Circuit and method for detecting and controlling charging current in a charging circuit

Abstract

A method for detecting and controlling a charging current in a charging circuit is disclosed. The charging circuit includes a bus terminal for providing a bus voltage, a charging terminal for providing the charging current, and a switching circuit coupled between the bias terminal and a reference ground. The method includes comparing a voltage of the charging terminal to the bus voltage, and when the voltage of the charging terminal is less than the bus voltage and a difference between the voltage of the charging terminal and the bus voltage is greater than a reference threshold voltage, the charging current flows from the bus terminal through a current detection transistor and a current control transistor to the charging terminal. The method also includes when the voltage of the charging terminal is less than the bus voltage and the difference between the voltage of the charging terminal and the bus voltage is less than the reference threshold voltage, the charging current flows from the bus terminal through the switching circuit and the current control transistor to the charging terminal.

Description

Technical Field

[0001] This invention relates to electronic circuits, and more specifically, to a circuit for detecting and controlling charging current in a bidirectional power supply system. Background Technology

[0002] In existing power supply systems, bidirectional voltage conversion circuits are widely used in applications requiring uninterrupted power supply because they can provide backup power to other circuits in the system when the external input voltage fails, thanks to the storage capacitor. When the external input voltage is normal, it powers the bidirectional voltage conversion circuit and other circuits in the system. When the external input voltage fails, the bidirectional voltage conversion circuit outputs a power supply voltage to power other circuits in the system. Therefore, other circuits in the system can safely retain sufficient power to save data or perform other operations.

[0003] Normally, when the external input voltage is normal, the bidirectional voltage conversion circuit converts the input voltage into a higher voltage and stores it in the capacitor, which is to charge the storage capacitor. Due to the overall power supply and application requirements of the system, the magnitude of the charging current needs to be accurately detected and controlled when charging the storage capacitor.

[0004] Therefore, a charging circuit is needed that can accurately detect and control the charging current. Summary of the Invention

[0005] One embodiment of the present invention provides a power supply circuit, which includes a bus terminal for providing a bus voltage, a charging terminal for providing a charging current, a current detection circuit, and a current control circuit. The current detection circuit includes a current detection transistor coupled between the bus terminal and a bias terminal. The current control circuit includes a current control transistor coupled between the bias terminal and the charging terminal.

[0006] An embodiment of the present invention provides a method for detecting and controlling charging current in a charging circuit. The charging circuit includes a bus terminal for providing a bus voltage, a charging terminal for providing charging current, a current detection transistor coupled between the bus terminal and a bias terminal, a current control transistor coupled between the bias terminal and the charging terminal, and a switching circuit coupled between the bias terminal and a reference ground. The method includes: comparing the voltage of the charging terminal with the bus voltage; when the voltage of the charging terminal is less than the bus voltage and the difference between the voltage of the charging terminal and the bus voltage is greater than a reference threshold voltage, the charging current flows from the bus terminal through the current detection transistor and the current control transistor to the charging terminal; and when the voltage of the charging terminal is less than the bus voltage and the difference between the voltage of the charging terminal and the bus voltage is less than the reference threshold voltage, the charging current flows from the bus terminal through the switching circuit and the current control transistor to the charging terminal.

[0007] The charging circuit provided by the present invention enables precise sampling and control of the charging current during the pre-charging stage. Attached Figure Description

[0008] To better understand the present invention, embodiments thereof will be described with reference to the following accompanying drawings, which are for illustrative purposes only. The drawings typically show only some features of the embodiments and are not necessarily drawn to scale.

[0009] Figure 1 A schematic diagram of the circuit structure of a charging circuit 100 according to an embodiment of the present invention is provided.

[0010] Figure 2 A schematic diagram of the circuit structure of a charging circuit 200 according to an embodiment of the present invention is provided.

[0011] Figure 3 An embodiment of the present invention is given. Figure 2 The diagram shows the path of the charging current ICH when the charging circuit 200 is operating in the pre-charging stage.

[0012] Figure 4 An embodiment of the present invention is given. Figure 2 The diagram shows the path of the charging current ICH when the charging circuit 200 is operating in the switching charging stage.

[0013] Figure 5 An embodiment of the present invention is given. Figure 2 The waveforms of the charging current ICH and the voltage VSTRG at the charging terminal of the charging circuit 200 during the pre-charging stage and the switching charging stage are shown.

[0014] Figure 6 A flowchart illustrating a method 600 for detecting and controlling charging current in a charging circuit according to an embodiment of the present invention is provided.

[0015] The same reference numerals in different schematic diagrams indicate the same or similar parts or features. Detailed Implementation

[0016] Specific embodiments of the present invention will now be described in detail. It should be noted that the embodiments described herein are for illustrative purposes only and are not intended to limit the invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known circuits, materials, or methods have not been specifically described in order to avoid obscuring the invention.

[0017] In this specification and claims, the use of terms such as "left," "right," "inner," "outer," "upper," "lower," "above," and "below" is merely for descriptive convenience and does not indicate a necessary or permanent relative position of components / structures. Those skilled in the art should understand that such terms are interchangeable where appropriate, for example, so that embodiments of this disclosure can still operate in orientations different from those depicted in this specification. In the context of this disclosure, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or there may be an intermediate layer / element between them. Furthermore, the term "coupled" means a connection, directly or indirectly, electrically or non-electrically. "A / this / that" is not used specifically to refer to the singular but may encompass the plural form. The phrases "an embodiment," "embodiment," "an example," and "example" appearing throughout the specification do not necessarily refer to the same embodiment or example. Those skilled in the art should understand that the various useful terms "and / or" disclosed in one or more embodiments of this disclosure include any and all combinations of one or more of the associated listed items.

[0018] Figure 1 A schematic diagram of the circuit structure of a charging circuit 100 according to an embodiment of the present invention is provided. Figure 1 As shown, the charging circuit 100 includes a bus terminal for providing a bus voltage VBUS, a charging terminal for providing a charging current ICH to the storage capacitor C2, a current sensing circuit 11 coupled between the bus terminal and the bias terminal, and a current control circuit 12 coupled between the bias terminal and the charging terminal, wherein the voltage at the bias terminal is defined as the bias voltage VBO. The current sensing circuit 11 includes a current sensing transistor MS coupled between the bus terminal and the bias terminal, and the current control circuit 12 includes a current control transistor MC coupled between the bias terminal and the charging terminal. Figure 1In the charging circuit 100 shown, when the bus voltage VBUS provided at the bus terminal charges the storage capacitor C2, the charging circuit 100 operates in the charging phase, which includes a pre-charging phase and a switching charging phase. When the voltage VSTRG at the charging terminal is less than the bus voltage VBUS, and the difference between the voltage VSTRG at the charging terminal and the bus voltage VBUS is greater than the reference threshold voltage VTH, the charging circuit 100 operates in the pre-charging phase. At this time, the current sensing transistor MS operates in the linear region, the current control transistor MC operates in the saturation region, and the charging current ICH flows from the bus terminal through the current sensing transistor MS and the current control transistor MC to the charging terminal. When the voltage VSTRG at the charging terminal is less than the bus voltage VBUS, and the difference between the two is less than the reference threshold voltage VTH, or when the voltage VSTRG at the charging terminal is greater than the bus voltage VBUS, the charging circuit 100 operates in the switching charging phase. At this time, the current sensing transistor MS is turned off, and the current control transistor MC operates in the linear region. The switching charging stage includes a first stage and a second stage. When the voltage at the charging terminal, VSTRG, is less than the bus voltage, VBUS, and the difference between them is less than the reference threshold voltage, VTH, the charging circuit 100 operates in the first stage of the switching charging stage. When the voltage at the charging terminal, VSTRG, is greater than the bus voltage, VBUS, the charging circuit 100 operates in the second stage of the switching charging stage. In one embodiment, the reference threshold voltage, VTH, is between 200mV and 400mV.

[0019] continue Figure 1 The explanation, Figure 1 The charging circuit 100 shown also includes a switching circuit 13 coupled between the bias terminal and the reference ground. During the pre-charging phase, the current flowing through the switching circuit 13 is zero. At this time, the charging current ICH flows from the bus terminal through the current sensing transistor MS and the current control transistor MC to the charging terminal, generating a bias voltage VBO at the bias terminal. During the pre-charging phase, the bias voltage VBO is less than the bus voltage VBUS. In one embodiment, the switching circuit 13 includes at least one switch MH, which is turned off during the pre-charging phase. When the voltage VSTRG at the charging terminal is less than the bus voltage VBUS, and the difference between the two is less than the reference threshold voltage VTH, the pre-charging phase ends, and the charging circuit 100 enters the switching charging phase. During the switching charging phase, the charging current ICH flows from the bus terminal through the switching circuit 13 and the current control transistor MC to the charging terminal. In one embodiment, the switching circuit 13 includes at least one switch MH. During the switching charging phase, the switching circuit 13 provides the charging current ICH and converts the bus voltage VBUS into the bias voltage VBO at the bias terminal by controlling the on and off states of the at least one switch MH.

[0020] Figure 2A schematic diagram of the circuit structure of a charging circuit 200 according to an embodiment of the present invention is provided. Figure 2 The specific circuit structures of the current detection circuit 21 and the current control circuit 22 are given respectively. Besides the current detection transistor MS, the current detection circuit 21 also includes a first transistor M1, a second transistor M2, a first operational amplifier OP1, and a resistor R. The source terminal of the current detection transistor MS is coupled to the bus terminal, the drain terminal is coupled to the bias terminal, and the gate terminal receives the gate control signal VGS generated by the control circuit. The gate control signal VGS controls the conduction and turn-off of the current detection transistor MS according to the voltage VSTRG at the charging terminal. Figure 2 In the illustrated embodiment, the control circuit compares the charging terminal voltage VSTRG with the bus voltage VBUS. When the charging terminal voltage VSTRG is less than the bus voltage VBUS, and the difference between the two is greater than the reference threshold voltage VTH, the gate control signal VGS controls the current sensing transistor MS to turn on. When the charging terminal voltage VSTRG is less than the bus voltage VBUS, and the difference between the two is less than the reference threshold voltage VTH, or when the charging terminal voltage VSTRG is greater than the bus voltage VBUS, the gate control signal VGS controls the current sensing transistor MS to turn off. The source terminal of the first transistor M1 is coupled to the bus terminal, the gate terminal is coupled to the gate terminal of the current sensing transistor MS, and the drain terminal is coupled to the first input terminal of the first operational amplifier OP1. The source terminal of the second transistor M2 is coupled to the drain terminal of the first transistor M1, and the gate terminal is coupled to the output terminal of the first operational amplifier OP1. The second input terminal of the first operational amplifier OP1 is coupled to the bias terminal. A resistor R is coupled between the drain terminal of the second transistor M2 and the reference ground, and outputs a current sensing signal VSEN to characterize the charging current ICH.

[0021] The current control circuit 22 includes a current control transistor MC and a second operational amplifier OP2, wherein the current control transistor MC is coupled between the bias terminal and the charging terminal. Figure 2 In the illustrated embodiment, the source terminal of the current-controlled transistor MC is coupled to the charging terminal, and the drain terminal of the current-controlled transistor MC is coupled to the bias terminal. Figure 2 In this circuit, the first input of the second operational amplifier OP2 receives the current detection signal VSEN, and the second input receives the reference voltage VREF. The second operational amplifier OP2 generates a current control signal VGB based on the current detection signal VSEN and the reference voltage VREF, which is sent to the gate of the current control transistor MC to control the charging current ICH to a preset value. The working principle of the current control circuit 22 controlling the charging current ICH is that when the charging current ICH increases, the current detection signal VSEN, which characterizes the charging current ICH, increases, the current control signal VGB decreases, and the gate-source voltage of the current control transistor MC decreases, thereby reducing the charging current ICH. It should be understood that... Figure 2The current detection circuit 21 and current control circuit 22 shown are merely illustrative examples, and the specific circuit structures of the current detection circuit 21 and current control circuit 22 of the present invention are not limited to those described above. Figure 2 As shown, any circuit that can realize the detection or regulation of the charging current ICH is covered by this invention.

[0022] continue Figure 2 The explanation is in Figure 2 In the circuit, switching circuit 23 includes an upper switch MH and a lower switch ML. During the pre-charging phase, both the upper switch MH and the lower switch ML are turned off, and the current flowing through inductor L is zero. During the switching charging phase, the current detection transistor MS is turned off, and the charging current ICH flows sequentially through switching circuit 23 and the current control transistor MC to the charging terminal. During the switching charging phase, switching circuit 23 provides the charging current ICH to the charging terminal by controlling the on and off states of the upper switch MH and the lower switch ML. During the switching charging phase, switching circuit 23 converts the bus voltage VBUS received by switching circuit 23 into a bias voltage VBO by controlling the on and off states of the upper switch MH and the lower switch ML. During the switching charging phase, the current flowing through inductor L is the charging current ICH, or in other words, the average current flowing through inductor L is the charging current ICH. In one embodiment, the charging current ICH during the pre-charging phase is less than the charging current ICH during the switching charging phase. In one embodiment, during the switching charging phase, the charging current ICH is controlled by detecting the current flowing through the lower switch ML of switching circuit 23.

[0023] exist Figure 2 In this embodiment, the charging circuit 200 further includes an input protection circuit 24, which receives the input voltage VIN and generates a bus voltage VBUS based on VIN. In one embodiment, when the input voltage VIN is greater than a reference threshold voltage VREG, the bus voltage VBUS is equal to the reference threshold voltage VREG; when the input voltage VIN is less than or equal to the reference threshold voltage VREG, the bus voltage VBUS is equal to the input voltage VIN. In another embodiment, the input protection circuit 24 also detects the current flowing through it; if the current exceeds a certain threshold, the input protection circuit 24 shuts down, disconnecting the input voltage VIN from the bus terminal.

[0024] Figure 3 An embodiment of the present invention is given. Figure 2 The diagram shows the path of the charging current ICH when the charging circuit 200 is operating in the pre-charging phase. From... Figure 3It can be seen that when the charging circuit 200 is operating in the pre-charging stage, the charging current ICH flows sequentially from the bus terminal through the current sensing transistor MS and the current control transistor MC to the charging terminal to charge the storage capacitor C2. At this time, the current flowing through the inductor L, i.e., the inductor current IL, or the current flowing through the switching circuit 23, is zero. During the pre-charging stage, the voltage VSTRG at the charging terminal increases linearly, and the slope of the increase is determined by the charging current ICH.

[0025] Figure 4 An embodiment of the present invention is given. Figure 2 The diagram shows the path of the charging current ICH when the charging circuit 200 is operating in the switching charging phase. From... Figure 4 As can be seen, when the charging circuit 200 operates in the switching charging stage, the charging current ICH flows from the bus terminal through the inductor L, the switching circuit 23 to the bias terminal, and then through the current control transistor MC to the charging terminal to charge the storage capacitor C2. At this time, the current detection transistor MS is turned off. During the switching charging stage, the voltage VSTRG at the charging terminal increases to the preset value as charging progresses.

[0026] Figure 5 An embodiment of the present invention is given. Figure 2 The waveforms of the charging current ICH and the voltage VSTRG at the charging terminal of the charging circuit 200 during the pre-charging and switching charging phases are shown. Figure 5 In the charging circuit 200, when the voltage VSTRG at the charging terminal is less than the bus voltage VBUS, and the difference between the two is greater than the reference threshold voltage VTH, the charging circuit 200 operates in the pre-charging phase, and the charging current ICH is equal to the current flowing through the current detection transistor MS (in...). Figure 5 In this circuit, the current sensing transistor MS is denoted by IMS. At this time, the current flowing through inductor L is zero, i.e., the inductor current IL is zero, and the charging terminal voltage VSTRG increases linearly. When the charging terminal voltage VSTRG is less than the bus voltage VBUS, and the difference between the two is less than the reference threshold voltage VTH, the charging circuit 200 operates in the first stage of the switching charging phase. When the charging terminal voltage VSTRG is greater than the bus voltage VBUS, the charging circuit 200 operates in the second stage of the switching charging phase. During the switching charging phase, the charging current ICH is equal to the inductor current IL flowing through inductor L. At this time, the current sensing transistor MS is turned off (IMS = 0), and the charging terminal voltage VSTRG increases to a preset value as charging progresses. The preset value of the charging terminal voltage VSTRG is greater than the bus voltage VBUS.

[0027] Figure 6 A schematic flowchart of a method 600 for detecting and controlling charging current in a charging circuit according to an embodiment of the present invention is provided. For clarity, reference will be made to... Figure 2The charging circuit 200 shown describes method 600. The charging circuit 200 includes a bus terminal for providing a bus voltage VBUS, a charging terminal for providing a charging current ICH, a current sensing transistor MS coupled between the bus terminal and a bias terminal, a current control transistor MC coupled between the bias terminal and the charging terminal, and a switching circuit 23 coupled between the bias terminal and a reference ground. The method includes steps S1-S2. In step S1, the voltage VSTRG at the charging terminal is compared with the bus voltage VBUS. Step S2 includes steps S2a and S2b. In step S2a, when the voltage VSTRG at the charging terminal is less than the bus voltage VBUS, and the difference between the voltage VSTRG at the charging terminal and the bus voltage VBUS is greater than a reference threshold voltage VTH, the charging current ICH flows from the bus terminal sequentially through the current sensing transistor MS and the current control transistor MC to the charging terminal. In step S2b, when the voltage VSTRG at the charging terminal is less than the bus voltage VBUS, and the difference between the voltage VSTRG at the charging terminal and the bus voltage VBUS is less than the reference threshold voltage VTH, or when the voltage VSTRG at the charging terminal is greater than the bus voltage VBUS, the charging current ICH flows from the bus terminal through the switching circuit 23 and the current control transistor MC to the charging terminal. In one embodiment, when the voltage VSTRG at the charging terminal is less than the bus voltage VBUS, and the difference between the voltage VSTRG at the charging terminal and the bus voltage VBUS is greater than the reference threshold voltage VTH, the current sensing transistor MS operates in the linear region, and the current control transistor MC operates in the saturation region. When the voltage VSTRG at the charging terminal is less than the bus voltage VBUS, and the difference between the voltage VSTRG at the charging terminal and the bus voltage VBUS is less than the reference threshold voltage VTH, or when the voltage VSTRG at the charging terminal is greater than the bus voltage VBUS, the current sensing transistor MS is turned off, and the current control transistor MC operates in the linear region.

[0028] exist Figure 2 In the illustrated embodiment, the switching circuit 23 includes at least one switch MH, wherein the at least one switch MH is turned off when the charging terminal voltage VSTRG is less than the bus voltage VBUS, and the difference between the charging terminal voltage VSTRG and the bus voltage VBUS is greater than the reference threshold voltage VTH. When the charging terminal voltage VSTRG is less than the bus voltage VBUS, and the difference between the charging terminal voltage VSTRG and the bus voltage VBUS is less than the reference threshold voltage VTH, or when the charging terminal voltage VSTRG is greater than the bus voltage VBUS, the switching circuit 23 converts the bus voltage VBUS into the bias terminal voltage, i.e., the bias voltage VBO, by controlling the on and off states of the at least one switch MH. Figure 2In the charging circuit 200 shown, when the voltage VSTRG at the charging terminal is less than the bus voltage VBUS, and the difference between the voltage VSTRG at the charging terminal and the bus voltage VBUS is greater than the reference threshold voltage VTH, the voltage VBO at the bias terminal is less than the bus voltage VBUS. Figure 2 In the charging circuit 200 shown, the charging circuit 200 further includes an inductor L. When the voltage VSTRG at the charging terminal is less than the bus voltage VBUS, and the difference between the voltage VSTRG at the charging terminal and the bus voltage VBUS is greater than the reference threshold voltage VTH, the current flowing through the inductor L, i.e., the inductor current IL, is zero. When the voltage VSTRG at the charging terminal is less than the bus voltage VBUS, and the difference between the voltage VSTRG at the charging terminal and the bus voltage VBUS is less than the reference threshold voltage VTH, or when the voltage VSTRG at the charging terminal is greater than the bus voltage VBUS, the current flowing through the inductor L, i.e., the inductor current IL, is equal to the charging current ICH. In one embodiment, the reference threshold voltage VTH is between 200mV and 400mV.

[0029] The charging circuit of this invention operates in the linear region during the pre-charging stage to detect the charging current ICH and generate a current detection signal VSEN characterizing the charging current ICH. The current control transistor MC operates in the saturation region and controls the magnitude of the charging current ICH according to the current detection signal VSEN, thereby realizing accurate sampling and control of the charging current during the pre-charging stage.

[0030] The specific embodiments described above are merely illustrative of the high-voltage period and its manufacturing method according to embodiments of the present invention. These embodiments are not exhaustive and are not intended to limit the scope of the invention. Variations and modifications to the disclosed embodiments are possible, and other feasible alternative embodiments and equivalent variations of elements in the embodiments can be understood by those skilled in the art. Other variations and modifications to the embodiments disclosed in this invention do not depart from the spirit of the invention and the scope of protection defined by the claims.

Claims

1. A power supply circuit, comprising: A bus terminal provides a bus voltage, and the bus terminal is adapted to be coupled to an inductor; The charging terminal serves as the output terminal of the power supply circuit, providing charging current to the outside. The bias terminal provides the bias voltage. A switching circuit, coupled to the bias terminal and a reference ground, wherein the switching circuit includes at least one switch; The switching circuit is adapted to be configured to be coupled to the inductor; A current sensing circuit, including a current sensing transistor coupled between a bus terminal and a bias terminal; as well as A current control circuit includes a current control transistor coupled between a bias terminal and a charging terminal.

2. The power supply circuit as described in claim 1, wherein when the voltage at the charging terminal is less than the bus voltage, and the difference between the voltage at the charging terminal and the bus voltage is greater than the reference threshold voltage, the current sensing transistor operates in the linear region, the current control transistor operates in the saturation region, and the charging current flows from the bus terminal through the current sensing transistor and the current control transistor to the charging terminal.

3. The power supply circuit as described in claim 1, wherein when the voltage at the charging terminal is less than the bus voltage, and the difference between the voltage at the charging terminal and the bus voltage is less than the reference threshold voltage, the current sensing transistor is turned off, and the current control transistor operates in the linear region.

4. In the power supply circuit as described in claim 1, when the voltage at the charging terminal is less than the bus voltage and the difference between the voltage at the charging terminal and the bus voltage is greater than the reference threshold voltage, the current flowing through the switching circuit is zero, and the charging current flows from the bus terminal through the current detection transistor and the current control transistor to the charging terminal; when the voltage at the charging terminal is less than the bus voltage and the difference between the voltage at the charging terminal and the bus voltage is less than the reference threshold voltage, the current flowing through the current detection transistor is zero, and the charging current flows from the bus terminal through the switching circuit and the current control transistor to the charging terminal.

5. In the power supply circuit as described in claim 1, when the voltage at the charging terminal is less than the bus voltage and the difference between the voltage at the charging terminal and the bus voltage is greater than the reference threshold voltage, the at least one switch is turned off; when the voltage at the charging terminal is less than the bus voltage and the difference between the voltage at the charging terminal and the bus voltage is less than the reference threshold voltage, the switching circuit provides charging current to the charging terminal by controlling the on and off of the at least one switch.

6. The power supply circuit as claimed in claim 1, wherein when the voltage at the charging terminal is less than the bus voltage, and the difference between the voltage at the charging terminal and the bus voltage is greater than the reference threshold voltage, the bias voltage is less than the bus voltage.

7. The power supply circuit as claimed in claim 6, wherein the reference threshold voltage is between 200-400mV.

8. The power supply circuit as claimed in claim 1, wherein the current detection circuit detects the current flowing through the current detection transistor and generates a current detection signal, and the current control circuit receives the current detection signal and controls the charging current according to the current detection signal.

9. The power supply circuit as described in claim 1 further includes a switching terminal, wherein an inductor is coupled between the switching terminal and the bus terminal, and when the voltage at the charging terminal is less than the bus voltage, and the difference between the voltage at the charging terminal and the bus voltage is greater than a reference threshold voltage, the current flowing through the inductor is zero.

10. The power supply circuit as claimed in claim 1 further includes an input protection circuit, wherein the input protection circuit receives an input voltage and generates a bus voltage based on the input voltage.

11. The power supply circuit of claim 10, wherein when the input voltage is greater than the reference threshold voltage, the bus voltage is equal to the reference threshold voltage, and when the input voltage is less than or equal to the reference threshold voltage, the bus voltage is equal to the input voltage.

12. A method for detecting and controlling charging current in a charging circuit, the charging circuit including a bus terminal for providing a bus voltage, a charging terminal for providing charging current, a current sensing transistor coupled between the bus terminal and a bias terminal, a current control transistor coupled between the bias terminal and the charging terminal, and a switching circuit coupled between the bias terminal and a reference ground, wherein the bus terminal is adapted to be configured to be coupled to an inductor, and the switching circuit is adapted to be coupled to the inductor. The method includes: Compare the voltage at the charging end with the bus voltage; When the voltage at the charging terminal is less than the bus voltage, and the difference between the voltage at the charging terminal and the bus voltage is greater than the reference threshold voltage, the charging current flows from the bus terminal through the current sensing transistor and the current control transistor to the charging terminal. as well as When the voltage at the charging terminal is less than the bus voltage, and the difference between the voltage at the charging terminal and the bus voltage is less than the reference threshold voltage, the charging current flows from the bus terminal through the switching circuit and the current control transistor to the charging terminal.

13. The method for detecting and controlling charging current in a charging circuit as described in claim 12, wherein the reference threshold voltage is between 200 and 400 mV.

14. The method for detecting and controlling charging current in a charging circuit as described in claim 12, wherein... When the voltage at the charging terminal is less than the bus voltage, and the difference between the charging terminal voltage and the bus voltage is greater than the reference threshold voltage, the current sensing transistor operates in the linear region, and the current control transistor operates in the saturation region; and When the voltage at the charging terminal is less than the bus voltage, and the difference between the voltage at the charging terminal and the bus voltage is less than the reference threshold voltage, the current sensing transistor is turned off, and the current control transistor operates in the linear region.

15. The method for detecting and controlling charging current in a charging circuit as described in claim 12, wherein the switching circuit comprises at least one switch. Wherein, when the voltage at the charging terminal is less than the bus voltage, and the difference between the voltage at the charging terminal and the bus voltage is greater than a reference threshold voltage, the at least one switch is turned off; and When the voltage at the charging terminal is less than the bus voltage, and the difference between the voltage at the charging terminal and the bus voltage is less than the reference threshold voltage, the switching circuit controls at least one switch to turn on and off to provide charging current.

16. The method for detecting and controlling charging current in a charging circuit as described in claim 12, wherein the voltage at the bias terminal is less than the bus voltage when the voltage at the charging terminal is less than the bus voltage and the difference between the voltage at the charging terminal and the bus voltage is greater than a reference threshold voltage.

17. The method for detecting and controlling charging current in a charging circuit as described in claim 12, wherein when the voltage at the charging terminal is less than the bus voltage and the difference between the voltage at the charging terminal and the bus voltage is greater than a reference threshold voltage, the current flowing through the inductor is zero.

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