A power supply circuit, a power supply system and an electronic device

Abstract

The present application discloses a power supply circuit, which includes a low dropout linear voltage regulator module and a bandgap reference module. The low dropout linear voltage regulator module is configured to output an output voltage according to the reference voltage output by the bandgap reference module; the bandgap reference module is configured to adjust the reference voltage output by itself according to the output voltage output by the low dropout linear voltage regulator module. It can be seen from this that in the power supply circuit provided by the present application, the input end of the low dropout linear voltage regulator module is connected to the output end of the low dropout linear voltage regulator module through the bandgap reference module to form a feedback circuit. In this way, for the power supply rejection ratio (PSRR) of the reference voltage VBG in the technical solution of the present application, PSRR = ab / (1 - a / β). Since a is much smaller than 1, the PSRR is approximately ab. And since b is less than 1, the PSRR of the reference voltage in the solution provided by the present application is less than the PSRR in the traditional solution.

Description

Technical Field

[0001] The present application relates to the field of power supplies, and in particular, to a power supply circuit, a power supply system, and an electronic device. Background Art

[0002] A bandgap reference circuit (BANDGAP) is a basic circuit in analog circuits and is used to generate a reference voltage that does not change with the power supply voltage and temperature. The index for measuring the stability of the reference voltage generated by the bandgap reference circuit under the change of the power supply voltage is the power supply rejection ratio (PSRR). The smaller the power supply rejection ratio, the better the stability of the reference voltage of the circuit under the change of the power supply voltage.

[0003] See Figure 1 , which is a schematic structural diagram of a bandgap reference circuit. As Figure 1 shown, in this bandgap reference circuit, the power supply voltage is connected to the bandgap reference module, and the reference voltage output by the bandgap reference module is connected to the low dropout linear voltage regulator module, and the low dropout linear voltage regulator module outputs an output voltage. See Figure 2 , which is a PSRR schematic diagram of the reference voltage of a bandgap reference circuit. As Figure 2 shown, the power supply voltage is connected to the bandgap reference module (Bandgap, BG), BG is connected to the low dropout linear voltage regulator module (Low dropout regulator, LDO), LDO outputs an output voltage Vout, and BG outputs a voltage VBG. The PSRR of the output VBG of BG is equivalent to the PSRR of BG, which is a.

[0004] With the wide application of portable electronic products, the requirement for chip accuracy is getting higher and higher. In order to improve the PSRR of the reference voltage of the bandgap reference circuit, additional enhancement circuits and bias circuits need to be added to the bandgap reference circuit. These additional circuits not only increase the complexity of the entire bandgap reference circuit, but also generate additional power consumption during use, increasing the production cost and use cost of the bandgap reference circuit. Summary of the Invention

[0005] In order to solve the above technical problems, the present application provides a power supply circuit, a power supply system, and an electronic component for reducing the PSRR of the reference voltage provided by the bandgap reference circuit.

[0006] In order to achieve the above object, the technical solutions provided by the embodiments of the present application are as follows:

[0007] The embodiments of the present application provide a power supply circuit, including: a low dropout linear voltage regulator module and a bandgap reference module;

[0008] The low dropout linear voltage regulator module is used to output an output voltage according to the reference voltage output by the bandgap reference module;

[0009] The bandgap reference module is used to adjust the reference voltage output by itself according to the output voltage output by the low dropout linear voltage regulator module.

[0010] Optionally, the circuit further includes: a first voltage judgment module;

[0011] The first voltage judgment module is used to receive the power supply voltage and the reference voltage output by the bandgap reference module, and when the reference voltage is less than a preset voltage, output a first reference voltage according to the power supply voltage; the low dropout linear voltage regulator module is specifically used to output the output voltage according to the first reference voltage;

[0012] The first voltage judgment module is further used to, when the reference voltage is greater than the preset voltage, output a second reference voltage according to the reference voltage; the low dropout linear voltage regulator module is further used to output the output voltage according to the second reference voltage.

[0013] Optionally, the first voltage judgment module is specifically used to, when the reference voltage is less than the preset voltage, output the preset voltage as the first reference voltage according to the power supply voltage.

[0014] Optionally, the first voltage judgment module is specifically used to, when the reference voltage is greater than the preset voltage, output the reference voltage as the second reference voltage.

[0015] Optionally, the first voltage judgment module includes: a preset voltage unit, a comparator and a two-way switch;

[0016] The preset voltage unit is connected to the power supply voltage; two input ends of the comparator are respectively connected to the preset voltage unit and the reference voltage; an output end of the comparator controls the two-way switch; two input ends of the two-way switch are respectively connected to the preset voltage unit and the reference voltage; an output end of the two-way switch is connected to the low dropout linear voltage regulator module;

[0017] The preset voltage unit is used to output the preset voltage according to the power supply voltage;

[0018] The comparator is used to control the two-way switch to output the larger value of the preset voltage and the reference voltage.

[0019] Optionally, the preset voltage unit includes: a reference switching switch;

[0020] The first voltage determination module further includes a delay unit; an input end of the delay unit is connected to an output end of the comparator; an output end of the delay unit controls the reference switching switch;

[0021] The delay unit is configured to send a power supply switching signal to the reference switching switch after a first preset time when an output signal of the comparator indicates that the reference voltage is greater than the preset voltage;

[0022] The reference switching switch is configured to switch a power supply circuit in the preset voltage unit when obtaining the power supply switching signal, so as to reduce the preset voltage.

[0023] Optionally, the preset voltage unit further includes:

[0024] A first diode and a second diode;

[0025] The first diode and the second diode are connected in series in the forward direction between the power supply voltage and the ground wire;

[0026] Two ends of the reference switching switch are respectively connected to the ground wire and between the first diode and the second diode;

[0027] The reference switching switch is specifically configured to close when obtaining the power supply switching signal.

[0028] Optionally, the circuit further includes: a second voltage determination module;

[0029] The second voltage determination module is configured to receive the power supply voltage and the reference voltage output by the bandgap reference module, and output a first reference voltage according to the power supply voltage when the time for receiving the power supply voltage is less than a second preset time; specifically, the low-dropout linear voltage regulator module is configured to output a reference voltage according to the first reference voltage;

[0030] The second voltage determination module is further configured to output a second reference voltage according to the reference voltage when the time for receiving the power supply voltage is greater than the second preset time; the low-dropout linear voltage regulator module is further configured to output a reference voltage according to the second reference voltage.

[0031] Optionally, the second voltage determination module includes: a preset voltage unit, a digital counter, and a two-way selector switch;

[0032] The preset voltage unit is connected to the power supply voltage; two input ends of the digital counter are respectively connected to the preset voltage unit and the reference voltage; an output end of the digital counter controls the two-way selector switch; two input ends of the two-way selector switch are respectively connected to the preset voltage unit and the reference voltage; an output end of the two-way selector switch is connected to the low-dropout linear voltage regulator module;

[0033] The preset voltage unit is configured to output the preset voltage according to the power supply voltage;

[0034] The digital counter is configured to control the two - way selector switch to output the reference voltage after a preset time when the reference voltage is greater than the preset voltage.

[0035] An embodiment of the present application provides a power supply system, the system includes: a plurality of the above - mentioned power supply circuits;

[0036] A plurality of the power supply circuits are cascaded, and the output voltage output by the low - dropout linear voltage regulator module of the upper - level power supply circuit is used as the power supply voltage of the lower - level power supply circuit; the output voltage of the last - level power supply circuit is used to provide voltage for the load.

[0037] An embodiment of the present application provides an electronic device, the electronic device includes the power supply circuit as described above, an input port, a first output terminal, a second output port, and a ground port;

[0038] The input port is connected to the power supply voltage, the first output port outputs the output voltage, the second output port outputs the reference voltage, and the ground port is connected to the ground wire.

[0039] It can be seen from the above technical solutions that the present application has the following beneficial effects:

[0040] An embodiment of the present application provides a power supply circuit, the power supply circuit includes: a low - dropout linear voltage regulator module and a bandgap reference module. The low - dropout linear voltage regulator module is configured to output an output voltage according to the reference voltage output by the bandgap reference module; the bandgap reference module is configured to adjust the reference voltage output by itself according to the output voltage output by the low - dropout linear voltage regulator module.

[0041] It can be seen from this that in the power supply circuit provided by the present application, the input end of the low - dropout linear voltage regulator module is connected to the output end of the low - dropout linear voltage regulator module through the bandgap reference module, forming a feedback circuit. Thus, the reference voltage in the technical solution of the present application is VBG. The PSRR of VBG = ab / (1 - a / β), since a is much less than 1, so the PSRR is approximately ab. And since b is less than 1, therefore, the PSRR (ab) of the reference voltage in the solution provided by the present application is less than the PSRR (a) in the traditional solution. At the same time, since the solution provided by the present application does not add additional enhancement circuits or bias circuits, it will not increase the production cost and usage cost of the bandgap reference circuit. Description of the Drawings

[0042] To more clearly illustrate the technical solutions in the embodiments of the present application or the conventional solutions, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the conventional solutions. Obviously, the accompanying drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0043] Figure 1 It is a schematic structural diagram of a bandgap reference circuit;

[0044] Figure 2 It is a PSRR schematic diagram of the reference voltage of a bandgap reference circuit;

[0045] Figure 3 It is a schematic structural diagram of a power supply circuit provided by an embodiment of the present application;

[0046] Figure 4 It is a PSRR schematic diagram of a power supply circuit provided by an embodiment of the present application;

[0047] Figure 5 It is a schematic structural diagram of a power supply circuit provided by an embodiment of the present application;

[0048] Figure 6 It is a schematic structural diagram of a first voltage judgment module provided by an embodiment of the present application;

[0049] Figure 7 It is a schematic structural diagram of a power supply system provided by an embodiment of the present application. Detailed implementation manners

[0050] To help better understand the solutions provided by the embodiments of the present application, before introducing the methods provided by the embodiments of the present application, the application scenarios of the solutions of the embodiments of the present application will be introduced first.

[0051] The bandgap reference circuit (BANDGAP) is a basic circuit in analog circuits and is used to generate a reference voltage that does not change with the power supply voltage and temperature. The index for measuring the stability of the reference voltage generated by the bandgap reference circuit under the change of the power supply voltage is the power supply rejection ratio (PSRR). The smaller the power supply rejection ratio, the better the stability of the reference voltage of the circuit under the change of the power supply voltage.

[0052] See Figure 1 , this figure is a schematic structural diagram of a bandgap reference circuit. As Figure 1 shown, in this bandgap reference circuit, the power supply voltage is connected to the bandgap reference module, the bandgap reference module is connected to the low-dropout linear voltage regulator module, and the low-dropout linear voltage regulator module outputs the reference voltage. See Figure 2, This figure is a PSRR schematic diagram of the reference voltage of a bandgap reference circuit. As Figure 2 shown, the power supply voltage is connected to the bandgap reference module (Bandgap, BG), BG is connected to the low dropout regulator module (Lowdropout regulator, LDO), the LDO outputs the reference voltage Vout, and the BG outputs the voltage VBG. The PSRR of the output VBG of BG is equal to the PSRR of BG, which is a.

[0053] With the wide application of portable electronic products, the requirements for chip accuracy are getting higher and higher. In order to improve the PSRR of the bandgap reference circuit, additional enhancement circuits and bias circuits need to be added to the bandgap reference circuit. These additional circuits not only increase the complexity of the entire bandgap reference circuit, but also generate additional power consumption during use, increasing the production cost and usage cost of the bandgap reference circuit.

[0054] To solve the above technical problems, an embodiment of the present application provides a power supply circuit, which includes: a low dropout regulator module and a bandgap reference module. The low dropout regulator module is used to output an output voltage according to the reference voltage output by the bandgap reference module; the bandgap reference module is used to adjust the reference voltage output by itself according to the output voltage output by the low dropout regulator module.

[0055] It can be seen from this that in the power supply circuit provided by the present application, the input end of the low dropout regulator module is connected to the output end of the low dropout regulator module through the bandgap reference module, forming a feedback circuit. In this way, the reference voltage in the technical solution of the present application is VBG. The PSRR of VBG = ab / (1 - a / β). Since a is much smaller than 1, the PSRR is approximately ab. And since b is less than 1, the PSRR (ab) of the reference voltage in the solution provided by the present application is less than the PSRR (a) in the traditional solution. At the same time, since the solution provided by the present application does not add additional enhancement circuits or bias circuits, it will not increase the production cost and usage cost of the bandgap reference circuit.

[0056] To make the above objects, features, and advantages of the present application more obvious and understandable, the following further details the embodiments of the present application in conjunction with the drawings and specific embodiments.

[0057] See Figure 3 , This figure is a schematic diagram of the structure of a power supply circuit provided by an embodiment of the present application. As Figure 3 shown, the power supply circuit provided by an embodiment of the present application includes: a low dropout regulator module 100 and a bandgap reference module 200.

[0058] The low dropout regulator module 100 is used to output an output voltage according to the reference voltage output by the bandgap reference module.

[0059] The bandgap reference module 200 is used to adjust the reference voltage output by itself according to the output voltage output by the low dropout linear regulator module.

[0060] See Figure 4 , which is a PSRR schematic diagram of a power supply circuit provided by an embodiment of the present application. As Figure 4 shown, in the embodiment of the present application, the reference voltage VBG output by BG is the reference voltage, and the reference voltage is often used to provide a stable calibration voltage. The PSRR of the output VBG of BG is PSRR = ab / (1 - a / β). Since a is much smaller than 1, the PSRR is approximately ab. And since b is less than 1, the PSRR (ab) of the reference voltage in the solution provided by the present application is less than Figure 2 the PSRR (a) in

[0061] It should be noted that the solution provided by the embodiment of the present application can not only reduce the PSRR of the reference voltage VBG provided by the power supply circuit, but also reduce the PSRR of the output voltage Vout provided by the power supply circuit. In practical applications, the output voltage Vout is often used to provide voltage for the load.

[0062] As Figure 2 shown, the forward gain A of the LDO is much greater than 1, and the feedback coefficient β is less than 1. The reference voltage Vout output by the LDO = 1 / β * VBG. The PSRR of VBG is determined by the PSRR of BG and is a. Therefore, the PSRR of Vout in the traditional solution = a * A / (1 + βA) + b. Since A is much greater than 1, the PSRR of Vout can be approximated as a / β + b. As Figure 4 shown, the PSRR of Vout of the power supply circuit provided by the embodiment of the present application = b / (1 - a / β). Since a is much smaller than 1, the PSRR is approximately PSRR = b. Therefore, the PSSR (b) of Vout provided by the technical solution of the embodiment of the present application is less than Figure 2 the PSRR (a / β + b) of Vout in the traditional solution shown in

[0063] In the embodiment of the present application, considering that the LDO cannot be started before the output of BG is established, as a possible implementation manner, the first voltage judgment module. See Figure 5 , which is a schematic diagram of a power supply circuit structure provided by an embodiment of the present application. As Figure 5As shown in the figure, the power supply circuit provided by the embodiment of the present application may further include: a first voltage judgment module 300, configured to receive the power supply voltage and the reference voltage output by the bandgap reference module 200, and when the reference voltage is less than a preset voltage, output a first reference voltage according to the power supply voltage; a low dropout linear regulator module 100, specifically configured to output an output voltage according to the first reference voltage; the first voltage judgment module 300 is further configured to, when the reference voltage is greater than the preset voltage, output a second reference voltage according to the reference voltage; the low dropout linear regulator module 100 is further configured to output an output voltage according to the second reference voltage.

[0064] It can be understood that in the embodiment of the present application, a voltage is required to start the LDO before the reference output by BG is established. As a possible implementation manner, the first voltage judgment module can be used to judge whether the reference voltage output by BG is established. When it is judged that the reference voltage output by BG is not established, that is, when the reference voltage is less than the preset voltage, a first reference voltage is output through the power supply voltage, so that BG establishes an effective reference voltage. When it is judged that the establishment of the reference voltage output by BG is completed, that is, when the reference voltage is greater than the preset voltage, the output circuit of the first voltage judgment module is switched, so that the first voltage judgment module outputs a second reference voltage according to the reference voltage.

[0065] In the embodiment of the present application, as a possible implementation manner, the first voltage judgment module is specifically configured to, when the reference voltage is less than the preset voltage, output the preset voltage as the first reference voltage according to the power supply voltage. In the embodiment of the present application, as a possible implementation manner, the first voltage judgment module is specifically configured to, when the reference voltage is greater than the preset voltage, output the reference voltage as the second reference voltage.

[0066] See Figure 6 , this figure is a schematic structural diagram of a first voltage judgment module provided by the embodiment of the present application. As Figure 6 shown, in the embodiment of the present application, as a possible implementation manner, the first voltage judgment module includes: a preset voltage unit, a comparator and a two-way selector switch; the preset voltage unit is connected to the power supply voltage; two input ends of the comparator are respectively connected to the preset voltage unit and the reference voltage; the output end of the comparator controls the two-way selector switch; two input ends of the two-way selector switch are respectively connected to the preset voltage unit and the reference voltage; the output end of the two-way selector switch is connected to the low dropout linear regulator module; the preset voltage unit is configured to output a preset voltage according to the power supply voltage; the comparator is configured to control the two-way selector switch to output the larger value of the preset voltage and the reference voltage.

[0067] Further, as Figure 6As shown in the figure, the preset voltage unit provided by the embodiment of the present application includes: a reference switching switch P; the first voltage judgment module further includes a delay unit; the input end of the delay unit is connected to the output end of the comparator; the output end of the delay unit controls the reference switching switch P; the delay unit is configured to send a power supply switching signal to the power supply switching P switch after a first preset time when the output signal of the comparator indicates that the reference voltage is greater than the preset voltage; the reference switching switch P is configured to switch the power supply circuit in the preset voltage unit to reduce the preset voltage when the power supply switching signal is obtained.

[0068] Among them, as Figure 6 shown in the figure, the preset voltage unit provided by the embodiment of the present application further includes: a first diode Q and a second diode W; the first diode Q and the second diode W are connected in series in the forward direction between the power supply voltage and the ground wire; both ends of the reference switching switch P are respectively connected to the ground wire and the middle of the first diode Q and the second diode W; the reference switching switch P is specifically configured to close when the power supply switching signal is obtained.

[0069] In the embodiment of the present application, as a possible implementation manner, the power supply circuit may further include: a second voltage judgment module. The second voltage judgment module is configured to receive the power supply voltage and the reference voltage output by the bandgap reference module, and output a first reference voltage according to the power supply voltage when the time of receiving the power supply voltage is less than a second preset time; the low dropout linear voltage regulator module is specifically configured to output a reference voltage according to the first reference voltage; the second voltage judgment module is further configured to output a second reference voltage according to the reference voltage when the time of receiving the power supply voltage is greater than the second preset time; the low dropout linear voltage regulator module is further configured to output a reference voltage according to the second reference voltage.

[0070] Further, the second voltage judgment module may include: a preset voltage unit, a digital counter, and a two-way selector switch. The preset voltage unit is connected to the power supply voltage; two input ends of the digital counter are respectively connected to the preset voltage unit and the reference voltage; the output end of the digital counter controls the two-way selector switch; two input ends of the two-way selector switch are respectively connected to the preset voltage unit and the reference voltage; the output end of the two-way selector switch is connected to the low dropout linear voltage regulator module; the preset voltage unit is configured to output a preset voltage according to the power supply voltage; the digital counter is configured to control the two-way selector switch to output the reference voltage after a preset time when the reference voltage is greater than the preset voltage.

[0071] It can be understood that in the embodiment of the present application, it is possible to judge whether the reference voltage output by BG is established through the first voltage judgment module or the second voltage judgment module. Of course, the method provided by the embodiment of the present application can judge whether the reference voltage output by BG is established through other judgment modules, and the embodiment of the present application does not make any limitation here.

[0072] In summary, in the power supply circuit provided by the present application, the input end of the low dropout linear regulator module is connected to the output end of the low dropout linear regulator module through the bandgap reference module to form a feedback circuit. Thus, the reference voltage in the technical solution of the present application is VBG. The PSRR of VBG is ab / (1 - a / β). Since a is much smaller than 1, the PSRR is approximately ab. And since b is less than 1, the PSRR (ab) of the reference voltage in the solution provided by the present application is less than the PSRR (a) in the traditional solution. At the same time, since the solution provided by the present application does not add an additional enhancement circuit or bias circuit, it will not increase the production cost and usage cost of the bandgap reference circuit.

[0073] According to the power supply circuit provided in the above embodiment, as a possible implementation manner, in order to further reduce the PSRR of the output voltage Vout and the reference voltage, the embodiment of the present application further provides a power supply system. Refer to Figure 7 , which is a schematic structural diagram of a power supply system provided by an embodiment of the present application. As Figure 7 shown, the power supply system provided by the embodiment of the present application includes: a plurality of power supply circuits such as those provided in the above embodiment; a plurality of power supply circuits are cascaded, and the output voltage output by the low dropout linear regulator module of the upper-level power supply circuit is the power supply voltage of the lower-level power supply circuit; the output voltage of the last-level power supply circuit is used to provide voltage for the load.

[0074] According to the power supply circuit and the power supply system provided in the above embodiment, the embodiment of the present application further provides an electronic device, which includes a power supply circuit, an input port, a first output end, a second output port, and a ground port such as those provided in the above embodiment. Among them, the input port is connected to the power supply voltage, the first output end outputs the output voltage, the second output port outputs the reference voltage, and the ground port is connected to the ground wire.

[0075] From the description of the above embodiments, those skilled in the art can clearly understand that all or part of the steps in the above embodiment methods can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the traditional solution, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network communication device such as a media gateway, etc.) to execute the methods described in each embodiment or some parts of the embodiments of the present application.

[0076] It should be noted that the various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other. For the methods disclosed in the embodiments, since they correspond to the systems disclosed in the embodiments, the descriptions are relatively simple. For the relevant parts, reference can be made to the descriptions of the system part.

[0077] It should also be noted that in this text, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such a process, method, article or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the said element.

[0078] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power supply circuit, characterized in that, it includes: a low dropout linear regulator module and a bandgap reference module; the low dropout linear regulator module is used to output an output voltage according to the reference voltage output by the bandgap reference module; the bandgap reference module is used to adjust the reference voltage output by itself according to the output voltage output by the low dropout linear regulator module; the circuit further includes: a first voltage judgment module; the first voltage judgment module is used to receive the power supply voltage and the reference voltage output by the bandgap reference module. When the reference voltage is less than a preset voltage, it outputs a first reference voltage according to the power supply voltage; the low dropout linear regulator module is specifically used to output the output voltage according to the first reference voltage; the first voltage judgment module is further used to, when the reference voltage is greater than the preset voltage, output a second reference voltage according to the reference voltage; the low dropout linear regulator module is further used to output the output voltage according to the second reference voltage.

2. The circuit according to claim 1, characterized in that, the first voltage judgment module is specifically used to, when the reference voltage is less than the preset voltage, output the preset voltage as the first reference voltage according to the power supply voltage.

3. The circuit according to claim 1, characterized in that, the first voltage judgment module is specifically used to, when the reference voltage is greater than the preset voltage, output the reference voltage as the second reference voltage.

4. The circuit according to claim 1, characterized in that, the first voltage judgment module includes: a preset voltage unit, a comparator and a two-way selector switch; the preset voltage unit is connected to the power supply voltage; two input terminals of the comparator are respectively connected to the preset voltage unit and the reference voltage; the output terminal of the comparator controls the two-way selector switch; two input terminals of the two-way selector switch are respectively connected to the preset voltage unit and the reference voltage; the output terminal of the two-way selector switch is connected to the low dropout linear regulator module; the preset voltage unit is used to output the preset voltage according to the power supply voltage; the comparator is used to control the two-way selector switch to output the larger value of the preset voltage and the reference voltage.

5. The circuit according to claim 4, characterized in that, the preset voltage unit includes: a reference switching switch; the first voltage judgment module further includes a delay unit; the input terminal of the delay unit is connected to the output terminal of the comparator; the output terminal of the delay unit controls the reference switching switch; the delay unit is used to, when the output signal of the comparator indicates that the reference voltage is greater than the preset voltage, send a power supply switching signal to the reference switching switch after a first preset time; the reference switching switch is used to switch the power supply circuit in the preset voltage unit when obtaining the power supply switching signal, and reduce the preset voltage.

6. The circuit according to claim 5, characterized in that, the preset voltage unit further includes: a first diode and a second diode; The first diode and the second diode are connected in series forward between the power supply voltage and the ground wire; Both ends of the reference switching switch are respectively connected between the ground wire and the middle of the first diode and the second diode; The reference switching switch is specifically configured to close when the power supply switching signal is obtained.

7. The circuit according to claim 1, wherein, the circuit further includes: a second voltage judgment module; The second voltage judgment module is configured to receive the power supply voltage and the reference voltage output by the bandgap reference module. When the time of receiving the power supply voltage is less than a second preset time, a first reference voltage is output according to the power supply voltage; the low-dropout linear voltage regulator module is specifically configured to output a reference voltage according to the first reference voltage; The second voltage judgment module is further configured to output a second reference voltage according to the reference voltage when the time of receiving the power supply voltage is greater than a second preset time; the low-dropout linear voltage regulator module is further configured to output a reference voltage according to the second reference voltage.

8. The circuit according to claim 7, wherein, the second voltage judgment module includes: a preset voltage unit, a digital counter, and a two-way selector switch; The preset voltage unit is connected to the power supply voltage; two input ends of the digital counter are respectively connected to the preset voltage unit and the reference voltage; an output end of the digital counter controls the two-way selector switch; two input ends of the two-way selector switch are respectively connected to the preset voltage unit and the reference voltage; an output end of the two-way selector switch is connected to the low-dropout linear voltage regulator module; The preset voltage unit is configured to output the preset voltage according to the power supply voltage; The digital counter is configured to control the two-way selector switch to output the reference voltage after a preset time when the reference voltage is greater than the preset voltage.

9. A power supply system, wherein, the system includes: a plurality of power supply circuits according to any one of claims 1 to 8; A plurality of the power supply circuits are cascaded, and the output voltage output by the low-dropout linear voltage regulator module of the upper-level power supply circuit is the power supply voltage of the lower-level power supply circuit; the output voltage of the last-level power supply circuit is used to provide a voltage for a load.

10. An electronic device, wherein, the electronic device includes a power supply circuit, an input port, a first output port, a second output port, and a ground port according to any one of claims 1 to 8; The input port is connected to the power supply voltage, the first output port outputs the output voltage, the second output port outputs the reference voltage, and the ground port is connected to the ground wire.

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