Reference voltage setting circuit, driving circuit and driving device

Abstract

To smoothly switch a stepping motor from a stop state to a driving state and to suppress step-out of the stepping motor in switching of the stepping motor from the driving state to the stop state.SOLUTION: A reference voltage setting circuit 1 for setting a reference voltage value Vref used in driving control of a stepping motor includes a non-inverting ideal diode circuit 10, an integral circuit 20 and a non-inverting amplifier circuit 30. An input voltage value Vin is inputted to the non-inverting ideal diode circuit 10. The integral circuit 20 is connected to an output terminal of the non-inverting ideal diode circuit 10. The non-inverting amplifier circuit 30 is connected to an output terminal of the integral circuit 20 and outputs the reference voltage value Vref.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a reference voltage setting circuit for setting a reference voltage value used in driving control of a stepping motor, a driving circuit of a stepping motor including this reference voltage setting circuit, and a driving device including this driving circuit and the stepping motor.

Background Art

[0002] In Patent Document 1, within the settling time during which damped oscillation (repetition of overshoot and undershoot) occurs in a stepping motor, the excitation current value is reduced from the rotational operating current value required for driving the stepping motor to the stop position holding current value for holding the stepping motor at a predetermined position, so as to converge the damped oscillation in a short time.

[0003] Patent Document 1 describes that when the load of the stepping motor is large, the switching from the reference voltage VREF-H to the reference voltage VREF-L may be gradually decreased (paragraph

[0036] ). Here, the reference voltage VREF-H is a voltage for outputting the rotational operating current value, and the reference voltage VREF-L is a voltage for outputting the stop position holding current value.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Patent Document 1 does not disclose any specific circuit configuration for gradually decreasing the reference voltage.

[0006] On the one hand, in Patent Document 1, the time for switching from the reference voltage VREF-L to the reference voltage VREF-H is made equal to the time for switching from the reference voltage VREF-H to the reference voltage VREF-L. Here, in the drive control of the stepping motor, it is preferable that the switching from the stop state of the stepping motor (the state corresponding to the reference voltage VREF-L) to the drive state (the state corresponding to the reference voltage VREF-H) is performed smoothly.

Means for Solving the Problems

[0007] The present invention is a reference voltage setting circuit for setting a reference voltage value used in the drive control of a stepping motor, and includes a non-inverting ideal diode circuit, an integrating circuit, and a non-inverting amplifier circuit. An input voltage value is input to the non-inverting ideal diode circuit. The integrating circuit is connected to the output terminal of the non-inverting ideal diode circuit. The non-inverting amplifier circuit is connected to the output terminal of the integrating circuit and outputs a reference voltage value.

[0008] The non-inverting ideal diode circuit can be composed of an operational amplifier, a first diode, a second diode, and a resistive element. The operational amplifier has a non-inverting input terminal to which an input voltage value is input. The anode of the first diode is connected to the output terminal of the operational amplifier, and the cathode of the first diode is connected to the inverting input terminal of the operational amplifier. The cathode of the second diode is connected to the connection point of the operational amplifier and the first diode. The resistive element is connected to the connection point of the cathode of the first diode and the resistive element of the integrating circuit.

[0009] The resistance value of the resistive element included in the non-inverting ideal diode circuit can be made higher than the resistance value of the resistive element included in the integrating circuit.

[0010] The drive circuit of the stepping motor can be constituted by the reference voltage setting circuit of the present invention and a control circuit. Here, the control circuit controls the drive current of the stepping motor based on the reference voltage value set by the reference voltage setting circuit.

[0011] A drive device can be configured by the drive circuit described above, a stepping motor driven by the drive circuit, and a drive unit driven by the stepping motor.

Advantages of the Invention

[0012] According to the present invention, it is possible to make the switching time of the reference voltage value relatively short when switching the stepping motor from the stopped state to the driving state, and to make the switching time of the reference voltage value relatively long when switching the stepping motor from the driving state to the stopped state. As a result, the switching from the stopped state to the driving state can be performed smoothly, and the out-of-step of the stepping motor can be suppressed when switching from the driving state to the stopped state.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0014] This embodiment is for setting a reference voltage value Vref used in driving control of a stepping motor. Specifically, when switching the stepping motor from a stopped state (hold state) to a driving state (rotating state), the rising time of the reference voltage value Vref is made relatively short, and when switching the stepping motor from a driving state to a stopped state, the falling time of the reference voltage value Vref is made relatively long. Thereby, the switching from the stopped state to the driving state can be performed smoothly, and detuning of the stepping motor can be suppressed in the switching from the driving state to the stopped state.

[0015] (Drive circuit 100 of stepping motor) A drive circuit (an example) 100 of a stepping motor will be described with reference to FIG. 1. The drive circuit 100 shown in FIG. 1 is a circuit for driving a bipolar stepping motor (not shown). Note that the present invention can also be applied to a unipolar stepping motor.

[0016] The control circuit 110 controls the driving of a stepping motor (not shown). Two bridge circuits 121 and 122 are respectively connected to the control circuit 110, and the control circuit 110 outputs a control signal to a plurality of switch elements (transistors) constituting each of the bridge circuits 121 and 122.

[0017] Coils 131 and 132 for driving the stepping motor are respectively connected to the bridge circuits 121 and 122. By switching on / off the switch elements included in each of the bridge circuits 121 and 122, the energization to each of the coils 131 and 132 can be controlled to control the rotation of the stepping motor.

[0018] The bridge circuit 121 is connected with a resistance element 141 for detecting the current flowing through the coil 131, and the connection point of the bridge circuit 121 and the resistance element 141 is connected to the non-inverting input terminal of the comparator 151. Also, the reference voltage value Vref is input from the reference voltage setting circuit 1 to the inverting input terminal of the comparator 151. The control circuit 110 outputs a control signal to the bridge circuit 121 based on the output signal of the comparator 151.

[0019] The bridge circuit 122 is connected with a resistance element 142 for detecting the current flowing through the coil 132, and the connection point of the bridge circuit 122 and the resistance element 142 is connected to the non-inverting input terminal of the comparator 152. Also, the reference voltage value Vref is input from the reference voltage setting circuit 1 to the inverting input terminal of the comparator 152. The control circuit 110 outputs a control signal to the bridge circuit 122 based on the output signal of the comparator 152.

[0020] (Reference voltage setting circuit 1) The reference voltage setting circuit 1 outputs a reference voltage value Vref based on the input voltage value Vin. The circuit configuration of the reference voltage setting circuit 1 will be described with reference to FIG. 2. The reference voltage setting circuit 1 includes a non-inverting ideal diode circuit 10, an integrating circuit 20, and a non-inverting amplifier circuit 30. The output terminal of the non-inverting ideal diode circuit 10 is connected to the input terminal of the integrating circuit 20, and the output terminal of the integrating circuit 20 is connected to the input terminal of the non-inverting amplifier circuit 30. Also, the input voltage value Vin is input to the non-inverting ideal diode circuit 10, and the reference voltage value Vref is output from the non-inverting amplifier circuit 30.

[0021] The non-inverting ideal diode circuit 10 includes an operational amplifier 11, a first diode 12, a second diode 13, and a resistor element 14. An input voltage value Vin is input to the non-inverting input terminal of the operational amplifier 11. The anode of the first diode 12 is connected to the output terminal of the operational amplifier 11, and the cathode of the second diode 13 is connected to the connection point of the operational amplifier 11 and the first diode 12. The anode of the second diode 13 is grounded. The cathode of the first diode 12 is connected to the inverting input terminal of the operational amplifier 11 as negative feedback.

[0022] The cathode of the first diode 12 is connected to one end of a resistor element 21 in the integrating circuit 20. Also, one end of the resistor element 14 is connected to the connection point of the first diode 12 and the resistor element 21, and the other end of the resistor element 14 is grounded.

[0023] The integrating circuit 20 includes a resistor element 21 and a capacitor 22. The other end of the resistor element 21 is connected to the non-inverting input terminal of an operational amplifier 31 in the non-inverting amplifier circuit 30. One end of the capacitor 22 is connected to the connection point of the resistor element 21 and the operational amplifier 31, and the other end of the capacitor 22 is grounded.

[0024] The non-inverting amplifier circuit 30 includes an operational amplifier 31 and resistor elements 32, 33, and amplifies the output voltage value of the integrating circuit 20 to output a reference voltage value Vref. A negative feedback circuit composed of the resistor elements 32, 33 is connected to the operational amplifier 31. Here, one end of the resistor element 32 is connected to the output terminal of the operational amplifier 31, the other end of the resistor element 32 is connected to the resistor element 33, and the connection point of the resistor elements 32, 33 is connected to the inverting input terminal of the operational amplifier 31.

[0025] Figure 3 shows the behavior of the input voltage value Vin input to the reference voltage setting circuit 1 and the behavior of the reference voltage value Vref output from the reference voltage setting circuit 1. In order to maintain the stepping motor in a stopped state, a stop input voltage value Vin_L is input to the reference voltage setting circuit 1, and a stop reference voltage value Vref_L corresponding to the stop input voltage value Vin_L is output from the reference voltage setting circuit 1.

[0026] At time t1, when the input voltage value Vin is increased from the stop input voltage value Vin_L to the drive input voltage value Vin_H (Vin_H > Vin_L), the reference voltage value Vref increases from the stop reference voltage value Vref_L to the drive reference voltage value Vref_H (Vref_H > Vref_L). The drive reference voltage value Vref_H corresponds to the drive input voltage value Vin_H. While the reference voltage value Vref increases from the stop reference voltage value Vref_L to the drive reference voltage value Vref_H, the capacitor 22 of the integration circuit 20 is charged.

[0027] At time t2, when the input voltage value Vin is decreased from the drive input voltage value Vin_H to the stop input voltage value Vin_L, the reference voltage value Vref decreases from the drive reference voltage value Vref_H to the stop reference voltage value Vref_L. At this time, the capacitor 22 of the integration circuit 20 is charged, and discharge occurs through the resistance element 14 of the non-inverting ideal diode circuit 10. The input voltage value Vin decreases from the drive input voltage value Vin_H to the stop input voltage value Vin_L at time t2, but the reference voltage value Vref decreases from the drive reference voltage value Vref_H toward the stop reference voltage value Vref_L after a time interval Δt from time t2 and reaches the stop reference voltage value Vref_L at time t3.

[0028] According to this embodiment, the time constant τa when the reference voltage value Vref is decreased from the driving reference voltage value Vref_H to the stop reference voltage value Vref_L is made larger than the time constant τb when the reference voltage value Vref is increased from the stop reference voltage value Vref_L to the driving reference voltage value Vref_H. Thereby, as shown in FIG. 3, the time until the reference voltage value Vref is decreased from the driving reference voltage value Vref_H to the stop reference voltage value Vref_L can be made longer than the time until the reference voltage value Vref is increased from the stop reference voltage value Vref_L to the driving reference voltage value Vref_H.

[0029] When the reference voltage value Vref is increased from the stop reference voltage value Vref_L to the driving reference voltage value Vref_H, it is affected by the time constant τ (τ = C * R) of the integrating circuit 20 as the time constant τb. Here, C is the capacitance of the capacitor 22, and R is the resistance value R21 of the resistance element 21.

[0030] When the reference voltage value Vref is decreased from the driving reference voltage value Vref_H to the stop reference voltage value Vref_L, it is also affected by the time constant τa. Here, since discharge is performed through the resistance element 14 of the non-inverting ideal diode circuit 10 as described above, the resistance value used for calculating the time constant τa is the sum of the resistance value R14 of the resistance element 14 and the resistance value R21 of the resistance element 21. Thereby, the time constant τa becomes larger than the time constant τb.

[0031] The resistance value R14 of the resistance element 14 is higher than the resistance value R21 of the resistance element 21, and the resistance value R14 can be 10 3 times or more that of the resistance value R21. For example, the resistance value R14 can be set to 10 MΩ, and the resistance value R21 can be set to 1 kΩ. Also, the capacitance of the capacitor 22 can be set to 0.1 μF, for example. In this case, the time constant τa is 1.0 s (= 0.1 μF * (1 kΩ + 10 MΩ)), and the time constant τb is 100 μs (= 0.1 μF * 1 kΩ).

[0032] As shown in FIG. 4, when the reference voltage value Vref changes in the same manner as the input voltage value Vi, there is a risk that out-of-step of the stepping motor may occur when the reference voltage value Vref is decreased from the driving reference voltage value Vref_H to the stop reference voltage value Vref_L. To suppress the out-of-step of the stepping motor, the stop reference voltage value Vref must be increased, which increases the driving current of the stepping motor, making the stepping motor prone to heat generation and increasing the power consumption.

[0033] On the other hand, according to the present embodiment, as shown in FIG. 3, since the reference voltage value Vref is decreased from the driving reference voltage value Vref_H to the stop reference voltage value Vref_L using the time interval Δt, out-of-step of the stepping motor can be suppressed. Also, since there is no need to increase the stop reference voltage value Vref, an increase in the driving current of the stepping motor can be suppressed, and heat generation of the stepping motor can be suppressed or power consumption can be reduced.

[0034] FIGS. 5 and 6 show a drive mechanism (an example) using a stepping motor as a drive source. This drive mechanism drives a dispensing / conveying module (corresponding to the drive unit in the present invention) that dispenses and conveys a biological sample in an automatic analyzer (corresponding to the drive device in the present invention) that analyzes the biological sample.

[0035] In the drive mechanism shown in FIG. 5, a stepping motor M1 and a driven pulley 202 are fixed to a base 201, and a drive belt 203 is wound around a drive pulley (not shown) attached to the output shaft of the stepping motor M1 and the driven pulley 202. A dispensing / conveying module 204 is connected to the drive belt 203, and by moving the drive belt 203 by driving the stepping motor M1, the dispensing / conveying module 204 can be moved.

[0036] In the drive mechanism shown in FIG. 6, a stepping motor M2 and a driven pulley (not shown) are fixed to a base 301, and a drive belt 303 is wound around a drive pulley 302 attached to the output shaft of the stepping motor M2 and a driven pulley (not shown). A dispensing / conveying module 304 is connected to the drive belt 303, and the dispensing / conveying module 304 can be moved by moving the drive belt 303 by driving the stepping motor M2.

[0037] In the drive mechanisms shown in FIGS. 5 and 6, the dispensing / conveying module 204 (for example, 3 kg) or the dispensing / conveying module 304 (for example, 2 kg), which is relatively heavy, may be moved at a high speed (for example, at a maximum speed of 600 mm / s). Here, as shown in FIG. 4, when the reference voltage value Vref is decreased from the drive reference voltage value Vref_H to the stop reference voltage value Vref_L at time t2, the stepping motors M1 and M2 may become out of step. On the other hand, as shown in FIG. 3, if the reference voltage value Vref is decreased from the drive reference voltage value Vref_H to the stop reference voltage value Vref_L at the time interval Δt, the out-of-step of the stepping motors M1 and M2 can be suppressed.

[0038] FIG. 7 shows the results of measuring the surface temperature of the stepping motor M1 shown in FIG. 5 and the surface temperature of the stepping motor M2 shown in FIG. 6. Specifically, the results of measuring the surface temperature of the stepping motor M1 when the input voltage value Vin_L when stopping the drive of the stepping motor M1 is set to 250 mV and 80 mV are shown. Further, the results of measuring the surface temperature of the stepping motor M2 when the input voltage value Vin_L when stopping the drive of the stepping motor M2 is set to 250 mV and 80 mV are shown.

[0039] As can be seen from FIG. 7, setting the input voltage value Vin_L to 80 mV can suppress the heat generation of the stepping motors M1 and M2 and also reduce the power consumption. Further, by using the reference voltage setting circuit 1 shown in FIG. 2, as shown in FIG. 3, the reference voltage value Vref can be decreased from the driving reference voltage value Vref_H to the stop reference voltage value Vref_L during the time interval Δt, and even when the input voltage value Vin_L is set to 80 mV, the out-of-step of the stepping motors M1 and M2 can be suppressed.

Explanation of Signs

[0040] 1: Reference voltage setting circuit, 10: Non-inverting ideal diode circuit, 11: Operational amplifier, 12: First diode, 13: Second diode, 14: Resistance element, 20: Integrating circuit, 21: Resistance element, 22: Capacitor, 30: Non-inverting amplifier circuit, 31: Operational amplifier, 32, 33: Resistance elements, 100: Driving circuit, 110: Control circuit, 121, 122: Bridge circuits, 131, 132: Coils, 141, 142: Resistance elements, 151, 152: Comparators, 201, 301: Bases, 202: Driven pulley, 302: Driving pulley, 203, 303: Driving belts, 204, 304: Dispensing and conveying modules

Claims

1. A reference voltage setting circuit for setting a reference voltage value used in driving control of a stepping motor, comprising: A non-inverting ideal diode circuit to which an input voltage value is input; An integrating circuit connected to an output terminal of the non-inverting ideal diode circuit; A non-inverting amplifier circuit connected to an output terminal of the integrating circuit and outputting the reference voltage value; A reference voltage setting circuit characterized by comprising the above.

2. The non-inverting ideal diode circuit includes: An operational amplifier having a non-inverting input terminal to which the input voltage value is input; A first diode having an anode connected to an output terminal of the operational amplifier and a cathode connected to an inverting input terminal of the operational amplifier; A second diode having a cathode connected to a connection point of the operational amplifier and the first diode; A resistor element connected to a connection point between the cathode of the first diode and a resistor element of the integrating circuit. The reference voltage setting circuit according to claim 1, characterized by comprising the above.

3. The resistance value of the resistor element included in the non-inverting ideal diode circuit is higher than the resistance value of the resistor element included in the integrating circuit. The reference voltage setting circuit according to claim 2, characterized by the above.

4. The reference voltage setting circuit according to claim 1; A control circuit for controlling a drive current of the stepping motor based on the reference voltage value set by the reference voltage setting circuit; A drive circuit for a stepping motor, characterized by comprising the above.

5. The drive circuit according to claim 4; A stepping motor driven by the drive circuit; A drive unit driven by the stepping motor; A drive device, characterized by comprising the above.

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