Patent Publication Number: US-2012044787-A1

Title: Stepping motor control circuit and analogue electronic watch

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a stepping motor control circuit and an analogue electronic watch using the stepping motor control circuit. 
     2. Description of the Related Art 
     In the related art, a stepping motor including a stator having a rotor storage through hole and a positioning portion for determining a stop position of a rotor, the rotor disposed in the rotor storage through hole, and a coil, and being configured to rotate the rotor by causing the stator to generate a magnetic flux by supplying alternating signals to the coil and stop the same at a position corresponding to the positioning portion is used in an analogue electronic watch, for example. 
     A method employed as a method of controlling the stepping motor is a correction drive system configured to detect whether or not the stepping motor is rotated by detecting an induced signal generated in the stepping motor when the stepping motor is driven by a main drive pulse P 1  and, according to the result of detection of whether or not the stepping motor is rotated, change the pulse width of the main drive pulse P 1  and drive the stepping motor by the changed main drive pulse P 1  or forcedly rotate the stepping motor by a correction drive pulse P 2  having a pulse width larger than that of the main drive pulse P 1  (for example, JP-B-61-15385). 
     WO2005/119377 discloses a device for comparatively discriminating a detected time and a reference time in addition to the detection of the induced signal when detecting the rotation of the stepping motor. If the detected signal is lower than a predetermined reference threshold voltage Vcomp after having rotated the stepping motor by a main drive pulse P 11 , the correction drive pulse P 2  is supplied, and the subsequent main drive pulse P 1  is changed to a main drive pulse P 12  having a larger energy than the main drive pulse P 11  for driving the stepping motor (pulse up). If the detected time of the rotation by the main drive pulse P 12  is earlier than the reference time, the main drive pulse P 12  is changed to the main drive pulse P 11  (pulse down), so that the stepping motor is rotated by the main drive pulse P 1  according to the load generated during the driving and hence the power consumption is reduced. 
     In contrast, in the invention described in JP-A-62-194484, there is provided a device which changes its clocking cycle to move a second hand by two seconds at a time (to move the second hand by two seconds at a time twice consecutively) to notify a user of an electric charge shortage when the voltage of a secondary battery used as a power source is lowered and, when the driving of the stepping motor is stopped, memorizes drive pulse information when the operation is stopped. However, since a voltage detection circuit is employed, there is a problem of complex configuration. In addition, in an electronic watch having a secondary battery as represented by a solar energy powered watch, a stop of clocking resulted from lowering of source voltage of a movement may be performed in a state in which clocking is unstable due to variations of the movement, so that there is a risk of erroneous memorization of drive pulse information when the clocking is stopped. If the incorrect drive pulse information is memorized, normal driving cannot be restored when the clocking is once stopped due to the lowering of the source voltage and then is restarted by the recovery of the power source. 
     SUMMARY OF INVENTION 
     It is an aspect of the present application to achieve detection of a source voltage without providing a voltage detection circuit and allow a drive stop while holding correct drive pulse information when the source voltage is lowered to a predetermined level or below. 
     According to the application, there is provided a stepping motor control circuit including: a power source; a rotation detection device configured to detect an induced signal generated by the rotation of a rotor of a stepping motor and detect the state of rotation of the stepping motor according to whether or not the induced signal exceeds a predetermined reference threshold voltage in a predetermined detection segment; and a drive control device configured to select any one of drive pulses having energies different from each other according to the result of detection detected by the rotation detection device and control the driving of the stepping motor with a predetermined polarity, wherein the detection segment is divided into a plurality of detection segments, and the drive control device controls to stop the driving of the stepping motor in a state in which the polarity of the drive pulse to be used for restarting the driving after the voltage of the power source is restored to a voltage exceeding the predetermined voltage is known when the power source is determined to be lowered to a predetermined voltage value or below on the basis of a pattern of the segments in which the rotation detection device detects the induced signal exceeding the predetermined reference threshold voltage when the stepping motor is driven by the drive pulse having a predetermined energy. 
     According to an analogue electronic watch in the embodiment of the application, the analogue electronic watch includes the stepping motor configured to rotate time-of-day hands and a stepping motor control circuit configured to control the stepping motor and is characterized in that the stepping motor control circuit is employed as the stepping motor control circuit. 
     The motor control circuit according to the application enables detection of a source voltage without providing a voltage detection circuit and allows a drive stop while holding correct drive pulse information when the source voltage is lowered to a predetermined level or below. 
     According to the analogue electronic watch in the application, since the source voltage can be detected without providing the voltage detection circuit and the driving can be stopped in a state of holding the correct drive pulse information when the source voltage is lowered to the predetermined voltage or below, the driving can be started by the correct drive pulse when the source voltage is restored, so that correct clocking is achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a stepping motor control circuit and an analogue electronic watch according to a first embodiment of the invention; 
         FIG. 2  is a configuration drawing of a stepping motor used in respective embodiments of the invention; 
         FIG. 3  is a timing chart for explaining actions in the respective embodiments of the invention; 
         FIG. 4  is a determination chart for explaining the actions in the respective embodiments of the invention; 
         FIG. 5  is a flowchart showing an action in the first embodiment of the invention; 
         FIG. 6  is a block diagram showing a stepping motor control circuit and an analogue electronic watch according to a second embodiment of the invention; 
         FIG. 7  is a flowchart showing an action in the second embodiment of the invention; 
         FIG. 8  is a block diagram showing a stepping motor control circuit and an analogue electronic watch according to a third embodiment of the invention; 
         FIG. 9  is a flowchart showing an action in the third embodiment of the invention; 
         FIG. 10  is a block diagram showing a stepping motor control circuit and an analogue electronic watch according to a fourth embodiment of the invention; and 
         FIG. 11  is a flowchart showing an action in the fourth embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a block diagram of an analogue electronic watch using a stepping motor control circuit according to a first embodiment of the invention, and shows an example of an analogue electronic wrist watch. 
     In  FIG. 1 , the analogue electronic watch includes an oscillation circuit  101  configured to generate signals of a predetermined frequency, a frequency divider circuit  102  configured to divide the frequency of the signals generated by the oscillation circuit  101  and generate a time signal which serves as a reference when counting the time, a control circuit  103  configured to perform control of respective electronic circuit elements which constitute the electronic watch and control of drive pulse change, a drive pulse selection circuit  104  configured to select and output a drive pulse for rotating a motor on the basis of a control signal from the control circuit  103 , a stepping motor  105  configured to be rotated by the drive pulse from the drive pulse selection circuit  104 , and an analogue display unit  106  configured to be rotated by the stepping motor  105  which includes time-of-day hands indicating the time of day (three types; namely, an hour hand  107 , a minute hand  108 , and a second hand  109  in an example shown in  FIG. 1 ). 
     The analogue electronic watch also includes a rotation detection circuit  110  configured to detect induced signals VRs representing the state of rotation of the stepping motor  105  in a predetermined detection segment, and a detection segment determination circuit  111  configured to compare a time and a segment where the rotation detection circuit  110  detects the induced signal VRs exceeding a predetermined reference threshold voltage Vcomp and determine the segment where the induced signal VRs is detected. As described later, the detection segment for detecting whether or not the stepping motor  105  is rotated is divided into three segments. 
     The analogue electronic watch includes a solar energy generation element  112  configured to receive light and generate electricity and a secondary battery  113  which is charged by the solar photovoltaic element  112  and serves as a power source for supplying a drive power to the respective electronic circuit elements  101  to  105 ,  110 , and  111  of the analogue electronic watch. 
     The control circuit  103  controls the stepping motor  105  so as to be driven alternately by main drive pulses P 1  having different polarities in a state in which the stepping motor  105  rotates normally, and hence includes a polarity memory  103   a  configured to memorize a polarity currently used for driving the stepping motor  105  as polarity information for determining the polarity for the next driving every time when the stepping motor  105  is driven. For the driving using the main drive pulse P 1  for the next time, the control circuit  103  drives the stepping motor  105  by a main drive pulse P 1  having a polarity opposite from that memorized in the polarity memory  103   a,  and memorizes the polarity of the main drive pulse P 1  used at that time in the polarity memory  103   a  as the polarity information. 
     It is also possible to memorize information on the polarity to be used in the next driving as the polarity information for determining the polarity used in the next driving. In this case, the control circuit  103  controls the stepping motor  105  to be driven by the main drive pulse P 1  having the polarity memorized in the polarity memory  103   a  in the next driving, and memorizes the polarity information to be used for the subsequent driving in the polarity memory  103   a  as the polarity information. 
     The rotation detection circuit  110  has a configuration in which the induced signal VRs is detected using the same principle as the rotation detection circuit described in JP-B-61-15385, and the reference threshold voltage Vcomp is set as follows. When the speed of the rotation is high as in the case where the stepping motor  105  rotates, the induced signal VRs exceeding the predetermined reference threshold voltage Vcomp is generated, and when the speed of rotation is low as in the case where the motor  105  does not rotate, the induced signal VRs does not exceed the reference threshold voltage Vcomp. 
     The oscillation circuit  101  and the frequency divider circuit  102  constitute a signal generating device, and the analogue display unit  106  constitutes a time-of-day display device. The rotation detection circuit  110  constitutes a rotation detecting device, and the control circuit  103 , the drive pulse selection circuit  104 , the rotation detection circuit  110  and the detection segment determination circuit  111  constitute a drive control device. The polarity memory  103   a  constitutes the polarity information memory device. 
       FIG. 2  is a configuration drawing of the stepping motor  105  which is used commonly in the respective embodiments of the invention, and shows an example of a stepping motor for a watch which is generally used in the analogue electronic watch. 
     In  FIG. 2 , the stepping motor  105  includes a stator  201  having a rotor storage through hole  203 , a rotor  202  disposed in the rotor storage through hole  203  so as to be capable of rotating therein, a magnetic core  208  joined to the stator  201 , and a coil  209  wound around the magnetic core  208 . When the stepping motor  105  is used in the analogue electronic watch, the stator  201  and the magnetic core  208  are fixed to a base panel (not shown) with screws (not shown) and are joined to each other. The coil  209  has a first terminal OUT 1  and a second terminal OUT 2 . 
     The rotor  202  is magnetized in two polarities (S-polar and N-polar). A plurality of (two in this embodiment) notched portions (outer notches)  206  and  207  are provided on outer end portions of the stator  201  formed of a magnetic material at positions opposing to each other with the intermediary of the rotor storage through hole  203 . Provided between the respective outer notches  206  and  207  and the rotor storage through hole  203  are saturable portions  210  and  211 . 
     The saturable portions  210  and  211  are configured not to be magnetically saturated by a magnetic flux of the rotor  202  and to be magnetically saturated when the coil  209  is excited so that the magnetic resistance is increased. The rotor storage through hole  203  is formed into a circular hole shape having a plurality of (two in this embodiment) semicircular notched portions (inner notches)  204  and  205  integrally formed at opposed portions of the through hole having a circular contour. 
     The notched portions  204  and  205  constitute positioning portions for positioning a stop position of the rotor  202 . In a state in which the coil  209  is not excited, the rotor  202  is stably stopped at a position corresponding to the above-described positioning portions, in other words, at a position (at an angular position θ 0 ) where the direction of an axis of magnetic pole A of the rotor  202  extends orthogonally to a segment connecting the notched portions  204  and  205  as shown in  FIG. 2 . An XY-coordinate space extending around an axis of rotation (center of rotation) of the rotor  202  as a center is divided into four quadrants (first to fourth quadrants I to IV). 
     When the drive pulse selection circuit  104  supplies a rectangular drive pulse to between the terminals OUT 1  and OUT 2  of the coil  209  (for example, the first terminal OUT 1  side is the positive pole and the second terminal OUT 2  side is the negative pole), and allows an electric current i to flow in the direction indicated by an arrow in  FIG. 2 , a magnetic flux in the direction of an arrow of a broken line is generated in the stator  201 . Accordingly, the saturable portions  210  and  211  are saturated and the magnetic resistance is increased, and then the rotor  202  rotates in the direction indicated by an arrow in  FIG. 2  by 180° by a mutual action between a magnetic pole generated in the stator  201  and a magnetic pole of the rotor  202 , and the axis of magnetic pole stops stably at an angular position θ 1 . The direction of rotation (counterclockwise rotation in  FIG. 2 ) for causing the stepping motor  105  to rotate and putting the same into a normal action (the movement of the time-of-day hands because the watch in this embodiment is an analogue electronic watch) is defined to be a normal direction and the reverse direction (clockwise direction) is defined to be a reverse direction. 
     Subsequently, when the drive pulse selection circuit  104  supplies square-wave drive pulses having an opposite polarity to the terminals OUT 1  and OUT 2  of the coil  209  (the first terminal OUT 1  side is the negative pole and the second terminal OUT 2  side is the positive pole, so that the polarity is inverted from the driving described above), and allows an electric current to flow in the direction opposite from that indicated by an arrow in  FIG. 2 , a magnetic flux is generated in the stator  201  in the opposite direction from that indicated by an arrow of a broken line. Accordingly, the saturable portions  210  and  211  are saturated first, and then the rotor  202  rotates in the same direction (normal direction) as that described above by 180° by the mutual action between the magnetic pole generated in the stator  201  and the magnetic pole of the rotor  202 , and the axis of magnetic pole stops stably at the angular position θ 0 . 
     In this manner, by supplying the signals having different polarities (alternating signals) to the coil  209 , the operation is repeatedly performed, so that the rotor  202  is rotated continuously in the direction indicated by an arrow by 180° each. In this embodiment, a plurality of main drive pulses P 10  to P 1 n having energies different from each other and a correction drive pulse P 2  having energy larger than the respective main drive pulses P 1  are used as the drive pulses as described later. 
     The control circuit  103  basically drives the stepping motor  105  to rotate by driving by the main drive pulses P 1  having polarities different from each other alternately and, when the rotation cannot be achieved by the main drive pulse P 1 , drives the stepping motor  105  to rotate by the correction drive pulse P 2  having the same polarity as the corresponding main drive pulse P 1 . However, in the respective embodiments in the invention, driving is also performed in different modes. 
       FIG. 3  is a timing chart when the stepping motor  105  is driven by the main drive pulse P 1  in the respective embodiments of the invention, and also shows patterns and pulse control actions indicating magnitudes of the load, and rotational positions and the state of rotation of the rotor  202 . 
     In  FIG. 3 , reference sign P 1  designates the main drive pulse P 1  and also a segment in which the rotor  202  is rotated by the main drive pulse P 1 . Reference signs a to e designate areas showing the rotational positions of the rotor  202  due to free vibrations after the stop of drive by the main drive pulse P 1 . 
     A predetermined time immediately after the drive by the main drive pulse P 1  is designated as a first segment T 1 , a predetermined time after the first segment T 1  is designated as a second segment T 2 , and a predetermined time after the second segment T 2  is designated as a third segment T 3 . In this manner, an entire detection segment T starting from a timing immediately after the drive by the main drive pulse P 1  is divided into a plurality of segments (in this embodiment, three segments T 1  to T 3 ). In this embodiment, a mask segment, which is a segment in which the induced signal VRs is not detected, is not provided. 
     When the XY-coordinate space where a main magnetic pole of the rotor  202  is situated by its rotation is divided into first to fourth quadrants I to IV about the rotor  202 , the first to third segments T 1  to T 3  can be expressed as follows. 
     In other words, in the state of the normal load, the first segment T 1  corresponds to a segment in which the state of rotation of the rotor  202  in the normal direction is determined and a segment in which the first state of rotation in the reverse direction is determined in the third quadrant III of the space around the rotor  202 , the second segment T 2  corresponds to a segment in which the first state of rotation of the rotor  202  in the reverse direction is determined in the third quadrant III, and the third segment T 3  corresponds to a segment in which the state of rotation after the first rotation of the rotor  202  in the reverse direction is determined in the third quadrant III. 
     Here, the normal load means a load applied at the normal driving state, and in this embodiment, the normal load is defined to be a load applied at the time of driving the time-of-day hands (hour hand  107 , minute hand  108 , and second hand  109 ). 
     In the state in which the load is increased from the normal load by a very small amount (load increase is vary small), the first segment T 1  corresponds to a segment for determining the state of rotation of the rotor  202  in the normal direction in the second quadrant II and the first state of rotation of the rotor  202  in the normal direction in the third quadrant III, the second segment T 2  corresponds to a segment for determining the first state of rotation of the rotor  202  in the normal direction and the first state of rotation in the reverse direction in the third quadrant III, and the third segment T 3  corresponds to a segment for determining the state of rotation after the first rotation of the rotor  202  in the reverse direction in the third quadrant III. 
     The reference threshold voltage Vcomp represents a reference threshold voltage for determining the voltage level of the induced signal VRs generating in the stepping motor  105 . The reference threshold voltage Vcomp is set in such a manner that the induced signal VRs exceeds the reference threshold voltage Vcomp when the rotor  202  performs a certain fast action as in the case where the stepping motor  105  rotates, and the induced signal VRs does not exceed the reference threshold voltage Vcomp when the rotor  202  does not perform the certain fast action as in the case where the stepping motor  105  does not rotate. 
     For example, in  FIG. 3 , in the stepping motor control circuit according to this embodiment, the induced signal VRs generated in an area b in the state of normal load is detected in the first segment T 1 , the induced signal VRs generated in an area c is detected in the first segment T 1  and the second segment T 2 , and the induced signal VRs generated after the area c is detected in the third segment T 3 . 
     The case where the rotation detection circuit  110  detects the induced signal VRs exceeding the reference threshold voltage Vcomp is expressed as a determination value “1”, and the case where the rotation detection circuit  110  cannot detect the induced signal VRs exceeding the reference threshold voltage Vcomp is expressed as a determination value “0”. In the example of the normal load driving shown in  FIG. 3 , a pattern (0, 1, 0) is obtained as a pattern indicating the state of rotation (the determination value in the first segment, the determination value in the second segment, and the determination value in the third segment). Therefore, the control circuit  103  determines that a driving energy is excessive (rotation with reserve), and performs pulse control to downgrade the driving energy of the main drive pulse P 1  by a rank (pulse down). 
     In the state in which the load increase is very small, the induced signal VRs generated in an area a is detected in the first segment T 1 , the induced signal generated in the area b is detected in the first segment T 1  and the second segment T 2 , and the induced signal generated in the area c is detected in the second segment T 2  and the third segment T 3 . In the example shown in  FIG. 3 , a pattern (0, 1, 1) is obtained. Therefore, the control circuit  103  determines that it is a rotation with reserve as described above and performs the pulse control so as to downgrade the driving energy of the main drive pulse P 1  by a rank. 
       FIG. 4  is a determination chart showing all the actions in the respective embodiments of the invention. In  FIG. 4 , as described above, the case where the induced signal VRs exceeding the reference threshold voltage Vcomp is detected is expressed as the determination value “1”, and the case where the induced signal VRs exceeding the reference threshold voltage Vcomp cannot be detected is expressed as the determination value “0”. The expression “1/0” means that the determination values “1” and “0” are both applicable. 
     As shown in  FIG. 4 , the rotation detection circuit  110  detects the presence or absence of the induced signal VRs exceeding the reference threshold voltage Vcomp. Then, the detection segment determination circuit  111  references the determination chart in  FIG. 4  stored in the control circuit  103  on the basis of a pattern of determination of a detection timing of the induced signal VRs. The control circuit  103  and the drive pulse selection circuit  104  control the rotation of the stepping motor  105  by performing the drive pulse control such as upgrade or downgrade for the main drive pulse P 1 , or the driving by the correction drive pulse P 2 , described later. 
     For example, in the case of a pattern (1/0, 0, 0), the control circuit  103  determines that the stepping motor  105  is not rotating (non-rotation), and controls the drive pulse selection circuit  104  so as to drive the stepping motor  105  by the correction drive pulse P 2 , and then controls the drive pulse selection circuit  104  so as to drive the stepping motor  105  next time by the main drive pulse P 1  which is upgraded by a rank. 
     In the case of a pattern (1/0, 0, 1), the control circuit  103  determines that the stepping motor  105  rotates but is in the state with a load increased by a large amount from the normal load (load increase is large) and hence the stepping motor  105  may become the non-rotatable state at the time of next driving (rotation with least energy). Accordingly, the control circuit  103  does not perform the driving by the correction drive pulse P 2 , but controls the drive pulse selection circuit  104  so as to drive the stepping motor  105  by the main drive pulse P 1  upgraded by a rank at the time of next driving in advance. 
     In the case of a pattern (1, 1, 1/0), the control circuit  103  determines that the stepping motor  105  rotates, the load is being increased, and the driving energy is adequate (rotation without reserve), and controls the drive pulse selection circuit  104  so as to drive the stepping motor  105  without changing the main drive pulse P 1  for the next driving. 
     In the case of a pattern (0, 1, 1/0), the control circuit  103  determines that the stepping motor  105  rotates and the load is the normal load or the load with very small amount of increase, and hence there is a reserve in the driving energy (rotation with reserve), and controls the drive pulse selection circuit  104  so as to drive the stepping motor  105  by the main drive pulse P 1  degraded by a rank for the next driving. 
       FIG. 5  is a flowchart showing the action of the stepping motor control circuit and the analogue electronic watch according to the first embodiment of the invention, and is a flowchart mainly showing a process in the control circuit  103 . 
     Referring now to  FIG. 1  to  FIG. 5 , the actions of the stepping motor control circuit and the analogue electronic watch according to the first embodiment of the invention will be described in detail. 
     In  FIG. 1 , the oscillation circuit  101  generates a reference clock signal of a predetermined frequency, and the frequency divider circuit  102  divides the signal generated by the oscillation circuit  101  and generates a time signal as a reference of time counting, and outputs the same to the control circuit  103 . 
     The control circuit  103  counts the time signal and performs a time counting action. Then, the control circuit  103  firstly sets an energy rank n and the number of times N of the main drive pulse P 1 n to zero (Step S 501  in  FIG. 5 ), and then outputs a control signal to rotate the stepping motor  105  by the main drive pulse P 10  by a minimum pulse width (Steps S 502 , S 503 ). 
     The control circuit  103  at this time outputs the control signal so as to drive the stepping motor  105  by a main drive pulse P 10  having a polarity opposite from the polarity of the polarity information memorized in the polarity memory  103   a  and memorizes the reverse polarity information in the polarity memory  103   a  as the polarity information. Accordingly, the polarity memory  103   a  rewrites the memorized polarity information from old polarity information used at the previous driving to polarity information having a polarity to be used for driving this time (the reverse polarity) and memorizes the same. 
     The drive pulse selection circuit  104  rotates the stepping motor  105  by the main drive pulse P 10  having a polarity specified by the control signal in response to a control signal from the control circuit  103 . The stepping motor  105  is rotated by the main drive pulse P 10  and then rotates the time-of-day hands  107 ,  108 , and  109 . Accordingly, when the stepping motor  105  is normally rotated, the current time is always displayed by the time-of-day hands  107 ,  108 , and  109  in the analogue display unit  106 . 
     The control circuit  103  determines whether the energy rank n of the main drive pulse P 1  is a main drive pulse P 1 max of a maximum rank m or not (Step S 602 ). 
     If the energy rank n of the main drive pulse P 1  is determined not to be the main drive pulse P 1 max of the maximum rank m in the process Step S 602 , the control circuit  103  performs determination whether or not the rotation detection circuit  110  detects the induced signal VRs of the stepping motor  105  exceeding the predetermined reference threshold voltage Vcomp, and whether or not the detection segment determination circuit  111  determines that a detected time t of the induced signal VRs falls within the segment T 1  (that is, determination whether or not the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the first segment T 1 ) (Step S 504 ). 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is not detected within the segment T 1  in the process step S 504  (It is a case of the pattern (0, x, x), provided that the determination value “x” means that the determination value may other be “1” or “0”). In the same manner, whether or not the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 2  is determined (Step S 505 ). 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is not detected within the segment T 2  in the process step S 505  (It is a case of the pattern (0, 0, x)). In the same manner, whether or not the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 3  is determined (Step S 506 ). 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is not detected within the segment T 3  in the process step S 506  (It is a case of the pattern (x, 0, 0), and the case of non-rotation in  FIG. 3 ), the stepping motor  105  is driven by the correction drive pulse P 2  having the same polarity as the main drive pulse P 1  of the process step S 503  (Step S 507 ) and, if the rank n of the main drive pulse P 1  is not the maximum rank m, the main drive pulse P 1  is upgraded by a rank to a main drive pulse P 1  (n+1). Then, the procedure goes back to the process step S 502 , and the main drive pulse P 1  (n+1) is used for the next driving (Steps S 508 , S 510 ). 
     If the rank n of the main drive pulse P 1  is the maximum rank m in the process step S 508 , the control circuit  103  downgrades the main drive pulse P 1  by a rank to a main drive pulse P 1  (n−a) having a smaller energy by a predetermined amount. Then, the procedure goes back to the process step S 502 , and the main drive pulse P 1  (n−a) is used for the next driving (Step S 509 ). In this case, since the rotation is not possible even by the drive pulse P 1 max, which is the drive pulse having the maximum energy rank m in the main drive pulse P 1 , waste of energy caused by driving by the main drive pulse P 1 max having the maximum energy rank m for the next driving is avoided. At this time, the main drive pulse may be changed to the main drive pulse P 10  having the minimum energy in order to achieve a high power-saving effect. 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 3  in the process step S 506  (It is a case of the pattern (x, 0, 1)), when the rank n of the main drive pulse P 1  is not the maximum rank m, the main drive pulse P 1  is upgraded by a rank to a main drive pulse P 1  (n+1). Then, the procedure goes back to the process step S 502 , and the main drive pulse P 1  is used for the next driving (Steps S 511 , S 510 ; which is a case where the load increase is large in  FIG. 3 ). 
     If the rank n of the main drive pulse P 1  is the maximum rank m in the process step S 511 , the control circuit  103  cannot change the rank, and hence the main drive pulse P 1  is not changed. Then the procedure goes back to the process step S 502 , and this main drive pulse P 1  is used for the next driving (Step S 513 ). 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 1  in the process step S 504  (It is a case of the pattern (1, x, x)), in the same manner, whether or not the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 2  is determined (Step S 512 ). 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is not detected within the segment T 2  in the process step S 512  (It is a case of the pattern (1, 0, x)), the procedure goes to the process step S 506  to perform the above-described process. 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 2  in the process step S 512  (It is a case of the pattern (1, 1, x)), the procedure goes to the process step S 513 . 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 2  in the process step S 505  (It is a case of the pattern (0, 1, x)), the rank cannot be downgraded if the rank n of the main drive pulse P 1  is the lowest rank  0 , and hence is maintained without change, then the procedure goes back to the process step S 502  (Step S 514  and S 518 ). 
     If the control circuit  103  determines that the rank n of the main drive pulse P 1  is not the lowest rank  0  in the process step S 514 , the control circuit  103  increments the number of times of continuous occurrence N by one (Step S 515 ), and determines whether or not the number of times N reaches a predetermined number of times (eighty times in this embodiment) (Step S 516 ). If the predetermined number of times is not reached, the procedure goes back to the process step S 502  without changing the rank of the main drive pulse P 1  (Step S 518 ), and if the predetermined number of times is reached, the rank of the main drive pulse P 1  is downgraded by a rank, the number of times of continuous occurrence N is reset to “0”, and the procedure goes back to the process step S 502  (Step S 517 ). 
     In contrast, if the control circuit  103  determines that the main drive pulse P 1  is the main drive pulse having the predetermined energy (the main drive pulse P 1 max whose energy rank n is the maximum rank m in this embodiment) in the process Step S 602 , whether or not the induced signal VRs exceeding the reference threshold voltage Vcomp is detected in the first segment T 1  is determined (Step S 603 ). 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is not detected within the segment T 1  in the process step S 603  (It is a case of the pattern (0, x, x)), whether or not the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 2  is determined (Step S 604 ). 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 2  in the process Step S 604 , procedure goes to the process Step S 514 . 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is not detected within the segment T 2  in the process step S 604  (It is a case of the pattern (0, 0, x)), it is determined that the voltage of the secondary battery  113  is lowered to a predetermined value or below, the control circuit  103  drives the stepping motor  105  by the correction drive pulse P 2  (the correction drive pulse P 2  having the same polarity as the main drive pulse P 1  used for driving this time (the main drive pulse P 1  in the process step S 503 )) to rotate the stepping motor  105  (Step S 605 ). Accordingly, even when the stepping motor  105  is not rotated in the process Step S 503  because the voltage of the secondary battery  113  is low, the stepping motor  105  can be rotated for sure. 
     Subsequently, the control circuit  103  memorizes the polarity of the correction drive pulse P 2  used for driving this time (the same polarity as that of the main drive pulse P 1  used for driving this time) in the polarity memory  103   a  as the polarity information (Step S 606 ), stops the driving of the stepping motor  105 , and stops the clocking (Step S 607 ). Accordingly, the stepping motor  105  is brought into a sleep state. 
     Also, if the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 1  in the process step S 603  (It is a case of the pattern (1, x, x)), it is determined that the source voltage of the secondary battery  113  is lowered to a predetermined value or below, the processes from the process step S 605  onward are performed in the same manner as described above, and the control circuit  103  memorizes the polarity of the correction drive pulse P 2  used for driving this time in the polarity memory  103   a  as the polarity information (Step S 606 ), stops the driving of the stepping motor  105 , and stops the clocking (Step S 607 ). Accordingly, the stepping motor  105  is brought into the sleep state. 
     When the secondary battery  113  is charged by the solar photovoltaic element  112 , and hence the control circuit  103  determines that the voltage of the secondary battery  113  is increased to the predetermined voltage or higher sufficient for the stable driving, the control circuit  103  references the polarity information memorized in the polarity memory  103   a  and restarts driving by the main drive pulse P 1  having the polarity opposite from the polarity information. 
     As described thus far, the stepping motor control circuit according to the first embodiment of the invention includes the power source (the secondary battery  113  in this embodiment), the rotation detection device configured to detect the induced signal VRs generated by the rotation of the rotor  202  of the stepping motor  105  and detect the state of rotation of the stepping motor  105  depending on whether or not the induced signal VRs exceeds the predetermined reference threshold voltage Vcomp in the predetermined detection segment T, and the drive control device configured to select either the drive pulse P 1  or P 2  having energies different from each other according to the result of detection detected by the rotation detection device and control the driving of the stepping motor  105  with the predetermined polarity, and is characterized in that the detection segment T is divided into a plurality of segments (three segments T 1  to T 3  in this embodiment), and the drive control device controls to stop the driving of the stepping motor  105  in a state in which the polarity of the drive pulse to be used for restarting the driving after the voltage of the power source is restored to the voltage exceeding the predetermined voltage is known when the power source is determined to be lowered to the predetermined voltage value or below on the basis of the pattern of the segments in which the rotation detection device detects the induced signal VRs exceeding the reference threshold voltage Vcomp when the stepping motor  105  is driven by the drive pulse having the predetermined energy (the main drive pulse P 1 max of the maximum energy rank m in this embodiment). 
     Also, when the voltage of the power source is determined to be lowered to the predetermined value or below, the drive control device memorizes the polarity information which decides the polarity of the drive pulse used when restarting the driving after the source voltage is restored in the polarity memory  103   a,  and restarts the driving of the stepping motor  105  by the drive pulse having the polarity decided using the polarity information when restarting the driving after the source voltage is restored. 
     When the stepping motor  105  is driven by the drive pulse having the predetermined energy, if it is determined that the voltage of the power source is lowered to the predetermined voltage value or below, which can hardly achieve the stable driving, that is, when the pattern of the induced signal VRs becomes the predetermined pattern (the pattern (1, x, x) or (0, 0, x) in this embodiment), the drive control unit determines that the voltage of the power source is lowered to the predetermined voltage value or below, and memorizes the polarity information and stops the driving. 
     Therefore, the stepping motor control circuit according to the first embodiment has a simple configuration because the source voltage can be detected without providing the voltage detection circuit, and can stop the driving in the state of holding accurate information of the drive pulse when the voltage of the secondary battery  113  is lowered to the predetermined voltage or below. 
     When the stepping motor  105  is driven by the drive pulse having the predetermined energy, if it is determined that the voltage of the power source is lowered to the predetermined voltage value or below which can hardly achieve the stable driving, the drive control unit memorizes the polarity information after having rotated for sure by the correction drive pulse P 2 , so that the correct polarity information can be memorized, and hence the driving can be started by the drive pulse having the correct polarity when restarting the driving. 
     The analogue electronic watch according to the first embodiment has a simple configuration because the source voltage can be detected without providing the voltage detection circuit and the driving can be stopped in a state of holding correct driving pulse information when the voltage of the secondary battery  113  is lowered to a predetermined voltage or below, so that the driving can be started by the correct drive pulse when the voltage of the secondary battery  113  is restored and hence correct clocking is advantageously achieved. 
       FIG. 6  is a block diagram of an analogue electronic watch using a motor control circuit according to a second embodiment of the invention showing an example of an analogue electronic wrist watch and the same components as in  FIG. 1  are designated by the same reference numerals. 
     In  FIG. 6 , the control circuit  103  includes a polarity determining unit  103   b  which constitutes a polarity determining device. The polarity determining unit  103   b  has a function to determine the polarity of the correction drive pulse P 2  when driven by the correction drive pulse P 2 . When stopping the driving as a result of lowering of the voltage of the secondary battery  113 , the control circuit  103  controls to stop driving forcedly after having performed the driving of the stepping motor  105  by the drive pulse having the predetermined polarity, which is specified in advance. 
       FIG. 7  is a flowchart showing the action of the stepping motor control circuit and the analogue electronic watch according to the second embodiment of the invention, and is a flowchart mainly showing the process in the control circuit  103 , and the same components as in  FIG. 5  are designated by the same reference numerals. 
     Referring now to  FIG. 6 ,  FIG. 7 , FIG. and  FIG. 2  to  FIG. 4 , the actions in the second embodiment different from the first embodiment will be described. 
     In  FIG. 7 , after the control circuit  103  determines that the voltage of the secondary battery  113  is lowered to the predetermined voltage or below by the pattern determination process in the process steps S 603  and S 604 , and controls to drive the stepping motor  105  by the correction drive pulse P 2  having the same polarity as the main drive pulse P 1  in the process step S 603  in the process step S 605 , the polarity determining unit  103   b  determines whether or not the polarity of the correction drive pulse P 2  is a predetermined polarity OUT 1  (Step S 701 ). 
     If the polarity determining unit  103   b  determines that the polarity of the correction drive pulse P 2  is the predetermined polarity OUT 1  in the process step S 701 , the control circuit  103  stops the drive control of the stepping motor  105 , and stops the clocking (Step S 607 ). Accordingly, the stepping motor  105  is brought into the sleep state. 
     In contrast, if the polarity determining unit  103   b  determines that the polarity of the correction drive pulse P 2  is not the predetermined polarity OUT 1  in the process step S 701  (in other words, it is an opposite polarity OUT 2  of the predetermined polarity), the control circuit  103  controls to drive the stepping motor  105  by the correction drive pulse P 2  of the predetermined polarity OUT 1  (Step S 702 ), and then stops the drive control of the stepping motor  105  and stops the clocking (Step S 607 ). Accordingly, the stepping motor  105  is brought into the sleep state. 
     When the secondary battery  113  is charged by the solar photovoltaic element  112 , and hence the control circuit  103  determines that the voltage of the secondary battery  113  is increased to the predetermined voltage or higher sufficient for the stable driving, and restarts driving by the main drive pulse P 1  having the opposite polarity OUT 2  opposite from the predetermined polarity OUT 1 . 
     As described thus far, according to the second embodiment of the invention, the voltage detection circuit is not necessary because whether or not the voltage of the power source is lowered to the predetermined voltage or below by the pattern of the induced signal VRs as in the first embodiment described above, so that the simple configuration is achieved. 
     Also, according to the second embodiment of the invention, when it is determined that the power source is lowered to the predetermined value or below, the drive control device controls to stop driving after having driven forcedly by the drive pulse having the predetermined polarity OUT 1  and start the driving of the stepping motor  105  by the drive pulse having the opposite polarity OUT 2  opposite from the predetermined polarity OUT 1  when restarting the driving after the source voltage is restored, rotation of the stepping motor  105  is ensured when restarting the driving, and the reliable clocking is achieved. 
     Since the correction drive pulse P 2  is used as the drive pulse having the predetermined polarity OUT 1 , rotation of the stepping motor  105  by driving with the predetermined polarity OUT 1  is ensured, so that the stepping motor  105  can be rotated for sure when restarting the driving. 
       FIG. 8  is a block diagram of an analogue electronic watch using a motor control circuit according to a third embodiment of the invention showing an example of an analogue electronic wrist watch and the same components as in  FIG. 1  are designated by the same reference numerals. 
     In  FIG. 8 , the control circuit  103  includes an irregular movement controller  103   c  which constitutes an irregular movement control device. The irregular movement controller  103   c  has a function to control the driving of the stepping motor  105  in a mode different from the mode at the time of normal driving when predetermined conditions such that the state of rotation of the stepping motor  105  becomes a predetermined state, which will be described in detail later. Here, the normal driving is an action to rotate the stepping motor  105  at a constant predetermined cycle so as to display the time of day by driving the time-of-day hands  107  to  109  to clock at a constant predetermined cycle (for example, one-second cycle). By driving the stepping motor  105  in a mode different from the mode at the time of normal driving, the time-of-day hands  107  to  109  perform clocking in a mode different from the normal driving. Accordingly, a notification such as the notification of necessity to charge the secondary battery  113  is performed. 
       FIG. 9  is a flowchart showing the action of the stepping motor control circuit and the analogue electronic watch according to the third embodiment of the invention, and is a flowchart mainly showing the process in the control circuit  103 , and the same components as in  FIG. 5  are designated by the same reference numerals. 
     Referring now to  FIG. 8 ,  FIG. 9 , and  FIG. 2  to  FIG. 4 , the actions in the third embodiment of the invention different from the first embodiment will be described. 
     In the process step S 602  shown in  FIG. 9 , when the control circuit  103  determines that the energy rank n of the main drive pulse P 1  is the main drive pulse P 1 max of the maximum rank m, the irregular movement controller  103   c  outputs the control signal to the drive pulse selection circuit  104  so as to drive the stepping motor  105  to rotate in a driving mode in a first notification clocking cycle different from the mode at the time of normal driving (first mode) (Step S 608 ). 
     The driving mode in the first notification clocking cycle is a driving action in a mode different from the mode at the time of normal driving, and in this embodiment, it is a driving mode which drives the stepping motor  105  to rotate by two seconds at a time at every two seconds (two seconds clocking). The drive pulse selection circuit  104  drives the stepping motor  105  to rotate by two seconds together at every two seconds in response to the control signal from the irregular movement controller  103   c.  Accordingly, the fact that a predetermined action (for example, charging) is necessary although it is not necessarily urgent is notified to the user. The main drive pulse P 1  used for the driving at this time is the main drive pulse P 1 max whose energy rank n is the maximum rank m. 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is not detected within the segment T 1  in the process step S 603  (It is a case of the pattern (0, x, x)), the procedure goes to the process step S 604 . 
     Also, if the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 1  in the process step S 603  (It is a case of the pattern (1, x, x)), whether or not the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 2  is determined (Step S 609 ). 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is not detected within the segment T 2  in the process step S 609  (It is a case of the pattern (1, 0, x)), whether or not the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 3  is determined (Step S 610 ). 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is not detected within the segment T 3  in the process step S 610  (It is a case of the pattern (1, 0, 0)), the process in the process step S 605  to S 607  is performed. 
     Accordingly, even when the stepping motor  105  is not rotated in Step S 608  because the voltage of the secondary battery  113  is low, the stepping motor  105  can be rotated for sure by the correction drive pulse P 2  (Step S 605 ). Also, the control circuit  103  memorizes the polarity of the correction drive pulse P 2  used for driving this time (the same polarity as that of the main drive pulse P 1  used for driving this time) in the polarity memory  103   a  as the polarity information (Step S 606 ), stops the driving of the stepping motor  105 , and stops the clocking (Step S 607 ). Accordingly, the stepping motor  105  is brought into the sleep state. 
     Also, if the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 3  in the process step S 610  (It is a case of “rotation with least energy having the pattern (1, 0, 1)), the irregular movement controller  103   c  outputs the control signal to the drive pulse selection circuit  104  so as to drive the stepping motor  105  to rotate in a driving mode in a second notification clocking cycle (second mode), and the procedure goes to the process step S 518  (Step S 611 ). 
     The second notification clocking cycle is a driving action in a mode different from the mode at the time of normal driving and the driving mode in the first notification clocking cycle (first mode), and in the third embodiment, it is a driving mode which drives the stepping motor  105  to rotate by three seconds at a time at every three seconds (three seconds clocking). Accordingly, the fact that a quick action is necessary (the voltage of the secondary battery  113  is significantly lowered, and the action such as charging is needed immediately) is notified to the user. The main drive pulse P 1  used for the driving at this time is the main drive pulse P 1 max whose energy rank n is the maximum rank m. 
     Also, if the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 2  in the process step S 609  (It is a case of the pattern (1, 1, x)), the procedure goes to the process step S 518 . 
     As described above, according to the third embodiment of the invention, not only the same effects as the first embodiment are achieved, but also the notification saying that the charging is necessary although it is not urgent can be given to the user because when the stepping motor  105  is driven by selecting the main drive pulse P 1 max having the maximum energy rank m, the stepping motor  105  is driven in the first mode, which is different from the mode at the time of normal driving while the stable rotation is performed. 
     Also, since the drive control device is configured to drive the stepping motor  105  in the second mode which is different from the mode at the time of normal driving and the first mode when a pattern in which the induced signal VRs exceeding the reference threshold voltage Vcomp is detected only in the first segment T 1  and the third segment T 3  is obtained when driving the stepping motor  105  by the main drive pulse P 1 max having the maximum energy rank m, the urgency when the voltage of the secondary battery  113  is significantly lowered can be notified to the user. 
       FIG. 10  is a block diagram of an analogue electronic watch using a motor control circuit according to a fourth embodiment of the invention showing an example of an analogue electronic wrist watch and the same components as in  FIG. 6  and  FIG. 8  are designated by the same reference numerals. 
     In  FIG. 10 , the control circuit  103  includes an irregular movement controller  103   c  which constitutes an irregular movement control device. In the same manner as the third embodiment, the irregular movement controller  103   c  has a function to control the driving of the stepping motor  105  in the first mode or the second mode different from the mode at the time of normal driving when the predetermined conditions such that the state of rotation of the stepping motor  105  becomes a predetermined state are satisfied. By driving the stepping motor  105  in a mode different from the normal driving, the time-of-day hands  107  to  109  perform clocking in the first mode or the second mode. Accordingly, a notifying action such as the notification of necessity to charge the secondary battery  113  is performed. 
       FIG. 11  is a flowchart showing the action of the stepping motor control circuit and the analogue electronic watch according to the fourth embodiment of the invention, and is a flowchart mainly showing the process in the control circuit  103 , and the same components as in  FIG. 7  and  FIG. 9  are designated by the same reference numerals. 
     Referring now to  FIG. 10 ,  FIG. 11 , and  FIG. 2  to  FIG. 4 , the actions in the fourth embodiment of the invention different from the second embodiment will be described. 
     In the process step S 602  shown in  FIG. 11 , when the control circuit  103  determines that the energy rank n of the main drive pulse P 1  is the main drive pulse P 1 max of the maximum rank m, the irregular movement controller  103   c  outputs the control signal to the drive pulse selection circuit  104  so as to drive the stepping motor  105  to rotate in a driving mode in a first notification clocking cycle different from the mode at the time of normal driving (first mode) (Step S 608 ). 
     The first notification clocking cycle is a driving action in a mode different from the mode at the time of normal driving in the same manner as the third embodiment described above, and in this embodiment, it is a driving mode which drives the stepping motor  105  to rotate by two seconds at a time at every two seconds (two seconds clocking). The drive pulse selection circuit  104  drives the stepping motor  105  to rotate by two seconds together at every two seconds in response to the control signal from the irregular movement controller  103   c.  Accordingly, the fact that a predetermined action (for example, charging) is necessary although it is not necessarily urgent is notified to the user. 
     The main drive pulse P 1  used for the driving at this time is the main drive pulse P 1 max whose energy rank n is the maximum rank m. 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is not detected within the segment T 1  in the process step S 603  (It is a case of the pattern (0, x, x)), the procedure goes to the process step S 604 . 
     Also, if the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 1  in the process step S 603  (It is a case of the pattern (1, x, x)), whether or not the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 2  is determined (Step S 609 ). 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is not detected within the segment T 2  in the process step S 609  (It is a case of the pattern (1, 0, x)), whether or not the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 3  is determined (Step S 610 ). 
     If the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is not detected within the segment T 3  in the process step S 610  (It is a case of the pattern (1, 0, 0)), the process in the process steps S 605 , S 607 , S 701 , S 702  is performed. 
     Accordingly, in the same manner as the second embodiment described above, the clocking is stopped after having driven to rotate by the correction drive pulse P 2  having the predetermined polarity OUT 1 , and then the stepping motor  105  is brought into the sleep state. 
     Also, if the control circuit  103  determines that the induced signal VRs exceeding the reference threshold voltage Vcomp is detected within the segment T 3  in the process step S 610  (It is a case of “rotation with least energy having the pattern (1, 0, 1)), the irregular movement controller  103   c  outputs the control signal to the drive pulse selection circuit  104  so as to drive the stepping motor  105  to rotate in a driving mode in a second notification clocking cycle (second mode), and the procedure goes to the process step S 518  (Step S 611 ). 
     The second notification clocking cycle is a driving action in a mode different from the mode at the time of normal driving and the driving mode in the first notification clocking cycle (first mode), and as in the third embodiment, it is a driving mode which drives the stepping motor  105  to rotate by three seconds at a time at every three seconds (three seconds clocking). Accordingly, the fact that a quick action is necessary (the voltage of the secondary battery  113  is significantly lowered, and the action such as charging is needed immediately) is notified to the user. The main drive pulse P 1  used for the driving at this time is the main drive pulse P 1 max whose energy rank n is the maximum rank m. 
     As described above, according to the fourth embodiment of the invention, in the same manner as the third embodiment, the notification saying that the charging is necessary although it is not urgent can be given to the user because when the stepping motor  105  is driven by selecting the main drive pulse P 1 max having the maximum energy rank m, the stepping motor  105  is driven in the first mode, which is different from the mode at the time of normal driving while the stable rotating state is performed. 
     Also, since the drive control device is configured to drive the stepping motor  105  in the second mode which is different from the mode at the time of normal driving and the first mode when a pattern in which the induced signal VRs exceeding the reference threshold voltage Vcomp is detected only in the first segment T 1  and the third segment T 3  is obtained when driving the stepping motor  105  by the main drive pulse P 1 max having the maximum energy rank m, the urgency when the voltage of the secondary battery  113  is significantly lowered can be notified to the user. 
     In the respective embodiments described above, the main drive pulse P 1 max having the maximum rank m is used as the drive pulse for determining whether the voltage of the secondary battery  113  is lowered to a predetermined voltage value or below. However, the drive pulse having other predetermined energy may be used. 
     Although the secondary battery  113  is exemplified as the power source in the respective embodiments, a primary battery is also applicable. 
     In the respective embodiments described above, the energy of the respective drive pulses is changed by differentiating the pulse width. However, the driving energy can be changed also by changing the number of comb-teeth pulses, or by changing the pulse voltage. 
     Also, although the analogue electronic watch has been described as the example of the application of the stepping motor, it may be applicable to electronic instruments which use the motor. 
     The stepping motor control circuit according to the invention may be applicable to various electronic instruments using the stepping motor. 
     The electronic watch according to the invention is applicable to various analogue electronic watches such as analogue electronic wrist watches with calendar function, or chronograph watches.