Power supply circuit and image pickup apparatus

Abstract

The utility model provides a power supply circuit and an image pickup apparatus. The power supply circuit comprises a power supply input end, a power supply output end, an anti-reverse connection circuit, a main switch and a switch control circuit. And the anti-reverse connection circuit is electrically connected with the power supply input end. The main switch and the anti-reverse-connection circuit are connected in series between the power input end and the power output end, and the main switch is used for controlling on-off of the power input end and the power output end. The switch control circuit comprises a control input end and a control output end, the control input end is electrically connected with the power supply input end, and the control output end is electrically connected with the main switch; when the voltage of the power input end is not greater than the voltage threshold value, the main switch is controlled to be switched on; when the voltage of the power input end is larger than the voltage threshold value, the main switch is controlled to be switched off. When the voltage of the power input end is larger than the voltage threshold value, the main switch can be controlled to be switched off, the situation that a load is burnt out due to the fact that the power supply is wrongly connected with an external power supply with high voltage is avoided, and safety is improved.

Description

Technical Field

[0001] The present application relates to the technical field of integrated circuits, and in particular to a power supply circuit and a camera device. Background Art

[0002] When the camera is installed on site, one installation interface can be connected to multiple devices with different power supplies. When the power supply is actually supplied, the installation interface may be connected to the wrong power supply. When the power supply is connected to the wrong power supply, the load may be burned out, which is not very safe. Utility Model Content

[0003] The present application provides a power supply circuit and a camera device with improved safety.

[0004] The present application provides a power supply circuit, comprising:

[0005] A power input terminal, the power input terminal is used to connect to an external power source;

[0006] A power output terminal, wherein the power output terminal is used to connect a load;

[0007] An anti-reverse connection circuit, electrically connected to the power input terminal;

[0008] A main switch connected in series with the anti-reverse connection circuit between the power input terminal and the power output terminal, the main switch being used to control the on / off of the power input terminal and the power output terminal; and

[0009] The switch control circuit comprises a control input terminal and a control output terminal, wherein the control input terminal is electrically connected to the power input terminal, and the control output terminal is electrically connected to the main switch; when the voltage at the power input terminal is not greater than a voltage threshold, the main switch is controlled to be turned on; when the voltage at the power input terminal is greater than the voltage threshold, the main switch is controlled to be turned off.

[0010] Preferably, the switch control circuit includes an overvoltage protection branch, which is electrically connected between the control input terminal and the control output terminal; when the voltage at the power input terminal is not greater than the voltage threshold, the overvoltage protection branch is inactive, causing the main switch to be turned on; when the voltage at the power input terminal is greater than the voltage threshold, the overvoltage protection branch is disconnected, causing the main switch to be turned off.

[0011] Preferably, the switch control circuit includes a switch branch, which is electrically connected between the overvoltage protection branch and the control output terminal; when the voltage at the power input terminal is not greater than the voltage threshold, the overvoltage protection branch is inactive, causing the switch branch to be turned on, so that the main switch is turned on; when the voltage at the power input terminal is greater than the voltage threshold, the overvoltage protection branch is open, causing the switch branch to be disconnected, so that the main switch is disconnected.

[0012] Preferably, the overvoltage protection branch includes a fuse and a transient diode, and the fuse and the transient diode are connected in series between the control input terminal and the ground terminal; the switch branch includes a switch tube, and the switch tube is electrically connected to the fuse, the transient diode and the control output terminal respectively; when the voltage at the power input terminal is not greater than the voltage threshold, the fuse and the transient diode are both inactive, so that the switch tube is turned on; when the voltage at the power input terminal is greater than the voltage threshold, the transient diode is short-circuited and the fuse is disconnected, so that the switch tube is disconnected.

[0013] Preferably, the switch control circuit includes a first voltage-dividing circuit, the first voltage-dividing circuit includes a first voltage-dividing resistor and a second voltage-dividing resistor, the first voltage-dividing resistor is electrically connected between the anti-reverse connection circuit and the control output end, and the second voltage-dividing resistor is electrically connected between the switch branch and the control output end.

[0014] Preferably, the switch control circuit comprises a current limiting branch electrically connected between the first voltage divider circuit and the control output terminal.

[0015] Preferably, the main switch includes a first end and a second end, the first end is electrically connected to the first voltage divider circuit, and the second end is electrically connected to the anti-reverse connection circuit; the power supply circuit includes a buffer capacitor, and the buffer capacitor is electrically connected between the first end and the second end of the main switch.

[0016] Preferably, the power supply circuit comprises at least one filter branch electrically connected between the main switch and the power supply output terminal.

[0017] Preferably, the anti-reverse connection circuit includes at least one anti-reverse connection diode.

[0018] The present application also provides a camera device, comprising:

[0019] load; and

[0020] As in any one of the above embodiments, the power supply circuit has a power output terminal electrically connected to the load.

[0021] The power supply circuit and camera device provided by the embodiment of the present application. The power supply circuit includes an anti-reverse connection circuit, a main switch and a switch control circuit, the anti-reverse connection circuit is electrically connected to the power input terminal, the main switch and the anti-reverse connection circuit are connected in series between the power input terminal and the power output terminal, and are used to control the on and off of the power input terminal and the power output terminal, the control input terminal of the switch control circuit is electrically connected to the power input terminal, and the control output terminal of the switch control circuit is electrically connected to the power output terminal, so that when the voltage at the power input terminal is greater than the voltage threshold, the main switch can be controlled to be disconnected, thereby avoiding the situation where the load is burned out due to the power supply being wrongly connected to an external power supply with a higher voltage, thereby improving safety.

[0022] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Shown is a functional block diagram of an embodiment of a power supply circuit of the present application.

[0024] Figure 2 Shown Figure 1 A schematic block diagram of another embodiment of a power supply circuit is shown.

[0025] Figure 3 Shown Figure 1 A functional block diagram of another embodiment of a power supply circuit is shown.

[0026] Figure 4 Shown Figure 3 The circuit diagram of the power supply circuit is shown. DETAILED DESCRIPTION

[0027] The power supply circuit and the camera device provided in the embodiments of the present application are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the features of the following embodiments and implementations can be combined with each other at will.

[0028] Figure 1 FIG. 1 is a schematic diagram of a power supply circuit 1 according to an embodiment of the present invention. Figure 1As shown, the power supply circuit 1 includes a power supply input terminal 11, a power supply output terminal 12, an anti-reverse connection circuit 13, a main switch 14 and a switch control circuit 15. Among them, the power supply input terminal 11 is used to connect an external power supply (not shown). The external power supply can be a DC power supply. The power supply output terminal 12 is used to connect a load (not shown). The load can be an electrical device. The anti-reverse connection circuit 13 is electrically connected to the power supply input terminal 11. The main switch 14 is connected in series with the anti-reverse connection circuit 13 between the power supply input terminal 11 and the power supply output terminal 12. The main switch 14 is used to control the on and off of the power supply input terminal 11 and the power supply output terminal 12. The switch control circuit 15 includes a control input terminal 151 and a control output terminal 152, the control input terminal 151 is electrically connected to the power supply input terminal 11, and the control output terminal 152 is electrically connected to the main switch 14. The switch control circuit 15 is electrically connected to the power supply input terminal 11 through the control input terminal 151. The switch control circuit 15 is electrically connected to the main switch 14 through the control output terminal 152. When the voltage at the power input terminal 11 is not greater than the voltage threshold, the main switch 14 is controlled to be turned on. When the voltage at the power input terminal 11 is greater than the voltage threshold, the main switch 14 is controlled to be turned off.

[0029] In this embodiment, the voltage threshold can be set according to actual needs. For example, the voltage threshold can be set to DC24V (direct current 24V). In some embodiments, when the voltage of the power input terminal 11 is DC12V, the DC12V is not greater than DC24V. At this time, the main switch 14 is controlled to be turned on, so that the input voltage of DC12V is output to the power output terminal 12 through the anti-reverse connection circuit 13 to supply power to the load of the subsequent stage. In some embodiments, when the voltage of the power input terminal 11 is DC36V, the DC36V is greater than DC24V. At this time, the main switch 14 is controlled to be disconnected, so that the input voltage of DC36V cannot be output to the power output terminal 12 through the anti-reverse connection circuit 13, and no power is supplied to the load of the subsequent stage. In the above scheme, the anti-reverse connection circuit 13 has a unidirectional conduction characteristic, which plays an anti-reverse connection role and improves safety.

[0030] In the above scheme, the power supply circuit 1 includes an anti-reverse connection circuit 13, a main switch 14 and a switch control circuit 15. The anti-reverse connection circuit 13 is electrically connected between the power input terminal 11 and the power output terminal 12. The main switch 14 is connected in series with the anti-reverse connection circuit 13 to control the on and off of the power input terminal 11 and the power output terminal 12. The control input terminal 151 of the switch control circuit 15 is electrically connected to the power input terminal 11, and the control output terminal 152 of the switch control circuit 15 is electrically connected to the power output terminal 12. In this way, when the voltage at the power input terminal 11 is greater than the voltage threshold, the main switch 14 can be controlled to be disconnected, thereby avoiding the situation where the load is burned out due to the power supply being mistakenly connected to an external power supply with a higher voltage, thereby improving safety.

[0031] Figure 2 Shown Figure 1FIG. 1 is a schematic block diagram of another embodiment of the power supply circuit 1. Figure 2 As shown, in some embodiments, the switch control circuit 15 includes an overvoltage protection branch 153, which is electrically connected between the control input terminal 151 and the control output terminal 152. The overvoltage protection branch 153 is used to control the on-off between the control input terminal 151 and the control output terminal 152. When the voltage of the power input terminal 11 is not greater than the voltage threshold, the overvoltage protection branch 153 does not act, so that the main switch 14 is turned on. When the voltage of the power input terminal 11 is greater than the voltage threshold, the overvoltage protection branch 153 is disconnected, so that the main switch 14 is disconnected. For example, in this embodiment, the voltage threshold can be set to DC24V (direct current 24V). In some embodiments, when the voltage of the power input terminal 11 is DC12V, the DC12V is not greater than DC24V, and the overvoltage protection branch 153 does not act to control the main switch 14 to turn on, so that the input voltage of DC12V is output to the power output terminal 12 through the anti-reverse connection circuit 13 to supply power to the load of the subsequent stage. In some embodiments, when the voltage of the power input terminal 11 is DC36V, the DC36V is greater than DC24V, and the overvoltage protection branch 153 is disconnected, causing the main switch 14 to be disconnected, so that the DC36V input voltage cannot be output to the power output terminal 12 through the anti-reverse connection circuit 13, and cannot supply power to the subsequent load. With such a configuration, when the power supply circuit 1 is connected to an external power supply with a higher voltage, the overvoltage protection branch 153 can be disconnected in time, and the main switch 14 can be controlled to be disconnected in time, thereby avoiding the situation where the load is burned out due to the power supply being wrongly connected to an external power supply with a higher voltage, thereby improving safety.

[0032] Figure 3 Shown Figure 1 FIG. 1 is a schematic block diagram of another embodiment of the power supply circuit 1. Figure 3 The embodiment shown is Figure 2 The embodiments shown are similar, the main difference being that Figure 3In the illustrated embodiment, the switch control circuit 15 further includes a switch branch 154, which is electrically connected between the overvoltage protection branch 153 and the control output terminal 152. The switch branch 154 is used to control the on-off between the overvoltage protection branch 153 and the control output terminal 152. When the voltage at the power input terminal 11 is not greater than the voltage threshold, the overvoltage protection branch 153 does not act, so that the switch branch 154 is turned on, so that the main switch 14 is turned on. When the voltage at the power input terminal 11 is greater than the voltage threshold, the overvoltage protection branch 153 is disconnected, so that the switch branch 154 is disconnected, so that the main switch 14 is disconnected. For example, in this embodiment, the voltage threshold can be set to DC24V (direct current 24V). In some embodiments, when the voltage of the power input terminal 11 is DC12V, the DC12V is not greater than DC24V. At this time, the overvoltage protection branch 153 does not operate to output a high level, so that the switch branch 154 is turned on, thereby controlling the main switch 14 to be turned on, so that the DC12V input voltage is output to the power output terminal 12 through the anti-reverse connection circuit 13 to supply power to the subsequent load.

[0033] In some embodiments, when the voltage of the power input terminal 11 is DC36V, the DC36V is greater than DC24V. At this time, the overvoltage protection branch 153 is disconnected to output a low level, so that the switch branch 154 is disconnected, thereby controlling the main switch 14 to be disconnected, so that the DC36V input voltage cannot be output to the power output terminal 12 through the anti-reverse connection circuit 13, and cannot supply power to the subsequent load. In this way, the switch branch 154 is added between the overvoltage protection branch 153 and the main switch 14 to achieve dual control of the main switch 14, so that the control process is stable and reliable. When the power supply circuit 1 is connected to an external power supply with a higher voltage, the overvoltage protection branch 153 and the switch branch 154 are used to timely control the on and off of the main switch 14, so that the power supply circuit 1 is connected to an external power supply with a lower voltage, and at the same time, the external power supply with a higher voltage cannot be connected, and the power supply that is compatible with the load is screened out, thereby ensuring that the device can be powered on normally.

[0034] Figure 4 Shown Figure 3 The circuit diagram of the power supply circuit 1 is shown in FIG. Figure 3 and Figure 4As shown, in some embodiments, the overvoltage protection branch 153 includes a fuse F1 and a transient diode D1, and the fuse F1 and the transient diode D1 are connected in series between the control input terminal 151 and the ground terminal GND. The switch branch 154 includes a switch tube Q1, and the switch tube Q1 is electrically connected to the fuse F1, the transient diode D1 and the control output terminal 152 respectively. When the voltage of the power input terminal 11 is not greater than the voltage threshold, the fuse F1 and the transient diode D1 are not in action, so that the switch tube Q1 is turned on; when the voltage of the power input terminal 11 is greater than the voltage threshold, the transient diode D1 is short-circuited and the fuse F1 is disconnected, so that the switch tube Q1 is disconnected. In this embodiment, the fuse F1 can be a 2A fuse. The transient diode D1 can be a TVS tube (Transient Voltage Suppressor). The voltage threshold can be the rated voltage of the transient diode, for example, it can be DC24V. The switch tube Q1 can be a transistor, and the transistor can be an NPN transistor. The first electrode of the transistor may be a base electrode, which is connected to the fuse F1 and one end of the transient diode D1 through a current limiting resistor R2. The second electrode of the transistor may be a collector electrode, which is connected to the anti-reverse connection circuit 13 and the control output terminal 152. The third electrode of the transistor may be an emitter electrode, which is connected to the ground terminal GND. The overvoltage protection branch 153 also includes a pull-down resistor R1, which is connected in parallel with the transient diode D1 between the fuse F1 and the ground terminal GND.

[0035] In some embodiments, when the voltage of the power input terminal 11 is DC12V, the DC12V is not greater than DC24V. At this time, the fuse F1 and the transient diode D1 are inactive to output a high level, so that the transistor is turned on, thereby controlling the main switch 14 to be turned on, so that the DC12V input voltage is output to the power output terminal 12 through the anti-reverse connection circuit 13 to supply power to the load at the subsequent stage. In some embodiments, when the voltage of the power input terminal 11 is DC36V, the DC36V is greater than DC24V. At this time, the transient diode D1 will be short-circuited because it exceeds the rated voltage of the transient diode D1, and the fuse F1 will be burned out due to the short circuit of the transient diode D1. At this time, the switch control circuit 15 is pulled down to the ground terminal GND under the action of the pull-down resistor R1, and outputs a low level, so that the transistor is turned off, thereby controlling the main switch 14 to be turned off, so that the DC36V input voltage cannot be output to the power output terminal 12 through the anti-reverse connection circuit 13, and cannot supply power to the load. With such arrangement, when the power supply circuit 1 is connected to an external power supply with a higher voltage, the fuse F1, the transient diode D1 and the switch tube Q1 are used to timely control the on and off of the main switch 14, so that the power supply circuit 1 is connected to an external power supply with a lower voltage, while the external power supply with a higher voltage cannot be connected, and the power supply adapted to the load is screened out to ensure normal power-on and avoid the load burning due to wrong power connection, thereby improving safety, reducing maintenance difficulties and reducing waste of resources.

[0036] exist Figure 4 In the embodiment shown, the switch branch 154 includes a first resistor R2 and a second resistor R3, the first resistor R2 is electrically connected between the fuse F1 and the switch tube Q1, and the second resistor R3 is electrically connected between the first resistor R2 and the ground terminal GND. In this embodiment, when the voltage of the power input terminal 11 is DC12V, the DC12V is not greater than DC24V. At this time, the fuse F1 and the transient diode D1 are not in action to output a high level. Under the voltage division effect of the first resistor R2 and the second resistor R3, the triode is turned on, thereby controlling the main switch 14 to turn on, so that the DC12V input voltage is output to the power output terminal 12 through the anti-reverse connection circuit 13 to supply power to the load of the subsequent stage. The first resistor R2 plays a current limiting role, and the second resistor R3 plays a protective role to improve safety.

[0037] exist Figure 4 In the illustrated embodiment, the switch control circuit 15 includes a first voltage divider circuit 155, the first voltage divider circuit 155 includes a first voltage divider resistor R4 and a second voltage divider resistor R5, the first voltage divider resistor R4 is electrically connected between the anti-reverse connection circuit 13 and the control output terminal 152, and the second voltage divider resistor R5 is electrically connected between the switch branch 154 and the control output terminal 152. Figure 3 and Figure 4In the embodiment shown, when the voltage of the power input terminal 11 is DC12V, the DC12V is not greater than DC24V. At this time, the fuse F1 and the transient diode D1 are not in action to output a high level, and the transistor is turned on under the voltage division effect of the first resistor R2 and the second resistor R3. When the transistor is turned on, under the voltage division effect of the first voltage division resistor R4 and the second voltage division resistor R5, the main switch 14 is turned on, so that the input voltage of DC12V is output to the power output terminal 12 through the anti-reverse connection circuit 13. In the above process, the first voltage division resistor R4 and the second voltage division resistor R5 play a voltage division role, provide a conduction voltage for the main switch 14, effectively control the on and off of the main switch 14, ensure that the power circuit 1 can be connected to a power supply whose voltage is not greater than the voltage threshold, thereby screening out a power supply that is compatible with the load, ensuring that the device can be powered on normally, avoiding the occurrence of load burnout due to wrong power connection, improving safety, reducing maintenance difficulties, and reducing resource waste.

[0038] exist Figure 4 In the illustrated embodiment, the switch control circuit 15 includes a current limiting branch 156 electrically connected between the first voltage divider circuit and the control output terminal 152. Figure 3 and Figure 4 In the embodiment shown, the current limiting branch 156 plays a current limiting role. In this embodiment, the current limiting branch 156 can be a current limiting resistor R6, which plays a current limiting role to protect the main switch 14 from damage caused by excessive current and improve safety.

[0039] exist Figure 4In the illustrated embodiment, the main switch 14 includes a first end 141, a second end 142 and a third end 143, the first end 141 is electrically connected to the first voltage divider circuit 155, the second end 142 is electrically connected to the anti-reverse connection circuit 13, and the third end 143 is electrically connected to the power output end 12. In this embodiment, the main switch 14 can be a P-type MOS tube. The first end 141 of the main switch 14 can be a gate, the second end 142 of the main switch 14 can be a source, and the third end 143 of the main switch 14 can be a drain. In some embodiments, when the voltage of the power input end 11 is DC12V, the DC12V is not greater than DC24V. At this time, the fuse F1 and the transient diode D1 are not in action to output a high level, and the transistor is turned on under the voltage division of the first resistor R2 and the second resistor R3. When the transistor is turned on, the voltage of the gate of the main switch 14 is divided from 12V to 6V under the action of the first voltage divider resistor R4 and the second voltage divider resistor R5. According to the characteristics of the P-type MOS tube, when Vg is less than Vs, the main switch 14 is turned on, so that the input voltage of DC12V is output to the power output terminal 12 through the anti-reverse connection circuit 13. In some embodiments, when the voltage of the power input terminal 11 is DC36V, the DC36V is greater than DC24V, at this time, the transient diode D1 will be short-circuited because it exceeds the rated voltage of the transient diode D1, and the fuse F1 will be burned out due to the short circuit of the transient diode D1. At this time, the switch control circuit 15 is pulled down to the ground terminal GND under the action of the pull-down resistor R1, and outputs a low level to disconnect the transistor. At this time, the level of the gate of the main switch 14 is consistent with the level of the source of the main switch 14 at a high level, so that the main switch 14 is disconnected, so that the input voltage of DC36V cannot be output to the power output terminal 12 through the anti-reverse connection circuit 13, and DC36V will not supply power to the load. In this way, the power supply that is compatible with the load is selected to ensure that the equipment can be powered on normally, avoid the load burning due to wrong power connection, improve safety, reduce maintenance difficulties, and reduce resource waste.

[0040] exist Figure 4 In the illustrated embodiment, the power circuit 1 includes a buffer capacitor C1, which is electrically connected between a first terminal 141 and a second terminal 142 of the main switch 14. In this embodiment, the buffer capacitor C1 is electrically connected between the gate and the source of the main switch 14, and can slow down the opening speed of the main switch 14. By adjusting the capacitance of the buffer capacitor C1, the opening time of the main switch 14 can be controlled. When the voltage at the power input terminal 11 is DC36V, before the transient diode D1 is short-circuited, the main switch 14 is prevented from opening and entering the subsequent load, causing the load to burn out, thereby improving safety.

[0041] exist Figure 4In the illustrated embodiment, the power supply circuit 1 includes at least one filter branch 157, which is electrically connected between the main switch 14 and the power supply output terminal 12. The power supply circuit 1 includes one or more filter branches 157. The filter branch 157 includes a filter capacitor C2, which is electrically connected between the drain of the main switch 14 and the power supply output terminal 12, effectively filtering out high-frequency noise and interference in the signal, making the output signal more stable, thereby improving the anti-interference ability and stability of the power supply circuit 1.

[0042] exist Figure 4 In the illustrated embodiment, the power circuit 1 further includes a fuse F2, which is electrically connected between the power input terminal 11 and the reverse connection protection circuit 13. The fuse F2 may be a 300V 10A fuse. When a short circuit occurs in the subsequent circuit, the fuse F2 automatically blows, disconnecting the circuit, protecting the circuit, and improving safety.

[0043] exist Figure 4 In the illustrated embodiment, the reverse connection prevention circuit 13 includes at least one reverse connection prevention diode. The positive electrode of the reverse connection prevention diode is electrically connected to the power input terminal 11, and the negative electrode of the reverse connection prevention diode is electrically connected to the power output terminal 12. The unidirectional conduction characteristic of the reverse connection prevention diode is utilized to prevent reverse connection and improve safety.

[0044] exist Figure 4 In the embodiment shown, through the switching characteristics of the MOS tube, when the DC36V power supply is connected incorrectly, the MOS tube is not turned on, and the DC36V will not be input to the subsequent load, protecting the subsequent circuit from being damaged in large quantities. Only the fuse F1 and the transient diode D1 are damaged in the primary power supply part, which is convenient for maintenance. In this way, the DC12V equipment can be effectively protected. When the DC36V power supply is connected incorrectly, only one transient diode D1 and one fuse F1 are damaged, which is convenient for maintenance and reduces resource waste. Therefore, the state of the transient diode D1 and one fuse F1 can be used to determine that the equipment is not powered on due to the incorrect power supply connection, which is conducive to finding the problem and facilitating maintenance.

[0045] The present application also provides a camera device, including a load and Figures 1 to 4 In the power supply circuit 1 shown in the embodiment, the power output terminal 12 of the power supply circuit 1 is electrically connected to a load. In this embodiment, the load may be a camera. Figures 1 to 4 The power supply circuit 1 shown in the embodiment can effectively screen out the power supply that is compatible with the load, ensure that the equipment can be powered on normally, avoid the load burning due to the power supply being wrongly connected to an external power supply with a higher voltage, improve safety, reduce maintenance difficulties, and reduce resource waste.

[0046] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A power supply circuit, characterized in that: include: A power input terminal, the power input terminal is used to connect to an external power source; A power output terminal, wherein the power output terminal is used to connect a load; An anti-reverse connection circuit, electrically connected to the power input terminal; A main switch, connected in series with the anti-reverse connection circuit between the power input terminal and the power output terminal, the main switch is used to control the on and off of the power input terminal and the power output terminal; and The switch control circuit comprises a control input terminal and a control output terminal, wherein the control input terminal is electrically connected to the power input terminal, and the control output terminal is electrically connected to the main switch; when the voltage at the power input terminal is not greater than a voltage threshold, the main switch is controlled to be turned on; when the voltage at the power input terminal is greater than the voltage threshold, the main switch is controlled to be turned off.

2. The power supply circuit according to claim 1, characterized in that: The switch control circuit includes an overvoltage protection branch, which is electrically connected between the control input terminal and the control output terminal; when the voltage at the power input terminal is not greater than a voltage threshold, the overvoltage protection branch does not operate, causing the main switch to be turned on; when the voltage at the power input terminal is greater than the voltage threshold, the overvoltage protection branch is disconnected, causing the main switch to be turned off.

3. The power supply circuit according to claim 2, characterized in that: The switch control circuit includes a switch branch, which is electrically connected between the overvoltage protection branch and the control output terminal; when the voltage at the power input terminal is not greater than the voltage threshold, the overvoltage protection branch is inactive, causing the switch branch to be turned on, so that the main switch is turned on; when the voltage at the power input terminal is greater than the voltage threshold, the overvoltage protection branch is disconnected, causing the switch branch to be disconnected, so that the main switch is disconnected.

4. The power supply circuit according to claim 3, characterized in that: The overvoltage protection branch includes a fuse and a transient diode, and the fuse and the transient diode are connected in series between the control input terminal and the ground terminal; the switch branch includes a switch tube, and the switch tube is electrically connected to the fuse, the transient diode and the control output terminal respectively; when the voltage at the power input terminal is not greater than the voltage threshold, the fuse and the transient diode are both inactive, so that the switch tube is turned on; when the voltage at the power input terminal is greater than the voltage threshold, the transient diode is short-circuited and the fuse is disconnected, so that the switch tube is disconnected.

5. The power supply circuit according to claim 3, characterized in that: The switch control circuit includes a first voltage-dividing circuit, which includes a first voltage-dividing resistor and a second voltage-dividing resistor. The first voltage-dividing resistor is electrically connected between the anti-reverse connection circuit and the control output end, and the second voltage-dividing resistor is electrically connected between the switch branch and the control output end.

6. The power supply circuit according to claim 5, characterized in that: The switch control circuit includes a current limiting branch electrically connected between the first voltage dividing circuit and the control output terminal.

7. The power supply circuit according to claim 5, characterized in that: The main switch includes a first end and a second end, the first end is electrically connected to the first voltage divider circuit, and the second end is electrically connected to the anti-reverse connection circuit; the power supply circuit includes a buffer capacitor, and the buffer capacitor is electrically connected between the first end and the second end of the main switch.

8. The power supply circuit according to claim 1, characterized in that: The power supply circuit includes at least one filter branch electrically connected between the main switch and the power supply output terminal.

9. The power supply circuit according to claim 1, characterized in that: The reverse connection protection circuit includes at least one reverse connection protection diode.

10. A camera device, characterized in that: include: load; and The power supply circuit according to any one of claims 1 to 9, wherein a power output terminal of the power supply circuit is electrically connected to the load.

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