JPS5821713B2 - Matrix type display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a display device used in an all-electronic wristwatch, etc., which has a matrix type electrode and is driven in a time-division manner. The present invention relates to a display device characterized in that an AC pulse of a threshold value or higher is applied in a time-sharing manner to half-selected points and non-selected points, and an AC pulse of a threshold value or higher is applied to half-selected points and non-selected points.

The present invention introduces a time-division drive method to the drive method of liquid crystal displays, etc., and by configuring it with only a circuit having a simple switch function, it simplifies the circuit and at the same time reduces the number of power supplies with different voltage levels. It is an object of the present invention to provide a display device which has a simplified electric circuit structure, lowers power consumption, and has good display contrast by reducing the electric circuit structure and eliminating the use of resistors and the like.

Conventionally, the driving method of the display device of an all-electronic wristwatch with a liquid crystal display method is a method called a static method, in which a waveform of opposite phase is applied to the common electrode and the segment electrode to the selection segment, and a waveform of opposite phase is applied to the selection segment. This method applies in-phase waveforms to the common electrode and segment electrodes.

This type of method requires a decoder for each digit, so
The chip area is large and the cost is high, and the number of wire bondings, that is, the number of connections is large, which inevitably reduces reliability.

In addition, a time-division drive method has been proposed, which has recently been attracting attention, but it has the disadvantage that it not only increases the number of circuits but also increases power consumption because it requires a large number of power supplies with different voltage levels and uses resistors. Therefore, it could not be said that this drive method could fully take advantage of the important characteristic of low power consumption of liquid crystals.

The present invention relates to a driving method for a liquid crystal display system that eliminates the above-mentioned conventional drawbacks, and will be described below with reference to the drawings.

An overall block diagram of an embodiment of the liquid crystal display type all-electronic wristwatch of the present invention is shown in FIG.

1 is an oscillation circuit using a crystal resonator and outputs a steady oscillation signal.

2 converts the output of 1 to IHz or X using a frequency dividing circuit group such as a flip-flop circuit.

Divide down to Hz. Further, the output of the frequency dividing circuit 2 is input to a counter circuit group 3, and the number of pulses thereof is counted.

The output of the counter circuit 3 is passed through a control function that periodically inputs information to the decoder 5 only during a certain time interval, a so-called gate circuit for time division, and then converted into this binary lO
The base number is input to a decoder 5 for conversion into segment signals.

Furthermore, the decoder output is input to the segment drive electrode 6 for converting it into a signal for driving the liquid crystal display device.

Here, the gate signal of the gate circuit 4 that time-divides the counter output is generated by the gate signal generation circuit 8, and this gate signal is further passed through the level shifter 11 to select the digit electrode and drive the digit electrode to the digit electrode drive circuit. 9 is input.

The segment electrode drive circuit 6 acts as a switch that selectively opens and closes the output to determine whether or not to display a liquid crystal display in accordance with the segment signal of the decoder 5, and the digit electrode drive circuit 9 operates to select whether or not to display a digit. The segment electrode signals and the digit electrode signals which have been switched are inputted to the liquid crystal display device 7 to display a desired display.

In addition, DC voltages of different levels are input to the drive electrodes, and the DC voltage from the DC power supply 12, the output of the oscillation circuit 1, and the frequency-divided signal divided into several stages are transferred to a C-MOS inverter, a capacitor, and a diode. The voltage is inputted to the booster circuit 10 to obtain the required voltage.

An embodiment of the present invention is limited to a four-digit display liquid crystal display device, and its driving method and operation will be described below.

FIG. 2 is a block diagram of a gate signal generation circuit that sequentially generates gate signals shifted by a certain time to each gate circuit 4 in order to time-divide the output of each counter circuit and transmit information.

When the output from the n + l p n + 2nd stage of the frequency dividing circuit 2 is input to the AND circuit 13, the pulse is changed to the duty, and this output is input to the 4-stage shift register 14, and the n-th stage division output is input to the AND circuit 13. When used as a clock signal, each output stage of the shift register 14 outputs Φ1. Φ2. Φ3. The gate control signal of Φ4 is changed.

The waveforms of these circuits are shown in FIG.

FIG. 4 shows a detailed drive circuit.

For ease of understanding, the waveforms of each part are shown in FIG.

The reference voltage VDD of the DC power supply 12, the DC voltage 2vI)I) doubled by the booster circuit 10, and 3VDD tripled by the booster circuit 10 are used as drive sources.

C-1 is a segment electrode control circuit, which includes two transmission gates TG1. Different voltage levels of reference voltages VDD and 2VDD are input to TG2, the gate electrodes are connected oppositely to each other via an inverter 15, and the outputs are connected in common.

Furthermore, two transmission gates TG as above
3. Different reference voltages 3DD and 0VDD are connected to TG1, the gate electrodes are connected via an inverter 16, and the outputs are commonly connected.

The control signal of this segment electrode control circuit c-i is the n+3rd stage output f of frequency divider circuit 2: 3VDD amplifier 1T
is amplified by

Further, C-2 is a digit electrode control circuit which has the same configuration as the segment electrode control circuit C71, but the input voltage level to each transmission gate is different and the control signal to the transmission gate is inverted by the inverter 18. The difference is that

In these configurations, when control signal n+3 is 3VDD, transmission gate TG2. TG4. T.G.
TG7 is ONL, other transmission gates are OF
F.

Also, when it is 0VDD, the transmission gate TG
,,TG3. TG, TG8 are ONL, and other transmission gates are OFF.

Therefore, the signal waveforms of the control signal O2P output from the segment electrode control circuit C-1 and the control signals Q and R output from the digit electrode control circuit C-2 are as shown in FIG.

6 is a segment electrode drive circuit, and similarly to the segment electrode control circuit C-1, two transmission gates TG0.6 are paired. A number of circuits constituted by inverters 19 connecting between TG1o and the gate of one transmission are provided corresponding to the segment parts a to g of the decoder 5, and the input thereof is the segment electrode control signal O5P, and the control signal is the control signal of the decoder. 5 segment signal.

9 is a digit electrode drive circuit, which is connected to the segment drive circuit 6.
It has the same configuration as the inverter 20 for inverting the signal, and the outputs Q and R of the digit electrode control circuit C-2 are 2
transmission gates TG1□, TG12. These circuits are provided according to the number of digits, and the example in the figure shows an example of four digits.

The control signal for each digit is sent to the gate control signal. Φ2. Φ3. is amplified by the level shifter 11 and input.

In a display device having electrodes arranged in a matrix, consider a case where a selected point (X□, Yl) of a matrix (Xi, Yi) consisting of horizontal electrodes Xi and vertical electrodes Y i l is displayed.

In the horizontal electrode drive circuit 6, when the decoder output a is at the 3vDTP level, TG is turned on and TGlo is turned off.

On the other hand, when the voltage is 0VDD, TG9 is 0FFL and TGl. is O
Do N.

Similarly, the control signals Φ1 to Φ4 of the vertical electrode drive circuit 9 are controlled by signals in which the duty pulses are shifted from each other by the pulse width, and if Φ is at the level of 3VDD, TG, 1 is ONL.

TG12 is turned off.

On the other hand, when the voltage is 0VDD, the operation is reversed.

Therefore, the signals X1 to X4 input to the horizontal electrodes. The signals Y□, ¥2 input to the vertical electrodes have the waveform shown in FIG.

When you want to display the selection point (Xl, Y□), use the switch SX1 composed of a transmission gate and an inverter.
．． SX2. SY1 and SX2 operate as shown in FIG.

Therefore, as shown in Fig. 5, the selection point (Xl, ¥1) has a cycle of +3VDD, and the last period has an opposite phase of -3V.
A driving voltage for the DD will be applied.

Also, other semi-selected points and non-selected points have very active soil VD.
Only voltage D is applied.

According to the drive circuit of the present invention described above, +3VD is applied to the selection point.
Apply voltage D, and apply voltage V to other non-selected points.
Since only the DD voltage is applied, crosstalk can be completely prevented, and by using a material with a display device threshold voltage slightly higher than VDD, a display with good contrast can be achieved by using a material with a threshold voltage slightly higher than VDD. is obtained.

Further, since the voltage can be easily obtained using a booster circuit instead of dividing the voltage using resistors, power consumption can be reduced.

Furthermore, since only one decoder is required, the IC chip area can be reduced, and the number of connectors and wire bonders can be greatly reduced, thereby improving reliability.

Furthermore, since it is equivalently driven by alternating current, it has various effects such as making it possible to maintain the life of the liquid crystal for a long time.

[Brief explanation of the drawing]

FIG. 1 is an overall block diagram of an embodiment of the present invention, and FIG.
The figure is a diagram of the gate control signal generation circuit, Figure 3 is a waveform diagram of each signal in Figure 2, Figure 4 is a block diagram of the segment electrode and digit electrode drive circuit, and Figure 5 is each part of the drive circuit in Figure 4. A signal waveform diagram, a waveform diagram of selected points and non-selected points in the matrix electrode, and FIG. 6 is a switch state diagram of the matrix electrode drive circuit. 1... Oscillation circuit, 2... Frequency dividing circuit, 3
... Counter circuit, 4 ... Gate circuit, 5 ... Decoder, 6 ... Segment electrode drive circuit, 7 ... Liquid crystal display device , 8...
... Gate signal generation circuit, 9 ... Digit electrode drive circuit, 10 ... Boost circuit, 11 ... Level shifter, 12 ... DC power supply, 13・・・・・・
...AND circuit, 14...Shift register, T
G,~TG,. ...Transmission gate, SX1. SX
2. SYl. SX2...Switch,...Gate control signal, C-1...Segment electrode control circuit, C
-2... Digit electrode control circuit.

Claims (1)

[Scope of Claims] 1. In a matrix type display device in which a plurality of horizontal electrodes and a plurality of vertical electrodes are arranged in a matrix and display is performed at the intersections of the horizontal electrodes and the vertical electrodes,
a first signal having a voltage level VDD of 2VDD and a second voltage level 2VDD higher than the first voltage in another half cycle; 3 voltage level 3VDD and other half period 0VDD
a second signal that is synchronized with the first signal and has an opposite phase; and a fourth signal that is synchronized with the second signal and has an opposite phase; The second signal is connected to the switch group of horizontal electrodes (or vertical electrodes), and the third and fourth signals are connected to the switch group of horizontal electrodes (or vertical electrodes).
Connect the signal to the switch group of vertical electrodes (or horizontal electrodes),
A matrix type display characterized in that the switch group is operated by a control signal to apply a voltage higher than a threshold voltage to selected points and a voltage lower than the threshold voltage to non-selected points and half-selected points. Device. 2. In the matrix type display device according to claim 1, each voltage level of the first voltage level VDD, the second tE level 2VDD, and the third voltage level 3VDD is connected to the output terminal of the booster circuit. A matrix type display device characterized by: