JPH0832196B2 - Driving circuit for stepping motor - Google Patents

Description

The present invention relates to a drive circuit for a stepping motor.

(B) Related Art Conventionally, various proposals have been made as a drive circuit for a stepping motor, which will be described with reference to FIG. 1 as an example.

FIG. 1 is a circuit diagram showing a conventional drive circuit for a stepping motor.

In the figure, 10 is a constant current chopper circuit, which includes a semiconductor chopper 12 for controlling the DC current 11 and the output of the DC power supply 11, a diode 14, a choke 15 inserted in series on the output side of the semiconductor chopper 12, and a small capacity. Smoothing capacitor
It is composed of 16 mag.

Reference numeral 20 is a control circuit having one end connected to the detection resistor 13 and the other end connected to the base of the semiconductor chopper 12. The control circuit 20 is configured by connecting a smoothing circuit 22 composed of a resistor and a grounded capacitor to the plus side of the comparator 21 and a predetermined reference voltage V REF to the minus side of the comparator 21, respectively.

Reference numeral 30 is a drive winding switching circuit of, for example, a four-phase stepping motor which is so-called standard connection.
However, one phase is shown and other phases are omitted. And diodes 35, 36, 37, 38 for passing a counter electromotive current between the emitters and collectors of the transistors 31, 32, 33, 34.
Are connected respectively.

The operation of the conventional circuit shown in FIG. 1 will be described below, and its problems will be pointed out.

FIGS. 4 to 6 show operation waveforms of respective parts when the four-phase stepping motor is excited in one phase at a low frequency, a middle frequency and a high frequency.

In each figure, (a) shows a control signal given to terminals A and of the drive winding switching circuit 30. (B) shows the waveform of the exciting current I W1 flowing in the motor winding at each frequency. (C) shows the motor applied voltage at each frequency. (D) is the current flowing through the detection resistor 13 at each frequency
I W2 is shown. FIG. 7 shows the relationship between the driving frequency and the power consumption (however, the broken line shows the characteristic example of the conventional example, and the solid line shows the characteristic diagram of the embodiment according to the present invention). The above (b)
In and and (d), + is the motor winding 39 shown in FIG.
When current I W1 flows from A to A, − is from A
It shows the time when the flow was flowing in each direction.

First, "H" is applied to the terminal A of the drive winding switching circuit 30.
When the control signal is input, the transistors 31 and 34 are turned on, and a current I W1 flows in the motor winding 39 in the direction from A. The exciting current I W1 flows to the ground via the detection resistor 13 to detect the exciting current I W1 as the voltage value of the detecting resistor 13. Next, when the control signal of "H" is input to, the transistors 32 and 33 are turned on, and the exciting current I W1 flows from the motor winding 39 in the A direction. At this time as well, the voltage value of the detection resistor 13 is obtained in the same manner as described above.

Next, the voltage value of the detection resistor 13 is given to the smoothing circuit 22 of the control circuit 20, and the average value thereof is detected. The comparator 21 compares the detected value with a predetermined reference voltage V REF. The constant current chopper circuit 10 is controlled by this comparison output.

Therefore, according to the conventional circuit, the average value of the voltage values generated in the detection resistor 13 is detected and the comparison output of the detected value and the reference voltage V REF is used regardless of the frequency of driving. The constant current chopper circuit 10 is controlled. Therefore, as a result of the constant current chopper circuit 10 being controlled so as to supplement the counter electromotive current IR, the maximum value of the exciting current I W1 increases as shown by the solid line in FIG. 5 (b).

In this type of motor, the ratio of the counter electromotive current IR (which occurs when the control signal applied to the terminals A and changes) tends to increase as the driving frequency increases. Therefore, the average value of the waveform is detected by the control circuit 20,
If this detected value is compared with the reference voltage V REF, the difference between the voltage value at the time of stop and the reference voltage V REF becomes large as shown in FIG. 8 (d). That is, the constant current chopper circuit 10 is controlled in the direction of increasing the motor applied voltage Vw as the driving frequency is increased.

Then, for example, when driving at a low frequency (about 100 pulses / second), as shown in FIG. 4 (d), the ratio of the counter electromotive current IR (I W1 in one direction) to the current I W2 in the + direction. Therefore, the difference (V1) between the averaged detection value at this time and the detection value when the motor is stopped is small.
Therefore, the amount of increase in the voltage Vw applied to the motor is small, and the power consumption of the motor is not significantly increased (see FIG. 7). Therefore, there is no problem in increasing the temperature of the motor.

Further, when driving at a high frequency (about 5 K pulses / second), the motor applied voltage Vw becomes maximum as described above,
Due to the high frequency, the phases are inverted before the exciting current I W1 rises sufficiently. Therefore, the current I flowing through the motor winding 39
W1 decreases and power consumption does not increase (see Fig. 7). As a result, no significant temperature rise of the motor occurs.

However, the following problems occur when driving at a medium frequency (about 500 pulses / second). Specifically, as indicated by the solid line in FIG. 5 (b), the exciting current I
Since the maximum value of W1 increases, the motor applied voltage Vw also increases as shown in FIG. 5 (c). Then, the exciting current I
When the rise time of W1 and the phase switching frequency match, both the applied voltage Vw and the exciting current I W1 are close to the maximum, and the power consumption increases. This is like a conventional device
If the control is performed using the mere average value of the exciting current without considering the back electromotive current I W2, the value including the back electromotive current I W2 is averaged, and the average value becomes low. This is because the maximum value of the exciting current I W1 becomes larger than necessary. As a result, a relatively large current I W1 flows through the motor winding 39 as shown by the solid line in FIG. Therefore, power consumption (see FIG. 7) increases in the middle frequency range, which causes a temperature rise of the motor winding 39 of the control circuit 20 and the drive winding switching circuit 30. as a result,
Also, the motor overheats, resulting in a decrease in reliability.

(C) Purpose The present invention is a drive for a stepping motor, which suppresses power consumption of the motor and each drive circuit when driven at a mid-range frequency, improves reliability of the stepping motor, and reduces power consumption. It is intended to provide a circuit.

(D) Configuration A drive circuit for a stepping motor according to the first aspect of the present invention is a bridge-type bipolar drive circuit including four transistors each having a diode connected between a collector and an emitter for supplying a counter electromotive current to the power supply side. A constant current chopper drive circuit connected between the direct current power supply and the drive winding switching circuit, and the drive winding switching circuit that generates the exciting current of the stepping motor using the direct current voltage generated by the direct current power supply as an input. And a constant current chopper drive circuit which is connected between the constant current chopper drive circuit and the stepping motor and which detects a current flowing between them as a voltage, and controls the constant current chopper drive circuit based on a detection signal of the current detection resistor. It has a basic configuration including a control circuit, and the control circuit rectifies the detection signal to obtain the signal. The reverse electromotive current component of the reverse polarity contained in is removed, the signal after rectification is averaged, the averaged signal is compared with a predetermined reference voltage, and the constant current chopper drive is performed according to the comparison result. The feature is that the circuit is operated.

A drive circuit for a stepping motor according to a second aspect of the present invention is a bridge type bipolar drive circuit including four transistors each having a diode connected between a collector and an emitter for flowing a back electromotive current to the power supply side. A drive winding switching circuit that generates an exciting current for a stepping motor by using a DC voltage generated by a power supply as an input, a constant current chopper drive circuit connected between the DC power supply and the drive winding switching circuit, and a constant current A current detection resistor that is connected between the chopper drive circuit and the stepping motor and that detects a current flowing between them as a voltage, and a control circuit that controls the constant current chopper drive circuit based on a detection signal of the current detection resistor are provided. By rectifying the detection signal, the counter electromotive current component of the reverse polarity included in the signal is obtained. While removing and averaging the rectified signal, separately rectify the signal obtained by inverting the detection signal in the same manner as above, average the rectified signals, and then average both signals. Is added, the signal after the addition is compared with a predetermined reference voltage, and the constant current chopper drive circuit is operated according to the comparison result.

(E) Embodiment First Invention FIG. 2 is a circuit diagram showing an extracted control circuit of a drive circuit for a stepping motor according to an embodiment of the first invention. The constant current chopper circuit 10 and the drive winding switching circuit 30 are the same as those shown in FIG.

40 is a control circuit, on the positive side of the comparator 41,
Amplify the voltage value (corresponding to the detection signal of the current detection resistor) obtained by the current I W2 (current flowing between the constant current chopper drive circuit 10 and the stepping motor) flowing through the detection resistor 13 (current detection resistor). An exciting current amplifying circuit 44, a diode 43 for half-wave rectifying the amplified voltage, and a smoothing circuit 42 for smoothing the half-wave rectified voltage waveform are connected in series and input. On the other hand, to the minus side of the comparator 41, a predetermined reference voltage V REF (triangular wave set so as to slightly add the motor applied voltage Vw when the motor is stopped) is input. That is, the control circuit 40 smoothes the voltage value obtained by removing the negative voltage related to the back electromotive force from the voltage value of the detection resistor 13 by the comparator 41 and the reference voltage V RE.
The constant current chopper circuit 10 is controlled by comparing with F.

Hereinafter, the operation of the drive circuit for the stepping motor including the control circuit 40 described above will be described.

When driving a stepping motor at a mid-range frequency, which is a conventional problem, first, by sending a control signal as shown in FIG. 5 (a), the exciting current I W1 (see FIG. 5 (b)) (See dashed line). On the other hand, the voltage value is detected by the current I W2 flowing through the detection resistor 13 (see the broken line in FIG. 5 (d)). The detected value is amplified by the exciting current amplifier circuit 44. (See FIG. 8 (a)). The amplified output is half-wave rectified by the diode 43 (FIG. 8 (b)). The half-wave rectified output is extracted by the smoothing circuit 42 into a smooth waveform (FIG. 8 (c)) close to the maximum value. That is, back electromotive current
Since the IR is removed, the smoothed waveform does not become significantly lower than the current value at the time of stop unlike the conventional circuit described above (see FIG. 8 (d)). Therefore, as shown by the broken line in FIG. 5 (c), the motor applied voltage Vw does not rise significantly, and it is possible to suppress a significant increase in power consumption at the mid-range frequency (see FIG. 7).

In addition, stepping motor under the following conditions, 1K, 2K,
Figure 10 shows the experimental data when driven by 5KPPS as supplementary data.

FIG. 10 is a measured waveform diagram of the voltage across the detection resistor 13 measured with an oscilloscope.

Output voltage of DC power supply 11 40v Switching frequency 30KHz Detection resistance 13 resistance value 0.05Ω Stepping motor 5 phase ・ 2.8A PS599H (made by Mycom) Second invention Fig. 3 is for stepping motor according to the embodiment of the second invention. FIG. 3 is a circuit diagram showing a control circuit of the drive circuit extracted from FIG. The constant current chopper circuit 10 and the drive winding switching circuit 30 are the same as those shown in FIG.

50 is a control circuit, and an exciting current amplifying circuit 54 for amplifying a voltage value obtained by the current I W2 flowing through the detection resistor 13,
A diode 53 for half-wave rectifying the amplified voltage and a smoothing circuit 52 for smoothing the half-wave rectified voltage waveform are connected in series. On the other hand, a counter electromotive current amplifier circuit 55 for inverting and amplifying the voltage value, a diode 56 for half-wave rectifying the inverted and amplified voltage, and an average value holding circuit for detecting an average value of the half-wave rectified voltage waveform. 57 and 57 are connected in series, and these are connected in parallel and input to the positive side of the comparator 51. A predetermined reference voltage V REF is input to the negative side of the comparator 51. That is, the control circuit 50, the maximum value of the voltage appearing in the detection resistor 13,
The constant current chopper circuit 10 is controlled by synthesizing the average value of the voltages obtained by inverting the voltage and comparing the synthesized value with the reference voltage V REF by the comparator 51. In the present embodiment, attention is paid to the change of the counter electromotive current IR due to the motor load, and as described later, further power saving is achieved as compared with the first embodiment.

Hereinafter, the operation of the drive circuit for the stepping motor including the control circuit 50 described above will be described.

When driving at a mid-range frequency, which is a problem from the past, by driving the drive winding switching circuit 30, the voltage value obtained by the current I W2 flowing through the detection resistor 13 is amplified by the excitation current amplification circuit 54. After the diode 53
The half-wave rectification is performed by and the detection value of the substantially smooth waveform is taken out by the smoothing circuit 52. On the other hand, the voltage value is set to the counter electromotive current amplifier circuit 55.
After inverting amplification at (see Fig. 9 (a)), diode 56
The half-wave rectification is performed by (see FIG. 9B), and the half-wave rectified waveform is averaged by the average value holding circuit 57 and detected. The comparator 51 compares the sum of the two detected values (see FIG. 9D) with the reference voltage V REF. That is, since the smoothed waveform of the current I W2 is combined with the averaged waveform of the back electromotive current IR, the combined value should be closer to the integrated current flowing through the motor winding 39. Becomes As shown in FIG. 7, according to the present invention, the counter electromotive current is generated when the motor is unloaded.
The IR is large, and the exciting current I W1 is suppressed by that amount. On the other hand, the counter electromotive current IR decreases when the load increases, so the exciting current I W1 is increased by that amount. Power consumption can be further reduced.

When implementing this method, it is desirable to insert a series connection of a capacitor and a resistor between the motor application portion and the comparator 21 in order to suppress the oscillation of the winding voltage Vw.

Further, although the drive winding switching circuit 10 in each of the above-described embodiments is described as a bipolar type drive, the present invention is not limited to this, and may be, for example, a unipolar type drive, depending on the type of the stepping motor. An appropriate circuit may be selected.

The gains and offsets of the exciting current amplification circuits 54 and 55 are appropriately determined so that the rated current flows through each motor winding 39 when the motor is stopped.

Further, the amplifier circuits 44, 54, 55 described in the above-mentioned embodiments are
Even if a so-called zero-cross comparator is used, the same effect as the present invention can be obtained.

(F) Effect As described above, in the case of the drive circuit for the stepping motor according to the first aspect of the present invention, the counter electromotive force of the reverse polarity included in the detection signal of the current detection resistor is removed, and the constant current chopper drive is performed based on the signal. Since the circuit is operated to perform constant current control, the significant increase in motor power consumption in the middle frequency range, which was caused by the reverse electromotive force of the reverse polarity contained in the detection signal, must be kept low. Is possible. as a result,
Motor etc. does not generate abnormal heat in the mid frequency range,
Reliability can be improved.

In the case of the stepping motor drive circuit according to the second aspect of the invention, since the counter electromotive current that changes according to the load state is taken into consideration, the motor power consumption is lower than that of the case of the first aspect of the invention. It can be made even smaller, and great advantages can be expected in improving the performance of the motor.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a conventional drive circuit for a stepping motor, and FIG. 2 is a circuit diagram showing an extracted control circuit of a drive circuit for a stepping motor according to an embodiment of the first invention, and FIG. FIG. 4 is a circuit diagram showing an extracted control circuit of a drive circuit for a stepping motor according to an embodiment of the second invention, and FIG. 4 is an operation waveform of each part when a four-phase stepping motor is excited in one phase at a low frequency. Fig. 5 is an operation waveform diagram of each part when the four-phase stepping motor is excited by one phase at the middle frequency, and Fig. 6 is an operation waveform of each part when the four-phase stepping motor is excited by one phase at the high frequency. FIG. 7 is an explanatory diagram showing the relationship between drive frequency and power consumption, FIG. 8 is a waveform diagram in each part of the control circuit of the drive circuit for the stepping motor according to the embodiment of the first invention, and FIG. In the embodiment of the second invention Waveform diagram of each part of the control circuit of the stepping motor drive circuit, Fig. 10 is the experimental result when the stepping motor was driven by 1K, 2K and 5KPPS respectively, and the voltage across the detection resistor was measured with an oscilloscope. It is the actually measured waveform diagram. 10 …… Constant current chopper circuit, 20, 40, 50 …… Control circuit, 2
1, 41, 51 …… Comparator, 22, 42, 52 …… Smoothing circuit, 4
3, 53, 56 …… Diode, 44, 54 …… Winding current amplification circuit, 55 …… Back electromotive current amplification circuit, 57 …… Average value holding circuit, 30
...... Drive winding switching circuit.

Continuation of the front page (56) Reference JP 62-285693 (JP, A) JP 60-237886 (JP, A) JP 60-216785 (JP, A) JP 54-164206 (JP , A) Actually open 53-78414 (JP, U) Actually open 58-72999 (JP, U) Actually open 58-73000 (JP, U) Actually open 55-35871 (JP, U) Special public 61-22560 (JP, B2)

Claims (2)

[Claims] 1. A bridge-type bipolar drive circuit comprising four transistors each having a diode connected between a collector and an emitter for allowing a counter electromotive current to flow to the power supply side, wherein a direct-current voltage generated by a direct-current power supply is used. Between the drive winding switching circuit that generates the excitation current of the stepping motor as an input, the constant current chopper drive circuit connected between the DC power supply and the drive winding switching circuit, and the constant current chopper drive circuit and the stepping motor. In a drive circuit for a stepping motor, which is connected to a current detection resistor that detects a current flowing between them as a voltage, and a control circuit that controls a constant current chopper drive circuit based on a detection signal of the current detection resistor. The control circuit rectifies the detection signal to generate a reverse electromotive force component of reverse polarity included in the signal. The signal after removal and rectification is averaged, the averaged signal is compared with a predetermined reference voltage, and the constant current chopper drive circuit is operated according to the comparison result. Drive circuit for stepping motor. 2. A bridge type bipolar drive circuit comprising four transistors each having a diode connected between a collector and an emitter for flowing a back electromotive current to the power supply side, wherein a DC voltage generated by a DC power supply is supplied. Between the drive winding switching circuit that generates the excitation current of the stepping motor as an input, the constant current chopper drive circuit connected between the DC power supply and the drive winding switching circuit, and the constant current chopper drive circuit and the stepping motor. In a drive circuit for a stepping motor, which is connected to a current detection resistor that detects a current flowing between them as a voltage, and a control circuit that controls a constant current chopper drive circuit based on a detection signal of the current detection resistor. The control circuit rectifies the detection signal to generate a reverse electromotive force component of reverse polarity included in the signal. While removing and averaging the rectified signals, separately rectify the signal obtained by inverting the detection signal, average the rectified signals, and add both signals after averaging A driving circuit for a stepping motor, wherein the added signal is compared with a predetermined reference voltage, and the constant current chopper driving circuit is operated according to the comparison result.