JP2004088995A - Motor driving method and motor driving device - Google Patents

Abstract

An object of the present invention is to reduce vibration of a motor and electromagnetic noise by using a smaller number of current detection resistors than the number of phase currents and preventing a plurality of phase currents from changing abruptly.
A motor drive device includes a plurality of output circuits having upper and lower arm-side switching elements connected in series, and a current detection resistor connected in series with the plurality of output circuits and commonly connected. A motor driving method, wherein one of the output circuits has one of the switching elements conducting for a period corresponding to a predetermined electrical angle, and the other of the output circuits has the other one of the other switching elements. Performing a switching operation. In the step of performing the switching operation, in each of the plurality of periods into which the period is divided, a first period in which one of the switching elements performing the switching operation is turned on and a second period in which the other is turned on are set. To be present.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a motor driving technique, and more particularly to a PWM (pulse width modulation) type motor driving technique.
[0002]
[Prior art]
As a PWM drive method of a brushless motor, a triangular wave slice method and a peak current detection method are known. The triangle wave slicing method uses an error amplifier that sends a coil current to a detection resistor and outputs a difference between a voltage generated in the detection resistor and a torque command voltage as a slice level, and slices a triangle wave having a constant cycle at this slice level. This is a method for determining the current supply period to the coil. The peak current detection method is a method in which the supply of current to the coil is stopped when the voltage generated in the current detection resistor through which the coil current flows reaches the torque command voltage without using an error amplifier, and a regenerative current mode is set. .
[0003]
FIG. 18 is a block diagram of a conventional peak current detection type motor driving device. In FIG. 18, Hall elements 21A, 21B, and 21C detect the position of the rotor of motor 10 and output Hall element outputs S11, S12, and S13 to position detection circuit 22, respectively. The position detection circuit 22 obtains position signals S21, S22 and S23 based on the Hall element outputs S11, S12 and S13, and outputs them to the energized phase switching circuit 93. The position signals S21, S22 and S23 are signals obtained by shifting the phases of the Hall element outputs S11, S12 and S13 by 30 °.
[0004]
The energized phase switching circuit 93 determines the energized phase according to the position signals S21, S22 and S23. At this time, the current-carrying phase switching circuit 93 does not pass one of the three phases to make it easier to measure the phase current. The logic control circuit 95 is set when the reference pulse PI is input, changes the level of a signal output to the energized phase switching circuit 93, and controls the supply of current to the motor 10. The reference pulse PI is a periodic pulse.
[0005]
FIG. 19 is a graph showing a change over time of each phase current of the motor driven by the motor driving device of FIG. FIG. 19 shows the phase currents I1, I2, and I3 of the U, V, and W phases, respectively, and the current flowing from each of the drive transistors 1 to 6 toward the motor 10 is a positive current. As shown in FIG. 19, since the phase current of one phase is always zero, any one of the phase currents rapidly changes every 60 electrical degrees.
[0006]
Now, it is assumed that the logic control circuit 95 is set by the reference pulse PI. The energized phase switching circuit 93 makes only the W-phase upper-arm drive transistor 5 and the U-phase lower-arm drive transistor 2 conductive, for example. At this time, since a current flows through the current detection resistor 7 via the W-phase coil 13 and the U-phase coil 11, the magnitude of this current can be detected as a voltage generated in the current detection resistor 7. Since this current flows through the inductive coil, it gradually increases after the drive transistors 2 and 5 conduct.
[0007]
When the current increases and the voltage generated in the current detection resistor 7 reaches the torque command voltage TI, the output level of the comparator 96 changes, and the logic control circuit 95 is reset. The logic control circuit 95 inverts the level of the signal output to the energized phase switching circuit 93, and the energized phase switching circuit 93 turns off the drive transistor 2.
[0008]
Thus, the period from when the logic control circuit 95 is set to when it is reset is the on-duty period of the switching operation. After the logic control circuit 95 is reset, the current flowing through the coils 11 and 13 continues to flow, so that a regenerative current flows through the diode 1D existing between the source and the drain of the driving transistor 1. Since the regenerative current does not pass through the current detection resistor 7, the voltage generated at the current detection resistor 7 during regeneration becomes zero.
[0009]
The regenerative current gradually decreases, but when the reference pulse PI is input again, the logic control circuit 95 is set, and the energized phase switching circuit 93 makes the drive transistor 2 conductive. Such an operation is repeated until the energized phase switching circuit 93 switches the energized phase. As described above, as a result of the drive current flowing when the logic control circuit 95 is set and the regenerative current flowing when the logic control circuit 95 is reset flowing alternately, a phase current substantially corresponding to the torque command voltage TI flows through a predetermined coil. Can be.
[0010]
FIG. 20 is a graph showing the current detection resistance voltage (motor current detection signal) MC and the phase currents I2 and I3 of the V and W phases near the time t = tz in FIG. In FIG. 20, a period T91 is a period in which the drive currents of the U-phase current and the V-phase current flow, and this current flows through the current detection resistor 7. The period T92 is a period during which U-phase and V-phase currents flow as regenerative currents. The period T93 is a period in which the drive currents of the U-phase current and the W-phase current flow, and this current flows through the current detection resistor 7. The period T94 is a period during which U-phase and W-phase currents flow as regenerative currents.
[0011]
Such techniques and related techniques are disclosed in Patent Documents 1 and 2.
[0012]
[Patent Document 1]
JP-A-11-18474
[Patent Document 2]
JP 2003-79182 A
[0013]
[Problems to be solved by the invention]
However, in the conventional motor driving device as shown in FIG. 18, since the phase current changes rapidly as shown in FIG. 19, when the phase current is switched, there is a problem that the motor vibrates or generates electromagnetic noise. Was.
[0014]
In order to prevent such a problem from occurring, control may be performed so that each phase current is not suddenly changed.However, in order to detect and control a plurality of phase currents, the number of phases equal to the number of phases is required. A current detection resistor was required. Since it is difficult to incorporate a current detection resistor into an integrated circuit, there is a problem that if the number of current detection resistors is large, the scale of the device becomes large and costs increase.
[0015]
Further, since the characteristics of the resistors generally vary, there is a problem that the current detection characteristics are different for each phase when the current detection resistors corresponding to the respective phases are used. For example, even if the magnitudes of the two phase currents are actually the same, the magnitudes of the detected currents may be different.
[0016]
SUMMARY OF THE INVENTION It is an object of the present invention to reduce motor vibration and electromagnetic noise by controlling a plurality of phase currents so as not to change abruptly by using a smaller number of current detection resistors than the number of phase currents.
[0017]
[Means for Solving the Problems]
The motor driving method of the present invention includes a plurality of output circuits having an upper-arm switching element and a lower-arm switching element connected in series, and is serially connected to the plurality of output circuits, and commonly connected, A motor including a current detection resistor for detecting a current supplied to the plurality of output circuits, and supplying a current to the motor from a connection point between an upper arm switching element and a lower arm switching element in each of the output circuits; A method of driving a motor in a driving device, comprising: obtaining a position signal corresponding to a position of a rotor of the motor; and setting one switching element in one of the plurality of output circuits according to the position signal. Selecting and conducting in a period corresponding to a predetermined electrical angle; and When the switching element is an arm switching element, the lower arm switching element in any one of the plurality of output circuits performs a switching operation, and when the switching element to be turned on is the lower arm switching element, the plurality of outputs are output. Causing the upper-arm switching element in any one of the remaining plurality of circuits to perform a switching operation.In the step of performing the switching operation, in each of the plurality of periods in which the period corresponding to the predetermined electrical angle is divided. The input is performed so that there is a first period during which one switching element is turned on among the switching elements that perform the switching operation, and a second period during which a switching element different from the first switching element is turned on. Torque command signal and current detection Depending on the voltage generated in the anti, and controls the switching operation.
[0018]
According to this, since there are a first period in which one switching element is turned on and a second period in which a switching element different from the first switching element is turned on, the number of phase currents equal to or more than the number of current detection resistors is provided. Can be controlled. For this reason, it is possible to perform the PWM control in which the magnitudes of the phase currents do not vary, to avoid a sudden change in the phase current, and to reduce the vibration and the electromagnetic noise of the motor at the time of the phase switching.
[0019]
According to another motor driving method of the present invention, there are provided at least four even-numbered output circuits each having an upper-arm switching element and a lower-arm switching element connected in series, and the four or more even-numbered output circuits. A current detection resistor for detecting a current supplied to the even numbered output circuits of 4 or more, and an upper arm side switching element and a lower side in each of the output circuits; A method of driving a motor in a motor driving device for supplying a current to a motor from a connection point with an arm-side switching element, wherein a step of obtaining a position signal corresponding to a position of a rotor of the motor, One of the switching elements is selected according to the position signal, and the selected switching element is an upper arm side switch. If the selected switching element is a switching element, the selected switching element sets the pair of the lower arm side switching element and the selected switching element corresponding to the opposite phase of the corresponding phase to the selected switching element. When the element is a lower arm side switching element, a set of the upper arm side switching element and the selected switching element of the output circuit corresponding to the opposite phase of the phase corresponding to the selected switching element, Conducting the conduction in a period corresponding to the predetermined electrical angle, and, when the selected switching element is an upper arm switching element, each of the lower arm switching elements in any one of the remaining plurality of output circuits. The upper arm side switch of the output circuit corresponding to the opposite phase of the phase corresponding to each of these Switching operation with each of the sets of the switching elements, and when the selected switching element is a lower-arm switching element, each of the upper-arm switching elements in any of the remaining plurality of output circuits and Performing a switching operation on each of a set of an output circuit and a lower arm side switching element corresponding to a phase opposite to the phase corresponding to each of the phases. In each of a plurality of periods in which a period corresponding to is divided, a first period in which one set of switching elements is turned on among a set of switching elements performing the switching operation is different from the one set of switching elements. So that there is a second period for conducting the set of switching elements. The switching operation is controlled in accordance with the applied torque command signal and the voltage generated in the current detection resistor.
[0020]
In the motor driving method, in the step of performing the switching operation, the first period may start when a reference pulse is input, and end when a voltage generated in the current detection resistor reaches a target signal. preferable.
[0021]
In the motor driving method, in the step of performing the switching operation, it is preferable that when the reference pulse is input, the first period is started after all the switching elements to be switched are turned off.
[0022]
Further, another motor driving method of the present invention includes a plurality of output circuits having an upper arm switching element and a lower arm switching element connected in series, and in series with the plurality of output circuits, and And a current detection resistor for detecting a current supplied to the plurality of output circuits, and a plurality of phases from a connection point between the upper arm switching element and the lower arm switching element in each of the output circuits. A motor driving method for a motor driving device for supplying a current to a motor coil, wherein a section in which the phase currents of the plurality of phases of the motor coils flow simultaneously is divided into a PWM (pulse width modulation) control period. In the PWM control period, the current flowing through the current detection resistor is set to the upper arm side or the lower arm side. Selectively select each of the switching elements until a signal corresponding to a current value to be passed for each of the switching elements matches a signal obtained from the current detection resistor so as to match a current passing through one of the switching elements. The PWM control is performed so as to have a period in which the phase current is turned on and a period in which a phase current other than the phase related to the specific switching element is in a regenerative state.
[0023]
Further, the motor driving device of the present invention includes a plurality of output circuits each having an upper arm switching element and a lower arm switching element connected in series, and each of the output circuits includes an upper arm switching element and a lower arm side. A motor driving device for supplying a current to a motor from a connection point with a switching element, wherein the motor driving device is connected in series with the plurality of output circuits, and is commonly connected to detect a current supplied to the plurality of output circuits. A current detecting resistor, a position detecting unit that outputs a position signal corresponding to the position of the rotor of the motor, and selecting one switching element in any one of the plurality of output circuits according to the position signal. Then, while conducting during a period corresponding to a predetermined electrical angle, the switching element to be conducted is an upper arm side switching element In the case where the switching operation is performed on the lower arm side switching element in any one of the remaining plurality of output circuits, and when the switching element to be turned on is the lower arm side switching element, any one of the remaining output circuits is used. And an energizing phase switching circuit that causes the upper arm switching element to perform a switching operation, and a plurality of switching elements that perform the switching operation in each of a plurality of periods separated by a period corresponding to the predetermined electrical angle. The input torque command signal and the voltage generated in the current detection resistor so that there is a first period in which the switching element is turned on and a second period in which the switching element different from the first switching element is turned on. The switching operation by the energized phase switching circuit is controlled according to It generates switching operation control signal, in which a conduction period control unit to output.
[0024]
Further, in the motor driving device, the energization period control unit may be configured to control a first value corresponding to a target value of a current to be passed through the current detection resistor in the first period in accordance with the torque command signal and the position signal. A target signal, a second target signal corresponding to a target value of a current to be passed through the current detection resistor in the second period, and a phase-specific torque signal generating circuit that outputs the target signal; and a voltage generated in the current detection resistor. A first comparator for determining whether or not the voltage exceeds the first target signal and outputting the result; and a determination whether or not a voltage generated at the current detection resistor exceeds the second target signal. And a second comparator for outputting the result, and a switching operation control signal generated and output in response to a reference pulse defining a cycle of the switching operation and outputs of the first and second comparators. Wherein the logic control circuit determines that a voltage generated in the current detection resistor exceeds the first target signal. Terminating the first period, and when the result of the determination by the second comparator indicates that the voltage generated at the current detection resistor exceeds the second target signal, the second period is terminated. It is preferable to generate and output the switching operation control signal so as to end the operation.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, as an example, a case where a motor driving device drives a three-phase brushless motor will be described.
[0026]
(1st Embodiment)
FIG. 1 is a block diagram of the motor drive device according to the first embodiment of the present invention. 1 includes a U-phase, V-phase, and W-phase upper-arm drive transistors 1, 3, and 5, a U-phase, V-phase, and W-phase lower-arm drive transistors 2, 4, and 6, and a diode 1D. , 2D, 3D, 4D, 5D, 6D, the current detection resistor 7, the Hall element circuit 21, the position detection circuit 22, the conduction phase switching circuit 23, the pre-drive circuit 24, the amplifier 27, and the torque for each phase. The circuit includes a signal generation circuit 30, a logic control circuit 40, and comparators 51 and 52. On the other hand, the motor 10 includes a U-phase coil 11, a V-phase coil 12, and a W-phase coil 13. The phase-specific torque signal generation circuit 30, the logic control circuit 40, and the comparators 51 and 52 constitute an energization period control unit 100. The Hall element circuit 21 and the position detection circuit 22 constitute a position detection unit.
[0027]
It is assumed that drive transistors 1 to 6 are n-type MOS (metal oxide semiconductor) transistors. The anode and cathode of the diode 1D are connected to the source and drain of the driving transistor 1, respectively. Similarly, diodes 2D to 6D are connected to the driving transistors 2 to 6, respectively. The drains of the driving transistors 1, 3, 5 are connected to the power supply VCC, and the sources of the driving transistors 2, 4, 6 are connected to one end of the current detection resistor 7. The other end of the current detection resistor 7 is grounded. The driving transistors 1 to 6 operate as switching elements.
[0028]
The drive transistors 1 and 2 and the diodes 1D and 2D constitute a U-phase output circuit (half-bridge circuit). The driving transistors 3 and 4 and the diodes 3D and 4D constitute a V-phase output circuit. The drive transistors 5, 6 and the diodes 5D, 6D constitute a W-phase output circuit. A current supplied to these output circuits from the power supply VCC flows through the current detection resistor 7.
[0029]
The source of the driving transistor 1 is connected to the drain of the driving transistor 2, and further connected to one end of the U-phase coil 11 of the motor 10. The source of the driving transistor 3 is connected to the drain of the driving transistor 4, and further connected to one end of the V-phase coil 12 of the motor 10. The source of the driving transistor 5 is connected to the drain of the driving transistor 6 and further connected to one end of the W-phase coil 13 of the motor 10. The other end of U-phase coil 11 is connected to the other ends of V-phase coil 12 and W-phase coil 13.
[0030]
Here, a current flowing from the drive transistors 1 and 2 toward the U-phase coil 11 is defined as a U-phase current I1. Similarly, the current flowing from drive transistors 3 and 4 toward V-phase coil 12 is referred to as V-phase current I2, and the current flowing from drive transistors 5 and 6 toward W-phase coil 13 is referred to as W-phase current I3. A current flowing from the drive transistors 1 to 6 toward the coils 11 to 13 is referred to as a discharge current, and a current in the opposite direction is referred to as a sink current. The direction of the discharge current is the positive direction of each phase current. Since coils 11 to 13 of motor 10 are Y-connected, each phase current is equal to the current flowing in the corresponding coil.
[0031]
The Hall element circuit 21 includes Hall elements 21A, 21B, and 21C. Each of the Hall elements 21A, 21B, 21C detects the position of the rotor of the motor 10 and outputs Hall element outputs S11, S12, S13 to the position detection circuit 22. The position detection circuit 22 obtains the position signals S21, S22, S23 and PS based on the Hall element outputs S11, S12 and S13, and outputs the position signals S21, S22 and S23 to the energized phase switching circuit 23 and the position signal PS for each phase. Output to the torque signal generating circuit 30.
[0032]
The phase-specific torque signal generation circuit 30 generates voltage signals TS1 and TS2 corresponding to a target value of a current flowing through the current detection resistor 7 based on the position signal PS and the torque command voltage (torque command signal) TI, and compares the signals. And outputs to the positive input terminals of the devices 51 and 52, respectively. The amplifier 27 is connected to both ends of the current detection resistor 7 and outputs a motor current detection signal MC corresponding to a voltage generated at the current detection resistor 7 to negative input terminals of the comparators 51 and 52.
[0033]
The comparators 51 and 52 output the results of comparing the input signals to the logic control circuit 40 as outputs CP1 and CP2, respectively. A reference pulse PI is further input to the logic control circuit 40. The logic control circuit 40 generates switching operation control signals F1 and F2 that define a period during which the drive transistors 1 to 6 are turned on, and outputs the generated switching operation control signals to the energized phase switching circuit 23.
[0034]
Based on the position signals S21, S22, S23 and the control signals F1, F2, the energized phase switching circuit 23 selects one of the drive transistors 1 to 6 to be made conductive and instructs the pre-drive circuit 24. The pre-drive circuit 24 outputs a signal to the gates of the driving transistors 1 to 6 according to the output of the energized phase switching circuit 23, and controls conduction / non-conduction of the driving transistors 1 to 6.
[0035]
FIG. 2 is a graph showing a target waveform of each phase current I1 to I3 of the motor 10 of FIG. The motor drive device of FIG. 1 controls the current supply to the motor 10 as shown in FIG. 2 so that the phase currents I1 to I3 of the motor 10 do not suddenly change. The motor drive device of FIG. 1 divides the electric angle 360 ° of the motor 10 into six, for example, and divides the electric angle 360 into six at every period corresponding to the divided electric angle, that is, the angle of the rotor of the motor 10 corresponding to the divided electric angle. Each time the motor rotates, the current of the motor 10 is controlled while switching the energized phase.
[0036]
For example, a period TU1 in FIG. 2 is a period corresponding to an electrical angle of 60 °. In the period TU1, the U-phase current I1 is a discharge current, and its magnitude is substantially constant. The V-phase current I2 is a sink current, and its magnitude gradually decreases with time t. The W-phase current I3 is a sink current, and its magnitude gradually increases from 0 with time t. Therefore, in the period TU1, the U-phase upper-arm drive transistor 1 is continuously turned on. The V-phase and W-phase lower arm side drive transistors 4 and 6 perform a switching operation so that the V-phase current I2 and the W-phase current I3 become as shown in FIG. And control.
[0037]
FIG. 3 is a block diagram showing an example of the configuration of the phase-specific torque signal generation circuit 30 of FIG. The phase-specific torque signal generating circuit 30 in FIG. 3 includes a double edge differentiating circuit 31, constant current sources 32 and 36, switches 33 and 37, capacitors 34 and 38, and level control circuits 35 and 39. .
[0038]
FIG. 4 is a graph showing signals related to the position detection circuit 22 and the phase-specific torque signal generation circuit 30. The position detection circuit 22 obtains a position signal S21 indicating the rotor position of the motor 10 based on the Hall element outputs S11 and S12. Here, as an example, the difference between the Hall element outputs S11 and S12 is set as a position signal S21 (S21 = S11-S12). The Hall element outputs S11 and S12 are approximate sine waves, and when the phase of the Hall element output S11 is ahead of S12 by 120 °, the phase of the position signal S21 is ahead of the Hall element output S11 by 30 °. Similarly, the position detection circuit 22 obtains the position signals S22 and S23 by, for example, S22 = S12-S13 and S23 = S13-S11.
[0039]
The position detection circuit 22 obtains a position signal PS based on the obtained position signals S21, S22, S23. The position signal PS rises when the position signal S21 changes from negative to positive, falls when the position signal S23 changes from positive to negative, and rises when the position signal S22 changes from negative to positive. This signal is a signal that repeats a pulse that falls when the signal S21 changes from positive to negative, a pulse that rises when the position signal S23 changes from negative to positive, and a pulse that falls when the position signal S22 changes from positive to negative. . The timing of the edge of the position signal PS is a timing at which the waveforms of the Hall element outputs S11, S12, and S13 cross as shown in FIG.
[0040]
The operation of the phase-specific torque signal generation circuit 30 will be described with reference to FIGS. The position signal PS output from the position detection circuit 22 is input to the both edge differentiating circuit 31. When the edge of the position signal PS is detected, the both-edge differentiating circuit 31 outputs a reset pulse signal S31 that becomes “L” for a certain period of time and becomes “H” otherwise, as a control signal to the switch 33 (“H”, “H”). L ″ represents a logical high potential and a low potential, respectively).
[0041]
One end of the capacitor 34 is connected to one end of the constant current source 32, and the capacitor 34 is connected to the power supply VCC via the switch 33. The other end of the capacitor 34 is grounded. The switch 33 conducts only when the reset pulse signal S31 is "L" to charge the capacitor 34, and the capacitor 34 is discharged by the current flowing from the constant current source 32.
[0042]
One end of the capacitor 38 is connected to the output of the constant current source 36 and is grounded via the switch 37. The other end of the capacitor 38 is grounded. The capacitor 36 is charged by the current flowing from the constant current source 32, and the switch 37 conducts only when the reset pulse signal S31 is "L" to discharge the capacitor 38. Therefore, the voltages S33 and S34 of the capacitors 34 and 38 are sawtooth waves as shown in FIG.
[0043]
The level control circuit 35 receives the torque command voltage TI and the voltage S33 as inputs, and converts a signal TS1 obtained by multiplying the voltage S33 by a gain such that a peak of the voltage S33 becomes equal to the torque command voltage TI as a first target signal. Is output to the comparator 51. Similarly, the level control circuit 39 receives the torque command voltage TI and the voltage S34 as inputs, and converts the signal TS2 obtained by multiplying the voltage S34 by a gain such that the peak of the voltage S34 becomes equal to the torque command voltage TI to a second signal. Is output to the comparator 52 as the target signal of
[0044]
FIG. 5 is a block diagram showing an example of the configuration of the logic control circuit 40 of FIG. The logic control circuit 40 of FIG. 5 includes an RS flip-flop 41 as a first latch circuit, an RS flip-flop 42 as a second latch circuit, inverters 44 and 45, and a NAND gate 46. The inverters 44 and 45 and the NAND gate 46 constitute a logic circuit 49. FIG. 6 is a graph showing input / output signals of the logic control circuit 40 and the comparators 51 and 52 of FIG. FIG. 7 is a graph showing a phase current in the motor drive device of FIG. FIGS. 6 and 7 are enlarged views of the vicinity of t = t1 in FIGS.
[0045]
The operation of the logic control circuit 40 and the current flowing through the motor 10 will be described with reference to FIGS. As shown in FIG. 6, the reference pulse PI is a pulse signal having a substantially constant cycle, and this cycle is a reference for the cycle of the PWM control. Each of the periods between the reference pulses PI is also referred to as a PWM control period.
[0046]
The reference pulse PI is input to the set terminals of the RS flip-flops 41 and 42 in FIG. When the reference pulse PI falls, the RS flip-flop 41 is set, so that the control signal F1 becomes “H”. Then, the output of the logic circuit 49 becomes "L", the RS flip-flop 42 is reset, and the control signal F2 becomes "L".
[0047]
It is assumed that the energized phase switching circuit 23 has determined based on the position signals S21, S22, and S23 that the current time is within the period TU1 of FIG. As shown in FIG. 2, this period TU1 is a period in which the U-phase current I1 is a discharge current having a substantially constant magnitude. In the period TU1, since the U-phase current I1 is the only discharge current, the energized phase switching circuit 23 keeps the drive transistor 1 conductive. Since the V-phase current I2 and the W-phase current I3 are sink currents and need to be changed in magnitude, the energized phase switching circuit 23 performs a switching operation on the drive transistors 4, 6 according to the control signals F1, F2. Let In the period TU1, the energized phase switching circuit 23 turns on the drive transistor 4 when the control signal F1 is "H", and turns on the drive transistor 6 when the control signal F2 is "H". The drive transistors 2, 3, and 5 are turned off.
[0048]
When the control signals F1 and F2 become “H” and “L”, respectively, the energized phase switching circuit 23 turns on the drive transistor 4 (first period T1). At this time, a current flows from the drive transistor 1 toward the U-phase coil 11 as a discharge current. The current flowing through the U-phase coil 11 flows through the V-phase coil 12 toward the drive transistor 4 as a sink current.
[0049]
When the drive transistor 4 is conducting, the V-phase current I2 flowing through the V-phase coil 12 flows through the current detection resistor 7. The magnitude of the current flowing through the current detection resistor 7 is equal to the U-phase current I1 flowing through the U-phase coil 11. A voltage proportional to the magnitude of the current flowing through the current detection resistor 7 is generated, and the amplifier 27 outputs this voltage to the negative input terminal of the comparator 51 as a motor current detection signal MC.
[0050]
Since the U-phase coil 11, V-phase coil 12, and W-phase coil 13 are inductive loads, the V-phase current I2 gradually increases during the period T1 after the drive transistor 4 is turned on (see FIG. 7). Therefore, the motor current detection signal MC also gradually increases. When the voltage of the motor current detection signal MC reaches the voltage of the signal TS1 (see FIG. 6), the comparator 51 changes the output CP to “L”. Then, the RS flip-flop 41 is reset, and its output is inverted to “L”. Since the control signal F1 becomes "L", the RS flip-flop 42 is set, the control signal F2 becomes "H", and the process shifts to the second period T2.
[0051]
During the period T2, the control signals F1 and F2 become “L” and “H”, respectively, so that the energized phase switching circuit 23 turns off the drive transistor 4 and turns on the drive transistor 6. When the driving transistor 4 is turned off, a regenerative current of the V-phase coil 12 flows through the diode 3D between the source and the drain of the driving transistor 3 and the driving transistor 1. The V-phase current I2 flowing as the regenerative current gradually decreases (see FIG. 7). At this time, only the current flowing through the W-phase coil 13 flows through the current detection resistor 7, so that the current of the W-phase coil 13 can be detected without being affected by the current of the V-phase coil 12.
[0052]
During the period T2, since the drive transistors 1 and 6 are conducting, the current of the W-phase coil 13 continues to increase (see FIG. 7), and the current flowing to the current detection resistor 7 continues to increase. When the voltage of the motor current detection signal MC increases and reaches the voltage of the signal TS2 output from the phase-specific torque signal generator 30, the comparator 52 changes the output CP2 to "L". Then, the RS flip-flop 42 is reset, the control signal F2 becomes “L”, and the operation shifts to the operation in the period T3.
[0053]
During the period T3, since the control signals F1 and F2 are both at "L", the conduction phase switching circuit 23 turns off the drive transistors 4 and 6.
[0054]
As described above, while the control signal F1 is at “H”, the drive transistor 4 is turned on, and while the control signal F2 is at “H”, the drive transistor 6 is turned on. During the period T1 in which the control signals F1 and F2 are “H” and “L”, respectively, the current flowing through the V-phase coil 12 is controlled to a value corresponding to the signal TS1, and the control signals F1 and F2 are set to “ In the period T2 in which the current is L "and" H ", the current flowing through the W-phase coil 13 is controlled so as to have a value corresponding to the signal TS2.
[0055]
That is, of the two-phase (V-phase and W-phase) drive transistors 4 and 6 that perform the switching operation in the period TU1, the drive transistor 4 in the phase (V-phase) in which the magnitude of the current is to be reduced in the period TU1 is first. And the transistor is turned off, and at the same time, the drive transistor 6 of the phase (W phase) in which the magnitude of the current is to be increased is turned on (see FIG. 2). The W-phase drive transistor 4 may be turned on first, and the V-phase drive transistor 4 may be turned on at the same time as turning off this transistor.
[0056]
In a period T3 in which the control signals F1 and F2 are both "L", only the regenerative current flows through the coils 11 to 13. V-phase current I2 and W-phase current I3 flowing as regenerative currents gradually decrease (see FIG. 7). When the reference pulse PI is input to the logic control circuit 40, the control signals F1 and F2 become "H" and "L", respectively, and the same process is repeated thereafter.
[0057]
FIG. 8 is an explanatory diagram illustrating a path of a current flowing through the motor 10 during the period T1. As shown in FIG. 8, in the period T1, the V-phase current I2 flowing through the V-phase coil 12 is changed from the power supply to the drive transistor 1, the U-phase coil 11, the V-phase coil 12, the drive transistor 4, and the current detection resistor 7 in this order. Flows. On the other hand, the W-phase current I3 flowing through the W-phase coil 13 is a regenerative current, and flows in a loop in the order of the drive transistor 1, the U-phase coil 11, the W-phase coil 13, and the diode 5D. Therefore, only the V-phase current I2 can be detected from the voltage generated at the current detection resistor 7.
[0058]
FIG. 9 is an explanatory diagram illustrating a path of a current flowing through the motor 10 during the period T2. As shown in FIG. 9, in the period T2, the V-phase current I2 flowing through the V-phase coil 12 is a regenerative current, and forms a loop in the order of the driving transistor 1, the U-phase coil 11, the V-phase coil 12, and the diode 3D. Flows. On the other hand, the W-phase current I3 flowing through the W-phase coil 13 flows from the power supply in the order of the drive transistor 1, the U-phase coil 11, the W-phase coil 13, the drive transistor 6, and the current detection resistor 7. Therefore, only the W-phase current I3 can be detected from the voltage generated at the current detection resistor 7.
[0059]
FIG. 10 is an explanatory diagram illustrating a path of a current flowing through the motor 10 during the period T3. As shown in FIG. 10, in the period T3, the V-phase current I2 flowing through the V-phase coil 12 is a regenerative current, and flows in a loop as in FIG. On the other hand, the W-phase current I3 flowing through the W-phase coil 13 is also a regenerative current and flows in a loop shape as in FIG. Therefore, no current flows through the current detection resistor 7. As described above, in the coils 11 to 13, the drive current flowing when the drive transistors of the output circuits of the respective phases are conducted and the regenerative current flowing through the diodes of the output circuits of the respective phases alternately flow.
[0060]
Next, the operation of the motor drive device of FIG. 1 during the period TU2 of FIG. 2 will be described. As shown in FIG. 2, this period TU2 is a period in which the U-phase current I1 is a sink current having a substantially constant magnitude. In the period TU2, since the U-phase current I1 is the only sink current, the energized phase switching circuit 23 keeps the drive transistor 2 conductive. Since the V-phase current I2 and the W-phase current I3 are discharge currents and need to be changed in magnitude, the energized phase switching circuit 23 causes the drive transistors 3 and 5 to perform a switching operation. In the period TU2, the energized phase switching circuit 23 makes the drive transistor 3 conductive when the control signal F1 is "H", and makes the drive transistor 5 conductive when the control signal F2 is "H". The drive transistors 1, 4, and 6 are turned off.
[0061]
When the control signals F1 and F2 become “H” and “L”, respectively, the energized phase switching circuit 23 turns on the drive transistor 3 and turns off the drive transistor 5. When the control signals F1 and F2 become “L” and “H”, respectively, the driving transistor 3 is turned off and the driving transistor 5 is turned on. When the control signals F1 and F2 both become "L", the drive transistors 3 and 5 are both turned off.
[0062]
As a result, in the period TU2, the directions in which the U-phase current I1, the V-phase current I2, and the W-phase current I3 flow are opposite to the directions in the period TU1. The other points are the same as those in the period TU1, and a detailed description thereof will be omitted.
[0063]
The operation of the motor driving device in FIG. 1 in the periods TV1 and TW1 is the same as that in the period TU1 except for the following points. That is, in the period TV1 in which the V-phase current I2 is a discharge current having a substantially constant magnitude, the energized phase switching circuit 23 causes the drive transistor 3 instead of the drive transistor 1 to be continuously turned on. Further, the energized phase switching circuit 23 causes the driving transistors 6 and 2 to perform a switching operation instead of the driving transistors 4 and 6, respectively, so that the driving transistors 1, 4 and 5 are turned off.
[0064]
In the period TW1 in which the W-phase current I3 is a discharge current having a substantially constant magnitude, the energized phase switching circuit 23 causes the drive transistor 5 instead of the drive transistor 1 to be continuously turned on. The energized phase switching circuit 23 causes the driving transistors 2 and 4 to perform a switching operation instead of the driving transistors 4 and 6, respectively, so that the driving transistors 1, 3 and 6 are turned off.
[0065]
The operation of the motor driving device in FIG. 1 in the periods TV2 and TW2 is the same as that in the period TU2 except for the following points. That is, in the period TV2 in which the V-phase current I2 is a sink current having a substantially constant magnitude, the energized phase switching circuit 23 causes the drive transistor 4 instead of the drive transistor 2 to be continuously turned on. The energized phase switching circuit 23 causes the driving transistors 5 and 1 to perform a switching operation instead of each of the driving transistors 3 and 5, and brings the driving transistors 2, 3 and 6 into a non-conductive state.
[0066]
In a period TW2 in which the W-phase current I3 is a sink current having a substantially constant magnitude, the energized phase switching circuit 23 causes the drive transistor 6 instead of the drive transistor 2 to be continuously turned on. The energized phase switching circuit 23 causes the driving transistors 1 and 3 to perform a switching operation instead of the driving transistors 3 and 5, respectively, so that the driving transistors 2, 4 and 5 are turned off.
[0067]
Although an example has been described in which control is performed in units of a period corresponding to the electric angle of 360 degrees of the motor 10 divided into six, the energized phase may be switched for each shorter period, for example, divided into twelve.
[0068]
Further, when the PWM control of the current of all phases is not completed within one cycle of the reference pulse PI, that is, the reference pulse PI may be input before all the driving transistors for performing the switching operation are not turned off. This occurs when the repetition frequency of the reference pulse PI is improperly set. For this reason, it is desirable that the logic control circuit 40 be configured so that, when the reference pulse PI is input, the drive transistors that perform the switching operation are all turned off once, and then the switching operation is started. Then, it is possible to prevent a through current from flowing through the driving transistors connected in series.
[0069]
As described above, according to the motor driving device of the present embodiment, the phase currents I1 to I3 of the motor 10 are controlled so as to have a substantially trapezoidal waveform having an amplitude corresponding to the torque command voltage TI as shown in FIG. Therefore, the change of the phase current at the time of the energized phase switching can be moderated.
[0070]
When PWM control is performed on three-phase currents, three current detection resistors are usually required. However, the motor drive device of the present embodiment can control three-phase currents using one current detection resistor, and enables PWM control in which the magnitudes of the phase currents do not vary. Since the number of current detection resistors is small, the scale of the device can be reduced.
[0071]
(Second embodiment)
FIG. 11 is a block diagram of a motor drive device according to the second embodiment of the present invention. The motor drive device of FIG. 11 is obtained by replacing the energization period control unit 100 with an energization period control unit 200 in the motor drive device of FIG. The other components are the same as those described with reference to FIG. 1, and thus the same reference numerals are given and the description will be omitted.
[0072]
The energization period control section 200 includes a phase-specific torque signal generation circuit 230, a triangular wave generator 60, error amplifiers 71 and 72, comparators 75 and 76, and an offset addition limiter circuit 80.
[0073]
FIG. 12 is a circuit diagram showing an example of the configuration of the offset adding limiter circuit 80. The offset adding limiter circuit 80 includes an operational amplifier 81 and an offset setting voltage source 82. The voltage source 82 is connected between one input terminal of the offset adding limiter circuit 80 and one of the positive input terminals of the operational amplifier 81. The other one of the positive input terminals of the operational amplifier 81 is the other input terminal of the offset adding limiter circuit 80. One of the input signals to the offset adding limiter circuit 80 is directly output as the slice level signal SU. The operational amplifier 81 outputs a slice level signal SL.
[0074]
FIG. 13 is a graph showing the phase current and the signal of the conduction period control unit 200 in the motor drive device of FIG. FIG. 13 is an enlarged view of the vicinity of t = t1 in FIGS. With reference to FIG. 11 and FIG. 13, an operation of the energization period control unit 200 and a current flowing through the motor 10 will be described.
[0075]
The phase-specific torque signal generation circuit 230 generates two phase-specific torque signals in accordance with the torque command voltage, and outputs them to the error amplifiers 71 and 72, similarly to the phase-specific torque signal generation circuit 30. The error amplifiers 71 and 72 have a function of sampling and holding a signal output from the amplifier 27. For example, the error amplifiers 71 and 72 sample and hold the output value of the amplifier 27 immediately before the end of a period in which a current flows through the current detection resistor 7. The error amplifiers 71 and 72 amplify the difference between the respective input torque signals and the output of the amplifier 27 and output the amplified difference signal to the offset adding limiter circuit 80.
[0076]
The offset adding limiter circuit 80 outputs the first slice level signal SU and the second slice level signal SL to the comparators 75 and 76 according to the outputs of the error amplifiers 71 and 72, respectively. The slice level signal SU is a signal that decreases as the torque command voltage TI increases, and the slice level signal SL is a signal that increases as the torque command voltage TI increases.
[0077]
The triangular wave generator 60 generates a triangular wave SA having a substantially constant cycle as shown in FIG. The comparator 75 outputs “H” when the triangular wave SA is larger than the slice level signal SU, and outputs “L” otherwise as the switching operation control signal F2 to the energized phase switching circuit 23. The comparator 76 outputs “H” when the slice level signal SL is larger than the triangular wave SA, and outputs “L” as the switching operation control signal F1 to the energized phase switching circuit 23 in other cases.
[0078]
The offset adding limiter circuit 80 provides an offset between the two so that the slice level signal SU is always larger than the slice level signal SL, and outputs the slice level signal SU with the level limited. Therefore, the periods in which the control signals F2 and F1 output from the comparators 75 and 76 become “H” can be prevented from overlapping. Therefore, as in the first embodiment, a plurality of phase currents do not flow through the current detection resistor 7 at the same time.
[0079]
As described above, the motor driving device according to the present embodiment can moderate the change in the phase current when the energized phase is switched, and controls the three-phase current using one current detection resistor. Can be.
[0080]
(Third embodiment)
In the above embodiment, the case where the three-phase motor is driven so that the waveform of the phase current becomes a trapezoidal wave has been described. The waveform of the phase current need not be a trapezoidal wave, but may be a sine wave or another waveform. Further, the present invention can be applied to driving not only three-phase but also four-phase or more even-phase motors. Hereinafter, the case where the waveform of the phase current is other than the trapezoidal wave will be described. In this embodiment, a modified version of the motor drive device of FIG. 1 is used.
[0081]
FIG. 14 is a graph showing the output current waveform of each phase when a three-phase motor is driven so that the phase current becomes a sine wave. In order to perform such an operation, the output of the phase-specific torque generating circuit 30 in FIG. 1 may be a sine wave instead of the sawtooth wave shown in FIG. That is, a signal that repeats a waveform of a sine wave in a section of 0 to 60 ° may be used as the signal TS2, and a signal that repeats a waveform of a sine wave in a section of 120 to 180 ° may be used as the signal TS1.
[0082]
In this case, for example, the magnitude of the W-phase current is equal to the sum of the currents of the other two phases (the U-phase current and the V-phase current) whose phases are different from each other by 120 °. The opposite of the phase current.
[0083]
FIG. 15 is a graph showing the output current waveform of each phase when a four-phase motor is driven so that the phase current becomes a sine wave. Although not particularly shown, in the case of four-phase driving, it is assumed that the driving transistors and the coils of each phase of the motor are connected as follows.
[0084]
That is, the motor driving device is configured such that the upper-arm driving transistor and the lower-arm driving transistor are connected in series, as in the circuit including the driving transistors 1 and 2 and the diodes 1D and 2D in FIG. Has four circuits (half-bridge circuits) in which diodes are connected between the drain and the source of the semiconductor device. These four half bridges respectively correspond to the respective phases and are connected in parallel. One end of each half bridge is commonly connected to a power supply VCC, and the other end is commonly connected to a current detection resistor. The other end of the current detection resistor is grounded. A connection point between the upper arm drive transistor and the lower arm drive transistor of each half bridge is connected to one end of a coil of a corresponding phase. The other ends of the coils are connected to each other.
[0085]
In order to make the operation such that the phase current becomes as shown in FIG. 15, the output of the phase-specific torque generating circuit 30 in FIG. 1 may be a sine wave instead of the sawtooth wave as shown in FIG. That is, a signal that repeats a waveform of a sine wave in a phase of 0 ° to 90 ° is used as the signal TS2, and a signal that repeats a waveform of a sine wave in a phase of 90 ° to 180 ° is used as the signal TS1. .
[0086]
In the case of driving an even-numbered phase motor, one of the upper-arm drive transistor and the other of the lower-arm drive transistor are driven in two phases (phases opposite to each other) having different current directions and substantially equal magnitudes. Since it suffices to drive the transistors simultaneously as a set, control can be performed in the same manner as when a motor having substantially half the number of phases is driven. That is, the four-phase motor can be operated by two-phase sine wave driving using sine waves having phases different from each other by 90 ° as target values of the respective phase currents.
[0087]
In a period T41 in FIG. 15, as in periods T1 and T2 in FIG. 6, a period in which the U-phase upper-arm drive transistor and the W-phase lower-arm drive transistor are simultaneously made conductive, and a V-phase lower-arm drive transistor and X A period in which the upper-arm drive transistors are simultaneously turned on is alternately provided.
[0088]
During the period in which the U-phase upper-arm drive transistor and the W-phase lower-arm drive transistor are conducted, current passing through these drive transistors, the U-phase coil, and the W-phase coil flows through the current detection resistor. At this time, the V-phase current and the X-phase current flow as regenerative currents. Since only the U-phase current (W-phase current) flows through the current detection resistor, the U-phase current can be detected, and the feedback control can be performed so that the U-phase and W-phase currents become the target values.
[0089]
Further, during a period in which the V-phase lower arm drive transistor and the X-phase upper arm drive transistor are conducted, a current passing through the drive transistor, the V-phase coil, and the X-phase coil flows through the current detection resistor. At this time, the U-phase current and the W-phase current flow as regenerative currents. Since only the V-phase current (X-phase current) flows through the current detection resistor, the V-phase current can be detected, and the feedback control can be performed so that the V-phase and X-phase currents become the target values. In this way, the period in which the phase current to be detected flows through the current detection resistor does not overlap with the period in which another phase current flows through the current detection resistor.
[0090]
Similarly, in the period T42, the U-phase upper-arm drive transistor and the W-phase lower-arm drive transistor are simultaneously turned on, and the V-phase upper-arm drive transistor and the X-phase lower-arm drive transistor are turned on simultaneously. And a period. In the period T43, a period during which the U-phase lower-arm drive transistor and the W-phase upper-arm drive transistor are simultaneously conducted, and a period during which the V-phase upper-arm drive transistor and the X-phase lower-arm drive transistor are simultaneously conducted. Provide. In the period T44, a period during which the U-phase lower-arm drive transistor and the W-phase upper-arm drive transistor are simultaneously conducted, and a period during which the V-phase lower-arm drive transistor and the X-phase upper-arm drive transistor are simultaneously conducted. Provide. As a result, the four-phase motor can be driven so that the phase current becomes a sine wave.
[0091]
FIG. 16 is a graph showing the output current waveform of each phase when a six-phase motor is driven so that the phase current becomes a sine wave. Although not shown, in the case of six-phase driving, it is assumed that the driving transistors and the coils of each phase of the motor are connected as follows.
[0092]
That is, the motor drive device has six half bridges. These six half bridges correspond to each phase, respectively, and are connected in parallel. One end of each half bridge is commonly connected to a power supply VCC, and the other end is commonly connected to a current detection resistor. The other end of the current detection resistor is grounded. A connection point between the upper arm drive transistor and the lower arm drive transistor of each half bridge is connected to one end of a coil of a corresponding phase. The other ends of the coils are connected to each other.
[0093]
In order to make the operation such that the phase current becomes as shown in FIG. 16, the output of the phase-specific torque generating circuit 30 in FIG. 1 may be a sine wave instead of the sawtooth wave as shown in FIG. That is, a signal that repeats the waveform of the sine wave in the interval of 0 ° to 60 °, 60 ° to 120 °, or 120 ° to 180 ° may be used.
[0094]
When a six-phase motor is driven, the phase is an even-numbered phase, as in the case of the four-phase motor. What is necessary is just to drive simultaneously at the same time with the lower arm side drive transistor of a phase. Therefore, control can be performed in substantially the same manner as when a motor having half the number of phases is driven. That is, the six-phase motor can be operated by three-phase sine wave driving using sine waves having phases different from each other by 60 ° as target values of the respective phase currents.
[0095]
In a period T61 of FIG. 16, a period in which the U-phase upper-arm drive transistor and the X-phase lower-arm drive transistor are simultaneously turned on, and a period in which the V-phase lower-arm drive transistor and the Y-phase upper-arm drive transistor are turned on simultaneously. A period and a period in which the W-phase lower-arm drive transistor and the Z-phase upper-arm drive transistor are simultaneously turned on are sequentially provided.
[0096]
During a period in which the U-phase upper-arm drive transistor and the X-phase lower-arm drive transistor are conducted, current passing through these drive transistors, the U-phase coil, and the X-phase coil flows through the current detection resistor. At this time, currents other than the U-phase and X-phase currents flow as regenerative currents. Since only the U-phase current (X-phase current) flows through the current detection resistor, the U-phase current can be detected, and the feedback control can be performed so that the U-phase current and the X-phase current become the target values.
[0097]
Further, during a period in which the V-phase lower arm drive transistor and the Y-phase upper arm drive transistor are conducted, a current passing through the drive transistor, the V-phase coil, and the Y-phase coil flows through the current detection resistor. At this time, currents other than the V-phase and Y-phase currents flow as regenerative currents. Since only the V-phase current (Y-phase current) flows through the current detection resistor, the V-phase current can be detected, and the feedback control can be performed so that the V-phase and Y-phase currents become the target values.
[0098]
Similarly, during a period in which the W-phase lower-arm drive transistor and the Z-phase upper-arm drive transistor are simultaneously turned on, feedback control can be performed so that the W-phase and Z-phase currents become target values. In this way, the period in which the phase current to be detected flows through the current detection resistor does not overlap with the period in which another phase current flows through the current detection resistor.
[0099]
Similarly, in the period T62, the U-phase upper-arm drive transistor and the X-phase lower-arm drive transistor are simultaneously turned on, and the V-phase upper-arm drive transistor and the Y-phase lower-arm drive transistor are turned on simultaneously. A period and a period in which the W-phase lower-arm drive transistor and the Z-phase upper-arm drive transistor are simultaneously turned on are sequentially provided.
[0100]
In the period T63, a period during which the U-phase upper-arm drive transistor and the X-phase lower-arm drive transistor are simultaneously turned on, a period during which the V-phase upper-arm drive transistor and the Y-phase lower-arm drive transistor are simultaneously turned on, A period in which the W-phase upper-arm drive transistor and the Z-phase lower-arm drive transistor are simultaneously turned on is sequentially provided. Hereinafter, the transistors to be turned on are similarly switched in the periods T64 to T66. As a result, the six-phase motor can be driven so that the phase current becomes a sine wave.
[0101]
When driving a six-phase motor, the transistors to be turned on may be switched as follows. That is, in the period T62 in FIG. 16, the U-phase upper-arm drive transistor and the X-phase lower-arm drive transistor are simultaneously turned on. In this period, a period during which the W-phase lower-arm drive transistor and the Z-phase upper-arm drive transistor are simultaneously turned on, and a period during which the Y-phase lower-arm drive transistor and the V-phase upper-arm drive transistor are simultaneously turned on. Provide repeatedly.
[0102]
In the period T63, the V-phase upper-arm drive transistor and the Y-phase lower-arm drive transistor are simultaneously turned on. In this period, a period during which the X-phase lower-arm drive transistor and the U-phase upper-arm drive transistor are simultaneously conducted, and a period during which the Z-phase lower-arm drive transistor and the W-phase upper-arm drive transistor are simultaneously conducted. Provide repeatedly.
[0103]
Similarly, in the period T64, the W-phase upper-arm drive transistor and the Z-phase lower-arm drive transistor are simultaneously turned on. In this period, a period in which the Y-phase lower-arm drive transistor and the V-phase upper-arm drive transistor are simultaneously turned on, and a period in which the U-phase lower-arm drive transistor and the X-phase upper-arm drive transistor are turned on simultaneously. Provide repeatedly. Hereinafter, the transistors to be turned on are similarly switched in the periods T65, T66, and the like.
[0104]
FIG. 17 is a graph showing an output current waveform of each phase when an 8-phase motor is driven so that the phase current becomes a sine wave. Although not particularly shown, in the case of eight-phase driving, it is assumed that the driving transistors and the coils of each phase of the motor are connected as follows.
[0105]
That is, the motor drive device has eight half bridges. These eight half bridges correspond to the respective phases and are connected in parallel. One end of each half bridge is commonly connected to a power supply VCC, and the other end is commonly connected to a current detection resistor. The other end of the current detection resistor is grounded. A connection point between the upper arm drive transistor and the lower arm drive transistor of each half bridge is connected to one end of a coil of a corresponding phase. The other ends of the coils are connected to each other.
[0106]
In order to make the operation such that the phase current becomes as shown in FIG. 17, the output of the phase-specific torque generating circuit 30 in FIG. 1 may be a sine wave instead of the sawtooth wave as shown in FIG. That is, a signal that repeats the waveform of the sine wave in the phase of 0 ° to 45 °, 45 ° to 90 °, 90 ° to 135 °, or 135 ° to 180 ° may be used.
[0107]
When an 8-phase motor is driven, the phase is an even-numbered phase as in the case of the 4-phase motor. What is necessary is just to drive simultaneously at the same time with the lower arm side drive transistor of a phase. Therefore, control can be performed in substantially the same manner as when a motor having half the number of phases is driven. That is, the eight-phase motor can be operated by four-phase sine wave driving using sine waves having phases different from each other by 45 ° as target values of the respective phase currents.
[0108]
In a period T81 in FIG. 17, a period in which the U-phase upper-arm drive transistor and the Y-phase lower-arm drive transistor are simultaneously conducted, and a period in which the V-phase lower-arm drive transistor and the Z-phase upper-arm drive transistor are simultaneously conducted. A period, a period in which the W-phase lower arm side drive transistor and the A-phase upper arm side drive transistor are simultaneously conducted, and a period in which the X-phase lower arm side drive transistor and the B-phase upper arm side drive transistor are simultaneously conducted. Provide.
[0109]
During a period in which the U-phase upper-arm drive transistor and the Y-phase lower-arm drive transistor are conducted, a current passing through the drive transistor, the U-phase coil, and the Y-phase coil flows through the current detection resistor. At this time, currents other than the U-phase and Y-phase currents flow as regenerative currents. Since only the U-phase current (Y-phase current) flows through the current detection resistor, the U-phase current can be detected, and the feedback control can be performed so that the U-phase current and the Y-phase current become the target values.
[0110]
Further, during a period in which the V-phase lower arm drive transistor and the Z-phase upper arm drive transistor are conducted, a current passing through the drive transistor, the V-phase coil, and the Z-phase coil flows through the current detection resistor. At this time, currents other than the V-phase and Z-phase currents flow as regenerative currents. Since only the V-phase current (Z-phase current) flows through the current detection resistor, the V-phase current can be detected, and the feedback control can be performed so that the V-phase and Z-phase currents become the target values.
[0111]
Similarly, during a period in which the W-phase lower-arm drive transistor and the A-phase upper-arm drive transistor are simultaneously turned on, feedback control can be performed so that the W-phase and A-phase currents have target values. During the period in which the X-phase lower-arm drive transistor and the B-phase upper-arm drive transistor are simultaneously turned on, feedback control can be performed so that the X-phase and B-phase currents become target values. In this way, the period in which the phase current to be detected flows through the current detection resistor does not overlap with the period in which another phase current flows through the current detection resistor.
[0112]
Similarly, in the period T82, a period in which the U-phase upper-arm drive transistor and the Y-phase lower-arm drive transistor are simultaneously turned on, and a period in which the V-phase upper-arm drive transistor and the Z-phase lower-arm drive transistor are turned on simultaneously. A period, a period in which the W-phase lower arm side drive transistor and the A-phase upper arm side drive transistor are simultaneously conducted, and a period in which the X-phase lower arm side drive transistor and the B-phase upper arm side drive transistor are simultaneously conducted. Provide. Hereinafter, the transistors to be turned on are similarly switched in the periods T83 to T88. As a result, the eight-phase motor can be driven so that the phase current becomes a sine wave.
[0113]
Further, a case where a motor of an even-numbered phase of 10 or more phases is driven can be similarly described.
[0114]
Note that in the third embodiment, the peak current control as described in the first embodiment may be performed, or the PWM control using a triangular wave slice as described in the second embodiment may be performed. .
[0115]
In the above embodiments, the motor driving device has been described as including the diodes 1D to 6D. Alternatively, each of the driving transistors 1 to 6 may include a parasitic diode. That is, a diode may be structurally present in each of the drive transistors 1 to 6.
[0116]
Further, the driving transistors 1 to 6 may be transistors other than the n-type MOS transistor.
[0117]
Also, the case where the current detection resistor 7 is provided between the sources of the lower arm side drive transistors 2, 4, and 6 and the ground has been described. May be provided with a current detection resistor.
[0118]
Also, the connection of the motor has been described as a Y connection, but may be a delta connection.
[0119]
Also, the case has been described where the three-phase currents are set to the U-phase, V-phase, and W-phase in order from the one with the leading phase. However, in order to reverse the motor, the W-phase, the V-phase, and the U-phase are used in order. The same applies to the case where
[0120]
Further, the case where the position detection is performed using the Hall element has been described, but it is not always necessary to use the Hall element. For example, a CR filter circuit is provided for each of the U-phase, V-phase, and W-phase to filter harmonic components of the PWM drive current, and for each phase, the filter output and the reference potential of the motor (that is, Y-connected The position of the rotor of the motor can be detected by comparing with the potential of the connection point of the three coils. However, in consideration of a malfunction caused by a harmonic component of the PWM drive current, it is more advantageous to use a Hall element.
[0121]
In addition, it is possible to perform synchronous rectification drive by synchronizing one of the driving transistors connected in series with the other driving transistor and inverting the phase of the driving transistors forming the half bridge. It is.
[0122]
It is also possible to drive the motor without using a sensor. That is, before and after the zero crossing point at which the direction of the phase current is switched, the drive transistor of the phase is turned off to provide a mask period in which the phase current of the phase is zero. Can be obtained. By providing a torque command signal so that the phase current before and after the mask period is zero, a steep change in the phase current at the time of transition to the mask period is prevented. Driving can be realized.
[0123]
Also, the case where one detection resistor is used has been described. However, in the case of multi-phase, the number of detection resistors may be increased to two or more. That is, taking the case of eight phases as an example, the number of detection resistors is two, the drive transistors of four phases are commonly connected to one of the detection resistors, and the drive transistors of the remaining phases are commonly used for the other detection resistors. You may connect. Then, since there is no restriction that the phase using one detection resistor and the phase using the other detection resistor must use each other's regeneration periods, it is possible to increase the maximum duty of the PWM control. it can.
[0124]
【The invention's effect】
According to the motor drive device of the present invention, it is possible to prevent the phase current from suddenly changing, so that it is possible to suppress the occurrence of motor vibration and noise during phase switching. Since the number of current detection resistors used is smaller than the number of phases, the size of the device can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram of a motor drive device according to a first embodiment of the present invention.
FIG. 2 is a graph showing a target waveform of each phase current of the motor of FIG. 1;
FIG. 3 is a block diagram illustrating an example of a configuration of a phase-specific torque signal generation circuit of FIG. 1;
FIG. 4 is a graph showing signals related to a position detection circuit and a phase-specific torque signal generation circuit.
FIG. 5 is a block diagram illustrating an example of a configuration of a logic control circuit in FIG. 1;
FIG. 6 is a graph showing input / output signals of the logic control circuit and the comparator of FIG. 1;
FIG. 7 is a graph showing a phase current in the motor drive device of FIG. 1;
FIG. 8 is an explanatory diagram illustrating a path of a current flowing through a motor during a period T1.
FIG. 9 is an explanatory diagram illustrating a path of a current flowing through a motor during a period T2.
FIG. 10 is an explanatory diagram illustrating a path of a current flowing through a motor during a period T3.
FIG. 11 is a block diagram of a motor drive device according to a second embodiment of the present invention.
FIG. 12 is a circuit diagram illustrating an example of a configuration of an offset adding limiter circuit.
13 is a graph showing a phase current and a signal of a conduction period control unit in the motor drive device of FIG. 11;
FIG. 14 is a graph showing the output current waveform of each phase when a three-phase motor is driven so that the phase current becomes a sine wave.
FIG. 15 is a graph showing an output current waveform of each phase when a four-phase motor is driven so that the phase current becomes a sine wave.
FIG. 16 is a graph showing an output current waveform of each phase when a six-phase motor is driven so that the phase current becomes a sine wave.
FIG. 17 is a graph showing the output current waveform of each phase when an 8-phase motor is driven so that the phase current becomes a sine wave.
FIG. 18 is a block diagram of a conventional motor drive device using a peak current detection method.
FIG. 19 is a graph showing a change over time of each phase current of a motor driven by the motor drive device of FIG. 18;
20 is a graph showing the current detection resistance voltage (motor current detection signal) and the V-phase and W-phase currents near time t = tz in FIG. 19, with the time axis enlarged.
[Explanation of symbols]
1-3 Upper-arm drive transistor (upper-arm switching element)
4 to 6 Lower arm drive transistor (Lower arm switching element)
1D to 6D diode
7 Current detection resistor
10 Motor
11 U-phase coil
12 V phase coil
13 W phase coil
21 Hall element circuit
22 Position detection circuit
23 Energized phase switching circuit
24 pre-drive circuit
30,230 Phase-specific torque signal generation circuit
40 logic control circuit
51 first comparator
52 Second comparator
100, 200 energization period control unit

Claims (9)

A plurality of output circuits having an upper-arm switching element and a lower-arm switching element connected in series are provided, and the output circuits are connected to the plurality of output circuits in series and commonly, and supplied to the plurality of output circuits. A motor driving method for a motor driving device comprising a current detection resistor for detecting a current flowing through the motor, and supplying a current to the motor from a connection point between the upper arm switching element and the lower arm switching element in each of the output circuits. hand,
Obtaining a position signal according to the position of the rotor of the motor;
Selecting one switching element in any one of the plurality of output circuits according to the position signal, and conducting the switching element in a period corresponding to a predetermined electrical angle;
When the switching element to be turned on is the upper arm switching element, the lower arm switching element in any one or more of the plurality of output circuits performs a switching operation, and the switching element to be turned on is the lower arm switching element. In some cases, the step of causing the upper arm side switching element in any one or more of the plurality of output circuits to perform a switching operation,
The step of causing the switching operation,
In each of a plurality of periods in which a period corresponding to the predetermined electrical angle is divided, a first period in which one switching element is turned on among the switching elements performing the switching operation, and the first switching element A motor driving method for controlling the switching operation according to an input torque command signal and a voltage generated at the current detection resistor so that there is a second period in which different switching elements are turned on. The motor driving method according to claim 1,
In the step of performing the switching operation,
The motor driving method according to claim 1, wherein the first period starts when a reference pulse is input, and ends when a voltage generated at the current detection resistor reaches a target signal. The motor driving method according to claim 2,
In the step of performing the switching operation,
When the reference pulse is input, the first period is started after all the switching elements to be switched are turned off. With an even number of four or more output circuits having an upper arm switching element and a lower arm switching element connected in series, and in series with the four or more even number output circuits, and commonly connected, A current detection resistor for detecting a current supplied to the four or more even-numbered output circuits, and a current flowing to a motor from a connection point between an upper arm switching element and a lower arm switching element in each of the output circuits. A motor driving method in a motor driving device for supplying
Obtaining a position signal according to the position of the rotor of the motor;
Selecting one switching element in any one of the plurality of output circuits in accordance with the position signal; and selecting the selected switching element when the selected switching element is an upper arm side switching element. The set of the lower arm switching element and the selected switching element corresponding to the phase opposite to the corresponding phase is the lower arm switching element, if the selected switching element is a lower arm switching element, A step of conducting a set of the upper arm side switching element and the selected switching element corresponding to the phase opposite to the phase corresponding to the selected switching element in a period corresponding to a predetermined electrical angle; ,
If the selected switching element is an upper-arm switching element, it corresponds to each of the lower-arm switching elements in any one of the remaining plurality of the plurality of output circuits and a phase opposite to the phase corresponding to each of the lower-arm switching elements. Each of the sets of the output circuit and the upper-arm switching element that performs a switching operation, and when the selected switching element is a lower-arm switching element, the upper arm of any of the remaining plurality of output circuits. Causing each of the sets of the side switching elements and the lower arm side switching elements of the output circuit corresponding to the phase of the opposite phase of the phase corresponding to each of the side switching elements to perform a switching operation,
The step of causing the switching operation,
In each of a plurality of periods into which a period corresponding to the predetermined electrical angle is divided, a first period in which one set of switching elements is turned on among a set of switching elements for performing the switching operation, The switching operation is controlled in accordance with the input torque command signal and the voltage generated in the current detection resistor so that there is a second period in which a set of switching elements different from the switching element is conducted. Motor drive method. The motor driving method according to claim 4,
In the step of performing the switching operation,
The motor driving method according to claim 1, wherein the first period starts when a reference pulse is input, and ends when a voltage generated at the current detection resistor reaches a target signal. The motor driving method according to claim 5,
In the step of performing the switching operation,
When the reference pulse is input, the first period is started after all the switching elements to be switched are turned off. A plurality of output circuits having an upper-arm switching element and a lower-arm switching element connected in series are provided, and the output circuits are connected to the plurality of output circuits in series and commonly, and supplied to the plurality of output circuits. Motor in a motor drive device that includes a current detection resistor for detecting a current flowing through the motor and supplies current to a multi-phase motor coil from a connection point between an upper arm switching element and a lower arm switching element in each of the output circuits. A driving method,
A section in which the phase currents of the plurality of phases of the motor coils are flowing simultaneously is divided into a PWM (pulse width modulation) control period.
A signal corresponding to a current value to be passed for each switching element and the current detection so that a current flowing through the current detection resistor matches a current passing through one specific switching element on the upper arm side or the lower arm side. A motor that performs PWM control so as to have a period in which each of the switching elements is selectively turned on until a signal obtained from a resistor matches, and a period in which a phase current other than a phase related to the specific switching element is in a regenerative state. Drive method. A plurality of output circuits having an upper arm switching element and a lower arm switching element connected in series are provided, and a current is supplied to the motor from a connection point between the upper arm switching element and the lower arm switching element in each of the output circuits. A motor drive device for supplying
A current detection resistor for detecting a current supplied to the plurality of output circuits, in series with the plurality of output circuits, and commonly connected;
A position detection unit that outputs a position signal according to the position of the rotor of the motor,
One switching element in any one of the plurality of output circuits is selected according to the position signal, and is turned on for a period corresponding to a predetermined electrical angle, and the switching element to be turned on is an upper arm side switching. If the element is an element, the lower arm switching element in any one of the plurality of output circuits performs a switching operation, and if the switching element to be turned on is the lower arm switching element, the remaining of the plurality of output circuits An energizing phase switching circuit that causes the upper arm switching element in any one of the plurality to perform a switching operation;
In each of a plurality of periods in which a period corresponding to the predetermined electrical angle is divided, a first period in which one switching element is turned on among the switching elements performing the switching operation, and the first switching element A switching operation control signal for controlling a switching operation by the energized phase switching circuit in accordance with the input torque command signal and the voltage generated at the current detection resistor so that there is a second period for conducting different switching elements. A motor drive device comprising: an energization period control unit that generates and outputs a current. The motor drive device according to claim 8,
The energization period control unit,
In response to the torque command signal and the position signal, a first target signal corresponding to a target value of a current to be passed through the current detection resistor in the first period, and a current detection resistor in the second period. A second target signal corresponding to a target value of the current to be passed, and a phase-specific torque signal generating circuit for outputting the target signal;
A first comparator that determines whether or not the voltage generated at the current detection resistor exceeds the first target signal, and outputs a result of the determination;
A second comparator for determining whether or not the voltage generated at the current detection resistor exceeds the second target signal, and outputting the result;
A logic control circuit that generates and outputs the switching operation control signal in accordance with a reference pulse that defines a cycle of the switching operation and outputs of the first and second comparators,
The logic control circuit,
When the determination result of the first comparator indicates that the voltage generated at the current detection resistor exceeds the first target signal, the first period is terminated, and the second comparator And generating and outputting the switching operation control signal so as to end the second period when the determination result indicates that the voltage generated in the current detection resistor exceeds the second target signal. A motor drive device characterized by the following.

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