Power switching circuit, system and control method thereof

Abstract

The present invention provides a power switching circuit, a system and a control method thereof. The power switching circuit selects a first power input terminal or a second power input terminal to supply power to a power supply terminal through a power switching module. Specifically, when the first power input terminal and the second power input terminal are supplying power at the same time, the second power input terminal is disconnected, or when the first power input terminal is supplying power but the second power input terminal is not supplying power, only the first power input terminal supplies power to the power supply terminal; and when the first power input terminal is not supplying power, the second power input terminal is supplied power, so that the first power input terminal and the second power input terminal can both supply power to the load normally and independently, thereby ensuring the normal power supply of the power supply terminal.

Description

Technical Field

[0001] The present invention relates to the field of display technology, and in particular to a power switching circuit, system and control method thereof. Background Art

[0002] In order to ensure the normal power supply of the equipment, the equipment will generally be equipped with multiple power supplies, such as Figure 1 As shown, it mainly includes external power supply VDD and internal power supply VCC. If the external power supply VDD and the internal power supply VCC are connected to the device power interface IN at the same time, this will cause a short circuit between the external power supply VDD and the internal power supply VCC. The voltages provided by the external power supply VDD and the internal power supply VCC are generally different. Therefore, the voltage difference between the external power supply VDD and the internal power supply VCC will form a current inside the device, causing the device to be interfered with or even burned.

[0003] In view of this, a switching module 1 is often set between the external power supply VDD and the internal power supply VCC, so that only one of the external power supply VDD and the internal power supply VCC supplies power to the device, to prevent the two power supplies from being short-circuited together, causing interference or even burning of the device. However, the current switching module 1 is usually composed of a single transistor T and a single pull-down resistor R. If the transistor T is a P-type tube, the switching module 1 can cut off the P-type tube and cut off the internal power supply VCC when the external power supply VDD is used for power supply. However, when the internal power supply VCC is used for power supply, the P-type tube is turned on. When the internal power supply VCC causes the drain potential of the P-type tube to gradually increase, the gate potential of the P-type tube is also gradually increased because the gate and drain of the P-type tube are connected, which will cause the gate-source voltage difference Vgs of the P-type tube to gradually increase until it gradually approaches its threshold voltage Vth, so that the conduction degree of the P-type tube gradually decreases, and the supply current of the internal power supply VCC gradually decreases until the internal power supply VCC cannot supply power to the device, causing the device to fail to work normally.

[0004] Therefore, there is an urgent need to provide a power switching circuit so that when the power supply of the device is switched between the external power supply VDD and the internal power supply VCC, both the external power supply VDD and the internal power supply VCC can independently supply power to the device normally. Summary of the invention

[0005] In order to solve the above problems, an embodiment of the present invention provides a power switching circuit, system and control method thereof.

[0006] In a first aspect, an embodiment of the present invention provides a power switching circuit, comprising a first power input terminal, a second power input terminal, a power supply terminal and a power switching module; the power switching module is connected to the first power input terminal, the second power input terminal and the power supply terminal, and is used to cut off the second power input terminal when the first power input terminal supplies power, so that the first power input terminal supplies power to the power supply terminal, and, when the first power input terminal does not supply power, so that the second power input terminal supplies power to the power supply terminal.

[0007] In some embodiments, the power switching module includes a first power switching unit, a second power switching unit, and an isolation unit;

[0008] The control end of the first power switching unit is connected to the first node, the input end of the first power switching unit is connected to the first power input end, and the output end of the first power switching unit is connected to the power supply end;

[0009] The control end of the second power switching unit is connected to the first power input end, the input end of the second power switching unit is connected to the second power input end, and the output end of the second power switching unit is connected to the first node;

[0010] The control end of the isolation unit is connected to the first power input end, the input end of the isolation unit is connected to the first node, and the output end of the isolation unit is connected to the power supply end.

[0011] In some embodiments, the first power switching unit includes a first transistor and a first pull-down resistor;

[0012] The gate of the first transistor is connected to the first node, the source of the first transistor is connected to the first power input terminal, and the drain of the first transistor is connected to the power supply terminal;

[0013] A first end of the first pull-down resistor is connected to the first node, and a second end of the first pull-down resistor is connected to a constant voltage low potential end.

[0014] In some embodiments, the second power switching unit includes a second transistor and a second pull-down resistor:

[0015] The gate of the second transistor is connected to the first power input terminal, the source of the second transistor is connected to the second power input terminal, and the drain of the second transistor is connected to the first node;

[0016] A first end of the second pull-down resistor is connected to the first power input end, and a second end of the second pull-down resistor is connected to the constant voltage low potential end.

[0017] In some embodiments, the isolation unit includes a third transistor; the gate of the third transistor is connected to the first power input terminal, the source of the third transistor is connected to the first node, and the drain of the third transistor is connected to the power supply terminal.

[0018] In some embodiments, the first transistor, the second transistor, and the third transistor are P-type thin film transistors.

[0019] In a second aspect, an embodiment of the present invention further provides a control method for a power switching circuit, comprising:

[0020] When the first power input terminal supplies power, the power switching module cuts off the second power input terminal, so that the first power input terminal supplies power to the power supply terminal;

[0021] When the first power input terminal does not supply power, the power switching module enables the second power input terminal to supply power to the power supply terminal.

[0022] In some embodiments, when the first power input terminal supplies power, the power switching module cuts off the second power input terminal so that the first power input terminal supplies power to the power supply terminal, specifically including:

[0023] The first power input terminal provides a high level to turn off the second transistor and the third transistor;

[0024] The potential of the first node is pulled down by the first pull-down resistor to turn on the first transistor, so that the first power input terminal supplies power to the power supply terminal.

[0025] In some embodiments, when the first power input terminal does not supply power, the power switching module enables the second power input terminal to supply power to the power supply terminal, specifically including:

[0026] The first power input terminal provides a low level or a high impedance state, and the second transistor and the third transistor are turned on through the second pull-down resistor;

[0027] The second power input terminal provides a high level to supply power to the power supply terminal, and pulls up the potential of the first node to turn off the first transistor.

[0028] In a third aspect, an embodiment of the present invention further provides a power switching system, comprising a first power supply, a second power supply, a load, and the power switching circuit as described above; the first power supply is connected to the first power input terminal of the power switching circuit, the second power supply is connected to the second power input terminal of the power switching circuit, and the load is connected to the power supply terminal of the power switching circuit.

[0029] The power switching circuit, system and control method thereof provided by the embodiment of the present invention select the first power input terminal or the second power input terminal to supply power to the power supply terminal through the power switching module. Specifically, when the first power input terminal and the second power input terminal are supplying power at the same time, the second power input terminal is disconnected, or when the first power input terminal is supplying power but the second power input terminal is not supplying power, only the first power input terminal supplies power to the power supply terminal; and when the first power input terminal is not supplying power, the second power input terminal is supplied power, so that the first power input terminal and the second power input terminal can both supply power to the load normally and independently, thereby ensuring the normal power supply of the power supply terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The technical solutions and other beneficial effects of the present invention will be made apparent by describing in detail the specific embodiments of the present invention in conjunction with the accompanying drawings.

[0031] Figure 1 It is a structural schematic diagram of a power switching circuit in the prior art;

[0032] Figure 2 A schematic diagram of the overall structure of a power switching circuit provided by an embodiment of the present invention;

[0033] Figure 3 A schematic diagram of a specific structure of a power switching circuit provided in an embodiment of the present invention;

[0034] Figure 4 A schematic diagram of a first current path when the first power input terminal provides power supply according to an embodiment of the present invention;

[0035] Figure 5 A schematic diagram of a second current path when the first power input terminal provides power supply according to an embodiment of the present invention;

[0036] Figure 6 A schematic diagram of a first current path when the second power input terminal provides power supply according to an embodiment of the present invention;

[0037] Figure 7 A schematic diagram of a second current path when the second power input terminal provides power supply according to an embodiment of the present invention;

[0038] Figure 8 A schematic flow chart of a control method for a power switching circuit provided by an embodiment of the present invention;

[0039] Fig. 9 A schematic diagram of the structure of a power switching system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0041] It should be noted that in all embodiments of the present invention, in order to distinguish the two poles of the transistor other than the gate, one of the poles is called the source and the other is called the drain. Since the source and drain of the transistor are symmetrical, the source and drain are interchangeable. According to the form in the accompanying drawings, the middle end of the transistor is specified as the gate, the signal input end is the source, and the signal output end is the drain. In addition, the transistors used in all embodiments of the present application may include P-type and / or N-type transistors, wherein the P-type transistor is turned on when the gate is at a low potential and is turned off when the gate is at a high potential; the N-type transistor is turned on when the gate is at a high potential and is turned off when the gate is at a low potential.

[0042] like Figure 2 As shown, an embodiment of the present invention provides a power switching circuit, including a first power input terminal VDD1, a second power input terminal VDD2, a power supply terminal IN and a power switching module 10; wherein the power switching module 10 is connected to the first power input terminal VDD1, the second power input terminal VDD2 and the power supply terminal IN, and is used to cut off the second power input terminal VDD2 when the first power input terminal VDD1 supplies power, so that the first power input terminal VDD1 supplies power to the power supply terminal IN, and, when the first power input terminal VDD1 does not supply power, the second power input terminal VDD2 supplies power to the power supply terminal IN.

[0043] The power switching circuit provided by the embodiment of the present invention selects the first power input terminal VDD1 or the second power input terminal VDD2 to supply power to the power supply terminal IN through the power switching module 10. Specifically, when the first power input terminal VDD1 and the second power input terminal VDD2 supply power at the same time, the second power input terminal VDD2 is disconnected, or when the first power input terminal VDD1 supplies power but the second power input terminal VDD2 does not supply power, only the first power input terminal VDD1 supplies power to the power supply terminal IN; and when the first power input terminal VDD1 does not supply power, the second power input terminal VDD2 supplies power, so that the first power input terminal VDD1 and the second power input terminal VDD2 can both supply power to the load normally and independently, thereby ensuring the normal power supply of the power supply terminal IN.

[0044] That is to say, when the first power input terminal VDD1 supplies power, no matter whether the second power input terminal VDD2 is connected or not, the first power input terminal VDD1 is selected to supply power to the power supply terminal IN; and when the first power input terminal VDD1 is not supplying power, the second power input terminal VDD2 is selected to charge the power supply terminal IN, thereby preventing the first power input terminal VDD1 and the second power input terminal VDD2 from supplying power to the power supply terminal IN at the same time, and when the first power input terminal VDD1 or the second power input terminal VDD2 is supplying power alone, both can supply power to the power supply terminal IN normally, so as to ensure the normal power supply to the load.

[0045] It should be noted that the power switching circuit also includes a power control module (not shown in the figure), which is used to enable the second power input terminal VDD2 to supply power when the first power input terminal VDD1 is not supplying power, so that when the first power input terminal VDD1 is not supplying power, the second power input terminal VDD2 can normally supply power to the load.

[0046] Combination Figure 2 and Figure 3 As shown, the power switching module 10 includes a first power switching unit 100, a second power switching unit 200 and an isolation unit 300; wherein:

[0047] The control end of the first power switching unit 100 is connected to the first node N, the input end of the first power switching unit 100 is connected to the first power input end VDD1, and the output end of the first power switching unit 100 is connected to the power supply end IN;

[0048] The control end of the second power switching unit 200 is connected to the first power input end VDD1, the input end of the second power switching unit 200 is connected to the second power input end VDD2, and the output end of the second power switching unit 200 is connected to the first node N;

[0049] The control end of the isolation unit 300 is connected to the first power input end VDD1 , the input end of the isolation unit 300 is connected to the first node N, and the output end of the isolation unit 300 is connected to the power supply end IN.

[0050] Specifically, the power switching module 10 of the power switching circuit is composed of a first power switching unit 100, a second power switching unit 200 and an isolation unit 300, wherein when the first power input terminal VDD1 supplies power, the first power switching unit 100 works and the second power switching unit 200 does not work, thereby cutting off the second power input terminal VDD2, so that the first power input terminal VDD1 supplies power to the power supply terminal IN through the first power switching unit 100, and at this time the isolation unit 300 is used to isolate the first power switching unit 100 and the second power switching unit 200, thereby isolating the first power input terminal V DD1 and the second power input terminal VDD2 are used to prevent the second power switching unit 200 from affecting the operation of the first power switching unit 100, resulting in the first power input terminal VDD1 being unable to normally supply power to the power supply terminal IN through the first power switching unit 100; and when the first power input terminal VDD1 is not supplying power, the first power switching unit 100 is not working, and the second power switching unit 200 is working, so that the second power input terminal VDD2 supplies power to the power supply terminal IN through the second power switching unit 200. At this time, the isolation unit 300 is used to conduct the current path between the second unit switching unit and the power supply terminal.

[0051] That is to say, the isolation unit 300 serves to isolate the first power switching unit 100 and the second power switching unit 200 when the first power input terminal VDD1 supplies power, and serves to conduct the second power switching unit 200 and the power supply terminal IN when the first power input terminal VDD1 does not supply power but the second power input terminal VDD2 supplies power.

[0052] It should be noted that the power input terminal can be grounded through a pull-down resistor. When there is no high-level input to the power input terminal, the pull-down resistor can make the power input terminal in a low-level state; when a high-level input is input to the power input terminal, the power input terminal is in a high-level state.

[0053] Based on this, please continue to refer to Figure 3 In some embodiments, the first power switching unit 100 includes a first transistor T1 and a first pull-down resistor R1; wherein:

[0054] The gate of the first transistor T1 is connected to the first node N, the source of the first transistor T1 is connected to the first power input terminal VDD1, and the drain of the first transistor T1 is connected to the power supply terminal IN;

[0055] A first end of the first pull-down resistor R1 is connected to the first node N, and a second end of the first pull-down resistor R1 is connected to the constant voltage low potential end.

[0056] Specifically, when the first power input terminal VDD1 supplies power, the first power input terminal VDD1 provides a high level, and the first pull-down resistor R1 pulls the potential of the first node N down to a low level, thereby turning on the first transistor T1, so that the first power input terminal VDD1 supplies power to the power supply terminal IN through the first transistor T1. Figure 4 The current path shown.

[0057] For further information, please refer to Figure 3 In some embodiments, the second power switching unit 200 includes a second transistor T2 and a second pull-down resistor R2:

[0058] The gate of the second transistor T2 is connected to the first power input terminal VDD1, the source of the second transistor T2 is connected to the second power input terminal VDD2, and the drain of the second transistor T2 is connected to the first node N;

[0059] A first end of the second pull-down resistor R2 is connected to the first power input terminal VDD1 , and a second end of the second pull-down resistor R2 is connected to the constant voltage low potential terminal.

[0060] Specifically, when the first power input terminal VDD1 does not supply power, the first power input terminal VDD1 provides a low level or is in a high impedance state, and the second pull-down resistor R2 pulls down the gate potential of the second transistor T2 to a low level, so that the second transistor T2 is turned on. At the same time, the second power input terminal VDD2 supplies power, and the second power input terminal VDD2 provides a high level. At this time, if the first node N is connected to the power supply terminal IN, the second power input terminal VDD2 can supply power to the power supply terminal IN through the second transistor T2. Figure 5 The current path shown.

[0061] It should be noted that the first node N and the power supply terminal IN are only in this embodiment ( Figure 5 ), that is, the first power input terminal VDD1 is not powered but is connected to each other only when the second power input terminal VDD2 is powered. In other words, the first node N and the power supply terminal IN cannot be connected all the time to avoid that when the first power input terminal VDD1 supplies power, the drain potential of the first transistor T1 rises, and the potential of the first node N also rises accordingly, so that the gate-source potential difference of the first transistor T1 gradually approaches its threshold voltage, resulting in a gradual decrease in the conduction degree of the first transistor T1, so that the first transistor T1 works in an unsaturated area or is cut off, so that the first power input terminal VDD1 cannot normally supply power to the power supply terminal IN.

[0062] In view of this, based on the above embodiments, please continue to refer to Figure 3In the embodiment of the present invention, an isolation unit 300 is further provided between the first power switching unit 100 and the second power switching unit 200. The isolation unit 300 includes a third transistor T3; a gate of the third transistor T3 is connected to the first power input terminal VDD1, a source of the third transistor T3 is connected to the first node N, and a drain of the third transistor T3 is connected to the power supply terminal IN.

[0063] Specifically, when the first power input terminal VDD1 supplies power, the first power input terminal VDD1 provides a high level, and the first pull-down resistor R1 pulls down the potential of the first node N to a low level, so that the second transistor T2 and the third transistor T3 are turned off, thereby cutting off the second power input terminal VDD2, and the third transistor T3 is turned off to isolate the first node N and the drain of the first transistor T1, so that when the drain potential of the first transistor T1 rises, it does not affect the potential of the first node N, so that the potential of the first node N can be maintained at a low potential, so that the first transistor T1 is continuously turned on, and the first power input terminal VDD1 can continue to supply power to the power supply terminal IN normally through the first transistor T1, such as Figure 6 The current path shown; when the first power input terminal VDD1 is not powered and the second power input terminal VDD2 is powered, the second pull-down resistor R2 pulls down the gate potential of the second transistor T2 and the third transistor T3 to a low potential, so that the second transistor T2 and the third transistor T3 are turned on, and the second power input terminal VDD2 supplies power to the power supply terminal IN through the second transistor T2 and the third transistor T3, as shown in FIG. Figure 7 The current path shown.

[0064] It should be noted that, since the power input terminal generally provides a high potential, in the embodiment of the present invention, the first transistor T1, the second transistor T2 and the third transistor T3 are P-type thin film transistors so that the power input terminal can turn on the first transistor T1, the second transistor T2 and the third transistor T3.

[0065] Based on the above embodiments, Figure 8 As shown, an embodiment of the present invention further provides a control method for a power switching circuit, comprising:

[0066] S1, when the first power input terminal VDD1 supplies power, the power switching module 10 cuts off the second power input terminal VDD2, so that the first power input terminal VDD1 supplies power to the power supply terminal IN;

[0067] S2. When the first power input terminal VDD1 does not supply power, the power switching module 10 enables the second power input terminal VDD2 to supply power to the power supply terminal IN.

[0068] Specifically, when the first power input terminal VDD1 and the second power input terminal VDD2 supply power at the same time, the second power input terminal VDD2 is disconnected, or when the first power input terminal VDD1 supplies power but the second power input terminal VDD2 does not supply power, only the first power input terminal VDD1 supplies power to the power supply terminal IN; and when the first power input terminal VDD1 does not supply power, the second power input terminal VDD2 supplies power, so that the first power input terminal VDD1 and the second power input terminal VDD2 can both supply power to the load normally and independently, thereby ensuring the normal power supply of the power supply terminal IN.

[0069] In some embodiments, when the first power input terminal VDD1 supplies power, the power switching module 10 cuts off the second power input terminal VDD2 so that the first power input terminal VDD1 supplies power to the power supply terminal IN, specifically including:

[0070] The first power input terminal VDD1 provides a high level, so that the second transistor T2 and the third transistor T3 are turned off;

[0071] The potential of the first node N is pulled down by the first pull-down resistor R1 to turn on the first transistor T1 so that the first power input terminal VDD1 supplies power to the power supply terminal IN.

[0072] Specifically, when the first power input terminal VDD1 supplies power, the first power input terminal VDD1 provides a high level, and the first pull-down resistor R1 pulls down the potential of the first node N to a low level, so that the second transistor T2 and the third transistor T3 are turned off, thereby cutting off the second power input terminal VDD2, and the third transistor T3 is turned off to isolate the first node N and the drain of the first transistor T1, so that when the drain potential of the first transistor T1 rises, it does not affect the potential of the first node N, so that the potential of the first node N can be maintained at a low potential, so that the first transistor T1 is continuously turned on, and the first power input terminal VDD1 continues to supply power to the power supply terminal IN normally through the first transistor T1, such as Figure 6 The current path shown.

[0073] In some embodiments, when the first power input terminal VDD1 does not supply power, the power switching module 10 enables the second power input terminal VDD2 to supply power to the power supply terminal IN, specifically including:

[0074] The first power input terminal VDD1 provides a low level or a high impedance state, and the second transistor T2 and the third transistor T3 are turned on through the second pull-down resistor R2;

[0075] The second power input terminal VDD2 provides a high level to supply power to the power supply terminal IN, and pulls up the potential of the first node N, so that the first transistor T1 is turned off.

[0076] Specifically, when the first power input terminal VDD1 is not powered and the second power input terminal VDD2 is powered, the second pull-down resistor R2 pulls down the gate potential of the second transistor T2 and the third transistor T3 to a low potential, so that the second transistor T2 and the third transistor T3 are turned on, and the second power input terminal VDD2 supplies power to the power supply terminal IN through the second transistor T2 and the third transistor T3. Figure 7 The current path shown.

[0077] Based on the above embodiments, Fig. 9 As shown, an embodiment of the present invention further provides a power switching system, comprising a first power supply 20, a second power supply 30, a load 40, and the power switching circuit 10 as described above; wherein: the first power supply is connected to the first power input terminal VDD1 of the power switching circuit, the second power supply is connected to the second power input terminal VDD2 of the power switching circuit, and the load is connected to the power supply terminal IN of the power switching circuit.

[0078] It is understandable that for portable devices, an external power supply VDD is generally used in indoor environments, and an internal power supply VCC is used when it is inconvenient to use the external power supply VDD in outdoor environments or indoor environments. Therefore, in the embodiments of the present invention, the first power supply generally refers to the external power supply VDD, and the second power supply generally refers to the internal power supply VCC.

[0079] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0080] The description of the above embodiments is only used to help understand the technical solutions and core ideas of the present invention. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power switching circuit, characterized in that: It includes a first power input terminal, a second power input terminal, a power supply terminal and a power switching module; The power switching module is connected to the first power input terminal, the second power input terminal and the power supply terminal, and is used to cut off the second power input terminal when the first power input terminal supplies power, so that the first power input terminal supplies power to the power supply terminal, and when the first power input terminal does not supply power, so that the second power input terminal supplies power to the power supply terminal; The power switching module includes a first power switching unit, a second power switching unit and an isolation unit; The control end of the first power switching unit is connected to the first node, the input end of the first power switching unit is connected to the first power input end, and the output end of the first power switching unit is connected to the power supply end; The control end of the second power switching unit is connected to the first power input end, the input end of the second power switching unit is connected to the second power input end, and the output end of the second power switching unit is connected to the first node; The control end of the isolation unit is connected to the first power input end, the input end of the isolation unit is connected to the first node, and the output end of the isolation unit is connected to the power supply end; The first power switching unit includes a first transistor and a first pull-down resistor; The gate of the first transistor is connected to the first node, the source of the first transistor is connected to the first power input terminal, and the drain of the first transistor is connected to the power supply terminal; A first end of the first pull-down resistor is connected to the first node, and a second end of the first pull-down resistor is connected to a constant voltage low potential end; The second power switching unit includes a second transistor and a second pull-down resistor: The gate of the second transistor is connected to the first power input terminal, the source of the second transistor is connected to the second power input terminal, and the drain of the second transistor is connected to the first node; A first end of the second pull-down resistor is connected to the first power input terminal, and a second end of the second pull-down resistor is connected to the constant voltage low potential terminal; The isolation unit includes a third transistor; the gate of the third transistor is connected to the first power input terminal, the source of the third transistor is connected to the first node, and the drain of the third transistor is connected to the power supply terminal.

2. The power switching circuit according to claim 1, wherein: The first transistor, the second transistor and the third transistor are P-type thin film transistors.

3. A control method for a power switching circuit, used in the power switching circuit according to claim 1 or 2, characterized in that: include: When the first power input terminal supplies power, the power switching module cuts off the second power input terminal, so that the first power input terminal supplies power to the power supply terminal; When the first power input terminal does not supply power, the power switching module enables the second power input terminal to supply power to the power supply terminal.

4. The control method of the power switching circuit according to claim 3, characterized in that: When the first power input terminal supplies power, the power switching module cuts off the second power input terminal so that the first power input terminal supplies power to the power supply terminal, specifically including: The first power input terminal provides a high level to turn off the second transistor and the third transistor; The potential of the first node is pulled down by the first pull-down resistor to turn on the first transistor, so that the first power input terminal supplies power to the power supply terminal.

5. The control method of the power switching circuit according to claim 4, characterized in that: When the first power input terminal does not supply power, the power switching module enables the second power input terminal to supply power to the power supply terminal, specifically comprising: The first power input terminal provides a low level or a high impedance state, and the second transistor and the third transistor are turned on through the second pull-down resistor; The second power input terminal provides a high level to supply power to the power supply terminal, and pulls up the potential of the first node to turn off the first transistor.

6. A power switching system, characterized in that: comprising a first power supply, a second power supply, a load, and a power switching circuit as claimed in claim 1 or 2; The first power supply is connected to a first power input terminal of the power switching circuit, the second power supply is connected to a second power input terminal of the power switching circuit, and the load is connected to a power supply terminal of the power switching circuit.

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