JPH05344793A - Constant-current control circuit for stepping motor - Google Patents

Abstract

PURPOSE:To prevent excess torque generated when a stepping motor is operated at a low speed by using an integrated circuit for controlling the motor and an integrated circuit for driving a motor containing a constant-current circuit. CONSTITUTION:The constant-current control circuit for a stepping motor comprises detecting means (line 1) for detecting a pulse interval of at least one phase of control pulse signal to be output from an integrated circuit 1 for controlling the motor, and voltage altering means 4, 5 for altering a constant-current reference voltage to an integrated circuit 3 for driving the motor according to a pulse width.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant current control circuit for a stepping motor, and more particularly to a stepping motor control integrated circuit for outputting a control pulse signal and a constant current reference voltage during a pulse output period of the control pulse signal. The present invention relates to a constant current control circuit used in a circuit for controlling and driving a stepping motor by a motor driving integrated circuit having a built-in constant current circuit that drives a stepping motor with a current value.

[0002]

2. Description of the Related Art Conventionally, an auto-dispenser used for supplying a liquid to a reagent or the like uses a stepping motor as a driving device for reciprocating a piston, and diluting a diluent liquid tank by reciprocating the piston. The liquid is sucked into the cylinder, and then the diluent is discharged from the cylinder to be mixed with the reagent. For controlling the stepping motor, a stepping motor control integrated circuit and a motor driving integrated circuit having a constant current circuit are generally used. The integrated circuit for controlling a stepping motor sequentially outputs a control pulse signal having a pulse width proportional to the control speed of a stepping motor operated according to a control command to the integrated circuit for driving a motor for each phase. The output control pulse signal is configured such that its pulse width becomes smaller as the stepping motor to be controlled is operated at high speed, that is, the number of pulses output at a constant time increases. A predetermined constant current reference voltage is applied to the REF terminal of the motor driving integrated circuit, and the motor driving integrated circuit supplies a constant current corresponding to the constant current reference voltage only for the pulse input time of the input control pulse signal. It is configured to feed the corresponding phase of the stepper motor.

[0003]

When the stepping motor is driven with the above configuration, the pulse width of the control pulse signal output from the stepping motor control integrated circuit is controlled stepwise according to the controlled speed. Since it is controlled digitally, its pulse width is fixed according to each control stage. Therefore, the constant current flows through the stepping motor only during the period corresponding to the pulse width of the control pulse signal. As a result, generally, the motor torque is large during low speed operation of the stepping motor, and decreases during high speed operation. Excessive torque during low speed operation means, for example, interaction between the torque and inertial force of the rotor when shifting from high speed operation to low speed operation, or residual magnetic field and rotation when stopping the stepping motor from low speed operation. There is a problem that the stepping motor vibrates at a low speed due to a force acting on the child or resonance generated at a low speed operation. In particular, in the dispenser used for supplying liquid to reagents, etc., there is a problem that the diluted liquid to be absorbed is discharged and the mixed amount of the diluted liquid becomes abnormal, and the movement of the liquid is detected. When applied to the sensor, there is a disadvantage that the same particle in the liquid is repeatedly sucked and discharged due to the vibration of the driven piston and the sensor cannot function as a sensor. Therefore, vibration due to excessive torque must be removed as much as possible. Further, an increase in current at low speed of the stepping motor consumes unnecessary power and is not preferable in terms of power saving.

A configuration may be considered in which input of all phases is cut off in order to prevent vibration of the constant current driven stepping motor at the time of stop and to save power, but it is practical when stop torque is required. Not.

The present invention provides a constant current limiting circuit for a stepping motor, which is capable of safely and power-saving operating the stepping motor by limiting the supply of an excessive current that causes an excessive torque when the stepping motor is operating at a low speed. That is.

[0006]

A constant current limiting circuit according to the present invention includes a detecting means for detecting a pulse width of a control pulse signal of at least one phase output from an integrated circuit for controlling a stepping motor, and the control pulse signal. Means for outputting a reference pulse signal having a specified pulse width in synchronization, comparing means for comparing the width of the control pulse signal with the width of the reference pulse signal, and the width of the control pulse signal being the width of the reference pulse signal And a voltage changing means for changing the constant current reference voltage to the motor driving integrated circuit when the voltage is larger than the above.

Further, according to the present invention, the detecting means for detecting the pulse width of the control pulse signal of at least one phase outputted from the stepping motor controlling integrated circuit, and the constant current reference voltage to the motor driving integrated circuit, And a voltage changing unit that changes according to the pulse width of the control pulse signal.

[0008]

The pulse width of the control pulse signal output from the integrated circuit for controlling the stepping motor is compared with the pulse width of the arbitrarily designated reference pulse signal in synchronization with this control pulse signal, and the pulse width of the control pulse signal becomes the reference. If it is larger than the width of the pulse signal, it is judged that it is a low-speed operation in which the constant current should be limited, and the constant current reference voltage to the motor drive integrated circuit is reduced. As the control pulse signal, a constant current reduced according to the reduced constant current reference voltage is supplied to the stepping motor to prevent excessive torque during low speed operation.

[0009]

1 is a schematic block diagram of the present invention, in which reference numeral 1 is an integrated circuit for controlling a stepping motor. This integrated circuit 1 is commercially available for controlling a stepping motor, and controls a pulse width corresponding to the speed of sequentially controlling the four phases of the stepping motor 2 in accordance with a control command instructing the speed of the stepping motor 2 to be controlled. Pulse signal to drive motor integrated circuit 3
Output to. In addition, in the case of the present embodiment, the case of the stepping motor operating in four phases is illustrated, but the number of controlled phases is not limited to this embodiment.
The stepping motor control integrated circuit 1 has a digitally defined pulse width of the control pulse signal output corresponding to the speed to be controlled, and cannot be freely changed.

Of the four-phase control pulse signals, the control pulse signal for one phase is supplied to the constant current changing circuit 4 via the line 1. The constant current changing circuit 4 detects the pulse width of the input control pulse signal S, and supplies a constant current changing signal C corresponding to the magnitude of the pulse width to a reference voltage circuit 5 that creates a constant current reference voltage. The reference voltage circuit 5 increases / decreases the constant current reference voltage in accordance with the constant current change signal C and applies it to the terminal REF of the motor drive integrated circuit 3.

The motor drive integrated circuit 3 has a built-in constant current circuit and is generally commercially available for driving a motor, and the stepping motor 2 is driven only during a pulse input period of the control pulse signal S to be input, that is, a period corresponding to a pulse width. A constant current D for driving is output for each phase. The motor drive circuit 3 is supplied with a detected value of the current actually flowing in the stepping motor 2, and the constant current D is adjusted so that the detected value matches the constant current designated by the constant current reference voltage at the terminal REF. Is controlled.

FIG. 2 shows a circuit configuration diagram of an embodiment of the constant current limiting circuit of the stepping motor of the present invention, which is illustrated by embodying FIG. In FIG. 2, the stepping motor control integrated circuit 1 and the motor drive integrated circuit 3 function as in FIG. The control pulse signals S1, S2, S3, S4 for four phases output from the integrated circuit 1 are output to one input terminals of the AND gates 11a, 11b, 11c, 11d, respectively, and the control pulse signal S1 outputs the line l. It is input to the input terminal A of the one-shot circuit 12 and the inverter 13 through the output of the inverter 13 becomes the clock input CK of the D-type flip-flop. On the other hand, the drive OFF signal for stopping the driving of the stepping motor 2 is input to the inverter 14 and its inverted output is given to the other input terminal of each AND gate, and the negative input terminals CD and D flip-flop of the one-shot circuit 12 are also provided. Fifteen negative reset input terminals R are provided. The one-shot circuit 12 is activated when a low level signal is input to the negative input terminal CD, and its resistance terminal R and capacitor terminal C are connected to the oscillation circuit 16 and the input terminal A
Set to high level at the rising edge of the input signal to Q
The output transits to a low level at the falling edge of the pulse of the oscillation circuit 16, and the one-shot pulse output as a result is given to the input terminal D of the D-type flip-flop 15 as a reference pulse signal. The pulse width of this one-shot pulse is arbitrarily set by the variable resistor VR that constitutes the oscillation circuit 16, and serves as a reference pulse width for limiting the constant current value.

The D-type flip-flop 15 reads the level applied to the input terminal D at the rising edge of the signal applied to the clock input terminal CK and outputs its inverted output to the inverted output terminal (Q
To the base of the NPN transistor 17 whose emitter is grounded. A resistor R is provided in the collector of the transistor 17.
3 is connected to one end, and the other end is connected to the connection point of the resistors R1 and R2 and the terminal REF of the motor driving integrated circuit 3. The transistor 17 turns off when a low level signal is applied to its base, and as a result, the resistor R1
The voltage divided by R2 and R2 is applied to the terminal REF as a constant current reference voltage. Further, when a high level signal is applied to the base of the transistor 17, the transistor 17 is turned on, and the resistors R2 and R3 are connected in parallel to the resistor R1.
A voltage lower than the F state is used as a constant current reference voltage at the terminal RE.
Given to F.

The AND gates 11a, 11b, 11
The control pulse signal outputs from c and 11d are correspondingly input to the input terminals A to D of the motor driving integrated circuit 3, and the constant currents corresponding to the constant current reference voltage are output from the corresponding output terminals A to D, respectively. It is sent to each phase of the stepping motor 2. A resistor R4 for detecting the value of the phase current of the stepping motor 2 is connected to the terminal RS of the motor driving circuit 3, and a voltage corresponding to the actual current value is applied to the terminal RS to correspond to the constant current reference voltage. Is adjusted to a constant current.

Next, the operation of the constant current limiting circuit of the stepping motor of FIG. 2 will be described with reference to the timing chart of FIG. As shown in FIG. 3A, when the drive OFF signal for stopping the driving of the stepping motor 2 is output, the low level signal inverted via the inverter 14 is the AND gates 11a to 11d.
The output of the applied control pulse signal is prohibited and the operations of the one-shot circuit 12 and the D-type flip-flop 15 are stopped. Each AND gate is opened at the time point t1 when the drive OFF signal switches to the low level, and the control pulse signal of each phase output from the stepping motor control integrated circuit 1 is sent to the motor drive integrated circuit 3 via the corresponding AND gate. Also, the one-shot circuit 12 and the D-type flip-flop 15 are made operable. When the low speed operation is performed in the driving state of the stepping motor 2, the control pulse signal S1 having a large pulse width is output for each phase as shown in FIG. 3B. The control pulse signal S1 is guided to the one-shot circuit 12, and at the rising time t2, the output terminal Q is set to the high level as shown in FIG. Become. As a result, a one-shot signal having a constant reference pulse width in synchronization with the rising time t2 of the control pulse signal S1 is generated every time the signal S1 rises.
It is output from the output terminal Q and given to the input terminal D of the D-type flip-flop 15. At time t3 when the control pulse signal S1 switches from the high level to the low level, the clock input terminal CK of the D-type flip-flop 15 transits from the low level to the high level via the inverter 13, and as a result, the control pulse signal S1 falls. At time t3, the D-type flip-flop 15 is set to the low level shown in FIG. 3C applied to its input terminal D, and the high level signal as shown in FIG. Is applied to the base of the transistor 17. Therefore, since the transistor 17 is turned on, the motor driving integrated circuit 3
A constant current reference voltage with a reduced voltage is applied to the input terminal REF of, as shown in FIG. Then, the motor driving integrated circuit 3 drives the stepping motor 2 with the reduced constant current corresponding to the reduced constant current reference voltage.

As described above, when the stepping motor 2 operates at a low speed, the pulse width of the control pulse signal becomes larger than the reference pulse width of the one-shot signal output from the one-shot circuit 12, so the D-type flip-flop 15 is controlled by the control pulse. When the signal S1 falls, a low level is detected, and the constant current reference voltage is reduced so that the constant current to the stepping motor 2 is reduced.

When the stepping motor 2 is operated at high speed, the pulse width of the control pulse signal becomes smaller than the reference pulse width of the one-shot signal, as shown in FIG. The high level of the shot signal is detected, and as a result, the D-type flip-flop 15
The inverted output of is switched from high level to low level, and the transistor 17 is switched from ON to OFF. Then, the designated constant current reference voltage divided by the resistors R1 and R2 is applied to the input terminal REF of the motor driving integrated circuit 3. As a result, in order to operate the stepping motor 2 at a high speed, when the control pulse signal having a pulse width smaller than the reference pulse width is output, the constant current reference voltage is not reduced and the first specified constant current reference The stepping motor 2 is driven by a constant current corresponding to the voltage. As shown in FIG. 3, when the operation is changed from the high speed to the low speed again, the pulse width of the control pulse signal exceeds the reference pulse width as shown at time t5, so that the constant current flowing through the stepping motor 2 is automatically limited. Although the constant current reference voltage is reduced by one step by comparing the pulse width of the control pulse signal with the predetermined reference pulse width in the above embodiment, the pulse width of the control pulse signal is divided into a plurality of widths. However, the constant current reference voltage may be switched to be reduced in a plurality of steps according to the pulse width.

The control pulse signal is input to a function generator, a voltage function inversely proportional to the pulse width of the signal is generated, and the current to the stepping motor is continuously changed as a constant current reference voltage. May be.

[0019]

As described above, according to the present invention, when the stepping motor is driven by using the stepping motor control integrated circuit and the motor driving integrated circuit having the built-in constant current circuit, the stepping motor which has been impossible in the past is provided. It is possible to change the constant current flowing through the motor depending on the operating speed. Therefore, it is possible to prevent the transient vibration that has been conventionally generated due to the increase of the constant current at the time of low speed operation, and it is possible to eliminate unnecessary power consumption and save labor.

In particular, when it is applied to drive a piston of an auto-dispenser used for supplying a liquid to a reagent or the like, the capacity accuracy is lowered when the stepping motor is operated at a low speed during the inhalation of the diluting liquid, and the device is not needed. Vibration can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic system configuration diagram of the present invention.

FIG. 2 is a circuit configuration diagram illustrating an embodiment of the present invention.

FIG. 3 is a timing chart for explaining the operation of FIG.

[Explanation of symbols]

 1 stepping motor control integrated circuit 2 stepping motor 3 motor driving integrated circuit 4 constant current changing circuit 5 reference voltage circuit 12 one-shot circuit 15 D-type flip-flop 17 NPN transistor

Claims (2)

[Claims] 1. An integrated circuit for controlling a stepping motor which outputs a control pulse signal, and a motor driving integrated circuit which includes a constant current circuit for driving a stepping motor at a constant current value according to a constant current reference voltage during a pulse output period of the control pulse signal. In a circuit for controlling and driving a stepping motor by a circuit, a detection unit that detects a pulse width of at least one phase control pulse signal output from the stepping motor control integrated circuit; A means for outputting a reference pulse signal having a pulse width, a comparing means for comparing the width of the control pulse signal with the width of the reference pulse signal, and the width of the control pulse signal is greater than the width of the reference pulse signal Voltage change means for changing the constant current reference voltage to the motor drive integrated circuit; Constant current control circuit of Ngumota. 2. A stepping motor control integrated circuit for outputting a control pulse signal, and a motor drive integrated circuit for driving a stepping motor with a constant current value according to a constant current reference voltage during a pulse output period of the control pulse signal. In a circuit for controlling and driving a stepping motor by a circuit, detection means for detecting a pulse width of at least one-phase control pulse signal output from the stepping motor control integrated circuit, and a constant current reference to the motor driving integrated circuit A constant current control circuit for a stepping motor, comprising: voltage changing means for changing the voltage according to the pulse width of the control pulse signal.