JP2011067086A - Stepping motor control circuit and analog electronic clock - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve rotation detection accuracy by performing a rotation detection operation based on the rotation state. <P>SOLUTION: At a rotation detection time point T2 after a stepping motor is rotationally driven by a main drive pulse, a stepping motor control circuit alternately switches between a first closed circuit including a high impedance element and a drive coil of the stepping motor, and a second closed circuit including a low impedance element and the drive coil at a predetermined time ratio, thereby detecting an induced signal VRs generated by the stepping motor. The stepping motor control circuit determines whether the stepping motor has rotated, based on whether the induced signal VRs has exceeded a predetermined reference threshold voltage Vcomp, and controls the rotation of the stepping motor. In the stepping motor control circuit, the rotation detection time period T2 is divided into a first duty period and a second duty period following the first duty period. The duty ratio that is a composition time ratio of the first closed circuit and the second closed circuit is made smaller in the second duty period than in the first duty period. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a stepping motor control circuit and an analog electronic timepiece using the stepping motor control circuit.

  Conventionally, it has a rotor housing hole and a stator having a positioning portion for determining the stop position of the rotor, a rotor disposed in the rotor housing hole, and a drive coil, and supplies an alternating signal to the drive coil. A stepping motor that rotates the rotor by generating magnetic flux in the stator and stops the rotor at a position corresponding to the positioning portion is used in an analog electronic timepiece or the like.

  In the conventional stepping motor control circuit, when detecting whether or not the stepping motor has rotated, the high impedance element and the driving coil of the stepping motor are installed in the rotation detection time after the stepping motor is rotated by the main drive pulse. The induced signal VRs generated by the stepping motor is amplified and detected by alternately switching a first closed circuit including the second closed circuit including a low impedance element and the driving coil at a predetermined time ratio. (For example, refer to Patent Document 1).

  When the stepping motor rotates, the maximum value Vmax of the induced signal VRs exceeds a predetermined reference threshold voltage Vcomp (see FIG. 9), and when the stepping motor does not rotate, the induced signal VRs becomes equal to or less than the reference threshold voltage Vcomp (FIG. 10). reference). Therefore, it is determined whether or not the induced signal VRs has rotated based on whether or not it has exceeded the reference threshold voltage Vcomp. When the induced signal VRs is not rotating, it is driven by the correction driving pulse P2 having a driving energy larger than the main driving pulse P1. It is forcibly rotated to achieve normal operation.

The induction signal VRs is output by increasing the ratio (duty ratio) between the time for forming the first closed circuit and the time for forming the second closed circuit (that is, by increasing the time for forming the first closed circuit). During this period, the braking effect is reduced.
When a time hand with a large moment is attached when the duty ratio is large, when the motor is not rotating, the rotational speed is originally slow and the induced signal VRs output should be small, but sufficient braking can be applied. Since this is not possible, a high induced signal VRs is generated in the second half of the rotation detection time, and there is a problem that erroneous rotation detection (detection of rotation but non-rotation and mishandling) occurs (see FIG. 11).

  Conversely, if the duty ratio is reduced (that is, the time for forming the first closed circuit is shortened), a high induced signal VRs should be generated at the time of rotation. However, since the braking is large, the amplification effect of the induced signal VRs is increased. Becomes smaller and the amplified signal VRs becomes lower, resulting in erroneous rotation detection (detection of non-rotation despite rotation, and large current consumption due to drive output by useless correction drive pulse P2). is there.

Japanese Patent Laid-Open No. 55-87977

  The present invention has been made in view of the above problems, and an object of the present invention is to improve rotation detection accuracy by performing a rotation detection operation in accordance with a rotation state.

  According to the present invention, the first closed circuit including the high impedance element and the driving coil of the stepping motor, the low impedance element and the first driving coil including the driving coil in the rotation detection time after the stepping motor is rotationally driven by the main driving pulse. The induced signal generated by the stepping motor is detected by alternately switching between two closed circuits at a predetermined time ratio, and the stepping motor rotates based on whether the induced signal exceeds a predetermined reference threshold voltage. In the stepping motor control circuit comprising control means for determining whether or not to control the rotation of the stepping motor, the rotation detection time is divided into a first section and a second section after the first section, The control means sets a duty ratio, which is a configuration time ratio of the first closed circuit and the second closed circuit, to the first section. When the stepping motor control circuit for causing different between the second section is provided.

  According to the invention, in the analog electronic timepiece having a stepping motor that rotationally drives the time hand and a stepping motor control circuit that controls the stepping motor, the stepping motor control circuit described above is used as the stepping motor control circuit. An analog electronic timepiece characterized by being used is provided.

According to the stepping motor control circuit of the present invention, it is possible to perform a rotation detection operation according to the rotation state.
According to the analog electronic timepiece according to the invention, it is possible to perform a rotation detection operation according to the rotation state, and thus it is possible to perform an accurate hand movement operation.

1 is a block diagram of an analog electronic timepiece according to an embodiment of the present invention. It is a block diagram of the stepping motor used for the analog electronic timepiece which concerns on embodiment of this invention. It is a partial detailed circuit diagram of the analog electronic timepiece and the stepping motor control circuit according to the embodiment of the present invention. It is explanatory drawing for demonstrating operation | movement of the analog electronic timepiece and stepping motor control circuit which concern on embodiment of this invention. It is explanatory drawing for demonstrating operation | movement of the analog electronic timepiece and stepping motor control circuit which concern on embodiment of this invention. It is a signal waveform diagram for demonstrating operation | movement of the analog electronic timepiece and stepping motor control circuit which concern on embodiment of this invention. It is a signal waveform diagram for demonstrating operation | movement of the analog electronic timepiece and stepping motor control circuit which concern on embodiment of this invention. It is a signal waveform diagram for demonstrating operation | movement of the analog electronic timepiece and stepping motor control circuit which concern on other embodiment of this invention. It is a signal waveform diagram for demonstrating operation | movement of the conventional analog electronic timepiece. It is a signal waveform diagram for demonstrating operation | movement of the conventional analog electronic timepiece. It is a signal waveform diagram for demonstrating operation | movement of the conventional analog electronic timepiece.

Hereinafter, a stepping motor control circuit and an analog electronic timepiece according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals.
FIG. 1 is a block diagram of an analog electronic timepiece using a stepping motor control circuit according to an embodiment of the present invention, and shows an example of an analog electronic wristwatch.
In FIG. 1, the analog electronic timepiece includes a stepping motor control circuit 101, a stepping motor 102 that rotationally drives a time hand and the like, and a power source 103 constituted by a battery.

  The stepping motor control circuit 101 includes a first closed circuit including a high impedance element and a driving coil of the stepping motor 102, a low impedance element, and the driving coil in a rotation detection time after the stepping motor 102 is rotationally driven by the main driving pulse P1. The induced signal VRs generated by the stepping motor 102 is detected by alternately switching the second closed circuit including the second closed circuit at a predetermined time ratio (duty ratio), and whether or not the induced signal VRs exceeds a predetermined reference threshold voltage Vcomp. This is a stepping motor control circuit that determines whether or not the stepping motor 102 has been rotated based on whether or not the rotation of the stepping motor 102 is controlled.

A stepping motor control circuit 101 constitutes an oscillation circuit 104 that generates a signal of a predetermined frequency, a frequency dividing circuit 105 that divides the signal generated by the oscillation circuit 104 and generates a clock signal that serves as a time reference, and an electronic timepiece. A control circuit 106 that performs control of each electronic circuit element, control of change of drive pulse, etc., a drive pulse circuit 107 that controls the rotation of the stepping motor 102 by a drive pulse corresponding to a control signal from the control circuit 106, Rotation detecting means 108 is provided for detecting an induced signal VRs representing a rotation state when the main drive pulse P1 is rotationally driven.
Here, the oscillation circuit 104, the frequency divider circuit 105, the control circuit 106, the drive pulse circuit 107, and the rotation detection means 108 constitute a control means.

  The rotation detection time T2 is divided into a first interval and a second interval after the first interval, and the control means includes a first closed circuit including a high impedance element and a driving coil of a stepping motor, a low impedance element, and the drive. The duty ratio, which is the configuration time ratio of the second closed circuit including the coil, can be made different between the first section and the second section. The control means can make the duty ratio smaller in the second section than in the first section. Further, it is possible to have a mask time T1 that is not used for determining the presence or absence of rotation before the rotation detection time T2. In addition, when detecting the induced signal VRs exceeding the reference threshold voltage Vcomp within the mask time T1, the control means can reduce the duty ratio by a predetermined amount in the second interval of the rotation detection time T2.

FIG. 2 is a configuration diagram of the stepping motor 102 used in the embodiment of the present invention, and shows an example of a timepiece stepping motor generally used in an analog electronic timepiece.
In FIG. 2, the stepping motor 102 is wound around a stator 201 having a rotor accommodating through hole 203, a rotor 202 rotatably disposed in the rotor accommodating through hole 203, a magnetic core 208 joined to the stator 201, and a magnetic core 208. A rotated coil 209 is provided. When the stepping motor 105 is used in an analog electronic timepiece, the stator 201 and the magnetic core 208 are fixed to a base plate (not shown) by screws or caulking (not shown) and joined to each other. The coil 209 has a first terminal OUT1 and a second terminal OUT2.

The rotor 202 is magnetized to two poles (S pole and N pole). A plurality of (two in this embodiment) notch portions (outer notches) 206 and 207 are provided at positions facing each other across the rotor accommodating through hole 203 at the outer end portion of the stator 201 formed of a magnetic material. Is provided. Saturable portions 210 and 211 are provided between the outer notches 206 and 207 and the rotor accommodating through hole 203.
The saturable portions 210 and 211 are configured not to be magnetically saturated by the magnetic flux of the rotor 202 but to be magnetically saturated when the coil 209 is excited to increase the magnetic resistance. The through hole 203 for accommodating the rotor has a circular hole shape in which a plurality of (two in the present embodiment) half-moon-shaped notches (inner notches) 204 and 205 are integrally formed at the opposing portion of the through hole having a circular outline. It is configured.

The notches 204 and 205 constitute a positioning part for determining the stop position of the rotor 202. In a state where the coil 209 is not excited, the rotor 202 has a position corresponding to the positioning portion as shown in FIG. 2, in other words, a line segment connecting the notches 204 and 205 with the magnetic pole axis A of the rotor 202. Is stably stopped at a position orthogonal to the angle (angle θ0 position).
Now, a rectangular-wave drive pulse is supplied from the drive pulse circuit 107 between the terminals OUT1 and OUT2 of the coil 209 (for example, the first terminal OUT1 side is positive and the second terminal OUT2 side is negative), and the direction of the arrow in FIG. When a current i is passed through the stator 201, a magnetic flux is generated in the stator 201 in the direction of the broken arrow. As a result, the saturable portions 210 and 211 are saturated and the magnetic resistance is increased, and then the rotor 202 is rotated 180 degrees in the direction of the solid arrow in FIG. 2 due to the interaction between the magnetic pole generated in the stator 201 and the magnetic pole of the rotor 202. It rotates and the magnetic pole axis A stops in a stable manner with the direction of the angle θ1.

Next, from the drive pulse selection circuit 104, a drive pulse having a reverse polarity rectangular wave is supplied to the terminals OUT1 and OUT2 of the coil 209 (the first terminal OUT1 side is connected to the negative electrode so that the drive polarity is opposite to that of the drive). When the second terminal OUT2 side is the positive electrode) and a current is passed in the direction indicated by the arrow in FIG. As a result, the saturable portions 210 and 211 are first saturated, and then the rotor 202 rotates 180 degrees in the same direction as described above due to the interaction between the magnetic poles generated in the stator 201 and the magnetic poles of the rotor 202, and the magnetic pole axis A Stops stably at the position of angle θ0.
Thereafter, by supplying signals with different polarities (alternating signals) to the coil 209 in this way, the above operation is repeated, and the rotor 202 can be continuously rotated 180 degrees in the direction of the arrow. It is configured as follows.

FIG. 3 is a detailed circuit diagram showing a part of the drive pulse circuit 107 and the rotation detection means 108. 4 and 5 are operation explanatory views of the rotation detection operation for detecting the rotation of the stepping motor 102. FIG.
In FIG. 3, N-channel MOS transistors Q1 and Q2, and P-channel MOS transistors Q3 and Q4 are components of the drive pulse circuit 107. The drain connection points of the transistors Q1 and Q3, the drain connection points of the transistors Q2 and Q4, and Between these, the coil 209 of the stepping motor 102 is connected.

On the other hand, the detection resistor 301 which is a high impedance element connected in series to the P-channel MOS transistors Q3 to Q6 and the transistor Q5, and the detection resistor 302 which is a high impedance element connected in series to the transistor Q6 are rotation detection means 108. Is a component of
The gates of the transistors Q1 to Q6 are controlled by the control circuit 106, whereby the transistors Q1 to Q6 are on / off controlled. A connection point OUT2 between the detection resistor 301 and the coil 209, and a connection point OUT1 between the detection resistor 302 and the coil 209 are connected to an input unit of a comparator (not shown) in the rotation detection means 108. A predetermined reference threshold voltage Vcomp is input to the reference input unit of the comparator, and the comparator determines whether the induced signal VRs exceeds the reference threshold voltage Vcomp.

  The transistor Q3 is a first switch element, the transistor Q1 is a second switch element, the transistor Q4 is a third switch element, the transistor Q2 is a fourth switch element, the transistor Q5 is a fifth switch element, the transistor Q6 is a sixth switch element, The detection resistor 301 constitutes a first detection element, and the detection resistor 302 constitutes a second detection element. The transistor Q5 and the detection resistor 301 constitute a first series circuit, and the transistor Q6 and the detection resistor 302 constitute a second series circuit. In addition, the transistors Q3 and Q4 function as low impedance elements when rotation is detected.

When the stepping motor 102 is rotationally driven during the rotational driving time for rotationally driving the stepping motor 102, the transistors Q2 and Q3 are simultaneously turned on in response to the rotational drive control signal from the control circuit 106, or By simultaneously turning on the transistors Q1 and Q4, a current is supplied to the coil 209 in the forward or reverse direction, thereby driving the stepping motor 102 to rotate.
In the case of detecting the induced signal VRs generated in the stepping motor 102 by the rotation drive at the rotation detection time T2 after the rotation drive time, the transistors Q4 and Q5 are turned on in response to the rotation detection control signal from the control circuit 106. In the held state, the on / off switching control of the transistor Q3 is performed at a predetermined period, and the induced signal VRs generated in the detection resistor 301 is taken out and compared with the reference threshold voltage Vcomp, or the transistors Q3 and Q6 are turned on. In the held state, the transistor Q4 is subjected to on / off switching control at a predetermined period, and the induced signal VRs generated in the detection resistor 302 is taken out and compared with the reference threshold voltage Vcomp. As a result, the rotation detecting means 108 amplifies and detects the induced signal VRs generated by the stepping motor 102, and determines whether or not it has rotated by comparing it with the reference threshold voltage Vcomp.

  That is, in the former rotation detection time, in response to the rotation detection control signal from the control circuit 106, the transistor Q3 is turned off while the transistors Q4 and Q5 are held on (the resistance that is a high impedance element). 301 and a state in which a first closed circuit including a stepping motor drive coil 209 is configured (see FIG. 4), and a state in which the transistor Q3 is turned on while the transistors Q4 and Q5 are kept on (a low impedance element). The induced signal VRs generated by the stepping motor 102 is amplified and detected by alternately switching the state (see FIG. 5) that constitutes the second closed circuit including the transistor Q3 and the drive coil 209 at a predetermined time ratio. The stepping mode is determined based on whether the signal VRs exceeds a predetermined reference threshold voltage Vcomp. Motor 102 controls the rotation of the stepping motor 102 to determine whether the rotation.

  In the present embodiment, a mask time T1, which is a period that is not used for determining whether or not it has been rotated, is provided immediately after the rotation drive time by the main drive pulse P1, and a time that is used for the rotation determination after the mask time T1. A certain rotation detection time T2 is provided. The rotation detection time T2 is divided into a plurality of sections (in this embodiment, a first section (first duty section) and a second section (second duty section) after the first section). The duty ratio that is the ratio between the first closed circuit configuration time and the second closed circuit configuration time is configured to be different. The mask time T1 is for preventing erroneous rotation detection due to noise immediately after the rotational driving, and is not necessarily required.

In the state shown in FIG. 4, the transistors Q4 and Q5, the detection resistor 301, and the drive coil 209 form a first closed circuit, so that the stepping motor 102 is not braked. On the other hand, in the state of FIG. 5, the transistors Q3 and Q4 and the coil 209 form a second closed circuit and the drive coil 209 is short-circuited, so that the stepping motor 102 is braked.
6 and 7 are signal waveform diagrams for explaining the operation of the embodiment of the present invention. FIG. 6 is a signal waveform diagram when the stepping motor 102 is rotated. FIG. 7 is a diagram showing the stepping motor 102 not rotating. FIG.

  In FIG. 6, a mask time T1 is provided for the degree of driving straightness by the main drive pulse P1, and a rotation detection time T2 is provided after the mask time T1. As described above, the mask time T1 is a period that is not used for determining whether or not the stepping motor 102 has rotated, and rotates even when the induced signal VRs generated within the mask time T1 exceeds the reference threshold voltage Vcomp. Not determined. Immediately after the stepping motor 102 is driven to rotate, an unstable induction signal VRs may be generated, and this is eliminated by the mask time T1, thereby improving the accuracy of rotation detection. As will be described later, the control circuit 106 changes the duty ratio by using the induced signal VRs generated within the mask time T1.

The control circuit 106 determines that rotation occurs when the maximum value Vmax of the induced signal VRs exceeds the reference threshold voltage Vcomp at the rotation detection time T2, and determines non-rotation when it does not exceed the reference threshold voltage Vcomp. .
The rotation detection time T2 is divided into two sections (a first duty section and a second duty section) in which the duty ratio of the switching operation during rotation detection is different. In the present embodiment, the duty ratio is made smaller in the second duty interval than in the first duty interval.

  The control circuit 106 performs the rotation detection operation at the first duty ratio in the first duty interval of the mask time T1 and the rotation detection interval T2 after the drive pulse circuit 107 finishes rotating the stepping motor 102 by the main drive pulse P1. The rotation detection means 108 is controlled at this time, and in response to this, the rotation detection means 108 detects the induced signal VRs. The control circuit 106 controls the rotation detection unit 108 to perform the rotation detection operation at the second duty ratio in the second duty period after the end of the first duty period, and the rotation detection unit 108 responds to the induced signal VRs. Detection is performed.

As shown in FIG. 6, the control circuit 106 determines that the rotation is detected when the rotation detection unit 108 detects an induced signal VRs exceeding the reference threshold voltage Vcomp at the rotation detection time T2. The control circuit 106 determines non-rotation when the rotation detection unit 108 does not detect the induced signal VRs exceeding the reference threshold voltage Vcomp at the rotation detection time T2. A plurality of main drive pulses P1 having different drive energies and correction drive pulses P2 having drive energies larger than the main drive pulses P1 are prepared in advance, and the drive pulses are selected and driven according to the rotation state. In the case of the correction driving system configured as described above, when the control circuit 106 determines that the rotation is not performed, the control circuit 106 rotates and drives the motor with the correction driving pulse P2, and then changes the main driving pulse P1 to the main driving pulse P1 with one rank driving energy and drives next time. To do.
Thus, in a normal operating state that is rotated by driving with the main drive pulse P1, the induced signal VRs that exceeds the reference threshold voltage Vcomp tends to be generated in the first duty interval, and the duty ratio in the first duty interval is By setting a large value, it is possible to accurately detect the induced signal VRs without braking the free vibration of the stepping motor 102.

  On the other hand, as shown in FIG. 7, when the rotation detection means 108 detects the induced signal VRs exceeding the reference threshold voltage Vcomp at the mask time T1, the control circuit 106 has no margin in the drive energy of the main drive pulse P1. Since this indicates that there is a high possibility of non-rotation at the time of the next rotation drive by the main drive pulse P1, the drive is performed so that the duty ratio in the second duty interval within the rotation detection time T2 is small. The pulse circuit 107 is controlled to increase braking. When the induced signal VRs exceeding the reference threshold voltage Vcomp is detected in the mask period T1, the rotation detection unit 108 detects the rotation by performing a switching operation with a duty ratio smaller than the previous time in the second duty interval. I do. Thereby, erroneous rotation detection can be prevented.

As described above, according to the stepping motor control circuit according to the embodiment of the present invention, at the rotation detection time T2 after the stepping motor 102 is rotationally driven by the main driving pulse P1, the high impedance element and the stepping motor 102 are driven. Rotation detecting means 108 detects the induced signal VRs generated by the stepping motor 102 by alternately switching the first closed circuit including the drive coil 209 and the second closed circuit including the low impedance element and the drive coil 209 at a predetermined time ratio. A stepping motor control circuit 101 for determining whether the stepping motor 102 has rotated based on whether the induced signal VRs exceeds a predetermined reference threshold voltage Vcomp and controlling the rotation of the stepping motor 102; When the rotation is detected, the control circuit 106 T2 is divided into a first duty interval and a second duty interval after the first duty interval, and a duty ratio, which is a time ratio between the first closed circuit and the second closed circuit, is set higher than that of the first duty interval. The rotation detecting means 108 is controlled so as to be small in the two-duty section.
Therefore, with a simple configuration without using complex control, the braking effect during the rotation operation is lowered in the first half of the rotation detection time T2 to make it easier to output the induced signal VRs, and the braking effect during the non-rotation operation is facilitated in the second half. By making it difficult to output the induced signal VRs, it is possible to improve the stability of rotation detection.

Further, the rotation detection time is divided into a first duty interval and a second duty interval, and the duty ratio of the first duty interval is set to 1/2, for example, and the duty ratio of the second duty interval is set to 1/8 or less, for example. As a result, the braking effect when the non-rotation behavior occurs is increased, and both the effect of stopping the time hand and the like at a predetermined position and the lowering of the induction signal VRs at the time of non-rotation to prevent erroneous detection. Can be obtained.
Further, when the induced signal VRs exceeding the reference threshold voltage Vcomp is detected at the mask time T1, it indicates that the drive margin has been lost, and the possibility of non-rotation at the next drive is high. By making the duty ratio in the second duty section within the rotation detection time T2 smaller than before, it is possible to increase the braking effect and prevent erroneous rotation detection.

  Further, according to the analog electronic timepiece according to the present embodiment, it is easy to output the induced signal VRs by reducing the braking effect in the first duty section during the rotation operation with a simple configuration without using complicated control. On the other hand, by increasing the braking effect in the second duty interval during the non-rotating operation and making it difficult to output the induced signal VRs, it is possible to improve the stability of rotation detection and perform an accurate hand movement operation. It becomes possible.

Next, another embodiment of the present invention will be described. Another embodiment of the present invention is characterized in that malfunction can be prevented by accurately detecting the rotation of the stepping motor 102 even when a DC magnetic field exists outside.
FIG. 8 is a signal waveform diagram for explaining the operation of the analog electronic timepiece and the stepping motor control circuit according to another embodiment of the present invention. The same parts as those in FIGS. ing.

The block diagram of the other embodiment of the present invention, the stepping motor, the control operation in the first duty section and the second duty section are the same as those in FIGS. Hereinafter, parts different from the above embodiment will be described with reference to FIGS. 1 to 5 and FIG. 8.
First, it is assumed that a DC magnetic field exists outside the analog electronic timepiece in a direction that assists the rotation of the stepping motor 102 in the state of FIG.

  In the state of FIG. 2, under the control of the control circuit 106, a drive pulse P1 of one polarity is supplied from the drive pulse circuit 107 between the terminals OUT1 and OUT2 of the coil 209 (for example, the first terminal OUT1 side is positive, When the current i flows in the direction of the arrow in FIG. 2, a magnetic flux is generated in the stator 201 in the direction of the broken arrow. As a result, the rotor 202 rotates 180 degrees in the direction of the solid arrow in FIG.

  The rotation detecting means 108 detects the maximum value Vmaxout1 of the induced signal VRs generated at this time. When the stepping motor 102 is rotating normally, the rotation of the stepping motor 102 is accelerated by the influence of the external DC magnetic field. Therefore, the rotation detecting means 108 detects the maximum value Vmaxout1 of the induced signal VRs exceeding the reference threshold voltage Vcomp at an earlier time within the detection time T2 (FIG. 8 (a)).

  Next, a drive pulse P1 having a reverse polarity is supplied from the drive pulse selection circuit 104 to the terminals OUT1 and OUT2 of the coil 209 (the first terminal OUT1 side has a negative polarity and a second polarity so as to have a reverse polarity to the drive). When the terminal OUT2 side is the positive electrode) and a current is passed in the opposite arrow direction in FIG. 2, a magnetic flux is generated in the stator 201 in the opposite arrow direction. As a result, the rotor 202 rotates 180 degrees in the same direction as described above.

  The rotation detecting means 108 detects the maximum value Vmaxout2 of the induced signal VRs generated at this time. When the stepping motor 102 is rotating normally, the rotation of the stepping motor 102 is slowed by the influence of the external DC magnetic field due to the relationship between the magnetic pole of the rotor 102 and the polarity of the external DC magnetic field. Therefore, in this case, the rotation detection means 108 detects the maximum value Vmaxout2 of the induced signal VRs exceeding the reference threshold voltage Vcomp later than the maximum value Vmaxout1 (FIG. 8B).

  When the difference between the detection time Out1 of the maximum value Vmaxout1 of the induced signal VRs and the detection time Out2 of the maximum value Vmaxout2 (for example, the absolute value | Out1-Out2 |) is larger than a predetermined time, the control circuit 106 has a predetermined value or more outside. It is determined that a DC magnetic field exists, and the duty ratio is controlled to be reduced by a predetermined amount in the second duty interval, so that the braking in the second duty interval is increased.

In the next cycle, the control circuit 106 next detects the difference between the detection time Out2 of the maximum value Vmaxout2 of the induced signal VRs and the detection time Out1 of the maximum value Vmaxout1 when driven last time when driven with the reverse polarity (here, Out1). If (for example, absolute value | Out2-Out1 |) is larger than a predetermined time, it is determined that a DC magnetic field of a predetermined value or more exists outside, and the duty ratio is controlled to be decreased by a predetermined amount in the second duty interval. The braking in the second duty section is increased.
The control circuit 106 repeats the duty ratio control operation every time the stepping motor 102 is alternately driven by the drive pulses P1 having different polarities.

  In the case of the stepping motor 102, in a state where an external magnetic field exists, if the braking effect after driving is small, the rotor 202 exceeds the normal stationary position and is rotated by one turn (ie, 1 round) in a form pushed by the external magnetic field. (2 seconds instead of seconds) may occur, but since braking to the stepping motor 102 increases in the second duty section, the rotor 202 rotates once in one drive. Can be prevented.

Thereafter, by supplying signals with different polarities (alternating signals) to the coil 209 in this way, the above operation is repeated, and the rotor 202 can be continuously rotated 180 degrees in the direction of the arrow. .
As described above, the control circuit 106 rotationally drives the stepping motor 102 alternately by the drive pulses P1 having different polarities, and induces signals VRs generated when the stepping motors 102 are driven by the drive pulses P1 having different polarities. When (Vmaxout1 and Vmaxout2) are separated by a predetermined time or more, the duty ratio is decreased by a predetermined amount in the second duty interval. As a result, even when an external DC magnetic field having a predetermined intensity or more is present, the rotation of the stepping motor 102 can be accurately detected and driven to rotate normally.

In addition to the time hand, the present invention can be applied to a stepping motor for driving a calendar or the like.
Further, although an example of an analog electronic timepiece has been described as an application example of a stepping motor, it can be applied to an electronic device using a motor.

The stepping motor control circuit according to the present invention is applicable to various electronic devices that use the stepping motor.
The electronic timepiece according to the present invention can be applied to various analog electronic timepieces, including analog electronic timepieces with various calendar functions such as an analog electronic wristwatch with a calendar function and an analog electronic table clock with a calendar function.

101 ... Stepping motor control circuit 102 ... Stepping motor 103 ... Power supply 104 ... Oscillation circuit 105 ... Division circuit 106 ... Control circuit 107 ... Drive pulse circuit 108 ... Rotation Detection means 201... Stator 202... Rotor 203... Rotor housing through-holes 204 and 205... Inner notch 206 and 207. 211... Saturable portion Q1 to Q6... Transistors 301 and 302... Detection resistors

Claims (6)

In a rotation detection time after the stepping motor is rotationally driven by the main drive pulse, a first closed circuit including a high impedance element and a driving coil of the stepping motor and a second closed circuit including a low impedance element and the driving coil are predetermined. An induced signal generated by the stepping motor is detected by alternately switching at a time ratio, and it is determined whether the stepping motor has rotated based on whether the induced signal exceeds a predetermined reference threshold voltage. In the stepping motor control circuit comprising control means for controlling the rotation of the stepping motor
The rotation detection time is divided into a first section and a second section after the first section,
The stepping motor control circuit characterized in that the control means varies a duty ratio, which is a configuration time ratio of the first closed circuit and the second closed circuit, between the first section and the second section.   2. The stepping motor control circuit according to claim 1, wherein the control means makes the duty ratio smaller in the second section than in the first section.   3. The stepping motor control circuit according to claim 1, wherein a mask time that is not used for determining whether or not there is rotation is provided before the rotation detection time.   4. The stepping motor control according to claim 3, wherein the control means reduces the duty ratio by a predetermined amount in the second section when detecting an induced signal exceeding the reference threshold voltage within the mask time. circuit.   The control means rotates the stepping motor alternately by drive signals having different polarities, and the induced signals generated when driven by the drive signals having different polarities are separated by a predetermined time or more. 5. The stepping motor control circuit according to claim 1, wherein the duty ratio is decreased by a predetermined amount in the second section. In an analog electronic timepiece having a stepping motor that rotationally drives a time hand and a stepping motor control circuit that controls the stepping motor,
6. An analog electronic timepiece using the stepping motor control circuit according to claim 1 as the stepping motor control circuit.

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