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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns a DC brushless motor apparatus allowing to control
the inverter circuit driving by position detection signal obtained through
the position detection of a motor apparatus, particularly.
2. Background of the Invention
As for the composition of such DC brushless motor apparatus, for example,
compositions as shown in FIG. 9, 21, 30 are disclosed by Japan Patent
Application Laid-Open Hei 8-182378. In FIG. 9, 21, 30, the power source
section 1, 11, 21 is a DC power source, and obtains an bus voltage Vcc of
the inverter circuit 2, 12, 22 for obtaining a pulse modified voltage
mentioned below, and obtains a DC power source, for example, by
rectification and flattening of the AC power source.
In FIG. 9, the inverter circuit 2, generates multi-phase, for instance,
three-phase pulse width modified voltage of U-phase, V-phase and W phase,
by controlling transistors TrU.about.TrZ, for instance, power transistor,
IGBT device or the like, by means of driving signal from the drive circuit
4, creates a rotational magnetic field, and rotates the rotor 3R by
supplying respective stator coils 3U, 3V, 3W of the DC brushless motor 3.
Though not illustrated, the rotor 3R is composed of a plurality of
magnetic poles, for example, by magnetizing two pairs of N pole and S
pole, as necessary, an embedded magnet type rotor as mentioned in FIG. 12
below is employed. In this invention, besides magnetic pole formed as
rotor and then magnetized, and magnetic pole formed by embedding or
fitting a permanent magnet in a rotor, the "magnetic pole" includes also
those formed by the other methods.
The driving of transistors TrU.about.TrZ by the drive circuit 4 is as shown
by [Transistor driving waveform] in FIG. 10; fine pulse waveform portions
correspond to chopping portions, and the voltage output to the terminal R
of U phase, terminal S of V phase and terminal T of W phase appear, for
instance, as waveforms before the partial voltage of [Terminal voltage
partial voltage waveform] in FIG. 10, FIG. 11.
Here, as U phase, V phase and W phase are alternative current, from the
time sequence viewpoint, U phase.fwdarw.V phase.fwdarw.W phase.fwdarw.U
phase.fwdarw.V phase.fwdarw.W phase . . . are repeated, for V phase, U
phase is the preceding phase, and W phase is the following phase, and for
W phase, V phase is the preceding phase, and U phase is the following
phase, and further, for U phase, W phase is the preceding phase, and V
phase is the following phase.
Consequently, divided by the bleeder circuit of the resistor Rau, Rbu,
bleeder circuit of the resistor Rav, Rbv and bleeder circuit of the
resistor Raw, Rbw, the waveform of respective voltages input to respective
positive terminals, namely respective + terminals of the comparator CPu,
comparator CPv and comparator CPw result in U phase partial voltage Ua, V
phase partial voltage Va and W phase partial voltage Wa having a waveform
like U phase, V phase and W phase of [Terminal voltage partial voltage
waveform] in FIG. 10.
The voltage waveform of the imaginary neutral point voltage E0 input to
respective negative terminals, namely - terminals of the resistance
comparator CPu, comparator CPv and comparator CPw, by dividing the buss
voltage Vcc with the bleeder circuit of the resistor Rd, Rc is as shown by
[Power source voltage partial voltage waveform (imaginary neutral point
voltage) in FIG. 11. Here, the imaginary neutral point voltage E0 is
positioned substantially at the center of the amplitude of U phase partial
voltage Ua, V phase partial voltage Va and W phase partial voltage Wa, be
setting the resistor Rd, Rc so that [Rb/(Ra+Rb)]=[2Rd/(Rc+Rd)] for
respective resistors Ra.about.Rd in respective bleeder circuit of U phase,
V phase and W phase.
Then, the comparator CPu becomes U phase position detection comparator, the
comparator CPv V phase position detection comparator, and the comparator
CPw W phase position detection comparator, and respective transistor
TrU.about.TrZ of the inverter circuit 2 are driven by delivering the
position detection signal Su, Sv and Sw obtained by detecting with
respective comparator CPu, CPv and CPw to the control processing portion
comprising mainly a microcomputer, namely to the microcomputer 5, by
controlling the drive circuit 4 through a predetermined control by the
microcomputer 5.
When the rotor 3R rotates, as an induction voltage appears at the stator
coil of the phase not conducted with pulse amplitude modified voltage
among the stator coils 3U, 3V and 3W, [Rising induction voltage] and
[Falling induction voltage] appear after respective spike voltage, as
shown in the same drawing.
Then, respective comparator CPu, CPv and CPw detect the intersection with
said neutral point voltage in the portion of [Rising induction voltage]
and [Falling induction voltage], namely zero cross point P by comparing
these voltages, and output this detection signal as position detection
signal.
For instance, taking the comparison detection state by the comparator CPu
as example, it is as [U phase position detection comparator positive
negative input voltage (overwrite)] of FIG. 11, and the zero cross point P
is detected, and "U phase rising position detection point" and "U phase
falling position detection point" are output as position detection signal,
as [U phase position detection comparator output voltage] in FIG. 11.
Here, the comparison detection state by the other comparator CPv, CPw is
the waveform state, in which the waveform of [U phase position detection
comparator positive negative input voltage (overwrite)] of FIG. 9 is
shifted by the phase of 120 degrees.
Such DC brushless motor has an advantage of effective use of reluctance
torque by performing weak field control, by using an embedded magnet type
rotor, namely IPM type rotor as shown in FIG. 12; however, when this IPM
rotor is used, a flat portion DX flat in the proximity of the zero cross
point P is generated in the induction voltage waveform, making the
position detection unstable. as shown in FIG. 13.
Therefore, Jpn. Pat. Appln. Publication Laid-Open No. HEI 11-146685
discloses a composition, wherein, a vertical variation type imaginary
neutral point voltage is generated by further adding a plurality of
resistors Rf, Rh at the portion where the bus voltage Vcc is divided by
respectively equal resistance value resistors Rd, Rc, and alternatively
short-circuiting these additional points by respective switching device
Tra, Trb according to the control signal from the microcomputer 5, and
wherein the zero cross point P is shifted to a position off said flat
portion Dx, by comparing and detecting the intersection of this vertical
variation type imaginary neutral point voltage and the aforementioned
[Rising induction voltage] and [Falling induction voltage] by means of
respective comparator CPu, CPv, CPw.
In addition, Jpn. Pat. Appln. Publication Laid-Open No. HEI 11-146685 or
the like disclose a composition (called, no chopping composition,
hereinafter) wherein the detection is performed by a detection composition
similar to said respective position detection, by modifying to the
waveform like FIG. 15, without performing the pulse amplitude modification
by said chopping.
Such prior art required, disadvantageously, to dispose a switching device,
and a composition to control its driving.
On the other hand, in FIG. 21, the inverter circuit 12 rotates the rotor
13R by generating a multi-phase, for instance, three-phased pulse
amplitude modified voltage of U phase, V phase and W phase by controlling
the transistor TrU.about.Trz, for example power transistor, IGBT device or
the like, with driving signal from the drive circuit 14, and generating a
rotary magnetic field by imparting to respective stator coils 13U, 13V and
13W of the DC brushless motor 13. Though not illustrated, the rotor 13R is
provided with a plurality of magnetized magnetic poles, for instance, two
pairs of N pole, and S pole.
The driving of transistors TrU.about.TrZ by the drive circuit 14 is as
shown by [Transistor driving waveform] in FIG. 22; fine pulse waveform
portions correspond to chopping portions, and the voltage output to the
terminal R of U phase, terminal S of V phase and terminal T of W phase
appear, for instance, as waveforms before the partial voltage of [Terminal
voltage partial voltage waveform] in FIG. 22, FIG. 23.
Here, as U phase, V phase and W phase are alternative current, from the
time sequence viewpoint, U phase.fwdarw.V phase.fwdarw.W phase.fwdarw.U
phase.fwdarw.V phase.fwdarw.W phase . . . are repeated, for V phase, U
phase is the preceding phase, and W phase is the following phase, and for
W phase, V phase is the preceding phase, and U phase is the following
phase, and further, for U phase, W phase is the preceding phase, and V
phase is the following phase.
Consequently, divided by the bleeder circuit of the resistor Rau, Rbu,
bleeder circuit of the resistor Rav, Rbv and bleeder circuit of the
resistor Raw, Rbw, the waveform of respective voltages input to respective
positive terminals, namely respective+ terminals of the comparator CPu,
comparator CPv and comparator CPw result in U phase partial voltage Ua, V
phase partial voltage Va and W phase partial voltage Wa having a waveform
like U phase, V phase and W phase of [Terminal voltage partial voltage
waveform] in FIG. 22.
The voltage waveform of the imaginary neutral point voltage E0 input to
respective negative terminals, namely - terminals of the resistance
comparator CPu, comparator CPv and comparator CPw, by dividing the bus
voltage Dcc with the bleeder circuit of the resistor Rd, Rc is as shown by
[Power source voltage partial voltage waveform (imaginary neutral point
voltage) in FIG. 23. Here, the imaginary neutral point voltage E0 is
positioned substantially at the center of the amplitude of U phase partial
voltage Ua, V phase partial voltage Va and W phase partial voltage Wa, be
setting the resistor Rd, Rc so that [Rb/(Ra+Rb)]=[2Rd/(Rc+Rd)] for
respective resistors Ra.about.Rd in respective bleeder circuit of U phase,
V phase and W phase.
Then, the comparator CPu becomes U phase position detection comparator, the
comparator CPv V phase position detection comparator, and the comparator
CPw W phase position detection comparator, and respective transistor
TrU.about.TrZ of the inverter circuit 2 are driven by delivering the
position detection signal Su, Sv and Sw obtained by detecting with
respective comparator CPu, CPv and CPw to the control processing portion
comprising mainly a microcomputer, namely to the microcomputer 15, by
controlling the drive circuit 14 through a predetermined control by the
microcomputer 15.
When the rotor 13R rotates, as an induction voltage appears at the stator
coil of the phase not conducted with pulse amplitude modified voltage
among the stator coils 13U, 13V and 13W, [Rising induction voltage] and
[Falling induction voltage] appear after respective spike voltage, as
shown in the same drawing.
Then, respective comparator CPu, CPv and CPw detect the intersection with
said neutral point voltage in the portion of [Rising induction voltage]
and [Falling induction voltage], namely zero cross point P by comparing
these voltages, and output this detection signal as position detection
signal Su, Sv and Sw.
For instance, taking the comparison detection state by the comparator CPu
as example, it is as [U phase position detection comparator positive
negative input voltage (overwrite)] of FIG. 23, and the zero cross point P
is detected, and "U phase rising position detection point" and "U phase
falling position detection point" are output as position detection signal,
as [U phase position detection comparator output voltage] in FIG. 23.
Here, the comparison detection state by the other comparator CPv, CPw is
the waveform state, in which the waveform of [U phase position detection
comparator positive negative input voltage (overwrite)] of FIG. 23 is
shifted by the phase of 120 degrees.
In this detection, the microcomputer 15 takes as position detection signal
Su1 the signal obtained by detecting, first, Low to High rising edge or
the output of the U phase position detection comparator CPu, when the time
has elapsed for the spike voltage in the previous conduction pattern ends,
and changes over to the conduction by the conduction pattern from the next
transistor TrU to the transistor TrY when the time for the rotor 13R
rotates by a certain angle has elapsed.
Then, the microcomputer 15 takes as position detection signal (not
illustrated) the signal obtained by detecting, first, High to Low falling
edge by the W phase position detection comparator CPw, when the time has
elapsed for the spike voltage in the conduction pattern from the previous
transistor TrU to the transistor TrY ends, and changes over to the
conduction by the conduction pattern from the next transistor Tru to the
transistor TrZ when the time for the rotor 13R rotates by a certain angle
has elapsed.
Similarly, during the conduction from the transistor TrU to the transistor
TrZ, the conduction is changed over from the transistor TrV to the
transistor TrZ by the position detection signal (not illustrated)
detecting the rising edge of the output of the V phase comparator CPv, and
during the conduction from the transistor TrV to the transistor TrZ, the
conduction is changed over from the transistor TrV to the transistor TrZ
by the position detection signal Su2 detecting the falling edge of the
output of the U phase comparator CPv.
During the conduction from the transistor TrV to the transistor TrX, the
conduction is changed over from the transistor TrW to the transistor TrX
by the position detection signal (not illustrated) detecting the rising
edge of the output of the W phase comparator CPW, and during the
conduction from the transistor TrW to the transistor TrX, it is operated
to change over the conduction from the transistor TrW to the transistor
TrY by the position detection signal (not illustrated) detecting the
falling edge of the output of the V phase comparator CPv.
Thus, the microcomputer 15 drives the inverter circuit 12 to keep the rotor
13R rotating, by obtaining the position information of the rotor 13R,
based on the output waveform of respective comparator CPu, CPv and CPw.
The aforementioned driving state corresponds to an operation state (called
stationary operation state, in the present invention) where the rotor 13R
can rotate following the increase/decrease of the inverter circuit 12
driving frequency, rotating synchronously with the driving of the inverter
circuit 12 by the position detection signal Su, Sv, Sw.
On the contrary, in the starting state where the rotor 13R begins to rotate
by starting the driving of the inverter circuit 12, the stationary inertia
of the rotor 13R, axial friction, load driven by the rotor 13R or the like
make the position detection of the rotor 13R unstable, and it is difficult
to operate in synchronization with the position detection signal Su, Sv,
Sw.
To solve these problems, Japanese Patent 92682164 or others disclose a
composition (called the first prior art, hereinafter) wherein the
conduction change over to the rotor coils 13U, 13V or 13W by the position
detection signal Su, Sv, Sw of the rotor 13R is not performed immediately
after the start of driving of the inverter circuit 12, a forced
synchronous operation of the inverter circuit 12 is performed to change
over by force the conduction to the rotor coils 13U, 13V or 13W, for
example, by means of a clock circuit disposed in the microcomputer 15, and
to transit to the synchronous operation by the stationary position
detection, after a predetermined operation increasing/decreasing as
prescribed by the output voltage of the inverter circuit 12 according to
the time.
Besides, without performing said forced synchronous operation, the position
of the rotor 13R is detected immediately after the start of the inverter
circuit 12; however, taking example of the points of the sections
"TrW.fwdarw.TrY", "TrUu.fwdarw.TrY", the detection of the position
detection signal Su1 is performed following the time point to execute the
changeover operation (called, conversion in the present invention) from
previously conducted and operating transistor, for instance, transistor
TrW, TrX to the next conductive transistor, for example, transistor TrW,
TrY, namely following the conversion time point Wt, as in the [normal
operation state] of FIG. 24.
In the detection of the position detection signal Su1, the inverter circuit
12 driving is controlled by setting the time interval (called, position
detection masking time) Mt for detecting the position after having
restricted not to perform the position detection during a predetermined
interval of time, and the delay time (called, conversion delay time in the
present invention) Lt for restricting the next conversion time Ut, namely
the time point for changing over, for instance, to the conduction of the
transistor TrU, and TrT to the time period delayed by a predetermined time
from the point of position detection.
In addition to this control, a composition (called, the second prior art,
hereinafter) for transiting to the synchronized operation by the
stationary position detection, all the way increasing/decreasing the
driving frequency of the inverter circuit 12.
Though the [normal operation state] of FIG. 24 does not show but the
portion corresponding to the "U phase rising position detection point", an
amplitude variation inverse to the amplitude variation of FIG. 24 appears,
similarly as in "U phase rising position detection point" of FIG. 23, also
in the portion corresponding to the "U phase falling position detection
point" of FIG. 23. Also, V phase and W phase, similarly, position
detection portions appear at two positions. There, as mentioned above, if
two pairs of N pole and S pole, namely two opposed pairs are magnetized to
the rotor 13R, (3 phase.times.2 points).times.points of number of two
opposed poles, in other words, 12 points of detection location portions
appear.
In the composition of such DC brushless motor, in relation to the
synchronous operation with the rotor 13R as shown in FIG. 25, it is well
known a composition wherein the imaginary neutral point voltage E0 is
detected by shifting vertically like E01, E02 in FIG. 25, by changing the
partial pressure ratio of the bleeder circuit obtaining the imaginary
neutral point voltage E0 or the bleeder circuit obtaining respective phase
divided voltage, for shifting the detection position of position detection
signal Su, Sv, Sw forward or backward the induction voltage, as the
intersection Pa or intersection Pb (called, the third prior art,
hereinafter), and it goes without saying that, in such a composition, the
position detection masking time Mt and the conversion delay time Lt are
set to correspond to the intersection Pa or intersection Pb.
As the synchronous operation is forced without position detection, the
aforementioned first prior art can not accelerate the time for transiting
to the synchronous operation by stationary position detection, and
requires a considerably long time, because the inverter circuit 12 output
voltage should be increased gradually, with a change in the extent not to
provoke the inverter circuit 12 emergency stop, by disordered or irregular
driving due to the variation of the load driven by the rotor 13R.
On the other hand, the second prior art has an advantage of being able to
transit to the synchronous operation by stationary position detection in a
period of time shorter than the first prior; however, when the load driven
by the rotor 13R varies, the position detection will be disordered by such
variation, and disadvantageously, it can not transit to the synchronous
operation by stationary position detection.
Further, in FIG. 30, the inverter circuit 22, generates multi-phase, for
instance, three-phase pulse width modified voltage of U-phase, V-phase and
W phase, by controlling transistors TrU.about.TrZ, for instance, power
transistor, IGBT device or the like, by means of driving signal from the
drive circuit 24, creates a rotational magnetic field, and rotates the
rotor 23R by supplying respective stator coils 3U, 3V, 3W of the DC
brushless motor 23. Though not illustrated, the rotor 3R is composed of a
plurality of "magnetized" poles, for example, magnetic poles composed of
two pairs of N pole and S pole.
In this invention, the "magnetic pole" includes both magnetic pole formed
as rotor and then magnetized, and magnetic pole formed by embedding or
fitting a permanent magnet in a rotor.
The driving of transistors TrU.about.TrZ by the drive circuit 24 is as
shown by [Transistor driving waveform] in FIG. 31; fine pulse waveform
portions correspond to chopping portions, and the voltage output to the
terminal R of U phase, terminal S of V phase and terminal T of W phase are
divided by the bleeder circuit of the resistor Rau, Rbu, bleeder circuit
of the resistor Rav, Rbv and bleeder circuit of the resistor Raw, Rbw,
then the waveform of respective voltages input to respective positive
terminals, namely respective+ terminals of the comparator CPu, comparator
CPv and comparator CPw result in U phase partial voltage Ua, V phase
partial voltage Va and W phase partial voltage Wa having a waveform like U
phase, V phase and W phase of [Terminal voltage partial voltage waveform]
in FIG. 31.
The voltage waveform of the imaginary neutral point voltage E0 input to
respective negative terminals, namely - terminals of the resistance
comparator CPu, comparator CPv and comparator CPw, by dividing the bus
voltage Dcc with the bleeder circuit of the resistor Rd, Rc is as shown by
[Power source voltage partial voltage waveform (imaginary neutral point
voltage) in FIG. 32. Besides, it is sometimes used a composition wherein
the imaginary neutral point voltage E0 is shifted upward or downward the
imaginary neutral point voltage E0 of FIG. 32, and the position detection
signal Su1.about.Sw2 is obtained by shifting the intersection P forward or
backward.
Then, the comparator CPu becomes U phase position detection comparator, the
comparator CPv V phase position detection comparator, and the comparator
CPw W phase position detection comparator, and respective transistor
TrU.about.tRz of the inverter circuit 22 are driven by delivering the
position detection signal Su, Sv and Sw obtained by detecting with
respective comparator CPu, CPv and CPw to the control processing portion
comprising mainly a microcomputer, namely to the microcomputer 25, by
controlling the drive circuit 24 through a predetermined control by the
microcomputer 25.
When the rotor 23R rotates, as an induction voltage appears at the stator
coil of the phase not conducted with pulse amplitude modified voltage
among the stator coils 23U, 23V and 23W, [Rising induction voltage] and
[Falling induction voltage] appear after respective spike voltage, as
shown in FIG. 32.
Then, respective comparator CPu, CPv and CPw detect the intersection with
said neutral point voltage in the portion of [Rising induction voltage]
and [Falling induction voltage], namely zero cross point P by comparing
these voltages, and output this detection signal as position detection
signal Su, Sv and Sw.
For instance, taking the comparison detection state by the comparator CPu
as example, it is as [U phase position detection comparator positive
negative input voltage (overwrite)] of FIG. 32, and the zero cross point P
is detected, and "U phase rising position detection point" and "U phase
falling position detection point" are output as position detection signal,
as [U phase position detection comparator output voltage] in FIG. 32.
Here, the comparison detection state by the other comparator CPv, CPw is
the waveform state, in which the waveform of [U phase position detection
comparator positive negative input voltage (overwrite)] of FIG. 33 is
shifted by 120 degrees in phase.
In other words, in [R,S,T terminal voltage partial waveform] of FIG. 31,
position detection signals are detected cyclically with a time interval
corresponding to the rotor 23R speed variation, in respect of one pair of
magnetic poles of the rotor 23R, during one revolution of the rotor 23R as
Su1.fwdarw.Sw2.fwdarw.Sv1.fwdarw.Su2.fwdarw.Sw1.fwdarw.Sv2 and delivered
to the microcomputer 25.
The microcomputer 25 calculates the number of revolution per unit time of
the rotor 23R (called number of revolution, in the present invention), for
instance, rpm or rps (called collectively "rpm", hereinafter) based on the
time interval for obtaining respective position detection signals
Su1.about.Sw2, and controls to change the frequency fm of chopping pulse
or respective phase voltage (chopping frequency, hereinafter) given from
inverter circuit 22 to respective stator coils 23U.about.W or the chopping
pulse duty rate du (duty rate, hereinafter) so that this number of
revolution rpm be the target number of revolution, for instance, number of
revolution rm. Here, the aforementioned number of revolution rpm is the
one called, generally, average number of revolution.
When the number of occurrence of position detection signals Su1.about.Sw2,
is twelve per revolution of the rotor 23r, the number of revolution rpm
can be obtained by dividing a unit time value, for instance, 1 minute or 1
second by a time value of the time from the time point when the previous
one of these twelve position detection signals is obtained to the time
point when the next is obtained, measured by an inner clock circuit (not
shown) of the microcomputer 25, or the number of revolution rpm in terms
of average value can be obtained by dividing a unit time by a time value
of the time from the time point when one of position detection signals is
obtained to the time point when a plurality of, for instance, ten position
detection signals are obtained, and then dividing by the number of
signals.
To be specific, as in FIG. 33, if a control with a tolerance of +/-.alpha.
is to be executed to the target number of revolution rm1, the control will
be executed based on position detection signals Su1.about.Sw2 by changing
the chopping frequency fm or the duty rate fm of respective phase voltage,
and when the number of revolution rpm obtained based on position detection
signals Su1.about.Sw2 attains the tolerated upper limit rm1+.alpha., the
output voltage Ua.about.Wa of respective phase (here, Ua.about.Wa mean
output voltage of transistors TrU.about.TrZ before said voltage division,
and the same applies below) is lowered by changing the chopping frequency
fm or the duty rate du.
On the other hand, if tolerated lower limit rm1-.alpha. is attained, it is
operated to lowers the respective phase output voltage, and in addition,
the operation to vary the output voltage Ua.about.Wa is performed, by PI
control based on the differential value of the detected number of rotation
rpm and the target number of rotation rm1 or others. Besides, the control
cycle T1 for this control is limited to a relatively small cycle, for
instance, 10 msec.about.1 sec, and it is controlled to vary often the
output voltage Ua.about.Wa.
In the aforementioned DC brushless motor apparatus, if the load driven by
the rotor 23R, namely the driving object of the DC brushless motor
apparatus is an air-conditioner, refrigerator or other compressor, it is
necessary to adjust the output voltage, by changing often the chopping
frequency fm or the duty rate du, as the load varies violently. Such
output voltage modification and adjustment increases, disadvantageously,
the vibration and noise of the motor itself or compressor.
Further, the present invention concerns an inverter driving electric motor
apparatus provided with a function to protect the inverter overcurrent.
Such an inverter driving electric motor apparatus 200 is used, for example,
as compression section for coolant compression of refrigeration equipment,
air-conditioner or the like, driving source of fan or the like, and
various motors such as DC brushless motor is used as electric motor
(motor, hereinafter) and, for example, a composition of inverter driving
electric motor apparatus 200 wherein a motor 33 is driven by an inverter
32 as shown in FIG. 38 is well-known. In respective drawings below,
portions referred to with the same symbol have the same function as
portions of the same symbol described in any of drawings.
In FIG. 38, the microcomputer 35 drives the inverter 32 by controlling the
drive circuit 34 by delivering a control signal to rotate continuously the
motor to the drive circuit 34, and the inverter 32 drives the motor 33 by
converting the DC power source 31 into a multiple phase, for instance,
three-phased AC power source by means of power transistors (called
transistor hereinafter) TU, TV, TW, TX, TZ.
The driving of transistors TU.about.TZ is controlled to rotate the rotor
33R synchronously by imparting signals from position detection portions
(not shown) for detecting the position of the rotor 33R to the
microcomputer 35. The DC power source 31 is, for example, a DC power
source obtained by rectifying and flattening the SC voltage obtained by
transforming an AC power source (not shown), for instance, commercial AC
power source to the required voltage.
The overcurrent detection circuit 36 is a portion for detecting if the DC
value detected by a current detection device for detecting current
supplying the inverter 32 with current from the DC power source 31, for
instance, a current detection resistor Rs disposed on the electric line of
the negative side of the inverter 32 exceeds a predetermined value or not,
namely overcurrent or not.
Upon the detection of overcurrent, the overcurrent detection circuit 36
delivers an overcurrent detection signal 36A announcing the overcurrent to
the microcomputer 35 through an overcurrent anomaly hold circuit 37, the
microcomputer 35 controls the operation of the drive circuit to stop
driving the inverter 32, and when the driving of the inverter 32 is
stopped by this overcurrent protection operation, a control signal from
the microcomputer 35 makes the anomaly cancellation circuit 38 cancel the
anomaly hold by the overcurrent anomaly hold circuit 37.
The overcurrent anomaly hold circuit 37 is composed, for instance, of
flip-flop circuit, and the anomaly cancellation circuit 38 is composed to
cancel the anomaly hold by said flip-flop circuit, for example, by a
transistor Tr provided with a protection resistor Rr disposed at the input
side.
The overcurrent detection circuit 36 is composed of comparator Cp, circuit
DC power source Vcc, overcurrent detection resistors R1, R2, reference
voltage resistors R3, R4 or like. Here the DC power current 31 is set to,
for example, a voltage of 280V and the circuit DC power source Vcc to a
voltage of 5.about.15V and, consequently, the DC power current 31 and the
circuit DC power source Vcc are separate power sources; however, when the
voltage of the DC power current 31 is low and composed of a voltage
similar to the circuit DC power source Vcc, the DC power current 31 and
the circuit DC power source Vcc may be composed of the same one. In this
case, it is necessary to compose so as not to vary the voltage of the
portion corresponding to the circuit DC power source Vcc during the
overcurrent.
Next, respective parts of the overcurrent detection circuit 36 are set to
the following operation conditions. In the following expressions, Vcc
represents the voltage of the circuit DC power source Vcc, and the voltage
Em1 of the positive terminal, namely, + terminal of the comparator Cp is
as represented by the following expression (1 | | |
