JP2011050164A - Stepping motor control circuit and analog electronic timepiece - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stepping motor control circuit which can exactly drive a stepping motor without being influenced by an external magnetic field. <P>SOLUTION: In the stepping motor control circuit having a control means which drives the stepping motor 105 by using a drive pulse selected from a plurality of drive pulses, the control means comprises a DC magnetic field detection circuit 111 which detects a magnetic field before the drive of the stepping motor 105 every time when driven by the drive pulse, and when the DC magnetic field detection circuit 111 detects the magnetic field exceeding a first reference threshold voltage Vcomp_J1, the control means drives the stepping motor 105 by using a fixed drive pulse Pw larger in energy than a main drive pulse P1 for normal drive. <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.

  2. Description of the Related Art Conventionally, a stator having a rotor housing hole and a positioning portion for determining a stop position of the rotor, a rotor disposed in the rotor housing hole, and a drive coil, two terminals OUT1 and OUT2 of the drive coil are provided. A stepping motor that supplies alternating drive signals having different polarities to each other to rotate the rotor by generating magnetic flux in the stator and stops the rotor at a position corresponding to the positioning portion is an analog electronic device. Used in watches and the like.

  As a control method of the stepping motor, when the stepping motor is driven by a main drive pulse, it detects whether or not it has rotated by detecting a detection signal based on a detection signal that is an induced voltage generated in the stepping motor, Depending on whether it has rotated or not, it is changed to a main drive pulse with a different pulse width (ranking up to change to a main driving pulse with large energy or rank down to change to a main driving pulse with low energy), or driving, or A correction driving method is used in which the rotation is forcibly rotated by a correction driving pulse having a pulse width larger than that of the main driving pulse, and the driving pulse is changed to a driving pulse corresponding to a load (see, for example, Patent Document 1).

On the other hand, in the configuration of the DC magnetic field detection in Patent Document 2, the change in the induced voltage due to the influence of the external magnetic field is stored a plurality of times by the detection resistor that detects the induced voltage due to the rotor free vibration after the drive pulse is cut off, A comparison judgment is made a plurality of times, and if they are different, the result of judging that the magnetic field is present is output.
In the conventional driving system, when the driving pulse ranks down in a state where the clock is exposed to a DC magnetic field, a high-level induced signal VRs is generated that is equivalent to the rotation even when the driving pulse does not rotate. Regardless, there is a possibility of erroneously determining that the rotation has occurred.

  In addition, since the time and voltage value at which the induced voltages of both terminals OUT1 and OUT2 are generated greatly change due to the DC magnetic field, normal rotation cannot be detected, and there is a possibility that correction drive pulses are continuously output. In addition, if it is erroneously determined that the motor has rotated despite non-rotation, the correction driving pulse is not driven, so that the stepping motor is not rotated, resulting in a malfunction of the actual measurement delay in the timepiece. is there.

Japanese Patent Publication No. 61-15385 Japanese Patent Publication No. 415917

The present invention has been made in view of the above problems, and an object thereof is to provide a stepping motor control circuit capable of accurately driving a stepping motor without being affected by an external magnetic field.
Another object of the present invention is to provide an analog electronic timepiece capable of accurately driving a stepping motor without being affected by an external magnetic field and performing an accurate hand movement operation.

  According to a first aspect of the present invention, in a stepping motor control circuit comprising a control means for driving a stepping motor by a drive pulse selected from a plurality of drive pulses, the control means is configured to drive the stepping motor before driving. Includes a magnetic field detecting means for detecting a magnetic field, and when the magnetic field detecting means detects a magnetic field exceeding the first level, the stepping motor is driven by a fixed driving pulse having a larger energy than the main driving pulse for the normal driving. A stepping motor control circuit is provided.

  According to a second aspect of the present invention, in the analog electronic timepiece having a stepping motor that rotationally drives a time hand and a stepping motor control circuit that controls the stepping motor, the stepping motor control circuit includes the above description. An analog electronic timepiece using the stepping motor control circuit is provided.

The stepping motor control circuit according to the present invention can provide a stepping motor control circuit that can accurately drive the stepping motor without being affected by an external magnetic field.
Further, according to the analog electronic timepiece according to the present invention, the stepping motor can be accurately driven without being influenced by the external magnetic field, and an accurate hand movement operation can be performed.

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 stepping motor control circuit according to the embodiment of the present invention. It is a timing diagram of the stepping motor control circuit which concerns on embodiment of this invention. It is a flowchart of the stepping motor control circuit which concerns on embodiment of this invention.

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, an analog electronic timepiece includes an oscillation circuit 101 that generates a signal of a predetermined frequency, a frequency dividing circuit 102 that divides the signal generated by the oscillation circuit 101 and generates a clock signal that serves as a time reference, and an electronic timepiece. Based on the control signal from the control circuit 103 and the control circuit 103 for performing control such as control of each electronic circuit element to be configured and drive pulse change control, a drive pulse is selected from a plurality of drive pulses for motor rotation driving. A driving pulse selection circuit 104 to output, a stepping motor 105 that is rotationally driven by a driving pulse from the driving pulse selection circuit 104, a time hand that is rotationally driven by the stepping motor 105 and displays the time (in the example of FIG. 1, hour hand 107, Rotation status of the analog display unit 106 having the minute hand 108 and the second hand 109) and the stepping motor 105 A rotation detection circuit 110 that detects the induced signal VRs_K and outputs a rotation detection signal that indicates whether the induced signal VRs_K exceeds a predetermined reference threshold voltage Vcomp_K. A DC magnetic field detection circuit 111 that detects a DC magnetic field is provided.

When the stepping motor 105 rotates, the rotation detection circuit 110 detects the induced signal VRs_K exceeding the reference threshold voltage Vcomp_K, and when the motor 105 does not rotate, the rotation detection circuit 110 exceeds the reference threshold value Vcomp_K. The reference threshold value Vcomp_K is set so as not to detect the induction signal VRs_K.
The direct-current magnetic field detection circuit 111 detects the state of the direct-current magnetic field outside the analog electronic timepiece by using predetermined reference threshold voltages Vcomp_J1 and Vcomp_J2. In the present embodiment, a magnetic field detection signal having a plurality of reference threshold voltages as the reference threshold voltage and indicating that a strong magnetic field exists in the case of a magnetic field exceeding the first reference threshold voltage Vcomp_J1, When the second reference threshold voltage Vcomp_J2 is smaller than the first reference threshold voltage Vcomp_J1, the magnetic field detection signal indicating that there is no magnetic field, and the second reference threshold voltage less than the first reference threshold voltage Vcomp_J1. When Vcomp_J2 is exceeded, a magnetic field detection signal indicating that a weak magnetic field exists is output.

The control circuit 103 determines whether or not the stepping motor 105 has rotated based on the rotation detection signal from the rotation detection circuit 110 after driving by each main drive pulse P1, and according to the load situation, The drive pulse selection circuit 104 is controlled such that the main drive pulse is changed to one of the plurality of main drive pulses P1, or the rotation drive is forcibly driven by the correction drive pulse P2 having a drive energy larger than each main drive pulse. .
Although details will be described later, the control circuit 103 selects a drive pulse so that the stepping motor 105 is driven to rotate by changing to an appropriate drive pulse according to the state of the external DC magnetic field detected by the DC magnetic field detection circuit 111. The circuit 104 is controlled.

  The oscillation circuit 101 and the frequency dividing circuit 102 constitute an example of a signal generation unit, and the analog display unit 106 constitutes an example of a time display unit. The rotation detection circuit 110 constitutes an example of rotation detection means, and the DC magnetic field detection circuit 111 constitutes an example of magnetic field detection means. The control circuit 103, the drive pulse selection circuit 104, the rotation detection circuit 110, and the DC magnetic field detection circuit 111 constitute an example of control means.

FIG. 2 is a configuration diagram of the stepping motor 105 used in the embodiment of the present invention, and shows an example of a time stepping motor generally used in an analog electronic timepiece.
In FIG. 2, a stepping motor 105 includes 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 winding around the magnetic core 208. A rotated drive coil 209 is provided. When the stepping motor 105 is used for 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 drive 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 in which the drive coil 209 is not excited, the rotor 202 is positioned corresponding to the positioning portion as shown in FIG. 2, in other words, the magnetic pole axis A of the rotor 202 is a line connecting the notches 204 and 205. It is stably stopped at a position orthogonal to the minute (a position that forms an angle θ0 with the direction X of the magnetic flux flowing through the stator 201).

  Now, a rectangular-wave drive pulse of one polarity is supplied from the drive pulse selection circuit 104 between the terminals OUT1 and OUT2 of the drive coil 209 (for example, the first terminal OUT1 side is positive and the second terminal OUT2 side is negative). 2, when a current i flows in the direction of the arrow in FIG. 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. Rotates and stops stably at the angle θ1 position.

  Next, the drive pulse selection circuit 104 supplies a drive pulse with a reverse polarity rectangular wave to the terminals OUT1 and OUT2 of the drive coil 209 (the first terminal OUT1 side is set to a negative polarity so as to have a reverse polarity to the drive). When the second terminal OUT2 side is the positive electrode) and a current is passed in the direction of 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 pole generated in the stator 201 and the magnetic pole of the rotor 202, and at the angle θ0 position. Stop stably.

  Thereafter, by supplying signals with different polarities (alternating signals) to the drive coil 209 in this way, the above operation is repeated, and the rotor 202 is continuously rotated 180 degrees in the direction of the solid arrow. It is configured to be able to. In the present embodiment, as will be described later, the drive energy is larger than the main drive pulse P1 and the main drive pulse P1, which are used for normal driving where the load can be operated normally, and the load is used as the drive pulse. A correction driving pulse P2 used for driving when the motor 105 cannot be rotated greatly, and a fixed driving pulse Pw having a driving energy larger than all the main driving pulses P1 in order to reliably rotate the stepping motor 105 when a DC magnetic field exists. Used. Each main drive pulse P1 is a drive pulse having different energy. The fixed drive pulse Pw may be used as either the main drive pulse P1 or the correction drive pulse P2.

FIG. 3 is a circuit diagram showing a part of the drive pulse selection circuit 104, the rotation detection circuit 110, and the DC magnetic field detection circuit 111 in detail.
In FIG. 3, N channel MOS transistors Q 1 and Q 2, P channel MOS transistors Q 3 and Q 4, and switch control circuit 303 are components of drive pulse selection circuit 104. A drive coil 209 of the stepping motor 105 is connected between the drain connection point of the transistors Q1 and Q3 and the drain connection point of the transistors Q2 and Q4.

  P-channel MOS transistors Q3 to Q6, a detection resistor 301 as an example of a detection element connected in series to the transistor Q5, a detection resistor 302 as an example of a detection element connected in series to the transistor Q6, a switch control circuit 303, and a comparator Reference numeral 304 denotes a component of the rotation detection circuit 110. The detection resistors 301 and 302 are detection elements that are used for both rotation detection and magnetic detection.

  The gates of the transistors Q1 to Q6 are connected to the switch control circuit 103. A connection point OUT2 between the detection resistor 301 and the drive coil 209 and a connection point OUT1 between the detection resistor 302 and the drive coil 209 are connected to an input portion of the comparator 304. A predetermined reference threshold voltage Vcomp_K is input to the input unit of the comparator 304 when rotation of the stepping motor 105 is detected, and predetermined first reference threshold voltage Vcomp_J1 and second reference threshold voltage Vcomp_J2 are detected when an external DC magnetic field is detected. (Vcomp_J1> Vcomp_J2) is input. An inverter may be used instead of the comparator 304.

  The control circuit 103 has a strong magnetic field (a magnetic field exceeding the first level) when the signal detected by the DC magnetic field detection circuit 111 exceeds the reference threshold voltage Vcomp_J1, and the signal detected by the DC magnetic field detection circuit 111 is the reference. A weak magnetic field (a magnetic field exceeding the second level) is present when the threshold voltage Vcomp_J1 is less than or equal to Vcomp_J2, and a signal detected by the DC magnetic field detection circuit 111 is less than the reference threshold voltage Vcomp_J2 and there is no magnetic field. As shown, Vcomp is set for each reference threshold voltage.

  In the present embodiment, a plurality of reference threshold voltages Vcomp_J1 and Vcomp_J2 are used when an external DC magnetic field is detected. However, one type of reference threshold voltage may be used. Further, the reference threshold voltage Vcomp_K may be set to the same value as one of the reference threshold voltages Vcomp_J1 and Vcomp_J2. The reference threshold voltages Vcomp_J1 and comp_J2 for magnetic field detection may be the same as or different from the reference threshold voltage Vcomp_K for rotation detection, but are preferably lower than the reference threshold voltage Vcomp_K for rotation detection.

Transistors Q 1, Q 2, Q 5, Q 6, detection resistors 301, 302 and control circuit 303 are components of the DC magnetic field detection circuit 111.
The control circuit 103 turns on the transistors Q1 and Q6 in the magnetic field detection period before driving the stepping motor 105 with each main drive pulse P1, detects the voltage generated in the detection resistor 302 (in other words, the terminal OUT1), The transistors Q2 and Q5 are turned on and the voltage generated at the detection resistor 301 (in other words, the terminal OUT2) is alternately detected a plurality of times to determine whether or not an external DC magnetic field exists. At this time, during the period in which the transistors Q1 and Q2 and the transistors Q2 and Q5 are alternately turned on, the stepping motor 105 is set to a small energy that does not rotate.

  Although details will be described later, in the case of no magnetic field, the voltages generated at the terminals OUT1 and OUT2 show substantially the same value, but when an external DC magnetic field is present, the detected induced signal VRs is driven according to the direction of the DC magnetic field. This is the sum or difference of the induced voltage caused by (transistors Q1 and Q6 or Q2 and Q5 turned on) and the induced voltage caused by the external DC magnetic field. When a magnetic field is present, a high induced signal VRS_J that is (coil induced voltage + induced voltage due to an external DC magnetic field) is generated at one of the terminals OUT1 or OUT2, and a low induced signal VRs_K is generated at the other terminal OUT2 or OUT1. Occurs. The comparator 304 compares the reference threshold voltages Vcomp_J1 and J2 with each other to determine whether or not a DC magnetic field is present. Depending on whether or not the magnetic field is present, a predetermined fixed drive pulse Pw and a plurality of main drive pulses are determined. The pulse is controlled so as to be driven by any of the main drive pulses in P1.

  When the stepping motor 105 is rotationally driven in the rotational drive period following the magnetic field detection period, the switch control circuit 303 responds to the rotational drive control pulse Vi corresponding to the drive pulse supplied from the control circuit 103, and the transistor Q2 , Q3 are turned on at the same time, or transistors Q1 and Q4 are turned on at the same time to supply current to the driving coil 209 in the forward or reverse direction, thereby driving the stepping motor 105 to rotate.

  In the rotation detection period following the rotation drive period, when detecting the induced signal VRs_K generated by the free vibration of the stepping motor 105 after the rotation drive, the switch control circuit 303 responds to the rotation detection control pulse Vi from the control circuit 103. Thus, by turning on / off the transistor Q4 in a predetermined cycle with the transistors Q3, Q6 turned on, or by turning on / off the transistor Q3 in a predetermined cycle with the transistors Q4, Q5 turned on, The induced signal VRs is detected by the comparator 304.

When the comparator 304 detects the induced signal VRs_K exceeding the reference threshold voltage Vcomp_K among the induced signals VRs_K induced in the stepping motor 105 (in other words, the driving coil 209), the comparator 304 detects the induced signal VRs_K exceeding the reference threshold voltage Vcomp_K. A detection signal indicating that this has occurred is output. When the control circuit 103 determines that the stepping motor 105 has rotated based on the detection signal, the control circuit 103 performs pulse control such as rank down control of the main drive pulse P1 to perform the next drive control.
The rotation drive control of the stepping motor 105 is performed while repeating in the order of the magnetic field detection period, the rotation drive period, and the rotation detection period.

FIG. 4 is a timing chart for explaining the operation of the present embodiment. FIG. 4A shows a case where an external DC magnetic field does not exist, and FIG. 4B shows a case where a strong external DC magnetic field (DC strong magnetic field) exists. FIG. 4C is a timing diagram when a weak external DC magnetic field (DC weak magnetic field) is present.
As shown in FIG. 4A, when no external DC magnetic field exists, the DC magnetic field detection circuit 111 detects the induced signal VRs_J exceeding the reference threshold voltages Vcomp_J1 and Vcomp_J2 from both the terminals OUT1 and OUT2 during the magnetic field detection period. Can not.

In this case, in the rotational drive period following the magnetic field detection period, the control circuit 103 drives the drive pulse so as to rotationally drive the stepping motor 105 by the previously driven main drive pulse P1n among the plurality of main drive pulses P1 used during the normal drive operation. The selection circuit 104 is controlled. In response to the control of the control circuit 103, the drive pulse selection circuit 104 outputs the drive pulse P1n from the terminal OUT1 to drive the stepping motor 105.
When the rotation detection circuit 110 detects the induced signal VRs_K exceeding the reference threshold voltage Vcomp_K in the rotation detection period following the rotation drive period, the control circuit 103 determines that the stepping motor 105 has rotated and maintains the main drive pulse P1. Pulse control such as rank down is performed.

In the next cycle, the magnetic field is detected in the magnetic field detection period, and in the subsequent rotation drive period, the main driving pulse P1n having the opposite polarity is output from the terminal OUT2 to drive the stepping motor, and in the subsequent rotation detection period, the stepping motor is detected. It is determined whether or not 105 has rotated, and a pulse control operation is performed.
Thereafter, when there is no DC magnetic field, the above operation is repeated, and the stepping motor 105 is driven by main drive pulses P1 having different polarities supplied from the terminals OUT1 and OUT2. When a situation occurs in which the stepping motor 105 does not rotate due to load fluctuation or the like, the control circuit 103 is forcibly driven to rotate by the correction driving pulse P2 having energy larger than each main driving pulse P1.

When a DC strong magnetic field exists as shown in FIG. 4B, the DC magnetic field detection circuit 111 detects the induced signal VRs_J exceeding the reference threshold voltage Vcomp_J1 from either the terminal OUT1 or OUT2 during the magnetic field detection period.
In this case, in the rotational drive period following the magnetic field detection period, the control circuit 103 uses a fixed drive pulse Pw having energy larger than all the main drive pulses P1 and smaller energy than the correction drive pulse P2 instead of the main drive pulse P1. The drive pulse selection circuit 104 is controlled to rotate the stepping motor 105. In response to the control of the control circuit 103, the drive pulse selection circuit 104 outputs a fixed drive pulse Pw from the terminal OUT1 to drive the stepping motor 105.

Since the fixed drive pulse Pw is set to a drive pulse having a predetermined energy that can reliably rotate the stepping motor 105 even in a strong magnetic field, the presence of a DC strong magnetic field can substantially increase the load. The stepping motor 105 can be reliably rotated. Further, when the rotation is driven by the fixed drive pulse Pw, the stepping motor 105 can be reliably driven to rotate, so that the rotation is not detected.
Thereafter, when a DC strong magnetic field exists, the above operation is repeated, and the stepping motor 105 is driven by fixed driving pulses Pw having different polarities supplied from the terminals OUT1 and OUT2.

As shown in FIG. 4C, when a DC weak magnetic field is present, the DC magnetic field detection circuit 111 sets the reference threshold voltage Vcomp_J2 below the reference threshold voltage Vcomp_J1 from either one of the terminals OUT1 and OUT2 during the magnetic field detection period. The induced signal VRs_J that exceeds is detected.
In this case, the control circuit 103 rotationally drives the stepping motor 105 with the main drive pulse P1max having the largest energy among all the main drive pulses P1 instead of the main drive pulse P1 in the rotation drive period following the magnetic field detection period. The drive pulse selection circuit 104 is controlled. In response to the control of the control circuit 103, the drive pulse selection circuit 104 drives the stepping motor 105 by outputting the main drive pulse P1max having the maximum energy from the terminal OUT1.

When the rotation detection circuit 110 detects the induced signal VRs_K exceeding the reference threshold voltage Vcomp_K in the rotation detection period following the rotation drive period, the control circuit 103 determines that the stepping motor 105 has rotated and maintains the main drive pulse P1. Pulse control such as rank down is performed.
In the next cycle, the magnetic field is detected in the magnetic field detection period, and in the subsequent rotation drive period, the main driving pulse P1n having the opposite polarity is output from the terminal OUT2 to drive the stepping motor, and in the subsequent rotation detection period, the stepping motor is detected. It is determined whether or not 105 has rotated, and a pulse control operation is performed.

Thereafter, when a DC weak magnetic field is present, the above operation is repeated, and the stepping motor 105 is driven by main drive pulses P1 having different polarities supplied from terminals OUT1 and OUT2. When a situation occurs in which the stepping motor 105 does not rotate due to load fluctuation or the like, the control circuit 103 is forcibly driven to rotate by the correction driving pulse P2 having energy larger than the main driving pulse P1max.
FIG. 5 is a flowchart of the stepping motor control circuit according to the embodiment of the present invention.

Hereinafter, the operation of the present embodiment will be described in detail with reference to FIGS.
During the magnetic field detection period, the control circuit 103 alternately turns on / off the set of the transistors Q1 and Q6 and the set of the transistors Q2 and Q5 at a predetermined period, and the DC magnetic field detection circuit 111 at that time has terminals OUT1, OUT2 The induced signal VRs_J generated at the time is detected.
The control circuit 103 determines that the induced signal VRs_J does not exceed both the reference threshold voltage Vcomp_J1 and the reference threshold voltage Vcomp_J2 during the magnetic detection period (steps S501 and S502), that is, there is no external DC magnetic field. If determined, the main drive pulse P1n is set to the lowest energy main drive pulse P10 (steps S503 and S504), and the drive pulse selection circuit 104 is controlled so as to drive the stepping motor 105 by the main drive pulse P10. (Step S505). The drive pulse selection circuit 104 rotationally drives the stepping motor 105 with the main drive pulse P10.

  The control circuit 103 determines that the rotation detection circuit 110 has not detected the induced signal VRs_K exceeding the reference threshold voltage Vcomp_K in the rotation detection period following the rotation drive period (step S506), that is, the stepping motor 105 If it is determined that the motor has not been rotated, the drive pulse selection circuit 104 is controlled so as to be driven by the correction drive pulse P2 (step S507). The drive pulse selection circuit 104 rotationally drives the stepping motor 105 with the correction drive pulse P2, and the pulse control is performed so that the stepping motor 105 is forcibly rotated.

Next, when the rank n of the main drive pulse P1 is not the maximum value m (the main drive pulse P1max with the maximum energy) (step S508), the control circuit 103 increases the rank of the main drive pulse P1 by one rank. After the pulse control, the process returns to the processing step S504 (step S509).
When the rank n of the main drive pulse P1 is determined to be the maximum value m in process step S508, the control circuit 103 performs pulse control so that the rank of the main drive pulse P1 is not changed, and then returns to process step S504 ( Step S514).

If the rotation detection circuit 110 determines in step S506 that the rotation detection circuit 110 has detected the induced signal VRs_K that exceeds the reference threshold voltage Vcomp_K, that is, if it is determined that the stepping motor 105 has rotated, the control circuit 103 determines the main drive pulse P1. When the rank is the lowest energy (n = 0) (step S512), pulse control is performed so as not to change the rank of the main drive pulse P1, and the process returns to step S504 (step S514).
When determining that the rank of the main drive pulse P1 is not the lowest energy (n = 0) in process step S512, the control circuit 103 performs pulse control so that the rank of the main drive pulse P1 is lowered by one rank, and then the process step The process returns to S504 (step S513).

  When it is determined that the induced signal VRs_J is equal to or lower than the reference threshold voltage Vcomp_J1 but exceeds the reference threshold voltage Vcomp_J2 in the magnetic detection period (steps S501 and S502), that is, it is determined that a DC weak magnetic field exists. In this case, the main drive pulse P1 is set to the main drive pulse P1max with the maximum energy (step S511), the process proceeds to processing step S504, and the main drive pulse P1max is driven. This makes it possible to rotate the stepping motor 105 even when a DC weak magnetic field is present.

  When the control circuit 103 determines that the induced signal VRs_J exceeds the reference threshold voltage Vcomp_J1 in the magnetic detection period (step S501), that is, when it is determined that a DC strong magnetic field exists, the control circuit 103 determines the main drive pulse P1 as a fixed drive pulse. Driving is set to Pw (step S510), and the process returns to step S501. As a result, the stepping motor 105 can be rotated even when the load substantially increases due to the influence of the DC strong magnetic field.

  As described above, according to the present embodiment, in the stepping motor control circuit including the control means for driving the stepping motor 105 by the drive pulse selected from the plurality of drive pulses, the control means is driven by the drive pulse. A DC magnetic field detection circuit 111 for detecting a magnetic field before driving the stepping motor 105 each time the DC magnetic field detection circuit 111 detects a magnetic field exceeding the first reference threshold voltage Vcomp_J1. The stepping motor 105 is driven by a fixed drive pulse Pw having energy larger than that of the drive pulse P1.

Therefore, it is possible to provide a stepping motor control circuit that can accurately drive the stepping motor without being affected by an external magnetic field. In addition, it is possible to provide an analog electronic timepiece that can accurately drive a stepping motor without being affected by an external magnetic field and perform an accurate hand movement operation.
Further, stable rotation control can be performed by driving with a fixed driving pulse Pw having a predetermined energy or driving with a main driving pulse P1max having the maximum energy according to the level of the DC magnetic field.

Further, it is possible to configure without using a complicated detection pulse generation circuit or a special magnetic field detection element.
In addition, rotation detection operation can be prohibited in a magnetic field, and erroneous determination can be prevented.
Further, in the case of an electronic timepiece, it is possible to provide a reliable hand movement by switching to a fixed drive pulse that is strong against a magnetic field.

In the above-described embodiment, the pulse width is changed in order to change the energy of each main drive pulse P1, but the drive energy can also be changed by changing the pulse voltage.
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 electronic timepiece having a single motor has been described as an application example of a stepping motor, it can be applied to an electronic timepiece having a plurality of motors such as a chronograph timepiece and various electronic devices using the 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 is applicable to various analog electronic timepieces such as analog electronic timepieces with calendar functions, analog electronic timepieces with various calendar functions such as analog electronic table clocks with calendar functions, and chronograph timepieces.

DESCRIPTION OF SYMBOLS 101 ... Oscillator 102 ... Frequency divider 103 ... Control circuit 104 ... Drive pulse selection circuit 105 ... Stepping motor 106 ... Analog display 107 ... Hour hand 108 ... Minute hand 109 ... Second hand 110 ... Rotation detection circuit 111 ... DC magnetic field detection circuit 201 ... Stator 202 ... Rotor 203 ... Rotor accommodating through holes 204, 205 ... Notches (inside notch)
206, 207 ... Notch (outer notch)
208 ... Magnetic core 209 ... Drive coils 210 and 211 ... Saturable part OUT1 ... First terminal OUT2 ... Second terminals Q1 to Q6 ... Transistors 301 and 302 ... Detection resistors 303 ... Switch control circuit 304 ... Comparator

Claims (6)

In a stepping motor control circuit comprising a control means for driving a stepping motor by a driving pulse selected from a plurality of driving pulses,
The control means includes magnetic field detection means for detecting a magnetic field before driving the stepping motor. When the magnetic field detection means detects a magnetic field exceeding a first level, energy is higher than that of the main drive pulse for normal driving. A stepping motor control circuit for driving the stepping motor by a fixed driving pulse having a large value.   The control means selects and drives a main drive pulse corresponding to a load from a plurality of main drive pulses when the magnetic field detection means detects a magnetic field of a second level or less that is smaller than the first level. The stepping motor control circuit according to claim 1, wherein:   When the magnetic field detection means detects a magnetic field that is less than the first level and exceeds a second level that is less than the first level, the control means uses the main drive pulse with the maximum energy among the plurality of main drive pulses. The stepping motor control circuit according to claim 1, wherein the motor is driven. The control means drives the stepping motor alternately by main drive pulses having different polarities during normal driving, and the magnetic field detection means has a detection element for detecting a current flowing in the driving coil of the stepping motor at the time of magnetic field detection. And
The magnetic field detection means detects whether the magnetic field exceeds the first level and a second level smaller than the first level based on a signal generated in the detection element. The stepping motor control circuit according to any one of the above.   The control means includes rotation detection means for detecting whether or not the stepping motor has rotated, and the rotation detection means detects whether or not the stepping motor has rotated based on a signal generated in the detection element. The stepping motor control circuit according to claim 4. 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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