Load multi-power supply switching circuit and device

Abstract

The invention discloses a load multi-power supply switching circuit and device, and relates to the technical field of load power supply control. The circuit comprises a controller, a first power supply, a first switch module, a second power supply, a second switch module and a third switch module, wherein the first power supply is connected to a load through the first switch module and the third switch module; the second power supply is connected to the load through the second switch module and the third switch module; the controller controls the first switch module and the third switch module to be switched on based on the power-on instruction, and the first power supply is used for supplying power to the load; the controller also obtains a voltage value U of the first charging loop so as to judge whether the first power supply meets the power utilization requirement of the load or not; and if not, the controller controls the first switch module to be switched off and the second switch module to be switched on, and the second power supply is used for supplying power to the load. According to the invention, the use of components is reduced, so that the cost and the occupied volume are reduced.

Description

Technical Field

[0001] The present application relates to the technical field of load power supply control, and in particular to a load multi-power supply switching circuit and device. Background Art

[0002] At present, in some application scenarios that require high reliability and uninterrupted power supply, such as data centers, medical equipment, industrial automation control systems, etc., the requirements for power management are increasing. When facing power failure or insufficient power supply capacity, the traditional single power supply system often cannot ensure the continuous and stable operation of the load equipment, which may lead to serious consequences such as data loss, equipment damage and even system paralysis.

[0003] In order to solve the above problems, the industry has gradually developed a variety of power supply redundancy and switching technologies, using multiple power supplies in load power supply. Each power supply is connected to the power supply end of the load through a corresponding path, and cooperates with the controller to control the power supply switching to ensure the continuous and stable operation of the load.

[0004] However, in this mode, since each power supply is connected to the load through an independent path, this simplifies the controller's switching control logic for the power supply, but each independent path requires the design of corresponding components. The system requires more components, has the disadvantages of high cost and large volume. Summary of the invention

[0005] In order to solve the problem in the prior art that when multiple power supplies are used to power a load, the system requires a large number of components, has high costs, and occupies a large volume, the present application provides a load multi-power supply switching circuit and device.

[0006] In a first aspect, the present application provides a load multi-power supply switching circuit, which adopts the following technical solution: A load multi-power supply switching circuit comprises a controller, a first power supply, a first switch module, a second power supply, a second switch module and a third switch module; the input end of the third switch module comprises a positive input end and a negative input end, and the output end comprises a positive output end and a negative output end; Wherein, the positive electrode of the first power supply is connected to the positive input terminal through the first switch module, and the negative electrode is connected to the negative input terminal through the first switch module; the positive electrode of the second power supply is connected to the positive input terminal through the second switch module, and the negative electrode is connected to the negative input terminal through the second switch module; the positive output terminal and the negative output terminal are connected to the positive electrode and the negative electrode of the load respectively; the controller is connected to the first switch module, the second switch module and the third switch module respectively; The controller is used to control the first switch module and the third switch module to be turned on based on the power-on instruction, so that the first power supply, the first switch module, the third switch module and the load constitute a first charging circuit, and the first power supply supplies power to the load; The controller is further used to obtain a voltage value U of the first charging circuit, and determine whether the first power supply meets the power demand of the load based on the voltage value U; if not, the controller controls the first switch module to be disconnected and the second switch module to be turned on, and the second power supply, the second switch module, the third switch module and the load constitute a second charging circuit, and the second power supply supplies power to the load.

[0007] By adopting the above technical solution, the first power supply is used as the default power supply source of the load, and the second power supply is used as the backup power supply of the load. The controller first controls the first power supply to supply power to the load, and detects the voltage value U in real time. When it is judged according to the voltage value U that the voltage fluctuation in the first charging circuit is large or the voltage is too low, it means that the first power supply is faulty or the power supply capacity is insufficient. Then the load power supply mode is switched and the second power supply is used to ensure continuous and stable operation of the load. In the circuit structure, by sharing a third switch module, when switching the power supply, it is only necessary to disconnect the first switch module and close the second switch module. The electric energy provided by the second power supply can still flow to the load through the third switch module, reducing the use of components, thereby reducing costs and volume occupancy, and to a certain extent speeding up the switching speed of the power supply.

[0008] In a specific implementation scheme, the third switch module includes a relay K1, a switch tube Q1 and a resistor R1; the relay K1 includes a normally open switch; Among them, the normally open switch of the relay K1 is connected between the positive input end and the positive output end; the switch tube Q1 is connected between the positive input end and the positive output end, and the control end of the switch tube Q1 is connected to the controller through the resistor R1.

[0009] By adopting the above technical solution and the specific design of the third switch module, the characteristics of the relay being able to withstand a large current and the switch tube being able to respond quickly are combined, which not only improves the safety of the circuit but also facilitates the subsequent rapid switching of the power supply.

[0010] In a specific implementation scheme, the controller is used to control the relay K1 to close the normally open switch based on the power-on instruction; then the positive electrode of the first power supply is connected to the positive electrode of the load through the first switch module and the normally open switch in sequence, so that the first power supply supplies power to the load; The controller is also used to drive the switch tube Q1 to turn on through the resistor R1 after controlling the normally open switch to close and wait for a first preset time, and to disconnect the normally open switch by controlling the relay K1; then the positive electrode of the first power supply is connected to the positive electrode of the load through the first switch module and the switch tube Q1 in sequence, so as to keep the first power supply supplying power to the load.

[0011] In a specific implementation scheme, the second switch module includes a relay K2, a fuse F1, a switch tube Q2, a resistor R2 and a diode D1; the relay K2 includes a contact a, a contact b, a contact c and a contact d; Among them, the first end of the fuse F1 is connected to the negative input end, and the second end is connected to the first end of the switch tube Q2; the second end of the switch tube Q2 is connected to the contact c; the contact d is connected to the negative electrode of the second power supply; the control end of the switch tube Q2 is connected to the controller through the resistor R2; the contact a is connected to the positive electrode of the second power supply, and the contact b is connected to the positive input end through the diode D1.

[0012] By adopting the above technical solution and designing the second switch module, when it is necessary to switch to the second power supply, the corresponding contacts in the relay K2 are connected, so that the positive and negative poles of the second power supply can be connected to the positive and negative input terminals, so that the second power supply can supply power to the load. At the same time, the diode D1 also plays a role in preventing backflow, further improving the safety of the circuit.

[0013] In a specific feasible implementation scheme, the controller is used to drive the switch tube Q2 to close through the resistor R2; and is also used to connect the contact a and the contact b, and the contact c and the contact d respectively by controlling the relay K2; then the positive electrode of the second power supply is connected to the positive input terminal through the contact a and the contact b in sequence, and the negative electrode of the second power supply is connected to the negative input terminal through the contact d, the contact c, the switch tube Q2 and the fuse F1 in sequence; the second power supply supplies power to the load.

[0014] In a specific implementation scheme, the load multi-power supply switching circuit further includes a first current feedback module; the first current feedback module includes a resistor R3, a resistor R4, a resistor R5, and an optical coupler H1; the optical coupler H1 includes a light-emitting diode D3 and a phototransistor Q3; the relay K2 also includes a contact e; Wherein, the contact e is connected to the positive electrode of the light-emitting diode D3 through the resistor R3, and the negative electrode of the light-emitting diode D3 is connected to the positive input terminal through the diode D2; the two ends of the resistor R4 are respectively connected to the positive electrode and the negative electrode of the light-emitting diode D3; the input end of the phototransistor Q3 is connected to the voltage VCC, and the output end is connected to the controller, and the output end of the phototransistor Q3 is also grounded through the resistor R5; The controller is used to control the relay K2 to connect the contact c and the contact e after controlling the first switch module and the third switch module to be turned on, and also drive the switch tube Q2 to be turned on through the resistor R2; then the controller obtains the current status of the first charging circuit through the first current feedback module.

[0015] By adopting the above technical solution and setting the first current feedback module, a feedback path for the loop current in the third switch module is constructed on the basis of the second switch module, thereby further saving the use of components and reducing costs.

[0016] In a specific implementation scheme, the load multi-power supply switching circuit further includes a current transformer; the current transformer is connected between the negative output terminal and the negative electrode of the load, and the current transformer is also connected to the controller; The controller is used to detect the required current I of the load through the current transformer when the first power supply is supplying power to the load; and based on the required current I, control the output of the second power supply when the second power supply is supplying power to the load.

[0017] By adopting the above technical solution, since the second power supply can include power supplies of multiple different specifications, when the first power supply is used to power the load, the controller can obtain the required current I of the load in advance, so as to accurately control the output of the second power supply when the power supply is switched.

[0018] In a specific implementation scheme, the third switch module further includes a varistor RV1; two ends of the varistor RV1 are respectively connected to the positive input end and the negative input end.

[0019] By adopting the above technical solution and using the varistor RV1, an overvoltage protection function is achieved.

[0020] In a second aspect, the present application provides a load multi-power supply switching device, the device comprising the load multi-power supply switching circuit in the above-mentioned first aspect or any possible implementation scheme of the first aspect.

[0021] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages: The first power supply is used as the default power supply source of the load, and the second power supply is used as the backup power supply of the load. The controller first controls the first power supply to supply power to the load, and detects the voltage value U in real time. When it is judged according to the voltage value U that the voltage fluctuation in the first charging circuit is large or the voltage is too low, it means that the first power supply is faulty or the power supply capacity is insufficient. It is determined that the first power supply cannot meet the power demand of the load, so the load power supply mode is switched and the second power supply is used to ensure the continuous and stable operation of the load. In the circuit structure, by sharing a third switch module, when switching the power supply, it is only necessary to disconnect the first switch module and close the second switch module. The electric energy provided by the second power supply can still flow to the load through the third switch module, reducing the use of components, thereby reducing costs and volume occupancy, and speeding up the switching speed of the power supply to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall structure of a load multi-power supply switching circuit in an embodiment of the present application; Figure 2 This is a specific circuit structure diagram of a load multi-power supply switching circuit in an embodiment of the present application; Figure 3 It is another specific circuit structure schematic diagram of the load multi-power supply switching circuit in the embodiment of the present application.

[0023] Description of reference numerals: 1. Controller; 2. First power supply; 3. First switch module; 4. Second power supply; 5. Second switch module; 6. Third switch module; 7. Voltage detection module; 8. First current feedback module; 9. Current transformer. DETAILED DESCRIPTION

[0024] In order to enable technicians in this field to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this application, not all of the embodiments.

[0025] In the description of the embodiments of the present application, words such as "for example" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "for example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "for example" or "for example" is intended to present related concepts in a specific way.

[0026] The present application embodiment provides a load multi-power supply switching circuit, such as Figure 1As shown, the control circuit includes a controller 1, a first power supply 2, a first switch module 3, a second power supply 4, a second switch module 5 and a third switch module 6; the input end of the third switch module 6 includes a positive input end and a negative input end, and the output end includes a positive output end and a negative output end; Wherein, the positive electrode of the first power supply 2 is connected to the positive input terminal through the first switch module 3, and the negative electrode is connected to the negative input terminal through the first switch module 3; the positive electrode of the second power supply 4 is connected to the positive input terminal through the second switch module 5, and the negative electrode is connected to the negative input terminal through the second switch module 5; the positive output terminal and the negative output terminal are connected to the positive electrode and the negative electrode of the load respectively; the controller 1 is connected to the first switch module 3, the second switch module 5 and the third switch module 6 respectively; The controller 1 is used to control the first switch module 3 and the third switch module 6 to be turned on based on the power-on instruction, so that the first power supply 2, the first switch module 3, the third switch module 6 and the load constitute a first charging circuit, and the first power supply 2 supplies power to the load; The controller 1 is further used to obtain the voltage value U of the first charging circuit, and judge whether the first power supply 2 meets the power demand of the load based on the voltage value U; if not, the controller 1 controls the first switch module 3 to be disconnected and the second switch module 5 to be turned on, and the second power supply 4, the second switch module 5, the third switch module 6 and the load constitute a second charging circuit, and the second power supply 4 supplies power to the load.

[0027] In a possible implementation, Figure 2 or Figure 3 As shown, the switching circuit also includes a voltage detection module 7, which is connected to the line between the output end of the third switch module 6 and the load, and the voltage detection module 7 is also connected to the controller 1; the controller 1 obtains the voltage value U of the first charging circuit through the voltage detection module 7.

[0028] In a possible implementation, Figure 2 or Figure 3 As shown, the first switch module 3 includes a switch S1 connected between the positive electrode of the first power supply 2 and the positive input terminal, and a switch S2 connected between the negative electrode of the first power supply 2 and the negative input terminal; the controller controls the on-off of the first switch module 3 by controlling the switch S1 and the switch S2.

[0029] In this way, the first power supply 2 is used as the default power supply source of the load, and the second power supply 4 is used as the backup power supply of the load. The controller 1 first controls the first power supply 2 to supply power to the load, and detects the voltage value U in real time. When it is judged according to the voltage value U that the voltage fluctuation in the first charging circuit is large, or the voltage is too low, it means that the first power supply 2 is faulty or the power supply capacity is insufficient. It is determined that the first power supply 2 cannot meet the power demand of the load, so the load power supply mode is switched, and the second power supply 4 is used for power supply to ensure the continuous and stable operation of the load. In the circuit structure, by sharing a third switch module 6, when switching the power supply, it is only necessary to disconnect the first switch module 3 and close the second switch module 5. The electric energy provided by the second power supply 4 can still flow to the load through the third switch module 6, reducing the use of components, thereby reducing costs and volume occupancy, and speeding up the switching speed of the power supply to a certain extent.

[0030] In a possible implementation, Figure 2 As shown, the third switch module 6 includes a relay K1, a switch tube Q1 and a resistor R1; the relay K1 includes a normally open switch; Among them, the normally open switch of the relay K1 is connected between the positive input end and the positive output end; the switch tube Q1 is connected between the positive input end and the positive output end, and the control end of the switch tube Q1 is connected to the controller 1 through the resistor R1.

[0031] The working process of this part of the circuit is described in detail below: The controller 1 is used to control the relay K1 to close the normally open switch based on the power-on instruction; the positive electrode of the first power supply 2 is connected to the positive electrode of the load through the first switch module 3 and the normally open switch in sequence, so that the first power supply 2 supplies power to the load; The controller 1 is also used to drive the switch tube Q1 to turn on through the resistor R1 after controlling the normally open switch to close and wait for a first preset time, and to disconnect the normally open switch by controlling the relay K1; then the positive electrode of the first power supply 2 is connected to the positive electrode of the load through the first switch module 3 and the switch tube Q1 in turn, so as to keep the first power supply 2 supplying power to the load.

[0032] It should be noted that at the moment of power-on, due to the large current in the circuit, if the load is powered through the path where the switch tube Q1 is located at this time, the switch tube may be damaged. Therefore, after receiving the power-on instruction, the controller 1 can first control the relay K1 to close the normally open switch, so that the current at the positive electrode of the first power supply 2 passes through the normally open switch of the relay K1 to supply power to the load; after the first preset time, the current tends to stabilize, and at this time, the normally open switch is disconnected by controlling the relay K1, and the switch tube Q1 is driven to turn on, so that the current at the positive electrode of the first power supply 2 passes through the switch tube Q1 to supply power to the load.

[0033] The technicians in this field can define the value of the first preset time according to the specifications and performance of the components. The purpose of waiting for the first preset time is to stabilize the current of the charging circuit and avoid damage to the switch tube Q1 caused by the large current shock at the moment of power-on. The reason for switching to the switch tube Q1 after waiting for the first preset time is that the switching speed of the switch tube is faster than that of the relay, and it has a faster response speed when the third switch module 6 is subsequently controlled to be disconnected.

[0034] Understandably, Figure 2 The connection method of the switch tube Q1 and the resistor R1 in the above description can be used when the first power source 2 is a direct current. If the first power source 2 is an alternating current, then Figure 3 Connections shown: Specifically, refer to Figure 3 , the third switch module 6 further includes a rectifier bridge element, such as an element of model KB610, which includes a positive pin, a negative pin and two AC pins; Among them, the normally open switch of relay K1 is still connected between the positive input terminal and the positive output terminal; the control end of the switch tube Q1 is still connected to the controller 1 through the resistor R1; one AC pin of the rectifier bridge element is connected to the positive input terminal, and the other AC pin is connected to the negative input terminal; the positive pin and the negative pin of the rectifier bridge element are respectively connected to the two ends of the switch tube Q1.

[0035] exist Figure 3 In this connection mode, the circuit works as follows: The controller 1 is used to control the relay K1 to close the normally open switch based on the power-on instruction; the positive electrode of the first power supply 2 is connected to the positive electrode of the load through the first switch module 3 and the normally open switch in sequence, so that the first power supply 2 supplies power to the load; The controller 1 is also used to drive the switch tube Q1 to turn on through the resistor R1 after controlling the normally open switch to close and waiting for a first preset time, so that the two AC pins of the rectifier bridge element are connected, and the controller 1 also controls the relay K1 to disconnect the normally open switch; the positive electrode of the first power supply 2 is connected to the positive electrode of the load through the first switch module 3 and the rectifier bridge element in turn, so as to keep the first power supply 2 supplying power to the load.

[0036] Therefore, through the specific design of the third switch module 6, the characteristics of the relay being able to withstand a large current and the switch tube being able to respond quickly are combined, which not only improves the safety of the circuit but also facilitates the subsequent rapid switching of the power supply.

[0037] In one possible implementation, refer to Figure 2 or Figure 3 The third switch module 6 further includes a varistor RV1; two ends of the varistor RV1 are respectively connected to the positive input end and the negative input end.

[0038] An overvoltage protection function is achieved by means of the varistor RV1.

[0039] In one possible implementation, continue to refer to Figure 2 or Figure 3 , the second switch module 5 includes a relay K2, a fuse F1, a switch tube Q2, a resistor R2 and a diode D1; the relay K2 includes a contact a, a contact b, a contact c and a contact d; Among them, the first end of the fuse F1 is connected to the negative input end, and the second end is connected to the first end of the switch tube Q2; the second end of the switch tube Q2 is connected to the contact c; the contact d is connected to the negative electrode of the second power supply 4; the control end of the switch tube Q2 is connected to the controller 1 through the resistor R2; the contact a is connected to the positive electrode of the second power supply 4, and the contact b is connected to the positive input end through the diode D1.

[0040] The working process of this part of the circuit is described in detail below: The controller 1 is used to drive the switch tube Q2 to close through the resistor R2; it is also used to control the relay K2 to connect the contact a and the contact b, and the contact c and the contact d respectively; then the positive pole of the second power supply 4 is connected to the positive input terminal through the contact a and the contact b in sequence, and the negative pole of the second power supply 4 is connected to the negative input terminal through the contact d, the contact c, the switch tube Q2 and the fuse F1 in sequence; the second power supply 4 supplies power to the load.

[0041] In a possible implementation, Figure 2 or Figure 3 As shown, the relay K2 further includes a contact f, and the contact f is connected to the positive electrode of the second power supply 4. When the second power supply 4 is not needed to supply power to the load, the contact a and the contact f can be connected.

[0042] Therefore, through the design of the second switch module 5, when it is necessary to switch to the second power supply 4 for power supply, the corresponding contacts in the relay K2 are connected, so that the positive and negative poles of the second power supply 4 can be connected to the positive and negative input terminals, so that the second power supply 4 can supply power to the load. At the same time, the diode D1 also plays a role in preventing backflow, further improving the safety of the circuit.

[0043] In a possible implementation manner, the load multi-power supply switching circuit further includes a first current feedback module 8; Figure 2 or Figure 3 As shown, the first current feedback module 8 includes a resistor R3, a resistor R4, a resistor R5, and an optical coupler H1; the optical coupler H1 includes a light emitting diode D3 and a phototransistor Q3; the relay K2 also includes a contact e; The contact e is connected to the positive electrode of the light-emitting diode D3 through the resistor R3, and the negative electrode of the light-emitting diode D3 is connected to the positive input terminal through the diode D2; the two ends of the resistor R4 are respectively connected to the positive electrode and the negative electrode of the light-emitting diode D3; The input end of the phototransistor Q3 is connected to the voltage VCC, and the output end is connected to the controller 1. The output end of the phototransistor Q3 is also grounded through the resistor R5. The controller 1 is used to control the relay K2 to connect the contact c and the contact e after controlling the first switch module 3 and the third switch module 6 to be turned on, and also drive the switch tube Q2 to be turned on through the resistor R2; then the controller 1 obtains the current status of the first charging circuit through the first current feedback module 8.

[0044] Those skilled in the art can understand that when there is current in the first charging circuit, the current can form a loop through the fuse F1, the switch tube Q2, the contact c, the contact e, the resistor R3, the diode D3 and the diode D2, so that the controller 1 can sense the current condition of the first charging circuit.

[0045] For example, the controller 1 can determine whether the conduction control of the third switch module 6 is normal according to the obtained current condition; if there is current in the first charging circuit, it means that the conduction control of the third switch module 6 is normal; if there is no current in the first charging circuit, it means that there is an abnormality in the conduction control of the third switch module 6, and the third switch module 6 is not normally turned on. Of course, other problems can also be analyzed according to the current condition, and those skilled in the art can set it by themselves.

[0046] It can be understood by those skilled in the art that the resistor R4 is provided to prevent the controller 1 from sensing the tiny current in the circuit, avoid misjudgment, and reduce the interference of the tiny current. For example, the resistance value of the resistor R3 can be 100K, and the resistance value of the resistor R4 can be 1K. In addition, the diode D2 plays a role in preventing backflow.

[0047] Therefore, by setting the first current feedback module 8, on the basis of the second switch module 5, a feedback path for the loop current in the third switch module 6 is constructed, which further saves the use of components and reduces costs.

[0048] In a possible implementation, Figure 2 or Figure 3 As shown, the load multi-power supply switching circuit also includes a current transformer 9; the current transformer 9 is connected between the negative output terminal and the negative pole of the load, and the current transformer 9 is also connected to the controller 1; The controller 1 is used to detect the load demand current I through the current transformer 9 when the first power supply 2 supplies power to the load; and based on the demand current I, when the second power supply 4 is used to supply power to the load, control the output of the second power supply 4, that is, control the output current and output voltage of the second power supply 4 to adapt to the load demand.

[0049] Since the second power supply 4 can include power supplies of multiple different specifications, such as 48V, 24V, etc., when the first power supply 2 is used to power the load, the controller 1 can obtain the load demand current I in advance, so as to accurately control the output of the second power supply 4 when the power supply is switched.

[0050] In practical applications, the first power supply may be a 220V AC power supply; the second power supply may be a 24V DC power supply.

[0051] An embodiment of the present application provides a load multi-power supply switching device, including the load multi-power supply switching circuit described in the above embodiment.

[0052] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A load multi-power supply switching circuit, characterized in that: The invention comprises a controller (1), a first power supply (2), a first switch module (3), a second power supply (4), a second switch module (5) and a third switch module (6); the input end of the third switch module (6) comprises a positive input end and a negative input end, and the output end comprises a positive output end and a negative output end; The positive electrode of the first power source (2) is connected to the positive input terminal through the first switch module (3), and the negative electrode is connected to the negative input terminal through the first switch module (3); the positive electrode of the second power source (4) is connected to the positive input terminal through the second switch module (5), and the negative electrode is connected to the negative input terminal through the second switch module (5); the positive output terminal and the negative output terminal are connected to the positive electrode and the negative electrode of the load respectively; the controller (1) is connected to the first switch module (3), the second switch module (5) and the third switch module (6) respectively; The controller (1) is used to control the first switch module (3) and the third switch module (6) to be turned on based on a power-on instruction, so that the first power source (2), the first switch module (3), the third switch module (6) and the load form a first charging circuit, and the first power source (2) supplies power to the load; The controller (1) is further used to obtain a voltage value U of the first charging circuit, and to determine whether the first power source (2) meets the power demand of the load based on the voltage value U; if not, the controller (1) controls the first switch module (3) to be disconnected and the second switch module (5) to be connected, and the second power source (4), the second switch module (5), the third switch module (6) and the load form a second charging circuit, and the second power source (4) supplies power to the load.

2. The load multi-power supply switching circuit according to claim 1, characterized in that: The third switch module (6) comprises a relay K1, a switch tube Q1 and a resistor R1; the relay K1 comprises a normally open switch; The normally open switch of the relay K1 is connected between the positive input terminal and the positive output terminal; the switch tube Q1 is connected between the positive input terminal and the positive output terminal, and the control terminal of the switch tube Q1 is connected to the controller (1) via the resistor R1.

3. The load multi-power supply switching circuit according to claim 2, characterized in that: The controller (1) is used to control the relay K1 to close the normally open switch based on the power-on instruction; the positive electrode of the first power source (2) is connected to the positive electrode of the load through the first switch module (3) and the normally open switch in sequence, so that the first power source (2) supplies power to the load; The controller (1) is further configured to, after controlling the normally open switch to close and waiting for a first preset time, drive the switch tube Q1 to conduct through the resistor R1, and disconnect the normally open switch by controlling the relay K1; the positive electrode of the first power source (2) is connected to the positive electrode of the load through the first switch module (3) and the switch tube Q1 in sequence, so that the first power source (2) keeps supplying power to the load.

4. The load multi-power supply switching circuit according to claim 1, characterized in that: The second switch module (5) comprises a relay K2, a fuse F1, a switch tube Q2, a resistor R2 and a diode D1; the relay K2 comprises a contact a, a contact b, a contact c and a contact d; The first end of the fuse F1 is connected to the negative input end, and the second end is connected to the first end of the switch tube Q2; the second end of the switch tube Q2 is connected to the contact c; the contact d is connected to the negative electrode of the second power supply (4); the control end of the switch tube Q2 is connected to the controller (1) through the resistor R2; the contact a is connected to the positive electrode of the second power supply (4), and the contact b is connected to the positive input end through the diode D1.

5. The load multi-power supply switching circuit according to claim 4, characterized in that: The controller (1) is used to drive the switch tube Q2 to close via the resistor R2; It is also used to control the relay K2 to connect the contact a and the contact b, and the contact c and the contact d, respectively; the positive electrode of the second power supply (4) is connected to the positive input terminal through the contact a and the contact b in sequence, and the negative electrode of the second power supply (4) is connected to the negative input terminal through the contact d, the contact c, the switch tube Q2 and the fuse F1 in sequence; the second power supply (4) supplies power to the load.

6. The load multi-power supply switching circuit according to claim 4, characterized in that: It also includes a first current feedback module (8); the first current feedback module (8) includes a resistor R3, a resistor R4, a resistor R5, and an optical coupler H1; the optical coupler H1 includes a light emitting diode D3 and a phototransistor Q3; the relay K2 also includes a contact e; The contact e is connected to the positive electrode of the light-emitting diode D3 through the resistor R3, and the negative electrode of the light-emitting diode D3 is connected to the positive input terminal through the diode D2; the two ends of the resistor R4 are respectively connected to the positive electrode and the negative electrode of the light-emitting diode D3; the input end of the phototransistor Q3 is connected to the voltage VCC, and the output end is connected to the controller (1), and the output end of the phototransistor Q3 is also grounded through the resistor R5; The controller (1) is used for, after controlling the first switch module (3) and the third switch module (6) to be turned on, controlling the relay K2 to connect the contact c and the contact e, and driving the switch tube Q2 to be turned on through the resistor R2; the controller (1) obtains the current status of the first charging circuit through the first current feedback module (8).

7. The load multi-power supply switching circuit according to claim 1, characterized in that: It also includes a current transformer (9); the current transformer (9) is connected between the negative output terminal and the negative pole of the load, and the current transformer (9) is also connected to the controller (1); The controller (1) is used to detect the required current I of the load through the current transformer (9) when the first power source (2) supplies power to the load; And based on the demand current I, when the second power supply (4) is used to power the load, the output of the second power supply (4) is controlled.

8. The load multi-power supply switching circuit according to claim 1, characterized in that: The third switch module (6) further comprises a varistor RV1; two ends of the varistor RV1 are respectively connected to the positive input end and the negative input end.

9. A load multi-power supply switching device, characterized in that: The invention comprises the load multi-power supply switching circuit as described in any one of claims 1 to 8.

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