System and method for automatically correcting fan motor speed

Abstract

This application discloses a system and method for automatically correcting the speed of a fan motor. After the fan is moved from an open space to a closed space, a sampling and holding circuit samples and holds the duty cycle of the drive signal required to drive the fan motor in different environments at a first speed and the duty cycle of the drive signal required to drive it at a second speed. An arithmetic circuit calculates the difference between the first sampling duty cycle and the first duty cycle required in the open space (as listed in the lookup table), and the difference between the second sampling duty cycle and the second duty cycle required in the open space (as listed in the lookup table), and calculates the duty cycle required to drive the fan motor at other speeds to update the lookup table.

Description

TECHNICAL FIELD

[0001] The present application relates to a motor, and in particular to a system and method for automatically correcting the rotation speed of a fan motor. BACKGROUND

[0002] In electronic devices such as notebook computers, a fan motor is used to cool a heat-generating component such as a processor. During the process of cooling the heat-generating component by the fan motor, the rotation speed of the fan motor needs to be accurately controlled so that the fan motor exhibits the most appropriate cooling performance to properly cool the heat-generating component. In motor applications with fixed rotation speed requirements, a common fixed rotation speed method is to use a proportional-integral-derivative controller (PID) control system, but the disadvantage is that when the rotation speed command changes, the PID control system needs a reaction action time, and too fast will cause a rotation speed surge. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a system for automatically correcting the rotation speed of a fan motor, which overcomes the deficiencies of the prior art. The system includes a lookup table module, a drive circuit, a sample and hold circuit, and a calculation circuit. The lookup table module stores a plurality of reference operation periods required for driving the fan motor to operate at different reference rotation speeds in a first environment. The plurality of reference operation periods include a first reference operation period and a second reference operation period corresponding to a first reference rotation speed and a second reference rotation speed included in the plurality of reference rotation speeds, respectively. The drive circuit is connected to the lookup table module and the fan motor. The drive circuit looks up a reference operation period corresponding to a reference rotation speed identical to an instruction rotation speed indicated by a rotation speed command from the lookup table module, and outputs a drive signal having the looked-up reference operation period to the fan motor. The sample and hold circuit is connected to the drive circuit and the fan motor. The sample and hold circuit is configured to sample and hold, in a second environment, an operation period of the drive signal output by the drive circuit when driving the fan motor to operate at the first reference rotation speed as a first sampled operation period, and an operation period of the drive signal output by the drive circuit when driving the fan motor to operate at the second reference rotation speed as a second sampled operation period. The calculation circuit is connected to the sample and hold circuit and the lookup table module. The calculation circuit calculates a difference between the first sampled operation period and the first reference operation period as a first difference value. The calculation circuit calculates a difference between the second sampled operation period and the second reference operation period as a second difference value. The calculation circuit judges a linear variation relationship of the first difference value and the second difference value to analyze linear variation data, and calculates a plurality of reference operation periods required for driving the fan motor to operate at the plurality of reference rotation speeds in the second environment, respectively, to update the lookup table module.

[0004] In one embodiment, the operation circuit is configured to generate a first equation yl = a x xl + b according to the first difference value and the first reference duty cycle, where yl represents the first difference value, xl represents the first reference duty cycle, a represents the first coefficient, and b represents the second coefficient. The operation circuit is configured to generate a second equation y2 = a x x2 + b according to the second difference value and the second reference duty cycle, where y2 represents the second difference value, and x2 represents the second reference duty cycle. The operation circuit is configured to subtract the first equation from the second equation to calculate the first coefficient, and substitute the first coefficient into the first equation or the second equation to calculate the second coefficient, to generate a general equation y = a x x + b, where y represents the difference of the reference duty cycle required in the first environment and the second environment, and x represents the reference duty cycle required in the first environment. The operation circuit is configured to substitute each reference duty cycle required in the first environment when the fan motor is operated at each reference speed into the general equation to calculate each reference duty cycle required in the second environment.

[0005] In one embodiment, the operation circuit is configured to construct a linear curve in a graph according to all x values and y values at the plurality of reference speeds, with the x values as the horizontal axis values of the graph and the y values as the vertical axis values of the graph.

[0006] In one embodiment, when the fan motor is maintained to operate at the same reference speed, the sample-and-hold circuit samples a duty cycle of the driving signal at a first time and samples a duty cycle of the driving signal at a second time, and the duty cycles are different, the system determines that the environment of the fan motor is changed, and instructs the operation circuit to update the lookup table module.

[0007] In one embodiment, the system for automatically correcting the speed of the fan motor further comprises a steady state detection circuit. The steady state detection circuit is connected to the sample-and-hold circuit. The steady state detection circuit is configured to time a first length of time that the fan motor is maintained to operate stably at the first reference speed, and determine that the first length of time reaches a first preset length of time, which indicates that the fan motor has reached a steady state, and instructs the sample-and-hold circuit to stop sampling and holding the first sampled duty cycle. The steady state detection circuit is configured to time a second length of time that the fan motor is maintained to operate stably at the second reference speed, and determine that the second length of time reaches a second preset length of time, which indicates that the fan motor has reached a steady state, and instructs the sample-and-hold circuit to stop sampling and holding the second sampled duty cycle.

[0008] In one embodiment, the first environment comprises an open space, and the second environment comprises a closed space inside a housing in which the fan motor is placed.

[0009] In addition, the present application provides a method for automatically correcting a fan motor speed, comprising the following steps: storing a plurality of reference duty cycles required for driving the fan motor to operate at a plurality of reference speeds in a first environment, respectively, in a lookup table, wherein the plurality of reference duty cycles comprises a first reference duty cycle and a second reference duty cycle corresponding to a first reference speed and a second reference speed comprised in the plurality of reference speeds, respectively; receiving a speed command; in the first environment, searching for a reference duty cycle corresponding to a reference speed identical to an instruction speed indicated by the speed command in the lookup table, and outputting a driving signal having the searched reference duty cycle to the fan motor; in a second environment, sampling and holding a duty cycle of the driving signal outputted when driving the fan motor to operate at the first reference speed as a first sampled duty cycle; calculating a difference between the first sampled duty cycle and the first reference duty cycle as a first difference; sampling and holding a duty cycle of the driving signal outputted when driving the fan motor to operate at the second reference speed as a second sampled duty cycle; calculating a difference between the second sampled duty cycle and the second reference duty cycle as a second difference; judging a linear variation relationship between the first difference and the second difference to analyze linear variation data; calculating a plurality of reference duty cycles required for driving the fan motor to operate at the plurality of reference speeds in the second environment, respectively, according to the linear variation data, to update the lookup table; and in the second environment, searching for an updated reference duty cycle corresponding to a reference speed identical to the instruction speed indicated by the speed command in the lookup table, and outputting a driving signal having the searched reference duty cycle to the fan motor.

[0010] In an embodiment, the method for automatically correcting a fan motor speed further comprises the following steps: generating a first equation y1=a×x1+b according to the first difference and the first reference duty cycle, wherein y1 represents the first difference, x1 represents the first reference duty cycle, a represents a first coefficient, and b represents a second coefficient; generating a second equation y2=a×x2+b according to the second difference and the second reference duty cycle, wherein y2 represents the second difference, x2 represents the second reference duty cycle; performing a subtraction operation between the first equation and the second equation to calculate the first coefficient, and substituting the first coefficient into the first equation or the second equation to calculate the second coefficient, thereby generating a general equation y=a×x+b, wherein y represents a difference between reference duty cycles required in the first environment and the second environment, and x represents a reference duty cycle required in the first environment; and substituting each reference duty cycle required in the first environment when driving the fan motor to operate at each reference speed into the general equation to calculate each reference duty cycle required in the second environment.

[0011] In one embodiment, the method of automatically correcting the fan motor speed further comprises the step of: constructing a linear curve in a graph according to all the x values and y values at the plurality of reference speeds.

[0012] In one embodiment, the method of automatically correcting the fan motor speed further comprises the step of: determining whether the duty cycle of the sampled and held drive signal at a first time is the same as the duty cycle of the sampled and held drive signal at a second time, if the fan motor is maintained at the same reference speed, if not, determining that the environment of the fan motor has changed, updating the lookup table module, and if yes, not updating the lookup table module.

[0013] In one embodiment, the method of automatically correcting the fan motor speed further comprises the steps of: timing a first length of time that the fan motor is maintained at a first reference speed; determining whether the first length of time has reached a first predetermined length of time, if yes, determining that the fan motor has reached a steady state condition, sampling and holding a first sampled duty cycle, and if no, re-timing; timing a second length of time that the fan motor is maintained at a second reference speed; and determining whether the second length of time has reached a second predetermined length of time, if yes, determining that the fan motor has reached a steady state condition, sampling and holding a second sampled duty cycle, and if no, re-timing.

[0014] As described above, the present application provides a system and method of automatically correcting the fan motor speed, which can automatically correct the duty cycle of the drive signal required to drive the fan motor at different speeds in different environments. Thus, after a target speed command is issued, the lookup table can be directly searched according to the speed indicated by the speed command, and a drive signal with the duty cycle found is output to the fan motor to quickly drive the fan motor to operate at the target speed without the traditional complex and slow PID control, and the speed surge can be avoided.

[0015] For further understanding of the features and technical contents of the present application, please refer to the following detailed description of the present application and the accompanying drawings. However, the accompanying drawings provided are only for reference and illustration, and are not intended to limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A block diagram of the system of automatically correcting the fan motor speed according to the first embodiment of the present application.

[0017] Figure 2 A flow chart of the steps of the method of automatically correcting the fan motor speed according to the first embodiment of the present application.

[0018] Figure 3Block diagram of the system for automatically correcting the fan motor speed for the second embodiment of the present application.

[0019] Figure 4 Flow chart of the steps of the method for automatically correcting the fan motor speed for the second embodiment of the present application.

[0020] Figure 5 Graph of the speed versus duty cycle curve stored in the lookup table for the system and method for automatically correcting the fan motor speed for the first and second embodiments of the present application.

[0021] Figure 6 Graph of the simulation test data for the system and method for automatically correcting the fan motor speed for the first and second embodiments of the present application at different environments and motor speeds.

[0022] Figure 7 Graph of the duty cycle versus PWM signal duty cycle curve for the system and method for automatically correcting the fan motor speed for the first and second embodiments of the present application applied to a 4 cm fan at the duty cycle at the inlet.

[0023] Figure 8 Graph of the difference in the duty cycle at the first and second environments versus the duty cycle at the first environment for the system and method for automatically correcting the fan motor speed for the first embodiment of the present application applied to a 4 cm fan.

[0024] Figure 9 Graph of the duty cycle versus the difference for the system and method for automatically correcting the fan motor speed for the second embodiment of the present application applied to a 4 cm fan sampled at the steady state.

[0025] Figure 10 Graph of the duty cycle versus speed curve for the system and method for automatically correcting the fan motor speed for the first and second embodiments of the present application applied to a 6 cm fan at different environments.

[0026] Figure 11 Graph of the difference in the duty cycle at the first and second environments versus the duty cycle at the first environment for the system and method for automatically correcting the fan motor speed for the first and second embodiments of the present application applied to a 6 cm fan. DETAILED DESCRIPTION

[0027] The advantages and effects of the present application can be understood by the following embodiments and the related description. The present application can be implemented or applied by other different embodiments, and the details in the description can be modified and changed based on different views and applications without departing from the concept of the present application. In addition, the drawings of the present application are simple schematic illustrations and not actual size depictions. The following embodiments will further describe the related technical content of the present application, but the disclosed content is not used to limit the protection scope of the present application. In addition, the term "or" used herein can include any one or more combinations of the associated listed items as possible.

[0028] Please refer to Figure 1 , Figure 2 and Figure 5 , wherein Figure 1 is a block diagram of the system for automatically correcting the fan motor speed of the first embodiment of the present application; Figure 2 is a flow chart of the steps of the method for automatically correcting the fan motor speed of the first embodiment of the present application; Figure 5 is a curve diagram of the speed versus duty cycle stored in the lookup table of the system and method for automatically correcting the fan motor speed of the first and second embodiments of the present application.

[0029] As shown in Figure 1 , the system for automatically correcting the fan motor speed of the present embodiment can include a lookup table module 10, a sample and hold circuit 20, an operation circuit 30, and a driving circuit 40, which are adapted to perform the steps S101 to S133 of the method for automatically correcting the fan motor speed as shown in Figure 2 . As shown in Figure 1 , the operation circuit 30 is connected to the lookup table module 10, the sample and hold circuit 20, and the driving circuit 40.

[0030] In step S101, the fan provided with the motor is placed in a first environment.

[0031] In step S103, the duty cycle required by the driving signal output from the driving circuit 40 to the fan motor when the driving circuit 40 drives the fan motor to operate at a plurality of different reference speeds in the first environment is tested to establish a lookup table stored in the lookup table module 10. That is, a plurality of different reference speeds and a plurality of different reference duty cycles required by the respective different reference speeds are listed on the lookup table of the lookup table module 10.

[0032] In order to update the look-up table to be suitable for the fan motor to operate at different rotation speed in a new environment (e.g. the second environment as described in the present case), the plurality of reference rotation speeds listed on the look-up table module 10 comprises at least a first reference rotation speed and a second reference rotation speed, which correspond to a first reference duty cycle and a second reference duty cycle respectively.

[0033] If necessary, the look-up table module 10 can establish a graph as shown in Figure 5 on the look-up table, with the vertical axis representing the reference rotation speed and the horizontal axis representing the reference duty cycle, to establish a non-linear curve in the graph according to the plurality of reference duty cycles required by the plurality of reference rotation speeds respectively.

[0034] For example, the reference rotation speed 1241.4 RPM corresponds to the reference duty cycle 12.5%, the reference rotation speed 2100.8 RPM corresponds to the reference duty cycle 25%, the reference rotation speed 2769.2 RPM corresponds to the reference duty cycle 37.5%, the reference rotation speed 3533.2 RPM corresponds to the reference duty cycle 50.0%, the reference rotation speed 4297.1 RPM corresponds to the reference duty cycle 62.5%, the reference rotation speed 4870.1 RPM corresponds to the reference duty cycle 75.0%, the reference rotation speed 5538.5 RPM corresponds to the reference duty cycle 87.5%, and the reference rotation speed 6016 RPM corresponds to the reference duty cycle 100%. These are only examples and are not limited thereto.

[0035] In step S105, the drive circuit 40 receives a rotation speed command from the external control circuit.

[0036] In step S107, the drive circuit 40 looks up a reference rotation speed from the look-up table which is the same as the command rotation speed indicated by the rotation speed command.

[0037] In step S109, the drive circuit 40 obtains a reference duty cycle required by the looked-up reference rotation speed from the look-up table.

[0038] In step S111, the drive circuit 40 outputs a drive signal with the looked-up reference duty cycle to the fan motor.

[0039] In step S113, the fan motor operates according to the drive signal.

[0040] In step S115, during the operation of the fan or when the fan is stopped, the fan can be moved to a different environment. For the convenience of description, the environment before the fan is moved is referred to as the first environment, and the environment after the fan is moved is referred to as the second environment. For example, the first environment is an open space outside the casing, and the second environment is a containing space (for containing the fan) inside the casing.

[0041] When the fan is moved to a different environment, if the aforementioned table lookup procedure is executed at the command speed, the drive signal having the duty cycle found is output to drive the fan motor, and the speed at which the fan motor actually operates is not equal to the command speed. That is, when the fan is moved to a different environment, the drive circuit 40 must change the duty cycle of the drive signal output to the fan motor in order to maintain the same operating speed of the fan motor in the second environment as in the first environment.

[0042] Therefore, when the fan is moved to a different environment (second environment), in order to still be able to quickly drive the fan motor to operate, the subsequent steps S117 to S133 must be executed to update the table.

[0043] In step S117, the drive circuit 40 outputs a drive signal to the fan motor to drive the fan motor to operate at a first reference speed.

[0044] In step S119, the sample-and-hold circuit 20 samples and holds the duty cycle of the drive signal output by the drive circuit 40 to drive the fan motor to operate at the first reference speed as a first sampled duty cycle.

[0045] In step S121, the arithmetic circuit 30 calculates the difference between the first sampled duty cycle of the drive signal to drive the fan motor to operate at the first reference speed in the second environment and the first reference duty cycle listed on the table as the first difference value. That is, the difference in the duty cycle of the drive signal required to drive the fan motor to operate at the same first reference speed in different environments is calculated.

[0046] In step S123, the drive circuit 40 outputs a drive signal to the fan motor to drive the fan motor to operate at a second reference speed.

[0047] In step S125, the sample-and-hold circuit 20 samples and holds the duty cycle of the drive signal output by the drive circuit 40 to drive the fan motor to operate at the second reference speed as a second sampled duty cycle.

[0048] In step S127, the arithmetic circuit 30 calculates the difference between the second sampled duty cycle of the drive signal to drive the fan motor to operate at the second reference speed in the second environment and the second reference duty cycle listed on the table as the second difference value. That is, the difference in the duty cycle of the drive signal required to drive the fan motor to operate at the same second reference speed in different environments is calculated.

[0049] At step S129, the linear variation relationship between the first difference value and the second difference value is determined by the operation circuit 30 to analyze the linear variation data.

[0050] At step S131, the reference operation periods required for the fan motor to operate at the reference rotation speeds in the second environment are calculated by the operation circuit 30 according to the linear variation data to update the lookup table module 10. As mentioned above, the reference operation periods required in the second environment are different from the reference operation periods required in the first environment.

[0051] At step S133, the reference operation periods required for the fan motor to operate at the reference rotation speeds in the second environment are substituted for the reference operation periods required for the fan motor to operate at the reference rotation speeds in the first environment listed on the lookup table.

[0052] After the lookup table is updated, when the fan motor operates in the second environment, the process can return to step S105, the drive circuit 40 receives the rotation speed command, and then the subsequent steps are executed to perform lookup according to the command rotation speed indicated by the rotation speed command to obtain the required operation period, output the drive signal with the operation period to drive the fan motor to operate at the command rotation speed.

[0053] Please refer to Figure 3 、 Figure 4 and Figure 9 , wherein Figure 3 is a block diagram of the system for automatically correcting the rotation speed of the fan motor according to the second embodiment of the present application; Figure 4 is a flowchart of the steps of the method for automatically correcting the rotation speed of the fan motor according to the second embodiment of the present application; Figure 9 is a curve diagram of the difference value versus the operation period sampled when the 4cm fan enters the steady state according to the system and the method for automatically correcting the rotation speed of the fan motor according to the second embodiment of the present application.

[0054] As shown in Figure 3 , the system for automatically correcting the rotation speed of the fan motor according to the present embodiment can include the lookup table module 10, the sample and hold circuit 20, the operation circuit 30, the drive circuit 40, and the steady state detection circuit 50, which is adapted to perform the steps S101 to S133 of the method for automatically correcting the rotation speed of the fan motor as shown in Figure 4 . It should be understood that the content, execution order and number of steps herein can be adjusted as needed. As shown in Figure 3 , the steady state detection circuit 50 is connected to the sample and hold circuit 20. The same as the first embodiment, the same parts are not described here.

[0055] As shown in Figure 9As shown, the difference between the duty cycle of the driving signal in the open space and in the closed space increases substantially linearly as the duty cycle of the driving signal in the open space increases. However, the fan motor can have a period of unstable running condition and the running speed can vary, for example, when the fan motor is just started, and the duty cycle data obtained at this time is not accurate.

[0056] Therefore, after the aforementioned steps S101 to S117 are performed, steps S201 to S205 can be performed.

[0057] In step S201, the first time length during which the fan motor runs at the first reference speed is timed by the stable state detection circuit 50.

[0058] In step S203, the stable state detection circuit 50 determines whether the first time length reaches the first preset time length. If the first time length does not reach the first preset time length, for example, 6 seconds, it is determined that the speed of the motor fan varies with time and the fan motor is in an unstable state, and thus the process returns to step S201 to re-time. Conversely, if the first time length reaches the first preset time length, it is determined that the motor fan runs stably at a constant speed, and the next step S205 is performed.

[0059] In step S205, the stable state detection circuit 50 instructs the sample-and-hold circuit 20 to sample and hold the duty cycle of the driving signal used to drive the fan motor to run at the first parameter speed as the aforementioned first sampled duty cycle.

[0060] Similarly, after step S123 is performed, steps S201 to S205 can also be performed to time the second time length during which the fan motor runs at the second reference speed, determine whether the second time length reaches the second preset time length. If not, re-time. If yes, instruct the sample-and-hold circuit 20 to sample the duty cycle of the driving signal used to drive the fan motor to run at the second parameter speed as the aforementioned second sampled duty cycle.

[0061] Please refer to Figures 1 to 11 wherein Figure 8 the curve of the difference between the duty cycles of the 4-inch fan in the first environment and the second environment versus the duty cycle in the first environment for the system and method of automatically correcting the speed of the fan motor according to the first embodiment of the present application; Figure 9 the curve of the sampled duty cycle versus the difference for the system and method of automatically correcting the speed of the fan motor according to the second embodiment of the present application when the 4-inch fan enters a stable state; Figure 11 the curve of the difference between the duty cycles of the 6-inch fan in the first environment and the second environment versus the duty cycle in the first environment for the system and method of automatically correcting the speed of the fan motor according to the first embodiment and the second embodiment of the present application.

[0062] As shown in FIG. 1 1, in order to make the fan motor operate at the same speed, the duty cycle of the driving signal outputted to the fan motor in the open space by the driving circuit 40 is different from the duty cycle of the driving signal outputted to the fan motor when the inlet or the outlet of the closed space of the casing in which the fan motor is accommodated is blocked. Figure 6

[0063] As shown in FIG. 12, the data shown in FIG. 1 1 is plotted in a graph as shown in FIG. 13 to form a first curve C1 and a second curve C2. The horizontal axis of the graph is the duty cycle of the PWM signal used to determine the frequency of the driving signal outputted to the fan motor by the driving circuit 40, which is proportional to the operating speed of the fan motor. The vertical axis of the graph is the duty cycle of the driving signal inputted to the fan motor. The first curve C1 represents the data curve sampled when the inlet of the casing is blocked, and the second curve C2 represents the data curve sampled when the outlet of the casing is blocked. Figure 6 Figure 7

[0064] As shown in FIG. 14, the duty cycle of the driving signal of the 4cm fan is not linear with respect to the duty cycle of the PWM signal for both the first curve C1 and the second curve C2. As shown in FIG. 15, the duty cycle of the driving signal of the 6cm fan is also not linear with respect to the duty cycle of the PWM signal for both the first curve C1 and the second curve C2. Figure 7 Figure 10

[0065] However, it is noted that the difference between the duty cycle of the driving signal inputted to the fan motor in the open space and the duty cycle of the driving signal inputted to the fan motor when the inlet of the casing is blocked, is proportional to the duty cycle of the driving signal inputted to the fan motor in the open space when the fan motor is operated at the same reference speed, as shown in the linear curve of FIG. 16. Figure 8 Figure 9 Figure 11

[0066] Therefore, as mentioned in step S131, the operating circuit 30 can calculate the reference duty cycles of the driving signal required for the fan motor to operate at other different reference speeds in the second environment based on the data of the linear curve with linear characteristics (i.e. the aforementioned linear variation data) to update the lookup table module 10.

[0067] For convenience of description, in this document, the duty cycle of the driving signal inputted to the fan motor in the first environment when the fan motor is operated at the same speed is denoted as the reference duty cycle, and the duty cycle of the driving signal inputted to the fan motor in the second environment is denoted as the sampled duty cycle.

[0068] ​​​​​​​​The operational circuit 30 calculates the difference between the first sampling working cycle and the first reference working cycle as the first difference value, and generates the following first equation based on the first difference value and the first reference working cycle:

[0069] y1 = a × x1 + b,

[0070] Where y1 represents the first difference, x1 represents the first reference working period, a represents the first coefficient, and b represents the second coefficient.

[0071] The operational circuit 30 calculates the difference between the second sampling working cycle and the second reference working cycle as the second difference value, and generates the following second equation based on the second difference value and the second reference working cycle:

[0072] y2 = a × x2 + b,

[0073] Where y2 represents the second difference, x2 represents the second reference working period, a represents the first coefficient, and b represents the second coefficient.

[0074] Next, the operational circuit 30 subtracts the first equation from the second equation to calculate the first coefficient, and substitutes it into the aforementioned first or second equation to calculate the second coefficient, generating the following general equation:

[0075] y = a × x + b

[0076] Where y represents the difference in reference working cycles required between the first and second environments, x represents the reference working cycles required in the first environment, a represents the first coefficient, and b represents the second coefficient.

[0077] The arithmetic circuit 30 substitutes the reference duty cycles of the drive signals required for the first environment at different speeds into the general equation to calculate the reference duty cycles of the drive signals required for the fan motor to maintain the same speed when moving from the first environment to the second environment.

[0078] For example, such as Figure 6 As shown, when the fan motor is driven to operate at a target speed of 16000 RPM in the first environment, the drive circuit 40 looks up the reference duty cycle of 50.5% corresponding to the speed of 16000 RPM from the lookup table module 10 before the update. The sampling and holding circuit 20 samples and holds the duty cycle of the drive signal used to drive the fan motor to operate at the same target speed of 16000 RPM in the second environment for 42.7%.

[0079] The operation circuit 30 calculates the difference between the reference duty cycle 50.5% in the first environment and the sampled duty cycle 42.7% in the second environment, which is 7.8%, and then substitutes the difference as the y value into the general equation and substitutes the reference duty cycle 50.5% in the first environment as the x value into the general equation to form a first expression: 7.8 = a x 50.5 + b.

[0080] In addition, when the fan motor is driven to operate at the target speed 8000 RPM, the driving circuit 40 looks up the reference duty cycle 26.7% corresponding to the speed 8000 RPM from the lookup table before updating. The sample-and-hold circuit 20 samples and holds the duty cycle of the driving signal used to drive the fan motor to operate at the same target speed 8000 RPM in the second environment as 24.4%.

[0081] The operation circuit 30 calculates the difference between the reference duty cycle 26.7% in the first environment and the sampled duty cycle 24.4% in the second environment, which is 2.3%, and then substitutes the difference as the y value into the general equation and substitutes the reference duty cycle 26.7% in the first environment as the x value into the general equation to form a second expression: 2.3 = a x 26.7 + b.

[0082] Then, the operation circuit 30 subtracts the second expression from the first expression to calculate the value of a as 0.231, and then substitutes the value of a into the first expression or the second expression to calculate the value of b as -3.87. The operation circuit 30 substitutes the values of a and b into the general equation to generate an equation applicable to the second environment: y = 0.231 x - 3.87. The operation circuit 30 calculates the reference duty cycles of the driving signal required to drive the fan motor to operate at other different reference speeds in the second environment according to the equation of the second environment to update the lookup table module 10.

[0083] In summary, the present application provides a system and a method for automatically correcting the speed of a fan motor, which can automatically correct the duty cycles of the driving signal required to drive the fan motor to operate at different speeds on the lookup table when the fan motor is moved to different environments, so that the fan can directly look up the driving signal with the duty cycle found on the lookup table according to the speed indicated by the speed command in any environment to quickly drive the fan motor to operate at the target speed.

[0084] The above disclosure is only the preferred embodiments of the present application, and is not intended to limit the claims of the present application. Any equivalent technical changes made according to the content of the present application and the drawings are included in the claims of the present application.

Claims

1. A system for automatically correcting fan motor speed, characterized by, The system for automatically correcting the fan motor speed comprises: a lookup table module storing a plurality of reference duty cycles required for driving the fan motor to operate at a plurality of reference speeds in a first environment, respectively, wherein the plurality of reference duty cycles comprises a first reference duty cycle and a second reference duty cycle corresponding to a first reference speed and a second reference speed included in the plurality of reference speeds, respectively; a driving circuit connected to the lookup table module and the fan motor, configured to find a reference duty cycle corresponding to a reference speed identical to an instruction speed indicated by a speed command from the lookup table module, and output a driving signal having the found reference duty cycle to the fan motor; a sample-and-hold circuit connected to the driving circuit and the fan motor, configured to sample and hold a duty cycle of the driving signal output by the driving circuit when driving the fan motor to operate at the first reference speed as a first sample duty cycle, and sample and hold a duty cycle of the driving signal output by the driving circuit when driving the fan motor to operate at the second reference speed as a second sample duty cycle in a second environment; and a calculation circuit connected to the sample-and-hold circuit and the lookup table module, configured to calculate a difference between the first sample duty cycle and the first reference duty cycle as a first difference, calculate a difference between the second sample duty cycle and the second reference duty cycle as a second difference, determine a linear variation relationship between the first difference and the second difference to analyze linear variation data, and calculate the plurality of reference duty cycles required for driving the fan motor to operate at the plurality of reference speeds in the second environment, respectively, based on the linear variation data, to update the lookup table module. The first environment comprises an open space, and the second environment comprises a closed space inside a housing in which the fan motor is placed.

2. The system for automatically correcting fan motor speed of claim 1, wherein, The calculation circuit is configured to generate a first equation as follows based on the first difference and the first reference duty cycle: y1 = a × x1 + b, wherein y1 represents the first difference, x1 represents the first reference duty cycle, a represents a first coefficient, and b represents a second coefficient. The calculation circuit is configured to generate a second equation as follows based on the second difference and the second reference duty cycle: y2 = a × x2 + b, wherein y2 represents the second difference, and x2 represents the second reference duty cycle. The calculation circuit is configured to subtract the first equation from the second equation to calculate the first coefficient, substitute the first coefficient into the first equation or the second equation to calculate the second coefficient, and generate a general equation as follows: y = a × x + b, wherein y represents a difference between the reference duty cycle required in the first environment and the reference duty cycle required in the second environment, and x represents the reference duty cycle required in the first environment. wherein the operation circuit is configured to substitute each of the reference duty cycles required in the first environment when the fan motor is driven to operate at each of the reference rotational speeds into the general equation to calculate each of the reference duty cycles required in the second environment.

3. The system for automatically correcting fan motor speed of claim 2, wherein, The operation circuit is configured to substitute the x values at each of the reference rotational speeds as the horizontal axis values of a graph, the y values as the vertical axis values of a graph, and to construct a linear curve in the graph according to all the x values and y values at the plurality of reference rotational speeds.

4. The system for automatically correcting fan motor speed of claim 1, wherein, When the fan motor maintains to operate at the same reference rotational speed, the sampling and holding circuit samples the duty cycle of the driving signal at a first time and the duty cycle of the driving signal at a second time are different, it is determined that the environment where the fan motor is located is changed, and the operation circuit is instructed to update the lookup table module.

5. The system for automatically correcting fan motor speed of claim 1, wherein, The system for automatically correcting the rotational speed of the fan motor further comprises a steady state detection circuit connected to the sampling and holding circuit, and configured to time a first length of time that the fan motor maintains to operate stably at the first reference rotational speed, and determine that the first length of time reaches a first preset length of time, which represents that the fan motor has reached a steady state, and instruct the sampling and holding circuit to stop sampling and holding the first sampled duty cycle. The steady state detection circuit is configured to time a second length of time that the fan motor maintains to operate stably at the second reference rotational speed, and determine that the second length of time reaches a second preset length of time, which represents that the fan motor has reached a steady state, and instruct the sampling and holding circuit to stop sampling and holding the second sampled duty cycle.

6. A method of automatically correcting the speed of a fan motor, characterized by, The method for automatically correcting the rotational speed of the fan motor comprises the following steps: In the lookup table, a plurality of reference duty cycles required for driving the fan motor to operate at a plurality of reference rotational speeds in a first environment are stored, wherein the plurality of reference duty cycles comprise a first reference duty cycle and a second reference duty cycle corresponding to a first reference rotational speed and a second reference rotational speed comprised in the plurality of reference rotational speeds, respectively. A rotational speed command is received. In the first environment, a reference duty cycle corresponding to a reference rotational speed identical to an instruction rotational speed indicated by the rotational speed command is searched from the lookup table to output a driving signal with the searched reference duty cycle to the fan motor. In a second environment, a duty cycle of the driving signal output when the fan motor is driven to operate at the first reference rotational speed is sampled and held as a first sampled duty cycle. A difference between the first sampled duty cycle and the first reference duty cycle is calculated as a first difference. A duty cycle of the driving signal output when the fan motor is driven to operate at the second reference rotational speed is sampled and held as a second sampled duty cycle. A difference between the second sampled duty cycle and the second reference duty cycle is calculated as a second difference. A linear change relationship between the first difference and the second difference is determined to analyze linear change data. According to the linear variation data, the reference operation periods required for driving the fan motor to operate at the reference rotation speeds in the second environment are calculated respectively to update the look-up table; and In the second environment, the updated reference operation period corresponding to the reference rotation speed identical to the instruction rotation speed indicated by the rotation speed command is looked up from the look-up table to output the driving signal with the looked-up reference operation period to the fan motor. The first environment includes an open space, and the second environment includes a closed space inside a housing in which the fan motor is placed.

7. The method of automatically correcting fan motor speed of claim 6, wherein, The method for automatically correcting the rotation speed of the fan motor further includes the following steps: According to the first difference and the first reference operation period, a first equation is generated as follows: y1=a×x1+b, where y1 represents the first difference, x1 represents the first reference operation period, a represents a first coefficient, and b represents a second coefficient; According to the second difference and the second reference operation period, a second equation is generated as follows: y2=a×x2+b, where y2 represents the second difference, and x2 represents the second reference operation period; The first coefficient is calculated by subtracting the second equation from the first equation, and the second coefficient is calculated by substituting the first coefficient into the first equation or the second equation, to generate a general equation as follows: y=a×x+b, where y represents the difference between the reference operation periods required in the first environment and the second environment, and x represents the reference operation period required in the first environment; and The reference operation period required in the second environment is calculated by substituting the reference operation period required in the first environment into the general equation. The method for automatically correcting the rotation speed of the fan motor further includes the following steps:

8. The method of automatically correcting fan motor speed of claim 7, wherein, The x values and y values under the reference rotation speeds are used to construct a linear curve in a graph. The method for automatically correcting the rotation speed of the fan motor further includes the following steps:

9. The method of automatically correcting fan motor speed of claim 6, wherein, When the fan motor maintains the same reference rotation speed, whether the operation period of the driving signal sampled and held at a first time is identical to the operation period of the driving signal sampled and held at a second time is determined, if not, it is determined that the environment of the fan motor is changed, the look-up table is updated, and if yes, the look-up table is not updated. The method for automatically correcting the rotation speed of the fan motor further includes the following steps:

10. The method of automatically correcting fan motor speed of claim 6, wherein, The first time length during which the fan motor maintains stable operation at the first reference rotation speed is timed; Whether the first time length reaches a first preset time length is determined, if yes, it is determined that the fan motor has reached a steady state, the first sampling operation period is sampled and held, and if not, the timing is restarted; The second time length during which the fan motor maintains stable operation at the second reference rotation speed is timed; and ​ determining whether the second time length reaches a second preset time length, if yes, determining that the fan motor has reached a steady state, sampling and holding the second sampling work period, if no, re-timing.

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