Load switch circuit, load switching device, and camera

Abstract

The application provides a load switch circuit, a load switch device and a camera, and relates to the field of switch circuits. The application comprises a MOS tube, a slow start unit, a fast turn-off unit and a control logic unit. The source and the drain of the MOS tube are respectively connected with the power input and output terminals. The source of the MOS tube is connected with the gate of the MOS tube through the slow start unit, the gate of the MOS tube is connected with the control logic unit through the fast turn-off unit, the control logic unit is connected with the drain of the MOS tube, and the input end of the control logic unit is used for receiving a turn-off control signal. The MOS tube is used for controlling the on-off of the main power path; the slow start unit is used for controlling the slow conduction of the MOS tube when the circuit is powered on; and the control logic unit is used for sending a driving voltage signal to the fast turn-off unit after receiving an external turn-off control signal, so as to drive the fast turn-off unit to discharge the gate charge of the MOS tube. The MOS tube slow start and fast turn-off functions are realized at low cost.

Description

Technical Field

[0001] This application relates to the field of switching circuits, and more specifically, to load switching circuits, load switching devices, and cameras. Background Technology

[0002] In electronic systems, load switches are widely used for switching on and off in different power domains. Among them, load switches using MOSFETs as switching elements are widely adopted due to their high efficiency and ease of control.

[0003] However, using MOSFETs as switching elements can easily lead to the following two problems: First, at the moment of turn-on, it is necessary to charge the large-capacity filter capacitor in the subsequent stage, which will generate a huge surge current, causing the power network voltage to drop, which may cause system reset or stress damage to the MOSFET itself; Second, when turning off, it usually relies solely on the pull-down resistor of the gate for turn-off, which is slow and cannot meet the needs of some application scenarios with strict power timing requirements.

[0004] To address these issues, existing technologies typically employ complex integrated circuits, which integrate multiple functions to attempt to comprehensively solve problems such as surge current and turn-off speed. However, this approach is costly and increases the overall cost of the circuit. Utility Model Content

[0005] To address the aforementioned issues, this application provides a load switching circuit, a load switching device, and a camera that can achieve the functions of slow start-up and fast turn-off when a MOSFET is used as a switching element in a low-cost manner.

[0006] This application is implemented as follows: In a first aspect, this application provides a load switching circuit, which includes a MOSFET M1, a soft-start unit, a fast-turn-off unit, and a control logic unit. The source of the MOSFET M1 is connected to a power input terminal, and the drain of the MOSFET M1 is connected to a power output terminal. The source of the MOSFET M1 is connected to its gate via the soft-start unit. The gate of the MOSFET M1 is also connected to the control logic unit via the fast-turn-off unit. The control logic unit is also connected to the drain of the MOSFET M1. The input terminal of the control logic unit is used to receive an external turn-off control signal. The MOSFET M1 is used to control the on / off state of the main power path; the soft-start unit is used to control the MOSFET M1 to turn on slowly when the circuit is powered on; the control logic unit, after receiving the external turn-off control signal, sends a drive voltage signal to the fast-turn-off unit to drive the fast-turn-off unit to discharge the gate charge of the MOSFET M1.

[0007] Secondly, this application provides a load switching device, which includes any of the load switching circuits described in the first aspect.

[0008] Thirdly, this application provides a camera that includes any of the load switching circuits described in the first aspect.

[0009] Compared with the prior art, this application has at least the following advantages or beneficial effects: This application proposes a load switching circuit. Firstly, a high-impedance charging path composed of a soft-start unit is established between the source and gate of a MOSFET M1. This path actively controls the gate voltage of MOSFET M1 to change slowly upon power-up, forcing MOSFET M1 to operate in the linear region, thereby achieving a smooth rise in output voltage and effectively suppressing inrush current. Simultaneously, a low-impedance discharge path composed of a fast turn-off unit is established between the gate of MOSFET M1 and ground. This path is normally open, only turning on momentarily upon receiving a command from the control logic unit, providing a "highway for discharge" for gate charge, thus achieving a turn-off speed much faster than RC natural discharge. Furthermore, the two paths are independent current paths and control mechanisms that do not interfere with each other, ensuring that the soft-start process is unaffected by the fast turn-off unit, and the fast turn-off process is unaffected by the RC constant of the soft-start unit, thus ensuring optimal performance for each. Attached Figure Description

[0010] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of the structure of an embodiment of a load switching circuit according to this application; Figure 2 This is a schematic diagram of another embodiment of a load switching circuit according to this application; Figure 3 This is a schematic diagram of another embodiment of a load switching circuit according to this application; Figure 4 This is a schematic diagram of the circuit principle of an embodiment of a load switching circuit according to this application.

[0012] Icons: 10, Soft Start Unit; 20, Fast Turn-Off Unit; 30, Control Logic Unit; 40, Gate Clamp Unit; 50, Filter Unit. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0014] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0015] Example: The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the various embodiments and features described below can be combined with each other.

[0016] This application provides a load switching circuit that, by constructing independent soft-start and fast-turn-off paths, achieves the soft-start and fast-turn-off functions of a MOSFET as a switching element at low cost with separate components.

[0017] Please refer to Figure 1 The load switching circuit includes a MOSFET M1, a soft-start unit 10, a fast-turn-off unit 20, and a control logic unit 30. The source of the MOSFET M1 is connected to the power input terminal, and the drain of the MOSFET M1 is connected to the power output terminal. The source of the MOSFET M1 is connected to its gate through the soft-start unit 10. The gate of the MOSFET M1 is also connected to the control logic unit 30 through the fast-turn-off unit 20. The control logic unit 30 is also connected to the drain of the MOSFET M1. The input of the control logic unit 30 is used to receive an external turn-off control signal. Specifically, the MOSFET M1 controls the on / off of the main power path; the soft-start unit 10 controls the MOSFET M1 to turn on slowly when the circuit is powered on; and the control logic unit 30 sends a drive voltage signal to the fast-turn-off unit 20 after receiving the external turn-off control signal, thereby driving the fast-turn-off unit 20 to discharge the gate charge of the MOSFET M1.

[0018] It should be noted that while simply using an RC circuit for a soft-start design of a MOSFET can suppress surges, it significantly prolongs the turn-off time. Furthermore, relying solely on the pull-down resistor of the MOSFET gate for turn-off not only results in a slow turn-off speed, but in some other technical solutions, the charge discharge path may also affect the normal soft-start process of the RC circuit. The inventors' research revealed that this is because there may be a contradiction between "large time constant soft-start" and "small time constant fast turn-off"—that is, a high-resistance gate resistor is key to achieving slow charging (soft start), but it is also a bottleneck hindering rapid discharging (fast turn-off).

[0019] In response, the above embodiments construct a simple and low-cost separation scheme by separating functional paths and optimizing the topology. This scheme builds independent and non-interfering current paths and control mechanisms for the "soft start" and "fast turn-off" functions, so that the soft start process is not affected by the fast turn-off unit 20, and the fast turn-off process is not affected by the RC constant of the soft start unit 10, thus ensuring the optimization of their respective performance.

[0020] For ease of understanding, the following explanation will assume that the MOSFET M1 is P-type, and will explain the working principle of the soft start unit 10 and the fast turn-off unit 20. It can be understood that after understanding the working principle when the MOSFET M1 is P-type, the working principle of the soft start unit 10 and the fast turn-off unit 20 when the MOSFET M1 is N-type can be understood simultaneously.

[0021] For the load switching circuit of this application, in the above embodiment, a high-impedance charging path composed of a soft-start unit 10 is provided between the source and gate of the MOSFET M1. This path actively controls the gate voltage of the MOSFET M1 to change slowly upon power-up, forcing the MOSFET M1 to operate in the linear region, thereby achieving a smooth rise in output voltage and effectively suppressing inrush current. This process is unaffected by the shutdown circuit.

[0022] The principle is as follows: the soft-start unit 10 is connected between the source (input power supply) and gate of the MOSFET M1, forming a high-impedance active charging path. At power-on, the voltage of the energy storage element (such as a capacitor) inside the soft-start unit 10 cannot change abruptly, effectively maintaining the gate voltage of the MOSFET M1 briefly near the source voltage, thus keeping the MOSFET M1 in a turned-off state. Subsequently, the input power supply charges the energy storage element through a resistor, causing its voltage to change slowly. This slowly changing voltage controls the conduction level of a transistor (such as a PNP transistor), gradually moving it from saturation conduction to cutoff, thereby actively and linearly pulling the gate voltage of the MOSFET M1 down from high (for PMOS, the more negative the gate voltage, the stronger the conduction). This process forces the MOSFET M1 through a relatively long linear region, where its on-resistance decreases, achieving a smooth rise in output voltage.

[0023] Meanwhile, a low-impedance discharge path consisting of a fast turn-off unit 20 is provided between the gate of MOSFET M1 and ground. This path is normally open, but turns on momentarily only upon receiving a command from the control logic unit 30, providing a "highway for discharging" of gate charge, thereby achieving a turn-off speed much faster than RC natural discharge. This action is unaffected by the slow-start RC constant.

[0024] The principle is as follows: the fast turn-off unit 20 is connected between the gate of MOSFET M1 and ground, and is controlled by the control logic unit 30, normally operating in a high blocking state. Upon receiving a drive voltage signal from the control logic unit 30, the transistor (such as an NPN transistor) inside the unit quickly saturates and conducts, instantly establishing an extremely low-impedance discharge path between the gate of MOSFET M1 and ground. This path acts like a "discharge highway," rapidly discharging the charge stored on the gate capacitor of MOSFET M1 to ground with a very large current in a very short time. The gate voltage is thus rapidly pulled up (for PMOS), causing MOSFET M1 to quickly transition from the on state to the fully off state. The turn-off speed of the low-impedance discharge path is several orders of magnitude faster than the traditional passive turn-off relying on pull-up resistors. Furthermore, its turn-off speed is determined only by its own on-resistance and gate charge, completely unaffected by the time constants of the slow-start unit 10.

[0025] Furthermore, the control logic unit 30 receives an external shutdown signal on one hand, and cleverly draws power from its output on the other, ensuring the stability of the logic operation. Thus, when the MOSFET M1 needs to be turned off, the fast shutdown unit 20 drives the fast shutdown path to operate, achieving seamless timing coordination between the two independent paths.

[0026] To facilitate understanding, the following is a simple explanation of the interaction of the load switching circuit in different operating stages. Among them, (1) During the power-on and soft start stage: When the power input terminal is powered on, the soft start unit 10 starts working, controlling the gate voltage of MOS transistor M1 to change slowly, MOS transistor M1 slowly turns on, and the output voltage on the power output terminal rises smoothly. The control logic unit 30 is silent because the turn-off signal is invalid, and the fast turn-off unit 20 is turned off. The two paths do not interfere with each other. (2) During the stable conduction stage: MOS transistor M1 is fully turned on, and the circuit normally transmits power. The soft start unit 10 completes its task, and the control logic and fast turn-off unit 20 remain in standby. (3) During the fast turn-off stage: The control logic unit 30 receives a valid external turn-off control signal, outputs a drive voltage signal, drives the fast turn-off unit 20 to act immediately, establishes a low-impedance discharge path, and quickly discharges the gate charge of MOS transistor M1, so that MOS transistor M1 is quickly turned off.

[0027] Please refer to Figure 2 Based on the aforementioned scheme, in some implementations of this application, the load switch circuit further includes a gate clamping unit 40; one end of the gate clamping unit 40 is connected to the source of the MOS transistor M1, and the other end is connected to the gate of the MOS transistor M1, in order to clamp the gate voltage of the MOS transistor M1.

[0028] In the above implementation, by connecting a gate clamping unit 40 between the source and gate of the MOSFET M1, the gate voltage of the MOSFET M1 can be actively limited and stabilized to prevent it from exceeding the safe range. Furthermore, during rapid turn-off or when subjected to external noise interference, the gate path of the MOSFET M1 (which has parasitic inductance and capacitance) may generate high-frequency ringing. The peak voltage of these ringings may exceed the safe value. The gate clamping unit 40 can also quickly smooth out these ringing spikes.

[0029] For example, please refer to Figure 4 In some implementations of this application, the gate clamping unit 40 includes a resistor R1 and a diode D1. The resistor R1 is connected in parallel with the diode D1, the anode of the diode D1 is connected to the gate of the MOSFET M1, and the cathode of the diode D1 is connected to the source of the MOSFET M1.

[0030] In the above implementation, diode D1 prevents damage to MOSFET M1 due to gate-source voltage overshoot. Resistor R1, acting as a pull-up resistor, works in conjunction with the soft-start unit 10 to determine the initial gate position and soft-start rate of MOSFET M1. This is because resistor R1, as a fixed pull-up resistor, provides a clear discharge / bias path to the high potential (source) for the soft-start unit 10. Together with the dynamic resistance of the soft-start unit 10, it forms a voltage divider, ensuring the controllability and predictability of the soft-start process. Furthermore, during rapid turn-off, although the main discharge path is through the rapid turn-off unit 20, when the gate voltage of MOSFET M1 is pulled up to near the source voltage, if a positive voltage spike exists, diode D1, in forward conduction mode, can also provide a small fast discharge loop from the gate to the source. This additional, secondary gate charge discharge path further enhances the stability and anti-interference capability of the turn-off process. For example, to better clamp the voltage, diode D1 can be selected as a Zener diode.

[0031] Please refer to Figure 3 Based on the aforementioned solution, in some implementations of this application, the load switching circuit further includes a filter unit 50. One end of the filter unit 50 is connected to the drain of the MOSFET M1, and the other end is connected to the power input terminal. By introducing the filter unit 50, high-frequency noise in the output voltage can be filtered out, ensuring the stability of the output voltage. For example, please refer to... Figure 4 In some implementations of this application, the filter unit 50 may include capacitor C1 and capacitor C2. One end of capacitor C1 is grounded, and the other end is connected to the drain of MOSFET M1. Capacitor C2 is connected in parallel with capacitor C1.

[0032] Please refer to Figure 4 Based on the aforementioned scheme, in some implementations of this application, MOSFET M1 is a P-type MOSFET, and the soft-start unit 10 includes a PNP-type transistor Q1, resistors R2 and R3, and capacitor C3. The source of MOSFET M1 is connected to the base of transistor Q1 through resistor R2, the gate of MOSFET M1 is connected to the emitter of transistor Q1 through resistor R3, the base of transistor Q1 is connected to the collector of transistor Q1 through capacitor C3, and the collector of transistor Q1 is grounded.

[0033] The above implementation utilizes the charging characteristics of the RC circuit and the current amplification effect of the transistor to achieve a soft start-up of the MOSFET Q1, making its conduction and output voltage rise curves closer to linear, and resulting in a smoother and more effective suppression of inrush current. Specifically, at the moment of power-on, the saturated transistor Q1 provides an extremely low impedance path, firmly clamping the gate of the MOSFET M1 at a low level, ensuring that the MOSFET M1 will not be accidentally turned on. Next, the power input terminal begins to charge the capacitor C3 through resistor R2. As charging progresses, the conduction level of transistor Q1 gradually weakens, and the current flowing through transistor Q1 and resistor R3 also decreases. Due to the weakening of the conduction of transistor Q1, its pull-down capability of MOSFET M1 also gradually weakens. MOSFET M1 begins to enter the linear region from the off region and slowly turns on. Its on-resistance gradually decreases from infinity, causing the output voltage to rise smoothly from 0V, thereby effectively limiting the charging current (inrush current) of the capacitors in the subsequent circuit. When capacitor C3 is fully charged, transistor Q1 is completely cut off and no longer pulls down MOSFET M1.

[0034] If the gate clamping unit 40, as described above, includes a resistor R1 and a diode D1, is provided, the pull-up resistor R1 will start to play its role when the conduction of the transistor Q1 gradually weakens. It will work synchronously with the soft-start unit 10 to make the MOS transistor M1 start to enter the linear region from the off region and slowly turn on, so as to better perform the soft-start action.

[0035] Please refer to Figure 4 Based on the aforementioned scheme, in some implementations of this application, the fast shutdown unit 20 includes an NPN transistor Q2, a diode D2, and a resistor R4. The gate of the MOSFET M1 is connected to the collector of the transistor Q2 via the resistor R4. The emitter of the transistor Q2 is connected to the anode of the diode D2. The cathode of the diode D2 is grounded. The base of the transistor Q2 is connected to the output terminal of the control logic unit 30.

[0036] In the above implementation, a low-impedance active charge discharge channel is constructed based on the switching characteristics of transistor Q2 to enable rapid turn-off of MOSFET M1. When the base of transistor Q2 does not receive a drive voltage signal from the control logic unit 30, transistor Q2 is in a completely off state. In the off state, there is an extremely high impedance (megaohm level) between the collector and emitter of transistor Q2. At this time, looking into the gate of MOSFET M1, the rapid turn-off unit 20 is equivalent to an open circuit. That is to say, the rapid turn-off unit 20 is completely isolated during normal circuit operation and soft start-up, without causing any impact, ensuring the independent operation of the soft start function. Similarly, when the base of transistor Q2 receives a drive voltage signal from the control logic unit 30, this drive voltage signal can drive transistor Q2 into a saturated conduction state. Once the transistor is saturated, an extremely low impedance path (usually only a few ohms or even lower) will be established between its collector and emitter. This path connects the gate of MOSFET M1 to ground via resistor R4 and diode D2. At this time, the negative charge stored on the gate capacitance of MOSFET M1 (for PMOS, the gate is negative when turned on) is rapidly discharged through the following path: MOSFET M1 gate → resistor R4 → transistor Q2 (CE) → diode D2 → ground. Due to the extremely low impedance of this path, the discharge current is very large, and the gate-source voltage of MOSFET M1 is rapidly pulled up (approaching 0V), causing the gate-source voltage of MOSFET M1 to decrease rapidly, thus turning off MOSFET M1 very quickly.

[0037] Please refer to Figure 4 Based on the aforementioned scheme, in some implementations of this application, the control logic unit 30 includes an NPN transistor Q3, resistors R5, R6, R7, R8, and R9. One end of resistor R8 is used to receive an external shutdown control signal. Figure 4 The other end of the IN SYS_PWR_OFF signal is connected to the base of transistor Q3. The base of transistor Q3 is connected to the emitter of transistor Q3 through resistor R9. The emitter of transistor Q3 is connected to the collector of transistor Q3 through resistor R7. The emitter of transistor Q3 is also grounded. The collector of transistor Q3 is connected to the drain of MOSFET M1 through resistor R5.

[0038] In the above implementation, the logic unit mainly uses the switching on and off of the PN transistor Q3 to convert the received external shutdown control signal (the shutdown control signal can be low or floating during normal circuit operation, and is pulled high when shutdown is required) into a drive voltage signal to control the switching on and off of the transistor Q2. Resistors R5 and R7 form a voltage divider bias at the collector of transistor Q3, ensuring the stability of the logic level.

[0039] Specifically, when resistor R8 does not receive an external shutdown control signal, transistor Q3 is reliably cut off due to the pull-down effect of resistor R9, and resistor R9 also prevents false turn-on caused by external noise interference. When transistor Q3 is cut off, transistor Q2 also remains cut off, thus the fast shutdown unit 20 does not work and does not affect the main circuit. When resistor R8 receives an external shutdown control signal, this high level provides sufficient base current through resistor R8, causing transistor Q3 to quickly enter saturation conduction. Once transistor Q3 is saturated and conducting, it will drive transistor Q2 to conduct, thereby ensuring the execution of the shutdown logic of the corresponding fast shutdown unit 20.

[0040] In the above implementation, the control logic unit 30 draws power from the power output terminal, which also ensures that even if the voltage input to the power input terminal drops or becomes unstable due to a fault, as long as there is still charge on the output capacitor, the control logic unit 30 can obtain the operating voltage, thereby reliably executing the shutdown command and further improving the reliability of the fast shutdown unit 20.

[0041] This application also provides a load switching device, which includes a load switching circuit as described above. For example, a load switching device can be made by encapsulating a circuit board with the load switching circuit inside a housing, thereby facilitating user operation and providing convenience.

[0042] This application also provides a camera that includes a load switching circuit as described above. The camera primarily integrates any of the load switching circuits described above to facilitate soft-start and fast-shutdown of the power supply to one or more functional modules within the camera (such as an image sensor, processor, lens motor drive, flash, etc.).

[0043] It should be noted that the soft-start function of this load switch circuit can effectively suppress the inrush current generated when charging the large-capacity filter capacitor inside the camera, avoiding system reset or image sensor malfunction caused by power network voltage drops. This contributes to ensuring image quality and system stability at the moment of power-on. Simultaneously, the fast shutdown function of this load switch circuit ensures the camera enters shutdown or standby mode promptly, guaranteeing that the camera can quickly cut off power to each module according to a predetermined sequence. This prevents reverse current or logic confusion caused by shutdown delays, thereby improving the camera's response speed and reliability.

[0044] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this application. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A load switching circuit, characterized in that, It includes a MOSFET M1, a soft-start unit, a fast-turn-off unit, and a control logic unit. The source of the MOSFET M1 is connected to the power input terminal, and the drain of the MOSFET M1 is connected to the power output terminal. The source of the MOSFET M1 is connected to the gate of the MOSFET M1 through the soft-start unit. The gate of the MOSFET M1 is also connected to the control logic unit through the fast-turn-off unit. The control logic unit is also connected to the drain of the MOSFET M1. The input terminal of the control logic unit is used to receive external turn-off control signals. Among them, MOSFET M1 is used to control the on and off of the main power path; the soft start unit is used to control MOSFET M1 to turn on slowly when the circuit is powered on; the control logic unit is used to send a drive voltage signal to the fast turn-off unit after receiving an external turn-off control signal, so as to drive the fast turn-off unit to discharge the gate charge of MOSFET M1.

2. The load switching circuit according to claim 1, characterized in that, It also includes a gate clamping unit; one end of the gate clamping unit is connected to the source of the MOS transistor M1, and the other end is connected to the gate of the MOS transistor M1, in order to clamp the gate voltage of the MOS transistor M1.

3. The load switching circuit according to claim 1 or 2, characterized in that, It also includes a filtering unit, one end of which is connected to the drain of the MOS transistor M1, and the other end is used to connect to the power input terminal.

4. The load switching circuit according to claim 1, characterized in that, The MOS transistor M1 is a P-type MOS transistor, and the soft-start unit includes a PNP transistor Q1, a resistor R2, a resistor R3, and a capacitor C3. The source of the MOS transistor M1 is connected to the base of the transistor Q1 through the resistor R2, the gate of the MOS transistor M1 is connected to the emitter of the transistor Q1 through the resistor R3, the base of the transistor Q1 is connected to the collector of the transistor Q1 through the capacitor C3, and the collector of the transistor Q1 is grounded.

5. The load switching circuit according to claim 4, characterized in that, The fast shutdown unit includes an NPN transistor Q2, a diode D2, and a resistor R4; The gate of the MOS transistor M1 is connected to the collector of the transistor Q2 through the resistor R4, the emitter of the transistor Q2 is connected to the anode of the diode D2, the cathode of the diode D2 is grounded, and the base of the transistor Q2 is connected to the output terminal of the control logic unit.

6. The load switching circuit according to claim 5, characterized in that, The control logic unit includes an NPN transistor Q3, resistors R5, R6, R7, R8, and R9. In this configuration, one end of resistor R8 is used to receive an external shutdown control signal, and the other end is connected to the base of transistor Q3. The base of transistor Q3 is connected to the emitter of transistor Q3 through resistor R9. The emitter of transistor Q3 is connected to the collector of transistor Q3 through resistor R7. The emitter of transistor Q3 is also grounded. The collector of transistor Q3 is connected to the drain of MOSFET M1 through resistor R5.

7. The load switching circuit according to any one of claims 4-6, characterized in that, It also includes a gate clamping unit, which includes a resistor R1 and a diode D1; The resistor R1 is connected in parallel with the diode D1, the anode of the diode D1 is connected to the gate of the MOS transistor M1, and the cathode of the diode D1 is connected to the source of the MOS transistor M1.

8. The load switching circuit according to any one of claims 4-6, characterized in that, It also includes a filtering unit, which includes capacitor C1 and capacitor C2; One end of capacitor C1 is grounded, and the other end is connected to the drain of MOS transistor M1. Capacitor C2 is connected in parallel with capacitor C1.

9. A load switch device, characterized in that, Includes the load switching circuit as described in any one of claims 1-8.

10. A camera, characterized in that, Includes the load switching circuit as described in any one of claims 1-8.

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