Electronic instrument

• US 6,327,127 B1
• Filed: 01/22/1999
• Issued: 12/04/2001
• Est. Priority Date: 01/28/1998
• Status: Expired due to Term

• Current Assignee: Ablic Inc. (Minebea Mitsumi, Inc.)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Utsunomiya, Fumiyasu, Yoshida, Yoshifumi
• Primary Examiner(s): Leja, Ronald W.
• Application Number:
  US09/235,675
• Time in Patent Office: 1,047 Days
• Field of Search: 361/86, 361/88, 361/92, 307/87, 307/38, 307/39, 307/103, 307/116, 307/125, 307/130, 368/66, 368/156, 368/157, 368/159, 368/203, 368/204, 368/327
• US Class Current: 361/92
• CPC Class Codes: G04C 10/00 Arrangements of electric power supplies in time pieces circuits G04G19/00; mounting, assembling of components of electromechanical watches G04C3/008, of electronic watches G04G17/00
• CPC Class Codes: H02M 3/1563 without using an external clock H02M3/158 takes precedence

Abstract

An electronic instrument in which erroneous operation after power is applied thereto even in the case where a power source voltage is not quickly raised. Power is generated by a power source such as a thermoelectric conversion device and stored in a secondary battery or charge storage device through a optional boosting circuit. A control circuit and a main circuit are supplied with the power. However, the control circuit has a lower minimum operating voltage than the main circuit. Thus, with the increase in level of the power source voltage, the control circuit starts to operate before the main circuit and outputs a control signal to prevent the main circuit from operating in such a manner that a through current is prevented and the main circuit is prevented from drawing appreciable current from the power source circuit, which would prevent the voltage of the secondary battery or the charge storage device from increasing. When the power source voltage is increased to a voltage level at which the main circuit can operate in a stable manner, the control circuit enables operation of the main circuit.

Claims

1. An electric instrument comprising:

a main circuit for performing a given function and having a minimum operation voltage at or above which stable operation may be achieved and below which unstable operation may be achieved;

a control circuit for producing a control signal and having a minimum operation voltage at or above which stable operation may be achieved, the minimum operation voltage of the control circuit being lower than the minimum operation voltage of the main circuit; and

a power source for supplying a power source voltage to the main circuit and the control circuit;

wherein the control circuit receives the power source voltage and outputs the control signal for stopping operation of the main circuit when the operation voltage is at a level between the minimum operation voltage level of the control circuit and the minimum operation voltage level of the main circuit, and for outputting the control signal for enabling operation of the main circuit when the operation voltage reaches the minimum operation voltage level of the main circuit.

2. An electronic instrument according to claim 1;

wherein the control circuit comprises a detection circuit for detecting an input voltage of the control circuit and producing a detection signal in accordance therewith, a timer circuit for inputting the detection signal output by the detection circuit and outputting the control signal in accordance therewith after counting for a predetermined delay time, and a switch circuit for receiving the control signal output by the timer circuit and selectively connecting the power source to the main circuit in accordance therewith so that the power source is disconnected from the main circuit the predetermined time after the detection circuit detects that the input voltage of the control circuit is lower than the minimum operating voltage of the main circuit.

3. An electronic instrument according to claim 1;

wherein the main circuit comprises a clock system for performing a timekeeping function.

4. An electronic instrument according to claim 3;

wherein the clock system comprises an oscillator, a frequency-dividing circuit for frequency dividing an output signal of the oscillator, and display means for displaying time, and wherein the control circuit resets the frequency-dividing circuit of the clock system.

5. An electronic instrument according to claim 1;

wherein the main circuit includes a switching element and the control circuit outputs the control signal for maintaining the switching element in an off state when the supply voltage output by the power source is not at least the minimum operation voltage of the main circuit to prevent the switching element from allowing a current to pass therethrough when the main circuit is disabled by the control circuit.

6. An electronic instrument according to claim 5;

wherein the main circuit includes a motor, and the switching element is a MOS transistor used for driving the motor.

7. An electronic instrument according to claim 1;

further comprising storage means disposed at an output side of the power source, wherein the control circuit includes a detection circuit for monitoring an output voltage of the power source, and a switch circuit for selectively supplying electric power from the storage means to the main circuit, and wherein the power supply to the main circuit is cut off when a voltage of the storage means is not higher than a prescribed voltage value near the minimum operation voltage of the main circuit.

8. An electronic instrument according to claim 7;

wherein the control circuit comprises a reference voltage generating circuit for generating a reference voltage equal to the prescribed voltage value, and a comparison circuit for comparing the reference voltage with an input voltage of the control circuit, and a MOS transistor, wherein an output signal of the comparison circuit is connected to a gate of the MOS transistor, and a source and a drain of the MOS transistor are respectively connected to an input terminal and an output terminal of the control circuit.

9. An electronic instrument according to claim 1;

wherein a threshold value of transistors used in the control circuit is made lower than that of transistors used in the main circuit.

10. An electronic instrument according to claim 1;

wherein the power source comprises electric power generating means for generating electric power, and storage means for storing the electric power generated by the electric power generating means.

11. An electronic instrument according to claim 10;

wherein the electric power generating means is a thermoelectric conversion element.

12. An electronic instrument according to claim 10;

further comprising a boosting circuit for boosting an output voltage of the electric power generating means to charge the storage means.

13. An electronic instrument according to claim 1;

wherein the main circuit comprises a clock circuit including an oscillator, a frequency-dividing circuit for frequency dividing an output signal of the oscillator and producing a frequency-divided output signal, time counting means for counting time based on the frequency-divided output signal, and display means for displaying time;

wherein the control signal is supplied as a reset signal to at least one of the frequency-dividing circuit, the time counting means and the display means.

14. An electronic instrument according to claim 13;

wherein the display means includes a display driven by a stepper motor and a motor driving transistor for driving the motor;

wherein the control signal is supplied as an input to the motor driving transistor so that current is not consumed thereby when the supply voltage is lower than the minimum operating voltage of the main circuit.

15. An electronic instrument according to claim 13;

wherein the power source includes a thermoelectric conversion device for producing an output voltage in response to a temperature difference thereacross.

16. An electronic instrument according to claim 15;

wherein the thermoelectric conversion device comprises a plurality of N-type and P-type thermoelectric material elements connected in series between a pair of opposing substrates.

17. An electronic instrument according to claim 15;

wherein the power source further comprises a boosting circuit for boosting the output voltage of the thermoelectric conversion device.

18. An electronic instrument according to claim 17;

further comprising a capacitor to be charged by the output of the boosting circuit.

19. An electronic instrument according to claim 18;

wherein the capacitance value of the capacitor is at least twice the capacitance value of the main circuit as seen from a power source input terminal thereof.

20. An electric instrument comprising:

a main circuit for performing a given function and having a minimum operation voltage at which the main circuit can perform the function in a stable manner, the main circuit including a switching element having a large driving capability;

a power source for producing electric power;

a storage device for storing electric power output by the power source and supplying stored electric power to the main circuit; and

a control circuit for maintaining the switching element in an off state until the stored electric power reaches the minimum operation voltage of the main circuit to prevent a through current in the switching element from preventing the stored electric power from increasing in voltage level.

21. An electronic instrument comprising:

a main circuit for performing a given function and having an electronic element serving as a current drain so that a power source voltage applied to the main circuit is not increased if the electronic element is turned on when the power source voltage is lower than a minimum operation voltage at which the main circuit performs the given function in a stable manner;

electric power generating means for generating electric power;

storage means for storing the electric power output by the electric power generating means and supplying stored power to the electronic element;

a control circuit for supplying the stored power to the electronic element only when a voltage of the stored power is higher than a first predetermined voltage which is higher than the minimum operation voltage of the electronic element, and for preventing the stored power from being supplied to the electronic element when a voltage of the stored power is lower than a second predetermined voltage which is lower than the first predetermined voltage and higher than the minimum operation voltage of the electronic element.

22. An electronic instrument comprising:

a main circuit for performing a given function and having an electronic element serving as a current drain so that a power source voltage applied to the main circuit is not increased if the electronic element is turned on when the power source voltage is lower than a minimum operation voltage at which the main circuit performs the given function in a stable manner;

electric power generating means for generating electric power;

storage means for storing the electric power output by the electric power generating means and for supplying a stored power to the electronic element;

a control circuit supplying the stored power to the electronic element during a predetermined time from the moment a voltage of the stored power reaches a predetermined voltage value which is higher than a minimum operation voltage of the electronic element, and, after the predetermined time, continuing to supply the stored power to the electronic element only if the voltage of the stored power is higher than the predetermined voltage.