invention, specifically Figure 6 The battery charging circuit shown is a structural diagram of the device, refer to Figure 6 and Figure 7The first comparison module 101 includes a first comparator OC1, the second comparison module 102 includes a second comparator OC2, the first second selection module 301 includes a first selector SE1, the second second selection module 302 includes a second selector SE2, the first selection module 20 includes a third selector SE3 and an operational amplifier OA, the first input end of the first comparator OC1 is connected to the first reference voltage VREF1, the second input end of the first comparator OC1 is connected to the first electrode of the battery U, the output end of the first comparator OC1 is connected to the first control end of the third selector SE3 and the control end of the first selector SE1, the first input end of the first selector SE1 is connected to the first node N1, the second input end of the first selector SE1 is connected to the charging voltage VCC or the battery voltage U+, and the output end of the first selector SE1 is connected to the control electrode of the first second transistor Q2-2-1.

[0078] A first input terminal of the second comparator OC2 is connected to the second reference voltage VREF2, a second input terminal of the second comparator OC2 is connected to the first electrode of the battery U, an output terminal of the second comparator OC2 is connected to the second control terminal of the third selector SE3 and the control terminal of the second selector SE2, a first input terminal of the second selector SE2 is connected to the first node N1, a second input terminal of the second selector SE2 is connected to the charging voltage VCC or the battery voltage U+, and an output terminal of the second selector SE2 is connected to the control electrode of the second second transistor Q2-2-2; a first input terminal of the third selector SE3 is connected to the first voltage V1, a second input terminal of the third selector SE3 is connected to the first target voltage Vtrick1, a third input terminal of the third selector SE3 is connected to the second target voltage Vtrick2, an output terminal of the third selector SE3 is connected to the first input terminal of the operational amplifier OA, a second input terminal of the operational amplifier OA is connected to the second node N2, and an output terminal of the operational amplifier OA is connected to the first node N1.

[0079] Specifically, when the battery voltage U+ is less than the first reference voltage VREF1 and greater than the second reference voltage VREF2, the first comparator OC1 outputs a low-level control signal, the second comparator OC2 outputs a high-level control signal, and the third selector SE3 selects the first target voltage Vtrick1 for output. The mirror current flowing through the input transistor Q1 is Vtrick1 / Rp. The first selector SE1 controls the first second transistor Q2-2-1 to turn off, and the second selector SE2 controls the second second transistor Q2-2-2 to turn on. The size of the output transistor Q2 is the sum of the sizes of the first transistor Q2-1 and the second second transistor Q2-2-2. After being mirrored by the current mirror, the charging current output by the output transistor Q2 is , where K2 is the ratio of the width-to-length ratio of the second transistor Q2-2-2 to the width-to-length ratio of the input transistor Q1.

[0080] When the battery voltage U+ is less than the second reference voltage, the first comparator OC1 outputs a low-level control signal, the second comparator OC2 outputs a low-level control signal, and the third selector SE3 selects the second target voltage Vtrick2 for output. The mirror current flowing through the input transistor Q1 is Vtrick2 / Rp. The first selector SE1 controls the first second transistor Q2-2-1 to turn off, and the second selector SE2 controls the second second transistor Q2-2-2 to turn off. The size of the output transistor Q2 is the same as that of the first transistor Q2-1. After being mirrored by the current mirror, the charging current output by the output transistor Q2 is .

[0081] When the battery voltage U+ is greater than or equal to the first reference voltage VREF1, the first comparator OC1 outputs a high-level control signal, the second comparator OC2 outputs a high-level control signal, and the third selector SE3 selects the first voltage V1 for output. The mirror current flowing through the input transistor Q1 is V1 / Rp. The first second transistor Q2-2-1 is turned on by the first selector SE1, and the second second transistor Q2-2-2 is turned on by the second selector SE2. After the current mirror, the charging current output by the output transistor Q2 is , where K1 is the ratio of the width-to-length ratio of the first second transistor Q2-2-1 to the width-to-length ratio of the input transistor Q1, K2 is the ratio of the width-to-length ratio of the second second transistor Q2-2-2 to the width-to-length ratio of the input transistor Q1, and K+K1+K2=N.

[0082] The first target voltage Vtrick1 is different from the second target voltage Vtrick2. Calculate the current. Depending on the battery voltage U+, different mirror currents can be adjusted to meet different charging requirements.

[0083] Optionally, the width-to-length ratios of the first second transistor Q2-2-1 and the second second transistor Q2-2-2 may be the same or different, and may be set according to actual conditions.

[0084] Optionally, in other embodiments, the first selector SE1 and the second selector SE2 may be configured differently so that when the battery voltage U+ is less than the first reference voltage VREF1 and greater than the second reference voltage VREF2, the first second transistor Q2-2-1 is turned off and the second second transistor Q2-2-2 is turned on; when the battery voltage U+ is less than the second reference voltage VREF2, the first second transistor Q2-2-1 is turned on and the second second transistor Q2-2-2 is turned off.

[0085] Figure 8A structural diagram of another battery charging circuit provided by an embodiment of the present invention, Figure 6 The difference between the structures shown is that the connection relationship of the second selection module 30 is different. Figure 8 In this embodiment, the third terminal of the first comparison module 101 is respectively connected to the first control terminal of the first selection module 20 and the control terminal of the first second selection module 301, the first terminal of the first second selection module 301 is connected to the second electrode of the first second transistor Q2-2-1, the second terminal of the first second selection module 301 is connected to the first electrode of the battery U, the first electrode of the first second transistor Q2-2-1 is connected to the first electrode of the first transistor Q2-1, and the control electrode of the first second transistor Q2-2-1 is connected to the first node N1; the third terminal of the second comparison module 102 is respectively connected to the second control terminal of the first selection module 20 and the control terminal of the second second selection module 302, the first terminal of the second second selection module 302 is connected to the second electrode of the second second transistor Q2-2-2, the second terminal of the second second selection module 302 is connected to the first electrode of the battery U, the first electrode of the second second transistor Q2-2-2 is connected to the first electrode of the first transistor Q2-1, and the control electrode of the second second transistor Q2-2-2 is connected to the first node N1.

[0086] Figure 9 A structural diagram of another battery charging circuit provided by an embodiment of the present invention, specifically Figure 8 The battery charging circuit shown is a schematic diagram of the device structure, refer to Figure 8 and Figure 9 The first second selection module 301 includes a first inverter INV1 and a first auxiliary transistor Q3-1, and the second second selection module 302 includes a second inverter INV2 and a second auxiliary transistor Q3-2. The output end of the first comparator OC1 is connected to the first control end of the third selector SE3 and the input end of the first inverter INV1, the output end of the first inverter INV1 is connected to the control electrode of the first auxiliary transistor Q3-1, the first electrode of the first auxiliary transistor Q3-1 is connected to the second electrode of the first second transistor Q2-2-1, and the second electrode of the first auxiliary transistor Q3-1 is connected to the first electrode of the battery U; the output end of the second comparator OC2 is connected to the second control end of the third selector SE3 and the input end of the second inverter INV2, the output end of the second inverter INV2 is connected to the control electrode of the second auxiliary transistor Q3-2, the first electrode of the second auxiliary transistor Q3-2 is connected to the second electrode of the second second transistor Q2-2-2, and the second electrode of the second auxiliary transistor Q3-2 is connected to the first electrode of the battery U; the structures of other modules are the same as those in the above embodiment.

[0087] Specifically, when the battery voltage U+ is less than the first reference voltage VREF1 and greater than the second reference voltage VREF2, the first comparator OC1 outputs a low-level control signal, the second comparator OC2 outputs a high-level control signal, and the third selector SE3 selects the first target voltage Vtrick1 for output. The mirror current flowing through the input transistor Q1 is Vtrick1 / Rp. The first inverter INV1 outputs a high-level control signal, the first auxiliary transistor Q3-1 is turned off, and the path where the first second transistor Q2-2-1 is located is cut off. The second inverter INV2 outputs a low-level control signal, the second auxiliary transistor Q3-2 is turned on, and the path where the second second transistor Q2-2-2 is located is turned on. After being mirrored by the current mirror, the charging current output by the output transistor Q2 is .

[0088] When the battery voltage U+ is less than the second reference voltage, the first comparator OC1 outputs a low-level control signal, the second comparator OC2 outputs a low-level control signal, the third selector SE3 selects the second target voltage Vtrick2 for output, and the mirror current flowing through the input transistor Q1 is Vtrick2 / Rp. The first inverter INV1 outputs a high-level control signal, the first auxiliary transistor Q3-1 is turned off, and the path of the first second transistor Q2-2-1 is cut off. The second inverter INV2 outputs a high-level control signal, the second auxiliary transistor Q3-2 is turned off, and the path of the second second transistor Q2-2-2 is cut off. After being mirrored by the current mirror, the charging current output by the output transistor Q2 is .

[0089] When the battery voltage U+ is greater than or equal to the first reference voltage VREF1, the first comparator OC1 outputs a high-level control signal, the second comparator OC2 outputs a high-level control signal, and the third selector SE3 selects the first voltage V1 for output. The mirror current flowing through the input transistor Q1 is V1 / Rp. The first inverter INV1 outputs a low-level control signal, the first auxiliary transistor Q3-1 is turned on, and the path where the first second transistor Q2-2-1 is located is turned on. The second inverter INV2 outputs a low-level control signal, the second auxiliary transistor Q3-2 is turned on, and the path where the second second transistor Q2-2-2 is located is turned on. After being mirrored by the current mirror, the charging current output by the output transistor Q2 is .

[0090] It should be noted that in the above embodiments, the transistors are all P-type transistors. In other embodiments, the transistors may all be N-type transistors, or some may be P-type transistors and the other may be N-type transistors, and the corresponding control signals need only be adjusted accordingly.

[0091] Optionally, an embodiment of the present invention further provides a battery charging system, which includes the battery charging circuit provided by any embodiment of the present invention. Therefore, the battery charging system also has the beneficial effects described in any of the above embodiments.

[0092] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present invention can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved. This is not limited herein.

[0093] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A battery charging circuit, characterized in that: include: at least one comparison module, a first selection module, at least one second selection module, a matching module, an input transistor, and an output transistor, wherein the output transistor includes a first transistor and at least one second transistor; The comparison module is used to transmit corresponding control signals to the control end of the first selection module and the control end of the second selection module according to the charging mode of the battery, and the charging mode includes at least a trickle charging mode and a constant current charging mode; A first terminal of the first selection module, a control terminal of the input transistor, and a control terminal of the first transistor are connected to a first node, the first terminal of the input transistor is connected to a charging voltage, a second terminal of the input transistor, a first terminal of the matching module, and a second terminal of the first selection module are connected to a second node, and a second terminal of the matching module is grounded, the first selection module is configured to transmit different voltages to the second node according to a control signal output by the comparison module, so as to adjust the mirror current of the input transistor in different charging modes and adjust the operating range of the input transistor to a saturation region; The first electrode of the first transistor is connected to the charging voltage, the second electrode of the first transistor is connected to the first electrode of the battery, the second transistor is connected in parallel with the first transistor, and each second transistor is correspondingly connected to a second selection module, and the second selection module is used to control whether the second transistor is turned on according to the control signal output by the comparison module.

2. The battery charging circuit according to claim 1, wherein: The aspect ratio of the first transistor is K times the aspect ratio of the input transistor, the sum of the aspect ratio of the first transistor and the aspect ratio of the at least one second transistor is N times the aspect ratio of the input transistor, N>K, and N and K are both positive numbers.

3. The battery charging circuit according to claim 2, characterized in that: The relationship between K and the voltage Vtrick transmitted to the second node in the trickle charging mode satisfies: ; Wherein, V0 is the voltage corresponding to the target charging current in the trickle charging mode.

4. The battery charging circuit according to claim 1, wherein: The second transistor is configured such that: in the trickle charge mode, the second transistor is turned off; in the constant current charge mode, the second transistor is turned on.

5. The battery charging circuit according to claim 1, wherein: The number of the comparison module is one, the number of the second selection module is one, and the number of the second transistor is one; A first terminal of the comparison module is connected to a first reference voltage, a second terminal of the comparison module is connected to a first terminal of the battery, and a second terminal of the battery is grounded. A third terminal of the comparison module is connected to a control terminal of the first selection module and a control terminal of the second selection module respectively. A first terminal of the second selection module is connected to the first node, a second terminal of the second selection module is connected to the charging voltage or the battery voltage, a third terminal of the second selection module is connected to a control terminal of the second transistor, a first terminal of the second transistor is connected to a first terminal of the first transistor, and a second terminal of the second transistor is connected to a first terminal of the battery. In which, the comparison module includes a first comparator, the second selection module includes a first selector, the first selection module includes a third selector and an operational amplifier, the first input end of the first comparator is connected to the first reference voltage, the second input end of the first comparator is connected to the first electrode of the battery, the output end of the first comparator is connected to the control end of the third selector and the control end of the first selector, the first input end of the first selector is connected to the first node, the second input end of the first selector is connected to the charging voltage or the battery voltage, the output end of the first selector is connected to the control electrode of the second transistor, the first input end of the third selector is connected to the first voltage, the second input end of the third selector is connected to the first target voltage, the output end of the third selector is connected to the first input end of the operational amplifier, the second input end of the operational amplifier is connected to the second node, and the output end of the operational amplifier is connected to the first node.

6. The battery charging circuit according to claim 1, wherein: The number of the comparison module is one, the number of the second selection module is one, and the number of the second transistor is one; A first terminal of the comparison module is connected to a first reference voltage, a second terminal of the comparison module is connected to a first terminal of the battery, and the second terminal of the battery is grounded; a third terminal of the comparison module is connected to a control terminal of the first selection module and a control terminal of the second selection module respectively; a first terminal of the second selection module is connected to a second terminal of the second transistor, a second terminal of the second selection module is connected to a first terminal of the battery, a first terminal of the second transistor is connected to a first terminal of the first transistor, and a control terminal of the second transistor is connected to the first node; In which, the comparison module includes a first comparator, the second selection module includes a first inverter and a first auxiliary transistor, the first selection module includes a third selector and an operational amplifier, the first input end of the first comparator is connected to the first reference voltage, the second input end of the first comparator is connected to the first pole of the battery, the output end of the first comparator is connected to the control end of the third selector and the input end of the first inverter, the output end of the first inverter is connected to the control pole of the first auxiliary transistor, the first pole of the first auxiliary transistor is connected to the second pole of the second transistor, the second pole of the first auxiliary transistor is connected to the first pole of the battery, the first input end of the third selector is connected to the first voltage, the second input end of the third selector is connected to the first target voltage, the output end of the third selector is connected to the first input end of the operational amplifier, the second input end of the operational amplifier is connected to the second node, and the output end of the operational amplifier is connected to the first node.

7. The battery charging circuit according to claim 1, wherein: The number of the comparison modules is two, the number of the second selection modules is two, and the number of the second transistors is two; A first terminal of the first comparison module is connected to a first reference voltage, a second terminal of the first comparison module is connected to a first terminal of the battery, and a second terminal of the battery is grounded. A third terminal of the first comparison module is connected to a first control terminal of the first selection module and a control terminal of the first second selection module respectively. A first terminal of the first second selection module is connected to the first node. A second terminal of the first second selection module is connected to the charging voltage or the battery voltage. A third terminal of the first second selection module is connected to a control terminal of the first second transistor. A first terminal of the first second transistor is connected to a first terminal of the first transistor. A second terminal of the first second transistor is connected to the first terminal of the battery. A first terminal of the second comparison module is connected to a second reference voltage, a second terminal of the second comparison module is connected to the first electrode of the battery, a third terminal of the second comparison module is connected to the second control terminal of the first selection module and the control terminal of the second second selection module respectively, a first terminal of the second second selection module is connected to the first node, a second terminal of the second second selection module is connected to the charging voltage or the battery voltage, a third terminal of the second second selection module is connected to the control electrode of the second second transistor, a first terminal of the second second transistor is connected to the first terminal of the first transistor, and a second terminal of the second second transistor is connected to the first electrode of the battery; the first reference voltage is greater than the second reference voltage; Wherein, the first comparison module includes a first comparator, the second comparison module includes a second comparator, the first second selection module includes a first selector, the second second selection module includes a second selector, the first selection module includes a third selector and an operational amplifier, the first input end of the first comparator is connected to the first reference voltage, the second input end of the first comparator is connected to the first electrode of the battery, the output end of the first comparator is connected to the first control end of the third selector and the control end of the first selector, the first input end of the first selector is connected to the first node, the second input end of the first selector is connected to the charging voltage or the battery voltage, and the output end of the first selector is connected to the control electrode of the first second transistor; A first input terminal of the second comparator is connected to the second reference voltage, a second input terminal of the second comparator is connected to the first terminal of the battery, an output terminal of the second comparator is connected to the second control terminal of the third selector and the control terminal of the second selector, a first input terminal of the second selector is connected to the first node, a second input terminal of the second selector is connected to the charging voltage or the battery voltage, and an output terminal of the second selector is connected to the control terminal of a second second transistor; The first input terminal of the third selector is connected to the first voltage, the second input terminal of the third selector is connected to the first target voltage, the third input terminal of the third selector is connected to the second target voltage, the output terminal of the third selector is connected to the first input terminal of the operational amplifier, the second input terminal of the operational amplifier is connected to the second node, and the output terminal of the operational amplifier is connected to the first node.

8. The battery charging circuit according to claim 1, wherein: The at least one comparison module includes a first comparison module and a second comparison module, the number of the second selection modules is two, and the number of the second transistors is two; A first terminal of the first comparison module is connected to a first reference voltage, a second terminal of the first comparison module is connected to a first terminal of the battery, and a second terminal of the battery is grounded. A third terminal of the first comparison module is respectively connected to a first control terminal of the first selection module and a control terminal of the first second selection module. A first terminal of the first second selection module is connected to a second terminal of the first second transistor, a second terminal of the first second selection module is connected to a first terminal of the battery, a first terminal of the first second transistor is connected to a first terminal of the first transistor, and a control terminal of the first second transistor is connected to the first node. The first terminal of the second comparison module is connected to the second reference voltage, the second terminal of the second comparison module is connected to the first electrode of the battery, the third terminal of the second comparison module is connected to the second control terminal of the first selection module and the control terminal of the second second selection module respectively, the first terminal of the second second selection module is connected to the second electrode of the second second transistor, the second terminal of the second second selection module is connected to the first electrode of the battery, the first electrode of the second second transistor is connected to the first electrode of the first transistor, and the control electrode of the second second transistor is connected to the first node; the first reference voltage is greater than the second reference voltage; Wherein, the first comparison module includes a first comparator, the second comparison module includes a second comparator, the first second selection module includes a first inverter and a first auxiliary transistor, the second second selection module includes a second inverter and a second auxiliary transistor, the first selection module includes a third selector and an operational amplifier, the first input end of the first comparator is connected to the first reference voltage, the second input end of the first comparator is connected to the first electrode of the battery, the output end of the first comparator is connected to the first control end of the third selector and the input end of the first inverter, the output end of the first inverter is connected to the control electrode of the first auxiliary transistor, the first electrode of the first auxiliary transistor is connected to the second electrode of the first second transistor, and the second electrode of the first auxiliary transistor is connected to the first electrode of the battery; A first input terminal of the second comparator is connected to the second reference voltage, a second input terminal of the second comparator is connected to the first terminal of the battery, an output terminal of the second comparator is connected to the second control terminal of the third selector and the input terminal of the second inverter, an output terminal of the second inverter is connected to the control terminal of the second auxiliary transistor, a first terminal of the second auxiliary transistor is connected to the second terminal of the second second transistor, and a second terminal of the second auxiliary transistor is connected to the first terminal of the battery; The first input terminal of the third selector is connected to the first voltage, the second input terminal of the third selector is connected to the first target voltage, the third input terminal of the third selector is connected to the second target voltage, the output terminal of the third selector is connected to the first input terminal of the operational amplifier, the second input terminal of the operational amplifier is connected to the second node, and the output terminal of the operational amplifier is connected to the first node.

9. The battery charging circuit according to any one of claims 1 to 8, characterized in that: The matching module includes a preset resistor, a first end of the preset resistor is connected to the second node, and a second end of the preset resistor is grounded; The resistance of the preset resistor is adjustable.

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

Images