JP2009171738A - Motor drive device - Google Patents

Abstract

Provided is a motor drive device capable of performing a start-up sequence including deliberately setting a motor in an idling state after solving a problem related to detection of a counter electromotive voltage generated when the motor is in an idling state. .
Among motor coils 11U, 11V, and 11W, a terminal voltage of a certain one-phase coil and an average value of a neutral point voltage or a terminal voltage of another two-phase coil excluding a certain one-phase coil. A comparison unit 40 for comparison is provided. When the stopped motor is driven, the motor is temporarily set in the idling state after forcibly starting, but the comparison result by the comparison unit 40 is masked for a certain period immediately after the idling state.
[Selection] Figure 1

Description

  The present invention relates to a motor drive device, and among other brushless motors composed of a three-phase motor coil and a permanent magnet, drives a sensorless motor that does not require a position sensor such as a Hall element for measuring a rotor position. It is suitable for this.

In a brushless motor that does not have a mechanical contact between the rotor and stator, the position (rotation angle) of the rotor is measured by a position sensor such as a Hall element, and commutation is performed accordingly (the motor coil is energized). The motor is driven by changing the amount and polarity of the driving current to be changed). The sensorless motor is designed to reduce cost and size by omitting this position sensor.
In a sensorless motor, the position of the rotor is estimated regardless of the position sensor by utilizing the counter electromotive voltage generated in the rotating motor coil, and commutation is performed.

For example, in the method of Patent Document 1, a change in counter electromotive voltage is detected by comparing the terminal voltage of each phase coil with a reference voltage, and commutation is performed according to a time delay (phase adjustment). . However, the counter electromotive voltage does not occur when the motor is stopped. Therefore, when driving a motor that is stopped, first, forced commutation (also called synchronous operation or separately-excited operation) that energizes the motor coil regardless of the position of the rotor is performed. The procedure is such that the motor is forcibly accelerated to the detected number of revolutions, and then the driving is switched to the position detection by the back electromotive voltage.
Here, as a method of energizing a three-phase motor coil, a 120 ° rectangular wave driving method in which a rectangular wave current flows through the coil as shown in FIG. 11 and a sine wave current as shown in FIG. 180 ° sine wave drive system. In FIGS. 11 and 12, the positive and negative currents are determined so that the direction of flowing out from the driver to the motor coil is positive and the direction of flowing from the motor coil into the driver is negative. For example, at the position where the electrical angle is 90 ° in FIG. 12, current is supplied from the driver toward the U-phase coil, the current flows in two ways, the V-phase and W-phase coils, and returns to the driver. It is.

The 180 ° sine wave drive is superior in terms of vibration and noise compared to the 120 ° rectangular wave drive because there is no sudden change in current. In addition, in the 120 ° rectangular wave drive, there are only six energization states and the same state until the electrical angle changes by 60 °, whereas in the 180 ° sine wave drive, the energization state is different for each electrical angle. Determined uniquely. The more the energized state, the more types of balance between the magnetic field produced by the coil and the magnetic field of the permanent magnet (equivalent to micro-step driving of a stepping motor). Therefore, when performing the aforementioned forced commutation, 180 ° Energization with sine wave drive can be started more reliably. Nevertheless, forced commutation is often performed by 120 ° rectangular wave drive. This is because, even during forced commutation regardless of the position of the rotor, it is always confirmed whether the back electromotive voltage is detected, and 180 ° sine wave drive This is because the back electromotive voltage cannot be detected. This is because the detection of the counter electromotive voltage is performed in the non-energized (open) phase of the three-phase coil, and all three phases are always energized in the 180 ° sine wave drive.
In order to perform 180 ° sine wave drive with a sensorless motor, it is necessary to estimate the position of the rotor by a method other than the back electromotive force. For example, as disclosed in Patent Document 2, the current of each phase coil is detected. , And A / D-convert it, fetch it into the control unit, and calculate the rotor position. However, this not only complicates the processing, but also requires an A / D converter and an arithmetic processor, and the cost merit due to sensorlessness is lost.
Japanese Patent No. 2642357 Japanese Patent No. 3577245

  Therefore, for example, 180 ° rectangular wave drive is performed during forced commutation, and during this time, the counter electromotive voltage is not detected and the motor is driven for a predetermined time, and then the drive unit is completely At this point, the detection of the back electromotive force is started. Since all the three-phase coils are in a non-energized state during idling, the back electromotive voltage can be detected from any phase. After obtaining the back electromotive voltage in this way, it is conceivable to perform 120 ° rectangular wave driving while detecting the rotor position by the back electromotive voltage.

However, there are two problems in carrying out the start-up sequence including intentionally putting the motor in the idling state in this way.
The first problem is that the waveform of the back electromotive voltage seen at the coil terminal during idling is different from that seen at the non-energized coil terminal during 120 ° rectangular wave driving. The back electromotive force voltage cannot be detected correctly by a method that compares the coil terminal voltage with the reference voltage. This will be described with reference to FIGS.
FIG. 13 is a diagram illustrating a configuration of a driving unit of a general brushless motor driving circuit.
The drive unit 20 shown in FIG. 13 includes three high-side transistors 21U, 21V, and 21W and three low-side transistors 22U, 22V, and 22W. Diodes 23U, 23V, 23W, 24U, 24V, and 24W connected in parallel with each transistor are called free-wheeling diodes (freewheel diodes), and instead flow a regenerative current immediately after the transistors are turned off. It works to prevent the destruction of the transistor. The pre-drive circuit 30 determines currents to be supplied to the coils 11U, 11V, and 11W of the brushless motor (hereinafter simply referred to as “motor”) 10 by turning on and off the six transistors of the drive unit 20.

First, the coil terminal voltage during driving, that is, energization will be described.
In the 120 ° rectangular wave drive, one of the high-side transistors in FIG. 13 and one of the low-side transistors are turned on to energize. However, a combination (such as the high-side transistor 21U and the low-side transistor 22U) that allows a through current to flow through the drive unit 20 is not selected. For example, when the high-side transistor 21V and the low-side transistor 22W are turned on and the other four are turned off, the current flows along the path of power source → high-side transistor 21V → V-phase coil 11V → W-phase coil 11W → low-side transistor 22W → ground. Flows, and the U-phase coil 11U enters a non-energized state. FIG. 14 is an equivalent view of the state of the motor 10 and the drive unit 20 at this time.

The resistance R is a resistance component of the coil. For the sake of simplicity, the inductance component of the coil is ignored). Back electromotive voltages Eu, Ev, and Ew are generated in the coils, respectively. The voltage at the neutral point where the three-phase coils are connected to each other is Vn, and the coil terminal voltages on the opposite side to the neutral point are Vu, Vv, and Vw.
Since the V-phase coil is short-circuited with the power source, Vv = Vcc. Since the W-phase coil is short-circuited to the ground, Vw = 0. The U-phase coil is open. Let I be the current flowing from the power source to the ground via the V-phase coil and W-phase coil.
At this time, the neutral point voltage is obtained by dividing (Vcc-Ev) and (-Ew) by two resistors R, and can be calculated as follows.
Vn = (Vcc−Ev−Ew) / 2 (Formula 1)
Here, since the counter electromotive voltages Eu, Ev, and Ew are sine waves whose phases are shifted by 120 °, the value k (k ≧ 0) and the electrical angle θ (0 ° ≦ θ <360 °) proportional to the rotation speed are used. ) And is expressed as follows.
Eu = k × sin θ
Ev = k × sin (θ−120 °) (Expression 2)
Ew = k × sin (θ + 120 °)
At this time, the following relationship can be obtained by calculating using the properties of the trigonometric function.
Ev + Ew = −Eu (Formula 3)
Substituting (Equation 3) into (Equation 1) results in the following.
Vn = (Vcc + Eu) / 2 (Formula 4)
Further, since the current I does not flow through the U-phase coil, there is no voltage drop due to the resistance component, so the U-phase coil terminal voltage Vu is as follows.
Vu = Vn + Eu (Formula 5)
When Vn represented by (Expression 4) is applied to (Expression 5), it can be modified as follows.
Vu = Vcc / 2 + 3/2 × Eu (Expression 6)
= (Vv + Vw) / 2 + 3/2 × Eu (Expression 7)
Although the case where the U phase is in the open state is shown here, the same applies when the V phase or the W phase is in the open state.

Next, the coil terminal voltage during idling will be described.
That is, idling means that all the transistors of the drive unit 20 shown in FIG. 13 are turned off. FIG. 15 is an equivalent view of the state of the motor 10 and the drive unit 20 at this time.
The difference from FIG. 14 is that the coil terminal on the side opposite to the neutral point is connected to the ground (GND) via the free-wheeling diodes 24U, 24V and 24W.
In the circuit of FIG. 15, since no current flows and there is no voltage drop across the resistor, the following relationship is established.
Vn = Vu−Eu = Vv−Ev = Vw−Ew (Equation 8)
However, since there are the freewheeling diodes 24U, 24V, and 24W, the conditions of Vu ≧ 0, Vv ≧ 0, and Vw ≧ 0 are added to (Equation 8). This is because if the coil terminal voltage of each phase is going to be slightly lower than 0, the diode immediately conducts and the coil terminal is short-circuited to the ground. Although it is lower than 0 by the amount corresponding to the forward voltage drop of the diode, it is omitted here. Therefore, it is necessary to consider the coil terminal voltage in different cases. From (Equation 8) and (Equation 2), it is as follows.
Vu = 0 (when Vu = 0)
= Eu-Ev = √3 × k × cos (θ−60 °) (when Vv = 0) (Equation 9U)
= Eu-Ew = -√3 × k × cos (θ + 60 °) (when Vw = 0)
Vv = Ew−Eu = −√3 × k × cos (θ−60 °) (when Vu = 0)
= 0 (when Vv = 0) (Equation 9V)
= Ev-Ew = -√3 × k × cos θ (when Vw = 0)
Vw = Ew−Eu = √3 × k × cos (θ + 60 °) (when Vu = 0)
= Ew-Ev = √3 × k × cos θ (when Vv = 0) (Equation 9W)
= 0 (when Vw = 0)

Let us consider expressing the conditions for the cases of (Equation 9U), (Equation 9V) and (Equation 9W) as an electrical angle θ.
For example, (Equation 9U) means that when both the second equation Vu = Eu-Ev and the third equation Vu = Eu-Ew are smaller than 0, Vu = 0 does not have to be satisfied. It is that you do not get. Therefore, the condition for Vu = 0 is when k ≧ 0 is considered and cos (θ−60 °) ≦ 0 and −cos (θ + 60 °) ≦ 0 are satisfied, that is, the electrical angle θ is 210 °. It is obtained when ≦ θ ≦ 330 °. Similarly, the range of θ where Vv = 0 and Vw = 0 is obtained, and (Expression 9U), (Expression 9V), and (Expression 9W) are rewritten as follows.
Vu = 0 (210 ° ≦ θ <330 °)
= √3 × k × cos (θ−60 °) (0 ° ≦ θ <90 °, 330 ° ≦ θ <360 °) (Formula 10U)
= −√3 × k × cos (θ + 60 °) (90 ° ≦ θ <210 °)
Vv = −√3 × k × cos (θ−60 °) (210 ° ≦ θ <330 °)
= 0 (0 ° ≦ θ <90 °, 330 ° ≦ θ <360 °) (Formula 10V)
= −√3 × k × cos θ (90 ° ≦ θ <210 °)
Vw = √3 × k × cos (θ + 60 °) (210 ° ≦ θ <330 °)
= √3 × k × cos θ (0 ° ≦ θ <90 °, 330 ° ≦ θ <360 °) (Formula 10W)
= 0 (90 ° ≦ θ <210 °)

FIG. 16 and FIG. 17 show voltage waveforms during driving and idling derived as described above.
FIG. 16 is a diagram showing waveforms of the U-phase back electromotive force Eu (dotted line) and the U-phase coil terminal voltage Vu (solid line) during driving. FIG. 16A shows (Formula 2) and (Formula 6). ), K = 1 and Vcc = 4. FIG. 16B shows a case where k = 0.5, assuming a state in which the motor rotation speed is reduced and the back electromotive force is reduced. However, in FIG. 16, Vu is drawn so that it can be seen at all electrical angles θ, but it actually appears only when it is in a non-energized state.
FIG. 17 is a diagram showing waveforms of the U-phase back electromotive force Eu (dotted line) and the U-phase coil terminal voltage Vu (solid line) during idling, and FIG. 17 (a) shows (Equation 2) and (Equation 10U). ), K = 1 and Vcc = 4. FIG. 17B shows a case where k = 0.5, assuming a state in which the motor rotation speed is reduced and the back electromotive force is reduced.
For example, let us consider a case where it is desired to detect a position of θ = 0 ° and 180 °, which is a point where the polarity of the back electromotive force Eu is reversed (hereinafter referred to as “back electromotive zero cross point”).
16 (a) and 16 (b), it can be seen that it is only necessary to determine the reference voltage = Vcc / 2 = 2 and compare it with the coil terminal voltage Vu. This is also apparent from the form of (Equation 6).
On the other hand, in FIG. 17A, it is necessary to set the reference voltage to about 1V, and in FIG. 17B, it is necessary to set the reference voltage to about 0.5V. This means that in order to correctly detect the back electromotive force by comparing the coil terminal voltage and the reference voltage, the value of the reference voltage must be changed between driving and idling. In this case, it is necessary to change the value of the reference voltage depending on the motor speed. The above is the first problem.

The second problem is that the back electromotive voltage cannot be detected correctly because noise occurs in the coil terminal voltage immediately after starting the idling. This will be described with reference to FIGS.
It is known that when 120 ° rectangular wave driving is performed, noise is generated in the coil terminal voltage when a phase in an energized state is switched to a non-energized state. This is shown in FIG. 18 (only for one phase). The noise generated immediately after the start of idling, which is a problem now, has the same cause as the phase switching noise, that is, due to the action of maintaining the current flowing in the coil until just before the non-energized state.

Next, a mechanism for generating noise in the direction of V = 0 in FIG. 18 will be described with reference to FIGS.
FIG. 19A shows a state in which the high-side transistor 21U and the low-side transistor 22W are turned on, and a current flows through a path of power source → high-side transistor 21U → U-phase coil 11U → W-phase coil 11W → low-side transistor 22W → ground. FIG. Note that V-phase coils and transistors unnecessary for explanation are omitted. At this time, the U-phase coil 11U is short-circuited with the power source, so Vu = Vcc, and the W-phase coil is short-circuited with the ground (GND), so Vw = 0.

FIG. 19B shows a state immediately after the high-side transistor 21U is turned off from this state, and in order to maintain the current that was flowing in the coil until immediately before, the free-wheeling diode 24U is turned on instead of the high-side transistor 21U, Current flows through a path of ground (GND) → freewheeling diode 24U → U-phase coil 11U → W-phase coil 11W → low-side transistor 22W → ground. Since both the high-side transistor 21U and the low-side transistor 22U are OFF, the U-phase coil terminal should normally be opened and a counter electromotive voltage should appear, but Vu = 0 because the diode is short-circuited to the ground (correctly the diode As a result, this becomes noise generated in the coil terminal voltage Vu. This state continues until the current that has flowed until just before flows completely and the diode becomes non-conductive.
This noise has a large amplitude, and always causes false detection when a method of detecting a counter electromotive voltage by comparing a coil terminal voltage with a reference voltage.

However, since it is known that the noise generation period is after the energized phase is set to the non-energized state, a method of preventing false detection by not detecting the back electromotive voltage during the corresponding period is widely used. Has been.
Since all of the transistors in the drive unit are turned off for idling, as in the case described above, the diode is turned on to pass the current that was flowing just before turning off, and noise is generated in the coil terminal voltage. In order to prevent erroneous detection of the back electromotive voltage, this noise must also be removed. This is the second problem.
An object of the present invention is to provide a motor drive device capable of performing a start-up sequence including intentionally putting a motor in an idle state after solving the above-mentioned two problems that occur when the motor is in an idle state. It is to be.

  In order to achieve the above object, the present invention according to claim 1 is a motor drive device for driving a brushless motor composed of a three-phase motor coil and a permanent magnet, and is driven by the three-phase motor coil. A drive unit that drives by energizing current, a terminal voltage of a certain one-phase coil among the three-phase motor coils, and a neutral point voltage or a terminal of another two-phase coil excluding the certain one-phase coil A comparison unit that compares an average value of the voltages; a mask generation unit that generates a mask signal for removing noise included in the comparison result signal by the comparison unit; and a phase of the comparison result signal masked by the mask signal A phase adjustment unit that generates a position signal by adjusting the motor, a rotation number detection unit that detects a motor rotation number, a target motor rotation number, and a motor rotation number at the time detected by the rotation number detection unit Based on the controller, and outputs a control signal for controlling the motor rotation speed, determines the energization phase of the motor coil based on the position signal, and determines the amount of current energized based on the control signal. A rectangular wave generator for applying a rectangular wave current to the motor coil via the drive unit, and a sine to the motor coil via the drive unit for an arbitrary time with an arbitrary frequency and an arbitrary amount of current. When driving a motor that is stopped, comprising a sine wave generator for energizing a wave-like current, and a selector for connecting either the rectangular wave generator or the sine wave generator to a drive unit The sine wave generator drives the drive unit for an arbitrary period of time to forcibly start the motor, and then temporarily stops the drive unit to cause the motor to idle, and during the idling period, the phase Key After the position signal is output from the unit, the driving unit is driven by the rectangular wave generating unit, and the mask generating unit switches the energized phase immediately after the motor is idled and the rectangular wave generating unit The generation of the mask signal is started immediately after, and the generation of the mask signal is stopped after an arbitrary time has elapsed.

  According to a second aspect of the present invention, in the motor control device according to the first aspect, the arbitrary time during which the mask generation unit generates the mask signal is the time output from the rotation speed detection unit. The time is variable according to the motor rotation speed.

  The present invention according to claim 3 is a motor driving device for driving a brushless motor constituted by a three-phase motor coil and a permanent magnet, and is driven by supplying a driving current to the three-phase motor coil. Compare the drive unit and the terminal voltage of a certain one-phase coil of the three-phase motor coil and the average value of the neutral point voltage or the terminal voltage of the other two-phase coils excluding the certain one-phase coil. A comparison unit, a mask generation unit for generating a mask signal for removing noise included in the comparison result signal by the comparison unit, and a position signal by adjusting a phase of the comparison result signal masked by the mask signal A phase adjustment unit to be generated, a rotation number calculation unit that calculates a motor rotation number based on the position signal, a target motor rotation number, and a motor rotation number at the time calculated by the rotation number calculation unit; Based on the control unit that outputs a control signal for controlling the motor rotation speed, the energization phase of the motor coil is determined based on the position signal, and the current amount to be energized is determined based on the control signal. A rectangular wave generator for applying a rectangular wave current to the motor coil via the drive unit, and a sine wave for the motor coil via the drive unit for an arbitrary time at an arbitrary frequency and an arbitrary amount of current. When driving a motor that is stopped, the sine wave generation unit that energizes the current and a selection unit that connects either the rectangular wave generation unit or the sine wave generation unit to the drive unit, The drive unit is driven for an arbitrary time by the sine wave generation unit to forcibly start the motor, and then the drive unit is temporarily stopped to cause the motor to idle, during the idle period. phase After the position signal is output from the adjusting unit, the rectangular wave generating unit drives the driving unit, and the mask generating unit starts generating the mask signal immediately after the motor is idled. Stop generation of the mask signal after elapse of time, and start generation of the mask signal immediately after the rectangular wave generation unit switches the energized phase, and the motor rotation at the time calculated by the rotation number calculation unit The generation of the mask signal is stopped after the elapse of an arbitrary time different from the above, which is variable according to the number.

  According to a fourth aspect of the present invention, in the motor control device according to any one of the first to third aspects of the present invention, the motor control device further includes a chattering removing unit for removing chattering generated in the comparison result signal. When the width of the comparison result signal is less than an arbitrary reference signal width, the comparison result signal is ignored, and the phase adjustment performed by the phase adjustment unit by an amount corresponding to the arbitrary reference signal width The correction is made in the direction of decreasing the amount.

According to the present invention, the configuration of the comparison unit compares the terminal voltage of a certain one-phase motor coil with the neutral point voltage or the average value of the terminal voltages of other two-phase coils excluding a certain one-phase coil. By solving this problem, and by masking the comparison results from the comparison unit for a certain period immediately after the motor is idling, the problem of the backlash zero-cross point not being detected correctly during idling can be solved. It becomes possible to perform a start-up sequence including intentionally setting the idling state.
According to the present invention, the rotation speed calculation unit that calculates the motor rotation speed based on the position signal is provided, and the mask period is set to an arbitrary fixed time that does not depend on the rotation speed immediately after the idling when the motor rotation speed is unknown. As a result, even a motor that does not have a speed sensor, such as FG, can be driven, so that the cost can be further reduced without the speed sensor.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a diagram illustrating a configuration example of a motor control device according to a first embodiment of the present invention.
In FIG. 1, the motor 10 includes motor coils 11 </ b> U, 11 </ b> V, and 11 </ b> W and an FG (Frequency Generator) 16. The FG 16 detects the rotation speed of the motor 10.
The drive unit 20 includes three high side transistors 21U, 21V, and 21W and three low side transistors 22U, 22V, and 22W. Diodes 23U, 23V, 23W, 24U, 24V, and 24W connected in parallel with each transistor are freewheeling diodes (freewheel diodes), and instead of flowing a regenerative current immediately after the transistors are turned off, It works to prevent transistor breakdown.
The comparison unit 40 compares the terminal voltages of the motor coils 11U, 11V, and 11W of the motor 10 and outputs a comparison result signal. The internal configuration of the comparison unit 40 will be described later.
The mask generation unit 50 generates a mask signal only for a time determined by an arbitrary mask time setting, and prevents a change in the comparison result signal from passing during the mask period, so that noise included in the comparison result signal Remove.

The phase adjustment unit 60 adjusts the phase of the masked comparison result signal and outputs a position signal indicating the position of the rotor.
The control unit 70 outputs a control signal for rotating the motor at the target rotational speed based on the target motor rotational speed and the motor rotational speed at the time detected by the FG 16.
The rectangular wave generator 80 switches the ON / OFF state of the transistor in the drive unit 20 so that a rectangular wave current is supplied to the motor coils 11U, 11V, and 11W. Is determined based on the position signal, and the amount of current is determined based on the control signal.
The sine wave generation unit 90 switches the ON / OFF state of the transistor in the drive unit 20 so that a sine wave current is supplied to the motor coils 11U, 11V, and 11W. The current frequency, current amount, and energization time can be set arbitrarily.
The selection unit 100 selects only one output of the rectangular wave generation unit 80 or the sine wave generation unit 90 and connects it to the transistor in the drive unit 20.

2A, 2B, and 2C are diagrams showing the internal configuration of the comparison unit 40. FIG.
2A, 2B, and 2C, the comparison unit 40 includes three comparators 41U, 41V, and 41W and a plurality of resistors.
It is assumed that the resistance values of all the resistors are sufficiently larger than the resistance components of the motor coils 11U, 11V, and 11W of the motor 10, and almost all of the current output from the drive unit flows through the motor coils. In addition, it is assumed that resistors with the same subscripts have the same resistance value.
The input signals of the comparison unit 40 are motor coil terminal voltages Vu, Vv, and Vw, and the output signals are comparator outputs Cu, Cv, and Cw.

FIG. 2A shows a configuration that is possible when a motor that outputs a neutral point voltage Vn is used, and that Vn is also added to the input signal of the comparison unit 40. Resistors R1 and R2 are provided to divide the coil terminal voltage and neutral point voltage so that they are within the input voltage range of the comparator used.
Each of the comparators 41U, 41V, 41W compares the coil terminal voltage of each phase with the neutral point voltage. With this configuration, the back electromotive voltage can be correctly detected during driving and idling.
First, consider a 120 ° rectangular wave drive. As shown in FIG. 14, it is assumed that the V-phase coil is short-circuited to the power source, the W-phase coil is short-circuited to the ground, and the U-phase coil is open.
In the U phase where the drive current does not flow, the above-described (Formula 5) is established.
When the above (formula 5) is transformed,
Vu−Vn = Eu (Expression 5) ′
Therefore, it can be understood that the back electromotive zero-cross point can be detected by comparing the terminal voltage of the coil in the open state and the neutral point voltage with a comparator.

Next, let's think about idling.
Each phase coil terminal voltage during idling is as shown in the above (Formula 10U) (Formula 10V) (Formula 10W).
The neutral point voltage Vn during idling is as follows from the above (Formula 2) (Formula 8) and the above (Formula 10U) (Formula 10V) (Formula 10W).
Vn = Vu−Eu = −k × sin θ (210 ° ≦ θ <330 °)
= Vv−Ev = −k × sin (θ−120 °) (0 ° ≦ θ <90 °, 330 ° ≦ θ <360 °) (Equation 11)
= Vw−Ew = −k × sin (θ + 120 °) (90 ° ≦ θ <210 °)
FIG. 3 and FIG. 4 show voltage waveforms during driving and idling derived as described above.

FIG. 3 is a diagram illustrating waveforms of the U-phase counter electromotive voltage Eu (dotted line), the U-phase coil terminal voltage Vu (solid line), and the neutral point voltage Vn (x mark) during driving.
FIG. 3A shows the case where k = 1 and Vcc = 4 in (Expression 2), (Expression 4), and (Expression 5). FIG. 3B shows a case where k = 0.5 assuming a state in which the motor rotation speed is reduced and the back electromotive force is reduced. However, in FIG. 3, the drawing is made so that Vu can be seen at all the electrical angles θ, but it actually appears only in the non-energized state.
FIG. 4 is a diagram showing waveforms of the U-phase counter electromotive voltage Eu (dotted line), the U-phase coil terminal voltage Vu (solid line), and the neutral point voltage Vn (x mark) during idling.
FIG. 4A shows a case where k = 1 and Vcc = 4 in (Expression 2) (Expression 10U) (Expression 11). FIG. 4B shows a case where k = 0.5 assuming a state in which the motor rotation speed is reduced and the back electromotive force is reduced.
3 (a) (b) and 4 (a) (b), the magnitude of the back electromotive force has changed due to the change in the number of revolutions during driving or idling. However, it can be seen that the intersection of the U-phase coil terminal voltage Vu and the neutral point voltage Vn is the zero-cross point of the U-phase counter electromotive voltage. That is, if the configuration of the comparison unit 40 is as shown in FIG. 2A, it is possible to detect the back electromotive zero-cross point without fail.

FIG. 2B is a configuration for obtaining the same effect even when a motor that does not output the neutral point voltage Vn is used. The resistor R3 is for generating a virtual neutral point Vn ′.
Each comparator 41U, 41V, 41W compares the coil terminal voltage of each phase with the above-mentioned virtual neutral point Vn ′. It is desirable to select a value such that 3 × R4 = R3 in consideration of the balance of input resistance to both input terminals of the comparators 41U, 41V, 41W.
The voltage of the virtual neutral point Vn ′ is expressed as follows using each phase coil terminal voltage.
Vn ′ = (Vu + Vv + Vw) / 3 (Formula 12)
Consider the relationship between the neutral point Vn and the virtual neutral point Vn ′.
First, consider a 120 ° rectangular wave drive.
As shown in FIG. 14, the V-phase coil is short-circuited to the power source, the W-phase coil is short-circuited to the ground, and the U-phase coil is open.
Since (Equation 4) and (Equation 5) hold when the U phase is in an open state, (Equation 12) is as follows.
Vn ′ = {(Vn + Eu) + Vcc + 0} / 3
= (Vcc + Eu) / 6 + Eu / 3 + Vcc / 3
= (Vcc + Eu) / 2
= Vn

Next, consider the idling. Since (Equation 8) holds during idling, (Equation 12) becomes as follows.
Vn ′ = {(Vn + Eu) + (Vn + Ev) + (Vn + Ew)} / 3
= Vn + (Eu + Ev + Ew) / 3
Since the back electromotive voltages Eu, Ev, and Ew are in the relationship of (Equation 2), Eu + Ev + Ew = 0, so that
Vn ′ = Vn
Eventually, Vn ′ = Vn is established during driving and idling.
That is, if the configuration of the comparison unit 40 is as shown in FIG. 2B, the same effect as that obtained when the configuration of FIG.

FIG.2 (c) is a more effective structure than FIG.2 (a) (b).
The resistor R5 is for generating an average value of a certain two-phase coil terminal voltage.
For example, the comparator 41U compares the U-phase coil terminal voltage with the average value of the V-phase and W-phase coil terminal voltages. It should be noted that it is desirable to select a value such that 2 × R6 = R5 in consideration of the balance of input resistance to both input terminals of each comparator 41U, 41V, 41W.
First, consider a 120 ° rectangular wave drive. As shown in FIG. 14, the V-phase coil is short-circuited to the power source, the W-phase coil is short-circuited to the ground, and the U-phase coil is open.
In the U phase where the drive current does not flow, the above-described (Expression 7) is established. When (Equation 7) is transformed,
Vu− (Vv + Vw) / 2 = 3/2 × Eu (Expression 7) ′
Therefore, it can be seen that the back electromotive zero-cross point can be detected by comparing the average value of the terminal voltage of the open coil and the terminal voltages of the other two phases with a comparator.

Next, let's think about idling.
The U-phase coil terminal voltage during idling is as shown in (Equation 10U).
The average values of the V-phase and W-phase coil terminal voltages during idling are as follows from (Equation 10V) (Equation 10W).
(Vv + Vw) / 2 = −3 / 2 × k × sin θ (210 ° ≦ θ <330 °)
= (√3) / 2 × k × cos θ (0 ° ≦ θ <90 °, 330 ° ≦ θ <360 °) (Equation 12)
=-(√3) / 2 × k × cos θ (90 ° ≦ θ <210 °)
FIG. 5 and FIG. 6 show voltage waveforms during driving and idling derived as described above.

FIG. 5 shows the U-phase back electromotive force Eu (dotted line), the U-phase coil terminal voltage Vu (solid line), and the average value of the V-phase and W-phase coil terminal voltages (Vv + Vw) / 2 (circles). It is the figure which showed the waveform.
FIG. 5A shows the case where k = 1 and Vcc = 4 in (Expression 2) and (Expression 7). FIG. 5B shows a case where k = 0.5 assuming a state in which the motor rotation speed is reduced and the back electromotive force is reduced. However, in FIG. 5, Vu is shown so that it can be seen at all electrical angles θ, but it actually appears only in a non-energized state.
FIG. 6 shows the U-phase back electromotive force Eu (dotted line), the U-phase coil terminal voltage Vu (solid line), and the average value (Vv + Vw) / 2 (circle) of the V-phase and W-phase coil terminal voltages during idling. It is the figure which showed the waveform.
FIG. 6A shows the case where k = 1 and Vcc = 4 in (Expression 2) (Expression 10U) (Expression 12). FIG. 6B shows a case where k = 0.5 assuming a state in which the motor rotation speed is reduced and the back electromotive force is reduced.
5 (a) (b) and 6 (a) (b), it is assumed that the back electromotive force has changed due to the change in the number of revolutions during driving or idling. It can also be seen that the intersection of the U-phase coil terminal voltage Vu and the neutral point voltage Vn is the zero-cross point of the U-phase back electromotive voltage. That is, if the configuration of the comparison unit is as shown in FIG. 2C, it is possible to detect the back electromotive zero-cross point without fail.
Further, comparing FIGS. 3 to 6, it can be seen that the way of adopting the configuration of FIG. 2C is sharper in the way of intersection at the intersection, but this is advantageous in making comparison with a comparator. Therefore, it can be said that the configuration of FIG. 2C is more effective than FIGS. 2A and 2B.
This is the description of the configuration of the motor drive device according to the first embodiment.

Next, the operation of the motor drive device according to the first embodiment will be described with reference to FIG.
FIG. 7 shows signals of respective parts of the motor control device having the configuration shown in FIG. The horizontal axis represents time, and the flow from the start of the motor to the transition to 120 ° rectangular wave drive will be described. In addition, although the coil terminal voltage etc. before the time t1 are not illustrated in FIG. 7, these are omitted because they are not necessary for the description.
Before starting the motor, the selection unit 100 selects the sine wave generation unit 90 and connects it to the transistor in the drive unit 20.
When starting the motor at time t0, the sine wave generator 90 applies a sine wave current to the motor coil to perform forced commutation. At a time t1 when a predetermined time has elapsed, all the transistors in the drive unit 20 are turned off, and the motor is idled. At this time t1, the detection of the back electromotive zero-cross point is started, but noise is generated in the coil terminal voltage at the moment when the transistor is turned off (in the example of FIG. 7, Iu flows out to the motor). Yes, since the transistors are turned off when Iv and Iw are in the direction of flowing into the drive unit, noises of Vu = 0 and Vv = Vw = Vcc are generated at the same time). 40, the comparison result signals Cu, Cv, and Cw also appear.

Therefore, the mask generation unit 50 generates a mask signal for a certain period of time immediately after the start of idling, and obtains Mu, Mv, and Mw from which noise has been removed by preventing the comparison result signal from changing. Yes.
The phase adjustment unit 60 adjusts the phases of Mu, Mv, and Mw and outputs position signals Pu, Pv, and Pw.
At time t2 when any one of the position signals is obtained, it is considered that the back electromotive voltage has been successfully detected, and the selection unit 100 selects the rectangular wave generation unit 80 and connects it to the driving unit 20 to perform 120 ° rectangular wave driving. Start. During the 120 ° rectangular wave drive, the energized phase is switched each time one of the position signals changes, and at the same time, mask generation is started.
In FIG. 7, the phase adjustment unit 60 is illustrated so as to adjust the phase only for a time corresponding to an electrical angle of about 30 °. However, this is because the phase of the energized phase is delayed by about 30 ° in electrical angle from the back electromotive zero cross point. This is only done because the motor efficiency is improved when switching, and it is not particularly limited to 30 °.
By using the motor control device having such a configuration and operation, it is possible to solve the problem that the back-electromotive zero cross point cannot be detected correctly during idling, and to perform a start-up sequence including intentionally causing the motor to idle. It becomes like this.

Next, a motor control device according to a second embodiment will be described.
The configuration of the motor control device of the second embodiment is the same as that of the first embodiment shown in FIG. 1, and is obtained from the FG 16 when setting an arbitrary mask time in the mask generation unit 50. The time is determined according to the motor rotation speed at the time.
As described above, the period in which noise is generated in the coil terminal voltage immediately after the start of idling or after the switching of the energized phase is a period until the current that has flowed immediately before the coil terminal voltage completely flows. The speed at which the current decreases depends on the electrical time constant (= τe = L / R, L: coil inductance component, R: coil resistance component) inherent to the motor. In a situation where the amount of current is large, the period during which noise is generated becomes longer.
A situation requiring a large amount of current is a situation immediately after startup or during acceleration, that is, a situation where the actual motor speed is lower than the target motor speed.
Therefore, in the motor control device of the second embodiment, if the mask period is made longer as the motor rotation speed obtained from the FG 16 is lower than the target rotation speed, noise can be reliably removed.
By doing in this way, it becomes possible to drive a motor more stably compared with the motor control device of the first embodiment.

Next, a motor control device according to a third embodiment will be described.
FIG. 8 is a diagram illustrating a configuration example of the motor control device according to the third embodiment.
The motor control apparatus according to the third embodiment enables driving even a motor 10 that does not have a speed sensor for detecting the motor rotation speed, such as the FG 16 in FIG.
There are two differences from the configuration of the motor control device of the first embodiment.
One is that a rotation speed calculation unit 110 that calculates the motor rotation speed based on the position signal is added, and the calculated motor rotation speed as a calculation result is input to the control unit 70.
The position signal is generated based on the comparison result by the comparison unit 40, in other words, the detected back electromotive zero cross point, and how many times the back electromotive zero cross point is detected per one rotation of the motor depends on the number of magnetic poles of the motor. Since it is determined, the motor speed can be easily calculated from the position signal.

The second difference is that two types of mask times set for the mask generation unit 50 are prepared, one for a mask immediately after the start of idling and one for a mask after switching the energized phase.
This corresponds to the fact that, in the third embodiment, since the counter electromotive voltage is not detected in the forced commutation period after startup, the motor speed cannot be calculated immediately after the idling is started. That is, immediately after the start of idling when the motor rotation speed is unknown, the mask generation time is set to an arbitrary fixed time regardless of the rotation speed, and the mask generation time after switching the energized phase is (this Since the counter electromotive voltage is detected at the time and the motor speed is also calculated)) As in the second embodiment, a longer time is set so that the actual motor speed is lower than the target speed. And By doing so, it becomes possible to drive even a motor that does not have a speed sensor for detecting the number of rotations of the motor such as FG, and not only the position sensor but also the speed sensor can be omitted. Cost reduction is possible.

Next, a motor control device according to a fourth embodiment will be described.
FIG. 9 is a diagram illustrating a configuration example of the motor control device according to the fourth embodiment.
The motor control device of the fourth embodiment has a configuration in which a chattering removal unit 130 is provided between the comparison unit 40 and the mask generation unit 50 of the motor control device of the first embodiment.
The chattering removal unit 130 removes chattering noise that may occur in the comparison result signal of the comparison unit 40.
The chattering removal unit 130 may be provided between the mask generation unit 50 and the phase adjustment unit 60. The second and third motor control devices may have the same configuration.

FIG. 10 is an explanatory diagram of the operation of the motor control device of the fourth embodiment.
Here, the configuration of the comparison unit 40 in FIG. 9 is the configuration shown in FIG. 2C, and the case where Vu is compared with (Vv + Vw) / 2 by the comparator 41U will be described. There is no difference in explanation.
When the two signals Vu and (Vv + Vw) / 2 are compared by the comparator in the comparison unit, there is a possibility that so-called chattering occurs in which the comparison result signal Cu is frequently switched when the two are close in magnitude. This chattering causes erroneous detection of the back electromotive zero-cross point, so it is necessary to remove it.
In order to eliminate chattering, there is a method of ignoring a signal whose level is constant at “H” or “L” for a short time, in other words, a thin pulse signal is judged to be noise. . The chattering removing unit 130 of claim 4 also adopts this method.
That is, every time the comparison result signal Cu changes, it is checked whether or not the signal level after the change continues for an arbitrary reference signal width Ts. In this case, it is determined that the signal is correct and is output as a chattering removal result Cu ′. However, this method has a side effect that a delay of Ts occurs between the change of Cu and the change of Cu ′. Further, since the position signal Pu is generated by adjusting the phase of Cu ′, a delay is propagated to Pu. Since the switching of the energized phase is performed at the timing when the position signal is changed, the switching of the energized phase is delayed, resulting in a decrease in motor efficiency.

Therefore, in the motor control device of the fourth embodiment, the phase adjustment amount performed by the phase adjustment unit 60 is compared with that performed by the first embodiment according to an arbitrary reference signal width Ts set in the chattering removal unit 130. The direction of decrease was corrected.
In FIG. 10, the phase adjustment amount is drawn so as to be reduced by the same amount as Ts, but the present invention is not limited to this. Since the switching timing of the energized phase becomes slower as the chattering generation period is longer, it is conceivable that the phase adjustment amount is reduced more than Ts.
As described above, according to the motor control device of the fourth embodiment, the chattering removal unit that removes chattering that occurs in the comparison result is provided, and the phase adjustment amount in the phase adjustment unit is reduced in consideration of the side effects of the chattering removal process. By doing so, it is possible to eliminate chattering to prevent erroneous detection of the back electromotive zero-cross point, and to prevent side effects that reduce motor efficiency.

It is a figure showing an example of composition of a motor control device concerning a 1st embodiment of the present invention. It is the figure which showed the internal structure of the comparison part. It is the figure which showed the waveform of U phase back electromotive force Eu during driving, U phase coil terminal voltage Vu, and neutral point voltage Vn. It is the figure which showed the waveform of the U-phase back electromotive force Eu, the U-phase coil terminal voltage Vu, and the neutral point voltage Vn during idling. It is the figure which showed the waveform of the average value (Vv + Vw) / 2 of the U phase back electromotive force Eu during driving, the U phase coil terminal voltage Vu, and the coil terminal voltage of V phase and W phase. It is the figure which showed the waveform of the average value (Vv + Vw) / 2 of the U-phase counter electromotive voltage Eu during idle, U-phase coil terminal voltage Vu, and V-phase and W-phase coil terminal voltage. It is operation | movement explanatory drawing of the motor drive device of 1st Embodiment. It is the figure which showed the structural example of the motor control apparatus of 3rd Embodiment. It is the figure which showed the structural example of the motor control apparatus of 4th Embodiment. It is operation | movement explanatory drawing of the motor control apparatus of 4th Embodiment. It is the figure which showed each phase coil current waveform at the time of a rectangular wave drive. It is the figure which showed each phase coil current waveform at the time of a sine wave drive. It is the figure which showed the structure of the drive part of a general brushless motor drive circuit. It is the figure which equivalently represented the mode of the motor and drive part when the high side transistor 21V and low side transistor 22W which are shown in FIG. 13 were turned ON. It is the figure which equivalently represented the mode of the motor and drive part when all the transistors of the drive part shown in FIG. It is the figure which showed the voltage waveform in drive. It is the figure which showed the voltage waveform during idling. It is explanatory drawing of the noise which generate | occur | produces at the time of the phase switch during a 120 degree rectangular wave drive. It is explanatory drawing of the mechanism in which the noise of the direction of V = 0 in FIG. 18 generate | occur | produces.

Explanation of symbols

  11U, 11V, 11W ... motor coil, 20 ... drive unit, 21U, 21V, 21W ... high side transistor, 22U, 22V, 22W ... low side transistor, 23U, 23V, 23W, 24U, 24V, 24W ... diode, 30 ... pre Drive circuit 40 ... comparison unit 41U, 41V, 41W ... comparator 50 ... mask generation unit 60 ... phase adjustment unit 70 ... control unit 80 ... rectangular wave generation unit 90 ... sine wave generation unit 100 ... selection 110, rotational speed calculator, 130 ... chattering removal unit

Claims (4)

A motor driving device for driving a brushless motor composed of a three-phase motor coil and a permanent magnet,
A drive unit that drives the three-phase motor coil by energizing a drive current;
A comparison unit that compares a terminal voltage of a certain one-phase coil of the three-phase motor coils with a neutral point voltage or an average value of terminal voltages of other two-phase coils excluding the certain one-phase coil; ,
A mask generation unit that generates a mask signal for removing noise included in the comparison result signal by the comparison unit;
A phase adjustment unit that adjusts the phase of the comparison result signal masked by the mask signal to generate a position signal;
A rotation speed detection unit for detecting the motor rotation speed;
A control unit that outputs a control signal for performing motor rotation number control based on the target motor rotation number and the motor rotation number at the time detected by the rotation number detection unit;
The energization phase of the motor coil is determined based on the position signal, and the amount of current to be energized is determined based on the control signal, and then a rectangular wave current is energized to the motor coil via the drive unit. A rectangular wave generator,
A sine wave generator for energizing the motor coil with a sinusoidal current through the drive unit for an arbitrary time at an arbitrary frequency and an arbitrary amount of current;
A selection unit that connects either the rectangular wave generation unit or the sine wave generation unit to a drive unit, and
When driving a stopped motor, the sine wave generator drives the drive unit for an arbitrary period of time to forcibly start the motor, and then temporarily stops the drive unit to make the motor idle. After the position signal is output from the phase adjustment unit during the idling period, the driving unit is driven by the rectangular wave generation unit,
Further, the mask generation unit starts generating the mask signal immediately after the motor is idled and immediately after the rectangular wave generation unit switches the energized phase, and stops generating the mask signal after an arbitrary time has elapsed. The motor drive device characterized by this.   2. The motor control device according to claim 1, wherein an arbitrary time during which the mask generation unit generates a mask signal is variable in accordance with a motor rotation number at the time output from the rotation number detection unit. A motor drive device characterized by time. A motor driving device for driving a brushless motor composed of a three-phase motor coil and a permanent magnet,
A drive unit that drives the three-phase motor coil by energizing a drive current;
A comparison unit that compares a terminal voltage of a certain one-phase coil of the three-phase motor coils with a neutral point voltage or an average value of terminal voltages of other two-phase coils excluding the certain one-phase coil; ,
A mask generation unit that generates a mask signal for removing noise included in the comparison result signal by the comparison unit;
A phase adjustment unit that adjusts the phase of the comparison result signal masked by the mask signal to generate a position signal;
A rotation speed calculation unit for calculating a motor rotation speed based on the position signal;
A control unit that outputs a control signal for performing motor rotation number control based on the target motor rotation number and the motor rotation number at the time calculated by the rotation number calculation unit;
The energization phase of the motor coil is determined based on the position signal, and the amount of current to be energized is determined based on the control signal, and then a rectangular wave current is energized to the motor coil via the drive unit. A rectangular wave generator,
A sine wave generator for energizing the motor coil with a sinusoidal current through the drive unit for an arbitrary time at an arbitrary frequency and an arbitrary amount of current;
A selection unit that connects either the rectangular wave generation unit or the sine wave generation unit to a drive unit, and
When driving a stopped motor, the sine wave generator drives the drive unit for an arbitrary time to forcibly start the motor, and then the drive unit is temporarily stopped to stop the motor. Let the idle state, after the position signal is output from the phase adjustment unit during the idle period, drive the drive unit by the rectangular wave generation unit,
Further, the mask generator starts generating a mask signal immediately after the motor is idled, stops generating the mask signal after an arbitrary time has elapsed, and the rectangular wave generator switches the energized phase. The generation of the mask signal is started immediately after, and the generation of the mask signal is stopped after the elapse of an arbitrary time different from the above, which is variable according to the motor rotation number at the time calculated by the rotation number calculation unit. The motor drive device characterized by the above-mentioned. In the motor control device according to any one of claims 1 to 3,
A chattering removing unit for removing chattering generated in the comparison result signal;
The chattering removal unit ignores the comparison result signal when the width of the comparison result signal is less than an arbitrary reference signal width, and further, the phase is increased by an amount corresponding to the arbitrary reference signal width. A motor driving device that corrects in a direction to reduce the amount of phase adjustment performed by the adjustment unit.

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