Method for inspecting a fan control board, and the fan control board

Abstract

To provide an inspection method of a fan control board capable of self-diagnosing an abnormality detection function of a PWM control fan.SOLUTION: An inspection method is for a fan control board 2 including: an output terminal 12 for outputting a PWM signal to a PWM control fan 4; and an input terminal 13 to which a rotational speed signal output from the PWM control fan 4 is input. The output terminal 12 and the input terminal 13 are directly connected with each other without the PWM control fan 4 and self-diagnosis is executed by an answer signal input to the input terminal 13 when an inspecting signal simulating the rotational speed signal is output from the output terminal 12.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an inspection method for a fan control board and a fan control board.

Background Art

[0002] Regarding the air cooling mechanism of electronic devices, PWM control fans with variable rotation speeds are widely used. The PWM control fan is driven at a rotation speed corresponding to the duty of the PWM signal input from the control board, for example, by being connected to the control board for controlling the electronic device, and outputs a rotation speed signal to the control board. Therefore, the control board of the electronic device can control the PWM control fan as a fan control board and can also grasp the driving state of the PWM control fan.

[0003] In addition, the fan control board as described above can diagnose a failure of the PWM control fan during operation by monitoring the deviation between the rotation speed signal input from the PWM control fan and the control signal output to the PWM control fan (see, for example, Patent Document 1). At this time, the fan control board has an abnormality detection function capable of detecting abnormalities including not only internal failures of the PWM control fan itself but also defects in the communication path between the PWM control fan, such as problems with the wiring or connector pins connecting the two.

[0004] By the way, the fan control board as described above is subjected to board inspection as quality control at the stage when the board alone is manufactured before the assembly process of connecting the PWM control fan and other control targets. In the board inspection, for example, by being connected to a general-purpose terminal such as a PC, it is confirmed whether each internal function operates normally and whether an appropriate abnormality determination can be made for an input of an abnormal signal.

[0005] In the inspection of the circuit board, when diagnosing the abnormality detection function of the PWM-controlled fan, one possible method is to connect a test PWM-controlled fan to the fan control board in the same manner as during operation, and then determine whether abnormality detection is possible when the drive of the test PWM-controlled fan is physically stopped. Alternatively, one possible method is to connect a test signal generator to the fan control board, generate normal and abnormal rotation speed signals respectively, and then determine whether abnormality detection is possible when these signals are input to the fan control board. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2021-60787 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, in circuit board testing that physically stops a PWM-controlled fan, a dedicated PWM-controlled fan is required even though the test is of the circuit board alone. Furthermore, it may become impossible to finely adjust the rotation speed signal input to the fan control board, potentially resulting in inaccurate testing. Additionally, in circuit board testing that uses a dedicated signal generator, it becomes necessary to permanently install the signal generator as a dedicated testing terminal.

[0008] The present invention has been made based on the above circumstances, and its objective is to provide a method for inspecting a fan control board that can self-diagnose the abnormality detection function for a PWM-controlled fan, and a fan control board. [Means for solving the problem]

[0009] To achieve the above objective, the fan control board inspection method according to the present invention is an inspection method for a fan control board comprising an output terminal that outputs a PWM signal to a PWM control fan and an input terminal to which a rotation speed signal output from the PWM control fan is input, wherein the output terminal and the input terminal are directly connected without going through the PWM control fan, and self-diagnosis is performed by a response signal input to the input terminal when an inspection signal that mimics the rotation speed signal is output from the output terminal.

[0010] Furthermore, in order to achieve the above objective, the fan control board according to the present invention comprises an output terminal that outputs a PWM signal to a PWM-controlled fan, an input terminal to which a rotational speed signal output from the PWM-controlled fan is input, and a control device that transmits the PWM signal via the output terminal and controls the PWM-controlled fan by receiving the rotational speed signal via the input terminal, wherein the control device performs a self-diagnosis based on a response signal input to the input terminal when an inspection signal mimicking the rotational speed signal is output from the output terminal while the output terminal and the input terminal are directly connected without going through the PWM-controlled fan. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a method for inspecting a fan control board that enables self-diagnosis of the abnormality detection function for a PWM-controlled fan, and a fan control board itself. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram of a battery backup unit using a fan control board. [Figure 2] This is a diagram showing the connection configuration of the fan control board used in circuit board inspection. [Figure 3] This is a flowchart illustrating the inspection method according to the first embodiment. [Figure 4] This is a flowchart illustrating the inspection method according to the second embodiment. [Figure 5]This graph shows the characteristics of a PWM-controlled fan connected to a fan control board according to the third embodiment. [Modes for carrying out the invention]

[0013] The embodiments will be described in detail below with reference to the drawings. However, this disclosure is not limited to the content described below, and can be modified and implemented as such without altering its essence. Furthermore, the drawings used in describing the embodiments are schematic representations of the components, and may have been partially emphasized, enlarged, reduced, or omitted to enhance understanding, and may not accurately represent the scale or shape of the components.

[0014] Figure 1 is a schematic diagram of a battery backup unit (BBU) using a fan control board 2. Here, an example is shown in which the fan control board 2 is used as a control mechanism for the BBU, but the fan control board 2 according to this disclosure may be used in other electronic devices as long as it is a control board for controlling an air cooling fan.

[0015] The battery backup unit 1 is a power supply device that supplies power to the load from a pre-charged secondary battery to continue operation even in the event of a power outage, and its main components include a fan control board 2, a battery module 3, and a PWM-controlled fan 4.

[0016] In this embodiment, the fan control board 2 functions as a control board for controlling the battery module 3 and also has the function of controlling the PWM-controlled fan 4. The control device 10 performs these functions and provides overall control of the battery backup unit 1. Here, the control device 10 is, for example, a known microcontroller control circuit and is mounted on the fan control board 2 as one of the mounted components.

[0017] The fan control board 2 is provided with a battery connection part 11, an output terminal 12, an input terminal 13, and a PC connection part 14 used during the substrate inspection described later. In addition, other electronic components (not shown) are also mounted on the fan control board 2.

[0018] The battery module 3 includes, for example, a battery pack capable of supplying power during a power outage. The battery module 3 can perform two-way communication with the fan control board 2 via the battery connection part 11, transmit the voltage and temperature of the internal battery pack to the fan control board 2, and is charge-discharge controlled by the fan control board 2.

[0019] The PWM control fan 4 is an air-cooling fan for cooling the fan control board 2 that generates heat as the battery backup unit 1 operates. The PWM control fan 4 is driven at a rotational speed N corresponding to the duty of the PWM signal input from the fan control board 2 via the output terminal 12. That is, the fan control board 2 can change the rotational speed N of the PWM control fan 4 by adjusting the duty of the PWM signal. In addition, the PWM control fan 4 may be used for cooling the battery module 3.

[0020] The PWM control fan 4 outputs a rotational speed signal to the fan control board 2 via the input terminal 13. Here, the rotational speed signal is expressed as a voltage corresponding to the rotational speed N of the PWM control fan 4. For this reason, the fan control board 2 can grasp the driving state of the PWM control fan 4 by calculating the rotational speed N of the PWM control fan 4 based on the voltage of the input terminal 13. Then, the fan control board 2 can detect an abnormality of the PWM control fan 4 during operation by monitoring the deviation of the rotational speed information between the rotational speed signal input from the PWM control fan 4 and the PWM signal output to the PWM control fan 4.

[0021] Next, we will explain the board inspection of the fan control board 2. The fan control board 2 is inspected when it is manufactured as a standalone board, before the PWM-controlled fan 4 and other components are attached. Below, we will explain the procedure for diagnosing the abnormality detection function of the fan control board 2 in response to input signals from the PWM-controlled fan 4, as part of this board inspection.

[0022] Figure 2 is a diagram showing the connection configuration of the fan control board 2 during board inspection. In this embodiment, the fan control board 2 is connected to a general-purpose terminal 5 via a PC connection unit 14 during board inspection. Here, the general-purpose terminal 5 is, for example, a known PC (Personal Computer) and can perform bidirectional communication with the fan control board 2. The board inspection may be performed on an application executed by the general-purpose terminal 5.

[0023] Furthermore, the board inspection of the fan control board 2 is performed with the output terminal 12 and the input terminal 13 directly connected by wiring 6, without going through the PWM-controlled fan 4 described above. Below, the inspection method for the fan control board 2 according to this disclosure will be described with examples of several embodiments.

[0024] <First Embodiment> Figure 3 is a flowchart illustrating the inspection method according to the first embodiment. In the inspection method according to the first embodiment, the general-purpose terminal 5 is primarily responsible for managing the inspection procedure. More specifically, the general-purpose terminal 5 transmits an inspection signal, which simulates the rotation speed signal, to the fan control board 2, and outputs the inspection signal from the output terminal 12.

[0025] Here, the test signal is formed to simulate both the normal and abnormal rotational speeds of the PWM-controlled fan 4. For example, if the rated rotational speed Nr of the PWM-controlled fan 4 is Nr = 3000 [min -1 If this is the case, the general-purpose terminal 5 first transmits the rated rotational speed Nr to the fan control board 2 and instructs it to output a rotational speed signal of the normal rotational speed (step S1).

[0026] At this time, the control device 10 of the fan control board 2 outputs a rotation speed signal corresponding to the received rated rotation speed Nr from the output terminal 12, which is supposed to output a PWM signal (step S2). The control device 10 also calculates the rotation speed N from the response signal input to the input terminal 13 via the wiring 6 (step S3).

[0027] The control device 10 then determines whether the calculated rotational speed N is within the normal range (step S4). At this time, it can be determined that the calculated rotational speed N is within the normal range if it falls within, for example, the range of rated rotational speed Nr ± 10%.

[0028] If the rotation speed N is determined to be outside the normal range (No in step S4), the control device 10 determines that the board inspection is NG (failed) because, despite a rotation speed signal corresponding to the normal rotation speed being input to the input terminal 13, the input signal has not been properly judged (step S5). The control device 10 then transmits the board inspection result to the general-purpose terminal 5 (step S6) and terminates the inspection procedure.

[0029] On the other hand, if it is determined that the rotational speed N is within the normal range (Yes in step S4), the control device 10 transmits a message to the general-purpose terminal 5 indicating that an appropriate judgment has been made regarding the normal rotational speed (step S7).

[0030] Having received the judgment result for the normal rotation speed, the general-purpose terminal 5 then transmits an inspection signal that mimics the rotation speed signal of the abnormal rotation speed to the fan control board 2 and instructs the output of the said rotation speed signal (step S8). More specifically, the general-purpose terminal 5 specifies, for example, a rotation speed N = 5000 [min -1 It transmits the rotation speed signal.

[0031] In response, the control device 10 sets N=5000[min -1 The control device 10 outputs a rotational speed signal corresponding to ] from the output terminal 12 (step S9). The control device 10 also calculates the rotational speed N from the response signal input to the input terminal 13 via the wiring 6 (step S10).

[0032] The control device 10 then determines whether or not an abnormality is detected based on the calculated rotational speed N (step S11). If it is determined that the rotational speed N is not an abnormal rotational speed (No in step S11), the control device 10 determines that the board inspection is NG (failed) because, despite a rotational speed signal corresponding to an abnormal rotational speed being input to the input terminal 13, an appropriate judgment has not been made regarding the input signal (step S5). The control device 10 also transmits the board inspection result to the general-purpose terminal 5 (step S6), and the inspection procedure ends.

[0033] On the other hand, if the rotation speed N is determined to be an abnormal rotation speed (Yes in step S11), the control device 10 determines that the abnormality detection function is working properly for the abnormal rotation speed and makes an OK judgment for the board inspection (step S12). The control device 10 also transmits the judgment result of the board inspection to the general-purpose terminal 5 (step S6) and ends the inspection procedure.

[0034] As described above, in the inspection method for the fan control board 2 according to the first embodiment, the board inspection is performed by the response signal input to the input terminal 13 when an inspection signal simulating the rotation speed signal is output from the output terminal 12. As a result, in the inspection method for the fan control board 2 according to the first embodiment, the fan control board 2 can perform a self-diagnosis of the abnormality detection function of the PWM control fan 4 without using the PWM control fan 4 used during operation or a signal generator as a dedicated terminal for inspection.

[0035] Furthermore, according to the inspection method for the fan control board 2 of the first embodiment, self-diagnosis is performed by receiving inspection signals used as normal rotation speed and abnormal rotation speed from an external general-purpose terminal 5. Therefore, in the self-diagnosis of the abnormality detection function, the inspection items can be freely changed, for example, by arbitrarily setting the rotation speed N of the inspection signal instructed from the general-purpose terminal 5, to check the response to multiple abnormal rotation speeds.

[0036] <Second Embodiment> Next, the inspection method according to the second embodiment will be described. Figure 4 is a flowchart showing the inspection method according to the second embodiment. In the inspection method according to the second embodiment, the control device 10, which receives a board inspection start signal from the general-purpose terminal 5, performs a self-diagnosis according to an inspection procedure set in advance. That is, in the board inspection in this embodiment, the fan control board 2 performs a self-diagnosis by executing the program shown in Figure 4, which is stored in advance in the control device 10 of the fan control board 2.

[0037] When the self-diagnosis program is started, the control device 10 of the fan control board 2 first determines whether or not it has received a diagnosis start signal from the external general-purpose terminal 5 (step S13). It waits until a diagnosis start signal is received (No in step S13).

[0038] Upon receiving the diagnostic start signal, the control device 10 outputs a test signal for a normal rotational speed N from the output terminal 12 (step S14). The predetermined test signal output here is predefined and stored in the control device 10, mimicking the rotational speed signal output when the PWM-controlled fan 4 is driven normally at its rated rotational speed Nr.

[0039] Furthermore, the control device 10 calculates the rotational speed N from the response signal input to the input terminal 13 via the wiring 6 (step S15).

[0040] The control device 10 then determines whether the calculated rotational speed N is within the normal range (step S16). At this time, it can be determined that the calculated rotational speed N is within the normal range if, for example, it falls within the range of rated rotational speed Nr ± 10%.

[0041] If it is determined that the rotational speed N is not within the normal range (No in step S16), the control device 10 determines that the board inspection is NG (failed) because, despite a rotational speed signal corresponding to the normal rotational speed being input to the input terminal 13, an appropriate judgment has not been made regarding the input signal (step S17), and terminates the inspection procedure.

[0042] On the other hand, if it is determined that the rotational speed N is within the normal range (Yes in step S16), the control device 10 then outputs an inspection signal from the output terminal 12 that mimics the rotational speed signal of an abnormal rotational speed (step S18). An abnormal rotational speed is, for example, rotational speed N = 5000 [min -1 This can be used as the rotation speed signal.

[0043] Furthermore, the control device 10 calculates the rotational speed N from the response signal input to the input terminal 13 via the wiring 6 (step S19). Then, the control device 10 determines whether or not an abnormality is detected based on the calculated rotational speed N (step S20).

[0044] If the rotation speed N is incorrectly determined not to be an abnormal rotation speed (No in step S20), the control device 10 determines that the board inspection is NG (failed) because, despite a rotation speed signal corresponding to an abnormal rotation speed being input to the input terminal 13, an appropriate judgment has not been made regarding the input signal (step S17).

[0045] On the other hand, if the rotation speed N is correctly determined to be an abnormal rotation speed (Yes in step S20), the control device 10 determines that the abnormality detection function is working appropriately for the abnormal rotation speed and makes an OK judgment for the board inspection (step S21). Here, if the fan control board 2 is provided with a buzzer, lamp, etc. to notify of abnormality detection during operation of the battery backup unit 1, the warning unit may be operated in the same way as during operation.

[0046] As described above, in the inspection method for the fan control board 2 according to the second embodiment, the board inspection is performed by the response signal input to the input terminal 13 when an inspection signal simulating the rotation speed signal is output from the output terminal 12. As a result, in the inspection method for the fan control board 2 according to the second embodiment, similar to the first embodiment, the fan control board 2 can perform a self-diagnosis of the abnormality detection function of the PWM control fan 4 without using the PWM control fan 4 or a signal generator as a dedicated terminal for inspection.

[0047] Furthermore, in the inspection method for the fan control board 2 according to the second embodiment, the inspection procedure can be completed using only the fan control board 2, except for receiving the diagnostic start signal. If the fan control board 2 is equipped with a DIP switch for starting the diagnostic process in place of the PC connection section 14, the general-purpose terminal 5 can also be eliminated by executing the board inspection procedure shown in Figure 4 based on the operation of the DIP switch.

[0048] <Third Embodiment> Next, the inspection method according to the third embodiment will be described. Figure 5 is a graph showing the characteristics of the PWM-controlled fan 4 connected to the fan control board 2 according to the third embodiment. In this embodiment, the PWM-controlled fan 4 rotates at a normal speed of N1 = 3500 [min] when the duty cycle of the PWM signal is 60%. -1 Driven at a rotational speed N, and with a PWM signal duty cycle of 100%, high-speed rotation is defined as N2 = 5000 [min -1 The fan shall be driven at a rotational speed N. This allows the PWM-controlled fan 4 to switch between two rotational speeds N depending on whether the battery module 3 described above is discharging or charging.

[0049] The fan control board 2 connected to the PWM-controlled fan 4 of the third embodiment can be inspected using the same inspection method as in the first or second embodiment described above, but it is also possible to perform inspections for two stages, normal rotation speed and abnormal rotation speed, together.

[0050] In other words, in the inspection method of the third embodiment, an inspection signal that mimics the rotational speed signal output when the PWM-controlled fan 4 continuously changes from a stopped state to the maximum value of the rotational speed N is output to the output terminal 12.

[0051] At this time, the control device 10 calculates the rotational speed N based on the response signal input to the input terminal 13 simultaneously with the output of the inspection signal, and determines whether the calculated rotational speed N changes according to the inspection signal. In other words, the control device 10 can determine the response to two normal rotational speeds and an abnormal rotational speed based on the timing when the rotational speed N falls within the range of N1 ± 10%, within the range of N2 ± 10%, and other ranges, and perform a self-diagnosis of the abnormality detection function.

[0052] As a result, according to the inspection method in the third embodiment, it is possible to collectively diagnose the abnormality detection function for multiple normal and abnormal rotation speeds.

[0053] <Embodiments of the Invention> A first embodiment of the present invention is a method for inspecting a fan control board, which includes an output terminal that outputs a PWM signal to a PWM-controlled fan and an input terminal that receives a rotational speed signal output from the PWM-controlled fan, wherein the output terminal and the input terminal are directly connected without going through the PWM-controlled fan, and self-diagnosis is performed by a response signal input to the input terminal when an inspection signal simulating the rotational speed signal is output from the output terminal.

[0054] The inspection method for a fan control board according to the first embodiment involves connecting the output terminal and input terminal of the fan control board, which will be connected to the PWM-controlled fan during operation, to each other, and outputting an inspection signal that simulates the rotation speed signal from the output terminal. At this time, the board can be inspected by determining whether or not the rotation speed calculated from the response signal input to the input terminal is appropriate. Thus, according to the inspection method for a fan control board according to the first embodiment, the fan control board's abnormality detection function for the PWM-controlled fan can be self-diagnosed without using a PWM-controlled fan or a signal generator as a dedicated terminal for inspection.

[0055] A second embodiment of the present invention is a method for inspecting a fan control board, in which the inspection signal is received from an external source and the self-diagnosis is performed, as in the first embodiment described above.

[0056] According to the second embodiment, there is no need to prepare the inspection signal in advance on the fan control board, and in the self-diagnosis of the abnormality detection function, the inspection items can be freely changed, for example, by arbitrarily setting the rotation speed of the inspection signal transmitted from an external source, to check the response to multiple abnormal rotation speeds.

[0057] A third embodiment of the present invention is a method for inspecting a fan control board, in which, in the first embodiment described above, when a diagnostic start signal is received from an external source, the self-diagnosis is performed using a predetermined inspection signal.

[0058] According to the third embodiment, by pre-setting the test signal on the fan control board, the self-diagnosis procedure can be completed solely by the fan control board, except for receiving the diagnostic start signal.

[0059] A fourth embodiment of the present invention is a method for inspecting a fan control board, wherein, in any of the first to third embodiments described above, the inspection signal is formed to simulate both the normal rotation speed and the abnormal rotation speed of the PWM-controlled fan.

[0060] According to the fourth embodiment, by performing circuit board inspections not only for abnormal rotation speeds but also for normal rotation speeds as inspection signals, the abnormality detection function can be diagnosed, including continuity abnormalities of output terminals and input terminals.

[0061] A fifth embodiment of the present invention is a method for inspecting a fan control board, which is the rotation speed signal of the PWM-controlled fan when the rotation speed of the PWM-controlled fan changes continuously from 0 to a maximum value, in any of the first to third embodiments described above.

[0062] According to the fifth embodiment, the abnormality detection function can be diagnosed for both normal and abnormal rotation speeds in a unified manner, and for example, substrate inspections for multiple normal rotation speeds can also be performed simultaneously.

[0063] A sixth embodiment of the present invention is a fan control board comprising: an output terminal that outputs a PWM signal to a PWM-controlled fan; an input terminal that receives a rotational speed signal output from the PWM-controlled fan; and a control device that transmits the PWM signal via the output terminal and receives the rotational speed signal via the input terminal to control the PWM-controlled fan, wherein the control device can perform self-diagnosis based on a response signal input to the input terminal when an inspection signal mimicking the rotational speed signal is output from the output terminal, while the output terminal and the input terminal are directly connected without going through the PWM-controlled fan.

[0064] The fan control board according to the sixth embodiment outputs a test signal simulating a rotational speed signal from the output terminal, with the output terminal and input terminal connected to each other, which will be connected to the PWM-controlled fan during operation. At this time, the board can be inspected by determining whether the rotational speed calculated from the response signal input to the input terminal is appropriate or not. Thus, the fan control board according to the sixth embodiment can perform self-diagnosis of the abnormality detection function for the PWM-controlled fan without using a PWM-controlled fan or a signal generator as a dedicated terminal for inspection.

[0065] A seventh embodiment of the present invention is, in the sixth embodiment described above, a fan control board that receives the inspection signal from an external source and performs the self-diagnosis.

[0066] According to the seventh embodiment, there is no need to prepare the inspection signal in advance on the fan control board, and in the self-diagnosis of the abnormality detection function, the inspection items can be freely changed, for example, by arbitrarily setting the rotation speed of the inspection signal transmitted from an external source, to check the response to multiple abnormal rotation speeds.

[0067] An eighth embodiment of the present invention is, in the sixth embodiment described above, a fan control board that performs the self-diagnosis with a predetermined test signal when it receives a diagnosis start signal from an external source.

[0068] According to the eighth embodiment, by pre-setting the test signal on the fan control board, the self-diagnosis procedure can be completed solely by the fan control board, except for receiving the diagnostic start signal.

[0069] A ninth embodiment of the present invention is a fan control board in which, in any of the sixth to eighth embodiments described above, the test signal is formed to mimic both the normal rotation speed and the abnormal rotation speed of the PWM-controlled fan.

[0070] According to the ninth embodiment, by performing circuit board inspections not only for abnormal rotation speeds but also for normal rotation speeds as inspection signals, the abnormality detection function can be diagnosed, including continuity abnormalities of output terminals and input terminals.

[0071] A tenth embodiment of the present invention is a fan control board, which is the rotation speed signal when the rotation speed of the PWM-controlled fan changes continuously from 0 to a maximum value, in any of the sixth to eight embodiments described above.

[0072] According to the tenth embodiment, the abnormality detection function can be diagnosed for both normal and abnormal rotation speeds in a unified manner, and for example, substrate inspections for multiple normal rotation speeds can also be performed simultaneously. [Explanation of symbols]

[0073] 1. Battery backup unit 2 Fan control board 3 Battery Modules 4 PWM controlled fans 5 General-purpose terminals 6 Wiring 10 Control device 11 Battery connection 12 output terminals 13 Input terminals 14. PC connection section

Claims

1. A method for testing a fan control board, comprising an output terminal that outputs a PWM signal to a PWM-controlled fan, and an input terminal that receives a rotational speed signal output from the PWM-controlled fan, The output terminal and the input terminal are connected directly without going through the PWM controlled fan. When an inspection signal mimicking the aforementioned rotational speed signal is output from the output terminal, a self-diagnosis is performed based on the response signal input to the input terminal. A method for inspecting a fan control board, wherein the inspection signal is formed to simulate both the normal rotation speed and the abnormal rotation speed of the PWM-controlled fan.

2. A method for inspecting a fan control board according to claim 1, comprising receiving the inspection signal from an external source and performing the self-diagnosis.

3. A method for inspecting a fan control board according to claim 1, wherein when a diagnostic start signal is received from an external source, the self-diagnosis is performed using a predetermined test signal.

4. The method for inspecting a fan control board according to any one of claims 1 to 3, wherein the inspection signal is the rotation speed signal when the rotation speed of the PWM-controlled fan changes continuously from 0 to a maximum value.

5. An output terminal that outputs a PWM signal to a PWM-controlled fan, An input terminal to which the rotational speed signal output from the PWM-controlled fan is input, The control device includes a device that transmits the PWM signal via the output terminal and controls the PWM-controlled fan by receiving the rotation speed signal via the input terminal, The control device can perform a self-diagnosis based on a response signal input to the input terminal when an inspection signal simulating the rotation speed signal is output from the output terminal, while the output terminal and the input terminal are directly connected without going through the PWM controlled fan. The aforementioned test signals are formed on a fan control board that simulates both the normal and abnormal rotation speeds of the PWM-controlled fan.

6. The control device receives the inspection signal from an external source and performs the self-diagnosis, as described in claim 5, for the fan control board.

7. The fan control board according to claim 5, wherein the control device performs the self-diagnosis using a predetermined test signal when it receives a diagnosis start signal from an external source.

8. The fan control board according to any one of claims 5 to 7, wherein the inspection signal is the rotation speed signal when the rotation speed of the PWM-controlled fan changes continuously from 0 to a maximum value.

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