A fan automatic speed regulating circuit based on thermistor control

Abstract

The utility model discloses a fan automatic speed regulation circuit based on thermistor control, including PWM adjusting circuit, PWM signal drive circuit and direct current speed regulation fan, the PWM adjusting circuit includes: clock pulse chip U1, electric capacity C1~C4, resistance R1, resistance R2, first diode D1, second diode D2, thermistor VR1, clock pulse chip U1 contains reset pin RST, power supply pin VCC1, discharge pin DIS, trigger pin TRI, threshold value pin THR, ground pin GND1, control voltage pin CON and output pin OUT, the PWM signal drive circuit includes resistance R3, resistance R4, NPN transistor Q1, the utility model discloses utilize thermistor to realize fan automatic speed regulation function, and not depending on CPU control, adopts pure hardware circuit composition, and stable operation is high in reliability, has stronger application expansibility.

Description

Technical Field

[0001] This utility model relates to the field of fan speed control circuit technology, specifically to a fan automatic speed control circuit based on thermistor control. Background Technology

[0002] With the continuous development of smart grids, power system equipment is becoming increasingly intelligent and digital, and the integration of control systems is becoming higher. The performance requirements of the main control system for power system equipment and corresponding testing equipment are also increasing, leading to higher power consumption. This necessitates heat dissipation for the main control system, with air cooling being the most common method. Currently, most methods for controlling fan speed use the CPU to generate adjustable PWM signals. This not only consumes CPU resources but also introduces some delay in speed feedback. Furthermore, the CPU program can crash, preventing fan speed adjustment and posing a risk of malfunction to the main control system. Utility Model Content

[0003] To address the aforementioned technical problems, this invention proposes a fan automatic speed control circuit based on thermistor control. This purely hardware circuit utilizes a small number of components, including a clock pulse chip, a thermistor, a transistor, resistors, and capacitors. By leveraging the temperature-dependent resistance of the thermistor, the clock pulse chip circuit outputs PWM signals with different duty cycles to control the DC speed-regulating fan to achieve varying speeds.

[0004] To achieve the above objectives, this utility model provides the following technical solution: an automatic fan speed control circuit based on thermistor control, including a PWM adjustment circuit, a PWM signal drive circuit, and a DC speed control fan;

[0005] The PWM regulation circuit includes: a clock pulse chip U1, capacitors C1 to C4, resistors R1 and R2, a first diode D1, a second diode D2, and a thermistor VR1.

[0006] The clock pulse chip U1 includes a reset pin RST, a power supply pin VCC1, a discharge pin DIS, a trigger pin TRI, a threshold pin THR, a ground pin GND1, a control voltage pin CON, and an output pin OUT.

[0007] The reset pin RST of clock pulse chip U1 is connected to the power supply pin VCC1 of clock pulse chip U1, one end of capacitor C1, one end of capacitor C4, and one end of resistor R1, and is connected to the power supply VCC. The other end of capacitor C1 is connected to the ground terminal GND, and the other end of capacitor C4 is connected to the ground terminal GND. The discharge pin DIS of clock pulse chip U1 is connected to the other end of resistor R1, the anode of the first diode D1, and the cathode of the second diode D2. The cathode of the first diode D1 is connected to the thermistor VR1, and the anode of the second diode is connected to one end of resistor R2. The other end of resistor R2 is connected to the other end of the thermistor VR1, one end of C2, the trigger pin TRI of clock pulse chip U1, and the threshold pin THR of clock pulse chip U1. The other end of capacitor C2 is connected to the ground terminal GND. The control voltage pin CON of clock pulse chip U1 is connected to the ground terminal GND through capacitor C3. The ground pin GND1 of clock pulse chip U1 is connected to the ground terminal GND. The output pin OUT of clock pulse chip U1 is connected to the PWM signal drive circuit.

[0008] Furthermore, the PWM signal driving circuit includes resistors R3 and R4, and an NPN transistor Q1. One end of resistor R3 is connected to the output pin OUT of the clock pulse chip U1, and the other end of resistor R3 is connected to the base of NPN transistor Q1. The emitter of NPN transistor Q1 is connected to the ground terminal GND. The collector of NPN transistor Q1 is connected to one end of resistor R4 and the speed control pin PWM of the DC speed-regulating fan. The other end of resistor R4 is connected to the power supply VCC. The power supply pin VCC2 of the DC speed-regulating fan is connected to the power supply VCC, and the ground pin GND2 of the DC speed-regulating fan is connected to the ground terminal GND.

[0009] Furthermore, the clock pulse chip is selected from 555 timer chips.

[0010] Furthermore, the thermistor is selected as a thermistor with a negative temperature coefficient.

[0011] The technical effects and advantages provided by this utility model in the above technical solution are as follows:

[0012] 1. This utility model utilizes a thermistor to achieve automatic fan speed control, without relying on CPU control;

[0013] 2. This utility model is composed of pure hardware circuits, which are stable in operation and highly reliable;

[0014] 3. The circuit of this utility model is simple to implement, low in cost, and has strong scalability. Attached Figure Description

[0015] Figure 1 This is a circuit diagram of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0017] Example

[0018] like Figure 1 As shown in the figure, the automatic fan speed control circuit based on thermistor control described in this embodiment includes a PWM adjustment circuit, a PWM signal driving circuit, and a DC speed control fan FAN1;

[0019] The PWM regulation circuit includes: a clock pulse chip U1, capacitors C1 to C4, resistors R1 and R2, a first diode D1, a second diode D2, and a thermistor VR1.

[0020] The clock pulse chip U1 includes a reset pin RST, a power supply pin VCC1, a discharge pin DIS, a trigger pin TRI, a threshold pin THR, a ground pin GND1, a control voltage pin CON, and an output pin OUT.

[0021] The reset pin RST of clock pulse chip U1 is connected to the power supply pin VCC1 of clock pulse chip U1, one end of capacitor C1, one end of capacitor C4, and one end of resistor R1, and is connected to the power supply VCC. The other end of capacitor C1 is connected to the ground terminal GND, and the other end of capacitor C4 is connected to the ground terminal GND. The discharge pin DIS of clock pulse chip U1 is connected to the other end of resistor R1, the anode of the first diode D1, and the cathode of the second diode D2. The cathode of the first diode D1 is connected to the thermistor VR1, and the anode of the second diode is connected to one end of resistor R2. The other end of resistor R2 is connected to the other end of the thermistor VR1, one end of C2, the trigger pin TRI of clock pulse chip U1, and the threshold pin THR of clock pulse chip U1. The other end of capacitor C2 is connected to the ground terminal GND. The control voltage pin CON of clock pulse chip U1 is connected to the ground terminal GND through capacitor C3. The ground pin GND1 of clock pulse chip U1 is connected to the ground terminal GND. The output pin OUT of clock pulse chip U1 is connected to the PWM signal drive circuit.

[0022] The PWM signal driving circuit includes resistors R3 and R4, and an NPN transistor Q1. One end of resistor R3 is connected to the output pin OUT of the clock pulse chip U1, and the other end of resistor R3 is connected to the base of NPN transistor Q1. The emitter of NPN transistor Q1 is connected to ground GND. The collector of NPN transistor Q1 is connected to one end of resistor R4 and the speed control pin PWM of DC speed-regulating fan FAN1. The other end of resistor R4 is connected to the power supply VCC. The power supply pin VCC2 of DC speed-regulating fan FAN1 is connected to the power supply VCC, and the ground pin GND2 of DC speed-regulating fan FAN1 is connected to the ground GND.

[0023] The clock pulse chip is a 555 timer chip, specifically the NE555.

[0024] The thermistor is a negative temperature coefficient thermistor. As the temperature increases, the resistance of the thermistor decreases. The thermistor monitors the heat source of the main control system in real time. Its model is MF5210K3470.

[0025] In the PWM regulation circuit, the NE555 clock pulse chip operates in astable mode, automatically triggering the circuit and outputting a square wave multivibrator. Its PWM output frequency depends on resistors R1, R2, VR1, and capacitor C2. The PWM duty cycle depends on the ratio of resistor R2 to thermistor VR1. The NE555 clock pulse chip controls the charging and discharging of capacitor C2, controlling the high and low levels of the output by comparing the voltage across the capacitor, thus controlling the PWM duty cycle. Resistor R2 and thermistor VR1 balance the charging and discharging time ratio of capacitor C2, indirectly controlling the output PWM duty cycle. Increasing the ratio of thermistor VR1 to resistor R2 lengthens the charging time and shortens the discharging time of capacitor C2, thereby increasing the output PWM duty cycle; conversely, decreasing the ratio shortens the charging time and lengthens the discharging time of capacitor C2, thus decreasing the output PWM duty cycle.

[0026] An automatic fan speed control circuit based on thermistor control, the automatic fan speed control process is as follows:

[0027] Step 1. The temperature of the main control system rises;

[0028] Step 2. Thermistor VR1 detects an increase in the temperature of the main control system, and its corresponding resistance decreases, thus reducing the ratio of thermistor VR1 to resistor R2.

[0029] Step 3. As the charging time of capacitor C2 decreases and the discharging time increases, the duty cycle of the PWM signal output from the OUT pin of the clock pulse chip NE555 decreases.

[0030] Step 4. After the PWM signal output from the OUT pin of the clock pulse chip NE555 passes through the PWM drive circuit, the PWM signal is reversed, that is, the duty cycle of the PWM signal actually output to the PWM control pin of the DC speed-regulating fan increases.

[0031] Step 5. After the DC speed-regulating fan receives the increased duty cycle PWM signal, its speed increases, which means that the airflow for cooling the main control system increases.

[0032] Step 6. After the heat dissipation airflow is increased, the temperature of the main control system decreases;

[0033] Step 7. After the main control temperature decreases, the resistance of thermistor VR1 increases, thus increasing the ratio of thermistor VR1 to resistor R2.

[0034] Step 8. As the charging time of capacitor C2 increases and the discharging time decreases, the duty cycle of the PWM signal output from the OUT pin of the clock pulse chip NE555 decreases.

[0035] Step 9. After the PWM signal output from the OUT pin of the clock pulse chip NE555 passes through the PWM drive circuit, the PWM signal is reversed, that is, the duty cycle of the PWM signal actually output to the PWM control pin of the DC speed-regulating fan is reduced.

[0036] Step 10. After the DC speed-regulating fan receives the reduced duty cycle PWM signal, its speed decreases, which means the airflow for cooling the main control system decreases.

[0037] Step 11. After the cooling airflow is reduced, the temperature of the main control system rises.

[0038] The automatic fan speed control circuit continuously adjusts the temperature of the main control system through steps 1 to 11 above, thereby keeping the temperature within a certain range.

[0039] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0040] The preferred embodiments of this utility model disclosed above are merely illustrative of the present utility model. These preferred embodiments do not exhaustively describe all details, nor do they limit the utility model to any specific implementation. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of this utility model, thereby enabling those skilled in the art to better understand and utilize it. This utility model is limited only by the claims and their full scope and equivalents.

Claims

1. A fan automatic speed control circuit based on thermistor control, characterized in that: Includes a PWM regulation circuit, a PWM signal drive circuit, and a DC speed-regulating fan; The PWM regulation circuit includes: a clock pulse chip U1, capacitors C1 to C4, resistors R1 and R2, a first diode D1, a second diode D2, and a thermistor VR1. The clock pulse chip U1 includes a reset pin RST, a power supply pin VCC1, a discharge pin DIS, a trigger pin TRI, a threshold pin THR, a ground pin GND1, a control voltage pin CON, and an output pin OUT. The reset pin RST of clock pulse chip U1 is connected to the power supply pin VCC1 of clock pulse chip U1, one end of capacitor C1, one end of capacitor C4, and one end of resistor R1, and is connected to the power supply VCC. The other end of capacitor C1 is connected to the ground terminal GND, and the other end of capacitor C4 is connected to the ground terminal GND. The discharge pin DIS of clock pulse chip U1 is connected to the other end of resistor R1, the anode of the first diode D1, and the cathode of the second diode D2. The cathode of the first diode D1 is connected to the thermistor VR1, and the anode of the second diode is connected to one end of resistor R2. The other end of resistor R2 is connected to the other end of the thermistor VR1, one end of C2, the trigger pin TRI of clock pulse chip U1, and the threshold pin THR of clock pulse chip U1. The other end of capacitor C2 is connected to the ground terminal GND. The control voltage pin CON of clock pulse chip U1 is connected to the ground terminal GND through capacitor C3. The ground pin GND1 of clock pulse chip U1 is connected to the ground terminal GND. The output pin OUT of clock pulse chip U1 is connected to the PWM signal drive circuit.

2. The automatic fan speed control circuit based on thermistor control according to claim 1, characterized in that: The PWM signal driving circuit includes resistors R3 and R4, and an NPN transistor Q1. One end of resistor R3 is connected to the output pin OUT of the clock pulse chip U1, and the other end of resistor R3 is connected to the base of NPN transistor Q1. The emitter of NPN transistor Q1 is connected to ground GND. The collector of NPN transistor Q1 is connected to one end of resistor R4 and the speed control pin PWM of the DC speed-regulating fan. The other end of resistor R4 is connected to the power supply VCC. The power supply pin VCC2 of the DC speed-regulating fan is connected to the power supply VCC, and the ground pin GND2 of the DC speed-regulating fan is connected to the ground GND.

3. The automatic fan speed control circuit based on thermistor control according to claim 1, characterized in that: The clock pulse chip is a 555 timer chip.

4. The automatic fan speed control circuit based on thermistor control according to claim 1, characterized in that: The thermistor is selected from those with a negative temperature coefficient.

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