JPH08163890A - Control method for brushless motor - Google Patents

Abstract

PURPOSE: To protect transistors in an inverter circuit for driving a brushless motor against deterioration and breakdown. CONSTITUTION: A voltage induced in the armature winding U of a brushless motor 5 is inputted to a position detecting circuit 6 where it is compared with a predetermined reference voltage. A comparison result signal is fed to a microcomputer 10a where a conduction switching timing for the brushless motor 5 is calculated. In such control method for brushless motor the microcomputer 10a stops the brushless motor 5 when the edge (the first edge after spike voltage) of the comparison result signal (positional detection signal) from the position detecting circuit 6 is not detected for a predetermined time after switching the conduction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation control technology for a sensorless DC brushless motor (hereinafter referred to as a brushless motor), and more particularly to a method for controlling a brushless motor for protecting an inverter circuit for driving the brushless motor. Is.

[0002]

2. Description of the Related Art In a brushless motor control method of this type, the energization of an armature winding of the brushless motor is switched on the basis of the position detection of the rotor of the brushless motor, while the rotational speed of the brushless motor is controlled. To do so, the duty cycle of the PWM signal (of the chopping signal) that chops the energization voltage (applied voltage) of the armature winding is changed.

As a position detecting circuit for detecting the position of the rotor of a brushless motor, a digital system, which has many advantages as compared with an analog system, has been adopted. In the case of this digital method, the induced voltage generated in the armature winding (position detection coil) of the brushless motor is compared with the reference voltage, the comparison result is input to the microcomputer, and the microcomputer supplies the energized state of the brushless motor. The timing for switching is calculated.

Therefore, for example, as shown in FIG. 3, when applied to an air conditioner, the control device converts the commercial power supply 1 into a direct current by a converter circuit 3 via a reactor 2 for power factor correction. The conversion DC power is switched by the inverter circuit 4 and supplied to the brushless motor 5 of the compressor motor as three-phase AC.

Further, the armature winding U of the brushless motor 5
The terminal voltage (induced voltage; see FIG. 4A) is input to the position detection circuit 6, and the position detection circuit 6 uses the induced voltage and the reference voltage (for example, 1 of the applied voltage of the brushless motor 5).
/ 2) and outputs a signal (position detection signal; see FIG. 4B) as a result of this comparison to the control circuit 7.

The control circuit 7 drives the switching element (transistor) of the inverter circuit 4 based on the position detection signal in order to control the rotation of the brushless motor 5 (switches the energization of the brushless motor 5), and Chopping the driving period.

The position detection circuit 6 divides the applied voltage of the brushless motor 5 into 1/2, and the terminal voltage (induced voltage) of the armature winding U with the divided voltage as a reference voltage. ) And a comparison circuit 6b. The control circuit 7 comprises a microcomputer 7a and a drive circuit 7b.

Further, the control device has a current sensor 8 for detecting the secondary side current (motor current) for the purpose of the overcurrent protection function.
And an overcurrent detection circuit 9 that outputs an overcurrent detection signal to the microcomputer 7a based on the detected current.

In the digital control device,
The microcomputer 7a changes the position detection signal (first edge after spike voltage; time B shown in FIG. 4).
The time interval is measured, and the energization switching timing of the armature winding is calculated based on this time measurement time. A drive signal for turning on / off one transistor of each of the upper and lower arms of the inverter circuit 4 is output to the drive circuit 7b according to the energization switching timing, while the rotation speed of the brushless motor 5 is detected from the input position detection signal to perform a predetermined rotation. The drive circuit 7b outputs a PWM signal for chopping the drive period of one transistor in order to adjust the applied voltage so that
Output to.

Further, the ON time of the duty cycle of the PWM signal is lengthened to increase the rotation speed of the brushless motor 5, and the ON time of the duty cycle is shortened to decrease the rotation speed of the brushless motor 5. By varying the ON time of the duty cycle in this manner, the rotation speed of the brushless motor 5 can be set to, for example, the target rotation speed.

The overcurrent detection circuit 9 outputs an overcurrent detection signal when the motor current (secondary side current) of the brushless motor 5 reaches a limit value, and integrates the secondary side current, The overcurrent detection signal is also output when the integration result reaches a predetermined value.

Therefore, when the motor current (secondary side current) of the brushless motor 5 becomes abnormally large for some reason and the secondary side current reaches the limit value, the microcomputer 7a stops the brushless motor 5. . Further, when the secondary side current gradually increases and this state elapses for a predetermined time, the microcomputer 7a lowers the frequency of the brushless motor 5. As a result, it is possible to improve the safety and reliability of the air conditioner.

[0013]

In the brushless motor control method, however, an error may occur in the position detection of the rotor 5a due to the effects of noise, sudden load fluctuations, spike voltage generation, and the like. Therefore, the energization switching timing of the brushless motor 5 is different, that is, the rotation of the brushless motor 5 becomes abnormal,
Finally, the brushless motor 5 stalls and stops.

For example, when the energized state (same state) between A and C shown in FIG. 4 continues for a long time, and the secondary side current becomes large due to this, the overcurrent protection function frequently operates and the operating efficiency is improved. Cause decline.

In addition, due to an abnormal situation such as the stall or stop of the brushless motor 5, the induced voltage does not occur in the position detection coil (armature winding) and the secondary side current becomes large. There was a problem that the transistor was subordinate and destroyed. When the abnormal secondary current occurs, it takes some time until the secondary current reaches the limit value of the overcurrent protection function or the predetermined value of the integration result and the overcurrent protection function operates. This is because a large current flows through the transistor during this time.

The present invention has been made in view of the above problems. An object of the present invention is to shorten the time for which a large current flows through the inverter means when the rotation of the brushless motor becomes abnormal. It is an object of the present invention to provide a method of controlling a brushless motor, which prevents the switching element of the inverter means from being deteriorated and prevents the switching element from being destroyed.

[0017]

To achieve the above object, the present invention compares an induced voltage generated in an armature winding of a brushless motor with a predetermined reference voltage, and based on the comparison result, the brushless motor While obtaining a signal synchronized with the rotation of the rotor and switching the energization state of the brushless motor based on the change of the obtained signal, the change of the obtained signal is within a predetermined time after the energization switching or The gist is that the brushless motor is stopped when it is not within a predetermined electrical angle of the rotor.

Further, according to the present invention, the induced voltage generated in the armature winding of the brushless motor is compared with a predetermined reference voltage, and a signal synchronized with the rotation of the rotor of the brushless motor is obtained based on the comparison result. While switching the energization state of the brushless motor based on the change of the obtained signal, a condition of one of a predetermined time and a predetermined electrical angle of the rotor or the same predetermined time and a predetermined electrical angle after switching the energization. The brushless motor is stopped when there is no change in the signal obtained based on the comparison result until the condition is satisfied.

Furthermore, the present invention is a brushless motor control method for controlling a brushless motor for driving a compressor of an air conditioner by means of an inverter, wherein at least one armature winding of the armature winding of the brushless motor is used. Compare the induced voltage generated in the line with a predetermined reference voltage,
A signal synchronized with the rotation of the rotor of the brushless motor is obtained from the comparison result, and the switching timing of the energized state of the brushless motor is calculated based on the change of the obtained signal, while the obtained signal is obtained. The control of the inverter means is stopped to stop the brushless motor when the change of the signal is not within a predetermined time after switching the energization at the calculation timing or within a predetermined electrical angle of the rotor.

Furthermore, the present invention is a brushless motor control method for controlling a brushless motor for driving a compressor of an air conditioner by means of an inverter, wherein at least one armature winding of the brushless motor is wound. The induced voltage generated in the line is compared with a predetermined reference voltage, a signal synchronized with the rotation of the rotor of the brushless motor is obtained based on the comparison result, and the brushless motor is based on the change of the obtained signal. While calculating the switching timing of the energization state of, while the predetermined time after energization switching at the calculation timing and the condition of any one of the predetermined electrical angle of the rotor or the same predetermined time, the predetermined electrical angle is satisfied, The brushless motor is stopped when there is no change in the signal obtained based on the comparison result. That.

[0021]

According to the above-mentioned means, the induced voltage generated in the armature winding of the brushless motor is compared with the reference voltage by the position detecting means, and between the intersections (first edge after spike voltage) of this comparison result. Time is measured by a microcomputer.

In the microcomputer, the energization switching timing of the brushless motor is calculated based on the measured time, and the plurality of switching elements of the inverter means are driven by this energization switching timing.

At this time, the brushless motor is stopped when the intersection point, which is the comparison result, cannot be obtained by a predetermined time after switching the energization or by a predetermined electrical angle of the rotor. Further, if the intersection, which is the comparison result, cannot be obtained by the lapse of a predetermined time after switching the energization and before the lapse of a predetermined electrical angle of the rotor, the brushless motor is stopped. This is because if the rotor of the brushless motor stalls or stops, the intersection, which is the comparison result, cannot be obtained.

For example, in the case where an intersection point resulting from the comparison result occurs between the spike voltage and the original position detection pulse (between A and B shown in FIG. 4) due to the generation of noise, the position of the rotor is detected in the microcomputer. Since the energization switching timing is calculated based on this erroneous position detection, the energization switching timing is deviated.
Further, if the pulse width of the spike voltage reaches the intersection of the above comparison results (time point B in FIG. 4), the microcomputer erroneously detects the position of the rotor, and the energization switching timing is deviated as described above.

As described above, the brushless motor stalls and stops due to the deviation of the energization switching timing. However, since the brushless motor is stopped as described above, it is largely used in the inverter means for driving the brushless motor. The current flow time is short, and as a result, the switching element of the inverter means is prevented from being deteriorated and destroyed.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. In the figure, the same parts as those in FIG. 3 are designated by the same reference numerals, and duplicate description will be omitted.

In FIG. 1, the control circuit 1 of this control device is shown.
In addition to the function of the control circuit 7 shown in FIG. 3, 0 cannot detect the change of the input position detection signal (the first edge after the spike voltage) from the switching of energization of the brushless motor 5 to the predetermined time. Sometimes the same brushless motor 5
It has a microcomputer 10a having a function of stopping.

The above-mentioned predetermined time is longer than the time during which the edge of the position detection signal (the first rising or falling edge after the spike voltage) may be detected in the operating state of the brushless motor 5, and the overcurrent protection function. The time is shorter than the time until the brushless motor 5 is stopped by the operation.

Next, the operation of the control device will be described in detail with reference to the flow chart of FIG. The brushless motor 5 has its rotor 5a rotated, that is, the brushless motor 5 is in an operating state.

First, the microcomputer 10a of the control circuit 10 calculates the energization switching timing of the brushless motor 5 based on the position detection signal from the position detection circuit 6, and changes the input position detection signal after switching the energization ( Edge) is detected.

At this time, it is determined whether or not there is a rising edge or a falling edge of the position detection signal from the time of switching the energization until a predetermined time has elapsed (steps ST1 and ST2).

Then, if the edge of the input position detection signal is not detected within the predetermined time, the process proceeds to step ST3,
The brushless motor 5 is stopped. When the edge of the input position detection signal is detected within the predetermined time, the process returns to step ST1 and the above steps are repeated.

For example, due to the generation of noise, the edge of the position detection signal from the position detection circuit 6 (the first edge after the spike voltage) is between the spike voltage and the original position detection pulse (between A and B shown in FIG. 4). ) Occurs. Then, the microcomputer 10a erroneously detects the position of the rotor 5a, and the energization switching timing is calculated based on this erroneous position detection, so that the energization switching timing is deviated.

When the pulse width of the spike voltage reaches the edge of the position detection signal (time B shown in FIG. 4), the microcomputer 10a makes an error in detecting the position of the rotor 5a, and the energization switching timing is shifted as described above. Will end up.

Then, since the brushless motor 5 stalls and stops at worst, the secondary current increases. In the case of the conventional example, the secondary side current is detected to operate the overcurrent protection function, that is, the brushless motor 5 is stopped. Since it takes a certain amount of time to stop the brushless motor 5 due to the overcurrent protection function, the transistor of the inverter circuit 4 may be deteriorated or destroyed.

However, according to the present invention, the brushless motor 5 is immediately stopped when the edge of the input position detection signal (the first edge after the spike voltage) does not appear by the predetermined time due to the abnormal situation of stall or stop. . Moreover, the predetermined time is shorter than the time until the operation of the overcurrent protection function, as described above.

Therefore, the time during which a large current flows through the inverter circuit 4 is shortened, and the inverter circuit 4 does not have the conventional structure.
It is possible to prevent the transistor from being degraded or broken.

In the above embodiment, the case of applying the method to the compressor motor of the air conditioner has been described, but it is obvious that the method can be applied to the method of controlling the motor used in other equipment. .

When the edge of the input position detection signal (the first edge after the spike voltage) does not appear by the above-mentioned predetermined time, the brushless motor 5 is stopped, but the rotor 5a is not stopped for a predetermined time. The rotation may be stopped when the edge does not appear before the rotation of a predetermined electrical angle, or the brushless motor 5 may be stopped when both of the edges are satisfied. Further, the brushless motor 5 may be stopped when either one of the conditions of the predetermined electrical angle is satisfied for the predetermined time.

[0040]

As described above, according to the present invention, the induced voltage generated in the armature winding of the brushless motor is compared with the predetermined reference voltage, and the energization switching timing of the brushless motor is determined based on the comparison result. A method for controlling a brushless motor that calculates and switches the energization at this calculation timing to control the rotation of the rotor, and the change in the signal obtained by the comparison result is not within a predetermined time or within a predetermined electrical angle after switching the energization. In this case, the brushless motor is stopped in such a case, so even if the rotor of the brushless motor stalls or an abnormal situation occurs in which it stops at worst, the time during which a large current flows through the inverter means can be shortened. In addition, it is possible to prevent the transistor of the inverter means from being deteriorated, and further, to prevent the destruction. There are useful effect that it is possible to apply the safety and improve the reliability of the air conditioner.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a control device to which an embodiment of the present invention is applied and to which a brushless motor control method is applied.

FIG. 2 is a schematic flowchart for explaining the operation of the control device shown in FIG.

FIG. 3 is a schematic block diagram of a conventional brushless motor control device.

FIG. 4 is a schematic time chart diagram for explaining the operation of the control device shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Reactor 3 Converter circuit 4 Inverter circuit (inverter means) 5 Brushless motor (sensorless DC brushless motor) 5a Rotor 6 Position detection circuit 6a Resistance circuit 6b Comparison circuit 7b Drive circuit 10 Control circuit 10a Microcomputer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H02P 6/02 371 C

Claims (4)

[Claims] 1. An induction voltage generated in an armature winding of a brushless motor is compared with a predetermined reference voltage, and a signal synchronized with the rotation of the rotor of the brushless motor is obtained based on the comparison result, and the obtained signal is obtained. While switching the energization state of the brushless motor based on the change of the signal, stop the brushless motor when the change of the obtained signal is not within a predetermined time after switching the energization or within a predetermined electrical angle of the rotor A method for controlling a brushless motor, characterized in that 2. An induction voltage generated in an armature winding of a brushless motor is compared with a predetermined reference voltage, a signal synchronized with the rotation of the rotor of the brushless motor is obtained from the comparison result, and the obtained signal is obtained. While switching the energization state of the brushless motor based on the change of the signal, until the condition of any one of the predetermined time and the predetermined electrical angle of the rotor or the same predetermined time and the predetermined electrical angle is satisfied after the switching of the energization. In the meantime, the brushless motor control method is characterized in that the brushless motor is stopped when there is no change in the signal obtained based on the comparison result. 3. A brushless motor control method for controlling a brushless motor for driving a compressor of an air conditioner by means of an inverter, wherein at least one of armature windings of the brushless motor is controlled.
The induced voltage generated in one armature winding is compared with a predetermined reference voltage, and a signal synchronized with the rotation of the rotor of the brushless motor is obtained based on the comparison result, and based on the change of the obtained signal. While calculating the switching timing of the energization state of the brushless motor, and when the change of the obtained signal is not within the predetermined time or within the predetermined electrical angle of the rotor after the energization switching at the calculation timing, the control of the inverter means Is stopped to stop the brushless motor. 4. A brushless motor control method in which a brushless motor for driving a compressor of an air conditioner is controlled by an inverter means, which occurs in at least one armature winding of an armature winding of the brushless motor. The induced voltage is compared with a predetermined reference voltage, a signal synchronized with the rotation of the rotor of the brushless motor is obtained from the comparison result, and the energized state of the brushless motor is determined based on the change of the obtained signal. While the switching timing is calculated, the comparison result is also calculated until a predetermined time after switching the energization at the calculation timing and a condition of one of the predetermined electrical angle of the rotor or the predetermined electrical time and the predetermined electrical angle are satisfied. Brushless motor characterized by stopping the brushless motor when there is no change in the signal obtained by Control method of chromatography data.