Battery charging circuit, DC-DC converter and battery charging method

Abstract

The present invention discloses a battery charging circuit, a DC-DC converter and a battery charging method, wherein the battery charging circuit comprises a controlled current source, a first switch module, a second switch module and a control module; the first end of the first switch module is electrically connected to the output end of the controlled current source, and the second end of the first switch module is electrically connected to the positive end of the battery; the first end of the second switch module is electrically connected to the negative end of the battery and the input end of the controlled current source, respectively, and the second end of the second switch module is electrically connected to the output end of the controlled current source; the control module is used to collect a first voltage between the second end of the first switch module and the first end of the second switch module, and control the conduction and disconnection of the first switch module and the second switch module according to the first voltage. According to the battery charging circuit of the present invention, the response speed is fast, the charging current is directly controlled and easy to adjust, the charging current has higher accuracy, and overcharging is not easy to occur.

Description

Technical Field

[0001] The present invention relates to the technical field of battery charging, and in particular to a battery charging circuit, a DC-DC converter and a battery charging method. Background Art

[0002] like Figure 1 The figure shows the constant current and constant voltage charging process of lithium batteries. During the charging process, constant current charging is first performed with a constant current. When the charging voltage reaches a predetermined value, constant voltage charging is switched. During the constant voltage charging process, the charging current will gradually decrease. When the charging current drops to a predetermined value, the battery is fully charged. During the charging process of lithium batteries, in order to achieve constant current and constant voltage charging, the charging and discharging currents are generally regulated and controlled, and the constant current and constant voltage are maintained by adjusting the charging current.

[0003] In the prior art, DC-DC converters for charging batteries generally use boost, buck, boost-buck and other topology circuits, such as Figure 2 The figure shows a common boost topology circuit. These topology circuits generally use a voltage source to provide charging current; however, in the battery charging process, whether it is constant current charging or constant voltage charging, the essence is to achieve constant current and constant voltage by adjusting the charging current, and using a voltage source as input, the control of the charging current is not direct enough, and the adjustment speed is not fast enough.

[0004] In addition, the existing topology circuit requires a certain recovery time when adjusting the charging voltage, and has the problem of insufficient response speed. Figure 2 The boost topology circuit shown in the figure needs to increase the on-time of the switch tube S3 when the output voltage is to be increased. However, in the first cycle, due to the increase in the on-time of S3, the on-time of S4 is reduced, and the output voltage is reduced. It takes a certain amount of time to return to the steady-state voltage. In order to avoid the influence of the non-minimum phase characteristics of this boost topology circuit on the stability of the system, the general method is to design the closed-loop bandwidth of the system to be much smaller than the turning frequency of the right half plane zero point, but this is undoubtedly at the expense of the rapidity of the system dynamic response. During the battery charging process, since the battery voltage is constantly changing, if constant voltage charging is to be maintained, the system needs to have a relatively fast response speed. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a battery charging circuit with a fast response speed and can effectively realize constant current and constant voltage charging of the battery.

[0006] The invention also provides a DC-DC converter having the battery charging circuit.

[0007] The invention also provides a battery charging method.

[0008] In a first aspect, a battery charging circuit according to an embodiment of the present invention comprises a controlled current source, a first switch module, a second switch module and a control module; a first end of the first switch module is electrically connected to an output end of the controlled current source, and a second end of the first switch module is electrically connected to a positive end of a battery; a first end of the second switch module is electrically connected to a negative end of the battery and an input end of the controlled current source, respectively, and a second end of the second switch module is electrically connected to an output end of the controlled current source; the control module is used to collect a first voltage between the second end of the first switch module and the first end of the second switch module, and control the conduction and disconnection of the first switch module and the second switch module according to the first voltage, thereby chopping the output current of the controlled current source to achieve constant voltage charging of the battery.

[0009] The battery charging circuit according to the embodiment of the present invention has at least the following beneficial effects: a controlled current source is used to provide charging current, and the conduction time of the first switch module and the second switch module is controlled by the control module, thereby realizing constant current and constant voltage charging of the battery; the response speed of the entire circuit is fast, the charging current is directly controlled and easy to adjust, the charging current has higher accuracy, and overcharging is not easy to occur.

[0010] According to some embodiments of the present invention, the first switch module includes a first switch tube, and the second switch module includes a second switch tube.

[0011] According to some embodiments of the present invention, a filter unit is further included, and the filter unit is disposed between the first switch module, the second switch module and the battery.

[0012] According to some embodiments of the present invention, the control module includes a hysteresis comparator and a driving unit, the positive input terminal of the hysteresis comparator is connected to the first voltage, and the reverse input terminal of the hysteresis comparator is connected to a reference voltage; the input terminal of the driving unit is electrically connected to the output terminal of the hysteresis comparator, and the output terminal of the driving unit is electrically connected to the controlled end of the first switch module and the controlled end of the second switch module, respectively.

[0013] According to some embodiments of the present invention, a current source generating module is further included, and the current source generating module is used to generate the controlled current source.

[0014] According to some embodiments of the present invention, the current source generating module adopts a three-level buck circuit or a full-bridge topology circuit.

[0015] In a second aspect, a DC-DC converter according to an embodiment of the present invention includes a battery charging circuit according to an embodiment of the first aspect of the present invention.

[0016] The DC-DC converter according to the embodiment of the present invention has at least the following beneficial effects: by adopting the above-mentioned battery charging circuit, the response speed is faster, the charging current is directly controlled and easy to adjust, the charging current is more accurate, overcharging is less likely to occur, and constant current and constant voltage charging of the battery can be effectively achieved.

[0017] In the third aspect, the battery charging method according to the embodiment of the present invention includes a constant voltage charging process, and the constant voltage charging process includes the following steps: presetting an upper limit voltage value and a lower limit voltage value; during the charging process, when the first voltage rises to the upper limit voltage value, the control module controls the first switch module to be disconnected and the second switch module to be turned on, so that the first voltage decreases; when the first voltage decreases to the lower limit voltage value, the control module controls the first switch module to be turned on and the second switch module to be disconnected, so that the first voltage increases to the upper limit voltage value; repeat the above process until the battery is fully charged. The battery charging method according to the embodiment of the present invention has at least the following beneficial effects: it can effectively realize constant voltage charging of the battery, the charging current is directly controlled and easy to adjust, the charging current has higher accuracy, it is not easy to overcharge, and the entire control method is relatively simple and reliable.

[0018] According to some embodiments of the present invention, a constant current charging process is also included, and the constant current charging process includes the following steps: presetting a first voltage value; performing constant current charging on the battery until the charging voltage of the battery rises to the first voltage value, and then starting the constant voltage charging process.

[0019] According to some embodiments of the present invention, the constant-current charging of the battery is performed until the charging voltage of the battery rises to the first voltage value, and then the constant-voltage charging process begins. Specifically, the control module controls the first switch module to be turned on and the second switch module to be turned off, and the controlled current source provides a constant current to perform constant-current charging of the battery until the charging voltage of the battery rises to the first voltage value, and then the constant-voltage charging process begins.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0022] Figure 1 Schematic diagram of the lithium battery charging process;

[0023] Figure 2 It is a circuit schematic diagram of a boost topology circuit in the prior art;

[0024] Figure 3 A schematic diagram of a circuit principle of a battery charging circuit according to an embodiment of the present invention;

[0025] Figure 4 for Figure 3 The circuit principle schematic diagram of the battery charging circuit shown when the first switch module is turned on;

[0026] Figure 5 for Figure 3 The circuit principle schematic diagram of the battery charging circuit shown when the second switch module is turned on;

[0027] Figure 6 A specific circuit schematic diagram of a battery charging circuit according to a first embodiment of the present invention;

[0028] Figure 7 A specific circuit schematic diagram of a battery charging circuit according to a second embodiment of the present invention;

[0029] Figure 8 for Figure 7 The schematic diagram of the working principle of the battery charging circuit in the constant voltage charging process is shown;

[0030] Fig. 9 for Figure 7 A schematic diagram showing the waveform changes of the charging voltage and charging current of the battery charging circuit during constant voltage charging;

[0031] Fig.10 is a circuit schematic diagram of a three-level buck circuit according to an embodiment of the present invention;

[0032] Fig.11 is a circuit schematic diagram of a full-bridge topology circuit according to an embodiment of the present invention;

[0033] Fig.12 A flowchart of the constant voltage charging process according to an embodiment of the present invention;

[0034] Fig.13 4 is a flowchart of the constant current charging process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0036] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0037] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0038] First, refer to Figures 3 to 7 , a battery charging circuit according to an embodiment of the present invention comprises a controlled current source, a first switch module 100, a second switch module 200 and a control module 300; wherein, a first end of the first switch module 100 is electrically connected to an output end of the controlled current source, and a second end of the first switch module 100 is electrically connected to a positive end of a battery; a first end of the second switch module 200 is electrically connected to a negative end of the battery and an input end of the controlled current source, respectively, and a second end of the second switch module 200 is electrically connected to an output end of the controlled current source; the control module 300 is used to collect a first voltage Uo between a second end of the first switch module 100 and a first end of the second switch module 200, and control the conduction and disconnection of the first switch module 100 and the second switch module 200 according to the first voltage Uo, thereby chopping the output current of the controlled current source to realize constant voltage charging of the battery.

[0039] Specifically, the battery charging circuit according to the embodiment of the present invention adopts a controlled current source to provide the charging current; Figures 3 to 5 As shown, during the constant current charging process, it is only necessary to close the first switch module 100 and disconnect the second switch module 200, and the controlled current source can provide a constant charging current for the battery to achieve constant current charging; during the constant current charging process, the charging voltage continues to rise, and when the charging voltage reaches a predetermined value, it is converted to constant voltage charging; during the constant voltage charging process, such as Figures 7 to 9As shown, an upper limit voltage value Ua and a lower limit voltage value Ub are preset, and the control module 300 collects the first voltage Uo. When the first voltage Uo rises to the upper limit voltage value Ua, the control module 300 controls the first switch module 100 to be disconnected and the second switch module 200 to be turned on. At this time, the current provided by the controlled current source does not pass through the battery, and the battery is not charged, and the first voltage Uo gradually decreases; when the first voltage Uo drops to the lower limit voltage value Ub, the control module 300 controls the first switch module 100 to be turned on and the second switch module 200 to be disconnected, and the controlled current source continues to charge the battery, so that the first voltage Uo gradually rises to Ua, and then the states of the first switch module 100 and the second switch module 200 are switched, so that the first voltage Uo drops to Ub again; the above process is repeated until the battery is fully charged. In the process of constant voltage charging of the battery, the pulse of the charging current is controlled by continuously switching the conduction state of the first switch module 100 and the second switch module 200, thereby controlling the average charging current of the battery, and finally achieving the average charging voltage of the battery to remain unchanged; that is, the output current of the controlled current source is chopper-controlled to achieve constant voltage charging of the battery. Figure 8 and Fig. 9 As shown in the figure, during the constant voltage charging process, as the charging process proceeds, more and more electricity is charged into the battery, the battery voltage becomes higher and higher, the voltage difference with the charging voltage becomes smaller, and the current that can be charged becomes smaller; the conduction time of the first switch module 100 gradually decreases, the conduction time of the second switch module 200 gradually increases, the average charging current gradually decreases, and the battery charging current also gradually decreases until the battery is fully charged; the constant voltage charging of the lithium battery is maintained throughout the entire stage. Among them, during the constant voltage charging process, the charging voltage will have very small fluctuations, but in Fig. 9 The waveform of the charging voltage is represented by a straight line.

[0040] It can be seen that according to the battery charging circuit of the embodiment of the present invention, a controlled current source is used to provide charging current, and the control module 300 is used to control the conduction time of the first switch module 100 and the second switch module 200, thereby realizing constant current and constant voltage charging of the battery; the response speed of the entire circuit is fast, the charging current is directly controlled and easy to adjust, the charging current is more accurate, and overcharging is not likely to occur, and the structure and control method of the entire circuit are relatively simple and reliable.

[0041] like Figure 6 and Figure 7As shown, in some embodiments of the present invention, the first switch module 100 includes a first switch tube S1, and the second switch module 200 includes a second switch tube S2. The first switch tube S1 and the second switch tube S2 may be MOS tubes, such as Si-type MOS tubes, GaN-type MOS tubes, etc. It is understandable that the first switch module 100 and the second switch module 200 may also use other common switch elements, such as relays, etc., but are not limited thereto.

[0042] like Figure 6 and Figure 7 As shown, in some embodiments of the present invention, a filter unit 400 is further included. The filter unit 400 is disposed between the first switch module 100 and the second switch module 200 and the battery.

[0043] Specifically, Figure 6 As shown, the filter unit 400 includes a first capacitor C1 and a first inductor L1, one end of the first capacitor C1 is electrically connected to the second end of the first switch module 100, and the other end of the first capacitor C1 is electrically connected to the negative end of the battery and the first end of the second switch module 200 respectively; one end of the first inductor L1 is electrically connected to one end of the first capacitor C1, and the other end of the first inductor L1 is electrically connected to the positive end of the battery. The first capacitor C1 and the first inductor L1 form the filter unit 400, filter the charging current, obtain a smooth current signal, and then charge the battery.

[0044] Or, if Figure 7 As shown, the filter unit 400 may also use a π-type filter. The π-type filter includes a capacitor C2, an inductor L2, and a capacitor C3. One end of the capacitor C2 is electrically connected to the second end of the first switch module 100, and the other end of the capacitor C2 is electrically connected to the negative end of the battery and the first end of the second switch module 200 respectively; one end of the inductor L2 is electrically connected to one end of the capacitor C2, and the other end of the inductor L2 is electrically connected to the positive end of the battery and one end of the capacitor C3 respectively, and the other end of the capacitor C3 is electrically connected to the negative end of the battery and the other end of the capacitor C2 respectively. The capacitor C2, the inductor L2, and the capacitor C3 form the filter unit 400, which filters the charging current to obtain a smooth current signal, and then charges the battery.

[0045] It is understandable that the filter unit 400 may also adopt other common filter circuits, but is not limited thereto.

[0046] like Figure 7As shown, in some embodiments of the present invention, the control module 300 includes a hysteresis comparator and a driving unit, the positive terminal of the hysteresis comparator is connected to the first voltage Uo, and the negative terminal of the hysteresis comparator is connected to the reference voltage Vref; the input terminal of the driving unit is electrically connected to the output terminal of the hysteresis comparator, and the output terminal of the driving unit is electrically connected to the controlled terminal of the first switch module 100 and the controlled terminal of the second switch module 200. The driving unit can adopt an existing IGBT module or a common driving chip to control the conduction time of the first switch module 100 and the second switch module 200.

[0047] like Figure 8 and Fig. 9 As shown, during the constant voltage charging process, at time t0, the first voltage Uo drops to Ub. At this time, the first voltage Uo connected to the positive input terminal of the hysteresis comparator is lower than the reference voltage Vref connected to the reverse input terminal. The hysteresis comparator outputs a high level, and the drive unit controls the first switch module 100 to turn on, the second switch module 200 to turn off, and the controlled current source charges the battery, and the first voltage Uo rises. At time t1, the first voltage Uo at the same input terminal of the hysteresis comparator has increased to be equal to the reference voltage Vref at the reverse input terminal, but according to the characteristics of the hysteresis comparator, the hysteresis comparator will continue to maintain its original state at this time; this state will be maintained until Uo rises to Ua, that is, at time t2, at which time the hysteresis comparator flips and outputs a low level. The drive unit controls the first switch module 100 to turn off, the second switch module 200 to turn on, the controlled current source does not charge the battery, the charging current decreases, and the first voltage Uo decreases. This state will be maintained until time t3. The above process is then repeated to finally complete the constant voltage charging process of the lithium battery. As shown Fig.10 and Fig.11 As shown, in some embodiments of the present invention, a current source generation module is further included, and the current source generation module is used to generate a controlled current source. The current source generation module can adopt an existing three-level buck circuit, a full-bridge topology circuit, or other switching power supply circuits.

[0048] like Fig.10The figure shows a three-level buck circuit, and the principle of generating a controlled current source is as follows: in the first stage, the switch tubes S5 and S7 are turned on, the switch tubes S6 and S8 are turned off, and the voltage source passes through the switch tube S5, the capacitor C5, the switch tube S7 and the inductor L4, the voltage Vc on the capacitor C5 increases, the current on the inductor L4 increases, and the output current increases; in the second stage, the switch tubes S5 and S6 are turned off, the switch tubes S7 and S8 are turned on, and since the capacitor C5 cannot form a loop, the voltage Vc remains unchanged, while the current on the inductor L4 decreases linearly, and the output current decreases; in the third stage, the switch tubes S6 and S8 are turned on, the switch tubes S5 and S7 are turned off, the capacitor C5 provides energy to the load through the switch tube S6, the voltage Vc decreases, the current on the inductor L4 increases, and the output current increases; in the fourth stage, the switch tubes S5 and S6 are turned off, the switch tubes S7 and S8 are turned on, and since the capacitor C5 cannot form a loop, the voltage Vc remains unchanged, while the current on the inductor L4 decreases linearly, and the output current decreases. The current can be increased by increasing the on-time of the switch tubes S5 and S6 , and the current can be reduced by reducing the on-time of S5 and S6 , thereby realizing charging and discharging of the controlled current source.

[0049] like Fig.11 The figure shows a full-bridge topology circuit. The principle of generating a controlled current source is as follows: when the switch tubes S9 and S12 are turned on and the switch tubes S10 and S11 are turned off, the current on the primary side of the transformer T1 flows from top to bottom. Through the coupling of the transformer T1, the switch tubes S13 and S16 are turned on, and the switch tubes S14 and S15 are turned off, so that energy rectification is realized, the current of the inductor L5 increases, and the output current increases; when the switch tubes S9, S10, S11 and S12 are turned off, the switch tubes S13, S14, S15 and S16 are turned off, and the inductor L5 The current of the inductor L5 gradually decreases, and the output current decreases; when the switch tubes S9 and S12 are turned off, and the switch tubes S10 and S11 are turned on, the primary current of the transformer T1 flows from bottom to top, and through the coupling of the transformer, the switch tubes S13 and S16 are turned off, and S14 and S15 are turned on to realize energy rectification, the current of the inductor L5 increases, and the output current increases; when the switch tubes S9, S10, S11 and S12 are turned off, the switch tubes S13, S14, S15 and S16 are turned off, the current of the inductor L5 gradually decreases, and the output current decreases. The current can be increased by increasing the on-time of the switch tubes S9 and S12 or the switch tubes S10 and S3, and the current can be reduced by reducing the on-time of the switch tubes S9 and S12 or the switch tubes S10 and S11, thereby realizing the charging and discharging of the controlled current source.

[0050] Secondly, the DC-DC converter according to the embodiment of the present invention adopts the above-mentioned battery charging circuit, so the response speed is fast, the charging current is directly controlled and easy to adjust, the charging current is more accurate, and overcharging is not easy to occur.

[0051] Thirdly, Fig.12 As shown, the battery charging method according to an embodiment of the present invention includes a constant voltage charging process, and the constant voltage charging process includes the following steps:

[0052] Step S100: Preset an upper voltage limit Ua and a lower voltage limit Ub.

[0053] Step S200: During the charging process, when the first voltage Uo rises to the upper limit voltage value Ua, the control module 300 controls the first switch module 100 to be disconnected and the second switch module 200 to be turned on, so that the first voltage Uo decreases; when the first voltage Uo decreases to the lower limit voltage value Ub, the control module 300 controls the first switch module 100 to be turned on and the second switch module 200 to be disconnected, so that the first voltage Uo increases to the upper limit voltage value Ua; the above process is repeated until the battery is fully charged.

[0054] Specifically, Figures 7 to 9 As shown, when the battery is charged at a constant voltage, in the initial state, the first switch module 100 is turned on and the second switch module 200 is turned off. At this time, the controlled current source charges the battery, and the first voltage Uo gradually increases; when the first voltage Uo rises to the upper limit voltage value Ua, the control module 300 controls the first switch module 100 to be turned off and the second switch module 200 to be turned on. At this time, the controlled current source does not charge the battery, so that the first voltage Uo decreases; at time t0, the first voltage Uo decreases to Ub. At this time, the first voltage Uo connected to the positive input terminal of the hysteresis comparator is lower than the reference voltage Vref connected to the reverse input terminal. The hysteresis comparator outputs a high level, the drive unit controls the first switch module 100 to be turned on, and the second switch module 200 to be turned off. The controlled current source charges the battery, and the first voltage Uo increases. At time t1, the first voltage Uo at the same-direction input terminal of the hysteresis comparator has increased to be equal to the reference voltage Vref at the reverse input terminal, but according to the characteristics of the hysteresis comparator, the hysteresis comparator will continue to maintain its original state at this time; this state will be maintained until Uo rises to Ua, that is, at time t2, at which time the hysteresis comparator flips and outputs a low level, the drive unit controls the first switch module 100 to be disconnected, the second switch module 200 to be turned on, the controlled current source does not charge the battery, the charging current decreases, and the first voltage Uo decreases. This state will be maintained until time t3. The above process is then repeated to finally complete the constant voltage charging process of the lithium battery.

[0055] In the process of constant voltage charging of the battery, the pulse of the charging current is controlled by continuously switching the conduction state of the first switch module 100 and the second switch module 200, thereby controlling the average charging current of the battery, and finally achieving the average charging voltage of the battery to remain unchanged; that is, the output current of the controlled current source is chopper-controlled to achieve constant voltage charging of the battery. Figure 8 and Fig. 9 As shown, during the constant voltage charging process, as the charging process proceeds, more and more electricity is charged into the battery, the battery voltage becomes higher and higher, the voltage difference with the charging voltage becomes smaller, and the current that can be charged becomes smaller; the conduction time of the first switch module 100 gradually decreases, the conduction time of the second switch module 200 gradually increases, the average charging current gradually decreases, and the battery charging current also gradually decreases until the battery is fully charged; the constant voltage charging of the lithium battery is maintained throughout the entire stage.

[0056] It should be noted that, regarding the specific values ​​of the upper limit voltage value Ua and the lower limit voltage value Ub, those skilled in the art can make reasonable selections according to the charging voltage of the battery. Assuming that the required charging voltage of the battery is 5V, Ua can be set to 5.05V and Ub to 4.95V. Of course, Ua and Ub can also be other more reasonable values.

[0057] like Fig.13 As shown, the battery charging method according to the embodiment of the present invention further includes a constant current charging process before the above-mentioned constant voltage charging process, and the constant current charging process includes the following steps:

[0058] Step S300: preset a first voltage value.

[0059] Step S400: the battery is charged at a constant current until the charging voltage of the battery rises to a first voltage value, and then the above-mentioned constant voltage charging process is started.

[0060] Specifically, Figure 7 As shown, in order to realize constant current charging of the battery, the control module 300 controls the first switch module 100 to be turned on and the second switch module 200 to be turned off, so that the controlled current source provides a constant current to perform constant current charging of the battery, so that the charging voltage gradually increases. When the control module 300 detects that the charging voltage rises to the first voltage value, it starts to enter the above-mentioned constant voltage charging process.

[0061] The battery charging method according to the embodiment of the present invention can effectively realize constant current and constant voltage charging of the battery. The charging current is directly controlled and easy to adjust. The charging current has higher accuracy and is less likely to overcharge. Moreover, the entire control method is relatively simple and reliable.

[0062] In the description of this specification, the description with reference to the terms "one embodiment", "further embodiments", "some specific embodiments" or "some examples" etc. means that the specific features, structures or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0063] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A battery charging circuit, characterized in that: include: controlled current source; A first switch module, wherein a first end of the first switch module is electrically connected to the output end of the controlled current source, and a second end of the first switch module is electrically connected to the positive terminal of the battery; a second switch module, wherein a first end of the second switch module is electrically connected to the negative terminal of the battery and the input end of the controlled current source respectively, and a second end of the second switch module is electrically connected to the output end of the controlled current source; a control module, configured to collect a first voltage between the second end of the first switch module and the first end of the second switch module, and control the on and off of the first switch module and the second switch module according to the first voltage, thereby chopping the output current of the controlled current source to realize constant voltage charging of the battery; The constant voltage charging process comprises the following steps: Preset upper voltage limit and lower voltage limit; During the charging process, when the first voltage rises to the upper limit voltage value, the control module controls the first switch module to be disconnected and the second switch module to be turned on, so that the first voltage decreases; when the first voltage decreases to the lower limit voltage value, the control module controls the first switch module to be turned on and the second switch module to be disconnected, so that the first voltage increases to the upper limit voltage value; the above process is repeated until the battery is fully charged.

2. The battery charging circuit according to claim 1, characterized in that: The first switch module includes a first switch tube, and the second switch module includes a second switch tube.

3. The battery charging circuit according to claim 1, characterized in that: The device further comprises a filter unit, wherein the filter unit is disposed between the first switch module, the second switch module and the battery.

4. The battery charging circuit according to claim 3, characterized in that: The control module comprises: a hysteresis comparator, wherein a positive input terminal is connected to the first voltage, and a negative input terminal of the hysteresis comparator is connected to a reference voltage; A driving unit, an input end of which is electrically connected to the output end of the hysteresis comparator, and an output end of the driving unit is electrically connected to the controlled end of the first switch module and the controlled end of the second switch module respectively.

5. The battery charging circuit according to claim 1, characterized in that: It also includes a current source generating module, and the current source generating module is used to generate the controlled current source.

6. The battery charging circuit according to claim 5, characterized in that: The current source generation module adopts a three-level buck circuit or a full-bridge topology circuit.

7. A DC-DC converter, characterized in that: The invention comprises a battery charging circuit as claimed in any one of claims 1 to 6.

8. A battery charging method, based on the battery charging circuit as claimed in claim 3 or 4, characterized in that: The constant voltage charging process includes the following steps: Preset upper voltage limit and lower voltage limit; During the charging process, when the first voltage rises to the upper limit voltage value, the control module controls the first switch module to be disconnected and the second switch module to be turned on, so that the first voltage decreases; when the first voltage decreases to the lower limit voltage value, the control module controls the first switch module to be turned on and the second switch module to be disconnected, so that the first voltage increases to the upper limit voltage value; the above process is repeated until the battery is fully charged.

9. The battery charging method according to claim 8, characterized in that: The constant current charging process is also included, and the constant current charging process includes the following steps: Preset a first voltage value; The battery is charged at a constant current until the charging voltage of the battery rises to the first voltage value, and then the constant voltage charging process is started.

10. The battery charging method according to claim 9, characterized in that: The constant current charging of the battery, until the charging voltage of the battery rises to the first voltage value, and then starting the constant voltage charging process, comprises: The control module controls the first switch module to be turned on and the second switch module to be turned off, and the controlled current source provides a constant current to charge the battery with a constant current until the charging voltage of the battery rises to the first voltage value, and then the constant voltage charging process begins.

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