JP5533140B2 - Motor drive device - Google Patents

Description

  The present invention relates to a motor drive device.

  For example, in the 120-degree energization method in which the motor is driven by switching the energization phase every 120 degrees of electrical angle, the rotor position detection information is acquired from the zero cross point of the induced voltage induced in the stator of the motor, and the micro is detected according to the position detection information. There is a position detection operation mode in which a drive signal is output from the computer to the inverter circuit to drive the motor.

  On the other hand, since an induced voltage necessary for detecting the rotor position cannot be obtained at the time of startup, the motor is driven in a synchronous operation mode in which the energized phase is forcibly switched at a fixed timing.

  In recent years, a compressor motor used in an air conditioner or the like has been required to have operation control in a lower rotational speed region because of a demand for energy saving. However, if the rotational speed is decreased from the state in which the motor is driven in the position detection operation mode, the induced voltage decreases in proportion to the rotational speed of the motor, so that the rotor position cannot be detected and the motor rotational control is disabled. It becomes possible. As a technique for solving such a problem, there is Patent Document 1 below.

  In the technique disclosed in Patent Document 1, when the motor rotation speed is reduced to an extremely low speed, the operation mode is switched from the position detection operation mode to the synchronous operation mode to enable the motor operation in the low rotation speed region. Technology is disclosed.

JP-A-5-227787

  However, when a motor with a torque ripple compressor is used as the load on the motor, the pulsation occurs in the rotational speed of the motor due to torque fluctuations in the low rotational speed region, and the rotational speed varies between rotations of the mechanical angle of the motor. Therefore, there are cases where the induced voltage can be detected and cases where it cannot be detected, the position detection operation mode and the synchronous operation mode are frequently switched, and the rotation control of the motor becomes unstable. Therefore, in the technique disclosed in Patent Document 1, the rotation speed threshold value for switching between the position detection operation mode and the synchronous operation mode is determined so that the position detection by the induced voltage is unstable in order to stably drive the motor. Because it is necessary to set a value larger than the rotation speed, the rotation speed range in which the rotor position can be detected cannot be expanded. In the low rotation speed range, the motor is finely controlled to save energy and to prevent step-out. There was a problem that it was not possible to control.

  The present invention has been made in view of the above, and extends the rotation speed region in which the rotation of the motor can be controlled by detecting the position of the rotor to a lower rotation speed region, so that energy can be saved even in the low rotation speed region. It is an object of the present invention to obtain a motor drive device that enables fine control of a motor and control for preventing step-out.

A motor drive device according to the present invention is a motor drive device that drives a motor having a rotor and a stator by an energization method having a non-energization section, and is connected to a DC power source and receives a DC voltage supplied from the DC power source. An inverter circuit that converts the AC voltage into the motor and supplies the motor; a position detection circuit that detects a zero-cross point of the induced voltage induced in the stator and outputs a position detection signal for detecting the position of the rotor; A position detection operation for switching the energized phase of the inverter circuit based on the position detection signal, and a synchronous operation for switching the energized phase of the inverter circuit every time a certain energization switching time elapses, according to the rotational speed of the motor. And a control circuit for driving and controlling the inverter circuit, and the control circuit includes a zero cross point of the induced voltage. When a rotation speed threshold value greater than the rotation speed at which detection becomes unstable is preset and the rotation speed of the motor is greater than the rotation speed threshold value, the position detection operation is performed, and the rotation speed of the motor is set to the rotation speed. If it is not more than the threshold and it is possible to detect the zero cross point of the induced voltage, the position is detected at every position detection timing during one rotation of the mechanical angle of the motor based on the position detection signal. Sequentially assigning detection sections, calculating each position detection section time for each position detection section, calculating an average section time of each position detection section time, the previous position detection section time is greater than the average section time, And the said synchronous driving | operation is started from the said position detection area from which the said position detection area time is below the said average area time .

  According to the present invention, the rotation speed range in which the rotation control of the motor can be controlled by detecting the position of the rotor is expanded to a lower rotation speed range, and even in the low rotation speed range, detailed control of the motor for energy saving and prevention of step-out are prevented. It is possible to perform control for this purpose.

FIG. 1 is a diagram illustrating a configuration example of a motor driving device according to an embodiment. FIG. 2 is a diagram illustrating an example of a timing chart in the position detection operation mode. FIG. 3 is a diagram illustrating an example of a timing chart in the synchronous operation mode. FIG. 4 is a diagram illustrating an example of variation in position detection timing in the low rotation region. FIG. 5 is a diagram illustrating an example of a timing chart when position detection is not performed correctly during synchronous operation. FIG. 6 is a diagram illustrating a relationship between the energization switching timing and the position detection timing when the position detection is not correctly performed during the synchronous operation. FIG. 7 is a diagram illustrating a relationship between the energization switching timing and the position detection timing when the position detection is correctly performed during the synchronous operation. FIG. 8 is a diagram illustrating differences depending on the presence / absence of the position detection combined synchronous operation mode. FIG. 9 is an operation mode switching main flowchart of the motor drive device according to the embodiment. FIG. 10 is a position detection section time calculation sub-flowchart. FIG. 11 is a sub-flowchart for determining the start interval of the position detection combined synchronous operation mode.

  Hereinafter, a motor driving apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by this embodiment.

Embodiment.
FIG. 1 is a diagram illustrating a configuration example of a motor driving device according to an embodiment. As shown in FIG. 1, the motor driving apparatus according to the first embodiment includes an inverter circuit 2, a position detection circuit 4, and a control circuit 5, and a DC voltage Vdc is supplied from a DC power supply 1 to the motor 3. Supply AC voltage.

  The inverter circuit 2 includes a U-phase switching element 21, a V-phase switching element 22, a W-phase switching element 23, an X-phase switching element 24, a Y-phase switching element 25, and a Z-phase switching element 26. , 23, 24, 25, and 26 are connected in a three-phase bridge, and are driven by drive signals to the switching elements 21, 22, 23, 24, 25, and 26 supplied from the control circuit 5.

  The motor 3 is a four-pole motor driven by a 120-degree energization method, and includes a stator 31 and a rotor 32. The number of poles of the motor 3 is not limited to four, and the motor drive system may be anything as long as it has a non-energized section.

  The position detection circuit 4 includes resistors 41 to 46 and a comparator 47. One end of each resistor 41 to 43 is connected to each phase of the stator 31, and the other end of each resistor 41 to 43 is connected. A resistor 44 is connected between the connection point of each of the resistors 41 to 43 and the ground, and the connection point of each of the resistors 41 to 44 is connected to the inverting input terminal of the comparator 47. Hereinafter, the voltage at the connection point of the resistors 41 to 44 is referred to as a virtual neutral point voltage. Further, a resistor 45 and a resistor 46 are connected in series between the positive electrode side of the DC power supply 1 and the ground, and the voltage at the connection point of the resistor 45 and the resistor 46 is used as a reference voltage and supplied to the non-inverting input terminal of the comparator 47. The This reference voltage is set to coincide with the voltage at the zero cross point (positive / negative inflection point) of the sine wave component of the virtual neutral point voltage. The comparator 47 detects the zero-cross point of the virtual neutral point voltage (that is, the zero-cross point of the induced voltage) by comparing the virtual neutral point voltage and the reference voltage, and detects the position of the rotor 32 (hereinafter simply referred to as the “zero cross point”). A position detection signal for “position detection” is output.

  The control circuit 5 performs position detection based on the position detection signal output from the position detection circuit 4, and switches each of the switching elements 21 and 22 based on the position detection result and an external rotation speed command signal (not shown). , 23, 24, 25, and 26 are generated and output.

  Next, the position detection operation mode and the synchronous operation mode will be described. FIG. 2 is a diagram illustrating an example of a timing chart in the position detection operation mode. FIG. 3 is a diagram illustrating an example of a timing chart in the synchronous operation mode.

  FIG. 2A shows a virtual neutral point voltage. In FIG. 2A, the horizontal axis indicates the passage of time, and the vertical axis indicates the virtual neutral point voltage value. FIG. 2B shows the position detection timing at which the zero-cross point of the virtual neutral point voltage is detected based on the position detection signal output from the position detection circuit 4, and FIG. 2C shows the position detection operation mode. The drive signals to the switching elements 21, 22, 23, 24, 25, 26 of each phase in FIG.

  FIG. 3A shows the energization switching timing in the synchronous operation mode. In FIG. 3A, the horizontal axis indicates the passage of time, and the vertical axis indicates the time until the energization switching is performed. FIG. 3B shows drive signals to the switching elements 21, 22, 23, 24, 25, and 26 of each phase in the synchronous operation mode.

  In the position detection operation mode, as shown in FIG. 2, the energized phase is switched at the zero-cross point of the virtual neutral point voltage (that is, the zero-cross point of the induced voltage), and the switching elements 21, 22, 23, 24, Drive signals to 25 and 26 are output.

  On the other hand, in the synchronous operation mode, as shown in FIG. 3, every time the energization switching time T elapses, the energized phase is switched at a constant timing, and the switching elements 21, 22, 23, 24, 25, 26 of each phase are switched to. Drive signal is output. Here, the energization switching time T is obtained as a time per rotation from the motor rotation speed command value, and this time is determined by the number of times of energization switching during one rotation determined by the number of poles and the number of phases of the motor (this embodiment). It is the time divided by 12 times in the form.

  Below, the concept of the operation mode of the motor drive device concerning embodiment is demonstrated. When the rotational speed decreases during the operation in the position detection operation mode, the operation in the low rotation speed region can be performed by switching from the position detection operation mode to the synchronous operation mode. However, for example, when the technique disclosed in Japanese Patent Application Laid-Open No. 5-227787 is used, the rotation speed threshold value for switching between the position detection operation mode and the synchronous operation mode is induced in order to stably drive the motor. It is necessary to set a value larger than the rotation speed at which the detection of the zero cross point of the voltage becomes unstable. Since the rotor position is not detected in this synchronous operation mode, it is impossible to perform fine control of the motor for energy saving or control for preventing step-out.

  However, as described above, if the rotation speed threshold value for switching between the position detection operation mode and the synchronous operation mode is set to a value larger than the rotation speed at which the detection of the zero cross point of the induced voltage becomes unstable, the induced voltage is changed from the rotation speed threshold value. Since the position can be detected in the rotational speed region up to the rotational speed where the detection of the zero cross point becomes unstable, the position detection result can be applied to the drive control of the motor 3 even in the synchronous operation mode. . Therefore, in the motor drive device according to the embodiment, in the rotation speed region where the rotation speed of the motor is equal to or less than the rotation speed threshold and the position can be detected, the position is detected while performing the synchronous operation, and the position detection is performed. By applying the result to the rotation control of the motor 3, it is possible to perform fine control of the motor 3 for energy saving and control for prevention of step-out. The operation mode in which the position detection result is applied to the rotation control of the motor 3 while performing the synchronous operation is hereinafter referred to as “position detection combined synchronous operation mode”.

  On the other hand, when a motor with a torque ripple is used as the motor load, the rotation speed fluctuates during one rotation due to torque fluctuation in the low rotation speed range, so the time between the zero cross points of the induced voltage of the motor fluctuates. The position detection timing varies.

  FIG. 4 is a diagram illustrating an example of variation in position detection timing in the low rotation region. In FIG. 4, the horizontal axis indicates the position detection section number assigned for convenience in each section between the position detection timings (hereinafter referred to as “position detection section”), and the vertical axis indicates each position detection section time. In the example shown in FIG. 4, this position detection section number is a number assigned for convenience in each position detection section during one rotation of the mechanical angle of the 4-pole motor driven by the 120-degree energization method. In the example shown in FIG. 4, the position detection section time is the shortest in the position detection section number “0”, that is, the rotational speed is fastest, and the position detection section time is the longest in the position detection section number “6”. It is long, that is, the rotation speed is the slowest.

  Switching between energized phases during the synchronous operation is performed at a certain energization switching timing every energization switching time T. Therefore, position detection is performed correctly when the zero cross point of the induced voltage appears before the energization switching timing, but if the position detection timing fluctuates and the zero cross point of the induced voltage appears after the energization switching timing, position detection is performed. Not done correctly.

  FIG. 5 is a diagram illustrating an example of a timing chart when position detection is not performed correctly during synchronous operation. FIG. 5A shows the energization switching timing in the synchronous operation mode. In FIG. 5A, the vertical axis indicates the time until the energization switching is performed, and the horizontal axis indicates the passage of time. FIG. 5B shows drive signals to the switching elements 21, 22, 23, 24, 25, and 26 of each phase in the synchronous operation mode. FIG. 5C shows a virtual neutral point voltage. In FIG. 5C, the vertical axis represents the virtual neutral point voltage value, and the horizontal axis represents the passage of time. FIG. 5D shows the position detection timing at which the zero-cross point of the virtual neutral point voltage is detected based on the position detection signal output from the position detection circuit 4.

  FIG. 5 shows an example in which the energization switching timing arrives earlier than the position detection timing (see FIG. 5A). In this case, as shown in FIGS. 5C and 5D, since the zero cross point of the chopping waveform superimposed on the induced voltage is detected, the zero cross point of the induced voltage cannot be correctly detected. The position cannot be detected correctly.

  FIG. 6 is a diagram illustrating a relationship between the energization switching timing and the position detection timing when the position detection is not correctly performed during the synchronous operation. FIG. 6A shows the energization switching timing, and the numbers “0” to “11” indicate the energization section numbers assigned corresponding to the respective position detection section numbers. FIG. 6B shows the position detection timing, and the numbers “0” to “11” show the position detection section numbers.

  In the example shown in FIG. 6, the position detection timing has come before the energization switching timing in the energization section numbers “0” to “7” and “11”, but in the energization section numbers “8” to “10”, The position detection timing comes after the energization switching timing. For this reason, as explained in FIG. 5, the zero cross point of the induced voltage cannot be detected correctly, and the position cannot be detected correctly.

  FIG. 7 is a diagram illustrating a relationship between the energization switching timing and the position detection timing when the position detection is correctly performed during the synchronous operation. FIG. 7A is a diagram illustrating an example of fluctuations in position detection timing in the low-rotation region described in FIG. 4, and a straight line indicated by a solid line in FIG. 7A indicates an average of each position detection section time. The value is shown.

  In the example shown in FIG. 7, a position detection section in which the immediately preceding position detection section time is larger than the average value of each position detection section time and the position detection section time is equal to or less than the average value of each position detection section time (see FIG. 7). In the example shown, the control is performed so that the synchronous operation is started from the position detection section (position detection section number “9”). As a result, as shown in FIG. 7B, the position detection timing comes before the energization switching timing in all the energization sections, so that position detection can be performed correctly. Therefore, in the motor drive device according to the embodiment, the position detection can be stably performed by applying the above-described control when shifting to the position detection combined synchronous operation mode.

  FIG. 8 is a diagram illustrating differences depending on the presence / absence of the position detection combined synchronous operation mode. FIG. 8A is a diagram showing mode transition when the position detection combined synchronous operation mode is not applied, and FIG. 8B is a diagram showing mode transition when the position detection combined synchronous operation mode is applied. is there. In any case, the rotation speed threshold is set to a value larger than the rotation speed at which detection of the zero cross point of the induced voltage becomes unstable. When the position detection combined synchronous operation mode is not applied (see FIG. 8A), the synchronous operation mode is set in the rotational speed region below the rotational speed threshold. As described above, position detection is not performed in this synchronous operation mode.

  On the other hand, when the position detection combined use synchronous operation mode is applied (see FIG. 8B), the position detection combined use synchronous operation mode is set in the rotation speed region that is equal to or less than the rotation speed threshold and the position can be detected. As described above, in this position detection combined synchronous operation mode, position detection is performed while performing synchronous operation, and the position detection result is applied to the rotation control of the motor 3, so that the position detection combined synchronous operation mode is not applied (FIG. 8 (a)), the rotation speed region in which the rotation control of the motor 3 can be controlled by position detection can be expanded to a lower rotation speed region.

  Next, the operation mode switching operation of the motor drive device according to the embodiment will be described with reference to FIG. 1, FIG. 9, FIG. 10, and FIG. FIG. 9 is an operation mode switching main flowchart of the motor drive device according to the embodiment. FIG. 10 is a position detection section time calculation sub-flowchart. FIG. 11 is a sub-flowchart for determining the start interval of the position detection combined synchronous operation mode.

  In FIG. 9, when the compressor is started, the control circuit 5 starts driving the motor 3 in the synchronous operation mode (step ST101). The control circuit 5 determines whether or not an induced voltage that can be driven in the position detection operation mode is obtained based on the position detection signal output from the position detection circuit 4 (step ST102), and the position detection operation mode. When the induced voltage is reached that can be driven by (step ST102; Yes), the mode shifts to the position detection operation mode (step ST103). If an induced voltage that can be driven in the position detection operation mode is not obtained (step ST102; No), the process returns to step ST101, and steps ST101 to ST100 are performed until the induced voltage that can be driven in the position detection operation mode is reached. The process of ST102 is repeatedly executed. Here, as a method of determining whether or not an induced voltage that can be driven in the position detection operation mode is obtained (step ST102), for example, detection of a zero cross point of the induced voltage during one rotation of the mechanical angle of the motor 3 is performed. The determination can be made based on whether the number of times is equal to or greater than a preset detection frequency threshold. In the case of the four-pole motor driven by the 120-degree energization method shown in FIG. 1, the maximum number of detections during one rotation of the mechanical angle of the motor 3 is 12, so the detection frequency threshold is 12 or less. You only have to set it.

  When driving in the position detection operation mode is started (step ST103), the control circuit 5 starts position detection based on the position detection signal, temporarily stores the first position detection time at that time as the previous position detection time, The position detection section number n until the next position detection time is set to “0” (step ST104).

  Subsequently, the control circuit 5 executes a position detection section time calculation subflow (step ST200) shown in FIG. In the position detection section time calculation subflow, the position detection section time of all sections during one rotation of the mechanical angle of the motor 3 is calculated. Here, the number of sections m during one rotation of the mechanical angle of the motor is determined by the number of poles of the motor and the energization method, but as described above, the 4-pole motor driven by the 120-degree energization method shown in FIG. In some cases, since the number of sections in one rotation of the mechanical angle of the motor is 12, m = 12.

  The control circuit 5 temporarily stores the position detection time next to the previous position detection time as the current position detection time (step ST201). Then, the previous position detection time is subtracted from the current position detection time and stored as the position detection section time t (n) in the position detection section number n (step ST202), and the current position detection time is temporarily stored as the previous position detection time. (Step ST203).

  Subsequently, the control circuit 5 determines whether or not the position detection section number n is the number of sections m-1 (step ST204). If n = m−1 is not satisfied (step ST204; No), the value of the position detection section number n is incremented (step ST206), the process returns to step ST201, and steps ST201 to ST204 are performed until n = m−1. Repeat the process. If n = m−1 (step ST204; Yes), the value of the position detection section number n is reset to “0” (step ST205), and the process returns to the operation mode switching main flow shown in FIG.

  Returning to the operation mode switching main flow shown in FIG. 9, the control circuit 5 executes the start interval determination subflow (step ST300) of the position detection combined use synchronous operation mode shown in FIG. In the start section determination subflow of the position detection combined synchronous operation mode, an average section time that is an average value of the position detection section times t (n) in all sections is calculated, and for each position detection section number, the position detection section time t ( n-1) is greater than the average interval time, and it is determined whether or not the condition that the position detection interval time t (n) is equal to or less than the average interval time is satisfied, and the position detection interval of the position detection interval number that satisfies this condition Is the start section of the synchronous operation mode with position detection.

  First, the control circuit 5 calculates the average interval time (step ST301), and sets the value of the position detection interval number n for determining whether or not the above-described condition is satisfied to “0” (step ST302).

  Subsequently, the control circuit 5 sets the position detection section time t (n) in the position detection section number n as the determination section time (step ST303). Then, it is determined whether or not the position detection section number n = 0 (step ST304). If n = 0 (step ST304; Yes), the position detection section time t (m) in the position detection section number m−1 is determined. -1) is set as the previous section time (step ST305). If n = 0 is not satisfied (step ST304; No), the position detection section time t (n-1) in the position detection section number n-1 is set as the previous section time (step ST306).

  Subsequently, the control circuit 5 determines whether or not the previous section time is larger than the average section time (step ST307). If the previous section time is equal to or less than the average section time (step ST307; No), the position detection section number is determined. The value of n is incremented (step ST309), and the process returns to step ST303. When the previous section time is larger than the average section time (step ST307; Yes), it is determined whether or not the determination section time is equal to or less than the average section time (step ST308). (Step ST308; No), the value of the position detection section number n is incremented (Step ST309), and the process returns to Step ST303. If the determination interval time is equal to or less than the average interval time (step ST308; Yes), the position detection interval of position detection interval number n is determined as the start interval of the position detection combined use synchronous operation mode (step ST310), and the operation shown in FIG. Return to the mode switching main flow.

  Returning to the operation mode switching main flow shown in FIG. 9, the control circuit 5 determines whether or not the rotation speed of the motor 3 is larger than a preset rotation speed threshold value Xrps based on the position detection signal (step ST105). . Here, the rotation speed threshold value Xrps is set to a value larger than the rotation speed at which detection of the zero cross point of the induced voltage becomes unstable.

  If the rotational speed of the motor 3 is larger than the rotational speed threshold value Xrps (step ST105; Yes), if the previous operation mode is the position detection operation mode, the position detection operation mode is continued, and the previous operation mode Is in the position detection combined use synchronous operation mode or the synchronous operation mode, the process shifts to the position detection operation mode (step ST106), executes step ST200 and step ST300, and returns to the process of step ST105.

  When the rotational speed of the motor 3 is equal to or lower than the rotational speed threshold value Xrps (step ST105; No), the control circuit 5 determines whether or not it is possible to detect the zero cross point of the induced voltage based on the position detection signal. Determination is made (step ST107).

  When it is impossible to detect the zero cross point of the induced voltage (step ST107; No), the control circuit 5 continues the synchronous operation mode when the previous operation mode is the synchronous operation mode. When the previous operation mode is the position detection operation mode or the position detection combined use synchronous operation mode, the operation mode is shifted to the synchronous operation mode (step ST109), and the step ST107 and the step ST107 are performed until the induced voltage is detected. The process of step ST109 is repeatedly executed.

  When it is possible to detect the zero cross point of the induced voltage (step ST107; Yes), the control circuit 5 performs the position detection combined synchronization determined in the start interval determination subflow (step ST300) of the position detection combined synchronous operation mode. Driving in the position detection combined use synchronous operation mode is started from the start section of the operation mode (step ST108), step ST200 and step ST300 are executed, and the process returns to step ST105.

  As described above, according to the motor drive device according to the embodiment, the rotation speed threshold value that is greater than the rotation speed at which the detection of the zero-cross point of the induced voltage becomes unstable as the rotation speed threshold value for shifting to the position detection combined synchronous operation mode. If the motor rotation speed is greater than the rotation speed threshold, a position detection operation is performed to switch the energized phase of the inverter circuit based on the position detection result, the motor rotation speed is equal to or less than the rotation speed threshold, and When it is possible to detect the zero-cross point of the induced voltage, since the synchronous operation for switching the energized phase of the inverter circuit every time a certain energization switching time elapses, the position detection is performed. The rotation speed range that can control the rotation of the motor by detecting the position of the rotor can be expanded to a lower rotation speed range. It is possible to perform control for fine control and step-out prevention of data. For example, in the synchronous operation mode, the energization switching time is determined not from the actual rotation speed but from the rotation speed command value, and therefore, the actual rotor position and the energization switching timing may be greatly shifted, leading to step-out. At this time, if the operation is performed in the position detection combined synchronous operation mode, the actual rotational speed and the rotor position can be grasped. Based on this, the energization switching time or the energization switching timing is controlled, or the rotation is temporarily performed. It is possible to protect against step-out by increasing the number to stabilize or stopping the operation.

  In addition, the position detection interval time is greater than the average value of each position detection section time, and the position detection section time is equal to or less than the average value of each position detection section time. Since the position detection timing comes before the energization switching timing in all energization sections during operation in the position detection combined synchronous operation mode, the position detection can be performed stably and accurately. The rotation control of the motor can be performed.

  In the synchronous operation mode with position detection, it is also possible to detect the pulsation of the rotation speed from the position detection result and adjust the output voltage based on the detected pulsation of the rotation speed, so that the motor vibration can be effectively suppressed. it can.

  Note that the configuration shown in the above embodiment is an example of the configuration of the present invention, and can be combined with another known technique, and a part thereof is omitted without departing from the gist of the present invention. Needless to say, it is possible to change the configuration.

  As described above, the motor drive device according to the present invention expands the rotation speed region in which the rotation of the motor can be controlled by detecting the position of the rotor to a lower rotation speed region, and the motor for energy saving even in the low rotation speed region. It is useful as an invention capable of performing detailed control and control for preventing step-out.

DESCRIPTION OF SYMBOLS 1 DC power supply 2 Inverter circuit 3 Motor 4 Position detection circuit 5 Control circuit 21 U phase switching element 22 V phase switching element 23 W phase switching element 24 X phase switching element 25 Y phase switching element 26 Z phase switching element 31 Stator 32 Rotor 41 , 42, 43, 44, 45, 46 Resistance 47 Comparator

Claims (1)

A motor drive device for driving a motor having a rotor and a stator by an energization method having a non-energization section,
An inverter circuit connected to a DC power source, converting a DC voltage supplied from the DC power source into an AC voltage and supplying the AC voltage;
A position detection circuit for detecting a zero cross point of an induced voltage induced in the stator and outputting a position detection signal for detecting the position of the rotor;
A position detection operation for switching the energized phase of the inverter circuit based on the position detection signal, and a synchronous operation for switching the energized phase of the inverter circuit every time a certain energization switching time elapses, according to the rotational speed of the motor. A control circuit for switching and controlling the inverter circuit,
With
The control circuit includes:
When a rotational speed threshold value larger than the rotational speed at which the detection of the zero cross point of the induced voltage becomes unstable is preset and the rotational speed of the motor is larger than the rotational speed threshold value, the position detection operation is performed, and the motor Is equal to or less than the rotation speed threshold value and it is possible to detect the zero-cross point of the induced voltage , based on the position detection signal during one rotation of the mechanical angle of the motor. A position detection section is sequentially assigned for each position detection timing, each position detection section time is calculated for each position detection section, an average section time of each position detection section time is calculated, and the previous position detection section time is calculated. greater than the average interval time and the motor, characterized in that from the position detecting section the position detection section time is equal to or less than the average interval hours, starting the synchronized operation It operated device.

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