Overload / short circuit protection circuit and electronic device

Abstract

The application provides an overload / short circuit protection circuit and electronic equipment. The protection circuit comprises a constant current control circuit, a load on-off control circuit, a driving circuit and a voltage reduction and stabilization circuit. The constant current control circuit is used for limiting the current of a front-end load CN1; the load on-off control circuit is used for controlling the power supply to a rear-end load CN2; the driving circuit is coupled with the load on-off control circuit and the constant current control circuit, and is used for driving the load on-off control circuit; and the voltage reduction and stabilization circuit is coupled with the driving circuit and the constant current control circuit, and is used for providing operating voltage and reference voltage for the operational amplifier on the driving circuit and the constant current control circuit. Therefore, the current output can be limited when the overload, short circuit or large-capacitance load starting occurs, so as to protect the rear-end power supply circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to an overload / short circuit protection circuit and electronic equipment. Background Art

[0002] The safety of electronic products is an important indicator of their quality. Overload protection is a protection mechanism when designing control boards for electronic products.

[0003] Currently, the system structure of DC 5V load protection overload and overcurrent products on the market is realized by using dedicated IC, such as Figure 1 As shown, the IC's EN port and the sampling resistor at the RSET port work together to limit the VOUT output current. If the output load current is excessive or short-circuited, the IC gradually shuts down the MOS transistors, protecting the preceding switching power supply circuit. Based on the withstand voltage characteristics of the IC's internal components, current market protection is for DC 5V load overload and overcurrent. The IC requires an MCU to control the high / low level of the EN port to complete the system circuit. Summary of the Invention

[0004] The present invention provides an overload / short circuit protection circuit, which comprises a constant current control circuit, a load on / off control circuit, a drive circuit and a voltage step-down and voltage stabilization circuit.

[0005] The constant current control circuit is used to limit the current of the front-end load CN1; the load on-off control circuit is used to control the power supply to the back-end load CN2; the drive circuit couples the load on-off control circuit and the constant current control circuit to drive the load on-off control circuit; the buck regulator circuit couples the drive circuit and the constant current control circuit to provide operating voltage and reference voltage to the operational amplifiers on the drive circuit and the constant current control circuit.

[0006] In one embodiment, the load on-off control circuit includes a resistor R3, a resistor R4, a resistor R5, a resistor R17, a PMOS transistor Q1, and a transistor Q2. The front end of the resistor R4 is connected to the gate of the PMOS transistor Q1 and the rear end of the resistor R5. The rear end of the resistor R4 is connected to the input end of the power supply, the source of the PMOS transistor Q1, and the positive end of the rear end load CN2. The drain of the PMOS transistor Q1 is connected to the output end of the power supply and the positive end of the front end load CN1. The front end of the resistor R5 is connected to the collector of the transistor Q2. The rear end of the resistor R3 is connected to the base of the transistor Q2 and the rear end of the resistor R17. The front end of the resistor R17 is grounded.

[0007] In one embodiment, the driving circuit includes a resistor R6, a resistor R7, a resistor R8, a diode D2, a capacitor C5, and an operational amplifier U1B. The front end of the resistor R6 is connected to the non-inverting input terminal PIN5 of the operational amplifier U1B and the rear end of the resistor R7. The rear end of the resistor R6 is connected to the output terminal PIN7 of the operational amplifier U1B and the front end of the resistor R3. The front end of the resistor R7 is connected to the resistor R8, the diode D2, and the rear end of the capacitor C5. The front end of the capacitor C5 is grounded.

[0008] In one embodiment, the constant current control circuit includes a resistor R9, a resistor R18, a transistor Q3 and an operational amplifier U1A, the front end of the resistor R9 is connected to the base of the transistor Q3, the rear end of the resistor R9 is connected to the resistor R8, the front end of the diode D2 and the output terminal PIN1 of the operational amplifier U1A, the rear end of the resistor R18 is connected to the emitter of the transistor Q3 and the inverting input terminal PIN2 of the operational amplifier U1A, the front end of the resistor R18 is grounded, and the collector of the transistor Q3 is connected to the negative end of the front end load CN1.

[0009] In one embodiment, the step-down voltage regulator circuit includes a diode D1, a resistor R10, a resistor R11, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, and a three-terminal voltage regulator. The front end of the diode D1 is connected to the rear ends of the resistor R10 and the resistor R11, the rear end of the diode D1 is connected to a power supply, the front ends of the resistor R10 and the resistor R11 are connected to the rear ends of the capacitor C1, the capacitor C2, and the input port of the three-terminal voltage regulator. The capacitor C1 and The front end of the capacitor C2 is grounded, the output port of the three-terminal voltage regulator is connected to the rear ends of the capacitor C3, the capacitor C4, the resistor R13 and the resistor R15, the front ends of the capacitor C3 and the capacitor C4 are grounded, the front end of the resistor R13 is connected to the rear end of the resistor R14 and the inverting input terminal PIN6 of the operational amplifier U1B, the front end of the resistor R14 is grounded, the front end of the resistor R15 is connected to the rear end of the resistor R16 and the non-inverting input terminal PIN3 of the operational amplifier U1A, and the front end of the resistor R16 is grounded.

[0010] In one embodiment, the overload / short circuit protection circuit further includes a resistor R1 connected to the positive terminal of the rear-end load CN2.

[0011] In one embodiment, the overload / short circuit protection circuit further includes a resistor R2 connected to the negative terminal of the rear-end load CN2.

[0012] In one embodiment, the step-down voltage regulator circuit provides an operating voltage and a reference voltage VREF1 to the operational amplifier U1A, and provides an operating voltage and a reference voltage VREF2 to the operational amplifier U1B.

[0013] In one embodiment, the reference voltage VREF1 at the non-inverting input terminal of the operational amplifier U1A is used to control the maximum current of the front-end load CN1.

[0014] The present invention further provides an electronic device, comprising the overload / short-circuit protection circuit described in any one of the above embodiments.

[0015] One advantage of the present invention is that it provides an overload / short-circuit protection circuit and electronic device. By combining a constant current control circuit, a load on / off control circuit, a drive circuit, and a step-down voltage regulator circuit, the present invention can limit the output current without the need for a dedicated IC in the event of an output overload, short circuit, or startup with a large capacitive load, thereby protecting the back-end power supply circuit. This circuit has low production costs and broad market application prospects. Furthermore, resistors R6 and R7 form a weak positive feedback circuit, which stabilizes the high and low level outputs of operational amplifier U1B.

[0016] Another advantage of the present invention is that it provides an overload / short-circuit protection circuit and electronic device. By adjusting the reference voltage VREF1, the load current limit can be conveniently adjusted. By adjusting the reference voltage VREF2, the load on / off duty cycle can be adjusted, thereby controlling the heating of the transistor Q3 and adapting to different load types. In addition, the overload / short-circuit protection circuit and electronic device have a wide applicable voltage range.

[0017] Other features and benefits of the present invention will be described in the following description and, in part, will become apparent from the description or be understood through practice of the present invention. The objectives and other benefits of the present invention can be achieved and obtained through the structures specifically pointed out in the description, claims, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work. The positional relationships described in the drawings in the following description are based on the directions of the components drawn in the diagrams, unless otherwise specified.

[0019] Figure 1 It is a circuit principle diagram of an overload protection circuit in the prior art;

[0020] Figure 2 1 is a schematic structural diagram of an overload / short-circuit protection circuit provided by one embodiment of the present invention;

[0021] Figure 3 4 is a circuit diagram of an overload / short-circuit protection circuit provided in one embodiment of the present invention.

[0022] Reference numerals:

[0023] 10-overload / short-circuit protection circuit; 12-constant current control circuit; 14-load on / off control circuit; 16-drive circuit; 18-step-down voltage stabilization circuit. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments; the technical features designed in different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] In the description of the present invention, it should be understood that the terms "center", "lateral", "up", "down", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more. In addition, the term "including" and any variations thereof all mean "at least including".

[0026] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integrally formed connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0027] The terms used herein are intended only to describe specific embodiments and are not intended to limit exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms "a", "an", "an item" used herein are also intended to include the plural. It should also be understood that the terms "comprise" and / or "include" used herein specify the presence of stated features, integers, steps, operations, units and / or components, and do not preclude the presence or addition of one or more other features, integers, steps, operations, units, components and / or combinations thereof.

[0028] See also Figure 2 and Figure 3 , Figure 2 1 is a schematic structural diagram of an overload / short circuit protection circuit 10 provided in one embodiment of the present invention. Figure 3 Figure 1 is a schematic diagram illustrating the principle of an overload / short-circuit protection circuit 10 according to one embodiment of the present invention. To achieve at least one of the aforementioned advantages, or other advantages, one embodiment of the present invention provides an overload / short-circuit protection circuit 10 suitable for DC loads, such as 12V / 24V / 36V DC loads. As shown in the figure, the overload / short-circuit protection circuit 10 is coupled to a front-end load CN1 and a rear-end load CN2. The overload / short-circuit protection circuit 10 includes a constant current control circuit 12, a load on / off control circuit 14, a drive circuit 16, and a buck regulator circuit 18.

[0029] The constant current control circuit 12 is used to limit the current of the front-end load CN1; the load on-off control circuit 14 is used to control the power supply to the back-end load CN2; the drive circuit 16 couples the load on-off control circuit 14 and the constant current control circuit 12, and is used to drive the load on-off control circuit 14; the buck regulator circuit 18 couples the drive circuit 16 and the constant current control circuit 12, and is used to provide an operating voltage and a reference voltage to the operational amplifiers on the drive circuit 16 and the constant current control circuit 12.

[0030] Specifically, the load on / off control circuit 14 includes resistors R3, R4, R5, R17, a PMOS transistor Q1, and a transistor Q2. The connections between the components of the load on / off control circuit 14 are as follows: the rear end of resistor R4 is connected to the input of the power supply, the source of PMOS transistor Q1, and the positive terminal of the rear end load CN2; the front end of resistor R4 is connected to the gate of PMOS transistor Q1 and the rear end of resistor R5; the drain of PMOS transistor Q1 is connected to the output of the power supply and the positive terminal of the front end load CN1; the front end of resistor R5 is connected to the collector of transistor Q2; the rear end of resistor R3 is connected to the base of transistor Q2 and the rear end of resistor R17; and the front end of resistor R17 is grounded.

[0031] The load on-off control circuit 14 operates as follows: when the voltage V3 at the front end of the resistor R3 is high, the transistor Q2 is turned on and the PMOS transistor Q1 is turned on, thereby connecting the 24V power supply to the rear-end load CN2; when the voltage V3 at the front end of the resistor R3 is low, the transistor Q2 is turned off and the PMOS transistor Q1 is turned off, thereby disconnecting the 24V power supply to the rear-end load.

[0032] Drive circuit 16 includes resistors R6, R7, R8, diode D2, capacitor C5, and operational amplifier U1B. The connections between the components of drive circuit 16 are as follows: the rear end of resistor R6 is connected to the output terminal PIN7 of operational amplifier U1B and the front end of resistor R3; the front end of resistor R6 is connected to the non-inverting input terminal PIN5 of operational amplifier U1B and the rear end of resistor R7; the front end of resistor R7 is connected to the rear end of resistor R8, diode D2, and capacitor C5; and the front end of capacitor C5 is grounded.

[0033] The operation of the drive circuit 16 is as follows: When the input voltage V1 increases, the input voltage V1 charges the capacitor C5 through the resistor R8. When the voltage of the capacitor C5 increases to the point where the voltage at the non-inverting input terminal PIN5 of the operational amplifier U1B is higher than the voltage at the inverting input terminal PIN2, the operational amplifier U1B outputs a high level. When the input voltage V1 decreases, the voltage of the capacitor C5 is rapidly discharged through the diode D2. When the voltage of the capacitor C5 drops to the point where the voltage at the non-inverting input terminal PIN5 of the operational amplifier U1B is lower than the voltage at the inverting input terminal PIN6, the operational amplifier U1B outputs a low level. In other words, when V1 increases, the voltage of capacitor C5 slowly rises through the RC charging of resistor R8 and capacitor C5. That is, when V1 is high, the driver circuit 16 can delay driving the load on / off control circuit 14, causing the PMOS transistor Q1 to turn on with a delay. When V1 decreases, the voltage of capacitor C5 quickly discharges through diode D2. That is, when V1 is low, the driver circuit 16 can quickly turn off the PMOS transistor Q1 of the load on / off control circuit 14, thereby quickly shutting off the 24V power supply when the back-end load CN2 is overloaded, providing protection. The driver circuit 16 can quickly shut off the PMOS transistor Q1 when a load anomaly occurs, disconnecting the back-end 24V load CN2. When the 24V load CN2 is disconnected, there is no current flowing, and the voltage of V1 increases. Due to the RC charging time (resistor R8 and capacitor C5), the PMOS transistor Q1 is delayed in turning on. This allows for a short on-state followed by a long off-state when a load anomaly occurs, protecting the transistor Q3 in the constant current control circuit 12.

[0034] The constant current control circuit 12 includes resistors R9 and R18, transistor Q3, and operational amplifier U1A. The connections between the components of constant current control circuit 12 are as follows: the rear end of resistor R9 is connected to the front end of resistor R8, diode D2, and output terminal PIN1 of operational amplifier U1A; the front end of resistor R9 is connected to the base of transistor Q3; the rear end of resistor R18 is connected to the emitter of transistor Q3 and the inverting input terminal PIN2 of operational amplifier U1A; the front end of resistor R18 is grounded; and the collector of transistor Q3 is connected to the negative terminal of front-end load CN1. Resistor R18 can be used for load circuit sampling.

[0035] The constant current control circuit 12 operates as follows: When the current increases, the voltage across resistor R18 increases until the voltage at the inverting input PIN2 of the operational amplifier U1A falls below the voltage at the non-inverting input PIN3. This causes the output voltage of the operational amplifier U1A to decrease, causing transistor Q3 to enter an amplification state. Finally, the voltage at the non-inverting input PIN3 and the voltage at the inverting input PIN2 reach consistency, balancing the driving voltage of transistor Q3. When the output voltage of the operational amplifier U1A decreases, it pulls down the voltage across capacitor C5 on the drive circuit 16, causing the output of the operational amplifier U1B to output a low level, thereby shutting off the PMOS transistor Q1 and disconnecting the 24V downstream load. When the current decreases, the voltage across resistor R18 decreases, causing the voltage at the inverting input PIN2 of the operational amplifier U1A to fall below the voltage at the non-inverting input PIN3. This causes the output voltage of the operational amplifier U1A to increase, causing transistor Q3 to enter a saturation state. When the current is normal, that is, the load current is less than the limit value, the high voltage output by the operational amplifier U1A drives the load on / off control circuit 14 through the drive circuit 16 to turn on the PMOS transistor Q1, thereby maintaining continuous power supply to the load CN2.

[0036] Preferably, resistors R6 and R7 form a weak positive feedback circuit, which can make the high and low level outputs of operational amplifier U1B more stable. The reference voltage VREF1 at the non-inverting input terminal PIN3 of operational amplifier U1A determines the maximum current of the load.

[0037] The step-down voltage regulator circuit 18 includes a diode D1 , a resistor R10 , a resistor R11 , a resistor R13 , a resistor R14 , a resistor R15 , a resistor R16 , a capacitor C1 , a capacitor C2 , a capacitor C3 , a capacitor C4 and a three-terminal voltage regulator U2 . The connection relationship of the various components of the step-down voltage regulator circuit 18 is as follows: the rear end of the diode D1 is connected to the power supply, the front end of the diode D1 is connected to the rear ends of the resistor R10 and the resistor R11, the front ends of the resistor R10 and the resistor R11 are connected to the rear ends of the capacitor C1, the capacitor C2 and the input port of the three-terminal voltage regulator U2, the front ends of the capacitor C1 and the capacitor C2 are grounded, the output port of the three-terminal voltage regulator U2 is connected to the rear ends of the capacitor C3, the capacitor C4, the resistor R13 and the resistor R15, the front ends of the capacitor C3 and the capacitor C4 are grounded, the front end of the resistor R13 is connected to the rear end of the resistor R14 and the inverting input terminal PIN6 of the operational amplifier U1B, the front end of the resistor R14 is grounded, the front end of the resistor R15 is connected to the rear end of the resistor R16 and the non-inverting input terminal PIN3 of the operational amplifier U1A, and the front end of the resistor R16 is grounded.

[0038] Buck regulator circuit 18 provides a stable power supply and reference voltages VREF1 and VREF2 to operational amplifiers U1A and U1B. Specifically, buck regulator circuit 18 provides operating voltage and reference voltage VREF1 to operational amplifier U1A, and provides operating voltage and reference voltage VREF2 to operational amplifier U1B. Reference voltage VREF1 limits the maximum current flowing through front-end load CN1, i.e., the maximum current that can flow through the constant current driver of constant current control circuit 12. When reference voltage VREF2 is increased, the RC charging voltage increases. Consequently, when operational amplifier U1A outputs a high voltage, a longer delay is required before operational amplifier U1B outputs a high level, turning on PMOS transistor Q1. When operational amplifier U1A outputs a low voltage, operational amplifier U1B outputs a low level more quickly, turning off PMOS transistor Q1. In other words, increasing reference voltage VREF2 reduces the duty cycle of PMOS transistor Q1 when the load is abnormal, thereby preventing excessive power consumption by transistor Q3 even under abnormal load conditions.

[0039] The overload / short circuit protection circuit may further include a resistor R1 and a resistor R2. The resistor R1 is connected to the positive terminal of the rear-end load CN2, and the resistor R2 is connected to the negative terminal of the rear-end load CN2. The resistors R1 and R2 may serve as an isolation to reduce the impact of external interference.

[0040] In general, when the front-end load CN1 is normal and the current is within the protection range, the voltage V at the PIN2 port of the operational amplifier U1A is less than the reference voltage VREF1, and the PIN1 port of the operational amplifier U1A outputs a high level V1, the base voltage of the transistor Q3 becomes high, and the transistor Q3 is turned on, so that it is always in a saturated conduction state; the voltage V1 synchronously charges the capacitor C5 through the resistor R8 until the voltage V2> the reference voltage VREF2, and the PIN7 port of the operational amplifier U1B outputs a high level V3, so that the base voltage of the transistor Q2 becomes high, and the transistor Q2 is turned on, so that the transistor Q2 is always in the on state, thereby making the gate input of the PMOS tube Q1 low level, and then turning on the PMOS tube Q1, so that it is always in the on state, ensuring that the front-end load CN1 is in a normal working state.

[0041] When the front-end load CN1 experiences a short circuit or overcurrent abnormality, after flowing through the constant current control circuit 12, transistor Q3 enters an amplified state, and the current is limited to I = VREF1 / R18. This causes transistor Q3 to bear the vast majority of the power dissipation P = 24V * I, while resistor R18 bears a small portion. To address the power dissipation problem of transistor Q3, an overload and short-circuit protection shutdown circuit consisting of components such as operational amplifier U1B, transistor Q2, capacitor C5, diode D2, resistor R8, and PMOS transistor Q1 is added, thereby reducing the power loss of transistor Q3. The specific working process is as follows: After entering the protection state, the voltage V at PIN2 of operational amplifier U1A is greater than VREF1, then the output voltage V1 at PIN1 of operational amplifier U1A becomes low, and the voltage V2 across capacitor C5 discharges to V1 through diode D2. When the voltage at PIN5 of operational amplifier U1B is <VREF2时,运算放大器U1B的PIN7口输出电压V3为低电平,电阻R6和电阻R7组成正反馈使V3输出稳定的低电平,三极管Q2的基极电压变低,关闭三极管Q2,使其一直处于截止状态,使PMOS管Q1的栅极输入高电平,从而关闭PMOS管Q1,切断+24V的电压输入。随着+24V的电压的切断,运算放大器U1A的PIN2电压V由高变低且V<VREF1,则运算放大器U1A的PIN1口输出电压V1变高电平,通过电阻R8对C5充电后电压为V2,且电压V2> After VREF2, PIN7 of operational amplifier U1B outputs high level V3. Resistors R6 and R7 form positive feedback to make V3 output a stable high level. The base voltage of transistor Q2 becomes high, turning on transistor Q2 and making it in the on state, thereby making the gate input of PMOS tube Q1 low level, and then turning on PMOS tube Q1 and making it in the on state.

[0042] It should be noted that if the fault in front-end load CN1 persists, the PMOS transistor Q1 and transistor Q3 in the entire circuit remain in an on-off cycle until the fault in load CN1 is resolved, at which point normal operation resumes. Furthermore, this embodiment is illustrated for a 24V load and is not intended to limit the present invention.

[0043] This embodiment further provides an electronic device, which includes the overload / short-circuit protection circuit 10 described in any one of the above embodiments.

[0044] One advantage of the present invention is that it provides an overload / short-circuit protection circuit 10 and electronic device. By combining a constant current control circuit 12, a load on / off control circuit 14, a drive circuit 16, and a step-down voltage regulator circuit 18, the circuit can limit the output current without the need for a dedicated IC when the output is overloaded, short-circuited, or started with a large capacitive load, thereby protecting the back-end power supply circuit. The circuit has low production costs and broad market application prospects. Furthermore, resistors R6 and R7 form a weak positive feedback circuit, making the high-level and low-level outputs of operational amplifier U1B more stable.

[0045] Another advantage of the present invention is that it provides an overload / short-circuit protection circuit 10 and electronic device. By adjusting the reference voltage VREF1, the current limit of the front-end load CN1 can be conveniently adjusted. By adjusting the reference voltage VREF2, the duty cycle of the on-off switching of the back-end load CN2 can be adjusted, thereby controlling the heating of the transistor Q3 and adapting to different load types. In addition, the overload / short-circuit protection circuit 10 and electronic device have a wide applicable voltage range.

[0046] In addition, those skilled in the art should understand that, although there are many problems in the prior art, each embodiment or technical solution of the present invention may be improved in only one or several aspects, without having to simultaneously solve all the technical problems listed in the prior art or background art. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as limiting the claim.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An overload / short-circuit protection circuit coupled to a front-end load CN1 and a rear-end load CN2, characterized in that: The overload / short circuit protection circuit comprises: A constant current control circuit, used to limit the current of the front-end load CN1; A load on-off control circuit, used to control the power supply to the rear-end load CN2; a driving circuit coupled to the load on-off control circuit and the constant current control circuit, and configured to drive the load on-off control circuit; a step-down voltage stabilization circuit, coupled to the driving circuit and the constant current control circuit, for providing an operating voltage and a reference voltage to the operational amplifiers on the driving circuit and the constant current control circuit; The load on / off control circuit includes a resistor R3, a resistor R4, a resistor R5, a resistor R17, a PMOS transistor Q1, and a transistor Q2. The rear end of the resistor R4 is connected to the input end of the power supply, the source of the PMOS transistor Q1, and the positive end of the rear end load CN2. The front end of the resistor R4 is connected to the gate of the PMOS transistor Q1 and the rear end of the resistor R5. The drain of the PMOS transistor Q1 is connected to the output end of the power supply and the positive end of the front end load CN1. The front end of the resistor R5 is connected to the collector of the transistor Q2. The rear end of the resistor R3 is connected to the base of the transistor Q2 and the rear end of the resistor R17. The front end of the resistor R17 is grounded. The driving circuit includes a resistor R6, a resistor R7, a resistor R8, a diode D2, a capacitor C5, and an operational amplifier U1B. The rear end of the resistor R6 is connected to the output terminal PIN7 of the operational amplifier U1B and the front end of the resistor R3. The front end of the resistor R6 is connected to the non-inverting input terminal PIN5 of the operational amplifier U1B and the rear end of the resistor R7. The front end of the resistor R7 is connected to the resistor R8, the diode D2, and the rear end of the capacitor C5. The front end of the capacitor C5 is grounded. The constant current control circuit includes a resistor R9, a resistor R18, a transistor Q3 and an operational amplifier U1A, the rear end of the resistor R9 is connected to the resistor R8, the front end of the diode D2 and the output terminal PIN1 of the operational amplifier U1A, the front end of the resistor R9 is connected to the base of the transistor Q3, the rear end of the resistor R18 is connected to the emitter of the transistor Q3 and the inverting input terminal PIN2 of the operational amplifier U1A, the front end of the resistor R18 is grounded, and the collector of the transistor Q3 is connected to the negative end of the front end load CN1; When the voltage at the front end of the resistor R3 is at a high level, the transistor Q2 is turned on and the PMOS tube Q1 is turned on, thereby connecting the power supply to the rear-end load CN2; when the voltage at the front end of the resistor R3 is at a low level, the transistor Q2 is turned off and the PMOS tube Q1 is turned off, thereby disconnecting the power supply to the rear-end load.

2. The overload / short circuit protection circuit according to claim 1, wherein: The step-down voltage stabilizing circuit includes a diode D1, a resistor R10, a resistor R11, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4 and a three-terminal voltage regulator. The rear end of the diode D1 is connected to a power supply, the front end of the diode D1 is connected to the rear ends of the resistor R10 and the resistor R11, the front ends of the resistor R10 and the resistor R11 are connected to the rear ends of the capacitor C1 and the capacitor C2 and the input port of the three-terminal voltage regulator. The capacitor C1 and the capacitor C2 are connected to the input port of the three-terminal voltage regulator. The front end of capacitor C2 is grounded, the output port of the three-terminal voltage regulator is connected to the rear ends of capacitor C3, capacitor C4, resistor R13 and resistor R15, the front ends of capacitor C3 and capacitor C4 are grounded, the front end of resistor R13 is connected to the rear end of resistor R14 and the inverting input terminal PIN6 of the operational amplifier U1B, the front end of resistor R14 is grounded, the front end of resistor R15 is connected to the rear end of resistor R16 and the non-inverting input terminal PIN3 of the operational amplifier U1A, and the front end of resistor R16 is grounded.

3. The overload / short circuit protection circuit according to claim 2, wherein: The overload / short circuit protection circuit further includes a resistor R1 connected to the positive terminal of the rear-end load CN2.

4. The overload / short circuit protection circuit according to claim 2, wherein: The overload / short circuit protection circuit further includes a resistor R2 connected to the negative end of the rear-end load CN2.

5. The overload / short circuit protection circuit according to claim 2, wherein: The step-down voltage stabilization circuit provides an operating voltage and a reference voltage VREF1 to the operational amplifier U1A, and provides an operating voltage and a reference voltage VREF2 to the operational amplifier U1B.

6. The overload / short circuit protection circuit according to claim 2, wherein: The reference voltage VREF1 at the non-inverting input terminal of the operational amplifier U1A is used to control the maximum current of the front-end load CN1.

7. An electronic device, characterized in that: The electronic device comprises: the overload / short circuit protection circuit according to any one of claims 1 to 6.

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