JP2008283782A - Motor driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make an effective value zero when an average value of currents flowing in coils wired independently is zero. <P>SOLUTION: A drive signal generation device 4 of a motor driving device comprises three signal generation portions 31, 32, 33 for the coils of a motor. The first signal generation portion 31 has a first drive signal generation circuit 41 and a second drive signal generation circuit 42. The first drive signal generation circuit 41 makes a first drive signal, which drives switching elements of one arm of an H bridge circuit controlling the currents flowing in the coils. The second drive signal generation circuit 42 makes a second drive signal, whose phase is shifted by 120° to the first drive signal as a drive signal, which drives switching elements of the other arm of the H bridge circuit controlling the currents flowing in the coils. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a motor driving device including a circuit for driving a motor.

For the connection of the motor coil, the star type and the delta type are known, but unlike these, the coils of each phase may be wired independently. Such an independent connection has an advantage that the current flowing through the coil can be controlled for each phase. A conventional example of a circuit for supplying a current to an independently connected coil is disclosed in Patent Document 1, for example. In this circuit, an H-bridge circuit is formed by using transistors, and two transistors arranged diagonally of the H-bridge circuit are ON / OFF controlled with the same PWM (pulse width modulation) signal, so that the coil is connected. The current flow and current direction were controlled. When the current flowing through the coil is set to zero, the average value of the current flowing through the coil is set to zero by alternately passing a positive current and a negative current through the coil.
JP 2004-180410 A

However, in the conventional method in which currents having different polarities are alternately flowed, the average value of the current can be made zero, but since the effective value of the current does not become zero, power is consumed by the resistance component of the coil. For this reason, it has been difficult to suppress the heat generation of the motor. Note that, as shown in FIG. 7 of Patent Document 1, if the output destination of the drive signal is switched to one of the two by switching the switch, current in the opposite direction can be prevented from flowing, but the current fluctuation increases. Therefore, it has been difficult to reduce the effective value.
The present invention has been made in view of such circumstances, and has as its main object to make the effective value zero when the average value of the current flowing through the independently wired coils is zero.

The invention according to claim 1 of the present invention for solving the above-described problems is a motor driving device for driving a motor configured to be able to energize independently to a plurality of phase coils, and two switching elements are connected in series to a power source. A drive circuit including two bridges connected in parallel to the power source and a bridge circuit connected to each of the coil terminals between the switching elements of each arm for each phase of the coil; A first drive signal generation circuit for generating a first drive signal for controlling the opening and closing of the switching element of one arm of the bridge circuit; and the opening and closing of the switching element of the other arm of the bridge circuit A second drive signal generating circuit for generating a pulse signal having a phase shifted by 180 ° with respect to the pulse of the first drive signal. If, and a motor driving apparatus comprising: a.
This motor drive device opens and closes one switching element of a pair of arms of a bridge circuit with a first drive signal, and opens and closes the other switching element with a second drive signal having a phase difference of 180 °. A positive voltage and a negative voltage are not applied alternately to the coil, and when the average value of the current is zero, the effective value is also zero. Further, the change in the current waveform is reduced even when a current is passed.

According to a second aspect of the present invention, in the motor drive device according to the first aspect, the first drive signal generation circuit generates a pulse signal by comparing a command value of the duty of the pulse width modulation signal with a triangular wave signal. The second drive signal generation circuit is configured to convert a duty command value of the pulse width modulation signal into a command value obtained by subtracting from 100%, a converted command value and the triangular wave signal And a comparator for generating a pulse signal.
This motor drive device creates a signal whose phase is shifted by 180 ° by calculating a value obtained by subtracting the duty command value from 100%.

  According to the present invention, the second drive signal whose phase is inverted by 180 ° with respect to the first drive signal is created, and the energization control of the motor is performed using these drive signals. When the average value of is zero, the effective value of the current can also be zero. Electricity consumption due to the resistance component of the coil is not generated, and heat generation of the motor due to energization is prevented. Further, even when the average value of the current is not zero, the change in the current can be reduced and the power consumption can be reduced.

The best mode for carrying out the invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the motor drive device 1 includes a PWM drive circuit 3 that switches energization to the coils U, V, and W of the servo motor 2, and drive signals Up 1, Un 1, Up 2 that are input to the PWM drive circuit 3. And a drive signal generation device 4 that generates Un2, Vp1, Vn1, Vp2, Vn2, Wp1, Wn1, Wp2, and Wn2.

  The PWM drive circuit 3 has an H bridge circuit provided for each phase of the servo motor 2. In this embodiment, since driving of a three-phase motor of U, V, and W is assumed, a first bridge circuit 11 that controls the coil U, a second bridge circuit 12 that controls the coil V, and The third bridge circuit 13 controls the coil W.

The first bridge circuit 11 includes an arm 21 composed of two switching elements Su11 and Su12 connected in series to the power supply 14, and an arm 22 connected in parallel to the arm 21 with respect to the power supply 14. The arm 22 includes two switching elements Su21 and Su22 connected in series. One terminal of the coil U is connected to each of a midpoint between the switching elements Su11 and Su12 of the arm 21 and a midpoint between the switching elements Su21 and Su22 of the arm 22. Each of the switching elements Su11 to Su22 has a configuration in which a field effect transistor and a diode for passing a reflux current are combined. Thereby, when only the switching element Su11 and the switching element Su22 are turned ON, a current flows in the coil U in the positive direction from the plus side to the minus side. When only the switching element Su21 and the switching element Su12 are turned on, a current flows in the reverse direction from the minus side to the plus side.
Driving signals are input to the switching elements Su11 and Su12 of the arm 21 through the gate drivers 23A and 23B, respectively. Driving signals are input to the switching elements Su21 and Su22 of the arm 22 through the gate drivers 24A and 24B, respectively.

  The second bridge circuit 12 and the third bridge circuit 13 have the same configuration. In the second bridge circuit 12, one terminal of the coil V is connected to each of the midpoint between the switching elements Sv11 and Sv12 of the arm 21 and the midpoint between the switching elements Sv21 and Sv22 of the arm 22. Yes. The third bridge circuit 13 has one terminal of the coil W connected to each of the midpoint between the switching elements Sw11 and Sw12 of the arm 21 and the midpoint between the switching elements Sw21 and Sw22 of the arm 22. Yes.

As shown in FIG. 2, the drive signal generation device 4 includes three generation devices 31, 32, and 33 according to the three coils U, V, and W. Each of the generation devices 31 to 33 has the same configuration, and each includes a first drive signal generation circuit 41 and a second drive signal generation circuit 42.
The first drive signal generation circuit 41 includes a comparison signal generation circuit 51 to which a PWM duty command value is input, a triangular wave generation circuit 52, and a comparator 53. The comparison signal generation circuit 51 is connected to the normal input terminal of the comparator 53, and the triangular wave generation circuit 52 is connected to the inverting input terminal of the comparator 53. The triangular wave generation circuit 52 is a circuit that generates and outputs a reference triangular waveform signal (hereinafter referred to as a reference triangular wave signal).
The output of the comparator 53 is connected to the first rising delay circuit 54 and also connected to the second rising delay circuit 56 via the inverting circuit 55. The first rising delay circuit 54 is connected to the gate driver 23 </ b> A of the first bridge circuit 11. The second rising delay circuit 56 is connected to the gate driver 23B of the first bridge circuit 11.

  The second drive signal generation circuit 42 includes a phase shift signal generation circuit 43 that generates a PWM drive signal whose phase is shifted by 180 °. The phase shift signal generation circuit 43 includes a duty conversion circuit 61 to which a PWM duty command value is input, a comparison signal generation circuit 62 to which an output of the duty conversion circuit 61 is connected, and a comparator 63. A comparison signal generation circuit 62 is connected to the inverting input terminal of the comparator 63. A triangular wave generation circuit 52 is connected to the normal rotation input terminal. The output of the comparator 63 is connected to the third rise delay circuit 65 through the inverting circuit 64 and is also connected to the fourth rise delay circuit 66. The third rise delay circuit 65 is connected to the gate driver 24 </ b> A of the first bridge circuit 11. The fourth rise delay circuit 66 is connected to the gate driver 24 </ b> B of the first bridge circuit 11.

The second generation device 32 has a similar configuration. The first rising delay circuit 54 of the second generation device 32 is connected to the gate driver 23 </ b> A of the second bridge circuit 12. The second rising delay circuit 56 is connected to the gate driver 23 </ b> B of the second bridge circuit 12. The third rise delay circuit 65 is connected to the gate driver 24A of the second bridge circuit 12. The fourth rise delay circuit 66 is connected to the gate driver 24B of the second bridge circuit 12.
Further, the third generation device 33 has the same configuration. The first rise delay circuit 54 of the third generation device 33 is connected to the gate driver 23 </ b> A of the third bridge circuit 13. The second rise delay circuit 56 is connected to the gate driver 23B of the third bridge circuit 13. The third rise delay circuit 65 is connected to the gate driver 24A of the third bridge circuit 13. The fourth rise delay circuit 66 is connected to the gate driver 24B of the third bridge circuit 13.

Next, the operation of this embodiment will be described.
When, for example, a signal for instructing 50% is input to the drive signal generation device 4 as a command value for PWM duty, the comparison signal generation circuit 51 of the first generation device 31 outputs a 50% reference signal corresponding to 50% duty. Create The comparator 53 compares the 50% reference signal with the reference triangular wave signal generated by the triangular wave generation circuit 52. The comparison result of the comparator 53 is input to the first rising delay circuit 54 as a 50% duty signal. The first rise delay circuit 54 delays the rise of the pulse by a predetermined time to generate the first drive signal Up1, and inputs it to the date of the transistor of the switching element Su11 through the gate driver 23A. On the other hand, the 50% duty signal is input to the second rising delay circuit 56 after the pulse is inverted by the inverting circuit 55. The second rise delay circuit 56 creates the first drive signal Un1 by delaying the rise of the pulse by a predetermined time, and inputs it to the date of the transistor of the switching element Su12 through the gate driver 23B.

  Further, the phase shift signal generation circuit 43 of the first generation device 31 calculates a value obtained by subtracting the duty command value from 100% by the duty conversion circuit 61 as the phase shift duty command value. In this case, since 100% -50% = 50%, the comparison signal generation circuit 62 creates a 50% reference signal. The comparator 63 compares the 50% reference signal with the reference triangular wave signal generated by the triangular wave generation circuit 52. The 50% duty signal is input to the third rise delay circuit 65 after the pulse is inverted by the inverter circuit 64. The third rise delay circuit 65 creates the second drive signal Up2 by delaying the rise of the pulse by a predetermined time, and inputs it to the date of the transistor of the switching element Su21 through the gate driver 24A. On the other hand, this duty 50% signal is also input to the fourth rise delay circuit 66. The fourth rise delay circuit 66 creates the second drive signal Un2 by delaying the rise of the pulse by a predetermined time, and inputs it to the date of the transistor of the switching element Su22 through the gate driver 24B. In each of the delay circuits 54, 56, 65, and 66, the same value is set for the time (dead time) for delaying the rise of the pulse.

  Signal processing is performed in the same manner for the other generation devices 32 and 33, and the drive signals Vp1 to Wn2 are input to the corresponding switching elements Sv11 to Sw22.

Here, FIG. 3 shows a specific example of a signal waveform when the duty command value is 50%. Although only the U-phase signal is shown in FIG. 3, similar signals are created for the other two phases.
A comparison between the reference triangular wave signal and the 50% reference signal is performed by the comparator 53, and a duty 50% signal Du is created. The duty 50% signal Du is a pulse signal in which a portion of the reference triangular wave signal that is below the 50% reference signal is at a high level and a portion that is above the 50% reference signal is at a low level. On the other hand, in the phase shift signal generation circuit 43, the reference triangular wave signal and the 50% reference signal are compared by the comparator 63, and a duty 50% signal DSu as a 180 degree phase shift signal is created. The duty 50% signal is a pulse signal in which a portion of the reference triangular wave signal that is below the 50% reference signal is at a low level and a portion that is above the 50% reference signal is at a high level.

The duty 50% signal Du is added with the dead time td by the first rising delay circuit 54 to become the first drive signal Up1, and the inverted time is also applied to the inverted signal by the second rising delay circuit 56. The first drive signal Un1 is added.
Similarly, the 50% duty signal DSu due to the phase shift is added with a dead time td by the third rising delay circuit 65 after inversion to become the second drive signal Up2, and at the fourth rising delay circuit 66, the dead time td is added to become the second drive signal Un2.

The first drive signal Up1 becomes a gate signal of the switching element Su11, and the second drive signal Un2 becomes a gate signal of the switching element Su22, and opens and closes the switching elements Su11 and Su22. In this case, since both the switching element Su11 and the switching element Su22 are not opened, no current in the positive direction flows through the coil U.
The first drive signal Un1 becomes a gate signal of the switching element Su12, and the second drive signal Up2 becomes a gate signal of the switching element Su21, and opens and closes the switching elements Su12 and Su21. In this case, since the switching element Su21 and the switching element Su12 do not both open, current in the reverse direction does not flow through the coil U.
That is, no voltage is applied to the coil U, and no current flows. Therefore, the average value and effective value of the current are also zero, and the coil U does not generate heat.

  As a comparison, FIG. 4 shows a case where the command value is set to 50% duty in the conventional control. Since the conventional control does not include the phase shift signal generation circuit 43, the drive signal Up obtained by adding the dead time td to the duty 50% signal and the drive signal obtained by inverting the same duty 50% signal and then adding the dead time td. Only two types of signals Un are generated. The drive signal Up is input to the high-side switching element Su11 of one arm 21 and the low-side switching element Su22 of the other arm 22. For this reason, when the pulse of the drive signal Up is at a high level, the two switching elements Su11 and Su22 are both turned on and applied to the positive power supply voltage across the coil U, and a current flows. On the other hand, the drive signal Un is input to the low-side switching element Su12 of one arm 21 and the high-side switching element Su21 of the other arm 22. For this reason, when the pulse of the drive signal Un is at a high level, the two switching elements Su12 and Su21 are both turned on and applied to the negative power supply voltage at both ends of the coil U, and a reverse current flows. In this case, since the positive power supply voltage and the negative power supply voltage of the coil U are alternately applied for the same time, the current flowing through the coil U has a triangular waveform, and its average value becomes zero. However, since the current itself is not zero, the effective value does not become zero and the coil U generates heat.

As control in this embodiment, FIG. 5 shows a case where the command value of the PWM duty is 75%, and FIG. 6 shows a case where it is 25%.
In the case of 75% duty shown in FIG. 5, the comparator 53 generates the duty 75% signal Du from the 75% reference signal and the triangular wave signal, and adds the dead time td, and the dead time td after inversion. The first drive signal Un1 to which is added is created. In the phase shift signal generation circuit 43, the duty conversion circuit 61 generates a command signal with a duty of 25% (= 100% −75%). The comparator 63 generates the duty 25% signal DSu from the 25% reference signal and the triangular wave signal, and generates the second drive signal Un2 to which the dead time td is added and the second drive signal Up2 to which the dead time td is added after inversion. To do.
The switching elements Su11 to Su22 are opened and closed by these drive signals Up1 to Un2, and when the switching elements Su11 and Su22 are both opened, a positive voltage is periodically applied between the terminals of the coil U, and current is supplied to the coil U. Flowing. In other cases, no voltage is applied between the terminals of the coil U, and the current value decreases due to natural discharge. This is because the switching element Su12 and the switching element Su21 do not open simultaneously. Then, when a positive voltage is applied again, the current value increases. Therefore, the current flowing through the coil U has a triangular waveform.

In the case of the 25% duty shown in FIG. 6, the comparator 53 generates the duty 25% signal Du from the 25% reference signal and the triangular wave signal and adds the dead time td, and the dead time td after inversion. A first drive signal Un1 to which is added is created. In the phase shift signal generation circuit 43, the duty conversion circuit 61 generates a command signal having a duty of 75% (= 100% −25%). The comparator 63 generates a 75% duty signal DSu from the 75% reference signal and the triangular wave signal, and generates a second drive signal Un2 to which a dead time td is added and a second drive signal Up2 to which a dead time td is added after inversion. Is done.
In this case, the switching element Su11 and the switching element Su22 are not simultaneously opened, and a negative voltage is periodically applied between the terminals of the coil U. Therefore, the current flowing through the coil U has a triangular waveform.

For comparison, the applied voltage and current of the coil at the conventional 75% duty and 25% duty are shown in FIGS. 7 and 8, respectively. As in the conventional example of 50% duty described above, when the pulse of the drive signal Up is at a high level and the drive signal Un is at a low level, a positive voltage is applied to the terminal of the coil U and a current flows. When the pulse of the drive signal Up is at a low level and the drive signal Un is at a high level, a negative voltage is applied to the terminal of the coil U, and a current flows through the coil U in the opposite direction.
With the conventional 75% duty shown in FIG. 7, a positive voltage and a negative voltage are alternately applied, and the change in the current flowing through the coil U is large. On the other hand, only the positive voltage is applied at the 75% duty of the driving device 1 of the present embodiment shown in FIG. Furthermore, in the prior art, the positive voltage is applied twice in a section where the positive voltage is applied once, which is equivalent to the case where the PWM frequency is doubled by the conventional method. Therefore, even if the average value of the current is the same, the fluctuation (dispersion with respect to the average value) is small. The same applies to the conventional 25% duty control shown in FIG. 8 and the 25% duty of the driving apparatus 1 of the present embodiment shown in FIG.

According to this embodiment, the phase shift signal generation circuit 43 is provided so that the drive signal whose phase is inverted by 180 ° is input to the switching element of the other arm 22. When the average value of the flowing current is zero, the effective value of the current can be zero. Power consumption due to the resistance components of the coils U, V, and W is not generated, and heat generation of the servo motor 2 due to energization is prevented.
Even when the average value of the current is not zero, only the voltage in the polarity direction in which the current is to flow is applied to the coils U, V, and W, so that the change in current can be reduced. For this reason, the effective value of an electric current can be made small and the power consumption by the resistance component of the coils U, V, and W can be reduced. This is because when the average of the two samples is the same, the magnitude relation of the variance and the magnitude relation of the square mean are the same. In other words, since the driving device 1 can reduce the current dispersion as compared with the conventional one, the effective value of the current that is the mean square can be reduced as compared with the conventional one.

Note that the present invention can be widely applied without being limited to the above-described embodiment.
The phase shift signal generation circuit 43 may be a circuit that shifts the phase by 180 ° by delaying the signal.

It is a block diagram of the motor drive device concerning an embodiment of the invention. It is a block diagram of a drive signal generation device. It is a figure which shows the signal waveform in 50% duty. It is a figure which shows the signal waveform in the conventional 50% duty. It is a figure which shows the signal waveform in 75% duty. It is a figure which shows the signal waveform in 25% duty. It is a figure which shows the signal waveform in the conventional 75% duty. It is a figure which shows the signal waveform in the conventional 25% duty.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive apparatus 2 Servo motor 3 Drive circuit 4 Drive signal generation apparatus U Coil V Coil W Coil 11 1st bridge circuit 12 2nd bridge circuit 13 3rd bridge circuit 21 and 22 Arm 41 1st drive signal generation circuit 42 Second drive signal generation circuit 43 Phase shift signal generation circuit 53, 63 Comparator Up1, Un1, Up2, Un2, Vp1, Vn1, Vp2, Vn2, Wp1, Wn1, Wp2, Wn2 Drive signals Su11, Su12, Su21, Su22 , Sv11, Sv12, Sv21, Sv22, Sw11, Sw12, Sw21, Sw22 switching elements

Claims (2)

In a motor drive device that drives a motor configured to be able to energize a plurality of phase coils independently,
A bridge circuit having two arms connected in series to a power supply in parallel to the power supply and having one terminal of the coil connected between the switching elements of each arm; A drive circuit for each phase of the coil;
A first drive signal generation circuit for generating a first drive signal for controlling opening and closing of the switching element of one of the arms of the bridge circuit;
A second drive signal for controlling opening and closing of the switching element of the other arm of the bridge circuit, the pulse signal having a phase shifted by 180 ° with respect to the pulse of the first drive signal. Two drive signal generation circuits;
A motor drive device comprising: The first drive signal generation circuit includes a comparator that generates a pulse signal by comparing a duty value command value of a pulse width modulation signal with a triangular wave signal,
The second drive signal generation circuit compares a duty conversion circuit that converts a duty command value of a pulse width modulation signal into a command value obtained by subtracting from 100%, and compares the converted command value with the triangular wave signal to generate a pulse signal. The motor drive device according to claim 1, further comprising a comparator that generates

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