Motor stalling protection circuit based on parallel sampling resistors

Abstract

The invention relates to the field of motor locked-rotor protection circuits, in particular to a motor locked-rotor protection circuit based on parallel sampling resistors, which comprises a motor driving module comprising an H-bridge circuit; the current sampling module comprises a first sampling resistor R9 and a second sampling resistor R91 which are connected in parallel and is used for converting motor current into sampling voltage; the filtering module comprises an inductor L2 and a first capacitor C3, one end of the inductor L2 is connected to a parallel node of the first sampling resistor R9 and the second sampling resistor R91, and the other end of the inductor L2 is grounded through the first capacitor C3; the control module comprises an MCU (Microprogrammed Control Unit), and the MCU is used for periodically collecting the filtered sampling voltage and converting the filtered sampling voltage into a corresponding current value; the MCU compares the current value with a preset reference current threshold value; and when it is detected that the current value continuously exceeds the reference current threshold value for a preset duration, the motor driving module is controlled to cut off power supply of the motor. Therefore, the motor is effectively prevented from being in a locked-rotor state for a long time and is protected from being damaged.

Description

Technical Field

[0001] The present invention relates to the field of motor stall protection circuits, and in particular to a motor stall protection circuit based on parallel sampling resistors. Background Art

[0002] Traditional electronic waste bin circuits often lack dedicated stall detection mechanisms. When the motor drives the lid to open or close, if the lid is restrained, the motor may continue to run and become stalled. In this case, the motor current rises sharply, but traditional circuits cannot detect this abnormality in time, making it impossible to take effective protective measures.

[0003] Even if some traditional circuits incorporate some form of protection mechanism, its response speed often lags behind the occurrence of stalling. This means that the protection mechanism may not be activated until the motor has already suffered damage or even caused a safety accident, thus failing to effectively prevent the damage caused by stalling.

[0004] Furthermore, traditional electronic waste bin circuits typically use a fixed motor operation time to drive the lid open or close. However, this design doesn't account for variations in battery charge and motor speed. When the battery is full, the motor speed increases, and the actual time required to open or close the lid may be far less than the set fixed time. This causes the motor to be stalled for the remaining time, wasting energy. Summary of the Invention

[0005] To address these issues, the present invention provides a motor stall protection circuit based on parallel sampling resistors. This circuit uses the parallel sampling resistors to monitor changes in motor current in real time. When a motor stalls, the current increases rapidly. The parallel sampling resistors quickly sense this change and feed back a signal to the control circuit. Upon receiving the abnormal signal, the control circuit immediately cuts off power to the motor, effectively preventing the motor from being in a stalled state for extended periods and protecting it from damage.

[0006] To achieve the above object, the present invention adopts a technical solution: a motor stall protection circuit based on parallel sampling resistors, comprising:

[0007] The motor drive module includes an H-bridge circuit to control the forward and reverse rotation and start and stop of the motor;

[0008] A current sampling module, comprising a first sampling resistor R9 and a second sampling resistor R91 connected in parallel. The first sampling resistor R9 and the second sampling resistor R91 are connected in series between the motor drive module and the ground, and are used to convert the motor current into a sampling voltage.

[0009] A filter module comprising an inductor L2 and a first capacitor C3, wherein one end of the inductor L2 is connected to a parallel node of a first sampling resistor R9 and a second sampling resistor R91, and the other end is grounded via the first capacitor C3;

[0010] The control module is connected to the output end of the filter module and includes an MCU. The MCU is used to periodically collect the sampled voltage after filtering and convert it into a corresponding current value; at the same time, the MCU compares the current value with a preset reference current threshold; when it is detected that the current value continues to exceed the reference current threshold for a preset period of time, the motor drive module is controlled to cut off the power supply to the motor.

[0011] Furthermore, the resistance range of the first sampling resistor R9 and the second sampling resistor R91 is 1.1Ω-1.6Ω, and the equivalent resistance range after being connected in parallel is 0.55Ω-0.8Ω.

[0012] Furthermore, the H-bridge circuit includes a first P-type transistor Q2, a first N-type transistor Q4, a second P-type transistor Q3 and a second N-type transistor Q5;

[0013] A first P-type transistor Q2 and a first N-type transistor Q4 are connected in series to form a forward bridge arm, the emitter of Q2 is connected to a +3.3V power supply terminal, the collector of the first P-type transistor Q2 and the collector of the first N-type transistor Q4 are connected to the positive and negative terminals of the motor respectively, and the emitter of the first N-type transistor Q4 is grounded;

[0014] The second P-type transistor Q3 and the second N-type transistor Q5 are connected in series to form an inverting bridge arm, wherein the emitter of the second P-type transistor Q3 is connected to the +3.3V power supply terminal, the collector of the second P-type transistor Q3 and the collector of the second N-type transistor Q5 are respectively connected to the positive and negative ends of the motor, and the emitter of the second N-type transistor Q5 is grounded.

[0015] Furthermore, the base of the first P-type transistor Q2 is connected to the first drive signal terminal MODRV C of the MCU through the first current limiting resistor R5; the base of the first N-type transistor Q4 is connected to the third drive signal terminal MODRV D of the MCU through the second current limiting resistor R7; the base of the second P-type transistor Q3 is connected to the second drive signal terminal MODRVA of the MCU through the third current limiting resistor R6; and the base of the second N-type transistor Q5 is connected to the fourth drive signal terminal MODRV B of the MCU through the fourth current limiting resistor R8.

[0016] Furthermore, the H-bridge circuit further includes a filter capacitor C2 , one end of the filter capacitor C2 is connected to the collector of the second P-type transistor Q3 , and the other end of the filter capacitor C2 is connected to the collector of the first P-type transistor Q2 .

[0017] Furthermore, the H-bridge circuit also includes a first diode D2 and a second diode D3, wherein the cathode of the first diode D2 is connected to the collector of the first N-type transistor Q4, and the anode of the first diode D2 is grounded; the cathode of the second diode D3 is connected to the collector of the second N-type transistor Q5, and the anode of the second diode D3 is grounded.

[0018] Furthermore, it also includes a connector JP2, wherein pins 2 and 3 of the connector JP2 are respectively connected to the positive and negative poles of the motor, while pin 1 is connected to the +3.3V power supply terminal and pin 4 is grounded.

[0019] The present invention has the beneficial effect of preventing ineffective power consumption by the motor during a stall by monitoring the motor current in real time and promptly cutting off the power supply when the motor stalls, thereby reducing the overall power consumption of the electronic device. Furthermore, long-term stalls can lead to motor overheating, damage, and even safety accidents. The stall protection circuit can promptly cut off the power supply to the motor, protecting it from damage and improving the reliability and service life of the device.

[0020] The present invention utilizes parallel sampling resistors and a simple filter circuit to achieve motor stall protection without the need for complex sensors and detection circuits, thereby simplifying circuit design and reducing manufacturing costs. Furthermore, by setting a preset timer, such as 25ms, the power supply can be quickly cut off when the motor stalls, improving the system's response speed and protective effectiveness. This circuit is suitable for a variety of DC motor-driven electronic devices, such as electronic waste bins, automatic doors, and electric curtains, demonstrating its versatility and adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a motor stall protection circuit diagram based on parallel sampling resistors. DETAILED DESCRIPTION

[0022] See also Figure 1 As shown, the present invention relates to a motor stall protection circuit based on parallel sampling resistors, comprising:

[0023] The motor drive module includes an H-bridge circuit to control the forward rotation, reverse rotation, and start and stop of the DC motor;

[0024] A current sampling module, comprising a first sampling resistor R9 and a second sampling resistor R91 connected in parallel, wherein the first sampling resistor R9 and the second sampling resistor R91 are connected in series between the motor drive module and ground, and are used to convert the motor current into a sampled voltage;

[0025] A filter module comprising an inductor L2 and a first capacitor C3, wherein one end of the inductor L2 is connected to a parallel node of a first sampling resistor R9 and a second sampling resistor R91, and the other end is grounded via the first capacitor C3;

[0026] The control module is connected to the output end of the filter module and includes an MCU. The MCU is used to periodically collect the sampled voltage after filtering and convert it into a corresponding current value; at the same time, the MCU compares the current value with a preset reference current threshold; when it is detected that the current value continues to exceed the reference current threshold for a preset period of time, the motor drive module is controlled to cut off the power supply to the motor.

[0027] The specific working principle is that the motor drive module controls the forward and reverse rotation, as well as the start and stop of the DC motor through an H-bridge circuit. The H-bridge circuit is composed of four transistors, such as P-type and N-type transistors. By controlling the on and off states of these transistors, different direction of rotation and start and stop control of the motor can be achieved.

[0028] The current sampling module consists of two parallel-connected sampling resistors, R9 and R91. Connecting the resistors in parallel reduces their equivalent resistance, minimizing the impact on motor circuit efficiency. These equivalent resistors are connected in series between the motor driver module and ground. When the motor is running, current flows through these two resistors, generating a sampled voltage. This sampled voltage is proportional to the motor current and can therefore be used to reflect the motor's real-time current.

[0029] The filtering module, consisting of inductor L2 and first capacitor C3, filters the sampled voltage. This filtering removes high-frequency noise and interference from the sampled voltage, improving the stability and accuracy of the sampled signal. Inductor L2 is connected to the parallel node of the sampling resistor and grounded via capacitor C3, forming a low-pass filter circuit.

[0030] The core of the control module is the MCU (Microcontroller). The MCU periodically samples filtered voltage samples and converts them into corresponding current values. The MCU compares the converted current value with a preset reference current threshold. If the current value exceeds the reference current threshold for a preset duration, such as 25ms, the motor is considered stalled. An internal timer within the MCU immediately controls the motor driver module to cut off power to the motor if it detects a motor stall, thus preventing energy waste and damage caused by prolonged motor stalling.

[0031] The beneficial effect of this solution is that by monitoring the motor current in real time and promptly cutting off the power supply when the motor stalls, it avoids ineffective energy consumption during the stalled state, thereby reducing the overall power consumption of the electronic equipment. Prolonged stalls can cause motor overheating, damage, and even safety accidents. The stall protection circuit can promptly cut off the power supply to the motor, protecting it from damage and improving the reliability and service life of the equipment.

[0032] The present invention utilizes parallel sampling resistors and a simple filter circuit to achieve motor stall protection without the need for complex sensors and detection circuits, thereby simplifying circuit design and reducing manufacturing costs. Furthermore, by setting a preset timer, such as 25ms, the power supply can be quickly cut off when the motor stalls, improving the system's response speed and protective effectiveness. This circuit is suitable for a variety of DC motor-driven electronic devices, such as electronic waste bins, automatic doors, and electric curtains, demonstrating its versatility and adaptability.

[0033] The resistance range of the first sampling resistor R9 and the second sampling resistor R91 is set to 1.1Ω-1.6Ω, a carefully considered range. First, this resistance range ensures that the sampling resistors have a minimal impact on the efficiency of the motor circuit. Because the sampling resistors are connected in series between the motor drive module and ground, excessively large resistances can increase the voltage drop during motor operation, thereby reducing motor efficiency. However, too small resistances can result in excessively low sampled voltages, affecting sampling accuracy. The 1.1Ω-1.6Ω resistance range ensures sampling accuracy while minimizing the impact on motor circuit efficiency. When two resistors of the same resistance are connected in parallel, the equivalent resistance is half that of a single resistor. Therefore, when the resistance of R9 and R91 is within the range of 1.1Ω-1.6Ω, the equivalent resistance of the parallel connection is (1.1Ω / 2)-(1.6Ω / 2), or 0.55Ω-0.8Ω. This equivalent resistance further minimizes the impact on the motor circuit while ensuring the accuracy and stability of the sampled voltage.

[0034] Furthermore, the H-bridge circuit includes a first P-type transistor Q2, a first N-type transistor Q4, a second P-type transistor Q3 and a second N-type transistor Q5;

[0035] A first P-type transistor Q2 and a first N-type transistor Q4 are connected in series to form a forward bridge arm, the emitter of Q2 is connected to a +3.3V power supply terminal, the collector of the first P-type transistor Q2 and the collector of the first N-type transistor Q4 are connected to the positive and negative terminals of the motor respectively, and the emitter of the first N-type transistor Q4 is grounded;

[0036] The second P-type transistor Q3 and the second N-type transistor Q5 are connected in series to form an inverting bridge arm, wherein the emitter of the second P-type transistor Q3 is connected to the +3.3V power supply terminal, the collector of the second P-type transistor Q3 and the collector of the second N-type transistor Q5 are respectively connected to the positive and negative ends of the motor, and the emitter of the second N-type transistor Q5 is grounded.

[0037] When the motor needs to rotate forward, the control module turns on the second P-type transistor Q3 and the second N-type transistor Q5, while simultaneously turning off the first P-type transistor Q2 and the first N-type transistor Q4. At this point, current flows from the +3.3V power supply through Q3, into the motor, out of the motor, through Q5, and back to ground. This forms a forward current path, driving the motor forward. When the motor needs to rotate backward, the control module turns on the first P-type transistor Q2 and the first N-type transistor Q4, while simultaneously turning off the second P-type transistor Q3 and the second N-type transistor Q5. At this point, current flows from the +3.3V power supply through Q2. However, because Q3 is turned off, current flows through the motor to Q4, and then returns to ground through Q4's emitter. This forms a reverse current path. Note that the actual current direction is opposite to that during forward rotation, driving the motor in reverse. When the motor needs to stop, the control module simultaneously turns off all four transistors Q2, Q3, Q4, and Q5. At this point, no current flows through the motor, and the motor stops rotating. The benefits of the H-bridge circuit include flexible motor rotation control: By controlling the on / off states of four transistors, the motor's forward, reverse, and shutdown directions can be flexibly controlled. The H-bridge circuit uses transistors as switching devices, which offer low on-resistance and fast switching speeds, improving circuit efficiency. The H-bridge circuit's simple and straightforward structure makes it easy to implement and integrate. Enhanced circuit reliability: Transistors offer a long lifespan and high reliability, improving the reliability of the entire motor drive circuit.

[0038] Furthermore, the base of the first P-type transistor Q2 is connected to the first drive signal terminal MODRV C of the MCU through the first current limiting resistor R5; the base of the first N-type transistor Q4 is connected to the third drive signal terminal MODRV D of the MCU through the second current limiting resistor R7; the base of the second P-type transistor Q3 is connected to the second drive signal terminal MODRVA of the MCU through the third current limiting resistor R6; and the base of the second N-type transistor Q5 is connected to the fourth drive signal terminal MODRV B of the MCU through the fourth current limiting resistor R8.

[0039] The base of the first P-type transistor Q2 is connected to the first drive signal terminal MODRVC of the MCU through a first current-limiting resistor R5. When MODRV C outputs a high level, Q2 is turned on; when it outputs a low level, Q2 is turned off. The base of the first N-type transistor Q4 is connected to the third drive signal terminal MODRV D of the MCU through a second current-limiting resistor R7. When MODRV D outputs a high level, Q4 is turned on; when it outputs a low level, Q4 is turned off. The base of the second P-type transistor Q3 is connected to the second drive signal terminal MODRV A of the MCU through a third current-limiting resistor R6. When MODRV A outputs a high level, Q3 is turned on; when it outputs a low level, Q3 is turned off. The base of the second N-type transistor Q5 is connected to the fourth drive signal terminal MODRV B of the MCU through a fourth current-limiting resistor R8. When MODRV B outputs a high level, Q5 is turned on; when it outputs a low level, Q5 is turned off.

[0040] Current-limiting resistors protect the MCU by limiting the current flowing into the transistor base, preventing excessive current from damaging the MCU's output. Adjusting the resistor's value adjusts the transistor base current, thereby affecting the transistor's switching speed and stability. Current-limiting resistors also reduce electromagnetic interference in the circuit, improving the circuit's anti-interference capabilities.

[0041] MCU Control of the H-Bridge Circuit: Forward Control: The MCU outputs a high level through MODRV A and MODRV B, turning on Q3 and Q5. Simultaneously, MODRV C and MODRV D output a low level, turning off Q2 and Q4. This allows current to flow from the +3.3V power supply through Q3, into the motor, out of the motor, through Q5, and back to ground, driving the motor forward. Reverse Control: The MCU outputs a high level through MODRV C and MODRV D, turning on Q2 and Q4. Simultaneously, MODRV A and MODRV B output a low level, turning off Q3 and Q5. This allows current to flow from the +3.3V power supply through Q2. However, since Q3 is off, current flows through the motor to Q4, then returns to ground through Q4's emitter, driving the motor in reverse. Shutdown Control: The MCU outputs a low level through all four drive signal terminals, MODRV A, B, C, and D, turning off Q2, Q3, Q4, and Q5. At this point, no current flows through the motor and the motor stops rotating.

[0042] The H-bridge circuit connects to the MCU's drive signal terminals via four transistors, enabling precise control of the motor's direction of rotation and start / stop. Current-limiting resistors play an important role in protecting the MCU, stabilizing control, and reducing interference. The MCU can flexibly control the on / off states of the H-bridge transistors by outputting different voltage levels, thereby controlling the motor's forward, reverse, and shutdown modes. This circuit structure has broad application prospects in the motor drive field.

[0043] Furthermore, the H-bridge circuit further includes a filter capacitor C2 , one end of the filter capacitor C2 is connected to the collector of the second P-type transistor Q3 , and the other end of the filter capacitor C2 is connected to the collector of the first P-type transistor Q2 .

[0044] When the MCU turns on Q3 and Q5 via the drive signal terminal, current flows from the +3.3V power supply terminal through Q3, enters the motor, and then flows out of the motor through Q5 and returns to ground. Filter capacitor C2 absorbs and releases current during this process, reducing voltage fluctuations and ensuring smoother forward rotation of the motor.

[0045] When the MCU turns on Q2 and Q4 via the drive signal terminal, current flows from the +3.3V power supply terminal through Q2, through the motor to Q4, and then returns to ground through the emitter of Q4. Filter capacitor C2 also plays a role in reducing voltage fluctuations and suppressing noise in this process.

[0046] When all transistors are turned off, the motor stops rotating. During this process, filter capacitor C2 can release the stored energy, providing a short-term maintenance current for the motor and reducing the voltage surge during shutdown.

[0047] Filter capacitor C2 in the H-bridge circuit is connected across the motor's terminals. By absorbing and releasing current, it reduces voltage fluctuations, suppresses noise, provides instantaneous power, and protects the transistors. It works in conjunction with the transistors, current-limiting resistors, and other components in the H-bridge circuit to achieve precise control and smooth operation of the motor. This circuit structure has broad application prospects in motor drives, particularly in applications requiring high precision, high stability, and low noise.

[0048] Furthermore, the H-bridge circuit also includes a first diode D2 and a second diode D3, wherein the cathode of the first diode D2 is connected to the collector of the first N-type transistor Q4, and the anode of the first diode D2 is grounded; the cathode of the second diode D3 is connected to the collector of the second N-type transistor Q5, and the anode of the second diode D3 is grounded.

[0049] When the MCU turns on Q3 and Q5 via the drive signal, current flows from the +3.3V power supply through Q3, into the motor, out of the motor, and back to ground through Q5. During this process, freewheeling diodes D2 and D3 are in reverse blocking mode, which does not affect the motor's forward rotation. When the MCU turns on Q2 and Q4 via the drive signal, current flows from the +3.3V power supply through Q2, through the motor, to Q4, and then back to ground through Q4's emitter. During this process, freewheeling diode D2 provides a conduction path for the reverse current in the motor. When the motor inertia generates a reverse electromotive force, D2 conducts, protecting Q4 from damage. Similarly, when the motor switches from forward to reverse rotation, freewheeling diode D3 performs the same function, protecting Q5 from damage. When all transistors are turned off, the motor stops rotating. At this point, freewheeling diodes D2 and D3 provide a conduction path for the reverse electromotive force generated by the motor, preventing damage to the transistors. In summary, freewheeling diodes D2 and D3 in the H-bridge circuit are connected in parallel between the collector of the N-type transistor and ground. They handle reverse electromotive force, protect the transistor, improve motor efficiency, and reduce electromagnetic interference. Working in conjunction with other components in the H-bridge circuit, they achieve precise control and smooth operation of the motor. This circuit structure has broad application prospects in motor drives, particularly in applications requiring high precision, stability, and reliability.

[0050] Furthermore, it also includes a connector JP2, wherein pins 2 and 3 of the connector JP2 are respectively connected to the positive and negative poles of the motor, while pin 1 is connected to the +3.3V power supply terminal and pin 4 is grounded.

[0051] When the MCU controls the transistors in the H-bridge circuit through the drive signal terminal, current flows into or out of the motor through pins 2 and 3 of connector JP2, thereby realizing forward rotation, reverse rotation, and shutdown control of the motor.

[0052] Connector JP2 ensures a stable power supply to the motor and provides grounding protection to prevent interference and noise from affecting the motor and circuits. The introduction of connector JP2 makes the connection between the motor and external circuits more flexible and reliable. When replacing the motor or performing circuit maintenance, simply unplug and replug the connector, eliminating the need for resoldering or changing the circuit layout.

[0053] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A motor stall protection circuit based on parallel sampling resistors, characterized in that: include: The motor drive module includes an H-bridge circuit to control the forward rotation, reverse rotation, and start and stop of the DC motor; The current sampling module comprises a first sampling resistor (R9) and a second sampling resistor (R91) connected in parallel with each other, wherein the first sampling resistor (R9) and the second sampling resistor (R91) are connected in series between the motor drive module and the ground, and are used to convert the motor current into a sampling voltage; A filter module comprising an inductor (L2) and a first capacitor (C3), wherein one end of the inductor (L2) is connected to a parallel node of a first sampling resistor (R9) and a second sampling resistor (R91), and the other end is grounded via the first capacitor (C3); The control module is connected to the output end of the filter module and includes an MCU. The MCU is used to periodically collect the sampled voltage after filtering and convert it into a corresponding current value; At the same time, the MCU compares the current value with a preset reference current threshold; when it is detected that the current value continues to exceed the reference current threshold for a preset time period, the motor drive module is controlled to cut off the power supply to the motor.

2. A motor stall protection circuit based on parallel sampling resistors according to claim 1, characterized in that: The resistance range of the first sampling resistor (R9) and the second sampling resistor (R91) is 1.1Ω-1.6Ω, and the equivalent resistance range after being connected in parallel is 0.55Ω-0.8Ω.

3. The motor stall protection circuit based on parallel sampling resistor according to claim 1, characterized in that: The H-bridge circuit includes a first P-type transistor (Q2), a first N-type transistor (Q4), a second P-type transistor (Q3) and a second N-type transistor (Q5); A first P-type transistor (Q2) and a first N-type transistor (Q4) are connected in series to form a forward bridge arm, the emitter of Q2 is connected to a +3.3V power supply terminal, the collector of the first P-type transistor (Q2) and the collector of the first N-type transistor (Q4) are respectively connected to the positive and negative ends of the motor, and the emitter of the first N-type transistor (Q4) is grounded; A second P-type transistor (Q3) and a second N-type transistor (Q5) are connected in series to form an inverting bridge arm, wherein the emitter of the second P-type transistor (Q3) is connected to a +3.3V power supply terminal, the collector of the second P-type transistor (Q3) and the collector of the second N-type transistor (Q5) are respectively connected to the positive and negative ends of the motor, and the emitter of the second N-type transistor (Q5) is grounded.

4. The motor stall protection circuit based on parallel sampling resistors according to claim 3, characterized in that: The base of the first P-type transistor (Q2) is connected to a first drive signal terminal (MODRV C) of the MCU via a first current-limiting resistor (R5); the base of the first N-type transistor (Q4) is connected to a third drive signal terminal (MODRVD) of the MCU via a second current-limiting resistor (R7); the base of the second P-type transistor (Q3) is connected to a second drive signal terminal (MODRVA) of the MCU via a third current-limiting resistor (R6); and the base of the second N-type transistor (Q5) is connected to a fourth drive signal terminal (MODRVB) of the MCU via a fourth current-limiting resistor (R8).

5. The motor stall protection circuit based on parallel sampling resistors according to claim 4, characterized in that: The H-bridge circuit also includes a filter capacitor (C2), one end of the filter capacitor (C2) is connected to the collector of the second P-type transistor (Q3), and the other end is connected to the collector of the first P-type transistor (Q2), and the two ends of the filter capacitor (C2) are respectively connected to the positive and negative ends of the motor.

6. The motor stall protection circuit based on parallel sampling resistors according to claim 5, characterized in that: The H-bridge circuit further includes a first diode (D2) and a second diode (D3), wherein the cathode of the first diode (D2) is connected to the collector of the first N-type transistor (Q4), and the anode of the first diode (D2) is grounded; the cathode of the second diode (D3) is connected to the collector of the second N-type transistor (Q5), and the anode of the second diode (D3) is grounded.

7. The motor stall protection circuit based on parallel sampling resistors according to claim 6, characterized in that: It also includes a connector (JP2), wherein pins 2 and 3 of the connector (JP2) are respectively connected to the positive and negative poles of the motor, while pin 1 is connected to the +3.3V power supply terminal, and pin 4 is grounded.

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