JPH0640253B2 - Liquid crystal display - Google Patents

Description

The present invention relates to a liquid crystal display device.

As is well known, the life of a liquid crystal display device is extremely shortened when a DC voltage is applied. Therefore, in driving the liquid crystal, AC driving is performed using a multi-valued pulse signal.

In addition, the liquid crystal display device generally has a negative temperature characteristic, and in order to eliminate erroneous display within the operating temperature range,
The liquid crystal display device must be operated with a driving voltage compensated for the temperature characteristics.

In the conventional liquid crystal drive circuit, a temperature compensation circuit is provided in the multi-value voltage generation circuit (power supply voltage of the drive circuit). This temperature compensation requires a complicated temperature compensation circuit for each voltage, and it is extremely difficult to form the temperature characteristic. Especially when a temperature compensation circuit is provided in a semiconductor integrated circuit, it is affected by variations in elements,
This causes deterioration of product yield.

The inventor of the present application forms a pulse width signal corresponding to the temperature characteristic of the liquid crystal display device based on the output signal from the temperature sensor, and uses the pulse width signal to output waveform of a column driver that dynamically drives the liquid crystal display device. It was considered that temperature compensation is performed by controlling the pulse duty of the above and controlling its effective voltage according to the above temperature characteristics.

An object of the present invention is to provide a liquid crystal display device having a simple circuit configuration and low power consumption, which performs temperature compensation suitable for a semiconductor integrated circuit device.

Other objects of the present invention will be apparent from the following description and drawings.

The outline of a typical one of the inventions disclosed in the present application will be briefly described as follows.

That is, a liquid crystal panel in which a dot matrix is composed of scan electrodes and signal electrodes, a row driver that regularly supplies a multi-value voltage to the scan electrodes according to a timing signal from a timing control circuit, and display data is subjected to the timing control. A latch circuit that captures in synchronization with the clock from the circuit, a column driver that supplies a multi-valued voltage to the signal electrode in synchronization with a display signal from the latch circuit in synchronization with a timing signal, and a reference frequency signal using a crystal oscillator A liquid crystal display device comprising: an oscillation circuit that forms a frequency division circuit; and a frequency divider circuit that divides the output of the oscillation circuit and outputs a timing signal to the timing control circuit. (1) Detecting the ambient temperature of the liquid crystal display device The output signal from the temperature sensor is converted to a digital value by the A / D converter. (2) Minimum operating temperature The pulse width at 0 is 1 and the pulse width becomes wider as the temperature rises, so that the pulse width becomes 1 among the plurality of pulse width signals formed by the frequency dividing circuit by the digital signal converted by the A / D converter. And a pulse signal having a pulse width corresponding to temperature is output from the multiplexer in synchronization with the timing control signal. (3) The pulse width signal selected by the multiplexer and the timing control circuit And the timing signal from the above are logically processed by the gate circuit to reduce the output pulse width of the timing signal to the column driver as the temperature rises. (4) The selection voltage waveform applied to the liquid crystal panel and the non-selection voltage waveform The effective voltage is controlled by reducing the pulse width of only the peak waveform of the selected voltage waveform. It is a crystal display device.

Hereinafter, the present invention will be described in detail together with examples.

FIG. 1 shows a block diagram of an embodiment of the present invention.

Reference numeral 11 indicates a liquid crystal panel, which is not particularly limited, but the scanning electrodes and the signal electrodes form a dot matrix.

A row driver 7 drives the scan electrodes. The row driver 7 regularly supplies the four-valued voltage to the scan electrodes according to the timing signal from the timing control circuit 6.

The column driver 9 drives the signal electrodes.
The column driver 9 supplies a four-valued voltage to the signal electrode in accordance with the display signal from the latch circuit 8 in synchronization with the timing signal passed through the gate circuit 10. This latch circuit 8
Is for fetching display data in synchronization with the clock from the timing control circuit 6. As a result, the acquisition of display data and the drive timing of the signal electrodes are synchronized.

The oscillator circuit 1 forms a reference frequency signal. Although not particularly limited, a known crystal oscillation circuit using a crystal oscillator is used. This oscillation output is frequency-divided by the frequency dividing circuit 2 to form a basic clock necessary for the operation of the timing control circuit 6.

The frequency dividing circuit 2 also forms a plurality of pulse width signals for temperature compensation described later.

The temperature sensor 3 detects ambient temperature. Although not particularly limited, this temperature sensor is composed of a temperature sensitive element such as a thermistor.

The output signal of the temperature sensor 3 is converted into a digital signal by the A / D converter 4.

The plurality of pulse width signals formed by the frequency dividing circuit 2 are input to the multiplexer 5, and one of the pulse width signals is selectively input to the gate circuit 10 by the converted digital signal. The gate circuit 10 logically processes the pulse width signal and the timing signal from the timing control circuit 6 to limit the output pulse width of the column driver 8.

Next, the temperature compensation operation of this embodiment will be described with reference to the timing chart of FIG.

The waveform shown by the solid line in FIG. 9A is a voltage waveform applied to both electrodes of the dot which is in the selected state at the minimum operating temperature. The waveform shown by the solid line in FIG. 7B is a waveform applied to both electrodes of the dot that is in the non-selected state at the minimum operating temperature. That is, the gate circuit 10 transmits the timing signal from the timing control circuit 6 to the column driver 9 as it is by the digital signal at the minimum operating temperature. At this time, the effective value of the voltage applied to the liquid crystal panel 11 becomes maximum.

Next, as the temperature rises, the multiplexer 5 outputs a pulse signal having a pulse width corresponding to the temperature as shown in FIG. The gate circuit 10 limits the timing to the column driver 9 by this pulse signal and selects / selects as shown by a broken line in FIGS.
The pulse width of only the peak waveform of the non-selected voltage waveform is limited to a small value. As a result, the effective voltage in the selected and non-selected states can be reduced. That is, a negative temperature coefficient can be given to the liquid crystal driving voltage.

Therefore, the temperature compensation can be performed by matching the negative temperature coefficient of the liquid crystal panel with the above pulse width limitation, in other words, the negative temperature coefficient of the effective voltage obtained by the pulse duty control of the liquid crystal drive voltage. it can.

In this embodiment, since the pulse duty is controlled by reducing the pulse width only in the peak waveform of the voltage waveforms during selection and non-selection, there are few dynamic changes and power consumption can be reduced. . Moreover, temperature compensation of the liquid crystal panel having various temperature coefficients can be realized with high accuracy by digital signal processing. Further, since the temperature compensation circuit can be configured by a digital circuit, it can be suitable for a semiconductor integrated circuit. The temperature compensation circuit has the advantage that it is not affected by variations in element characteristics.

The present invention is not limited to the above embodiment.

The liquid crystal may be composed of a common electrode and a segment electrode.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an operation waveform diagram for explaining the temperature compensation operation. 1 ... Oscillation circuit, 2 ... Dividing circuit, 3 ... Temperature sensor, 4 ... A / D converter, 5 ... Multiplexer, 6 ...
... Timing control circuit, 7 ... Row driver, 8 ... Latch circuit, 9 ... Column driver, 10 ... Gate circuit, 11 ... Liquid crystal panel

Claims (1)

[Claims] 1. A liquid crystal panel in which a dot matrix is composed of scan electrodes and signal electrodes, a row driver which regularly supplies a multi-valued voltage to the scan electrodes according to a timing signal from a timing control circuit, and display data. Using a latch circuit that captures in synchronization with the clock from the timing control circuit, a column driver that supplies a multi-valued voltage to the signal electrode in synchronization with a timing signal according to a display signal from the latch circuit, and a crystal oscillator A liquid crystal display device comprising: an oscillation circuit that forms a reference frequency signal; and a frequency divider circuit that divides the output of the oscillation circuit and outputs a timing signal to the timing control circuit. The output signal from the temperature sensor is converted into a digital value by the A / D converter, and the pulse value at the minimum operating temperature The width is 0, and the pulse width becomes wider as the temperature rises. One of the plurality of pulse width signals formed by the frequency dividing circuit is multiplexed by the digital signal converted by the A / D converter. Output from the multiplexer in synchronization with the timing control signal, the pulse signal having a pulse width corresponding to the temperature, and the pulse width signal selected by the multiplexer and the timing signal from the timing control circuit. It is logically processed by the gate circuit to reduce the output pulse width of the timing signal to the column driver as the temperature rises, and only the pulse width of the peak waveform of the selected voltage waveform and the non-selected voltage waveform applied to the liquid crystal panel is pulse width. A liquid crystal display device characterized in that its effective voltage is controlled by reducing the voltage.