JPS6073586A - Driving of liquid crystal display 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 [Technical Field of the Invention] The present invention relates to a driving method for a liquid crystal display device, and particularly to a suitable driving method for one that performs time-division driving.

[Technical background of the invention and its problems]

Liquid crystal display devices can be made small and thin and can be driven with very little power consumption, and the driving voltage is also low, so they play an important role in the miniaturization and portability of devices, and are used in a variety of fields. It can be applied to equipment and equipment, and its application is expanding to new fields.

Unlike light-emitting diodes, liquid crystal displays need to be operated on alternating current. However, as the amount of displayed information increases, the driving method of liquid crystal display devices is changing to high-duty devices, such as dot matrix type liquid crystal display devices. Divided driving is now required, and for this reason a temperature compensation circuit is used to vary the driving voltage of the liquid crystal display device depending on the temperature.

However, in the conventional drive method that performs temperature compensation, the power supply voltage of the device needs to be 0.6 V or more higher than the voltage required for the liquid crystal display because transistors are connected in series to perform temperature compensation. It has various drawbacks, such as not being able to meet the demand for low driving voltage as a liquid crystal display device, and being contrary to the demand for low power consumption as a liquid crystal display device due to the large current required for the temperature compensation circuit. was there.

[Purpose of the invention]

The present invention has been made in view of these points, and
It is an object of the present invention to provide a method for driving a liquid crystal display device that performs good temperature compensation in response to changes in ambient temperature, operates at a suitable applied voltage, and provides excellent display at a low driving voltage and low power consumption.

[Summary of the invention]

A method for driving a liquid crystal display device according to the present invention is a method in which a blanking period that varies depending on temperature is provided in the waveform of an applied voltage for driving a liquid crystal display device, thereby achieving an extremely excellent display. This enables a liquid crystal display device that achieves lower driving voltage and lower power consumption.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

(Figures 1 to 3) Actual example 1 In Figure 1, (1) is a 1/8 duty liquid crystal display.

(2) is a liquid crystal display driver circuit, (3) is a frame counter, (4) is a blanking time count circuit, and (5) is an oscillator. The liquid crystal display (1) has a scanning side electrode y1 + Ytl ``''' r Ya and a data signal side electrode xl l I2 t'''''+xn, which are connected to the liquid crystal display and the driver circuit (2). There is. This driver circuit (2) has terminals v, e vt l ”3 +V for determining the voltage level applied to the liquid crystal display.
It is equipped with an LCD, and the operating voltage of the liquid crystal display is VD.
It is determined by the voltage between D to vr and cn. There are v, , v, , between VDD and VLCf1 of driver circuit (2).
A transistor (12) is arranged in parallel with resistor 1 (Ll) for determining the potential of v3, and this transistor (12
A resistor 09 for current limiting is arranged in series.

The blanking time count circuit (4) includes an oscillator (5).
) and a frame counter (3), and when the pulses from the oscillator (5), whose oscillation frequency increases as the temperature rises and decreases as the temperature decreases, are counted to a predetermined constant, an output is generated. When the frame counter (3) counts a predetermined number of frames (2m), it is reset and the output is set to VLC.
It is considered as D level.

The output of the blanking time count circuit (4) is VLCD
When the level is high, the transistor (I2 is in the off state,
A specified voltage is applied to the liquid crystal display fil, and the output is V.
When the voltage is at the DD level, the transistor (121) is turned on, and VDD and VLCD are essentially short-circuited, and the voltage applied to the liquid crystal display (1) becomes 0, resulting in blanking.

The voltage waveform in this example is shown in FIG.

Figure 2 (,) shows the output waveform of the frame counter (3), and figure (b) shows the oscillator () whose frequency changes depending on the temperature.
5), and (c) in the figure is the output waveform of the blanking time count circuit (4). At this time, by synchronizing the switching timing of the output of the blanking time count circuit (4) to the VDD level with the voltage waveform applied to the scanning side electrode, the blanking time can be an even number times the time of one frame. In this case, application of a DC voltage component to the liquid crystal display due to blanking can be prevented.

FIG. 3 shows the voltage waveform applied to the liquid crystal display in this embodiment, where (,) shown in the figure shows the direction of the blanking time counting circuit, and (b) shows the direction of the blanking time counting circuit, and (b) shows the direction of the output of the scanning side electrode y1.・・・
・, Voltage waveform to y@, (c) is data signal side electrode X
The voltage waveforms applied to I, . . . , xn; (d) is the voltage waveform applied to the liquid crystal display. In FIG. 3, T is the blanking period.

The blanking period is provided once every O2m times the frame time (TF), and the blanking period T is twice the frame time (TF). (L here,
By making the value of t (m is an integer) variable with respect to temperature, the effective value of the voltage applied to the liquid crystal display can be made variable, and a temperature compensation circuit can be realized.

For example, by setting m -80 at 0℃ and t=05 and t=10 at θ℃, the effective value V of the voltage applied to the liquid crystal display is v (o℃) = 0.424 (VDD - VLCD )V
(50℃)=0.371(VBn-VLcn>,
In the case of vDD-■LcD=3.8v, it was possible to realize temperature compensation of 4mV/°C as an effective value calculated from the above.

Example 2 Example 2 will be explained with reference to FIG. Figure 4 shows the voltage waveform applied to the liquid crystal display, where (,) is the output of the blanking time count circuit, (bl is the voltage waveform to the scanning side electrode, and (C) is the data signal side electrode. (dl indicates the voltage waveform applied to the liquid crystal display.The blanking time °C, which was variable in the above embodiment, is T' =
2 T; is twice the frame time TY, and the blanking period is made variable depending on the temperature, thereby exhibiting the same effect as the previous embodiment.

Embodiment 3 As shown in FIG. 5, in this embodiment, the voltage waveform (b) to the data signal side electrode is the same as before, and the voltage waveform (a) to the scanning side electrode is changed only for the blanking time (VDD- VLC
(C)
is the voltage waveform applied to the liquid crystal display. At this time, the voltage applied to the liquid crystal display does not become 0 even during the blanking time T, but by increasing the blanking time,
The effective value applied to the liquid crystal display will not decrease;
Temperature compensation can be performed. 4 As described above, in the present invention, not only can the blanking time count circuit and the driver circuit etc. all be easily incorporated into one semiconductor integrated circuit, but also the external oscillator whose frequency can be varied depending on temperature is a component (C By simply changing -0, it is possible to configure a system that operates with the same circuit and the same power supply voltage for liquid crystal displays with different operating voltages and temperature coefficients, making it extremely useful industrially. It is.

〔Effect of the invention〕

By the method of the present invention, it is possible to drive a liquid crystal display device with a wide operating temperature range to display a predetermined number of times without changing the power supply voltage depending on the temperature, and it is also possible to drive a liquid crystal display device at a low driving voltage. , it has become possible to create a liquid crystal display device with even lower power consumption.

[Brief Description of the Drawings] Fig. 1 is a block diagram of a drive circuit of a liquid crystal display device of the present invention, Figs. 2 and 3 are diagrams showing voltage waveforms at various parts of the first embodiment of the invention, and Fig. FIG. 4, FIG. 5, and i are diagrams showing voltage waveforms at various parts of other embodiments of the present invention, respectively. 1...Liquid crystal display, 2...Driver circuit, 3...
7 frame counter, 4...Blanking time counter circuit. 5... Frequency variable oscillator. Agent Patent Attorney Mr. Inoue Figure 1 Figure 2 Figure 4 (cL) Figure 5 (cL) (C)

Claims (3)

[Claims] (1) In a method for driving a liquid crystal display device that performs time-division driving, a blanking time that changes depending on the ambient temperature is provided, and the drive voltage applied to the liquid crystal display is the same as the voltage when not selected during the blanking time. A method for driving a liquid crystal display device characterized in that the voltage is as follows. (2) The device according to claim 1, comprising a constant frequency oscillation source and a variable frequency oscillation source that varies depending on temperature, and determining the blanking time by comparing these two frequencies. A method for driving a liquid crystal display device. (3) A method for driving a liquid crystal display device according to claim 1, characterized in that the blanking time is an even multiple of one frame period.