JP2002165493A - Stepping motor drive method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stepping motor drive method which excites respective winding sets of a stepping motor, having a plurality of winding sets with stepping signals according to a prescribed procedure, and can dispense with a double-voltage power supply which has complex structure and high cost. SOLUTION: High-side switching devices and low-side switching devices have both excitation step switching functions and current control functions. That is, power feed states for feeding points are changed, so as to make respective winding currents sinusoidal for a motor, and further, two or more types of feed states which are apart from each other by maximum one full step of an electrical angle are repeated and the feeding states are changed according to stepping pulses. A feeding state (hereinafter referred to as the fundamental feed state) equivalent to a balanced state of two types of feeding states is changed by a prescribed value to obtain the change of the feeding state corresponding to every one change unit of the stepping pulse. Feed states, apart from the fundamental feed state in the leading direction and in the lagging direction respectively with same excitation step differences in terms of electrical angles, are set as two types of feeding states. The difference between the two types of steps is set according to the total current of the motor or the period of the stepping signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a driving current, that is, controlling a torque in a stepping motor.

[0002]

2. Description of the Related Art Torque control in driving a five-phase stepping motor is performed by drive current control. Conventionally, drive current control is performed by converting a power supply voltage of a motor in the following manner.

FIG. 13 shows a conventional example of a five-phase stepping motor drive circuit. The switching element Ql, which is a component of the current control unit 1, is a P-type FET (field effect transistor), and the high-side switching elements Pl to P5 that supply a drive excitation current to the stepping motor 6 are P-type FETs. The low-side switch elements N1 to N5 are N-type FETs.

[0004] The plus side of the motor power supply Vm is connected to the source of the switch element Ql, and the minus side is grounded. A signal SQl which is an output of the current control signal generator 11 is provided at the gate of the switch element Ql.
And the drain is connected to one end of the coil Ll. The other end of the coil Ll is connected to a capacitor Cl, and the other end of the capacitor C1 is connected to the sources of the switch elements Nl to Nl.

[0005] The switch elements Pl to P5
Are commonly connected to the source. Condenser Cl −
The side is commonly connected to the sources of the switch elements N1 to N5. The voltage between both ends of the condenser Cl is defined as VCl. The drains of the switch elements Pl to P5 are connected to the drains of the switch elements Nl to N5, respectively, and are connected to the feeding points A to O of the stepping motor.

[0006] The stepping motor 6 has five sets of excitation windings A, B,
C, D, E, the arrangement in the stator is ABCD-D-E-
The windings A to E are annularly connected as shown below in the order of A. One end of winding D and one end of winding A are connected to form a feed point a. Connect the other end of winding A and one end of winding C to supply point A. The other end of the winding C and one end of the winding E are connected to form a feeding point c. The other end of the winding E and one end of the winding B are connected to form a feeding point d. The other end of the winding B and the other end of the winding D are connected to form a feeding point e.

The power supply point A is connected to the drains of the switch elements Pl and Nl.
To P5 and the drains of N2 to N5. The sources of the switch elements Nl to N5 are commonly connected to one end of the resistor Rl and are input to the current control signal generator 11. The other end of the resistor Rl is grounded. The current flowing through the resistor Rl is denoted by i, and the voltage at both ends is denoted by VRl.

[0008] The voltage Vref is input to the current control signal generator 11. The excitation signal generator 2 receives a signal DIR and a signal MCLK. The signals SP10 to SP50 are output from the excitation signal generation unit 2, and are connected to the gates of the switch elements P1 to SP5 via the voltage conversion unit 3 as signals SP1 to SP5, respectively. The voltage converter 3 receives the positive voltage of the capacitor Cl. The signals SN1 to SN5 are output from the excitation signal generator 2 and connected to the gates of the switch elements N1 to N5.

[Current Control Operation] A voltage Vref corresponding to a control target value of the motor drive total current i is input to the current control signal generator 11, and the value is set according to a desired torque. The switching elements P1 to P5 and N1 to N
5 applies a voltage to the feeding points A to A in a predetermined order, whereby a current flows through the motor winding, and the total current i thereof generates a voltage VRl across the resistor Rl. The VRl and the Vref are compared by the current control signal generator 11, and a signal SQl is generated based on the result.

The signal SQl causes the source and drain of the switch element Ql to repeat the on (conduction) state and the off (cutoff) state, thereby adjusting the current supplied from the motor drive power supply Vm to the coil L. When the total current i is smaller than the target current, VR1 <
Vref, and the signal SQ1 is changed so that the ON period of the switch element Q1 is lengthened. As a result, VC1 rises and the total current i
Increase. VRl> Vref when the total current I is larger than the target current
, And the signal SQl is changed so that the ON period of the switch element Ql is shortened. As a result, VCl decreases and the total current i decreases.

In this way, the total current i, ie, the drive current is controlled to the target value by changing VCl, ie, the voltage applied to the motor.

[Rotation drive operation] The excitation signal generator 2 includes a signal DIR for determining a rotation direction and a signal M for determining a rotation speed as control signals for rotationally driving the stepping motor 6.
CLK is input. The excitation signal generation unit 2 controls the control signals SP10 to SP50 (SPl to SP5) and SNl to SN5 based on these two signals.
To generate switching element groups Pl to P5 and
N1 to N5 are operated in a predetermined procedure to excite the windings, and the rotor (not shown) is rotated in the rotation direction corresponding to the signal DIR to the signal MCLK.
Is driven to rotate at a speed according to.

Each of the feeding points A to O is turned on (conducted) and turned off (cut off) with the + side of the capacitor Cl by the high-side switch elements P1 to P5, and is turned on by the low-side switch elements N1 to N5. On / off with the minus side of Cl is performed.

In the present embodiment, the operation of the P-type FETs of the switch elements P1 to P5 is a simple operation as described below for convenience of explanation. If the gate voltage is "sufficiently" lower than the source voltage, the source-drain is turned on. If there is no difference between the gate voltage and the source voltage, the source and the drain are turned off. However, the source voltage, that is, "VCl + VR"
l changes, the output signals SP10 to SP10 of the excitation signal generation unit 2
The output signals SPl to SP5 of the voltage conversion unit 3 generated based on SP50
Must be converted with reference to “VCl + VRl”.

The N-type FETs of the switch elements N1 to N5 similarly operate as follows. If the gate voltage is "sufficiently" higher than the source voltage, the source-drain is turned on. If there is no difference between the gate voltage and the source voltage, the source and the drain are turned off. Voltage VRl across resistor Rl
Is sufficiently small and negligible compared to VCl.

[Excitation Drive Operation] FIG. 14 shows a four-phase excitation drive of the five-phase stepping motor. The feeding points A to A are indicated by vertices of the pentagon in FIG. 13, and the energized state is indicated by the following symbols. When the high-side switch elements Pl to P5 are on and the low-side switch elements Nl to N5 are off and are connected to the positive side of the capacitor Cl and almost VC1 is given as a voltage, a circle is given.

The switching elements Pl to P5 are off, and the switching elements Nl to
When N5 is on and connected to the negative side of the capacitor Cl and a voltage of almost zero volt is given, a circle is given. The direction of the current is positive in the clockwise direction in the figure.

The excitation step proceeds in synchronization with the signal MCLK. signal
DIR is a signal that determines the direction of rotation. For example, when the signal DIR is “H”, the excitation steps (1), (2), and (3) are synchronized with the rise of the signal MCLK. . . (10) (1). . . And proceed.
When the signal DIR is “L”, (1), (10), and (9). . . (1) (1
0). . . The rotation direction is opposite to that in the case of "H". However, since the power supply state of each excitation step is the same only in the direction of the excitation step, only the case of "H" will be described below.

In the excitation step (1), (1a) the feeding point A / I / O is connected to the + side,
(1b) Feeding point a is connected to the + side, and feeding point a, u, d
The state in which the o is connected to the-side is alternately repeated at a rate of 50% in time and sufficiently short in comparison with the cycle of the signal MCLK. When the excitation step proceeds to (2) in synchronization with the rise of the signal MCLK, (2a) a state in which the power supply point A is connected to the + side and the power supply point D is connected to the-side (2b) ) Feed point A / I is connected to + side, and feed point U / E
The state in which the o is connected to the-side is alternately repeated at a rate of 50% in time and sufficiently short in comparison with the cycle of the signal MCLK. Hereinafter, similarly, the process proceeds to the excitation step (10) and returns to the step (1) again.
This excitation method has advantages in that a voltage is applied to both ends of the winding in each step, the current changes quickly, and the motor can be rotated at a higher speed.

FIG. 15 shows the electric vector, that is, the torque vector in the excitation step. Depending on the direction of the winding currents of the windings A to E, the directions of the vectors generated independently by the windings are reversed, so that the total number of vectors generated by the windings alone becomes 10, and the angle between the adjacent vectors, that is, Electrical angle is 360
Degree divided by 10 = 36 degrees.

In the excitation step (1a), a current flows in the winding B in the negative direction, and a current flows in the winding C in the positive direction. In the excitation step (1b), a current flows through the winding A in the positive direction, and a current flows through the winding D in the negative direction. Since (1a) and (1b) have the same ratio,
The magnitude of the torque vector generated by each winding in this state is 1
Then, the composite vector of step (1) is Tl = TA−TB
+ TC−TD, and the magnitude | Tl | ≒ 3.08. Similarly, the resultant vector T2 of the excitation step (2) is as shown in FIG. 15, and the electrical angle changes by 36 degrees as the excitation step proceeds.

The above is the so-called full-step drive in which the number of excitation phases is always four, but the micro-step drive in which the unit of the rotation angle (electrical angle) is made finer than the full step will be described below. FIG. 16 shows the excitation steps of the 4-divided microstep in a time series. Let t be the excitation step cycle. The step position in the following is described as [integer + numerator / denominator], where the integer is the full step position, the denominator is the microstep division number, and the numerator is the microstep position.

In step [1], steps (1a) and (1b) are repeated at an equal ratio, that is, at a time of 4t / 8. In step [1 + 1/4], steps [1] and [2] are repeated at a ratio of 3: 1. That is, (1a) is 3t / 8, (2a) is t / 8, (1
b) is repeated at the time of 3t / 8, and (2b) is repeated at the time of t / 8. step 1
In [+2/4], steps [1] and [2] are repeated at a ratio of 2: 2. That is, (1a), (2a), (1b), and (2b) are repeated at a time of 2t / 8.

Thereafter, the process is repeated as shown in the figure. In step [2], only steps (2a) and (2b) are performed, and each is repeated in a time of 4t / 8. At this time, the vector between steps [1] and [2] is internally divided into four as shown in FIG. That is, in the composite vector Tl + 1/4 of the step [1 + 1/4], since the steps [1] and [2] are repeated at a ratio of 3: 1, the vector is internally divided into 1: 3.
Similarly, the vector of the subsequent microstep advances the internal dividing point between the vectors of the full step as shown in the figure, and the rotation angle (electrical angle) per cycle of the stepping pulse is subdivided into a quarter of the full step. Be transformed into However, as apparent from FIG. 17, the generated torque has a maximum value of about 3.0 at the full step position.
The minimum value is about 2. at the half-step position, which is the middle point.
93, and the torque fluctuates depending on the position.

[0025] As the number of divisions is reduced, the electrical angle per cycle of the stepping pulse is also reduced, and the stepping motor can be pseudo-continuously rotated in a stepwise rotation. However, even if the number of divisions is subdivided, the above-described torque fluctuation remains unchanged.

In this embodiment, the switching elements are all constructed using FETs, but there are also those using bipolar transistors.

[0027]

In the prior art, the high-side voltage is changed relatively to the low-side voltage by the current control unit so that a desired driving torque is obtained. The components of the current control unit, such as the switch element Ql, the coil Ll, and the capacitor Cl, need to use components that have a sufficient withstand voltage and a large current capacity, and the cost of the unit becomes extremely high. For example, in the case of a drive circuit having a drive power supply voltage of 40 volts and a motor drive current of a maximum of 3 amps, the cost of this part may occupy almost half of the entire drive circuit.

In the case where the drive current, that is, the generated torque is controlled to be constant, the required energy increases as the rotation speed increases. That is, in the conventional example, the higher the rotation speed, the higher the high-side voltage, and the lower the rotation speed, the lower the high-side voltage.

Here, looking at an application example of the document reading apparatus which is a component of the copying machine, after a reading period, a reading member (reading sensor or the like) is driven at a high speed to return to a reference position at a high speed. Between them, the high-side voltage is the highest.
On the other hand, in the reading period, the rotation speed is as slow as several tenths to several tenths as compared with the high-speed rotation period, so that the high-side voltage is very low. Therefore, a state in which a high withstand voltage and a large current capacity are required is for a short period of time, resulting in a very wasteful configuration and high cost in terms of circuit use efficiency.

Further, as described above, when the driving speed is low, the high-side voltage also decreases, and the gate signal voltage when the high-side switch element is turned on approaches the low-side voltage or becomes lower than the low-side voltage accordingly. You need to lower the voltage. So, for example,
The voltage conversion unit 3 in the conventional example must have a complicated configuration using a multi-voltage power supply, so that the entire driving circuit becomes more complicated and the overall cost becomes higher.

[0031]

In order to solve the above-mentioned problems, the high-side switch element and the low-side switch element are provided with a current control function as well as an excitation step switching. That is, the power supply state of the power supply point is changed so as to change each winding current of the motor in a sinusoidal manner, and two or more power supply states separated by more than 1 full step in electrical angle are repeated. The configuration changes in accordance with the stepping pulse. The change in the power supply state performed for each change unit of the stepping pulse is performed by changing a power supply state (hereinafter, referred to as a basic power supply state) equivalent to a balanced state by the two types of power supply states by a predetermined amount, and As the kind of power supply state, a state in which the same excitation step difference is taken in the leading direction and the lagging direction in electrical angle with respect to the basic power supply state is set. The difference between the above two steps is set according to the total current of the motor or the cycle of the step signal.

[0032]

(Embodiment 1) FIG. 1 shows the configuration of Embodiment 1 of the present invention. The components corresponding to those in FIG. 13 are denoted by the same reference numerals, and the description of the portions having the same configuration is omitted. .

The + side of the motor power supply Vm is directly connected to the + side of the capacitor Cl and the sources of the high side switching elements P1 to P5. The offset signal generator 101 receives the negative voltage of the capacitor Cl and the voltage Vref corresponding to the motor drive torque target value, and outputs a signal OFS. The excitation signal generator 2A also receives the signal OFS in addition to the signal MCLK and the signal DIR, and outputs switch element control signals SPl to SP5 and SNl to SN5. The signals SP1 to SP5 and the high-side voltage Vm are input to the voltage conversion unit 3A, and the signals SP1 to SP5 are output.

FIG. 2A shows the excitation state of the feeding point. It is assumed that the stepping signal does not change within the illustrated range. The excitation state of the feeding point is divided into current distribution periods 1 and 2 (details are described later) and
Divided into 1 and 2. The current distribution periods 1 and 2 are sections in which the connection time of the feed point to the high side or low side changes according to the excitation step position, and this operation distributes the feed point current to the two corresponding windings. It is a period to be done.

On the other hand, in the current holding periods 1 and 2, all feeding points are connected to the high side, and each winding current at the end of the current distribution period is held. Hereinafter, this state is described as HA. Note that the method of connecting to the low side has the same current holding effect in principle.

[Current distribution period] The step in which any one of the five feeding points is connected to the high side or the low side at a time rate of 100% corresponds to the full step of the conventional example, and is an integer corresponding to the conventional example. Let us represent the step state. Hereinafter, it is assumed that the value corresponding to the number of microstep divisions in the conventional example is sufficiently large, and that changes between full steps can be handled continuously.

FIG. 3 shows the PWM state of the feeding point, the feeding state of the winding, the winding current, and the feeding current. The horizontal axis is the excitation step, which is approximately
Steps for the second rotation are shown as step 11, and step 10 for the second rotation is shown as step 20 to step 21.

FIG. 3 (a) shows the PWM states of the five power supply points A to E by "ON time ratio in high-side example-ON time ratio in low side". Here, only the waveform of the thin line will be described, and the thick line will be described later.

For example, when viewed from the feeding point A, in Step 1, connection is made to the + side at a time ratio of 100% (+1.0), and in Step 6, connection is made to the-side at a time ratio of 100% (-1.0). Have been. During that time, the sine wave changes as shown in Fig. 3 (a), and thereafter, the same applies. The same applies to other feeding points, and the phase difference between adjacent feeding points changes in a sine wave shape of 72 degrees (= 360 degrees / 5).

FIG. 3 (b) shows the power supply state of the windings A to E by the difference between the PWM states of the power supply points at both ends of the windings. Here, only the waveform of the thin line will be described, and the thick line will be described later. For example, the feeding points at both ends of the winding A are A and A, and the state in which A is connected to the high side and A is connected to the low side is defined as the + direction. In step 1, a is "+1.0"
And A is “+0.31”, so the power supply state is “+0.6”.
9 ". Since the change of the power supply point is sinusoidal, the power supply state is also sinusoidal with a 10-step cycle. The same applies to other windings, and the phase difference between adjacent windings in the order of windings A, C, E, B, and D becomes a sine wave of 72 degrees.

FIG. 3C shows the winding current. Here, only the thin line waveform will be described, and the thick line will be described later. Since the change speed of the winding current is affected by the time constant at the time of forming the charging / discharging circuit due to the inductance L of the winding and the characteristics of the switching element, it is not easy to represent the actual waveform. Therefore,
In this case, the influence of the time constant can be ignored because the rotation speed is low and the current change is slow, and when the winding current is proportional to the power supply state, that is, when the power supply state is “+1.0”, the winding current is set to “+1”. .0 "(Even if the rotation speed is high and the relationship between the power supply state and the winding current becomes complicated, the description below is essentially the same).

Thus, similarly to the power supply state, the winding current is a sine with a phase difference of 72 degrees between adjacent windings in the order of windings A, C, E, B and D with a period of 10 steps. Become a wave.

FIG. 3D shows the feed point current corresponding to FIG. 3C, which is the difference between the corresponding winding currents. Here, only the thin line waveform will be described, and the thick line will be described later. For example, at the feeding point a, “winding current of winding A−winding current of winding D” is obtained. In step 1, “+1.38” is obtained. In step 6, “−1.38” is obtained.
And a sine wave having a phase difference of 72 degrees between adjacent feeding points. As described above, in the present invention, the PWM change at the feeding point has a sine wave shape, so that the feeding point current and the winding current all have a sine wave shape.

[Current Control Operation] In the present invention, as described above,
Based on the fact that the PWM change at the feeding point is a sinusoidal change, current control is performed by combining two different excitation steps, that is, torque vectors.

The details will be described below. Fig. 4 shows the excitation step
1 "indicates the torque vector Sl. Figure 3 shows the PWM state of the feeding point.
As shown in (a), a = + 1.0, b = + 0.31, c = −
Since 0.81, d = −0.81 and e = + 0.31, | S
1 | ≒ 2.94. Hereinafter, similarly, the excitation step 2,
The torque vectors in step 3... Are formed as shown in FIG. As is apparent from FIG. 3, since the five winding currents change in a so-called “five-phase sine wave (AC)” state, the torque vectors Sl... The magnitude of the torque vector between the full-step positions as well as the magnitude of the torque vector (not shown) are all the same.

The current distribution periods 1 and 2 in FIG. 2A are periods during which the operation in FIG. 3 is performed. FIG. 4 shows the current distribution period 1 (tdl) and the subsequent current holding period 1 (thl). One kind of the indicated torque vector (a vector directed from a center of the circumference formed by Sl, S2,... In FIG. 4 to a certain point on the circumference) is generated. Similarly, the current distribution period 2 (td2) and the current holding period 2 (th
2) generates one of the torque vectors shown in FIG. Repeat from tdl to th2 with one cycle as Tall. FIG. 2B is a schematic diagram of two types of vectors.

In the present invention, the cycle Tall is set sufficiently shorter than the step cycle of the signal MCLK, and the two types of torque vectors (FIG.
A combined vector Tl (hereinafter referred to as an effective vector) of (Sl, S2) of (b) is generated in a pseudo manner to drive the motor. At this time, the magnitude of the effective vector, that is, the magnitude of the torque (= current) is set by the change in the angle between the two types of vectors.
This is the current control of the present invention.

The angle θ between the effective vector and each of the two types of vectors is always equal, and this angle is hereinafter referred to as an offset angle. The offset angle represented by the step amount is the offset amount OFD, and the offset angle of 36 ° corresponds to the offset amount 1 (full step).

A specific description will be made using the excitation step. As an initial state, the excitation state when the offset amount is 2 will be described. FIG. 5 shows the combinations of the excitation steps, and FIG. 6 shows the corresponding torque vectors. Vector T3 direction T
Expressed as a combination of 1 and T5. The vector (corresponding to T3) corresponding to the direction to be expressed is referred to as a basic vector. Of the two vectors used to represent the basic vector, the one that is delayed from the basic vector (T3) when viewed clockwise is set as set vector 1, and the one that advances (T5) is set as set vector 2. The composite vector is the above-described effective vector.

The drive is divided into four microsteps, the change unit of the offset amount is divided into eight microsteps, and clockwise driving will be described. At a certain time, [3] is formed by [1] and [5] with the offset amount 2 as shown in FIG. Then, the magnitude of the vector “Tl + T5” is cos (72 °) times that when no vector operation is performed as shown in FIG. 6, that is, 2.94 × cos (72 °) ≒ 0.91. After that, the excitation step advances by the rising edge of the step signal, and the basic vector direction becomes [3 + 1/4].

When the torque, that is, the current is not changed, the offset amount 2 is not changed, and as shown in FIG. 5, the combination of the vectors is changed based on the basic vector with respect to the current distribution period 1 for [3 + 1/4] −2 = [1 + 1/4] vector [3 + 1/4] + 2 = [5 + 1/4] for current distribution period 2
Set with the vector of. As a result, as shown in FIG. 6, the effective vector is in the direction of T (3 + 1/4), and the magnitude remains about 0.91.
The direction advances 1/4 step.

When increasing the torque, that is, the current, the offset amount 2 is reduced by 1/8 to 1 + 7/8 (offset angle 6
7.5 °), and as shown in FIG. 5, the combination of vectors is set to [3 + 1/4] − (1 + 7/8) = [1
+3/8] vector [3 + 1/4] + (1 + 7/8) =
Set as [5 + 1/8] vector. As a result, as shown in FIG. 6, the effective vector has the same direction of T (3 + 1/4) as that of FIG. 6, but the size increases to 2.94 × cos (67.5 °) ≒ 1.12 and the direction becomes 1 Go / 4 steps.

When the torque, that is, the current is reduced, the offset amount 2 is increased by 1/8 to 2 + 1/8 (offset angle 7
6.5 °), and as shown in Fig. 5, the combination of vectors is set to [3 + 1/4]-(2 + 1/8) =
[1 + 1/8] vector For the current distribution period 2, [3 + 1/4] + (2 + 1/8) = [5
+3/8] vector. As a result, as shown in FIG. 6, the effective vector has the same direction of T (3 + 1/4) as that of FIG. 6, but the magnitude is reduced to 2.94 × cos (76.5 °) ≒ 0.69, and the direction is 1 Go / 4 steps.

In this embodiment, the combination vector 1
Instead of directly advancing the combination vector 2 or the combination vector 2, the combination vectors 1 and 2 are determined based on the basic vector via the offset amount according to the increase and decrease of the current to form the effective vector.

As described above, the magnitude of the combined torque vector, that is, the generated torque (drive current) is set by the offset angle θ. The magnitude of the effective vector at the offset angle θ is cos, based on the case where the offset angle is 0 degrees.
(Θ) times.

FIG. 7 shows the correspondence between the offset angle and the magnitude of the torque vector. When the offset angle is 0 degree, the magnitude of the vector becomes the theoretical maximum value of about 2.94, and if the offset angle is 90 degrees, that is, if the directions of the two types of vectors are exactly opposite, the magnitude of the torque vector is 0, that is, the minimum. Become. In the meantime, it changes like a sine wave as shown in the figure. Therefore, the generated torque is 0 from the maximum value according to the power supply voltage, motor characteristics, etc.
Can be controlled to any value up to, that is, a desired value.

In the case of the offset amount 2 (offset angle of 72 degrees), the PWM state, the winding supply state, the winding current, and the supply current are shown by thick lines in FIG. 3 described above. The bold line in FIG. 3 (a) shows the PWM state of the five feeding points A to E in comparison with the step difference 0 (thin line). The amplitude of the step difference 0 is ± 1.0, while the step difference 4 is about 0.31. The phase is the same as when the step difference is zero. Figure 3
(B) The bold line shows the power supply state of the windings A to E with the step difference of 0.
(Thin line). As in (a), only the amplitude changes in a similar manner without changing the period according to the difference between the steps. The amplitude is about ± 0.36 for the step difference 4 while the amplitude is about ± 1.18 for the offset amount 0. The thick line in Fig. 3 (c) shows the winding currents of windings A to E in comparison with the step difference 0 (thin line). Similarly to the power supply state, the cycle of the winding current does not change in accordance with the step difference, and only the amplitude changes in a similar manner. The thick line in FIG. 3 (d) is the feed point current corresponding to the thick line in (c).

As shown in FIG. 3, the phase does not change and only the amplitude changes in all the waveforms. This means that the change in the offset angle has no effect on the rotation operation, and only changes the magnitude of the effective vector = torque = current.

FIG. 8 shows details of the current distribution period. The period during which the feeding point is connected to the high side is tdp, and the period during which the feeding point is connected to the low side is tdn. In the above case, the current distribution period td (= tdp + tdn) and the ratio tdh of td to tdp
(= Tdp / td) due to the change of the excitation step.
It changes like

FIG. 9 shows the configuration of the excitation signal generator 2A that generates the excitation signal. The excitation step address generator 74 for generating the excitation step position of the basic vector has a signal MCLK.
And an offset signal OFS is input, and a signal corresponding to the excitation step position corresponding to the signal MCLK is output. The tdp width value LUT 75 is composed of a ROM or the like, receives a signal from the basic vector counter 74 as an address, and outputs a signal corresponding to the tdp width value as data. The PWM signal generation unit 76 generates an excitation signal according to the tdp width value. The tdp width value of the excitation signal is represented by the number of clocks, and is input to the PWM signal generator to form the excitation signal. Here, the tdp width value (clock number) is generated by the LUT.

As shown in FIG. 10, the tdp width value is made to correspond to the address corresponding to the step position as data. At this time, the shape is based on the number of microstep divisions that can satisfy the desired current control accuracy. For example, if the number of divisions corresponding to the required precision is 32, address 0 corresponds to full step 0, and full step 1 corresponds to address 32. In the case of 4 division drive, the address corresponding to the basic vector is used at intervals of 8 addresses such as 0 ⇒ 8 ⇒ 16 ⇒ 24 ⇒ 32 ⇒ 、, and based on this, two read addresses according to the offset amount are used. Calculate and use. In the case of eight-division driving, the same driving can be performed by using four addresses as addresses corresponding to the basic vector, such as 0 ⇒ 4 ⇒ 8 ⇒ 12 ⇒ 16 ⇒ ‥. In both cases, the minimum change unit of the offset amount is
It can be divided into 32, and desired current control accuracy can be realized.

Excitation signal generator for performing the above-described excitation signal generation operation
For 2A, the offset signal generator generates the total current of the motor.
i is detected as the voltage VRl by the current detection resistor Rl, and the value Vref corresponding to the torque target value (= current target value) is compared with the magnitude thereof. When the total current i is the same as the voltage corresponding to the torque target value (VRl = Vref) when the offset amount corresponding to the desired torque is set, so that the signal OFS outputs a signal corresponding to the above-mentioned "when the torque, that is, the current is not changed".

When the total current i is smaller than the voltage corresponding to the torque target value (VRl <Vref), since the offset amount is set so that the torque becomes smaller than the desired value, the signal OFS becomes the signal " When the torque, that is, the current is increased, is output.

When the total current i is larger than the voltage corresponding to the torque target value (VRl> Vref), the offset amount is set so that the torque becomes larger than the desired value. A signal corresponding to "increase the difference" is output.

In response to the signal OFS, the excitation signal generator 2A outputs signals SP10 to SP10 obtained by changing the above-described offset amount as described above.
SP50 and SN1 to SN5 are output to control the current.

Embodiment 2 FIG. 11 shows the configuration of Embodiment 2. FIG.
The same reference numerals are given to the constituent elements corresponding to No. 3, and the description of the parts having the same configuration is omitted.

The + side of the motor power supply Vm is directly connected to the sources of the high-side switch elements P1 to P5. Switch element Nl
The source of ~ N5 is directly grounded. Offset amount generator 10
2, the signal MCLK is input and the offset amount OFD is output. The excitation signal generator 28 receives the signal OFS in addition to the signal MCLK and the signal DIR, and outputs the switch element control signals SPl to SP5 and SNl to SN5. The offset amount OFD output from the offset amount generation unit 102 is input to the excitation signal generation unit 2B. The signals SP1 to SP5 and the high-side voltage Vm are input to the voltage conversion unit 3A, and the signals SP1 to SP5 are output.

In the second embodiment, the offset amount is set according to the cycle of the step signal of the microstep. The offset amount in the excitation signal generation unit 2A of the first embodiment is set relatively in accordance with the signal OFS, which is an increase / decrease signal of the offset amount, whereas the offset amount in the excitation signal generation unit 2B of the second embodiment is Is the offset amount OFD output from the offset amount generation unit 102
Is set directly by

FIG. 11 shows the configuration of the offset amount generation unit 102.
The cycle counter 41 receives the clock signal and the signal MCLK, and outputs a count value corresponding to the cycle of the signal MCLK. The offset value LUT is composed of a ROM or the like, receives the count value as an address, outputs data corresponding to the count value, and outputs the data as an offset amount OFD. A data set according to a desired drive current is set in the offset LUT. When the required power is small, such as when the motor is rotated at a low speed, and when it is difficult to detect the total current with a resistor, the drive current control is facilitated by the method of the second embodiment.

The present invention is not limited to the “five-phase” and “stepping motor”, and can be applied to a wide range of both rotary and direct-acting motors as long as the motor is configured to excite a plurality of windings in a predetermined order. It is.

[0071]

As described above, according to the present invention,
Circuit for converting the motor power supply (conventional current control unit
1) The switch element (Pl to P
5 and Nl to N5), the switch element Ql, which is a component of the motor power supply voltage converter,
Large components such as coil Ll and capacitor Cl are not required, and the high-side voltage is constant regardless of the magnitude of the torque. And the cost can be significantly reduced as compared with the conventional method, and the entire drive circuit can be further reduced in size.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a first embodiment;

2A is a diagram showing a combination of vectors and an effective vector in an excited state of a feed point in FIG. 2A; FIG.

FIG. 3 is a diagram illustrating a change over time in a power supply state, a current, and the like according to the first embodiment.

FIG. 4 is a diagram illustrating a torque vector according to the first embodiment;

FIG. 5 is a diagram showing combinations of excitation steps of a feeding point.

FIG. 6 is a diagram showing a vector by an excitation step.

FIG. 7 is a diagram illustrating an offset angle and a magnitude of a torque vector;

FIG. 8 is a diagram illustrating a current distribution period;

FIG. 9 is a diagram illustrating a configuration of an excitation signal generation unit.

FIG. 10 is a diagram for explaining tdp width value data;

FIG. 11 is a diagram illustrating a configuration of the first embodiment;

FIG. 12 is a diagram illustrating a configuration of an offset amount generation unit;

FIG. 13 is a diagram illustrating a configuration of a conventional technique.

FIG. 14 is a diagram for explaining a method of exciting a five-phase stepping motor.

FIG. 15 is a diagram showing a torque vector of a conventional example.

FIG. 16 is a timing chart of a micro step.

FIG. 17 is a diagram showing a torque vector of a micro step.

[Explanation of symbols]

 2, 2A, 2B excitation signal generator 3 voltage converter 6 stepping motor 101 offset signal generator 102 offset amount generator 41 MCLK cycle counter 51 offset amount LUT 74 basic vector counter 75 tdp width value LUT 76 PWM signal generator Pl ~ P5 Nl ~ N5 Ql Switch element Cl Capacitor Rl Resistance Vm Motor power supply

Claims (5)

[Claims] 1. A stepping motor driving method for exciting each winding set of a stepping motor having a plurality of winding sets in a predetermined procedure according to a stepping signal, wherein each winding current is changed in a sine wave shape. The power supply state of the power supply point is changed, and two types of power supply states separated by more than 1 full step in electrical angle are asynchronously repeated with the step signal at a cycle shorter than the step signal cycle. In the stepping motor driving method which changes together according to the stepping signal, the change in the power supply state performed for each change unit of the stepping signal is changed by a power supply state equivalent to a balanced state by the two power supply states (hereinafter referred to as a basic power supply state). The above two types of power supply states are set such that the same excitation step difference is respectively taken in the leading direction and the lagging direction in electrical angle around the basic power supply state. A stepping motor driving method. 2. The stepping motor driving method according to claim 1, wherein the difference between the two types of excitation steps is set according to the total current of the motor. 3. The stepping motor driving method according to claim 1, wherein a difference between the two types of excitation steps is set according to a cycle of a step signal. 4. The stepping motor driving method according to claim 1, wherein the windings of the stepping motor are connected in a ring shape. 5. The stepping motor driving method according to claim 1, wherein five winding sets, that is, feeding points, of the stepping motor are provided.