Abstract:
An electronic timepiece charging device for charging an electronic timepiece comprising: a generator for converting external energy into electric energy; a secondary power source for storing the electric energy generated by the generator; a timepiece driving circuit for performing a time-keeping operation; and a time display circuit for displaying time information from the timepiece driving circuit, wherein, the timepiece driving circuit is connected in parallel to the secondary power source; and the secondary power source comprises an equivalent capacitive component for storing an electric charge and a resistive component formed by a part of the equivalent capacitive component. The resistance value of the resistive component is set to a value such that a voltage drop is caused, whereby when the generator generates a current equal to or greater than a predetermined value, a voltage to be applied to the timepiece driving circuit by the generator is equal to or greater than the lowest operation starting voltage.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a charging device for an electronic timepiece having a generator for receiving at least one type of external energy and converting the external energy into electric energy and a charge storer for storing the electric energy generated by the generator. The present invention further relates to an electronic timepiece using such a charging device, and a method for controlling the charging device. 
     2. Description of the Related Art 
     A small-sized electronic timepiece such as a wristwatch has a time-keeping circuit for measuring time and a timepiece driving circuit including a driving circuit for driving a motor which is coupled to a hand moving mechanism, i.e., a mechanism to move hands of the timepiece. Electronic timepieces having a generator therein have been realized in the art, which can operate without having to replace a used battery. 
     In these electronic timepieces, the electric power generated by the generator can be once charged into a secondary power source such as a capacitor. Therefore, when no electric power is being generated, time display is performed by the electric power which is discharged from the secondary power source. This enables the timepiece to stably operate over a long period of time without a battery. 
     In view of the labor and time for replacing a used battery or the problems associated with the disposal of used batteries, it is expected that more electronic timepieces will be provided with a generator in the future. 
     Generators which are provided in a timepiece such as a wristwatch include a solar battery which converts incident light into electric energy, a power generation system which converts kinetic energy of the movement of the user&#39;s arm into electric energy, etc. 
     These generators are quite desirable in that they can utilize energy around the user by converting it into electric energy. However, the available energy density is small, and the energy cannot be obtained continuously. Therefore, power is not generated continuously. During the non-power-generation periods (i.e., when the generator is in an inoperative state), the electronic timepiece is operated by the electric power which has been stored in the secondary power source. 
     In the case of an electronic device with a solar battery installed, for example, no electric power is generated by the solar battery in the nighttime. In such an electronic device with a solar battery installed, a charge storer discharges to operate a processing device. Therefore, it is desired to increase the storage capacity of the charge storer so as to accommodate situations where no electric power is generated by the power generation system. However, an increase in the storage capacity of the charge storer also increases the time required to charge the capacitor device. As a result, once the capacitor device is completely discharged off, it then takes a long time for the capacitor device to be charged to a predetermined voltage sufficient to operate the processing device. Thus, once a device employing a solar battery stops operating, for example, it will take some time to start up the device even after the device is placed back into an environment where light is incident upon the solar battery and the power generation has been resumed. 
     A number of circuits have been devised in the art to shorten the processing device start-up time in such situations. 
     An example of such circuits is shown in FIG. 8 which is a block diagram illustrating portable electronic equipment (an electronic timepiece) having a solar battery as described in Japanese Patent Provisional Publication No. 9-264971, entitled “Power Control Device, Power Generation Device and Electronic Equipment”. 
     In FIG. 8, the electronic timepiece includes a solar battery  501 , a capacitor device  513 , and a power control section  520 . 
     The solar battery  501  converts energy of the sunlight into electric power. 
     The capacitor device  513  stores the electric power from the solar battery  501 . 
     The power control section  520  supplies the electric power from the solar battery  501  to the large-capacity capacitor device  513  and to a processing device  509  such as a time-keeping device. 
     The capacitor device  513  will now be described in detail. 
     The capacitor device  513  includes a capacitor  502 , diodes  517 ,  521 ,  522  and  529 , switches  518 ,  523  and  524 , a limit switch  519 , and a control circuit  530 . 
     The capacitor  502  is a large-capacity capacitor such as an electric doublelayer capacitor. 
     The switch  523  is coupled between the ground power rail (which in the present case is used as the reference high voltage VDD) and the anode of diode  522 . When switch  523  is actuated (i.e. is closed) it forms a bypass current path around diode  521 . Diodes  521  and  522  are coupled end-to-end such that when switch  523  is not actuated (i.e. is opened), diodes  521  and  522  are effectively serially connected with each other. In the electronic timepiece illustrated in FIG. 8, the reference high voltage VDD is the ground voltage power rail (reference voltage), and the VSS line is the relative low voltage. To emphasize that VDD is implemented by the ground power rail, the term “ground voltage VDD” is at times used to refer to the reference high source, i.e. high side, of the circuit. 
     The switch  524  is coupled between the VDD voltage and the cathode of diode  522 . When switch  524  is actuated (i.e. is closed), it forms a bypass current path around both of the diodes  521  and  522 . 
     The diode  529  is provided between the solar battery  501  and one of the terminals of the capacitor  502  which is on the VSS voltage (low voltage) side. The diode  529  functions as a reverse current flow prevention diode. Specifically, the diode  529  is operative to ensure that a voltage which is discharged from the capacitor  502  while no power is being generated from the solar battery  501  is not applied to the solar battery  501 . 
     The diode  517  is operative to ensure that a current does not flow in the reverse direction from an auxiliary capacitor device  516  including a small-capacity capacitor  503  to the solar battery  501 . 
     The switch  518  is a switch provided for controlling a discharge from the capacitor device  513  into the auxiliary capacitor device  516 . 
     The limit switch  519  short-circuits the high voltage side VDD and the low voltage side VSS with each other when the voltage supplied from the solar battery  501  is too high. In this way, it is possible to prevent the capacitor device  513  from being overcharged so that a high voltage is not applied to the processing device  509 , etc. 
     The control circuit  530  monitors various voltages in the power control section  520  and controls the switches. The control circuit  530  detects a voltage VSCP on the high voltage side of the capacitor device  513 , a voltage VSCN on the low voltage side of the capacitor device  513 , the voltage VSS which is supplied to the processing device  509 , etc. 
     Based on the detection results, the control circuit  530  outputs control signals for controlling the switch  523  and the switch  524 , respectively. The control circuit  530  also outputs a control signal for controlling the switch  518  (which is provided for controlling the discharge from the capacitor device  513  into the auxiliary capacitor device  516 ), and a control signal for controlling the limit switch  519 . 
     With the configuration as described above, a charge voltage VSC of the capacitor device  513  is equal to the difference between the terminal voltages thereof, i.e., between the high potential side voltage VSCP and the low potential side voltage VSCN. However, when light is illuminated onto the solar battery  501  while substantially no electric charge is stored in the capacitor device  513  and the charge voltage VSC is substantially 0 V, the switches  523  and  524  are turned OFF. 
     Therefore, the electric power supplied from the solar battery  501  is dropped by a forward bias voltage of the diodes  521  and  522 . Thereafter, the electric power is supplied to the capacitor device  513 . Thus, a voltage drop is caused by the diodes  521  and  522 . 
     In this way, it is possible to increase the voltage to be applied to the processing device  509  by an amount corresponding to the voltage drop. 
     As the charge voltage VSC of the capacitor  502  gradually increases and reaches a predetermined setting voltage, the switch  523  and the switch  524  are sequentially turned ON. Thus, the diodes  521  and  522  are bypassed, thereby increasing the charge voltage VSC to the capacitor  502 . 
     In the conventional example shown in FIG. 8, two diodes  521  and  522  are used in order to increase the voltage to be applied to the processing device  509 . However, in alternative circuit configurations, resistive elements may be used in place of the diodes  521  and  522  (see, for example, U.S. Pat. Nos. 5,001,685 and 4,730,287). 
     In the above-described conventional example, a voltage decreasing means such as a diode, a resistor, or the like, is provided between a capacitor, which is used as the secondary power source, and the ground voltage VDD in order to increase the voltage applied to the processing device such as a timepiece driving circuit at the beginning of power generation. Moreover, a line is provided and connected to the terminals of the capacitor for detecting the charge voltage of the capacitor (the voltage between VSCP and VSCN in FIG.  8 ). 
     In such a configuration, it is necessary to isolate one of the terminals of the secondary power source (terminal A in FIG. 8) from the ground voltage VDD. In addition, it is necessary to provide a power supply line for supplying the voltage at terminal A while isolating the power supply line from the ground voltage VDD to a circuit board mounting thereon a control circuit, a timepiece driving circuit, and the like. 
     FIG. 9 is a partial cross-sectional view illustrating how a circuit board is placed in an electronic timepiece. 
     In FIG. 9, a secondary power source (the capacitor  502 ) is provided separately from a circuit board  601 . The terminal A of the capacitor  502  is connected to a predetermined contact point on the circuit board  601  by a connection member  602 , e.g., a contact point spring, or the like. 
     A circuit hold plate  603  for holding down the circuit board  601  is made of an electrically conductive material such as a stainless having a potential equal to the ground voltage VDD. 
     A circuit spacer  604  is made of an insulating member. The circuit spacer  604  and the circuit hold plate  603  together sandwich the circuit board  601  therebetween. 
     The circuit board  601  is secured by a press-fit member  605 , which is press-fit through the circuit spacer  604 , and a screw  606 . 
     A circuit insulating plate  607  is provided between the circuit board  601  and the circuit hold plate  603 . The circuit insulating plate  607  is made of an insulating material. The circuit insulating plate  607  insulates lines on the circuit board  601  from the ground voltage VDD. 
     A base plate  608  is secured to the circuit spacer  604  by the press-fit member  605 . 
     The base plate  608  is further secured by a circuit case. 
     With the configuration as described above, where one of the terminals (terminal A) of the secondary power source (the capacitor  502 ) is connected to the predetermined contact point on the circuit board  601  by a contact point spring (the portion indicated by a broken line  602 ), or the like, the power source potential of the secondary power source may be instable. 
     This is because the contact resistance of the electrically conductive member varies due to a shock. 
     Moreover, it is necessary to ensure a sufficient ground space on the circuit board  601  to insulate signal lines and grounded points from the power supply line of the secondary power source by providing an insulating mechanism or a sufficient creepage distance. This has prevented the size of the circuit board  601  from being reduced. Therefore, it has not been possible to employ such a voltage-increasing configuration as described above in a small analog electronic timepiece for women. 
     Moreover, the positive terminal A of the secondary power source has a voltage that is different than the ground voltage VDD. Therefore, it is not possible to directly connect the positive terminal A of the secondary power source and the connection member  602  to the grounded points. Furthermore, it is necessary to provide the insulating member for providing an insulation from the contact point. 
     Moreover, as illustrated in FIG. 8, a circuit for causing a voltage drop is provided by using a diode. In such a case, no current flows through the diodes  521  and  522  while the switches  523  and  524  are OFF and no electric power is being generated. Therefore, the terminal and lines for detecting the voltage VSCP are brought into a high impedance state and thus are more likely to be influenced by noise. 
     OBJECTS OF THE INVENTION 
     In view of the above, an object of the present invention is to provide a charging device for an electronic timepiece having a function of boosting the voltage at the beginning of power generation, an electronic timepiece using such a charging device, and a method for controlling the charging device. The present invention also aims to allow the ground voltage side terminal of the secondary power source to be grounded directly. 
     SUMMARY OF THE INVENTION 
     In accordance with an aspect of the present invention, an electronic timepiece charging device for charging an electronic timepiece comprises: a generator for receiving at least one type of external energy and converting the external energy into electric energy; a capacitor device for storing the electric energy generated by said generator; a timepiece circuit connected in parallel to said capacitor device for performing a time-keeping operation, said timepiece circuit being driven by the electric energy generated by said generator or the electric energy stored in said capacitor device; and a display circuit for displaying time information from said timepiece circuit, wherein: 
     said timepiece circuit is connected in parallel to said capacitor device; 
     said capacitor device comprises an equivalent capacitive component for storing an electric charge and a resistive component formed by a part of said equivalent capacitive component; and 
     a resistance value of said resistive component is set in such manner that when the generator outputs a current equal to or greater than a predetermined value by means of a voltage drop caused by a charging current of said resistive component, a voltage to be applied to said timepiece circuit by the generator is equal to or greater than a voltage at which said timepiece circuit starts operating. 
     Preferably, said resistive component has a resistance value which is equal to or greater than a value obtained by dividing an operation starting voltage of the timepiece circuit by a current generated by said generator, or a value obtained by first subtracting a remaining charge voltage of said capacitor device at a time when the timepiece circuit stops operating from the operation starting voltage of the timepiece circuit to obtain a difference therebetween, and then dividing said difference by the current generated by said generator. 
     Preferably, said generator comprises a photoelectric power generator, a magnetoelectric power generator, a thermoelectric power generator, or a piezoelectric power generator. 
     Preferably, said capacitor device equivalently comprises one capacitive component and one resistive component which are serially connected with each other. 
     Preferably, said capacitor device equivalently comprises a plurality of pairs of capacitive components and resistive components which are connected in parallel to one another, each pair having one capacitive component and one resistive component which are serially connected with each other. 
     Preferably, said capacitor device is a lithium secondary battery comprising an electrolytic solution of an organic solvent having a lithium salt dissolved therein, a negative pole activator using titanium oxide, and a positive pole activator using manganese oxide. 
     Preferably, said capacitor device is a lithium secondary battery comprising an electrolytic solution of an organic solvent having a lithium salt dissolved therein, a negative pole activator using a carbon material, and a positive pole activator using lithium titanate. 
     Preferably, wherein said capacitor device comprises an electrolytic capacitor. 
     Preferably, said generator comprises an AC generator, and a charging time constant of said capacitor device is less than or equal to one cycle of a half-wave- or full-wave-rectified waveform of a current generated by said AC generator. 
     Preferably, one terminal of said capacitor device is grounded to a ground potential which is common among said generator, said timepiece circuit and said capacitor device. 
     Preferably, one terminal of said capacitor device is grounded to an electrically conductive attachment member having said ground potential. 
     In accordance with another aspect of the present invention an electronic timepiece comprises: 
     a generator for receiving at least one type of external energy and converting the external energy into electric energy; 
     a capacitor device for storing the electric energy generated by said generator; 
     a timepiece circuit connected in parallel to said capacitor device for performing a time-keeping operation, said timepiece circuit being driven by the electric energy generated by said generator or the electric energy stored in said capacitor device; 
     a display circuit for displaying time information from said timepiece circuit; and 
     the above-described charging device. 
     In accordance with another aspect of the present invention, a method for controlling a charging device for an electronic timepiece is provided. The charging device includes a generator for receiving at least one type of external energy and converting the external energy into electric energy; a capacitor device for storing the electric energy generated by said generator; a charging device for charging said capacitor device; a timepiece circuit connected in parallel to said capacitor device for performing a time-keeping operation, said timepiece circuit being driven by the electric energy generated by said generator or the electric energy stored in said capacitor device; and a display circuit for displaying time information from said timepiece circuit. The method comprises: 
     connecting the timepiece circuit in parallel to said capacitor device; 
     forming said capacitor device by an equivalent capacitive component for storing an electric charge and a resistive component formed by a part of said equivalent capacitive component; and 
     setting a resistance value of the resistive component in such manner that when said generator outputs a current equal to or greater than a predetermined value by means of resistance value of said resistive component, a voltage to be applied to said timepiece circuit by said generator is equal to or greater than a voltage at which said timepiece circuit starts operating. 
     In accordance with another aspect of the present invention, an electronic timepiece charging device comprises: 
     a generator for receiving at least one type of external energy and converting the external energy into electric energy; a capacitor device for storing the electric energy generated by said generator; a timepiece circuit connected in parallel to said capacitor device for performing a time-keeping operation, said timepiece circuit being driven by the electric energy generated by said generator or the electric energy stored in said capacitor device; and a display circuit for displaying time information from said timepiece circuit, wherein: 
     said timepiece circuit is connected in parallel to said capacitor device; 
     said capacitor device comprises at least an equivalent capacitive component for storing an electric charge and a resistive component; and 
     where a voltage in said capacitor device to be supplied to said timepiece circuit is less than an operation starting voltage of said timepiece circuit, and when said timepiece circuit has stopped operating and in addition when a charging current flows into said capacitor device due to power generation by said generator, said the capacitor device supplies to said timepiece circuit a voltage which is equal to or greater than the operation starting voltage of said timepiece circuit by utilizing at least a voltage difference caused by said resistive component. 
     In accordance with another aspect of the present invention, a method for controlling a charging device for an electronic timepiece including: a generator for receiving at least one type of external energy and converting the external energy into electric energy; a capacitor device for storing the electric energy generated by said generator; a timepiece circuit connected for performing a time-keeping operation, said timepiece circuit being driven by the electric energy generated by said generator or the electric energy stored in said capacitor device; and a display circuit for displaying time information from said timepiece circuit. The method comprises: 
     connecting said timepiece circuit in parallel to said capacitor device; 
     forming said capacitor device by at least an equivalent capacitive component for storing an electric charge and a resistive component; and 
     where a voltage in said capacitor device to be supplied to said timepiece circuit is less than an operation starting voltage of said timepiece circuit, and when said timepiece circuit has stopped operating and in addition when a charging current flows into said capacitor device due to power generation by said generator, controlling said capacitor device to supply to said timepiece circuit a voltage which is equal to or greater than the operation starting voltage of said timepiece circuit by utilizing at least a voltage difference caused by said resistive component. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, wherein like reference symbols refer to like parts: 
     FIG. 1 is a block diagram illustrating one embodiment of an electronic timepiece according to the present invention; 
     FIGS. 2A and 2B are diagrams respectively illustrating two exemplary equivalent circuits of a secondary power source SS illustrated in FIG. 1; 
     FIG. 3A illustrates the change over time in the voltage to be applied to a timepiece driving circuit  200  of the embodiment illustrated in FIG. 1; 
     FIG. 3B illustrates the change over time in the applied voltage, for comparison, where there is no resistive component R for charging; 
     FIG. 4 is a schematic cross-sectional view illustrating a part of the electronic timepiece illustrated in FIG. 1; 
     FIG. 5 is a block diagram illustrating a configuration as illustrated in FIG. 1 where a specific generator (a solar power generator  101 ) is employed for a generator  100 ; 
     FIG. 6 is a block diagram illustrating a variation of the embodiment illustrated in FIG. 1; 
     FIG. 7 is a waveform diagram illustrating the change over time in the generated current according to the embodiment illustrated in FIG. 6; 
     FIG. 8 is a block diagram illustrating a configuration of a conventional electronic timepiece; and 
     FIG. 9 is a schematic cross-sectional view illustrating a part of the electronic timepiece illustrated in FIG.  8 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. 
     FIG. 1 is a block diagram illustrating one embodiment of an electronic timepiece according to the present invention. 
     The electronic timepiece illustrated in FIG. 1 is a wristwatch which is worn by a user by passing a belt attached to the body of the timepiece around the user&#39;s wrist. 
     A generator  100  comprises a generator utilizing such generating effects as a photoelectric effect (particularly, a photoelectric effect using sunlight), a magnetoelectric effect, a thermoelectric effect or a piezoelectric effect. A secondary power source SS which stores the electric power generated by the generator  100  is connected to the generator  100  via a reverse flow prevention diode D 1 . One terminal of the secondary power source SS is connected directly to a common ground voltage VDD which is also connected to the positive side output terminal of the generator  100 , the positive side power source terminal of a timepiece driving circuit  200 , or the like. The other terminal of the secondary power source SS is connected to another terminal of the timepiece driving circuit  200  which is connected to the low potential side power source voltage VSS. In this example, the ground voltage VDD which is on the high potential side of the secondary power source SS having the high potential side voltage is used as the ground (reference) voltage GND, and the low potential side voltage is used as VSS. In alternative configurations, the voltage VSS may be used as the ground potential GND. 
     The timepiece driving circuit  200  keeps time based on the clock produced by oscillation of a quartz oscillator XTAL which has an oscillation frequency of 32 kHz, for example. The timepiece driving circuit  200  drives and controls a time display circuit  300  which may be an analog display circuit having an hour hand, a minute hand, etc., or a liquid crystal digital display circuit. 
     The timepiece driving circuit  200  also detects when the voltage generated by the generator  100  exceeds a predetermined voltage. When the generated voltage exceeds the predetermined voltage, a signal LIM is brought to a low level. This turns a switch S 1  to ON, which is connected in parallel to the respective output terminals of the generator  100 , to short-circuit the output terminals of the generator  100  with each other, thereby implementing a limit control to prevent a high voltage from being applied to the secondary power source SS or other circuits. 
     In this example, the switch S 1  may be a P-channel MOS (metal oxide semiconductor) transistor. A power source voltage between the high potential of the voltage VDD and the low potential of the voltage VSS is applied to the timepiece driving circuit  200 . The secondary power source SS and an auxiliary capacitor CB are each connected in parallel between the power source voltage terminals. 
     The secondary power source SS may be, for example, a lithium secondary battery. The secondary power source SS may equivalently include a capacitive component C for storing an electric charge, and a resistive component R which is formed by a constructing member of the equivalent capacitive component C. 
     The lithium secondary battery uses an organic (lithium) solvent as its electrolytic solution. Such a lithium secondary battery has a feature that the resistive component R takes a larger value as compared with other secondary batteries such as a Ni—Cd secondary battery using an aqueous (KOH+H 2 O) electrolytic solution. 
     According to the present invention, the resistive component R which is inherent to the structure of the secondary power source SS is used in place of the diodes  521  and  522  illustrated in FIG. 8, for example. 
     In the present invention, the voltage to be applied to the timepiece driving circuit  200  is increased at the beginning of power generation (when the charge voltage of the secondary power source SS is low) by means of a voltage drop which occurs at the resistive component R by the charging current from the generator  100 . 
     The secondary power source SS may suitably be a lithium secondary battery as described above which uses an organic solvent as its electrolytic solution. 
     Such lithium secondary batteries which can be suitably used as the secondary power source SS of the present invention include lithium batteries as disclosed in Japanese Patent Publication No. 63-1708, entitled “Organic Electrolytic Solution Secondary Battery,” or Japanese Patent Provisional Publication No. 10-64592, entitled “Lithium Secondary Battery.” 
     The “organic electrolytic solution secondary battery” as disclosed in Japanese Patent Publication No. 63-1708 includes an electrolytic solution of an organic solvent having a lithium salt dissolved therein, a negative pole activator using titanium oxide, and a positive pole activator using manganese oxide. 
     The “lithium secondary battery” as disclosed in Japanese Patent Provisional Publication No. 10-64592 includes an electrolytic solution of an organic solvent having a lithium salt dissolved therein, a negative pole activator using a carbon material, and a positive pole activator using lithium titanate. 
     These lithium secondary batteries have the feature that the resistive component R can be increased, and therefore can be suitably used as the secondary power source SS of the present invention. 
     As an alternative example of the secondary power source SS, an electrolytic capacitor may be used such as a super capacitor which uses an electrolytic solution. 
     As illustrated in FIG. 2A, the secondary power source SS may equivalently include one capacitive component C and one resistive component R which are serially connected with each other. 
     Alternatively, as illustrated in FIG. 2B, the secondary power source SS may equivalently include a plurality of pairs (n pairs) of capacitive components C 1  to Cn and resistive components R 1  to Rn which are connected in parallel to one another, each pair having one capacitive component C and one resistive component R which are serially connected with each other. 
     The resistance value of the resistive component R is used to drive a timepiece which has stopped operating. 
     Specifically, the resistance value of the resistive component R is used to drive timepiece in the situation in which the generator  100  is in an inoperative state and in addition the charge voltage of the secondary power source SS has reduced to a value which is insufficient to drive the timepiece driving circuit  200 . 
     More specifically, the resistance value of the resistive component R is set to a value such that the voltage to be applied to the timepiece driving circuit  200  can be increased to a voltage which is sufficient to drive the timepiece driving circuit  200  at the start-up of the generator  100  (at the beginning of power generation), as illustrated in FIG.  3 A. 
     The voltage to be applied to the timepiece driving circuit  200  is equal to the voltage between VDD and VSS. The voltage sufficient to drive the timepiece driving circuit  200  is a voltage (the lowest driving voltage) which is indicated by a broken line in FIG.  3 A. 
     FIG. 3B illustrates, for reference, the change over time in the voltage to be applied to the timepiece driving circuit  200  under similar power generation conditions to those of FIG. 3A, but where there is no charging resistive component. 
     Specifically, FIG.  3 ( a ) illustrates the change over time in the voltage to be applied to the timepiece driving circuit  200  in a configuration in which the resistive component R is removed from the configuration illustrated in FIG.  1 . 
     A specific value of the resistance of the resistive component R can be calculated based on the respective values of the oscillation starting voltage in the timepiece driving circuit  200 , the voltage remaining in the secondary power source SS when the timepiece stops operating, and the current generated by the generator  100  at the start-up of the timepiece. 
     More specifically, the resistance value of the resistive component R can be set based on the following formula: 
     
       
         Resistance value  R  [ 106  ]=(Oscillation starting voltage [ V ]−Remaining voltage when timepiece stops [ V ]) /Generated current [ A ] 
       
     
     For example, consider a case where the oscillation starting voltage is 0.7 V, the remaining voltage when the timepiece stops operating is 0.1 V, and the generated current is 0.006 A. 
     In this case, according to the formula shown above, the resistance value of the resistive component R is calculated as 100 Ω. Therefore, by setting the resistance value of the resistive component R to be 100 Ω, it is possible to quickly resume the operation of a timepiece after the timepiece has stopped operating. 
     In the formula shown above, the term representing the remaining voltage when the timepiece stops operating may be omitted if, for example, it is always 0 V. As long as the resistance value is equal to or greater than the value obtained from the above formula, it is possible to ensure that the voltage to be applied to the timepiece driving circuit  200  is, at the time of start-up, equal to or greater than the lowest driving voltage. However, as the value of the resistive component R increases, the voltage applied to the capacitive component C decreases, thereby hindering the charging operation. Therefore, it is desirable to set the resistance value within a certain range from the value obtained by the above formula. 
     The formula shown above also indicates that the value of the resistive component R can be reduced by employing a generator having a high power generation capability. 
     The formula shown above also indicates that with the use of a generator having a poor power generation capability, a sufficient voltage at the start-up can be ensured by means of increasing the value of the resistive component R. 
     In the above-described example, if the resistance value is equal to or greater than 100 Ω, it is possible to immediately start up the timepiece even when the voltage of the secondary power source is in the vicinity of 0 V. A resistive component having such a resistance value, about 100 Ω, can be implemented either with a lithium secondary battery using titanium oxide and manganese oxide or a lithium secondary battery using a carbon material and lithium titanate, as described above. 
     In the configuration illustrated in FIG. 1, the secondary power source SS and the auxiliary capacitor CB are connected in parallel to each other. 
     Alternatively, a voltage increasing/decreasing circuit which is formed by, for example, a charge pump circuit including a plurality of capacitors and switches can be interposed between the secondary power source SS and the auxiliary capacitor CB. In such a case, the charge voltage of the secondary power source SS or the voltage generated by the generator  100  may be increased or decreased to obtain an increased or decreased voltage which is then applied to the auxiliary capacitor CB and the timepiece driving circuit  200 . In such a case, it is not necessary to change the connection on the ground voltage VDD side if the voltage increasing/decreasing circuit is provided so as to increase/decrease the voltage between the VSS side terminal of the secondary power source SS and the VSS side terminal of the auxiliary capacitor CB. 
     As described above, according to the embodiment of the present invention illustrated in FIG. 1, the resistive component which is inherent to the structure of the secondary power source SS is used to cause a voltage drop which is required at the start-up. 
     Thus, it is possible to eliminate the connection and the power supply line which are used, in the conventional example described above with reference to FIG. 8, for detecting the voltage VSCP at one terminal of the capacitor  502 . 
     How to connect the secondary power source SS in the electronic timepiece illustrated in FIG. 1 will now be described with reference to FIG.  4 . 
     In FIG. 4, the same elements as those shown in FIG. 9 are denoted by the same reference numerals and will not be further described below. 
     In the present embodiment, the high voltage side (positive side) terminal of the secondary power source SS can be grounded directly to the VDD voltage point. Therefore, the high voltage side (positive side) terminal B of the secondary power source SS can be electrically directly connected to the circuit hold plate  603 , by connecting the terminal B either directly to the circuit hold plate  603  or via a securing member (the portion indicated by a broken line  401 ) using a connection terminal, a screw, or the like, which has a high rigidity. 
     On a circuit board  601   a,  it is no longer necessary to wire a power supply line for the terminal voltage VSCP which is required in the conventional configuration illustrated in FIG.  8 . Therefore, it is possible to save some area on the board corresponding to the area which would otherwise be required for insulation. 
     In addition, it is possible to eliminate the counterpart contact point for the contact point spring which is required for detecting the terminal voltage VSCP. Therefore, it is possible to reduce the size of the circuit board  601   a  as compared with that in the prior art. 
     Next, a more specific example and a variation of the embodiment of the present invention illustrated in FIG. 1 will be described with reference to FIGS. 5 and 6. 
     FIG. 5 is a block diagram showing a specific example of the generator  100  of FIG.  1 . 
     In FIG. 6, a solar power generator (a solar battery)  101  is employed in place of the generator  100  of FIG.  1 . Other DC generator such as a photoelectric power generator, a thermoelectric power generator, or the like, may be used with the present embodiment simply by replacing the generator  100  of FIG. 1 with such a generator. 
     FIG. 6 is a block diagram illustrating a configuration where the generator  100  of FIG. 1 is replaced with an AC power generator  102  such as an magnetoelectric power generator, a piezoelectric power generator, or the like. In this case, a full-wave rectifier circuit including four diodes D 2  to D 5  is used to rectify the voltage generated by the AC power generator  102  into a direct current. In such a case, it is not necessary to employ the reverse flow prevention diode D 1  of FIG.  1 . 
     A diode D 6  and a diode D 7  are further provided, whose anodes are both connected to the drain of the limit control switch S 1  and whose cathodes are connected to the respective output terminals of the AC power generator  102 , whereby it is possible to short-circuit the output terminals of the AC power generator  102  with each other by means of the switch S 1 . 
     FIG. 7 illustrates the change over time in the generated current after fullwave rectification where a magnetoelectric power generator is used as the AC power generator  102  illustrated in FIG.  6 . 
     In the case of an AC power generation, the generated current varies periodically, as illustrated in FIG.  7 . Therefore, it is desirable that the time constant for charging the secondary power source SS is within a range such that it is possible to respond to the change in the generated current (the cycle after fullwave or half-wave rectification). For example, where the zero crossing interval in the waveform of a generated AC current after full-wave rectification is 1 ms, as in the illustrated example, the time constant RtC based on the equivalent capacitive component C and the resistive component R of the secondary power source SS is desirably less than or equal to 1 ms. 
     As described above, according to the present embodiment, it is possible to eliminate the diodes and resistors for increasing the voltage. 
     Moreover, it is possible to eliminate the power supply line which is used for detecting the charge voltage of the secondary power source and the connection member which is used for connecting the power supply line. 
     As a result, it is possible to obtain the following effects: 
     (1) The power supply line for the terminal voltage VSCP which is required in a conventional circuit is eliminated, whereby it is possible to improve the spatial efficiency of circuit blocks on a circuit board; 
     (2) The power supply line for the terminal voltage VSCP is eliminated, whereby it is possible to eliminate an insulating member such as an insulating film, or the like, which is required in the prior art on the circuit board or on connecting points to the circuit board for providing an insulation from an outer package member; 
     (3) It is no longer necessary to provide an insulation between the positive side terminal of the secondary power source and an outer package member (VDD voltage); 
     (4) There is no longer an influence from variations in potential or noise along the power supply line for the terminal voltage VSCP, whereby it is possible to reduce the possibility of a malfunction of the entire circuit due to noise.