HK1069441B - Step motor control device and electronic timepiece - Google Patents

Description

Stepping motor control device and electronic timepiece

Technical Field

The present application relates to a stepping motor control apparatus which rotationally drives a stepping motor and detects presence/absence of rotation of the stepping motor, and an electronic timepiece using the stepping motor control apparatus.

Background

Heretofore, in an electronic timepiece, a stepping motor is used as a motor for rotationally driving a time hand such as an hour hand or a minute hand.

Fig. 5 shows a front view of a stepping motor currently used in an electronic timepiece such as an electronic wristwatch (see patent document 1, for example).

In fig. 5, the stepping motor includes a stator 501 made of a magnetic material, a coil 207 wound on the stator 501, and a bipolar rotor 502 disposed inside the stator 501. The stator 501 has saturated portions 503 and 504 and inner notches 505 and 506 for determining a stop position of the rotor 502.

When a square wave drive pulse is applied to the coil 207 to cause a current i to flow in the direction indicated by the arrow in fig. 5, a magnetic flux in the direction indicated by the arrow is generated in the stator 501. Thus, the saturation portions 503 and 504 are first saturated, and then the rotor 502 is rotated by 180 degrees in the direction indicated by the arrow in fig. 5 (counterclockwise) due to the interaction between the magnetic poles generated in the stator 501 and the magnetic poles generated in the rotor 502. Thus, the alternation allows a pulse current difference of different polarity to flow in the coil 207 to thereby perform the same action as above and rotate the rotor 502 counterclockwise in increments of 180 degrees.

Fig. 6 shows a circuit diagram of a stepping motor control apparatus which has been used for an electronic timepiece so far for performing rotation control of the stepping motor. The circuit is configured such that a rotation driving circuit and a rotation detecting circuit are integrated (for example, refer to patent document 1).

In fig. 6, p-channel MOS transistors Q1, Q2 and n-channel MOS transistors Q3, Q4 are constituent elements of a motor drive circuit, and a stepping motor coil 207 is connected between a source connection point of the transistor Q1 and the transistor Q3 and a source connection point of the transistor Q2 and the transistor Q4.

The gates of the transistors Q1-Q6 are connected to the control circuit 103. A connection point OUT2 of the detection resistor 208 and the coil 207 and a connection point OUT1 of the detection resistor 209 and the coil 207 are connected to an input portion of the comparator 210. Also, the input part of the comparator 210 inputs a predetermined threshold voltage V_SS。

The detection resistor 208 connected in series with the transistor Q5, the detection resistor 209 connected in series with the transistor Q6, and the comparator 210 are constituent elements of the rotation detection circuit.

Fig. 7 is a timing chart for performing rotation control and detection control of the stepping motor in the stepping motor control apparatus shown in fig. 6.

The operation of the conventional stepping motor control apparatus having the above-described structure will be described with reference to fig. 5 to 7. First, when one driving pulse P1 is applied to the input section Vi of the control circuit 103, the transistors Q2 and Q3 become a conductive state under the control of the control circuit 103. Thus, a current flows in the coil 207 in the direction indicated by the arrow, and the rotor 502 rotates counterclockwise as shown in fig. 5.

On the other hand, a non-detection period IT, which is a period of time during which the rotation of the stepping motor is not detected, is set to a given period T7 immediately after the motor driving period, and a rotation detection period DT for detecting whether the stepping motor is rotating is set to a given period T8 immediately after the non-detection period IT.

During the rotation detection period DT, a rotation detection control pulse SP1 is applied to the input section Vi of the control circuit 103. While the transistors Q3 and Q4 are in the on state in response to the rotation detection control pulse SP1, the control circuit 103 controls the on/off action of the transistor Q4 at a given frequency.

In this case, the detection signal V8 is taken OUT from the connection point OUT1 between the rotation detecting resistor 209 and the coil 207. A detection signal having a waveform as shown in fig. 7 is obtained as the detection signal V8. In fig. 7, a sensing voltage V8 below VDD is generated when the rotor 502 swings counterclockwise as in fig. 5, and a sensing voltage V8 above VDD is generated when the rotor 502 swings clockwise as in fig. 5.

When the rotor 502 rotates, the detection signal V8 exceeding a given threshold voltage (Vss in this conventional example) is obtained, and the rotation detection signal Vs of high level is output from the comparator 210. When the rotor 502 is not rotated, since the detection signal V8 does not reach the threshold voltage, the rotation detection signal Vs of a low level is output from the comparator 210. It is possible to detect whether the stepping motor is rotated or not based on the rotation detection signal Vs. After completion of the rotation detection, the transistors Q3 and Q4 are maintained in the on state to brake the stepping motor.

During the subsequent motor drive, the subsequent standard drive pulse P1 is applied to the input section Vi of the control circuit 103. The control circuit 103 controls the transistors Q1 and Q4 to be turned on, and a drive current flows in the coil 207 in the opposite direction (counterclockwise in fig. 5) to the above drive current to rotate the rotor 502 counterclockwise.

At this time, during the rotation detection, when the rotation detection control pulse SP1 is applied to the input section Vi of the control circuit 103, the control circuit 103 controls the transistors Q4 and Q5 to be conductive and controls the on/off operation of the transistor Q3 at a given frequency.

In this case, the detection voltage V is taken OUT from the connection point OUT2 between the resistor 208 and the coil 207. The level of the detection voltage V is determined by the comparator 210. In the same manner as above, when the rotor 502 is rotating, the comparator 210 outputs the high-level rotation detection signal Vs, and when the rotor 502 is not rotating, the comparator 210 outputs the low-level rotation detection signal Vs. It is impossible to detect whether the stepping motor is rotated based on the rotation detection signal Vs.

After completion of the rotation detection, the transistors Q3 and Q4 are maintained in the on state to brake the stepping motor.

[ patent document 1]

JP57-18440B (pages 1-2, FIG. 1)

In the stepping motor control apparatus of the above-described structure, after the stepping motor is driven by the drive pulse P1, the rotor 502 is freely swung at the center position where the rotor 502 should be stopped. Immediately after the application of the drive pulse P1 is finished, the free oscillation of the rotor 502 becomes large, and the rotor 502 oscillates in the same direction as the normal rotation direction (counterclockwise in the above-described conventional example) due to the inertia. When the rotor 502 swings counterclockwise, current flows in the direction of the arrows shown in fig. 6.

On the other hand, equivalent circuits of the transistors Q3 to Q6 are each constituted by a series circuit including a switch 804 and a resistor 803, and a diode 801 and a capacitor 802 connected in parallel to the series circuit, as shown in fig. 8. Each transistor Q3-Q6 is considered an equivalent element with a single phase diode.

Therefore, even if the stepping motor is not rotated, since the counterclockwise swing of the rotor 502 becomes large in a given period immediately after the application of the drive pulse P1 is completed, the detection voltage V7 higher than the threshold voltage Vss as shown in fig. 7 can be obtained. That is, in the detection signal V7, the detection signal V7 is obtained within a given period T7 immediately after the end of the application of the drive pulse P1, a detection voltage having a large peak value occurs in the detection resistance 209 due to the large free swing of the rotor 502, and false detection is caused due to the rotation of the stepping motor.

Heretofore, to prevent such false detection, the control circuit is configured such that a non-detection period IT having a given time width T7 is set to start at a time point immediately after the application of the drive pulse P1 is interrupted, thereby preventing rotation detection of the stepping motor from being performed during the non-detection period IT.

Similarly, in the non-detection period IT immediately after the interruption of the application of the driving pulse P1 and in the detection period DT, the on/off operation of the transistor Q4 is controlled at a given frequency while the transistors Q3 to Q6 are in the on state. That is, in the non-detection period IT and in the detection period DT, the on/off operation of the transistor Q4 is controlled to amplify the detection signal in the transient response. Therefore, there arises a problem that the stepping motor generates a braking force, resulting in an uneconomical consumption of energy.

Therefore, there arises a problem that the control circuit configuration becomes complicated due to the provision of the non-detection period IT.

An object of the present invention is to provide a stepping motor control apparatus which is effective in improving energy consumption.

Further, another object of the present invention is to provide a stepping motor control apparatus which realizes more secure detection of rotation of a stepping motor with a simple structure without any prescribed non-detection period IT.

Further, another object of the present invention is to provide an electronic timepiece which is effective in improving power consumption.

Further, another object of the present invention is to provide an electronic timepiece which realizes more safe detection of rotation of a stepping motor for driving an hour hand with a simple structure.

Disclosure of Invention

According to the present invention, there is provided a stepping motor control apparatus including first and second switching elements connected in series with each other; third and fourth switching elements connected in series with each other; a stepping motor coil connected between a connection point of the first and second switching elements and a connection point of the third and fourth switching elements; a first series circuit including a fifth switching element and a first detection element connected in parallel with the first switching element; a second series circuit including a sixth switching element and a second detection element connected in parallel with the third switching element; a control device which controls on/off actions of the first to fourth switching elements in response to a driving pulse so that a current flows in the coil to rotationally drive the stepping motor, and controls on/off actions of the first, third, fifth and sixth switching elements in response to a rotation detection control pulse which is applied during rotation detection immediately after rotational driving according to the driving pulse immediately after the end of application of the driving pulse; and a detection device that detects the presence/absence of rotation of the stepping motor based on a result of comparison of a voltage generated between the first and second detection elements and the coil with a given threshold voltage, the stepping motor control apparatus being characterized in that: the control means controls the on/off action of the first switching element at a given frequency during the detection when the third and fifth switching elements are in the on state, or controls the on/off action of the third switching element at a given frequency during the detection when the first and sixth switching elements are in the on state, and the detection means detects the presence/absence of rotation of the stepping motor when the control means controls the on/off action of the first switching element or the third switching element at a given frequency.

The control means controls the on/off action of the third switching element at a given frequency after a given period has elapsed when the fourth and fifth switching elements are in the on state, or controls the on/off action of the fourth switching element at a given frequency after a given period has elapsed when the third and sixth switching elements are in the on state. When the control means controls the on/off action of the third switching element or the fourth switching element at a given frequency, the detection means detects the presence/absence of rotation of the stepping motor.

Here, the first, third, fifth, and sixth switching elements may be formed of n-type channel MOS transistors, and the second and fourth switching elements may be formed of p-type channel MOS transistors.

Further, the first and second detection elements may be constituted by resistors.

Further, according to the present invention, there is provided an electronic timepiece including a stepping motor for rotating a time hand and a stepping motor control device for rotationally controlling the stepping motor, the timepiece being characterized in that any one of the above stepping motor control devices is adopted as the stepping motor control device.

Drawings

Preferred forms of the invention are described in the accompanying drawings, in which:

fig. 1 is a block diagram of an electronic timepiece according to an embodiment of the invention;

fig. 2 is a circuit diagram for explaining the operation of the stepping motor control apparatus according to the embodiment of the present invention;

fig. 3 is a circuit diagram for explaining the operation of the stepping motor control apparatus according to the embodiment of the present invention;

fig. 4 is a timing chart of the stepping motor control apparatus;

fig. 5 is a front view of a general stepping motor;

fig. 6 is a circuit diagram for explaining the action of the conventional stepping motor control apparatus;

fig. 7 is a timing chart of the conventional stepping motor control apparatus;

fig. 8 is an equivalent circuit diagram of a general n-channel MOS transistor.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 is a block diagram of an electronic timepiece employing a stepping motor control device according to an embodiment of the present invention, and shows an example of an analog electronic wristwatch.

Referring to fig. 1, an oscillation circuit 101 is connected to an input portion of a control circuit 103 through a frequency dividing circuit 102. A first output part of the control circuit 103 is connected to a stepping motor 105 through a motor drive circuit 104 for driving an hour hand. A second output section of the control circuit 103 is connected to a control input section of the rotation detecting circuit 106. A rotation detection circuit 106 for detecting whether the motor 105 rotates is connected between the motor 105 and the control circuit 103. The rotation detection circuit 106 constitutes rotation detection means.

The stepping motor 105 has the same structure as that of the stepping motor shown in fig. 5. Also, the motor drive circuit 104 and the rotation detection circuit 106 themselves have the same configuration as that shown in fig. 6, but the method of controlling the on/off actions of the respective transistors Q1-Q6 is different from the conventional example shown in fig. 6, which will be described later.

The frequency dividing circuit 102 divides the reference clock signal from the oscillation circuit 101 and outputs the divided reference clock signal to the control circuit 103. The control circuit 103 receives a signal from the frequency dividing circuit 102 and outputs a frequency-divided pulse to the motor drive circuit 104. Among the drive pulses, a standard drive pulse P1, which is a drive pulse of a given pulse width smaller in effective energy, and a correction drive pulse, which is a drive pulse of a wider width in effective energy than the standard drive pulse, are prepared, and the above-mentioned control circuit 103 selectively outputs the standard drive pulse and the correction drive pulse to the motor drive circuit 104 in accordance with the detection signal from the rotation detection circuit 106. In this example, the control circuit 103 is configured as a drive pulse generating device that generates a drive pulse.

Similarly, the control circuit 103 applies a rotation detection control pulse necessary for detecting the rotation of the motor 105 to the rotation detection circuit 106. In this example, the control circuit 103 is configured as a rotation detection control pulse generating device that generates a rotation detection control pulse.

The control circuit 103, the motor drive circuit 104, and the rotation detection circuit 106 constitute a control device.

Fig. 2 and 3 are explanatory configuration diagrams showing the operations of the motor drive circuit 104 and the rotation detection circuit 106 in the stepping motor control apparatus according to the embodiment of the present invention, respectively, in which fig. 2 shows an explanatory diagram of the operation when the motor is rotationally driven, and fig. 3 shows an explanatory diagram of the operation when the rotation of the motor is detected.

In fig. 2 and 3, a p-type channel MOS transistor Q1 (second switching element), a Q2 (fourth switching element), and an n-type channel MOS transistor Q3 (first switching element), a Q4 (third switching element) is a transistor included in the motor drive circuit 104, and the coil 207 of the motor 105 is connected between the source connection point of the transistors Q1 and Q3 and the source connection point of the transistor Q2 and the transistor Q4.

The rotation detecting circuit 106 includes an n-channel MOS transistor Q5 (fifth switching element), Q6 (sixth switching element), a rotation detecting resistor 208 (first detecting element) connected in series with the transistor Q5, a rotation detecting resistor 209 (second detecting element) connected in series with the transistor Q6, and a comparator 210.

Fig. 4 is a timing chart for the stepping motor control apparatus according to the embodiment, which is a timing chart in the case where the rotation detection of the motor 105 is performed by the rotation detection circuit 106 in response to the rotation detection control pulse SP1 after the motor 105 is rotated in accordance with the standard drive pulse P1.

Hereinafter, operations of the stepping motor control apparatus and the electronic timepiece according to the embodiment of the invention will be described with reference to fig. 1 to 4 in appropriate combination with fig. 5 and 8.

First, during motor driving, a standard driving pulse P1 is applied from the control circuit 103 to the motor driving circuit 104, whereby the motor driving circuit 104 controls the rotation of the motor 105.

At this time, as shown in fig. 2, the transistors Q2 and Q3 of the motor drive circuit 104 are controlled to be on due to the flow of the drive current in the coil 207, and the motor 105 rotates counterclockwise (in the direction indicated by the arrow) by 180 degrees as shown in the front view of fig. 5.

On the other hand, a rotation detection period DT is provided after the motor driving period, and a rotation detection operation of whether or not the motor 105 rotates is performed during this period DT.

In the rotation detection operation of the motor 105, first, at time t1 immediately after the motor rotation driving is stopped, a rotation detection control pulse SP1 is applied from the control circuit 103 to the rotation detection circuit 106.

The motor drive circuit 104 and the rotation detection circuit 106 control the transistors Q3 and Q6 to be turned on and the transistors Q1, Q2, Q4, and Q5 to be turned off in response to the rotation detection control pulse SP1 from the control circuit 103 during a given period T1 from time T1, as shown in fig. 3. In this state, since the transistor Q4 does not control the on/off operation, the detection signal is not amplified in the transient response, and the detection signal V1 of a low voltage is obtained.

Therefore, there is little possibility that a large detection signal is generated without rotating the motor 105 and that the motor rotation is detected although the motor does not rotate. Likewise, the transistors Q3, Q6 and the coil 207 become a closed circuit, and since the closed circuit includes the high-impedance resistor 209, the braking force applied to the motor 105 is extremely small. Thus, useless power consumption may be suppressed.

Then, at time T2 after a given period T1 from time T1, the detection period DT of time width T2 is started. In the detection period DT, in the case where the transistors Q3 and Q6 have been in the on state, the on/off action of the transistor Q4 is controlled at a given frequency in response to the rotation detection control pulse SP1 from the control circuit 103. In this way, since the voltage amplification of the detection signal is performed in the transient response, an appropriate detection signal V2 is obtained in response to the presence/absence of rotation, and it is possible to perform corresponding rotation detection.

In the case where the voltage of the detection signal becomes beyond the given threshold voltage Vss, that is, in the case where the motor 105 is rotated, the high-level rotation detection signal Vs indicating the rotation of the motor 105 is output from the comparator 210, and after the transistors Q3 and Q4 are turned on to make the motor stationary, the next motor driving period is started.

During the subsequent motor drive, when the subsequent standard drive pulse P1 is applied from the control circuit 103 to the motor drive circuit 104, the control transistors Q1 and Q4 are turned on, and a drive current flows in the coil 207 in the opposite direction to the above-described drive current to rotate the motor 105 by 180 degrees counterclockwise in the same direction.

Similarly, the same rotation detection period DT as above is set after the motor drive period, and a rotation detection operation of whether or not the motor 105 rotates is performed during this period DT.

That is, in the case of the rotation detecting operation of the motor 105, during a period T1 immediately after the motor drive is stopped, in response to the rotation detecting control pulse SP1 from the control circuit 103, the motor drive circuit 104 and the rotation detecting circuit 106 first control the transistors Q4 and Q5 to be turned on and control the other transistors Q1, Q2, Q3, and Q6 to be turned off.

In this state, since the on/off operation of the transistor Q3 is not controlled, the voltage of the detection signal is not amplified in the transient response. Therefore, the detection signal is generated without rotation, and the possibility that rotation is detected although there is no rotation is small.

Also, the transistors Q4, Q5 and the coil 207 become a closed circuit, and since the circuit includes the high-impedance resistor 208, the braking force applied to the motor 105 is extremely small. Thus, useless power consumption may be suppressed.

After that, the detection period DT of the time width T2 starts. In the detection period DT, in the case where the transistors Q4 and Q5 have been in the on state, the on/off action of the transistor Q3 is controlled at a given frequency in response to the rotation detection control pulse SP1 from the control circuit 103. In this way, the voltage of the detection signal is amplified in the transient response and a corresponding rotation detection is possible.

In the case where the voltage of the detection signal becomes beyond the given threshold voltage Vss, that is, in the case where the motor 105 is rotating, the high-level rotation detection signal Vs indicating the rotation of the motor 105 is output from the comparator 210, and after the transistors Q3 and Q4 are turned on and the motor is stationary, the next motor driving period is started.

Thereafter, the above operation is repeated to continue the counterclockwise rotation of the motor 105, and effective rotation detection is performed. In the case where it is detected that the motor 105 does not rotate, it is possible to rotate the motor 105 by applying a correction drive pulse having a width larger than the standard drive pulse P1 to the motor 105.

Although in this embodiment, an example in which the stepping motor control device is used for the electronic timepiece is described, it is possible to use the stepping motor control device for other electronic devices.

According to the stepping motor control apparatus of the present invention, it is possible to reduce power consumption. Also, IT is possible to detect the rotation of the stepping motor more safely with a simple structure without any prescribed non-detection period IT.

Also, according to the electronic timepiece of the invention, it is possible to reduce power consumption. Also, it is possible to more safely detect the rotation of the stepping motor for driving the hour hand with a simple structure in the electronic timepiece.

Claims (4)

1. A stepping motor control apparatus comprising:

first and second switching elements connected in series with each other;

third and fourth switching elements connected in series with each other;

a stepping motor coil connected between a connection point of the first and second switching elements and a connection point of the third and fourth switching elements;

a first series circuit including a fifth switching element and a first detection element connected in parallel with the first switching element;

a second series circuit including a sixth switching element and a second detection element connected in parallel with the third switching element;

a control device for controlling on/off operations of the first to fourth switching elements in response to a driving pulse so that a current flows in the coil to rotationally drive the stepping motor, and controlling on/off operations of the first, third, fifth and sixth switching elements in response to a rotation detection control pulse applied during a rotation detection period immediately after the rotational driving according to the driving pulse immediately after the end of the application of the driving pulse; and

a detection means for detecting the presence/absence of rotation of said stepping motor based on the result of comparison of the voltages generated between the first and second detection elements and said coil with a given threshold voltage;

the method is characterized in that: the control means controls the on/off action of the first switching element at a given frequency during the detection when the third and fifth switching elements are in the on state, or controls the on/off action of the third switching element at a given frequency during the detection when the first and sixth switching elements are in the on state, and

the detection means detects the presence/absence of rotation of the stepping motor when the control means controls the on/off operation of the first switching element or the third switching element at a predetermined frequency.

2. The stepping motor control apparatus according to claim 1, comprising:

wherein the first, third, fifth and sixth switching elements are constituted by n-type channel MOS transistors, and the second and fourth switching elements are constituted by p-type channel MOS transistors.

3. The stepping motor control apparatus according to claim 1, comprising:

wherein the first and second sensing elements are formed by resistors.

4. An electronic timepiece comprising:

a stepping motor for rotating the time hand; and

a stepping motor control device for rotationally controlling the stepping motor;

the method is characterized in that: a stepping motor control apparatus according to claim 1 is used as the above stepping motor control apparatus.