Electrical safety protection circuit of household electrical appliance circuit board
By combining the arc detection module and the smoke detection module, the problem of accidental power outages on the circuit boards of household appliances due to light source interference is solved, enabling precise power supply control and smoke alarm, and improving the safety of the circuit boards.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ZHONGSHAN YUTENG ELECTRONIC TECHNOLOGY CO LTD
- Filing Date
- 2025-01-20
- Publication Date
- 2026-04-17
AI Technical Summary
The circuit boards of existing household appliances are easily affected by external light sources when the box is damaged, which can lead to false power outages and low safety levels.
The electrical safety protection circuit consists of an arc detection module, a self-locking protection module, a power supply control module, a smoke detection module, an alarm module, and a false detection control module. Through arc detection and smoke detection, it achieves precise power supply control and alarm functions.
It improves the electrical safety of circuit boards in household appliances, avoids accidental power outages, ensures power restoration when an electric arc is present but there is no smoke, and triggers an alarm when smoke is detected.
Smart Images
Figure CN224138730U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of circuit board technology for household appliances, specifically a power safety protection circuit for a circuit board of a household appliance. Background Technology
[0002] Circuit boards are an indispensable component of household appliances, mainly used to realize electrical connections and signal transmission between various internal components. In the present technology, household appliance circuit boards are generally placed in a light-proof, sealed box. To prevent fires caused by arcing in the circuit, a power safety protection circuit composed of photoresistors is generally used. When an arc is detected, the circuit board is de-energized. However, if the box containing the circuit board is damaged, it is easily interfered with by external light sources, resulting in false detections and causing the circuit board to de-energize. Furthermore, the safety index of household appliance circuit boards is relatively low, so improvements are needed. Utility Model Content
[0003] This utility model provides an electrical safety protection circuit for a household appliance circuit board to solve the problems mentioned in the background art.
[0004] To achieve the above objectives, this utility model provides the following technical solution:
[0005] An electrical safety protection circuit for a household appliance circuit board includes: a power supply module, a household appliance circuit board power supply module, an arc detection module, a self-locking protection module, a power supply control module, a smoke detection module, an alarm module, and a false detection control module.
[0006] The power module is used to receive AC power, step down and rectify the AC power and output the first power, and then regulate the first power and output the second power.
[0007] The power supply module for the household appliance circuit board is used to transmit the received first electrical energy to the connected household appliance circuit board. When it receives the first protection signal output by the self-locking protection module, it stops receiving the first electrical energy and performs power-off protection. When it receives the first reset signal output by the false detection control module, it stops receiving the first protection signal.
[0008] The arc detection module is used to detect electric arcs under illumination and output a first control signal when an electric arc is detected.
[0009] The self-locking protection module is used to receive the first electrical energy and, upon receiving the first control signal, perform a high-level self-locking and output the first protection signal.
[0010] The power supply control module is used to output a second control signal and transmit the second electrical energy to the smoke detection module and the alarm module when it receives the first protection signal and the first control signal;
[0011] The smoke detection module is used to receive the second electrical energy and perform smoke detection, and output a second protection signal when the detected smoke exceeds the set smoke threshold;
[0012] The alarm module is used to receive the second electrical energy and to trigger a smoke alarm when a second protection signal is received.
[0013] The false detection control module is used to output a first reset signal and control the power supply module of the household appliance circuit board to restore power supply when no second protection signal is received but a first control signal and a second control signal are received.
[0014] As a further embodiment of this utility model: the power supply module includes a power interface, a first transformer, a first rectifier, a first capacitor, a first voltage regulator, and a second capacitor; the power supply module for the household appliance circuit board includes a first resistor, a first power transistor, a first switching transistor, a sixth resistor, a second switching transistor, and a household appliance circuit board interface;
[0015] Preferably, the first and second ends of the power interface are respectively connected to the first and second ends of the primary side of the first transformer; the first and second ends of the secondary side of the first transformer are respectively connected to the first and second ends of the first rectifier; the third end of the first rectifier is connected to the first end of the first voltage regulator, one end of the first capacitor, and the drain of the first power transistor, and is connected to the gate of the first power transistor and the collector of the first switching transistor through the first resistor; the source of the first power transistor is connected to the first end of the household appliance circuit board interface; the emitter of the first switching transistor is connected to the second end of the household appliance circuit board interface and ground; the third end of the first voltage regulator is connected to the first end of the second capacitor, the arc detection module, the self-locking protection module, and the power supply control module; the fourth end of the first rectifier is connected to the other end of the first capacitor, the second end of the first voltage regulator, the second end of the second capacitor, and ground; the base of the first switching transistor is connected to the collector of the second switching transistor through the sixth resistor; the emitter of the second switching transistor is grounded; and the base of the second switching transistor is connected to the false detection control module.
[0016] As a further embodiment of this utility model: the arc detection module includes a first photoresistor, a second resistor, a third resistor, a fourth resistor, and a first comparator;
[0017] Preferably, one end of the first photoresistor is connected to the first end of the second capacitor and is connected to the inverting input of the first comparator and one end of the fourth resistor through the third resistor. The non-inverting input of the first comparator is connected to the other end of the first photoresistor and is connected to the other end of the fourth resistor and the second end of the second capacitor through the second resistor. The output of the first comparator is connected to the self-locking protection module.
[0018] As a further improvement of this utility model: the self-locking protection module includes a first diode, a second diode, a fifth resistor, a first logic chip, and a seventh resistor;
[0019] Preferably, the anode of the first diode is connected to the output terminal of the first comparator, the cathode of the first diode is connected to the cathode of the second diode and the A terminal of the first logic chip, the B terminal of the first logic chip is connected to the first terminal of the second capacitor through the fifth resistor, and the Y terminal of the first logic chip is connected to the anode of the second diode and the power supply control module and connected to the collector of the second switching transistor through the seventh resistor.
[0020] As a further improvement of this utility model: the power supply control module includes a third diode, a second logic chip, a fourth diode, and a second power transistor;
[0021] Preferably, the anode of the third diode is connected to the output terminal of the first comparator, the A terminal of the second logic chip is connected to the Y terminal of the first logic chip, the cathode of the third diode is connected to the B terminal of the second logic chip and the cathode of the fourth diode, the anode of the fourth diode is connected to the Y terminal of the second logic chip, the gate of the second power transistor and the false detection control module, and the source of the second power transistor is connected to the smoke detection module and the alarm module.
[0022] As a further embodiment of this utility model: the smoke detection module includes a smoke sensor, a first potentiometer, a ninth resistor, an eighth resistor, and a second comparator; the alarm module includes a third switching transistor and a first speaker;
[0023] Preferably, the power supply terminal of the smoke sensor is connected to the source of the second power transistor and one end of the first speaker, and is connected to the non-inverting input of the second comparator and one end of the ninth resistor through the eighth resistor. The inverting input of the second comparator is connected to the slider of the first potentiometer. One end of the first potentiometer is connected to the output terminal of the smoke sensor. The other end of the first potentiometer is connected to the ground terminal of the smoke sensor, the other end of the ninth resistor, the emitter of the third switch transistor, and the ground terminal. The output terminal of the second comparator is connected to the base of the third switch transistor and the false detection control module. The collector of the third switch transistor is connected to the other end of the first speaker.
[0024] As a further improvement of this utility model: the false detection control module includes a third logic chip, a first inverter and a fourth logic chip;
[0025] Preferably, the A and B terminals of the third logic chip are connected to the output terminal of the first comparator and the Y terminal of the second logic chip, respectively. The Y terminal of the third logic chip is connected to the A terminal of the fourth logic chip. The B terminal of the fourth logic chip is connected to the output terminal of the first inverter. The input terminal of the first inverter is connected to the output terminal of the second comparator. The Y terminal of the fourth logic chip is connected to the base of the second switching transistor.
[0026] Compared with the prior art, the beneficial effects of this utility model are as follows: The electrical safety protection circuit of the household appliance circuit board of this utility model can detect whether an arc occurs on the household appliance circuit board connected to the power supply module and the power supply module of the household appliance circuit board by the arc detection module. When an arc is detected, the power supply module of the household appliance circuit board is controlled by the self-locking protection module to cut off the power. At the same time, if light is still detected after the power is cut off, the power supply control module will supply power to the smoke detection module and the alarm module. If smoke is detected at this time, an alarm will be triggered. If no smoke is detected at this time, the false detection control module will reset the power supply module of the household appliance circuit board, restore the power supply to the household appliance circuit board, and maintain the smoke detection state, thereby improving the electrical safety of the household appliance circuit board. Attached Figure Description
[0027] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments of this utility model 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.
[0028] Figure 1 This is a schematic block diagram of the principle of an electrical safety protection circuit for a household appliance circuit board, provided as an example of this utility model.
[0029] Figure 2 This invention provides a circuit diagram of an electrical safety protection circuit for a household appliance circuit board.
[0030] Figure 3 A connection circuit diagram of the false detection control module provided for this utility model embodiment. Detailed Implementation
[0031] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0032] In one embodiment, see Figure 1 A power safety protection circuit for a household appliance circuit board includes: a power supply module 1, a household appliance circuit board power supply module 2, an arc detection module 3, a self-locking protection module 4, a power supply control module 5, a smoke detection module 6, an alarm module 7, and a false detection control module 8.
[0033] Specifically, power module 1 is used to receive AC power, step down and rectify the AC power and output the first power, and stabilize the first power and output the second power.
[0034] The power supply module 2 for the household appliance circuit board is used to transmit the received first electrical energy to the connected household appliance circuit board. When it receives the first protection signal output by the self-locking protection module 4, it stops receiving the first electrical energy and performs power-off protection. When it receives the first reset signal output by the false detection control module 8, it stops receiving the first protection signal.
[0035] Arc detection module 3 is used to detect arcs under light and output a first control signal when an arc is detected;
[0036] The self-locking protection module 4 is used to receive the first electrical energy and, upon receiving the first control signal, perform a high-level self-locking and output the first protection signal.
[0037] The power supply control module 5 is used to output a second control signal and transmit the second electrical energy to the smoke detection module 6 and the alarm module 7 when it receives the first protection signal and the first control signal.
[0038] The smoke detection module 6 is used to receive the second electrical energy and perform smoke detection, and output a second protection signal when the detected smoke exceeds the set smoke threshold.
[0039] Alarm module 7 is used to receive the second electrical energy and to trigger a smoke alarm when the second protection signal is received;
[0040] The false detection control module 8 is used to output a first reset signal and control the power supply module 2 of the household appliance circuit board to restore power supply when no second protection signal is received but the first control signal and the second control signal are received.
[0041] In a specific embodiment, the power supply module 1 can be a power circuit composed of a power interface, transformer, rectifier, etc., which can connect to AC power and perform voltage reduction, rectification, filtering, and stabilization on the AC power; the power supply module 2 for the household appliance circuit board can be a power supply circuit composed of a household appliance circuit board interface, field-effect transistor, transistor, etc., which can perform power transmission control and supply power to the connected household appliance circuit board; the arc detection module 3 can be an arc detection circuit composed of a photoresistor, resistor, and comparator, which can detect arcs on household appliance circuit boards placed in a dark and sealed box and output a first control signal when an arc is detected; the self-locking protection module 4 can be a self-locking protection circuit composed of a resistor, logic chip, and diode, which can perform high-voltage protection when a high level is received. The power supply control module 5 can be a power supply control circuit composed of logic chips, diodes, and field-effect transistors. Upon detecting an electric arc, it performs high-level self-locking and power transmission control. The smoke detection module 6 can be a smoke detection circuit composed of smoke sensors, resistors, comparators, etc. It can detect smoke and output a second protection signal when the smoke concentration exceeds a set smoke threshold. The alarm module 7 can be an alarm circuit composed of a speaker and transistors. It can perform alarm operation. The false detection control module 8 can be a false detection control circuit composed of logic chips and inverters. It can perform logical calculations on the input signal and, when the power supply control module 5 is in a power supply state and continuously detects electric arc illumination but does not detect smoke, it determines that the electric arc detection module 3 has a detection fault.
[0042] In another embodiment, please refer to Figure 1 , Figure 2 and Figure 3 The power supply module 1 includes a power interface, a first transformer B1, a first rectifier T1, a first capacitor C1, a first voltage regulator IC1, and a second capacitor C2; the power supply module 2 for the household appliance circuit board includes a first resistor R1, a first power transistor Q1, a first switching transistor V1, a sixth resistor R6, a second switching transistor V2, and a household appliance circuit board interface.
[0043] Specifically, the first and second terminals of the power interface are respectively connected to the first and second terminals of the primary side of the first transformer B1. The first and second terminals of the secondary side of the first transformer B1 are respectively connected to the first and second terminals of the first rectifier T1. The third terminal of the first rectifier T1 is connected to the first terminal of the first voltage regulator IC1, one terminal of the first capacitor C1, and the drain of the first power transistor Q1, and is connected to the gate of the first power transistor Q1 and the collector of the first switching transistor V1 through the first resistor R1. The source of the first power transistor Q1 is connected to the first terminal of the home appliance circuit board interface. The first switching transistor V1... The emitter of the first voltage regulator IC1 is connected to the second terminal of the home appliance circuit board interface and the ground terminal. The third terminal of the first voltage regulator IC1 is connected to the first terminal of the second capacitor C2, the arc detection module 3, the self-locking protection module 4 and the power supply control module 5. The fourth terminal of the first rectifier T1 is connected to the other terminal of the first capacitor C1, the second terminal of the first voltage regulator IC1, the second terminal of the second capacitor C2 and the ground terminal. The base of the first switching transistor V1 is connected to the collector of the second switching transistor V2 through the sixth resistor R6. The emitter of the second switching transistor V2 is grounded. The base of the second switching transistor V2 is connected to the false detection control module 8.
[0044] In a specific embodiment, the first voltage regulator IC1 can be a 7809 voltage regulator; the first power transistor Q1 can be an N-channel MOSFET; the first switching transistor V1 can be an NPN transistor; and the home appliance circuit board interface is connected to the power supply terminal of the home appliance circuit board.
[0045] Furthermore, the arc detection module 3 includes a first photoresistor RT1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a first comparator A1;
[0046] Specifically, one end of the first photoresistor RT1 is connected to the first end of the second capacitor C2 and is connected to the inverting input of the first comparator A1 and one end of the fourth resistor R4 through the third resistor R3. The non-inverting input of the first comparator A1 is connected to the other end of the first photoresistor RT1 and is connected to the other end of the fourth resistor R4 and the second end of the second capacitor C2 through the second resistor R2. The output of the first comparator A1 is connected to the self-locking protection module 4.
[0047] In a specific embodiment, the first comparator A1 described above may be an LM358 comparator.
[0048] Furthermore, the self-locking protection module 4 includes a first diode D1, a second diode D2, a fifth resistor R5, a first logic chip J1, and a seventh resistor R7;
[0049] Specifically, the anode of the first diode D1 is connected to the output terminal of the first comparator A1, the cathode of the first diode D1 is connected to the cathode of the second diode D2 and the A terminal of the first logic chip J1, the B terminal of the first logic chip J1 is connected to the first terminal of the second capacitor C2 through the fifth resistor R5, and the Y terminal of the first logic chip J1 is connected to the anode of the second diode D2 and the power supply control module 5 and connected to the collector of the second switching transistor V2 through the seventh resistor R7.
[0050] In a specific embodiment, the first logic chip J1 can be an AND gate chip, which, together with the first diode D1, the second diode D2 and the fifth resistor R5, performs high-level self-locking processing.
[0051] Furthermore, the power supply control module 5 includes a third diode D3, a second logic chip J2, a fourth diode D4, and a second power transistor Q2;
[0052] Specifically, the anode of the third diode D3 is connected to the output terminal of the first comparator A1, the A terminal of the second logic chip J2 is connected to the Y terminal of the first logic chip J1, the cathode of the third diode D3 is connected to the B terminal of the second logic chip J2 and the cathode of the fourth diode D4, the anode of the fourth diode D4 is connected to the Y terminal of the second logic chip J2, the gate of the second power transistor Q2 and the false detection control module 8, and the source of the second power transistor Q2 is connected to the smoke detection module 6 and the alarm module 7.
[0053] In a specific embodiment, the second logic chip J2 can be an AND gate chip, which works with the third diode D3 and the fourth diode D4 to perform high-level self-locking; the second power transistor Q2 can be an N-channel field-effect transistor.
[0054] Furthermore, the smoke detection module 6 includes a smoke sensor, a first potentiometer RP1, a ninth resistor R9, an eighth resistor R8, and a second comparator A2; the alarm module 7 includes a third switch V3 and a first speaker BL1.
[0055] Specifically, the power supply terminal of the smoke sensor is connected to the source of the second power transistor Q2 and one end of the first speaker BL1, and is connected to the non-inverting terminal of the second comparator A2 and one end of the ninth resistor R9 through the eighth resistor R8. The inverting terminal of the second comparator A2 is connected to the slider terminal of the first potentiometer RP1. One end of the first potentiometer RP1 is connected to the output terminal of the smoke sensor. The other end of the first potentiometer RP1 is connected to the ground terminal of the smoke sensor, the other end of the ninth resistor R9, the emitter of the third switch transistor V3 and the ground terminal. The output terminal of the second comparator A2 is connected to the base of the third switch transistor V3 and the false detection control module 8. The collector of the third switch transistor V3 is connected to the other end of the first speaker BL1.
[0056] In a specific embodiment, the smoke sensor can be QM-25; the eighth resistor R8 and the ninth resistor R9 set the smoke threshold; the second comparator A2 can be an LM358 comparator; and the third switch V3 can be an NPN transistor.
[0057] Furthermore, the false detection control module 8 includes a third logic chip J3, a first inverter INV1, and a fourth logic chip J4;
[0058] Specifically, the A and B terminals of the third logic chip J3 are connected to the output terminal of the first comparator A1 and the Y terminal of the second logic chip J2, respectively. The Y terminal of the third logic chip J3 is connected to the A terminal of the fourth logic chip J4. The B terminal of the fourth logic chip J4 is connected to the output terminal of the first inverter INV1. The input terminal of the first inverter INV1 is connected to the output terminal of the second comparator A2. The Y terminal of the fourth logic chip J4 is connected to the base of the second switching transistor V2.
[0059] In a specific embodiment, both the third logic chip J3 and the fourth logic chip J4 can be AND gate chips; the first inverter INV1 can be a NOT gate chip.
[0060] In this embodiment, a power safety protection circuit for a household appliance circuit board includes an AC power input via a power interface. A first transformer B1, a first rectifier T1, and a first capacitor C1 perform voltage reduction, rectification, and filtering to output first electrical energy. This first electrical energy is then regulated by a first voltage regulator IC1 and a second capacitor C2, outputting second electrical energy. This first electrical energy is transmitted to the household appliance circuit board connected to the interface via a first power transistor Q1. A first photoresistor RT1 receives the second electrical energy and, in conjunction with a second resistor R2, performs arc detection. If the detected arc exceeds the voltage provided by a third resistor R3 and a fourth resistor R4, a first comparator A1 outputs a first control signal. After being latched by a first resistor R1, a second diode D2, a fifth resistor R5, and a first logic chip J1, a first protection signal is output. This first protection signal triggers a first switch V1 to conduct and a first power transistor Q1 to turn off, providing power-off protection. If an arc is still detected at this time... The second logic chip J2, in conjunction with the third diode D3 and the fourth diode D4, performs self-locking, outputs a second control signal, and controls the second power transistor Q2 to conduct. This controls the B terminal of the third logic chip J3 to go high, energizing the smoke sensor and enabling smoke detection. When the detected signal exceeds the smoke threshold set by the eighth resistor R8 and the ninth resistor R9, the second comparator A2 outputs a second protection signal, controlling the third switch V3 to conduct, and the first speaker BL1 alarms. If no smoke is detected at this time, the first inverter INV1 controls the B terminal of the fourth logic chip J4 to go high. Simultaneously, if an arc is detected, the first comparator A1 will cause the A terminal of the third logic chip J3 to go high. This indicates that the arc detection module 3 has malfunctioned or that the household appliance circuit board is under illumination. This causes the fourth logic chip J4 to control the second switch V2 to conduct, the first switch V1 to turn off, and the first power transistor Q1 to re-energize the household appliance circuit board interface, while maintaining the smoke sensor's smoke detection.
[0061] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.
[0062] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. An electrical safety protection circuit for a household appliance circuit board, used for arc protection of a household appliance circuit board placed in a dark, sealed enclosure, characterized in that, The electrical safety protection circuit of this household appliance circuit board includes: a power supply module, a household appliance circuit board power supply module, an arc detection module, a self-locking protection module, a power supply control module, a smoke detection module, an alarm module, and a false detection control module; The power module is used to receive AC power, step down and rectify the AC power and output the first power, and stabilize the first power and output the second power. The power supply module for the household appliance circuit board is used to transmit the received first electrical energy to the connected household appliance circuit board. When it receives the first protection signal output by the self-locking protection module, it stops receiving the first electrical energy and performs power-off protection. When it receives the first reset signal output by the false detection control module, it stops receiving the first protection signal. The arc detection module is used to perform light illumination detection on the arc of the circuit board of a household appliance placed in a dark and sealed box, and output a first control signal when an arc is detected. The self-locking protection module is used to receive the first electrical energy and, upon receiving the first control signal, perform a high-level self-locking and output the first protection signal. The power supply control module is used to output a second control signal and transmit the second electrical energy to the smoke detection module and the alarm module when it receives the first protection signal and the first control signal. The smoke detection module is used to receive the second electrical energy and perform smoke detection, and output a second protection signal when the detected smoke exceeds the set smoke threshold. The alarm module is used to receive the second electrical energy and to trigger a smoke alarm when it receives the second protection signal; The false detection control module is used to output a first reset signal and control the power supply module of the household appliance circuit board to restore power supply when no second protection signal is received and a first control signal and a second control signal are received.
2. A safety protection circuit for electric appliances according to claim 1, characterized in that, The power module includes a power interface, a first transformer, a first rectifier, a first capacitor, a first voltage regulator, and a second capacitor; the power supply module for the household appliance circuit board includes a first resistor, a first power transistor, a first switching transistor, a sixth resistor, a second switching transistor, and a household appliance circuit board interface. The first and second ends of the power interface are respectively connected to the first and second ends of the primary side of the first transformer. The first and second ends of the secondary side of the first transformer are respectively connected to the first and second ends of the first rectifier. The third end of the first rectifier is connected to the first end of the first voltage regulator, one end of the first capacitor, and the drain of the first power transistor, and is connected to the gate of the first power transistor and the collector of the first switching transistor through the first resistor. The source of the first power transistor is connected to the first end of the home appliance circuit board interface. The emitter of the first switching transistor is connected to the second end of the home appliance circuit board interface and ground. The third end of the first voltage regulator is connected to the first end of the second capacitor, the arc detection module, the self-locking protection module, and the power supply control module. The fourth end of the first rectifier is connected to the other end of the first capacitor, the second end of the first voltage regulator, the second end of the second capacitor, and ground. The base of the first switching transistor is connected to the collector of the second switching transistor through the sixth resistor. The emitter of the second switching transistor is grounded. The base of the second switching transistor is connected to the false detection control module.
3. A safety protection circuit for electric appliances according to claim 2, characterized in that, The arc detection module includes a first photoresistor, a second resistor, a third resistor, a fourth resistor, and a first comparator; One end of the first photoresistor is connected to the first end of the second capacitor and is connected to the inverting input of the first comparator and one end of the fourth resistor through the third resistor. The non-inverting input of the first comparator is connected to the other end of the first photoresistor and is connected to the other end of the fourth resistor and the second end of the second capacitor through the second resistor. The output of the first comparator is connected to the self-locking protection module.
4. A safety protection circuit for electric appliances according to claim 3, wherein The self-locking protection module includes a first diode, a second diode, a fifth resistor, a first logic chip, and a seventh resistor; The first logic chip is an AND gate chip. The anode of the first diode is connected to the output terminal of the first comparator. The cathode of the first diode is connected to the cathode of the second diode and the A terminal of the first logic chip. The B terminal of the first logic chip is connected to the first terminal of the second capacitor through the fifth resistor. The Y terminal of the first logic chip is connected to the anode of the second diode and the power supply control module, and is connected to the collector of the second switching transistor through the seventh resistor.
5. A safety circuit for use in an electrical appliance according to claim 4, wherein the circuit is arranged to be connected to the power supply of the electrical appliance. The power supply control module includes a third diode, a second logic chip, a fourth diode, and a second power transistor; The second logic chip is an AND gate chip. The anode of the third diode is connected to the output of the first comparator. The A terminal of the second logic chip is connected to the Y terminal of the first logic chip. The cathode of the third diode is connected to the B terminal of the second logic chip and the cathode of the fourth diode. The anode of the fourth diode is connected to the Y terminal of the second logic chip, the gate of the second power transistor, and the false detection control module. The source of the second power transistor is connected to the smoke detection module and the alarm module.
6. A safety circuit for use in an electrical appliance according to claim 5, wherein the circuit is arranged to be connected in series with the electrical circuit of the appliance. The smoke detection module includes a smoke sensor, a first potentiometer, a ninth resistor, an eighth resistor, and a second comparator; the alarm module includes a third switch and a first speaker. The power supply terminal of the smoke sensor is connected to the source of the second power transistor and one end of the first speaker, and is connected to the non-inverting terminal of the second comparator and one end of the ninth resistor through the eighth resistor. The inverting terminal of the second comparator is connected to the slider terminal of the first potentiometer. One end of the first potentiometer is connected to the output terminal of the smoke sensor. The other end of the first potentiometer is connected to the ground terminal of the smoke sensor, the other end of the ninth resistor, the emitter of the third switch transistor, and the ground terminal. The output terminal of the second comparator is connected to the base of the third switch transistor and the false detection control module. The collector of the third switch transistor is connected to the other end of the first speaker.
7. A safety circuit for use in an electrical appliance according to claim 6, wherein the safety circuit comprises a microprocessor. The false detection control module includes a third logic chip, a first inverter, and a fourth logic chip; Both the third and fourth logic chips are AND gate chips. The A and B terminals of the third logic chip are connected to the output terminal of the first comparator and the Y terminal of the second logic chip, respectively. The Y terminal of the third logic chip is connected to the A terminal of the fourth logic chip. The B terminal of the fourth logic chip is connected to the output terminal of the first inverter. The input terminal of the first inverter is connected to the output terminal of the second comparator. The Y terminal of the fourth logic chip is connected to the base of the second switching transistor.