Safety protection circuit and device for preventing control failure of heating wire

Abstract

The utility model discloses a safety protection circuit for preventing control failure of a heating wire, and the circuit comprises a central control module which is used for outputting a PWM signal when the working state is normal and outputting a DC voltage signal when the working state is abnormal; the conversion module is connected with the central control module, and the conversion module is used for converting the PWM signal into a turn-on signal and converting the direct-current voltage signal into a turn-off signal; and the heating wire driving circuit is connected with the conversion module, and the heating wire driving circuit is used for controlling the on-off of the heating wire according to the opening signal and the closing signal. Through the circuit, the heating wire driving circuit is controlled so as to further control the on-off of the heating wire, so that the problem that the heating wire cannot be normally closed under the conditions of control circuit board fault, MCU failure, program error and the like is avoided, the fire hazard is avoided, and the reliability and the safety are improved.

Description

Technical Field

[0001] The utility model relates to the field of electronic technology, and in particular to a safety protection circuit and device for preventing heating wire control failure. Background Art

[0002] Current home appliances using heating wires are subject to control circuit board failures, MCU failures, and program errors. This can cause the IO port to continuously output a high or low level, leaving the heating wire permanently on. Without human intervention, this can burn out the heating wire, damage the product, or even cause a fire. Therefore, addressing the potential fire safety hazards associated with current home appliances using heating wires is crucial. Utility Model Content

[0003] The embodiments of the present utility model provide a safety protection circuit and device to prevent heating wire control failure, which solves the problem that the heating wire cannot be normally closed when the control circuit board fails, the MCU fails, the program error occurs, etc., in household electrical appliances currently on the market that use heating wire for heating, thereby posing a fire safety hazard.

[0004] In the first aspect, the utility model provides a safety protection circuit to prevent heating wire control failure, including: a central control module, used to output a PWM signal when the working state is normal and to output a DC voltage signal when the working state is abnormal; a conversion module, connected to the central control module, the conversion module is used to convert the PWM signal into an on signal and the DC voltage signal into an off signal; a heating wire driving circuit, connected to the conversion module, the heating wire driving circuit is used to control the on and off of the heating wire according to the on signal and the off signal.

[0005] In the safety protection circuit for preventing heating wire control failure provided by the present invention, the conversion module includes a DC blocking unit, which is connected to the central control module, and is used to pass the PWM signal and block the DC voltage signal.

[0006] In the safety protection circuit for preventing heating wire control failure provided by the present invention, the conversion module also includes a signal conversion unit and a switch unit. The signal conversion unit is connected to the DC blocking unit. The signal conversion unit is used to convert the PWM signal into a high-level signal. The switch unit is respectively connected to the signal conversion unit and the heating wire driving circuit. The switch unit is used to be turned on according to the high-level signal to generate the start signal for controlling the heating wire driving circuit to turn on.

[0007] In the safety protection circuit for preventing heating wire control failure provided by the present invention, the conversion module further includes a filtering unit, and the filtering unit is connected to the signal conversion unit and the ground terminal respectively.

[0008] In the safety protection circuit for preventing heating wire control failure provided by the present invention, the heating wire driving circuit includes an isolation unit, the isolation unit is connected to the switch unit, and the isolation unit is used to conduct the start signal.

[0009] In the safety protection circuit for preventing heating wire control failure provided by the present invention, the heating wire driving circuit also includes an AC driving unit, which is connected to the isolation unit and is used to connect to the heating wire to control the working state of the heating wire.

[0010] In the safety protection circuit for preventing heating wire control failure provided by the present invention, the switching unit includes a first transistor, the base of the first transistor is connected to the conversion unit, the emitter of the first transistor is grounded, and the collector of the first transistor is connected to the isolation unit.

[0011] In the safety protection circuit for preventing heating wire control failure provided by the present invention, the isolation unit includes a bidirectional thyristor-driven photoelectric coupler, the anode of the transmitting end of the bidirectional thyristor-driven photoelectric coupler is used to connect to the first power supply end, the cathode of the transmitting end of the bidirectional thyristor-driven photoelectric coupler is connected to the collector of the first transistor, the first output end and the second output end of the receiving end of the bidirectional thyristor-driven photoelectric coupler are connected to the AC drive unit and are used to transmit the start signal to the AC drive unit, and the receiving end of the bidirectional thyristor-driven photoelectric coupler is also provided with a zero-crossing detection circuit for connecting to the gate of the first bidirectional thyristor in the receiving end of the bidirectional thyristor-driven photoelectric coupler.

[0012] In the safety protection circuit for preventing heating wire control failure provided by the present invention, the AC drive unit includes a first bidirectional thyristor, the gate of the first bidirectional thyristor is connected to the first output end of the receiving end of the bidirectional thyristor-driven optocoupler, the first main electrode of the first bidirectional thyristor is connected to the second power supply end, and the second main electrode of the first bidirectional thyristor is used for connection to the heating wire connected to the third power supply end.

[0013] In a second aspect, the utility model provides a safety protection device for preventing heating wire control failure, comprising the safety protection circuit for preventing heating wire control failure as described above.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] In the technical solution of the present invention, a central control module is relied upon to generate a PWM signal for outputting when the working state is normal and a DC voltage signal for outputting when the working state is abnormal, and then the PWM signal is converted into an on signal and the DC voltage signal is converted into an off signal through a conversion module, so as to control the heating wire drive circuit to further control the on and off of the heating wire, thereby avoiding the problem that the heating wire cannot be normally closed in situations such as control circuit board failure, MCU failure, program error, etc., avoiding fire hazards, and improving reliability and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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 paying any creative work.

[0017] Figure 1 This is a circuit logic diagram of a safety protection circuit for preventing heating wire control failure according to an embodiment of the present utility model;

[0018] Figure 2 This is a circuit diagram of an embodiment of a safety protection circuit for preventing heating wire control failure according to an embodiment of the present utility model;

[0019] Reference numerals:

[0020] 1. Central control module;

[0021] 2. Conversion module; 21. DC blocking unit; 22. Conversion unit; 23. Switching unit; 24. Filtering unit;

[0022] 3. Heating wire driving circuit; 31. Isolation unit; 32. AC driving unit;

[0023] 4. Heating wire. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0026] It should also be understood that the terms used in this utility model specification are only for the purpose of describing specific embodiments and are not intended to limit the utility model. As used in this utility model specification and the appended claims, the singular forms "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise.

[0027] It should be further understood that the term “and / or” used in the present specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0028] The present invention aims to solve the problem that the heating wire 4 cannot be normally closed when the control circuit board fails, the MCU fails, the program fails, etc., which may cause fire safety hazards in the current household electrical appliances on the market. A safety protection circuit is provided to prevent the heating wire from failing to control. Figure 1 and Figure 2The safety protection circuit for preventing heating wire control failure includes: a central control module 1, configured to output a PWM signal when operating normally and a DC voltage signal when operating abnormally; a conversion module 2, connected to the central control module 1, configured to convert the PWM signal into an on signal and the DC voltage signal into an off signal; and a heating wire drive circuit 3, connected to the conversion module 2, configured to control the on and off of the heating wire 4 based on the on and off signals. To ensure that small household appliances fully meet the needs of consumers in today's society, the addition of smart chips to various small household appliances to achieve more complex functions is often considered. However, products using smart chips can experience various faults due to hardware or software problems. These faults, such as control circuit board failure, MCU failure, and program errors, can lead to control failure of back-end components. In the case of the heating wire 4, this can prevent the heating wire 4 from shutting off properly, causing it to continue operating during a fault, creating a fire hazard. To this end, the present invention adds a program specifically designed to generate PWM signals during normal product operation to the central control module 1. This program provides the central control module 1 with a signal that indicates normal operating conditions to back-end components. In abnormal operating conditions, the program fails to operate properly and outputs a DC voltage signal. Whether this signal is a high-level or low-level voltage, it indicates that the central control module 1 is operating abnormally. This signal, indicating its operating status, is then extracted from the central control module 1 and connected to the conversion module 2. The conversion module 2 converts the signal into an on / off signal, enabling the converted signal to control the heating wire 4 on and off. In household appliances equipped with a heating wire 4, the heating wire 4 typically uses alternating current (AC). Therefore, a heating wire drive circuit 3 is required to control the heating wire 4 via the converter module 2 connected to the low-voltage circuit. The heating wire drive circuit 3 controls the on / off state of the heating wire 4 based on the on / off signals generated by the conversion module 2, ensuring that the heating wire 4 is automatically turned off in the event of a control failure, eliminating fire safety hazards.

[0029] Here, an example is given to illustrate the working steps of the safety protection circuit for preventing heating wire control failure of the present invention: when the central control module 1 is in a normal state and outputs a PWM signal, the conversion module 2 converts the PWM signal into an on signal, indicating that the heating wire 4 can work normally. When the heating wire drive circuit 3 receives the on signal, the drive circuit is energized and the heating wire 4 works; when the central control module 1 is in an abnormal state and outputs a DC voltage signal, the DC voltage signal is converted into an off signal, indicating that the power supply of the heating wire 4 needs to be cut off to prevent overheating or other safety hazards. When the heating wire drive circuit 3 receives the off signal, the drive circuit is powered off and the heating wire 4 stops working.

[0030] Compared with the existing technology, the safety protection circuit of the present invention to prevent the heating wire 4 from failing to control relies on the central control module 1 to generate a PWM signal for outputting when the working state is normal and a DC voltage signal for outputting when the working state is abnormal, and then converts the PWM signal into an on signal and the DC voltage signal into an off signal through the conversion module 2, thereby controlling the heating wire drive circuit 3 to further control the on and off of the heating wire 4, thereby avoiding the problem that the heating wire 4 cannot be normally closed when situations such as control circuit board failure, MCU failure, program error, etc. occur, avoiding fire hazards, and improving reliability and safety.

[0031] In one embodiment, referring to Figure 2 The conversion module 2 includes a DC blocking unit 21, which is connected to the central control module 1. The DC blocking unit 21 is used to pass the PWM signal and block the DC voltage signal. The DC blocking unit 21 is set in the conversion module 2 in order to achieve selective transmission of the signal. The DC blocking unit 21 allows the PWM signal to pass through, ensuring that under normal working conditions, the heating wire 4 can receive the correct control signal, thereby achieving precise control of the working state of the heating wire 4. The DC blocking unit 21 blocks the DC voltage signal to prevent the DC signal from adversely affecting the heating wire drive circuit 3 when the working state is abnormal, ensuring that the heating wire 4 will not malfunction. The DC blocking unit 21 can reduce the possibility of interference and enhance the overall safety of the safety protection circuit to prevent heating wire control failure, especially when the equipment fails, to ensure that the heating wire 4 will not restart accidentally.

[0032] In one embodiment, referring to Figure 2 The conversion module 2 also includes a signal conversion unit 22 and a switch unit 23. The signal conversion unit 22 is connected to the DC blocking unit 21 and is used to convert the PWM signal into a high-level signal. The switch unit 23 is connected to the signal conversion unit 22 and the heating wire driving circuit 3 respectively. The switch unit 23 is used to turn on according to the high-level signal to generate a start signal for controlling the heating wire driving circuit 3 to turn on. The signal conversion unit 22 in the conversion module 2 mainly plays the role of converting the PWM signal passing through the DC blocking unit 21 into a high-level signal. The high-level signal is used for the subsequent control logic of the switch unit 23. The switch unit 23 is turned on according to the high-level signal from the signal conversion unit 22. When receiving the high-level signal, the switch unit 23 is turned on and generates a signal for controlling the heating wire driving circuit 3 to turn on, that is, the start signal, to enable the heating wire 4 to operate. The switching of the switch unit 23 directly affects the subsequent heating wire driving circuit 3, which can make the control more accurate and precise.

[0033] Further, refer to Figure 2The conversion module 2 also includes a filtering unit 24, which is connected to the signal conversion unit 22 and the ground terminal respectively. In order to make the opening signal and closing signal received by the switch unit 23 more stable and to ensure accurate control, the filter unit 24 is designed to be connected to the switch unit 23 and the conversion unit 22 to filter high-frequency noise in the signal, smooth the signal waveform, enhance the anti-interference ability of the safety protection circuit to prevent the failure of the heating wire control, reduce the possibility of malfunction, further enhance the safety of the circuit, and avoid accidents caused by unstable signals.

[0034] In one embodiment, referring to Figure 2 The heating wire driving circuit 3 includes an isolation unit 31, which is connected to the switch unit 23 and is used to conduct the start signal. Figure 2 For example, the heating wire 4 uses a high-voltage AC circuit, while the safety protection circuit to prevent the heating wire 4 from failing to control is a low-voltage DC circuit. In order to carry out signal interaction between the two different circuits, an isolation unit 31 needs to be set. The isolation unit 31 is connected to the switch unit 23 to isolate the power supply turn-on signal to ensure that the control signal can be correctly transmitted to the heating wire drive circuit 3. While transmitting the turn-on signal, the isolation unit 31 also provides electrical isolation to prevent high voltage or interference signals from affecting the safety and stability of the control circuit. In actual use, the switch unit 23 is turned on after receiving the high-level signal from the signal conversion unit 22. After the isolation unit 31 receives the turn-on signal generated by the switch unit 23 being turned on, it transmits it between the two different circuits to ensure that the heating wire drive circuit 3 can receive a valid control signal, thereby allowing the heating wire 4 to work normally. This embodiment effectively isolates the control circuit from the high-voltage circuit used for the operation of the heating wire 4, reducing the risk of damage to the control circuit due to the high-voltage circuit.

[0035] In one embodiment, referring to Figure 2 The heating wire driving circuit 3 also includes an AC driving unit 32, which is connected to the isolation unit 31. The AC driving unit 32 is used to connect to the heating wire 4 to control the working state of the heating wire 4. The heating wire driving circuit 3 is connected to the isolation unit 31 and directly connected to the heating wire 4. It is used to control the working state of the heating wire 4 and heat or stop the heating wire 4 by providing AC power. After receiving the signal from the isolation unit 31, the AC driving unit 32 starts to provide AC power to the heating wire 4 to control the heating state of the heating wire 4. If a system failure or abnormality is detected, the switch unit 23 will not be turned on, the isolation unit 31 will remain in the disconnected state, the AC driving unit 32 will not receive the start signal, and the heating wire 4 will remain in the non-working state to ensure the safety of the equipment.

[0036] In one embodiment, referring to Figure 2The switch unit 23 includes a first transistor, the base of the first transistor is connected to the conversion unit 22, the emitter of the first transistor is grounded, and the collector of the first transistor is connected to the isolation unit 31. Figure 2 For example, a transistor is used as a component to realize the function of the switch unit 23, the base of which is connected to the signal conversion unit 22 for receiving the control signal, the emitter is grounded, and the collector is connected to the isolation unit 31. When the signal conversion unit 22 sends a high-level signal to the base of the first transistor, the first transistor is turned on, and the base current causes a conduction path to be formed between the collector and the emitter, thereby transmitting the signal to the isolation unit 31. After receiving the start signal generated by the conduction of the first transistor, the isolation unit 31 transmits the start signal to the AC drive unit 32, thereby controlling the working state of the heating wire 4. If the signal conversion unit 22 does not send a high-level signal, the first transistor is in the cut-off state. At this time, no conduction path is formed between the collector and the emitter, the isolation unit 31 will not receive the start signal, and the heating wire 4 remains in an inoperative state. By using a transistor as a switch, the circuit design is simple, easy to implement, and has high reliability.

[0037] In one embodiment, referring to Figure 2 The isolation unit 31 includes a bidirectional thyristor driven photoelectric coupler, the anode of the transmitting end of the bidirectional thyristor driven photoelectric coupler is used to connect to the first power supply end, the cathode of the transmitting end of the bidirectional thyristor driven photoelectric coupler is connected to the collector of the first transistor, the first output end and the second output end of the receiving end of the bidirectional thyristor driven photoelectric coupler are connected to the AC drive unit 32 and are used to transmit a start signal to the AC drive unit 32, and the receiving end of the bidirectional thyristor driven photoelectric coupler is also provided with a zero-crossing detection circuit for connecting to the gate of the bidirectional thyristor in the receiving end of the bidirectional thyristor driven photoelectric coupler. The function of the isolation unit 31 is achieved by using a bidirectional thyristor driven photoelectric coupler. Figure 2For example, the transmitting end of the bidirectional thyristor-driven optocoupler is connected to a DC low-voltage circuit. The transmitting end is a light-emitting diode, the anode of which is connected to the first power supply end, and the cathode of which is connected to the collector of the transistor. When a conductive path is formed between the collector and the emitter of the transistor, light is emitted when power is turned on, and a light signal is transmitted to the receiving end. The receiving end is connected to a high-voltage AC circuit, and its first output end and second output end are connected to a step-down resistor, and then connected to the AC drive unit 32, so as to control the working state of the heating wire 4. Among them, a zero-crossing detection circuit is also provided in the transmitting end. The zero-crossing detection circuit in the transmitting end can enable the transmitting end to judge whether there is light input each time the AC power connected to it passes through zero, that is, whether there is a pre-current If. If so, it will be turned on within the cycle of the AC power to transmit the start signal to the AC drive unit 32. By arranging the zero-crossing detection circuit, the transmission of the start signal can be achieved more quickly and accurately, so as to quickly control the heating wire to be turned off when there is no start signal, thereby enhancing safety and stability.

[0038] In one embodiment, referring to Figure 2 The AC drive unit 32 includes a first bidirectional thyristor, the gate of the first bidirectional thyristor is connected to the first output terminal of the receiving end of the bidirectional thyristor-driven photocoupler, the first main electrode of the first bidirectional thyristor is connected to the second power supply terminal, and the second main electrode of the first bidirectional thyristor is used to connect to the heating wire 4 connected to the third power supply terminal. As the core component of the AC drive unit 32, the first bidirectional thyristor is responsible for controlling the on and off of the heating wire 4, and its gate is connected to the first output terminal of the receiving end of the bidirectional thyristor-driven photocoupler, and receives the control signal from the photocoupler. The first main electrode of the first bidirectional thyristor is connected to the live wire, the second main electrode is connected to the heating wire 4, and the other end of the heating wire 4 is connected to the neutral wire. The provision of the first bidirectional thyristor ensures a rapid response to the control signal, so that the current of the heating wire 4 can be cut off in time, and the failure and malfunction of the central control module 1 can be responded to in time, further enhancing the safety and stability of the overall circuit.

[0039] The present invention also provides a safety protection device for preventing heating wire control failure, including the safety protection circuit for preventing heating wire 4 control failure described above. This device monitors the operating status of the heating wire 4 in real time and immediately cuts off power when an anomaly is detected, preventing overheating from causing fire or other safety hazards. This prevents the heating wire 4 from failing to shut down properly in situations such as control circuit board failure, MCU failure, or program errors, ensuring safe use and improving reliability and safety.

[0040] In one embodiment, the safety protection device for preventing heating wire control failure further includes a plurality of safety protection circuits for preventing heating wire control failure to achieve a redundant design, thereby further improving reliability.

[0041] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A safety protection circuit to prevent heating wire control failure, characterized in that: include: The central control module is used to output PWM signals when the working state is normal and output DC voltage signals when the working state is abnormal; a conversion module connected to the central control module, the conversion module being configured to convert the PWM signal into an on signal and convert the DC voltage signal into an off signal; A heating wire driving circuit is connected to the conversion module, and the heating wire driving circuit is used to control the on and off of the heating wire according to the on signal and the off signal.

2. The safety protection circuit for preventing heating wire control failure according to claim 1, characterized in that: The conversion module includes a DC blocking unit, which is connected to the central control module and is configured to pass the PWM signal and block the DC voltage signal.

3. The safety protection circuit for preventing heating wire control failure according to claim 2, characterized in that: The conversion module also includes a signal conversion unit and a switch unit. The signal conversion unit is connected to the DC blocking unit. The signal conversion unit is used to convert the PWM signal into a high-level signal. The switch unit is respectively connected to the signal conversion unit and the heating wire driving circuit. The switch unit is used to be turned on according to the high-level signal to generate the start signal for controlling the heating wire driving circuit to turn on.

4. The safety protection circuit for preventing heating wire control failure according to claim 3, characterized in that: The conversion module further includes a filtering unit, and the filtering unit is connected to the signal conversion unit and a ground terminal respectively.

5. The safety protection circuit for preventing heating wire control failure according to claim 3, characterized in that: The heating wire driving circuit includes an isolation unit connected to the switch unit, and the isolation unit is used to conduct the start signal.

6. The safety protection circuit for preventing heating wire control failure according to claim 5, characterized in that: The heating wire driving circuit further includes an AC driving unit, which is connected to the isolation unit and is used to connect to the heating wire to control the working state of the heating wire.

7. The safety protection circuit for preventing heating wire control failure according to claim 6, characterized in that: The switch unit includes a first transistor, a base of the first transistor is connected to the conversion unit, an emitter of the first transistor is grounded, and a collector of the first transistor is connected to the isolation unit.

8. The safety protection circuit for preventing heating wire control failure according to claim 7, characterized in that: The isolation unit includes a bidirectional thyristor-driven photoelectric coupler, wherein the anode of the transmitting end of the bidirectional thyristor-driven photoelectric coupler is used to be connected to the first power supply end, the cathode of the transmitting end of the bidirectional thyristor-driven photoelectric coupler is connected to the collector of the first transistor, the first output end and the second output end of the receiving end of the bidirectional thyristor-driven photoelectric coupler are connected to the AC drive unit and are used to transmit the start signal to the AC drive unit, and the receiving end of the bidirectional thyristor-driven photoelectric coupler is further provided with a zero-crossing detection circuit for being connected to the gate of the first bidirectional thyristor in the receiving end of the bidirectional thyristor-driven photoelectric coupler.

9. The safety protection circuit for preventing heating wire control failure according to claim 8, characterized in that: The AC drive unit includes a first bidirectional thyristor, the gate of the first bidirectional thyristor is connected to the first output end of the receiving end of the bidirectional thyristor-driven photoelectric coupler, the first main electrode of the first bidirectional thyristor is connected to the second power supply end, and the second main electrode of the first bidirectional thyristor is used to connect to the heating wire connected to the third power supply end.

10. A safety protection device for preventing heating wire control failure, characterized in that: The invention comprises a safety protection circuit for preventing heating wire control failure as claimed in any one of claims 1 to 9.

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