JPS6130713B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic timepiece, and more particularly to an alarm buzzer drive circuit and a lighting circuit for an illumination element that illuminates an indicator.

BACKGROUND ART Conventionally, a buzzer driving means of an electronic watch with an alarm amplifies an alarm signal from an electronic circuit using a bipolar transistor.

FIG. 1 shows an example of a conventional buzzer drive circuit, in which 1 is an electronic circuit, 2 is a transistor, 3 is a booster coil, 4 is a piezoelectric buzzer, 5 is a current limiting resistor,
6 is a battery.

Here, when an alarm signal is supplied from electronic circuit 1 to the base of transistor 2, transistor 2
By repeating ON and OFF, current flows from the battery 6 to the boost coil 3, and 10
A flyback voltage of several volts is generated, and this flyback voltage is applied to the piezoelectric buzzer 4 to generate an alarm sound.

The current limiting resistor 5 is inserted on the emitter side of the transistor 2, and by applying a current return to the transistor 2, it limits an increase in the collector current due to variations in _hFF of the transistor 2 or temperature changes.

On the other hand, electronic watches using a liquid crystal display device as a display means are very difficult to see in places where there is no surrounding light, such as at night, so it is necessary to attach an illumination element such as an illumination lamp.

Conventionally, for example, the contacts of an operating switch were used directly to turn on the lighting lamp, but for wristwatches, etc., where the number of operating switches is limited, it is necessary to use an operating switch exclusively for lighting the lamp. It is difficult to provide such a switch, and in many cases, the switch for turning on the lamp also serves other functions, such as adjusting the time.

However, in this case, the lamp would always turn on every time an operation was performed to adjust the time, resulting in a shortened battery life and lamp life.

For this reason, a method was devised to control the lighting of the lamp by a signal from an electronic circuit and turn on the lamp only when necessary, but this method was constructed using commonly used C-MOS. Since the output impedance of the electronic circuit is relatively large, it must be amplified by a bipolar transistor, similar to the buzzer drive circuit.

Figure 2 shows a conventional lamp lighting circuit for this purpose, where 7 is an electronic circuit, 8 is a lamp lighting switch that also serves other functions, 9 is an illumination lamp, 10 is a transistor, and 11 is a lamp switch. The light signal line 12 is a battery.

With such a circuit, when a predetermined condition is met, the signal from the lamp lighting switch 8 is received, the lamp lighting signal line 11 is set to logic "1", the transistor 10 is turned on, and the lamp 9 is turned on. can do.

However, in an electronic clock with an alarm, two transistors are required for the buzzer drive circuit and two transistors for the lamp lighting circuit, and the number of terminals in the electronic circuit is two, one for the buzzer signal line and one for the lamp lighting signal line.
Since the number of books would increase, this would cause a major hindrance to miniaturization of modules, rationalization of work processes, reduction of costs, etc.

The present invention is made to address the above-mentioned drawbacks.
By using both a buzzer drive circuit and a lighting element lighting circuit, there is only one transistor and one signal line from the electronic circuit, thereby providing an electronic clock with an alarm that satisfies both functions. .

Next, embodiments of the present invention will be described based on the drawings.

FIG. 3 shows a buzzer/lamp driving circuit according to an embodiment of the present invention, in which 13 is a lamp lighting switch that also serves other functions, 14 is an electronic circuit, 15 is a buzzer signal line, 16 is a transistor, 17 is a boost coil, 18 is a piezoelectric buzzer, 19 is a lamp, 2
0 is a battery.

Now, to explain the case where this circuit works as a buzzer drive circuit, when the time currently displayed by this electronic clock matches the alarm sounding time set in advance in the electronic circuit 14, the buzzer signal line 15 receives a signal of 2 to 4 KHZ. A ringing signal is output.

The base terminal of the transistor 16 is connected to the buzzer signal line 15, and it repeats switching according to the buzzing signal, and when the transistor 16 is turned on, the voltage is transferred from the battery 20 to the boost coil 17 and the lamp 19 connected in series. current flows in.

Since the current at this time changes in an alternating current manner, the ratio of the impedance of the booster coil and the lamp is
9 is about 120Ω, while boost coil 17
is an AC impedance, so if the inductance is 50mH and the ringing signal is 4KHZ, it will be about 1.2KΩ, and the impedance of the boost coil is about 10 times larger than the impedance of the lamp 19, so the impedance of the lamp can be ignored. can. That is, when the circuit shown in FIG. 3 works as a buzzer drive circuit, a current flows through the boost coil 17 regardless of the resistance of the lamp 19, the voltage is boosted, the piezoelectric buzzer 18 vibrates, and an alarm sound is generated. . Next, the case where this circuit works as a lamp lighting circuit will be explained. Lamp lighting switch 1
3 is turned ON, when the buzzer signal line 15 is set to logic "1" under the control of the electronic circuit 14, the transistor 16 is turned ON and current from the battery 20 flows through the boost coil 17 and the lamp 19. .

If the buzzer signal line 15 holds the logic "1", the current flowing through the boost coil 17 will be direct current, so the impedance of the boost coil 17 will be only for the direct current, and the winding of the coil may be made slightly thicker. It is possible to achieve a low impedance of about 10Ω. The DC impedance of the boost coil 17 is about 10Ω, whereas the impedance of the lamp 19 is about 120Ω as described above, so the voltage drop due to the boost coil 17 can be almost ignored, and the lamp 1
9 is definitely lit. That is, according to the circuit shown in FIG. 3, an alarm sounds when a rectangular AC signal is output to the buzzer signal line 15, and a lamp is lit when a DC signal is output.

As described above, the electronic clock with alarm provided by this embodiment can serve as both the buzzer drive circuit and the illumination lamp lighting circuit, so the number of external transistors can be reduced to just one, and the electronic circuit The number of signal lines from can also be reduced to one.

In addition, the resistance of the lamp 19 connected in series with the boost coil 17 has the function of limiting the current when driving the buzzer, so it suppresses variations in _hFF of the transistor 16 and variations in the inductance of the boost coil 17. Therefore, the current limiting resistor 5 explained in FIG. 1 becomes unnecessary. Furthermore, since the resistance of the booster coil 17 connected in series with the lamp 19 has a very large resistance value at the moment the lamp is turned on, it is possible to reliably absorb the surge current when the lamp 19 is turned on. This makes it possible to completely prevent the voltage drop in the battery caused by the surge current of the lamp, which adversely affects the electronic circuitry.

Therefore, according to the present invention, the number of circuit components for driving the buzzer and turning on the lighting elements can be greatly reduced, which has a great effect on downsizing the module, streamlining the work process, and reducing costs. This is highly effective in preventing circuit malfunctions and extending lamp and battery life.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional buzzer drive circuit.
Fig. 2 is a circuit diagram showing a conventional lamp lighting circuit, Fig. 3 is a circuit diagram showing a buzzer and lamp driving circuit of the present invention, 13... switch, 14... electronic circuit, 15...
...Buzzer signal line, 16...Transistor, 17...
...Boost coil, 18...Piezoelectric buzzer, 19...
Lighting element, 20...battery.

Claims (1)

[Claims] 1. An electronic device comprising a display means, a lighting element for illuminating the display means, an alarm buzzer, a booster coil for the buzzer, and an electronic circuit for controlling the buzzer and the lighting element. In the watch, the lighting element and the boosting coil form a circuit configuration connected in series, and when the buzzer is driven, an AC voltage controlled by the electronic circuit is applied to the lighting element when the lighting element is turned on. An electronic timepiece with an alarm, characterized in that a DC voltage controlled by an electronic circuit is applied to each of the series circuits.