An external watchdog circuit and electronic device

Abstract

The utility model relates to electronic circuit technical field discloses a kind of externally-hung watchdog circuit and electronic equipment, through the PWM conversion module and hardware reset module of ingenious design, when MCU normal operation, PWM conversion module can accurately identify and convert PWM signal, maintain the high level state of RST pin, ensure system stable operation, and when detecting PWM signal exception, RST pin can be quickly pulled low, and trigger MCU to carry out software reset. In addition, hardware reset module as backup guarantee, when software reset is invalid, can intervene in time, to carry out hardware reset, ensure that equipment can be reliably recovered under abnormal condition, to significantly improve the reliability and stability of equipment, avoid the equipment paralysis even scrap due to abnormality, reduce the maintenance cost and failure risk of equipment, simultaneously, the circuit structure is simple, low in cost, easy to integrate and popularize, with higher practicality and market application value.

Description

Technical Field

[0001] This utility model relates to the field of electronic circuit technology, and in particular to an external watchdog circuit and electronic device. Background Technology

[0002] In various electronic devices, watchdog circuits are typically designed as timer T1 circuits. When the device is operating normally, it resets the watchdog circuit at preset time intervals, serving as an indicator of its normal working state. However, if an abnormal situation occurs during operation and the watchdog circuit is not reset within the specified time limit, the watchdog circuit will automatically determine that the device has malfunctioned. In this case, the watchdog circuit will take a series of corresponding measures, such as triggering a device reset or generating an alarm signal, thereby prompting the device to return to normal operation.

[0003] In the current electronics market, some functional MCUs (microcontroller units) often omit the watchdog circuit from their design to reduce production costs. In this case, if an anomaly occurs, the MCU will be unable to detect it due to the lack of a watchdog circuit. This can directly lead to the malfunction of the device using the MCU, and in some extreme cases, the device may even be rendered unusable.

[0004] Therefore, designing an external watchdog circuit that can promptly trigger a reset operation and generate an alarm signal after detecting a device malfunction has become one of the technical challenges that urgently needs to be solved by those skilled in the art.

[0005] The above information is provided as background information only to aid in understanding this disclosure and does not constitute an assertion or admission that any of the above content can be used as prior art relative to this disclosure. Utility Model Content

[0006] This invention provides an external watchdog circuit and electronic device to solve the problems existing in the prior art.

[0007] To achieve the above objectives, this utility model provides the following technical solution:

[0008] In a first aspect, this utility model provides an external watchdog circuit for triggering an MCU to reset, comprising a PWM conversion module and a hardware reset module; wherein...

[0009] The PWM conversion module is connected to the PWM pin and RST pin of the MCU respectively. It is used to receive and convert the PWM signal output by the PWM pin. When the PWM signal output by the PWM pin is normal, it maintains the high level of the RST pin. When the PWM signal output by the PWM pin is abnormal, it provides a low level to the RST pin to trigger the MCU to perform a software reset.

[0010] The hardware reset module is connected to the RST pin and is used to perform a hardware reset when the MCU software reset is ineffective.

[0011] Furthermore, in the external watchdog circuit, the PWM conversion module includes a capacitor C1, a first diode D1, and a second diode D2;

[0012] One end of the capacitor C1 is connected to the PWM pin, and the other end is connected to the positive terminal of the second diode D2;

[0013] The cathode of the second diode D2 is connected to the RST pin;

[0014] The positive terminal of the first diode D1 is grounded, and the negative terminal of the first diode D1 is connected between the capacitor C1 and the positive terminal of the second diode D2.

[0015] Furthermore, in the external watchdog circuit, the hardware reset module includes a MOSFET Q1, a resistor R1, a timer T1, and a power switch K1;

[0016] The gate of the MOS transistor Q1 is connected to the RST pin, the source of the MOS transistor Q1 is grounded, and the drain of the MOS transistor Q1 is connected to one end of the timer T1.

[0017] The first end of the resistor R1 is connected to the pull-up source, and the second end of the resistor R1 is connected to the drain of the MOS transistor Q1.

[0018] The other end of the timer T1 is connected to the power switch K1, and the power switch K1 is connected to the MCU.

[0019] Furthermore, in the external watchdog circuit, the MOS transistor Q1 is an NMOS transistor.

[0020] Furthermore, in the external watchdog circuit, the timer T1 is a 555 timer T1.

[0021] Furthermore, in the external watchdog circuit, the hardware reset module also includes an alarm B1;

[0022] The alarm B1 is connected to the second end of the resistor R1.

[0023] Furthermore, in the external watchdog circuit, the alarm B1 is a buzzer.

[0024] In a second aspect, this utility model provides an electronic device, including an MCU and an external watchdog circuit as described in the first aspect above;

[0025] The external watchdog circuit is connected to the MCU and is used to trigger the MCU to reset.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention provides an external watchdog circuit and electronic device. Through a cleverly designed PWM conversion module and hardware reset module, it offers a reliable external monitoring and reset solution for MCUs without built-in watchdog functionality. During normal MCU operation, the PWM conversion module accurately identifies and converts the PWM signal, maintaining the RST pin at a high level to ensure stable system operation. When an abnormal PWM signal is detected, it quickly pulls the RST pin low, triggering a software reset of the MCU to correct the abnormal state promptly. Furthermore, the hardware reset module serves as a backup, intervening promptly to perform a hardware reset when the software reset fails. This ensures reliable recovery of the device under abnormal conditions, significantly improving its reliability and stability, preventing equipment failure or even scrapping due to abnormalities, and reducing maintenance costs and failure risks. Simultaneously, the circuit structure is simple, low-cost, easy to integrate and promote, and possesses high practicality and market application value.

[0028] This invention has other features and advantages that will be apparent from or will be set forth in detail in the accompanying drawings and the following detailed description, which together serve to explain the particular principles of this invention. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a functional module diagram of an external watchdog circuit provided in Embodiment 1 of this utility model;

[0031] Figure 2 This is one of the circuit principle diagrams of an external watchdog circuit provided in Embodiment 1 of this utility model;

[0032] Figure 3 This is the second schematic diagram of the circuit principle of an external watchdog circuit provided in Embodiment 1 of this utility model.

[0033] Figure label:

[0034] PWM conversion module 1, hardware reset module 2. Detailed Implementation

[0035] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to limit the scope of protection of this application.

[0036] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0037] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0038] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" logical relationship.

[0039] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order relationship between these entities or operations.

[0040] Unless otherwise specified, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0041] In this application, expressions such as "greater than", "less than", and "exceeding" are understood to exclude the stated number; expressions such as "above", "below", and "within" are understood to include the stated number. Furthermore, in the description of the embodiments of this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times", unless otherwise explicitly specified.

[0042] In the description of the embodiments of this application, the space-related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the purpose of describing the specific embodiments of this application or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0043] Unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this application, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. For those skilled in the art to which this application pertains, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0044] Example 1

[0045] Please refer to Figure 1 This utility model embodiment provides an external watchdog circuit, the main function of which is to trigger the MCU to perform a reset operation. The circuit consists of two key modules: a PWM conversion module 1 and a hardware reset module 2.

[0046] Specifically, the PWM conversion module 1 is connected to the PWM pin and RST pin of the MCU. Its main function is to receive and convert the PWM (Pulse Width Modulation) signal output from the MCU's PWM pin. Under normal operating conditions, when the PWM signal output from the PWM pin is normal, the module can maintain a high level on the RST pin, thereby ensuring stable operation of the MCU. However, once an abnormality is detected in the PWM signal output from the PWM pin, the PWM conversion module 1 will respond quickly by providing a low-level signal to the RST pin, thereby triggering a software reset operation on the MCU. This mechanism can effectively correct potential problems caused by abnormal PWM signals and ensure the normal operation of the system.

[0047] The hardware reset module 2 is connected to the RST pin, serving as a backup mechanism for software reset. When the software reset operation triggered by the PWM conversion module 1 fails to restore normal system operation, the hardware reset module 2 will be activated to perform a hardware reset operation. This dual reset mechanism design provides strong protection for the system's reliability and stability.

[0048] In summary, this embodiment, through its carefully designed PWM conversion module 1 and hardware reset module 2, provides an efficient and reliable external monitoring and reset solution for MCUs without built-in watchdog functionality. During normal MCU operation, the PWM conversion module 1 accurately identifies and converts the PWM signal, maintaining the RST pin at a high level to ensure stable system operation. When an abnormality in the PWM signal is detected, the module quickly pulls the RST pin low, triggering a software reset of the MCU to promptly correct the abnormal state. Furthermore, the hardware reset module 2 serves as a backup mechanism, intervening promptly to perform a hardware reset if the software reset fails, ensuring reliable recovery of the device under abnormal conditions.

[0049] Through the above design, this embodiment significantly improves the reliability and stability of the equipment, effectively avoiding the risk of equipment failure or even scrapping due to abnormal conditions. Meanwhile, this external watchdog circuit has a simple structure, low cost, and is easy to integrate and promote, possessing high practicality and market application value. It can significantly reduce equipment maintenance costs and failure risks, providing strong technical support for the stable operation of electronic equipment.

[0050] Please refer to Figure 2 In one embodiment of this invention, the PWM conversion module 1 adopts a simple and efficient circuit design, mainly including capacitor C1, first diode D1 and second diode D2. These components realize the monitoring and conversion function of PWM signal through a specific connection method.

[0051] The specific connection relationships are as follows:

[0052] One end of capacitor C1 is connected to the PWM pin of the MCU to receive the PWM signal output from the PWM pin. The other end of capacitor C1 is connected to the positive terminal of the second diode D2. Its function is to charge during the high level of the PWM signal and discharge through other components during the low level, thereby realizing the filtering and delay functions of the PWM signal.

[0053] The positive terminal of the second diode D2 is connected to the other end of capacitor C1, while its negative terminal is connected to the RST pin. When capacitor C1 charges to a certain level, the second diode D2 conducts, maintaining a high level on the RST pin to ensure normal MCU operation. However, if an abnormal PWM signal causes capacitor C1 to fail to charge properly, the second diode D2 turns off, changing the level of the RST pin and triggering a MCU reset.

[0054] The positive terminal of the first diode D1 is grounded, and its negative terminal is connected between the capacitor C1 and the positive terminal of the second diode D2. The function of the first diode D1 is to provide a low-impedance path for the discharge of capacitor C1, ensuring that capacitor C1 can discharge quickly when the PWM signal is abnormal, thereby enabling the level state of the RST pin to switch to a low level quickly, thus triggering the MCU's software reset operation.

[0055] Through the circuit design described above, PWM conversion module 1 can maintain the high level of the RST pin by charging capacitor C1 and conducting the second diode D2 when the PWM signal is normal, ensuring the normal operation of the MCU. However, when the PWM signal is abnormal, capacitor C1 cannot charge properly, and the first diode D1 quickly conducts and discharges, switching the RST pin to a low level, thereby triggering the MCU's software reset operation. This design is not only simple in structure but also efficiently realizes the monitoring and conversion function of the PWM signal, providing an important guarantee for the reliable operation of the external watchdog circuit.

[0056] Please refer to this again. Figure 2 In one embodiment of this invention, the hardware reset module 2 employs the collaborative operation of multiple electronic components to achieve the hardware reset function of the MCU. The hardware reset module 2 mainly includes a MOS transistor (metal-oxide-semiconductor field-effect transistor) Q1, a resistor R1, a timer T1, and a power switch K1. These components are precisely connected in a circuit to form a highly efficient hardware reset mechanism.

[0057] The specific connection relationships are as follows:

[0058] The gate of MOSFET Q1 is connected to the RST pin to receive control signals from the RST pin. The source of MOSFET Q1 is grounded, while its drain is connected to one end of the timer T1. In this embodiment, MOSFET Q1 is selected as an NMOS transistor, which conducts when the gate voltage is lower than its threshold voltage, thereby enabling control of subsequent circuits.

[0059] The first terminal of resistor R1 is connected to a pull-up source (+3.3V), which provides a stable high-level reference for the circuit. The second terminal of resistor R1 is connected to the drain of MOSFET Q1. Through the pull-up resistor, it ensures that the drain of MOSFET Q1 can maintain a stable high-level state when MOSFET Q1 is not turned on.

[0060] The other end of timer T1 is connected to the power switch K1. Its main function is to generate a pulse signal at a preset time interval after receiving a trigger signal, thereby realizing the hardware reset operation of the MCU. In this embodiment, the timer T1 is the classic 555 timer, which is widely used in various electronic circuits because of its simplicity, reliability and ease of configuration.

[0061] The power switch K1 is connected to the MCU and is used to restore power to the MCU after the hardware reset operation is completed, so as to ensure that it can restart and enter normal operation.

[0062] In this embodiment, when the software reset operation triggered by the PWM conversion module 1 fails to restore the normal operation of the MCU, the hardware reset module 2 will be activated. At this time, the low-level signal on the RST pin will pass through the gate of the MOSFET Q1, turning it on. The conduction of the MOSFET Q1 will cause a change in the level state of its drain, thereby triggering timer T1 to generate a pulse signal. This pulse signal passes through the power switch K1, ultimately realizing the hardware reset operation of the MCU.

[0063] Through the above design, hardware reset module 2 provides a reliable backup reset mechanism for the MCU. In the event of an ineffective software reset, hardware reset module 2 can intervene promptly, ensuring that the device can reliably resume operation under abnormal conditions. This design not only improves system reliability but also provides dual protection for the stable operation of the device.

[0064] Specifically, when the MCU is working normally, both the high-level signal and the PWM signal are output normally. During this time, capacitor C1 charges and discharges. When the PWM is high, capacitor C1 is charging, and the first diode D1 is conducting. Due to the clamping effect of the first diode D1, the voltage across capacitor C1 is stabilized at a stable high level, meaning the RST pin is high. When the PWM is low, the first diode D1 is off. Since the voltage across capacitor C1 cannot change abruptly, VC remains constant. At this time, the voltage across capacitor C1 is negative, and capacitor C1 discharges to the back of the second diode D2. Because the PWM signal has a high frequency, the charging and discharging process of capacitor C1 continues, but it will not be fully charged or fully discharged. In this situation, the voltage across capacitor C1 gradually rises, and the average voltage across the back of the second diode D2 will be higher than the average voltage of the PWM signal, thus always satisfying the high-level condition, meaning the RST pin is high. This indicates that the MCU is in normal working condition and will not trigger a reset operation.

[0065] When the MCU malfunctions, the PWM output will also be abnormal, which can be categorized into the following two states:

[0066] (1) The PWM output is continuously low (no output). At this time, there is no signal at the back end of capacitor C1, the RST pin is at low level, triggering the MCU to perform a software reset and try to restore the MCU's operation. At the same time, the MOS transistor Q1 is turned off, and the timer T1 starts to work. When the continuous software reset is ineffective, the high level duration of the input timer T1 reaches the trigger condition, controlling the back end power switch K1 to cut off the power and try a hardware reset.

[0067] (2) When the PWM output is continuously high, the capacitor C1 will generate a momentary high level and then immediately power off. When the power off reaches a low level, the RST pin will detect that it is at a low level, triggering the MCU to reset and attempt to restore the MCU to work. At the same time, it may perform subsequent hardware reset operations.

[0068] Please refer to Figure 3 In one embodiment of this invention, the hardware reset module 2 further expands its functionality based on the original design by introducing an alarm B1 to enhance the system's ability to alert to abnormalities. This improvement enables the hardware reset module 2 not only to trigger a hardware reset operation when a system abnormality is detected, but also to issue an alarm signal through the alarm B1 to remind users or maintenance personnel to pay attention to the abnormal state of the equipment.

[0069] The specific connection relationships are as follows:

[0070] Alarm B1 is connected to the second terminal of resistor R1. This connection allows alarm B1 to receive a trigger signal through the second terminal of resistor R1 when hardware reset module 2 is activated, thereby issuing an alarm. The function of alarm B1 is to provide users with a clear indication of the abnormality so that appropriate measures can be taken in a timely manner.

[0071] In this embodiment, the alarm B1 is selected as a buzzer. A buzzer is a common electronic sound-emitting device that can emit a continuous buzzing sound after receiving an electrical signal. It has the characteristics of small size, low power consumption, and clear sound, making it very suitable for abnormal alarm scenarios of electronic devices.

[0072] In the operating mechanism of this embodiment, when the hardware reset module 2 detects a system abnormality and triggers a hardware reset operation, the MOSFET Q1 is turned on, causing a change in the voltage level of its drain. This change is transmitted to the alarm B1 through resistor R1 (i.e., resistor R1 is pulled low to ground, and alarm B1 is pulled low and triggered), triggering the buzzer to sound an alarm. Simultaneously, timer T1 generates a pulse signal, which completes the hardware reset operation of the MCU through power switch K1. This dual mechanism not only ensures that the device can resume operation under abnormal conditions but also reminds the user to check the device status in a timely manner through the buzzer alarm, avoiding potential safety hazards or further malfunctions.

[0073] By introducing alarm B1, the hardware reset module 2 in this embodiment is significantly enhanced in functionality. It not only effectively ensures the stable operation of the equipment but also promptly notifies the user of any abnormal equipment status via the buzzer's alarm function, thereby further improving the equipment's safety and reliability. This design has significant practical value in real-world applications, especially in scenarios requiring timely responses to equipment malfunctions, providing strong support for equipment maintenance and management.

[0074] Although this application uses terms such as MCU and reset frequently, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of this utility model; interpreting them as any additional limitation would contradict the spirit of this utility model.

[0075] Example 2

[0076] This utility model embodiment provides an electronic device, including an MCU and an external watchdog circuit as provided in Embodiment 1 above;

[0077] The external watchdog circuit is connected to the MCU.

[0078] It should be noted that the external watchdog circuit, as an important component of the electronic device, operates based on monitoring the PWM signal of the MCU. When the MCU is running normally, the PWM signal is in a normal state, and the watchdog circuit maintains a high-level state connected to the MCU's RST pin through its internal PWM conversion module, ensuring stable MCU operation. However, if the MCU malfunctions, causing the PWM signal to fail to output normally, the watchdog circuit will respond quickly, triggering a MCU reset operation through a hardware reset module, and, if necessary, issuing an alarm signal to alert users or maintenance personnel to the abnormal state of the equipment.

[0079] By integrating an external watchdog circuit into the design of electronic devices, this embodiment not only provides a reliable monitoring and reset mechanism for the MCU, but also significantly improves the electronic device's ability to cope with abnormal situations through the dual protection of a hardware reset module and an alarm. This design enables the electronic device to quickly resume operation when a fault occurs, while avoiding equipment damage or data loss caused by prolonged abnormal operation, thereby enhancing the reliability and stability of the equipment.

[0080] Furthermore, the external watchdog circuit in this embodiment features a simple structure, low cost, and easy integration into various types of electronic devices. It is suitable not only for industrial equipment with high reliability requirements but also for consumer electronics, demonstrating broad market application prospects. Through this design, electronic devices can significantly improve their performance and user experience without incurring excessive costs.

[0081] Finally, it should be noted that although the above embodiments have been described in the text and drawings of this application, this should not limit the scope of patent protection of this application. Any technical solutions that are based on the essential concept of this application and utilize the content described in the text and drawings of this application, resulting in equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this application.

Claims

1. An external watchdog circuit for triggering an MCU to reset, characterized in that, It includes a PWM conversion module and a hardware reset module; among which, The PWM conversion module is connected to the PWM pin and RST pin of the MCU respectively. It is used to receive and convert the PWM signal output by the PWM pin. When the PWM signal output by the PWM pin is normal, it maintains the high level of the RST pin. When the PWM signal output by the PWM pin is abnormal, it provides a low level to the RST pin to trigger the MCU to perform a software reset. The hardware reset module is connected to the RST pin and is used to perform a hardware reset when the MCU software reset is ineffective.

2. The external watchdog circuit according to claim 1, characterized in that, The PWM conversion module includes a capacitor C1, a first diode D1, and a second diode D2; One end of the capacitor C1 is connected to the PWM pin, and the other end is connected to the positive terminal of the second diode D2; The cathode of the second diode D2 is connected to the RST pin; The positive terminal of the first diode D1 is grounded, and the negative terminal of the first diode D1 is connected between the capacitor C1 and the positive terminal of the second diode D2.

3. The external watchdog circuit according to claim 2, characterized in that, The hardware reset module includes a MOSFET Q1, a resistor R1, a timer T1, and a power switch K1; The gate of the MOS transistor Q1 is connected to the RST pin, the source of the MOS transistor Q1 is grounded, and the drain of the MOS transistor Q1 is connected to one end of the timer T1. The first end of the resistor R1 is connected to the pull-up source, and the second end of the resistor R1 is connected to the drain of the MOS transistor Q1. The other end of the timer T1 is connected to the power switch K1, and the power switch K1 is connected to the MCU.

4. The external watchdog circuit according to claim 3, characterized in that, The MOS transistor Q1 is an NMOS transistor.

5. The external watchdog circuit according to claim 3, characterized in that, The timer T1 is a 555 timer T1.

6. The external watchdog circuit according to claim 3, characterized in that, The hardware reset module also includes an alarm B1; The alarm B1 is connected to the second end of the resistor R1.

7. The external watchdog circuit according to claim 6, characterized in that, The alarm B1 is a buzzer.

8. An electronic device, characterized in that, Includes an MCU and an external watchdog circuit as described in any one of claims 1-7; The external watchdog circuit is connected to the MCU and is used to trigger the MCU to reset.

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