Fan voltage regulating circuit

Abstract

The invention discloses a fan voltage regulating circuit, aims to solve the problem that a fan needs different rotating speeds in different application scenes, and provides a circuit design which is simple in structure, stable in performance and low in cost. The circuit comprises a DC voltage source, an enabling circuit, a DC-DC chip, a voltage regulating circuit and a feedback circuit. The feedback circuit comprises a third resistor R48, a fourth resistor R56 and an RC circuit. A feedback pin of the DC-DC chip is grounded through a third resistor R48 and a fourth resistor R56 in sequence; the voltage regulating circuit comprises a PWM signal source, an integrating circuit, a first voltage regulating resistor R49 and a second voltage regulating resistor R57; the PWM signal source is connected to a node between the third resistor R48 and the fourth resistor R56 through the integrating circuit, the first voltage regulating resistor R49 and the second voltage regulating resistor R57 in sequence; according to the invention, accurate adjustment of the fan voltage is realized, and the circuit cost is low.

Description

Technical Field

[0001] The present application relates to the technical field of integrated circuits, and in particular to a fan voltage regulation circuit. Background Art

[0002] In the existing technical system, the speed control of the fan generally depends on the adjustment of its power supply voltage. This principle is based on the basic rules of electrical engineering: when the voltage applied to the fan motor increases, the magnetic field strength generated inside the motor increases, thereby driving the fan blades to rotate at a faster speed. Conversely, a decrease in voltage causes the speed to slow down. This feature makes precise voltage control an effective means of regulating the fan speed, which is crucial to meeting the wind speed requirements in different application scenarios.

[0003] However, in actual applications, fans often need to operate in changing environments. For example, server rooms require efficient heat dissipation to reduce equipment temperature, while offices or home environments require a balance between heat dissipation and noise control. Traditional fan control methods often lack flexibility and are difficult to automatically adjust to the optimal speed according to different scenarios, resulting in problems such as low energy efficiency or insufficient heat dissipation.

[0004] In order to solve the above problems, some methods have begun to appear on the market to try to adjust the speed of the fan by changing the voltage. However, existing solutions often have disadvantages such as complex circuits, high costs, and difficulty in obtaining materials, which limits their widespread application. In addition, some solutions fail to fully consider the stability and reliability in actual applications, affecting the user experience. Summary of the invention

[0005] The present application provides a fan voltage regulation circuit, which aims to solve the problem that the fan requires different speeds in different application scenarios, thereby optimizing product performance, and at the same time providing a circuit design with simple structure, stable performance and low cost.

[0006] In a first aspect, a fan voltage regulation circuit is provided, comprising: a DC voltage source, an enabling circuit, a DC-DC chip, a voltage regulation circuit and a feedback circuit; wherein:

[0007] The DC voltage source is connected to the input pin of the DC-DC chip;

[0008] The enabling circuit includes a switch signal ON / OFF and a second resistor R50; the switch signal ON / OFF is connected to the enabling pin of the DC-DC chip via the second resistor R50;

[0009] The output pin of the DC-DC chip is connected to the drive end of the fan through the filter inductor L5;

[0010] The bootstrap pin of the DC-DC chip is connected to the node between the output pin of the DC-DC chip and the filter inductor L5 via the bootstrap capacitor C52;

[0011] The feedback circuit includes a third resistor R48, a fourth resistor R56 and an RC circuit; wherein the feedback pin of the DC-DC chip is connected to the ground via the third resistor R48 and the fourth resistor R56 in sequence; one end of the RC circuit is connected to the output node between the filter inductor L5 and the driving end of the fan, and the other end is connected to the node between the third resistor R48 and the fourth resistor R56;

[0012] The voltage regulating circuit includes a PWM signal source, an integration circuit, a first voltage regulating resistor R49 and a second voltage regulating resistor R57; the PWM signal source is connected to the node between the third resistor R48 and the fourth resistor R56 via the integration circuit, the first voltage regulating resistor R49 and the second voltage regulating resistor R57 in sequence; the output voltage of the fan voltage regulating circuit is adjusted by adjusting the duty cycle of the PWM signal.

[0013] In the above solution, further optionally, a third capacitor C47 is connected to ground at a node between the second resistor R50 and the enable pin of the DC-DC chip to smooth the signal and prevent the switch from being triggered by an external interference signal.

[0014] In the above solution, optionally, a filter capacitor is connected to ground at a node between the DC voltage source and the input pin of the DC-DC chip.

[0015] In the above solution, optionally, a plurality of filter capacitors are connected to ground before and after the output node between the filter inductor L5 and the driving end of the fan.

[0016] In the above solution, optionally, the model of the DC-DC chip is MT3571.

[0017] Compared with the prior art, this application has at least the following beneficial effects:

[0018] Based on further analysis and research of the prior art problems, the present application recognizes that the methods of adjusting the speed of a fan by changing its voltage in the prior art often have the disadvantages of complex circuits, high costs, and difficulty in obtaining materials. At the same time, some solutions fail to fully consider the stability and reliability in practical applications, affecting the user experience. By using a feedback resistor in the input circuit, the output voltage range of the circuit can be adjusted by adjusting the feedback resistor. Since different application scenarios may require different air volumes, the feedback resistor allows the user to adjust the output voltage range according to the actual situation, thereby changing the fan speed to meet the needs of various environments. Through independent input circuits and enable circuits, the power supply can be independently controlled to be turned on and off. Even if the power supply is connected, the fan can be started or stopped by controlling the enable signal, increasing the flexibility of control. By using an integral circuit in the voltage regulation circuit, the integral circuit can smooth the PWM signal, so that the fan speed changes more gradually rather than abruptly, which not only reduces noise but also improves the user experience. In the voltage regulation circuit, by using two or more voltage regulation resistors, the voltage divider ratio in the feedback circuit can be adjusted more finely, thereby achieving more accurate and smooth control of the fan speed.

[0019] In the solution provided by the present application, the fan speed can be flexibly adjusted according to the needs of the actual application scenario, thereby achieving the effect of reducing noise, reducing energy consumption, and controlling heat, thereby improving the overall performance of the product and user satisfaction. At the same time, the electronic components selected by the present invention are all common materials in the market, which are easy to purchase and are conducive to large-scale production and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A circuit diagram of a fan voltage regulation circuit provided in accordance with an embodiment of the present application. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0022] In the description of this application: unless otherwise specified, the meaning of "plurality" is two or more. The terms "first", "second", "third", etc. in this application are intended to distinguish the objects referred to, and do not have special meanings in terms of technical connotations (for example, they should not be understood as emphasizing the importance or order, etc.). Expressions such as "including", "comprising", "having", etc. also mean "not limited to" (certain units, components, materials, steps, etc.).

[0023] In one embodiment, Figure 1As shown, a fan voltage regulation circuit is provided, comprising: a DC voltage source, an enabling circuit, a DC-DC chip, a voltage regulation circuit and a feedback circuit; wherein,

[0024] The DC voltage source is connected to the input pin of the DC-DC chip;

[0025] The enabling circuit includes a switch signal ON / OFF and a second resistor R50; the switch signal ON / OFF is connected to the enabling pin of the DC-DC chip via the second resistor R50;

[0026] The output pin of the DC-DC chip is connected to the drive end of the fan through the filter inductor L5;

[0027] The bootstrap pin of the DC-DC chip is connected to the node between the output pin of the DC-DC chip and the filter inductor L5 via the bootstrap capacitor C52;

[0028] The feedback circuit includes a third resistor R48, a fourth resistor R56 and an RC circuit; wherein the feedback pin of the DC-DC chip is connected to ground via the third resistor R48 and the fourth resistor R56 in sequence; one end of the RC circuit is connected to the output node between the filter inductor L5 and the drive end of the fan, and the other end is connected to the node between the third resistor R48 and the fourth resistor R56;

[0029] The voltage regulating circuit includes a PWM signal source, an integration circuit, a first voltage regulating resistor R49 and a second voltage regulating resistor R57; the PWM signal source is connected to the node between the third resistor R48 and the fourth resistor R56 via the integration circuit, the first voltage regulating resistor R49 and the second voltage regulating resistor R57 in sequence; the output voltage of the fan voltage regulating circuit is adjusted by adjusting the duty cycle of the PWM signal.

[0030] In one embodiment, a third capacitor C47 is connected to ground at a node between the second resistor R50 and the enable pin of the DC-DC chip to smooth the signal and prevent the switch from being triggered by an external interference signal.

[0031] In one embodiment, a filter capacitor is connected to ground at a node between the DC voltage source and an input pin of the DC-DC chip.

[0032] In one embodiment, a plurality of filter capacitors are connected to ground before and after the output node between the filter inductor L5 and the driving end of the fan.

[0033] In one embodiment, the model of the DC-DC chip is MT3571.

[0034] The circuit provided in this embodiment can realize the following functions: (1) Autonomous switch enable. When it is necessary to turn on or off, it can be realized by simply pulling up or pulling down the enable pin. (2) Output voltage regulation function. The output voltage can be achieved by adjusting the PWM duty cycle of the external IO port. When a specific voltage is required, it only needs to be adjusted to the corresponding duty cycle. (3) The output voltage range can be adjusted by adjusting the feedback resistor.

[0035] In this embodiment, by using a feedback resistor at the input end, the output voltage range of the circuit can be adjusted by adjusting the feedback resistor. Different application scenarios may require different air volumes. The feedback resistor allows the user to adjust the output voltage range according to actual conditions, thereby changing the fan speed to meet the needs of various environments. For example, in an environment with high silent requirements, a lower speed can be selected; and in the case of high heat dissipation requirements, the speed can be increased. When the input voltage rises abnormally, the feedback resistor can help limit the maximum current flowing into the DC-DC chip, play a certain protective role, and ensure the safe operation of the circuit. For manufacturers, using feedback resistors to set the output voltage is a cost-effective method because it does not require additional complex circuit design and can provide sufficient adjustment flexibility.

[0036] In this embodiment, by controlling the enable terminal and the input terminal of the DC-DC chip separately, the power supply can be independently controlled to be turned on and off. Even if the power supply is connected, the fan can be started or stopped by controlling the enable signal, thereby increasing the flexibility of control. By controlling the enable terminal and the input terminal of the DC-DC chip separately, it is possible to accurately control when power is supplied to the DC-DC converter, thereby avoiding unnecessary energy consumption. When the fan is not needed to run, the operation of the DC-DC chip can be directly cut off by pulling down the enable pin, thereby reducing standby power consumption. Since the enable terminal can be controlled separately, the fan can be kept out of operation at the moment of power-on or when the voltage is unstable until the conditions are suitable for restarting, which helps prevent excessive startup current or other potential problems.

[0037] In this embodiment, by using an integral circuit in the voltage regulation circuit, the integral circuit can smooth the PWM signal so that the fan speed change is more gradual rather than abrupt, which not only reduces noise but also improves the user experience. Especially in environments such as bedrooms or offices, smooth speed transition is very important. Through filtering, the integral circuit ensures the stability of the output voltage and maintains the accuracy of the fan speed even when the load changes rapidly. This is especially important for applications that require precise temperature control, such as precision instrument cooling, data center thermal management, etc. The improved dynamic response characteristics mean that the fan can react faster to changes in ambient temperature and adjust to the required speed in time, improving the efficiency and performance of the overall system.

[0038] In addition, in the voltage regulating circuit, the present application also uses multiple voltage regulating resistors. In fan applications, accurate control of fan speed is essential for optimizing heat dissipation and reducing noise. By using two or more voltage regulating resistors (in some embodiments, users can use multiple voltage regulating resistors as needed), the voltage divider ratio in the feedback circuit can be adjusted more finely, thereby achieving more accurate and smooth control of the fan speed. Multiple voltage regulating resistors allow the output voltage to vary over a wider range, which means that the fan can operate in a wider range of speeds. This provides users with more options and can flexibly adjust the working state of the fan according to different application scenarios (such as from silent mode to high-performance cooling mode). Stable voltage output is directly related to the smooth operation of the fan motor, reducing mechanical wear and power loss, thereby extending the service life of the fan. During the production process, engineers can calibrate the product by simply adjusting the value of one or more voltage regulating resistors without complex hardware modifications. This flexibility reduces production costs and simplifies the later maintenance process. In addition, if a resistor is damaged, only the component needs to be replaced without replacing the entire circuit board.

[0039] In one embodiment, the DCDC chip MT3571 is used as the core. MT3571 is a synchronous buck chip with wide voltage input, supporting 4.7V-18V input and 0.8-12V output. It supports 100% duty cycle output. The input voltage is 12V, which is input to the DCDC pin 3 through the FB1 / 0R resistor. C41 and C42 are used as filter capacitors to provide a stable input voltage for the DCDC. The switch signal ON / OFF is given to the pin 5 through the resistor R50, and C47 plays the role of smoothing the signal to prevent the external interference signal from triggering the switch by mistake. Pin 2 is the output pin. The MOS tube inside the DCDC generates a PWM signal and outputs it to L5 through pin 2. L5 is a filter inductor. Here, the principle that the current in the inductor does not change suddenly is used to convert the unstable current into a stable current and give it to the filter capacitors C43, C44, C25, C26 and C27 at the back end. C43, C44, C25, C26 and C27 play the role of filtering out clutter and stabilizing the voltage. C52 is a bootstrap capacitor that provides driving voltage for the high-side MOS inside the DCDC. Pin 1 is the ground pin. Pin 4 is the feedback pin. The filtered voltage is divided by R54 and R56 and then given to R48, and then to pin 4. After passing through the internal comparator, the output duty cycle is adjusted, and then the output voltage is adjusted.

[0040] FAN1_PWM is a PWM pulse signal provided by the external IO. In this method, a 3.3V amplitude PWM signal is used, and the duty cycle adjustment range is 0-100%. R58 and C51 form an integration circuit, and the external PWM becomes a stable DC signal after passing through the integration circuit. R49 and R57 play the role of adjusting the output voltage range.

[0041] CN3 and CN6 are fan sockets that provide interfaces for fans.

[0042] In this embodiment, when the EN pin is at a low level, the circuit does not work, and the output voltage is 0. When the EN pin is at a high level, the circuit works, and the output voltage is determined by the feedback loop and the regulation loop.

[0043] Output voltage calculation:

[0044] Assume that the voltage of the pulse signal input by the PWM signal source FAN1_PWM is Vdac, and the output voltage is Vout (i.e., the voltage at the output node, Figure 1 The node marked as FAN_AVCC), the voltage at the feedback pin is VFB, the current flowing through the resistor R54 is I1, the current of the voltage regulator circuit is If, and the current passing through the resistor R56 is I2, then the following calculation formula is obtained:

[0045] I1=(Vout-VFB) / R54

[0046] If=(Vdac-VFB) / Rf

[0047] Rf=R58+R49+R57

[0048] I2=I1+If

[0049] I2=VFB / R56

[0050] After sorting out:

[0051] Vout=VFB(1+R54 / R56)-(Vdac-VFB)*R54 / Rf

[0052] Will Figure 1 Substitute the values ​​in into the formula after sorting:

[0053] Vout=VFB(1+R54 / R56)-(Vdac-VFB)*R54 / Rf

[0054] =0.8(1+62 / 5.1)-(Vdac-0.8)*62 / 28

[0055] =12.3-2.214*Vdac

[0056] When Vdac=0, Vout=12.3V;

[0057] When Vdac=3.3V, Vout=5.0V.

[0058] It can be concluded that when the duty cycle changes from 0 to 100%, the fan output voltage changes between 12V and 5.0V, thus realizing the voltage regulation function. When a given output voltage is required, it is only necessary to reversely calculate the corresponding Vdac through the formula to obtain the duty cycle, and then write the duty cycle.

[0059] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A fan voltage regulation circuit, characterized in that: include: A DC voltage source, an enabling circuit, a DC-DC chip, a voltage regulating circuit and a feedback circuit; wherein, The DC voltage source is connected to the input pin of the DC-DC chip; The enabling circuit includes a switch signal ON / OFF and a second resistor R50; the switch signal ON / OFF is connected to the enabling pin of the DC-DC chip via the second resistor R50; The output pin of the DC-DC chip is connected to the drive end of the fan through the filter inductor L5; The bootstrap pin of the DC-DC chip is connected to the node between the output pin of the DC-DC chip and the filter inductor L5 via the bootstrap capacitor C52; The feedback circuit includes a third resistor R48, a fourth resistor R56 and an RC circuit; wherein the feedback pin of the DC-DC chip is connected to the ground via the third resistor R48 and the fourth resistor R56 in sequence; one end of the RC circuit is connected to the output node between the filter inductor L5 and the driving end of the fan, and the other end is connected to the node between the third resistor R48 and the fourth resistor R56; The voltage regulating circuit includes a PWM signal source, an integration circuit, a first voltage regulating resistor R49 and a second voltage regulating resistor R57; the PWM signal source is connected to the node between the third resistor R48 and the fourth resistor R56 via the integration circuit, the first voltage regulating resistor R49 and the second voltage regulating resistor R57 in sequence; the output voltage of the fan voltage regulating circuit is adjusted by adjusting the duty cycle of the PWM signal.

2. The fan voltage regulation circuit according to claim 1, characterized in that: A third capacitor C47 is connected to ground at a node between the second resistor R50 and the enable pin of the DC-DC chip to smooth the signal and prevent the switch from being triggered by an external interference signal.

3. The fan voltage regulation circuit according to claim 1, characterized in that: A filter capacitor is connected to ground at a junction between the DC voltage source and the input pin of the DC-DC chip.

4. The fan voltage regulation circuit according to claim 1, characterized in that: A plurality of filter capacitors are connected to ground before and after the output node between the filter inductor L5 and the driving end of the fan.

5. The fan voltage regulation circuit according to claim 1, characterized in that: The model of the DC-DC chip is MT3571.

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