U.S. patent application number 15/225023 was filed with the patent office on 2017-06-29 for fan driver system and analog fan drive chip.
The applicant listed for this patent is NUVOTON TECHNOLOGY CORPORATION. Invention is credited to Ming-Che HUNG.
Application Number | 20170187310 15/225023 |
Document ID | / |
Family ID | 59088458 |
Filed Date | 2017-06-29 |
United States Patent
Application |
20170187310 |
Kind Code |
A1 |
HUNG; Ming-Che |
June 29, 2017 |
FAN DRIVER SYSTEM AND ANALOG FAN DRIVE CHIP
Abstract
A fan driver system is provided, which includes a PWM generator,
a DC generator, a control unit, a pull-down resistor and an
integrator. The DC generator generates a DC test voltage, and a
voltage of the pull-down resistor is detected to generate a
determination signal. The PWM generator provides first and second
PWM test signals having different duty cycles to the fan,
respectively. The integrator integrates speed signal from the fan
and corresponding to the first PWM test signal, to output a first
integral signal, and integrates the speed signal corresponding to
the second PWM test signal, to output a second integral signal.
According to the first and second integral signals, and the
determination signal, the control unit drives the PWM generator to
selectively provide PWM working signal to the fan, and drive the DC
generator to provide DC working voltage to the fan.
Inventors: |
HUNG; Ming-Che; (Hsinchu
Science Park, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NUVOTON TECHNOLOGY CORPORATION |
Hsinchu City |
|
TW |
|
|
Family ID: |
59088458 |
Appl. No.: |
15/225023 |
Filed: |
August 1, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02P 7/29 20130101 |
International
Class: |
H02P 7/29 20060101
H02P007/29 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 2015 |
TW |
104143307 |
Claims
1. A fan driver system, applied to detect a type of a fan and drive
the fan according to a detection result, and the fan driver system
comprising: a direct current (DC) generator electrically connected
to the fan and configured to provide a DC test voltage to the fan;
a pull-down resistor selectively connected to the fan; an input
determination circuit electrically connected to the pull-down
resistor, and configured to detect a voltage of the pull-down
resistor and output a determination signal according to the
detected voltage; a control unit electrically connected to the
input determination circuit and the DC generator, and configured to
receive the determination signal; a pulse width modulation (PWM)
generator electrically connected to the fan and the control unit,
and configured to respectively provide a first PWM test signal and
a second PWM test signal to the fan, wherein a first duty cycle of
the first PWM test signal is different from a second duty cycle of
the second PWM test signal; an integrator electrically connected to
the fan, and configured to integrate a speed signal from the fan
and corresponding to the first PWM test signal, so as to output a
first integral signal, and integrate the speed signal corresponding
to the second PWM test signal, so as to output a second integral
signal; and a voltage sensing circuit electrically connected the
integrator and the control unit; wherein according to the first
integral signal, the second integral signal and the determination
signal, the control unit is configured to drive the PWM generator
to selectively provide a PWM working signal to the fan, and drive
the DC generator to provide a DC working voltage to the fan.
2. The fan driver system according to claim 1, further comprising:
a switch electrically connected to the control unit, the integrator
and the fan; wherein under a condition that the PWM generator is
switched to output the second PWM test signal, after the second PWM
test signal is output for a predetermined period, the control unit
is configured to turn off the switch to disconnect the integrator
and the fan.
3. The fan driver system according to claim 1, wherein when the
first integral signal is not equal to the second integral signal
and the determination signal indicates that the voltage of the
pull-down resistor is in high-level, the fan is determined as a
four-wire PWM fan with a built-in pull-up resistor, and the speed
of the fan is adjustable by changing a duty cycle of the PWM
working signal.
4. The fan driver system according to claim 1, wherein when the
first integral signal is not equal to the second integral signal
and the determination signal indicates that the voltage of the
pull-down resistor is in low-level, the fan is determined as a
four-wire PWM fan without a built-in pull-up resistor, and the
speed of the fan is adjustable by changing a duty cycle of the PWM
working signal.
5. The fan driver system according to claim 1, wherein when the
first integral signal is equal to the second integral signal and
the determination signal indicates that the voltage of the
pull-down resistor is in low-level, the fan is determined as a
three-wire DC fan, and the speed of the fan is adjustable by
changing amplitude of the DC working voltage.
6. An analog fan drive chip, applied to detect a type of a fan and
drive the fan according to a detection result, and the analog fan
drive chip comprising: a first pin electrically connected to the
fan selectively; a second pin electrically connected to the fan; a
third pin electrically connected to the fan; a DC generator
electrically connected to the third pin and configured to provide a
DC test voltage to the fan; a pull-down resistor electrically
connected to the first pin; an input determination circuit
electrically connected to the pull-down resistor and configured to
detect a voltage of the pull-down resistor while the DC test
voltage is provided, and output a determination signal according to
the detected voltage; a control unit electrically connected to the
input determination circuit and the DC generator, and configured to
receive the determination signal; a PWM generator electrically
connected to the first pin and the control unit, and configured to
respectively provide a first PWM test signal and a second PWM test
signal to the fan, wherein a first duty cycle of the first PWM test
signal is different from a second duty cycle of the second PWM test
signal; an integrator electrically connected to the second pin, and
configured to integrate a speed signal from the fan and
corresponding to the first PWM test signal, so as to output a first
integral signal, and integrate the speed signal corresponding to
the second PWM test signal, so as to output a second integral
signal; and a voltage sensing circuit electrically connected to the
integrator and the control unit; wherein according to the first
integral signal, the second integral signal and the determination
signal, the control unit is configured to drive the PWM generator
to selectively provide a PWM working signal to the fan, and drive
the DC generator to provide a DC working voltage to the fan.
7. The analog fan drive chip according to claim 6, further
comprising: a switch electrically connected to the control unit,
the integrator and the second pin; wherein under a condition that
the PWM generator is switched to output the second PWM test signal,
after the second PWM test signal is output for a predetermined
period, the control unit is configured to turn off the switch to
disconnect the integrator and the second pin.
8. The analog fan drive chip according to claim 6, wherein when the
first integral signal is not equal to the second integral signal
and the determination signal indicates that the voltage of the
pull-down resistor is in high-level, the fan is determined as a
four-wire PWM fan with a built-in pull-up resistor, and the speed
of the fan is adjustable by changing a duty cycle of the PWM
working signal.
9. The analog fan drive chip according to claim 6, wherein when the
first integral signal is not equal to the second integral signal
and the determination signal indicates that the voltage of the
pull-down resistor is in low-level, the fan is determined as a
four-wire PWM fan without a built-in pull-up resistor, and the
speed of the fan is adjustable by changing a duty cycle of the PWM
working signal.
10. The analog fan drive chip according to claim 6, wherein when
the first integral signal is equal to the second integral signal
and the determination signal indicates that the voltage of the
pull-down resistor is in low-level, the fan is determined as a
three-wire DC fan, and the speed of the fan is adjustable by
changing an amplitude of the DC working voltage.
11. An analog fan drive chip, applied to detect a type of a fan and
drive the fan according to a detection result, the analog fan drive
chip connected to a switch and an integrator, and the analog fan
drive chip comprising: a first pin electrically connected to the
fan selectively; a second pin electrically connected to the switch;
a third pin electrically connected the fan through the integrator
and the switch; a fourth pin electrically connected to the fan; a
DC generator electrically connected to the fourth pin and
configured to provide a DC test voltage to the fan; a pull-down
resistor electrically connected to the first pin; an input
determination circuit electrically connected to the pull-down
resistor and configured to detect a voltage of the pull-down
resistor while the DC test voltage is provided, and output a
determination signal according to the detected voltage; a control
unit electrically connected to the input determination circuit and
the DC generator, and configured to receive the determination
signal; a PWM generator electrically connected to the first pin and
the control unit, and configured to respectively provide a first
PWM test signal and a second PWM test signal to the fan, wherein a
first duty cycle of the first PWM test signal is different from a
second duty cycle of the second PWM test signal; and a voltage
sensing circuit electrically connected to the first pin and the
control unit; wherein the integrator integrates a speed signal from
the fan and corresponding to the first PWM test signal, so as to
output a first integral signal, and integrate the speed signal
corresponding to the second PWM test signal, so as to output a
second integral signal; wherein under a condition that the PWM
generator is switched to output the second PWM test signal, after
the second PWM test signal is output for a predetermined period,
the control unit turns off the switch to disconnect the integrator
and the fan; and wherein the control unit is electrically connected
to the integrator through the second pin, and according to the
first integral signal, the second integral signal and the
determination signal, the control unit is configured to drive the
PWM generator to provide a PWM working signal to the fan, and drive
the DC generator to provide a DC working voltage to the fan.
12. A fan driver system, applied to detect a type of a fan and
drive the fan according to a detection result, and the fan driver
system comprising: a PWM generator electrically connected to the
fan and configured to respectively provide a first PWM test signal
and a second PWM test signal to the fan, wherein a first duty cycle
of the first PWM test signal is different from a second duty cycle
of the second PWM test signal; an integrator electrically connected
to the fan and configured to integrate a speed signal from the fan
corresponding to the first PWM test signal, so as to output a first
integral signal, and integrate the speed signal corresponding to
the second PWM test signal, so as to output a second integral
signal; a voltage sensing circuit electrically connected to the
integrator; a control unit electrically connected to the PWM
generator and the voltage sensing circuit, and configured to drive
the PWM generator to selectively provide a PWM working signal to
the fan according to comparison between the first integral signal
and the second integral signal; and a DC generator electrically
connected the fan and the control unit, wherein the control unit is
configured to drive the DC generator to provide a DC working
voltage to the fan according to comparison between the first
integral signal and the second integral signal.
13. The fan driver system according to claim 12, wherein when the
first integral signal is not equal to the second integral signal,
the PWM generator changes a duty cycle of the PWM working signal to
control the speed of the fan, and when the first integral signal
and the second integral signal are almost the same and the first
integral signal is not equal to zero substantially, the DC
generator changes amplitude of the DC working voltage to control
the speed of the fan.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of Taiwan Patent
Application No. 104143307, filed on Dec. 23, 2015, the disclosure
of which is incorporated herein in its entirety by reference, in
the Taiwan Intellectual Property Office.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present disclosure relates to a fan driver system and an
analog fan drive chip, more particularly to an analog fan drive
chip capable of automatically detecting a type of a fan.
[0004] 2. Description of the Related Art
[0005] With progress in electronic technologies, various electronic
devices (such as processor, display card or other device) have
higher and higher working frequencies and power consumption, but
also generate more heat during operations. In order to prevent the
devices from being damaged because of overheat, cooling devices are
usually required to decrease temperatures of these devices.
Generally, fans are cooling devices widely used. A fan is usually
disposed near the electronic device to be cooled, and configured to
generate air flow around the electronic device for heat
dissipation. The fan operated in a higher speed can blow hot air
away from the electronic component more quickly, so as to provide
higher cooling efficiency. Currently, commercially available fans
can be classified into three-wire direct current (DC) fan and
four-wire pulse width modulation (PWM) fan. According to a
specification defined by the INTEL Corporation, the four-wire PWM
fan must be provided with a built-in pull-up resistor. However,
many four-wire PWM fans which do not meet the requirement of the
specification of the INTEL Corporation are also commercially
available. That is, some commercially available four-wire PWM fans
do not have the built-in pull-up resistor.
[0006] Please refer to FIG. 1 which shows an interface 102 of a
general three-wire DC fan 104. The interface 102 includes a ground
terminal 106, a DC signal terminal 108 and a speed signal terminal
110. The speed signal terminal 110 is configured to provide a speed
signal of the fan, and the speed signal is a square wave having a
frequency proportional to the speed of the three-wire DC fan 104.
The speed of the three-wire DC fan 104 can be controlled by the
voltage input in the DC signal terminal 108. During operation of
the fan, the voltage applied to the DC signal terminal 108 is
adjustable, for example, in a range from 4V to 12V, for fan speed
control. The speed of the three-wire DC fan 104 is positively
relevant to amplitude of the voltage applied to the DC signal
terminal 108. Higher the voltage input to the DC signal terminal
108 is, faster the speed of the fan is.
[0007] Please refer to FIG. 2 which shows an interface 202 of a
general four-wire PWM fan 204. The four-wire PWM fan 204 may be
provided with/without a built-in pull-up resistor. The four-wire
PWM fan 204 has a ground terminal 206, a DC signal terminal 208, a
speed signal terminal 210 and a PWM control terminal 212. The DC
signal terminal 208 and the speed signal terminal 210 of the
four-wire PWM fan 204 are similar to the DC signal terminal 108 and
the speed signal terminal 110 of the three-wire DC fan 104. The
speed of the four-wire PWM fan 204 is controlled by a duty cycle of
the PWM signal applied to the PWM control terminal 212, but not the
voltage applied to the DC signal terminal 208. For the four-wire
PWM fan 204, the DC signal terminal 208 is usually kept as a fixed
voltage. When the duty cycle of the PWM signal applied to the PWM
control terminal 212 is 50%, the speed of the four-wire PWM fan 204
is 50% of a full speed of the four-wire PWM fan 204. Similarly,
when the duty cycle of the PWM signal input to the PWM control
terminal 212 is 80%, the speed of the four-wire PWM fan 204 is 80%
of the full speed. That is, when the duty cycle of the PWM signal
applied to the PWM control terminal 212 is increased or decreased,
the speed of the four-wire PWM fan 204 is increased or decreased
correspondingly.
[0008] Generally speaking, the electronic device is usually
designed to just support a certain type of the fan, so the user is
required to connect a correct type of the fan to the electronic
device for better heat-dissipation performance; however, it is
inconvenient for the user who does not know the type of the fan
supported by the electronic device. For example, prior to selection
of the fan for a computer, the user had better check a motherboard
of the computer to know the supportable type of the fan.
[0009] In prior art, a tachometer is used to detect the type of the
fan, so as to solve above-mentioned problem. The tachometer
requires a clock signal to count a number of cycles of the speed
signal of the fan in a preset period, but a clock circuit cannot be
designed in an analog chip.
SUMMARY OF THE INVENTION
[0010] In order to solve the problem in prior art, an objective of
the present disclosure is to provide a fan driver system and an
analog fan drive chip capable of automatically detecting the type
of the fan, and the relevant circuit components can be produced in
similar manufacturing process.
[0011] To achieve the objective, the present disclosure provides a
fan driver system applied to detect the type of the fan and drive
the fan according to a detection result. The fan driver system
includes a direct current (DC) generator, a pull-down resistor, an
input determination circuit, a control unit, a pulse width
modulation (PWM) generator, an integrator and a voltage sensing
circuit. The DC generator is electrically connected to the fan, the
pull-down resistor is electrically connected to the fan
selectively, and the input determination circuit is electrically
connected to the pull-down resistor and configured to detect a
voltage of the pull-down resistor, and output a determination
signal according to the detected voltage. The control unit is
electrically connected to the input determination circuit and the
DC generator, and configured to receive the determination signal.
The PWM generator is electrically connected to the fan and the
control unit, and configured to provide a first PWM test signal and
a second PWM test signal to the fan, respectively. A first duty
cycle of the first PWM test signal is different from a second duty
cycle of the second PWM test signal. The integrator is electrically
connected to the fan and configured to integrate a speed signal
from the fan and corresponding to the first PWM test signal, so as
to output a first integral signal, and integrate the speed signal
corresponding to the second PWM test signal, so as to output a
second integral signal. The voltage sensing circuit is electrically
connected the integrator and the control unit. According to the
first integral signal, the second integral signal and the
determination signal, the control unit is configured to drive the
PWM generator to selectively provide a PWM working signal to the
fan, and drive the DC generator to provide a DC working voltage to
the fan.
[0012] Preferably, the fan driver system further includes a switch
electrically connected to the control unit, the integrator and the
fan. Under a condition that the PWM generator is switched from the
first PWM test signal to the second PWM test signal, after the
second PWM test signal is output for a predetermined period, the
control unit is configured to turn off the switch to disconnect the
integrator and the fan.
[0013] Preferably, when the first integral signal is not equal to
the second integral signal and the determination signal indicates
that the voltage of the pull-down resistor is in high-level, the
fan is determined as a four-wire PWM fan with a built-in pull-up
resistor, and the speed of the fan is adjustable by changing a duty
cycle of the PWM working signal. When the first integral signal is
not equal to the second integral signal and the determination
signal indicates that the voltage of the pull-down resistor is in
low-level, the fan is determined as a four-wire PWM fan without the
built-in pull-up resistor, and the speed of the fan is adjustable
by changing a duty cycle of the PWM working signal. When the first
integral signal is equal to the second integral signal and the
determination signal indicates that the voltage of the pull-down
resistor is in low-level, the fan is determined as a three-wire DC
fan, and the speed of the fan is adjustable by changing amplitude
of the DC working voltage.
[0014] To achieve the objective, the present disclosure further
provides an analog fan drive chip applied to detect a type of a fan
and drive the fan according to detection result. The analog fan
drive chip includes a first pin, a second pin, a third pin, a DC
generator, a pull-down resistor, an input determination circuit, a
control unit, a PWM generator, an integrator and a voltage sensing
circuit. The first pin is electrically connected to the fan
selectively. The second pin is electrically connected to the fan.
The third pin is electrically connected to the fan. The DC
generator is electrically connected to the third pin and configured
to provide a DC test voltage to the fan. The pull-down resistor is
electrically connected to the first pin. The input determination
circuit is electrically connected to the pull-down resistor and
configured to detect a voltage of the pull-down resistor while the
DC test voltage is provided, and output a determination signal
according to the detected voltage. The control unit is electrically
connected to the input determination circuit and the DC generator,
and configured to receive the determination signal. The PWM
generator is electrically connected to the first pin and the
control unit, and configured to provide a first PWM test signal and
a second PWM test signal to the fan. A first duty cycle of the
first PWM test signal is different from a second duty cycle of the
second PWM test signal. The integrator is electrically connected to
the second pin and configured to integrate a speed signal which is
from the fan and corresponds to the first PWM test signal, so as to
output a first integral signal, and integrate the speed signal
corresponding to the second PWM test signal, so as to output a
second integral signal. The voltage sensing circuit is electrically
connected to the integrator and the control unit. According to the
first integral signal, the second integral signal and the
determination signal, the control unit is configured to drive the
PWM generator to selectively provide a PWM working signal to the
fan, and drive the DC generator to provide a DC working voltage to
the fan.
[0015] To achieve the objective, the present disclosure further
provides an analog fan drive chip applied to detect a type of a fan
and drive the fan according to detection result. The analog fan
drive chip is electrically connected to a switch and an integrator,
and includes a first pin, a second pin, a third pin, a fourth pin,
a DC generator, a pull-down resistor, an input determination
circuit, a control unit, a PWM generator and a voltage sensing
circuit. The first pin is electrically connected to the fan
selectively. The second pin is electrically connected to the
switch. The third pin is electrically connected to the fan through
the integrator and the switch. The fourth pin is electrically
connected to the fan. The DC generator is electrically connected to
the fourth pin and configured to provide a DC test voltage to the
fan. The pull-down resistor is electrically connected to the first
pin. The input determination circuit is electrically connected to
the pull-down resistor and configured to detect a voltage of the
pull-down resistor while the DC test voltage is provided, and
output a determination signal according to the detected voltage.
The control unit is electrically connected to the input
determination circuit and the DC generator, and configured to
receive the determination signal. The PWM generator is electrically
connected to the first pin and the control unit, and configured to
provide a first PWM test signal and a second PWM test signal to the
fan. A first duty cycle of the first PWM test signal is different
from a second duty cycle of the second PWM test signal. The voltage
sensing circuit is electrically connected to the first pin and the
control unit. The integrator integrates a speed signal from the fan
and corresponding to the first PWM test signal, so as to output a
first integral signal, and integrate the speed signal corresponding
to the second PWM test signal, so as to output a second integral
signal. Under a condition that the PWM generator switches from the
first PWM test signal to the second PWM test signal, after the
second PWM test signal is output for a predetermined period, the
control unit turns off the switch to disconnect the integrator and
the fan. The control unit is electrically connected to the
integrator through the second pin, and according to the first
integral signal, the second integral signal and the determination
signal the control unit drives the PWM generator to provide a PWM
working signal to the fan, and drives the DC generator to provide a
DC working voltage to the fan.
[0016] To achieve the objective, the present disclosure further
provides a fan driver system applied to detect a type of the fan
and drive the fan according to a detection result. The fan driver
system includes a PWM generator, an integrator, a voltage sensing
circuit, a control unit and a DC generator. The PWM generator is
electrically connected to the fan selectively and configured to
provide a first PWM test signal and a second PWM test signal to the
fan. A first duty cycle of the first PWM test signal is different
from a second duty cycle of the second PWM test signal. The
integrator is electrically connected to the fan and integrates a
speed signal from the fan corresponding to the first PWM test
signal, so as to output a first integral signal, and integrate the
speed signal corresponding to the second PWM test signal, so as to
output a second integral signal. The voltage sensing circuit is
electrically connected to the integrator. The control unit is
electrically connected to the PWM generator and the voltage sensing
circuit and configured to control the PWM generator to selectively
provide a PWM working signal to the fan according to comparison
between the first integral signal and the second integral signal.
The DC generator is electrically connected to the fan and the
control unit, and the control unit is configured to control the DC
generator to provide a DC working voltage to the fan according to
the comparison between the first integral signal and the second
integral signal.
[0017] Preferably, when the first integral signal is not equal to
the second integral signal, the PWM generator is configured to
change a duty cycle of the PWM working signal to control the speed
of the fan. When the first integral signal and the second integral
signal are almost the same and the first integral signal is not
equal to zero substantially, the DC generator is configured to
change amplitude of the DC working voltage to control the speed of
the fan.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The detailed structure, operating principle and effects of
the present disclosure will now be described in more details
hereinafter with reference to the accompanying drawings that show
various embodiments of the present disclosure as follows.
[0019] FIG. 1 is a schematic view of a general three-wire DC
fan.
[0020] FIG. 2 is a schematic view of a general four-wire PWM
fan.
[0021] FIG. 3 is a block diagram of a fan driver system of a first
embodiment of the invention.
[0022] FIG. 4 is a flowchart of an embodiment of driving the fan
driver system shown in FIG. 3.
[0023] FIG. 5 is a flowchart of other embodiment of driving the fan
driver system shown in FIG. 3.
[0024] FIG. 6 is a waveform diagram of a speed signal Vtach
corresponding to the first PWM test signal and a first integral
signal V1 of the fan driver system of FIG. 3.
[0025] FIG. 7 is a waveform diagram of a speed signal Vtach
corresponding to the second PWM test signal and a second integral
signal V2 of the fan driver system of FIG. 3.
[0026] FIG. 8 is a block diagram of a fan driver system of a second
embodiment of the present disclosure.
[0027] FIG. 9 is a block diagram of a fan driver system of a third
embodiment of the present disclosure.
[0028] FIG. 10 is a block diagram of a fan driver system of a
fourth embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] Reference will now be made in detail to the exemplary
embodiments of the present disclosure, examples of which are
illustrated in the accompanying drawings. Therefore, it is to be
understood that the foregoing is illustrative of exemplary
embodiments and is not to be construed as limited to the specific
embodiments disclosed, and that modifications to the disclosed
exemplary embodiments, as well as other exemplary embodiments, are
intended to be included within the scope of the appended claims.
These embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the inventive concept
to those skilled in the art. The relative proportions and ratios of
elements in the drawings may be exaggerated or diminished in size
for the sake of clarity and convenience in the drawings, and such
arbitrary proportions are only illustrative and not limiting in any
way. The same reference numbers are used in the drawings and the
description to refer to the same or like parts.
[0030] It will be understood that, although the terms `first`,
`second`, `third`, etc., may be used herein to describe various
elements, these elements should not be limited by these terms. The
terms are used only for the purpose of distinguishing one component
from another component. Thus, a first element discussed below could
be termed a second element without departing from the teachings of
embodiments. As used herein, the term "or" includes any and all
combinations of one or more of the associated listed items.
[0031] Please refer to FIG. 3 which shows a block diagram of a fan
driver system of a first embodiment of the invention. The fan
driver system includes a pulse width modulation (PWM) signal
generator 310, a direct current (DC) generator 320, an input
determination circuit 330, an integrator 350, a voltage sensing
circuit 360 and a control unit 370. The PWM generator 310 is
selectively connected to a PWM control terminal 212 of a fan. The
DC generator 320 is connected to a DC signal terminal 208 of the
fan. The input determination circuit 330 is selectively connected
to the PWM control terminal 212 of the fan. The PWM generator 310,
the DC generator 320 and the input determination circuit 330 are
connected with the control unit 370. The pull-down resistor 340 is
electrically connected to the input determination circuit 330 and
selectively connected to the PWM control terminal 212 of the fan.
The integrator 350 is electrically connected to a fan speed signal
terminal 210 of the fan, and further connected to the control unit
370 through the voltage sensing circuit 360. During a test stage,
the DC generator 320 is configured to provide a DC test voltage,
and the input determination circuit 330 is configured to detect a
voltage of the pull-down resistor 340 while the DC test voltage is
provided, and further output a determination signal to the control
unit 370 according to the detected voltage. The PWM generator 310
is configured to provide a first PWM test signal having a first
duty cycle, and a second PWM test signal having a second duty cycle
which is different from the first duty cycle. During the first PWM
test signal the integrator 350 is configured to integrate a speed
signal from the fan to output a first integral signal, and during
the second PWM test signal the integrator 350 integrates the speed
signal to output a second integral signal. The first integral
signal and the second integral signal are transmitted to the
control unit 370. During an operation stage, according to the first
integral signal, the second integral signal and the determination
signal the control unit 370 is configured to selectively control
the PWM generator 310 to provide a PWM working signal to the fan,
and control the DC generator 320 to provide a DC working voltage to
the fan.
[0032] It should be noted that the fan connected with the fan
driver system shown in FIG. 3 is the four-wire PWM fan of FIG. 2
for convenience in explanation; however, the fan driver system of
FIG. 3 can also be connected with the three-wire DC fan of FIG. 1.
Under a condition that the fan driver system is connected with the
three-wire DC fan, a first pin 301 of the fan driver system is an
empty pin, and a second pin 302, third pin 303 and a fourth pin 304
are respectively connected with the speed signal terminal 110, the
DC signal terminal 108 and the ground terminal 106. The first pin
301 of the fan driver system is not connected with the fan when the
fan is the three-wire DC fan, and connected with the PWM control
terminal 212 of the fan when the fan is the four-wire PWM fan, so
in description of the present disclosure the PWM generator 310, the
input determination circuit 330 and the pull-down resistor
pull-down resistor 340 are selectively connected to the PWM control
terminal 212 of the fan. Similarly, the fan driver systems of the
present disclosure shown in FIGS. 8 through 10 are also applicable
to the three-wire DC fan, and the connection between the fan driver
system and the three-wire DC fan can be with reference to FIG. 3
and above-mentioned description.
[0033] In addition, as shown in FIG. 3, the first pin 301 of the
fan driver system is connected to the PWM control terminal 212 of
the fan, the second pin 302 and the third pin 303 are respectively
connected to the speed signal terminal 210 and the DC signal
terminal 208 through a speed signal application circuit 710 and a
DC application circuit 708, and the fourth pin 304 is connected to
the ground terminal 206 of the fan. When the fan driver system is
connected to the three-wire DC fan, the connections between the
pins 302, 303, 304 and the three-wire DC fan are the same as the
above-mentioned content, but the first pin 301 is an empty pin. The
speed signal application circuit 710 and the DC application circuit
708 are configured to adjust amplitude of the signal transmitted
from the fan driver system to the fan. For example, the amplitude
of the speed signal output from the fan can be up to 12V but the
acceptable amplitude of the signal for the integrator 350 is just
3.3V, so the speed signal application circuit 710 can lower the
signal to adjust the amplitude of the speed signal to a range
acceptable for the integrator 350. Similarly, the DC application
circuit 708 can include a boost circuit, a buck circuit or a
combination thereof.
[0034] In the fan driver system of FIG. 3, the integrator 350 is
connected to the control unit 370 through the voltage sensing
circuit 360, and the input determination circuit 330 is also
connected to the control unit 370. The voltage sensing circuit 360
is configured to sense a signal from the integrator 350, such as
the first integral signal and the second integral signal. The input
determination circuit 330 is configured to sense the voltage of the
pull-down resistor 340 to generate the determination signal. The
control unit may include a circuit configured to receive and
analyze the determination signal from the input determination
circuit 330, a comparison circuit configured to compare the signal
from the voltage sensing circuit 360, and a sampling circuit
configured to determine a signal sampling timing. Upon receipt of
information from the input determination circuit 330 and the
voltage sensing circuit 360, the control unit 370 controls the DC
generator 320 and the PWM generator 310 to drive the fan.
[0035] The operation of the fan driver system of FIG. 3 is
illustrated in cooperation with FIG. 4. FIG. 4 is a flow chart of
an embodiment of driving the fan driver system of FIG. 3. Before
the fan driver system of the embodiment of the present disclosure
generates the determination, the type of the fan is unknown, so the
fan driver system must performs a series of tests to check the type
of the fan. In addition, it should be noted that the input
terminals and the output terminals defined in the flowcharts of
FIGS. 4 and 5 are for the fan driver system.
[0036] At the beginning of the flow, the test stage is performed to
determine the type of the fan for further providing a proper
driving manner. In step S101, the DC generator 320 provides the DC
test voltage to the DC signal terminal of the fan. Preferably, the
DC test voltage is in a range from 50% to 100% of the voltage of
power supplied to the fan, for example, when the fan is supplied
with 12V of voltage, the DC test voltage can be in the range from
6V to 12V. The 12V of voltage is a normal working voltage of the
four-wire PMW and close to the maximal input voltage of the
three-wire DC fan. The first pin 301 is set as the input terminal
to receive the signal from the fan.
[0037] In step S102, if the fan is the four-wire PWM fan having a
built-in pull-up resistor at the PWM control terminal 212 thereof,
the PWM control terminal 212 of the fan is connected to the ground
through the first pin 301 and the pull-down resistor 340, so as to
form a loop. When the fan receives the DC voltage from the DC
generator, the voltage Vpl of pull-down resistor 340 is in
relatively high-level, and the input determination circuit 330
receives and records the voltage Vpl. On the other hand, if the fan
is the three-wire DC fan, the first pin 301 is the empty pin, so
the pull-down resistor 340 fails to receive the voltage from the
fan, and the voltage Vpl is in relatively low-level. The input
determination circuit 330 also receives and records the voltage
Vpl. If the fan is the four-wire PWM fan without the built-in
pull-up resistor at the PWM control terminal 212 thereof, the
pull-down resistor 340 does not receive voltage from the fan, so
the voltage Vpl of the pull-down resistor 340 is still in
relatively low-level. The input determination circuit 330 receives
and records the voltage Vpl.
[0038] When the voltage Vpl received by the input determination
circuit 330 is in relatively high-level, step S103 is executed. In
the step S103, the pull-down resistor 340 can receive voltage from
the fan only when the fan is the four-wire PWM with the built-in
pull-up resistor at the PWM control terminal 212, so the input
determination circuit 330 determines the fan as the PWM fan and the
way of driving the PWM fan is described in below steps. The type of
the fans is determined, so the test stage is ended and an operation
stage is started. In step S104, the first pin 301 is switched from
the input terminal to an output terminal. Next, in step S105, the
PWM generator 310 outputs the PWM working signal, and the speed of
the PWM fan can be adjusted by changing the duty cycle of the PWM
working signal. The DC generator 320 outputs a fixed voltage (such
as 12V) as the working voltage of the four-wire PWM fan.
[0039] In the step S102, when the voltage Vpl received by the input
determination circuit 330 is in relatively low-level, the fan may
be the three-wire DC fan or the four-wire PWM fan without the
built-in pull-up resistor at the PWM control terminal 212, so the
input determination circuit 330 cannot directly determine the type
of the fan and must execute steps after step S106 for further test.
In the step S106, the first pin 301 is set as the output terminal,
and in the step S107 the PWM generator 310 then outputs the first
PWM test signal having the first duty cycle. If the fan is the
four-wire PWM fan without the built-in pull-up resistor at the PWM
control terminal 212 thereof, the first PWM test signal can be
input to the fan through the first pin 301; if the fan is the
three-wire DC fan, the first pin 301 is the empty pin, so the fan
does not receive the first PWM test signal, and has no response for
the first PWM test signal. The speed signal output from the speed
signal terminal 210 of the fan is in response to the first PWM test
signal. In step S108, the integrator 350 integrates the speed
signal from the fan to output the first integral signal V1. It
should be noted that when the speed signal application circuit 710
is not connected with the fan, the first integral signal V1 may not
be zero because of existence of the pull-up resistor of the speed
signal application circuit 710. Therefore, if the integral signal
V1 is equal to zero substantially, it can be determined that the
fan does not work because of failure, abnormal or error connection
in step S115, and the fan driver system may alert the user to check
the connection of the fan for troubleshooting the problem. If the
first integral signal V1 is not equal to zero substantially, step
S109 is executed next. In the step S109, the PWM generator 310
outputs the second PWM test signal having the second duty cycle
which is different from the first duty cycle. In step S110, the
integrator 350 integrates the speed signal from the fan again, so
as to output the second integral signal V2.
[0040] According to the first integral signal V1 and the second
integral signal V2, the fan can be determined as the three-wire DC
fan or the four-wire PWM fan without the built-in pull-up resistor
at the PWM control terminal 212 thereof. More specifically, when
the first integral signal V1 is different from the second integral
signal V2, it means the fan can respond to the PWM test signals
having different duty cycles, so in step S111 the fan is determined
as the four-wire PWM fan without the built-in pull-up resistor at
the PWM control terminal 212 thereof, and the test stage is ended
and the operation stage is started. In step S112, the PWM generator
310 outputs the PWM working signal, and the speed of the fan can be
adjusted by changing the duty cycle of the PWM working signal. The
DC generator 320 outputs the constant voltage (such as 12V) as the
working voltage of the four-wire PWM fan.
[0041] In the other hand, if the first integral signal V1 and the
second integral signal V2 are almost the same, it means that the
connected fan does not respond to the PWM test signals having
different duty cycles, so in step S113, the fan is determined as
the three-wire DC fan, and the test stage is ended and the
operation stage is started. In step S114, the DC generator 320
outputs the DC working voltage, and the speed of the fan can be
adjusted by changing the amplitude of the DC working voltage. In
this case, the PWM generator 310 is not necessary to generate any
signal, so in the operation stage the PWM generator 310 selectively
provides the PWM working signal to the fan.
[0042] In accordance with the fan driver system of the embodiment
of the present disclosure, in the test stage the DC generator 320
and the PWM generator 310 respectively output the test signals, and
the type of the fan can be determined according to the outputs of
the input determination circuit 330 and the integrator 350.
According to the detected type of the fan, in operation stage the
DC generator 320 and the PWM generator 310 outputs the suitable
signal for driving the fan and further controlling the speed of the
fan.
[0043] The method of driving the fan driver system of the
embodiment of present disclosure is not limited to the method shown
in FIG. 4. For example, the method shown in FIG. 5 can also be
applied to the fan driver system of the embodiment of the present
disclosure. Please refer to FIG. 5 which shows a flowchart of other
embodiment of the method of driving the fan driver system of FIG.
3. The main difference between the method of FIG. 5 and the method
of FIG. 4 is that the method of FIG. 5 is used to merely determine
whether the fan is the three-wire DC fan. More specifically, in
step S201 the DC generator 320 provides a DC voltage to the fan. In
this case, the first pin 301 is an output terminal. The step S202
through S205 are executed to obtain the first integral signal V1
and the second integral signal V2 which are then compared with each
other to check whether the fan is the three-wire DC fan. When the
first integral signal V1 is almost equal to the second integral
signal V2, the fan is determined as the three-wire DC fan and,
next, in step S209 the DC generator 320 outputs the DC working
voltage to the fan and the speed of the fan can be adjusted by
changing the amplitude of the DC working voltage. When the first
integral signal V1 is not equal to the second integral signal V2,
in the step S206 the fan is determined as the four-wire PWM fan
and, next, in the step S207 the PWM generator 310 outputs the PWM
working signal and the speed of the fan can be adjusted by changing
the duty cycle of the PWM working signal.
[0044] Please refer to FIGS. 6 and 7 which respectively show a
waveform diagram of speed signal Vtach corresponding to the first
PWM test signal and the first integral signal V1, and a waveform
diagram of the speed signal Vtach corresponding to the second PWM
test signal and the second integral signal V2. Here, the fan to be
detected is the four-wire PWM fan. In FIG. 6, the duty cycle of the
first PWM test signal is 50% and the DC test voltage is 12V. In
FIG. 7, the duty cycle of the first PWM test signal is 100% and the
DC test voltage is 12V. In the embodiment of the present
disclosure, the integrator can be formed by at least resistor and
at least capacitor. Generally speaking, the integration result of a
square wave is similar to a sawtooth wave. However, a resistor with
high resistance and a capacitor with high capacitance can be used
in the fan driver system of the first embodiment of the invention,
so as to obtain an almost constant value of the integration result
while the integrator 350 integrates the square wave. In FIG. 6, the
integrator 350 integrates the speed signal Vtach corresponding to
the first PWM test signal, to output the first integral signal V1
which is about 0.738 V in FIG. 6. In FIG. 7, the integrator 350
integrates the speed signal Vtach corresponding to the second PWM
test signal, so as to output the second integral signal V2 which is
about 0.731 V in FIG. 7. The difference between the first integral
signal V1 and the second integral signal V2 is up to 7 mV. In the
tests performed by the above-mentioned method, when the connected
fan is the four-wire PWM fan, the difference between the first
integral signal V1 and the second integral signal V2 is in a range
from 2 mV to 7 mV, and such voltage difference can be detected by a
general circuit easily. When the connected fan is the three-wire DC
fan, the first integral signal V1 and the second integral signal V2
are almost the same. Therefore, the type of the fan can be
determined according to the difference between the first integral
signal V1 and the second integral signal V2.
[0045] Please refer back to FIG. 3. The fan driver system of the
first embodiment of the invention can be integrated into an analog
fan drive chip 300. In FIG. 3, a part enclosed by a dashed line
includes the components of the analog fan drive chip 300. More
specifically, the analog fan drive chip 300 may include all
components of the fan driver system of the first embodiment, and
the first pin 301, the second pin 302, the third pin 303 and the
fourth pin 304 configured to connect with the components. The first
pin 301 is selectively connected to the PWM control terminal of the
fan, the second pin 302 is connected to the speed signal terminal
of the fan, the third pin 303 is connected to the DC signal
terminal of the fan, and the fourth pin 304 is connected to the
ground terminal of the fan. The other components are illustrated in
above paragraphs, so their detailed descriptions are omitted. The
PWM generator 310, the DC generator 320, the input determination
circuit 330, the pull-down resistor 340, the integrator 350, the
voltage sensing circuit 360 and the control unit 370 all included
in the analog fan drive chip 300 can be implemented by analog
circuits or components, and their production can be performed and
integrated in an analog device manufacturing process, so that the
manufacturing process of the analog fan drive chip 300 can be
further simpler and has reduced cost. In an example, compared with
the conventional technology in which a tachometer is used to detect
the fan speed and the tachometer is a kind of digital circuit
manufactured by digital manufacturing process and has a
significantly large circuit area, the present disclosure has an
advantage in that the system and the chip of the present disclosure
can be implemented by pure analog design and manufacturing process
without using the tachometer. In addition, the integrator 350
occupies a relatively low circuit area, so the fan driver system of
the present disclosure is more flexible in entire circuit
design.
[0046] Please refer to FIG. 8 which is a block diagram of a fan
driver system of a second embodiment of the present disclosure. The
difference between the second embodiment and the first embodiment
is that the fan driver system of the second embodiment further
includes a switch 480. The switch 480 is connected to the control
unit 470, and the integrator 450 is connected to the speed signal
terminal 210 of the fan through the switch 480. In the test stage,
the PWM generator 410 outputs the first PWM test signal first and
then switches to the second PWM test signal. After the second PWM
test signal is output for a predetermined period and the voltage
sensing circuit 460 receives the first integral signal V1 and the
second integral signal V2 both, the control unit 470 turns off the
switch 480 to disconnect the integrator 450 and the speed signal
application circuit 710, so as to prevent other chip or circuit of
the system from being affected by the integrator 450 while the
other chip or circuit uses the signal from the speed signal
application circuit 710 to calculate the fan speed.
[0047] When the duty cycle of the input PWM signal is changed, the
four-wire PWM fan does not instantly change its speed in response
to the change of PWM signal but gradually change to a predetermined
speed corresponding to the new duty cycle after a time period.
Similarly, the speed signal output from the fan completely responds
the change of the fan speed after the time period, and the response
time of the speed signal is second-scale. That is to say, if the
integrator 450 instantly integrates the speed signal output from
the fan after the output of the PWM generator 410 is switched from
the first PWM test signal to the second PWM test signal, the second
integral signal is possibly the same as the first integral signal
and the fan driver system misdetermines the fan as the three-wire
DC fan. In order to solve the problem, the voltage sensing circuit
460 can actively sense and record the first integral signal V1 and
the second integral signal V2 output from the integrator 450 at
every predetermined period, and the predetermined period can be 1,
2, 3, or 5 seconds. After the voltage sensing circuit 460 collects
the first integral signal V1 and the second integral signal V2, the
control unit 470 determines the type of the fan according to
comparison between the first integral signal V1 and the second
integral signal V2, and selectively controls the PWM generator 410
and the DC generator 420 to drive the fan, and then the control
unit 470 turns off the switch 470. Finally, the process is
ended.
[0048] The functions of other components of the second embodiment
are similar to that of the first embodiment, so their detailed
descriptions are omitted.
[0049] In addition, similar to the first embodiment, the fan driver
system of the second embodiment can also be integrated into the
analog fan drive chip 400. Substantially, the analog fan drive chip
400 includes the components inside the dashed line block shown in
FIG. 8.
[0050] Please refer to FIG. 9 which shows a block diagram of a fan
driver system of a third embodiment of the present disclosure and
an analog fan drive chip 500 corresponding thereto. As show in FIG.
9, the speed signal terminal 210 of the fan is connected to the
integrator 750 through the switch 770. The analog fan drive chip
500 includes a first pin 501, a second pin 502, a third pin 503, a
fourth pin 504, a fifth pin 505, a PWM generator 510, a DC
generator 520, an input determination circuit 530, a pull-down
resistor 540, a voltage sensing circuit 560 and a control unit 570.
The first pin 501 is selectively connected to the PWM control
terminal 212 of the fan. The second pin 502 is connected with the
control terminal of the switch 770. The third pin 503 is connected
with the integrator 750. The fourth pin 504 is connected with the
DC signal terminal 208 of the fan. The fifth pin 505 is connected
with the ground terminal 206 of the fan. The PWM generator 510 is
connected to the first pin 501. The DC generator 520 is connected
to the fourth pin 504. The input determination circuit 530 is
connected to the control unit 570 and the first pin 501. The
pull-down resistor 540 is connected to the input determination
circuit 530 and the first pin 501. The voltage sensing circuit 560
is connected to the control unit 570 and the third pin 503. The
control unit 570 is connected to the PWM generator 510, the DC
generator 520, the input determination circuit 530 and the voltage
sensing circuit 560, and connected to the switch 770 through the
second pin 502. In the test stage, the DC generator provides a DC
test voltage. While the DC test voltage is provided, the input
determination circuit 530 detects a voltage of the pull-down
resistor 540 and outputs a determination signal according to the
detected voltage. In the test stage, the PWM generator 510 provides
a first PWM test signal having a first duty cycle, and a second PWM
test signal having a second duty cycle different from the first
duty cycle. The integrator 750 integrates the speed signal from the
fan and corresponding to the first PWM test signal and then outputs
a first integral signal to the voltage sensing circuit 560, and
integrates the speed signal corresponding to the second PWM test
signal to output a second integral signal to the voltage sensing
circuit 560. The voltage sensing circuit 560 then compares the
first integral signal and the second integral signal to output a
comparison result. When the PWM generator 510 switches from the
first PWM test signal to the second PWM test signal, and after the
second PWM test signal is outputted for the predetermined period,
the control unit 570 turns off the switch 770 to disconnect the
integrator 750 and the speed signal application circuit 710. In the
operation stage, according to the comparison result and the
determination signal, the control unit 570 controls the PWM
generator 510 to provide the PWM working signal to the fan, and
controls the DC generator 520 to provide the DC working voltage to
the fan, respectively.
[0051] More specifically, the integrator generally has a small size
but still occupies a certain area in the analog fan drive chip, so
in the third embodiment the integrator 750 and the switch 770 are
disposed outside of the analog fan drive chip 500, so as to further
reduce the size of the analog fan drive chip. In FIG. 9, the analog
fan drive chip 500 includes the components enclosed by the dashed
line block, and does not includes the integrator 750 and the switch
770. Compared with the fan driver chip 400 of aforesaid embodiment,
the analog fan drive chip 500 of the third embodiment has an extra
external pin (such as the second pin 502 shown in FIG. 9) to
connect the control terminal of the switch 770 for control of the
switching of the integrator 750, so that the fan speed signal can
be controlled to selectively transmit to the integrator 750 through
the speed signal application circuit 710 and the switch 770. The
operations of the fan driver system and the analog fan drive chip
500 of the third embodiment are similar to the fan driver system
and the analog fan drive chip 400 shown in FIG. 8, so their
detailed descriptions are omitted.
[0052] Under a condition that the fan is only determined whether
the fan is the three-wire DC fan or the four-wire PWM fan and not
determined whether the four-wire PWM fan has the built-in pull-up
resistor, the fan driver system or the fan driver chip of the
present disclosure can be further simplified. Please refer to FIG.
10 which shows a block diagram of a fan driver system of a fourth
embodiment of the present disclosure. In FIG. 10, the fan driver
system includes a PWM generator 610, a DC generator 620, an
integrator 650, a voltage sensing circuit 660 and a control unit
670. The PWM generator 610 is selectively connected to the PWM
control terminal 212 of the fan, and the generator 620 is connected
to the DC signal terminal 208 of the fan. The integrator 650 is
connected to the speed signal terminal 210 of the fan. In the test
stage, the PWM generator 610 provides the first PWM test signal
having the first duty cycle, and the second PWM test signal having
the second duty cycle different from the first duty cycle. The
integrator 650 integrates the speed signal corresponding to the
first PWM test signal to output the first integral signal, and
integrates the speed signal corresponding to the second PWM test
signal to output the second integral signal. In the operation
stage, according to the first integral signal and the second
integral signal, the control unit 670 controls the PWM generator
610 to selectively provide the PWM working signal to the fan and
controls the DC generator 620 to provide the DC working voltage to
the fan. An analog fan drive chip 600 is also shown in FIG. 10, and
includes components enclosed by the dashed line block, and a first
pin 601, a second pin 602, a third pin 603 and a fourth pin
604.
[0053] Please refer to FIG. 5 for the method of driving the fan
driver system of FIG. 10. The step of using the input determination
circuit to determine the voltage of the pull-down resistor to be in
relatively high-level or low-level is omitted, so the fan driver
system of FIG. 10 cannot determine whether the built-in pull-up
resistor is disposed at the PWM control terminal of the fan. By
executing the steps S201 through S205, it can determine whether the
fan speed is changed in response to the PWM test signals having
different duty cycles, so the fans can be determined as the
four-wire PWM fan in the step S206, or as the three-wire DC fan in
the step S208. More specifically, when the first integral signal is
different from the second integral signal, the PWM generator 610
changes the duty cycle of the PWM working signal to control the
speed of the fan in the step S207. In the other hand, when the
first integral signal and the second integral signal are almost the
same and the first integral signal is not equal to zero
substantially, the DC generator 620 can change the DC working
voltage to control the speed of the fan in the step S209. When the
first integral signal is equal to zero substantially, the fan can
be determined as failure or abnormal, or to have error connection
in step S210, so the fan driver system or the analog fan drive chip
600 can generate an alert signal to notice the user for further
troubleshooting.
[0054] Therefore, the fan driver system and the analog fan drive
chip 600 without the input determination circuit and the pull-down
resistor can has a simplified circuit structure and reduced circuit
space. In addition, the first pin 601 of the fan driver system and
the analog fan drive chip 600 can be kept as the signal output
terminal without being switched between the signal input terminal
and the signal output terminal, so the time for determining the
type of the fan can be saved and the complexity of the method of
driving the fan driver system can also be reduced.
[0055] In some embodiments, the fan driver system or the analog fan
drive chip of the present disclosure has at least one of following
advantages.
[0056] (1) The fan driver system or the analog fan drive chip of
the present disclosure can provide the DC test voltage and the PWM
test signals having different duty cycles in the test stage, so as
to automatically detect the type of the connected fan.
[0057] (2) The fan driver system or the analog fan drive chip of
the present disclosure uses the integrator circuit rather than the
tachometer, so as to facilitate the system or the chip to be
integrated with the analog device.
[0058] (3) The fan driver system or the analog fan drive chip of
the present disclosure extracts the integral signal from the
integrator after the PWM test signals are switched for the
predetermined period, so as to prevent the error caused by delay of
the speed signal.
[0059] The above-mentioned descriptions represent merely the
exemplary embodiment of the present disclosure, without any
intention to limit the scope of the present disclosure thereto.
Various equivalent changes, alternations or modifications based on
the claims of present disclosure are all consequently viewed as
being embraced by the scope of the present disclosure.
* * * * *