Precise intelligent fan speed regulation control system applied to charger

Abstract

The utility model discloses a precise intelligent fan speed regulation control system applied to a charger, and relates to the technical field of fan electric control. The temperature detection module is adaptively connected with the MCU and used for detecting the temperature of the environment where the fan FN1 is located, generating a temperature value signal and transmitting the temperature value signal to the MCU; the power supply adjusting module is adaptively connected with the fan FN1 and the MCU and is used for providing power supply voltage VCCFAN for the fan FN1; the switch control module is adaptively connected with the MCU and the fan FN1; based on a temperature value signal generated by the temperature detection module, the MCU is used for controlling the on-off state of the fan FN1 through the on-off control module and adjusting the power supply voltage VCCFAN of the fan FN1 through the power supply adjusting module so as to adjust the rotating speed of the fan FN1. The control system can effectively prolong the service life of the fan, reduce the damage rate of the fan and realize noise reduction and energy conservation of the charger.

Description

Technical Field

[0001] The utility model relates to the technical field of fan electric control, in particular to a precise intelligent fan speed regulation control system applied to a charger. Background Art

[0002] In order to dissipate heat, two-wheeled electric vehicle chargers generally use air cooling. The fan is a component in the charger that is prone to failure, such as blade damage, hydraulic oil depletion, motor damage, abnormal fan noise, mechanical wear, etc. Long-term full-load operation of the fan will greatly affect its service life. Therefore, it is necessary to properly control the working mode and intensity of the fan so that it does not affect the heat dissipation of the charger and can increase the service life of the fan. However, the cooling fans of chargers currently on the market are basically fixed in full-speed operation mode, or only set to a fixed gear operation mode, and cannot finely and on-demand control of the fan's operating conditions. This not only reduces the fan's service life and increases the failure rate, but also increases the noise and energy loss during the charger's operation. Utility Model Content

[0003] In response to the above problems and technical requirements, the applicant has proposed a precise intelligent fan control system for a charger.

[0004] The technical solution of the utility model is as follows:

[0005] A precise intelligent fan speed control system for a charger, comprising:

[0006] MCU;

[0007] A temperature detection module, adapted to be connected to the MCU, is used to detect the temperature of the environment in which the fan FN1 is located, generate a temperature value signal and transmit it to the MCU;

[0008] a power supply regulating module, adapted to be connected to the fan FN1 and the MCU, and configured to provide a power supply voltage VCC_FAN to the fan FN1;

[0009] A switch control module adapted to connect with the MCU and the fan FN1;

[0010] Based on the temperature value signal generated by the temperature detection module, the MCU controls the on / off state of the fan FN1 through the switch control module, and adjusts the power supply voltage VCC FAN of the fan FN1 through the power regulation module to adjust the speed of the fan FN1.

[0011] Its further technical solution is that the power supply adjustment module includes a resistor R16, a resistor R18, a resistor R20, a resistor R23, a capacitor C5, a regulating tube Q6 and a voltage stabilizing chip U4, wherein,

[0012] One end of the resistor R16 is connected to the third electrode of the regulating tube Q6, and the other end of the resistor R16 is connected to the second electrode of the regulating tube Q6 and the cathode end of the voltage stabilizing chip U4, and the anode end of the voltage stabilizing chip U4 is grounded;

[0013] The reference end of the voltage stabilizing chip U4 is connected to one end of the resistor R23 and one end of the capacitor C5, the other ends of the resistor R23 and the capacitor C5 are grounded, and the reference end of the voltage stabilizing chip U4 is connected to the MCU through the resistor R20;

[0014] One end of the resistor R18 is connected to the reference end of the voltage stabilizing chip U4 , and the other end of the resistor R18 is connected to the first electrode of the regulating tube Q6 .

[0015] A further technical solution is that the reference end of the voltage stabilizing chip U4 is connected to the PWM signal output pin of the MCU through the resistor R20, and the PWM signal output pin is used to output a PWM signal to the reference end of the voltage stabilizing chip U4. The MCU is used to adjust the power supply voltage VCC_FAN of the fan FN1 by configuring the duty cycle of the PWM signal to adjust the speed of the fan FN1.

[0016] A further technical solution is that the switch control module includes a switch tube Q3 and a resistor R7, wherein:

[0017] The second electrode of the switch tube Q3 is connected to the control signal output pin of the MCU through the resistor R7, the third electrode of the switch tube Q3 is connected to the negative electrode of the fan FN1, and the positive electrode of the fan FN1 is connected to the resistor R18 and the first electrode of the regulating tube Q6.

[0018] A further technical solution is that the switch control module further includes a diode D1 , a cathode of the diode D1 is connected to the positive electrode of the fan FN1 , and an anode of the diode D1 is connected to the negative electrode of the fan FN1 .

[0019] A further technical solution is that the regulating tube Q6 and the switching tube Q3 are triodes.

[0020] A further technical solution is to further include a current detection module for detecting the working current and working current waveform of the fan FN1, wherein the current detection module includes a resistor R11, a resistor R12, a resistor R13 and a capacitor C3, wherein:

[0021] One end of the resistor R11 is connected to the second electrode of the switch tube Q3, and the other end of the resistor R11 is grounded. One end of the resistor R13 is connected to one end of the resistor R12 and the first electrode of the switch tube Q3, and the other end of the resistor R13 is grounded. One end of the resistor R12 is connected to one end of the capacitor C3 and the signal receiving pin of the MCU, and the other end of the capacitor C3 is grounded.

[0022] A further technical solution thereof is to further include a current limiting filter module, which includes a capacitor EC1, a diode D3 and a resistor R14, wherein:

[0023] The anode of the diode D3 is connected to the power supply voltage, and the cathode of the diode D3 is connected to the third electrode of the regulating tube Q6 through the resistor R14 and is grounded through the capacitor EC1.

[0024] A further technical solution is that the capacitor EC1 is an electrolytic capacitor, the positive electrode of the capacitor EC1 is connected to the cathode of the diode D3 and one end of the resistor R14, and the negative electrode of the capacitor EC1 is grounded.

[0025] A further technical solution is that the resistor R13 and the resistor R14 are power resistors.

[0026] The beneficial technical effects of the utility model are:

[0027] (1) The fan speed control system provided by the utility model can adjust the fan's supply voltage by configuring the duty cycle of the PWM signal output by the MCU, thereby flexibly and finely adjusting the fan's speed. There is no need to configure a special speed-regulating fan to dissipate heat for the charger, which effectively reduces product costs and improves competitive advantages.

[0028] (2) The system can also reasonably configure the fan speed based on the ambient temperature, and can also directly control the fan's switch. By controlling the fan's working time and working intensity on demand, it can effectively increase the fan's service life and reduce the damage rate. At the same time, it can also reduce the noise when the charger is working, reduce energy loss, and achieve noise reduction and energy saving.

[0029] (3) The system is equipped with a current detection module for detecting the fan's operating current and operating current waveform. It can monitor the fan's operating status and respond promptly when the fan is blocked or damaged.

[0030] (4) A limited current filter module is set up in the system, which not only suppresses interference but also shares the voltage reduction power consumption and heat consumption on the fan power supply main circuit, thereby improving the stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1This is a system block diagram of an embodiment of a precise intelligent fan speed control system for a charger provided by the utility model.

[0032] Figure 2 This is a circuit diagram of an embodiment of a precise intelligent fan speed control system for a charger provided by the utility model. DETAILED DESCRIPTION

[0033] The specific implementation of the present utility model will be further described below with reference to the accompanying drawings.

[0034] The utility model provides a precise intelligent fan speed control system for chargers, such as Figure 1 As shown, the control system includes:

[0035] MCU;

[0036] A temperature detection module, adapted to be connected to the MCU, is used to detect the temperature of the environment in which the fan FN1 is located, generate a temperature value signal and transmit it to the MCU;

[0037] A power supply regulating module 1 is adapted to be connected to the fan FN1 and the MCU, and is used to provide a power supply voltage VCC_FAN to the fan FN1;

[0038] A switch control module 2 adapted to connect with the MCU and the fan FN1;

[0039] Based on the temperature value signal generated by the temperature detection module, the MCU controls the on / off state of the fan FN1 through the switch control module 2 and adjusts the power supply voltage VCC_FAN of the fan FN1 through the power regulation module 1 to adjust the speed of the fan FN1.

[0040] Specifically, the temperature detection module detects the temperature of the environment in which the fan FN1 is located and generates a temperature value signal. The temperature of the environment in which the fan FN1 is located is the temperature of the environment described by the charger. After receiving the temperature value signal, the MCU defines the working condition of the fan FN1 according to the temperature value signal:

[0041] (1) When the real-time temperature value indicated by the temperature value signal is lower than the low temperature threshold T L When , the MCU turns off the fan FN1 through the switch control module 2, and the fan FN1 does not work.

[0042] (2) When the real-time temperature value indicated by the temperature value signal is greater than the low temperature threshold T L And is less than the high temperature threshold T HWhen the fan FN1 is turned on, the MCU turns on the fan FN1 through the switch control module 2, sets the fan target speed according to the real-time temperature value, and adjusts the power supply voltage VCC_FAN of the fan FN1 through the power supply adjustment module 1 to achieve precise stepless adjustment of the fan FN1 speed, so that the fan is configured at the target speed.

[0043] (3) When the real-time temperature value indicated by the temperature value signal is greater than the high temperature threshold T H When the power is on, the MCU makes the fan FN1 run at full speed through the power regulation module 1 to maximize the heat dissipation effect.

[0044] In order to improve the safety of the charger, the MCU can also control the working state of the charger according to the temperature value. When the real-time temperature value indicated by the temperature value signal is greater than the limit threshold T MAX When the temperature reaches 0, the charger is controlled to stop working, protecting the charger from adverse events due to abnormal heat dissipation, or even from explosions caused by short circuits or overheating, or fires caused by abnormal short circuits. The temperature detection module 1 can be a temperature sensor. The specific form and working principle of the power supply adjustment module 1 and the switch control module 2 can be referred to in the following description.

[0045] Figure 2 FIG. 1 shows a circuit diagram of an embodiment of a fan speed control system. Figure 2 As shown, the power supply regulation module 1 includes a resistor R16, a resistor R18, a resistor R20, a resistor R23, a capacitor C5, a regulating tube Q6 and a voltage stabilizing chip U4, wherein one end of the resistor R16 is connected to the third electrode of the regulating tube Q6, the other end of the resistor R16 is connected to the second electrode of the regulating tube Q6 and the cathode end (C end) of the voltage stabilizing chip U4, and the anode end (A end) of the voltage stabilizing chip U4 is grounded; the reference end (R end) of the voltage stabilizing chip U4 is connected to one end of the resistor R23 and one end of the capacitor C5, the other ends of the resistor R23 and the capacitor C5 are grounded, and the reference end of the voltage stabilizing chip U4 is connected to the MCU through the resistor R20; one end of the resistor R18 is connected to the reference end of the voltage stabilizing chip U4, and the other end of the resistor R18 is connected to the first electrode of the regulating tube Q6.

[0046] Specifically, the regulating transistor Q6 in this embodiment is an NPN transistor. For a transistor, the first electrode is the emitter, the second electrode is the base, and the third electrode is the collector. The reference terminal (R terminal) of the voltage regulator chip U4 is connected to the PWM signal output pin of the MCU via resistor R20. The voltage regulator chip U4 may be a TL431. The MCU outputs a PWM (Pulse Width Modulation) signal to the reference terminal of the voltage regulator chip U4 via the PWM signal output pin. The MCU can precisely adjust the duty cycle of the PWM signal from 0% to 100%. By configuring the duty cycle of the PWM signal, the supply voltage VCC_FAN of the fan FN1 is adjusted to adjust the speed of the fan FN1. When the power supply regulation module 1 is in operation, the MCU configures the duty cycle of the PWM signal to a target duty cycle corresponding to the fan's target speed. This controls the supply voltage VCC_FAN to reach the target supply voltage corresponding to the fan's target speed by adjusting the voltage value at the reference terminal of the voltage regulator chip U4, thereby enabling the fan FN1 to operate at the target fan speed.

[0047] In the power supply regulation module 1, the NPN transistor Q6 regulates the supply voltage VCC_FAN. Resistor R16 is a bias resistor for the NPN transistor Q6, providing the bias current required for operation of the NPN transistor Q6 and the current required for operation of the voltage regulator chip U4. The NPN transistor Q6, the voltage regulator chip U4, resistors R18 and R23, and capacitor C5 form a voltage-stabilizing negative feedback circuit. The supply voltage VCC_FAN is divided by resistors R18 and R23, and the feedback voltage Vreg_out is applied to the reference terminal of the voltage regulator chip U4. The PWM signal output by the MCU, after passing through resistor R20, generates a voltage V_PWM, which is also applied to the reference terminal of voltage regulator chip U4. When the reference terminal voltage V_R of voltage regulator chip U4 is greater than the reference voltage Vreg of voltage regulator chip U4, voltage regulator chip U4 turns on to ground, thereby lowering the base voltage of NPN transistor Q6, causing NPN transistor Q6 to turn off, thereby reducing the power supply voltage VCC_FAN. Conversely, when the reference terminal voltage V_R of voltage regulator chip U4 is less than the reference voltage Vreg of voltage regulator chip U4, voltage regulator chip U4 turns off to ground. Due to the presence of bias resistor R16, the base voltage of NPN transistor Q6 increases. When the base voltage of NPN transistor Q6 exceeds the current power supply voltage VCC_FAN, and a voltage greater than the on-saturation voltage exists between the base and emitter of NPN transistor Q6, NPN transistor Q6 turns on, thereby increasing the power supply voltage VCC_FAN. By repeating the above negative feedback regulation process, the power supply voltage VCC_FAN can be stabilized at the target power supply voltage. In this embodiment, the reference voltage Vreg of the voltage stabilizing chip U4 is 2.5V.

[0048] The reference voltage V_R of the voltage regulator chip U4 is composed of the feedback voltage Vreg_out and the voltage V_PWM. The supply voltage VCC_FAN is stabilized at the difference between the reference voltage Vreg and the voltage V_PWM. Therefore, the voltage V_PWM, and thus the supply voltage VCC_FAN, can be adjusted by adjusting the duty cycle of the PWM signal. The greater the duty cycle of the MCU's PWM signal, the greater the voltage V_PWM, and the lower the supply voltage VCC_FAN. Conversely, the smaller the duty cycle of the MCU's PWM signal, the lower the voltage V_PWM, and the higher the supply voltage VCC_FAN. Therefore, this system can finely adjust the supply voltage VCC_FAN of fan FN1 by adjusting the duty cycle of the PWM signal, thereby providing precise, intelligent, and stepless speed regulation of fan FN1. This eliminates the need for a dedicated speed-regulating fan in the charger, effectively reducing product costs and enhancing competitive advantage.

[0049] Furthermore, the switch control module 2 includes a switch tube Q3, a diode D1, and a resistor R7. The second electrode of the switch tube Q3 is connected to the control signal output pin of the MCU via the resistor R7. The third electrode of the switch tube Q3 is connected to the cathode of the fan FN1. The anode of the fan FN1 is connected to the resistor R18 and the first electrode of the regulating tube Q6. The cathode of the diode D1 is connected to the anode of the fan FN1, and the anode of the diode D1 is connected to the cathode of the fan FN1.

[0050] In this embodiment, the switch Q3 is an NPN transistor. The definitions of the first, second, and third electrodes of the switch Q3 are the same as those for the first, second, and third electrodes of the transistor described above and are not further elaborated here. In specific implementations, the switch Q3 may also utilize other power devices with switching functions. The MCU outputs a control signal via a control signal output pin to control the on / off state of the NPN transistor Q3, thereby controlling the on / off state of the fan FN1. When the MCU determines that the fan FN1 should be turned on, the MCU outputs a high-level control signal, which, through resistor R7, drives the transistor Q3 to conduct, connecting the cathode of the fan FN1 to ground. This creates a voltage difference between the positive and negative electrodes of the fan FN1, thereby enabling normal operation of the fan FN1. When the MCU determines that the fan FN1 should be turned off, the MCU outputs a low-level control signal, pulling the base potential of the transistor Q3 down to ground, turning off the transistor Q3. This eliminates the voltage difference between the positive and negative electrodes of the fan FN1, causing the fan FN1 to stop operating, thereby controlling the fan on and off.

[0051] Since the fan's internal drive motor is an inductive element, there will be an uncertain voltage spike at the moment of state switching. Therefore, the diode D1 is connected in reverse parallel with the positive and negative electrodes of the fan FN1 to clamp the voltage spike caused by the moment of switching the fan FN1 on and off, thereby preventing the transistor Q3 from being damaged by breakdown due to excessive voltage between the collector and emitter.

[0052] Furthermore, the control system also includes a current detection module 3 for detecting the working current and working current waveform of the fan FN1, the current detection module 3 includes a resistor R11, a resistor R12, a resistor R13 and a capacitor C3, wherein one end of the resistor R11 is connected to the second electrode of the transistor Q3, the other end of the resistor R11 is grounded, one end of the resistor R13 is connected to one end of the resistor R12 and the first electrode of the transistor Q3, the other end of the resistor R13 is grounded, one end of the resistor R12 is connected to one end of the capacitor C3 and the signal receiving pin of the MCU, and the other end of the capacitor C3 is grounded.

[0053] Specifically, to monitor the operating status of fan FN1, the system also includes a current monitoring module 3. Resistor R11 provides a static bias for transistor Q3, preventing malfunction of transistor Q3 due to floating voltage when the MCU output level is unknown. Fan FN1's normal operating current Ifn flows through transistor Q3 and then returns to ground through resistor R13. When the operating current Ifn flows through resistor R13, a detection voltage Vfn appears across resistor R13, according to Ohm's law (U = IR). Resistor R12 and capacitor C3 form a filter circuit, filtering the detection voltage Vfn and transmitting it to the MCU's signal receiving pin for acquisition. The MCU calculates the operating current Ifn using the detection voltage Vfn and the resistance value of resistor R13. By continuously monitoring the operating current waveform, the MCU monitors the operating status of fan FN1. If fan FN1 experiences an abnormality such as stalling, the MCU can promptly detect the abnormality by monitoring the operating current Ifn and its waveform, stopping fan FN1 and controlling the charger to either stop or operate only briefly. The manner in which the MCU determines the working state of the fan FN1 by monitoring the working current Ifn and the working current waveform is consistent with the prior art.

[0054] The resistor R13 needs to be a power resistor. The rated power Pr of the resistor R13 needs to be at least twice its working power consumption. The working power consumption of the resistor R13 is determined by the current Ifn flowing through it and its own resistance value R. The working power consumption P of the resistor R13 can be expressed as P=Ifn 2 R.

[0055] Furthermore, the system also includes a current limiting filter module 4, which includes a capacitor EC1, a diode D3 and a resistor R14, wherein the anode of the diode D3 is connected to the power supply voltage, the cathode of the diode D3 is connected to the third electrode of the regulating tube Q6 through the resistor R14, and is grounded through the capacitor EC1.

[0056] Specifically, the capacitor EC1 is an electrolytic capacitor, the positive electrode of the capacitor EC1 is connected to the cathode of the diode D3 and one end of the resistor R14, and the negative electrode of the capacitor EC1 is grounded. The current limiting protection module 4 can prevent power supply anomalies from damaging the circuit, while also providing anti-interference capabilities, enabling the system to operate stably and reliably, and providing a good working environment for the overall circuit. Among them, the diode D3 and capacitor EC1 are used for rectification and filtering, respectively. When the external power supply has local instability or transient interference input, the capacitor EC1 can absorb or accommodate this local fluctuation, providing a relatively stable voltage source for the subsequent circuit.

[0057] Diode D3 and resistor R14 form a self-current limiting protection circuit. Due to the diode's conduction characteristics, when a large current flows through diode D3, a large forward voltage drop (VF) is generated across the diode. This forward voltage drop (VF) partially distributes the voltage across subsequent circuits, reducing power consumption and heat generation in subsequent circuits while maintaining the same circuit current.

[0058] Resistor R14 is connected in series with the fan FN1's main power supply circuit, which is the current path formed by diode D1, resistor R14, and transistor Q6. Resistor R14 must be a power resistor with an operating power rating no greater than 50% of its rated power to prevent abnormal heating due to excessive power. The resistance of resistor R14 is appropriately set according to the power calculation formula and Ohm's law. This allows it to distribute the voltage drop and power consumption caused by the voltage difference across transistor Q6, effectively reducing the thermal effects on transistor Q6.

[0059] In summary, this fan speed control system can reasonably configure the fan speed based on the ambient temperature, and can also directly control the fan's on / off state. It can control the fan's working time and working intensity as needed, effectively increasing the service life of the charger's cooling fan and reducing the damage rate. At the same time, it can also reduce the noise of the charger during operation, reduce energy loss, and achieve noise reduction and energy saving.

[0060] The above description is only a preferred embodiment of the present invention, and the present invention is not limited to the above embodiment. It is understood that other improvements and variations directly derived or imagined by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the scope of protection of the present invention.

Claims

1. A precise intelligent fan speed control system for a charger, characterized in that: include: MCU; A temperature detection module, adapted to be connected to the MCU, is used to detect the temperature of the environment in which the fan FN1 is located, generate a temperature value signal and transmit it to the MCU; a power supply regulating module, adapted to be connected to the fan FN1 and the MCU, and configured to provide a power supply voltage VCC_FAN to the fan FN1; A switch control module adapted to connect with the MCU and the fan FN1; Based on the temperature value signal generated by the temperature detection module, the MCU is used to control the on / off state of the fan FN1 through the switch control module, and adjust the power supply voltage VCC_FAN of the fan FN1 through the power regulation module to adjust the speed of the fan FN1.

2. The precise intelligent fan speed control system for chargers according to claim 1 is characterized in that: The power supply adjustment module includes a resistor R16, a resistor R18, a resistor R20, a resistor R23, a capacitor C5, a regulating tube Q6 and a voltage stabilizing chip U4, wherein: One end of the resistor R16 is connected to the third electrode of the regulating tube Q6, and the other end of the resistor R16 is connected to the second electrode of the regulating tube Q6 and the cathode end of the voltage stabilizing chip U4, and the anode end of the voltage stabilizing chip U4 is grounded; The reference end of the voltage stabilizing chip U4 is connected to one end of the resistor R23 and one end of the capacitor C5, the other ends of the resistor R23 and the capacitor C5 are grounded, and the reference end of the voltage stabilizing chip U4 is connected to the MCU through the resistor R20; One end of the resistor R18 is connected to the reference end of the voltage stabilizing chip U4 , and the other end of the resistor R18 is connected to the first electrode of the regulating tube Q6 .

3. The precise intelligent fan speed control system for chargers according to claim 2 is characterized in that: The reference end of the voltage stabilizing chip U4 is connected to the PWM signal output pin of the MCU through the resistor R20. The PWM signal output pin is used to output a PWM signal to the reference end of the voltage stabilizing chip U4. The MCU is used to adjust the power supply voltage VCC_FAN of the fan FN1 by configuring the duty cycle of the PWM signal to adjust the speed of the fan FN1.

4. The precise intelligent fan speed control system for chargers according to claim 2 is characterized in that: The switch control module includes a switch tube Q3 and a resistor R7, wherein: The second electrode of the switch tube Q3 is connected to the control signal output pin of the MCU through the resistor R7, the third electrode of the switch tube Q3 is connected to the negative electrode of the fan FN1, and the positive electrode of the fan FN1 is connected to the resistor R18 and the first electrode of the regulating tube Q6.

5. The precise intelligent fan speed control system for chargers according to claim 4 is characterized in that: The switch control module further includes a diode D1 , wherein a cathode of the diode D1 is connected to a positive electrode of the fan FN1 , and an anode of the diode D1 is connected to a negative electrode of the fan FN1 .

6. The precise intelligent fan speed control system for chargers according to claim 4 is characterized in that: The regulating tube Q6 and the switching tube Q3 are triodes.

7. The precise intelligent fan speed control system for chargers according to claim 4 is characterized in that: It also includes a current detection module for detecting the working current and working current waveform of the fan FN1, and the current detection module includes a resistor R11, a resistor R12, a resistor R13 and a capacitor C3, wherein: One end of the resistor R11 is connected to the second electrode of the switch tube Q3, and the other end of the resistor R11 is grounded. One end of the resistor R13 is connected to one end of the resistor R12 and the first electrode of the switch tube Q3, and the other end of the resistor R13 is grounded. One end of the resistor R12 is connected to one end of the capacitor C3 and the signal receiving pin of the MCU, and the other end of the capacitor C3 is grounded.

8. The precise intelligent fan speed control system for chargers according to claim 7 is characterized in that: It also includes a current limiting filter module, which includes a capacitor EC1, a diode D3 and a resistor R14, wherein: The anode of the diode D3 is connected to the power supply voltage, and the cathode of the diode D3 is connected to the third electrode of the regulating tube Q6 through the resistor R14 and is grounded through the capacitor EC1.

9. The precise intelligent fan speed control system for a charger according to claim 8, characterized in that: The capacitor EC1 is an electrolytic capacitor. The positive electrode of the capacitor EC1 is connected to the cathode of the diode D3 and one end of the resistor R14 , and the negative electrode of the capacitor EC1 is grounded.

10. The precise intelligent fan speed control system for chargers according to claim 8, characterized in that: The resistor R13 and the resistor R14 are power resistors.

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