JP3447938B2 - Drive control device for brushless motor and refrigeration cycle device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control device and a refrigeration cycle device for a brushless motor mounted in a compressor of a refrigeration cycle device such as an air conditioner.

[0002]

2. Description of the Related Art Conventionally, a brushless motor is disclosed in Japanese Patent Laid-Open No. 9-47.
As disclosed in Japanese Patent Publication No. 076, it is composed of a stator having a plurality of phase windings and a rotor having a permanent magnet. For driving the brushless motor, a DC voltage circuit that outputs a DC voltage and a switching circuit to which the output voltage of the DC voltage circuit is applied are prepared.

The switching circuit has a plurality of series circuits in each of which a pair of switching elements are connected in series in an upstream side and a downstream side of a current. The interconnection point of each switching element of these series circuits is connected to each phase winding of the brushless motor.

Of the switching element on the upstream side of one series circuit of the switching circuit and the switching element on the downstream side of another series circuit, one is continuously turned on and the other is intermittently turned on, and the continuous on and intermittent on are performed. By sequentially switching the switching elements, each phase winding of the brushless motor is sequentially energized. By energizing each phase winding, a magnetic field is generated from each phase winding. The interaction of this magnetic field with the magnetic field generated by the permanent magnets of the rotor causes the rotor to rotate. The switching of energization to each phase winding is called commutation.

When the rotor rotates, a voltage is induced in the non-energized phase winding. This induced voltage is taken out, and the rotational position of the rotor is detected from the change in the induced voltage. Specifically, the level of the induced voltage generated in the phase winding in the non-energized state is compared with the level of the predetermined reference voltage, and when both levels intersect, the rotational position of the rotor at that timing is the reference rotation. Detected as a position.

The timing of energization switching (commutation) for each phase winding is controlled according to the reference rotational position thus detected. Then, the rotation of the rotor is continued by repeating this energization switching.

Further, the on / off duty of the switching element which is intermittently turned on is adjusted, and thereby the speed of the brushless motor is controlled. The above rotational position detection and energization switching are effectively continued regardless of the speed change based on this control.

[0008]

Naturally, a phase current flows in the energized phase winding, and the phase current ceases to flow when the commutation changes to the non-energized state. However, as shown in FIG. 10, which is not energized after the commutation, the phase current does not immediately become zero but gradually attenuates, and the induced voltage does not rise during the attenuation.

The decay of the phase current after the commutation changes depending on the current value immediately before the commutation, the circuit inductance, the magnitude of the induced voltage (depending on the rotation speed), and the PWM duty of the other phase during decay. , The rotation speed is low, the induced voltage is small (compared to high speed), the PWM duty is small,
Moreover, the decay time becomes longer as the load increases (the input current increases). At this time, as shown by the broken line in FIG. 10, when the phase current flows longer than the timing (position detection point) at which the induced voltage crosses the reference voltage and the rise of the induced voltage is delayed, It becomes impossible to detect the rotational position by comparing with the level of the reference voltage. If the rotational position cannot be detected, it is difficult to drive the brushless motor properly.

The present invention takes the above circumstances into consideration,
It is an object of the present invention to provide a drive control device for a brushless motor, which can reliably detect the rotational position of the rotor, and thereby can continue appropriate drive of the brushless motor, with high reliability.

[0011]

[Means for Solving the Problems] First invention (Claim 1)
Drive controller for a brushless motor detects a rotational position of a rotor of a brushless motor having a stator and a rotor, and sequentially switches energization to each phase winding of the stator in accordance with the detected position to drive the motor. At the same time, in the drive control device of the brushless motor that controls the speed by adjusting the energization rate for each phase winding, the control means for forcibly reducing the energization rate for each phase winding in a predetermined period immediately before energization switching , Energizing each phase winding
The rate is forcibly expanded in the specified period immediately after the energization switching.
And a control means for controlling .

[0012]

A second aspect of the invention the drive control device for a brushless motor (Claim 2), in the drive control device for a brushless motor comprising a rotor having a stator and a magnet having a plurality of phase windings, the pair of switching elements A switching circuit having a plurality of series circuits connected in series in the relationship of the upstream side and the downstream side of the current, and the interconnection point of each switching element of these series circuits is connected to each phase winding, and each of the switching circuits. One of a DC voltage circuit that outputs a DC voltage to be applied to the series circuit, an upstream switching element of one series circuit of the switching circuit, and a downstream switching element of another series circuit is continuously turned on. To turn each other on and off, and switch the switching elements that turn on continuously and on intermittently to each phase winding. Drive control means for sequentially switching the energization, and detection means for detecting the rotational position of the rotor from the change in the induced voltage generated in the non-energized phase winding of each phase winding,
The speed of the brushless motor is controlled by adjusting the ON / OFF duty of the energization switching control unit that controls the timing of the energization switching by the drive control unit and the switching element that is turned on and off according to the detection position of the detection unit. Speed control means and on controlled by the speed control means,
A duty control means for forcibly reducing the off-duty in the last predetermined period of the intermittent on-period, and a speed control hand.
The on / off duty adjusted by the stage
Duty system forcibly expanding in the first predetermined period
It is equipped with a means .

[0014]

A third aspect of the invention the drive control device for a brushless motor (claim 3), in the second aspect, the detection means, the level with a predetermined reference of the induced voltage across the phase winding de-energized The voltage level is compared, and when the two levels cross each other, the rotational position of the rotor is detected as the reference rotational position.

The fourth invention the drive control device for a brushless motor (Claim 4), in the first aspect, the control means, rotational speed or duty at a low speed less than a predetermined value,
In addition, it operates at a high load when the drive current is a predetermined value or more.

The drive control device for a brushless motor of the fifth aspect of the present invention (Claim 5), in the first aspect, the control means, with an increase in drive current, changes the length of the reduced period of the duty factor.

The drive control device for a brushless motor of the sixth invention (Claim 6), in the first aspect, the control means, with an increase in drive current, changes the length of the expansion period of the duty ratio.

The seventh drive control device for a brushless motor of the present invention (Claim 7), in the first aspect, the control means, with the decrease of the rotational speed or duty, changing the length of the reduction period duty ratio To do.

The drive control device for a brushless motor of the eighth invention (Claim 8), in the first aspect, the control means, with the decrease of the rotational speed or duty, changing the length of the expansion period of duty ratio To do. Ninth refrigeration cycle apparatus of the present invention (claim 9) of the controls brushless motor for driving the compressor by the drive controller.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 is a brushless motor, which includes a stator to which three phase windings Lu, Lv, and Lw connected in a star shape around a neutral point P are attached, and a rotor (not shown) to which a permanent magnet is attached. . Terminals Su, Sv, Sw are connected to the non-connection ends of the phase windings Lu, Lv, Lw, respectively.

A DC voltage circuit 3 is connected to the three-phase AC power supply 2. The DC voltage circuit 3 rectifies the voltage of the three-phase AC power supply 2 and outputs a DC voltage. The switching circuit 4 is connected to the output terminal of the DC voltage circuit 3. The switching circuit 4 has three series circuits in which a pair of switching elements are connected in series in the relationship of upstream side and downstream side of current, one for U phase, one for V phase, and one for W phase. The DC voltage output from the DC voltage circuit 3 is applied to these series circuits.

The U-phase series circuit comprises a transistor Tu + which is an upstream switching element and a transistor Tu- which is a downstream switching element. The series circuit for the V phase includes a transistor T that is an upstream switching element.
It is composed of v + and a transistor Tv- which is a downstream switching element. The series circuit for the W phase includes a transistor Tw + which is an upstream side switching element and a transistor Tw- which is a downstream side switching element. The flywheel diode D is connected in parallel with each transistor.

The terminals Su, Sv, Sw of the brushless motor 1 are connected to the interconnection points of the transistors Tu +, Tu-, the interconnection points of the transistors Tv +, Tv-, and the interconnection points of the transistors Tw +, Tw- in the switching circuit 4. Connected.

The switching circuit 4 turns on and off each transistor to turn on and off the phase winding Lu of the brushless motor 1.
It works to sequentially energize Lv and Lw. A series circuit of resistors 5 and 6 is connected to the output terminal of the DC voltage circuit 3. The voltage generated in the resistor 6 is input to the inverting input terminals (−) of the comparators 7, 8 and 9 as the reference voltage Vo. The resistance values of the resistors 5 and 6 are selected so that the voltage generated at the resistor 6 becomes a level of 1/2 of the output voltage of the DC voltage circuit 3.

The voltage V ₁ induced in the phase winding Lu is input to the non-inverting input terminal (+) of the comparator 7. The voltage V ₁ induced in the phase winding Lv is input to the non-inverting input terminal (+) of the comparator 8. The voltage V ₁ induced in the phase winding Lw is
Is input to the non-inverting input terminal (+).

The comparators 7, 8 and 9 output a logic "0" signal when the level of the induced voltage V ₁ is lower than the level of the reference voltage Vo, and the input voltage to the non-inverting input terminal (+). When the level of is equal to or higher than the level of the reference voltage Vo, the logic "1" signal is output. That is, the level of each induced voltage V ₁ is compared with the level of the reference voltage Vo, and the logical level of the output signal of the comparators 7, 8, 9 changes at the point where both levels intersect.

The outputs of the comparators 7, 8 and 9 are input to the control unit 10. The control unit 10 controls the phase windings Lu, Lv, Lw.
The voltages V ₁ to induce and monitored through a comparator 7, 8, 9, the brushless motor 1 based on the change of the induced voltages V ₁
The rotational position of the rotor is detected, and a drive signal for each transistor of the switching circuit 4 is created according to the rotational position of the rotor. These drive signals are supplied to the bases of the respective transistors of the switching circuit 4, so that the respective transistors are turned on and off. By turning on and off these transistors, the phase windings Lu and L of the brushless motor 1
Two v and Lw are sequentially energized. The phase winding L
Switching of energization to u, Lv, and Lw is called commutation.

The control unit 10 has the following functional means. [1] Of the upstream side transistor of one series circuit of the switching circuit 4 and the downstream side transistor of another one series circuit, one is continuously turned on and the other is intermittently turned on, and a transistor which is continuously turned on and intermittently turned on is selected. Drive control means for sequentially switching and energizing the phase windings Lu, Lv, Lw sequentially.

[2] Detecting means for detecting the rotational position of the rotor from the change in the logic level of the output signals of the comparators 7, 8 and 9. Specifically, the rotational position of the rotor at the timing when the logic level changes is detected as the reference rotational position.

[3] Energization switching control means for controlling the timing of energization switching to the phase windings Lu, Lv, Lw by the drive control means in accordance with the rotational position detected by the detection means. This energization switching control means is controlled by the phase windings Lu, Lv, Lw.
This is for setting the energization period to the electrical angle of 120 °.

[4] Speed control means for controlling the speed of the brushless motor 1 by adjusting the on / off duty (conductivity of the phase winding) of the transistor which is intermittently turned on by the drive control means.

[5] Duty control means for forcibly reducing the ON / OFF duty adjusted by the speed control means in the last predetermined period of the intermittent ON period. This control unit 10
FIG. 2 shows specific blocks of the above.

The outputs of the comparators 7, 8 and 9 are input to the position detection circuit 20. The position detection circuit 20 has a count value (energization mode A,
One of the output signals of the comparators 7, 8 and 9 is selected based on the count values corresponding to B, C, D, E and F). That is, the phase windings Lv and Lw are energized and the phase winding L
When u is in the non-conducting state, the output signal of the comparator 7 corresponding to the phase winding Lu in the non-conducting state is selected. Phase winding Lw, L
When u is energized and the phase winding Lv is de-energized, the output signal of the comparator 8 corresponding to the de-energized phase winding Lv is selected. When the phase windings Lu and Lv are energized and the phase winding Lw is in the non-energized state, the output signal of the comparator 9 corresponding to the non-energized phase winding Lw is selected. Then, the position detection circuit 20 determines that the rotor is at the reference rotation position when the logic level of the selected output signal changes, and outputs the position detection signal.

The position detection signal output from the position detection circuit 20 is sent to the timer counter 21 and the control circuit 22. The timer counter 21 starts a new time count each time the position detection signal is received. That is, the timer counter 21 measures the elapsed time (electrical angle) after the rotation reference position of the rotor is detected. Further, the timer counter 21 measures a time T (corresponding to a period of an electrical angle of 60 °) from the detection of the rotation reference position of the rotor to the detection of the next rotation reference position. The time count value of the timer counter 21 is notified to the control circuit 22.

When the control circuit 22 receives the position detection signal from the position detection circuit 20, the control circuit 22 calculates the rotation speed of the rotor from the time count value (time T) of the timer counter 21, and the rotation speed and a predetermined target speed. The ON / OFF duty of the ON / OFF signal output from the drive circuit 25 is adjusted so that the difference between the ON and OFF signals becomes zero.

In addition, the control circuit 22 controls the on,
It has a function of forcibly reducing the off-duty during the last predetermined period of the intermittent on-period. In addition, the control circuit 22
Of the time count value (time T) of the timer counter 21
A value of 1/2 (= T / 2; corresponding to a period of an electrical angle of 30 °) is calculated and set in the register 31.

The set value of the register 31 "T / 2" (electrical angle
30 °) corresponds to the remaining period from the detection of the reference rotational position of the rotor to the switching of energization (commutation) to the phase windings Lu, Lv, Lw.

The set value of the register 31 is compared with the time count value of the timer counter 21 by the comparator 34. When the time count value of the timer counter 21 reaches the set value of the register 31, the comparator 34 issues an energization mode switching command. This energization mode switching command is sent to the energization mode counter 23.

The energization mode counter 23 is a hexadecimal counter whose count value repeats "1" to "6" and counts the number of energization mode switching commands issued from the comparator 34. The count values are the six conduction modes A, B, and B for each transistor of the switching circuit 4.
It corresponds to C, D, E, and F and is notified to the position detection circuit 20 and the memory 24.

The memory 24 is provided with energization modes A, B, C,
Six types of drive signal patterns corresponding to D, E, and F are stored. Any one of these storage patterns is read according to the count value of the energization mode counter 23 and sent to the drive circuit 25.

The drive circuit 25 outputs a drive signal to each transistor of the switching circuit 4 according to a drive signal pattern read from the memory 24 and according to a command from the control circuit 22. The drive signal includes an on signal for continuously turning on the transistor, an on / off signal for intermittently turning on the transistor, and an off signal for turning off the transistor.

Next, the operation of the above configuration will be described. Energization modes A, B, C, D, E, F and switching circuit 4
3 shows the correspondence with the operation pattern of each transistor. “ON” in the figure represents the continuous ON operation of the transistor. PWM in the figure represents the pulse width modulation control, that is, the operation of intermittently turning on the transistor. The blank space in the figure indicates that the transistor is off.

The waveforms of the voltage and current generated in the phase windings Lu, Lv, Lw are shown in FIG. First, when the count value of the energization mode counter 23 is "1", energization is performed from the phase winding Lu to the phase winding Lv (energization mode A). That is, the transistor Tu + on the upstream side is intermittently turned on, the transistor Tv- on the downstream side is continuously turned on, and the other transistors are turned off.

When a magnetic field is generated in the phase windings Lu and Lv, a rotational torque is generated in the rotor by the interaction between the magnetic field generated by the permanent magnets of the rotor and the magnetic field, and the rotor starts rotating. At this time, the voltage V ₁ is induced in the non-energized one phase winding Lw by the magnetic action caused by the rotation of the permanent magnet.

The induced voltage V ₁ to the phase winding Lw is calculated by the comparator 9
Is compared with the reference voltage Vo. When the level of the induced voltage V _{1 and} the level of the reference voltage Vo intersect and the logical level of the output signal of the comparator 9 changes, the rotational position of the rotor at that time is detected as the reference rotational position.

When the reference rotational position of the rotor is detected, a comparator 34 issues an energization mode switching command after a lapse of an electrical angle of 30 degrees. In response to this energization mode switching command, the count value of the energization mode counter 23 becomes "2".

When the count value of the energization mode counter 23 becomes "2", the energization (energization mode B) from the phase winding Lu to Lw is switched. That is, the transistor Tu + on the upstream side is continuously turned on and the transistor Tw- on the downstream side is turned on.
Turns on and off, and other transistors turn off.

When a magnetic field is generated in the phase windings Lu and Lw, a rotational torque is generated in the rotor due to the interaction between the magnetic field generated by the permanent magnets of the rotor and the magnetic field, and the rotor continues to rotate. At this time, the voltage V ₁ is induced in one phase winding Lv in the non-energized state by the magnetic action caused by the rotation of the permanent magnet.

The induced voltage V ₁ to the phase winding Lv is calculated by the comparator 8
Is compared with the reference voltage Vo. When the level of the induced voltage V _{1 and} the level of the reference voltage Vo intersect and the logical level of the output signal of the comparator 8 changes, the rotational position of the rotor at that time is detected as the reference rotational position.

When the reference rotational position of the rotor is detected, a comparator 34 issues an energization mode switching command after a period of 30 electrical degrees has elapsed. In response to this energization mode switching command, the count value of the energization mode counter 23 becomes "3".

When the count value of the energization mode counter 23 becomes "3", the energization from the phase windings Lv to Lw (energization mode C) is switched. That is, the transistor Tv + on the upstream side is intermittently turned on and the transistor Tw- on the downstream side is turned on.
Turns on continuously, and other transistors turn off.

When a magnetic field is generated in the phase windings Lv, Lw, a rotational torque is generated in the rotor due to the interaction between the magnetic field and the magnetic field generated by the permanent magnet of the rotor, and the rotor continues to rotate. At this time, the voltage V ₁ is induced in the non-energized one phase winding Lu by the magnetic action caused by the rotation of the permanent magnet.

The induced voltage V ₁ to the phase winding Lu is determined by the comparator 7
Is compared with the reference voltage Vo. When the level of the induced voltage V _{1 and} the level of the reference voltage Vo intersect and the logical level of the output signal of the comparator 7 changes, the rotational position of the rotor at that time is detected as the reference rotational position.

Similarly, each time the electrical angle of 30 degrees elapses after the reference rotational position of the rotor is detected, the comparator 34 issues an energization mode switching command, and in response thereto, the energization mode counter 23. Repeats counting from "1" to "6".

When the count value of the energization mode counter 23 becomes "4", the energization from the phase winding Lv to the phase winding Lu (energization mode D) is switched. Energization mode counter 23
When the count value of “5” becomes “5”, the current is switched from the phase winding Lw to the phase winding Lu (energization mode E). When the count value of the energization mode counter 23 becomes “6”, the phase winding L
Switching from energization to the phase winding Lv from w (energization mode F). When the count value of the energization mode counter 23 returns to "1", the energization (energization mode A) from the phase winding Lu to the phase winding Lv is switched.

As described above, the continuous ON / intermittent ON operation of each transistor of the switching circuit 4 is sequentially switched, and the phase windings Lu, Lv, Lw are sequentially energized, whereby the rotor continues to rotate. To do.

Further, the transistor which is turned on and off is turned on,
By adjusting the off-duty, the rotation speed of the rotor, that is, the speed of the brushless motor 1 is controlled. By the way, as shown in FIG. 4, in the energization mode D, the phase current flowing through the phase winding Lv is commutated to the energization mode E in the non-energized state and then attenuated. The induced voltage V ₁ is clamped to the zero level of the output voltage of the DC voltage circuit 3 (in the energization mode B, it is clamped to the peak level) while the decaying phase current exists. After the phase current decays to zero, the induced voltage V ₁ rises. The induced voltage V _{1 that} has risen changes to a decrease, the level of the induced voltage V ₁ is compared with the level of the reference voltage Vo, and when both levels intersect, the rotational position of the rotor at that timing is detected as the reference rotational position. To be done.

The time it takes for the phase current to decay to zero after commutation depends on the value of the phase current immediately before commutation (depending on the motor load), the inductance of the circuit, and the magnitude of the induced voltage V ₁ (depending on the rotation speed). It depends on the on / off duty of the transistor which is intermittently turned on in the same energization mode period. That is, the larger the value of the phase current immediately before commutation (the larger the motor load), the larger the inductance of the circuit, and the smaller the induced voltage V ₁ (the lower the rotation speed), the transistor that is turned on and off in the same energization mode period. The smaller the on / off duty of (lower rotation speed), the longer the time required for the phase current to decay to zero after commutation.

If it takes a long time for the phase current to decay to zero after the commutation, as shown by the broken line in FIG.
_A situation occurs in which the rising level of ₁ changes to decrease before the level of the reference voltage Vo is reached, and the rotational position of the rotor cannot be detected. If the rotational position cannot be detected, the proper drive of the brushless motor cannot be continued.

Therefore, as shown in FIG. 5, the ON / OFF duty is forcibly reduced irrespective of the value for speed control in the predetermined period immediately before the last energization switching of the intermittent ON period of the transistor. This reduction reduces the value of the phase current immediately before commutation. The broken line shows the phase current change when the on / off duty is not reduced.

The value of the phase current immediately before commutation is one of the factors that influence the time it takes for the phase current to decay to zero after commutation. That is, since the value of the phase current immediately before the commutation is reduced, the time taken for the phase current to decay to zero after the commutation is shortened.

Thus, the time required for the phase current to decay to zero after commutation is shortened, so that the induced voltage V
The rising level of ₁ always drops after exceeding the level of the reference voltage Vo, so that the rotational position of the rotor is surely detected. Therefore, the proper drive of the brushless motor is continued.

In particular, stable driving can be performed even when the motor load is large, at low speed operation, and even with a motor having a large inductance, and the operating range can be expanded.

As an example of a motor having a large inductance, there is a motor having a salient-pole-structured permanent-magnet-embedded rotor capable of utilizing a reactance torque, and stable driving can be performed also in this case. Since stable driving can be performed, the reactance torque can be increased, and the operating efficiency of the motor is improved.

Further, the control for reducing the above-mentioned duty (conductivity) is operated only when the drive current is in a high load state of a predetermined value or more and the rotation speed (or duty) is a low speed of a predetermined value or less. Alternatively, the length of the period for reducing the duty may be changed (for example, increased) in accordance with the increase of the drive current and the decrease of the rotation speed (or duty).

By doing so, it is possible to adjust the change rate of the PWM duty to the minimum level for stable driving,
It is possible to minimize the torque fluctuation within one cycle due to the PWM duty change.

Next, a second embodiment of the present invention will be described. As the functional means of the control unit 10, the following [6] is added in addition to [1] to [5] of the first embodiment.

[6] Duty control means for forcibly expanding the on / off duty adjusted by the speed control means in the first predetermined period of the intermittent on period. The control circuit 22, which is a specific configuration of the control unit 10, forcibly reduces the adjusted on / off duty in the final predetermined period of the intermittent on-period, and adjusts the adjusted on / off duty to the beginning of the intermittent on-period. Has the function of forcibly expanding during the prescribed period.

The other structure is the same as that of the first embodiment. According to such a configuration, as shown in FIG. 6, the on / off duty is forcibly reduced irrespective of the value for speed control in the final predetermined period of the intermittent on period of the transistor. This reduction reduces the value of the phase current immediately before commutation and reduces the time it takes for the phase current to decay to zero after commutation. The process up to this point is the same as in the first embodiment.

Further, in the first predetermined period of the intermittent ON period of the transistor, the ON / OFF duty is forcibly expanded irrespective of the value for speed control. FIG. 7 shows a state in which the phase current is attenuated with time expanded. During the on period of the transistor that is intermittently turned on, the slope of the attenuation of the phase current increases (decays faster), and during the off period, the slope of the attenuation of the phase current decreases (decays slower).

Therefore, by increasing the on / off duty, that is, by increasing the ratio of the on period, the time taken for the phase current to decay to zero after commutation is shortened. The broken line in FIG. 6 shows the phase current change when the on / off duty is not reduced.

Here, the difference in the manner of attenuating the phase current when the transistor that is turned on and off is turned on and off will be described with reference to FIGS. 8 and 9. 8, voltage e _u generated in each phase winding in the energized mode B, e _v, shows the relationship between e _w and phase currents, the transistors Tu + continuous ON operation, the transistors Tw- intermittently turned on, Transistor T
v + is off. FIG. 9 shows the voltages _eu , _ev , _ew.
The waveforms in the energization modes A and B are shown.

In the energization mode B, the phase winding Lv which is a non-energized phase when the transistor Tw- which is intermittently turned on is turned on.
The output voltage E of the DC voltage circuit 3 and the phase voltages _eu , _ev ,
A voltage E ₁ determined by the relationship with e _w is applied. When the transistor Tw- is off, only the phase voltage e _v having the opposite polarity to the direction of the V-phase current is generated in the phase winding Lv which is the non-conduction phase.

[0075] The relationship between the transistor Tw- the level of the voltage E ₁ applied to the phase winding Lv when turned on, the level of the voltage e _v occurring in the phase winding Lv when the transistor Tw- is turned off, E ₁ > the e _v. Therefore, the slope of the attenuation of the V-phase current is larger when the switch is on (decreases faster) than when the switch is off.

As described above, the two-stage control is adopted in which the ON / OFF duty is reduced in the first predetermined period of the intermittent ON period of the transistor and the ON / OFF duty is expanded in the final predetermined period of the intermittent ON period. By doing so, the time taken for the phase current to decay to zero after commutation is further shortened as compared with the case of the first embodiment.
Therefore, the reliability of rotor rotational position detection is improved,
As a result, the reliability of motor drive is improved.

Further, the control for reducing and expanding the above-mentioned duty (conductivity) is operated only when the drive current is in a high load state of a predetermined value or more and the rotation speed (or duty) is a low speed of a predetermined value or less. Alternatively, the length of the period in which the duty is reduced or the period in which the duty is increased may be appropriately changed (for example, increased) as the drive current increases and the rotation speed (or duty) decreases.

By doing so, the change rate of the PWM duty can be adjusted to the minimum level for stable driving,
It is possible to minimize the torque fluctuation within one cycle due to the PWM duty change.

By the drive control device of the brushless motor shown in the first and second embodiments described above, refrigeration such as an air conditioner having a refrigeration cycle in which a compressor, a condenser, a pressure reducer and an evaporator are connected. The brushless motor for driving the compressor of the cycle device may be controlled. In this case, stable driving can be performed when the refrigeration cycle has a high load, and reliability can be improved.

The present invention is not limited to the above-described embodiment, but can be variously modified without departing from the scope of the invention, and can be applied to a brushless motor fan arranged opposite to a condenser or an evaporator. You can

[0081]

As described above, according to the present invention, it is possible to provide a highly reliable drive control device for a brushless motor which can reliably detect the rotational position of the rotor and continue the proper drive of the brushless motor.

[Brief description of drawings]

FIG. 1 is a block diagram of a control circuit according to each embodiment of the present invention.

FIG. 2 is a block diagram showing a specific configuration of a control unit in FIG.

FIG. 3 is a diagram showing a relationship between an energization mode and an operation pattern of a transistor in each example.

FIG. 4 is a diagram showing waveforms of voltage and current generated in each phase winding of each example.

FIG. 5 is a diagram showing the relationship between the operation of each transistor and the phase current of the first embodiment.

FIG. 6 is a diagram showing the relationship between the operation of each transistor of the second embodiment and the phase current.

FIG. 7 is a diagram showing the state of attenuation of the phase current in each example with time enlarged.

FIG. 8 is a diagram for explaining the relationship between voltage and current generated in each phase winding of each embodiment.

FIG. 9 is a diagram showing a waveform of a voltage generated in each phase winding of each example.

FIG. 10 is a diagram showing a waveform of a phase current of a conventional device.

[Explanation of symbols] 1 ... Brushless motor 3 ... DC voltage circuit 4 ... Switching circuit 7, 8, 9 ... Comparator 10 ... Control unit

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02P 6/18 F04B 49/06

Claims (9)

(57) [Claims] 1. For a brushless motor having a stator and a rotor, the rotational position of the rotor is detected, and the energization to each phase winding of the stator is sequentially switched according to the detected position to drive the motor and each phase. A drive control device for a brushless motor that controls a speed by adjusting a duty ratio of a winding, and a control unit that forcibly reduces the duty ratio of each phase winding in a predetermined period immediately before the switching of the energization. A drive control device for a brushless motor, comprising: a control unit for forcibly increasing the energization rate to the phase winding for a predetermined period immediately after the energization switching. 2. A drive control device for a brushless motor comprising a stator having a plurality of phase windings and a rotor having a magnet, in which a pair of switching elements are connected in series in a relation of upstream side and downstream side of current. And a switching circuit in which the interconnection points of the switching elements of these series circuits are connected to the phase windings, and a DC voltage circuit that outputs a DC voltage to be applied to each series circuit of the switching circuit. And one of the upstream side switching element of one series circuit of the switching circuit and the downstream side switching element of another series circuit, one of which is continuously turned on and the other of which is intermittently turned on, and the continuous on and intermittently turned on. Drive control means for sequentially switching the energization to each phase winding by sequentially switching the switching elements; Detection means for detecting the rotational position of the rotor from the change in the induced voltage generated in the phase winding in the non-energized state of the line, and controlling the timing of energization switching by the drive control means according to the detected position of the detection means. Control means for controlling energization switching, speed control means for controlling the speed of the brushless motor by adjusting the on / off duty of the switching element that is intermittently turned on, and the on / off duty adjusted by the speed control means for intermittent on A duty control means for forcibly reducing in the last predetermined period of the period, and a duty control means for forcibly increasing the on / off duty adjusted by the speed control means in the first predetermined period of the intermittent on period. A drive control device for a brushless motor, comprising: 3. The drive control device for a brushless motor according to claim 2, wherein the detection means compares the level of the induced voltage generated in the phase winding in the non-energized state with the level of a predetermined reference voltage. A drive control device for a brushless motor, wherein the rotational position of the rotor is detected as a reference rotational position when both levels intersect. 4. The drive control device for a brushless motor according to claim 1, wherein the control means operates at a low speed in which a rotation speed or a duty is a predetermined value or less and a high load in which a drive current is a predetermined value or more. A drive control device for a brushless motor. 5. The brushless motor drive control device according to claim 1, wherein the control means changes the length of the reduction period of the duty ratio as the drive current increases. Drive controller. 6. The drive control device for a brushless motor according to claim 1, wherein the control means changes the length of the energization rate expansion period as the drive current increases. Drive controller. 7. The brushless motor drive control device according to claim 1, wherein the control means changes the length of the reduction period of the energization rate as the rotation speed or the duty decreases. Motor drive control device. 8. The brushless motor drive control device according to claim 1, wherein the control unit changes the length of the energization period with a decrease in rotation speed or duty. Motor drive control device. 9. A drive for a brushless motor according to claim 1.
In a dynamic control device, the drive control device controls a brushless motor for driving a compressor.