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Claims  |
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What is claimed is:
1. A brushless motor driving circuit comprising:
a three-phase bridge circuit which outputs a signal which is subjected to
pulse width modulation;
a brushless motor which is connected to and driven by said three-phase
bridge circuit;
terminal voltage detecting means for detecting a terminal voltage which
includes induced voltage information in a phase in which a current supply
to said brushless motor is stopped; and
controlling means for controlling the current supply to said three-phase
bridge circuit based on a result of the detection by said terminal voltage
detecting means,
wherein said terminal voltage detecting means is adjusted so that a time
constant at falling of the detected pulse-like voltage is larger than a
time constant at rising.
2. A brushless motor driving circuit comprising: (1) a three-phase bridge
circuit; (2) a brushless motor which is connected to and driven by said
three-phase bridge circuit; (3) reference voltage outputting means for
outputting a voltage corresponding to a preset number of rotation of said
brushless motor as a motor driving voltage reference value; (4) pulse
generating means for generating a pulse for sampling three-phase pulse at
a same frequency; (5) terminal voltage detecting means for detecting a
terminal voltage of at least one line in a non-current-supplying period of
said brushless motor; and (6) a comparator which compares a value of the
detected terminal voltage at rising with a value at falling, the driving
voltage reference value being variable in accordance with an output of
said comparator,
wherein at a timing after an intermediate timing in the
non-current-supplying period, (a) if the detected induced voltage at
rising is a potential which is equal to or higher than a predetermined
value, or (b) if the detected induced voltage at falling is a potential
which is equal to or lower than a predetermined value, a frequency phase
of said pulse generating means is adjusted to lead.
3. A brushless motor driving circuit comprising: (1) a three-phase bridge
circuit; (2) a brushless motor which is connected to and driven by said
three-phase bridge circuit; (3) reference voltage outputting means for
outputting a voltage corresponding to a preset number of rotation of said
brushless motor as a motor driving voltage reference value; (4) pulse
generating means for generating a three-phase pulse at a same frequency;
(5) terminal voltage detecting means for detecting a terminal voltage of
at least one line in a non-current-supplying period of said brushless
motor; and (6) a comparator which compares a value o f the detected
terminal voltage at rising with a value at falling, the driving voltage
reference value being variable in accordance with an output of said
comparator,
wherein at a timing after an intermediate timing in the
non-current-supplying period, (a) if the detected induced voltage is a
voltage of a line of an increasing voltage and the induced voltage value
is a potential which is lower than a predetermined voltage between a
power-source potential on a plus side a nd a power-source potential on a
minus side, or (b) if the detected induced voltage is a voltage of a line
of a decreasing voltage and the induced voltage value is a potential which
is higher than a predetermined voltage between a power-source potential on
a plus side and a power-source potential on a minus side, a frequency
phase of said pulse generating means is caused to lag.
4. A brushless motor driving circuit comprising:
a three-phase bridge circuit;
a brushless motor which is connected to and driven by said three-phase
bridge circuit;
first detecting means for detecting a terminal voltage of a line in which a
current supply to said brushless motor is stopped;
second detecting means for detecting a terminal voltage of a line in which
a current supply from a plus side of a power-source voltage is conducted
by means of pulse width modulation or continuously;
third detecting means for detecting a terminal voltage of a line in which a
current supply from a minus side of the power-source voltage is conducted
by means of pulse width modulation or continuously; and
controlling means for controlling a current supply to said three-phase
bridge circuit by performing pulse width modulation on the plus side or on
the minus side of the power-source voltage,
wherein a result of the detection by said second detecting means and a
result of the detection by said third detecting means is used in a
calculation of an amount of modulation of the pulse width modulation as
power-source voltage information.
5. A brushless motor driving circuit comprising:
a three-phase bridge circuit;
a brushless motor which is connected to and driven by said three-phase
bridge circuit;
first detecting means for detecting a terminal voltage of a line in which a
current supply to said brushless motor is stopped;
second detecting means for detecting a terminal voltage of a line in which
a current supply from a plus side of a power-source voltage is conducted
by means of pulse width modulation or continuously;
third detecting means for detecting a terminal voltage of a line in which a
current supply from a minus side of the power-source voltage is conducted
by means of pulse width modulation or continuously; and
controlling means for controlling a current supply to said three-phase
bridge circuit by performing pulse width modulation on the plus side or on
the minus side of said power-source voltage,
wherein said controlling means compares a half of a difference between a
result of the detection by said second detecting means and a result of the
detection by said third detecting means with a detection value of said
first detecting means, and switches over a current-supplying phase at a
timing delayed by a predetermined angle from a timing when a result of the
comparison is inverted.
6. A brushless motor driving circuit according to claim 5, wherein said
controlling means does not use a result of the comparison which is
obtained immediately after the current-supplying phase is switched over.
7. A brushless motor driving circuit comprising: a three-phase bridge
circuit;
a brushless motor which is connected to and driven by said three-phase
bridge circuit;
detecting means for detecting a terminal voltage of a line in which a
current supply to said brushless motor is stopped; and
controlling means for controlling the current supply to said three-phase
bridge circuit based on a result of the detection by said terminal voltage
detecting means,
wherein said controlling means compares the result of the detection by said
detecting means with a neutral point potential of a power-source voltage,
and
(a) if the result of the detection by said detecting means is in an
increasing direction, said controlling means detects a first timing period
in which the result of the detection by said detecting means becomes lower
than the neutral point potential for a first time after phase switching,
and a second timing when said detection result subsequently becomes higher
than the neutral point potential,
(b) if the result of the detection by said detecting means is in a
decreasing direction, said controlling means detects a third timing period
in which the result of the detection by said detecting means becomes
higher than the neutral point potential for a first time after phase
switching, and a fourth timing when said detection result subsequently
becomes lower than the neutral point potential,
(c) if the result of the detection by said detecting means is in an
increasing direction, said controlling means detects the second timing,
and then performs phase switching at a timing delayed by a value obtained
by subtracting a half of said third timing period from a predetermined
current-supplying angle, and
(d) if the result of the detection by said detecting means is in a
decreasing direction, said controlling means detects the fourth timing,
and then performs phase switching at a timing delayed by a value obtained
by subtracting a half of said first timing period from a predetermined
current-supplying angle.
8. A method of controlling a brushless motor driving circuit, said
brushless motor driving circuit including:
a three-phase bridge circuit;
a brushless motor which is connected to and driven by said three-phase
bridge circuit;
a reference voltage outputting means for outputting a voltage corresponding
to a preset number of rotations of said brushless motor as a motor driving
voltage reference value;
pulse generating means for generating a pulse for sampling three-phase
pulse at a same frequency;
terminal voltage detecting means for detecting a terminal voltage of at
least one line in a non-current-supplying period of said brushless motor;
and
a comparator which compares a value of the detected terminal voltage at
rising with a value at falling, the driving voltage reference value being
variable in accordance with an output of said comparator,
wherein, at a timing after an intermediate timing in the current-supplying
period, said method comprising the steps of:
controlling the frequency phase of said pulse generating means to lead if
the detected induced voltage is a potential which is equal to or higher
than a predetermined value at rising, or a potential which is equal to or
lower than a predetermined value at falling; and
controlling the frequency phase of said pulse generating means to lag if
the detected induced voltage is a potential which is equal to or lower
than a predetermined value at rising, or a potential which is equal to or
lower than a predetermined value at falling.
9. A method of controlling a brushless motor driving circuits said
brushless motor driving circuit including:
a three-phase bridge circuit;
a brushless motor which is connected to and driven by said three-phase
bridge circuit;
first detecting means for detecting a terminal voltage of a line in which a
current supply to said brushless motor is stopped;
second detecting means for detecting a terminal voltage in a
current-supplying condition of a line in which a current supply from a
plus side of power-source voltage is conducted by means of pulse width
modulation or continuously;
third detecting means for detecting a terminal voltage in a
current-supplying condition of a line in which a current supply from a
minus side of power-source voltage is conducted by means of pulse width
modulation or continuously; and
controlling means for controlling a current supply to said three-phase
bridge circuit by performing pulse width modulation on the plus side or on
the minus side of said power-source voltage,
said method comprising the steps of:
comparing a half of a difference between a result of the detection by said
second detecting means and a result of the detection by said third
detecting means with a detection value of said first detecting means, and
switching over a current supplying phase at a timing delayed by a
predetermined angle from a timing when a result of the comparison is
inverted.
wherein said comparing and switching steps are performed by said
controlling means.
10. A method of controlling a brushless motor driving circuit that
includes,
a three-phase bridge circuit;
a brushless motor which is connected to and driven by said three-phase
bridge circuit;
a reference voltage outputting means for outputting a voltage corresponding
to a preset number of rotations of said brushless motor as a motor driving
voltage reference value;
pulse generating means for generating a pulse for sampling three-phase
pulse at a same frequency;
terminal voltage detecting means for detecting a terminal voltage of at
least one line in a non-current-supplying period of said brushless motor;
and
a comparator which compares a value of the detected terminal voltage at
rising with a value at falling, the driving voltage reference value being
variable in accordance with an output of said comparator,
wherein at the starting of said brushless motor, said method comprising:
controlling said brushless motor driving circuit by controlling the
frequency phase of said pulse generating means to lead if the detected
induced voltage is a potential which is equal to or higher than a
predetermined value at rising, or a potential which is equal to or lower
than a predetermined value at falling; and
controlling the frequency phase of said pulse generating means to lag if
the detected induced voltage is a potential which is equal to or lower
than a predetermined value at rising, or a potential which is equal to or
lower than a predetermined value at falling, and wherein said brushless
motor driving circuit further includes
first detecting means for detecting a terminal voltage of a line in which a
current supply to said brushless motor is stopped:
second detecting means for detecting a terminal voltage in a
current-supplying condition of a line in which a current supply from a
plus side of power-source voltage is conducted by means of pulse width
modulation or continuously;
third detecting means for detecting a terminal voltage in a
current-supplying condition of a line in which a current supply from a
minus side of power-source voltage is conducted by means of pulse width
modulation or continuously; and
controlling means for controlling a current supply to said three-phase
bridge circuit by performing pulse width modulation on the plus side or on
the minus side of said power-source voltage and, when it is detected that
a difference between an induced voltage at rising and an induced voltage
at falling is continuously in a predetermined range for a predetermined
period, said method of controlling is switched to comparing a half of a
difference between a result of the detection by said second detecting
means and a result of the detection by said third detecting means with a
detection value of said first detecting means, and
switching over a current supplying phase at a timing delayed by a
predetermined angle from a timing when a result of the comparison is
inverted,
wherein said comparing and switching steps are performed by said
controlling means. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a driving circuit for a so-called
brushless motor in which, for example, a permanent magnet is used as a
rotor, and a rotational alternating magnetic field is generated as a
field, and also to a method of controlling such a circuit, and more
particularly to a driving circuit for driving a brushless motor without
requiring a rotational position sensor for a rotor.
2. Description of the Related Art
As a method of regulating a cooling ability of a refrigerating air
conditioning apparatus by driving a compressor and the like at a variable
speed, a method is generally employed in which an electric motor serving
as a driving source for the compressor is driven at a variable speed.
Particularly, it is known that a brushless motor in which an armature
winding is wound on the stator, and a permanent magnet is mounted on the
rotor operates efficiently. In a brushless motor, it is necessary to
switch over magnetic poles for the field in accordance with the rotational
position of the rotor, and therefore a sensor for detecting the rotational
position is attached to the motor. In the case where a brushless motor is
used in a hermetic compressor or the like, however, it is difficult to
attach a rotational position sensor to the motor because the electric
motor itself is closed and the interior of the electric motor has a high
temperature. As a result, a driving circuit for the brushless motor has a
somewhat complicated configuration.
As a driving circuit for a brushless motor in which a rotational position
sensor is not used, conventionally, a circuit described in pages 241 to
243 of "Introduction to Power Electronics (revised second edition), 1991"
edited by Yamamura and written by Ohno is used.
FIG. 14 is a diagram showing a conventional brushless motor driving circuit
described in the above-specified literature. Hereinafter, with reference
to the figure, the configuration of the conventional brushless motor
driving circuit will be described.
In FIG. 14, 18 denotes a brushless motor driven in a 120-degree
current-supplying system, 19 denotes a three-phase bridge circuit
connected to three-phase terminals of the brushless motor 18, 20 denotes a
voltage phase detecting circuit which detects an induced voltage of the
brushless motor 18, 21 denotes a control circuit which performs the
generation of a timing pulse for driving the brushless motor 18 in the
120-degree current-supplying system with respect to a preset number of
rotation, and other operations, and 22 denotes a voltage doubler
rectifying circuit which is connected between an AC power source 23 and
the three-phase bridge circuit 19.
Referring to the figure, a variable rate limiting circuit 1211 is used for
slowly accelerating the rotational speed from a very slow speed condition
at the starting. A judging circuit 1212 judges, when the speed has been
increased to some extent, whether it is necessary to change the control
method to a method by a magnetic pole position detecting circuit, or not.
A V/f converting circuit 1213 generates a pulse width modulation signal
which becomes a three-phase AC voltage that is substantially proportional
to the rotation speed. Selector switches 1214a to 1214c select outputs of
the control circuit 21 and the V/f converting circuit 1213 in accordance
with an output of the judging circuit 1212.
Next, with reference to FIG. 15, the principle of the magnetic pole
position detection by the brushless motor driving circuit will be
described.
FIGS. 15(a) to 15(f) are diagrams illustrating the principle of the
magnetic pole position detection by the brushless motor driving circuit.
FIG. 15(a) shows waveforms of the u, v, and w lines of an induced voltage
of the brushless motor. FIG. 15(b) shows waveforms of line currents of the
u, v, and w lines caused by a driving voltage of the brushless motor 18.
FIG. 15(c) shows a waveform of a terminal voltage 1201 of the u line
output from a first-order lag filter 20a (see FIG. 14). FIG. 15(d) shows a
waveform of an output voltage 1202 of a comparator 20b into which the
u-line terminal voltage 1201 is input (see FIG. 14). FIG. 15(e) shows a
waveform of an integral voltage obtained by integrating the comparator
output voltage 1202. FIG. 15(f) shows a waveform of an output voltage of a
comparator (included in the control circuit 21) into which the integral
voltage is input. The u-line terminal voltage is simply referred to also
as the u-line voltage. The other line voltages are referred to in the same
way.
In the brushless motor driving circuit, a line current is supplied to the
armature winding of the brushless motor 18 only in a phase angle of 120
degrees by the three-phase bridge circuit 19, and the current is not
supplied in a phase angle of 60 degrees. In the non-current-supplying
period in which the current is not supplied, a voltage induced in the
armature winding is detected by the voltage phase detecting circuit 20. In
FIG. 15(c), the non-current-supplying period in which the u-line current
does not flow is designated by .theta.u. As shown in the figure, in the
non-current-supplying period .theta.u, only the u-line induced voltage
appears. As shown in FIG. 15(c), a high frequency voltage caused by PWM is
smoothed by the first-order lag filter 20a.
As shown in FIG. 15(b), the line current is an AC current of a square wave
at a phase angle of about 120 degrees, and its fundamental wave flows so
as to be in line with the induced voltage of each phase. Because the
brushless motor is originally a synchronous motor, the frequency of the
voltage is proportional to the number of rotation. The voltage phase
detecting circuit 20 is configured so as to detect a timing when the
induced voltage of each line becomes zero. For three phases, such a timing
appears 6 times in one cycle. The number of rotation can be detected by
measuring the intervals between respective timings. By using this, a
feedback loop is configured, and the number of rotation is controlled by
using the output of the number of rotation controller as a voltage
instruction. Usually, this control is performed by using a microcomputer.
In FIG. 15(c), the timing of the zero cross is-designated by
.theta..sub.0.
Specifically, in the brushless motor driving circuit, the current supply is
sequentially performed in respective phases for every 120 degrees on the
three-phase terminals of the brushless motor 18. In contrast, by using the
60-degree period as a non-current-supplying period, the induced voltage of
the brushless motor 18 is detected. The field magnetic poles are switched
over at a zero-cross timing (in FIG. 15(f), designated by .theta.'.sub.0)
of a waveform which is obtained by delaying the induced voltage waveform
by 90 degrees.
In the above-described configuration of the conventional brushless motor
driving circuit, the induced voltage is a voltage proportional to the
rotation speed. At the starting of the motor, therefore, the induced
voltage has a very small value. In addition, the terminal voltage is
subjected to pulse width modulation, and hence a low-pass filter (the
first-order lag filter 20a) for removing the pulse width modulation signal
is used. As shown in FIG. 15(c), the induced voltage which is actually
used has a further reduced amplitude, so that it is very difficult to
detect the induced voltage. Accordingly, the rotational phase cannot be
substantially detected. At the starting, therefore, it is impossible to
drive the brushless motor by using the above-mentioned induced voltage
waveform.
To comply with this, a technique is employed in which, at the starting, the
V/f converting circuit 1213 is used in the same manner as the case of an
induction motor and the like, so as to perform a V/f control which is a
control for maintaining a uniform relationship between a voltage and a
frequency. Thereafter, at a timing when the induced voltage can be
detected, the control is switched to the above-described control using the
induced voltage waveform, by means of the judging circuit 1212 and the
selector switches 1214a to 1214c.
At the switching from the starting control to the normal control, an
excessive current may flow because of a delay of the control or the
deviation of parameters. For this reason, the technique has problems such
as that it is necessary to use large-size power transistors for motor
driving, and that there is a possibility that the permanent magnet is
demagnetized by the excessive current.
There exists another problem in that, in the case where low-speed rotation
in which the induced voltage cannot be detected is to be maintained, it is
difficult to control the number of rotation by the starting control method
described above.
Even if the induced voltage in the low speed rotation is tried to be
detected by increasing the accuracy of the detecting circuit, the time
width in which the induced voltage superimposed on a pulse width
modulation signal can be detected is very narrow because a low voltage is
applied at the start and in a low speed rotation and the ON duty of the
pulse width modulation is small. Such a control can be realized by a
microcomputer. There is a time lag between the ON timing instruction
output from the microcomputer and the actual ON timing of the switching
element. If the ON time width is narrow, therefore, an erroneous detection
timing may occur. Accordingly, there exists a further problem in that it
is difficult to control the low speed rotation with good accuracy.
SUMMARY OF THE INVENTION
The invention has been conducted in order to solve the problems. It is an
object of the invention to provide a brushless motor driving circuit which
can drive a brushless motor by using the same control method and without
requiring the switching from the starting control to the normal control.
The 1st invention of the present invention is a brushless motor driving
circuit comprising:
a three-phase bridge circuit which outputs a signal which is subjected to
pulse width modulation;
a brushless motor which is connected to and driven by said three-phase
bridge circuit;
terminal voltage detecting means for detecting a terminal voltage of a
phase in which a current supply to said brushless motor is stopped; and
controlling means for controlling the current supply to said three-phase
bridge circuit based on a result of the detection by said terminal voltage
detecting means,
wherein said terminal voltage detecting means is adjusted so that a time
constant at falling of the detected pulse-like voltage is larger than a
time constant at rising.
The 2nd invention of the present invention is a brushless motor driving
circuit comprising: (1) a three-phase bridge circuit; (2) a brushless
motor which is connected to and driven by said three-phase bridge circuit;
(3) reference voltage outputting means for outputting a voltage
corresponding to a preset number of rotation of said brushless motor as a
motor driving voltage reference value; (4) pulse generating means for
generating a pulse for sampling three-phase pulse at a same frequency; (5)
terminal voltage detecting means for detecting a terminal voltage of at
least one line in a non-current-supplying period of said brushless motor;
and (6) a comparator which compares a value of the detected terminal
voltage at rising with a value at falling, the driving voltage reference
value being variable in accordance with an output of said comparator,
Wherein at a timing after an intermediate timing in the
non-current-supplying period, (a) if the detected induced voltage at
rising is a potential which is equal to or higher than a predetermined
value, or (b) if the detected induced voltage at falling is a potential
which is equal to or lower than a predetermined value, a frequency phase
of said pulse generating means is adjusted to lead.
The 3rd invention of the present invention is a brushless motor driving
circuit comprising: (1) a three-phase bridge circuit; (2) a brushless
motor which is connected to and driven by said three-phase bridge circuit;
(3) reference voltage outputting means for outputting a voltage
corresponding to a preset number of rotation of said brushless motor as a
motor driving voltage reference value; (4) pulse generating means for
generating a three-phase pulse at a same frequency; (5) terminal voltage
detecting means for detecting a terminal voltage of at least one line in a
non-current-supplying period of said brushless motor; and (6) a comparator
which compares a value of the detected terminal voltage at rising with a
value at falling, the driving voltage reference value being variable in
accordance with an output of said comparator,
Wherein at a timing after an intermediate timing in the
non-current-supplying period, (a) if the detected induced voltage is a
voltage of a line of an increasing voltage and the induced voltage value
is a potential which is lower than a predetermined voltage between a
power-source potential on a plus side and a power-source potential on a
minus side, or (b) if the detected induced voltage is a voltage of a line
of a decreasing voltage and the induced voltage value is a potential which
is higher than a predetermined voltage between a power-source potential on
a plus side and a power-source potential on a minus side, a frequency
phase of said pulse generating means is caused to lag.
The 4th invention of the present invention is a brushless motor driving
circuit comprising:
a three-phase bridge circuit;
a brushless motor which is connected to and driven by said three-phase
bridge circuit;
first detecting means for detecting a terminal voltage of a line in which a
current supply to said brushless motor is stopped;
second detecting means for detecting a terminal voltage of a line in which
a current supply from a plus side of a power-source voltage is conducted
by means of pulse width modulation or continuously;
third detecting means for detecting a terminal voltage of a line in which a
current supply from a minus side of the power-source voltage is conducted
by means of pulse width modulation or continuously; and
controlling means for controlling a current supply to said three-phase
bridge circuit by performing pulse width modulation on the plus side or on
the minus side of the power-source voltage,
wherein a result of the detection by said second detecting means and a
result of the detection by said third detecting means is used in a
calculation of an amount of modulation of the pulse width modulation as
power-source voltage information.
The 5th invention of the present invention is a brushless motor driving
circuit comprising:
a three-phase bridge circuit;
a brushless motor which is connected to and driven by said three-phase
bridge circuit;
first detecting means for detecting a terminal voltage of a line in which a
current supply to said brushless motor is stopped;
second detecting means for detecting a terminal voltage of a line in which
a current supply from a plus side of a power-source voltage is conducted
by means of pulse width modulation or continuously;
third detecting means for detecting a terminal voltage of a line in which a
current supply from a minus side of the power-source voltage is conducted
by means of pulse width modulation or continuously; and
controlling means for controlling a current supply to said three-phase
bridge circuit by performing pulse width modulation on the plus side or on
the minus side of said power-source voltage,
wherein said controlling means compares a half of a difference between a
result of the detection by said second detecting means and a result of the
detection by said third detecting means with a detection value of said
first detecting means, and switches over a current-supplying phase at a
timing delayed by a predetermined angle from a timing when a result of the
comparison is inverted.
The 6th invention of the present invention is a brushless motor driving
circuit according to said 5th invention, wherein said controlling means
does not use a result of the comparison which is obtained immediately
after the current-supplying phase is switched over.
The 7th invention of the present invention is a brushless motor driving
circuit comprising: a three-phase bridge circuit;
a brushless motor which is connected to and driven by said three-phase
bridge circuit;
detecting means for detecting a terminal voltage of a line in which a
current supply to said brushless motor is stopped; and
controlling means for controlling the current supply to said three-phase
bridge circuit based on a result of the detection by said terminal voltage
detecting means,
wherein said controlling means compares the result of the detection by said
detecting means with a neutral point potential of a power-source voltage,
and
(a) if the result of the detection by said detecting means is in an
increasing direction, said controlling means detects a first timing period
in which the result of the detection by said detecting means becomes lower
than the neutral point potential for a first time after phase switching,
and a second timing when said detection result subsequently becomes higher
than the neutral point potential,
(b) if the result of the detection by said detecting means is in a
decreasing direction, said controlling means detects a third timing period
in which the result of the detection by said detecting means becomes
higher than the neutral point potential for a first time after phase
switching, and a fourth timing when said detection result subsequently
becomes lower than the neutral point potential,
(c) if the result of the detection by said detecting means is in an
increasing direction, said controlling means detects the second timing,
and then performs phase switching at a timing delayed by a value obtained
by subtracting a half of said third timing period from a predetermined
current-supplying angle, and
(d) if the result of the detection by said detecting means is in a
decreasing direction, said controlling means detect s the fourth timing,
and then performs phase switching at a timing delayed by a value obtained
by subtracting a half of said first timing period from a predetermined
current-supplying angle.
The 8th invention of the present invention is a method of controlling a
brushless motor driving circuit comprising: (1) a three-phase bridge
circuit; (2) a brushless motor which is connected to and driven by said
three-phase bridge circuit; (3) reference voltage outputting means for
outputting a voltage corresponding to a preset number of rotation of said
brushless motor as a motor driving voltage reference value; (4) pulse
generating means for generating a pulse for sampling three-phase pulse at
a same frequency; (5) terminal voltage detecting means for detecting a
terminal voltage of at least one line in a non-current-supplying period of
said brushless motor; and (6) a comparator which compares a value of the
detected terminal voltage at rising with a value at falling, the driving
voltage reference value being variable in accordance with an output of
said comparator, wherein,
at a timing after an intermediate timing in the non-current-supplying
period,
(1) if the detected induced voltage is (1-a) a potential which is equal to
or higher than a predetermined value at rising, or (1-b) a potential which
is equal to or lower than a predetermined value at falling, the frequency
phase of said pulse generating means is controlled to lead, and
(2) if the detected induced voltage is (2-a) a potential which is equal to
or lower than a predetermined value at rising, or (2-b) a potential which
is equal to or lower than a predetermined value at falling, the frequency
phase of said pulse generating means is controlled to lag.
The 9th invention of the present invention is a method of controlling a
brushless motor driving circuit comprising: a three-phase bridge circuit;
a brushless motor which is connected to and driven by said three-phase
bridge circuit; first detecting means for detecting a terminal voltage of
a line in which a current supply to said brushless motor is stopped;
second detecting means for detecting a terminal voltage in a
current-supplying condition of a line in which a current supply from a
plus side of power-source voltage is conducted by means of pulse width
modulation or continuously; third detecting means for detecting a terminal
voltage in a current-supplying condition of a line in which a current
supply from a minus side of power-source voltage is conducted by means of
pulse width modulation or continuously; and controlling means for
controlling a current supply to said three-phase bridge circuit by
performing pulse width modulation on the plus side or on the minus side of
said power-source voltage, wherein
said controlling means compares a half of a difference between a result of
the detection by said second detecting means and a result of the detection
by said third detecting means with a detection value of said first
detecting means, and switches over a current-supplying phase at a timing
delayed by a predetermined angle from a timing when a result of the
comparison is inverted.
The 10th invention of the present invention is a method of controlling a
brushless motor driving circuit wherein at the starting of said brushless
motor, said method of controlling a brushless motor driving circuit
according to said 8th invention is used, and, when it is detected that a
difference between an induced voltage at rising and an induced voltage at
falling is continuously in a predetermined range for a predetermined
period, the method is switched to said method of controlling a brushless
motor driving circuit according to said 9th invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a brushless motor driving circuit of
Embodiment 1 of the invention.
FIG. 2 is a waveform chart showing various timings in the brushless motor
driving circuit of Embodiment 1.
FIG. 3 is a waveform chart of signals in the brushless motor driving
circuit of Embodiment 1.
FIG. 4(a) is a waveform chart of terminal voltages in the brushless motor
driving circuit of Embodiment 1;
FIG. 4(b) is a chart of timing signals in the brushless motor driving
circuit of Embodiment 1; and
FIG. 4(c) is a chart showing output voltages of sample and hold circuits in
Embodiment 1.
FIG. 5 is a waveform chart showing the principle of a phase advancing
adjustment in the brushless motor driving circuit of Embodiment 1.
FIG. 6 is a waveform chart showing the principle of a phase delaying
adjustment in the brushless motor driving circuit of Embodiment 1.
FIG. 7 is a waveform chart showing the principle of a phase advancing
adjustment at rising in Embodiment 1.
FIG. 8 is a waveform chart showing the principle of a phase delaying
adjustment at falling in Embodiment 1.
FIG. 9 is a block diagram of a brushless motor driving circuit of
Embodiment 2 of the invention.
FIG. 10(a) is a block diagram of timings generating means and PWM means
included in the brushless motor driving circuit of Embodiment 2; and
FIG. 10(b) is a diagram illustrating a timing of switching of voltage
information, a timing of changing clamp sources, and the like in
Embodiment 2.
FIG. 11 is a waveform chart of terminal voltages of the brushless motor
driving circuit of Embodiment 2.
FIG. 12 is a waveform chart showing a phase relationship between a motor
current and a terminal voltage in Embodiment 2.
FIG. 13 is a block diagram of a brushless motor driving circuit of
Embodiment 3 of the invention.
FIG. 14 is a block diagram of a brushless motor driving circuit of the
prior art.
FIGS. 15(a) to 15(f) are diagrams illustrating the principle of the
magnetic pole position detection by the brushless motor driving circuit of
the prior art.
LEGEND OF REFERENCE NUMERALS
1, 18 brushless motor
2, 19 three-phase bridge circuit
PWM modulating circuit
120-degree current-supplying pulse and timing generation circuit
5 selecting circuit
6, 7, 13 sample and hold circuit
8, 10 comparing circuit
9 control compensation circuit
11 V/f converting circuit
12u 12v, 12w terminal voltage waveform processing circuit
14 judging circuit
20 voltage phase detecting circuit
21 control circuit
22 voltage doubler rectifying circuit
23 AC power source
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, the invention will be described with reference to the drawings
showing embodiments thereof.
Embodiment 1
FIG. 1 is a block diagram showing the configuration of a brushless motor
driving circuit according to Embodiment 1 of the invention (corresponding
to claims 1, 2, and 3). With reference to the figure, the configuration of
the embodiment and the operations of circuits will be briefly described.
As shown in FIG. 1, a number of rotation (frequency) instruction f is
supplied to a V/f converting circuit 11, and also to a 120-degree
current-supplying pulse and timing generation circuit 4.
The 120-degree current-supplying pulse and timing generation circuit 4
generates 120-degree curr | | |
