A fan control circuit

Abstract

The utility model relates to fan control technical field discloses a kind of fan control circuit that convenient operation and higher safety, when the voltage value of feedback is in threshold range, the control signal of main control circuit (140) output is high level, to control power voltage switch control circuit keeps on, and main control circuit (140) adjusts the duty cycle of drive signal according to the working mode signal corresponding to obtain, to control the rotational speed of load (M1).

Description

Technical Field

[0001] This utility model relates to the field of wind turbine control technology, and more specifically, to a wind turbine control circuit. Background Technology

[0002] Currently, many fans on the market use 220VAC or low-voltage input power supplies. They adjust the speed by changing the coil turns ratio, or the coils are not made of copper wire or the current is limited to cut corners. This makes the fans larger and less portable. Although some products use large resistors to reduce voltage to achieve speed control, these fans are noisy, generate a lot of heat, and are very easy to damage. Utility Model Content

[0003] The technical problem to be solved by this utility model is to address the shortcomings of existing products that use large resistors to reduce voltage to achieve speed regulation, which result in loud fan noise, high product heat generation, and easy damage to the product. This utility model provides a fan control circuit that is easy to operate and has high safety.

[0004] The technical solution adopted by this utility model to solve its technical problem is: to construct a fan control circuit, which includes: Input switch control circuit, which is used to control the on / off state of the power supply voltage input circuit; A power supply circuit, the input terminal of which is connected to the output terminal of the input switch control circuit, is used to receive the voltage signal output by the input switch control circuit; The main control circuit has its power input terminal connected to the output terminal of the power supply circuit, and is used to receive the voltage signal; A power supply voltage switch control circuit, the input terminal of which is connected to the output terminal of the input switch control circuit, is used to receive the voltage signal. A signal input terminal of the power supply voltage switch control circuit is connected to a signal output terminal of the main control circuit for receiving control signals. A load circuit, one of whose input terminals is connected to the output terminal of the power supply voltage input circuit; The speed control circuit has one input terminal connected to a signal output terminal of the main control circuit for receiving drive signals. An input voltage detection circuit, whose input terminal is connected to the output terminal of the power supply voltage switch control circuit, is used to acquire the voltage value. The output terminal of the input voltage detection circuit is coupled to the signal feedback terminal of the main control circuit. When the feedback voltage value is within the threshold range, the control signal output by the main control circuit is high-level to keep the power supply voltage switch control circuit on. The main control circuit adjusts the duty cycle of the drive signal according to the acquired working mode signal to control the speed of the load.

[0005] In some embodiments, a gear mode adjustment circuit is also included, the power input terminal of which is connected to the output terminal of the input switch control circuit. One signal input terminal of the gear mode adjustment circuit is connected to the signal output terminal of the main control circuit for receiving control levels. The other signal input terminal of the gear mode adjustment circuit is connected to the output terminal of the power supply circuit. The signal output terminal of the gear mode adjustment circuit is connected to the input terminal of the power supply voltage switch control circuit.

[0006] In some embodiments, the input switch control circuit includes a rocker switch. The first terminal of the rocker switch is connected to the output terminal of the power supply voltage input circuit. The second terminal of the rocker switch is connected to the first input terminal of the gear mode adjustment circuit. The third terminal of the rocker switch is connected to the second input terminal of the gear mode adjustment circuit.

[0007] In some embodiments, the power supply voltage switching control circuit includes at least a second resistor, a second capacitor, a first MOSFET, and a second MOSFET. One end of the second resistor and the source of the first MOS transistor are respectively connected to the output terminal of the gear mode adjustment circuit. The other end of the second resistor is coupled to one end of the second capacitor. The gate of the second MOS transistor is connected to a signal output terminal of the main control circuit and the other end of the second capacitor, respectively. The source of the second MOSFET is connected to the gate of the first MOSFET through a fourth resistor. The drain of the first MOSFET is connected to the input terminals of both the power supply voltage switch control circuit and the input voltage detection circuit. The drain of the second MOSFET is connected to the common terminal.

[0008] In some embodiments, the input voltage detection circuit includes at least a seventh resistor, an eighth resistor, a ninth resistor, a sixth capacitor, and a ninth capacitor. One end of the seventh resistor is connected to the drain of the first MOS transistor. The seventh resistor is connected in series with the ninth resistor. The eighth resistor is connected in parallel with the ninth capacitor, and then connected in parallel with the seventh resistor and the ninth resistor. One end of the sixth capacitor is connected to the connection terminal of the seventh resistor and the ninth resistor. One end of the sixth capacitor is connected to the other end of the ninth resistor. One end of the eighth resistor and one end of the ninth capacitor are connected to the signal feedback terminal of the main control circuit.

[0009] In some embodiments, the speed control circuit includes at least a fifteenth MOSFET. The source of the fifteenth MOS transistor is connected to the other end of the load circuit. The gate of the fifteenth MOS transistor is connected to another signal output terminal of the main control circuit through the thirteenth resistor, and is used to receive the drive signal. The drain of the fifteenth MOS transistor is connected to the common terminal through the twenty-second resistor.

[0010] In some implementations, the main control circuit includes a main controller. The signal feedback terminal of the main controller is connected to one end of the eighth resistor and one end of the ninth capacitor, respectively. One signal output terminal of the main controller is connected to the gate of the second MOS transistor through a fifth diode. The other signal output terminal of the main controller is connected to the gate of the fifteenth MOS transistor. The signal output terminal of the main controller is connected to the signal input terminal of the gear mode adjustment circuit.

[0011] In some embodiments, the gear mode adjustment circuit includes at least a sixth MOSFET and a seventh MOSFET. The gate of the sixth MOS transistor is connected to the signal output terminal of the main controller through the twenty-ninth resistor. The source of the sixth MOS transistor is connected to the second terminal of the rocker switch. The drain of the sixth MOS transistor is connected to the common terminal through the thirty-first resistor. The gate of the seventh MOS transistor is connected to the output terminal of the power supply circuit through the thirty-sixth resistor. The source of the seventh MOS transistor is connected to the third terminal of the rocker switch through the thirty-fourth resistor. The drain of the seventh MOS transistor is connected to the common terminal through the thirty-fifth resistor.

[0012] In the fan control circuit described in this utility model, when the feedback voltage value is within the threshold range, the control signal output by the main control circuit is high-level to control the power supply voltage switch control circuit to remain on. The main control circuit adjusts the duty cycle of the drive signal according to the acquired working mode signal to control the speed of the load. Compared with the prior art, using a rocker switch (belonging to the power supply circuit) to regulate the load speed and using a low-voltage power supply as the input is safer and more convenient for people to carry. In addition, the main control circuit determines the user's current mode by the toggle signal from the rocker switch (belonging to the power supply circuit), thereby performing 40KHz high-frequency PWM speed regulation on the load to reduce noise. By continuously feeding back the load's working status current signal to the main control circuit to make corresponding actions, the load is less prone to damage, thus extending the load's lifespan. Attached Figure Description

[0013] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 This is a circuit diagram of an embodiment of the fan control circuit provided by this utility model. Detailed Implementation

[0014] To provide a clearer understanding of the technical features, objectives, and effects of this utility model, the specific embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0015] like Figure 1 As shown, in the first embodiment of the fan control circuit of this utility model, the fan control circuit includes a power supply voltage input circuit 110, an input switch control circuit 120, a power supply circuit 130, a main control circuit 140, a power supply voltage switch control circuit 150, a gear mode adjustment circuit 160, a speed control circuit 170, a load circuit 180, and an input voltage detection circuit 190. The input terminals of the power supply voltage input circuit 110 (corresponding to CN3 and CN4) are connected to the electrodes of the battery (corresponding to BAT). The 15~21V or 24VDC power supply voltage signal is rectified by the first diode D1 or the second diode D2 and then filtered by the seventeenth capacitor C17, the inductor TR2 and the eighteenth capacitor C18 to remove EMC radiation interference. It is then output to the input switch control circuit 120 and the load circuit 180 through the fuse F1. The input switch control circuit 120 is used to control the on / off state of the power supply voltage input circuit 110 on the load side and to adjust the speed of the load M1; The power supply circuit 130 has the functions of voltage regulation and filtering, and is used to output a 5V voltage signal; The main control circuit 140 is equipped with a voltage threshold or preset value, and has the functions of logic operation, output of drive signal / PWM pulse signal / control signal and voltage signal processing and comparison. The power supply voltage switch control circuit 150 is used to control the on / off state of the load-side current signal; The gear mode adjustment circuit 160 is used to adjust the speed of the load M1; The speed control circuit 170 is used to receive the drive signal / PWM pulse signal input from the main control circuit 140, and control the speed of the load M1 according to the drive signal / PWM pulse signal; The load circuit 180 is used to receive the voltage signal from the power supply voltage input circuit 110 to drive the load M1 to work. The input voltage detection circuit 190 is used to detect the voltage value / voltage signal output by the power supply voltage switch control circuit 150 and feed it back to the main control circuit 140. The current feedback voltage value / voltage signal is compared with the voltage threshold or preset value. When the voltage value / voltage signal is within the range of the voltage threshold or preset value, the main control circuit 140 outputs a high-level control signal to control the power supply voltage switch control circuit 150 to remain on. Specifically, one end of the input switch control circuit 120 is connected to one output terminal of the power supply voltage input circuit 110 to control the on / off state of the power supply voltage input circuit 110. Furthermore, the input terminal of the power supply circuit 130 is connected to the output terminal of the input switch control circuit 120 to receive the voltage signal output by the input switch control circuit 120, and to perform voltage regulation / filtering on the input voltage signal to output a 5V voltage signal. The power input terminal of the main control circuit 140 is connected to the output terminal of the power supply circuit 130 to receive the 5V voltage signal output by the power supply circuit 130. The input terminal of the power supply voltage switch control circuit 150 is connected to the output terminal of the input switch control circuit 120 to receive a voltage signal. This voltage signal is used to trigger the power supply voltage switch control circuit 150 to turn on, so as to output a voltage signal. In this circuit, a signal input terminal of the power supply voltage switch control circuit 150 is connected to a signal output terminal of the main control circuit 140, and is used to receive control signals. When the control signal input to the main control circuit 140 is low, the power supply voltage switch control circuit 150 is turned off. When the control signal input to the main control circuit 140 is high, the power supply voltage switch control circuit 150 is turned on. One input terminal of the speed control circuit 170 is connected to a signal output terminal of the main control circuit 140 to receive drive signals. The main control circuit 140 adjusts the speed of the load M1 by adjusting the duty cycle of the drive signal. Furthermore, one input terminal of the load circuit 180 is connected to the output terminal of the power supply voltage input circuit 110 to receive a 15~21V or 24VDC power supply voltage signal, which is used to trigger the load M1 to work. Specifically, the input terminal of the input voltage detection circuit 190 is connected to the output terminal of the power supply voltage switch control circuit 150, and is used to acquire the voltage value or voltage signal output when the power supply voltage switch control circuit 150 is turned on. The output terminal of the input voltage detection circuit 190 is coupled to the signal feedback terminal of the main control circuit 140, and the acquired voltage value or voltage signal is input to the main control circuit 140 for comparison and processing. When the feedback voltage value is within the threshold range, the control signal output by the main control circuit 140 is high-level to keep the power supply voltage switch control circuit 150 on. The main control circuit 140 adjusts the duty cycle of the drive signal according to the acquired working mode signal to control the speed of the load M1.

[0016] Using this technical solution, a rocker switch (part of the power supply circuit) is used to regulate the speed of the load, and the use of low-voltage power supply as input is safer and convenient for people to carry. In addition, the main control circuit determines the user's current mode by the toggle signal from the rocker switch (part of the power supply circuit), and then performs 40KHz high-frequency PWM speed regulation on the load, which can reduce noise. By continuously feeding back the load's working status current signal to the main control circuit to make corresponding actions, the load is not easily damaged, thus extending the load's lifespan.

[0017] In some implementations, to improve the user experience of the fan, a speed mode adjustment circuit 160 can be set in the control circuit, which adjusts the speed of the load M1 by switching speeds. Specifically, the power input terminal of the gear mode adjustment circuit 160 is connected to the output terminal of the input switch control circuit 120 to receive a 15~21V or 24VDC power supply voltage signal. A signal input terminal of the gear mode adjustment circuit 160 is connected to the signal output terminal of the main control circuit 140 to receive a control level, which is used to control the gear mode adjustment circuit 160 to output the first gear mode. Another signal input terminal of the gear mode adjustment circuit 160 is connected to the output terminal of the power supply circuit 130 to receive a 5V voltage signal, which is used to control the gear mode adjustment circuit 160 to output a second gear mode. Furthermore, the signal output terminal of the gear mode adjustment circuit 160 is connected to the input terminal of the power supply voltage switch control circuit 150 to receive the voltage signal output after the gear is adjusted.

[0018] In some implementations, to improve the user experience of the fan, a rocker switch SW1 can be provided in the input switch control circuit 120. The first terminal (corresponding to pin 2) of the rocker switch SW1 is connected to the output terminal of the power supply voltage input circuit to receive a 15~21V or 24VDC power supply voltage signal. The second end (corresponding to pin 1) of rocker switch SW1 is connected to the first input end (corresponding to pin 1) of gear mode adjustment circuit 160, and the first input end (corresponding to pin 1) of gear mode adjustment circuit 160 corresponds to high speed gear mode; The third terminal (corresponding to pin 3) of rocker switch SW1 is connected to the second input terminal (corresponding to pin 3) of gear mode adjustment circuit 160, and the second input terminal (corresponding to pin 3) of gear mode adjustment circuit 160 corresponds to low speed gear mode.

[0019] In some embodiments, the power supply voltage switch control circuit 150 includes at least a second resistor R2, a second capacitor C2, a first MOSFET Q1, and a second MOSFET Q2. Among them, the first MOSFET Q1 is selected as a P-channel MOSFET, and the second MOSFET Q2 is selected as an N-channel MOSFET, both of which have the function of switching; Specifically, one end of the second resistor R2 and the source of the first MOSFET Q1 are connected to the output terminal of the gear mode adjustment circuit 160, respectively. The other end of the second resistor R2 is coupled to one end of the second capacitor C2. The gate of the second MOSFET Q2 is connected to a signal output terminal of the main control circuit 140 and the other end of the second capacitor C2, respectively. The source of the second MOSFET Q2 is connected to the gate of the first MOSFET Q1 through the fourth resistor R4. The drain of the first MOSFET Q1 is connected to the input terminals of the power supply voltage switch control circuit 150 and the input voltage detection circuit 190, respectively. The drain of the second MOSFET Q2 is connected to the common terminal.

[0020] Specifically, when the rocker switch SW1 is switched to pin 1, the power supply voltage is continuously charged from the fourth diode D4 rectifier diode in the gear mode adjustment circuit 160 through the power supply voltage switch control circuit 150 and the second resistor R2 to the second capacitor C2. When the voltage is greater than 0.7V, the second MOSFET Q2 turns on, thereby making the gate of the first MOSFET Q1 low voltage, and turning on the first MOSFET Q1. Through the power supply circuit 130 and the power supply voltage switch control circuit 150, the power supply circuit 130 regulated and outputs a 5V circuit to power the main control circuit 140 and provide a voltage signal to the input voltage detection circuit 190.

[0021] In some embodiments, the input voltage detection circuit 190 includes at least a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a sixth capacitor C6, and a ninth capacitor C9. One end of the seventh resistor R7 is connected to the drain of the first MOSFET Q1. The seventh resistor R7 and the ninth resistor R9 are connected in series. The eighth resistor R8 and the ninth capacitor C9 are connected in parallel, and then connected in parallel with the seventh resistor R7 and the ninth resistor R9. One end of the sixth capacitor C6 is connected to the connection terminals of the seventh resistor R7 and the ninth resistor R9. One end of the sixth capacitor C6 is connected to the other end of the ninth resistor R9. One end of the eighth resistor R8 and the ninth capacitor C9 are connected to the signal feedback terminal of the main control circuit 140.

[0022] Specifically, when the voltage signal input from the external power supply / battery is input to the first MOSFET Q1, the voltage divider signal composed of the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, the sixth capacitor C6, and the ninth capacitor C9 is detected by the internal ADC of the signal feedback terminal (corresponding to pin 16) of the main control circuit 140, when the input voltage is 15~21V or 24V, the voltage signal at pin 2 of the main control circuit 140 changes from low to high, and is output to the second MOSFET Q2 after passing through the fifth diode D5, so that the second MOSFET Q2 and the first MOSFET Q1 remain in the conducting state. Conversely, the LDO power supply is turned off to stop the fan or load M1 from working.

[0023] In some implementations, to ensure the reliability of speed regulation of load M1, a fifteenth MOSFET Q15 can be provided in the speed control circuit 170. It is selected as an N-channel MOSFET and has the function of a switch. Specifically, the source of the fifteenth MOSFET Q15 is connected to the other end of the load circuit 180. The gate of the fifteenth MOSFET Q15 is connected to another signal output terminal of the main control circuit 140 through the thirteenth resistor R13, and is used to receive drive signals. The drain of the fifteenth MOSFET Q15 is connected to the common terminal through the twenty-second resistor R22.

[0024] In some implementations, the main control circuit 140 includes a main controller U1, which has the functions of calculation, signal output and signal processing; Specifically, the signal feedback terminal (corresponding to pin 16) of the main controller U1 is connected to one end of the eighth resistor R8 and the ninth capacitor C9 respectively, and is used to receive voltage signals; One signal output terminal (corresponding to pin 2) of the main controller U1 is connected to the anode of the fifth diode D5, and the cathode of the fifth diode D5 is connected to the gate of the second MOSFET Q2. The control signal output by the main controller U1 is input to the gate of the second MOSFET Q2 through the fifth diode D5 to control its working state. Another signal output terminal of the main controller U1 (corresponding to pin 13) is connected to the gate of the fifteenth MOSFET Q15. The drive signal / pulse signal output by the main controller U1 is input to the gate of the fifteenth MOSFET Q15 through the thirteenth resistor R13 to adjust the conduction angle of the fifteenth MOSFET Q15, thereby adjusting the speed of the load M1. The signal output terminal (corresponding to pin 7) of the main controller U1 is connected to the signal input terminal of the gear mode adjustment circuit 160 to output a control signal to the gear mode adjustment circuit 160.

[0025] In some implementations, the gear mode adjustment circuit 160 includes at least a sixth MOSFET Q6 and a seventh MOSFET Q7, both of which are N-channel MOSFETs and function as switches. Specifically, the gate of the sixth MOSFET Q6 is connected to the signal output terminal (corresponding to pin 7) of the main controller U1 through the twenty-ninth resistor R29. The source of the sixth MOSFET Q6 is connected to the second terminal (pin 1) of the rocker switch SW1. The drain of the sixth MOSFET Q6 is connected to the common terminal through the thirty-first resistor R31. The gate of the seventh MOSFET Q7 is connected to the output terminal of the power supply circuit 130 through the thirty-sixth resistor R36. The source of the seventh MOSFET Q7 is connected to the third terminal (pin 3) of the rocker switch SW1 through the thirty-fourth resistor R34. The drain of the seventh MOSFET Q7 is connected to the common terminal through the thirty-fifth resistor R35.

[0026] Specifically, when rocker switch SW1 is connected to pin 1, and when power supply circuit 130 and main control circuit 140 are working normally, the control signal triggers the sixth MOS transistor to conduct. When the output terminal of the main controller U1 (corresponding to pin 7) outputs a high-mode detection pin level signal, this level signal is divided by the thirtieth resistor R30 and the thirty-first resistor R31, causing the input level signal to change from low level to high level. When the main controller U1 receives a high-mode signal, it controls its pin 13 to output a 40kHz voltage signal with a 90% duty cycle. This signal passes through the thirteenth resistor R13, causing the fifteenth MOSFET Q15 to turn on. This provides a circuit for the third inductor L3, the thirteenth capacitor C13, the fourteenth capacitor C14, the sixteenth capacitor C16, the fifteenth capacitor C15, the twelfth capacitor C12, the seventh diode D7, and the load M1. When the load M1 operates at a frequency of 40kHz, the noise of the load M1 is reduced. At this time, the 23rd resistor R23 and the 22nd resistor R22 form a current detection resistor to voltage signal of load M1. The signal is fed back to the internal ADC detection of pin 15 of the main controller U1 through the 23rd resistor R23. When the load M1 current is too large or short-circuited, the 15th MOSFET Q15 is turned off, so that the load M1 stops working, thereby protecting the life of the load M1, keeping the overall current heat generation low, and preventing the electronic components of the circuit from being burned out. Similarly, when rocker switch SW1 is switched to pin 3, with power supply circuit 130 and main control circuit 140 operating normally, gear mode adjustment circuit 160 also operates normally. The voltage signal at pin 3 of main controller U1 changes from low to high as the voltage is divided by resistors R34 and R35 and then by resistor R38. When pin 3 of the main controller U1 goes high, the internal program of the main controller U1 controls pin 13 to output a voltage signal with a 50% duty cycle and a frequency of 40KHz. This signal passes through the thirteenth resistor R13, causing the fifteenth MOSFET Q15 to operate at a 50% duty cycle voltage, thus entering a low-noise mode.

[0027] The power supply is controlled by a rocker switch SW1. The operating current status signal of the load M1 is fed back to the main controller U1 in a timely manner through program design. When the load M1 is detected to be in a high current or short circuit, the main controller U1 will reduce the PWM duty cycle output, so that the voltage of the load M1 will decrease until the load M1 stops working. This ensures the safety of the product, extends the life of the load M1, and is safe and reliable.

[0028] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A fan control circuit, characterized in that, have: Input switch control circuit, which is used to control the on / off state of the power supply voltage input circuit; A power supply circuit, the input terminal of which is connected to the output terminal of the input switch control circuit, is used to receive the voltage signal output by the input switch control circuit; The main control circuit has its power input terminal connected to the output terminal of the power supply circuit, and is used to receive the voltage signal; A power supply voltage switch control circuit, the input terminal of which is connected to the output terminal of the input switch control circuit, is used to receive the voltage signal. A signal input terminal of the power supply voltage switch control circuit is connected to a signal output terminal of the main control circuit for receiving control signals. A load circuit, one of whose input terminals is connected to the output terminal of the power supply voltage input circuit; The speed control circuit has one input terminal connected to a signal output terminal of the main control circuit for receiving drive signals. An input voltage detection circuit, whose input terminal is connected to the output terminal of the power supply voltage switch control circuit, is used to acquire the voltage value. The output terminal of the input voltage detection circuit is coupled to the signal feedback terminal of the main control circuit. When the feedback voltage value is within the threshold range, the control signal output by the main control circuit is high-level to keep the power supply voltage switch control circuit on. The main control circuit adjusts the duty cycle of the drive signal according to the acquired working mode signal to control the speed of the load.

2. The fan control circuit according to claim 1, characterized in that, It also includes a gear mode adjustment circuit, whose power input terminal is connected to the output terminal of the input switch control circuit. One signal input terminal of the gear mode adjustment circuit is connected to the signal output terminal of the main control circuit for receiving control levels. The other signal input terminal of the gear mode adjustment circuit is connected to the output terminal of the power supply circuit. The signal output terminal of the gear mode adjustment circuit is connected to the input terminal of the power supply voltage switch control circuit.

3. The fan control circuit according to claim 2, characterized in that, The input switch control circuit includes a rocker switch. The first terminal of the rocker switch is connected to the output terminal of the power supply voltage input circuit. The second terminal of the rocker switch is connected to the first input terminal of the gear mode adjustment circuit. The third terminal of the rocker switch is connected to the second input terminal of the gear mode adjustment circuit.

4. The fan control circuit according to claim 3, characterized in that, The power supply voltage switch control circuit includes at least a second resistor, a second capacitor, a first MOSFET, and a second MOSFET. One end of the second resistor and the source of the first MOS transistor are respectively connected to the output terminal of the gear mode adjustment circuit. The other end of the second resistor is coupled to one end of the second capacitor. The gate of the second MOS transistor is connected to a signal output terminal of the main control circuit and the other end of the second capacitor, respectively. The source of the second MOSFET is connected to the gate of the first MOSFET through a fourth resistor. The drain of the first MOSFET is connected to the input terminals of both the power supply voltage switch control circuit and the input voltage detection circuit. The drain of the second MOSFET is connected to the common terminal.

5. The fan control circuit according to claim 4, characterized in that, The input voltage detection circuit includes at least a seventh resistor, an eighth resistor, a ninth resistor, a sixth capacitor, and a ninth capacitor. One end of the seventh resistor is connected to the drain of the first MOS transistor. The seventh resistor is connected in series with the ninth resistor. The eighth resistor is connected in parallel with the ninth capacitor, and then connected in parallel with the seventh resistor and the ninth resistor. One end of the sixth capacitor is connected to the connection terminal of the seventh resistor and the ninth resistor. One end of the sixth capacitor is connected to the other end of the ninth resistor. One end of the eighth resistor and one end of the ninth capacitor are connected to the signal feedback terminal of the main control circuit.

6. The fan control circuit according to claim 5, characterized in that, The speed control circuit includes at least a fifteenth MOSFET. The source of the fifteenth MOS transistor is connected to the other end of the load circuit. The gate of the fifteenth MOS transistor is connected to another signal output terminal of the main control circuit through the thirteenth resistor, and is used to receive the drive signal. The drain of the fifteenth MOS transistor is connected to the common terminal through the twenty-second resistor.

7. The fan control circuit according to claim 6, characterized in that, The main control circuit includes a main controller. The signal feedback terminal of the main controller is connected to one end of the eighth resistor and one end of the ninth capacitor, respectively. One signal output terminal of the main controller is connected to the gate of the second MOS transistor through a fifth diode. The other signal output terminal of the main controller is connected to the gate of the fifteenth MOS transistor. The signal output terminal of the main controller is connected to the signal input terminal of the gear mode adjustment circuit.

8. The fan control circuit according to claim 7, characterized in that, The gear mode adjustment circuit includes at least a sixth MOSFET and a seventh MOSFET. The gate of the sixth MOS transistor is connected to the signal output terminal of the main controller through the twenty-ninth resistor. The source of the sixth MOS transistor is connected to the second terminal of the rocker switch. The drain of the sixth MOS transistor is connected to the common terminal through the thirty-first resistor. The gate of the seventh MOS transistor is connected to the output terminal of the power supply circuit through the thirty-sixth resistor. The source of the seventh MOS transistor is connected to the third terminal of the rocker switch through the thirty-fourth resistor. The drain of the seventh MOS transistor is connected to the common terminal through the thirty-fifth resistor.

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