JP5910380B2 - Sensorless brushless motor drive device - Google Patents

Description

  The present invention relates to a sensorless brushless motor driving apparatus that performs trapezoidal wave driving using a pulse width modulation method.

  As a method of a brushless motor, a sensorless motor that does not include a sensor for detecting the rotational position of a rotor has been put into practical use. In a sensorless brushless motor driving apparatus, in order to adjust the output torque, a pulse width modulation signal that variably adjusts the duty ratio is used to energize during a duty-on time period. In place of the rotational position sensor, a position detection circuit that detects an induced voltage induced at the terminal of the armature winding of the stator and detects a relative rotational positional relationship with the magnetic pole pair of the rotor is generally used. Provided. The drive device controls the energization phase and energization time zone for energizing the armature winding based on the detected rotational position. In motors with three-phase armature windings, a trapezoidal wave drive system that switches the energized phases sequentially at an electrical angle of 60 ° according to the rotational position of the rotor is often used, sometimes overlapping the energization of multiple phases Has also been done.

  The induced voltage detected by the above-described position detection circuit is generated when the magnetic flux from the magnetic pole pair of the rotor is linked to the armature winding in the time zone that is not energized. Therefore, the induced voltage changes depending on the relative rotational position relationship between the armature winding and the rotor, and can be an index for detecting the rotational position. However, the phase in which the induced voltage is generated is switched sequentially with the switching of the energized phase. As a circuit method for detecting the induced voltage, two methods, a three-phase synthesis method and a three-phase independent method, have been conventionally used. In either method, it is common to use a comparator to compare the induced voltage with a reference voltage and detect a specific rotational position of the rotor with the change timing of the comparison result. As the reference voltage, an intermediate level value that is half the power supply voltage or a neutral point voltage of the Y-connected armature winding is used.

  A technical example of this type of sensorless brushless motor driving apparatus is disclosed in Patent Document 1. The sensorless brushless motor step-out detection device according to claim 1 of Patent Document 1 compares a current detection means for detecting a motor current, a means for detecting a current cycle of the motor current, and a current cycle and a voltage cycle of an output voltage. Period comparison means for determining step-out. Furthermore, claim 2 discloses a mode in which driving is performed by vector control by performing calculation using dq coordinates instead of trapezoidal wave driving. Thus, it is described that the erroneous detection of the step-out can be prevented by checking when the output torque becomes large and when the step-out occurs.

JP 2001-25282 A

  By the way, the technical example of Patent Document 1 is preferable in that step-out can be reliably detected. However, since the current detection unit is provided and complicated vector control is performed, the driving device is expensive. Therefore, in order to reduce the cost of the driving device, it is necessary to be able to determine abnormality such as step-out while omitting the current detection means and adopting simple trapezoidal wave driving. The determination of step-out is based on the premise that the rotational position of the rotor is accurately detected. In a drive device in which the current detection means is omitted, a technique for setting a mask time so that the position detection circuit does not malfunction by a counter electromotive voltage generated immediately after the switching timing of the energized phase is known. That is, it is possible to prevent a step-out from occurring due to an abnormality in detecting the rotational position of the rotor.

  However, in a drive device that omits the current detection means, the rotational position detection is reliable when a voltage with a low duty ratio that cannot drive the motor is applied, or when the motor output shaft bites foreign matter. There is a concern of decline. In such a special situation where the motor is not rotated while the voltage is applied and energized, a frequent noise voltage is generated in the induced voltage. Then, the effect of setting the mask time is lost, and the position detection circuit detects an incorrect rotational position based on the noise voltage, and recognizes an erroneously large rotational speed, so that the energized phase is frequently switched. There is no risk of falling into a conditioned state or its precursor state.

  The present invention has been made in view of the above-described problems of the background art, and has a function of determining abnormality in rotational position detection, and is a sensorless brushless motor that suppresses an increase in cost while improving reliability of rotational position detection. Providing a driving device is a problem to be solved.

  An invention of a sensorless brushless motor driving apparatus according to claim 1 for solving the above-mentioned problems is provided. A terminal of the armature winding of a sensorless brushless motor including a stator having a three-phase armature winding and a rotor having a magnetic pole pair. An inverter circuit that is energized during a duty-on time period of the pulse width modulation signal, an inverter control circuit that generates the pulse width modulation signal and commands the inverter circuit based on the instructed duty ratio, and the pulse width modulation A position detection circuit that operates by a signal, detects an induced voltage induced in the terminal during a non-energized time period, and detects a rotational position of the rotor based on the induced voltage; and the position detection circuit includes the rotor Based on the position detection timing at which the rotational position of the motor is detected, the switching timing for switching the energized phase between the terminals is set. A sensorless brushless motor driving device comprising: an energization timing circuit that commands the inverter control circuit; and a counter electromotive voltage detection circuit that detects a counter electromotive voltage generated at the terminal immediately after the switching timing; An abnormality determination unit that compares the time zone in which the counter electromotive voltage detection circuit detects the counter electromotive voltage and the position detection timing of the position detection circuit to determine whether there is an abnormality in rotation position detection; Further provided.

  According to a second aspect of the present invention, in the first aspect, the abnormality determination unit has detected that an abnormality in rotational position detection has occurred when the position detection timing overlaps in a time zone in which the back electromotive voltage is detected. judge.

  According to a third aspect of the present invention, in the first or second aspect, the inverter circuit is connected in parallel to the switching unit in which a conduction state and a cutoff state are selectively controlled by the pulse width modulation signal, and the switching unit. Six switching elements each including a diode portion that allows energization by the counter electromotive voltage are connected to a DC power source in a three-phase bridge, and the counter electromotive voltage detection circuit has a voltage at the terminal that is the DC voltage. At least one of a positive counter electromotive voltage that is larger than the voltage of the positive terminal of the power supply and a negative counter electromotive voltage that is smaller than the voltage of the negative terminal of the DC power supply is detected.

  According to a fourth aspect of the present invention, in the third aspect, the back electromotive voltage detection circuit is connected between the terminal and a positive side terminal of the DC power supply, and a positive switching effect is generated by the positive side back electromotive voltage. It is configured to include at least one of a side transistor element and a negative side transistor element that is connected between the terminal and the negative side terminal of the DC power source and generates a switching action by the negative side counter electromotive voltage.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the position detection circuit pauses for a predetermined mask time immediately after the position detection timing, and erroneously rotates due to the back electromotive voltage. Avoid position detection.

  In the invention of the sensorless brushless motor driving device according to claim 1, the back electromotive voltage detection circuit detects the back electromotive voltage generated at the terminal immediately after the switching timing for switching the energized phase, and the abnormality determination unit includes the back electromotive voltage. The time zone in which the detection circuit detects the back electromotive voltage and the position detection timing at which the position detection circuit detects the rotational position of the rotor are compared to determine whether there is an abnormality in rotational position detection. Here, since the switching timing of the energized phase is set with a certain delay from the position detection timing, the generation time zone of the back electromotive voltage and the position detection timing have a generation time difference. Therefore, the abnormality determination unit can determine whether or not the rotational position detection is performed satisfactorily by monitoring whether or not the occurrence time difference is appropriate.

  As a specific example, when a voltage with a low duty ratio is applied or the output shaft of the motor bites in a foreign object, the position detection circuit may fail due to noise voltage when the motor is not actually rotating. Even if the rotational position is detected, the abnormality determination unit can determine this abnormality. More specifically, when the output shaft of the motor is not rotating while a voltage is applied and a current is applied, the rotor repeats slight vibration without rotating. Then, the magnetic flux interlinked with the armature winding slightly changes due to the slight vibration, and a noise voltage having a high occurrence frequency is induced at the terminal. The position detection circuit misdetects this noise voltage as a normal induced voltage, and as a result, the drive device erroneously recognizes a large rotational speed and frequently switches the meaningless energized phase. Become. In such erroneous position detection, the relationship between the position detection timing and the back electromotive voltage generation time generated immediately after the energized phase switching timing is clearly different from that during normal driving. Detection abnormality can be determined.

  Further, according to the present invention, it is possible to determine an abnormality in which the rotational position is erroneously determined during high-speed rotation. More specifically, the number of times the induced voltage is generated during high-speed rotation increases, but the time period for generating each induced voltage is shortened. On the other hand, since the position detection circuit operates with a pulse width modulation signal, there is a risk that the position detection circuit may deviate from the induced voltage generation time zone due to the influence of a time lag inside the circuit. Then, normal position detection cannot be performed or position detection cannot be performed at all. Therefore, the abnormality determination unit can determine the abnormality of the rotational position detection from the shift of the position detection timing with respect to the back electromotive voltage generation time zone or the undetected rotational position.

  Furthermore, according to the present invention, it is possible to determine an abnormality in which the rotational position is erroneously determined when the load becomes heavier than expected (above the upper limit of performance guarantee). More specifically, when the load becomes heavy and an extremely large energizing current flows, the generation time zone of the back electromotive voltage when this is interrupted is prolonged. The back electromotive voltage is superimposed on the induced voltage, but when it is normal, it is far from the position detection timing and does not become an obstacle. However, if the back electromotive voltage generation time zone is prolonged, it will overlap the position detection timing and become an obstacle to position detection. There is a fear. The abnormality determination unit can determine an abnormality in which the back electromotive voltage generation time period is prolonged and overlapped at the normal position detection timing and the position cannot be detected.

  The three examples of abnormalities described above are difficult to determine in the prior art, and can be determined by the abnormality determination unit of the present invention. Therefore, the present invention improves the reliability of rotational position detection. Furthermore, it is possible to prevent the step-out state caused by the erroneous detection of the rotational position or the precursor state thereof from continuing. Further, when implementing the present invention, the current detection means and complicated vector control disclosed in Patent Document 1 are unnecessary, and an increase in cost can be suppressed.

  In the invention according to claim 2, the abnormality determination unit determines that an abnormality in the rotational position detection has occurred when the position detection timing overlaps the time zone in which the back electromotive voltage is detected. For example, in the first example described above, if the position detection circuit detects a position with a noise voltage when the motor is not rotating, a large rotation speed is erroneously recognized. As a result, the energized phase is frequently switched, the back electromotive voltage generation time zone increases, and the noise voltage generation timing, that is, the position detection timing overlaps in time. Therefore, in the invention according to claim 2, since the generation time zone of the counter electromotive voltage that cannot be overlapped in normal time and the position detection timing overlap, it is possible to reliably determine the abnormality of the rotational position detection.

  In the invention according to claim 3, the inverter circuit is configured by connecting six switching elements to a DC power source in a three-phase bridge connection, and the counter electromotive voltage detection circuit includes the positive counter electromotive voltage of the terminal of the armature winding. At least one of the negative counter electromotive voltage is detected. Here, due to the action of the forward voltage drop of the diode part included in the switching element, the back electromotive voltage does not become excessive and becomes larger than the voltage of the positive side terminal of the DC power supply by the forward voltage drop, Or it becomes smaller than the voltage of the negative terminal of the DC power supply by the forward voltage drop. Therefore, the back electromotive voltage detection circuit can be appropriately configured according to the level of the generated back electromotive voltage, and the back electromotive voltage can be reliably detected to determine whether or not the rotational position is detected.

  In the invention according to claim 4, the back electromotive voltage detection circuit includes at least one of a positive side transistor element in which a switching action is caused by a positive side back electromotive voltage and a negative side transistor element in which a switching action is caused by a negative back electromotive voltage. Consists of. That is, the counter electromotive voltage detection circuit can be easily configured with general-purpose transistor elements and their peripheral circuits, and the increase in cost can be suppressed.

  In the invention according to claim 5, the position detection circuit pauses for a predetermined mask time immediately after the position detection timing to avoid erroneous rotation position detection due to the back electromotive voltage. In the present invention, the effects of the first to fourth aspects described above become more remarkable when used in combination with the mask function of the back electromotive force.

It is a figure explaining the whole device composition of the drive device of the sensorless brushless motor of an embodiment. It is a figure of the list of terminal states explaining the method of driving a sensorless brushless motor with the drive device of an embodiment. It is the figure which illustrated the voltage waveform which generate | occur | produces in each phase terminal when the drive control shown by FIG. 2 is performed. It is a wave form diagram explaining the function of a position detection circuit. It is a wave form diagram explaining the function of a position detection circuit and an energization timing circuit. It is a wave form diagram of a position detection circuit when rotation position detection is normal. It is a wave form diagram of a position detection circuit when rotation position detection is abnormal. It is a figure explaining the function of a back electromotive force detection circuit, (1) has shown the time of positive side back electromotive voltage generation | occurrence | production, (2) has shown the time of negative side back electromotive voltage generation | occurrence | production. It is a wave form diagram explaining the abnormal state of rotation position detection by way of example.

  The configuration, operation, and effect of the sensorless brushless motor driving apparatus according to the embodiment of the present invention will be described with reference to FIGS. Drawing 1 is a figure explaining the whole device composition of drive 1 of sensorless brushless motor 9 of an embodiment. The drive device 1 is a device that drives the sensorless brushless motor 9 in a trapezoidal manner using the inverter circuit 2 that makes the duty ratio of the power supply voltage E variable by a pulse width modulation method.

  The sensorless brushless motor 9 includes a stator 91 having Δ-connected three-phase armature windings 92, 93, 94, and a rotor having a magnetic pole pair (not shown), and a sensor for detecting the rotational position of the rotor. Absent. The stator 91 is provided with a U-phase terminal 95U, a V-phase terminal 95V, and a W-phase terminal 95W. An inter-UV armature winding 92 is connected between the U-phase terminal 95U and the V-phase terminal 95V, and similarly, an inter-VW armature winding 93 is connected between the V-phase terminal 95V and the W-phase terminal 95W. The WU armature winding 94 is connected between the W-phase terminal 95W and the U-phase terminal 95U. In the present embodiment, there are no particular restrictions on the number of poles of the armature windings 92, 93, 94 of the stator 91 and the number of magnetic pole pairs of the rotor.

  The drive device 1 includes an inverter circuit 2, an inverter control circuit 3, a position detection circuit 4, an energization timing circuit 5, a back electromotive voltage detection circuit 6, and an abnormality determination unit 7. A DC power supply device 26 is connected between an input terminal 21P common to the three phases of the inverter circuit 2 and a ground terminal 21N, and a power supply voltage E is supplied.

  The inverter circuit 2 is a circuit that energizes the phase terminals 95U, 95V, and 95W of the armature windings 92, 93, and 94 of the sensorless brushless motor 9 during the duty-on time period of the pulse width modulation signal PWM. The inverter circuit 2 is composed of a three-phase bridge circuit, and FIG. 1 shows only the U phase as a representative. More specifically, a U-phase positive switching element 22U and a U-phase negative switching element 23U are connected in series between the input terminal 21P and the ground terminal 21N, and a U-phase output terminal 24U is connected between the elements 22U and 23U. Is provided. The input terminal 21P is connected to the positive terminal 26P of the DC power supply device 26. The ground terminal 21N is connected to the negative terminal 26N of the DC power supply device 26 through a ground point. The V phase and W phase of the inverter circuit 2 also have the same circuit configuration as the U phase. The V-phase output terminal is connected to the V-phase terminal 95V of the stator 91 by a power line 25V, and the W-phase output terminal is connected to the W-phase terminal 95W of the stator 91 by a power line 25W.

  For example, a field effect transistor (FET) can be used for each of the switching elements 22U and 23U. Each of the switching elements 22U and 23U includes a switching unit 27 and a diode unit 28 which are electrically connected in parallel. The switching unit 27 is selectively controlled in a conduction state and a cutoff state by an energization control signal SC. The diode unit 28 is connected so as to allow energization by the counter electromotive voltage generated at the terminals 95U, 95V, and 95W. That is, the diode section 28 of the positive-side switching element 22U of each phase allows energization from the terminals 95U, 95V, and 95W to the positive-side terminal 26P of the DC power supply device 26. Further, the diode section 28 of the negative side switching element 23U of each phase allows energization from the ground point to the terminals 95U, 95V, and 95W.

  By opening / closing control of the switching elements 22U and 23U of the inverter circuit 2, the phase terminals 95U, 95V, and 95W of the stator 91 take three states. Since these three states are the same in each phase, the U-phase terminal 95 will be described as an example. U-phase terminal 95U is in a state constrained by power supply voltage E (power supply voltage E constrained state) when U-phase positive side switching element 22U is in a conductive state and U-phase negative side switching element 23U is in a cut-off state. In addition, U-phase terminal 95U is constrained to zero voltage (zero-voltage constrained state) when U-phase positive switching element 22U is cut off and U-phase negative switching element 23U is conductive. Furthermore, U-phase terminal 95U is in a high impedance state when both U-phase positive side switching element 22U and negative side switching element 23U are cut off. Here, the power supply voltage E constrained state does not occur independently, but occurs alternately with the zero voltage constrained state according to the on / off control by the duty ratio, and this state is referred to as a PWM control state.

  A U-phase induced voltage viU is induced at the U-phase terminal 95U in the high impedance state. The U-phase induced voltage viU is generated when the magnetic flux from the rotor magnetic pole pair is linked to the UV armature winding 92 and the WU armature winding 94 connected to the U-phase terminal 95U. Therefore, the U-phase induced voltage viU varies depending on the relative rotational position relationship between the UV and WU armature windings 92 and 94 and the rotor, and can serve as an index for detecting the rotational position. It should be noted that control in which both the U-phase positive side switching element 22U and the U-phase negative side switching element 23U are in a conductive state is prohibited, and a power supply voltage short-circuit failure is prevented.

  The inverter control circuit 3 is a circuit that generates a pulse width modulation signal PWM based on the instructed duty ratio and commands the inverter circuit 2 as a three-phase positive and negative energization control signal SC. The inverter control circuit 3 first generates a pulse width modulation signal PWM by a known pulse width modulation circuit. The pulse frequency of the pulse width modulation signal PWM may be a fixed value or variably controlled. The duty ratio of the pulse width modulation signal PWM may be instructed directly from an external device, or may be obtained by calculation inside by receiving an instruction of the motor speed. In the latter case, the relationship between the motor rotation speed and the duty ratio is grasped in advance. For example, when the inertia of the load of the motor 9 is constant, a positive correlation in which the duty ratio is increased in order to increase the motor rotation speed is obtained in advance.

  Next, the inverter control circuit 3 acquires the three-phase phase switching signals SU, SV, and SW from the energization timing circuit 5. The phase switching signals SU, SV, and SW are signals that select one of the states of the phase terminals 95U, 95V, and 95W among the power supply voltage E restraint state, the zero voltage restraint state, and the high impedance state, respectively. Thirdly, the inverter control circuit 3 generates the energization control signal SC by adding the phase switching signals SU, SV, SW to the pulse width modulation signal PWM. There are six energization control signals SC in total for the positive and negative phases of the three phases of the inverter circuit 2, and each switching element 22U, 23U is individually controlled to open and close. The inverter control circuit 3 commands the energization control signal SC to the inverter circuit 2.

  The position detection circuit 4 operates with the pulse width modulation signal PWM, detects an induced voltage induced in the terminals 95U, 95V, and 95W during a non-energized time period, and determines a specific rotational position of the rotor based on the induced voltage. It is a circuit to detect. The position detection circuit 4 is a three-phase synthesis method, and includes three-phase synthesis resistors 41U, 41V, 41W, a comparator 44, and a position detection unit 47. The three-phase combined resistors 41U, 41V, and 41W have the same resistance value R, and are connected between the power supply lines 25U, 25V, and 25W of the respective phases and the common combined point 42, respectively. That is, the three-phase combined resistors 41U, 41V, and 41W are Y-connected, and the combined point 42 is a Y-connected neutral point. A composite voltage Vmix is generated at the composite point 42 by combining the induced voltages viU, viV, and viW of the phase terminals 95U, 95V, and 95W. The composite point 42 is connected to the positive side input terminal 44P of the comparator 44, and the composite voltage Vmix is sent out.

  On the other hand, an intermediate level value VM (= E / 2) obtained by dividing the power supply voltage E of the DC power supply device 26 in half by an equal resistance value r is input to the negative input terminal 44N of the comparator 44 as a reference voltage. Yes. The comparator 44 compares the composite voltage Vmix of the positive input terminal 44P with the intermediate level value VM of the negative input terminal 44N, and outputs a position signal SX. At the output terminal 45 of the comparator 44, when the combined voltage Vmix is smaller than the intermediate level value VM, the position signal SX becomes low level, and when the combined voltage Vmix becomes equal to or higher than the intermediate level value VM, the position signal SX becomes high level. The output terminal 45 of the comparator 44 is connected to the position detector 47, and a position signal SX is sent out.

  The position detection unit 47 operates in synchronization with the pulse width modulation signal PWM as described in detail later with reference to waveform examples. The position detection unit 47 receives the position signal SX of the comparator 44 and detects the rotational position of the rotor at the timing when the position signal SX switches between a low level and a high level. There are two rotational positions to be detected for each of the three phases, that is, the rising and falling positions of the position signal SX, and there are six in total within 360 ° of the electrical angle. When the motor is rotating at a constant speed, the specific position detection signal SY that is the output of the position detection unit 47 has a waveform in which rising and falling indicating position detection timing are alternately repeated at a 60 ° pitch. The position detection unit 47 sends a specific position detection signal SY to the energization timing circuit 5 and the abnormality determination unit 7.

  The energization timing circuit 5 sets a switching timing for switching the energized phase between the terminals 95U, 95V, and 95W based on the position detection timing when the position detection circuit 4 detects the rotational position of the rotor, and commands the inverter control circuit 3 It is. The energization timing circuit 5 creates three-phase phase switching signals SU, SV, and SW based on the specific position detection signal SY by the functions of three types of timers TM1 to TM3 described in detail later, and the inverter control circuit 3 To Each of the phase switching signals SU, SV, and SW includes information on switching timing for switching the energized phase. When the motor is rotating at a constant speed, the phase switching signals SU, SV, and SW of each phase are as follows: a power supply voltage E constraint state of 120 ° electrical angle, a high impedance state of 60 °, a zero voltage constraint state of 120 °, and The signal repeats a high impedance state of 60 °. Further, among the three phases, the phase switching signals SU, SV, SW are shifted by 120 ° of the electrical angle.

  With the configuration described so far, the sensorless brushless motor driving apparatus 1 of the embodiment can drive the motor 9. FIG. 2 is a table of terminal states for explaining a method of driving the sensorless brushless motor 9 by the driving device 1 according to the embodiment. As shown in the figure, the inverter control circuit 3 performs state control of the phase terminals 95U, 95V, and 95W in six periods 1) to 6). Each column in the list represents the state of each phase terminal 95U, 95V, 95W in the corresponding period, “PWM” indicates the PWM control state, “L” indicates the zero voltage restraint state, “Hi” “−Z” indicates a high impedance state.

  For example, in the period 1), the U-phase terminal column is “Hi-Z”, and both the U-phase positive side switching element 22U and the U-phase negative side switching element 23U of the inverter circuit 2 are cut off. It shows that the terminal 95U is in a high impedance state. The column of the V-phase terminal is “L”, the V-phase positive switching element of the inverter circuit 2 is turned off, the V-phase negative switching element is turned on, and the V-phase terminal 95V is set to zero voltage. It shows that it is restrained. The column of the W-phase terminal is “PWM”, and the W-phase negative side switching element of the inverter circuit 2 is cut off and the W-phase positive side switching element is controlled to be switched between the conductive state and the cut-off state based on the duty ratio. Is shown. Thereby, the rectangular wave which vibrates to the power supply voltage E and zero voltage is applied to the W-phase terminal 95W. Therefore, the inter-VW armature winding 93 connected between the W-phase terminal 95W and the V-phase terminal 95V is energized by the pulse width modulation control. In the period 1), the U-phase terminal 95U is not energized, and the U-phase induced voltage viU is induced.

  Similarly, in the period 2), the column of the U-phase terminal is “PWM”, and a rectangular wave that oscillates to the power supply voltage E and the zero voltage with a duty ratio is applied to the U-phase terminal 95U. The column of the V-phase terminal is “L”, which indicates that the constraint on the zero voltage of the V-phase terminal 95V continues. The column of the W-phase terminal is “Hi-Z”, which indicates that the W-phase terminal 95W is in a high impedance state. As a result, the inter-UV armature winding 92 connected between the U-phase terminal 95U and the V-phase terminal 95V is energized by the pulse width modulation control. In period 2), the W-phase terminal 95W is not energized, and the W-phase induced voltage viW is induced. Similarly, in the periods 3) to 6), the state of each phase terminal 95U, 95V, 95W, the phase of the armature winding to be energized, and the terminal where the induced voltage is generated are controlled in turn.

  Periods 1) to 6) correspond to an electrical angle of 60 °, respectively. After period 6), the process returns to period 1) and is similarly controlled repeatedly. Further, the rotational speed of the motor 9 and the duration of each of the periods 1) to 6) are approximately inversely proportional.

  As shown in FIG. 2, when the state of the terminals 95U, 95V, and 95W of the sensorless brushless motor 9 is controlled and driven, a terminal voltage waveform illustrated in FIG. 3 is generated. FIG. 3 is a diagram illustrating voltage waveforms generated at the phase terminals 95U, 95V, and 95W when the control shown in FIG. 2 is performed. The horizontal axis in FIG. 3 is a common time axis, and the periods 1) to 6) correspond to FIG. The waveforms indicate the U-phase terminal voltage VU, the V-phase terminal voltage VV, and the W-phase terminal voltage VW in order from the top. As shown in the figure, the phase terminal voltages VU, VV, and VW change in a trapezoidal waveform, and the motor 9 is driven in a trapezoidal manner.

  In the waveform of the U-phase terminal voltage VU in the drawing, periods 2) and 3) indicate energization time zones in the PWM control state. Periods 5) and 6) indicate energization time periods in a zero voltage restraint state. Further, a waveform in which the increasing slope generated in period 1) and the pulse width modulation rectangular wave overlap, and a waveform in which the decreasing slope generated in period 4) and the pulse width modulation rectangular wave overlap. Indicates an induced voltage viU induced in a non-energized time zone. The V-phase terminal voltage VV and the W-phase terminal voltage VW in the figure also have the same waveform except that the phase is delayed by 120 ° (by two periods).

  Further, counter electromotive voltage waveforms Z due to opening / closing of the switching elements 22U and 23UW of each phase are superimposed on the waveforms of the phase terminal voltages VU, VV, and VW. The counter electromotive voltage waveform Z is generated at the boundary between the periods 1) to 6), that is, immediately after the energized current is interrupted by switching the energized phase. The length of the time period in which the back electromotive voltage waveform Z continues varies depending on the magnitude of the energization current that was flowing immediately before.

  Next, functions of the position detection circuit 4 and the energization timing circuit 5 will be described. A combined voltage Vmix obtained by combining the induced voltages viU, viV, and viW of the respective phases is generated at the combined point 42 of the position detection circuit 4. The waveform of the composite voltage Vmix is the increase in the U-phase induced voltage viU in period 1) in FIG. 3, the decrease in the W-phase induced voltage viW in period 2), the increase in the V-phase induced voltage viV in period 3), and the period 4). It is similar to the waveform in which the decrease in the U-phase induced voltage viU, the increase in the W-phase induced voltage viW in the period 5), and the decrease in the V-phase induced voltage viV in the period 6) are continued. Further, the counter electromotive voltage waveform Z at the boundary between the periods 1) to 6) is superimposed on the waveform of the composite voltage Vmix.

  This combined voltage Vmix is input to the positive input terminal 44P of the comparator 44 of the position detection circuit 4. FIG. 4 is a waveform diagram for explaining the function of the position detection circuit 4, and is expanded in the time width direction as compared with FIG. In FIG. 4, the horizontal axis is a common time axis, and the waveforms are, in order from the top, the pulse width modulation signal PWM, the terminal voltage in the PWM control state, the combined voltage Vmix and the intermediate level value VM input to the comparator 44, A position signal SX sent from the comparator 44 and a specific position detection signal SY sent from the position detector 47.

  As illustrated, the rectangular wave of the terminal voltage in the PWM control state is slightly delayed with respect to the pulse width modulation signal PWM, and the waveform of the composite voltage Vmix is slightly delayed from the rectangular wave of the terminal voltage. . The combined voltage Vmix gradually increases in the duty-on time zone in the illustrated range, and reaches the intermediate level value VM at time ta. As a result, the position signal SX rises from the low level to the high level at time tb delayed by the calculation time inside the comparator 44 from time ta. Here, the combined voltage Vmix reaching the intermediate level value VM means that the intermediate point of the magnetic pole pair of the rotor is located in front of the armature windings 92 to 94. Therefore, in this embodiment, the rotation position of the rotor to be detected is set to electrical angles of 30 °, 90 °, 150 ° 210 °, 270 °, and 330 °.

  On the other hand, the position detection unit 47 operates in synchronization with times t1, t2, and t3, which are the falling timings of the pulse width modulation signal PWM, and detects the level of the position signal SX. In the waveform example of FIG. 4, the position signal SX is at a low level at time t1, and the position signal SX changes to a high level at time t2. The position detection unit 47 determines that the rotor has reached a specific rotational position at time t2, and raises the specific position detection signal SY from the low level to the high level.

  FIG. 5 is a waveform diagram for explaining the functions of the position detection circuit 4 and the energization timing circuit 5 and includes the periods 1) to 6) in FIG. In FIG. 5, the horizontal axis is a common time axis, and the waveforms are sent from the phase terminal voltages VU, VV, VW, the position signal SX sent from the comparator 44, and the position detector 47 in order from the upper side. The specific position detection signal SY, the output of the 60 ° detection timer TM1 of the energization timing circuit 5, the output of the phase switching timer TM2, the output of the mask timer TM3, and the three-phase phase switching signals SU, SV, SW. In the waveforms of the phase terminal voltages VU, VV, VW and the position signal SX in the figure, the rectangular wave by the pulse width modulation control is omitted and is simply shown.

  As shown in the figure, the position detection unit 47 generates a specific position detection signal SY that changes in synchronization with the rising and falling times t11 to t18 of the position signal SX. At this time, the position detection unit 47 pauses for a mask time Tmsk of a mask timer TM3 described later, and does not detect the counter electromotive voltage waveform Z superimposed on the position signal SX, thereby detecting an erroneous rotational position by the counter electromotive voltage. To avoid.

The energization timing circuit 5 includes a 60 ° detection timer TM1, a phase switching timer TM2, and a mask timer TM3. The 60 ° detection timer TM1 detects a time difference between the rising edge and the falling edge of the specific position detection signal SY every time as the period time T. The period time T means the time required for the rotor to rotate 60 °. When the motor 9 is rotating at a constant speed, the cycle time T of each time is substantially constant as shown by the following equation.
Cycle time T = t12−t11≈t13−t12≈t14−t13≈t15−t14
≒ t16-t15 ≒ t17-t16 ≒ t18-t17 ≒ (hereinafter abbreviated)
If the motor 9 is accelerating, the cycle time T is gradually shortened, and if the motor 9 is decelerating, the cycle time T is gradually increased.

  The phase switching timer TM2 sets a delay time Tdly corresponding to half of the cycle time T detected by the 60 ° detection timer TM1. In the example of the figure, the delay time Tdly = (T / 2) is set immediately after the time t12 with respect to the cycle time T from the time t11 to the time t12. Thereby, the time t22 when the rotor has rotated approximately 30 ° after the time t12 can be set as the energized phase switching timing. The phase switching timer TM2 performs this setting for each cycle time T, and sets each time t21 to t28 as the energized phase switching timing each time. Based on the setting of the phase switching timer TM2, three-phase phase switching signals SU, SV, and SW for controlling the states of the phase terminals 95U, 95V, and 95W shown in FIG. 2 are generated.

  The mask timer TM3 sets a mask time Tmsk corresponding to three quarters of the cycle time T detected by the 60 ° detection timer TM1. In the example of the figure, the mask time Tmsk = (3T / 4) is set immediately after the time t12 for the cycle time T from the time t11 to the time t12. As a result, the position detection unit 47 pauses from time t12 to time t32. The mask time Tmsk is set for each cycle time T.

  However, the present invention is not limited to this, and the power supply voltage E constraint state and the zero voltage constraint state may be controlled to be longer than 120 °. Further, the delay time Tdly of the phase switching timer TM2 and the mask time Tmsk of the mask timer TM3 may be set other than those described above.

  Next, the difference between when the rotational position detection is normal and when it is abnormal will be described as an example. FIG. 6 is a waveform diagram of the position detection circuit 4 when the rotational position detection is normal, and FIG. 7 is a waveform diagram of the position detection circuit 4 when the rotational position detection is abnormal. 6 and 7, the horizontal axis is a common time axis, and the waveform of the upper stage is the combined voltage Vmix and the intermediate level value VM, the middle stage is the position signal SX, and the lower stage is the specific position detection signal SY.

  When the rotational position detection shown in FIG. 6 is normal, the composite voltage Tmix increases at the time t41, intersects the intermediate level value VM, and the position signal SX rises. The specific position detection signal SY rises at the fall time t42 of the pulse width modulation signal PWM immediately after that. The mask time Tmsk1 starts from time t42, and the back electromotive voltage waveform Z generated at time t43 within the mask time Tmsk1 is not detected by the position detector 47. At time t44 after the mask time Tmsk1 ends, the combined voltage Tmix decreases while crossing the intermediate level value VM, and the position signal SX falls. Then, at the falling time t45 of the pulse width modulation signal PWM immediately after that, the specific position detection signal SY falls and the mask time Tmsk2 starts. As shown in FIG. 6, when the rotational position detection is good, the generation time t43 of the counter electromotive voltage waveform Z and the position detection timings t42 and t45 have a generation time difference, and this generation time difference is approximately 30 ° of the electrical angle. Corresponds to minutes.

  On the other hand, FIG. 7 shows an abnormality in rotational position detection when the output shaft of the motor 9 is not rotating due to a foreign object. At this time, since the rotor does not rotate and repeats a slight vibration, the armature windings 92, 93, and 94 vibrate slightly, and a noise voltage having a high frequency of occurrence is induced in the composite voltage Tmix. As shown in the figure, the combined voltage Tmix frequently intersects the intermediate level value VM, and the position signal SX frequently changes to a high level and a low level. In the example shown in the figure, at the falling time t51 of the pulse width modulation signal PWM immediately after the mask time Tmsk3 ends, the position detection is immediately performed by the position detection unit 47, and the specific position detection signal SY rises.

  At this time, the period time T detected by the 60 ° detection timer TM1 becomes shorter than the original time, phase switching is performed at a time interval shorter than the original time, and the next mask time Tmsk4 is also shortened. Further, at the falling time t52 of the pulse width modulation signal PWM immediately after the end of the next mask time Tmsk4, the position detection unit 47 immediately detects the position and the specific position detection signal SY falls. Therefore, the cycle time T is further shortened, and the next mask time Tmsk5 is further shortened. In this manner, erroneous detection of the rotational position is repeated, and an erroneously large rotational speed is recognized even though the rotor is not rotating, and the energized phase is frequently switched.

  The step-out state due to the erroneous rotation position detection described above or the precursor state thereof has been difficult to determine in the prior art. Therefore, the sensorless brushless motor driving apparatus 1 according to the present embodiment further includes a back electromotive voltage detection circuit 6 and an abnormality determination unit 7.

  The counter electromotive voltage detection circuit 6 is a circuit that detects a positive counter electromotive voltage VPr and a negative counter electromotive voltage VNr generated at the terminals 95U, 95V, and 95W immediately after the energized phase switching timing. The counter electromotive voltage detection circuit 6 has the same circuit configuration in three phases, and the U phase shown as a representative in FIG. 1 will be described in detail. As shown in the figure, the back electromotive voltage detection circuit 6 includes a positive side transistor element 61, a positive side detection unit 62, a negative side transistor element 63, a negative side detection unit 64, and the like.

  As the positive side transistor element 61, a general PNP type bipolar transistor can be used. The emitter E1 of the positive-side transistor element 61 is connected to the U-phase terminal 95U of the stator 91 via the resistor r1, and receives the U-phase terminal voltage VU. The base B1 of the positive transistor element 61 is connected to the positive terminal 26P of the DC power supply device 26, and the collector C1 is connected to the positive detector 62. The positive side detection unit 62 determines the magnitude of the collector current flowing through the collector C1, and sends the positive side counter electromotive voltage detection signal SP to the abnormality determination unit 7 only during a time period when the collector current is large.

  As the negative side transistor element 63, a general NPN type bipolar transistor can be used. The emitter E3 of the negative-side transistor element 63 is connected to the U-phase terminal 95U via the resistor r3, and receives the U-phase terminal voltage VU. The base B3 of the negative side transistor element 63 is grounded to the ground point, and the collector C3 is connected to the negative side detector 64. The negative side detection unit 64 determines the magnitude of the collector current flowing through the collector C3, and sends the negative side counter electromotive voltage detection signal SN to the abnormality determination unit 7 only during a time period when the collector current is large.

  8A and 8B are diagrams for explaining the function of the back electromotive voltage detection circuit 6. FIG. 8A shows the time when a positive back electromotive voltage is generated, and FIG. 8B shows the time when a negative back electromotive voltage is generated. Consider the case where the U-phase negative side switching element 23U is controlled from the conductive state to the cut-off state at the first instant of period 1) in FIG. 8 (1), and the energization current of the WU armature winding 94 is cut off. . Since the energization current of the inter-WU armature winding 94 continues to flow as it is, the positive counter electromotive voltage VPr is generated at the U-phase terminal 95U. Since the positive side counter electromotive voltage VPr exceeds the power supply voltage E of the positive side terminal 26P of the DC power supply device 26, a current IPr in a direction opposite to the normal direction flows through the diode portion 28 of the U-phase positive side switching element 22U. The current IPr flows from the U-phase terminal 95U to the positive terminal 26P, and the positive counter electromotive voltage VPr of the U-phase terminal 95U is higher than the power supply voltage E by the forward voltage drop Vd of the diode unit 29, which is excessively large. Don't be. The positive counter electromotive voltage VPr is input to the emitter E1 of the positive transistor element 61 of the counter electromotive voltage detection circuit 6.

  The emitter voltage of the emitter E1 of the positive side transistor element 61 is normally equal to or lower than the power supply voltage E, and the collector current IC1 flowing through the collector C1 is small only by the base current. Here, when the positive-side counter electromotive voltage VPr is input to the emitter E1, a switching action occurs, a large emitter current flows, and the collector current IC1 increases remarkably as the sum of the base current and the emitter current. The positive side detection unit 62 sends the positive side back electromotive voltage detection signal SP to the abnormality determination unit 7 only during a time period in which a large collector current IC1 is flowing. Thereby, the abnormality determination part 7 can recognize the generation | occurrence | production time zone of the positive side back electromotive voltage VPr.

  The generation of the negative counter electromotive voltage VNr shown in (2) of FIG. 8 is similar to the generation of the positive counter electromotive voltage VPr. More specifically, let us consider a case where the U-phase positive side switching element 22U is controlled from the conductive state to the cut-off state at the first moment of the period 4), and the conduction current of the UV armature winding 92 is cut off. Since the energization current of the UV armature winding 92 continues to flow as it is, the negative counter electromotive voltage VNr is generated at the U-phase terminal 95U. Since the negative side counter electromotive voltage VNr is lower than the zero voltage at the ground point, a current INr in the direction opposite to that of the normal current flows through the diode portion 29 of the U phase negative side switching element 23U. The current INr flows from the ground point to the U-phase terminal 95U, and the negative-side counter electromotive voltage VNr of the U-phase terminal 95U is lower than the zero voltage by the forward voltage drop Vd of the diode portion 29 and does not become excessive. The negative counter electromotive voltage VNr is input to the emitter E3 of the negative transistor element 63 of the counter electromotive voltage detection circuit 6.

  The emitter voltage of the emitter E3 of the negative side transistor element 63 is normally zero voltage or higher, and the collector current IC3 flowing through the collector C3 is small only by the base current. Here, when the negative counter electromotive voltage VNr is input to the emitter E3, a switching action occurs and a large emitter current flows, and the collector current IC3 increases remarkably as the sum of the base current and the emitter current. The negative side detection unit 64 sends the negative side back electromotive voltage detection signal SN to the abnormality determination unit 7 only during a time period during which a large collector current IC3 flows. Thereby, the abnormality determination part 7 can recognize the generation | occurrence | production time zone of the negative side back electromotive voltage VNr.

  The abnormality determination unit 7 compares the time zone in which the counter electromotive voltage detection circuit 6 detects the counter electromotive voltages VPr and VNr with the position detection timing of the position detection circuit 4 to determine whether there is an abnormality in rotational position detection. It is a part to be determined. In the present embodiment, the abnormality determination unit 7 receives the positive counter electromotive voltage detection signal SP and the negative counter electromotive voltage detection signal SN from the counter electromotive voltage detection circuit 6, and receives the specific position detection signal SY from the position detection circuit 4. . Then, when the position detection timing overlaps the time zone in which the counter electromotive voltage is detected in the time excluding the mask time Tmsk, in other words, the abnormality determination unit 7 is, in other words, the positive side counter electromotive voltage detection signal SP and the negative side. When the specific position detection signal SY overlaps the back electromotive voltage detection signal SN, it is determined that an abnormality in rotational position detection has occurred.

  In addition, the determination method of the abnormality determination part 7 is not limited to the above, You may use another determination method. If the rotational position detection is normal, the position detection timing is delayed by a time corresponding to about 30 ° of the electrical angle with respect to the counter electromotive voltages VPr and VNr. Therefore, the abnormality determination unit 7 determines whether or not this condition is satisfied. Can be determined. The determination method described above is a simple method for detecting a remarkable abnormal state in which there is no delay corresponding to 30 ° of the electrical angle.

  FIG. 9 is a waveform diagram illustrating an abnormal state of rotational position detection. The horizontal axis in the figure is the time axis, and shows the waveform of the U-phase terminal voltage VU, the intermediate level value VM, the position detection timings t62 and 64, and the energized phase switching timings t61, t63, and t65. FIG. 9 shows a state where the abnormal state of the rotational position detection shown in FIG. 7 has further progressed.

  When the energized phase is switched at time t61 in FIG. 9, a positive counter electromotive voltage VPr is generated on the waveform of the U-phase terminal voltage VU. As described above, the positive counter electromotive voltage VPr is higher than the power supply voltage E by the forward voltage drop Vd of the diode unit 28. When the mask time Tmsk6 ends during the generation of the positive-side back electromotive voltage VPr, erroneous position detection is performed with the noise voltage immediately after time t62 (similar to FIG. 7). Due to erroneous position detection, a mask time Tmsk7 after time t62 is set, and the energized phase is switched at time t63. At time t63, the positive counter electromotive voltage VPr is continuing, and the negative counter electromotive voltage VNr is generated by switching the energized phase.

  Similarly, when the mask time Tmsk7 ends during the generation of the negative side counter electromotive voltage VNr, erroneous position detection is performed with the noise voltage immediately after time t64 (similar to FIG. 7). Due to erroneous position detection, a mask time Tmsk8 after time t64 is set, and the energized phase is switched at time t65. At time t65, the negative counter electromotive voltage VNr is continuing, and the positive counter electromotive voltage VPr is generated by switching the energized phase.

  In FIG. 9, the abnormality determination unit 7 includes a positive side counter electromotive voltage detection signal SP in a time zone (time t61 to t63) in which the counter electromotive voltage detection circuit 6 detects the positive side counter electromotive voltage VPr, and a position detection unit. Since the position detection timing (time t62) of the 4 specific position detection signal SY overlaps, it is possible to determine the abnormality of the rotational position detection. Similarly, the abnormality determination unit 7 compares the negative side counter electromotive voltage detection signal SN in the time zone (time t63 to t65) during which the negative side electromotive voltage VNr is detected and the specific position detection signal SY of the position detection unit 4. Since the position detection timing (time t64) overlaps, it is possible to determine the abnormality of the rotational position detection. The abnormality determination unit 7 performs predetermined abnormality processing when it is determined that there is an abnormality. For example, the inverter control circuit 3 is reset and restarted, or an alarm is issued.

  The abnormality in rotational position detection shown in FIG. 9 is difficult to determine with the prior art, and can be determined by the abnormality determination unit 7 of the present embodiment. Thereby, the reliability of the rotational position detection of the sensorless brushless motor 9 was improved. Furthermore, it has become possible to prevent the step-out state caused by the erroneous detection of the rotational position or its precursor state from continuing. In addition, the abnormality determination unit 7 determines that an abnormality in rotational position detection has occurred when the position detection timing overlaps in the time zone in which the back electromotive voltage is detected, and this timing overlap cannot occur at normal times. Therefore, the abnormality can be determined with certainty.

  In addition, since the back electromotive voltage detection circuit 6 can be appropriately configured according to the forward voltage drop Vd of the diode part 29 included in the switching elements 22U and 23U of the inverter circuit 2, the back electromotive voltage can be reliably detected, Whether the rotational position is detected or not can be determined. Further, the back electromotive voltage detection circuit 6 can be simply configured including the positive side transistor element 61 and the negative side transistor element 63. Moreover, the current detection means and complicated vector control of Patent Document 1 are not required. As these comprehensive effects, an increase in the cost of the driving device 1 can be suppressed. In addition, in the present embodiment, the mask function of the counter electromotive voltages VPr and VNr by the mask timer TM3 is used in combination, and the above-described effects become more remarkable.

  The configuration of the back electromotive voltage circuit 6 and the determination method of the abnormality determination unit 7 according to the embodiment can be changed as appropriate. In addition, the setting of the energization time width in the energization timing circuit 5, the delay time Tdly of the phase switching timer TM2, and the mask time Tmsk of the mask timer TM3 can be changed. Various other applications and modifications are possible for the present invention.

1: Sensorless brushless motor drive device 2: Inverter circuit
21P: Input terminal 21N: Ground terminal
22U: U-phase positive switching element 23U: U-phase negative switching element
24U: U-phase output terminal 25U, 25V, 25W: Power line
26: DC power supply device 26P: positive terminal 26N: negative terminal
27: Switching unit 28: Diode unit 3: Inverter control circuit 4: Position detection circuit
41U, 41V, 41W: Composite resistance 42: Composite point
44: Comparator 45: Output terminal 47: Position detection unit 5: Energization timing circuit 6: Back electromotive voltage detection circuit
61: Positive side transistor element 62: Positive side detection unit
63: Negative side transistor element 64: Negative side detection unit 7: Abnormality determination unit 9: Sensorless brushless motor
91: Stator
92, 93, 94: Armature winding between UV, VW, WU
95U, 95V, 95W: U phase, V phase, W phase terminal E: Power supply voltage VU, VV, VW: U phase, V phase, W phase terminal voltage viU, viV, viW: U phase, V phase, W phase induction Voltage Vmix: Composite voltage VM: Intermediate level value SC: Energization control signal PWM: Pulse width modulation signal SU, SV, SW: U phase, V phase, W phase switching signal SX: Position signal SY: Specific position detection signal Z: Reverse Electromotive voltage waveform VPr: Positive counter electromotive voltage VNr: Negative counter electromotive voltage

Claims (5)

An inverter circuit for energizing a terminal of the armature winding of a sensorless brushless motor having a stator having a three-phase armature winding and a rotor having a magnetic pole pair during a duty-on time zone of a pulse width modulation signal;
An inverter control circuit for generating the pulse width modulation signal and instructing the inverter circuit based on the instructed duty ratio;
A position detection circuit that operates with the pulse width modulation signal, detects an induced voltage induced in the terminal in a non-energized time zone, and detects a rotational position of the rotor based on the induced voltage;
A sensorless brushless comprising: an energization timing circuit that sets a switching timing for switching an energization phase between the terminals and commands the inverter control circuit based on a position detection timing at which the position detection circuit detects the rotational position of the rotor A motor drive device,
A counter electromotive voltage detection circuit for detecting a counter electromotive voltage generated at the terminal immediately after the switching timing;
An abnormality determination unit that compares the time zone in which the counter electromotive voltage detection circuit detects the counter electromotive voltage and the position detection timing of the position detection circuit to determine whether there is an abnormality in rotational position detection; A sensorless brushless motor drive device further comprising:   The sensorless brushless motor drive device according to claim 1, wherein the abnormality determination unit determines that an abnormality in rotational position detection has occurred when the position detection timing overlaps in a time zone in which the back electromotive voltage is detected. . In claim 1 or 2,
The inverter circuit includes a switching unit in which a conduction state and a cutoff state are selectively controlled by the pulse width modulation signal, and a diode unit that is connected in parallel to the switching unit and allows energization by the counter electromotive voltage. Six switching elements are connected to a DC power supply in a three-phase bridge connection.
The counter electromotive voltage detection circuit includes a positive counter electromotive voltage at which the voltage at the terminal is larger than a voltage at the positive terminal of the DC power supply, and a voltage at the terminal is smaller than a voltage at the negative terminal of the DC power supply. A sensorless brushless motor driving device that detects at least one of the negative counter electromotive voltages. The back electromotive force detection circuit according to claim 3,
A positive-side transistor element connected between the terminal and the positive-side terminal of the DC power source, and generating a switching action by the positive-side counter-electromotive voltage; and
A sensorless brushless motor driving apparatus including at least one of negative-side transistor elements connected between the terminal and a negative-side terminal of the DC power source and generating a switching action by the negative-side counter-electromotive voltage.   5. The sensorless brushless motor according to claim 1, wherein the position detection circuit pauses for a predetermined mask time immediately after the position detection timing to avoid erroneous rotation position detection due to the counter electromotive voltage. 6. Drive device.

Images