JP3247281B2 - Motor drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive circuit for selectively supplying a drive current to a plurality of stator coils provided on a stator to rotate a rotor provided with a plurality of rotor magnets, and in particular, to improve the startup of the motor drive circuit. About.

[0002]

2. Description of the Related Art Conventionally, brushless motors have been used as driving sources for various devices. This brushless motor selectively supplies a drive current to a plurality of stator coils provided on a stator, generates a rotating magnetic field, and rotates a rotor provided with a plurality of rotor magnets.

In order to rotate the rotor, the rotating magnetic field generated by the stator coil must be determined according to the position of the rotor. Therefore, the rotor position (rotational phase) is detected by a Hall element which is a magnetic field detection element,
Control of motor drive current has been performed.

That is, in the case of a three-phase motor, three Hall elements are provided to detect the rotation phase of each phase rotor, and the output of the three Hall elements is used to drive the stator coil. Switch the current.

A floppy disk drive (FD)
The motor used in D) also needs to detect the absolute position of the floppy disk. In a normal case, magnetization for an index is applied to a predetermined point of the rotor, and this is detected by a Hall element for the index. Therefore, in a three-phase motor, four Hall elements are required. Such an n-phase motor has n + 1 Hall elements (sensors)
Is provided as a full sensor type.

[0006] In the full sensor system, the motor drive current supplied to the stator coil is controlled (controls the switching of the output transistor) by using the rotation phase signal from each Hall element, thereby ensuring the control of the motor drive current. Can be done. In addition, since the position of the rotor can always be detected, reliable starting can be performed.

However, in order to reduce the weight, size, and cost of the motor including the motor drive circuit, there is a demand to reduce the number of Hall elements (sensors).

[0008] Therefore, a motor drive device of a type not provided with a sensor (0 sensor type) is also known. In the zero-sensor type, the back electromotive force generated with the rotation of the rotor is detected, and the energization of the stator coil is switched accordingly. There is also a type in which a change in a magnetic field caused by the rotation of a rotor is detected by a frequency generator (FG), and the energization of the stator coil is switched based on the change.

However, these rotation detecting means have no problem when the rotation speed is high, but cannot detect the rotation when the rotation speed is low, particularly at the time of startup. Therefore,
There was a problem that reliable start control could not be performed.

Therefore, in the case of the 0-sensor type, activation is achieved by the following control.

(I) At start-up, a predetermined pulse voltage is applied to the stator coil, and the impedance of the stator coil is measured to detect the rotor position. Then, based on the detected rotor position, the energization of the stator coil is controlled to start.

(Ii) The rotor position during automatic operation is not detected.
According to a predetermined energizing sequence, the rotor is gradually rotated to start.

[0013]

However, the above (i)
In the method of (1), a special circuit is required for impedance measurement, and there is a problem that the circuit scale becomes considerably large. In addition, there is another problem that in order to reliably measure the impedance, there are many restrictions on the manufacture of the stator coil.

In the method (ii), when the load of the motor fluctuates, a desired start cannot be performed in some cases, and there is a problem that it is difficult to start reliably over a wide load range.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a motor drive circuit that can start reliably with a small number of sensors.

[0016]

SUMMARY OF THE INVENTION The present invention provides a motor drive circuit for selectively supplying a drive current to a plurality of stator coils provided on a stator and rotating a rotor provided with a plurality of rotor magnets. It has a rotor position detector for detecting a position, a frequency generator for generating a frequency signal according to the rotation of the rotor by rotation of the rotor, and an energization unit for controlling energization to the stator coil. .

Then, at the time of startup, the energizing means first energizes the stator coil in a predetermined direction to stop the rotor at a stable point. Next, a plurality of stator coils are sequentially energized in a predetermined energization pattern to rotate the rotor at a stable point in a predetermined direction. In this way, when the rotor starts to rotate in a predetermined direction, since a correct frequency signal is obtained, the drive current to the plurality of stator coils is controlled based on the rotor position and the frequency signal. In this way, the rotor position detector and the frequency generator
Just by providing them one by one, reliable starting can be achieved.

In the first energization at the time of starting, the energizing direction to the stator coil is determined in a predetermined direction in accordance with the rotor position detected by the rotor position detector, and the energization is held for a predetermined time. As a result, the rotor can be reliably rotated in the predetermined direction from the initial position. In particular, the rotation of the rotor can be easily detected as a phase change by the rotor position detector, and the control is facilitated.

Further, the present invention further comprises voltage detecting means for detecting whether or not the voltage across the at least one stator coil is within a predetermined range. Is not within a predetermined range, reverse rotation is detected, and when the reverse rotation is performed, the power supply means controls the power supply so as to perform the pre-start power supply, the start power supply, and then perform the steady-state power supply. . This makes it possible to automatically restart the vehicle when it is reversed.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of the circuit of the embodiment, and FIG. 2 is a waveform diagram of each part.

The motor 10 has a three-phase stator coil 10.
U, 10 V, and 10 W, and a predetermined current is selectively passed from the output circuit 12 to the stator coils 10 U, 10 V, and 10 W to rotate a rotor 10 R having a multi-pole rotor magnet.

A frequency generator 14 is provided at a position facing the rotor 10R, and generates an AC signal FG0 synchronized with the rotation of the rotor 10R. And this FG0
Is shaped into a rectangular wave by the Schmitt comparator 16.

The U-phase Hall element 18 is provided at a position where the magnetic flux of the driving magnetic pole can be detected, and outputs an AC signal HU0 corresponding to the position of the rotor 10R. And this HU
0 is shaped into a rectangular wave by the Schmitt comparator 20.

The output FG 1 of the Schmitt comparator 16 is supplied to a first clock switching circuit 22 and a second clock switching circuit 24. The first and second clock switching circuits 22 and 24 invert and output FG1 during normal rotation. The output of the first clock switching circuit 22 is supplied to a U-phase waveform shaping circuit 26. The U-phase waveform shaping circuit 26 captures HU1 output from the Schmitt comparator 20 using FG1 as a clock, and outputs a signal HU2. In this example, since FG1 is inverted by the first clock switching circuit 22, the U-phase waveform shaping circuit 26
Captures HU1 at the fall of FG1. For this reason, HU2 is delayed from HU1 by half a cycle of FG1.

On the other hand, the output of the second clock switching circuit 24 is supplied to a 012 counter 28. The 012 counter is a counter that repeats three types of outputs of “0”, “1”, and “2”. Note that the second clock switching circuit 24 also has F
To invert G1, the 012 counter 28 sequentially counts up at the fall of FG1.

Then, the U-phase waveform shaping circuits 26 and 012
The output of the counter 28 is supplied to the output circuit 12. That is, the output circuit 12 is sequentially supplied with six types of signals H0, H1, H2, L0, L1, and L2 based on FG0 and HU0. Then, the output circuit 12 switches on / off of the built-in switching transistor,
The currents flowing through the stator coils 10U, 10V, and 10W are sequentially switched, and drive currents having a phase difference of 120 ° flow to generate a predetermined rotating magnetic field.

As shown in FIG. 3, the current in this example is H0 (V → U), H1 (W → U), H2 (W → W).
V), L0 (U → V), L1 (U → W), L2 (V →
As shown in W), the stator coil is energized.

Here, the output circuit 12 is composed of three series-connected source-side and sink-side transistors provided between the power supply and the ground, and the midpoint is connected to each of the stator coils 10U, 10V, and 10W. Have been. Therefore, by sequentially turning on these transistors, the above-described energization can be performed.

The output HU1 of the Schmitt comparator 20 is supplied to the polarity determination latch 30. The polarity determination latch 30 latches the “H” and “L” signals HU1 sent from the Schmitt comparator 20 at the timing of the pulse supplied from the system reset circuit 32. Here, the system reset circuit 32 generates a reset pulse when the power supply rises at the time of startup, and the like.
The polarity determination latch 30 latches the signal HU1 at that time.

The output of the polarity determination latch 30 and the signal H
U1 is input to the exclusive OR 34, and when both are different, "H" is output from this. That is, after the latch in the polarity determination latch 30, the rotor 1
When OR rotates and the signal HU1 switches between “H” and “L”, “H” is output from the exclusive OR 34. As can be seen from FIG. 2, when HU1 is "H", H2 is energized, and when it is "L", L2 is L2.
, The rotor 10 </ b> R rotates, and “H” is output from the exclusive OR 34.

The output of the exclusive OR 34 is input to an edge extracting circuit 36, where the rising and falling edges are detected and converted into one-shot pulses of a predetermined length. The output of the edge elimination circuit 36 is input to the reset terminal of the start timer 38 via the OR gate 37. The OR gate 37 is also supplied with a reset signal from the system reset circuit 32, and the start-up timer 38 uses the output pulse of the edge removal circuit 36 and the reset signal to
Reset. Then, the activation timer 38 counts the clock from the clock generator 40 and measures a predetermined time.

The output of the polarity determination latch 30 is also supplied to the U-phase waveform shaping circuit 26, and the "H" of HU1 is output.
“L” is taken into the U-phase waveform shaping circuit 26 as it is.

The start timer 38 measures two types of time, a stop determination time T0 and an energization switching time T1, and outputs a second energization switching clock and a third and fourth energization switching clock.

Then, the second energization switching clock is supplied to the mask determination circuit 42. The output of the exclusive OR 34 and the output FG1 of the Schmitt comparator 16 are also supplied to the mask determination circuit 42.
Then, the mask determination circuit 42 generates three signals M1, M2, and M3 for controlling the timing of the energization pattern at the time of startup from the input signals.

M1 is supplied to a logic fixing circuit 44,
The logic fixing circuit 44 fixes the logic in the output circuit 12 to a predetermined one when M1 is "L".

In the steady mode where M1 = H, the HG edge removal signal is generated at a cycle corresponding to the rotation speed, and the start timer 38 is reset by the edge removal signal.
Cannot count up to T0. However, if the motor speed decreases due to some abnormality, the second energization switching clock is output, the system is reset, and the system is restarted.

Further, the start-up timer 38 generates third and fourth energizing clocks in accordance with the count value, and supplies this to the second clock switching circuit 24. The second clock switching circuit 24 is also supplied with M2 and M3 from the mask determination circuit 42, and the second switching circuit 24 supplies F
Whether to output G1 as it is, to output the third and fourth switching clocks, or to generate pulses independently M2, M
3 to control. The first clock switching circuit 22 receives M2 from the mask determination circuit 42, and switches whether or not to output FG1.

Next, the operation at the time of starting the circuit will be described.
A description will be given based on FIG. First, the signal S / S falls according to the start command. This S / S is input to the system reset circuit 32 and the system reset circuit 3
2 generates a reset pulse in response to the fall of the signal S / S.

Thus, the first energizing period is started.
In the first energization period, first, a reset pulse
The polarity determination latch 30 then takes in HU1. The example in the figure shows a case where HU1 at this time is “L”. The value of the polarity determination latch 30 is taken into the U-phase waveform shaping circuit 26, from which "L" is output. On the other hand, the mask determination circuit 42 sets all of M1, M2, and M3 to "L" in response to the system reset. The logic fixing circuit 44 fixes the output of the output circuit 12 to H2 based on “L” of M1 and the value of the polarity determination latch 30. If the value captured by the U-phase waveform shaping circuit 26 is “H”, the value is fixed to L2.

The logic of the output of the output circuit 12 is H2, that is, the current of the stator coil is fixed to the current of W → U. The output torque of the motor in such a logic H2 is different from the rotor position determined by the output of the HU in FIG.
It becomes a value as shown in. In the figure, the positive region is the forward rotation direction and the negative region is the reverse rotation direction, and the rotor 10R moves to the point P in the diagram, that is, the point where the HU becomes the lowest.

As described above, the energization of a certain logic in accordance with the position of the rotor 10R causes the rotor position to move toward a predetermined point. In addition, when the rotor 10R vibrates, the output from the exclusive OR 34 changes, and a plurality of pulses may be output from the edge removal circuit 36. However, each time, only the activation timer 38 is reset. .

The activation timer 38 counts after being reset by the output of the exclusive OR 34, and outputs a pulse as the second energization switching clock when T0 is measured. Thereby, the rotor position at the time of the second energization switching is substantially in the vicinity of the point P. The mask determination circuit 42 raises M1 by a second current switching clock that can prevent reverse rotation during the second current. Thus, the logic fixing by the logic fixing circuit 44 is released.

The signal 012 is reset to "H" and reset to "0", and the 012 counter 28 continues to output "0" even when the logic fixing by the logic fixing circuit 44 is released. Therefore, in the second energization period, the energization logic is set to L0.

The activation timer 38 counts the time T1 and outputs a third energization switching clock.

The third and fourth energization switching clocks are:
The signal is supplied to the second clock switching circuit 24, and 012
It is input to the counter 28. Therefore, 012 counter 2
The count value of 8 is set to “1” in the third energizing period and “2” in the fourth energizing period. Therefore, in the energization logic fixed to the first energization period H2, the second energization period is set to L0 by the second energization switching clock, and then the third energization period is set to L1 by the third energization switching clock. The fourth energization period is set to L2 according to the fourth energization switching clock.
become. Note that, during the time T1, the rotor 10R is moved to an electrical angle of 60 degrees.
時間 A sufficient time has been set for rotation.

In the fourth energizing period, the mask determination circuit 4
2 sees the output of exclusive OR 34. At this stage, the output of the polarity determination latch 30 is "L", but the rotation of the rotor 10R causes the HU1 to go high, and at this stage the output of the exclusive OR 34 goes high. The mask determination circuit 42 raises M2 according to the "H" of HU1.

On the other hand, the rotational speed of the rotor is such that the FG0 is sufficiently generated by the rotational driving of the rotor. Therefore, the first clock switching circuit 22 is switched by the rising edge of M2 so as to output FG1 as it is. Then, at the next fall of FG1,
The U-phase waveform shaping circuit 26 outputs H at every falling edge of FG1.
The operation shifts to the steady rotation for taking in U1. In this example, the rising edge of FG1 after the rising edge of M2 causes the U-phase waveform shaping circuit 2
6 reads "H".

On the other hand, the mask judgment circuit 42 raises M3 at the fall of FG1. Then, the second clock switching circuit 24 uses the M3 to set the 012 counter 28
Is set to 0, and FG1 is set to 012 counter 2
8 and a steady rotation mode is set. Thus M2
The current is "L2" at the fall of FG1 after the rise of
After switching from “H0” to “H0”, the steady energization pattern “H1” continues to “H2”.

Here, when the load is light, the rotor may rotate sufficiently during the second energizing period or the third energizing period to reach the point Q in FIG. In this case, since the mask determination circuit 42 rises M2, the second clock switching circuit gives priority to the rise of M2 and the first FG1
M3 rises at the fall of, and the value of the 012 counter 28 is set to 0. Note that the U-phase waveform shaping circuit 26
Since H is taken in at the fall of FG1 after the rise of M2, the energization logic becomes H0.

Here, the rotor is normally rotated by such control, but may be reversed under some conditions. Therefore, in the present embodiment, a reverse rotation detecting unit 48 is provided. The reverse rotation detecting section 48 detects the state of the stator coil 10 during driving after the timing of M3.
U, 10V, and 10W voltages, that is, voltages at the output terminal of the output circuit 12, are detected, and when this voltage value is not within a predetermined range, reverse rotation is detected. That is, during reverse rotation, torque generation is smaller than during forward rotation, and the back electromotive voltage is also different from that during forward rotation. Then, the voltage value of the stator coil is different from that at the time of normal rotation, and the reverse rotation detecting section 48 detects the reverse rotation by this detection. Further, the section to be detected is performed in a short time at the timing of the edge of the FG or the like so that the reverse rotation can be detected without malfunction.

The output of the reverse rotation detecting circuit 48 is supplied to the system reset circuit 32, and the same operation as at the time of starting is repeated, so that the normal rotation of the motor is ensured.

FIG. 5 is a flowchart showing the operation of this embodiment. A reset is performed to start the motor (S11). Then, the position of the rotor 10R at this time is determined based on the output state of the Hall element 18 (S1).
2). If the output of the Hall element 18 is H, the energization logic is fixed to H2 for T0 time (S13). As a result, the rotor 10R stops at the predetermined position, and the logic is set to L0 for the T1 time to rotate the rotor 10R forward from this state (S14). Thereby, the rotor 10R rotates by 60 °. Next, in order to further rotate the rotor 10R by 60 °, it is held at L1 for T1 time (S
15).

Next, the logic is set to L2 (S16), and this logic is maintained until the polarity of the output of the Hall element 18 is inverted (S17). If the polarity is reversed, the logic is set to H0 next because the rotor has been further rotated by 60 ° (S18). As a result, the rotor 10R should be rotated so that the FG signal can be output from the frequency generator 14 normally.

In S12, if the polarity is L, L
2, L0, L1, L2, and H0 in this order (S21).
To S26), and then proceed to S19. After entering the normal logic, it is determined whether or not the rotation is the reverse. If the rotation is the reverse, the process may return to S11 and start again.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of an embodiment.

FIG. 2 is a waveform chart showing waveforms of respective units.

FIG. 3 is a diagram showing an energization logic and an energization direction.

FIG. 4 is a timing chart showing timing at the time of starting.

FIG. 5 is a flowchart showing an operation.

[Explanation of symbols]

10 motors, 12 output circuits, 14 frequency generators,
18 Hall element, 22 1st clock switching circuit, 24
2nd clock switching circuit, 26 U-phase waveform shaping circuit, 2
8 012 counter, 30 polarity judgment latch, 32 system reset circuit, 38 start timer, 42 mask judgment circuit, 44 logic fixing circuit.

Continuation of front page (56) References JP-A-7-31184 (JP, A) JP-A-7-87785 (JP, A) JP-A-7-143790 (JP, A) (58) Fields studied (Int .Cl. ⁷ , DB name) H02P 6/20 H02P 6/14

Claims (2)

(57) [Claims] 1. A rotor position detector for detecting a position of a rotor in a motor drive circuit for selectively supplying a drive current to a plurality of stator coils provided on a stator and rotating the rotor provided with a plurality of rotor magnets. A frequency generator that generates a frequency signal in accordance with the rotation of the rotor by rotation of the rotor; a pre-start energization that energizes the stator coil in a predetermined direction to stop the rotor at a stable point; and a predetermined energization pattern. In the energization at start-up to sequentially energize a plurality of stator coils and rotate the rotor at a stable point in a predetermined direction, energization at steady-state to control the drive current to the plurality of stator coils based on the rotor position and frequency signal, have a, energizing means for performing startup before power was detected by the rotor position detector rotor
Depending on the position, the direction of energizing the stator coil
A motor drive circuit characterized in that the direction is determined and the energization is maintained for a predetermined time . 2. The motor drive circuit according to claim 1 , further comprising voltage detection means for detecting whether a voltage between both ends of at least one stator coil is within a predetermined range, and when the constant-time power supply means is energized. A control means for detecting reverse rotation by detecting that the voltage across the detected stator coil is not within a predetermined range, and performing power supply before starting and power supply at start-up by the above-described power supply means at the time of reverse rotation, and then performing control to perform power supply at steady state. A motor drive circuit comprising: