Constant current charging system and linear charging chip

Abstract

The embodiment of the invention provides a constant-current charging system and a linear charging chip. The constant-current charging system comprises a charging circuit, a clamping module, a constant-current control module, a temperature control module and a reference voltage adjusting module, and the charging circuit provides charging current for a battery through a first transistor by using input voltage; the clamping module converts the first current and / or the second current into a control voltage, clamps the control voltage to a first reference voltage during charging, and outputs a control electrode voltage of the first transistor; the constant current control module is used for outputting a first current according to a feedback signal representing the charging current and a second reference voltage; the temperature control module is used for outputting a second current according to the junction temperature indication signal and a third reference voltage; and the reference voltage adjusting module is configured to adjust the voltage value of the second reference voltage according to the second current. The problems that in the prior art, when the junction temperature rises, the charging current cannot be decreased in time, the chip further heats, and safe work of the chip is affected are solved.

Description

Technical Field

[0001] The embodiments of the present disclosure relate to the field of integrated circuit technology, and in particular, to a constant current charging system and a linear charging chip. Background Art

[0002] The circuit system architecture of a linear charging chip usually includes multiple control loops, such as a constant current charging loop, a constant voltage charging loop, a temperature control loop, etc. Different loops are used for control under different working conditions. When the working conditions change, the corresponding loop is switched to achieve the control target. For example, when the linear charger is working in a constant current charging state, the constant current charging loop controls the charging current. When the junction temperature of the power tube rises, the temperature control loop begins to intervene. The temperature control loop linearly reduces the charging current, controls the chip to further heat up, and ensures the chip's safe operation.

[0003] like Figure 1 As shown, it is an exemplary circuit diagram of a constant current charging system 100 in an existing linear charging chip, which includes a constant current charging loop and a temperature control loop. The inventors found in actual applications that: when the constant current charging loop is working, I2=I B , I1=0, when the junction temperature gradually approaches the target temperature, V tj As the junction temperature increases, I1 also increases, and the temperature control loop begins to intervene. However, when the junction temperature reaches the target temperature, due to the high gain of the constant current charging loop, I2 will not decrease to 0, and the constant current charging loop is still involved in the control. The charging current Iout cannot be reduced quickly, which leads to further heating of the chip and affects the safe operation of the chip. Summary of the invention

[0004] The embodiments described in this article provide a constant current charging system and a linear charging chip, in order to solve the problem that in the constant current charging system of the existing linear charging chip, after the junction temperature reaches the target temperature, the charging current cannot be reduced in time, causing the chip to further heat up and affecting the safe operation of the chip.

[0005] According to a first aspect of the present disclosure, a constant current charging system is provided, the system comprising: a charging circuit, a clamping module, a constant current control module, a temperature control module, and a reference voltage adjustment module, wherein the charging circuit is configured to provide a charging current to a battery via a first transistor using an input voltage; the clamping module is configured to convert a first current and / or a second current into a control voltage, and to clamp the control voltage to a first reference voltage during charging via a first operational amplifier, and output a control electrode voltage, wherein the control electrode voltage is a voltage for controlling a control electrode of the first transistor; the constant current control module is configured to output a first current via a first error amplifier according to a feedback signal and a second reference voltage. , so as to control the charging circuit to provide a constant charging current for the battery according to the first current, and the feedback signal is a voltage feedback signal for characterizing the charging current; the temperature control module is configured to output a second current through a second error amplifier according to a junction temperature indication signal and a third reference voltage, so as to reduce the charging current and control the junction temperature according to the second current, and the junction temperature indication signal is a voltage signal for characterizing the junction temperature of the first transistor; the reference voltage adjustment module is coupled to the temperature control module and the constant current control module respectively, and is configured to adjust the voltage value of the second reference voltage according to the second current, so that after the junction temperature reaches the target temperature, the voltage value of the second reference voltage is reduced.

[0006] Optionally, the reference voltage regulation module includes: a current mirror unit and a voltage regulation unit, wherein the current mirror unit is configured to copy the second current according to a preset ratio to obtain a third current; the voltage regulation unit is configured to adjust the voltage value of the second reference voltage according to the change of the third current, and when the third current is greater than a preset current threshold, control the voltage value of the second reference voltage to start decreasing.

[0007] Optionally, the charging circuit includes: the first transistor, wherein a control electrode of the first transistor is coupled to the control electrode voltage, a first electrode of the first transistor outputs the charging current, and a second electrode of the first transistor is coupled to the input voltage.

[0008] Optionally, the clamping module includes: the first operational amplifier, a first current source, a first resistor, and a second resistor, wherein the positive input terminal of the first operational amplifier is respectively coupled to one end of the first resistor, the first current output by the constant current control module, and the second current output by the temperature control module, the negative input terminal of the first operational amplifier is respectively coupled to one end of the second resistor and one end of the first current source, and the output terminal of the first operational amplifier is coupled to the control electrode of the first transistor; the other end of the first current source is coupled to the ground terminal, and the other end of the first resistor and the other end of the second resistor are both coupled to the power supply voltage.

[0009] Optionally, the constant current control module includes: the first error amplifier and a second transistor, wherein the first error amplifier is configured to generate the first current according to the feedback signal and the second reference voltage; and the second transistor is configured to output the first current through a current mirror.

[0010] Optionally, the temperature control module includes: the second error amplifier and a third transistor, wherein the second error amplifier is configured to generate the second current based on the junction temperature indication signal and the third reference voltage; and the third transistor is configured to output the second current through a current mirror.

[0011] Optionally, the current mirror unit includes: a fourth transistor, wherein the control electrode of the fourth transistor is coupled to the control electrode of the third transistor in the temperature control module, the first electrode of the fourth transistor is coupled to the ground terminal, the second electrode of the fourth transistor is coupled to the voltage regulating unit, and the third current is obtained at the second electrode of the fourth transistor; the voltage regulating module includes a second current source, a fifth transistor, a third resistor, and a second operational amplifier, wherein one end of the second current source is coupled to the power supply voltage, the other end of the second current source is respectively coupled to the second electrode of the fourth transistor and the second electrode of the fifth transistor, the control electrode of the fifth transistor is coupled to the output end of the second operational amplifier, the first electrode of the fifth transistor is respectively coupled to one end of the third resistor, the negative input end of the second operational amplifier, and the second reference voltage, the other end of the third resistor is coupled to the ground terminal, and the positive input end of the second operational amplifier is coupled to the fourth reference voltage, and the fourth reference voltage is equal to the voltage value of the second reference voltage during constant current charging.

[0012] Optionally, the first error amplifier includes a third current source and sixth to ninth transistors, wherein one end of the third current source is coupled to the power supply voltage, and the other end of the third current source is respectively coupled to the first electrode of the sixth transistor and the first electrode of the seventh transistor; the control electrode of the sixth transistor is coupled to the feedback signal, and the second electrode of the sixth transistor is respectively coupled to the control electrode of the eighth transistor and the second electrode of the eighth transistor; the control electrode of the seventh transistor is coupled to the second reference voltage, and the second electrode of the seventh transistor is respectively coupled to the control electrode of the ninth transistor, the second electrode of the ninth transistor, and the control electrode of the second transistor; the first electrode of the eighth transistor and the first electrode of the ninth transistor are both coupled to the ground terminal.

[0013] Optionally, the second error amplifier includes a fourth current source and tenth to thirteenth transistors, wherein one end of the fourth current source is coupled to the power supply voltage, and the other end of the fourth current source is respectively coupled to the first electrode of the tenth transistor and the first electrode of the eleventh transistor; the control electrode of the tenth transistor is coupled to the junction temperature indication signal, and the second electrode of the tenth transistor is respectively coupled to the control electrode of the twelfth transistor and the second electrode of the twelfth transistor; the control electrode of the eleventh transistor is coupled to the third reference voltage, and the second electrode of the eleventh transistor is respectively coupled to the control electrode of the thirteenth transistor, the second electrode of the thirteenth transistor, and the control electrode of the third transistor; the first electrode of the twelfth transistor and the first electrode of the thirteenth transistor are both coupled to the ground terminal.

[0014] Optionally, the preset current threshold is determined according to the following formula: preset current threshold=second current source-(fourth reference voltage / third resistor).

[0015] Optionally, the system further includes a sampling module configured to sample the charging current to obtain a sampling current, and obtain the feedback signal according to the sampling current and a fourth resistor.

[0016] According to a second aspect of the present disclosure, a linear charging chip is provided, wherein the chip comprises the constant current charging system described in any one of the first aspects above.

[0017] In the constant current charging system of the embodiment of the present disclosure, a reference voltage regulation module is added, which is coupled to the temperature control module and the constant current control module respectively. The reference voltage regulation module can adjust the voltage value of the second reference voltage according to the second current, so that after the junction temperature reaches the target temperature, the voltage value of the second reference voltage is reduced, thereby rapidly reducing the output current. Applying it to the linear charging chip can effectively prevent the chip from further heating and ensure the safe operation of the chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly described below. It should be noted that the drawings described below only relate to some embodiments of the present disclosure, but are not intended to limit the present disclosure, wherein:

[0019] Figure 1 A schematic circuit diagram of a constant current charging system in an existing linear charging chip is shown;

[0020] Figure 2 A schematic block diagram of a constant current charging system according to an embodiment of the present disclosure is shown;

[0021] Figure 3 A schematic circuit diagram of a constant current charging system according to an embodiment of the present disclosure is shown;

[0022] Figure 4 An exemplary circuit diagram of a constant current control module according to an embodiment of the present disclosure is shown;

[0023] Figure 5 An exemplary circuit diagram of a temperature control module according to an embodiment of the present disclosure is shown;

[0024] Figure 6 A schematic diagram showing waveforms of charging currents corresponding to the embodiment of the present disclosure and the prior art respectively;

[0025] The elements in the drawings are schematic and not drawn to scale. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative work also fall within the scope of protection of the present disclosure.

[0027] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by a person skilled in the art to which the subject matter of the present disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the specification and the relevant art, and will not be interpreted in an idealized or overly formal form unless otherwise explicitly defined herein. As used herein, a statement that two or more parts are "connected" or "coupled" together shall mean that the parts are joined together directly or through one or more intermediate components.

[0028] In all embodiments of the present disclosure, since the source and drain of a metal oxide semiconductor (MOS) transistor are symmetrical, and the conduction current directions between the source and drain of an N-type transistor and a P-type transistor are opposite, in the embodiments of the present disclosure, the controlled middle terminal (gate or gate terminal) of the MOS transistor is referred to as a control terminal, and the remaining two terminals of the MOS transistor are referred to as a first terminal and a second terminal, respectively. In addition, terms such as "first" and "second" are only used to distinguish one component (or a portion of a component) from another component (or another portion of a component).

[0029] In order to solve the problem that in the constant current charging system of the existing linear charging chip, after the junction temperature reaches the target temperature, the charging current cannot be reduced in time, causing the chip to further heat up and affecting the safe operation of the chip, a new constant current charging system is proposed. The constant current charging system of the embodiment of the present disclosure adds a reference voltage adjustment module. After the junction temperature reaches the target temperature, the second reference voltage in the constant current control module is adjusted to reduce the second reference voltage, thereby quickly reducing the charging current, thereby preventing the chip from further heating and ensuring the safe operation of the chip. The constant current charging system of the present disclosure is described in detail below.

[0030] Figure 2 FIG. 2 shows a schematic block diagram of a constant current charging system 200 according to an embodiment of the present disclosure. Figure 2 As shown, the constant current charging system 200 includes: a charging circuit 210, a clamping module 220, a constant current control module 230, a temperature control module 240, and a reference voltage adjustment module 250.

[0031] The charging circuit 210 is a main circuit, and the charging circuit 210 is respectively coupled to the clamping module 220 and the external battery Bat. The charging circuit 210 is configured to provide a charging current Iout to the battery Bat via the first transistor through the input voltage Vin. Figure 3 As shown, the charging circuit 210 includes: a first transistor M1, wherein the control electrode of the first transistor M1 is coupled to the control electrode voltage V output by the clamping module 220 G A first electrode of the first transistor M1 outputs a charging current Iout, and a second electrode of the first transistor M1 is coupled to an input voltage Vin.

[0032] The clamping module 220 is configured to convert the first current I1 and / or the second current I2 into a control voltage, and clamp the control voltage to a first reference voltage during charging through a first operational amplifier, and output a control electrode voltage V G , control electrode voltage V G is used to control the voltage of the control electrode of the first transistor M1. Figure 3As shown, the clamp module 220 includes: a first operational amplifier OPA1, a first current source IB1, a first resistor R1, and a second resistor R2, wherein the positive input terminal of the first operational amplifier OPA1 is respectively coupled to one end of the first resistor R1, the first current I1 output by the constant current control module 230, and the second current I2 output by the temperature control module 240. Figure 3 The corresponding control voltage in the above is the voltage at point C or point B; the negative input terminal of the first operational amplifier OPA1 is respectively coupled to one end of the second resistor R2 and one end of the first current source IB1, Figure 3 In the above, the corresponding first reference voltage is the voltage of the negative input terminal of OPA1, that is, the voltage at point A; the output terminal of the first operational amplifier OPA1 is coupled to the control electrode of the first transistor M1; the other end of the first current source IB1 is coupled to the ground terminal, and the other end of the first resistor R1 and the other end of the second resistor R2 are both coupled to the power supply voltage VDD. It should be noted that the resistance values ​​of the first resistor R1 and the second resistor R2 are equal. The value of the first current source IB1 is equal to the current value of the first current I1 output by the constant current control module 230 during constant current charging.

[0033] The constant current control module 230 is configured to FB and the second reference voltage V ref2 The first error amplifier outputs the first current I1, and controls the charging circuit 210 to provide a constant charging current Iout for the battery Bat according to the first current I1. The feedback signal V FB is a voltage feedback signal used to characterize the charging current Iout. The constant current control module 230, the clamping module 220, and the charging circuit 210 form a constant current control loop. FB The voltage value is equal to the second reference voltage V ref2 When , the charging current Iout is a constant value. Figure 3 As shown, the feedback signal V FB The sampling module 260 can be used to obtain the sampling current Is by sampling the charging current Iout, and obtain the feedback signal V according to the sampling current Is and the fourth resistor R4. FB Specifically, the feedback signal V can be obtained by multiplying the sampling current Is and the fourth resistor R4. FB , where the sampling current Is is a small current proportional to the charging current Iout.

[0034] Further, such as Figure 4 As shown, the constant current control module 230 includes: a first error amplifier 231, a second transistor M2, and the first error amplifier 231 is configured to FB and the second reference voltage V ref2The first error amplifier 231 includes a third current source IB3 and sixth to ninth transistors (M6-M9), wherein one end of the third current source IB3 is coupled to the power supply voltage VDD, and the other end of the third current source IB3 is respectively coupled to the first electrode of the sixth transistor M6 and the first electrode of the seventh transistor M7; the control electrode of the sixth transistor M6 is coupled to the feedback signal V FB The second electrode of the sixth transistor M6 is coupled to the control electrode of the eighth transistor M8 and the second electrode of the eighth transistor M8 respectively; the control electrode of the seventh transistor M7 is coupled to the second reference voltage V ref2 The second electrode of the seventh transistor M7 is respectively coupled to the control electrode of the ninth transistor M9, the second electrode of the ninth transistor M9, and the control electrode of the second transistor M2; the first electrode of the eighth transistor M8 and the first electrode of the ninth transistor M9 are both coupled to the ground terminal. The mirror ratio of the eighth transistor M8, the ninth transistor M9, and the second transistor M2 is 1:1:1.

[0035] The temperature control module 240 is configured to tj and the third reference voltage V ref3 The second error amplifier outputs the second current I2 to reduce the charging current Iout and control the junction temperature according to the second current I2. The junction temperature indication signal V tj The temperature control module 240, the clamping module 220 and the charging circuit 210 form a temperature control loop. When the junction temperature rises close to the target temperature, the second current I2 starts to rise, and the temperature control loop intervenes in the control. When the junction temperature indication signal V tj The voltage value is equal to the third reference voltage V ref3 When the temperature control loop is fully controlled, the constant current control loop exits. The target temperature is set according to the actual situation.

[0036] Further, such as Figure 5 As shown, the temperature control module 240 includes: a second error amplifier 241, a third transistor M3, and the second error amplifier 241 is configured to tj and the third reference voltage V ref3 The second error amplifier 241 includes a fourth current source IB4 and tenth to thirteenth transistors (M10-M13), wherein one end of the fourth current source IB4 is coupled to the power supply voltage VDD, and the other end of the fourth current source IB4 is respectively coupled to the first electrode of the tenth transistor M10 and the first electrode of the eleventh transistor M11; the control electrode of the tenth transistor M10 is coupled to the junction temperature indication signal Vtj The second electrode of the tenth transistor M10 is coupled to the control electrode of the twelfth transistor M12 and the second electrode of the twelfth transistor M12 respectively; the control electrode of the eleventh transistor M11 is coupled to the third reference voltage V ref3 , the second electrode of the eleventh transistor M11 is respectively coupled to the control electrode of the thirteenth transistor M13, the second electrode of the thirteenth transistor M13, and the control electrode of the third transistor M3; the first electrode of the twelfth transistor M12 and the first electrode of the thirteenth transistor M13 are both coupled to the ground terminal. The mirror ratio of the twelfth transistor M12, the thirteenth transistor M13, and the third transistor M3 is 1:1:1. The current value of the fourth current source IB4 is equal to that of the third current source IB3.

[0037] The reference voltage regulating module 250 is coupled to the temperature control module 240 and the constant current control module 230 respectively. The reference voltage regulating module 250 is configured to regulate the second reference voltage V according to the second current I2. ref2 After the junction temperature reaches the target temperature, the voltage value of the second reference voltage V is reduced. ref2 The second reference voltage V is adjusted according to the second current I2. ref2 The voltage value means that after the temperature control loop intervenes, the corresponding second current I2 rises. When the second current I2 rises to a certain value, the second reference voltage V ref2 voltage value, which can speed up the decrease of the charging current Iout, so that the charging current Iout can be reduced in time after the junction temperature rises to the target temperature, reducing further heating of the chip and ensuring safe operation of the chip.

[0038] Further, such as Figure 3 As shown, the reference voltage regulating module 250 includes: a current mirror unit 251 and a voltage regulating unit 252, wherein the current mirror unit 251 is configured to copy the second current I2 according to a preset ratio to obtain a third current I3; the voltage regulating unit 252 is configured to adjust the second reference voltage V according to the change of the third current I3. ref2 When the third current I3 is greater than the preset current threshold, the second reference voltage V ref2 The voltage value of the second current source IB2 begins to decrease. The preset current threshold is determined according to the following formula: Preset current threshold = second current source IB2 - (fourth reference voltage V ref4 / third resistor R3), wherein the fourth reference voltage V ref4 The voltage value is equal to the second reference voltage V ref2 The voltage value during constant current charging. In addition, the setting of the preset ratio needs to satisfy the condition that the third current I3 can be greater than the preset current threshold. Further, as Figure 3As shown, the current mirror unit 251 includes: a fourth transistor M4, wherein the control electrode of the fourth transistor M4 is coupled to the control electrode of the third transistor M3 in the temperature control module 240, the first electrode of the fourth transistor M4 is coupled to the ground terminal, the second electrode of the fourth transistor M4 is coupled to the voltage regulation unit 252, and the third current I3 is obtained at the second electrode of the fourth transistor M4; the voltage regulation module includes a second current source IB2, a fifth transistor M5, a third resistor R3, and a second operational amplifier OPA2, wherein one end of the second current source IB2 is coupled to the power supply voltage VDD, the other end of the second current source IB2 is respectively coupled to the second electrode of the fourth transistor M4 and the second electrode of the fifth transistor M5, the control electrode of the fifth transistor M5 is coupled to the output terminal of the second operational amplifier OPA2, and the first electrode of the fifth transistor M5 is respectively coupled to one end of the third resistor R3, the negative input terminal of the second operational amplifier OPA2, and the second reference voltage V ref2 The other end of the third resistor R3 is coupled to the ground, and the positive input end of the second operational amplifier OPA2 is coupled to the fourth reference voltage V ref4 .

[0039] The following is a specific example and combined Figure 3-5 The working principle of the constant current charging system 200 in the embodiment of the present disclosure is explained more clearly: Assuming that IB2=2IB3=2IB4=4IB1=4Ib, the mirror ratio of M3 and M4 is 1:3, the target temperature of the junction temperature is 125°C, in the constant current charging mode, the constant current control loop composed of the constant current control module 230, the clamping module 220 and the charging circuit 210 controls the output of a constant charging current Iout, at this time V FB =V ref2 , I1=Ib,Iout=k×(V ref2 / R4), where k is the ratio between the charging current Iout (also the output current) and the sampling current Is, and when the junction temperature is not high, V tj With V ref3 The difference is large, I2 is 0, when the junction temperature is close to the target temperature, V tj Close to V ref3 , I2 starts to rise, I1 starts to fall, the temperature control loop starts to intervene, and Iout also starts to decrease; I2 rises, I3 also rises, and at the beginning V ref2 With V ref4 When the junction temperature reaches the target temperature, I3 rises to greater than 4*I b -(V ref4 / R3), that is, when the sum of the current in the branch where R3 is located and the current of I3 is greater than the current value of IB2, V ref2 The junction temperature starts to decrease, which further reduces Iout. Compared with the existing technology, the speed of Iout reduction is accelerated. When the junction temperature reaches a certain level, Vtj =V ref3 , I2=Ib, I1=0, I3=3*Ib, V ref2 It no longer decreases, the constant current control loop loses its control ability, and is completely switched to the temperature control loop for control.

[0040] In order to further illustrate the effect of the embodiment of the present disclosure, a waveform diagram of the charging current Iout corresponding to the prior art and the embodiment of the present disclosure under the same parameters is given, as shown in FIG. Figure 6 As shown, line a represents the prior art, and line b represents the embodiment of the present disclosure. By comparison, it can be seen that compared with the prior art, the linearity of the charging current Iout of the embodiment of the present disclosure is greatly improved. When the junction temperature rises to the target temperature ( Figure 6 The heat generation of the chip is related to the power. The greater the power, the faster the heat generation. The power is related to Iout. Reducing the output current Iout in time can reduce the heat generation of the chip and thus ensure the safety of the chip.

[0041] An embodiment of the present disclosure also provides a linear charging chip, which includes the constant current charging system described in the aforementioned embodiment. Applying the constant current charging system described in the aforementioned embodiment to the linear charging chip can alleviate chip heating and ensure the safety of the chip.

[0042] In summary, the constant current charging system and the linear charging chip in the embodiments of the present disclosure can reduce the charging current in time when the junction temperature reaches the target temperature, alleviate chip heating, and ensure the safety of the chip.

[0043] Unless the context clearly indicates otherwise, the singular form of the words used herein and in the appended claims includes the plural and vice versa. Thus, when referring to the singular, the plural form of the corresponding term is generally included. Similarly, the words "comprise" and "include" are to be interpreted as inclusive rather than exclusive. Likewise, the terms "include" and "or" should be interpreted as inclusive, unless such interpretation is expressly prohibited herein. Where the term "example" is used herein, particularly when it is placed after a group of terms, "example" is merely exemplary and illustrative and should not be considered exclusive or comprehensive.

[0044] Further aspects and scopes of adaptability become apparent from the description provided herein. It should be understood that various aspects of the present disclosure can be implemented individually or in combination with one or more other aspects. It should also be understood that the description and specific embodiments herein are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

[0045] Several embodiments of the present disclosure are described in detail above, but it is obvious that those skilled in the art can make various modifications and variations to the embodiments of the present disclosure without departing from the spirit and scope of the present disclosure. The protection scope of the present disclosure is defined by the attached claims.

Claims

1. A constant current charging system, the system comprising: Charging circuit, clamping module, constant current control module, temperature control module, reference voltage adjustment module, Wherein, the charging circuit is configured to provide a charging current to the battery through the first transistor using the input voltage; The clamping module is configured to convert the first current and / or the second current into a control voltage, and clamp the control voltage to a first reference voltage during charging through a first operational amplifier, and output a control electrode voltage, wherein the control electrode voltage is a voltage for controlling a control electrode of the first transistor; The constant current control module is configured to output a first current through a first error amplifier according to a feedback signal and a second reference voltage, so as to control the charging circuit to provide a constant charging current for the battery according to the first current, and the feedback signal is a voltage feedback signal for characterizing the charging current; The temperature control module is configured to output a second current through a second error amplifier according to a junction temperature indication signal and a third reference voltage, so as to reduce the charging current and control the junction temperature according to the second current, wherein the junction temperature indication signal is a voltage signal for characterizing the junction temperature of the first transistor; The reference voltage adjustment module is coupled to the temperature control module and the constant current control module respectively, and is configured to adjust the voltage value of the second reference voltage according to the second current, so as to reduce the voltage value of the second reference voltage after the junction temperature reaches the target temperature.

2. The constant current charging system according to claim 1, characterized in that: The reference voltage adjustment module includes: a current mirror unit and a voltage adjustment unit. Wherein, the current mirror unit is configured to copy the second current according to a preset ratio to obtain a third current; The voltage regulating unit is configured to regulate the voltage value of the second reference voltage according to the change of the third current, and control the voltage value of the second reference voltage to start decreasing when the third current is greater than a preset current threshold.

3. The constant current charging system according to claim 1, characterized in that: The clamping module includes: the first operational amplifier, a first current source, a first resistor, and a second resistor. Wherein, the positive input terminal of the first operational amplifier is respectively coupled to one end of the first resistor, the first current output by the constant current control module, and the second current output by the temperature control module; the negative input terminal of the first operational amplifier is respectively coupled to one end of the second resistor and one end of the first current source; and the output terminal of the first operational amplifier is coupled to the control electrode of the first transistor; The other end of the first current source is coupled to the ground, and the other end of the first resistor and the other end of the second resistor are both coupled to a power supply voltage.

4. The constant current charging system according to claim 1, characterized in that: The constant current control module includes: the first error amplifier, a second transistor, The first error amplifier is configured to generate the first current according to the feedback signal and the second reference voltage; The second transistor is configured to output the first current through a current mirror.

5. The constant current charging system according to claim 1, characterized in that: The temperature control module includes: the second error amplifier, a third transistor, The second error amplifier is configured to generate the second current according to the junction temperature indication signal and the third reference voltage; The third transistor is configured to output the second current through a current mirror.

6. The constant current charging system according to claim 2, characterized in that: The current mirror unit comprises: a fourth transistor, wherein a control electrode of the fourth transistor is coupled to a control electrode of a third transistor in the temperature control module, a first electrode of the fourth transistor is coupled to a ground terminal, a second electrode of the fourth transistor is coupled to the voltage regulating unit, and the third current is obtained at the second electrode of the fourth transistor; The voltage regulation module includes a second current source, a fifth transistor, a third resistor, and a second operational amplifier, wherein one end of the second current source is coupled to the power supply voltage, the other end of the second current source is respectively coupled to the second electrode of the fourth transistor and the second electrode of the fifth transistor, the control electrode of the fifth transistor is coupled to the output end of the second operational amplifier, the first electrode of the fifth transistor is respectively coupled to one end of the third resistor, the negative input end of the second operational amplifier, and the second reference voltage, the other end of the third resistor is coupled to the ground end, the positive input end of the second operational amplifier is coupled to the fourth reference voltage, and the fourth reference voltage is equal to the voltage value of the second reference voltage during constant current charging.

7. The constant current charging system according to claim 4, characterized in that: The first error amplifier includes a third current source, sixth to ninth transistors, Wherein, one end of the third current source is coupled to the power supply voltage, and the other end of the third current source is coupled to the first electrode of the sixth transistor and the first electrode of the seventh transistor respectively; The control electrode of the sixth transistor is coupled to the feedback signal, and the second electrode of the sixth transistor is coupled to the control electrode of the eighth transistor and the second electrode of the eighth transistor respectively; The control electrode of the seventh transistor is coupled to the second reference voltage, and the second electrode of the seventh transistor is respectively coupled to the control electrode of the ninth transistor, the second electrode of the ninth transistor, and the control electrode of the second transistor; The first electrode of the eighth transistor and the first electrode of the ninth transistor are both coupled to the ground terminal.

8. The constant current charging system according to claim 5, characterized in that: The second error amplifier includes a fourth current source, tenth to thirteenth transistors, One end of the fourth current source is coupled to the power supply voltage, and the other end of the fourth current source is coupled to the first electrode of the tenth transistor and the first electrode of the eleventh transistor respectively; The control electrode of the tenth transistor is coupled to the junction temperature indication signal, and the second electrode of the tenth transistor is respectively coupled to the control electrode of the twelfth transistor and the second electrode of the twelfth transistor; The control electrode of the eleventh transistor is coupled to the third reference voltage, and the second electrode of the eleventh transistor is respectively coupled to the control electrode of the thirteenth transistor, the second electrode of the thirteenth transistor, and the control electrode of the third transistor; The first electrode of the twelfth transistor and the first electrode of the thirteenth transistor are both coupled to the ground terminal.

9. The constant current charging system according to claim 6, characterized in that: The preset current threshold is determined according to the following formula: Preset current threshold=second current source−(fourth reference voltage / third resistor).

10. A linear charging chip, characterized in that: The chip includes the constant current charging system described in any one of claims 1 to 9 above.

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