Drive circuit of stepping motor, drive method thereof, and electronic apparatus using the same
阅读说明:本技术 步进马达的驱动电路及其驱动方法、使用其的电子机器 (Drive circuit of stepping motor, drive method thereof, and electronic apparatus using the same ) 是由 土桥正典 冈田光央 小林良太 于 2020-02-25 设计创作,主要内容包括:本发明在短时间内优化电流设定值。本发明涉及一种步进马达的驱动电路及其驱动方法、使用其的电子机器。电流值设定电路(210)产生电流设定值(I<Sub>REF</Sub>)。恒流斩波电路(250)产生脉冲调制信号(S<Sub>PWM</Sub>),该脉冲调制信号(S<Sub>PWM</Sub>)以使线圈(L1)中流过的线圈电流的检测值(I<Sub>NF</Sub>)靠近电流设定值(I<Sub>REF</Sub>)的方式作脉冲调制。逻辑电路(250)根据脉冲调制信号控制连接在步进马达(102)的线圈的桥接电路(202)。电流值设定电路(210)在旋转开始后的第1期间将电流设定值(I<Sub>REF</Sub>)设为指定的全转矩设定值(I<Sub>FULL</Sub>)。在接下来的第2期间,使电流设定值(I<Sub>REF</Sub>)按指定方式下降至小于第1设定值的指定的第2设定值。其后,转变为高效率模式,通过反馈控制调整电流设定值(I<Sub>REF</Sub>)。(The invention optimizes the current set value in a short time. The present invention relates to a drive circuit of a stepping motor, a drive method thereof, and an electronic apparatus using the same. The current value setting circuit (210) generates a current setting value (I) REF ). The constant current chopper circuit (250) generates a pulse modulation signal (S) PWM ) The pulse modulation signal (S) PWM ) So that the detected value (I) of the coil current flowing through the coil (L1) NF ) Close to the current set point (I) REF ) The mode of (2) is pulse modulated. A logic circuit (250) controls a bridge circuit (202) connected to a coil of the stepping motor (102) in accordance with the pulse modulation signal. The current value setting circuit (210) is in the 1 st period after the start of rotationWill current set value (I) REF ) Set as a specified full torque set value (I) FULL ). In the next 2 nd period, the current set value (I) is set REF ) Down to a specified 2 nd set point that is less than the 1 st set point in a specified manner. Thereafter, the system shifts to a high efficiency mode, and adjusts a current set value (I) by feedback control REF )。)
1. A drive circuit, characterized by: which is a drive circuit of the stepping motor,
the disclosed device is provided with:
a current value setting circuit for generating a current setting value;
a constant current chopper circuit that generates a pulse modulation signal that is pulse-modulated so that a detection value of a coil current flowing through a coil approaches a target value based on the current setting value;
a logic circuit for controlling a bridge circuit connected to a coil of the stepping motor according to the pulse modulation signal; and is
The current value setting circuit
Setting the current set value to a specified 1 st set value in a 1 st period after the start of rotation,
during the following 2 nd period, so that the current set value is decreased to a specified 2 nd set value smaller than the 1 st set value in a specified manner,
thereafter, the operation mode is changed to the high efficiency mode, and the current set value is adjusted by feedback control.
2. The drive circuit according to claim 1, wherein: the current value setting circuit changes the current setting value from the 1 st setting value to the 2 nd setting value in N steps (N ≧ 2) in the 2 nd period.
3. The drive circuit according to claim 1 or 2, characterized in that:
the current value setting circuit includes:
a calculation unit that generates at least one intermediate value obtained by dividing the 1 st set value and the 2 nd set value;
a multiplexer for receiving the 1 st set value, the 2 nd set value and the at least one set value and selecting one corresponding to control data; and
a waveform controller to vary the control data with time during the 2 nd period.
4. The drive circuit according to claim 2, wherein: the step widths are equal.
5. The drive circuit according to any one of claims 1 or 2, wherein: the logic circuit generates a mask signal that specifies a trigger for transition from the 1 st period to the 2 nd period based on a cycle of an input clock.
6. The drive circuit according to any one of claims 1 or 2, wherein: further comprises a counter electromotive force detection circuit for detecting the counter electromotive force generated by the coil, and
the current value setting circuit performs feedback control of the current setting value based on the counter electromotive force in the high efficiency mode.
7. The drive circuit according to claim 6, wherein:
the current value setting circuit further includes:
a load angle estimating unit that estimates a load angle based on the back electromotive force; and
a feedback controller that generates the current setting value so that the estimated load angle approaches a predetermined target angle.
8. The drive circuit according to any one of claims 1 or 2, wherein: which is integrated on a semiconductor substrate.
9. An electronic apparatus, comprising: a stepping motor; and
the drive circuit according to any one of claims 1 to 8, to drive the stepping motor.
10. A driving method characterized by: which is a driving method of a stepping motor, and
comprises the following steps:
setting the current set value as a specified 1 st set value in a 1 st period after the rotation is started;
during the next 2 nd period, so that the current set value is lowered to a specified 2 nd set value smaller than the 1 st set value in a specified manner;
then, the high-efficiency mode is changed, and the current set value is adjusted through feedback control;
generating a pulse modulation signal that is pulse-modulated in such a manner that a detection value of a coil current flowing through a coil approaches the current setting value; and
and controlling a bridge circuit connected to a coil of the stepping motor according to the pulse modulation signal.
Technical Field
The present invention relates to a driving technique of a stepping motor.
Background
Stepping motors are widely used in electronic machines, industrial machines, and robots. The stepping motor is a synchronous motor that rotates in synchronization with an input clock generated by the main controller, and has excellent controllability in starting, stopping, and positioning. Further, the stepping motor can realize position control in the open loop, and has characteristics suitable for digital signal processing.
Fig. 1 is a block diagram of a motor system including a conventional stepping motor and a drive circuit thereof. The
Fig. 2 is a diagram illustrating an excitation position. The excitation position is regarded as a coil current (drive current) I flowing through the 2 coils L1, L2 of the stepping
In a normal state, the rotor of the stepping motor is rotated synchronously in units of step angles proportional to the number of input clocks. However, if a sudden load change or speed change occurs, the synchronization is deviated. This is called out-of-sync. Once step-out occurs, special processing is necessary to thereafter normally drive the stepping motor, and therefore it is desirable to prevent step-out.
In order to solve this problem, in how many cases, the drive circuit is designed so as to obtain an output torque in consideration of the step-out margin by setting a margin with respect to an assumed maximum load. However, if the margin is made large, the power loss becomes large.
[ background Art document ]
[ patent document ]
[ patent document 1] Japanese patent laid-open No. Hei 9-103096
[ patent document 2] Japanese patent laid-open publication No. 2004-120957
[ patent document 3] Japanese patent laid-open No. 2000-184789
[ patent document 4] Japanese patent laid-open No. 2004-180354
[ patent document 5] Japanese patent No. 6258004
Disclosure of Invention
[ problems to be solved by the invention ]
Fig. 3 is a diagram illustrating a procedure at the time of starting the stepping motor. When at time t0When the input clock signal IN is given, the motor is started. The frequency of the input clock signal IN, i.e., the rotation number command of the motor, increases with time (trapezoidal wave drive). Since the motor is particularly likely to be out of step at the start of starting, the feedback control of the output torque is invalidated and the motor is driven at the maximum torque (maximum current). Specifically, the current is set to the value IREFIs set to the maximum value IFULL. Then, when the rotation of the motor is stabilized, at time t1The feedback control of the output torque (drive current) is switched to be effective. The current set value I is controlled by feedbackREFClose to the most suitable current amount I corresponding to the load at that time or the likeOPTAnd is stable.
Time t1Thereafter, the current is set to the value IREFIs regulated by feedback control so that it is stabilized at a certain optimum current amount IOPTThe stabilization time (delay time) τ is requiredS. In order to further reduce power consumption, it is desirable to shorten the settling time τS。
The present invention has been made in view of the above problems, and an exemplary object of one aspect of the present invention is to provide a drive circuit capable of optimizing a current set value in a short time.
[ means for solving problems ]
The present invention relates to a drive circuit for a stepping motor. The drive circuit includes: a current value setting circuit for generating a current setting value; a constant current chopper circuit that generates a pulse modulation signal that is pulse-modulated so that a detection value of a coil current flowing through the coil approaches a target value based on a current setting value; and a logic circuit for controlling a bridge circuit connected to a coil of the stepping motor according to the pulse modulation signal. The current value setting circuit sets the current setting value to a specified 1 st setting value in a 1 st period after the start of rotation, lowers the current setting value to a specified 2 nd setting value smaller than the 1 st setting value in a specified manner in a subsequent 2 nd period, and thereafter, shifts to a high efficiency mode and adjusts the current setting value by feedback control.
The convergence value of the current setting value in the high efficiency mode can be predicted (including measurement and calculation) in advance from the load of the stepping motor. By giving the predicted convergence value as the 2 nd set value, the current set value can be changed to the predicted convergence value in a short time in the 2 nd period. Thereafter, by shifting to the high efficiency mode, the current set value converges to the actual convergence value in a short time. This enables the current set value to be optimized in a short time.
The current value setting circuit may change the current setting value from the 1 st setting value to the 2 nd setting value in N steps (N ≧ 2) in the 2 nd period. The number of steps N may be variable.
The current value setting circuit may include: a calculation unit for generating at least one intermediate value obtained by dividing the 1 st set value and the 2 nd set value; a multiplexer for receiving the 2 nd set value and at least one set value and selecting one corresponding to the control data; and a waveform controller for varying the control data with time during the 2 nd period.
The step widths may be equal.
The logic circuit may generate a mask signal that specifies a trigger for transition from the 1 st period to the 2 nd period based on a cycle of the input clock.
The drive circuit may further include a counter electromotive force detection circuit that detects a counter electromotive force generated by the detection coil. The current setting circuit may perform feedback control of the current setting value based on the counter electromotive force in the high efficiency mode.
The current value setting circuit may further include: a load angle estimating unit that estimates a load angle based on the back electromotive force; and a feedback controller for generating the current set value so that the estimated load angle approaches the predetermined target angle.
The drive circuit may be integrated on one semiconductor substrate. "integrated" includes a case where all the components of the circuit are formed on the semiconductor substrate and a case where the main components of the circuit are integrated, and some resistors, capacitors, and the like may be provided outside the semiconductor substrate to adjust the circuit constant. By integrating the circuit on 1 chip, the circuit area can be reduced and the characteristics of the circuit element can be kept balanced.
Another aspect of the present invention relates to an electronic apparatus. An electronic apparatus includes a stepping motor and a drive circuit according to any one of the above aspects.
In addition, any combination of the above-described constituent elements, and an invention in which the constituent elements and expressions of the present invention are mutually replaced among a method, an apparatus, a system, and the like are also effective as aspects of the present invention.
[ Effect of the invention ]
According to an aspect of the present invention, the current setting value can be optimized in a short time.
Drawings
Fig. 1 is a block diagram of a motor system including a conventional stepping motor and a drive circuit thereof.
Fig. 2 is a diagram illustrating an excitation position.
Fig. 3 is a diagram illustrating a procedure at the time of starting the stepping motor.
Fig. 4 is a block diagram showing a configuration of a driving circuit according to the embodiment.
Fig. 5(a) is an operation waveform diagram of the drive circuit of fig. 4, and fig. 5(b) is an operation waveform diagram of a conventional drive circuit.
Fig. 6(a) to (d) are waveform diagrams showing another transition form of the current setting value in the 2 nd period.
Fig. 7 is a circuit diagram showing an example of the configuration of the current value setting circuit.
Fig. 8 is a diagram showing a specific configuration example of the drive circuit.
Fig. 9 is a diagram showing another configuration example of the current value setting circuit.
Fig. 10(a) to (c) are perspective views showing examples of electronic devices provided with a drive circuit.
Detailed Description
The present invention will be described below with reference to preferred embodiments and drawings. The same or equivalent constituent elements, members and processes shown in the respective drawings are denoted by the same reference numerals, and redundant description thereof will be omitted as appropriate. The embodiments are not intended to limit the invention and are merely exemplary, and all the features and combinations thereof described in the embodiments are not necessarily essential features of the invention.
In the present specification, the phrase "a state in which a component a and a component B are connected" includes not only a case in which the component a and the component B are directly physically connected but also a case in which the component a and the component B are indirectly connected via another component which does not substantially affect the electrical connection state therebetween or impair the function and effect of the combination thereof.
Similarly, the phrase "the member C is provided between the members a and B" includes not only the case where the members a and C are directly connected, but also the case where the members B and C are indirectly connected via another member which does not substantially affect the electrical connection state thereof or impair the function and effect of the combination thereof.
For convenience of understanding, the vertical and horizontal axes of the waveform diagrams and the timing diagrams referred to in the present specification are appropriately enlarged or reduced, and the waveforms shown are also simplified, exaggerated, or emphasized for convenience of understanding.
Fig. 4 is a block diagram showing the configuration of the
The input clock CLK is input from the
The
The
In the present embodiment, the stepping
The bridge circuit 202_1 of the 1 st channel CH1 is connected to the 1 st coil L1. The bridge circuit 202_2 of the 2 nd channel CH2 is connected to the 2 nd coil L2.
The bridge circuits 202_1 and 202_2 are H-bridge circuits (full bridge circuits) each including 4 transistors M1 to M4 and a pre-driver (not shown). The transistors M1 to M4 of the bridge circuit 202_1 are switched based on the control signal CNT1 from the
The bridge circuit 202_2 is configured in the same manner as the bridge circuit 202_1, and switches the voltage V of the 2 nd coil L2 (also referred to as the 2 nd coil voltage) by switching the transistors M1 to M4 based on the control signal CNT2 from the
The current
The bridge circuits 202_1 and 202_2 respectively include a current detection resistor RNFCurrent detecting resistor RNFIs reduced to a coil current ILThe detection value of (3). In addition, the current detection resistor RNFThe position of (a) is not limited, and may be provided on the power supply side, or may be provided between 2 outputs of the bridge circuit in series with the coil.
The
The
The current
The
Then, the high efficiency mode is switched to, and the current set value I is adjusted through feedback controlREF。
The above is the configuration of the driving
In order to clarify the effect of the driving
Next, the operation of the
At time t2Moving to the 2 nd period T2. During period 2T2Current set value IREFTo a high efficiency setpoint ILOWAnd (4) descending. In this example, the current set value IREFThrough 1 intermediate value, the torque is changed in a step shape, and the intermediate value is a full torque set value IFULLAnd a high efficiency setpoint ILOWThe midpoint of (a).
At
This operation of the driving
Current set value I in high efficiency modeREFConvergence value of IOPTThe load of the stepping motor can be predicted (including measurement and calculation) in advance. And, by applying the predicted convergence value IOPTIs set as a high efficiency set value ILOWCan be in the 2 nd period T2Make the current set value IREFChange to predicted convergence value I in short timeOPTAnd a. Prediction value IOPTA convergence value I close to the actualOPTTherefore, after the high efficiency mode is switched to, the current setting value I can be set in a short timeREFConvergence to the actual convergence value IOPT。
The present invention can be understood by the block diagram and circuit diagram of fig. 4, or various apparatuses and methods derived from the above description, and is not limited to a specific configuration. Hereinafter, more specific configuration examples and examples will be described to help understand the nature and operation of the present invention and to make them more clear, but the scope of the present invention is not limited thereto.
FIGS. 6(a) to (d) show the 2 nd period T2Current set point I inREFThe waveform diagram of another transition pattern. In FIG. 6(a), during the 1 st period T1To the 2 nd period T2When moving, the high efficiency setting value I is directly converted without intermediate valueLOW。
In FIG. 6(b), during the 1 st period T1To the 2 nd period T2When moving, the high-efficiency setting value I is converted into a high-efficiency setting value I in N steps through a plurality of, namely N intermediate valuesLOW. The number N of intermediate values is not limited.
In FIG. 6(c), during the 2 nd period T2In the current setting value IREFFrom full torque setpoint IFULLLinearly changing to a high efficiency setpoint ILOW。
In FIG. 6(d), during the 2 nd period T2In the current setting value IREFFrom full torque setpoint IFULLTo a high efficiency setpoint ILOWAnd (4) attenuation.
Fig. 7 is a circuit diagram showing an example of the configuration of the current
The
The
The computing part 242 generates the total torque set value IFULLAnd a high efficiency setpoint ILOWAt least one intermediate value I obtained by internal divisionM1~IMN. In this example, N is 3.
For example, the intermediate setting value IM1~IM3Can be produced in the following manner.
IM1=(3×IFULL+1×ILOW)/(N+1)
IM2=(2×IFULL+2×ILOW)/(N+1)
IM3=(1×IFULL+3×ILOW)/(N+1)
In this case, the step widths are equal. To summarize, the ith intermediate setting is set as
IMi={(N+1-i)×IFULL+i×ILOW}/(N+1)
And (4) finishing.
The multiplexer 244 receives the high efficiency setting ILOWAnd at least one set value IM1~IMNOne corresponding to the control data SW is selected. In this example, the control data SW is 2 bits, [00 ]]Time selection IM1,[01]Time selection IM2,[10]Time selection IM3,[11]Time selection ILOW。
Multiplexer 248 receives the full torque setting IFULLAnd the output of multiplexer 244. The period during which the MASK signal MASK is asserted (high) is the 1 st period T1Selecting a full torque setpoint IFULL. When the MASK signal MASK is negated (low), the output of the multiplexer 244 is selected and transits to the 2 nd period T2。
The waveform controller 246 changes the control data SW with time when the MASK signal MASK is negated. The number of steps may be set according to the order of the control data SW. The waveform controller 246 may vary the control data SW in synchronization with the input clock S1. The control data SW may be changed, for example, at the positive edge of each input clock S1.
The timing at which the transition is completed is known to the waveform controller 246, and thus the MODE control signal MODE may be generated by the waveform controller 246.
For example, if T is during
In this way, various transition modes can be generated by the same hardware using the current
Fig. 8 is a diagram showing a specific configuration example of the
The counter electromotive
The rotation
The
The
Counter electromotive force V in detection intervalBEMF1Is provided by the following formula.
VBEMF1=KE·ω·cosφ
KEω is the number of revolutions for the induced voltage constant. Therefore, by measuring the back electromotive force VBEMFA detection value having a correlation with the load angle phi can be generated. For example, cos Φ may be set as a detection value, and in this case, the detection value is expressed by the following expression.
cosφ=VBEMF1·ω-1/KE
=VBEMF1·(T/2π)·KE -1
The method of optimizing the current set value Iy is not limited to this. For example, the back electromotive force V may be predeterminedBEMF1Target value V ofBEMF(REF)So that the back electromotive force VBEMF1Close to the target value VBEMF(REF)Form a feedback loop.
The constant-current chopper circuit 250_1 includes a D/a (Digital Analog)
Fig. 9 is a diagram showing another configuration example of the current
Finally, the use of the driving
The electronic apparatus shown in fig. 10(a) is an
The electronic device in fig. 10(b) is a
The electronic device in fig. 10(c) is a
The present invention has been described above based on the embodiments. The present embodiment is an example, and it should be understood by those skilled in the art that various modifications may be made to the combination of the components and the processing steps, and such modifications are also included in the scope of the present invention. Hereinafter, such a modification will be described.
(modification 1)
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