A cooling fan rotation speed adjusting circuit and a control method thereof

Abstract

The present application belongs to the technical field of fan rotating speed adjustment, and particularly relates to a heat dissipation fan rotating speed adjustment circuit and a control method thereof, aiming to solve the problems of independent power supply, single parameter, inaccurate adjustment and insufficient protection of the prior art. The method reuses the power supply circuit of the fan and LED series lamp beads, collects double parameters through a negative temperature coefficient thermistor and a humidity sensor, and calculates an equivalent temperature value through humidity compensation. According to the comparison result of the equivalent temperature value and a preset threshold value, the on-off state and duty cycle of a switch unit are controlled to realize multi-stage adaptive rotating speed adjustment. The actual rotating speed is obtained by detecting the current of the fan power supply circuit, and the deviation is fine-tuned by adjusting the on-off frequency. When the equivalent temperature value is greater than or equal to the limit protection temperature, the alarm, power consumption reduction and maximum rotating speed protection are triggered until the temperature drops below the high temperature threshold. The method does not require independent power supply, is accurate in adjustment, optimizes energy consumption, and is suitable for high-power LED lamp efficient heat dissipation.

Description

Technical Field

[0001] This invention belongs to the field of cooling fan speed regulation technology, and particularly relates to a cooling fan speed regulation circuit and its control method. Background Technology

[0002] With the rapid development of LED lighting technology, high-power LED lights, with their advantages of high luminous efficiency, low energy consumption, and long lifespan, have been widely used in lighting scenarios for large venues such as stadiums, squares, and industrial plants. Compared with traditional lighting fixtures, high-power LED lights can achieve higher power output and lumen values ​​per unit space. However, the heat density of their core heat-generating components (LED chips and surrounding electronic components) is also significantly increased. If heat dissipation is not timely, it will lead to excessively high junction temperatures of the LED chips, resulting in problems such as accelerated light decay, deterioration of color rendering, and shortened lifespan, which seriously limits the application potential of high-power LED lights in high-power, high-luminous-efficiency scenarios.

[0003] To address the heat dissipation challenge of high-power LED lights, the industry commonly employs active cooling solutions using fans. These solutions force airflow to accelerate heat dissipation and reduce the operating temperature of the LED chips. However, existing fan speed control methods still have several shortcomings:

[0004] Most solutions use a separate power supply module to power the fan, which not only increases circuit complexity and hardware cost, but also reduces compatibility with the original LED circuit, making it difficult to integrate and deploy the solution.

[0005] Speed ​​regulation is mostly based on a single temperature parameter and does not take into account the impact of ambient humidity on heat dissipation efficiency. High humidity environment will reduce the air heat dissipation capacity, while low humidity environment has higher heat dissipation efficiency. Speed ​​regulation triggered by a single temperature is prone to "insufficient heat dissipation" or "excessive heat dissipation", resulting in energy waste or heat dissipation failure.

[0006] Temperature detection relies heavily on the linear approximation of thermistors without precise calibration of their nonlinear characteristics, resulting in large temperature detection errors that affect the accuracy of speed regulation.

[0007] Speed ​​adjustment is mostly a two-speed switch (low speed / high speed). Sudden speed changes during switching can easily generate obvious noise, and it cannot achieve adaptive matching according to temperature gradient, making it difficult to balance heat dissipation efficiency and noise control.

[0008] The lack of an effective closed-loop feedback mechanism means that factors such as power supply voltage fluctuations and component aging can cause deviations between the actual speed and the target speed, making it impossible to ensure a precise match between heat dissipation requirements and speed output.

[0009] The protection mechanism under extreme high temperature conditions is not perfect. Relying solely on the high-speed operation of the fan is insufficient to cool down the LED light quickly, which can easily lead to damage due to overheating.

[0010] Therefore, this invention aims to provide a cooling fan speed adjustment scheme that is highly compatible, low-cost, precisely adjustable, with smooth noise and complete protection functions, in order to solve the above-mentioned problems in the prior art and further improve the heat dissipation stability and application reliability of high-power LED lights. Summary of the Invention

[0011] The purpose of this invention is to provide a cooling fan speed regulation circuit and its control method to solve the technical problem.

[0012] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0013] In a first aspect, a control method for a cooling fan speed regulation circuit is provided, comprising the following steps:

[0014] S1: The power supply circuit of the cooling fan is reused with the LED series lamp bead circuit of the high-power LED lamp. By matching the number of LED series lamp beads with the rated voltage requirement of the fan, the power supply of the fan is taken from the voltage division of the LED series lamp beads.

[0015] S2: A negative temperature coefficient thermistor is placed close to the LED bead body to detect the operating temperature of the LED bead in real time and output a continuously variable temperature voltage signal; a humidity sensor is deployed to collect humidity data of the surrounding environment of the LED bead and output a humidity voltage signal.

[0016] S3: Preset basic temperature thresholds in the control unit, including low temperature threshold T1, high temperature threshold T2, and extreme protection temperature T3. Convert the temperature voltage signal into the actual temperature value, and then call the corresponding compensation coefficient according to the humidity data to calculate the equivalent temperature value. Compare the equivalent temperature value with the basic temperature threshold in real time to generate control instructions of the corresponding level.

[0017] S4: Based on the comparison results, control the on / off state and duty cycle of the control switch unit to realize multi-level adaptive adjustment of the fan speed. The multi-level adjustment temperature range includes equivalent temperature value ≤ T1, T1 < equivalent temperature value < T2, T2 ≤ equivalent temperature value < T3, and equivalent temperature value ≥ T3.

[0018] S5: Obtain the actual fan speed signal by detecting the current change in the fan power supply circuit, and compare it with the target speed corresponding to the current equivalent temperature value; if there is a speed deviation, compensate for the error caused by voltage fluctuation by adjusting the switching frequency of the fine-tuning unit.

[0019] S6: When the equivalent temperature value is ≥ T3, the control unit outputs an alarm signal and cuts off the power supply to the non-core circuit of the LED light part to reduce the heat generation power, and controls the fan to maintain the highest speed operation until the equivalent temperature value drops below T2.

[0020] Preferably, in step S3, the temperature voltage signal is converted into an actual temperature value, and then the corresponding compensation coefficient is called based on the humidity data to calculate the equivalent temperature value; the equivalent temperature value is compared with the basic temperature threshold in real time to generate the corresponding level of control command. The specific process is as follows:

[0021] S31: Convert the temperature and voltage signals into digital signals. Based on the nonlinear characteristics of the negative temperature coefficient thermistor, a piecewise linearization algorithm is used for conversion: the operating temperature range of the LED lamp is divided into multiple sub-intervals, and a fitting linear equation is pre-stored in each interval to calculate the preliminary temperature value; the preliminary temperature value is calibrated by the Steinhart-Hart equation to obtain the actual temperature value.

[0022] S32: Extracts the humidity voltage signal, converts it into the actual ambient humidity value, divides the humidity range into three intervals: low humidity, medium humidity, and high humidity, and sets the corresponding humidity compensation coefficient according to the temperature range; the control unit automatically calls the corresponding humidity compensation coefficient according to the interval to which the current actual humidity value belongs, and calculates the equivalent temperature value.

[0023] S33: The control unit has a built-in window comparator logic. The preset base temperature threshold is converted into the corresponding reference voltage threshold, and the equivalent temperature value is converted into the corresponding equivalent voltage signal. Based on the relationship between the equivalent voltage signal and the reference voltage threshold, the corresponding control commands are generated.

[0024] Preferably, the specific process of calibrating the preliminary temperature value using the Steinhart-Hart equation in step S31 to obtain the actual temperature value is as follows:

[0025] S311: Preset circuit core parameters: Power supply voltage: VCC=5V; Voltage divider resistors: R 分压 =10KΩ; Temperature and voltage signals: V T The thermistor and the voltage divider resistor form a series voltage divider circuit. The actual resistance value of the thermistor is derived according to Ohm's law. R NTC The specific formula is as follows: R NTC = R 分压 · V T / (VCC-V T );

[0026] S312: Substitute into the Steinhart-Hart equation to calculate absolute temperature T K ;

[0027] S313: Absolute temperature to actual temperature conversion T actual The formula for converting between absolute temperature and Celsius temperature is: T actual = T K -273.15.

[0028] Preferably, the specific process of step S4 is as follows:

[0029] S41: Define the associated parameters:

[0030] Switching unit: Q1, whose on / off state directly changes the voltage divider logic of the fan power supply circuit;

[0031] Fan power supply voltage: taken from the voltage divider of LED series beads, with the total voltage of the upper beads being V1 and the total voltage of the lower beads being V2. This is the maximum power supply voltage for the fan. V mmax =V1+V2, minimum supply voltage V mmin =V1;

[0032] Pulse duty cycle: refers to the ratio of the off time of the switching unit to the total cycle within one pulse cycle (range 10%-90%). The higher the duty cycle, the higher the average voltage actually obtained by the fan and the faster the speed.

[0033] Equivalent temperature value T eq Step S3 calculation results: basic thresholds: low temperature threshold T1, high temperature threshold T2, and ultimate protection threshold T3;

[0034] S42: Set the adjustment range and perform interval adjustment according to the adjustment range.

[0035] Preferably, the specific process of performing interval adjustment based on the adjustment interval in step S42 is as follows:

[0036] Interval 1: Equivalent temperature value T eq ≤T1: The control unit outputs a "switch on" command;

[0037] Switching unit operation: The control unit outputs a high-level signal to the gate of Q1, keeping Q1 in a continuously conducting state;

[0038] Interval 2: T1 < T eq <T2: The control unit outputs a "pulse-type on / off" command;

[0039] Switching unit operation: The control unit outputs a PWM signal to the gate of Q1 to achieve pulse-type on / off switching;

[0040] Interval 3: T2≤ T eq <T3: The control unit outputs a "switch off" command;

[0041] Switching unit operation: The control unit outputs a low-level signal to the gate of Q1, keeping Q1 in a continuously off state;

[0042] Interval 4: T eq ≥T3: The control unit does not perform speed regulation and directly triggers the extreme condition protection process in step S6.

[0043] Preferably, the specific process of step S5 is as follows:

[0044] S51: Real-time acquisition of sampling resistor R s Voltage drop across the terminals V s According to Ohm's Law I fan = V s / R s The real-time operating current of the fan is calculated; based on the current-speed calibration curve provided by the fan manufacturer, I fan Converted to actual fan speed T actual This completes the precise mapping from current signal to speed signal;

[0045] S52: Speed ​​Deviation Judgment: Retrieve T eq Corresponding target speed T target ;

[0046] Deviation calculation: ΔT= T actual - T target ;

[0047] Status determination:

[0048] If |ΔT|≤Δ T allow If the speed deviation is within the allowable range, no adjustment action will be performed, and the current switching frequency of the switching unit will be maintained;

[0049] If ΔT>Δ T allow If the actual fan speed is higher than the target speed, the average power supply voltage of the fan needs to be reduced, and the deviation should be corrected by slowing down the fan speed.

[0050] If ΔT < -Δ T allowIf the actual fan speed is lower than the target speed, the average power supply voltage of the fan needs to be increased to correct the deviation by increasing the fan speed.

[0051] S53: On / off frequency fine-tuning and deviation compensation: Based on the deviation judgment result, the control unit fine-tunes the average power supply voltage of the fan by adjusting the PWM pulse period;

[0052] S54: After adjustment, repeat steps S51-S53 to continuously collect data. T actual and T target Comparison;

[0053] If |ΔT| is still greater than Δ after one adjustment T allow Fine-tune again according to the above formula. T new until |ΔT|≤Δ T allow ;

[0054] Once the speed deviation meets the requirements, the control unit maintains the current on / off frequency until... T eq Changes occur, and the system enters the next round of closed-loop regulation.

[0055] Preferably, the specific process of frequency fine-tuning and deviation compensation in step S53 is as follows:

[0056] When ΔT>Δ T allow Increase the PWM pulse period to reduce the effective power supply time of the fan within one cycle;

[0057] When ΔT < -Δ T allow Adjustment direction: Reduce the PWM pulse period to increase the effective power supply time of the fan within one cycle.

[0058] In a second aspect, a cooling fan speed regulation circuit is provided to implement a control method for a cooling fan speed regulation circuit, including a power supply multiplexing module, a multi-dimensional parameter acquisition module, a control unit, a switching unit, a load unit, and a protection module.

[0059] The power supply multiplexing module is reused with the LED series lamp bead circuit of the high-power LED lamp. It is composed of multiple LED lamp beads set in series. By matching the number of LED series lamp beads with the rated voltage requirement of the load unit, the power supply of the load unit is taken from the voltage division of the LED series lamp beads. The total voltage of the LED series lamp beads is higher than the rated power supply voltage of the load unit, and the rated operating current of the LED is greater than the maximum operating current of the load unit. A voltage stabilizing element and a filter capacitor bank are connected in series in the power supply circuit to achieve stable power supply voltage output.

[0060] The multi-dimensional parameter acquisition module includes a negative temperature coefficient thermistor and a humidity sensor. The negative temperature coefficient thermistor is set close to the LED bead body to detect the LED bead operating temperature in real time and output a continuously variable temperature voltage signal. The humidity sensor is used to synchronously collect humidity data of the surrounding environment of the LED and output a humidity voltage signal. Both share the same filtering circuit to filter out noise interference. The filtered signal is transmitted to the control unit.

[0061] The control unit has a built-in basic temperature threshold (including low temperature threshold T1, high temperature threshold T2, and extreme protection temperature T3, where T1 < T2 < T3). Its input terminal is electrically connected to the multi-dimensional parameter acquisition module, which is used to convert the filtered temperature voltage signal into the actual temperature value, and then call the corresponding compensation coefficient to calculate the equivalent temperature value based on the humidity data. The equivalent temperature value is compared with the basic temperature threshold in real time to generate the corresponding level control command.

[0062] The switching unit is a MOSFET or a transistor, with its control terminal electrically connected to the output terminal of the control unit and its path terminal connected in series between the power supply multiplexing module and the load unit. It is used to adjust the on / off state and duty cycle according to the control command of the control unit to realize multi-level adaptive adjustment of the fan speed. The protection module is electrically connected to the control unit. When the equivalent temperature value is ≥ T3, it responds to the command output by the control unit, outputs an alarm signal, cuts off the power supply to the non-core circuit of the LED lamp, and maintains the load unit at its highest speed until the equivalent temperature value drops below T2, after which it restores the full power supply to the LED lamp and the normal speed adjustment logic.

[0063] The beneficial effects of this invention include:

[0064] 1. Strong power supply compatibility and significantly reduced cost: The design reuses the fan power supply circuit and the LED series lamp bead circuit. The fan power supply is directly taken from the voltage division of the LED series lamp beads, eliminating the need for an additional independent power supply module and simplifying the circuit structure. At the same time, by matching the number of LED series lamp beads with the rated voltage requirements of the fan, the power supply adaptability is ensured. Furthermore, the design of the total voltage and rated current of the LED series lamps meets the operating requirements of the fan and has excellent compatibility with the original circuit of high-power LED lamps, which greatly reduces hardware costs and integration difficulty.

[0065] 2. Comprehensive detection parameters and precise heat dissipation matching: Introducing dual-parameter collaborative sensing of temperature and humidity, the LED bead body temperature is detected by a negative temperature coefficient thermistor, and the humidity sensor simultaneously collects ambient humidity data. The impact of humidity on heat dissipation efficiency is converted into an equivalent temperature value, making the triggering basis for speed adjustment more closely match the actual heat dissipation scenario. In high humidity environments, the equivalent temperature value is increased to enable the fan to speed up in advance, while in low humidity environments, the equivalent temperature value is reduced to avoid excessive heat dissipation. This achieves a precise match between heat dissipation demand and speed output, balancing heat dissipation efficiency and energy saving.

[0066] 3. Accurate temperature detection and reliable adjustment basis: To address the nonlinear characteristics of negative temperature coefficient thermistors, a dual processing method of piecewise linearization algorithm + Steinhart-Hart equation calibration is adopted. First, the preliminary temperature value is quickly obtained by fitting the linear equation piecewise. Then, the error is corrected by using the high-precision Steinhart-Hart equation, which greatly reduces the temperature conversion error and ensures the accuracy of the actual temperature value detection, providing a reliable data basis for subsequent speed adjustment.

[0067] 4. Multi-level linear adjustment with smooth and controllable noise: The fan speed is adaptively adjusted in multiple levels by controlling the on / off state of the switching unit and the PWM duty cycle to form differentiated adjustment logic in different temperature ranges: in the low temperature range, the fan maintains low speed or stops; in the medium temperature range, the duty cycle increases linearly from 10% to 90% with the equivalent temperature value, and the fan speed increases linearly accordingly; in the high temperature range, the fan maintains the highest speed, avoiding the sudden speed changes of traditional two-level adjustment and effectively suppressing operating noise; at the same time, the linear adjustment mode makes the fan speed and temperature gradient precisely matched, improving the rationality of heat dissipation efficiency.

[0068] 5. Closed-loop feedback correction ensures stable and reliable fan speed: A closed-loop feedback mechanism for fan power supply circuit current detection is introduced. The sampling resistor detects current changes and converts them into an actual speed signal, which is compared with the target speed in real time. If there is a deviation, the switching frequency of the fine-tuning unit is used to compensate for errors caused by voltage fluctuations, component aging, etc., ensuring that the deviation between the actual speed and the target speed is controlled within the allowable range. This ensures a stable match between heat dissipation requirements and speed output, and improves the solution's anti-interference capability and long-term operational reliability. Attached Figure Description

[0069] Figure 1 This is a schematic flowchart of the control method for the cooling fan speed regulation circuit of the present invention.

[0070] Figure 2 This is a schematic diagram of a cooling fan speed regulation circuit in a specific embodiment of the present invention. Detailed Implementation

[0071] The following is in conjunction with the appendix Figures 1-2The present invention will be further described in detail below:

[0072] Example 1

[0073] See appendix Figure 1 As shown, a control method for a cooling fan speed regulation circuit includes the following steps:

[0074] S1: Power Supply Reuse and Adaptation Configuration: The power supply circuit of the cooling fan is reused with the LED series lamp bead circuit of the high-power LED lamp. By matching the number of LED series lamp beads with the rated voltage requirements of the fan, the fan power supply is taken from the voltage division of the LED series lamp beads, without the need to add an additional independent power supply module. At the same time, it ensures that the total voltage of the LED series lamp beads is higher than the rated power supply voltage of the fan and the rated operating current of the LED is greater than the maximum operating current of the fan. A voltage regulator and a filter capacitor bank are connected in series in the power supply circuit to achieve a stable output of the power supply voltage, laying the foundation for subsequent precise speed adjustment.

[0075] S2: Multi-dimensional environmental parameter acquisition: A negative temperature coefficient thermistor is placed close to the LED bead body to detect the working temperature of the LED bead in real time and output a continuously variable temperature voltage signal; at the same time, a humidity sensor is deployed to collect humidity data of the surrounding environment of the LED and output a humidity voltage signal. After the two signals are filtered out by the same filtering circuit, they are transmitted to the control unit to realize the coordinated perception of temperature and humidity dual parameters.

[0076] S3: Composite threshold comparison and compensation calculation: In the control unit, a basic temperature threshold is preset (including low temperature threshold T1, high temperature threshold T2, and extreme protection temperature T3, where T1 < T2 < T3). First, the filtered temperature voltage signal in step S2 is converted into the actual temperature value. Then, the corresponding compensation coefficient is called according to the humidity data to calculate the equivalent temperature value. Subsequently, the equivalent temperature value is compared with the basic temperature threshold in real time to generate the corresponding level of control command.

[0077] S4: Graded linear speed regulation: Based on the comparison results of step S3, control the on / off state and duty cycle of the control switch unit to achieve multi-level adaptive adjustment of the fan speed: When the equivalent temperature value ≤ T1, the control switch unit remains on, and the fan runs at the lowest speed or stops; when T1 < equivalent temperature value < T2, the control switch unit performs pulse on / off switching, and the duty cycle increases linearly from 10% to 90% as the equivalent temperature value increases, and the fan speed increases synchronously and linearly; when the equivalent temperature value ≥ T2 and < T3, the control switch unit remains off, and the fan runs at the rated maximum speed; when ≥ T3, the extreme condition protection process of step S6 is executed.

[0078] S5: Closed-loop feedback and deviation correction: The actual fan speed signal is obtained by detecting the current change in the fan power supply circuit and compared with the target speed corresponding to the current equivalent temperature value; if there is a speed deviation, the error caused by voltage fluctuation is compensated by fine-tuning the switching frequency of the switching unit to ensure that the speed accurately matches the heat dissipation requirements.

[0079] S6: Extreme operating condition protection: When the equivalent temperature value calculated in step 3 is ≥ T3, the control unit immediately outputs an alarm signal, cuts off the power supply of the non-core circuit of the LED lamp to reduce the heat generation power, and controls the fan to maintain the highest speed operation; until the equivalent temperature value drops below T2, the full power supply of the LED lamp and the normal speed adjustment logic are gradually restored to avoid damage to the LED lamp due to overheating.

[0080] Example 2

[0081] Based on Example 1, the specific process of first converting the filtered temperature-voltage signal from Step S2 into an actual temperature value in step S3, then calculating the equivalent temperature value by calling the corresponding compensation coefficient based on the humidity data, and subsequently comparing the equivalent temperature value with the base temperature threshold in real time to generate the corresponding level of control command is as follows:

[0082] S31: Conversion of temperature voltage signal to actual temperature value, i.e., correction based on thermistor characteristics:

[0083] First, the filtered temperature and voltage signal from step S2 is acquired. The analog voltage signal is then converted into a digital signal by the built-in ADC module of the control unit to eliminate noise interference in signal transmission.

[0084] Based on the nonlinear characteristics of negative temperature coefficient thermistors, a piecewise linearization algorithm is used for conversion: the operating temperature range of the LED lamp is divided into multiple sub-intervals, and each interval has a corresponding pre-stored fitting linear equation. The correspondence is shown in Table 1. The control unit calls the corresponding equation according to the interval to which the input voltage signal belongs and calculates the preliminary temperature value.

[0085] Table 1. Correspondence between temperature ranges and fitted linear equations

[0086]

[0087] Precision calibration is performed using the Steinhart-Hart equation. By substituting the calibration constants A, B, and C of the thermistor, the initial temperature value is corrected, ultimately outputting a precise actual temperature value in °C. This resolves the conversion error caused by the thermistor's nonlinearity. The implementation logic is as follows: The Steinhart-Hart equation is a high-precision mathematical model describing the nonlinear relationship between the thermistor's resistance and temperature. Its core is to directly deduce the precise temperature from the filtered voltage signal using the thermistor's calibration constants A, B, and C, correcting the systematic error caused by piecewise linear fitting.

[0088] S32: Humidity compensation coefficient call and equivalent temperature value calculation:

[0089] Extract the humidity voltage signal from step S2 and convert it into the actual ambient humidity value, in %RH. Divide the humidity range into three intervals: low humidity (≤40%RH), medium humidity (40%~70%RH), and high humidity (≥70%RH). Set the corresponding humidity compensation coefficient according to the temperature range, as shown in Table 2 below.

[0090] Table 2 Correspondence between Temperature Range and Humidity Compensation Coefficient

[0091]

[0092]

[0093] The control unit automatically calls the corresponding humidity compensation coefficient based on the current humidity range and calculates the equivalent temperature value using the formula "Equivalent temperature value = Actual temperature value × Humidity compensation coefficient". T eq .

[0094] The compensation logic is as follows: high humidity environment will reduce heat dissipation efficiency, so the fan speeds up in advance by increasing the equivalent temperature value; low humidity environment has higher heat dissipation efficiency, so the fan is prevented from running excessively by reducing the equivalent temperature value, thus achieving a balance between heat dissipation and energy consumption.

[0095] S33: Comparison of equivalent temperature value with basic threshold and generation of control command:

[0096] The control unit has a built-in window comparator logic. The preset base temperature thresholds (T1, T2, T3) are converted into corresponding reference voltage thresholds (V1, V2, V3), and the equivalent temperature value is converted into the corresponding equivalent voltage signal.

[0097] Real-time comparison is performed: when the equivalent voltage signal ≤ V1 (i.e., the equivalent temperature value ≤ T1), a "low speed / stop" control command is generated; when V1 < equivalent voltage signal < V2 (i.e., T1 < equivalent temperature value < T2), a "linear speed increase" control command is generated; when V2 ≤ equivalent voltage signal < V3 (i.e., T2 ≤ equivalent temperature value < T3), a "maximum speed" control command is generated; when the equivalent voltage signal ≥ V3 (i.e., the equivalent temperature value ≥ T3), an "over-temperature protection" control command is generated.

[0098] The control commands are output to the switching unit in the form of digital level signals, providing a precise control basis for subsequent speed regulation and protection actions.

[0099] The specific process of converting the temperature voltage signal to the actual temperature value in step S31 is as follows:

[0100] S311: From voltage signal V T Derivation of the actual resistance value of the thermistor R NTC :

[0101] Based on the circuit architecture, the fan is connected in parallel with LED beads, and the thermistors are connected in series for voltage division. The core circuit parameters are preset as follows:

[0102] Power supply voltage: VCC=5V;

[0103] Voltage divider resistors: R 分压 =10KΩ, corresponding to the equivalent resistance of the R3 / R9 voltage divider network;

[0104] Filtered temperature and voltage signals: V T That is, the simulated voltage signal in step S2, in V;

[0105] The thermistor and the voltage divider resistor form a series voltage divider circuit. The actual resistance value of the thermistor can be derived according to Ohm's law. R NTC The specific formula is as follows:

[0106] R NTC = R 分压 · V T / (VCC-V T );

[0107] For example: when V T =2.5V, R 分压 =10KΩ, VCC=5V, then:

[0108] R NTC =10KΩ×(2.5 / (5-2.5))=10KΩ.

[0109] S312: Substitute into the Steinhart-Hart equation to calculate absolute temperature T K :

[0110] The standard form of the Steinhart-Hart equation applies to temperatures from -50°C to 150°C, covering the entire operating temperature range of high-power LED lights.

[0111] ;

[0112] in, T K This is the absolute temperature of the thermistor, in K, which needs to be converted to °C. R NTC : Actual resistance value of the thermistor, unit: Ω; A, B, C: Calibration constants of the thermistor; Common calibration constants for NTC thermistors are: A = 1.4051 × 10⁻⁶ - ³K - ¹, B = 2.3696 × 10 -4 K - ¹, C = 1.263 × 10 -7 K - ¹.

[0113] Methods for obtaining calibration constants A, B, and C:

[0114] Prioritize using the calibration values ​​provided by the thermistor manufacturer, which are usually indicated in the product datasheet;

[0115] If manufacturer data is unavailable, a three-point calibration method can be used for practical testing: Measure the corresponding values ​​at three known precise temperatures (e.g., 0℃, 25℃, 85℃). V T And calculate R NTC Substituting these values ​​into the Steinhart-Hart equation, we can solve the system of three linear equations to obtain A, B, and C.

[0116] S313: Absolute temperature to actual temperature conversion T actual Unit: °C; The formula for converting between absolute temperature and Celsius temperature is: T actual = T K -273.15;

[0117] Integration with piecewise linear fitting results: First, calculate the preliminary temperature value using the preceding piecewise linear equation.T 初 Then, the precise temperature value is calculated using the Steinhart-Hart equation described above. T actual ; Calculate the correction difference Δ T = T actual - T 初 The difference is used as the correction offset for the corresponding temperature range; the control unit stores the Δ value for each temperature range. T Subsequent collection V T Then, first obtain the linear equation. T 初 Then superimpose the Δ of the corresponding interval T Fast output of high precision T actual This avoids redundant calculations of the natural logarithm and improves response speed.

[0118] Taking a specific scenario as an example: When a high-power LED light is working, the filtered temperature and voltage signal... V T =1.8V, the accurate actual temperature calculation process is as follows:

[0119] Given parameters: VCC = 5V, R 分压 =10KΩ, A=1.4051×10 - ³K - ¹, B = 2.3696 × 10 -4 K - ¹, C = 1.263 × 10 -7 K - ¹;

[0120] calculate R NTC : R NTC =10000Ω×1.8V / (5V-1.8V)=5625Ω;

[0121] Substitute into the Steinhart-Hart equation to find T K =283.1K;

[0122] Convert to actual temperature: T actual = T K -273.15≈10℃.

[0123] Error comparison: If the linear equation in the 0~30℃ range is passed... V T=-0.015×T+2.75 (inverse calculation):

[0124] T 初 =(2.75-1.8) / 0.015=63.33℃, which is a huge error; after correction by the Steinhart-Hart equation, the temperature error is within (-0.5℃, +0.5℃), thus solving the nonlinearity problem of the thermistor.

[0125] Example 3

[0126] Based on Example 1, Example 2, or Example 3, the specific process of step S4 is as follows:

[0127] S41: Define the associated parameters:

[0128] Switching unit: Q1, whose on / off state directly changes the voltage divider logic of the fan power supply circuit;

[0129] Fan power supply voltage: taken from the voltage divider of LED series beads, the total voltage of the upper beads is V1, the total voltage of the lower beads is V2, the maximum power supply voltage of the fan is Vm_max=V1+V2 (when Q1 is off), and the minimum power supply voltage is Vm_min=V1 (when Q1 is on).

[0130] Pulse duty cycle: refers to the ratio of the off time of the switching unit to the total cycle within one pulse cycle, ranging from 10% to 90%. The higher the duty cycle, the higher the average voltage actually obtained by the fan and the faster the speed.

[0131] Equivalent temperature value: T eq (Calculation results of step S3), basic thresholds T1 (low temperature threshold), T2 (high temperature threshold), T3 (ultimate protection threshold).

[0132] S42: Set the adjustment range and perform interval adjustment according to the adjustment range.

[0133] Interval 1: Equivalent temperature value T eq ≤T1 (Low Temperature Condition):

[0134] Triggering condition: Determined in step S3 T eq ≤T1, the control unit outputs a "switch on" command;

[0135] Switching unit operation: The control unit outputs a high-level signal to the gate (G) of Q1, keeping Q1 continuously on;

[0136] Fan power supply logic: After Q1 is turned on, it is connected in parallel with the lower LED. The fan only obtains the voltage V1 (Vm=V1) from the upper LED. This voltage is the minimum operating voltage or the critical voltage for stopping the fan.

[0137] Speed ​​status: The fan runs at the lowest speed (to meet basic heat dissipation requirements). If V1 is lower than the fan's starting voltage, the fan will stop directly to avoid noise and energy waste caused by ineffective operation under low voltage.

[0138] Interval 2: T1 < T eq <T2 (Medium Temperature Condition):

[0139] Triggering condition: Step S3 determines T1 < T eq <T2, the control unit outputs a "pulse-type on / off" command;

[0140] Switching unit operation: The control unit outputs a PWM (Pulse Width Modulation) signal to the gate of Q1 to achieve pulse-type on / off switching. The core is to achieve smooth voltage increase by adjusting the duty cycle. Specific logic:

[0141] Initial duty cycle value: when T eq Just after T1, the duty cycle is set to 10%. At this time, Q1's off time accounts for 10% and its on time accounts for 90%. The average power supply voltage to the fan is... V mavg =V1+(V2×10%);

[0142] Duty cycle increases linearly: The control unit has a built-in duty cycle-temperature mapping algorithm, and the duty cycle increases linearly with temperature. T eq The increase is linear, as shown by the formula:

[0143] Duty cycle D(%) = 10% + [( T eq [-T1) / (T2-T1)]×80%;

[0144] For example, T1=30℃, T2=60℃, T eq At 45℃, D = 10% + (15 / 30) × 80% = 50%;

[0145] Duty cycle limit: when T eq As the voltage approaches T2, the duty cycle rises to 90%, at which point the average power supply voltage to the fan... V mavg =V1+(V2×90%), the speed is close to 90% of the maximum speed.

[0146] Speed ​​characteristics: The fan speed is linearly positively correlated with the duty cycle. Because the fan speed is approximately linearly related to the power supply voltage, the speed increases linearly with each 1°C increase in temperature, avoiding noise fluctuations caused by sudden speed changes, and accurately matching the increased heat dissipation demand in the mid-temperature range.

[0147] Interval 3: T2≤ T eq <T3 (High Temperature Condition):

[0148] Triggering condition: Step S3 determines T2 ≤ T eq <T3, the control unit outputs a "switch off" command;

[0149] Switching unit operation: The control unit outputs a low-level signal to the gate of Q1, keeping Q1 in a continuously off state;

[0150] Fan power supply logic: After Q1 is turned off, the voltage divider V2 of the lower LED chips is connected to the fan power supply circuit, and the fan obtains the total voltage of all series-connected LED chips. V m =V1+V2 (i.e.) V mmax This voltage is the fan's rated maximum supply voltage;

[0151] Speed ​​status: The fan runs at its rated maximum speed to maximize heat dissipation efficiency, quickly reduce the temperature of the LED beads, and prevent the temperature from rising further to the extreme threshold T3.

[0152] Interval 4: T eq ≥T3 (Ultra-high temperature condition, triggering protection linkage):

[0153] Triggering condition: Determined in step S3 T eq ≥T3, the control unit does not perform the speed adjustment in this step, and directly triggers the extreme condition protection process in step S6;

[0154] Connection logic: The control unit outputs a "protection trigger" signal, which on the one hand maintains the Q1 cut-off state and the fan continues to run at the highest speed to ensure uninterrupted heat dissipation, and on the other hand activates the LED power limiting and alarm mechanism in step S6 to form a dual protection of maximizing heat dissipation and controlling heat source.

[0155] Step S5 is a closed-loop control process based on "speed signal acquisition - deviation judgment - dynamic compensation". Its core purpose is to eliminate speed deviations caused by factors such as power supply voltage fluctuations and component aging, and to ensure that the actual fan speed is accurately matched with the target speed corresponding to the equivalent temperature value. The specific process is as follows:

[0156] Prerequisite parameters:

[0157] Core testing target: Fan power supply circuit current (denoted as...) I fan The operating current is positively correlated with the fan speed; the higher the fan speed, the greater the operating current.

[0158] Current detection method: A sampling resistor is connected in series in the fan power supply circuit. R s Resistance value 1Ω~5Ω, passed testing R s Voltage drop across the terminals V s calculate I fan ( I fan = V s / R s This eliminates the need for an additional speed sensor, reducing costs.

[0159] Target speed: T target The equivalent temperature value from step S3 T eq Mapped to, preset T eq - T target For details, please refer to Table 3 below;

[0160] Table 3 T eq - T target Comparison Table

[0161]

[0162] Deviation judgment threshold: Δ T allow (Maximum permissible speed deviation) is set to ±5% of the target speed, for example... T target At 3000 rpm, Δ T allow =±150rpm;

[0163] Adjustment target: the switching frequency (i.e., PWM pulse period) of the switching unit (Q1, MOSFET / transistor), the original base period is 20ms, and the adjustment range is 15ms~25ms.

[0164] S51: Actual Speed ​​Signal Acquisition and Conversion

[0165] Current sampling: The control unit (U1, MCU) acquires the sampling resistor in real time. Rs Voltage drop across the terminals V s The built-in filter circuit filters out current ripple interference, resulting in a stable current output. V s Valid values;

[0166] Current calculation: According to Ohm's law I fan = V s / R s The real-time operating current of the fan is calculated, in mA.

[0167] Speed ​​conversion: based on the fitting equation pre-stored in the control unit T actual =0.5× I fan +500 is used for conversion, where T actual The actual rotational speed, in rpm. I fan Converted to actual fan speed T actual This completes the precise mapping from current signal to speed signal.

[0168] S52: Speed ​​Deviation Judgment

[0169] Data retrieval: The control unit synchronously retrieves step S3. T eq Corresponding target speed T target ;

[0170] Deviation calculation: ΔT= T actual - T target ;

[0171] Status determination:

[0172] If |ΔT|≤Δ T allow If the speed deviation is within the allowable range, no adjustment action will be performed, and the current switching frequency of the switching unit will be maintained;

[0173] If ΔT>Δ T allow If the actual fan speed is higher than the target speed, the average power supply voltage of the fan needs to be reduced, and the deviation should be corrected by slowing down the fan speed.

[0174] If ΔT < -Δ T allow If the actual fan speed is lower than the target speed, the average power supply voltage of the fan needs to be increased to correct the deviation by increasing the fan speed.

[0175] S53: On / off frequency fine-tuning and deviation compensation:

[0176] Based on the deviation determination results, the control unit fine-tunes the average power supply voltage of the fan by adjusting the PWM pulse period, i.e., the switching frequency of the switching unit. The specific logic is as follows:

[0177] S54: Dynamic Closed-Loop Iteration

[0178] Real-time monitoring: After adjustment, the control unit continues to repeat steps S51-S53 to continuously collect data. T actual and T target Comparison;

[0179] Iterative correction: If |ΔT| is still greater than Δ after one adjustment T allow Fine-tune again according to the above formula. T new Each adjustment should not exceed ±5% of the original cycle to avoid sudden changes in speed, until |ΔT|≤Δ T allow ;

[0180] Steady-state maintenance: Once the speed deviation meets the requirements, the control unit maintains the current on / off frequency until... T eq A change occurs, triggered by step S3. T target Updated, entering the next round of closed-loop adjustment.

[0181] The specific process of frequency fine-tuning and deviation compensation in step S53 is as follows:

[0182] When ΔT>Δ T allow (Actual speed is higher than expected):

[0183] Adjustment direction: Increase the PWM pulse period, reduce the on / off frequency, and reduce the effective power supply time of the fan within one cycle;

[0184] Adjustment formula: New cycle T new = T old +k×ΔT, where T old The original cycle is represented by k, which is an adjustment coefficient with a value of 0.002 ms / rpm. It can be calibrated according to actual working conditions.

[0185] For example, the original cycle T old =20ms T target=3000rpm, T actual =3200rpm, ΔT=200rpm, then T new =20 + 0.002 × 200 = 20.4 ms;

[0186] Voltage impact: With increased cycle time, the average power supply voltage to the fan... V mavg = V m ×D, where D is the duty cycle, remains constant, but the pulse interval is extended, the effective power supply time is shortened, and the actual speed gradually decreases. T target .

[0187] When ΔT < -Δ T allow (Actual speed is lower than expected):

[0188] Adjustment direction: Reduce the PWM pulse period, increase the on / off frequency, and increase the effective power supply time of the fan within one cycle;

[0189] Adjustment formula: New cycle T new = T old - k ×|ΔT|;

[0190] For example, the original cycle T old =20ms T target =3000rpm, T actual =2700rpm, ΔT=-300rpm, then T new =20 - 0.002 × 300 = 19.4 ms;

[0191] Voltage impact: With a reduced cycle time, the pulse interval shortens, the effective power supply time increases, and the average power supply voltage of the fan indirectly increases, causing the actual speed to gradually rise. T target .

[0192] A cooling fan speed regulation circuit includes a power supply multiplexing module, a multi-dimensional parameter acquisition module, a control unit, a switching unit, a load unit, and a protection module;

[0193] The power supply multiplexing module is reused with the LED series lamp bead circuit of the high-power LED lamp. It is composed of multiple LED lamp beads set in series. By matching the number of LED series lamp beads with the rated voltage requirement of the load unit, the power supply of the load unit is taken from the voltage division of the LED series lamp beads. The total voltage of the LED series lamp beads is higher than the rated power supply voltage of the load unit, and the rated operating current of the LED is greater than the maximum operating current of the load unit. A voltage stabilizing element and a filter capacitor bank are connected in series in the power supply circuit to achieve stable power supply voltage output.

[0194] The multi-dimensional parameter acquisition module includes a negative temperature coefficient thermistor and a humidity sensor. The negative temperature coefficient thermistor is set close to the LED bead body to detect the LED bead operating temperature in real time and output a continuously variable temperature voltage signal. The humidity sensor is used to synchronously collect humidity data of the surrounding environment of the LED and output a humidity voltage signal. Both share the same filtering circuit to filter out noise interference. The filtered signal is transmitted to the control unit.

[0195] The control unit has a built-in basic temperature threshold (including low temperature threshold T1, high temperature threshold T2, and extreme protection temperature T3, where T1 < T2 < T3). Its input terminal is electrically connected to the multi-dimensional parameter acquisition module, which is used to convert the filtered temperature voltage signal into the actual temperature value, and then call the corresponding compensation coefficient to calculate the equivalent temperature value based on the humidity data. The equivalent temperature value is compared with the basic temperature threshold in real time to generate the corresponding level control command.

[0196] The switching unit is a MOSFET or a transistor, with its control terminal electrically connected to the output terminal of the control unit and its path terminal connected in series between the power supply multiplexing module and the load unit. It is used to adjust the on / off state and duty cycle according to the control command of the control unit to realize multi-level adaptive adjustment of the fan speed. The protection module is electrically connected to the control unit. When the equivalent temperature value is ≥ T3, it responds to the command output by the control unit, outputs an alarm signal, cuts off the power supply to the non-core circuit of the LED lamp, and maintains the load unit at its highest speed until the equivalent temperature value drops below T2, after which it restores the full power supply to the LED lamp and the normal speed adjustment logic.

[0197] In another embodiment, a cooling fan speed regulation circuit can be configured as follows: Figure 2 As shown, the circuit uses LED series lamp beads as the power supply multiplexing carrier, and the control unit U1 (operational amplifier) ​​as the decision core. The temperature detection unit feeds back the LED working status, and the switching unit switches the fan power supply voltage. With the help of auxiliary units such as voltage stabilization filtering and voltage division matching, a closed-loop speed regulation topology is formed.

[0198] Specifically, this includes a power supply and overvoltage protection unit, providing a stable power supply to the entire circuit while suppressing transient overvoltage protection. The core components include a ZVS transistor (Zenith diode) and filter capacitors C3, C4, and C5. The ZVS transistor is connected in parallel at the power input terminal to clamp the voltage and absorb transient overvoltage pulses in the circuit; C3, C4, and C5 are power supply filter capacitors, connected in parallel in the power supply circuit, filtering out ripple and noise in the power supply voltage and outputting a stable power supply voltage VDD to power the control unit U1 and other components.

[0199] The temperature detection and signal acquisition unit includes a negative temperature coefficient thermistor NTC1, voltage divider resistors R3 / R4, and filter capacitor C2. It monitors the operating temperature of the LED beads in real time and converts the temperature signal into a comparable voltage signal. NTC1 is positioned close to the LED bead group connected in series, forming a temperature detection branch with R3 and R4, and connected to a stable power supply VDD. C2 is connected in parallel across NTC1 to filter out noise in the temperature detection signal. The resistance of NTC1 changes with the LED temperature, thus altering the voltage divider value in the branch, achieving the signal conversion from "temperature → resistance → voltage".

[0200] The reference voltage and voltage divider matching unit, including voltage divider resistors R1 and R2 and filter capacitor C1, provides a stable reference voltage for the control unit, ensuring the accuracy of temperature-voltage comparison. R1 and R2 are connected in series to form a reference voltage divider branch, with one end connected to the power supply VDD and the other end grounded; C1 is connected in parallel between R1 and ground to filter out fluctuations in the reference voltage; the middle node of the branch outputs a stable reference voltage V-, which is connected to the inverting input terminal ("-") of the control unit U1 as the comparison reference for the temperature-voltage signal.

[0201] The control unit, including an operational amplifier / voltage comparator U1, a phase compensation capacitor C3, and a feedback resistor R9, compares the temperature detection voltage with a reference voltage and outputs corresponding control signals. The non-inverting input ("+") of U1 is connected to the detection voltage V+ output from the temperature detection unit, and the inverting input is connected to the reference voltage V-. C3 is connected in parallel between the output and inverting input of U1 for phase compensation, preventing oscillation during U1's operation. R9 is the feedback resistor, stabilizing the output state of U1 and ensuring the reliability of the control signal. The power supply terminal of U1 is connected to a stable voltage VDD, and the ground terminal is grounded.

[0202] The switching unit, including MOSFET Q1 (the core switch) and drive resistor R8, responds to control unit signals and switches operating states to change the fan supply voltage. The gate of Q1 is connected to the output of U1 via R8 to receive control signals; its drain is connected to one end of the lower LED series group, and its source is grounded. R8 provides current limiting protection, preventing excessive gate current from damaging Q1 and ensuring the stability of its switching operation.

[0203] The load unit, comprising an LED series lamp group (divided into an upper lamp group and a lower lamp group) and a fan motor M, performs the core functions of lighting and heat dissipation and is the object of the circuit's operation. The LED series lamp group has a series structure, and its total voltage is the sum of the voltage V1 of the upper lamp group and the voltage V2 of the lower lamp group. The fan motor M is connected in parallel with the LED series lamp group and is directly drawn from the voltage divider of the LED lamps. Its supply voltage switches with the on / off state of Q1.

[0204] The auxiliary protection unit includes a current-limiting resistor R5, load resistors R6 and R7, which protect circuit components from overcurrent, signal interference, and other problems. R5 is connected in series in the LED lamp bead power supply circuit to limit the circuit current and prevent the LED lamp beads from being damaged by overcurrent. R6 and R7 are load resistors, connected between the output terminal of U1 and the gate of Q1, and in the power supply circuit, respectively, to serve as voltage dividers and stabilize the circuit operating point.

[0205] In this embodiment, the circuit is powered by the operating voltage of the LED series lamp bead group. The voltage is clamped by a ZVS (Zenith diode) to suppress instantaneous overvoltage, and then filtered by capacitors C5, C4, and C3 to remove power supply noise, providing a stable voltage for the control unit (U1) and subsequent circuits. Simultaneously, R1, R2, and C1 form a voltage divider filter branch to provide a reference voltage for the control unit. NTC1 (Negative Temperature Coefficient Thermistor) + R3, R4, and C2 form a temperature detection branch. NTC1 is positioned close to the LED lamp beads to detect the LED operating temperature in real time. The resistance of NTC1 changes with the LED temperature (temperature increases → NTC1 resistance decreases; temperature decreases → NTC1 resistance increases): when the LED temperature is low, the resistance of NTC1 is high, and the voltage divider voltage of the temperature detection branch (input to the "+" terminal of U1) is low; when the LED temperature increases, the resistance of NTC1 is low, and the voltage divider voltage of the temperature detection branch (input to the "+" terminal of U1) increases. The "-" terminal of the control unit U1 (operational amplifier / voltage comparator) is connected to the reference voltage (obtained by voltage division by R1 and R2), and the "+" terminal is connected to the temperature detection voltage of NTC1. By comparing the voltages at both ends, a control signal is output: Low temperature condition (LED temperature < preset threshold): Temperature detection voltage ("+" terminal) < reference voltage ("-" terminal), U1 outputs a high level; High temperature condition (LED temperature ≥ preset threshold): Temperature detection voltage ("+" terminal) > reference voltage ("-" terminal), U1 outputs a low level. The switching unit is Q1 (MOSFET), whose gate receives the control signal from U1 through R8. The on / off state directly changes the supply voltage of the fan (M): When U1 outputs a high level (low temperature): Q1's gate receives a high level, Q1 is turned on. At this time, Q1 is connected in parallel with some LED beads, and the fan (M) only obtains part of the voltage division of the LED series beads group (low voltage), and the fan runs at a low speed; When U1 outputs a low level (high temperature): Q1's gate receives a low level, Q1 is turned off, and the fan (M) obtains the full voltage of the LED series beads group (high voltage), and the fan runs at a high speed.

Claims

1. A control method for a cooling fan speed regulation circuit, characterized in that, Includes the following steps: S1: The power supply circuit of the cooling fan is reused with the LED series lamp bead circuit of the high-power LED lamp. By matching the number of LED series lamp beads with the rated voltage requirement of the fan, the power supply of the fan is taken from the voltage division of the LED series lamp beads. S2: A negative temperature coefficient thermistor is placed close to the LED bead body to detect the operating temperature of the LED bead in real time and output a continuously variable temperature voltage signal; a humidity sensor is deployed to collect humidity data of the surrounding environment of the LED bead and output a humidity voltage signal. S3: Preset basic temperature thresholds in the control unit, including low temperature threshold T1, high temperature threshold T2, and extreme protection temperature T3. Convert the temperature voltage signal into the actual temperature value, and then call the corresponding compensation coefficient according to the humidity data to calculate the equivalent temperature value. The equivalent temperature value is compared with the basic temperature threshold in real time to generate control commands of the corresponding level. S4: Based on the comparison results, control the on / off state and duty cycle of the control switch unit to achieve multi-level adaptive adjustment of the fan speed. The temperature range of multi-level adaptive adjustment includes equivalent temperature value ≤ T1, T1 < equivalent temperature value < T2, T2 ≤ equivalent temperature value < T3, and equivalent temperature value ≥ T3. S5: Obtain the actual fan speed signal by detecting the current change in the fan power supply circuit, and compare it with the target speed corresponding to the current equivalent temperature value; if there is a speed deviation, compensate for the error caused by voltage fluctuation by adjusting the switching frequency of the fine-tuning unit. S6: When the equivalent temperature value is ≥ T3, the control unit outputs an alarm signal and cuts off the power supply to the non-core circuit of the LED light part to reduce the heat generation power. It also controls the fan to maintain the highest speed until the equivalent temperature value drops below T2.

2. The control method for a cooling fan speed regulation circuit according to claim 1, characterized in that, In step S3, the temperature voltage signal is converted into an actual temperature value, and then the corresponding compensation coefficient is called based on the humidity data to calculate the equivalent temperature value. The specific process of comparing the equivalent temperature value with the base temperature threshold in real time to generate the corresponding level of control command is as follows: S31: Convert the temperature and voltage signals into digital signals. Based on the nonlinear characteristics of the negative temperature coefficient thermistor, a piecewise linearization algorithm is used for conversion: the operating temperature range of the LED lamp is divided into multiple sub-intervals, and a fitting linear equation is pre-stored in each interval to calculate the preliminary temperature value; the preliminary temperature value is calibrated by the Steinhart-Hart equation to obtain the actual temperature value. S32: Extracts the humidity voltage signal, converts it into the actual ambient humidity value, divides the humidity range into three intervals: low humidity, medium humidity, and high humidity, and sets the corresponding humidity compensation coefficient according to the temperature range; the control unit automatically calls the corresponding humidity compensation coefficient according to the interval to which the current actual humidity value belongs, and calculates the equivalent temperature value; S33: The control unit has a built-in window comparator logic. The preset base temperature threshold is converted into the corresponding reference voltage threshold, and the equivalent temperature value is converted into the corresponding equivalent voltage signal. Based on the relationship between the equivalent voltage signal and the reference voltage threshold, the corresponding control commands are generated.

3. The control method for a cooling fan speed regulation circuit according to claim 2, characterized in that, The specific process of calibrating the preliminary temperature value using the Steinhart-Hart equation in step S31 to obtain the actual temperature value is as follows: S311: Preset circuit core parameters: power supply voltage VCC, voltage divider resistors R 分压、 Temperature and voltage signals V T The thermistor and the voltage divider resistor form a series voltage divider circuit. The actual resistance value of the thermistor is derived according to Ohm's law. R NTC ; S312: Substitute into the Steinhart-Hart equation to calculate absolute temperature T K ; S313: Absolute temperature to actual temperature conversion T actual .

4. The control method for a cooling fan speed regulation circuit according to claim 3, characterized in that, The specific process of step S4 is as follows: S41: Define associated parameters: Switching unit Q1, fan supply voltage, pulse duty cycle, equivalent temperature value T eq and basic threshold; equivalent temperature value T eq The calculation results for step S3 include the low temperature threshold T1, the high temperature threshold T2, and the ultimate protection threshold T3. S42: Set the adjustment range and perform interval adjustment according to the adjustment range.

5. The control method for a cooling fan speed regulation circuit according to claim 4, characterized in that, The specific process of performing interval adjustment based on the adjustment interval in step S42 is as follows: Interval 1: Equivalent temperature value T eq ≤T1: The control unit outputs a switch-on command; Switching unit operation: The control unit outputs a high-level signal to the gate of Q1, keeping Q1 in a continuously conducting state; Interval 2: T1 < T eq <T2: The control unit outputs pulse-type on / off commands; Switching unit operation: The control unit outputs a PWM signal to the gate of Q1 to achieve pulse-type on / off switching; Interval 3: T2≤ T eq <T3: Control unit outputs switch off command; Switching unit operation: The control unit outputs a low-level signal to the gate of Q1, keeping Q1 in a continuously off state; Interval 4: T eq ≥T3: The control unit does not perform speed regulation and directly triggers the extreme condition protection process in step S6.

6. The control method for a cooling fan speed regulation circuit according to claim 1, characterized in that, The specific process of step S5 is as follows: S51: Real-time acquisition of sampling resistor R s Voltage drop across the terminals V s According to Ohm's Law I fan = V s / R s The real-time operating current of the fan is calculated; based on the current-speed calibration curve provided by the fan manufacturer, I fan Converted to actual fan speed T actual This completes the precise mapping from current signal to speed signal; S52: Speed ​​Deviation Judgment: Retrieve T eq Corresponding target speed T target ; Deviation calculation: ΔT= T actual - T target ; Status determination: If |ΔT|≤Δ T allow If the speed deviation is within the allowable range, no adjustment action will be performed, and the current switching frequency of the switching unit will be maintained; If ΔT>Δ T allow If the actual fan speed is higher than the target speed, the average power supply voltage of the fan needs to be reduced, and the deviation should be corrected by slowing down the fan speed. If ΔT < -Δ T allow If the actual fan speed is lower than the target speed, the average power supply voltage of the fan needs to be increased to correct the deviation by increasing the fan speed. S53: On / off frequency fine-tuning and deviation compensation: Based on the deviation judgment result, the control unit fine-tunes the average power supply voltage of the fan by adjusting the PWM pulse period; S54: After adjustment, repeat steps S51-S53 to continuously collect data. T actual and T target Comparison; If |ΔT| is still greater than Δ after one adjustment T allow Fine-tune again according to the above formula. T new until |ΔT|≤Δ T allow ; Once the speed deviation meets the requirements, the control unit maintains the current on / off frequency until... T eq Changes occur, and the system enters the next round of closed-loop regulation.

7. The control method for a cooling fan speed regulation circuit according to claim 6, characterized in that, The specific process of frequency fine-tuning and deviation compensation in step S53 is as follows: When ΔT>Δ T allow Increase the PWM pulse period to reduce the effective power supply time of the fan within one cycle; When ΔT < -Δ T allow Adjustment direction: Reduce the PWM pulse period to increase the effective power supply time of the fan within one cycle.

8. A cooling fan speed regulation circuit, used to implement the control method for a cooling fan speed regulation circuit according to any one of claims 1-7, characterized in that, It includes a power supply multiplexing module, a multi-dimensional parameter acquisition module, a control unit, a switching unit, a load unit, and a protection module; The power supply multiplexing module is reused with the LED series lamp bead circuit of the high-power LED lamp. It is composed of multiple LED lamp beads arranged in series. By matching the number of LED series lamp beads with the rated voltage requirement of the load unit, the power supply of the load unit is taken from the voltage division of the LED series lamp beads. The multi-dimensional parameter acquisition module includes a negative temperature coefficient thermistor and a humidity sensor, which are used to output the temperature voltage signal of the LED lamp bead operating temperature and the humidity voltage signal of the humidity data of the surrounding environment of the LED lamp, respectively. The control unit has a built-in basic temperature threshold. Its input terminal is electrically connected to the multi-dimensional parameter acquisition module, which is used to convert the filtered temperature voltage signal into the actual temperature value, and then call the corresponding compensation coefficient to calculate the equivalent temperature value based on the humidity data. After comparing the equivalent temperature value with the basic temperature threshold in real time, the corresponding level control command is generated. The switching unit is a MOSFET or a transistor. Its control terminal is electrically connected to the output terminal of the control unit, and its pass terminal is connected in series between the power supply multiplexing module and the load unit. It is used to adjust the on / off state and duty cycle according to the control command of the control unit to realize multi-level adaptive adjustment of the fan speed.

Images