JP2017118018A - Fan controller and control method and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce discrete frequency noise (DTN).SOLUTION: An embedded controller 30 controls the fan of a heat radiation unit. The embedded controller 30 includes a number of revolution setting section 32 for acquiring the temperatures detected by temperature sensors 50a-50d for detecting the temperature in an information processing unit, and setting the number of revolutions of the fan based on these temperatures, and a number of revolution varying section 33 for periodically varying the number of revolutions set by the number of revolution setting section 32.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a fan control device, a control method, and an electronic apparatus.

  Electronic devices such as notebook personal computers (hereinafter referred to as “notebook PCs”), workstations, servers, and the like are equipped with fans for discharging heat generated from devices housed in a casing ( For example, see Patent Document 1).

JP 2014-42385 A

  In an electronic device equipped with a fan, discrete frequency noise (Discrete Tone Noise) in which a noise level protruding in a specific frequency component appears may occur. It is desirable to remove discrete frequency noise (hereinafter referred to as “DTN”) as much as possible in order to generate an annoying sound such as a high-pitched beep. However, DTN is often generated by complicatedly intertwining many factors such as fan intake / exhaust, internal turbulence, and manufacturing variations. For this reason, it is difficult to specify the cause and it is difficult to reduce noise.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fan control device, a control method, and an electronic apparatus that can reduce discrete frequency noise (DTN).

  A first aspect of the present invention is a fan control device mounted on an electronic device, the rotation number setting unit for setting the rotation number of the fan based on the temperature in the electronic device, and the rotation number setting unit Is a fan control device that includes a rotation speed changing section that periodically changes the rotation speed set by.

  A second aspect of the present invention is an electronic device including a fan and the fan control device.

  A third aspect of the present invention is a method for controlling a fan mounted on an electronic device, wherein the number of rotations of the fan is set based on the temperature in the electronic device, and the set number of rotations is periodically changed. This is a fan control method.

  FIG. 9 shows an example of discrete frequency noise (DTN). In FIG. 9, the horizontal axis represents the frequency, the vertical axis represents the noise level, the broken line represents the low rotational speed, the thick solid line represents the medium rotational speed, and the alternate long and short dash line represents the high rotational speed characteristic. As shown by the arrows in FIG. 9, it can be seen that DTN appears in a specific frequency component. As the rotational speed increases, the DTN peak increases and the number of appearances increases. Further, if the rotation speed is different, the frequency at which DTN appears also changes.

The inventors paid attention to the fact that the frequency component at which DTN appears varies with the number of rotations. That is, by periodically changing the rotation speed, the frequency component generated by DTN can be periodically changed as shown in FIG. Thereby, as shown in FIG.6 (c), the bandwidth of DTN can be expanded and it becomes possible to bury DTN in a surrounding sound. As a result, it is possible to remove or reduce the annoying sound of a high-pitched beep.
In the present invention, “periodic” does not mean only a certain period. In other words, “periodic” is only required to repeatedly realize fluctuations in the rotational speed, and the fluctuation period at this time is not necessarily constant. In addition, “periodic” includes a meaning that is repeated intermittently.

  According to the present invention, there is an effect that discrete frequency noise (DTN) can be reduced.

It is the top view which showed typically the inside of the housing | casing of the information processing apparatus which concerns on one Embodiment of this invention. It is a top view of the thermal radiation unit shown in FIG. It is a schematic block diagram of the fan control apparatus which concerns on one Embodiment of this invention. It is a functional block diagram of the control apparatus of the fan which concerns on one Embodiment of this invention. It is the flowchart which showed the procedure of the rotation speed control of the fan which concerns on one Embodiment of this invention. It is explanatory drawing for demonstrating the effect by the control apparatus of the fan which concerns on one Embodiment of this invention. It is the figure which compared and showed the measurement result of the noise level when not changing the rotation speed of a fan, and when changing the rotation speed of a fan. It is the figure which expanded and showed the frequency band of 3500 Hz to 5000 Hz in FIG. It is the figure which showed an example of the discrete frequency noise (DTN).

  Hereinafter, an embodiment of a fan control device, a control method, and an electronic apparatus according to the present invention will be described with reference to the drawings. In the present embodiment, the information processing apparatus 10 such as a notebook PC will be described as an example of one aspect of the electronic device, but the application example of the present invention is not limited to this aspect.

  FIG. 1 is a plan view schematically showing the inside of the housing of the information processing apparatus 10. Inside the housing of the information processing apparatus 10, a CPU 11, a heat radiating unit 12, a mother board (not shown) on which a large number of electronic components and the like are mounted are arranged. FIG. 2 is a plan view of the heat dissipation unit 12. As shown in FIG. 2, the heat dissipation unit 12 includes, for example, a fan 13 and heat sinks 14a and 14b. The fan 13 is a centrifugal fan, for example, and houses a plurality of blades attached to the shaft of the fan motor 21 (see FIG. 3) in a thin chamber.

The heat sinks 14a, 14b are directly attached to the chamber so that their positions are aligned with the openings formed in the side surfaces of the chamber. When the fan 13 rotates, the heat dissipating unit 12 passes the air between the plurality of fins of the heat sinks 14a and 14b and discharges the ambient air taken in from the suction ports formed on the upper and lower surfaces of the chamber. Exchange.
The air exhausted by the heat dissipation unit 12 is released from an exhaust port formed on the side surface of the housing. In addition, an air inlet (not shown) for taking in ambient air is formed in the housing.

  The CPU 11 is a processor that executes an application program and performs general processing. Each of the CPUs 11 is thermally coupled to a heat receiving plate 15 provided on the lower surface. The heat receiving plate 15 and the heat sinks 14a and 14b are thermally coupled by the two heat pipes 16a and 16b.

  Temperature sensors 50a to 50d are arranged in the housing. The positions and the number of the temperature sensors 50a to 50d are an example, and the present invention is not limited to this example. The temperature detected by each of the temperature sensors 50a to 50d is used for controlling the heat dissipation unit 12 for monitoring the temperature of the corresponding device or maintaining the surface temperature of the housing within a predetermined value.

  FIG. 3 is a schematic configuration diagram illustrating an example of a fan control device in the information processing apparatus 10. As shown in FIG. 3, the fan control device includes a motor drive unit 20 and an embedded controller (control unit) 30.

The motor drive unit 20 includes an inverter 22 and a control unit 23 for supplying a desired voltage to the fan motor 21.
The fan motor 21 is a DC motor such as a three-phase DC brushless motor. The inverter 22 has a configuration in which, for example, six switching elements (eg, FET, IGBT, etc.) are bridge-connected. The control unit 23 controls on / off of each switching element included in the inverter 22 based on a control signal input from an embedded controller (hereinafter referred to as “EC”) 30, for example, a PWM control signal. As a result, a voltage controlled to a desired voltage value is supplied to the fan motor 21, and the fan motor 21 can be driven at a desired rotational speed. The control unit 23 stores various data such as a fan ID, detects the rotational speed of the fan motor 21, and outputs the detected rotational speed to the EC 30.

  The EC 30 is a microcomputer that includes, for example, a CPU, a ROM that stores firmware, and a RAM that executes the firmware. Further, the EC 30 includes a plurality of A / D input terminals, a plurality of D / A output terminals, a timer, a digital input / output terminal, and the like. The EC 30 is connected to the motor drive unit 20 and the temperature sensors 50 a to 50 d via their input / output terminals, and executes a program related to the management of the internal operating environment of the information processing apparatus 10 independently of the CPU 11. be able to.

  FIG. 4 is a functional block diagram showing functions realized by the EC 30 and the motor driving unit 20. As shown in FIG. 4, the EC 30 periodically stores the rotational speed set by the storage section 31, the rotational speed setting section 32 that sets the rotational speed of the fan based on the temperature in the electronic device, and the rotational speed setting section 32. The main component is provided with a rotation speed fluctuation portion 33 that fluctuates in the following manner. The functions of these units are mainly realized by the CPU included in the EC 30 executing a rotation control program stored in the ROM.

The storage unit 31 stores various information such as temperature-rotation number information in which the temperature and the rotation number are associated, a fluctuation range of the rotation number, and a fluctuation frequency. A method for determining the fluctuation range and fluctuation frequency of the rotational speed will be described later.
The rotational speed setting unit 32 refers to the temperature detected by the temperature sensors 50a to 50d and the temperature-rotational speed information stored in the storage unit 31, and sets and sets the rotational speed according to the current temperature state. The rotation speed is output to the rotation speed fluctuation unit 33. For example, the rotation speed setting unit 32 calculates the average value of the temperatures detected by the temperature sensors 50a to 50d, acquires the rotation speed corresponding to the average value from the temperature-rotation speed information, and sets the rotation speed. In addition, instead of the average value, weighting coefficients corresponding to the highest temperature or the lowest temperature of the received detection temperatures or the arrangement positions of the temperature sensors 50a to 50d are set in advance, and these weighting coefficients are set. The rotation speed may be set using a weighted average using. Further, in the case of more complex rotation speed control, for example, as disclosed in JP 2014-42385 A, a thermal action table (TAT) is prepared and based on this table. It is good also as setting rotation speed. Thus, in this embodiment, the method for setting the number of rotations from the temperature is not particularly limited, and a known method can be applied.

  The rotation speed variation unit 33 generates a variation control signal in which the rotation number input from the rotation number setting unit 32 is varied with the variation frequency and variation range stored in the storage unit 31, and the variation control signal is generated by the motor drive unit. 20 is output. For example, the rotation speed variation section 33 generates a PWM signal corresponding to the rotation speed input from the rotation speed setting section 32, and the duty of this PWM signal varies with the variation frequency and variation width stored in the storage section 31. The generated fluctuation PWM signal is generated, and the fluctuation PWM signal is output to the motor drive unit 20.

Next, a method for determining the fluctuation frequency and fluctuation width stored in advance in the storage unit 31 will be described.
For example, the fluctuation frequency needs to be set to a period at which a person does not perceive the influence of the fluctuation. The faster the fluctuation frequency, the harder it is for humans to perceive the fluctuation. Therefore, the lower limit value of the fluctuation frequency is determined by, for example, human perception ability. On the other hand, the upper limit value of the fluctuation frequency cannot be a value larger than the carrier frequency of the employed rotational speed control, for example, PWM control. From the above, the fluctuation frequency is set to an arbitrary value within a range not less than a frequency at which a person cannot perceive fluctuation and less than a carrier frequency of PWM control. For example, the variation frequency is set to an arbitrary value within a range of 0.05 Hz to 5 Hz, and an example is 0.5 Hz.

  It can be said that the greater the fluctuation range, the greater the effect of reducing discrete frequency noise (DTN). Therefore, the fluctuation range is preferably set to a large value. On the other hand, the rotation speed range that can be varied at the variation frequency is finite due to the performance of the fan motor 21 and its peripheral devices. Therefore, the fluctuation range may be determined from the performance of the fan motor 21 and the like and the fluctuation frequency. For example, when a fan whose upper limit of the change speed of the rotational speed is 500 rpm / sec is employed, when the fluctuation frequency is set to 0.5 Hz, the fluctuation width is set to ± 250 rpm at the maximum.

Here, the fluctuation range may be registered as the rotation speed, that is, the rotation speed fluctuation width, or may be registered as the duty, that is, registered as the duty fluctuation width. When the rotation speed fluctuation range is registered, the rotation speed fluctuation section 33 generates a fluctuation PWM signal for changing the rotation speed from the rotation speed setting section 32 by the rotation speed fluctuation width.
If the duty fluctuation width is registered, a PWM signal corresponding to the rotation speed from the rotation speed setting unit 32 is generated, and a fluctuation PWM signal is generated by changing the PWM signal with the duty fluctuation width.

  Next, the procedure for controlling the rotational speed of the fan according to the present embodiment will be described with reference to FIG. FIG. 5 is a flowchart showing a procedure for controlling the rotational speed of the fan according to the present embodiment. The fan control device repeatedly executes the following processing at a predetermined sampling period.

  First, at startup, the EC 30 acquires a fan ID from the motor drive unit 20 (step SA1). Subsequently, the temperature is measured by the temperature sensors 50a to 50d, and temperature information is input to the EC 30 (step SA2). The rotational speed setting unit 32 sets the rotational speed using the input temperature and the temperature-rotational speed information in the storage unit 31 (step SA3). Thereby, the rotation speed according to the temperature environment in the information processing apparatus 10 is determined.

  Subsequently, the rotation speed fluctuation unit 33 uses the fluctuation frequency and fluctuation width stored in the storage unit 31 and the rotation speed of the fan motor 21 fed back from the motor drive unit 20 to determine the rotation speed of the fan motor 21. A fluctuation PWM signal for fluctuating at a predetermined fluctuation frequency and fluctuation width is generated (step SA4). Thereby, the fluctuation PWM signal becomes a PWM signal whose duty fluctuates periodically. The rotation speed variation unit 33 outputs the generated variation PWM signal to the motor drive unit 20 (step SA5).

  The motor drive unit 20 drives the inverter 22 based on the fluctuation PWM signal from the EC 30. Specifically, on / off of each switching element provided in the inverter 22 is controlled based on the duty of the variable PWM signal (step SA6). As a result, the voltage supplied to the fan motor 21 fluctuates periodically, and the rotational speed of the fan 13 fluctuates periodically.

  As described above, according to the fan control device, the control method, and the electronic apparatus according to the present embodiment, the rotational speed is set based on the temperatures detected by the temperature sensors 50a to 50d, and the rotational speed is varied. Such a fluctuation PWM signal is generated, and the motor drive unit 20 is driven based on the fluctuation PWM signal. Thereby, it becomes possible to change the rotation speed of the fan motor 21 periodically. For example, the rotational speed of the fan motor 21 can be varied with a predetermined fluctuation range around the rotational speed corresponding to the temperature detected by the temperature sensors 50a to 50d. Further, the fluctuation cycle at this time is a fluctuation frequency stored in the storage unit 31.

  In this way, by periodically changing the rotation speed of the fan, as shown in FIG. 6A, DTN that has conventionally appeared in a specific frequency component is shown in FIG. 6B. In addition, it is possible to periodically vary the frequency component generated by DTN. Thereby, as shown in FIG.6 (c), the bandwidth of DTN can be expanded and it becomes possible to bury DTN in a surrounding sound. As a result, it is possible to remove or reduce the annoying sound of a high-pitched beep.

  FIG. 7 is a diagram comparing the measurement results of the noise level when the fan speed is not changed and when the fan speed is changed, and FIG. 8 is a graph of 3500 Hz to 5000 Hz in FIG. It is the figure which expanded and showed the frequency band. 7 and 8, the horizontal axis represents frequency and the vertical axis represents noise level. 7 and 8, the broken line indicates the measurement result of the noise level when the fan motor 21 is driven with a duty of 75%, and the solid line indicates the duty with a fluctuation period of 0.5 Hz and a duty fluctuation width of 15 with a duty of 75%. The measurement result of the noise level when fluctuating by% is shown. As shown in FIGS. 7 and 8, it can be seen that DTN is substantially removed by changing the rotational speed.

  As mentioned above, although this invention was demonstrated using the said embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various changes or improvements can be added to the above-described embodiment without departing from the gist of the invention, and embodiments to which the changes or improvements are added are also included in the technical scope of the present invention.

  For example, as shown in FIG. 9, when the rotation speed is low, DTN does not occur so much. Therefore, for example, when the rotation speed at which DTN starts to occur is registered in advance as a threshold value, and the rotation speed set by the rotation speed setting unit 32 is equal to or greater than the threshold value, the rotation speed fluctuation by the rotation speed fluctuation unit 33 is changed. It may be carried out.

  Moreover, in the said embodiment, although the aspect which registers the fluctuation range and fluctuation frequency corresponding to one fan 13 in the memory | storage part 31 was described, for example, in order to apply to multiple types of fans 13, the following It is good also as a structure. For example, the fluctuation range and the fluctuation frequency are registered for each fan ID or fan type, and the corresponding fluctuation range and fluctuation frequency are extracted and extracted based on the fan ID acquired from the motor drive unit 20 at the time of startup. It is good also as changing the rotation speed of a fan using a fluctuation range and a fluctuation frequency.

  Furthermore, the fluctuation range and the fluctuation frequency may be set according to the rotation speed. For example, the storage unit 31 stores a fluctuation range and a fluctuation frequency for each fan ID and each rotation speed, the rotation speed fluctuation unit 33 is associated with the corresponding fan ID, and the rotation speed. The fluctuation range and fluctuation frequency corresponding to the rotation speed set by the setting unit 32 may be read from the storage unit 31 and the duty of the PWM signal may be changed using the read fluctuation width and fluctuation frequency.

10 Information processing equipment (electronic equipment)
12 Heat Dissipation Unit 13 Fan 20 Motor Drive Unit 21 Fan Motor 30 Embedded Controller (Control Unit)
31 Storage Unit 32 Rotational Speed Setting Unit 33 Rotational Speed Variation Units 50a to 50d Temperature Sensor

Claims (7)

A control device for a fan mounted on an electronic device,
A rotational speed setting unit that sets the rotational speed of the fan based on the temperature in the electronic device;
A fan control device comprising: a rotation speed variation section that periodically varies the rotation speed set by the rotation speed setting section.   2. The fan control device according to claim 1, wherein the rotation speed changing section changes the rotation speed set by the rotation speed setting section with a preset fluctuation range and a preset fluctuation frequency.   The fan control device according to claim 2, wherein the fluctuation frequency is set within a range of 0.05 Hz or more and less than a control frequency of the fan rotation speed control.   The rotation speed variation section periodically varies the rotation speed set by the rotation speed setting section when the rotation speed set by the rotation speed setting section is greater than or equal to a preset threshold value. The fan control device according to any one of claims 1 to 3. A motor drive unit for driving the fan motor;
The motor driving unit includes an inverter including a switching element,
The rotation speed fluctuation unit generates a fluctuation PWM signal in which the duty according to the rotation speed set by the rotation speed setting unit is periodically fluctuated,
5. The fan control device according to claim 1, wherein the motor driving unit drives the inverter based on a fluctuation PWM signal output from the rotation speed fluctuation unit. With fans,
The fan control device according to any one of claims 1 to 5,
Electronic equipment comprising. A method for controlling a fan mounted on an electronic device,
Set the rotation speed of the fan based on the temperature in the electronic device,
A fan control method that periodically changes the set rotation speed.

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