JPH0631725B2 - Electronic clock with charging function - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electronic timepiece including a charging unit and a power storage unit. More specifically, charging in the electronic timepiece-
The present invention relates to improvement of a power storage mechanism.

[Prior art]

Electronic timepieces equipped with a charging means (primary power source) are used for the purpose of supplementing energy for long-term use, and in particular, with the rapid reduction in the cost of solar cells, they are widely used for the purpose of extending their life. It has come to be put to practical use. In addition, as a backup when the energy supply from the primary power supply is stopped at night or the like, various storage means (secondary power supply) have been devised. For example, JP-A-52-6767
A button type battery as shown in Fig. 3 can be applied, and it can be advantageously developed to extend the life of a small timepiece having a limited space.

Furthermore, these charging-electricity storage systems are also disclosed in JP-A-51-
121366, JP-A-55-13498, etc., have been devised to prevent overcharging of the primary power source and put to practical use. Further, the operation system of the electronic timepiece is also devised such as switching the power source between the solar cell and the chemical cell by detecting the amount of incident light as shown in JP-A-58-137784.

Further, recently, in place of the secondary power source described above, a device using a storage means applying a solid electrolyte or a capacitor, which is expected to have a longer life, has been devised, and a device for obtaining a more reliable long life clock has been made. (For example, there is JP-A-58-176570 as a method of fast-forwarding the stop time when the charge amount becomes a certain value or less). Since these secondary power sources with high reliability have small capacities, some kind of ingenuity is required for the charge-storage system and the charge-discharge system.

In these electronic timepieces with a charging function, when the power supply system that controls the electronic circuit of the electronic timepiece falls below the operating range of the electronic circuit, the operation becomes unstable with respect to the supply of the charging energy to come. Things become a problem.

Further, from the empty state of the secondary power source, there is a problem that the timepiece does not operate until the energy supply from the primary power source is sufficient and the operating voltage of the electronic timepiece is exceeded. In particular,
When the current supply of the primary power source is low (in the example of the solar cell described above, when the electronic timepiece is placed in low illuminance), it takes a considerable time to start its operation.

Conventionally, including the above-mentioned conventional example, no suitable solution has been proposed for these problems, and the user is forced to charge the secondary power source before the secondary power source becomes empty.

〔Purpose〕

The present invention can prevent a secondary power source from being overcharged by a power generation unit, and can set a power supply system to a state in which the secondary power source can be recharged even when the voltages of the power generation unit and the secondary power source drop below a predetermined level. It can be set automatically, and when the voltage of the power generation means exceeds a predetermined voltage, the secondary power supply can be charged efficiently, and the power consumption of the secondary power supply can be minimized while keeping the clock circuit. It is an object of the present invention to provide an electronic timepiece with a charging function capable of favorably supplying electric power to an electronic timepiece.

To achieve the above object, the present invention provides a power generation unit that generates power based on energy applied from the outside, a secondary power source charged by the power generation unit, and selectively from the power generation unit or the secondary power source. A clock circuit driven by a supplied power supply voltage; an overcharge prevention switching unit connected in parallel with the power generation unit and being on-controlled when overcharge of the secondary power source by the power generation unit is detected; And an off control means for forcibly turning off the overcharge prevention switching means when the voltage of the secondary power supply drops below a predetermined value, and the off control means is connected in series between the power generation means and the secondary power supply. When it is detected that the voltage supplied from the power generation means to the timepiece circuit is equal to or higher than the operable voltage of the timepiece circuit, it is on-controlled, and the charge control switch for charging the secondary power source. Connecting means in series between the secondary power supply and the timepiece circuit, which is normally turned off to drive the timepiece circuit by the voltage supplied from the power generation means to the timepiece circuit, and the timepiece is operated from the secondary power source. A discharge switching means that is on-controlled when the voltage supplied to the circuit exceeds the voltage supplied from the power generation means to the timepiece circuit, and that drives the timepiece circuit by the output voltage of the secondary power supply. Characterize.

〔Example〕

 The present invention will be described in detail below based on examples.

FIG. 1 is a block diagram showing an outline of the present invention. 10
1 is a primary power source that takes in external energy such as solar cells. A secondary power source 102 stores the energy supplied from the primary power source. Since the life of the secondary power source determines the life of the system, it is preferable to use a non-liquid electrolyte element such as a solid electrolyte battery or a capacitor as the secondary power source. Of course it may also be used containers liquid electrolyte batteries, such as Ag 2 _O and Ni-Cd batteries. Reference numeral 103 denotes a limiter switch, which is the voltage Vsc of the secondary power source 102.
Is compared with the voltage V ₁ generated by the reference voltage generation circuit 104 by the voltage comparison circuit 105 to determine whether it becomes higher than the withstand voltage V ₁ of the secondary power supply 102, and when Vsc> V ₁ , the limiter switch 103 Turn on, primary power supply 10
Prevent overcharging above 1. Reference numerals 106 and 107 are resistance elements used to accurately set the withstand voltage V ₁ of the secondary power source. The high voltage is applied to the high voltage comparison circuit 105, and the divided voltage is applied to the resistors 106 and 107 with respect to Vsc, and the reference voltage generation circuit 104 applies the withstand voltage V ₁ to the resistor 106. And a value obtained by multiplying the partial pressure ratio of 107 are applied. This relatively compares Vsc with V ₁ . It is preferable that these resistance elements have a high resistance of several tens of megohms in order to suppress energy consumption. In addition, it is desirable that the operation time of the voltage comparison circuit 110 be compared by sampling for the same reason that energy consumption is suppressed. Reference numeral 108 denotes an initial setting circuit, which sets the limiter switch 103 to a fixed position when the above-mentioned primary power source and secondary power source _fall below the operating voltage CV _TH of the electronic circuit (IC). This is the point of the present invention and will be described later in detail. 109 is a charging switch, which is a drive circuit 1
The voltage generated by the reference voltage generation circuit 104 and the voltage comparison circuit 110 indicate that the voltage Vss of 19 becomes equal to or higher than the voltage V ₂ sufficient to operate the electric-display conversion device 121.
Are compared with each other and turned on when Vss> V ₂ . As a result, the energy taken in from the primary power supply 101 can be supplied to the secondary power supply 102 without waste, and the charging speed of the secondary power supply is accelerated. Reference numerals 111 and 112 denote resistance elements, which adjust and set the voltage Vss in the same manner as 106 and 107 described above.
It is also the same as setting a high resistance to suppress energy consumption. The same applies to sampling the voltage comparison.

Reference numerals 113 and 114 denote backflow prevention circuits, which are used to prevent the energy of the stored secondary power source 102 from being consumed through the primary power source when the energy supply of the primary power source 101 is stopped. It is customary to use. Reference numeral 115 denotes a discharge switch, which is the voltage Vsc of the secondary power source and the drive circuit voltage Vs described above.
s is compared by the voltage comparison circuit 116, and when Vsc> Vss, the switch is turned on and the drive circuit 119 is operated.
An oscillation circuit 117 generates a clock of an electronic circuit related to this system. Reference numeral 118 denotes a frequency dividing circuit that steps down the signal to the drive circuit 119 at appropriate intervals. An electric display conversion device 121 receives a signal from the drive circuit 119, performs electromechanical conversion, and moves a pointer of the display device 122. In addition, the electric display conversion device 121 performs electro-optical conversion to display the display device 12.
The same applies when a display panel is used for 2.

An oscillation stop detection circuit 120 gives a signal for keeping the output of the drive circuit 119 at the same level when the oscillation of the oscillation circuit 117 is stopped. This system will be described in detail later. Reference numeral 123 denotes a smoothing capacitor, which absorbs a load variation of the electric display conversion device, but is not essential to the charge-discharge-power storage system of the present invention.

Next, the first object of the present invention will be described in detail about various measures for raising the secondary power source from the non-operating state of the electronic circuit in the vicinity of 0 V to the operating state without any problem.

First, an improvement measure of the overcharge prevention means (limiter circuit) from the primary power supply to the secondary power supply will be described. In this regard, the point is to prevent erroneous short circuit of the overcharge protection transistor when the secondary power supply voltage is within the circuit operating range. This will be described by taking the case where the primary power source is a solar cell as an example, but the charging method may be thermal energy kinetic energy or magnetic energy instead of light energy.

In the conventional overcharge prevention means for an electronic timepiece with a solar cell (hereinafter referred to as a limiter), when the secondary power source becomes equal to or lower than the operating voltage of the limiter, the open / closed state of the switching transistor in the limiter becomes indefinite and the solar cell is short-circuited. The loop may remain as it is (originally, a short circuit occurs when the secondary power supply becomes overvoltage). Therefore, no matter how much charge is made from this state, no current flows in the secondary power supply. In particular, in a place where the light is weak, the electromotive force generated by the solar cell is small, so that the solar cell is not charged no matter how long the light is applied. This is the most fatal defect of the charging device. In the past, without this preventive measure, it was forced to charge the secondary power supply before it was completely emptied (before falling below the threshold voltage of the transistor).

The present invention prevents the above-mentioned drawbacks, and an example thereof is the second
It is shown in Figure- (a). In FIG. 2A, 201 is a solar cell, 202, 203 and 204 are resistors, 205 is a reference voltage generation circuit, and 206 is a voltage comparison circuit (comparator). 207 is a limiter switch, 208 is a backflow prevention diode, and 209 is a main circuit, which includes other circuits not related to the limiter. 210 is a secondary power source. In FIG. 2 (a), the voltage divided by the resistors 203 and 204 changes in proportion to the voltage of the secondary power source 210 and becomes one input of the comparator 206. The input to the other side of the comparator 206 is the reference voltage generation circuit 205.
Output a constant voltage regardless of the voltage change of the secondary power supply. These two inputs are compared, and when the resistance-divided voltage becomes higher than the reference voltage, the comparator 206 outputs a LOW potential and short-circuits the transistor 207 of the summit switch. Here, the secondary power supply voltage is the comparator 206, the reference voltage generation circuit 2
When it becomes lower than the operating voltage of 05, the transistor 20
Since the gate voltage of 7 becomes indefinite, the resistor 202
This prevents the transistor 207 from turning on by pulling up. The impedance of the resistor 202 is
If the gate voltage of the transistor (abbreviated as Tr) is set to a value (several MΩ to several tens MΩ) such that the gate voltage does not float, the increase in current consumption is small (several nA to several tens nA).

Another circuit system will be described based on the same idea. In FIG. 2 (b), 211, 212, 21
3, 214, 215 are MOS-FETs (hereinafter abbreviated as Tr), 216 is a resistor, 208 is a diode for preventing backflow from the secondary power source side to the solar cell, 209 is the main circuit described above, and 210 is the secondary power source. Indicates. The characteristics of Tr214 indicate the scope of the claims of the present invention, and the basic operating principle of the limiter is the same as that of the conventional one. That is, the circuit diagram is the same as the conventional circuit diagram.

The basic operation will be described below. The voltage of the secondary power source is applied to the gates of Tr211 and Tr212, and when the secondary battery voltage rises, the current flowing through the resistor 216 becomes Tr
It increases in proportion to the square of the gate-source voltage of 211 (hereinafter abbreviated as gate voltage). As a result, Tr21
Since the gate voltage of No. 3 increases, Tr213 turns on, the gate voltage of Tr215 rises, and Tr215 turns on. The secondary power supply voltage for turning on the Tr 215 is called a limiter voltage, and the threshold voltage and the amplification factor of each Tr are normally determined so as to be about 1.8V to 2.0V. Further, the resistor 216 is desirably variable in order to finally adjust the limiter voltage. Here, consider the case where the secondary power supply voltage becomes equal to or lower than the threshold voltage (hereinafter, referred to as V _TH ) of each Tr. At this time, T
Since each of r211, 212, and 213 is an enhancement-type MOS-FET, when the gate voltage becomes V _TH or less, the operation of Tr becomes impossible and the gate potential of Tr 215 becomes a floating state. Therefore, Tr21 connected between the gate and the + electrode of Tr215
Only the characteristic of No. 4 is that even if the voltage of the secondary power source 210 drops, Tr2 holds a certain level of impedance.
It is necessary to pull up the gate of 15 to the + side.
Therefore, Tr214 is a depletion type MOS-FET.
Is used so that current flows even when the gate voltage is 0V. Of course, the Tr 214 may be replaced with a resistor, but in this circuit format, an example in which a transistor is used as a resistance element for bias setting has been shown.

The present invention as described above eliminates the limiter short circuit at a low voltage (a region of 0.6 V or less) which has been given up in the past.
It has a simple circuit configuration, and also reliably prevents it.
By doing so, the remaining capacity of the secondary power source is eliminated, and the power system can be automatically set to a chargeable state even when the voltage value becomes the limiter inactive state.

Secondly, the purpose of this embodiment will be to explain the measures for preventing the energy loss when the voltage becomes lower than the low voltage at which the oscillation of the oscillation circuit is stopped, using the example of the pointer type display electronic timepiece. The description will be made while including some conventional methods.

In a conventional pointer-type display electronic timepiece, a motor drive method of driving a motor, which is an electric display converter, from a drive circuit is performed by controlling a final stage flip-flop (hereinafter, referred to as FF) by a motor terminal (hereinafter, referred to as O _1. (Referred to as O ₂ ) is alternately applied with a pulse. Therefore, when the potential of the input and the output of the FF are different in the state where the oscillation is stopped, a potential difference also occurs between O _{1 and} O _2, so that a current of several hundred μA to several mA is applied to the motor unless the oscillation is restarted. Will continue to flow. This probability is 50% in principle
It can happen, so when oscillation stops for some reason, 2
One clock will empty the secondary power supply in a short period of time. For an electronic timepiece with a solar cell that needs to be restarted by charging even after the secondary power supply voltage has dropped below the oscillation stop voltage, suppress the discharge of the secondary power supply as much as possible during that time, making it easier to restart. You need to do it. However, in the conventional motor drive system, as described above, the potential of O ₁ · O ₂ when oscillation is stopped is not guaranteed, and therefore the generated energy of the solar cell is lost between O _{1 and} O ₂ even when trying to charge ( (Because current flows to the motor), it becomes impossible to charge the secondary power supply.

The embodiment is one in which the above-mentioned drawbacks are eliminated, and its basic circuit block is shown in Fig. 3 (a). FIG. 3- (a) shows the minimum required circuit configuration for this embodiment, which is simpler than the actual circuit. In FIG. 3- (a), 301 is an oscillation circuit, 302 is a frequency dividing circuit, 303 is a motor drive circuit which is a drive circuit, 304 is an oscillation stop detection circuit, and 30
Reference numeral 5 denotes a motor which is an electric display conversion device. The reference signal (32768 Hz) of the oscillator circuit 301 is applied to the frequency divider circuit 30.
The signal is divided by 2 for 2 seconds, and the motor drive circuit 30
At 3 the pulse width is differentiated to drive the motor. The pulse width is determined by the clock output from the frequency dividing circuit 302, and is generally about 6 to 7 msec. When the oscillation is stopped, the output of the oscillation stop detection circuit 304 changes to control the drive of the motor drive circuit 303.

Next, a circuit plan of the oscillation stop detection circuit 304 motor drive circuit 303 in FIG. 3A is presented, and the principle of the present invention will be described in more detail.

FIG. 3- (b) shows an embodiment of the oscillation stop detection circuit. Three
Reference numeral 06 denotes an oscillation output (32768 Hz) of the oscillation circuit, and a line to be input to the exclusive OR gate 312 (hereinafter referred to as EXOR) via the inverters 310 and 311;
There is a line directly connected to the other input terminal of the EXOR. Here, the signal 30 that has passed through the inverter 311
7 causes a delay due to the inverter, and the oscillation output 306 is multiplied by the output 308 of the EXOR 312 (65536H).
z) waveform appears. The phase relationship of this operation is shown in the timing chart of FIG. The numbers in FIG. 3 (c) indicate the voltage waveforms of the signals of the same numbers in FIG. 3 (b). Then, in FIG. 3- (b), the signal 308 is Hi.
At the gh level (hereinafter abbreviated as H), since the diode 313 is in the forward direction, charges are accumulated in the capacitor 315 and the signal line 309 indicates H. Here, low potential (Vs
Although the accumulated charge is constantly discharged by the resistor 314 pulled down to (s), a CR time constant larger than the frequency of the signal 308 is set (the capacitor 315 is 10P).
If it is about F and the resistance 314 is about 10 MΩ, charging is superior to discharging and H is maintained. Fig. 3-(c) 30
9'shows the waveform of the terminal voltage of the capacitor 315. When the oscillation is stopped and the signal 306 remains at H level or LOW level (hereinafter abbreviated as L), the signal 308 always remains at L, so that the diode 313 is blocked in the reverse direction. The capacitor 315 is not charged, electric charge flows through the resistor 314, and the signal line 309 holds L. In this way, a circuit showing L when oscillation is stopped and H when oscillation is realized is realized. In order to improve the circuit performance, it is practically necessary to invert the signal 309 to shape the waveform and stabilize the charge / discharge time constant. Further, the control by the diode has a large forward voltage loss (0.3-0.
6V), so it is preferable to use a transmission gate. Although the above circuit is omitted in this section for simplification of description, there is no problem in principle. Next, the motor drive circuit will be described. FIG. 3- (d) is an example of the motor drive circuit, and FIG. 3- (e) is a timing chart for explaining the circuit operation of FIG. 3- (d). Fig. 3-(d)
In the figure, 316 is a 2-second signal from the frequency dividing circuit, 317 is a 128 Hz signal from the frequency dividing circuit, and 318 is a waveform-shaped output of the oscillation stop detection circuit described above. First signal 3
In the state where 18 is H, that is, oscillating, the signal 3
The rising edge of L from 16 to H is differentiated by the signal 317 and output to the NAND gate 323. Further, the falling edge from H to L is output to the NAND gate 324. Therefore, a pulse current flows in the motor 305 in alternate directions once a second, and the hands of the clock can be moved. This operation is similar to the conventional drive circuit. Signal 318 is always H
If so, it becomes a conventional drive circuit. For example, signal 31
Oscillation stops when 8 remains H, the signal 316 is L, and the Q output of the D-type flip-flop (hereinafter abbreviated as FF) 322 is L.
If the state is maintained, the output of the NAND gate 323 becomes H and the output of the NAND gate 324 becomes L, which is widened by the drivers 325 and 326, and a large current remains in the motor 305. However, when the oscillation is stopped, the signal 318 becomes L and the NAND gates 323, 32
Motor terminals 319, 3
Both 20 become L, and the motor current does not flow. That is, the inverter 321, the FF 322, and the NAND gate 3
The output control of the differentiation circuit composed of 23 and 324 is controlled by the signal 318.
It is done in. Here, in order to set O ₁ and O ₂ to the same potential, the drivers 325 and 326 are set to NA as another circuit.
Even if the control is performed by the signal 318 instead of the ND gate or the clocked gate, the same effect can be obtained, which is another embodiment. Alternatively, the signal 316 may be set to L and the FF 322 may be set to H.

A timing chart of the above control is shown in FIG. In FIG. 3 (e), 316 is a 2 second signal waveform, 317 is a 128 Hz signal waveform, 318 is an oscillation stop detection signal waveform,
Reference numerals 319 and 320 denote the driver 32 in FIG. 3- (d).
The output waveforms of 5 and 326 are shown respectively. 316,317 in the figure
The shaded area in indicates that it is indefinite between H and L because the oscillation is stopped. As described in FIG. 3- (d), 319 and 320 hold L in this oscillation stop section. In an actual clock circuit, because of V _DD ground, O ₁ ,
The O ₂ output is normally H and active L negative logic, but this section is all positive logic for the sake of discussion.

By doing this, the energy consumption of the motor can be stopped when the electronic circuit is in the non-operating state, and the charging energy of the primary power source can be smoothly performed even when the electronic circuit is in the non-operating state when the secondary power source is around 0V. It can be used to store secondary power.
Therefore, it is also useful for accelerating the speed at which the electronic timepiece operation is started.

FIG. 4 is one specific example showing the system part of the charging-storage-discharging part in the block diagram shown in FIG. In FIG. 4, a solar cell 401 is used as a primary power source, and a high capacity electric double layer capacitor 402 is used as a secondary power source. Reference numeral 403 is a limiter switch, 404 is a charge switch, and 405 is a discharge switch, which use MOS transistors to suppress energy consumption. Reference numerals 406 and 407 are diodes for preventing backflow. Reference numeral 408 denotes an electronic circuit including the above-mentioned drive circuit, which includes an oscillation circuit for operating the crystal oscillator 409, a frequency dividing circuit, and other necessary circuits. Four
Reference numeral 10 is a coil for driving the motor, and 411 is a condenser for smoothing the load fluctuation of the motor, which is several μm.
It is about F. The operation relationship of each component is as described in FIG.

〔effect〕

As described above, according to the present invention, the overcharge of the secondary power source by the power generation means is detected, and when the overcharge is detected, the overcharge prevention switching means is used to control the short circuit of the power generation means. It is possible to reliably prevent overcharge of the secondary power supply.

Further, according to the present invention, when the voltages of the power generation means and the secondary power source drop below the normal operating voltage of the overcharge prevention switching means, the overcharge prevention switching means is forcibly turned off. Due to the configuration,
For example, even if the remaining capacity of the secondary power supply decreases and the output voltage falls below the normal operating voltage of the switching means, the power system is automatically set to a rechargeable state and the secondary power supply is recharged smoothly. It becomes possible.

Further, according to the present invention, the charging control switching means is connected in series between the power generation means and the secondary power source, and the voltage supplied from the power generation means to the timepiece circuit becomes equal to or higher than the operable voltage of the timepiece circuit. In this case, the charging control switching means is ON-controlled to charge the secondary power source, so that the energy taken in from the power generation means can be supplied to the secondary power source without waste, and the charging speed of the secondary power source can be improved. Can be increased.

In addition to this, according to the present invention, discharge switching means is connected in series between the secondary power source and the timepiece circuit, and normally this discharge switching means is turned off, and the timepiece is controlled by the output voltage of the power generation means. When the circuit is driven and the voltage supplied from the secondary power supply to the timepiece circuit exceeds the voltage supplied from the power generation means to the timepiece circuit, this switching means is turned on and the timepiece circuit is activated by the output voltage of the secondary power supply. With the driving configuration, the clock circuit can be driven by selectively using the higher voltage of the power generation means or the charging means, and thus the power consumption of the secondary power supply can be minimized and It is possible to operate the clock circuit with stable time.

As described above, according to the present invention, it is possible to prevent the secondary power source from being overcharged by the power generation unit, and further, the voltages of the power generation unit and the secondary power source are lowered, and the voltage value is the non-operating voltage state of the overcharge prevention switching unit. Even if it happens, the power supply system can be automatically set to a state where the secondary power supply can be recharged, and when the voltage of the power generation means exceeds a predetermined voltage, the secondary power supply is efficiently charged. Further, there is an effect that it is possible to obtain an electronic timepiece with a charging function, that is, the power supply to the timepiece circuit can be satisfactorily performed while suppressing the power consumption of the secondary power supply to the minimum. Although the embodiments have been described focusing on a pointer type display device, the present invention can be similarly applied to a liquid crystal display device using an optical display element.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the overall configuration of the present invention. FIG. 2A is a first embodiment showing a limiter circuit section according to the present invention. FIG. 2B is a second embodiment showing the limiter circuit unit according to the present invention. FIG. 3A is a block diagram of an electronic circuit that transmits an electric signal to the display device. FIG. 3- (b) is an example of the oscillation stop detection circuit. FIG. 3- (c) is a timing chart diagram in FIG. 3 (b). FIG. 3- (d) shows an embodiment of the motor drive circuit. FIG. 3- (e) is a timing chart diagram in FIG. 3- (d). FIG. 4 is an embodiment showing a charging-storage-discharging system.

Claims (1)

[Claims] 1. A power generating means for generating power based on energy applied from the outside, a secondary power source charged by the power generating means, and a power source voltage selectively supplied from the power generating means or the secondary power source. A clock circuit to be driven; an overcharge preventing switching unit that is connected in parallel with the power generation unit and is on-controlled when overcharge of the secondary power source by the power generation unit is detected; An off control means for forcibly turning off the overcharge preventing switching means when the voltage drops below a predetermined value, and an off control means connected in series between the power generation means and a secondary power source, and connected from the power generation means to a clock circuit. When the voltage supplied to the watch circuit is detected to be equal to or higher than the operable voltage of the timepiece circuit, it is on-controlled, and charging control switching means for charging the secondary power supply, and the secondary Is connected in series between the power source and the clock circuit, is normally off-controlled, and drives the clock circuit by the voltage supplied from the power generation means to the clock circuit, and the voltage supplied from the secondary power source to the clock circuit. A discharge switching means that is on-controlled when the voltage supplied from the power generation means to the timepiece circuit is exceeded and that drives the timepiece circuit by the output voltage of the secondary power source. Electronic clock.