JP4240832B2 - Three-phase motor phase detection circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a phase waveform detection circuit that detects a motor power generation waveform when a motor of each phase of a three-phase motor in which three-phase coils are commonly connected at a midpoint.
[0002]
[Prior art]
Conventionally, three-phase motors have been used for rotational driving in various devices, and three-phase motors have also been used for rotational driving of MD, CD, and the like. In such a three-phase motor, U, V, and W phase motor drive currents that are 120 degrees out of phase from each other are generated from the DC power from the battery by an inverter including six switching transistors, and this is used as the motor U, V , Supply to the W-phase coil to drive the motor.
[0003]
Here, it is necessary to control the phases of the U, V, and W phase motor driving currents in accordance with the rotation of the rotor of the motor, and Hall elements are widely used for rotor position detection. On the other hand, there is a great demand for omitting the Hall element, and a sensorless drive circuit that detects a rotor position by detecting a counter electromotive force from a waveform of a motor drive current is widely used.
[0004]
[Problems to be solved by the invention]
In this sensorless drive circuit, the voltage at the midpoint of the U, V, and W phase coils of the motor connected in common is compared with the voltage at the other end of each phase coil, and the back electromotive force generated in the coil from this voltage change state. The rotor position is detected by detecting electric power. Therefore, three comparators for comparing the voltages at both ends of each phase coil are required. For this reason, there has been a problem that a circuit for detecting the motor becomes large.
[0005]
The present invention has been made in view of the above problems, and an object thereof is to provide a motor waveform detection circuit capable of simplifying the circuit.
[0006]
[Means for Solving the Problems]
The present invention is a phase waveform detection circuit for detecting a motor power generation waveform at the time of driving a motor of each phase of a three-phase motor in which three-phase coils are commonly connected at a midpoint, and a drive current to each phase of the motor The first switch that selects the end of the one- phase motor coil that is turned off in response to a control signal that controls the motor, the voltage supplied through this switch, and the midpoint voltage of the motor coil are compared. As the waveform of the difference between the comparator and the voltage at the end of the motor coil of two phases that are energized and the midpoint voltage, the difference of the difference determined according to the control signal that controls the drive current to each phase of the motor A waveform synthesis output circuit that outputs a preset waveform equivalent to the waveform, an output from the comparator, and an output from the waveform synthesis output circuit are input to the comparator as one phase output that is not energized. Selects the output of, and a second switch for selecting the output of the corresponding phase from the waveform synthesis output circuit as the output of the two phases is energized, the respective phases of the waveform output from the second switch characterized in that it forces out as a.
[0007]
Thus, the motor current waveforms of a plurality of phases can be detected by one comparator. For this reason, the circuit scale can be reduced.
[0008]
Further , a signal similar to that provided with three comparators can be obtained, and the subsequent signal processing may be performed by the same circuit.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0010]
FIG. 1 is a diagram showing a schematic configuration of a system for driving a motor. The motor 10 has three-phase coils 10U, 10V, and 10W. The DSP 12 determines the timing for driving the motor, and supplies signals S 1, S 2, and S 3 to the driver 14. The driver 14 incorporates an inverter, and controls the current supply to the coils 10U, 10V, and 10W of each phase of the motor 10 by turning on and off the switching transistor of the inverter based on a signal from the DSP 12. Thereby, the motor 10 is rotationally driven.
[0011]
Here, the driver 14 detects a motor power generation waveform when the motor of each phase is driven, and supplies this information to the DSP 12. The DSP 12 detects the rotor rotational position of the motor 10 based on this detection waveform, and determines the phase of the motor drive current. As a result, the motor 10 is driven to rotate in a predetermined manner.
[0012]
FIG. 2 is a diagram schematically illustrating the inverter 10 and the waveform generating portion of the driver 14 and the motor 10. The inverter includes switching transistors 20a to 20f. The switching transistors 20a and 20b (U phase), 20c and 20d (V phase), 20e and 20f (W phase) are connected in series, respectively, and the power source VM and the ground Arranged between. That is, the switching transistors 20a, 20c, and 20e are source side switching transistors, and the switching transistors 20b, 20d, and 20f are sink side switching transistors.
[0013]
Connection points of the source side transistors 20a, 20c, and 20e and the sink side switching transistors 20b, 20d, and 20f are connected to ends of the coils 10U, 10V, and 10W of the motor 10, respectively. The other ends of the coils 10U, 10V, and 10W are commonly connected to form a midpoint.
[0014]
Accordingly, by turning on the source-side switching transistor of one phase and the sink-side switching transistor of the other phase, two coils are connected in series, and a motor driving current flows through the motor 10. For example, when the switching transistors 20a and 20d are turned on, a current flows through the coils 10U and 10V.
[0015]
Here, the motor 10 of this embodiment is 120 ° energized, and as shown in FIG. 3, 120 ° current is supplied to the coils of each phase. In addition, the motor drive current of each phase is shifted by 120 °. Therefore, the motor drive current supply phase is six phases.
[0016]
That is, switching transistors that are turned on are described as follows: (1) 20a, 20d, (2) 20a, 20f, (3) 20c, 20f, (4) 20c, 20b, (5) 20e, 20b, (6) 20e , 20d. Which phase is determined by the control signals S1, S2, and S3 from the DSP 14, the switching transistors 20a to 20f are switched on and off.
[0017]
And in this embodiment, the edge part of each phase coil of a motor is input into the switch 30, and one of these is selected. That is, in the above six phases, current does not always flow through one phase coil. The switch 30 selects the coil end of the phase in which no current flows in accordance with a control signal from the DSP 14. That is, the coil ends of the respective phases are sequentially selected in the order of (1) W, (2) V, (3) U, (4) W, (5) V, (6) U.
[0018]
The output of the switch 30 is supplied to the comparator 32. The midpoint voltage of the motor 10 is supplied to the other end of the comparator 32. Therefore, in the comparator 32, the midpoint voltage of the motor 10 and the end voltage of the coil of the phase that is not energized are sequentially compared. When the motor 10 is rotating, the current flows through the coils sequentially as shown in FIG. 3, the end of the source side coil is connected to the power source VM, and the end of the sink side coil is connected to the ground. Yes. Accordingly, the midpoint potential is an intermediate voltage (basically, VM / 2). On the other hand, the end of the coil that is not energized changes due to the counter electromotive force generated by the rotor around VM / 2. Therefore, the voltage input to the comparator 32 is a signal regarding the rotor position.
[0019]
The output of the comparator 32 is input to the switch 34. The switch 34 is controlled for switching by a control signal from the DSP 14 as in the switch 30, and sequentially outputs the respective phases from the output of the comparator 32.
[0020]
The three outputs of the switch 34 are supplied to the switches 36a to 36c, respectively. The switches 36a to 36c are supplied with a signal from the logic circuit 40, and the switches 36a to 36c select and output either the signal supplied from the switch 34 or the signal from the logic circuit 40.
[0021]
Here, the logic circuit 40 outputs either + VM / 2 or -VM / 2. That is, when comparing the motor coil end of each phase and the midpoint voltage, if the corresponding source side switching transistor is on, the voltage is VM, and this is compared with the midpoint voltage VM / 2. Become. On the other hand, when the corresponding sink-side switching transistor is ON, the voltage at the motor coil end is the ground, and when this is compared with the motor intermediate voltage, 0 and VM / 2 are compared. The logic circuit 40 generates a signal equivalent to the comparison result and outputs it.
[0022]
In the switch 36a, when the U-phase comparison result signal is output from the switch 34, the signal from the switch 34 is selected, and in the other period (energization period), the signal from the logic circuit 40 is selected. Select. Further, in the switches 36b and 36c, when the signal of the V and W phase comparison results is output from the switch 34, the signal from the switch 34 is selected, and in other periods (energization periods), the logic A signal from the circuit 40 is selected.
[0023]
As a result, the same signals as those obtained when the coil ends of the respective phases of the motor 10 and the midpoint are compared by different comparators are obtained as outputs from the switches 36a to 36c.
[0024]
Since this signal is supplied to the DSP 14, the DSP 14 is provided with the same signal as that obtained by continuously comparing the coil end and the middle point by providing three comparators. A control signal for on / off control of the switching transistor can be created.
[0025]
As described above, in the present embodiment, one comparator for detecting the waveform of the motor drive current is provided, but a waveform similar to that provided by three can be obtained.
[0026]
【The invention's effect】
As described above, according to the present invention, the motor current of each phase is sequentially compared with the midpoint voltage by one comparator. Therefore, the motor current waveforms of a plurality of phases can be detected. For this reason, the circuit scale can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing an entire motor drive system.
FIG. 2 is a diagram showing an inverter and a waveform detection circuit.
FIG. 3 is a diagram illustrating timing of motor drive current.
[Explanation of symbols]
10 motor, 12 DSP, 14 driver, 20 inverter, 30, 34, 36a, 36b, 36c switch, 32 comparator, 40 logic circuit.

Claims (1)

Each phase waveform detection circuit that detects a motor power generation waveform at the time of driving a motor of each phase of a three-phase motor in which three-phase coils are commonly connected at a midpoint;
A first switch that selects the end of one phase of the motor coil that is off in response to a control signal that controls the drive current to each phase of the motor;
A comparator that compares the voltage supplied through this switch with the midpoint voltage of the motor coil;
As the waveform of the difference between the voltage at the end of the motor coil of the two energized phases and the midpoint voltage, it is equivalent to the waveform of the difference determined according to the control signal that controls the drive current to each phase of the motor A waveform synthesis output circuit for outputting a preset waveform,
The output from the comparator and the output from the waveform synthesis output circuit are input, the output from the comparator is selected as the output of one phase that is not energized, and the waveform synthesis is output as the output of the two phases that are energized A second switch for selecting the output of the corresponding phase from the output circuit;
Have
Motor waveform detection circuit for power output by the output from the second switch and each phase of the waveform.

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