US 20020185986A1
(19) United States
(12) Patent Application Publication (10) Pub. N0.: US 2002/0185986 A1
Sekl
(54)
(43) Pub. Date:
APPARATUS FOR DRIVING BRUSHLESS
(52)
Dec. 12, 2002
US. Cl. ............................................................ .. 318/599
MOTOR
(76) Inventor: Kunio Seki, Tokyo (JP)
(57)
ABSTRACT
Correspondence Address:
FRISHAUF, HOLTZ, GOODMAN & CHICK:
A circuit for a three-phase brushless motor, Which can
PC
change phase stator Windings With keeping a predetermined
phase difference to a phase of a back electromagnetic force
OARVENUE
NEW YORK, NY 10017_2023 (Us)
generated in any one of the phase stator Windings, even if a
number of rotation changes extremely, and thereby Which
(21) App1_ No;
(22)
10/131,265
Filed:
Apr- 23, 2002
_
(30)
can reduce a change of a torque and alWays keep the most
suitable efficiency in driving. The circuit for the three-phase
brushless motor comprises a ?rst counter for checking a time
_
_
_
_
of a cycle of a Zero cross of a back electromagnetic force
Forelgn Apphcatlon Pnonty Data
Jun 7 2001
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’
(JP)
detected by a back electromagnetic force detector, and a
2001472513
second counter for counting the time checked by the ?rst
""""""""""""""""""" "
counter at a clock having tWo times as high a frequency as
publication Classi?cation
(51)
the ?rst counter, and determines a timing of changing the
phase stator Windings on the basis of an output outputted
Int. Cl.7 ................................................... .. G05B 11/28
from the second counter.
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Patent Application Publication Dec. 12, 2002 Sheet 1 0f 7
US 2002/0185986 A1
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Patent Application Publication Dec. 12, 2002 Sheet 2 0f 7
US 2002/0185986 A1
BACK-EMFU (TORQUE C(‘)7NSTANT)
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Patent Application Publication Dec. 12, 2002 Sheet 3 0f 7
US 2002/0185986 A1
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Patent Application Publication Dec. 12, 2002 Sheet 4 0f 7
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Patent Application Publication Dec. 12, 2002 Sheet 6 0f 7
US 2002/0185986 A1
BACK-EMF(TORQUE CONSTANT)
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Patent Application Publication Dec. 12, 2002 Sheet 7 0f 7
US 2002/0185986 A1
IFACK-EMIPJKTORQUE CQINSTANT) i
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Dec. 12, 2002
US 2002/0185986 A1
APPARATUS FOR DRIVING BRUSHLESS MOTOR
[0009]
FIGS. 1A to 1G are timing charts shoWing a state
of signals changing in the circuit for driving the three-phase
BACKGROUND OF THE INVENTION
[0001]
1. Field of the Invention
[0002]
The invention relates to a controlling technique for
driving a multiphase brushless motor and further a sensor
less motor, and in particular to a controlling technique for
driving a motor so as to reduce a torque ripple and an
unevenness of rotation.
brushless motor, and the three-phase brushless motor.
[0010]
FIG. 1A is a timing chart shoWing back-EMFs
(back electromagnetic forces) generated in U-phase,
V-phase and W-phase stator Windings of the motor. FIG. 1B
is a timing chart shoWing input voltages inputted to the
back-EMF detector (the back electromagnetic force detec
tor), the phases of Which are shifted by the time constant
circuit. FIG. 1C is a timing chart shoWing a rotational signal
RTS generated on the basis of the Zero cross timing detected
[0003] 2. Description of Related Art
by the back-EMF detector. FIGS. 1D, 1E and 1F are timing
[0004] Athree-phase brushless motor is frequently used as
charts shoWing currents for driving the U-phase, V-phase
a main motor of various types of disc apparatuses of a
personal computer, a portable AV (audiovisual) apparatus,
and other types of OA (office automation) apparatuses,
because the three-phase brushless motor is highly efficient in
being driven, has a small torque ripple and changes a
direction of rotation easily. In recent years, a ratio of a
so-called sensorless type motor requiring no position detect
ing element such as a hall element and so on in the
three-phase brushless motor used for the above-described
apparatuses is increasing, and a large number of speci?c ICs
for driving the sensorless type motor is put to practical.
[0005] The sensorless type motor usually adopts an algo
rithm of detecting a Zero cross timing of a back electromag
and W-phase stator Windings respectively. FIG. 1G is a
timing chart shoWing the torque ripple generated in the
motor rotating.
[0011]
As shoWn in FIGS. 1A to 1G, it is understood that
if the time constant of the time constant circuit is determined
so that the phase difference betWeen the back-EMF of each
of the stator Windings and the input voltage inputted to the
back-EMF detector is just 30 degrees, it is possible to reduce
the torque ripple to 13% substantially.
[0012] Therefore, the method can be applied to the pur
pose of alWays rotating the motor With a predetermined
number of rotation. HoWever, When the method is applied to
netic force generated in a non current-carrying phase of
the purpose of rotating the motor With a number of rotation
Which alWays changes, or of rotating the motor With a
three phases by a back electromagnetic force detector, and
predetermined number of rotation Which changes according
changing a path for supplying a current to a stator Winding
keep rotating.
to the type of the motor, the method prevents the circuit for
driving the motor from forming an integrated circuit,
because the frequency of the back-EMF changes according
[0006] HoWever, because the relationship betWeen the
to the number of rotation of the motor so that it is necessary
to adjust the time constant of the time constant circuit.
on the basis of the detected Zero cross timing, in order to
back electromagnetic force and the torque constant is one to
one, that is, the back electromagnetic force and the torque
constant have the same phases as each other, there is a phase
shift of an electric angle of 30 degrees betWeen the Zero
cross timing of the back electromagnetic force and the
reciprocal cross timing of the torque constants of the three
phases. That is, the phase of the Zero cross timing of the back
electromagnetic force is 30 degrees in advance of the phase
of the reciprocal cross timing of the torque constants.
[0007] Accordingly, if the current-carrying phase is
changed just at the Zero cross timing of the back electro
magnetic force, the big torque ripple is generated in the
sensorless type motor. Specially, in case of a three-phase
half-Wave drive brushless motor, the torque becomes Zero
for a moment just after the current-carrying phase is
changed. As a result, because not only the torque ripple
increases, but also the average torque constant reduces
extremely, the efficiency of the three-phase half-Wave drive
brushless motor in being driven groWs Worse.
[0013] For eXample, FIGS. 2A to 2G are timing charts
shoWing a state of signals When the time constant of the time
constant circuit provided betWeen the stator Windings and
the back-EMF detector is the same as the case shoWn in
FIGS. 1A to 1G, and the number of rotation of the motor is
half one of the case shoWn in FIGS. 1A to 1G.
[0014] When the number of rotation becomes half, the
frequency of the back-EMF also becomes half. That is, When
the number of rotation becomes half, the cycle of rotation
becomes tWo times. HoWever, because the input voltage
inputted to the back-EMF detector is shifted by the time
constant circuit by the same phase, the phase difference
betWeen the back-EMF and the torque constant is 15 degrees
Which is half 30 degrees of case shoWn in FIG. 1. As a
result, the torque ripple increases from 13.3% to 29%
extremely.
[0015] Further, although it is not shoWn in ?gures, it is
understood that When the number of rotation becomes one
[0008] In order to reduce the torque ripple, the controlling
technique for driving the sensorless type motor according to
tenth, the torque ripple increases more. Therefore, in the
case, the torque ripple gets to about 50%.
an earlier development adopts an algorithm of providing a
time constant circuit betWeen the stator Winding generating
the back electromagnetic force and the back electromagnetic
force detector, shifting back the phase of the back electro
Wherein another technique for reducing the torque ripple
magnetic force inputted to the back electromagnetic force
[0016]
FIGS. 3A to 3G are timing charts shoWing a case
according to an earlier development is applied to the circuit
for driving the three-phase brushless motor.
detector by about 30 degrees, and adjust the Zero cross
[0017] The technique is aiming at that the half cycle of the
timing of the back electromagnetic force to the reciprocal
rotational signal RTS Which is the Zero cross timing of the
cross timing of the torque constants.
back-EMF is an electric angle of 60 degrees, and the timing
Dec. 12, 2002
US 2002/0185986 A1
of the phase difference of 30 degrees is not obtained on the
basis of the rotational signal RTS. Therefore, the circuit
adopts a VCO (voltage controlled oscillator) and a PLL
circuit to the output circuit; and a clock generator for
(phase lock loop). Accordingly, the circuit generates the
control circuit comprises a ?rst counter circuit for counting
oscillating signal having four times or tWo times as high the
a ?rst clock signal generated by the clock generator and
checking a time of a cycle of the detection signal outputted
from the back electromagnetic force, and a second counter
circuit for counting a counter number counted by the ?rst
counter circuit according to a second clock signal having
frequency as the rotational signal RTS, generates the cycle
of the electric angle 30 degrees neWly, and uses the cycle as
the timing at Which the phase is changed.
[0018]
According to the above-described method, in case
the lock of the PLL is not opened, even if the number of
rotation is changed, it is possible to alWays obtain the
preferable timing at Which the phase is changed. HoWever,
because the PLL alWays requires a phase compensating
circuit comprising a capacity element and so on in order to
keep the stability of the loop thereof certainly, the PLL has
many technical dif?culties in order to keep the stability of
the loop thereof certainly Within the large range of more than
ten times as large the number of rotation as the case shoWn
in FIGS. 1A to 1G. Further, because the capacity value of
the phase compensation have to be greater as the range of the
number of rotation becomes larger, there occurs the problem
that the folloWing becomes Worse and the torque ripple
becomes bigger, When the number of rotation is changed,
according to the time constant of the phase compensating
circuit.
generating a clock signal required for the control logic
circuit and the timing control circuit, Wherein the timing
tWo times as high a frequency as the ?rst clock signal, and
determines the start timing and the end timing of the control
signal supplied from the control logic circuit to the output
circuit at a rise timing or a fall timing of an output outputted
from the second counter circuit.
[0023] According to the apparatus of the aspect of the
present invention, because the counter circuits for counting
the clock signals generate a phase difference betWeen a Zero
cross point of the back electromagnetic force and a timing of
changing the phase stator Windings, in case the counter
circuits do not over?oW, even if a number of rotation of the
multiphase brushless motor is changed, it is possible to
obtain the stable phase difference. Consequently, it is pos
sible to realiZe the noiseless apparatus for driving the
multiphase brushless motor, Which can reduce a torque
ripple and a rotational unevenness of the multiphase brush
less motor With keeping the most suitable ef?ciency in
SUMMARY OF THE INVENTION
[0019]
The present invention Was developed in vieW of the
above-described problems.
[0020]
It is an object of the present invention to provide a
controlling technique for driving a three-phase brushless
motor, Which can change phase stator Windings of the
three-phase brushless motor With keeping a predetermined
phase difference to a phase of a back electromagnetic force
generated in any one of the phase stator Windings, reduce a
change of a torque of the three-phase brushless motor, and
driving the multiphase brushless motor.
[0024] Preferably, in the apparatus for driving the mul
tiphase brushless motor, of the aspect of the present inven
tion, the clock generator generates a reference clock signal
having at least 100 times as high a frequency as the back
electromagnetic force generated in the multiphase brushless
motor, and the control logic circuit operates on the basis of
the reference clock signal generated by the clock generator.
[0025] Accordingly, because the control logic circuit
detects a change of a rotational signal based on the detection
alWays keep the most suitable ef?ciency in driving the
signal of the back electromagnetic force and generates a
three-phase brushless motor, even if a number of rotation of
series of control signals, and the counter circuits operates on
the basis of the control signals, it is possible to reduce a
the three-phase brushless motor changes eXtremely, for
eXample, from a minimum to ten times as large a maXimum
lagging time before a timing signal of changing the phase
as the minimum.
stator Windings is outputted to a negligible eXtent. Conse
quently, it is possible to improve a response from the control
[0021] According to the present invention, the circuit for
counter for checking a time of a cycle of a Zero cross of a
logic circuit.
[0026] Preferably, in the apparatus for driving the mul
back electromagnetic force detected by a back electromag
tiphase brushless motor, as described above, the control
netic force detector, and a second counter for counting the
time checked by the ?rst counter at a clock having tWo times
logic circuit controls the output circuit so as to drive each of
the phase stator Windings according to a full Wave of each
of the phase stator Winding, or the control logic circuit
controls the output circuit so as to drive each of the phase
stator Windings according to a half Wave of each of the phase
driving a three-phase brushless motor comprises a ?rst
as high a frequency as the ?rst counter.
[0022] More speci?cally, in accordance With an aspect of
the present invention, an apparatus for driving a multiphase
brushless motor comprising a plurality of phase stator Wind
ings, by changing a current supplied to each of the phase
stator Windings, comprises: an output circuit for supplying
the current to each of the phase stator Windings selectively;
a back electromagnetic force detector for detecting a back
electromagnetic force induced in one to Which the current is
not supplied of the phase stator Windings, and outputting a
detection signal; a control logic circuit for controlling the
output circuit on the basis of the detection signal outputted
from the back electromagnetic force detector; a timing
control circuit for determining a start timing and an end
timing of a control signal supplied from the control logic
stator Winding.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The present invention Will become more fully
understood from the detailed description given hereinafter
and the accompanying draWing given by Way of illustration
only, and thus are not intended as a de?nition of the limits
of the present invention, and Wherein:
[0028]
FIGS. 1A to 1G are timing charts shoWing a state
signals change When a circuit for driving a three-phase
brushless motor rotates the three-phase brushless motor,
according to an earlier development;
Dec. 12, 2002
US 2002/0185986 A1
[0029]
FIGS. 2A to 2G are timing charts showing a state
signals change When a number of rotation of the three-phase
brushless motor is half one of the three-phase brushless
motor rotating at a timing shoWn in FIGS. 1A to 1G;
[0030]
FIGS. 3A to 3G are timing charts shoWing a state
even at a Zero cross timing of the back-EMF generated in
any one of the three Windings.
[0039]
Further, for example, in case the circuit shoWn in
FIG. 4 is mounted as a monolithic integrated circuit, a
temperature detector for detecting a rise of an unusual
signals changes When another circuit for a three-phase
temperature of a chip may be provided besides the above
full-Wave brushless motor rotates the three-phase full-Wave
brushless motor, according to an earlier development;
described circuits, as the occasion may demand.
[0031]
FIG. 4 is a block diagram shoWing an exemplary
construction of an effective circuit for driving a three-phase
full-Wave brushless motor, to Which the present invention is
[0040] FIG. 5 is a block diagram shoWing an exemplary
construction of the clock generator 14 and the timing
generator 15 as described above.
applied;
[0041] In FIG. 5, the reference numeral “14” denotes a
clock generating unit including a oscillator for generating an
[0032] FIG. 5 is a block diagram shoWing a clock gen
erator and a timing generator of the circuit shoWn in FIG. 4;
oscillating signal having a suf?ciently higher frequency than
[0033]
FIGS. 6A to 6G are timing charts shoWing a state
signals change When a circuit for driving a three-phase
full-Wave brushless motor, to Which the present invention is
applied, rotates the three-phase full-Wave brushless motor;
and
[0034]
FIGS. 7A to 7G are timing charts shoWing a state
signals change When a circuit for driving a three-phase
half-Wave brushless motor, to Which the present invention is
applied, rotates the three-phase half-Wave brushless motor.
a frequency of the back-EMF of the three-phase full-Wave
drive brushless motor. Further, the reference numeral “42”
denotes a frequency divider for dividing a frequency f0 of a
clock signal CLKO generated by the clock generating unit
41, by N Which is a positive integral number, and outputting
a clock signal CLK2 having a frequency 2f1, and “43”
denotes a frequency divider for further dividing the fre
quency 2f1 of the clock signal CLK2 divided by the fre
quency divider 42, by 2, and outputting a clock signal CLK1
having a frequency f1. Therefore, the clock generator 14
comprises the clock generating unit 41, and the frequency
dividers 42 and 43.
PREFERRED EMBODIMENTS OF THE
INVENTION
[0035] Hereinafter, a preferred embodiment of the present
invention Will be explained With reference to ?gures, as
[0042]
Further, the reference numeral “44” denotes a ?rst
counter for counting the clock signal CLK1 having the
frequency f1, outputted from the frequency divider 43, and
“45” denotes a second counter for counting the clock signal
folloWs.
CLK2 having the frequency 2f1, outputted from the fre
[0036]
quency divider 42. Therefore, the timing generator 15 com
prises the ?rst counter 44 and the second counter 45.
FIG. 4 is a block diagram shoWing an exemplary
construction of an effective circuit for driving a three-phase
full-Wave drive brushless motor, to Which a present inven
tion is applied.
[0037]
The reference characters “U”, “V” and “W” denote
three phase stator Windings Which are Wound on a stator core
of the three-phase full-Wave drive brushless motor, and
“Q1” to “Q6” denote output transistors for supplying a
driving current to the U-phase, V-phase and W-phase stator
Windings. Further, the reference numeral “11” denotes a
back-EMF (back electromagnetic force) detector for detect
ing a position of a rotor magnet of the three-phase full-Wave
drive brushless motor rotating on the basis of a Zero cross
point of a back-EMF generated in a non current-carrying
phase of the three phase stator Windings of the three-phase
full-Wave drive brushless motor, “13” denotes a control
logic circuit for observing and controlling the Whole circuit,
“14” denotes a clock generator for generating a clock signal
[0043] Herein, the frequency f0 of the CLKO is deter
mined so as to be suf?ciently higher than the frequency 2f1
of the CLK2, for example, so that the frequency dividing
ratio N of the frequency divider 42 is more than 10.
[0044] The clock signal CLKO generated by the clock
generating unit 41 of the clock generator 14 is supplied to
not only the frequency divider 42 but also the control logic
circuit 13 as a operation clock signal.
[0045] The ?rst counter 44 and the second counter 45 have
the same bit numbers as each other, and counts according to
an instruction of the control logic circuit 13. For example,
the ?rst counter 44 comprises an up counter circuit, and the
second counter 45 comprises a doWn counter circuit. For
example, the second counter 45 outputs a high level signal
While counting the clock signal CLK2, and outputs a loW
level signal When ?nishing counting the clock signal CLK2,
required for the control logic circuit 13 of controlling the
circuit, and “15” denotes a timing generator for generating
that is, When the result of counting is 0.
a timing signal of changing phases.
[0038] The back-EMF detector 11 comprises, for example,
Wave drive brushless motor driven by the circuit having the
three comparators each of Which compares a potential of an
output terminal to Which one terminal of any one of three
Windings is connected With a potential of a center tap CT to
Which another terminal of each of the three Windings is
[0046] Hereinafter, the motion of the three-phase full
above-described construction, according to the embodiment
Will be explained.
[0047]
The back-EMF detector 12 detects the Zero cross
timing of the back-EMF generated in the non current
commonly connected, a trigger type ?ip ?op for inverting an
carrying phase, generates the rotational signal RTS having a
output even When an output outputted from any one of the
comparators rises, and so on. Therefore, the back-EMF
detector 11 outputs a rotational signal RTS changing from a
high level to a loW level or from a loW level to a high level
cycle Which is an electric angle of 120 degrees Within the
range of Which the rotational signal RTS changes from the
high level to the loW level and after from the loW level to the
high level even at the detected Zero cross timing of the
Dec. 12, 2002
US 2002/0185986 A1
back-EMF generated in the non current-carrying phase, and
outputs the rotational signal RTS to the control logic circuit
13.
[0048] Then, the control logic circuit 13 outputs the fol
loWing control signals S1 and S2 to the ?rst counter 44 and
the second counter 45 respectively, even When the rotational
signal RTS rises up or falls doWn.
[0049]
When the ?rst counter 44 receives the control
[0055]
FIG. 6A is a timing chart shoWing back-EMFs
generated in the U-phase, V-phase and W-phase stator
Windings of the three-phase full-Wave brushless motor. FIG.
6B is a timing chart shoWing the rotational signal RTS
outputted from the back-EMF detector 12. FIG. 6C is a
timing chart shoWing the output outputted from the second
counter 45. FIGS. 6D to 6F are timing charts shoWing
currents for driving the U-phase, V-phase and W-phase
respectively. FIG. 6G is a timing chart shoWing the torque
signal S1 outputted from the control logic circuit 13, the ?rst
ripple generated in the three-phase full-Wave brushless
counter 44 stops counting the CLK1. Then, the ?rst counter
44 outputs the counter number CN to the second counter 45,
and resets the counter number CN. Thereafter, the ?rst
motor.
counter 44 and the second counter 45 start counting the
CLK1 and the CLK2, respectively. The ?rst counter 44 and
the second counter 45 performs the above-processing even
When the rotational signal RTS rises up or falls doWn,
continuously.
[0050] The ?rst counter 44 is an up counter. Further,
because the ?rst counter 44 resets the counter number CN
continuously even When the rotational signal RTS rises up or
[0056] The ?rst counter 44 checks the time of the half
cycle of the rotational signal RST. Then, the second counter
45 checks the time of the half time checked by the ?rst
counter 44, in the neXt half of the cycle of the rotational
signal RST. Therefore, the timing at the electric angle of 30
degrees can be eXtracted Without lagging from the Zero cross
timing of the back-EMF substantially. Accordingly, it is
possible to ideally drive the three-phase full-Wave drive
brushless motor With alWays keeping the small torque ripple,
in case the number of rotation changes every moment.
falls doWn, the ?rst counter 44 checks the time of the half
[0057] According to the embodiment, the phase difference
cycle of the rotational signal RTS, that is, the time corre
sponding to the electric angle of 60 degrees. On the other
betWeen the Zero cross timing of the back-EMF and the
hand, the second counter 45 is a doWn counter. Further,
because the second counter 45 counts the clock signal CLK2
having tWo times as high the frequency as the clock signal
CLK1 counted by the ?rst counter 44, the second counter 45
checks the time Which is 1/2 of the half cycle of the rotational
signal RTS, that is, the time corresponding to the electric
angle of 30 degrees.
[0051] Then, When the second counter 45 supplies the
count up signal to the control logic circuit 13, as a phase
changing timing signal PCS, the control logic circuit 13
controls the direction of the current supplied to each phase,
phase changing timing is determined on the basis of the ratio
of the frequency of the clock inputted to the ?rst counter 44
to the frequency of the clock inputted to the second counter
45. Therefore, the phase difference has nothing to do With
the number of rotation of the motor. Accordingly, because
the time constant is not used in the circuit, there does not
occur the problem about the following. Further, in case the
counter circuits 44 and 45 do not over?oW, the phase
difference does not change. Accordingly, if the circuit is
designed so that the counter circuits 44 and 45 do not
over?oW Within the range of the determined number of
rotation, it is possible to ideally drive the three-phase
according to the phase changing timing signal PCS.
full-Wave drive brushless motor With keeping the small
torque ripple Within the range of all the number of rotation.
[0052] According to the embodiment, the accuracy of the
[0058]
phase shift from the Zero cross timing of the back-EMF to
of the clock is uneven, in case the ratio of the frequencies of
the clocks inputted to the counters is not shifted, the deter
the phase changing timing is dependent on the bit numbers
of the ?rst counter 44 and the second counter 45. Therefore,
for eXample, if the accuracy is required Within the range of
:3 degrees, at least 5-bit counter circuit is used as the ?rst
counter 44 and the second ?rst counter 45.
[0053] On the other hand, because the frequency of the
clock CLKO inputted to the control logic circuit 13 from the
clock generator 14 is determined to be more than 100 times
as high the frequency as the rotational signal RTS, the time
required for the control logic circuit 13 of detecting the
change of the rotational signal RTS and generating a series
of control signals is extremely shorter than the frequency of
the rotational signal RTS, that is, the time is about 4% of the
frequency of the rotational signal RTS. Accordingly, the
lagging time before the control logic circuit 13 detects the
Further, even if the absolute value of the frequency
mined phase shift is kept. Accordingly, it is easy to incor
porate the clock generator in the integrated circuit.
[0059] FIGS. 7A to 7G are timing charts shoWing a case
the present invention is applied to a circuit for driving a
three-phase half-Wave brushless motor, and the circuit
rotates the three-phase half-Wave brushless motor.
[0060] The circuit for driving the three-phase half-Wave
brushless motor has the construction Wherein the output
transistors Q1, Q3 and Q5 or the output transistors Q2, Q4
and Q6 are omitted from the circuit shoWn in FIG. 4, and the
center tap CT is connected to the poWer supply voltage Vcc
or the ground potential. Therefore, it is omitted to shoW the
circuit for driving the three-phase half-Wave brushless motor
change of the rotational signal RTS and generates a series of
control signals and the counter circuits 44 and 45 perform on
in ?gures.
[0061] In the circuit for driving the three-phase half-Wave
the basis of the control signals and output the phase chang
ing timing signal is Within a negligibly time substantially.
brushless motor, only When the back-EMF is positive or
negative, the current is supplied to Windings.
[0054]
FIGS. 6A to 6G are timing charts shoWing a case
the present invention is applied to the circuit for driving the
three-phase full-Wave brushless motor, and the circuit
rotates the three-phase full-Wave brushless motor.
[0062]
FIGS. 7A to 7G are an exemplary case the current
is supplied to the Windings When the back-EMF is negative.
[0063] According to the embodiment as Well as one shoWn
in FIGS. 6A to 6G, the ?rst counter 44 counts up the half
Dec. 12, 2002
US 2002/0185986 A1
time of the cycle of the rotational signal RTS, and the second
counter 45 counts doWn the half time of the time counted by
the ?rst counter 44 in the neXt half of the cycle. Therefore,
the phase is changed at the timing of the counter number “0”
counted by the second counter 45. Accordingly, even if the
number of rotation is changed, it is possible to reduce the
torque ripple generated in the three-phase half-Wave brush
less motor.
[0064] Although the present invention has been explained
according to the above-described embodiment, it should also
be understood that the present invention is not limited to the
embodiment and various chanted and modi?cations may be
made to the invention Without departing from the gist
thereof.
[0065] According to the present invention, the folloWing
current is not supplied of the phase stator Windings, and
outputting a detection signal;
a control logic circuit for controlling the output circuit on
the basis of the detection signal outputted from the back
electromagnetic force detector;
a timing control circuit for determining a start timing and
an end timing of a control signal supplied from the
control logic circuit to the output circuit; and
a clock generator for generating a clock signal required
for the control logic circuit and the timing control
circuit,
Wherein the timing control circuit comprises a ?rst
counter circuit for counting a ?rst clock signal gener
ated by the clock generator and checking a time of a
effects Will be indicated.
cycle of the detection signal outputted from the back
[0066] The circuit can change phase stator Windings of the
multiphase brushless motor With keeping the predetermined
phase difference to the phase of the back electromagnetic
electromagnetic force, and a second counter circuit for
counting a counter number counted by the ?rst counter
circuit according to a second clock signal having tWo
times as high a frequency as the ?rst clock signal, and
force generated in any one of the phase stator Windings, even
if the number of rotation of the multiphase brushless motor
changes eXtremely. Consequently, it is possible to realiZe the
circuit for driving the multiphase brushless motor, Which can
reduce the change of the torque of the multiphase brushless
motor, and alWays keep the most suitable efficiency in
driving the multiphase brushless motor.
[0067] Herein, the technique for controlling the brushless
motor according to the present invention can be applied to
not only the three-phase brushless motor but also a tWo
phase full-Wave drive brushless motor.
[0068] The entire disclosure of Japanese Patent Applica
tion No. Tokugan 2001-172513 ?led on Jun. 7, 2001 includ
ing speci?cation, claims, draWings and summary are incor
porated herein by reference in its entirety.
What is claimed is:
1. An apparatus for driving a multiphase brushless motor
comprising a plurality of phase stator Windings, by changing
a current supplied to each of the phase stator Windings, the
apparatus comprising:
an output circuit for supplying the current to each of the
phase stator Windings selectively;
a back electromagnetic force detector for detecting a back
electromagnetic force induced in one to Which the
determines the start timing and the end timing of the
control signal supplied from the control logic circuit to
the output circuit at a rise timing or a fall timing of an
output outputted from the second counter circuit.
2. The apparatus for driving the multiphase brushless
motor, as claimed in claim 1,
Wherein the clock generator generates a reference clock
signal having at least 100 times as high a frequency as
the back electromagnetic force generated in the mul
tiphase brushless motor, and
the control logic circuit operates on the basis of the
reference clock signal generated by the clock generator.
3. The apparatus for driving the multiphase brushless
motor, as claimed in any one of claims 1 and 2,
Wherein the control logic circuit controls the output circuit
so as to drive each of the phase stator Windings accord
ing to a full Wave of each of the phase stator Winding.
4. The apparatus for driving the multiphase brushless
motor, as claimed in any one of claims 1 and 2,
Wherein the control logic circuit controls the output circuit
so as to drive each of the phase stator Windings accord
ing to a half Wave of each of the phase stator Winding.
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