Electronic apparatus and control method for electronic apparatus

Abstract: The invention provides a method and apparatus to detect the power-generating state of a power generating unit in a power-saving mode and to positively switch to a normal operation mode. The power-generation voltage of a power generating unit is detected in a power-generation-voltage detection process (steps S2 and S12), and the operation mode of a unit to be driven is switched between a normal operation mode and a power-saving mode according to the power-generating state of the power generating unit or according to the manipulation state of manipulation means in an operation-mode control process (steps S3 to S7, and S10 to S15). In a limiter control process (step S8), the operation of a limiter is disabled when the operation mode of the unit to be driven is the power-saving mode. As a result, it is possible in the power-saving mode that the power-generating state of the power generating unit is detected and the operation mode is positively switched to the normal operation mode in the power-generation-voltage detection process. In a limiter-operation disablement release process (step S13), the limiter is again operated after the operation mode is switched to the normal operation mode.

Description: The present invention relates to electronic apparatuses and control methods for electronic apparatuses, and more particularly, to the control technology of electronically controlled time-measurement apparatuses including a power generating mechanism. In recent years, compact electronic time-measurement apparatuses, such as wristwatches, which include a power generating unit such as a solar cell and operate without replacing a battery cell, have been implemented. These time-measurement apparatuses have a function for accumulating the power generated by the power generating unit in a large-capacity capacitor, and time is indicated by the power discharged from the capacitor while power is not generated. Therefore, a stable operation is allowed for a long period of time without a battery. With troublesome work of replacing the cell and how to discard a used cell being taken into account, it is expected that many electronic time-measurement apparatuses will include a power generating unit in the near future. Such an electronic time-measurement apparatus having a power generating unit is provided with a limiter circuit for limiting an applied voltage such that the power-generation voltage of the power generating unit does not exceed the dielectric strength of a power source unit having a power accumulating function, such as a large-capacity capacitor, and such that the power source voltage of the power source unit to be applied to a time-indication circuit does not exceed the dielectric strength of the time-indication circuit. This limiter circuit electrically separates the power generating unit from the power source unit at the preceding stage of the power source unit, short-circuits the output of the power supply unit so as not to send the power-generation voltage to subsequent stages, and electrically separates the power source unit from the time-indication circuit at the subsequent stage of the power supply unit, in order to prevent a power-generation voltage of the power generating unit exceeding the dielectric strength of the power source unit from being applied to the power source unit and to prevent a power-source voltage exceeding the dielectric strength of the time-indication circuit from being applied to the time-indication circuit. In the electronic time-measurement apparatus including the power generating unit, when the power generating unit is in a non-power-generating state for a predetermined period of time or more, that state is detected and the operation mode is switched from a normal operation mode (indication mode) to a power-saving mode, where time is not indicated, in order to supply stable power. When the limiter circuit is in an operation state (limiter-on state), since the electrical information of the power generating unit is not sent at all to subsequent stages, the power generating state of the power generating unit cannot be detected after the operation mode is switched to the power-saving mode, and therefore, the operation mode cannot be returned to the normal operation mode. US 4,653,931 discloses a timepiece having a primary power source for converting externally supplied energy to electrical energy for powering a timekeeping circuitry. A secondary power source stores the energy from the primary power source and powers the timekeeping circuitry. A power controller, coupled to the timekeeping circuitry, primary power source and secondary power source controls the source of power of the timekeeping circuitry. Accordingly, it is an object of the present invention to provide an electronic apparatus and a control method for an electronic apparatus which allow the operation mode to be positively switched to a normal operation mode by detecting the power generating state of a power generating unit in a power-saving mode. According to a first aspect of the present invention, there is provided a portable electronic apparatus including power generating means for generating power by converting a first energy to a second energy, which is electrical energy; power source means for accumulating the electrical energy obtained by the power generation; means to be driven by electrical energy supplied from the power source means; power-generation detection means for determining whether the power generating means is generating power or not; voltage detection means for determining whether the power-generation voltage at the power generating means or the accumulated voltage at the power source means exceeds a predetermined reference voltage; limiter means for limiting the voltage of the electrical energy supplied to the power source means to a predetermined reference voltage, according to the detection result of the voltage detection means; operation-mode control means for switching the operation mode of the means to be driven between a normal operation mode and a power-saving mode, according to the detection result of the power-generation detection means; and limiter control means for disabling the operation of the limiter means when the operation mode of the means to be driven is the power-saving mode. Preferably, the means to be driven in the structure described in Claim 1 is time-indication means for indicating time. preferably, the operation-mode control means stops the time-indication operation performed by the time-indication means in the power-saving mode; and makes the time-indication means indicate the current time and restart the time-indication operation when the power-saving mode is switched to the normal operation mode. Preferably, the time-indication means includes an analog indicator for performing analog time indication and indicator driving means for driving the analog indicator; and the operation-mode control means comprises operation stopping means for stopping the operation of the indicator driving means in the power-saving mode. Preferably, the limiter control means includes operation disablement releasing means for releasing the operation disablement of the limiter means when the operation mode of the means to be driven is switched from the power-saving mode to the normal operation mode. Preferably, the operation-mode control means switches the operation mode according to the detection result of the voltage detection means. Preferably, manipulation means are provided with which the user performs various manipulations, and is characterized in that the operation-mode control means switches the operation mode according to the manipulation state of the manipulation means. According to a second aspect of the present invention, there is provided a control method for a portable electronic apparatus including a power generating unit for generating power by converting a first energy to a second energy, which is electrical energy, a power source unit for accumulating the electrical energy obtained by the power generation, a unit to be driven by the electrical energy, and a limiter unit for limiting the voltage of the electrical energy supplied from the power generating unit to the power source unit to a predetermined reference voltage, said control method includes a power-generation detection step for determining whether the power generating unit is generating power or not; a voltage detection step for determining whether the power-generation voltage at the power generating unit or the accumulated voltage at the power source unit exceeds a predetermined reference voltage; an operation-mode control step for switching the operation mode of the unit to be driven between a normal operation mode and a power-saving mode, according to the detection result in the power-generation detection step; and a limiter control step for disabling the operation of the limiter unit when the operation mode of the unit to be driven is the power-saving mode. Preferably, the unit to be driven is a time-indication unit including an analog indicator for performing analog time indication and an indicator driving unit for driving the analog indicator; and the operation-mode control step comprises an operation stopping step for stopping the operation of the indicator driving unit. Preferably, the limiter control step includes an operation disablement releasing step for releasing the operation disablement of the limiter unit when the operation mode of the unit to be driven is switched from the power-saving mode to the normal operation mode. Embodiments of the invention will now be described in more detail and by way of further example only, and with reference to the accompanying drawings, in which:- Fig. 1 is a view showing an outlined structure of a time-measurement apparatus according to an embodiment of the present invention. Fig. 2 is a functional block diagram of a control section and its peripheral structure according to the embodiment. Fig. 3 is a view showing the principle of a limiter circuit. Fig. 4 is an operational flowchart in the embodiment. Fig. 5 is a block diagram showing details of a peripheral circuit of a mode storage section 94 in a time-measurement apparatus 1 shown in Fig. 2. A preferred embodiment of the present invention will be described below by referring to the drawings. [1] Outlined structure Fig. 1 shows an outlined structure of a time-measurement apparatus 1 according to an embodiment of the present invention. The time-measurement apparatus 1 is a wristwatch used by the user by winding a watchband connected to the body of the apparatus on a wrist. The time-measurement apparatus 1 according to the present embodiment is schematically formed of a power generating section A for generating alternating electrical power; a power source section B for rectifying the alternating voltage sent from the power generating section A, for accumulating a boosted voltage, and for supplying electrical power to each component section; a control section 23 which is provided with a power-generating-state detection section 91 (see Fig. 2) and detects the power-generating state of the power generating section A, for controlling the entire apparatus according to the detection result; a second-hand moving mechanism CS for driving a second hand 55 with the use of a stepper motor 10; an hour-hand-and-minute-hand moving mechanism CHM for driving a minute hand and an hour hand with the use of a stepper motor; a second-hand driving section 30S for driving the second-hand moving mechanism CS according to a control signal sent from the control section 23; an hour-hand-and-minute-hand driving section 30HM for driving the hour-hand-and-minute-hand moving mechanism CHM according to a control signal sent from the control section 23; and an external input unit 100 (see Fig. 2) for performing a specifying operation such that the operation mode of the time-measurement apparatus 1 is switched from a time-indication mode to a calendar correction mode, to a time correction mode, or forcibly to a power-saving mode, described later. The control section 23 switches, according to the power-generating state of the power generating section A, between the indication mode (normal operation mode) in which the moving mechanisms CS and CHM are driven to perform time indication and the power-saving mode in which power is saved by stopping power from being sent to the second-hand moving mechanism CS and the hour-hand-and-minute-hand moving mechanism CHM. When the user holds the time-measurement apparatus 1 by hand and shakes it to forcibly generate power, if a predetermined power-generation voltage is detected, the power-saving mode is forcibly switched to the indication mode. [2] Detailed structure Each component section of the time-measurement apparatus 1 will be described below. The control section 23 will be described later by the use of functional blocks. [2.1] Power generating section The power generating section A will be described first. The power generating section A is formed of a power generating unit 40, an oscillating weight 45, and a speed-increasing gear 46. As the power generating unit 40, an electromagnetic-induction-type alternating power generating unit is employed in which a power generating rotor 43 rotates inside a power generating stator 42 and electrical power induced in a power generating coil 44 connected to the power generating stator 42 can be output externally. The oscillating weight 45 functions as means for transferring kinetic energy to the power generating rotor 43. The movement of this oscillating weight 45 is transferred to the power generating rotor 43 through the speed-increasing gear 46. This oscillating weight 45 can turn in the wristwatch-type time-measurement apparatus 1 by catching the movement of an arm of the user. Therefore, energy expended by the user's everyday activities is used for power generation and the time-measurement apparatus 1 is driven by the electrical power. [2.2] Power source section The power source section B will be described next. The power source section B is formed of a limiter circuit LM for preventing an excessive voltage from being applied to a subsequent circuit, a diode 47 serving as a rectifying circuit, a large-capacity capacitor 48, and a buck-boost converting circuit 49. As shown in Fig. 1, the limiter circuit LM, the rectifying circuit (diode 47), and the large-capacity capacitor 48 are disposed in that order from the power generating section A. They can be disposed in the order of the rectifying circuit (diode 47), the limiter circuit LM, and the large-capacity capacitor 48. The buck-boost converting circuit 49 increases or reduces a voltage in multiple steps with the use of a plurality of capacitors 49a, 49b, and 49c. According to a control signal 11 sent from the control section 23, a voltage sent to the second-hand driving section 30S and the hour-hand-and-minute-hand driving section 30HM can be adjusted. The power source section B uses Vdd (a higher voltage) as a reference voltage (GND), and Vss (a lower voltage) as a power voltage. An example of the limiter circuit LM will be described below by referring to Fig. 3. The limiter circuit LM functions in an equivalent manner to a switch for short-circuiting the power generating section A, as shown in Fig. 3. When the power-generation voltage VGEN of the power generating section A exceeds a predetermined limit reference voltage VLM, the limiter circuit is turned on (closed). The switch portion of the limiter circuit LM is formed of a transistor, and it is controlled ON and OFF by a control signal output from a central control circuit 93 shown in Fig. 2. As a result, the power generating section A is electrically separated from the large-capacity capacitor 48. In the present embodiment, the power generating section A is short-circuited to control the limiter. The path of the power generating section A may be opened to control the limiter. With this operation, an excessive power-generation voltage VGEN is not applied to the large-capacity capacitor 48. A power-generation voltage VGEN exceeding the dielectric strength of the large-capacity capacitor is prevented from being applied, and thereby damage of the large-capacity capacitor 48 is avoided and further damage of the time-measurement apparatus 1 is avoided. A diode shown in Fig. 3 serves as a reverse-current-prevention diode, and prevents the large-capacity capacitor 48 from being short-circuited when the limiter circuit LM is on. The limiter circuit LM may be configured such that the connection of the power generating section A and the large-capacity capacitor 48 is opened by a switch. [2.3] Hand moving mechanisms The hand moving mechanisms CS and CHM will be described below. [2.3.1] Second-hand moving mechanism The second-hand moving mechanism CS will be described first. The stepper motor 10 used in the second-hand moving mechanism CS is also called a step-servo motor, which is used as an actuator in digital control apparatuses in many cases, and is driven by a pulse signal. Many compact and lightweight stepper motors have been employed as actuators in portable, compact electronic apparatuses and information apparatuses in recent years. Time-measurement apparatuses, such as electronic time-measurement units, time switches, and chronographs, are representative of such electronic apparatuses. The stepper motor 10 according to the present embodiment is provided with a driving coil 11 for generating magnetic power by a driving pulse sent from the second-hand driving section 30S, a stator 12 excited by this driving coil 11, and a rotor 13 which rotates inside the stator 12 by an excited magnetic field. The stepper motor 10 is of a PM type (permanent-magnet rotation type), in which the rotor 13 is formed of a disc-shaped two-pole permanent magnet. The stator 12 is provided with a magnetic saturation section 17 such that different magnetic poles are generated at phases (poles) 15 and 16 around the rotor 13 by the magnetic power generated by the driving coil 11. To specify the rotation direction of the rotor 13, an inner notch 18 is provided at an appropriate position in the inner periphery of the stator 12. Cogging torque is generated to stop the rotor 13 at an appropriate position. The rotation of the rotor 13 in the stepper motor 10 is transferred to the second hand 55 through a wheel train 50 formed of an intermediate second wheel 51 and a second wheel (second-indicator wheel) 52 engaged with the rotor 13 through a pinion, and seconds indication is performed. [2.3.2] Hour-hand-and-minute-hand moving mechanism The hour-hand-and-minute-hand moving mechanism CHM will be described next. A stepper motor 60 used in the hour-hand-and-minute-hand moving mechanism CHM has the same structure as the stepper motor 10. The stepper motor 60 according to the present embodiment is provided with a driving coil 61 for generating magnetic power by a driving pulse sent from the hour-hand-and-minute-hand driving section 30HM, a stator 62 excited by this driving coil 61, and a rotor 63 which rotates inside the stator 62 by an excited magnetic field. The stepper motor 60 is of the PM type (permanent-magnet rotation type), in which the rotor 63 is formed of a disc-shaped two-pole permanent magnet. The stator 62 is provided with a magnetic saturation section 67 such that different magnetic poles are generated at phases (poles) 65 and 66 around the rotor 63 by the magnetic power generated by the driving coil 61. To specify the rotation direction of the rotor 63, an inner notch 68 is provided at an appropriate position in the inner periphery of the stator 62. Cogging torque is generated to stop the rotor 63 at an appropriate position. The rotation of the rotor 63 in the stepper motor 60 is transferred to each hand through a wheel train 70 formed of a second wheel 71, a third wheel 72, a center wheel (minute-indicator wheel) 73, a minute wheel 74, and a hour wheel (hour-indicator wheel) 75 engaged with the rotor 63 through a pinion. The center wheel 73 is connected to the minute hand 76, and the hour wheel 75 is connected to the hour hand 77. With these hands, the hour and the minute are indicated by the rotation of the rotor 63. Although not shown in the figure, a transfer system (to indicate the day, for example, an intermediate hour wheel, an intermediate data wheel, a date indicator driving wheel, and a date indicator) for indicating the year, month, and day (calendar) can be, of course, connected to the wheel train 70. In this case, a calendar-corrector wheel train (such as a first calendar corrector transfer wheel, a second calendar corrector transfer wheel, a calendar corrector wheel, and a date indicator) can further be provided. [2.4] Second-hand driving section and hour-hand-and-minute-hand driving section The second-hand driving section 30S and the hour-hand-and-minute-hand driving section 30HM will be described next. In this case, since the second-hand driving section 30S and the hour-hand-and-minute-hand driving section 30HM have the same structure, only the second-hand driving section 30S will be described. The second-hand driving section 30S sends various driving pulses to the stepper motor 10 under the control of the control section 23. The second-hand driving section 30S is provided with a bridge circuit formed of a p-channel MOS 33a and an n-channel MOS 32a connected in series and a p-channel MOS 33b and an n-channel MOS 32b. The second-hand driving section 30S is also provided with rotation detecting resistors 35a and 35b connected in parallel to the p-channel MOSs 33a and 33b, and p-channel sampling MOSs 34a and 34b for sending chopper pulses to the resistors 35a and 35b. Therefore, when control pulses having different polarities and different pulse widths are applied from the control section 23 to the gate electrodes of the MOSs 32a, 32b, 33a, 33b, 34a, and 34b at various timings, driving pulses having different polarities are sent to the driving coil 11 or a detection pulse for exciting an induction voltage used for detecting the rotation of the rotor 13 and for detecting a magnetic field is sent. [2.5] Control section The structure of the control section 23 will be descried next by referring to Fig. 2. Fig. 2 shows the control section 23 and the functional blocks of its peripheral structure. The control section 23 is schematically formed of a pulse combination circuit 22, a mode setting section 90, a time-information storage section 96, and a driving control circuit 24. The pulse combination circuit 22 is provided with an oscillating circuit for oscillating a reference pulse having a stable frequency with the use of a reference oscillation source 21 such as a crystal resonator, and a combination circuit for combining the reference pulse and scaled pulses obtained by scaling the reference pulse to generate pulse signals having different pulse widths and different timings. The mode setting section 90 is formed of the power-generating-state detection section 91, a setting-switching section 95 for switching a setting used for detecting a power-generating state, a voltage detection circuit 92 for detecting a charged voltage Vc of the large-capacity capacitor 48, the central control circuit 93 for controlling the time-indication mode according to the power-generating state and for controlling a boost magnification according to the charged voltage, and a mode storage section 94 for storing the mode. The power-generating-state detection section 91 is provided with a first detection circuit 97 for comparing the generated voltage Vgen of the power generating unit 40 with a specified voltage Vo to determine whether power generation is detected or not, and a second detection circuit 98 for comparing a specified time period To with a power-generation lasting time Tgen for which the generated voltage Vgen obtained is equal to or higher than a specified voltage Vbas which is much lower than the specified voltage Vo to determine power generation is detected or not. When either condition is satisfied in the first and second detection circuits 97 and 98, the power-generating-state detection section 91 determines that a power-generating state is detected. The specified voltages Vo and Vbas are negative voltages against Vdd (= GND), and indicate potential differences from Vdd. The specified voltage Vo and the specified time period To can be switchably controlled by the setting-switching section 95. The setting-switching section 95 changes the settings Vo and To of the first and second detection circuits 97 and 98 in the power-generation detection circuit 91 when the indication mode is switched to the power-saving mode. In the present embodiment, settings Va and Ta for the indication mode are set lower than settings Vb and Tb for the power-saving mode. Therefore, to switch from the power-saving mode to the indication mode, larger power generation is required. The required degree of power generation is not sufficient if the time-measurement apparatus 1 is always carried. The user needs to forcibly perform charging by shaking their hand to obtain a large power. In other words, the settings Vb and Tb are set for the power-saving mode such that forced charging caused by hand shaking can be detected. The central control circuit 93 is provided with a non-power-generating-time measuring circuit 99 for measuring a non-power-generating time Tn for which power generation is not detected in the first and second detection circuits 97 and 98. When the non-power-generating time Tn lasts for a predetermined specified time period or more, the indication mode is switched to the power-saving mode. On the other hand, when the power-generating-state detection section 91 determines that the power generating section A is in the power-generating state and the charged voltage VC of the large-capacity capacitor 48 is sufficient, the power-saving mode is switched to the indication mode. In this case, in the power-saving mode, when the limiter circuit LM is operated to be turned on (closed), the power generating section A is in a short-circuit state. Since the power-generating-state detection section 91 cannot detect power generation even if the power generating section A is in the power-generating state, the power-saving mode cannot be switched to the indication mode. Therefore, in the present embodiment, when the operation mode is the power-saving mode, the limiter circuit LM is set to the off (open) state irrespective of the power-generating state of the power generating section A so that the power-generating-state detection section 91 can positively detect the power-generating state of the power generating section A. Since the power source section B is provided with the buck-boost converting circuit 49 in the present embodiment, if the charged voltage VC is some degree lower, the power source voltage is increased with the use of the buck-boost converting circuit 49 to allow the hand moving mechanisms CS and CHM to be driven. Conversely, if the charged voltage VC is some degree higher and is higher than the driving voltages of the hand moving mechanisms CS and CHM, the power source voltage is reduced with the use of the buck-boost converting circuit 49 to allow the hand moving mechanisms CS and CHM to be driven. The central control circuit 93 determines the voltage magnification according to the charged voltage VC and controls the buck-boost converting circuit 49. If the charged voltage VC is too low, however, a power source voltage required for operating the hand moving mechanisms CS and CHM cannot be obtained even if the charged voltage is increased. In such a case, when the power-saving mode is switched to the indication mode, correct time indication cannot be performed and in addition, power is wasted. Therefore, in the present embodiment, the charged voltage VC is compared with the predetermined specified voltage Vo to determine whether the charged voltage VC is sufficient. This determination is a condition for switching the power-saving mode to the indication mode. The central control circuit 93 is provided with a power-saving-mode counter 101 for determining whether a predetermined specifying operation of forced switching to the power-saving mode is performed within a predetermined time period when the user manipulates the external input unit 100, and a second-hand-position counter 102 which always counts cyclically and in which the second-hand position obtained when the count is zero corresponds to a predetermined power-saving-mode indication position (for example, the position of one o'clock). The mode specified in this way is stored in the mode storage section 94, and the information is sent to the driving control circuit 24, the time-information storage section 96, and the setting-switching section 95. When the indication mode is switched to the power-saving mode, the driving control circuit 24 stops sending pulse signals to the second-hand driving section 30S and the hour-hand-and-minute-hand driving section 30HM to stop the operations of the second-hand driving section 30S and the hour-hand-and-minute-hand driving section 30HM. Then, the motor stops rotating and time indication is halted. The time-information storage section 96 is, more precisely, formed of an up/down counter (not shown). When the indication mode is switched to the power-saving mode, the time-information storage section 96 receives a reference signal generated by the pulse combination circuit 22, starts time measurement, and increases the count to measure a power-saving-mode lasting time. When the power-saving mode is switched to the indication mode, the count of the up/down counter is reduced. While the count is being reduced, the driving control circuit 24 sends fast-feed pulses to the second-hand driving section 30S and the hour-hand-and-minute-hand driving section 30HM. When the count of the up/down counter reaches zero, that is, when the fast-feed hand moving time corresponding to the power-saving-mode lasting time, which also corresponds to the fast-feed-hand-moving elapsed time, elapses, a control signal for stopping the sending of the fast-feed pulses is generated and sent to the second-hand driving section 30S and the hour-hand-and-minute-hand driving section 30HM. As a result, time indication again shows the current time. As described above, the time-information storage section 96 also includes the function for recovering the current time on a re-indicated time indicator. The driving control circuit 24 generates driving pulses for a mode according to various pulses output from the pulse combination circuit 22. In the power-saving mode, the sending of driving pulses is stopped. Immediately after the power-saving mode is switched to the indication mode, the fast-feed pulses, having a short pulse interval, are sent to the second-hand driving section 30S and the hour-hand-and-minute-hand driving section 30HM as driving pulses, in order to recover the current time on the re-indicated time indicator. When sending of the fast-feed pulses is finished, driving pulses having a normal pulse interval are sent to the second-hand driving section 30S and the hour-hand-and-minute-hand driving section 30HM. [3] Operation in the present embodiment Fig. 4 is a flowchart of the operation of the time-measurement apparatus according to the present invention. The control circuit 23 determines whether the operation mode is the power-saving mode or not (in a step S1). When it is determined in the determination performed in the step S1 that the operation mode is the power-saving mode (the reply is Yes in the step S1), the processing proceeds to a step S8, described later. When it is determined in the determination performed in the step S1 that the operation mode is not the power-saving mode, that is, that the operation mode is the indication mode, which is the normal operation mode (the reply is No in the step S1), the central control circuit 93 determines according to the detection signal of the power-generating-state detection unit 91 whether there is an electromotive force, that is, whether the power generating unit 40 is generating power (in a step S2). When it is determined in the determination performed in the step S2 that there is an electromotive force (the reply is Yes in the step S2), the processing proceeds to a step S15, time indication continues (in a step S15 , and then the processing returns to the step 1 again. When it is determined in the determination performed in a step S2 that there is no electromotive force, that is, that power generation is not performed (the reply is No in the step S2 ), the non-power-generating-time measuring circuit 99 increases the count of the non-power-generating time Tn (in the step S3). The central control circuit 93 determines whether the non-power-generating time Tn lasts longer than the predetermined specified time period (in a step S4). When it is determined in the determination performed in the step S4 that the non-power-generating time Tn does not exceed the predetermined specified time period (the reply is No in the step S4), the processing proceeds to the step S2 again and the processes from the step S2 to the step S4 are repeated. When it is determined in the determination performed in the step S4 that the non-power-generating time Tn lasts longer than the predetermined specified time period (the reply is Yes in the step S4), the count of the second-hand-position counter 102, which always counts cyclically, is increased (in a step S5), and it is determined (in a step S6) whether the count of the second-hand-position counter 102 is zero, that is, whether the second hand reaches the predetermined power-saving-mode indication position (for example, the position of one o'clock). When it is determined in the determination performed in the step S6 that the count of the second-hand-position counter 102 is not zero, that is, that the second hand does not reach the predetermined power-saving-mode indication position (for example, the position of one o'clock) (the reply is No in the step S6), the processing proceeds to the step S5 again, and the count of the second-hand-position counter 102 is increased. When it is determined in the determination performed in the step S6 that the count of the second-hand-position counter 102 is zero, that is, that the second hand reaches the predetermined power-saving-mode indication position, the second hand is stopped at the current position, time indication is halted, and the operation mode is switched to the power-saving mode (in a step S7 ). As a result, since the user notices that the second hand is stopped at the power-saving-mode indication position, the user easily understands that the time-measurement apparatus 1 is in the power-saving mode. When a power-saving-mode control signal sent from the mode storage section 94 is set to an "H" level, the limiter circuit LM is turned off (opened), and the power-generating-state detection section 91 is allowed to positively detect the power-generating state of the power generating section A. Then, the central control circuit 93 controls the buck-boost converting circuit 49 so as to stop boost control (in a step S9). The reason why the boost control is stopped in the power-saving mode will be described here. In general, to maintain the operation voltage of the time-measurement apparatus within an appropriate range for a long period with limited energy, the power source unit needs to control the buck-boost converting circuit 49 for the boost control. In the indication mode, if the power source voltage is lowered and the driving voltage for moving the hands becomes lower than a predetermined driving voltage, the boost control is performed to increase the driving voltage to continue moving the hands. On the other hand, in the power-saving mode, to perform time recovery processing (in a step S14), described later, it is necessary at a voltage level lower than a time-recovery-possible voltage to suppress energy consumption as much as possible and to perform charging until the voltage level reaches a voltage at which the time-recovery processing can promptly be performed when the power-saving mode is switched to the indication mode. Therefore, in the present embodiment, the boost control is stopped in the power-saving mode. The time-information storage section 96 increases the time-information count corresponding to the elapsed time in the power-saving mode in order to perform the time-recovery processing (in the step S14), described later, and then determines (in a step S11) whether the user manipulates the external input unit (the crown and a position detection unit) to switch the operation mode of the time-measurement apparatus 1 to the time correction mode. When it is determined in the determination performed in the step S11 that the user does not manipulate the external input unit 100 to switch to the time correction mode (the reply is No in the step S11), it is determined (in a step S12) whether the power generating unit 40 is generating electrical power with an electromotive force equal to or more than the predetermined electromotive force used for determining whether the operation mode is switched to the indication mode. When it is determined in the determination performed in the step S12 that the power generating unit 40 is not generating electrical power with an electromotive force equal to or more than the predetermined electromotive force used for determining whether the operation mode is switched to the indication mode, that is, when the power-saving mode needs to continue, the processing proceeds to the step S10 again and the time-information count corresponding to the elapsed time in the power-saving mode is increased. When it is determined in the determination performed in the step S12 that the power generating unit 40 is generating electrical power with an electromotive force equal to or more than the predetermined electromotive force used for determining whether the operation mode is switched to the indication mode, that is, when the operation mode needs to be switched to the indication mode (the reply is Yes in the step S12), the control of the limiter circuit LM is restarted (in a step S13), the operation mode is switched from the power-saving mode to the indication mode, and the time-recovery processing is performed (in the step S14) in which the current time is recovered according to the count of the time-information storage section 96. Then, time indication continues (in a step S15), the processing proceeds to the step S1 again, and the same processing is repeated. When it is determined in the determination performed in the step S11 that the user manipulates the external input unit 100 to switch to the time correction mode (the reply is Yes in the step S11), the count of the time-information storage section 96 is reset (in a step S16). When the user manipulates the external input unit to release the time correction mode, the processing proceeds to the step S10 again. The time-information count corresponding to the elapsed time in the power-saving mode is increased in step S10 for the time-recovery processing (in the step S14), and the same processes are repeated until the power-saving mode is released. [4] Advantage of the present embodiment As described above, according to the time-measurement apparatus 1 of the present embodiment, when the operation mode is switched to the power-saving mode, the limiter circuit LM is turned off (opened) to allow the power-generating-state detection section 91 to positively detect the power-generating state of the power generating section A. Therefore, a case in which the power-generating state cannot be detected because the power generating unit is set to a short-circuited condition in the power-saving mode does not happen, and the power-saving mode can be positively switched to the normal operation mode. [5] Modified embodiments [5.1] First modification In the above embodiment, the time-measurement apparatus in which the stepper motor 10 and the stepper motor 60 are used to drive the analog indicators for time indication has been described. The present invention can also be applied to a digital time-measurement apparatus which performs time indication by the use of an LCD. [5.2] Second modification In the above embodiment, the two stepper motors 10 and 60 are simultaneously stopped when the operation mode is switched to the power-saving mode. It is also possible that a plurality of power-saving-mode stages are specified, only the stepper motor 10, corresponding to the second hand, is stopped in a first stage of power-saving mode, and the stepper motor 60, corresponding to the hour and minute hands, is further stopped in a second stage of power-saving mode. [5.3] Third modification In the above embodiment, the time-measurement apparatus in which the two motors are used to indicate the hour and the minute and the second is taken as an example. The present invention can also be applied to a time-measurement apparatus in which one motor is used to indicate the hour, the minute, and the second. The present invention can further be applied to a time-measurement apparatus having three or more motors (motors separately controlling the second hand, the minute hand, the hour hand, the calendar, and the chronograph). [5.4] Fourth modification In the above embodiment, the electromagnetic power-generation unit is employed as the power generating unit 40, in which the rotational movement of the oscillating weight 45 is transferred to the rotor 43 and the rotation of the rotor 43 causes the electromotive force Vgen at the output coil 44. The present invention is not limited to this case. For example, a power generating unit which generates an electromotive force by rotational movement caused by the restitutive force (corresponding to the first energy) of a spring, or a power generating unit which generates electrical power by a piezoelectric effect by applying external- or self-vibration or displacement (corresponding to the first energy) to a piezoelectric member may be used. A power generating unit which generates electrical power by photoelectric conversion by the use of optical energy (corresponding to the first energy) such as sunlight may further be used. Furthermore, a power generating unit which generates electrical power by thermal power generation by the use of a temperature difference (thermal energy, corresponding to the first energy) between one portion and another portion may be used. An electromagnetic-induction-type power generating unit which receives stray electromagnetic waves, such as broadcasting waves and communication waves, and uses their energy (corresponding to the first energy) can also be used. [5.5] Fifth modification In the above embodiment, the wristwatch-type time-measurement apparatus 1 has been described as an example. The present invention is not limited to this case. In addition to wristwatches, the present invention can be applied to pocket watches. The present invention can also be applied to electronic apparatuses such as pocket calculators, portable phones, portable personal computers, electronic pocketbooks, portable radios, and portable VTRs. [5.6] Sixth modification In the above embodiment, the reference potential (GND) is set to Vdd (a higher potential). The reference potential (GND) may, of course, be set to Vss (a lower potential). In this case, the specified voltages Vo and Vbas indicate potential differences from the detection level set to the higher potential with Vss being set to the reference. [5.7] Seventh modification In the above embodiment, the indication mode is automatically switched to the power-saving mode. It is also possible that the operation of the limiter circuit is disabled even when the operation mode is forcibly switched to the power-saving mode by detecting a user's manipulation on the external input apparatus, for example, a special manipulation on the crown, and the operation of the limiter circuit is enabled again when the operation mode is forcibly switched to the normal operation mode. [6] Detailed example structure in the above embodiment A detailed example structure of a peripheral circuit of the mode storage section 94 shown in Fig. 2 will be described below by referring to Fig. 5. In Fig. 5, the same symbols as those in Fig. 2 are assigned to the components corresponding to those shown in Fig. 2. The mode storage section 94 shown in Fig. 5 is formed of two SR flip-flop circuits 941 and 942, and a two-input NOR circuit 943 receiving the outputs of the SR flip-flop circuits 941 and 942 as input signals. The SR flip-flop circuit 941 is formed of two cross-connected NOR circuits 941a and 941b. When the NOR circuit 941a outputs a positive-logic signal Q, the input signal of the NOR circuit 941a corresponds to a reset signal R and the input signal of the NOR circuit 941b corresponds to a set signal S. The SR flip-flop circuit 942 is formed of two cross-connected NOR circuits 942a and 942b. When the NOR circuit 942a outputs a positive-logic signal Q, the input signal of the NOR circuit 942a corresponds to a reset signal R and the input signal of the NOR circuit 942b corresponds to a set signal S. The output Q of the SR flip-flop circuit 941 serves as a current-time-recovery control signal (an "H" level indicates a current-time-recovery mode), the output Q of the SR flip-flop circuit 942 serves as a normal-operation-mode control signal (an "H" level indicates the normal operation mode), and the output of the NOR circuit 943 serves as a power-saving-mode control signal (an "H" level indicates the power-saving mode). The power-saving-mode control signal output from the NOR circuit 943 is input to the limiter circuit LM. When the power-saving-mode control signal has an "H" level, the limiter circuit LM is turned off (a short-circuit node is opened). The time-information storage section 96 measures the power-saving-mode lasting time as the count of the up/down counter, and reduces the count when the power-saving mode is switched to the normal operation mode, as described by referring to Fig. 2. The time-information storage section 96 receives the power-saving-mode control signal output from the NOR circuit 943. The time-information storage section 96 shown in Fig. 5 outputs an output signal O1 which has an "L" level when the counter holds the count (time information). This signal O1 is input to the SR flip-flop circuit 941 as a reset signal R and also input to the SR flip-flop circuit 942 as a set signal S. A carrying detection section 201 receives the electromotive force Vgen of the power generating section A as an input signal, and sets an output signal 02 to an "H" level when a matching condition is satisfied according to the electromotive force Vgen and its change-in-time state, which indicates that the time-measurement apparatus 1 is being carried. The power-generating-state detection section 91 can be used as the carrying detection section 201. Alternatively, the carrying detection section 201 can be configured such that it is separated from the power-generating-state detection section 91 and uses a carrying detection sensor which can detect a carrying state, such as an acceleration sensor or a contact sensor. The output signal O2 of the carrying detection section 201 is input to one input terminal of a two-input AND circuit 202. The power-saving-mode control signal output from the NOR circuit 943 is input to the other input terminal of the AND circuit 202. The output signal of the AND circuit 202 is input to the RS flip-flop circuit 941 as the set signal S. The non-power-generating-time measuring circuit 99 outputs an output signal O3 which has an "H" level when the non-power-generating time Tn is equal to or more than the predetermined specified time period according to the detection result of the power-generating state detected by the power-generating-state detection section 91, as described by referring to Fig. 2. In the structure shown in Fig. 5, the power-saving-mode control signal and an initializing signal are also input to the non-power-generating-time measuring circuit 99, and the time measurement value is initialized in the power-saving mode and at initialization. This initializing signal is a signal used for initializing each circuit of the device . It has a predetermined time width and is generated at a predetermined condition according to an external input or the state of the internal circuit. The initializing signal is also input to the RS flip-flop circuit 941 as a reset signal and to the RS flip-flop circuit 942 as a set signal, as well as to the non-power-generating-time measuring circuit 99. A forced PS (power saving) signal is generated when a specifying manipulation for forcibly switching to the power-saving mode is performed on the external input unit 100, and is input to the RS flip-flop circuit 942 as a reset signal R. In the above structure: (1) In the initial state, the initializing signal pulse having the predetermined time width is input and the mode storage section 94 is set to the normal operation mode (the RS flip-flop circuit 941 is in a reset state and the RS flip-flop circuit 942 is in a set state), the normal-operation-mode control signal is set to an "H" level, the current-time-recovery control signal is set to an "L" level, the power-saving-mode control signal is set to an "L" level, and the operation mode is set to the normal operation mode. (2) When the non-power-generating state is maintained and the output O3 of the non-power-generating-time measuring circuit 99 has an "H" level, or when the forced PS signal (a forced signal for switching to the power-saving mode, output when switching to the power-saving mode is forcibly specified by manipulating the crown, or for some other reason) is input, the power-saving-mode control signal is set to an "H" level and the operation mode is switched to the power-saving mode (both RS flip-flop circuit 941 and RS flip-flop circuit 942 are in a reset state). (3) In the power-saving mode, the time-information storage section 96 counts the elapsed time of the power-saving mode. The output signal O1 of the time-information storage section 96 becomes an "L" level (time information is being stored). The limiter circuit LM is turned off in the power-saving mode. (4) When the carrying detection section 201 detects a carrying state in the power-saving mode, since the output signal O2 of the carrying detection section 201 becomes an "H" level, the current-time-recovery control signal is set to an "H" level (the RS flip-flop circuit 941 is in a set state and the RS flip-flop circuit 942 is in a reset state), and the current-time-recovery operation is started. The current-time-recovery operation is executed with the counter of the time-information storage section 96 being reduced. When the counter reaches zero, the output signal O1 of the time-information storage section 96 becomes an "H" level, and the operation mode is switched from the current-time-recovery mode to the normal operation mode (the RS flip-flop circuit 941 is in a reset state and the RS flip-flop circuit 942 is in a set state). According to the present invention, the power-generation voltage of power generating means (the power generating unit) is detected, and the operation mode of means to be driven is switched between the normal operation mode and the power-saving mode according to the power-generating state of the power-generating means or according to the manipulation state of manipulation means. When the operation mode of the unit to be driven is the power-saving mode, since the operation of the limiter is disabled, it is possible in the power-saving mode that the power-generating state of the power generating unit is detected and the operation mode is positively switched to the normal operation mode.

Claims: An electronic apparatus (1), which is portable, comprising: power generating means (A) for generating power by converting a first energy to a second energy, which is electrical energy; power source means (B) for accumulating the electrical energy obtained by the power generation; means (CS, CHM) to be driven by electrical energy supplied from said power source means (B); power-generation detection means (91) for determining whether said power generating means (A) is generating power or not; the electronic apparatus characterised by further comprising: voltage detection means (92) for determining whether the power-generation voltage at said power generating means (A) or the accumulated voltage at the power source means (B) exceeds a predetermined reference voltage; limiter means (LM) for limiting the voltage of the electrical energy supplied to said power source means(B) to a predetermined reference voltage, according to the detection result of said voltage detection means (92); operation-mode control means (23) for switching the operation mode of said means (CS, CHM) to be driven between a normal operation mode and a power-saving mode, according to the detection result of said power-generation detection means (91); and limiter control means (93) for disabling the operation of said limiter means (LM) when the operation mode of said means (CS, CHM) to be driven is the power-saving mode. An electronic apparatus according to Claim 1, characterized in that said means (CS, CHM) to be driven is time-indication means for indicating time. An electronic apparatus according to Claim 2, characterized in that said operation-mode control means (23) is adapted to stop the time-indication operation performed by said time-indication means in the power-saving mode; and makes said time-indication means indicate the current time and restart the time-indication operation when the power-saving mode is switched to the normal operation mode. An electronic apparatus according to one of Claims 2 and 3, characterized in that said time-indication means comprises an analog indicator for performing analog time indication and indicator driving means (24) for driving said analog indicator; and said operation-mode control means (23) comprises operation stopping means for stopping the operation of said indicator driving means (24) in the power-saving mode. An electronic apparatus according to one of Claims 1 to 4, characterized in that said limiter control means (93) comprises operation-disable releasing means for releasing the operation disablement of said limiter means (LM) when the operation mode of said means (CS, CHM) to be driven is switched from the power-saving mode to the normal operation mode. An electronic apparatus according to Claim 1, characterized in that said operation-mode control means (23) switches the operation mode according to the detection result of said voltage detection means (92). An electronic apparatus according to Claim 1, characterized by further comprising manipulation means (100) with which the user performs various manipulations, and wherein said operation-mode control means (23) switches the operation mode according to the manipulation state of said manipulation means (100). A control method for a portable electronic apparatus (1) including a power generating unit (A) for generating power by converting a first energy to a second energy, which is electrical energy, a power source unit (B) for accumulating the electrical energy obtained by the power generating unit (A), a unit (CS, CHM) to be driven by the electrical energy, and a limiter unit for limiting the voltage of the electrical energy supplied from the power generating unit to the power source unit to a predetermined reference voltage, said control method characterized by comprising: a power-generation detection step for determining whether the power generating unit (A) is generating power or not; a voltage detection step for determining whether the power-generation voltage at the power generating unit (A) or the accumulated voltage at the power source unit (B) exceeds a predetermined reference voltage; an operation-mode control step for switching the operation mode of the unit to be driven between a normal operation mode and a power-saving mode, according to the detection result in said power-generation detection step; and a limiter control step for disabling the operation of the limiter unit (LM) when the operation mode of the unit (CS, CHM) to be driven is the power-saving mode. A control method for an electronic apparatus (1) according to Claim 8, characterized in that the unit (CS, CHM) to be driven is a time-indication unit including an analog indicator for performing analog time indication and an indicator driving unit (24) for driving the analog indicator; and said operation-mode control step comprises an operation stopping step for stopping the operation of the indicator driving unit (24) in the power-saving mode. A control method for an electronic apparatus (1) according to one of Claims 8 and 9, characterized in that said limiter control step comprises an operation disablement releasing step for releasing the operation disablement of the limiter unit (LM, when the operation mode of the unit (CS, CHM) to be driven is switched from the power-saving mode to the normal operation mode.

Inventors: OKEYA MAKOTO, YABE HIROSHI, OKEYA, MAKOTO, YABE, HIROSHI, Yabe, Hiroshi c/o Seiko Epson Corp.,
Applicants: SEIKO EPSON CORP, SEIKO EPSON CORPORATION
Application year: 1999
Main classification: G04C10
IPC codes: H02J7, G04G19, G04C10