Control circuit for heating fan

Abstract

The present invention discloses a control circuit for a heating fan. The circuit includes a fuse, a switch circuit, a first thermistor, a second thermistor, a main circuit, and a safety capacitor. One end of the fuse is connected to a first voltage input terminal, and the other end is connected to the first input terminal of the main circuit, a positive connection terminal, one end of the safety capacitor, and one end of the thermistor. The second voltage input terminal is connected to the other end of the first thermistor, a negative connection terminal, and one end of the second thermistor. The other end of the safety capacitor is connected to the other end of the second thermistor and the second input terminal of the main circuit. The first thermistor is a negative temperature coefficient thermistor. The other end of the second inductor in the main circuit is connected to the first connection terminal of the switch circuit. The second connection terminal of the switch circuit is grounded. The above-mentioned test circuit automatically connects the switch circuit to blow the fuse when a fan fails, preventing the heating fan from catching fire, thereby improving the safety of the heating fan during operation.

Description

Technical Field

[0001] The present invention relates to the technical field of control circuits, and in particular to a control circuit for heating a blower. Background Art

[0002] The heating duct can draw in air through a fan and heat the air through a heating device. However, the fan is prone to malfunction during operation. For example, the blades of a high-speed motor are fixed to the bearing by a tight fit and gluing method. Due to production process issues such as manual gluing and glue reliability, there is a certain probability that the blades will fall off during mass production and user use. If the fan fails and falls off during operation, the fan blades will hit the control panel, which can easily cause the control panel to fail and cause the heating duct to catch fire and smoke. Therefore, the heating duct in the prior art is prone to safety hazards caused by fan blade failure during use. Summary of the Invention

[0003] An embodiment of the present invention provides a control circuit for a heating duct, aiming to solve the problem in the prior art that a heating duct is prone to safety hazards caused by fan blade failure during use.

[0004] In a first aspect, an embodiment of the present invention discloses a control circuit for a heating air duct, the control circuit comprising a fuse, a switch circuit, a first thermistor, a second thermistor, a main circuit, a safety capacitor, a first heating control circuit, and a second heating control circuit;

[0005] One end of the fuse is connected to the first voltage input end, and the other end is connected to the first input end of the main circuit, the positive connection end, one end of the safety capacitor, and one end of the first thermistor; the second voltage input end is connected to the other end of the first thermistor, the negative connection end, and one end of the second thermistor; the other end of the safety capacitor is connected to the other end of the second thermistor and the second input end of the main circuit; the first thermistor is a negative temperature coefficient thermistor;

[0006] The second input terminal of the main circuit is connected to one end of the second inductor and the working voltage terminal, and the other end of the second inductor is connected to the first connection terminal of the switch circuit; the second connection terminal of the switch circuit is grounded; and the control terminal of the switch circuit is connected to the control chip;

[0007] The input end of the first heating control circuit and the input end of the second heating control circuit are both connected to the first voltage input end.

[0008] The control circuit for heating the air duct, wherein the switching circuit includes a switching resistor and a field effect transistor with a damping diode;

[0009] One end of the switching resistor is connected to the control chip as the control end of the switching circuit, the other end of the switching resistor is connected to the gate of the field-effect transistor with a damping diode, the emitter of the field-effect transistor with a damping diode serves as the first connection end of the switching circuit, and the collector of the field-effect transistor with a damping diode serves as the second connection end of the switching circuit; the positive pole of the damping diode in the field-effect transistor with a damping diode is connected to the emitter of the field-effect transistor with a damping diode.

[0010] The control circuit for heating the air duct, wherein the rated working voltage of the safety capacitor is 275V.

[0011] The control circuit for heating the air duct, wherein the control circuit further includes a thirteenth resistor and a fourteenth resistor, the thirteenth resistor and the fourteenth resistor are connected in series and then arranged in parallel at both ends of the safety capacitor.

[0012] In the control circuit for heating the air duct, the resistance values ​​of the thirteenth resistor and the fourteenth resistor are equal.

[0013] The control circuit for heating the air duct, wherein the main circuit further includes an eighth capacitor, a first connecting socket and a second connecting socket;

[0014] One end of the second inductor serves as the first input end of the main circuit, and the other end of the second inductor is connected to one end of the eighth capacitor, the working voltage end, and the first connecting socket;

[0015] The other end of the eighth capacitor is connected to the second connecting base and the second connecting end of the switch circuit, and the connection point is grounded and serves as the second input end of the main circuit.

[0016] The control circuit for heating the air duct, wherein the main circuit further includes a third diode, a fourth diode, a fifth diode and a sixth diode;

[0017] The anode of the third diode is connected to the cathode of the fourth diode, and the connection point is connected to the second connection end of the switch circuit; the cathode of the third diode is connected to the cathode of the fifth diode, and the connection point is connected to one end of the second inductor;

[0018] The anode of the fourth diode is connected to the anode of the sixth diode and the connection point is connected to the other end of the eighth capacitor; the anode of the fifth diode is connected to the cathode of the sixth diode and the connection point is connected to the other end of the first thermistor.

[0019] The control circuit for heating the air duct, wherein the first heating control circuit comprises a third bidirectional thyristor, a forty-third resistor, a forty-fourth resistor, an eighth optocoupler switch, a forty-fifth resistor and a forty-sixth resistor;

[0020] The first connection end of the third bidirectional thyristor serves as the input end of the first heating control circuit, the second connection end of the third bidirectional thyristor is connected to one end of the forty-third resistor, and the connection point serves as a load connection end to be connected to a load;

[0021] One end of the forty-third resistor is connected to one end of the forty-fourth resistor, and the other end of the forty-fourth resistor is connected to the fourth connection end of the eighth optocoupler switch; the third connection end of the eighth optocoupler switch is connected to the control end of the third bidirectional thyristor; the first connection end of the eighth optocoupler switch is connected to one end of the forty-fifth resistor, and the other end of the forty-fifth resistor is connected to one end of the forty-sixth resistor and the second connection end of the eighth optocoupler switch; the other end of the forty-sixth resistor is connected to the control chip as the first heating control signal input end.

[0022] The control circuit for heating the air duct, wherein the second heating control circuit comprises a first bidirectional thyristor, a ninth resistor, a tenth resistor, a third optocoupler switch, a fifteenth resistor and a sixteenth resistor;

[0023] The first connection end of the first bidirectional thyristor serves as the input end of the second heating control circuit, the second connection end of the first bidirectional thyristor is connected to one end of the ninth resistor, and the connection point serves as a load connection end to connect to a load;

[0024] One end of the ninth resistor is connected to one end of the tenth resistor, and the other end of the tenth resistor is connected to the fourth connection end of the third optocoupler switch; the third connection end of the third optocoupler switch is connected to the control end of the first bidirectional thyristor; the first connection end of the third optocoupler switch is connected to one end of the fifteenth resistor, and the other end of the fifteenth resistor is connected to one end of the sixteenth resistor and the second connection end of the third optocoupler switch; the other end of the sixteenth resistor is connected to the control chip as the second heating control signal input end.

[0025] In the control circuit for heating the air duct, the maximum current value of the fuse is 3.15A.

[0026] The embodiment of the present application discloses a control circuit for a heating air duct, the control circuit comprising a fuse, a switch circuit, a first thermistor, a second thermistor, a main circuit, a safety capacitor, a first heating control circuit and a second heating control circuit; one end of the fuse is connected to a first voltage input terminal, and the other end is connected to a first input terminal of the main circuit, a positive connection terminal, one end of the safety capacitor and one end of the thermistor; the second voltage input terminal is connected to the other end of the first thermistor, a negative connection terminal and one end of the second thermistor; the other end of the safety capacitor is connected to the other end of the second thermistor and the second input terminal of the main circuit; the first thermistor is a negative temperature coefficient thermistor; the second input terminal of the main circuit is connected to one end of a second inductor and a working voltage terminal, and the other end of the second inductor is connected to the first connection terminal of the switch circuit; the second connection terminal of the switch circuit is grounded; and the control terminal of the switch circuit is connected to a control chip. The above-mentioned test circuit automatically connects the switch circuit to blow the fuse when a fan fails, thereby preventing the heating air duct from catching fire and improving the safety of the heating air duct during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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.

[0028] Figure 1 This is a circuit structure diagram of a control circuit for heating a wind tube provided in an embodiment of the present invention.

[0029] Reference numerals: F1, fuse; K1, switch circuit; RV1, first thermistor; NTC1, second thermistor; Z, main circuit; X1, safety capacitor; S1, first heating control circuit; S2, second heating control circuit; L-IN1, first voltage input terminal; N-IN1, second voltage input terminal; R1A, switch resistor; Q1A, field-effect transistor with damping diode; R13, thirteenth resistor; R14, fourteenth resistor; L2, second inductor; C8, eighth capacitor; P2, first connector; P3, second connector; D3, third diode; D4, fourth diode; D5, fifth diode; D6, sixth diode; Q3, third bidirectional thyristor; R43, forty-third resistor; R44, forty-fourth resistor; U8, eighth optocoupler switch;

[0030] R45, the forty-fifth resistor; R46, the forty-sixth resistor; Q1, the first bidirectional thyristor; R9, the ninth resistor; R10, the tenth resistor; U3, the third optocoupler switch; R15, the fifteenth resistor; R16, the sixteenth resistor. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] 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.

[0033] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0034] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0035] The embodiment of the present invention also discloses a control circuit for heating a hair dryer, which includes a fuse F1, a switch circuit K1, a first thermistor RV1, a second thermistor NTC1, a main circuit Z, a safety capacitor X1, a first heating control circuit S1 and a second heating control circuit S2; one end of the fuse F1 is connected to the first voltage input terminal L-IN1, and the other end is connected to the first input terminal of the main circuit Z, the positive connection terminal, one end of the safety capacitor X1 and one end of the first thermistor; the second voltage input terminal N-IN1 is connected to the other end of the first thermistor RV1, the negative connection terminal and the second thermistor NTC 1; the other end of the safety capacitor X1 is connected to the other end of the second thermistor NTC1 and the second input end of the main circuit Z; the first thermistor RV1 is a negative temperature coefficient thermistor; the second input end of the main circuit Z is connected to one end of the second inductor L2 and the working voltage end, and the other end of the second inductor L2 is connected to the first connection end of the switch circuit K1; the second connection end of the switch circuit K1 is grounded; the control end of the switch circuit K1 is connected to the control chip; the input end of the first heating control circuit S1 and the input end of the second heating control circuit S2 are both connected to the first voltage input end L-IN1.

[0036] The control chip connects both ends of the fan motor to obtain the fan's operating power and fan speed. Based on these values, the control chip determines whether the fan is abnormal. For example, if the control chip detects that the fan motor speed remains unchanged but the fan power suddenly drops to less than 50% of its original value, it determines that the fan is abnormal. If the control chip determines that the fan is abnormal, it sends a conduction control signal to the switch circuit K1. Switch circuit K1 conducts, directing a high current to the fuse F1. This current flows through the fuse F1, causing it to melt and disconnect the entire heating duct circuit. Blowing fuse F1 protects the entire heating duct circuit, including the control circuit. The first thermistor RV1 is used to connect or disconnect the positive terminal F+ and the negative terminal F-. The first thermistor RV1 has a negative temperature coefficient (NTC). When the temperature of the first thermistor RV1 decreases, its resistance increases, thereby disconnecting the positive terminal F+ and the negative terminal F-. When the temperature of the first thermistor RV1 increases, the positive terminal F+ and the negative terminal F- are connected. The second thermistor NTC1 is used to protect the entire circuit. When the current flowing through the second thermistor NTC1 increases, its temperature increases with the current, and the resistance of the second thermistor NTC1 increases, thereby reducing the current flowing through it. When the current flowing through the second thermistor NTC1 decreases, its temperature also decreases, and the resistance of the second thermistor NTC1 decreases, thereby increasing the current flowing through it. The second thermistor NTC1 can control the current flowing through it to remain within a reasonable range, thereby further improving the overall safety of the control circuit.

[0037] In a more specific embodiment, the switching circuit K1 includes a switching resistor R1A and a field-effect transistor Q1A with a damping diode; one end of the switching resistor R1A serves as the control end of the switching circuit K1 and is connected to the control chip; the other end of the switching resistor R1A is connected to the gate of the field-effect transistor Q1A with a damping diode; the emitter of the field-effect transistor Q1A with a damping diode serves as the first connection end of the switching circuit K1; and the collector of the field-effect transistor Q1A with a damping diode serves as the second connection end of the switching circuit K1; the anode of the damping diode in the field-effect transistor Q1A with a damping diode is connected to the emitter of the field-effect transistor Q1A with a damping diode. Specifically, the rated operating voltage of the safety capacitor X1 is 275V. The maximum current value of the fuse F1 is 3.15A.

[0038] The switch circuit K1 can be configured to consist of a switch resistor R1A and a field-effect transistor (FET) Q1A with a damping diode. The control terminal Ruin of the switch circuit K1 is connected to the control chip to receive the conduction control signal from the control chip. The switch resistor R1A is used to provide current limiting protection for the path between the gate of the field-effect transistor (FET) Q1A with a damping diode and the control chip.

[0039] In a more specific embodiment, the control circuit further includes a thirteenth resistor R13 and a fourteenth resistor R14, which are connected in series and then arranged in parallel at both ends of the safety capacitor X1. The resistance values ​​of the thirteenth resistor R13 and the fourteenth resistor R14 are equal. To further protect the control circuit, the thirteenth resistor R13 and the fourteenth resistor R14 can also be provided, and the resistance values ​​of the two resistors can be set to be equal.

[0040] In a more specific embodiment, the main circuit Z also includes an eighth capacitor C8, a first connecting socket P2 and a second connecting socket P3; one end of the second inductor L2 serves as the first input end of the main circuit Z, and the other end of the second inductor L2 is connected to one end of the eighth capacitor C8, the working voltage end and the first connecting socket P2; the other end of the eighth capacitor C8 is connected to the second connecting socket P3 and the second connection end of the switch circuit K1, and the connection point is grounded and serves as the second input end of the main circuit Z. Specifically, the main circuit Z further includes a third diode D3, a fourth diode D4, a fifth diode D5, and a sixth diode D6. The anode of the third diode D3 is connected to the cathode of the fourth diode D4, and the connection point is connected to the second connection terminal of the switch circuit K1. The cathode of the third diode D3 is connected to the cathode of the fifth diode D5, and the connection point is connected to one end of the second inductor L2. The anode of the fourth diode D4 is connected to the anode of the sixth diode D6, and the connection point is connected to the other end of the eighth capacitor C8. The anode of the fifth diode D5 is connected to the cathode of the sixth diode D6, and the connection point is connected to the other end of the first thermistor RV1. The provision of the third diode D3, the fourth diode D4, the fifth diode D5, and the sixth diode D6 further improves the safety of the main circuit Z when connected to other components.

[0041] In a more specific embodiment, the first heating control circuit S1 includes a third bidirectional thyristor Q3, a forty-third resistor R43, a forty-fourth resistor R44, an eighth optocoupler switch U8, a forty-fifth resistor R45, and a forty-sixth resistor R46; the first connection end of the third bidirectional thyristor Q3 serves as the input end of the first heating control circuit S1, the second connection end of the third bidirectional thyristor Q3 is connected to one end of the forty-third resistor R43, and the connection point is connected to the load as a load connection end; one end of the forty-third resistor R43 is connected to the forty-fourth resistor R44. One end of resistor R44 and the other end of the forty-fourth resistor R44 are connected to the fourth connection end of the eighth optocoupler switch U8; the third connection end of the eighth optocoupler switch U8 is connected to the control end of the third bidirectional thyristor Q3; the first connection end of the eighth optocoupler switch U8 is connected to one end of the forty-fifth resistor R45, the other end of which is connected to one end of the forty-sixth resistor R46 and the second connection end of the eighth optocoupler switch U8; the other end of the forty-sixth resistor R46 serves as the first heating control signal input end and is connected to the control chip. The connection point between the third bidirectional thyristor Q3 and the forty-third resistor R43 serves as a load connection end and can be connected to the first heating wire, outputting current through the load connection end to heat the first heating wire.

[0042] In a more specific embodiment, the second heating control circuit S2 includes a first bidirectional thyristor Q1, a ninth resistor R9, a tenth resistor R10, a third optocoupler switch U3, a fifteenth resistor R15 and a sixteenth resistor R16; the first connection end of the first bidirectional thyristor Q1 serves as the input end of the second heating control circuit S2, the second connection end of the first bidirectional thyristor Q1 is connected to one end of the ninth resistor R9, and the connection point serves as a load connection end to connect the load; one end of the ninth resistor R9 is connected to one end of the tenth resistor R10, and the other end of the tenth resistor R10 is connected to the fourth connection end of the third optocoupler switch U3; the third connection end of the third optocoupler switch U3 is connected to the control end of the first bidirectional thyristor Q1; the first connection end of the third optocoupler switch U3 is connected to one end of the fifteenth resistor R15, and the other end of the fifteenth resistor R15 is connected to one end of the sixteenth resistor R16 and the second connection end of the third optocoupler switch U3; the other end of the sixteenth resistor R16 is connected to the control chip as the second heating control signal input end. The connection point between the first bidirectional thyristor Q1 and the ninth resistor R9 serves as a load connection terminal and can be connected to the second heating wire. Current is output through the load connection terminal to heat the second heating wire.

[0043] The present invention discloses a control circuit for a heating fan, the control circuit comprising a fuse, a switch circuit, a first thermistor, a second thermistor, a main circuit, a safety capacitor, a first heating control circuit, and a second heating control circuit; one end of the fuse is connected to a first voltage input terminal, and the other end is connected to a first input terminal of the main circuit, a positive connection terminal, one end of the safety capacitor, and one end of the thermistor; the second voltage input terminal is connected to the other end of the first thermistor, a negative connection terminal, and one end of the second thermistor; the other end of the safety capacitor is connected to the other end of the second thermistor and the second input terminal of the main circuit; the first thermistor is a negative temperature coefficient thermistor; the second input terminal of the main circuit is connected to one end of a second inductor and an operating voltage terminal, and the other end of the second inductor is connected to the first connection terminal of the switch circuit; the second connection terminal of the switch circuit is grounded; and the control terminal of the switch circuit is connected to a control chip. The above-mentioned test circuit automatically turns on the switch circuit to blow the fuse when a fan fails, thereby preventing the heating fan from catching fire and improving the safety of the heating fan during operation.

[0044] 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 are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A control circuit for heating a wind tube, characterized in that: The control circuit includes a fuse, a switch circuit, a first thermistor, a second thermistor, a main circuit, a safety capacitor, a first heating control circuit and a second heating control circuit; One end of the fuse is connected to the first voltage input end, and the other end is connected to the first input end of the main circuit, the positive connection end, one end of the safety capacitor, and one end of the first thermistor; the second voltage input end is connected to the other end of the first thermistor, the negative connection end, and one end of the second thermistor; the other end of the safety capacitor is connected to the other end of the second thermistor and the second input end of the main circuit; the first thermistor is a negative temperature coefficient thermistor; The second input terminal of the main circuit is connected to one end of the second inductor and the working voltage terminal, and the other end of the second inductor is connected to the first connection terminal of the switch circuit; the second connection terminal of the switch circuit is grounded; and the control terminal of the switch circuit is connected to the control chip; The input end of the first heating control circuit and the input end of the second heating control circuit are both connected to the first voltage input end.

2. The control circuit for heating the air duct according to claim 1, characterized in that: The switching circuit includes a switching resistor and a field effect transistor with a damping diode; One end of the switching resistor is connected to the control chip as the control end of the switching circuit, the other end of the switching resistor is connected to the gate of the field-effect transistor with a damping diode, the emitter of the field-effect transistor with a damping diode serves as the first connection end of the switching circuit, and the collector of the field-effect transistor with a damping diode serves as the second connection end of the switching circuit; the positive pole of the damping diode in the field-effect transistor with a damping diode is connected to the emitter of the field-effect transistor with a damping diode.

3. The control circuit for heating the air duct according to claim 1, characterized in that: The rated working voltage of the safety capacitor is 275V.

4. The control circuit for heating the air duct according to any one of claims 1 to 3, characterized in that: The control circuit further includes a thirteenth resistor and a fourteenth resistor. The thirteenth resistor and the fourteenth resistor are connected in series and then arranged in parallel at both ends of the safety capacitor.

5. The control circuit for heating the air duct according to claim 4, characterized in that: The resistance values ​​of the thirteenth resistor and the fourteenth resistor are equal.

6. The control circuit for heating the air duct according to any one of claims 1 to 3, characterized in that: The main circuit further includes an eighth capacitor, a first connecting socket and a second connecting socket; One end of the second inductor serves as the first input end of the main circuit, and the other end of the second inductor is connected to one end of the eighth capacitor, the working voltage end, and the first connecting socket; The other end of the eighth capacitor is connected to the second connecting base and the second connecting end of the switch circuit, and the connection point is grounded and serves as the second input end of the main circuit.

7. The control circuit for heating the air duct according to claim 6, characterized in that: The main circuit further includes a third diode, a fourth diode, a fifth diode and a sixth diode; The anode of the third diode is connected to the cathode of the fourth diode, and the connection point is connected to the second connection end of the switch circuit; the cathode of the third diode is connected to the cathode of the fifth diode, and the connection point is connected to one end of the second inductor; The anode of the fourth diode is connected to the anode of the sixth diode and the connection point is connected to the other end of the eighth capacitor; the anode of the fifth diode is connected to the cathode of the sixth diode and the connection point is connected to the other end of the first thermistor.

8. The control circuit for heating the air duct according to any one of claims 1 to 3, characterized in that: The first heating control circuit includes a third bidirectional thyristor, a forty-third resistor, a forty-fourth resistor, an eighth optocoupler switch, a forty-fifth resistor, and a forty-sixth resistor; The first connection end of the third bidirectional thyristor serves as the input end of the first heating control circuit, the second connection end of the third bidirectional thyristor is connected to one end of the forty-third resistor, and the connection point serves as a load connection end to be connected to a load; One end of the forty-third resistor is connected to one end of the forty-fourth resistor, and the other end of the forty-fourth resistor is connected to the fourth connection end of the eighth optocoupler switch; the third connection end of the eighth optocoupler switch is connected to the control end of the third bidirectional thyristor; the first connection end of the eighth optocoupler switch is connected to one end of the forty-fifth resistor, and the other end of the forty-fifth resistor is connected to one end of the forty-sixth resistor and the second connection end of the eighth optocoupler switch; the other end of the forty-sixth resistor is connected to the control chip as the first heating control signal input end.

9. The control circuit for heating a wind tube according to any one of claims 1 to 3, characterized in that: The second heating control circuit includes a first bidirectional thyristor, a ninth resistor, a tenth resistor, a third optocoupler switch, a fifteenth resistor, and a sixteenth resistor; The first connection end of the first bidirectional thyristor serves as the input end of the second heating control circuit, the second connection end of the first bidirectional thyristor is connected to one end of the ninth resistor, and the connection point serves as a load connection end to connect to a load; One end of the ninth resistor is connected to one end of the tenth resistor, and the other end of the tenth resistor is connected to the fourth connection end of the third optocoupler switch; the third connection end of the third optocoupler switch is connected to the control end of the first bidirectional thyristor; the first connection end of the third optocoupler switch is connected to one end of the fifteenth resistor, and the other end of the fifteenth resistor is connected to one end of the sixteenth resistor and the second connection end of the third optocoupler switch; the other end of the sixteenth resistor is connected to the control chip as the second heating control signal input end.

10. The control circuit for heating the air duct according to any one of claims 1 to 3, characterized in that: The maximum current value of the fuse is 3.15A.

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