Multi-power switching circuit based on voltage threshold

Abstract

The invention provides a multi-power-supply switching circuit based on a voltage threshold value, and belongs to the technical field of electronic circuits. The circuit comprises a main power supply input circuit, an auxiliary power supply input circuit, a control switching power supply circuit, a switch element and a protection circuit, the main power supply input circuit is connected with a main power supply and a load, the auxiliary power supply input circuit is connected with an auxiliary power supply and the switching element, the switching power supply circuit is controlled to control the switching element to be switched on and off according to a comparison result of a main power supply voltage and a 7V set threshold value, and when the main power supply voltage is larger than or equal to 7V, the switching element is switched off, and the main power supply independently supplies power; when the main power supply voltage is less than 7V, the switch element is closed, and the auxiliary power supply supplies power; the protection circuit comprises a transient voltage suppressor and a diode and is used for preventing voltage spikes and current backflow. Stable switching of the main power supply and the auxiliary power supply is achieved, stability of load end voltage is guaranteed, reliability and safety of the system are improved, and a double-path power supply switching circuit can be expanded to increase power supply redundancy.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electronic circuits, and more particularly relates to a multi-power supply switching circuit based on a voltage threshold. BACKGROUND

[0002] In the field of electronic circuits, multi-power supply systems are widely used in various controller scenarios that require stable power supply. The normal operation of the controller highly depends on continuous and stable power supply input. When the system is configured with a main power supply and an auxiliary power supply to achieve power supply redundancy, the switching control between the main and auxiliary power supplies becomes a key link to ensure system stability.

[0003] In the prior art, the multi-power supply switching scheme has the problems of immature switching timing and unclear switching conditions. For example, when the main power supply voltage decreases due to load fluctuation, external power supply abnormality, etc., due to the lack of clear voltage judgment threshold and reliable switching control logic, the switching action is often delayed or mis-switched. The former will cause the controller to fail to switch to the auxiliary power supply in time when the main power supply voltage is insufficient, thereby causing instantaneous power loss. The latter may frequently switch when the main power supply voltage fluctuates temporarily, thereby destroying the continuity of system power supply. The above problems will directly affect the normal operation of the controller and reduce the stability and reliability of the multi-power supply system, which cannot meet the requirements of electronic devices with high power supply quality. SUMMARY

[0004] To solve the above technical problems, the present application provides a multi-power supply switching circuit based on a voltage threshold, which solves the technical problems of immature and unclear power supply switching timing in the existing multi-power supply system, and may cause instantaneous power loss of the controller and affect the stability of the system when the main power supply voltage decreases.

[0005] A multi-power supply switching circuit based on a voltage threshold, comprising a main power supply input circuit, an auxiliary power supply input circuit, a control switching power supply circuit, a switching element, and a protection circuit;

[0006] The first end of the main power supply input circuit is used for connecting the main power supply, the second end is used for connecting the load connection end, and the third end is connected with the input end of the control switching power supply circuit;

[0007] The first end of the auxiliary power supply input circuit is used for connecting the auxiliary power supply, the second end is connected with the first end of the switching element, and the third end is connected with the input end of the control switching power supply circuit;

[0008] The output end of the control switching power supply circuit is connected with the control end of the switching element, and is used for controlling the on-off state of the switching element according to the comparison result of the main power supply voltage and the set voltage threshold;

[0009] The second end of the switching element is connected with the load connection end;

[0010] The protection circuit is integrated into the main power input circuit and the auxiliary power input circuit to prevent the circuit from being damaged by voltage spikes and to avoid current backflow.

[0011] The voltage threshold is set to 7V;

[0012] When the main power supply voltage is ≥7V, the control switching circuit disconnects the control switching element, and the main power supply input circuit supplies power to the load separately.

[0013] When the main power supply voltage is <7V, the control switching circuit closes the control switch element, and the auxiliary power supply input circuit supplies power to the load through the switch element.

[0014] Preferably, the main power input circuit includes a first transient voltage suppressor, a first diode, and a first resistor; one end of the first transient voltage suppressor serves as the first terminal of the main power input circuit and is connected to the main power supply, and the other end is connected to the anode of the first diode and one end of the first resistor, respectively; the cathode of the first diode serves as the second terminal of the main power input circuit and is connected to the load connection terminal; the other end of the first resistor serves as the third terminal of the main power input circuit and is connected to the input terminal of the control switching power supply circuit.

[0015] Preferably, the auxiliary power input circuit includes a second transient voltage suppressor, a third transient voltage suppressor, a second diode, and a third diode; one end of the second transient voltage suppressor serves as the first terminal of the auxiliary power input circuit and is connected to the auxiliary power supply, and the other end is connected to one end of the third transient voltage suppressor, the anode of the second diode, and the anode of the third diode, respectively; the other end of the third transient voltage suppressor is grounded; the cathode of the second diode serves as the second terminal of the auxiliary power input circuit and is connected to the first terminal of the switching element; the cathode of the third diode serves as the third terminal of the auxiliary power input circuit and is connected to the input terminal of the control switching power supply circuit.

[0016] Preferably, the control switching power supply circuit includes a first MOSFET, a second MOSFET, a first transistor, and seven resistors, namely a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and an eighth resistor; the third terminal of the main power input circuit is connected to the base of the first transistor via the second resistor, the emitter of the first transistor is grounded, the collector of the first transistor is connected to the third terminal of the auxiliary power input circuit via the third resistor, and the collector of the first transistor is also connected to the gate of the first MOSFET; the source of the first MOSFET is connected to the third terminal of the auxiliary power input circuit, and the drain of the first MOSFET is connected to the gate of the second MOSFET via the fourth resistor; the source of the second MOSFET is grounded, and the drain of the second MOSFET serves as the output terminal of the control switching power supply circuit and is connected to the control terminal of the switching element; the fifth resistor is connected in parallel between the base of the first transistor and ground, the sixth resistor is connected in parallel between the gate and source of the first MOSFET, the seventh resistor is connected in parallel between the gate and source of the second MOSFET, and the eighth resistor is connected in series between the drain of the second MOSFET and the control terminal of the switching element.

[0017] Preferably, the switching element is a crystal electronic switch, which is selected from MOSFETs or IGBTs.

[0018] Preferably, when the crystal electronic switch is a third MOS transistor, the source of the third MOS transistor is connected to the second terminal of the auxiliary power supply input circuit as the first terminal of the switching element, the gate of the third MOS transistor is connected to the output terminal of the control switching power supply circuit as the control terminal of the switching element, and the drain of the third MOS transistor is connected to the load connection terminal as the second terminal of the switching element.

[0019] Preferably, when the crystal electronic switch is a first IGBT, the collector of the first IGBT is connected to the second terminal of the auxiliary power input circuit as the first terminal of the switching element, the emitter of the first IGBT is connected to the load connection terminal as the second terminal of the switching element, and the base of the first IGBT is connected to the output terminal of the control switching power circuit as the control terminal of the switching element.

[0020] Preferably, the voltage spike protection component in the protection circuit is a transient voltage suppressor, which includes a first transient voltage suppressor in the main power input circuit, a second transient voltage suppressor in the auxiliary power input circuit, and a third transient voltage suppressor; the reverse current protection component in the protection circuit is a diode, which includes a first diode in the main power input circuit, a second diode in the auxiliary power input circuit, and a third diode.

[0021] Preferably, when the main power supply voltage recovers from <7V to ≥7V, the control switching power supply circuit detects the change in main power supply voltage in real time, and after detecting that the main power supply voltage is stable at ≥7V, the control switching element switches from the closed state to the open state, and the power supply circuit of the load switches from the auxiliary power supply input circuit back to the main power supply input circuit.

[0022] Preferably, in the control switching power supply circuit, the resistance of the second resistor is 4.7KΩ, the resistance of the third resistor is 100KΩ, the resistance of the fourth resistor is 100KΩ, the resistance of the seventh resistor is 10KΩ, and the resistance values ​​of the fifth, sixth, and eighth resistors are adapted to the voltage division requirements of the circuit.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] Clearly define the switching timing to avoid instantaneous power loss of the controller: This invention sets a 7V main power supply switching threshold. The control switching power supply circuit detects the relationship between the main power supply voltage and this threshold to precisely control the on / off state of the switching elements. When the main power supply voltage is ≥7V, the main power supply is maintained; when it is <7V, the power supply is immediately switched to the auxiliary power supply. This completely solves the problem of immature and unclear switching timing in the prior art, effectively avoids instantaneous power loss of the controller due to improper switching, and ensures the continuity of system power supply.

[0025] Integrated multiple protections enhance circuit stability and safety: The protection circuit effectively absorbs transient interference such as voltage spikes and surges through transient voltage suppressors (TVS tubes) in the main and auxiliary power input circuits, preventing circuit components from being damaged by high voltage; at the same time, the diodes in the circuit utilize unidirectional conductivity to prevent current backflow between the main and auxiliary power supplies, ensuring that the main and auxiliary power supply circuits operate independently, further enhancing the overall stability and safety of the circuit.

[0026] Achieve seamless switching and ensure stable load voltage: When the main power supply voltage recovers from <7V to ≥7V, the control switching circuit can detect the voltage change in real time. After the main power supply voltage stabilizes and meets the standard, it automatically controls the switching element to disconnect and switches the power supply circuit from the auxiliary power supply back to the main power supply. The entire switching process does not require manual intervention, and there is no significant fluctuation in the load voltage before and after the switching. This achieves seamless and stable switching between the main and auxiliary power supplies, ensuring that the load (such as the controller) is always in a stable power supply environment.

[0027] The structure is expandable and adaptable to more application scenarios: Based on the single-channel main and auxiliary power supply switching circuit, this invention can be expanded into a dual-channel power supply switching circuit (adding one main and auxiliary power supply input circuit and an adapted control module). After expansion, the circuit still maintains the original switching logic and protection functions, and can provide dual power supply redundancy for the load. It is suitable for scenarios with higher power supply reliability requirements (such as industrial control equipment, emergency power supply systems, etc.), improving the application flexibility and applicability of the circuit.

[0028] Overall system reliability is improved and maintenance costs are reduced: Through precise switching control and multiple protection designs, this invention effectively reduces system failures caused by power switching problems and extends the service life of circuit components; at the same time, the circuit structure is simple and the core modules (main and auxiliary power input, control switching, and protection circuit) have clear functions, which facilitates later inspection and maintenance and reduces the operation and maintenance costs of multi-power supply systems. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the circuit configuration of the present invention;

[0030] Figure 2 This is a schematic diagram of the circuit principle of the present invention;

[0031] Figure 3 This is a schematic diagram of the dual-power switching circuit in an embodiment of the present invention. Detailed Implementation

[0032] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0033] The following is in conjunction with the appendix Figures 1-3 This invention provides a detailed description of a multi-power supply switching circuit based on a voltage threshold. This embodiment is only used to explain the invention and is not intended to limit the scope of protection of the invention.

[0034] In multi-power supply systems, the controller needs a stable power input to ensure normal operation. However, in existing technologies, the timing of main and auxiliary power switching is immature and unclear, which can easily lead to the controller losing power momentarily when the main power voltage drops, affecting system stability. This embodiment designs a multi-power switching circuit based on a voltage threshold (set to 7V) to achieve stable switching between main and auxiliary power supplies, ensuring stable voltage at the load end and improving system reliability and safety.

[0035] The multi-power supply switching circuit includes a main power input circuit, an auxiliary power input circuit, a control switching power circuit, switching elements, and a protection circuit. The connection relationships of each part are as follows:

[0036] Main power input circuit: the first terminal is connected to the main power supply, the second terminal is connected to the load connection terminal, and the third terminal is connected to the input terminal of the control switching power circuit;

[0037] Auxiliary power input circuit: The first terminal is connected to the auxiliary power supply (in this embodiment, the auxiliary power supply input voltage is 12V), the second terminal is connected to the first terminal of the switching element, and the third terminal is connected to the input terminal of the control switching power supply circuit.

[0038] Control switching power supply circuit: The input terminal is connected to the third terminal of the main and auxiliary power supply input circuits, and the output terminal is connected to the control terminal of the switching element. By detecting the relationship between the main power supply voltage and the 7V threshold, the switching element is controlled to turn on and off.

[0039] Switching element: The second end is connected to the load connection terminal, and the on / off state determines whether the auxiliary power supply supplies power to the load;

[0040] Protection circuit: Integrated into the main and auxiliary power input circuits, used to protect against voltage spikes and prevent current backflow.

[0041] The main power input circuit consists of a transient voltage suppressor (TVS transistor, corresponding to...) Figure 2 D3 in the diagram), and a diode (anti-reverse current diode, corresponding to the attached diagram). Figure 2 DA1 in the middle) and a resistor (corresponding to the attached) Figure 2 The circuit consists of R1 (with a resistance of 4.7KΩ), and the specific connection relationship is as follows:

[0042] One end of TVS diode D3 serves as the first terminal of the main power input circuit and is directly connected to the main power supply.

[0043] The other end of TVS diode D3 is simultaneously connected to the anode of diode DA1 and one end of resistor R1.

[0044] The cathode of diode DA1 serves as the second terminal of the main power input circuit, connected to the load connection terminal to supply the main power voltage to the load.

[0045] The other end of resistor R1 serves as the third terminal of the main power input circuit, connected to the input terminal of the control switching power circuit, providing the control circuit with the main power voltage detection signal.

[0046] The auxiliary power input circuit consists of two transient voltage suppressors (TVS transistors, corresponding to the attached circuit). Figure 2 D5 and D6 in the middle), two diodes (anti-reverse current diodes, corresponding to the attached... Figure 2 It consists of DA2 and DA3, and the specific connection relationship is as follows:

[0047] One end of TVS diode D5 serves as the first terminal of the auxiliary power input circuit and is directly connected to the auxiliary power supply (12V).

[0048] The other end of TVS diode D5 is simultaneously connected to one end of TVS diode D6, the anode of diode DA2, and the anode of diode DA3;

[0049] The other end of TVS diode D6 is grounded, working together with D5 to protect against voltage spikes on the auxiliary power source side;

[0050] The cathode of diode DA2 serves as the second terminal of the auxiliary power input circuit, connected to the first terminal of the switching element, and is used to supply auxiliary power voltage to the load when the switching element is closed.

[0051] The cathode of diode DA3 serves as the third terminal of the auxiliary power input circuit, connected to the input terminal of the control switching power circuit, providing auxiliary power supply and signals to the control circuit.

[0052] The power switching control circuit consists of two MOSFETs (corresponding to the attached circuit). Figure 2 Q2 and Q1, where Q2 is the control-side MOSFET and Q1 is the switching element MOSFET), and a transistor (corresponding to the attached diagram). Figure 2 Q3 in the middle) and seven resistors (corresponding to the attached) Figure 2 The circuit consists of resistors R3, R4, R5, R6, R7, R8, and R9, where R3 has a resistance of 100KΩ, R4 has a resistance of 100KΩ, R7 has a resistance of 10KΩ, and the resistance values ​​of R5, R6, R8, and R9 are adjusted according to the voltage division requirements of the circuit. The specific connection relationships and functions are as follows:

[0053] The third terminal of the main power input circuit (the other end of resistor R1) is connected to the base of transistor Q3 via resistor R3, and is used to input the main power voltage detection signal to the base of Q3;

[0054] The emitter of transistor Q3 is grounded, and the collector is connected to the third terminal of the auxiliary power input circuit (the cathode of diode DA3) via resistor R4. At the same time, the collector of transistor Q3 is connected to the gate of MOSFET Q2.

[0055] The source of MOSFET Q2 is connected to the third terminal of the auxiliary power input circuit (cathode of diode DA3), and the drain is connected to the gate of MOSFET Q1 (switching element) via resistor R7.

[0056] Resistor R5 is connected in parallel between the base of transistor Q3 and ground to stabilize the base potential of Q3 and prevent false triggering;

[0057] Resistor R6 is connected in parallel between the gate and source of MOSFET Q2 to release the gate charge when Q2 is turned off, ensuring that Q2 is reliably turned off;

[0058] Resistor R8 is connected in parallel between the gate and source of MOSFET Q1 to release the gate charge when Q1 is turned off, ensuring that Q1 is reliably turned off;

[0059] Resistor R9 is connected in series between the drain of MOSFET Q2 and the gate of MOSFET Q1 to limit the gate current of Q1 and protect the gate of Q1.

[0060] The core function of this circuit is to detect the main power supply voltage through the voltage divider between resistors R3 and R5, control the on / off state of transistor Q3, then control the on / off state of MOSFET Q2, and finally control the on / off state of switching element Q1 to achieve the switching between main and auxiliary power supplies.

[0061] The switching element is a crystal electronic switch, which can be either a MOSFET or an IGBT. The specific selection and connection relationship are as follows:

[0062] The selected type is a MOSFET (corresponding to the attached...) Figure 2 Q1);

[0063] The source of MOSFET Q1 serves as the first terminal of the switching element and is connected to the second terminal of the auxiliary power input circuit (the cathode of diode DA2).

[0064] The gate of MOSFET Q1 serves as the control terminal of the switching element and is connected to the output terminal (drain of MOSFET Q2) of the control switching power supply circuit.

[0065] The drain of MOSFET Q1 serves as the second terminal of the switching element and is connected to the load connection terminal.

[0066] The collector of the IGBT transistor serves as the first terminal of the switching element and is connected to the second terminal of the auxiliary power input circuit (the cathode of diode DA2).

[0067] The emitter of the IGBT transistor serves as the second terminal of the switching element and is connected to the load connection terminal.

[0068] The base of the IGBT transistor serves as the control terminal of the switching element, connected to the output terminal (drain of MOSFET Q2) of the power supply control circuit.

[0069] In this embodiment, MOSFETs are preferred as the switching element because they have fast switching speed and low driving power, making them more suitable for the need for rapid switching between multiple power supplies.

[0070] The protection circuit consists of transient voltage suppressors (TVS transistors) and diodes in the main and auxiliary power input circuits, and its specific functions are as follows:

[0071] Voltage spike protection: When the circuit encounters voltage spikes (such as surges or lightning-induced voltages), TVS diodes D3 (main power side), D5, and D6 (auxiliary power side) will break down and conduct instantly, clamping the spike voltage within a safe range and preventing damage to subsequent circuit components.

[0072] Anti-current backflow: Diodes DA1 (main power supply side), DA2, and DA3 (auxiliary power supply side) have unidirectional conductivity, which can prevent auxiliary power current from flowing back into the main power supply circuit when the main power supply voltage is abnormal, or prevent the main power supply current from flowing back into the auxiliary power supply circuit when the auxiliary power supply voltage is abnormal, ensuring that the main and auxiliary power supply circuits are independent and avoiding circuit failure.

[0073] Circuit operation process:

[0074] This embodiment takes an auxiliary power input voltage of 12V and a main power switching threshold of 7V as an example to illustrate the circuit operation process under three working conditions:

[0075] Operating Condition 1: Main power supply voltage ≥ 7V (normal power supply state):

[0076] When the main power supply voltage is stable at ≥7V:

[0077] After the main power supply voltage is divided by resistors R1 (main power input circuit), R3 (control switching circuit) and R5 (control switching circuit), the base voltage of transistor Q3 reaches the conduction threshold, and transistor Q3 is turned off (because the base current is insufficient after voltage division, it cannot drive Q3 to conduct).

[0078] When transistor Q3 is off, its collector potential is equal to the auxiliary power supply voltage (12V). This potential is applied to the gate of MOSFET Q2, causing MOSFET Q2 to conduct.

[0079] After MOSFET Q2 is turned on, the auxiliary power supply voltage is applied to the gate of switching element Q1 through the source-drain of Q2 and resistor R7. At this time, the voltage difference between the gate and source of Q1 meets the cutoff condition, and switching element Q1 is turned off.

[0080] When the switching element Q1 is turned off, the auxiliary power supply cannot supply power to the load. The main power supply voltage is directly supplied to the load connection terminal through TVS diode D3 and diode DA1, and the load is powered by the main power supply alone.

[0081] Operating Condition 2: Main power supply voltage < 7V (switching to auxiliary power supply mode):

[0082] When the main power supply voltage drops to <7V:

[0083] After the main power supply voltage is divided by R1, R3 and R5, the base voltage of transistor Q3 is lower than the conduction threshold, and transistor Q3 conducts.

[0084] When transistor Q3 is turned on, its collector potential is close to ground potential (approximately 0V), and the gate potential of MOSFET Q2 is pulled down to ground potential, causing MOSFET Q2 to be turned off.

[0085] After MOSFET Q2 is turned off, it cannot provide voltage to the gate of switching element Q1. The gate charge of Q1 is released through resistor R8. The voltage difference between the gate and the source meets the conduction condition, and switching element Q1 is turned on.

[0086] When the switching element Q1 is turned on, the auxiliary power supply voltage (12V) is delivered to the load connection terminal through TVS transistor D5, diode DA2, and the source-drain of Q1. The load is powered by the auxiliary power supply, avoiding load power loss due to insufficient main power supply voltage.

[0087] Operating Condition 3: Main power supply voltage recovers from <7V to ≥7V (switching back to main power supply mode):

[0088] When the main power supply voltage recovers and stabilizes at ≥7V:

[0089] After the main power supply voltage is divided by R1, R3 and R5, the base voltage of transistor Q3 reaches the cutoff condition again, and transistor Q3 is cut off.

[0090] After transistor Q3 is turned off, its collector potential rises back to 12V (auxiliary source voltage), and the gate of MOSFET Q2 receives sufficient voltage, so MOSFET Q2 is turned on again.

[0091] After MOSFET Q2 is turned on, the auxiliary source voltage is applied to the gate of Q1 again. The voltage difference between the gate and source of Q1 meets the cutoff condition, and the switching element Q1 is turned off.

[0092] After the switching element Q1 is turned off, the auxiliary power supply stops supplying power to the load, and the main power supply voltage is delivered to the load through DA1. The load power supply circuit switches back from the auxiliary power supply to the main power supply, achieving uninterrupted and stable switching.

[0093] Optional embodiment (dual power supply switching circuit):

[0094] Based on the above Figure 1 , Figure 2 The single-channel main / auxiliary power supply switching circuit shown can be extended into a dual-channel power supply switching circuit (as shown in the attached diagram). Figure 3 As shown), its core structure and working principle are the same as the single-channel embodiment, only the number of main and auxiliary power input circuits is expanded:

[0095] The dual-channel switching circuit includes two channels (main power input circuit + auxiliary power input circuit), corresponding to two independent main power supply and auxiliary power supply respectively;

[0096] A set of voltage-dividing resistors and a switching transistor are added to the control switching power supply circuit to synchronously detect the voltage of the two main power supplies;

[0097] The switching elements and load connection terminals are designed in parallel to ensure that the two power supplies can independently or collaboratively power the load, further improving the system's power supply redundancy and reliability.

[0098] The protection circuit, switching threshold (still 7V), and operating logic of this optional embodiment are consistent with those of the single-channel embodiment. Only the number of input channels and the control terminal adaptation design have been adjusted according to the dual-channel power supply requirements, without the need to add any additional core functional modules.

[0099] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A multi-power supply switching circuit based on voltage threshold, characterized in that: It includes the main power input circuit, the auxiliary power input circuit, the control switching power circuit, the switching elements, and the protection circuit; The first terminal of the main power input circuit is connected to the main power supply, the second terminal is connected to the load connection terminal, and the third terminal is connected to the input terminal of the control switching power circuit. The first terminal of the auxiliary power input circuit is connected to the auxiliary power source, the second terminal is connected to the first terminal of the switching element, and the third terminal is connected to the input terminal of the control switching power circuit. The output terminal of the control switching power supply circuit is connected to the control terminal of the switching element, and the on / off state of the switching element is controlled according to the comparison result between the main power supply voltage and the set voltage threshold. The second terminal of the switching element is connected to the load connection terminal; The protection circuit is integrated into the main power input circuit and the auxiliary power input circuit; Set the voltage threshold to 7V; When the main power supply voltage is ≥7V, the control switching circuit disconnects the control switching element, and the main power supply input circuit supplies power to the load separately. When the main power supply voltage is <7V, the control switching circuit closes the control switching element, and the auxiliary power supply input circuit supplies power to the load through the switching element.

2. The multi-power supply switching circuit based on voltage threshold according to claim 1, characterized in that, The main power input circuit includes a first transient voltage suppressor, a first diode, and a first resistor; One end of the first transient voltage suppressor is connected to the main power supply as the first end of the main power input circuit, and the other end is connected to the anode of the first diode and one end of the first resistor, respectively. The cathode of the first diode is connected to the load terminal as the second terminal of the main power input circuit. The other end of the first resistor serves as the third terminal of the main power input circuit, which is connected to the input terminal of the control switching power circuit.

3. The multi-power supply switching circuit based on voltage threshold according to claim 1, characterized in that, The auxiliary power input circuit includes a second transient voltage suppressor, a third transient voltage suppressor, a second diode, and a third diode; One end of the second transient voltage suppressor is connected to the auxiliary power supply as the first end of the auxiliary power supply input circuit, and the other end is connected to one end of the third transient voltage suppressor, the anode of the second diode, and the anode of the third diode, respectively. The other end of the third transient voltage suppressor is grounded; The cathode of the second diode is connected to the first terminal of the switching element as the second terminal of the auxiliary power input circuit. The cathode of the third diode serves as the third terminal of the auxiliary power input circuit, which is connected to the input terminal of the control switching power circuit.

4. The multi-power supply switching circuit based on voltage threshold according to claim 1, characterized in that, The control switching power supply circuit includes a first MOSFET, a second MOSFET, a first transistor, and seven resistors, namely the second resistor, the third resistor, the fourth resistor, the fifth resistor, the sixth resistor, the seventh resistor, and the eighth resistor; The third terminal of the main power input circuit is connected to the base of the first transistor via the second resistor. The emitter of the first transistor is grounded. The collector of the first transistor is connected to the third terminal of the auxiliary power input circuit via the third resistor. The collector of the first transistor is also connected to the gate of the first MOSFET. The source of the first MOSFET is connected to the third terminal of the auxiliary power input circuit, and the drain of the first MOSFET is connected to the gate of the second MOSFET through the fourth resistor. The source of the second MOSFET is grounded, and the drain of the second MOSFET is connected to the control terminal of the switching power supply circuit as the output terminal. The fifth resistor is connected in parallel between the base of the first transistor and ground; the sixth resistor is connected in parallel between the gate and source of the first MOSFET; the seventh resistor is connected in parallel between the gate and source of the second MOSFET; and the eighth resistor is connected in series between the drain of the second MOSFET and the control terminal of the switching element.

5. The multi-power supply switching circuit based on voltage threshold according to claim 1, characterized in that, The switching element is a crystal electronic switch, which is selected from MOSFETs or IGBTs.

6. The multi-power supply switching circuit based on voltage threshold according to claim 5, characterized in that, When the crystal electronic switch is a third MOS transistor, the source of the third MOS transistor is connected to the second terminal of the auxiliary power input circuit as the first terminal of the switching element, the gate of the third MOS transistor is connected to the output terminal of the control switching power circuit as the control terminal of the switching element, and the drain of the third MOS transistor is connected to the load connection terminal as the second terminal of the switching element.

7. The multi-power supply switching circuit based on voltage threshold according to claim 5, characterized in that, When the crystal electronic switch is the first IGBT, the collector of the first IGBT is connected to the second terminal of the auxiliary power input circuit as the first terminal of the switching element, the emitter of the first IGBT is connected to the load connection terminal as the second terminal of the switching element, and the base of the first IGBT is connected to the output terminal of the control switching power circuit as the control terminal of the switching element.

8. The multi-power supply switching circuit based on voltage threshold according to claim 1, characterized in that, The voltage spike protection component in the protection circuit is a transient voltage suppressor, which includes a first transient voltage suppressor in the main power input circuit, a second transient voltage suppressor in the auxiliary power input circuit, and a third transient voltage suppressor. The reverse current protection component in the protection circuit is a diode, which includes a first diode in the main power input circuit, a second diode in the auxiliary power input circuit, and a third diode.

9. The multi-power supply switching circuit based on voltage threshold according to claim 1, characterized in that, When the main power supply voltage recovers from <7V to ≥7V, the control switching circuit detects the change in main power supply voltage in real time. After detecting that the main power supply voltage is stable at ≥7V, the control switching element switches from the closed state to the open state, and the power supply circuit of the load switches back from the auxiliary power supply input circuit to the main power supply input circuit.

10. The multi-power supply switching circuit based on voltage threshold according to claim 4, characterized in that, In the control switching power supply circuit, the resistance of the second resistor is 4.7KΩ, the resistance of the third resistor is 100KΩ, the resistance of the fourth resistor is 100KΩ, the resistance of the seventh resistor is 10KΩ, and the resistance values ​​of the fifth, sixth, and eighth resistors are adapted to the voltage division requirements of the circuit.

Images