Automatic variable-voltage speed regulation system for direct-current fan

Abstract

This invention discloses an automatic variable voltage speed control system for a DC fan, relating to the field of fan speed control technology. The system includes a DC-DC unit for achieving adjustable output voltage DC-DC power conversion over a wide input voltage range; a feedback automatic adjustment unit for acquiring the output voltage of the DC-DC unit and comparing it with a control quantity input from a fan speed control unit to obtain an error signal, and adjusting the output voltage of the DC-DC unit based on the error signal; a fan speed control unit for generating a control voltage based on temperature detection to achieve automatic control of the DC fan speed; and a control voltage generated based on pulse signal conditioning to achieve active control of the DC fan speed. This invention achieves dynamic control of the fan speed by automatically adjusting the DC fan input voltage, enabling automatic or active speed control modes based on temperature changes or external PWM signals, and also making the fan compatible with a wider range of power supply voltages.

Description

Technical Field

[0001] This invention relates to the field of fan speed control technology, and more specifically, to an automatic variable voltage speed control system for DC fans. Background Technology

[0002] In energy storage temperature control systems, fans typically run continuously at a constant speed, with the power supply providing a fixed, constant voltage. They are always under full load for heat dissipation to ensure the system's safety and stability under high-temperature conditions. While this saturation-based operation satisfies temperature control, it lacks intelligent adjustment capabilities, specifically manifested in the following ways:

[0003] The fan speed is not adjustable and always runs at a fixed speed, making it impossible to dynamically adjust the heat dissipation capacity according to changes in system load or when entering a sleep state, resulting in a mismatch in operating efficiency; the fan runs at a constant high speed for a long time, which aggravates mechanical wear and thus limits the working life of the fan; even when the system load is low, the fan continues to run at high power, resulting in increased overall energy consumption and long-term high noise.

[0004] No effective solutions have yet been proposed to address the problems in the relevant technologies. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides an automatic variable voltage speed control system for DC fans, which has the advantage of dynamically controlling the fan speed by automatically adjusting the input voltage of the DC fan, thus solving the problem of traditional fan speed control systems lacking intelligent adjustment capabilities.

[0007] (II) Technical Solution

[0008] To achieve the aforementioned advantages of dynamically controlling fan speed by automatically adjusting the DC fan input voltage, the specific technical solution adopted by this invention is as follows:

[0009] An automatic variable voltage speed control system for a DC fan, comprising a DC-DC unit, a feedback automatic adjustment unit, and a fan speed control unit, wherein the DC-DC unit is electrically connected to the feedback automatic adjustment unit and the fan speed control unit in sequence;

[0010] Among them, the DC-DC unit is used to realize DC-DC power conversion with adjustable output voltage under a wide input voltage range;

[0011] The feedback automatic adjustment unit is used to collect the output voltage of the DC-DC unit and compare it with the control quantity input from the fan speed control unit to obtain an error signal, and adjust the output voltage of the DC-DC unit based on the error signal;

[0012] The fan speed control unit is used to generate a control voltage based on temperature detection, and use the control voltage as a control quantity to drive the feedback automatic adjustment unit to achieve automatic control of DC fan speed; and to generate a control voltage based on pulse signal conditioning, and use the control voltage as a control quantity to drive the feedback automatic adjustment unit to achieve active control of DC fan speed.

[0013] Preferably, the output voltage of the DC-DC unit is acquired and compared with the control quantity input from the fan speed control unit to obtain an error signal. Adjusting the output voltage of the DC-DC unit based on the error signal includes:

[0014] The output voltage of the DC-DC unit is sampled, and the sampled output voltage is conditioned and then input to the first pin of the operational amplifier in the feedback automatic adjustment unit.

[0015] The control input from the fan speed control unit is sent to the third pin of the operational amplifier. The operational amplifier compares the output voltage with the control input to obtain the error signal.

[0016] The feedback regulation network, consisting of several capacitors and resistors, is driven by an error signal. The output voltage of the DC-DC unit is adjusted through the feedback regulation network, and the speed of the DC fan is adjusted according to the output voltage.

[0017] Preferably, adjusting the DC fan speed according to the output voltage includes:

[0018] When the output voltage increases, the DC fan speed increases; when the output voltage decreases, the DC fan speed decreases.

[0019] Preferably, the fan speed control unit includes a temperature detection module, a reference voltage module, and a pulse signal conditioning module, and the temperature detection module is electrically connected to the reference voltage module;

[0020] Among them, the temperature detection module is used to generate a control voltage signal based on the temperature characteristics of the thermistor and input the control voltage signal as a control quantity to the feedback automatic adjustment unit.

[0021] The reference voltage module is used to provide a reference voltage for the temperature detection module;

[0022] The pulse signal conditioning module is used to process the pulse signal to obtain the reference voltage.

[0023] Preferably, the thermistor is a negative temperature coefficient thermistor.

[0024] Preferably, generating a control voltage signal based on the temperature characteristics of the thermistor and inputting the control voltage signal as a control quantity to the feedback automatic adjustment unit includes:

[0025] When the temperature rises, the resistance of the negative temperature coefficient thermistor decreases, which increases the voltage output to the control input pin. At the same time, the output voltage of the DC-DC unit increases, and the speed of the DC fan increases.

[0026] When the temperature decreases, the resistance of the negative temperature coefficient thermistor increases, which reduces the voltage output to the control input pin. At the same time, the output voltage of the DC-DC unit decreases, and the speed of the DC fan decreases.

[0027] Preferably, when the temperature rises, the resistance of the negative temperature coefficient thermistor decreases, thus increasing the voltage output to the control input pin. Simultaneously, the output voltage of the DC-DC unit increases, leading to an increase in the DC fan speed, including:

[0028] When the temperature rises, the resistance of the negative temperature coefficient thermistor decreases, and the control voltage output by the temperature detection module increases. When the control voltage increases, the fourth pin of the operational amplifier in the feedback automatic adjustment unit dynamically decreases, the on-resistance of the field-effect transistor dynamically increases, the base current of the transistor dynamically decreases, and the on-resistance of the circuit composed of the transistor and one of the resistors increases, so as to increase the output voltage of the DC-DC unit and increase the speed of the DC fan.

[0029] Preferably, when the temperature decreases, the resistance of the negative temperature coefficient thermistor increases, thus reducing the voltage output to the control input pin. Simultaneously, the output voltage of the DC-DC unit decreases, leading to a decrease in the DC fan speed, including:

[0030] When the temperature decreases, the resistance of the negative temperature coefficient thermistor increases, and the control voltage output by the temperature detection module decreases. When the control voltage decreases, the fourth pin of the operational amplifier in the feedback automatic adjustment unit dynamically increases, the on-resistance of the field-effect transistor dynamically decreases, the base current of the transistor dynamically increases, and the on-resistance of the circuit composed of the transistor and one of the resistors decreases, so as to reduce the output voltage of the DC-DC unit and reduce the speed of the DC fan.

[0031] Preferably, processing the pulse signal to obtain the reference voltage includes:

[0032] Based on the duty cycle of the pulse signal, the pulse signal is filtered and smoothed to obtain a reference voltage, which is then input into the feedback automatic adjustment unit.

[0033] Preferably, the fifth pin of the chip in the DC-DC unit serves as the feedback input pin for the output voltage of the DC-DC unit;

[0034] When the on-resistance of the circuit consisting of the transistor and one of the resistors increases, the feedback input voltage at the fifth pin of the chip in the DC-DC unit decreases, while the output voltage of the DC-DC unit increases, and the speed of the DC fan increases. When the on-resistance of the circuit consisting of the transistor and one of the resistors decreases, the feedback input voltage at the fifth pin of the chip in the DC-DC unit increases, while the output voltage of the DC-DC unit decreases, and the speed of the DC fan decreases.

[0035] (III) Beneficial Effects

[0036] Compared with the prior art, the present invention provides an automatic variable voltage speed control system for DC fans, which has the following advantages:

[0037] (1) The present invention achieves dynamic control of fan speed by automatically adjusting the DC fan input voltage. It can not only realize automatic or active speed adjustment mode according to temperature changes or external PWM signals, thus improving the system's adaptability to different working states, but also make the fan compatible with a wider range of power supply voltages, thereby enhancing the flexibility and stability of the overall system.

[0038] (2) The present invention can adjust the fan speed in real time according to the heat load, and automatically reduce the speed or turn off when the system load is low or in a dormant state, which not only realizes intelligent temperature control but also reduces unnecessary energy consumption and noise output, effectively improving the system energy efficiency ratio; in addition, the fan operates in a non-full load state for a long time, which significantly reduces mechanical wear and thermal aging, extends bearing life, and reduces maintenance frequency and cost. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic block diagram of an automatic variable voltage speed control system for DC fans according to an embodiment of the present invention;

[0041] Figure 2 This is a circuit diagram of the DC-DC unit and the feedback automatic adjustment unit in the DC fan automatic variable speed control system according to an embodiment of the present invention;

[0042] Figure 3 This is a circuit diagram of a temperature detection module in an automatic variable voltage speed control system for a DC fan according to an embodiment of the present invention.

[0043] Figure 4 This is a circuit diagram of the reference voltage module in an automatic variable speed control system for a DC fan according to an embodiment of the present invention;

[0044] Figure 5 This is a circuit diagram of the pulse signal conditioning module in an automatic variable speed control system for DC fans according to an embodiment of the present invention.

[0045] In the picture:

[0046] 1. DC-DC unit; 2. Feedback automatic adjustment unit; 3. Fan speed control unit; 301. Temperature detection module; 302. Reference voltage module; 303. Pulse signal conditioning module. Detailed Implementation

[0047] To further illustrate the various embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these drawings, those skilled in the art should be able to understand other possible implementation methods and the advantages of the present invention.

[0048] According to an embodiment of the present invention, an automatic variable voltage speed control system for DC fans is provided.

[0049] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments, such as... Figure 1 As shown, according to an embodiment of the present invention, the DC fan automatic variable speed control system includes a DC-DC unit 1, a feedback automatic adjustment unit 2, and a fan speed control unit 3, wherein the DC-DC unit 1 is electrically connected to the feedback automatic adjustment unit 2 and the fan speed control unit 3 in sequence.

[0050] Among them, DC-DC unit 1 is used to realize DC-DC power conversion with adjustable output voltage under a wide input voltage range.

[0051] Specifically, such as Figure 2 As shown, DC-DC unit 1 includes chip U2, capacitors C7, C10, C8, C14, resistors R14, C13, R15, inductor L1, resistor R17, capacitors C18, C11, C15, C9 and DC fan F1.

[0052] In this configuration, the first pin of chip U2 is connected to one end of capacitor C13; the other end of capacitor C16 is connected to inductor L1 and the second pin of chip U2; the other end of inductor L1 is connected to one end of capacitor C11, one end of capacitor C15, one end of capacitor C9, one end of resistor R17, one end of capacitor C18, and the first pin of DC fan F1, which is connected to V-OUT; the other end of resistor R17 is connected to the other end of capacitor C18, one end of resistor R15, the fifth pin of chip U2, and the feedback automatic adjustment unit 22; and the other end of resistor R15 is connected to capacitor C14. One end of capacitor C14 is connected to ground, and the other end of capacitor C14 is connected to the fourth pin of chip U2. The second pin of DC fan F1 is connected to the other ends of capacitors C11, C15, C9, C8, and C10 respectively and grounded. The other end of capacitor C10 is connected to the other end of capacitor C8, the seventh and eighth pins of chip U2 and connected to VIN. The third pin of chip U2 is connected to one end of resistor R14 and the other end of resistor R14 is connected to VIN. The sixth pin of chip U2 is connected to one end of capacitor C7 and the other end of capacitor C7 is grounded.

[0053] The feedback automatic adjustment unit 2 is used to collect the output voltage of the DC-DC unit 1 and compare it with the control quantity input from the fan speed control unit 3 to obtain an error signal, and adjust the output voltage of the DC-DC unit 1 based on the error signal.

[0054] The process of acquiring the output voltage of DC-DC unit 1 and comparing it with the control quantity input from fan speed control unit 3 to obtain an error signal, and adjusting the output voltage of DC-DC unit 1 based on the error signal includes:

[0055] The output voltage of DC-DC unit 1 is sampled, and the sampled output voltage is conditioned and input to the first pin of the operational amplifier in feedback automatic adjustment unit 2.

[0056] The control input of the fan speed control unit 3 is sent to the third pin of the operational amplifier. The operational amplifier compares the output voltage with the control input to obtain the error signal.

[0057] The feedback regulation network, consisting of several capacitors and resistors, is driven by the error signal. The output voltage of the DC-DC unit 1 is adjusted through the feedback regulation network, and the speed of the DC fan is adjusted according to the output voltage.

[0058] The adjustment of DC fan speed based on output voltage includes:

[0059] When the output voltage increases, the DC fan speed increases; when the output voltage decreases, the DC fan speed decreases.

[0060] Specifically, such as Figure 2 As shown, the feedback automatic adjustment unit 22 includes: operational amplifier U1, transistor Q1, resistor R1, resistor R2, resistor R4, resistor R13, capacitor C1, resistor R8, capacitor C2, field-effect transistor Q2, resistor R5, diode D1, capacitor C17, resistor R6, resistor R7, resistor R9, capacitor C3, and resistor R11.

[0061] The first pin of operational amplifier U1 is connected to one end of capacitor C2, one end of capacitor C1, and one end of resistor R6. The other end of capacitor C1 is connected to one end of resistor R8, one end of resistor R4, and the drain of MOSFET Q2. The other end of resistor R8 is connected to the other end of capacitor C2. The other end of resistor R4 is connected to one end of resistor R2, the base of transistor Q1, and one end of resistor R13. The other end of resistor R13 is connected to the collector of transistor Q1 and the fifth pin of chip U2. The emitter of transistor Q1 is connected to one end of resistor R1. The other end of resistor R1 is connected to the other end of resistor R2 and one end of resistor R9, and connected to V-OUT. The other end of R9 is connected to one end of resistor R11, one end of capacitor C3, and the other end of resistor R6. The other end of resistor R11 is connected to the other end of capacitor C3 and grounded. The second pin of operational amplifier U1 is grounded. The third pin of operational amplifier U1 is connected to one end of resistor R7, and the other end of resistor R7 is connected to Ref. The fourth pin of operational amplifier U1 is connected to one end of resistor R5, and the other end of resistor R5 is connected to the gate of field-effect transistor Q2 and the cathode of diode D1. The anode of diode D1 is connected to the source of field-effect transistor Q2 and grounded. The fifth pin of operational amplifier U1 is connected to one end of capacitor C17 and connected to VIN. The other end of capacitor C17 is grounded.

[0062] The fan speed control unit 3 is used to generate a control voltage based on temperature detection, and use the control voltage as a control quantity to drive the feedback automatic adjustment unit 2 to achieve automatic control of DC fan speed; and to generate a control voltage based on pulse signal conditioning, and use the control voltage as a control quantity to drive the feedback automatic adjustment unit 2 to achieve active control of DC fan speed.

[0063] Specifically, the wind speed and rotation speed control methods include: temperature sensing adjustment; main control PWM adjustment to achieve multiple speeds; and potentiometer adjustment.

[0064] The fan speed control unit 3 includes a temperature detection module 301, a reference voltage module 302, and a pulse signal conditioning module 303, and the temperature detection module 301 is electrically connected to the reference voltage module 302.

[0065] The temperature detection module 301 is used to generate a control voltage signal based on the temperature characteristics of the thermistor and input the control voltage signal as a control quantity to the feedback automatic adjustment unit 2.

[0066] The thermistor is a negative temperature coefficient thermistor. A control voltage signal is generated based on the temperature characteristics of the thermistor, and this control voltage signal is input as a control quantity to the feedback automatic adjustment unit 2, which includes:

[0067] When the temperature rises, the resistance of the negative temperature coefficient thermistor decreases, which increases the voltage output to the control input pin. At the same time, the output voltage of DC-DC unit 1 increases, and the speed of the DC fan increases.

[0068] Specifically, when the temperature rises, the resistance of the negative temperature coefficient thermistor decreases, thus increasing the voltage output to the control input pin. Simultaneously, the output voltage of DC-DC unit 1 increases, leading to an increase in the DC fan speed.

[0069] When the temperature rises, the resistance of the negative temperature coefficient thermistor decreases, and the control voltage output by the temperature detection module 301 increases.

[0070] When the control voltage increases, the fourth pin of the operational amplifier in the feedback automatic adjustment unit 2 decreases dynamically, the on-resistance of the field-effect transistor increases dynamically, the base current of the transistor decreases dynamically, and the on-resistance of the circuit composed of the transistor and one of the resistors increases, so as to increase the output voltage of the DC-DC unit 1 and increase the speed of the DC fan.

[0071] When the temperature decreases, the resistance of the negative temperature coefficient thermistor increases, which reduces the voltage output to the control input pin. At the same time, the output voltage of DC-DC unit 1 decreases, and the speed of the DC fan decreases.

[0072] Specifically, when the temperature decreases, the resistance of the negative temperature coefficient thermistor increases, thus reducing the voltage output to the control input pin. Simultaneously, the output voltage of DC-DC unit 1 decreases, leading to a decrease in the DC fan speed.

[0073] When the temperature decreases, the resistance of the negative temperature coefficient thermistor increases, and the control voltage output by the temperature detection module 301 decreases. When the control voltage decreases, the fourth pin of the operational amplifier in the feedback automatic adjustment unit 2 dynamically increases, the on-resistance of the field-effect transistor dynamically decreases, the base current of the transistor dynamically increases, and the on-resistance of the circuit composed of the transistor and one of the resistors decreases, so as to reduce the output voltage of the DC-DC unit 1 and reduce the speed of the DC fan.

[0074] In DC-DC unit 1, the fifth pin of the chip serves as the feedback input pin for the output voltage of DC-DC unit 1. When the on-resistance of the loop composed of the transistor and one of the resistors increases, the feedback input voltage of the fifth pin of the chip in DC-DC unit 1 decreases, while the output voltage of DC-DC unit 1 increases, and the speed of the DC fan increases. When the on-resistance of the loop composed of the transistor and one of the resistors decreases, the feedback input voltage of the fifth pin of the chip in DC-DC unit 1 increases, while the output voltage of DC-DC unit 1 decreases, and the speed of the DC fan decreases.

[0075] Specifically, such as Figure 3 As shown, the temperature detection module 301 includes a thermistor R12, a resistor R10, and a capacitor C5.

[0076] One end of the thermistor R12 is connected to 3.3VREF. The other end of the thermistor R12 is connected to one end of the resistor R10 and one end of the capacitor C5 and connected to Ref. The other end of the resistor R10 is connected to the other end of the capacitor C5 and grounded.

[0077] The reference voltage module 302 is used to provide a reference voltage for the temperature detection module 301.

[0078] Specifically, such as Figure 4 As shown, the reference voltage module 302 includes capacitor C12, diode U3, resistor R16, resistor R18, resistor R19 and capacitor C16.

[0079] One end of capacitor C12 is connected to one end of resistor R16 and connected to VIN. The other end of resistor R16 is connected to one end of resistor R18, the negative terminal of diode U3, and one end of capacitor C16 and connected to 3.3VREF. The other end of capacitor C12 is connected to the positive terminal of diode U3, one end of resistor R19, and the other end of capacitor C16 and grounded. The other end of resistor R19 is connected to the other end of resistor R18.

[0080] The pulse signal conditioning module 303 is used to process the pulse signal to obtain a reference voltage. Based on the duty cycle of the pulse signal, the pulse signal is filtered and smoothed to obtain the reference voltage, which is then input to the feedback automatic adjustment unit 2.

[0081] Specifically, such as Figure 5 As shown, the pulse signal conditioning module 303 (equivalent to the PWM input signal conditioning circuit) includes resistor R3, capacitor C4 and capacitor C6;

[0082] One end of resistor R3 is connected to the PWM signal, and the other end of resistor R3 is connected to one end of capacitor C4 and one end of capacitor C6 respectively and connected to Ref. The other end of capacitor C4 is connected to the other end of capacitor C6 and grounded.

[0083] To facilitate understanding of the above technical solutions of the present invention, the working principle or operation method of the present invention in actual process will be described in detail below.

[0084] In practical applications, the present invention consists of a DC-DC unit 1 with a wide input voltage range and adjustable output voltage, a feedback automatic adjustment unit 2, and a fan speed control unit 3. The fan speed control unit 3 includes a temperature detection module 301, a reference voltage module 302, and a pulse signal conditioning module 303.

[0085] Specifically, the wide input voltage range and adjustable output voltage DC-DC unit 1 of chip U2 mainly realizes adjustable output voltage DC-DC power conversion, and its models or types include but are not limited to Figure 2 The DC-DC unit 1 is located in the middle. The fifth pin of chip U2 is the feedback input pin for the output voltage of DC-DC unit 1. F1 is a DC fan connected to the output of DC-DC unit 1.

[0086] Operational amplifier U1 is part of feedback automatic adjustment unit 2, where resistor R1, transistor Q1, and resistor R17 are connected in parallel. U1 is the operational amplifier, and resistors R9 and R11 in feedback automatic adjustment unit 2 sample the voltage from the output of chip U2, which is then conditioned and input to the first pin of operational amplifier U1. The third pin of operational amplifier U1 is the control input pin, connected to temperature detection module 301 composed of resistors R12 and R10, and capacitor C5. Resistor R12 is a negative temperature coefficient NTC resistor, whose resistance decreases as temperature increases. The control input pin can also be connected to pulse signal conditioning module 303 (PWM input signal conditioning circuit) composed of resistors R3, capacitors C4 and C6. By controlling the PWM duty cycle and filtering and smoothing by capacitors C4 and C6, a stable reference voltage is obtained. Capacitor C1, resistor R8, and capacitor C2 form a feedback regulation network, which adjusts the field-effect transistor Q2 and the transistor Q1, thereby adjusting the feedback input of chip U2 and regulating the output voltage of chip U2. The DC fan speed will change according to the voltage magnitude. Part U3 is the reference voltage module 302, which provides a reference voltage to the temperature detection module 301 composed of capacitor R12, resistor R10, and capacitor.

[0087] 1. When the temperature rises: the resistance of thermistor R12 decreases, the control voltage Ref increases, the fourth pin of operational amplifier U1 decreases dynamically, the gate voltage of field-effect transistor Q2 decreases, the on-resistance of field-effect transistor Q2 increases dynamically, the base current of transistor Q1 (a PNP transistor) decreases dynamically, the on-resistance of the circuit of resistor R1 and transistor Q1 increases, the voltage feedback input voltage of the fifth pin of chip U2 decreases instantaneously, chip U2 dynamically adjusts and increases the V-OUT output voltage, and as the output voltage increases, the fan speed increases.

[0088] 2. When the temperature decreases: the resistance of thermistor R12 increases, the control voltage Ref decreases, the fourth pin of operational amplifier U1 increases dynamically, the gate voltage of field-effect transistor Q2 increases, the on-resistance of field-effect transistor Q2 decreases dynamically, the base current of transistor Q1 (a PNP transistor) increases dynamically, the on-resistance of the circuit of resistor R1 and transistor Q1 decreases dynamically, the voltage feedback input voltage of the fifth pin of chip U2 increases instantaneously, chip U2 dynamically adjusts and decreases the V-OUT output voltage, and as the output voltage decreases, the fan speed decreases.

[0089] In summary, by utilizing the above-mentioned technical solution of this invention, the present invention achieves dynamic control of fan speed by automatically adjusting the DC fan input voltage. This not only enables automatic or active speed adjustment based on temperature changes or external PWM signals, improving the system's adaptability to different operating states, but also allows the fan to be compatible with a wider range of power supply voltages, thereby enhancing the overall system's flexibility and stability. Furthermore, this invention can adjust the fan speed in real time according to the thermal load, automatically reducing the speed or shutting down when the system load is low or in a dormant state. This achieves intelligent temperature control while reducing unnecessary energy consumption and noise output, effectively improving the system's energy efficiency ratio. In addition, the fan operates under non-full load conditions for extended periods, significantly reducing mechanical wear and thermal aging, extending bearing life, and reducing maintenance frequency and costs.

[0090] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "setting," "connection," "fixing," "screw connection," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An automatic variable voltage speed control system for a DC fan, characterized in that, The system includes a DC-DC unit, a feedback automatic adjustment unit, and a fan speed control unit, wherein the DC-DC unit is electrically connected to the feedback automatic adjustment unit and the fan speed control unit in sequence; The DC-DC unit is used to achieve DC-DC power conversion with adjustable output voltage under a wide input voltage range; The feedback automatic adjustment unit is used to collect the output voltage of the DC-DC unit and compare it with the control quantity input from the fan speed control unit to obtain an error signal, and adjust the output voltage of the DC-DC unit based on the error signal; The fan speed control unit is used to generate a control voltage based on temperature detection, and use the control voltage as a control quantity to drive the feedback automatic adjustment unit to achieve automatic control of DC fan speed; and to generate a control voltage based on pulse signal conditioning, and use the control voltage as a control quantity to drive the feedback automatic adjustment unit to achieve active control of DC fan speed. The fan speed control unit includes a temperature detection module, a reference voltage module, and a pulse signal conditioning module, and the temperature detection module is electrically connected to the reference voltage module. The temperature detection module is used to generate a control voltage signal based on the temperature characteristics of the thermistor and input the control voltage signal as a control quantity to the feedback automatic adjustment unit. The reference voltage module is used to provide a reference voltage for the temperature detection module; The pulse signal conditioning module is used to process the pulse signal to obtain a reference voltage, including: Based on the duty cycle of the pulse signal, the pulse signal is filtered and smoothed to obtain a reference voltage, which is then input into the feedback automatic adjustment unit.

2. The DC fan automatic variable speed control system according to claim 1, characterized in that, The step of acquiring the output voltage of the DC-DC unit and comparing it with the control quantity input from the fan speed control unit to obtain an error signal, and adjusting the output voltage of the DC-DC unit based on the error signal includes: The output voltage of the DC-DC unit is sampled, and the sampled output voltage is conditioned and then input to the first pin of the operational amplifier in the feedback automatic adjustment unit. The control input of the fan speed control unit is sent to the third pin of the operational amplifier. The operational amplifier compares the output voltage with the control input to obtain an error signal. The feedback regulation network, consisting of several capacitors and resistors, is driven by an error signal. The output voltage of the DC-DC unit is adjusted through the feedback regulation network, and the speed of the DC fan is adjusted according to the output voltage.

3. The DC fan automatic variable speed control system according to claim 2, characterized in that, The method of adjusting the DC fan speed according to the output voltage includes: When the output voltage increases, the DC fan speed increases; when the output voltage decreases, the DC fan speed decreases.

4. The DC fan automatic variable speed control system according to claim 1, characterized in that, The thermistor is a negative temperature coefficient thermistor.

5. The DC fan automatic variable speed control system according to claim 4, characterized in that, The step of generating a control voltage signal based on the temperature characteristics of a thermistor and inputting the control voltage signal as a control quantity to the feedback automatic adjustment unit includes: When the temperature rises, the resistance of the negative temperature coefficient thermistor decreases, which increases the voltage output to the control input pin. At the same time, the output voltage of the DC-DC unit increases, and the speed of the DC fan increases. When the temperature decreases, the resistance of the negative temperature coefficient thermistor increases, which reduces the voltage output to the control input pin. At the same time, the output voltage of the DC-DC unit decreases, and the speed of the DC fan decreases.

6. The DC fan automatic variable speed control system according to claim 5, characterized in that, When the temperature rises, the resistance of the negative temperature coefficient thermistor decreases, thus increasing the voltage output to the control input pin. Simultaneously, the output voltage of the DC-DC unit increases, leading to an increase in the DC fan speed. When the temperature rises, the resistance of the negative temperature coefficient thermistor decreases, and the control voltage output by the temperature detection module increases. When the control voltage increases, the fourth pin of the operational amplifier in the feedback automatic adjustment unit dynamically decreases, the on-resistance of the field-effect transistor dynamically increases, the base current of the transistor dynamically decreases, and the on-resistance of the circuit composed of the transistor and one of the resistors increases, thereby increasing the output voltage of the DC-DC unit and increasing the speed of the DC fan.

7. The DC fan automatic variable speed control system according to claim 5, characterized in that, When the temperature decreases, the resistance of the negative temperature coefficient thermistor increases, thus reducing the voltage output to the control input pin. Simultaneously, the output voltage of the DC-DC unit decreases, leading to a reduction in the DC fan speed. When the temperature decreases, the resistance of the negative temperature coefficient thermistor increases, and the control voltage output by the temperature detection module decreases. When the control voltage decreases, the fourth pin of the operational amplifier in the feedback automatic adjustment unit dynamically increases, the on-resistance of the field-effect transistor dynamically decreases, the base current of the transistor dynamically increases, and the on-resistance of the circuit composed of the transistor and one of the resistors decreases, so as to reduce the output voltage of the DC-DC unit and the speed of the DC fan decreases.

8. The DC fan automatic variable speed control system according to claim 1, characterized in that, The fifth pin of the chip in the DC-DC unit serves as the feedback input pin for the output voltage of the DC-DC unit. When the circuit conduction impedance increases, the feedback input voltage of the fifth pin of the chip in the DC-DC unit decreases, while the output voltage of the DC-DC unit increases, and the speed of the DC fan increases. When the circuit conduction impedance decreases, the feedback input voltage of the fifth pin of the chip in the DC-DC unit increases, while the output voltage of the DC-DC unit decreases, and the speed of the DC fan decreases.

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