Power switching circuit and portable device

Abstract

The embodiment of the utility model provides a power supply switching circuit and portable equipment. The power supply switching circuit comprises a first output circuit coupled to a power supply end; the second output circuit is coupled to the power supply end; the connection / disconnection of the first switch unit correspondingly connects / disconnects a first line, coupled to the power supply end, of the second power supply. The connection / disconnection of the second switch unit corresponds to the connection / disconnection of the first switch unit; the switching unit disconnects the second switch unit based on the existence of the first power supply connected with the third input end, so that the first switch unit is disconnected, and the first power supply supplies power to the power supply end through the first output circuit. Through cooperative work of the switching unit, the first switch unit and the second switch unit, when the first power supply exists, power can be supplied preferentially through the first power supply no matter whether the first power supply is larger than the second power supply or not, and power supply switching can be achieved without voltage comparison with the second power supply.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of power supply circuit, and in particular to a power supply switching circuit and a portable device. BACKGROUND

[0002] In many portable devices, power management is an important link, especially in the scenario of switching between the main power supply (such as an external power adapter) and the auxiliary power supply (such as a built-in battery). In the related art, the power switching method usually uses diodes and MOS tubes to realize power switching, ensuring that when the external power supply exists, the external power supply is used preferentially, and the battery is charged at the same time; when the external power supply is disconnected, the power supply is automatically switched to the battery. However, the traditional double-diode switching circuit has some obvious limitations: the traditional double-diode switching circuit can only be applied to the application scenario where the external supply voltage is greater than the battery voltage. If the external power supply voltage is lower than the battery voltage, the diode will not be effectively turned on, resulting in power switching failure. SUMMARY

[0003] In view of the above-mentioned shortcomings of the prior art, the purpose of the present disclosure is to provide a power supply switching circuit and a portable device to solve the problems in the related art.

[0004] The first aspect of the present disclosure provides a power supply switching circuit, comprising:

[0005] A first output circuit comprising a first input end and a diode; the first input end is coupled to a first power supply and coupled to a power supply end through the forwardly arranged diode;

[0006] A second output circuit comprising a second input end and a first switch unit; the second input end is coupled to a second power supply and coupled to the power supply end through the first switch unit; the on / off of the first switch unit corresponds to the on / off of the first circuit in which the second power supply is coupled to the power supply end;

[0007] A second switch unit connected to the first switch unit; the on / off of the second switch unit corresponds to the on / off of the first switch unit;

[0008] A switching unit having one end coupled to the second switch unit and the other end coupled to a third input end; the third input end is coupled to the first power supply; the switching unit disconnects the second switch unit based on the presence of the first power supply connected to the third input end, so that the first switch unit is disconnected, and the first power supply supplies power to the power supply end through the first output circuit; and

[0009] When the first power source connected to the third input end is present, the first switch element turns on the first end and the second end, so that the second switch element is turned off.

[0010] In an embodiment of the first aspect, the switching unit comprises a first switch element; a first end of the first switch element is coupled to a fourth input end and the second switch element via a first resistor; the fourth input end is coupled to the first power source; a second end of the first switch element is grounded; a third end of the first switch element for controlling the first end and the second end is coupled to the third input end.

[0011] Wherein, the first switch element turns on the first end and the second end based on the presence of the first power source coupled to the third input end, so that the second switch element is turned off; and,

[0012] When the first power source coupled to the third input end is not present, the first end and the second end are turned off, so that the second switch element is turned on.

[0013] In an embodiment of the first aspect, the switching unit comprises an N-type triode or an NMOS tube; and,

[0014] The second switch unit comprises an NMOS tube; and,

[0015] The first switch unit comprises at least one PMOS tube.

[0016] In an embodiment of the first aspect, the switching unit further comprises:

[0017] A second resistor, one end of the second resistor is coupled to the third input end, and the other end of the second resistor is coupled to the ground via a third resistor;

[0018] The third end of the first switch element is coupled to a voltage division point between the second resistor and the third resistor.

[0019] In an embodiment of the first aspect, the first switch unit comprises:

[0020] A first MOS tube, the gate of the first MOS tube is coupled to the second switch unit, and the source of the first MOS tube is coupled to the power supply end;

[0021] A second MOS tube, the gate of the second MOS tube is coupled to the second switch unit, and the source of the second MOS tube is coupled to the second input end; the first MOS tube and the second MOS tube share a common drain; the turn-on / off of the first MOS tube and the second MOS tube corresponds to the turn-on / off of the first switch element.

[0022] In an embodiment of the first aspect, the first output circuit comprises:

[0023] a first diode connected in forward direction, with its anode coupled to the first input terminal and its cathode coupled to the power supply terminal.

[0024] In an embodiment of the first aspect, the second output circuit further comprises:

[0025] a fourth resistor coupled between the second input terminal and the second switch unit.

[0026] In an embodiment of the first aspect, further comprising a fifth resistor, one end of which is coupled to the first resistor and the other end of which is grounded; the second switch unit is coupled to a voltage dividing point between the first resistor and the fifth resistor.

[0027] In an embodiment of the first aspect, further comprising:

[0028] a power supply chip comprising a chip input terminal, a chip output terminal and a chip ground terminal; the chip input terminal is coupled to the power supply terminal, the chip output terminal is coupled to an external load, and the chip ground terminal is grounded; the power supply chip is configured to convert and match the input voltage value of the power supply terminal to a preset voltage value of the external load.

[0029] The second aspect of the present disclosure provides a portable device comprising the power supply switching circuit according to any one of the above embodiments.

[0030] The present disclosure has the following advantages: through the cooperative work of the switching unit, the first switch unit and the second switch unit, when the first power supply exists, the first power supply can be used for power supply regardless of whether it is greater than the second power supply, and the power supply switching can be realized without voltage comparison with the second power supply. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 FIG. 1 shows a structure block diagram of a power supply switching circuit according to an embodiment of the present disclosure.

[0032] Figure 2 FIG. 2 shows a circuit schematic diagram of a power supply switching circuit according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0033] The advantages and features of the present disclosure will become apparent from specific examples which are given as thorough and complete descriptions of the present disclosure. It will be obvious to those skilled in the art that various other modifications or changes can be made thereto without departing from the spirit and scope of the present disclosure. It is to be understood that the embodiments and features of the present disclosure can be combined with each other, if not incompatible.

[0034] The embodiments of the present disclosure will be described in detail with reference to the drawings, so that those skilled in the art can easily implement the present disclosure. The present disclosure can be embodied in various ways, and is not limited to the embodiments described herein.

[0035] In the present disclosure, the expressions of "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" mean that the specific features, structures, materials, or characteristics expressed in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. Also, the specific features, structures, materials, or characteristics expressed can be combined in any one or a set of embodiments or examples in a suitable manner. In addition, the different embodiments or examples expressed in the present disclosure and the features of the different embodiments or examples can be combined and integrated by those skilled in the art without contradiction.

[0036] In addition, the terms "first", "second", etc. are used only to indicate the purpose, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In the present disclosure, the meaning of "a set" is two or more, unless specifically limited.

[0037] In order to clearly explain the present disclosure, devices irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar constituent elements throughout the specification.

[0038] Throughout the specification, when it is said that a device is "connected" to another device, it includes not only the case of "direct connection", but also the case of "indirect connection" in which other elements are interposed therebetween. In addition, when it is said that a device "includes" a certain constituent element, unless specifically stated to the contrary, other constituent elements are not excluded, but it means that other constituent elements can also be included.

[0039] Although the terms first, second, etc. can be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first interface and a second interface, etc. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises", "comprising", "includes" and / or "including", when used herein, specify the presence of stated features, steps, operations, elements, modules, items, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, operations, elements, modules, items, components, and / or groups thereof. As used herein, the terms "or" and "and / or" are construed to be inclusive, or mean any one or any combination of the listed items. Thus, "A, B or C" or "A, B and / or C" means any of the following: A; B; C; A and B; A and C; B and C; A, B and C. Exceptions to this definition are only present when items are grouped in conjunction with the phrase "one of X, Y or Z" or "one of X, Y and / or Z" unless otherwise stated.

[0040] The professional terms used herein are used only to refer to specific embodiments and are not intended to limit the present disclosure. The singular form used herein, unless the context clearly indicates otherwise, also includes the plural form. The meaning of "include" used in the specification is to specify a particular characteristic, region, integer, step, operation, element, and / or component, and does not exclude the presence or addition of other characteristics, regions, integers, steps, operations, elements, and / or components.

[0041] Although not differently defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Terms defined in commonly used dictionaries are to be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and should not be interpreted in an idealized or overly formal sense unless clearly defined otherwise.

[0042] With the development of the times, portable devices have gradually become very important in daily life. Common portable devices include smartphones, tablets, laptops, portable music players, portable game consoles, smartwatches, and the like. Portable devices usually rely on two types of power sources for charging or maintaining normal operation, namely a main power source (external power adapter) and a secondary power source (built-in battery). The main power source is usually an external power adapter, which is connected to the portable device through a power cord to provide stable power supply. The secondary power source usually refers to the built-in battery, which is the main power source when the external power source is unavailable. In the related art, when the external power source is present, the device preferentially uses the external power source for power supply to reduce the burden on the battery and prolong the battery life. However, the switching between the main power source and the secondary power source in the related art is usually realized by using a diode, so it can only be applied to the application scenario where the main power source voltage is greater than the secondary power source voltage. If the main power source voltage is lower than the secondary power source voltage, the diode will not be effectively turned on, resulting in power switching failure.

[0043] To solve the above problems, an embodiment of the present disclosure provides a power switching circuit, wherein through the cooperative work of a switching unit and a first switching unit and a second switching unit, when the first power source exists, whether the first power source is greater than the second power source or not, the first power source can be preferentially used for power supply, and the power switching can be realized without voltage comparison with the second power source. Wherein the first power source is the main power source in the above content, and in the following content, the main power source is expressed as the first power source, and the secondary power source is expressed as the second power source.

[0044] In Figure 1 In an embodiment, the power switching circuit includes a first output circuit 100, a second output circuit 200, a second switching unit 300, and a switching unit 400. In Figure 1 In an example, the conduction of the switching unit 400 is associated with the presence or absence of the first power source. The switching unit 400 can control the on-off of the second switching unit 300 according to the presence of the first power source, and the on-off of the second switching unit 300 further controls the on-off of the second output circuit 200, thereby controlling the on-off of the line through which the second power source supplies power to the power supply end via the second output circuit 200. In some embodiments, when the first power source exists, the first power source supplies power to the power supply end through the first output circuit 100, and when the first power source does not exist, the second power source supplies power to the power supply end through the second output circuit 200.

[0045] Specifically, the first output circuit 100 includes a first input end 101; the first power source is coupled to a power supply end via the first input end 101.

[0046] The second output circuit 200 comprises a second input end 201 and a first switch unit 202; the second input end 201 is coupled with a second power supply and is coupled to the power supply end via the first switch unit 202; the on / off of the first switch unit 202 corresponds to the on / off of the first line through which the second power supply is coupled to the power supply end.

[0047] The second switch unit 300 is connected to the first switch unit 202; the on / off of the second switch unit 300 corresponds to the on / off of the first switch unit 202.

[0048] One end of the switch unit 400 is coupled to the second switch unit 300, and the other end is coupled to a third input end 500; the third input end 500 is coupled to the first power supply; the switch unit 400 disconnects the second switch unit 300 based on the presence of the first power supply connected to the third input end 500, so that the first switch unit 202 is disconnected, and the first power supply supplies power to the power supply end via the first output circuit 100.

[0049] When the first power supply connected to the third input end 500 is absent, the second switch unit 300 is turned on, so that the first switch unit 202 is turned on, and the second power supply supplies power to the power supply end via the second output circuit 200.

[0050] Specifically, when the switch unit 400 detects the presence of the first power supply, the second switch unit 300 is disconnected. The second switch unit 300 controls the on / off of the first switch unit 202, so that the first switch unit 202 is also in the off state at this time, preventing the second power supply from supplying power to the power supply end. At this time, the current can only flow from the first power supply to the power supply end through the first diode D1, and the system is powered by the first power supply. When the switch unit 400 cannot detect the presence of the first power supply, the second switch unit 300 is turned on. At this time, the first switch unit 202 is also in the on state, thereby establishing a current path from the second power supply to the power supply end. At this time, the power supply can be switched from the first power supply to the second power supply, thereby ensuring the continuous operation of the system.

[0051] In some embodiments, one end of the first output circuit 100 is connected to the power supply end via a forwardly arranged first diode D1. The forwardly arranged first diode D1 ensures that the current can only flow from the first power supply to the power supply end in one direction, preventing reverse current. Specifically, when the first power supply is working normally, the diode is in a forward conduction state, allowing current to flow from the first power supply to the power supply end through the first diode D1 to power the load device. When the first power supply is not present, the reverse blocking property of the first diode D1 can prevent current from flowing from the second power supply to the first input end through the first output circuit 100, thereby avoiding the first input end from being electrified, effectively isolating the mutual influence between the two output circuits, and improving the reliability and safety of the entire power switching circuit.

[0052] Optionally, in Figure 2 In an example, the switching unit 400 includes a first switch element Q1; a first end of the first switch element Q1 is coupled to a fourth input end 700 and the second switching unit 300 via a first resistor R1; the fourth input end 700 is coupled to the first power supply; a second end of the first switch element Q1 is grounded; and a third end of the first switch element Q1 for controlling the first end and the second end is coupled to the third input end 500.

[0053] In an example, the first switch element Q1 is turned on based on the presence of the first power supply coupled to the third input end 500, so as to turn off the second switching unit 300. And the first switch element Q1 is turned off based on the absence of the first power supply coupled to the third input end 500, so as to turn on the second switching unit 300.

[0054] Specifically, in Figure 2In an example, the second switch unit 300 is an NMOS transistor, the gate of which is coupled between the first resistor R1 and the first terminal of the first switch element Q1, the drain of which is connected to the first switch element Q1, and the source of which is grounded. The first switch element Q1 is an NPN transistor, the base of which is coupled to the first power source via the third input terminal 500, the emitter of which is grounded, and the collector of which is coupled to the fourth input terminal 700 via the first resistor R1, and the second switch unit 300 is coupled between the collector of the first switch element Q1 and the first resistor R1. When the first power source is present, a high level signal is output to the third terminal (base) of the first switch element Q1, and because the third terminal (base) receives the high level signal, the voltage relationship between the second terminal and the third terminal of the first switch element Q1 causes the transistor to be turned on. The first terminal and the second terminal of the first switch element Q1 are thus turned on, and the voltage of the first terminal of the first switch element Q1 is pulled low by the second terminal which is grounded, so that the second switch unit 300 receives a low level. Because the second switch unit 300 is an NMOS transistor, it is turned on for a high level, and thus the second switch unit 300 is turned off.

[0055] Conversely, when the first power source is not present, a low level signal is output to the base of the first switch element Q1, and the first switch element Q1 is turned off accordingly. The second power source is transmitted to the gate of the second switch unit 300 via the fourth input terminal 700 through the first resistor R1, so that the gate receives a high level signal, and the high level signal causes the second switch unit 300 to be turned on.

[0056] In some embodiments, the first switch element Q1 can also be implemented as an NMOS transistor, the gate of which is coupled to the third input terminal 500, the source of which is grounded, and the drain of which is coupled to the fourth input terminal 700 via the first resistor R1, and the gate of the second switch unit 300 is coupled between the first resistor R1 and the drain of the first switch element Q1. When the first power source is present, a high level signal is output to the gate, and the first switch element Q1 which is an NMOS transistor is turned on. The fourth input terminal 700 is grounded via the first switch element Q1, so that the gate of the second switch element receives a low level signal, and the second switch unit 300 is turned off. When the first power source is not present, a low level signal is output to the gate of the first switch element Q1, and the first switch element Q1 is turned off. The second power source is output to the gate of the second switch unit 300 via the fourth input terminal 700 to a high level signal, and the second switch unit 300 is turned on.

[0057] Optionally, to match the logic of switching the second power supply based on the presence or absence of the first power source, the switching unit 400 includes an N-type transistor or an NMOS transistor, the second switch unit 300 includes an NMOS transistor, and the first switch unit 202 includes at least one PMOS transistor.

[0058] In particular, the switching unit 400 comprises an N-type transistor or NMOS transistor, when it is an N-type transistor, which is turned on when a high level is received at the base (i.e. one end coupled to the third input 500) and turned off when a low level is received. When the first power source exists (high level), the first power source sends a high level to the switching unit 400 through the third input 500, the switching unit 400 is turned on, and vice versa. The NMOS transistor is turned on when a high level is received at the gate (i.e. Vgs > threshold value) and turned off when a low level is received. The base of the N-type transistor or the gate of the NMOS transistor in the switching unit 400 is coupled to the third input 500, so that the switching unit 400 can be turned on or off according to the presence or absence of the first power source. The second switch unit 300 is implemented as an NMOS transistor, so it is also turned on for a high level. The second switch unit 300 is coupled between the fourth input 700 and the switching unit 400. When the switching unit 400 is turned on, the second power source is grounded via the fourth input 700 and the switching unit 400, so the second switch unit 300 receives a low level and is turned off; vice versa, if the switching unit 400 is turned off, the second power source applies a high level to the second switch unit 300 via the fourth input 700, so that the second switch unit 300 is turned on. The first switch unit 202 comprises at least one PMOS transistor. When the second switch unit 300 is turned on, the first switch unit 202 is grounded, so it receives a low level and is turned off, which corresponds to turning off the second output circuit 200.

[0059] Optionally, in Figure 2 In an embodiment, the switching unit 400 further comprises:

[0060] A second resistor R2, one end of the second resistor R2 is coupled to the third input 500, and the other end of the second resistor R2 is coupled to ground via a third resistor R3.

[0061] The third end of the first switch element Q1 is coupled to a voltage division point between the second resistor R2 and the third resistor R3.

[0062] In particular, the second resistor R2 and the third resistor R3 form a resistor voltage division network, which divides the high level signal and transmits it to the gate of the first switch element Q1. It ensures that the gate voltage of the first switch element Q1 is within a safe range. The second resistor R2 is connected in parallel with a first capacitor C1. An RC circuit is formed, which can prevent transient impact to some extent during power switching and protect other elements in the circuit.

[0063] Optionally, inFigure 2 In some embodiments, the first switch unit 202 comprises:

[0064] a first MOS transistor Q2, a gate of the first MOS transistor Q2 being coupled to the second switch unit 300, a source of the first MOS transistor Q2 being coupled to the power supply end;

[0065] a second MOS transistor Q3, a gate of the second MOS transistor Q3 being coupled to the second switch unit 300, a source of the second MOS transistor Q3 being coupled to the second input end 201; the first MOS transistor Q2 and the second MOS transistor Q3 being coupled in common drain; the turn-on / off of the first MOS transistor Q2 and the second MOS transistor Q3 corresponding to the turn-on / off of the first switch unit 202.

[0066] Optionally, the second output circuit 200 further comprises a fourth resistor R4 coupled between the second input end 201 and the second switch unit 300. Specifically, one end of the fourth resistor R4 is coupled to the second input end 201 and the source of the first MOS transistor Q2, and the other end of the fourth resistor R4 is coupled to the gate of the first MOS transistor Q2.

[0067] Specifically, in some embodiments, the first MOS transistor Q2 and the second MOS transistor Q3 are both PMOS transistors, thus being turned on at low level, the source of the first MOS transistor Q2 is coupled to the second power supply via the second input end 201, and the gate of the first MOS transistor Q2 is grounded via the second switch unit 300, thus the first MOS transistor Q2 receives low level when the second switch unit 300 is turned on.

[0068] Specifically, when the first power supply does not exist, Q1 is turned off, corresponding to the second switch unit 300 being turned on. The gate voltage of the first MOS transistor Q2 and the second MOS transistor Q3 is pulled down by the turn-on of the second switch unit 300, and since the source of the first MOS transistor Q2 is coupled to the second power supply via the second input end 201, the gate voltage of the first MOS transistor Q2 is less than the source voltage, thus the first MOS transistor Q2 is turned on. Since the first MOS transistor Q2 is coupled in common drain with the second MOS transistor Q3, when the first MOS transistor Q2 is turned on, the second power supply reaches the source of the second MOS transistor Q3 via the body diode of the second MOS transistor Q3 after passing through the first MOS transistor Q2, thus the gate voltage of the second MOS transistor Q3 is also less than the source voltage, thus the second MOS transistor Q3 is turned on. In this way, the first MOS transistor Q2 and the second MOS transistor Q3 are both turned on, the second output circuit 200 is turned on, thus the second power supply supplies power to the power supply end through the second output circuit 200.

[0069] When the first switch unit 202 exists, the first switch element Q1 is turned on, so that the second switch unit 300 is turned off, thus the second power supply forms the gate voltage of the first MOS tube Q2 via the second input terminal 201 and a fourth resistor R4, the source of the first MOS tube Q2 is coupled to the second power supply via the second input terminal 201, thus the voltage difference between the source and the gate of the first MOS tube Q2 is not enough to turn on the first MOS tube Q2; the gate voltage of the second MOS tube Q3 is the same as that of the first MOS tube Q2; the source of the second MOS tube Q3 is coupled to the first power supply via the first diode D1, thus the voltage difference between the source and the gate of the second MOS tube Q3 is also not enough to turn on the second MOS tube Q3. Therefore, when the first power supply exists, the second output circuit 200 is turned off, and at this time, the first power supply supplies power via the first output circuit 100.

[0070] Optionally, when the first power supply exists, the body diode of the second MOS tube Q3 is reversed relative to the first input terminal 101, for protecting the first MOS tube Q2 from the first power supply flowing through the body diode of the first MOS tube Q2 to the second input terminal 201.

[0071] Optionally, a fifth resistor R5 is further included, one end of which is coupled to the first resistor R1 and the other end is grounded, and a voltage dividing network is formed between the first resistor R1 and the fifth resistor R5; the second switch unit 300 is coupled to the voltage dividing point between the first resistor R1 and the fifth resistor R5.

[0072] Specifically, the fifth resistor R5 is used for protecting the second switch unit 300 from the voltage flowing to the second switch unit 300 being too large.

[0073] Optionally, in Figure 2 In an embodiment, the power supply switching circuit can further include:

[0074] a power supply chip 600 including a chip input terminal 601, a chip output terminal 602 and a chip ground terminal 603; the chip input terminal 601 is coupled to the power supply terminal, the chip output terminal 602 is coupled to an external load, and the chip ground terminal 603 is grounded; the power supply chip 600 is used for converting and matching the input voltage value of the power supply terminal to the preset voltage value of the external load (for example, converting to 3.3V output), and in some embodiments, a second capacitor C2 is further arranged between the power supply chip 600 and the power supply terminal.

[0075] In another embodiment of the present disclosure, a portable device is provided, which includes the power supply switching circuit in any of the above embodiments.

[0076] The above embodiments are only illustrative of the principles of the present disclosure and its effects, and are not intended to limit the present disclosure. Any modification or change made by any person skilled in the art without departing from the spirit and scope of the present disclosure shall be covered by the protection scope of the present disclosure.

Claims

1. A power switching circuit, characterized by, The application relates to a power supply circuit. The first output circuit comprises a first input terminal; a first power supply is coupled to a power supply terminal via the first input terminal; The second output circuit comprises a second input terminal and a first switch unit; The second input terminal is coupled to a second power supply and is coupled to the power supply terminal via the first switch unit; The on / off of the first switch unit corresponds to the on / off of a first line through which the second power supply is coupled to the power supply terminal; A second switch unit is connected to the first switch unit; The on / off of the second switch unit corresponds to the on / off of the first switch unit; A switching unit is coupled to the second switch unit at one end and is coupled to a third input terminal at the other end; the third input terminal is coupled to the first power supply; the switching unit is based on the presence of the first power supply connected to the third input terminal to disconnect the second switch unit, so that the first switch unit is disconnected, and the first power supply supplies power to the power supply terminal via the first output circuit; When the first power supply connected to the third input terminal is absent, the second switch unit is turned on, so that the first switch unit is turned on, and the second power supply supplies power to the power supply terminal via the second output circuit. The switching unit comprises a first switch element; a first end of the first switch element is coupled to a fourth input terminal and the second switch unit via a first resistor; 2. The power switching circuit of claim 1, wherein The fourth input terminal is coupled to the first power supply; a second end of the first switch element is grounded, and a third end of the first switch element for controlling the on / off of the first end and the second end is coupled to the third input terminal; When the first power supply connected to the third input terminal is present, the first end and the second end of the first switch element are turned on, so that the second switch unit is turned off; and When the first power supply connected to the third input terminal is absent, the first end and the second end of the first switch element are turned off, so that the second switch unit is turned on. The switching unit comprises an N-type triode or an NMOS tube; and 3. The power switching circuit of claim 1, wherein, The second switch unit comprises an NMOS tube; and The first switch unit comprises at least one PMOS tube. The switching unit further comprises:

4. The power switching circuit of claim 2, wherein, A second resistor, one end of the second resistor is coupled to the third input terminal, and the other end of the second resistor is coupled to the ground via a third resistor; The third end of the first switch element is coupled to a voltage division point between the second resistor and the third resistor. The first switch unit comprises:

5. The power switching circuit of claim 1, wherein, A first MOS tube, a gate of the first MOS tube is coupled to the second switch unit, and a source of the first MOS tube is coupled to the power supply terminal; A second MOS tube, a gate of the second MOS tube is coupled to the second switch unit, and a source of the second MOS tube is coupled to the second input terminal; the first MOS tube and the second MOS tube share a drain; the on / off of the first MOS tube and the second MOS tube corresponds to the on / off of the first switch unit. The first output circuit comprises:

6. The power switching circuit of claim 1, wherein, A first diode arranged in a forward direction, a positive electrode of the first diode is coupled to the first input terminal, and a negative electrode of the first diode is coupled to the power supply terminal. ​ 7. The power switching circuit of claim 1, wherein, The second output circuit further comprises: a fourth resistor coupled between the second input end and the second switch unit.

8. The power switching circuit of claim 2, wherein, Further comprising a fifth resistor, one end of which is coupled to the first resistor and the other end of which is grounded; the second switch unit is coupled to a voltage division point between the first resistor and the fifth resistor.

9. The power switching circuit of claim 1, wherein, Further comprising: a power supply chip comprising a chip input end, a chip output end and a chip ground end; the chip input end is coupled to the power supply end, the chip output end is coupled to an external load, and the chip ground end is grounded; the power supply chip is used to convert and match the input voltage value of the power supply end to a preset voltage value of the external load.

10. A portable device, characterized by The power supply switching circuit comprises the power supply switching circuit according to any one of claims 1-9.

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