Fan speed regulation circuit based on real-time temperature monitoring

Abstract

The present invention relates to a fan speed regulating circuit based on real-time temperature monitoring, comprising a power supply circuit, a temperature sensor, a temperature conditioning circuit, a triangular wave generating circuit, a polarity selection circuit, a comparison circuit and a signal isolation output circuit; the temperature sensor is attached to a component to be cooled, and the temperature sensor outputs a real-time temperature signal to the temperature conditioning circuit, and the temperature signal collected by the sensor is converted into a level signal by the temperature conditioning circuit, and is compared with the triangular wave generated by the triangular wave generating circuit after passing through the polarity selection circuit to obtain a PWM control signal, and then the fan operation is controlled through the signal isolation output circuit. The pure hardware design is adopted, with low cost, small size, precise control and fast response speed, and the fan speed can be automatically adjusted according to the loss of the equipment, which can not only save energy and reduce emissions, but also achieve the purpose of reducing vibration and noise.

Description

Technical Field

[0001] The invention relates to an electronic circuit technology, and in particular to a fan speed regulating circuit based on real-time temperature monitoring. Background Art

[0002] For power electronic equipment, the commonly used heat dissipation method is to install a cooling fan on the radiator for forced air cooling. For equipment with large losses, a larger fan is required to achieve the heat dissipation effect. However, when the equipment is running at low power, the loss is small. A fan with a higher speed not only causes energy waste, but also reduces the vibration and noise level of the equipment. Therefore, it is very important to control the fan speed according to the loss size.

[0003] The existing fan speed regulation method has poor real-time regulation performance and a large system size, which affects the high integration of the overall system. Summary of the invention

[0004] Aiming at the problem of fan heat dissipation and speed regulation balance, a fan speed regulation circuit with real-time temperature monitoring is proposed to solve the problem of efficient fan heat dissipation.

[0005] The technical solution of the present invention is: a fan speed regulation circuit based on real-time temperature monitoring, comprising a power supply circuit, a temperature sensor, a temperature conditioning circuit, a triangular wave generating circuit, a polarity selection circuit, a comparison circuit and a signal isolation output circuit; the temperature sensor is attached to the component to be cooled, and the temperature sensor outputs a real-time temperature signal to the temperature conditioning circuit, and the temperature conditioning circuit converts the temperature signal collected by the sensor into a level signal, which is compared with the triangular wave generated by the triangular wave generating circuit after passing through the polarity selection circuit and then sent to the comparison circuit to obtain a PWM control signal, and then the fan operation is controlled through the signal isolation output circuit.

[0006] Preferably, the triangular wave generating circuit includes a time base chip, a trigger input pin of the time base chip is connected to a threshold input pin, so that the timer is self-triggered and operates as a multivibrator, the trigger input pin and the threshold input pin are connected to GND through a charge and discharge capacitor, and a triangular wave signal is generated by charging and discharging the charge and discharge capacitor, the charge and discharge capacitor is connected to VCC through two charge and discharge resistors in series, and the charge and discharge capacitor is charged and discharged between the threshold level and the trigger level.

[0007] Preferably, the temperature conditioning circuit includes a two-stage series operational amplifier circuit, and the full-speed rotation and the lowest rotation of the fan correspond to the set temperature, which is converted into a threshold level and a trigger level in the corresponding triangle wave signal circuit through the two-stage operational amplifier circuit.

[0008] Preferably, the polarity selection circuit is composed of four polarity resistors, two inputs are respectively connected to one polarity resistor connected to one of the two outputs, and through the matching of the resistors, the level signal waveforms of the same direction and reverse input terminals of the comparator of the input comparison circuit are changed, thereby changing the comparator output PWM level polarity.

[0009] Preferably, the comparison circuit includes a comparator, and the signal waveforms output by the triangular wave generating circuit and the temperature conditioning circuit are respectively input into the comparator for level comparison after passing through a polarity selection circuit, and then a control signal is output.

[0010] Preferably, the signal isolation output circuit uses a high-speed optical coupler that integrates a high-gain high-speed photodetector and a high-output GaACAs light-emitting diode.

[0011] The beneficial effects of the present invention are as follows: the fan speed regulation circuit with real-time temperature monitoring of the present invention adopts a pure hardware design, has low cost, small size, precise control and fast response speed, and can automatically adjust the fan speed according to the loss of the equipment, which can not only save energy and reduce emissions, but also achieve the purpose of reducing vibration and noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a structural block diagram of a fan speed regulation circuit for real-time temperature monitoring of the present invention;

[0013] Figure 2 It is the power supply circuit diagram of the present invention;

[0014] Figure 3 This is a circuit diagram of a triangle wave generator in the present invention;

[0015] Figure 4 It is the temperature conditioning circuit diagram of the present invention;

[0016] Figure 5 This is a polarity selection circuit diagram of the present invention;

[0017] Figure 6 A comparison circuit diagram in the present invention;

[0018] Figure 7 This is a signal isolation output circuit diagram of the present invention. DETAILED DESCRIPTION

[0019] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0020] like Figure 1The fan speed control circuit structure block diagram of the real-time temperature monitoring is shown, and the circuit includes a power supply circuit, a temperature sensor, a temperature conditioning circuit, a triangular wave generating circuit, a polarity selection circuit, a comparison circuit, a signal isolation output circuit and a fan. The present invention selects the fan as a 4-wire speed control fan, the red and black wires are respectively the positive and negative DC inputs, the rated working voltage is VCC, the third wire is the fan control signal line, which is in the form of PWM, and the fan speed can be adjusted by the duty cycle, and the fourth wire can be unused. The temperature of the component to be dissipated is detected by the temperature sensor, and the temperature conditioning circuit converts the temperature signal collected by the sensor into a level form, and the triangular wave signal generated by the triangular wave generating circuit is sent to the comparison circuit for comparison through the polarity selection circuit, and then the PWM control signal is obtained, and the fan operation is controlled by the isolation output circuit, wherein the polarity selection circuit can change the signal at the same direction and reverse input end of the comparator according to the actual application situation, and then change the positive and negative proportional relationship between the PWM duty cycle and the temperature signal.

[0021] Figure 2 The power conversion circuit is an external power supply VCC of the fan speed control circuit. The level conversion chip 1 converts VCC into VDD, where VCC and VDD share the same ground, GND. The VCC value selects the fan rated voltage, and the VDD value selects the fan control signal high level voltage. The level conversion chip 1 needs to select a non-isolated conversion chip.

[0022] Figure 3The invention is a triangular wave generating circuit, which takes the time base chip 2 as the core and cooperates with the peripheral resistors and capacitors to generate a triangular wave signal. The 8th and 1st pins of the time base chip 2 are the power input terminals, which are connected to VCC and GND respectively, and the filter capacitor 3 is connected in parallel between the two pins. The specific capacitance value can be selected according to the recommended type in the chip user manual. The capacitance value of this design is C1 = 0.1μF; the 3rd pin is connected to VCC through the load resistor 4, and the resistance value of the load resistor 4 is RL. The specific resistance value can be selected according to the recommended type in the chip user manual. The RL value of this design is 1kΩ; the 4th pin is directly connected to VCC; the 7th pin is connected to VCC through the charge and discharge resistor 5, and the resistance value of the charge and discharge resistor 5 is RA, and is connected to the 2nd pin through the charge and discharge resistor 6, and the resistance value of the charge and discharge resistor 6 is RB; the 2nd pin (input terminal) of the trigger is connected to the 6th pin (threshold input), so that the timer is self-triggered and operates as a multivibrator. The 2nd and 6th pins are connected to GND through the capacitor 7, and the triangular wave signal is generated by charging and discharging the capacitor 7. The capacitance value of the capacitor 7 is C2; the 5th pin is connected to GND through the capacitor 8. Capacitor 7 is charged through charging and discharging resistors 5 and 6, and then discharged only through charging and discharging resistor 6, so the triangular wave waveform is controlled by the values ​​RA and RB. In this working mode, capacitor 7 is charged and discharged between the threshold level (2 / 3VCC) and the trigger level (1 / 3VCC). In the monostable circuit, the number of charge and discharge times, that is, the frequency and duty cycle, are independent of the power supply voltage. The duration of the rising process of the triangular wave voltage is tH, and the duration of the falling process is tL, where tH=0.693(RA+RB)C2, tL=0.693(RB)C2, single wave period P=tH+tL, frequency f=1.44 / (RA+2RB) / C2, duty cycle D=tH / P=1-RB / (RA+2RB). The output terminal A is output to the polarity selection circuit A'.

[0023] Figure 4It is a temperature sensor and a temperature conditioning circuit. The temperature sensor 9 is an NTC negative temperature coefficient thermistor. The resistance end is attached to the surface of the component whose temperature needs to be detected, and the lead end is connected to the wiring terminal 10 of the temperature conditioning circuit. The temperature sensor 9 has a variable resistance value RT. The wiring terminal 10 is in the form of 2 pins. Pin 1 is connected to the power supply VDD, and pin 2 is divided into two paths. One path passes through the voltage-dividing resistor 11 and is connected to GND. A filter capacitor 12 is connected in parallel across both ends of the voltage-dividing resistor 11. The capacitance value of the filter capacitor 12 is C41, and the value of the voltage-dividing resistor 11 is R41. The other path passes through the current-limiting resistor 13 and is connected to the non-inverting input terminal 5 of the operational amplifier 14. The resistance value of the current-limiting resistor is R42. Among them, the voltage-dividing resistor 11 and the temperature sensor 9 interact to distribute the VDD voltage, so that the temperature level signal UT input to the operational amplifier changes with the temperature. Among them, UT = VDD*R41 / (R41 + RT), so the change in the value of UT can be used to characterize the high and low of the collected temperature. R42 is related to the operating current I1 of the operational amplifier chip 14 and the level UT. R42 < UT / I1, and R42 = 0.5UT / I1 can be selected. C41 is selected as a 1 μF chip capacitor according to experience. The 8th and 4th pins of the operational amplifier 14 are power input pins, which are connected to VCC and GND respectively. The input pins are 5 and 6, and the output pin is 7. The inverting input terminal 6 and the output terminal 7 are connected through the amplification resistor 15, and the inverting input terminal 6 is connected to GND through the amplification resistor 16. The resistance value of the amplification resistor 15 is R43, and the resistance value of the amplification resistor 16 is R44. The level output by the 7th pin of the operational amplifier 14 is U41.

[0024] According to the design assumption, the temperature at which the fan rotates at full speed is T1, the corresponding RT resistance value is RT1, the maximum temperature corresponding to the lowest speed operation of the temperature level signal UT1 of the fan is T0, the corresponding RT resistance value is RT0, and the temperature level signal is UT0. After calculation, UT1 = VDD*R41 / (R41 + RT1), UT0 = VDD*R41 / (R41 + RT0). Assuming that the amplification factor of the amplification circuit composed of the operational amplifier 14 and the peripheral circuit is a, since the peak level of the triangular wave signal is 2VCC / 3 and the trough level is VCC / 3, therefore, after the temperature level signals TIT0 are amplified, the corresponding level values U41 should be 2VCC / 3 and VCC / 3. So there are: a*UT1 = 2VCC / 3, a*UT0 = VCC / 3. It can be obtained that: R41 = RT0 - 2RT1, the amplification factor a = (2VCC / 3VDD)(RT0 - RT1) / (RT0 - 2RT1), that is, (R43 + R44) / R44 = (2VCC / 3VDD)(RT0 - RT1) / (RT0 - 2RT1). The values of R43 and R44 can be obtained through the proportional relationship.

[0025] The output terminal 7 is connected to the non-inverting input terminal of the operational amplifier 18, i.e., pin 3, through the current-limiting resistor 17. The resistance value of the current-limiting resistor 17 is R45, which is related to the operating current I2 of the operational amplifier chip 18 and the output level U41 of the operational amplifier 14. R45 < U41 / I2, and R45 = 0.5U41 / I2 can be selected. The operational amplifier 18 and the operational amplifier 14 can select two operational amplifier modules integrated in the same chip to save volume. The inverting input terminal 2 and the output terminal 1 are connected through the amplification resistor 19, and the inverting input terminal 2 is connected to GND through the amplification resistor 20. The resistance value of the amplification resistor 19 is R46, and the resistance value of the amplification resistor 20 is R47. This operational amplifier and its peripheral circuit act as a voltage follower, where R46 is taken as 0Ω and R47 is taken as infinity. The output terminal B outputs to the polarity selection circuit B'.

[0026] Figure 5 It is a polarity selection circuit, which is realized by four polarity selection resistors 21, 22, 23, and 24. When in use, the user can perform resistance value matching according to the actual situation. When the resistors 21 and 23 are 0Ω and the resistors 22 and 24 are infinite, at this time, the A' signal is transmitted to the next-stage circuit through the output terminal C, and B' is transmitted to the next-stage circuit through the output terminal D; when the resistors 21 and 23 are infinite and the resistors 22 and 24 are 0Ω, at this time, the A' signal is transmitted to the next-stage circuit through the output terminal D, and B' is transmitted to the next-stage circuit through the output terminal C. By matching the resistors, the waveform of the level signal at the non-inverting and inverting input terminals of the input comparator is changed, and the purpose of changing the polarity of the output PWM level is achieved, so as to control the detection temperature to be proportional or inversely proportional to the PWM duty cycle. The output terminals C and D output to the comparison circuits C' and D'.

[0027] Figure 6 It is a comparison circuit. The signal waveforms output by the triangular wave generation circuit and the temperature conditioning circuit are input to the comparison circuit through C' and D' respectively after passing through the polarity selection circuit. C' is input to the non-inverting input terminal 3 of the comparator 27 through the current-limiting resistor 25, and D' is input to the inverting input terminal 2 of the comparator 27 through the current-limiting resistor 26. The resistance value of the current-limiting resistor 25 is R61, and the resistance value of the current-limiting resistor 26 is R62. Their resistance values are related to the input current I2 of the comparator, and R61 = R62 > 2 / 3VCC / I2. The supply voltage of the comparator 27 includes VCC and is powered by VCC. Pins 8 and 4 are connected to VCC and GND respectively. The input and output voltage capabilities of the comparator 27 are greater than VCC. The output terminal 1 outputs to the next-stage circuit. At the same time, the output terminal 1 is connected to VCC through the pull-up resistor 28. The resistance value R63 of the pull-up resistor 28 is selected as 10kΩ according to the empirical value. The output terminal E outputs to the isolation signal output circuit E'.

[0028] Figure 7It is an isolated signal output circuit. The input signal E’ is input to the input terminal 2 of the high-speed optocoupler 29. The input terminal 1 of the high-speed optocoupler 29 is connected to VCC through the current-limiting resistor 30. The high-speed optocoupler 29 is preferably a product integrating a high-gain high-speed photodetector and a high-output GaACAs light-emitting diode, and its maximum transmission rate is not less than the frequency of the fan control PWM. The resistance value of the current-limiting resistor 30 is R71, and its value is related to the maximum operating current I3 and the threshold input current I4 of the input pin of the high-speed optocoupler 29, where VCC / I4 < R71 < VCC / I3. The 6th pin of the high-speed optocoupler 29 is connected to VDD, the 4th pin is connected to GND, and the 5th pin is the signal output terminal, which outputs the fan control signal to the fan. At the same time, the signal output terminal 5 is connected to VDD through the pull-up resistor R31, and the resistance value R72 of the pull-up resistor 31 is selected as 10 kΩ according to the empirical value.

[0029] The above embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A fan speed control circuit based on real-time temperature monitoring, characterized in that: It includes a power supply circuit, a temperature sensor, a temperature conditioning circuit, a triangular wave generating circuit, a polarity selection circuit, a comparison circuit and a signal isolation output circuit; the temperature sensor is an NTC negative temperature coefficient thermistor type, the temperature sensor is attached to the component to be cooled, the temperature sensor outputs a real-time temperature signal and sends it to the temperature conditioning circuit, the temperature conditioning circuit converts the temperature signal collected by the sensor into a level signal, and the triangular wave signal generated by the triangular wave generating circuit is sent to the comparison circuit after passing through the polarity selection circuit to obtain a PWM control signal, and then the fan operation is controlled through the signal isolation output circuit; The triangular wave generating circuit comprises a time base chip, a trigger input pin of the time base chip is connected to a threshold input pin, so that the timer is self-triggered and operates as a multivibrator, the trigger input pin and the threshold input pin are connected to GND through a charge-discharge capacitor, and a triangular wave signal is generated by charging and discharging the charge-discharge capacitor, the charge-discharge capacitor is connected to VCC through two charge-discharge resistors connected in series, and the charge-discharge capacitor is charged and discharged between the threshold level and the trigger level; The temperature conditioning circuit includes a two-stage series operational amplifier circuit. The full-speed rotation and the lowest rotation of the fan correspond to the set temperature, which is converted into the threshold level and trigger level in the corresponding triangle wave signal circuit through the two-stage operational amplifier circuit; the polarity selection circuit is composed of 4 polarity resistors, and the two inputs are respectively connected to 1 polarity resistor and one of the two outputs. Through the matching of resistors, the level signal waveform of the comparator in the same direction and reverse input terminals of the input comparison circuit is changed, and the comparator output PWM level polarity is changed.

2. The fan speed control circuit based on real-time temperature monitoring according to claim 1, characterized in that: The comparison circuit includes a comparator. The signal waveforms output by the triangle wave generating circuit and the temperature conditioning circuit are respectively input into the comparator for level comparison after passing through the polarity selection circuit, and then the control signal is output.

3. The fan speed control circuit based on real-time temperature monitoring according to claim 2 is characterized in that: The signal isolation output circuit uses a high-speed optical coupler that integrates a high-gain high-speed optical detector and a high-output GaACAs light-emitting diode.

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