Stepping motor control circuit and analog electronic watch

1. Field of the Invention

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

2. Description of the Related Art

In the related art, a 2 pole PM (Permanent Magnet) type stepping motor is used for an analog electronic watch and the like. The stepping motor includes a stator provided with a rotor receiving hole and a position determining portion for determining a stop position of a rotor, the rotor provided in the rotor receiving hole, and a coil. Further, the stepping motor rotates the rotor by magnetic flux generated in the stator by an alternating signal supplied to the coil, and stops the rotor at a position corresponding to the position determining portion.

As a low consumption driving scheme for the 2 pole PM type stepping motor, a correction driving scheme of a stepping motor has been put to practical use, which uses a main driving pulse P 1 with low energy in a normal time, and a correction driving pulse P 2 with high energy for performing driving in load variation. The energy of the main driving pulse P 1 is reduced/increased according to rotation/non-rotation of a rotor, so that the stepping motor is driven with lower energy as much as possible (for example, refer to JP-B-61-15385).

The correction driving scheme is performed as follows: (1) the main driving pulse P 1 is output to one pole O 1 of a coil, and an induced voltage generated in the coil is detected by rotor vibration immediately after the main driving pulse P 1 is output thereto; (2) the case in which the induced voltage exceeds a reference threshold voltage arbitrarily set is regarded as rotation, the main driving pulse P 1 maintaining the energy is output to the other pole O 2 of the driving coil, and the output of the main driving pulse P 1 is repeated by a certain number of times so long as the rotor is rotated. If the number of times of output thereof reaches the certain number of times (PCD), the main driving pulse P 1 with lower energy is output to the other pole O 2 , and this process is repeated again; and (3) the case in which the induced voltage does not exceed the reference threshold voltage is regarded as non-rotation, the correction driving pulse P 2 with high energy is immediately output to the same pole, so that the rotor is forcibly rotated. In the next driving, a main driving pulse P 1 with energy higher than the main driving pulse P 1 , which causes the non-rotation of the rotor, is output to the other pole, and the steps (1) to (3) are repeated.

Further, in the invention according to WO2005/119377, when detecting the rotation of the stepping motor, in addition to the detection of the induced signal, after a means is provided to compare a detection time with a reference time and the stepping motor is rotated by the main driving pulse P 11 , the correction driving pulse P 2 is output if a detection signal is less than a predetermined reference threshold voltage Vcomp, and a next main driving pulse P 1 is changed (pulse up) to a main driving pulse P 12 having energy higher than that of the main driving pulse P 11 so that the stepping motor is driven by the main driving pulse P 12 . If the detection time when the stepping motor has been rotated by the main driving pulse P 12 is earlier than the reference time, the main driving pulse P 12 is changed (pulse down) to the main driving pulse P 11 , so that the stepping motor is rotated by the main driving pulse P 1 according to a load during the driving thereof, resulting in reduction of current consumption.

However, when the stepping motor is used for an analog electronic watch, the rotation or non-rotation state occurs according to the driving pulse as described above. However, when force acting on the rotor is significantly changed as in the case of calendar feed or variation in supply voltage, a case may occur in which the rotor infrequently stays in an intermediate position different from a stationary position, so called a case may occur in which the rotor is in an intermediate stationary position, a problem may occur in which rotation or non-rotation is abnormally determined, or hand movement delay may occur.

It is an aspect of the invention to accurately determine a rotation state of a stepping motor to perform a reliable and stable correction operation.

That is, according to the aspect of the invention, a stepping motor control circuit includes: a rotation detecting means which detects an induced signal generated by rotation of a rotor of a stepping motor, and detects a rotation state of the stepping motor according to whether the induced signal exceeds a predetermined reference threshold voltage in a predetermined detection section, and a control means which controls driving of the stepping motor by using any one of a plurality of main driving pulses having energies different from each other or a correction driving pulse with energy higher than energy of each main driving pulse according to a detection result of the rotation detecting means, wherein the detection section is divided into a first section immediately after driving by the main driving pulse, a second section after the first section and a third section after the second section, and, during the driving of the stepping motor by the main driving pulse, when the rotation detecting means has detected an induced signal exceeding a first reference threshold voltage in the first section and the second section, if an induced signal exceeding a second reference threshold voltage lower than the first reference threshold voltage is not detected in the third section, the control means drives the stepping motor by using the correction driving pulse.

During the driving of the stepping motor by a main driving pulse, when the rotation detecting means has detected the induced signal exceeding the first reference threshold voltage in the first section and the second section of the detection section, if the induced signal exceeding the second reference threshold voltage lower than the first reference threshold voltage cannot be detected in the third section, the control means drives the stepping motor by using the correction driving pulse.

Further, after the stepping motor is driven by the correction driving pulse, the control means may allow the main driving pulse to be up.

Further, when the rotation detecting means has detected the induced signal exceeding the second reference threshold voltage in the third section, the control means may not drive the stepping motor by using the correction driving pulse.

Furthermore, when the rotation detecting means has detected the induced signal exceeding the second reference threshold voltage in the third section so that the stepping motor is not driven by the correction driving pulse, the control means may not change the main driving pulse.

In addition, according to the invention, there is provided an analog electronic watch including a stepping motor for rotating time hands and a stepping motor control circuit for controlling the stepping motor, wherein the above-described stepping motor control circuit is used as the stepping motor control circuit.

According to the stepping motor control circuit of the present embodiment, the rotation state of the stepping motor can be accurately determined and a reliable and stable correction operation can be performed.

Further, according to the analog electronic watch of the present embodiment, the rotation state of the stepping motor can be accurately determined and a reliable and stable correction operation can be performed, so that hand movement can be accurately performed.

FIG. 1 is a block diagram illustrating a stepping motor control circuit and an analog electronic watch according to an embodiment of the invention;

FIG. 2 is a diagram illustrating the configuration of a stepping motor used for an analog electronic watch according to an embodiment of the invention;

FIG. 3 is a timing diagram illustrating the operations of a stepping motor control circuit and an analog electronic watch according to an embodiment of the invention; and

FIG. 4 is a flowchart illustrating the operations of a stepping motor control circuit and an analog electronic watch according to an embodiment of the invention.

Hereinafter, a stepping motor control circuit and an analog electronic watch using the same according to an embodiment of the invention will be described. In each drawing, the same reference numerals are used to designate the same elements.

FIG. 1 is a block diagram illustrating an analog electronic watch using the stepping motor control circuit according to the embodiment of the invention, which illustrates an example of an analog electronic wrist watch.

In FIG. 1 , the analog electronic watch includes a stepping motor control circuit 101 , a stepping motor 102 which is rotated under the control of the stepping motor control circuit 101 to rotate time hands, a calendar mechanism (not shown) and the like, and a power supply 103 , such as a battery, which supplies driving power to circuit elements such as the stepping motor control circuit 101 and the stepping motor 102 .

The stepping motor control circuit 101 includes an oscillating circuit 104 for generating a signal with a predetermined frequency, a divider circuit 105 for dividing the signal generated by the oscillating circuit 104 to generate a watch signal serving as a reference of a watch, a control circuit 106 for controlling electronic circuit elements constituting the electronic watch or controlling the change of a driving pulse, a stepping motor driving pulse circuit 107 for selectively outputting a driving pulse for driving the rotation of a motor to the stepping motor 102 based on a control signal from the control circuit 106 , a rotation detecting circuit 108 for detecting an induced signal, which represents a rotation state, from the stepping motor 102 in a predetermined detection section, and a detection time comparing/determining circuit 109 for determining a detection section of the induced signal by performing a comparison operation based on a time and a section at which the rotation detecting circuit 108 has detected the induced signal exceeding a predetermined reference threshold voltage. Further, as described later, a detection section used for detecting the rotation state of the stepping motor 102 is divided into three sections.

The rotation detecting circuit 108 has the same configuration as that of a rotation detecting circuit according to JP-B-61-15385. The rotation detecting circuit 108 detects whether the induced signal generated by free vibration immediately after the driving of the stepping motor 102 exceeds a predetermined reference threshold voltage Vcomp in a predetermined detection section, and gives notice to the detection time comparing/determining circuit 109 whenever detecting an induced signal VRs exceeding the reference threshold voltage Vcomp. According to the present embodiment, the reference threshold voltage Vcomp uses two types of the reference threshold voltage Vcomp having voltages different from each other, that is, a first reference threshold voltage Vcomp 1 of a first predetermined voltage and a second reference threshold voltage Vcomp 2 , which is a second predetermined voltage lower than the first reference threshold voltage Vcomp 1 , and the reference threshold voltage is selectively used according to the rotation state of the stepping motor.

In addition, the oscillating circuit 104 and the divider circuit 105 constitute a signal generating means. The rotation detecting circuit 108 and the detection time comparing/determining circuit 109 constitute a rotation detecting means. Further, the oscillating circuit 104 , the divider circuit 105 , the control circuit 106 and the stepping motor driving pulse circuit 107 constitute a control means.

The rotation detecting means can detect the induced signal VRs generated by the rotation of the rotor of the stepping motor 102 , and detect the rotation state of the stepping motor 102 according to whether the induced signal VRs exceeds the predetermined reference threshold voltage in a predetermined detection section.

During the driving of the stepping motor 102 by a main driving pulse P 1 , when the rotation detecting means has detected the induced signal VRs exceeding the first reference threshold voltage Vcomp 1 in a first section T 1 and a second section T 2 of the detection section, if the induced signal VRs exceeding the second reference threshold voltage Vcomp 2 lower than the first reference threshold voltage Vcomp 1 cannot be detected in a third section T 3 , the control means drives the stepping motor 102 by using a correction driving pulse P 2 .

FIG. 2 is a diagram illustrating the configuration of the stepping motor 102 used for the embodiment of the invention, which illustrates an example of a 2 pole PM type stepping motor generally used for an analog electronic watch.

In FIG. 2 , the stepping motor 102 includes a stator 201 formed with a rotor receiving through hole 203 , a rotor 202 rotatably provided in the rotor receiving through hole 203 , a magnetic core 208 bonded to the stator 201 , and a coil 209 wound around the magnetic core 208 . When the stepping motor 102 is used for an analog electronic watch, the stator 201 and the magnetic core 208 are fixed to a ground plane (not shown) by screws (not shown) while being bonded to each other. The coil 209 has a primary terminal OUT 1 and a secondary terminal OUT 2 .

The rotor 202 is magnetized to two poles (S and N poles). The stator 201 made of a magnetic material is formed at the outer end portion thereof with a plurality (two in the present embodiment) of cutout parts (outer notches) 206 and 207 which face each other while interposing the rotor receiving through hole 203 therebetween. Saturable parts 210 and 211 are provided between each of the notches 206 and 207 and the rotor receiving through hole 203 .

The saturable parts 210 and 211 are not saturated by the magnetic flux of the rotor 202 , but are saturated when the coil 209 is excited so that magnetic resistance becomes large. The rotor receiving through hole 203 is formed in circular hole shape in which a plurality (two in the present embodiment) of semilunar cutout parts (inner notches) 204 and 205 are integrally formed with each other at opposite positions of the through hole which is circular in outline.

The cutout parts 204 and 205 serve as position determining portions for determining a stop position of the rotor 202 . In the state in which the coil 209 is not excited, the rotor 202 is stably stopped at a position corresponding to the position determining portions as illustrated in FIG. 2 , in other words, a magnetic pole axis A of the rotor 202 is stably stopped at a position (position of an angle of θ 0 ) which is perpendicular to a line segment which connects the cutout part 204 to the cutout part 205 . An XY coordinate space, in which a rotation axis (rotation center) of the rotor 202 is employed as a center, is divided into four quadrants (first to fourth quadrants I to IV).

If an electric current i flows in the arrow direction of FIG. 2 by a rectangular waveform driving pulse supplied between the terminals OUT 1 and OUT 2 of the coil 209 from the stepping motor driving pulse circuit 107 (e.g., the primary terminal OUT 1 is referred to as a positive pole and the secondary terminal OUT 2 is referred to as a negative pole), magnetic flux is generated in the stator 201 in the broken line arrow direction. Therefore, the saturable parts 210 and 211 are saturated so that magnetic resistance becomes large. Thereafter, due to an interaction between magnetic poles generated in the stator 201 and the magnetic poles of the rotor 202 , since the rotor 202 is rotated at an angle of 180° in the arrow direction of FIG. 2 , the magnetic pole axis of the rotor 202 is stably stopped at a position of an angle of θ 1 . Herein, the rotation direction (the counterclockwise direction in FIG. 2 ), in which a normal operation (a hand moving operation in the analog electronic watch of the present embodiment) is performed by the rotation of the stepping motor 102 , will be referred to as the forward direction, and the opposite (the clockwise direction) will be referred to as the backward direction.

Next, if an electric current flows in the opposite arrow direction of FIG. 2 by a rectangular waveform driving pulse having a reverse polarity supplied between the terminals OUT 1 and OUT 2 of the coil 209 from the stepping motor driving pulse circuit 107 (the primary terminal OUT 1 is referred to as a negative pole and the secondary terminal OUT 2 is referred to as a positive pole such that reverse polarity occurs as compared with the above driving), magnetic flux is generated in the stator 201 in the direction opposite to the broken line arrow direction. Therefore, the saturable parts 210 and 211 are first saturated. Thereafter, due to the interaction between the magnetic poles generated in the stator 201 and the magnetic poles of the rotor 202 , since the rotor 202 is rotated at the angle of 180° in the same direction (forward direction) as that in the above case, the magnetic pole axis of the rotor 202 is stably stopped at a position of the angle of θ 0 .

Then, the above operation is repeated by supplying the coil 209 with signals (alternating signals) having different polarities, so that the rotor 202 can be continuously rotated by 180° in the arrow direction. According to the present embodiment, as described later, a plurality of main driving pulses P 10 to P 1 n having different energies and a correction driving pulse P 2 are used as the driving pulse.

FIG. 3 is a timing diagram when the stepping motor 102 is driven by the main driving pulse P 1 according to the present embodiment, which collectively illustrates a detection pattern (determination value representing whether the induced signal VRs of the sections T 1 to T 3 exceeds the reference threshold voltage Vcomp) representing a rotation state, the rotation position of the rotor 202 , and a pulse control operation of changing the rank of the main driving pulse P 1 or performing driving by the correction driving pulse P 2 .

In FIG. 3 , P 1 denotes both the main driving pulse P 1 and a section in which the rotor 202 is rotated by the main driving pulse P 1 , and “a” to “d” denote regions representing the rotation positions of the rotor 202 by free vibration after driving of the main driving pulse P 1 is stopped.

A predetermined time immediately after driving by the main driving pulse P 1 is defined as a first section T 1 , a predetermined time after the first section T 1 is defined as a second section T 2 , and a predetermined time after the second section T 2 is defined as a third section T 3 . In this way, the entire detection section T starting from immediately after the driving by the main driving pulse P 1 is divided into a plurality of sections (in the present embodiment, three sections T 1 to T 3 ). However, in the present embodiment, a mask section, in which the induced signal VRs is not detected, is not provided.

When the rotor 202 is employed as the center and the XY coordinate space, in which the main magnetic pole of the rotor 202 is located by the rotation thereof, is divided into first to fourth quadrants I to IV, the first to third sections T 1 to T 3 can be defined as follows.

That is, in a state of a normal load, the first section T 1 serves as a section for determining the rotation state of the rotor 202 in the forward direction and the initial rotation state of the rotor 202 in the backward direction in the third quadrant III of the space employing the rotor 202 as the center, the second section T 2 serves as a section for determining the initial rotation state of the rotor 202 in the backward direction in the third quadrant III, and the third section T 3 serves as a section for determining a rotation state after the initial rotation of the rotor 202 in the backward direction in the third quadrant III. Herein, the normal load means a load driven in a normal time. According to the present embodiment, a load when driving time hands (an hour hand, a minute hand and a second-hand) for displaying a time is defined as the normal load.

The first reference threshold voltage Vcomp 1 serves as a reference threshold voltage for determining a voltage level of the induced signal VRs generated in the stepping motor 102 . When the rotor 202 performs a constant high speed operation as in the case in which the stepping motor 102 is rotated, the induced signal VRs exceeds the first reference threshold voltage Vcomp 1 . When the rotor 202 does not perform the constant high speed operation as in the case in which the stepping motor 102 is not rotated, the first reference threshold voltage Vcomp 1 is set such that the induced signal VRs does not exceed the first reference threshold voltage Vcomp 1 .

Further, the second reference threshold voltage Vcomp 2 is set to be lower than the first reference threshold voltage Vcomp 1 . When the induced signal VRs of the first and second sections T 1 and T 2 exceeds the voltage Vcomp 1 , since it is determined whether the rotor 202 is stationary in an intermediate position, the second reference threshold voltage Vcomp 2 serves as a reference for determining whether the signal VRs exceeding a predetermined level has been generated in the third section T 3 . According to the present embodiment, for example, the first reference threshold voltage Vcomp 1 is set to 1.5V and the second reference threshold voltage Vcomp 2 is set to 0.3V.

In the stepping motor control circuit according to the present embodiment, in the state of the normal load, the induced signal VRs generated in the area “b” is detected in the first section T 1 , the induced signal VRs generated in the area “c” is detected in the first section T 1 and the second section T 2 , and the induced signal VRs generated in the area “d” is detected in the third section T 3 .

Further, in the first to third sections T 1 to T 3 , a determination value “1” is given when the induced signal VRs exceeds the reference threshold voltage Vcomp serving as a comparison reference, and a determination value “0” is given when the induced signal VRs does not exceed the reference threshold voltage Vcomp. In addition, “1/0” is given when a determination value may be any one of “1” and “0”.

In FIG. 3 , for example, when (0, 1, 0) is generated as a pattern (including a determination value of the first section T 1 , a determination value of the second section T 2 , and a determination value of the third section T 3 ), the control circuit 106 determines the rotation of the rotor 202 as surplus rotation, does not perform the driving by the correction driving pulse P 2 , and maintains the rank of the main driving pulse P 1 without changing the same. When a pattern (0, 1, 0) has been continuously generated by a predetermined number of times, the control circuit 106 determines that driving energy is left to allow the main driving pulse P 1 to be down (pulse down) by one rank ((a) of FIG. 3 ).

In the case of a pattern (1, 1, 0), when the induced signal VRs exceeding the second reference threshold voltage Vcomp 2 has been generated in the third section T 3 (when a determination value through the second reference threshold voltage Vcomp 2 is “1”), the control circuit 106 determines the rotation of the rotor 202 as slightly low rotation, does not perform the driving by the correction driving pulse P 2 , and performs pulse control of maintaining the rank of the main driving pulse P 1 without changing the same ((b) of FIG. 3 ). When the induced signal VRs exceeding the second reference threshold voltage Vcomp 2 has not been generated in the third section T 3 (when a determination value through the second reference threshold voltage Vcomp 2 is “0”), the control circuit 106 determines that the rotor 202 is in an intermediate stationary state with a heavy load, and allows the main driving pulse P 1 to be up (pulse up) by one rank after performing the driving by the correction driving pulse P 2 ((e) of FIG. 3 ).

In the case of a pattern (1/0, 0, 1), the control circuit 106 determines the rotation of the rotor 202 as completely low rotation, and allows the main driving pulse P 1 to be up (pulse up) by one rank without performing the driving by the correction driving pulse P 2 ((c) of FIG. 3 ).

In the case of a pattern (1, 0, 0), the control circuit 106 determines that the rotor 202 is stationary in an intermediate position, and allows the main driving pulse P 1 to be up by one rank after performing the driving by the correction driving pulse P 2 ((d) of FIG. 3 ).

In the case of a pattern (1/0, 0, 0), the control circuit 106 determines the rotation of the rotor 202 as non-rotation, and allows the main driving pulse P 1 to be up by one rank after performing the driving by the correction driving pulse P 2 ((f) of FIG. 3 ).

FIG. 4 is a flowchart illustrating the operations of the stepping motor control circuit and the analog electronic watch according to the embodiment of the invention, which is a flowchart mainly illustrating the processing of the control circuit 106 .

Hereinafter, the operations of the stepping motor control circuit and the analog electronic watch according to the embodiment of the invention will be described in detail with reference to FIGS. 1 to 4 .

In FIG. 1 , the oscillating circuit 104 generates a reference clock signal with a predetermined frequency, and the divider circuit 105 divides the signal generated by the oscillating circuit 104 to generate the watch signal serving as the reference of the watch, and outputs the watch signal to the control circuit 106 .

The control circuit 106 performs a time counting operation by counting the watch signal. First, the control circuit 106 sets a rank “n” of the main driving pulse P 1 n and the number N of times of repetition to “0” (Step S 401 of FIG. 4 ), and outputs a control signal such that the stepping motor 102 is rotated by the main driving pulse P 10 with a minimum pulse width (Steps S 402 and S 403 ).

The stepping motor driving pulse circuit 107 rotates the stepping motor 102 by using the main driving pulse P 10 in response to the control signal from the control circuit 106 . The stepping motor 102 is rotated by the main driving pulse P 10 to rotate the time hands (not shown). In this way, when the stepping motor 102 is normally rotated, the current time display and the like is performed through the time hands.

The rotation detecting circuit 108 outputs a detection signal to the detection time comparing/determining circuit 109 whenever detecting the induced signal VRs of the stepping motor 102 exceeding the first reference threshold voltage Vcomp 1 . Then, the detection time comparing/determining circuit 109 determines the sections T 1 to T 3 , in which the induced signal VRs exceeding the first reference threshold voltage Vcomp 1 has been detected, based on the detection signal from the rotation detecting circuit 108 , and notifies the control circuit 106 of a determination value “1” or “0” in each of the sections T 1 to T 3 .

The control circuit 106 determines patterns (including a determination value in the first section T 1 , a determination value in the second section T 2 , and a determination value in the third section T 3 ) (VRs patterns), which represent the rotation states, based on the determination value from the detection time comparing/determining circuit 109 .

In the case in which the determination value is “1” in the first and second sections T 1 and T 2 of the VRs pattern as a result of the driving by the main driving pulse P 10 , that is, when the VRs pattern is (1, 1, 1/0) (Steps S 404 and S 405 ), when the maximum value Vmax of the induced signal VRs in the third section T 3 exceeds the second reference threshold voltage Vcomp 2 (Step S 406 ), the control circuit 106 determines the rotation of the rotor 202 as the slightly low rotation other than the intermediate stationary state, maintains the rank of the main driving pulse P 1 without changing the same, resets the number N of times to “0”, and then returns to the process step S 402 (Step S 407 ).

When it is determined that the induced signal VRs in the third section T 3 does not exceed the second reference threshold voltage Vcomp 2 in the process step S 406 (in the case of the pattern (1, 1, 0) representing the intermediate stationary state with the heavy load in ((e) of FIG. 3 ), the control circuit 106 controls the stepping motor driving pulse circuit 107 such that the stepping motor 102 is driven by the correction driving pulse P 2 (Step S 416 ). The stepping motor driving pulse circuit 107 rotates the stepping motor 102 by the correction driving pulse P 2 in response to the control of the control circuit 106 .

When the rank “n” of the main driving pulse P 1 is the maximum rank_nmax, the control circuit 106 resets the number N of times to “0”, and then returns to the process step S 402 (Steps S 414 and S 415 ). When the rank “n” of the main driving pulse P 1 is not the maximum rank_nmax, the control circuit 106 resets the number N of times to “0” while allowing the rank “n” of the main driving pulse P 1 to be up by one rank, and then returns to the process step S 402 (Steps S 414 and S 417 ).

In the case in which it is determined that the induced signal VRs in the second section T 2 does not exceed the first reference threshold voltage Vcomp 1 in the process step S 405 (i.e., the determination values of the sections T 1 and T 2 are (1, 0)), when the determination value of the third section T 3 is determined as “1”, that is, when the VRs pattern is (1, 0, 1), the control circuit 106 proceeds to the process step S 414 to perform the following pulse up control (Step S 413 ) ((c) of FIG. 3 ).

When the determination value of the third section T 3 is determined as “0” in the process step S 413 , that is, when the VRs pattern is (1, 0, 0), the control circuit 106 proceeds to the process step S 416 to perform the following driving by the correction driving pulse P 2 and pulse up control ((d) of FIG. 3 ).

In the case in which the determination value of the first section T 1 is “0” and the determination value of the second section T 2 is “1” in the process step S 404 (Step S 408 ), when the rank “n” of the main driving pulse P 1 is the minimum value “0”, the control circuit 106 proceeds to the process step S 407 (Step S 409 ). When the rank “n” of the main driving pulse P 1 is not the minimum value “0”, the control circuit 106 adds “1” to the number N of times (Step S 410 ).

When the number N of times has reached a predetermined number of times (PCD) in the process step S 410 , the control circuit 106 resets the number N of times to “0” while allowing the rank “n” of the main driving pulse P 1 to be down by one rank, and then returns to the process step S 402 . When the number N of times has not reached the predetermined number of times, the control circuit 106 immediately returns to the process step S 402 (Steps S 411 and S 412 ).

When the determination value of the second section T 2 is “0” in the process step S 408 , the control circuit 106 proceeds to the process step S 413 and performs the above process.

As described above, in the stepping motor control circuit and the analog electronic watch according to the embodiment of the invention, the generation time of the induced signal VRs is divided into a plurality of sections (in the present embodiment, the first section T 1 , the second section T 2 and the third section T 3 ), the induced signal VRs is compared with the first reference threshold voltage Vcomp 1 in each section, and the rotation state of the rotor is determined based on the patterns of the determination values, so that the driving pulse is controlled. For example, patterns (1/0, 1, 1/0) and (1/0, 0, 1) represent a rotation state and the pattern (1/0, 0, 0) represent a non-rotation state.

The 2 pole PM type stepping motor is in the rotation state or non-rotation state according to the driving pulse as described above. However, when force acting on the rotor is significantly changed as in the case of calendar feed or variation in supply voltage, a case may occur in which the rotor 202 infrequently stays in an intermediate position different from a stationary position, so called, a case may occur in which the rotor 202 is in an intermediate stationary position. Such a state typically represents the pattern (1, 0, 0) in the VRs pattern determination, and represents the VRs pattern as the same as that of the non-rotation state. However, such a state may represent the pattern (1, 1, 0) in the load state and represent the VRs pattern as the same as that of the rotation state. That is, although rotation cannot be normally performed, a case may occur in which it is erroneously determined as the rotor 202 having been rotated.

However, according to the present embodiment, the detection time comparing/determining circuit 109 is provided to compare the voltage value and the output time of the induced signal VRs generated by the vibration of the rotor 202 and store the voltage value and the output time as the VRs patterns. Separately from the rotation state and the non-rotation state, when variation in the rotor load is severe, the second reference threshold voltage Vcomp 2 is provided only in the third section T 3 of the VRs pattern in order to determine the intermediate stationary state infrequently occurring, and the energy of the driving pulse is controlled according to a specific VRs pattern and a VRs voltage value of the third section T 3 .

That is, in the case of the intermediate stationary, by paying attention to the fact that the rotor 202 does not completely vibrate in the third section T 3 , the second reference threshold voltage Vcomp 2 having a level lower than that of the first reference threshold voltage Vcomp 1 is set only in the third section T 3 , and the induced signal VRs detected in the third section T 3 is determined using the second reference threshold voltage Vcomp 2 only when the determination values of the first section T 1 and the second section T 2 are “1”. As a result of the determination, when the induced signal VRs of the third section T 3 is equal to or larger than the second reference threshold voltage Vcomp 2 , the driving by the correction driving pulse P 2 is not performed. However, when the induced signal VRs of the third section T 3 is smaller than the second reference threshold voltage Vcomp 2 , the driving by the correction driving pulse P 2 is performed.

Consequently, according to the stepping motor control circuit of the present embodiment, the rotation state of the stepping motor 102 can be accurately determined and a reliable and stable correction operation can be performed.

Further, according to the analog electronic watch of the present embodiment, the rotation state of the stepping motor can be accurately determined and a reliable and stable correction operation can be performed, so that hand movement can be accurately performed.

Further, it is possible to cope with various types of movement such as a function system with a calendar load from a straight system with a small load, and battery mounting in which a voltage is changed, without changing the specification of an integrated circuit (IC) or a motor which constitutes the stepping motor control circuit 101 .

Further, according to the embodiment, since the energy of each main driving pulse P 1 is changed, the pulse widths thereof may be different from each other. However, the driving energy can be changed by changing a pulse voltage and the like.

Furthermore, the example of the calendar function has been described as an example of a widely fluctuating load. However, it is possible to use various types of loads such as loads which cause a predetermined operation in a character provided in the display unit to inform of a predetermined time.

In addition, the electronic watch has been described as an application of the stepping motor. However, the invention can be applied to an electronic apparatus using a motor.

The stepping motor control circuit according to the invention can be applied to various electronic apparatuses using the stepping motor.

Moreover, the electronic watch according to the invention can be applied to various analog electronic watches including an analog electronic wrist watch having a calendar function, and an analog electronic watch having various calendar functions such as an analog electronic table clock having a calendar function.