Linear charging circuit and linear charger

Abstract

The invention discloses a linear charging circuit and a linear charger. The linear charging circuit comprises a charging module, a constant-voltage control module, a constant-current control module and a reverse current limiting module, when a load end is short-circuited, the reverse current limiting module can quickly respond, current limiting is realized by limiting the conduction degree of a constant-current control power tube in the charging module, so that reverse current output by a battery is accurately limited, and the service life of the battery is prolonged. The chip is prevented from being overheated and burnt due to large current, and the service life of the chip is greatly prolonged.

Description

Technical Field

[0001] The present invention relates to the field of electronic power technology, and in particular to a linear charging circuit and a linear charger. Background Art

[0002] With the development of electronic devices, the performance of charging circuits, as the core of battery life, has attracted much attention. Linear chargers are widely used in battery charging management systems due to their simple structure, low cost, and ease of control. They precisely control the conduction level of transistors to provide stable constant voltage and constant current charging for the battery, ensuring safe and efficient charging.

[0003] Figure 1 FIG. 1 shows a circuit diagram of a linear charging circuit in the prior art. Figure 1 As shown, the linear charging circuit 100 includes a charging module 110, a constant voltage control module 120, and a constant current control module 130. The charging module 110 includes a transistor Ms1, a power transistor Mn1, and a power transistor Mp1 connected in series between the input voltage VIN and the battery BAT. The intermediate node between the power transistors Mn1 and Mp1 is connected to the load RL to provide an output voltage VOUT thereto. The constant voltage control module 120 is configured to provide a gate control signal GATE1 to the power transistor Mn1 based on a feedback signal Vfb1 representing the output voltage VOUT and a reference voltage Vref1, thereby controlling the charging module 110 to provide a constant output voltage VOUT to the load. The constant current control module 130 is configured to provide a gate control signal GATE2 to the power transistor Mp1 based on a feedback signal Vfb2 representing the charging current and a reference voltage Vref2, thereby controlling the charging module 110 to provide a constant charging current to the battery BAT.

[0004] In actual use scenarios, the charging module 110 needs to provide an output voltage VOUT to the load RL while also providing a charging current to the battery BAT. At the same time, when the load is overloaded, the battery BAT is also required to reversely supply power to the load to maintain normal operation of the device. However, under existing technical conditions, once a short circuit occurs at the load, the linear charging circuit 100 lacks an effective reverse current limiting mechanism, and the battery BAT will output a very large reverse current in a short period of time. This current value may instantly climb to tens of amperes. Such a high-intensity current surge will cause the chip in the circuit to quickly accumulate a large amount of heat, causing the chip temperature to rise sharply. Overheating of the chip not only seriously affects its performance stability, but may also directly cause the chip to burn out, thereby paralyzing the entire device, causing great inconvenience to the user, and may even cause serious consequences such as device damage. Summary of the Invention

[0005] To address the aforementioned technical issues, the present invention provides a linear charging circuit and a linear charger. When a short circuit occurs at the load end, a reverse current limiting module rapidly responds by limiting the conduction level of the constant current control power tube in the charging module. This effectively limits the reverse current output by the battery, preventing the chip from overheating and burning due to high current, and significantly extending the chip's service life.

[0006] According to one aspect of the present invention, a linear charging circuit is provided, comprising: a charging module configured to provide an output voltage to a load based on an input voltage and a charging current to a battery, the charging module comprising a first transistor, a first power transistor, and a second power transistor connected in series between the input voltage and the battery, wherein an intermediate node between the first power transistor and the second power transistor is configured to provide the output voltage; the charging module further configured to provide a reverse supply current to the load based on the battery when the load is under heavy load; a constant voltage control module configured to provide a first gate control signal to the first power transistor based on a first feedback signal representing the output voltage and a first reference voltage, thereby controlling the charging module to provide a constant output voltage to the load; a constant current control module configured to provide a second gate control signal to the second power transistor based on a second feedback signal representing the charging current and a second reference voltage, thereby controlling the charging module to provide a constant charging current to the battery; and a reverse current limiting module configured to reduce the conduction level of the second power transistor when the reverse supply current is greater than a set threshold value, thereby achieving current limiting.

[0007] Optionally, the reverse current limiting module includes: a sampling transistor having the same conduction type as the second power tube, the control end of the sampling transistor being connected to the control end of the second power tube and the second gate control signal, the second end being connected to the second end of the second power tube and the battery, and the first end being used to provide a sampling current; and a current limiting unit being used to convert the sampling current into a voltage signal, and to increase the voltage of the control end of the second power tube when the voltage signal is greater than a reference voltage, so as to reduce a voltage difference between the control end and the second end of the second power tube.

[0008] Optionally, the current limiting unit includes: a second transistor and a third transistor forming a current mirror, the control ends of the second transistor and the third transistor and the first end of the second transistor are connected to the sampling current, and the second ends of the second transistor and the third transistor are connected to the output voltage; a first resistor, the first end of which is connected to the first power supply voltage, and the second end is connected to the first end of the third transistor; and a fourth transistor, the first end of which is connected to the first power supply voltage, the control end is connected to the second end of the first resistor, and the second end is connected to the control end of the second power tube.

[0009] Optionally, the first power supply voltage is selected from the higher one of the output voltage and the battery voltage.

[0010] Optionally, the constant voltage control module includes: a first driving unit, connected to the control end of the first transistor and the second power supply voltage, for providing the first gate control signal to the control end of the first power tube according to the second power supply voltage; and a first modulation unit, for providing a first regulating current to the first driving unit according to the first feedback signal and the first reference voltage to regulate the first gate control signal.

[0011] Optionally, the first driving unit includes: a fifth transistor, a first end of which is connected to the second power supply voltage and the control end of the first transistor, and the control end is used to be connected to the first bias signal; and a first current source, a first end of which is connected to the second end of the fifth transistor, and a second end of which is connected to the first regulating current, wherein the intermediate node between the fifth transistor and the first current source is used to provide the first gate control signal, and the first modulation unit includes: a first error amplifier, a positive input end of which is used to receive the first feedback signal, and a negative input end of which is used to receive the first reference voltage; and a sixth transistor, a first end of which is used to output the first regulating current, a control end of which is connected to the output end of the first error amplifier, and a second end of which is connected to ground.

[0012] Optionally, the constant current control module includes: a first driving unit, used to provide the second gate control signal to the control end of the second power tube according to the first power supply voltage; and a second modulation unit, used to provide a second regulating current to the second driving unit according to the second feedback signal and the second reference voltage to adjust the second gate control signal.

[0013] Optionally, the first driving unit includes: a seventh transistor, a first end of which is connected to the first power supply voltage, and a control end of which is connected to the second bias voltage; a second current source, a first end of which is connected to the second end of the seventh transistor, and a second end of which is connected to the second regulating current; a third current source, a first end of which is connected to the first power supply voltage; and an eighth transistor, a first end of which is connected to the second end of the third current source, a control end of which is connected to the intermediate node between the seventh transistor and the second current source, and a second end of which is connected to ground, wherein the intermediate node between the third current source and the eighth transistor is used to provide the second gate control signal, and the second modulation unit includes: a second error amplifier, a positive input end of which is used to receive the second feedback signal, and a negative input end of which is used to receive the second reference voltage; and a ninth transistor, a first end of which is used to output the second regulating current, a control end of which is connected to the output end of the second error amplifier, and a second end of which is connected to ground.

[0014] Optionally, the constant current control module further includes: a voltage selection unit, used to obtain the first power supply voltage according to the higher one of the output voltage and the battery voltage, wherein the voltage selection unit includes: a tenth transistor, a first end of which is connected to the output voltage, and a control end of which is connected to the battery voltage; and an eleventh transistor, a first end of which is connected to the battery voltage, and a control end of which is connected to the output voltage, wherein the second ends of the tenth transistor and the eleventh transistor are connected to each other and are used to output the first power supply voltage.

[0015] According to another aspect of the present invention, a linear charger is provided, comprising the above-mentioned linear charging circuit.

[0016] In summary, the linear charging circuit provided in the embodiment of the present invention is provided with a reverse current limiting module. When a short circuit occurs at the load end, the reverse current limiting module can react quickly and achieve current limiting by limiting the conduction degree of the constant current control power tube in the charging module, thereby accurately limiting the reverse current output by the battery, preventing the chip from overheating and burning due to large current, and significantly extending the service life of the chip.

[0017] In addition, the power supply voltage of the reverse current limiting module of the present invention is provided by the output voltage or the battery voltage. Therefore, the linear charging circuit of the present invention can still provide normal reverse current limiting protection when only the battery is connected, preventing the lithium battery from being damaged by abnormal reverse current, extending the battery life, and ensuring the safe and stable operation of the device in single power mode.

[0018] In addition, the operation of the reverse current limiting module of the present invention does not increase the additional power consumption of the battery end. While ensuring the circuit function, it avoids unnecessary consumption of battery power, improves battery utilization efficiency, optimizes device energy management, and extends device life. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings.

[0020] Figure 1 FIG. 4 is a circuit diagram showing a linear charging circuit in the prior art.

[0021] Figure 2 A circuit diagram of a linear charging circuit of the present invention is shown.

[0022] Figure 3 The figure shows a circuit diagram of the constant voltage control module of the present invention.

[0023] Figure 4 The figure shows a circuit diagram of the constant current control module of the present invention.

[0024] Figure 5The figure shows a circuit diagram of the reverse current limiting module of the present invention. DETAILED DESCRIPTION

[0025] Reference will now be made in detail to the exemplary embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings.Where possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.

[0026] In the specification, it should be noted that similar reference numerals that have been used to represent similar components in other drawings are used for these elements as much as possible. In the following description, when functions and configurations known to those skilled in the art are not related to the basic configuration of the present disclosure, their detailed description will be omitted. The terms described in the specification should be understood as follows.

[0027] The advantages and features of the present disclosure and their implementation methods will be described through the following embodiments described with reference to the accompanying drawings. However, the present disclosure can be implemented in different forms and should not be construed as limited to the embodiments described herein. Rather, these embodiments are provided to make the present disclosure comprehensive and complete, so as to fully convey the scope of the present disclosure to those skilled in the art. Furthermore, the present disclosure is limited only by the scope of the claims.

[0028] The shapes, sizes, ratios, angles, and quantities disclosed in the drawings used to describe the embodiments of the present disclosure are merely examples, and the present disclosure is therefore not limited to the details illustrated. Like reference numerals denote like elements throughout. In the following description, when it is determined that a detailed description of related known functions or structures would inevitably obscure the key points of the present disclosure, the detailed description will be omitted.

[0029] As will be fully understood by those skilled in the art, the features of the various embodiments of the present disclosure may be combined or combined in part or in whole, and may interoperate and technically drive each other in various ways. The embodiments of the present disclosure may be performed independently of each other, or may be performed together in a mutually dependent relationship.

[0030] In this application, a MOS transistor (Metal-Oxide-Semiconductor Field-Effect Transistor) includes a first terminal, a second terminal, and a control terminal. When the MOS transistor is in the on state, current flows from the first terminal to the second terminal. The first terminal, second terminal, and control terminal of a PMOS transistor are the source, drain, and gate, respectively. The first terminal, second terminal, and control terminal of an NMOS transistor are the drain, source, and gate, respectively.

[0031] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0032] Figure 2 FIG. 1 shows a circuit diagram of a linear charging circuit of the present invention. Figure 2 As shown, the linear charging circuit 200 of this embodiment includes a charging module 210, a constant voltage control module 220, a constant current control module 230, and a reverse current limiting module 240. The charging module 210 includes an input port for connecting to an input voltage VIN, a load port for connecting to an external load RL, and a charging port for connecting to a battery BAT. The charging module 210 is configured to provide an output voltage VOUT to the load RL based on the input voltage VIN and to provide a charging current to the battery BAT based on the input voltage VIN. Furthermore, when the load RL is overloaded, the charging module 210 is configured to provide a reverse supply current to the load RL based on the battery BAT to maintain normal operation of the device.

[0033] Furthermore, the charging module 210 of this embodiment includes a reverse polarity protection transistor Ms1, a power transistor Mn1, and a power transistor Mp1 connected in series between the input voltage VIN and the battery BAT. The reverse polarity protection transistor Ms1 and the power transistor Mn1 are, for example, NMOS transistors, and the power transistor Mp1 is, for example, a PMOS transistor. The source of the reverse polarity protection transistor Ms1 is connected to the input voltage VIN, the gate of the reverse polarity protection transistor Ms1 is connected to the power supply voltage Vpump, the drain of the reverse polarity protection transistor Ms1 is connected to the drain of the power transistor Mn1, the gate of the power transistor Mn1 is connected to the constant voltage control module 220, the source of the power transistor Mn1 is connected to the source of the power transistor Mp1, the gate of the power transistor Mp1 is connected to the constant current control module 230, the drain of the power transistor Mp1 is connected to the battery BAT, and the node between the power transistors Mn1 and Mp1 is used to provide the output voltage VOUT. Furthermore, the power transistor Mp1 of this embodiment is a 5V low-voltage PMOS transistor, whose drain and source are interchangeable, thereby allowing the battery BAT to provide reverse power supply current to the load end when a heavy load condition occurs at the load end of the linear charging circuit 200.

[0034] During normal operation, the charging module 210 of this embodiment supplies power to both the load RL and the battery BAT based on the input voltage VIN. The output voltage VOUT is greater than the battery voltage VBAT, and the input current Iin equals the sum of the load current Iload and the battery charging current Ibat. When the load is heavily loaded, the charging module 210 of this embodiment provides a reverse supply current Ic based on the battery BAT to maintain device stability.

[0035] The constant voltage control module 220 is configured to provide a gate control signal GATE1 to the gate of the power transistor Mn1 according to the feedback signal Vfb1 representing the output voltage VOUT and the reference voltage Vref1 , so as to control the charging module 210 to provide a constant output voltage VOUT to the load RL.

[0036] The constant current control module 230 is configured to provide a gate control signal GATE2 to the gate of the power transistor Mp1 according to the feedback signal Vfb2 representing the charging current and the reference voltage Vref2, so as to control the charging module 210 to provide a constant charging current to the battery BAT.

[0037] Reverse current limiting module 240 is connected to the gate of power transistor Mp1 and is used to detect the reverse supply current when the load is overloaded. When the reverse supply current exceeds a set threshold, it reduces the conduction level of power transistor Mp1 to achieve current limiting. Reverse current limiting module 240 of this embodiment can quickly respond to extreme load short circuit situations, limiting the magnitude of the reverse current output by the battery. This prevents excessive heat accumulation in the chip due to excessive current in a short period of time, effectively preventing the chip from burning out due to overheating, thereby significantly extending the chip's service life and reducing the risk of device damage.

[0038] Figure 3 FIG. 1 shows a circuit diagram of a constant voltage control module of the present invention. Figure 3 As shown, the constant voltage control module 220 of this embodiment includes a driving unit 221 and a modulation unit 222. The driving unit 221 is connected to the power supply voltage Vpump and the gate of the power transistor Mn1, and is configured to provide the gate control signal GATE1 to the gate of the power transistor Mn1 based on the power supply voltage Vpump. The modulation unit 222 is configured to provide a regulation current Ictr1 to the driving unit 221 based on the feedback signal Vfb1 and the reference voltage Vref1 to regulate the gate control signal GATE1.

[0039] Furthermore, the driving unit 221 includes a transistor M1 and a current source Isnk1. The transistor M1 is, for example, an NMOS transistor, whose drain is connected to the power supply voltage Vpump, the gate is connected to the bias voltage Vn1, the source is connected to the first end of the current source Isnk1, the second end of the current source Isnk1 is connected to the regulated current Ictr1, and the intermediate node between the transistor M1 and the current source Isnk1 is used to output the gate control signal GATE1.

[0040] Furthermore, the modulation unit 222 includes an operational amplifier OP1 and a transistor M2. The transistor M2 is, for example, an NMOS transistor, wherein the positive input terminal of the error amplifier OP1 is used to receive the feedback signal Vfb1, the negative input terminal is used to receive the reference voltage Vref1, the output terminal is connected to the gate of the transistor M2, the source of the transistor M2 is connected to the ground, and the drain of the transistor M2 is used to output the regulated current Ictr1.

[0041] Figure 4 FIG. 1 shows a circuit diagram of a constant current control module of the present invention. Figure 4 As shown, the constant current control module 230 includes a voltage selection unit 231, a driving unit 232, and a modulation unit 233. The voltage selection unit 231 is configured to obtain a power supply voltage VB based on the higher of the output voltage VOUT and the battery voltage VBAT. The power supply terminal of the driving unit 232 is connected to the power supply voltage VB. The driving unit 232 is configured to provide the gate control signal GATE2 to the gate of the power transistor Mp1 based on the power supply voltage VB. The modulation unit 233 is configured to provide a regulated current Ictr2 to the driving unit 232 based on the feedback signal Vfb2 and the reference voltage Vref2 to adjust the gate control signal GATE2.

[0042] Furthermore, the voltage selection unit 231 includes diode-connected transistors M3 and M4. The transistors M3 and M4 are, for example, PMOS transistors, with the drain of the transistor M3 and the gate of the transistor M4 connected to the output voltage VOUT, the drain of the transistor M4 and the gate of the transistor M3 connected to the battery voltage VBAT, and the sources of the transistors M3 and M4 configured to output the power supply voltage VB.

[0043] The driving unit 232 includes a transistor M5, a transistor M6, and current sources Isnk2 and Isnk3. Transistor M5 is, for example, an NMOS transistor, and transistor M6 is, for example, a PMOS transistor. The drain of transistor M5 is connected to the power supply voltage VB, the gate of transistor M5 is connected to the bias voltage Vn2, the source of transistor M5 is connected to the first end of current source Isnk2, and the second end of current source Isnk2 is connected to the regulated current Ictr2. The first end of current source Isnk3 is connected to the power supply voltage VB, the second end of current source Isnk3 is connected to the source of transistor M6, the gate of transistor M6 is connected to the intermediate node between transistor M5 and current source Isnk2, the drain of transistor M6 is connected to ground, and the intermediate node between current source Isnk3 and transistor M6 is used to output the gate control signal GATE2.

[0044] The modulation unit 233 includes an operational amplifier OP2 and a transistor M7. The transistor M7 is, for example, an NMOS transistor. The error amplifier OP2 has a positive input terminal for receiving the feedback signal Vfb2, a negative input terminal for receiving the reference voltage Vref2, an output terminal connected to the gate of the transistor M7, a source of the transistor M7 connected to ground, and a drain of the transistor M7 for outputting the regulated current Ictr2.

[0045] Figure 5 FIG. 1 shows a circuit diagram of the reverse current limiting module of the present invention. Figure 5 As shown, the reverse current limiting module 240 of this embodiment includes a sampling transistor Ms2 and a current limiting unit 241. The sampling transistor Ms2 has the same conduction type as the power transistor Mp1. For example, the sampling transistor Ms2 is also a PMOS transistor. The gate of the sampling transistor Ms2 is short-circuited with the gate of the power transistor Mp1, and the drain of the sampling transistor Ms2 is short-circuited with the drain of the power transistor Mp1. The source of the sampling transistor Ms2 is used to provide a sampling current Isen. The substrates of the sampling transistor Ms2 and the power transistor Mp1 are both connected to the power supply voltage VB. The current limiting unit 241 is used to convert the sampling current Isen into a voltage signal and, when the voltage signal is greater than a reference voltage, to increase the gate voltage of the power transistor Mp1 to reduce the voltage difference between the gate and drain of the power transistor Mp1.

[0046] Specifically, the current limiting unit 241 includes transistors M8 and M9, a transistor M10, and a resistor R1 that form a current mirror. Transistors M8 and M9 are NMOS transistors, and transistor M10 is a PMOS transistor. The gates of transistors M8 and M9 and the drain of transistor M8 are connected to the sampling current Isen, and the sources of transistors M8 and M9 are connected to the output voltage VOUT. The first end of resistor R1 is connected to the power supply voltage VB, the second end of resistor R1 is connected to the drain of transistor M9, the source of transistor M10 is connected to the power supply voltage VB, the gate of transistor M10 is connected to the second end of resistor R1, and the drain of transistor M10 is connected to the gate of power transistor Mp1.

[0047] In this embodiment, when a short circuit occurs at the load end, the output voltage VOUT rapidly drops to near 0V, and the load end is reversely powered by the battery. The current flows from the drain to the source of the power transistor Mp1. Since the area of the power transistor Mp1 is large and its capacitance Cgs can reach several hundred pF, the gate voltage GATE2 of the power transistor Mp1 is coupled to the output voltage VOUT and becomes low, causing the voltage difference between the battery voltage VBAT and the gate voltage GATE2 to increase instantaneously, thereby causing a large reverse charge current. In this embodiment, the size of the sampling transistor Ms2 is much smaller than that of the power transistor Mp1. For example, the size ratio of the sampling transistor Ms2 to the power transistor Mp1 is 1:M (M is an integer greater than 1, such as 1000). Therefore, the sampling current in the sampling transistor Ms2 is , this sampling current Isen passes through the mirror of transistors M8 and M9, and is then converted into a voltage signal on resistor R1 When the voltage signal VR1 is greater than the conduction threshold Vth_M10 of the transistor M10, the transistor M10 is turned on, and then quickly pulls up the gate voltage of the power tube Mp1 to reduce the voltage difference between the battery voltage VBAT and the gate voltage GATE2, achieving a rapid current limit of the μs level.

[0048] Furthermore, the power supply terminal of the current-limiting unit 241 of this embodiment is connected to the power supply voltage VB, and the reference ground is connected to the output voltage VOUT. It is not directly powered by the input voltage VIN. Therefore, when a problem occurs at the input voltage VIN terminal, the current-limiting unit 241 can still operate normally. When the output voltage VOUT is short-circuited, the power supply voltage VB is equal to the battery voltage VBAT. Therefore, a voltage difference exists between the power supply terminal and the reference ground in the current-limiting unit 241. Therefore, the current-limiting unit 241 of this embodiment can quickly start up when a short circuit occurs at the load terminal. When the linear charging circuit is operating normally, the output voltage VOUT is greater than the battery voltage VBAT. Therefore, the power supply voltage VB is equal to the output voltage VOUT, which in turn causes the voltage difference between the power supply terminal and the reference ground in the current-limiting unit 241 to be zero, causing the current-limiting unit 241 to naturally shut down, thereby achieving the purpose of zero power consumption, and without affecting the forward control loop of the power transistor Mp1.

[0049] In summary, the linear charging circuit provided in the embodiment of the present invention is provided with a reverse current limiting module. When a short circuit occurs at the load end, the reverse current limiting module can react quickly and achieve current limiting by limiting the conduction degree of the constant current control power tube in the charging module, thereby accurately limiting the reverse current output by the battery, preventing the chip from overheating and burning due to large current, and significantly extending the service life of the chip.

[0050] In addition, the power supply voltage of the reverse current limiting module of the present invention is provided by the output voltage or the battery voltage. Therefore, the linear charging circuit of the present invention can still provide normal reverse current limiting protection when only the battery is connected, preventing the lithium battery from being damaged by abnormal reverse current, extending the battery life, and ensuring the safe and stable operation of the device in single power mode.

[0051] In addition, the operation of the reverse current limiting module of the present invention does not increase the additional power consumption of the battery end. While ensuring the circuit function, it avoids unnecessary consumption of battery power, improves battery utilization efficiency, optimizes device energy management, and extends device life.

[0052] Furthermore, an embodiment of the present invention also provides a linear charger, which includes the linear charging circuit 200 described above.

[0053] Furthermore, an embodiment of the present invention also provides an electronic device, including the linear charging circuit or linear charger as described above.

[0054] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

[0055] Finally, it should be noted that the above embodiments are merely examples for the purpose of illustrating the present invention and are not intended to limit the embodiments. Those skilled in the art will readily appreciate that other variations or modifications based on the above description are possible. It is not necessary and impossible to provide an exhaustive list of all embodiments. However, obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A linear charging circuit comprising: a charging module, the charging module being configured to provide an output voltage to a load based on the input voltage, and to provide a charging current to a battery, the charging module comprising a first transistor, a first power transistor, and a second power transistor connected in series between the input voltage and the battery, wherein an intermediate node between the first power transistor and the second power transistor is configured to provide the output voltage, and the charging module being further configured to provide a reverse supply current to the load based on the battery when the load is under heavy load; a constant voltage control module, configured to provide a first gate control signal to the first power transistor according to a first feedback signal representing the output voltage and a first reference voltage, so as to control the charging module to provide a constant output voltage to the load; a constant current control module, configured to provide a second gate control signal to the second power transistor according to a second feedback signal representing the charging current and a second reference voltage, so as to control the charging module to provide a constant charging current to the battery; as well as The reverse current limiting module is used to reduce the conduction degree of the second power tube when the reverse supply current is greater than a set threshold value to achieve current limiting.

2. The linear charging circuit according to claim 1, wherein: The reverse current limiting module includes: a sampling transistor having the same conduction type as the second power tube, wherein the control terminal of the sampling transistor is connected to the control terminal of the second power tube and the second gate control signal, the second terminal of the sampling transistor is connected to the second terminal of the second power tube and the battery, and the first terminal is used to provide a sampling current; and The current limiting unit is used to convert the sampled current into a voltage signal, and when the voltage signal is greater than a reference voltage, increase the voltage of the control terminal of the second power tube to reduce the voltage difference between the control terminal and the second terminal of the second power tube.

3. The linear charging circuit according to claim 2, wherein: The current limiting unit includes: a second transistor and a third transistor forming a current mirror, wherein control terminals of the second transistor and the third transistor and a first terminal of the second transistor are connected to the sampling current, and second terminals of the second transistor and the third transistor are connected to the output voltage; a first resistor, having a first end connected to the first power supply voltage and a second end connected to the first end of the third transistor; and A fourth transistor has a first end connected to the first power supply voltage, a control end connected to the second end of the first resistor, and a second end connected to the control end of the second power transistor.

4. The linear charging circuit according to claim 3, wherein: The first power supply voltage is selected from the output voltage and the battery voltage, whichever is higher.

5. The linear charging circuit according to claim 1, wherein: The constant pressure control module includes: a first driving unit connected to the control terminal of the first transistor and a second power supply voltage, and configured to provide the first gate control signal to the control terminal of the first power transistor according to the second power supply voltage; and The first modulation unit is configured to provide a first regulating current to the first driving unit according to the first feedback signal and the first reference voltage, so as to regulate the first gate control signal.

6. The linear charging circuit according to claim 5, wherein: The first driving unit includes: a fifth transistor, a first terminal of which is connected to the second power supply voltage and the control terminal of the first transistor, and the control terminal is used to be connected to a first bias signal; and a first current source, a first end connected to the second end of the fifth transistor, and a second end connected to the first regulating current; The intermediate node between the fifth transistor and the first current source is used to provide the first gate control signal. The first modulation unit includes: a first error amplifier, having a positive input terminal for receiving the first feedback signal and a negative input terminal for receiving the first reference voltage; and A sixth transistor has a first end for outputting the first regulating current, a control end connected to the output end of the first error amplifier, and a second end connected to the ground.

7. The linear charging circuit according to claim 4, wherein: The constant current control module includes: a first driving unit, configured to provide the second gate control signal to the control terminal of the second power transistor according to the first power supply voltage; and The second modulation unit is configured to provide a second regulating current to the second driving unit according to the second feedback signal and the second reference voltage, so as to regulate the second gate control signal.

8. The linear charging circuit according to claim 7, wherein: The first driving unit includes: a seventh transistor, a first terminal connected to the first power supply voltage, and a control terminal connected to a second bias voltage; a second current source, a first end of which is connected to the second end of the seventh transistor, and a second end of which is connected to the second regulating current; a third current source, a first terminal of which is connected to the first power supply voltage; and an eighth transistor, having a first terminal connected to the second terminal of the third current source, a control terminal connected to an intermediate node between the seventh transistor and the second current source, and a second terminal connected to ground; The intermediate node between the third current source and the eighth transistor is used to provide the second gate control signal. The second modulation unit includes: a second error amplifier, having a positive input terminal for receiving the second feedback signal and a negative input terminal for receiving the second reference voltage; and A ninth transistor has a first end for outputting the second regulating current, a control end connected to the output end of the second error amplifier, and a second end connected to the ground.

9. The linear charging circuit according to claim 7, wherein: The constant current control module also includes: a voltage selection unit, configured to obtain the first power supply voltage according to the higher one of the output voltage and the battery voltage, Wherein, the voltage selection unit includes: a tenth transistor, having a first terminal connected to the output voltage and a control terminal connected to the battery voltage; and an eleventh transistor, a first terminal connected to the battery voltage, and a control terminal connected to the output voltage, The second ends of the tenth transistor and the eleventh transistor are connected to each other and are used to output the first power supply voltage.

10. A linear charger, wherein: The linear charging circuit comprises the linear charging circuit according to any one of claims 1 to 9.

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