JP2013229949A - Controller of two-phase brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driver of two-phase brushless motor applicable even to a DC power supply with no neutral point.SOLUTION: Upon detecting a zero-cross point during start-up of a U-phase inductive voltage, a control circuit 14 waits for elapse of standby time Tw. Upon elapsing a standby time Tw, the control circuit 14 turns on two switching elements SW1, SW4 corresponding to a first electrification pattern P1. Upon elapsing an electrification time Td, the control circuit 14 turns off the two switching elements SW1, SW4. Subsequently, when a zero-cross point is detected during start-up of a W-phase inductive voltage, the control circuit 14 waits for elapse of the standby time Tw. Upon elapsing a standby time Tw, the control circuit 14 turns on two switching elements SW2, SW3 corresponding to a second electrification pattern P2.

Description

  The present invention relates to a control device for a two-phase brushless motor that estimates a rotor position based on an induced voltage and drives a two-phase brushless motor using the estimated rotor position.

  A conventional general two-phase brushless motor includes a rotor having a magnet having at least one pair of magnetic pole pairs, and a stator having a stator coil connected in two phases. The control device for a two-phase brushless motor includes a hall element for detecting the rotor position and a drive circuit for supplying drive currents having different phases to the stator coils based on the output signal of the hall element.

However, since the control device for the above-described two-phase brushless motor requires a hall element and wiring accompanying it, there is a problem that it is difficult to reduce the size and cost of the two-phase brushless motor.
Therefore, a sensorless motor control device that drives a two-phase brushless motor without using a sensor for detecting the rotor position such as a hall element has been proposed (see Patent Document 1). In this conventional motor control circuit, as shown in FIG. 1 of Patent Document 1, the connection point between the S-phase stator coil and the M-phase stator coil is fixed at a neutral point potential. First, a drive current flowing in the DA direction is supplied to the S-phase stator coil. And this electric current is interrupted after energization by 90 degrees in phase. Next, a drive current flowing in the DB direction is supplied to the M-phase stator coil. And this electric current is interrupted after energization by 90 degrees in phase. Next, a driving current flowing in the DC direction is supplied to the S-phase stator coil. And this electric current is interrupted after energization by 90 degrees in phase. Next, a drive current flowing in the DD direction is supplied to the M-phase stator coil. And this electric current is interrupted after energization by 90 degrees in phase. Thereafter, a drive current flowing in the DA direction is supplied to the S-phase stator coil. By repeating such an operation, a rotating magnetic field is generated.

  The conventional motor control circuit includes a position detection circuit that detects the position of the rotor based on an induced voltage generated in the S-phase stator coil and the M-phase stator coil, a 90-degree energization circuit that outputs a 90-degree energization pulse signal, and the like. ing. The position detection circuit generates S-phase and M-phase induced voltage waveforms delayed by 45 degrees from the actual S-phase and M-phase induced voltages based on the S-phase and M-phase coil terminal voltages, respectively. By comparing the induced voltage waveforms of the S phase and M phase delayed by the middle point level, a rectangular wave signal corresponding to them is generated. The 90-degree energization circuit generates a zero-cross signal based on the S-phase and M-phase rectangular wave signals from the position detection circuit, and based on the zero-cross signal and the S-phase and M-phase rectangular wave signals, Outputs an energization pulse signal.

JP 07-274582 A Japanese Patent Laid-Open No. 06-253579

  In the control device for a two-phase brushless motor according to the above-described prior art, the phase difference of the drive current supplied to each stator coil is set to 90 degrees. In order to generate the S-phase and M-phase induced voltage waveforms, the drive current supplied to one stator coil is cut off, the induced voltage waveform generated from the stator coil is examined, and then the phase is advanced by 90 degrees. After a corresponding time has elapsed, the drive current supplied to the other stator coil is cut off, and the induced voltage waveform generated from the stator coil is examined. Thus, in order to cut off the drive currents supplied to both stator coils separately, a circuit is required that allows current to flow independently through both stator coils. Therefore, the connection point of both stator coils is fixed to the neutral point potential. For this reason, a power supply having a neutral point is required.

  An object of the present invention is to provide a drive device for a two-phase brushless motor that can be applied to a DC power supply having no neutral point.

  The invention described in claim 1 comprises a stator having a series circuit (5) of a first phase stator coil (3) and a second phase stator coil (4), and a rotor facing the stator. A control circuit (1) for a two-phase brushless motor (2), comprising: a drive circuit (12) including a plurality of switching elements (SW1 to SW4) for energizing / interrupting the series circuit and switching an energization pattern; When the energization to the series circuit is cut off, a reference voltage passing time point when the induced voltage corresponding to the first phase passes a predetermined reference voltage and an induced voltage corresponding to the second phase Reference voltage passage time detection means (13, 14) for detecting a reference voltage passage time that is a time when the reference voltage passes through the reference voltage, and a reference voltage detected by the reference voltage passage time detection means Control means (14) for controlling the plurality of switching elements based on an excess time, and the reference voltage passage time detection means includes a reference voltage passage time at a rise of the induced voltage of the first phase, A control device for a two-phase brushless motor configured to alternately detect a reference voltage passing point at the time of rising of an induced voltage of a second phase. In addition, although the alphanumeric character in parentheses represents a corresponding component in an embodiment described later, of course, the scope of the present invention is not limited to the embodiment. The same applies hereinafter.

  When attempting to perform sensorless control with a load on the two-phase brushless motor, depending on the two-phase brushless motor, the current supply to the series circuit of the first-phase and second-phase stator coils is interrupted It has also been found that there is a possibility that the waveform at the time of passing the reference voltage at the fall of the U-phase induced voltage and the W-phase induced voltage may not appear. In the present invention, the reference voltage passage time detection means alternately detects the reference voltage passage time when the first phase induced voltage rises and the reference voltage passage time when the second phase induced voltage rises. It is configured. For this reason, it becomes possible to drive a two-phase brushless motor in which the waveform when the reference voltage passes when the induced voltage falls at the time of load does not appear. Moreover, according to this invention, it is applicable also to DC power supply without a neutral point.

  The invention according to claim 2 includes a stator having a series circuit (5) of a first-phase stator coil (3) and a second-phase stator coil (4), and a rotor facing the stator. A control device (1) for a phase brushless motor (2), comprising a plurality of switching elements (SW1 to SW4) for energization / interruption and switching of energization patterns with respect to the series circuit; When energization to the series circuit is cut off, a reference voltage passing time point when the induced voltage corresponding to the first phase passes a predetermined reference voltage and an induced voltage corresponding to the second phase are Reference voltage passage time detection means (13, 14) for detecting a reference voltage passage time that is a time of passing the reference voltage, and reference voltage passage detected by the reference voltage passage time detection means. Control means (14) for controlling the plurality of switching elements based on time points, wherein the reference voltage passage time point detection means comprises a reference voltage passage time point when the first phase induced voltage falls, and A control device for a two-phase brushless motor configured to alternately detect a reference voltage passing point at the time of a fall of the induced voltage of the second phase.

  When attempting to perform sensorless control with a load on the two-phase brushless motor, depending on the two-phase brushless motor, the current supply to the series circuit of the first-phase and second-phase stator coils is interrupted It has also been found that the waveform at the time of passage of the reference voltage at the rise of the U-phase induced voltage and the W-phase induced voltage may not appear. In the present invention, the reference voltage passage time detection means alternately detects the reference voltage passage time when the first phase induced voltage falls and the reference voltage passage time when the second phase induced voltage falls. It is configured as follows. For this reason, it becomes possible to drive a two-phase brushless motor in which the waveform at the time of passage of the reference voltage at the rise of the induced voltage does not appear during the load. Moreover, according to this invention, it is applicable also to DC power supply without a neutral point.

  According to a third aspect of the present invention, the control means starts energizing the series circuit from the reference voltage passage time based on the time interval (T) of the reference voltage passage time detected by the reference voltage passage time detection means. Setting means (S12, S32) for setting a standby time (Tw) until starting and an energizing time (Td) from when energization to the series circuit is stopped until energization is stopped, and detection of the reference voltage passing time Means for controlling the plurality of switching elements based on the reference voltage passing time detected by the means, the standby time and the energization time set by the setting means, and the previous energization pattern (S13 to S16, The control device for a two-phase brushless motor according to claim 1 or 2, including S33 to S36).

FIG. 1 is an electric circuit diagram showing a schematic configuration of a control device for a two-phase brushless motor according to an embodiment of the present invention. FIG. 2 is an electric circuit diagram showing the configuration of the comparison circuit. FIG. 3 is a waveform diagram showing the waveform of the U-phase voltage and the waveform of the W-phase voltage when the switching elements SW1 to SW4 are controlled by the first control circuit already devised by the present applicant. FIG. 4 is a waveform diagram showing the waveform of the U-phase voltage and the waveform of the W-phase voltage when each switching element is controlled by the first method. FIG. 5 is a flowchart showing the operation of the control circuit when each switching element is controlled by the first method. FIG. 6 is a flowchart showing the operation of the control circuit when each switching element is controlled by the first method. FIG. 7 is a waveform diagram showing the waveform of the U-phase voltage and the waveform of the W-phase voltage when each switching element is controlled by the second method. FIG. 8 is a flowchart showing the operation of the control circuit when each switching element is controlled by the second method. FIG. 9 is a flowchart showing the operation of the control circuit when each switching element is controlled by the second method.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an electric circuit diagram showing a schematic configuration of a control device for a two-phase brushless motor according to an embodiment of the present invention.
The control device 1 for the two-phase brushless motor 2 includes a rectifier circuit 11, a drive circuit 12, a comparison circuit 13, and a control circuit 14. The two-phase brushless motor 2 is used as a motor for driving an electric pump, for example.

  The two-phase brushless motor 2 includes a rotor (not shown) having a pair of magnetic pole pairs, and a stator (not shown) having a U-phase stator coil 3 and a W-phase stator coil 4. Although the arrangement of the U-phase stator coil 3 and the W-phase stator coil 4 is arbitrary, in this embodiment, the U-phase stator coil 3 and the rotor rotation axis are point-symmetric. The U-phase stator coil 3 and the W-phase stator coil 4 are connected in series. That is, the stator has a series circuit 5 of a U-phase stator coil 3 and a W-phase stator coil 4.

The rectifier circuit 11 rectifies the alternating current output from the alternating current power supply 10 to create a direct current power supply.
The drive circuit 12 includes a plurality of switching elements SW1 to SW4 for energizing / interrupting the series circuit 5 of the stator coils 3 and 4 and switching the energization pattern. As the switching elements SW1 to SW4, for example, a field effect transistor (FET), an insulated gate bipolar transistor (IGBT), or the like is used. The energization pattern includes a first energization pattern in which a current flows from the U-phase stator coil 3 side toward the W-phase stator coil 4 side, and a first current that flows from the W-phase stator coil 4 side toward the U-phase stator coil 3 side. There are two energization patterns.

  In this embodiment, the drive circuit 12 is composed of an H bridge circuit. The drive circuit 12 includes a series circuit of a pair of switching elements SW1 and SW2 corresponding to the U phase of the two-phase brushless motor 2, and a series circuit of a pair of switching elements SW3 and SW4 corresponding to the W phase of the two-phase brushless motor 2. Are connected in parallel to the rectifier circuit 14. The U-phase stator coil 3 of the two-phase brushless motor 2 is connected to a connection point between a pair of switching elements SW1 and SW2 corresponding to the U-phase. The W-phase stator coil 4 of the two-phase brushless motor 2 is connected to a connection point between a pair of switching elements SW3 and SW4 corresponding to the W-phase.

The direction in which the current I _U flows from the one end connected to the drive circuit 12 to the connection point with the W-phase stator coil 4 is defined as the U + direction, and the opposite direction is defined as the U− direction. Define. In addition, the direction in which the current I _W flows from the one end connected to the drive circuit 12 to the connection point with the U-phase stator coil 3 is defined as the W + direction, and the opposite direction is defined as W−. Defined as direction.

U-phase voltage _VU and W-phase voltage _VW are input to comparison circuit 13. Comparison circuit 13, as shown in FIG. 2, the first operational amplifier 21 for detecting the reference voltage to the point at which the U-phase induced voltage on the basis of the U-phase voltage V _U passes a predetermined reference voltage, W based on the phase voltage V _w, W-phase induced voltage and a second operational amplifier 21 for detecting the reference voltage pass time of passing a predetermined reference voltage.

The “reference voltage” is set to a median value between the maximum value and the minimum value of the drive voltage waveform of the motor 2. In this embodiment, it is assumed that the reference voltage is 0 [V] for convenience of explanation. A reference voltage passage time at which the induced voltage passes through the reference voltage is referred to as a “zero cross point”.
The U-phase voltage _VU is input to the non-inverting input terminal of the first operational amplifier 21. The inverting input terminal of the first operational amplifier 21 receives a reference voltage (0 V in this embodiment) for detecting a reference voltage passage time (zero cross point in this embodiment) of the U-phase induced voltage. The output signal U _OUT of the first operational amplifier 21 is at the H level when the U phase voltage V _U is greater than the reference voltage, and is at the L level when the U phase voltage V _U is less than the reference voltage. The output signal U _OUT of the first operational amplifier 21 is given to the control circuit 14.

The W-phase voltage _VW is input to the non-inverting input terminal of the second operational amplifier 22. The inverting input terminal of the second operational amplifier 22 is supplied with a reference voltage (0 V in this embodiment) for detecting a reference voltage passage time point (zero cross point in this embodiment) of the W-phase induced voltage. The output signal W _OUT of the second operational amplifier 22 becomes H level when the W phase voltage V _W is larger than the reference voltage, and becomes L level when the W phase voltage V _W is less than the reference voltage. The output signal W _OUT of the second operational amplifier 22 is given to the control circuit 14.

Based on the output signal U _{OUT of} the first operational amplifier 21 and the output signal W _OUT of the second operational amplifier 22, the control circuit 14 performs on / off control of the switching elements SW1 to SW4 in the drive circuit 12. The control circuit 14 includes a microcomputer having a CPU and a memory (ROM, RAM, etc.).
Before describing the operation of the control circuit 14 in the present embodiment, the control circuit already devised by the present applicant (hereinafter referred to as the “first control circuit” to be distinguished from the control circuit 14 of the present embodiment). The control method of the drive circuit 12 by) will be described.

A case where the two-phase brushless motor 2 is driven and controlled in a no-load state will be described. The first control circuit outputs, for example, the output signal U _OUT of the first operational amplifier 21 in a state where the energization to the series circuit 5 of the stator coils 3 and 4 is cut off after the two-phase brushless motor 2 is started. Based on this, the zero cross point of the U-phase induced voltage is detected. Then, a time interval (zero cross interval) T between adjacent zero cross points is calculated. This zero-crossing interval T corresponds to the time required for the rotor to rotate 180 degrees in electrical angle (the time required for half rotation in this embodiment).

  Based on the zero cross interval T, the first control circuit energizes the series circuit 5 with a standby time Tw from the zero cross point until the energization of the series circuit 5 of the stator coils 3 and 4 starts (applying drive voltage). The energization time (drive voltage application time) Td from the start to the time when the energization is stopped is determined. Then, the first control circuit controls each of the switching elements SW1 to SW4 based on the determined standby time Tw and energization time Td, the detected zero cross point, and the previous energization pattern. The waiting time Tw is set to T / 6, for example. The energization time Td is set to 2T / 3, for example.

Figure 3 is a waveform diagram showing the waveforms of the waveform and the W-phase voltage V _W of the U-phase voltage V _U in the case of controlling the switching elements SW1~SW4 by the first control circuit described above.
In the waveform of the U-phase voltage V _U, the waveform in the energization time Td represents the U-phase drive voltage, the waveform of the other period shows a U-phase induced voltage. Similarly, the waveform of the W-phase voltage V _W, the waveform in the energization time Td represents the W-phase drive voltages, waveforms of the other periods represents the W-phase induced voltage.

As described above, the energization patterns include the first energization pattern P1 and the second energization pattern P2. The first energization pattern P1 is realized by turning on the switching elements SW1 and SW4. On the other hand, the second energization pattern P2 is realized by turning on the switching elements SW2 and SW3. The energization pattern is switched alternately.
When the first control circuit detects the zero-cross point of the U-phase induced voltage when the energization to the series circuit 5 is interrupted, the first control circuit waits for the standby time Tw to elapse. When the standby time Tw elapses, the first control circuit turns on the two switching elements corresponding to the current energization pattern with the current energization pattern different from the previous energization pattern as the current energization pattern. As a result, a drive voltage corresponding to the current energization pattern is applied to the series circuit 5. When the energization time Td elapses, the first control circuit turns off the two switching elements in the on state. Thereafter, when the first control circuit detects the zero-cross point of the U-phase induced voltage, it waits for the standby time Tw to elapse. When the standby time Tw elapses, the first control circuit turns on the two switching elements corresponding to the current energization pattern with the current energization pattern different from the previous energization pattern as the current energization pattern. When the energization time Td elapses, the first control circuit turns off the two switching elements in the on state. Thereafter, the first control circuit repeats the same operation.

  The two-phase brushless motor 2 is started by forced commutation in the same manner as the 120-degree energization rectangular wave sensorless drive of the three-phase brushless motor. That is, the initial value of the standby time Tw and the initial value of the energization time Td are set in advance. Then, the drive voltage corresponding to the first energization pattern P1 and the drive voltage corresponding to the second energization pattern P2 are alternately repeated to the motor 2 in accordance with the initial value of the standby time Tw and the initial value of the energization time Td. Apply. As a result, the rotor starts rotating although it is inefficient.

  By the way, when the sensorless control as described above is performed in a state where there is a load on the two-phase brushless motor 2, depending on the two-phase brushless motor 2, the energization to the series circuit 5 is interrupted. It has been found that there is a possibility that the zero cross at the time of falling of the induced voltage of the U phase and the induced voltage of the W phase (zero cross when the induced voltage decreases) may not appear. Further, depending on the two-phase brushless motor 2, even when the energization to the series circuit 5 is interrupted, a zero cross at the rise of the U-phase induced voltage and the W-phase induced voltage (when the induced voltage increases) It has been found that there is a possibility that a zero cross will appear.

  First, a control method (hereinafter referred to as “first method”) for the two-phase brushless motor 2 in which zero crossing at the time of falling of the U-phase induced voltage and the W-phase induced voltage does not appear at the time of load will be described. The U-phase induced voltage and the W-phase induced voltage are 180 degrees out of phase. Therefore, if the zero-cross point at the rise of the W-phase induced voltage and the zero-cross point at the rise of the U-phase induced voltage can be detected, the same control as the first control circuit described above is performed based on these two zero-cross points. Is possible.

Figure 4 is a waveform diagram showing the waveforms of the waveform and the W-phase voltage V _W of the U-phase voltage V _U in the case of controlling the switching elements SW1~SW4 by the first method.
In the waveform of the U-phase voltage V _U, the waveform in the energization time Td represents the U-phase drive voltage, the waveform of the other period shows a U-phase induced voltage. Similarly, the waveform of the W-phase voltage V _W, the waveform in the energization time Td represents the W-phase drive voltages, waveforms of the other periods represents the W-phase induced voltage.

  The control circuit 14 is one of the U-phase induced voltage and the W-phase induced voltage that tends to increase every time the energization to the series circuit 5 of the stator coils 3 and 4 is interrupted after the two-phase brushless motor 2 is started. The zero cross point at the rise of the induced voltage is detected. The control circuit 14 calculates a time interval (zero cross interval) T with respect to the previous zero cross point every time the zero cross point at the rise of the induced voltage is detected. Then, based on the zero cross interval T, the control circuit 14 waits until the energization of the series circuit 5 of the stator coils 3 and 4 from the zero cross point is started, and the energization after the energization of the series circuit 5 is started. The energization time Td until stopping is determined. The waiting time Tw is set to T / 6, for example. The energization time Td is set to 2T / 3, for example.

  Referring to FIG. 4, control circuit 14 waits for waiting time Tw to elapse when a zero-cross point at the rise of the U-phase induced voltage is detected while energization to series circuit 5 is interrupted. When the standby time Tw elapses, the control circuit 14 turns on the two switching elements SW1 and SW4 so that the drive voltage corresponding to the first energization pattern P1 is applied to the motor 2. As a result, a drive current flows in the U + direction in the U-phase stator coil 3, and a drive current flows in the W− direction in the W-phase stator coil 4.

  When the energization time Td elapses, the control circuit 14 turns off the two switching elements SW1 and SW4. Thereafter, when the control circuit detects the zero cross point at the rise of the W-phase induced voltage, it waits for the standby time Tw to elapse. When the standby time Tw elapses, the control circuit 14 turns on the two switching elements SW2 and SW3 so that the drive voltage corresponding to the second energization pattern P2 is applied to the motor 2. As a result, a drive current flows in the U− direction in the U-phase stator coil 3, and a drive current flows in the W + direction in the W-phase stator coil 4.

  When the energization time Td elapses, the first control circuit turns off the two switching elements SW2 and SW3. Thereafter, when the control circuit 14 detects the zero cross point at the rise of the U-phase induced voltage, it waits for the standby time Tw to elapse. When the standby time Tw elapses, the control circuit 14 turns on the two switching elements SW1 and SW4 so that the drive voltage corresponding to the first energization pattern P1 is applied to the motor 2. Thereafter, the control circuit 14 repeats the same operation. By such an operation, the stator coils 3 and 4 cause the magnetic fields corresponding to the current directions of “U +” and “W−” and the current directions of “U−” and “W +” depending on the rotational angle position of the rotor. Corresponding magnetic fields are alternately generated, and the rotor is rotated by these alternating magnetic fields. The starting method of the two-phase brushless motor 2 is the same as the starting method described above.

5 and 6 are flowcharts showing the operation of the control circuit 14 when the switching elements SW1 to SW4 are controlled by the first method.
The control circuit 14 has a first buffer, a second buffer, and a third buffer. The first buffer is used to store the current value of the output signal U _{OUT of} the first operational amplifier 21 or the output signal W _OUT of the second operational amplifier 22. The second buffer is used for storing the previous value of the output signal U _OUT or W _OUT . The third buffer is used to store the previous value of the output signal U _OUT or W _OUT . The initial values of these buffers are values (hereinafter referred to as “H”) corresponding to the H level of the output signal U _OUT or W _OUT . A value corresponding to the L level of the output signal U _OUT or W _OUT is represented by L.

The control circuit 14 determines the previous energization pattern (step S1). When the previous energization pattern is the first energization pattern P1, the control circuit 14 outputs the output signal W _OUT of the second operational amplifier 22 in order to detect the zero cross point at the rise of the W-phase induced voltage. The current value α _n is stored in the first buffer (step S2). Then, the process proceeds to step S4.

If it is determined in step S1 that the previous energization pattern is the second energization pattern P2, the control circuit 14 detects the zero cross point at the rise of the U-phase induced voltage in order to detect the first crossing point. The output signal U _OUT of the operational amplifier 21 is stored in the first buffer as the current value α _n (step S3). Then, the process proceeds to step S4.
In step S4, the control circuit 14 determines whether or not the current value α _n in the first buffer is H. When the current value α _n in the first buffer is not H (step S4: NO), the control circuit 14 stores the previous value α _n-1 in the second buffer in the third buffer as the previous value α _n-2 . After this (step S7), the current value α _n in the _first buffer is stored in the second buffer as the previous value α _n-1 (step S8). Then, the process returns to step S1.

When it is determined in step S4 that the current value α _n in the first buffer is H (step S4: YES), the control circuit 14 indicates that the previous value α _n-1 in the second buffer is H. Whether or not (step S5). When the previous value α _n-1 in the second buffer is not H (step S5: NO), the control circuit 14 sets the previous value α _n-1 in the second buffer as the previous value α _n-2 in the third buffer. (Step S7), the current value α _n in the _first buffer is stored in the second buffer as the previous value α _n-1 (step S8). Then, the process returns to step S1.

When it is determined in step S5 that the previous value α _n−1 in the second buffer is H (step S5: YES), the control circuit 14 determines that the previous value α _n−2 in the third buffer is L. It is discriminate | determined whether it is (step S6). When the previous value α _n−2 in the third buffer is not L (step S6: NO), the control circuit 14 sets the previous value α _n−1 in the second buffer as the previous value α _n−2 in the third buffer. (Step S7), the current value α _n in the _first buffer is stored in the second buffer as the previous value α _n-1 (step S8). Then, the process returns to step S1.

When it is determined in step S6 that the previous value α _n−2 in the third buffer is L (step S6: YES), the control circuit 14 determines that the zero-cross point at the rise of the induced voltage of the U phase or the W phase. Is detected. That is, when the previous value α _n−2 is L and the previous value α _n−1 and the current value α _n are both H, the control circuit 14 determines that the zero cross point at the rise of the induced voltage of the U phase or the W phase is Judge that it was detected. Then, the following processing is performed.

  After resetting the contents of the first to third buffers to the initial value H (step S9), the control circuit 14 stores the current time as the zero cross point (step S10). Next, the control circuit 14 calculates a zero cross interval T that is a time interval between the zero cross point detected last time and the zero cross point detected this time (step S11). Next, the control circuit 14 sets the standby time Tw and the energization time Td based on the zero cross interval T (step S12).

  Thereafter, the control circuit 14 waits for the standby time Tw to elapse (step S13). When the standby time Tw elapses (step S13: YES), the control circuit 14 turns on two switching elements corresponding to energization patterns different from the previous time (step S14). That is, when the previous energization pattern is the first energization pattern P1, the two switching elements SW2 and SW3 corresponding to the second energization pattern P2 are turned on. On the other hand, when the previous energization pattern is the second energization pattern P2, the two switching elements SW1 and SW4 corresponding to the first energization pattern P1 are turned on.

Thereafter, the control circuit 14 waits for the energization time Td to elapse (step S15). When the energization time Td elapses (step S15: YES), the two switching elements turned on in step S14 are turned off (step S16). Then, the process returns to step S1.
Next, a control method (hereinafter referred to as “second method”) for the two-phase brushless motor 2 in which the zero cross at the rise of the U-phase induced voltage and the W-phase induced voltage does not appear during the load will be described. If the zero cross point at the fall of the induced voltage of the W phase and the zero cross point at the fall of the induced voltage of the U phase can be detected, the same control as the first control circuit described above is performed based on the two zero cross points. Is possible.

Figure 7 is a waveform diagram showing the waveforms of the waveform and the W-phase voltage V _W of the U-phase voltage V _U in the case of controlling the switching elements SW1~SW4 by the second method.
In the waveform of the U-phase voltage V _U, the waveform in the energization time Td represents the U-phase drive voltage, the waveform of the other period shows a U-phase induced voltage. Similarly, the waveform of the W-phase voltage V _W, the waveform in the energization time Td represents the W-phase drive voltages, waveforms of the other periods represents the W-phase induced voltage.

  The control circuit 14 is one of the U-phase induced voltage and the W-phase induced voltage that tends to decrease every time the energization to the series circuit 5 of the stator coils 3 and 4 is interrupted after the two-phase brushless motor 2 is started. Detects the zero crossing point when the induced voltage falls. The control circuit 14 calculates a time interval (zero-crossing interval) T from the previous zero-crossing point every time a zero-crossing point when the induced voltage falls is detected. Then, based on the zero cross interval T, the control circuit 14 waits until the energization of the series circuit 5 of the stator coils 3 and 4 from the zero cross point is started, and the energization after the energization of the series circuit 5 is started. The energization time Td until stopping is determined. The waiting time Tw is set to T / 6, for example. The energization time Td is set to 2T / 3, for example.

  Referring to FIG. 7, control circuit 14 waits for waiting time Tw to elapse when a zero-cross point at the fall of the W-phase induced voltage is detected while energization to series circuit 5 is interrupted. When the standby time Tw elapses, the control circuit 14 turns on the two switching elements SW1 and SW4 so that the drive voltage corresponding to the first energization pattern P1 is applied to the motor 2. As a result, a drive current flows in the U + direction in the U-phase stator coil 3, and a drive current flows in the W− direction in the W-phase stator coil 4.

  When the energization time Td elapses, the control circuit 14 turns off the two switching elements SW1 and SW4. Thereafter, when the control circuit detects a zero-cross point at the fall of the U-phase induced voltage, it waits for the standby time Tw to elapse. When the standby time Tw elapses, the control circuit 14 turns on the two switching elements SW2 and SW3 so that the drive voltage corresponding to the second energization pattern P2 is applied to the motor 2. As a result, a drive current flows in the U− direction in the U-phase stator coil 3, and a drive current flows in the W + direction in the W-phase stator coil 4.

  When the energization time Td elapses, the first control circuit turns off the two switching elements SW2 and SW3. Thereafter, when the control circuit detects a zero-cross point at the fall of the W-phase induced voltage, it waits for the standby time Tw to elapse. When the standby time Tw elapses, the control circuit 14 turns on the two switching elements SW1 and SW4 so that the drive voltage corresponding to the first energization pattern P1 is applied to the motor 2. Thereafter, the control circuit 14 repeats the same operation. By such an operation, the stator coils 3 and 4 cause the magnetic fields corresponding to the current directions of “U +” and “W−” and the current directions of “U−” and “W +” depending on the rotational angle position of the rotor. Corresponding magnetic fields are alternately generated, and the rotor is rotated by these alternating magnetic fields. The starting method of the two-phase brushless motor 2 is the same as the starting method described above.

8 and 9 are flowcharts showing the operation of the control circuit 14 when the switching elements SW1 to SW4 are controlled by the second method.
The control circuit 14 has a first buffer, a second buffer, and a third buffer. The first buffer is used to store the current value of the output signal U _{OUT of} the first operational amplifier 21 or the output signal W _OUT of the second operational amplifier 22. The second buffer is used for storing the previous value of the output signal U _OUT or W _OUT . The third buffer is used to store the previous value of the output signal U _OUT or W _OUT . The initial value of these buffers is a value L corresponding to the L level of the output signal U _OUT or W _OUT .

The control circuit 14 determines the previous energization pattern (step S21). When the previous energization pattern is the first energization pattern P1, the control circuit 14 outputs the output signal U _{OUT of} the first operational amplifier 21 in order to detect the zero cross point at the fall of the U-phase induced voltage. Is stored in the first buffer as the current value α _n (step S22). Then, the process proceeds to step S24.

If it is determined in step S21 that the previous energization pattern is the second pattern P2, the control circuit 14 detects the zero cross point at the fall of the W-phase induced voltage in order to detect the second crossing point. The output signal W _OUT of the operational amplifier 22 is stored in the first buffer as the current value α _n (step S23). Then, the process proceeds to step S24.
In step S24, the control circuit 14 determines whether or not the current value α _n in the first buffer is L. When the current value α _n in the first buffer is not L (step S24: NO), the control circuit 14 stores the previous value α _n−1 in the second buffer as the previous value α _n−2 in the third buffer. After this (step S27), the current value α _n in the _first buffer is stored in the second buffer as the previous value α _n-1 (step S28). Then, the process returns to step S21.

When it is determined in step S24 that the current value α _n in the first buffer is L (step S24: YES), the control circuit 14 determines that the previous value α _n-1 in the second buffer is L. Whether or not (step S25). When the previous value α _n-1 in the second buffer is not L (step S25: NO), the control circuit 14 sets the previous value α _n-1 in the second buffer as the previous value α _n-2 in the third buffer. (Step S27), the current value α _n in the _first buffer is stored in the second buffer as the previous value α _n-1 (step S28). Then, the process returns to step S21.

When it is determined in step S25 that the previous value α _n−1 in the second buffer is L (step S25: YES), the control circuit 14 determines that the previous value α _n−2 in the third buffer is H. It is determined whether or not (step S26). When the previous value α _n−2 in the third buffer is not H (step S26: NO), the control circuit 14 sets the previous value α _n−1 in the second buffer as the previous value α _n−2 in the third buffer. (Step S27), the current value α _n in the _first buffer is stored in the second buffer as the previous value α _n-1 (step S28). Then, the process returns to step S21.

When it is determined in step S26 that the previous value α _n−2 in the third buffer is H (step S26: YES), the control circuit 14 performs zero crossing when the induced voltage of the U phase or W phase falls. It is determined that a point has been detected. That is, when the previous value α _n−2 is H and the previous value α _n−1 and the current value α _n are both L, the control circuit 14 determines the zero cross point at the time of falling of the induced voltage of the U phase or the W phase. Is detected. Then, the following processing is performed.

  After resetting the contents of the first to third buffers to the initial value L (step S29), the control circuit 14 stores the current time as the zero cross point (step S30). Next, the control circuit 14 calculates a zero cross interval T which is a time interval between the zero cross point detected last time and the zero cross point detected this time (step S31). Next, the control circuit 14 sets the standby time Tw and the energization time Td based on the zero cross interval T (step S32).

  Thereafter, the control circuit 14 waits for the standby time Tw to elapse (step S33). When the standby time Tw elapses (step S33: YES), the control circuit 14 turns on two switching elements corresponding to energization patterns different from the previous time (step S34). That is, when the previous energization pattern is the first energization pattern P1, the two switching elements SW2 and SW3 corresponding to the second energization pattern P2 are turned on. On the other hand, when the previous energization pattern is the second energization pattern P2, the two switching elements SW1 and SW4 corresponding to the first energization pattern P1 are turned on.

Thereafter, the control circuit 14 waits for the energization time Td to elapse (step S35). When the energization time Td elapses (step S35: YES), the two switching elements turned on in step S34 are turned off (step S36). Then, the process returns to step S21.
The present invention can be modified in various ways within the scope of the matters described in the claims.

  DESCRIPTION OF SYMBOLS 1 ... Control apparatus, 2 ... Two-phase brushless motor, 3 ... U-phase stator coil, 4 ... W-phase stator coil, 5 ... Series circuit, 12 ... Drive circuit, 13 ... Comparison circuit, 14 ... Control circuit, SW1-SW4 ... Switching element

Claims (3)

A control device for a two-phase brushless motor comprising a stator having a series circuit of a first-phase stator coil and a second-phase stator coil, and a rotor facing the stator,
A drive circuit including a plurality of switching elements for energizing / interrupting the series circuit and switching an energization pattern;
When energization to the series circuit is cut off, a reference voltage passing time point when the induced voltage corresponding to the first phase passes a predetermined reference voltage and an induced voltage corresponding to the second phase are A reference voltage passage time detection means for detecting a reference voltage passage time that is a point of passing the reference voltage;
Control means for controlling the plurality of switching elements based on a reference voltage passage time detected by the reference voltage passage time detection means,
The reference voltage passage time detection means is configured to alternately detect a reference voltage passage time when the induced voltage of the first phase rises and a reference voltage passage time when the induced voltage of the second phase rises. A control device for a two-phase brushless motor. A control device for a two-phase brushless motor comprising a stator having a series circuit of a first-phase stator coil and a second-phase stator coil, and a rotor facing the stator,
A drive circuit including a plurality of switching elements for energizing / interrupting the series circuit and switching an energization pattern;
When energization to the series circuit is cut off, a reference voltage passing time point when the induced voltage corresponding to the first phase passes a predetermined reference voltage and an induced voltage corresponding to the second phase are A reference voltage passage time detection means for detecting a reference voltage passage time that is a point of passing the reference voltage;
Control means for controlling the plurality of switching elements based on a reference voltage passage time detected by the reference voltage passage time detection means,
The reference voltage passage time detecting means alternately detects a reference voltage passage time when the induced voltage of the first phase falls and a reference voltage passage time when the induced voltage of the second phase falls. A control device for a two-phase brushless motor. The control means includes
Based on the time interval of the reference voltage passing time detected by the reference voltage passing time detecting means, the standby time from the reference voltage passing time to the start of energization of the series circuit, and the energization of the series circuit Setting means for setting the energization time from when the power is turned off until
The plurality of switching elements are controlled based on the reference voltage passage time detected by the reference voltage passage time detection means, the standby time and the energization time set by the setting means, and the previous energization pattern. And a control device for a two-phase brushless motor according to claim 1 or 2.

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