Charging and discharging control circuit, bidirectional power supply and mobile terminal

Abstract

The invention relates to a bidirectional power supply, and discloses a charging and discharging control circuit, a bidirectional power supply and a mobile terminal. And constant-current charging can be realized with lower cost. The charge and discharge control circuit comprises a first differential amplifier, the input end of which is connected to a current sampling voltage; the first analog switch is used for connecting the reference end of the first differential amplifier to a first reference level in a charging state and connecting the reference end of the first differential amplifier to a second reference level in a discharging state; the input end of the integrator is connected to the output end of the first differential amplifier, and the reference end of the integrator is connected to a third reference level; the input end of the phase inverter is connected with the output end of the integrator; the control signal output end is used for outputting a control signal for controlling the magnitude of the charging or discharging current; and the second analog switch is used for connecting the output end of the integrator to the control signal output end in the charging state and connecting the output end of the phase inverter to the control signal output end in the discharging state.

Description

Technical Field

[0001] The present application relates to a bidirectional power supply, and in particular to a charge and discharge control technology. Background Art

[0002] This section is intended to provide a background or context to the embodiments of the present application as recited in the claims. The description herein is not admitted to be prior art as disclosed by virtue of its inclusion in this section.

[0003] Rechargeable batteries are widely used in mobile terminals. The technique of charging with constant current first and then constant voltage after reaching a certain threshold is a common charging strategy for lithium-ion batteries and many other rechargeable batteries. This method combines two main charging stages to ensure that the battery is charged safely and efficiently while maximizing its service life.

[0004] 1. Constant current charging stage (CC, Constant Current):

[0005] · During this phase, the battery is charged at a constant current.

[0006] · When the battery voltage is low, constant current charging can quickly recharge the battery.

[0007] · The battery voltage will gradually increase as the charging process progresses.

[0008] · When the battery voltage reaches a predetermined threshold (usually close to the rated voltage of the battery), the charging process will enter the next stage.

[0009] 2. Constant Voltage Charging Stage (CV):

[0010] · During this phase, the battery voltage is maintained at a predetermined threshold and the charging current is gradually reduced.

[0011] · As the battery approaches full charge, the constant voltage strategy helps avoid overcharging, thereby protecting the battery and extending its life.

[0012] · When the charging current drops to a predetermined low value, the battery is usually considered to be fully charged and the charging process is terminated.

[0013] The current needs to be controlled during the charging and discharging process, and this control is implemented by the control circuit. The current control circuit is relatively expensive, and the reasons include but are not limited to the use of a high-cost instrumentation amplifier to amplify the sampling signal, or the use of multiple high-cost CSAs to amplify the charging and discharging current sampling signals, etc. Among them, the cost of an instrumentation amplifier is often higher than that of multiple CSAs. Summary of the invention

[0014] The purpose of this application is to provide a charge and discharge control circuit, a bidirectional power supply and a mobile terminal to achieve constant current charging at a lower cost.

[0015] The present application discloses a charge and discharge control circuit, comprising:

[0016] A first differential amplifier, whose input terminal is connected to a current sampling voltage, wherein the current sampling voltage is proportional to the magnitude of the charging or discharging current of the power supply;

[0017] a first analog switch, configured to connect the reference terminal of the first differential amplifier to a first reference level in a charging state, and to connect the reference terminal of the first differential amplifier to a second reference level in a discharging state;

[0018] an integrator, wherein an input terminal of the integrator is connected to the output terminal of the first differential amplifier, and a reference terminal of the integrator is connected to a third reference level;

[0019] an inverter, an input end of which is connected to the output end of the integrator;

[0020] A control signal output terminal, outputting a control signal for controlling the magnitude of the charging or discharging current;

[0021] The second analog switch is used to connect the output end of the integrator to the control signal output end in a charging state, and to connect the output end of the inverter to the control signal output end in a discharging state.

[0022] In a preferred example, the inverter includes a transistor, the base of the transistor is connected to the output end of the integrator through a resistor (R13), the collector of the transistor is connected to the power supply voltage through a resistor (R14), the emitter of the transistor is connected to the ground, and the collector of the transistor serves as the output end of the inverter.

[0023] In a preferred example, the integrator includes a first operational amplifier, a positive input terminal of the first operational amplifier is connected to a third reference level as a reference terminal of the integrator, a negative input terminal of the first operational amplifier is connected to the output terminal of the first differential amplifier via a resistor (R11), and the output terminal of the first operational amplifier is connected to the negative input terminal of the operational amplifier via a capacitor (C18).

[0024] In a preferred embodiment, it also includes:

[0025] a second differential amplifier having an input terminal connected to the output voltage of the power supply;

[0026] a second operational amplifier, wherein the negative input terminal of the second operational amplifier is connected to the output terminal of the second differential amplifier through a resistor (R15), and the positive input terminal of the second operational amplifier is connected to a fourth reference level through a resistor (R16); a resistor (R22) is connected between the output terminal of the second operational amplifier and the control signal output terminal; a capacitor (C8) is connected between the negative input terminal of the second operational amplifier and the control signal output terminal; and the output terminal of the second operational amplifier is connected to a fourth node through a resistor (R24);

[0027] a third analog switch, used to connect the second node to the fourth node in a charging state, and to connect the first node to the fourth node in a discharging state, wherein the first node is forwardly connected to the third node through a diode, and the second node is forwardly connected to the third node through a diode; the third node is connected to the positive input terminal of the first operational amplifier through a resistor (R23); and the third node is connected to the third reference level through a resistor (R12);

[0028] The control signal output terminal is connected to the power supply voltage through a resistor (R1).

[0029] In a preferred embodiment, the output terminal of the second operational amplifier is reversely connected to the control signal output terminal through a diode (D1);

[0030] The negative input terminal of the first operational amplifier is connected to the control signal output terminal through a capacitor (C5).

[0031] In a preferred example, the third node is connected to the ground via a capacitor (C6).

[0032] In a preferred example, the fourth reference level is set according to a target voltage of constant voltage charging.

[0033] In a preferred example, the third reference level is set according to the size of the charging or discharging current.

[0034] The present application also discloses a bidirectional power supply, comprising the charge and discharge control circuit as described above.

[0035] The present application also discloses a mobile terminal, comprising the charge and discharge control circuit as described above.

[0036] In the implementation manner of the present application, only one differential amplifier is required to implement constant current charging, which saves costs without affecting the charging and discharging control effect.

[0037] A local circuit with a triode as the core is used to realize bidirectional control of charging and discharging currents, reduce the use of operational amplifiers, and further solve the cost problem.

[0038] Combined with some low-cost components, the charging effect of constant current first and then constant voltage is further achieved.

[0039] Each technical feature disclosed in the above invention content, each technical feature disclosed in each implementation mode and example below, and each technical feature disclosed in the drawings can be freely combined with each other to form various new technical solutions (these technical solutions should be deemed to have been recorded in this specification), unless such combination of technical features is technically infeasible. For example, in one example, feature A+B+C is disclosed, and in another example, feature A+B+D+E is disclosed, and features C and D are equivalent technical means that play the same role. Technically, only one of them can be used, and it is impossible to use them at the same time. Feature E can be combined with feature C technically. Then, the solution of A+B+C+D should not be deemed to have been recorded because it is technically infeasible, while the solution of A+B+C+E should be deemed to have been recorded. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a schematic diagram of the structure of a charge and discharge control circuit according to an embodiment of the present application;

[0041] Figure 2 is a schematic diagram of the structure of a charge and discharge control circuit according to another embodiment of the present application;

[0042] Figure 3 yes Figure 2 An enlarged view of a part;

[0043] Figure 4 yes Figure 2 An enlarged view of a part;

[0044] Figure 5 yes Figure 2 An enlarged view of a part;

[0045] Figure 6It is an implementation method of an analog switch in one embodiment of the present application;

[0046] Figure 7 It is another implementation method of the analog switch in one embodiment of the present application;

[0047] Figure 8 yes Figure 2 A graph showing battery voltage and current changes over time in a state of charge embodiment. DETAILED DESCRIPTION

[0048] In the following description, many technical details are provided to help readers better understand the present application. However, those skilled in the art can understand that the technical solution claimed in the present application can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0049] Description of some concepts:

[0050] A bidirectional power supply is a power system that is capable of bidirectional energy flow. It can not only provide energy to the load (provided by the internal rechargeable battery), but also recover energy from other power systems and store it in the internal battery.

[0051] CSA is the abbreviation of "Current Sense Amplifier", which means "current sensing amplifier" in Chinese. It is a special amplifier used to accurately detect and amplify the tiny voltage changes of current flowing through a certain path. This voltage change is usually caused by the current flowing through a known small resistance (called a sensing resistor or shunt resistor). CSA amplifies this tiny voltage change so that it can be further processed or measured. In many applications, such as power management and battery management systems, CSA is used to monitor current and provide feedback to the control system.

[0052] MCU is the abbreviation of "Microcontroller Unit", which is usually called "microcontroller" in Chinese.

[0053] DAC is the abbreviation of "Digital-to-Analog Converter", which is called "digital analog converter" in Chinese. It is a device or integrated circuit used to convert digital signals (usually binary form) into analog signals (usually voltage or current).

[0054] An analog switch is an electronic switch that can perform on / off operations in an analog signal path. Unlike mechanical switches, analog switches are semiconductor devices, usually composed of field effect transistors (FETs), which can perform fast switching without mechanical moving parts. The main features of analog switches include: low insertion loss: when the analog switch is in the closed state, its resistance is usually very low, resulting in little signal loss; high isolation: when the analog switch is in the open state, it can provide high signal isolation; fast switching: analog switches can switch in nanosecond or microsecond time ranges; bidirectional operation: most analog switches can work in both directions, which means that signals can be transmitted from either end to the other end; wide operating voltage range: many analog switches can work in a wide voltage range, from low voltage to high voltage.

[0055] MOS tube is the abbreviation of "Metal-Oxide-Semiconductor Field-Effect Transistor", usually referred to as MOSFET. It is a field effect transistor (FET) whose working principle is based on the electric field effect controlled by voltage.

[0056] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below in conjunction with the accompanying drawings.

[0057] One embodiment of the present application relates to a charge and discharge control circuit, such as Figure 1 As shown, the charge and discharge control circuit includes:

[0058] The first differential amplifier has an input terminal connected to a current sampling voltage, wherein the current sampling voltage is proportional to the magnitude of the charging or discharging current of the power supply. Optionally, the first differential amplifier may be a CSA.

[0059] The first analog switch is used to connect the reference terminal of the first differential amplifier to a first reference level in a charging state, and to connect the reference terminal of the first differential amplifier to a second reference level in a discharging state.

[0060] An integrator, the input end of the integrator is connected to the output end of the first differential amplifier, and the reference end of the integrator is connected to a third reference level. The third reference level can be set according to the size of the charging or discharging current. Optionally, the third reference level can be set by a microcontroller (MCU) through a digital-to-analog converter (DAC).

[0061] An inverter has an input terminal connected to the output terminal of the integrator.

[0062] The control signal output terminal outputs a control signal for controlling the size of the charging or discharging current.

[0063] The second analog switch is used to connect the output end of the integrator to the control signal output end in the charging state, and to connect the output end of the inverter to the control signal output end in the discharging state.

[0064] The above embodiment only requires one differential amplifier to realize constant current charging, thus saving costs.

[0065] Another embodiment of the present application is Figure 2 shown. Figure 2 This is a charge and discharge control circuit, in which the specific values ​​of the components are only a special case, and other values ​​may be selected as needed, which does not constitute a limitation on the protection scope of this application. Figure 2 There are many components in the text box, and the font size is small. In order to see it clearly, you can refer to Figure 3 , Figure 4 and Figure 5 These pictures are Figure 2 A partial enlarged view of .

[0066] Figure 2 The technical solution can charge the battery at a predetermined (usually higher) current at a constant current in the initial stage. When the battery voltage reaches a predetermined threshold (usually close to the rated voltage of the battery), it is switched to constant voltage charging. At this time, the current will be greatly reduced to protect the battery.

[0067] CSA (U2) is equivalent to the first differential amplifier, whose input terminals ISVP and ISVN are respectively connected to a current sampling resistor ( Figure 2 The current of the bidirectional power supply flows through the current sampling resistor, and a current sampling voltage is generated at both ends of the circuit sampling resistor. It should be noted that in the charging state and the discharging state, because the direction of the current is opposite, the polarity of the current sampling voltage is also opposite.

[0068] The reference terminal (REF_CSA) of the CSA (U2) can be connected to the analog switch ( Figure 2 Specifically, the reference terminal (REF_CSA) is connected to the ground in the charging state, and the reference terminal of the first differential amplifier is connected to REF_OUT (i.e., the second reference level) in the discharging state. In other embodiments, the reference terminal (REF_CSA) may not be grounded, but may be connected to a preset level as required.

[0069] The integrator may include a first operational amplifier (U3A), a positive input terminal of the first operational amplifier being connected to a third reference level (ISET) as a reference terminal of the integrator, a negative input terminal of the first operational amplifier being connected to an output terminal of the CSA (U2) via a resistor (R11), and an output terminal of the first operational amplifier being connected to a negative input terminal of the operational amplifier via a capacitor (C18).

[0070] The inverter may include a transistor (Q1), the base of which is connected to the output of the first operational amplifier (U3A) via a resistor (R13), the collector of which is connected to a power supply voltage (e.g., +5V) via a resistor (R14), the emitter of which is connected to the ground, and the collector of which serves as the output of the inverter (ILoop_N). The inverter may also be implemented in other ways, such as using an operational amplifier as a core component to form an inverter. This inverter using an operational amplifier as a core is prior art and will not be described in detail here. Compared with the inverter using an operational amplifier as a core in the prior art, the implementation method using a transistor as a core in the present application is more cost-effective.

[0071] Figure 2 The position marked as ctrl in the lower right corner is the control signal output terminal, which outputs a control signal for controlling the size of the charging or discharging current. The control signal output terminal is coupled to ILoop_O. Optionally, the control signal output terminal (ctrl) can be forward connected to ILoop_O through a diode.

[0072] The second analog switch ( Figure 2 (not shown) the output terminal (ILoop_P) of the integrator is connected to ILoop_O in the charging state, and the output terminal (ILoop_N) of the inverter is connected to ILoop_O in the discharging state.

[0073] The second differential amplifier (U7) has its input terminals connected to the output voltages (BVP and BVN) of the power supply, wherein BVP is the positive electrode and BVN is the negative electrode. BVP and BVN can be connected to the positive and negative electrodes of the battery, respectively.

[0074] A second operational amplifier (U3B), wherein the negative input terminal of the second operational amplifier is connected to the output terminal of the second differential amplifier through a resistor (R15), and the positive input terminal of the second operational amplifier is connected to the fourth reference level (VSET) through a resistor (R16); a resistor (R22) is connected between the output terminal of the second operational amplifier and the control signal output terminal; a capacitor (C8) is connected between the negative input terminal of the second operational amplifier and the control signal output terminal; and the output terminal of the second operational amplifier is connected to the fourth node (VLoop_O) through a resistor (R24). Optionally, the fourth node (VLoop_O) can be reversely connected to the ground through a diode (D4).

[0075] The third analog switch ( Figure 2 (not shown in the figure), used to connect the second node (VLoop_P) to the fourth node (VLoop_O) in the charging state, and to connect the first node (VLoop_N) to the fourth node (VLoop_O) in the discharging state, wherein the first node (VLoop_N) is forward connected to the third node through a diode, and the second node (VLoop_P) is forward connected to the third node through a diode; the third node is connected to the positive input terminal of the first operational amplifier (U3A) through a resistor (R23); and the third node is connected to the third reference level (ISET) through a resistor (R12). Figure 2 The device D6 in FIG. 1 includes the two diodes mentioned here. The third node is the connection point between the two diodes. Optionally, the third node can be connected to ground via a capacitor (C6).

[0076] The control signal output can be connected to the supply voltage via a resistor (R1).

[0077] The output terminal of the second operational amplifier (U3B) can be reversely connected to the control signal output terminal through a diode (D1).

[0078] The negative input terminal of the first operational amplifier (U3A) can be connected to the control signal output terminal via a capacitor (C5).

[0079] The fourth reference level (VSET) may be set according to a target voltage of constant voltage charging.

[0080] The third reference level (ISET) can be set according to the size of the charging or discharging current.

[0081] Optionally, in one embodiment, the MCU may be used to output the third reference level (ISET) and / or the fourth reference level (VSET) through a DAC.

[0082] The analog switch in each embodiment of the present application can be implemented in a variety of ways.

[0083] Optionally, in one embodiment, the first analog switch can be used Figure 6 The method includes a MOS tube, the gate of which is a control signal of an analog switch (for example, the gate signal is high level in the charging state and low level in the discharging state), the source of which is grounded, and the drain of which is connected to Figure 2 The drain is also connected to REF_CSA (the reference terminal of the first differential amplifier) ​​through a resistor. Figure 2 In the charging state, the MOS tube is turned on, and the reference end of the first differential amplifier is grounded. In the discharging state, the MOS tube is turned off, and the reference end of the first differential amplifier is connected to the second reference level.

[0084] Optionally, in one embodiment, Figure 7 As shown, the first analog switch, the second analog switch and the third analog switch can be implemented in one device (U9).

[0085] The technical solution of the embodiment of the present application has a very low cost, a simple structure, and is easily applied to various power supplies, and can achieve bidirectional constant voltage and constant current control performance without loss due to cost reduction. Figure 2 In the embodiment, when charging, the voltage and current of the battery change as follows Figure 8 shown. Figure 8 The upper curve is the curve of battery current changing with time, and the lower curve is the curve of battery voltage changing with time. The horizontal axis of both curves is time. It can be seen that constant current charging is realized before time point 2500, and it automatically switches to constant voltage charging after time 2500, and the charging current continues to decrease to a trickle.

[0086] In each embodiment of the present application, A is forwardly connected to B through a diode, which means that the anode of the diode is connected to A, and the cathode of the diode is connected to B.

[0087] In each embodiment of the present application, A is reversely connected to B through a diode, which means that the cathode of the diode is connected to A, and the anode of the diode is connected to B.

[0088] The power supply voltage in each embodiment of the present application refers to the power supply voltage for powering the charge and discharge control circuit, for example +5V. The power supply in the power supply voltage refers to the power supply for powering the charge and discharge control circuit, not the power supply to be controlled by the charge and discharge control circuit.

[0089] An embodiment of the present application also relates to a bidirectional power supply, which refers to a power supply that can be charged and discharged. The bidirectional power supply includes the charge and discharge control circuit disclosed in the above embodiments.

[0090] An embodiment of the present application also relates to a mobile terminal, which includes the charge and discharge control circuit disclosed in the above embodiments. The mobile terminal can be a mobile phone, a laptop computer, a tablet computer, a dedicated handheld terminal, etc.

[0091] It should be noted that, in the disclosure, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "include", "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "include one" do not exclude the existence of other identical elements in the process, method, article or equipment including the elements. In this application, if it is mentioned that a certain action is performed according to a certain element, it means that at least the action is performed according to the element, which includes two situations: performing the action only according to the element and performing the action according to the element and other elements. Multiple, multiple, multiple, etc. expressions include 2, 2 times, 2 kinds and more than 2, more than 2 times, more than 2 kinds.

[0092] In this application, the term "connection", "coupling" or any variant thereof means any connection or coupling, direct or indirect, between elements, and may encompass the presence of an intermediate element between two elements, which are "connected" or "coupled" together via the intermediate element. The coupling and / or connection between elements may be physical, logical, or a combination thereof. As used herein, elements may be "connected" or "coupled" together using one or more wires, cables, and / or printed circuit connections, and by using electromagnetic energy. Electromagnetic energy may have a wavelength in the radio frequency region, microwave region, and / or light (both visible and invisible) region. The above examples are non-limiting and non-exhaustive.

[0093] This specification includes combinations of the various embodiments described herein. Individual references to an embodiment (e.g., "one embodiment" or "some embodiments" or "preferred embodiments") do not necessarily refer to the same embodiment; however, these embodiments are not mutually exclusive unless indicated as mutually exclusive or it is clear to a person skilled in the art that they are mutually exclusive. It should be noted that the word "or" is used in this specification in a non-exclusive sense unless the context clearly indicates or requires otherwise.

[0094] All documents mentioned in this application are considered to be included in the disclosure of this application as a whole, so that they can be used as the basis for modification when necessary. In addition, it should be understood that after reading the content of this application, those skilled in the art can make various changes or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. A charge and discharge control circuit, characterized in that: include: A first differential amplifier, whose input terminal is connected to a current sampling voltage, wherein the current sampling voltage is proportional to the magnitude of the charging or discharging current of the power supply; a first analog switch, configured to connect the reference terminal of the first differential amplifier to a first reference level in a charging state, and to connect the reference terminal of the first differential amplifier to a second reference level in a discharging state; an integrator, wherein an input terminal of the integrator is connected to the output terminal of the first differential amplifier, and a reference terminal of the integrator is connected to a third reference level; an inverter, an input end of which is connected to the output end of the integrator; A control signal output terminal, outputting a control signal for controlling the magnitude of the charging or discharging current; The second analog switch is used to connect the output end of the integrator to the control signal output end in a charging state, and to connect the output end of the inverter to the control signal output end in a discharging state.

2. The charge and discharge control circuit according to claim 1, characterized in that: The inverter includes a transistor, the base of which is connected to the output end of the integrator through a resistor, the collector of which is connected to the power supply voltage through a resistor, the emitter of which is connected to the ground, and the collector of which serves as the output end of the inverter.

3. The charge and discharge control circuit according to claim 1, characterized in that: The integrator includes a first operational amplifier, a positive input terminal of the first operational amplifier is connected to a third reference level as a reference terminal of the integrator, a negative input terminal of the first operational amplifier is connected to the output terminal of the first differential amplifier via a resistor, and the output terminal of the first operational amplifier is connected to the negative input terminal of the operational amplifier via a capacitor.

4. The charge and discharge control circuit according to claim 3, characterized in that: Also includes: a second differential amplifier having an input terminal connected to the output voltage of the power supply; a second operational amplifier, wherein the negative input terminal of the second operational amplifier is connected to the output terminal of the second differential amplifier through a resistor, and the positive input terminal of the second operational amplifier is connected to a fourth reference level through a resistor; a resistor is connected between the output terminal of the second operational amplifier and the control signal output terminal; a capacitor is connected between the negative input terminal of the second operational amplifier and the control signal output terminal; and the output terminal of the second operational amplifier is connected to a fourth node through a resistor; a third analog switch, used to connect the second node to the fourth node in a charging state, and to connect the first node to the fourth node in a discharging state, wherein the first node is forward connected to the third node through a diode, and the second node is forward connected to the third node through a diode; the third node is connected to the positive input terminal of the first operational amplifier through a resistor; and the third node is connected to the third reference level through a resistor; The control signal output terminal is connected to the power supply voltage through a resistor.

5. The charge and discharge control circuit according to claim 4, characterized in that: The output terminal of the second operational amplifier is reversely connected to the control signal output terminal through a diode; The negative input terminal of the first operational amplifier is connected to the control signal output terminal through a capacitor.

6. The charge and discharge control circuit according to claim 5, characterized in that: The third node is connected to ground via a capacitor.

7. The charge and discharge control circuit according to claim 6, characterized in that: The fourth reference level is set according to a target voltage of constant voltage charging.

8. The charge and discharge control circuit according to any one of claims 1 to 7, characterized in that: The third reference level is set according to the size of the charging or discharging current.

9. A bidirectional power supply, characterized in that: It comprises the charge and discharge control circuit as described in any one of claims 1 to 8.

10. A mobile terminal, characterized in that: It comprises the charge and discharge control circuit as described in any one of claims 1 to 8.

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