JPS6024969B2 - Electronics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic device equipped with an oscillation circuit and driven by a battery power source.

In recent years, electronic devices equipped with oscillation circuits and powered by batteries,
For example, small electronic computers, electronic clocks, and the like that incorporate sound generating devices, lamps, and the like have been commercialized.

The electronic devices described above have electronic circuits composed of ICs or LSIs, and their power consumption is extremely low. on the other hand,
Loads such as the above-mentioned sound generating device and lamp consume a large amount of power.
Activation of this load causes a significant voltage drop in the battery power supply. For example, if the battery power supply still has sufficient power to maintain the drive of the electronic circuit, but has already experienced a considerable voltage drop, the voltage of the battery power supply may decrease due to the operation of the load mentioned above. The voltage drops below the maintenance voltage, and the electronic circuit stops driving while the load is being operated. Moreover, the rapid power consumption due to the load during this period may completely exhaust the battery life.
Therefore, in conventional electronic desktop calculators, a voltage detection circuit detects when the battery is nearing the end of its life, and when the battery power drops below a predetermined reference voltage, some circuits of the electronic device are stopped. It is being considered to enable only the important parts of electronic equipment to operate. However, in electronic equipment equipped with an oscillation circuit, the lowest operating voltage of the oscillation circuit has large variations due to variations in the LSI, variations in the impedance of the crystal resonator, and the capacitance value of the trimmer capacitor that is the frequency adjustment means. Therefore, when setting the reference voltage, it is necessary to take the above-mentioned variations into consideration and set it to a high voltage, so even if the battery capacity is still sufficient and the electronic device is operating normally, A detection signal may be output from the voltage detection circuit.

Furthermore, if the reference voltage is set too low, detection may not occur until the entire electronic device has completely stopped. This invention was made in view of the above points, and it is an object of the present invention to effectively detect a voltage drop in a battery, stop the operation of the load, and effectively utilize the battery to operate an electronic device for a long period of time. The purpose is to Hereinafter, one embodiment of the present invention will be explained as follows.
This will be explained with reference to FIGS. 6 to 6.

In the figure, reference numeral 1 is an oscillator, and the pulse signal outputted from the oscillator 1 is frequency-divided by a frequency dividing circuit 2, and then clock circuit 3.
The clock circuit 3 obtains clock information such as hours, minutes, and seconds. These clock information is digitally displayed on a liquid crystal display section 5 via a decoder/driver 4. Usually, the oscillator 1 is a crystal oscillator and uses battery power. On the other hand, this electronic timepiece is provided with a lamp 6 for illuminating the liquid crystal display section 5, and is turned on via a manual switch 7.

Reference numeral 8 denotes an oscillation stop detection circuit to which a predetermined branch signal is supplied from the frequency dividing circuit 2, and the detection output of this oscillation stop detection circuit 8 is supplied to a set terminal of an FF (flip-flop) 9.

The FF 9 is normally in a reset state, and when a high potential (VDD) signal is input to the set terminal, the high potential signal is applied to the base of the transistor 10 connected in series with the lamp 6.

Note that the FF9 is reset when the battery power source is replaced. The oscillation stop detection circuit 8, as shown in FIG. C2
and a detection circuit 8c including an N-type MOS transistor 13 and a resistor R3.

Next, the operation of the above circuit will be explained.

First, in the normal state when the switch is not operated, the rectangular wave signal shown by a in FIG.
The signal inputted to the C-MOS inverter 11 of a and shown as b in FIG. 3 is supplied to the base of the MOS transistor 2 of the integrating circuit 8b.

The time constant at this time is determined by the resistor R and capacitor C of the differentiating circuit 8a. Since the MOS transistor 12 of the integrating circuit 8b is turned on for a time t by the threshold voltage (VTBI), at this time the capacitor C2 is discharged by the on-resistance of the transistor 12 and the time constant of the capacitor C2, and at other times, It is charged with a time constant determined by capacitor C2 and resistor R2. Therefore, the output signal of the integrating circuit 8b, which is based on the base of the MOS transistor 13 of the detection circuit 8c, becomes as shown by c in FIG.
Now, since the threshold voltage (VTB2) of the MOS transistor 13 is set lower than the voltage of the output signal c of the integrating circuit 8, the MOS transistor 3
is always kept on during normal oscillation. Therefore,
The output signal of the detection circuit 8c becomes as shown by d in FIG. This state is shown on the left side of the To-To line in FIG.

Therefore, the FF 9 to which the output signal d of the detection circuit 8c is supplied maintains the initial state, that is, the reset state, and the output signal continues to maintain the low potential (Vss). Therefore, the transistor 10 is in the on state, and the lamp 6 can be turned on and off by turning the switch 7 on and off, as described above. Therefore, if the switch 7 is operated when there is sufficient power in the battery power supply, the oscillator 1 continues to oscillate normally. Therefore, the oscillation stop detection circuit 8 is connected to the frequency dividing circuit 2.
receives the rectangular wave signal shown in Figure 3a from
Vss), the transistor 10 is maintained in the on state, and the lamp 6 continues to be lit while the switch 7 is operated. On the other hand, if the switch 7 is operated when a considerable voltage drop has already occurred in the battery power source, the driving voltage will be higher than that of the frequency divider circuit 2, timer circuit 3, etc. due to the voltage drop caused by the lighting of the lamp 6. Oscillator 1 stops oscillating. In this case, since no pulse signal enters the input terminal of the differentiating circuit 8a,
The state is on the right side of the line.

Therefore, the output signal b of the differentiating circuit 8a is a constant voltage (V).

. ), and the base voltage of the MOS transistor 13 of the detection circuit 6c becomes below the threshold voltage. At this point, FF9 is set and the output signal is at a high potential (Vo
o), the base voltage of the transistor 10 becomes a high potential (Voo), the transistor 0 is turned off, and the lamp 6 is immediately extinguished. Further, by turning off the lamp 6, the driving voltage of the electronic circuit returns to its initial state, so that the oscillation circuit 1 immediately resumes oscillation.

Although the clock error caused by the temporary stop of oscillation of the oscillation circuit 1 is extremely small, it is preferable to detect the falling edge of the output signal of the oscillation stop detection circuit 8, that is, the output signal d of the detection circuit 8c.
When the potential changes from a high potential (VDo) to a low potential (Vss), a correction of ±3 town sand is performed. However, the FF
Since the lamp 9 is maintained in the set state until the battery is replaced, the lamp 6 will no longer be turned on even if the light switch 7 is operated. Note that in the above embodiment, the output signal of the FF 9 is supplied only to the transistor 101; however,
A display for indicating that the battery life is running low may be provided on the liquid crystal display section 5, and a display command signal for this display may be sent to the liquid crystal display section 5.

Alternatively, the FF 9 may be reset using a signal that detects the off-operation of the switch 7. In this case, the above-mentioned modification of the soil 3 is more necessary. Further, the transistor 10 may be controlled directly by the output signal of the oscillation stop detection circuit 8 without going through F9. Of course, the configuration of the oscillation stop detection circuit is not limited to the above embodiment. 4 to 6 show the oscillation stop detection circuit 8.
Fig. 4 shows a modification of the diode D. The output of the detection circuit 8c is the same as in the previous embodiment.

Figure 5 shows the case where the transistor of the detection circuit 8c is a P-type MOS transistor, and Figure 6 shows the case where the transistor of the integrating circuit 8b is an N-type MOS transistor, and the transistor of the detection circuit 8c is a P-type MOS transistor. In both cases, the output of the detection circuit 8c is opposite to that of the previous embodiment.

Further, in the above embodiments, an electronic watch has been described, but the present invention is not limited to this. Of course, the load is not limited to a lamp, but may be a buzzer, a speaker, etc. as long as it is selectively activated. In short, any electronic device may be used as long as it has an oscillation circuit and a load that is selectively operated, and is configured to detect the stop of oscillation and stop the operation of the load. As described in detail above, the present invention includes a means for detecting when an oscillation circuit stops oscillating due to a drop in power transmission voltage caused by the operation of a load, and a means for detecting this, and a detection signal from this detection means to stop the operation of the load. As a result, the battery power source can be used for as long as possible, and the user can be made aware of the need to replace the battery power source at the most appropriate time and with a reasonable margin. It has the excellent effect of being able to do so.

[Brief explanation of the drawing]

Fig. 1 is a schematic block diagram showing one embodiment of the present invention, Fig. 2 is a configuration diagram of an oscillation stop detection circuit, Fig. 3 is a time chart thereof, and Figs. 4 to 6 are different versions of the oscillation stop detection circuit. It is a figure showing an example of. 1... Oscillator, 2... Frequency divider circuit, 3...
...Clock circuit, 4...Decoder driver,
5...Liquid crystal display section, 6...Lamp, 7...
...Switch, 8...Oscillation stop detection circuit, 8a
...Differential circuit, 8b...Integrator circuit, 8
c...Detection circuit, 9...Flip-flop, 10...Transistor. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. In an electronic device including a battery power source, an oscillation circuit driven by the battery power source to generate a reference pulse, and a load circuit driven by the battery power source, a detection means for detecting that the oscillation of the oscillation circuit has stopped; An electronic device comprising: load stopping means for stopping the operation of the load circuit in response to a detection signal from the detecting means.