JPS582886A - Power source circuit unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply circuit device for an electronic circuit, for example, an electronic clock in a calculator, etc., which is equipped with a display means for displaying information.

With the recent development of LSI (Large-Scale Integrated Circuits), electronic devices such as calculators and electronic watches have only one arithmetic circuit.
It has become common for devices to be implemented using only one L8X. Moreover, the current consumption is 1 at a voltage of about 3v or 1.5v.
It has become possible to realize products with very low power consumption, such as 0#A or less. With the progress of LSIs, their power supplies have also undergone drastic changes. In other words, small electronic devices such as calculators and electronic clocks use various types of batteries as power sources, but as products consume less power, the batteries used are also smaller, lighter, and have higher current capacity. The smaller ones are possible & the 9th.

Due to the above-mentioned background, solar cells have recently been used in electronic devices such as calculators and electronic watches. .

FIG. 1 shows an example of the load characteristics, that is, the voltage-current characteristics, when the illuminance of the solar cell is 100 to 500 lux. As shown in the figure, the solar cell has a characteristic that as the surrounding illuminance increases, the power capacity increases, and as the illuminance decreases, the power capacity decreases. Because of these characteristics, it is not possible to supply a constant voltage to the arithmetic circuits of electronic devices using solar cells, unlike a general battery such as a silver oxide battery. In other words, when the ambient illuminance changes, the power supply voltage changes greatly depending on the orientation of the product relative to the light source.
, the minimum operating voltage (vEIDMI) is required for the arithmetic circuits of electronic devices.
M), if the operating voltage becomes lower than this V, the arithmetic circuit D'11! My father-in-law malfunctions. The value of this vDDMIM is, for example, the standard operating voltage is -a, and the value of the ovo train LSI is -2.2Vli degrees. When using a solar cell, it is quite natural for the operating voltage to fluctuate by Km above or below the value of vDDMIII depending on the usage conditions of the product. This rounding often occurs when the product is made incorrectly.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an entire electronic circuit that can prevent malfunctions due to the influence of power supply voltage that varies depending on surrounding conditions.

An embodiment of this invention will be described below with reference to the drawings. First, when explaining an example of a different configuration, the present invention will be explained in detail. That is, as is clear from the characteristics of the solar cell shown in FIG. 1, if the resistance value of the load to be driven is constant, as the illuminance decreases, the voltage applied to the load decreases. For example, when the load resistance RL = 400 kΩ, the illuminance is 20
At 0 lux, the voltage applied to load K is -2.85 Vli degrees, but when the illuminance drops to 150 lux, the voltage becomes -2.6 V.
K becomes. However, when the illuminance is 150 lux and the load resistance is RL = 500 kΩ, the voltage applied to the load is -2,
It is 75V. From the above, when the power supply voltage decreases,
If an electronic circuit is realized in which the load resistance value applied to the power supply K increases, it is possible to reduce the drop in the power supply voltage by one degree.

This invention company provides a power supply device that makes it possible to realize such an electronic circuit.Specifically, when the power supply voltage drops, the drive of the display device is stopped, thereby reducing the load on the power supply. K is added to increase the resistance.

The present invention will be described in detail below, taking as an example an electronic device having the most common liquid crystal display device shown in FIGS. 2 and 3.

Figure 2 shows a 77 segment 1-1 liquid crystal display commonly used in trains and the like.

This example is i in 3? , -T, so the pack rate signals are COMJ, COMj.

There are three types of COM I, and three types of segment signals per digit: 80 + 81 + 8 m.

Figure 3 shows the signal waveform map 1 that drives the liquid crystal shown in Figure 2. As an example, as shown in the figure <O, -V, -V.

3! The liquid crystal is driven using four voltage levels of ID 3 0D ■□. or,
As shown in the figure, when each segment is on (lit), a potential difference of Klv□I is applied between the segment and the pack plate, and when it is off (not lit), a potential difference of 1HVoo is applied.
A potential difference of l is applied. These four voltage levels for driving the liquid crystal are generally generated by voltage division using resistors. When the current flows through the resistor K, which is used to divide the power supply voltage, and KfkD, which drives the liquid crystal, becomes a major factor in lowering the load resistance of the entire electronic circuit. FIG. 4 shows an example of a circuit in which the present invention is used to prevent current from flowing through the power supply type 5-voltage dividing resistor and stop driving the 't1 & crystal when the power supply voltage drops.

In Fig. 4, 11 is a liquid crystal drive circuit, 12 to 14 are power supply voltage dividing resistors, 1j is a capacitor, I6 to III IN channel type MOB), 20° and 21 are P channel, L type MOB), 7 transistors, 22. .

24 is a resistor, 25 is an arithmetic circuit, and 26 is a power source for, for example, a solar cell. The circuit in FIG. 4 shows the case of negative logic; 11. A negative voltage with respect to 09 is applied to the arithmetic circuit 25.

A stain source voltage detection circuit 21 is constituted by the transistors 11 to 19, the transistor 21, and the resistors 22 to 24. The transistor 1g is a constant voltage circuit, and the potential at point r-)A of this transistor 9 is the potential VDD of the power supply 26.
Threshold 1 hold voltage V of transistor 19 than I
□min r −) The potential at the 8 points is vI=lvl)gll−
vtll' B, +1. ], transistor 11
is turned on. However, RI is the resistance IJ% ms is the value of the resistance 24. The potential at the source point C of the transistor 180 is
On-resistance R0N and resistor 22 indicate the value of resistor 21.

From this, as the voltage between the dirt and the source of the transistor 1a, t'' 1vDll -1vnell IV,l, and , ■, and □ approach 0vllK, the smaller , and the on-resistance, l.1 suddenly becomes larger. ,vne
When t approaches 0vllK, the potential at point 0 suddenly -〇'llK
Approaching 3. This amount of change can be controlled by the value of the resistor 22. Transistor 11 and transistor 21 are CMOB inverters for waveform shaping, transistor 1σ and transistor 20 are liquid crystal drive circuit 11 and power supply voltage dividing resistor 12.
C&&)8 inverter which supplies drive voltage V□2 to ~14. Now, the power supply voltage V□ is lower than the voltage at the 0 point V
If c becomes below the threshold voltage (v,.) of the CMO 8-inch circuit consisting of transistor 1r, transistors 21.
1 and the drive voltage vDD2 applied to the power supply voltage dividing resistors 12 to 14 becomes Ov, which means that the power supply 2# of the display device is turned off. Further, the power supply voltage vDD stops, and the potential V at the 0 point becomes V□.

If it is above, the drive voltage vDD2 is vDD
, and the display device is powered on. The potential V at point 0 is V□. v when crossing
It is clear from the above explanation that the value of DD can be controlled by the resistor 22. So, for example, if the standard operating voltage is -av, the minimum operating voltage (V')
In the arithmetic circuit 25 of the -22v11D station, the potential vc at the 0 point is V□. - The value of VDDI when crossing V! --Assume that you have selected 43VK. The waveform of the driving voltage VD□ applied to the display device of this electronic circuit is as shown in FIG. 5 with respect to fluctuations in the power supply voltages V and □. As is clear from this figure, Ovlm is 4v□ from the potential V within the operating voltage range of the arithmetic circuit 25.
■1114 is Ov, vDI), Kavx
If Yoku is also increased, it becomes equal to V□2 a VDDI. Therefore, when the power supply voltage VDDI is sufficiently higher than the minimum operating voltage (V, □□) of the arithmetic circuit 25, the display device is driven. Then, vDD is the above (vD, Mx□
)K, the display drive voltage v0112 becomes Ov.

That is, by stopping the driving of the display device,
The load resistance value applied to the power supply increases, making it difficult for the power supply voltage to drop. Therefore, a situation in which the arithmetic circuit 25 malfunctions is less likely to occur.

As described above, according to the present invention, the power supply voltage can be set to any voltage V within the operating voltage range of the arithmetic circuit! 4.Equipped with an electric pressure detection circuit that detects whether it is high or low.
If the power supply voltage is higher than V, the calculation is concluded! Since we decided to drive the non-display device and stop driving the calculation result display device if it is low, 411 applies to electronic devices that use a power source whose electromotive voltage is likely to fluctuate depending on the surrounding conditions, such as a solar cell. It is effective in preventing shadow movement. Note that the meaning of the operation in the above-mentioned arithmetic circuit has a broad meaning indicating at least the production of a signal to be displayed.

9-

[Brief explanation of the drawing]

Fig. 1 is a voltage-current characteristic diagram of a solar cell, Fig. 2 is a display/arm turn diagram of a general liquid crystal display device, Fig. 3 is a driving voltage waveform diagram of the above display device, and Fig. 4 is a diagram of the display device of the present invention. A circuit diagram of a liquid crystal display device according to an embodiment, and FIG. 5 is a driving voltage waveform diagram of the above device. 11...Liquid crystal drive circuit, 12-14...Resistance for power supply voltage division, 1#-1#...N-channel m1MO8 transistor, 20-21...P-channel type MO8)
Ransistor, 22-24...resistance, 2C...power supply,
21...Power supply voltage detection circuit. Applicant's agent Patent attorney Takehiko Suzue 104- 1st Wi Figure 2 53 52 51 jl! 3W! i

Claims (1)

[Claims] A power source, an arithmetic circuit, an arithmetic result display means for displaying the arithmetic results of the arithmetic circuit, and detecting whether the voltage of the power source is higher or lower than any voltage within the operating voltage range of the arithmetic circuit. comprising: a power supply voltage detection circuit; and means for driving the arithmetic result display means when the power supply voltage is higher than the arbitrary voltage, and operating means when the distribution power supply voltage is lower than the arbitrary voltage. A power supply circuit device characterized by: