JPH0713517A - Liquid crystal module - Google Patents

Abstract

PURPOSE:To reduce the electric power consumption of a liquid crystal module and to improve the display quality thereof by controlling on and off of a liquid crystal power source by using the output signal from a liquid crystal controller and further, adding a delay circuit. CONSTITUTION:A liquid crystal driving power source 4 is controlled by using the signal obtd. by adding the delay circuit 5 consisting of a resistor, capacitor and Schmitt trigger IC as the on-off control signal for the liquid crystal driving power source to the enable signal outputted from the liquid crystal controller 1. The liquid crystal system power source is turned off after all the voltages impressed to a liquid crystal panel attain non-selection levels at the time of a display off. Then, the on and off of the liquid crystal system power source are controlled without freshly providing the control signals to be exclusively used. The electric power consumption is suppressed and the phenomenon that the lines of a high contrast remain at the liquid crystal panel at the time of on and off of the power source is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit for a liquid crystal module, and more particularly to display quality and low power consumption.

[0002]

2. Description of the Related Art A conventional liquid crystal module has a structure as shown in FIG. 5, and has two types of power supply systems: a logic system power supply and a liquid crystal system power supply. The power supply of the liquid crystal driver operated by these two kinds of power supply systems is turned on / off simultaneously by the logic power supply and the liquid crystal power supply. At this time, lines of strong contrast remain on the liquid crystal panel. This line does not disappear instantly, but it takes some time to disappear. To prevent this phenomenon, a control signal dedicated to the liquid crystal power supply is provided externally, the display enable signal output from the liquid crystal controller to the liquid crystal driver is disabled, and all voltages applied to the liquid crystal panel are unselected. After the level is reached, a method of turning off the power supply of the liquid crystal system by a control signal is used. When the display is turned off, if there is a control signal dedicated to the liquid crystal system power supply, it is turned off to suppress power consumption as much as possible, but if not, all the power supply systems are turned off.

[0003]

However, in the above-mentioned conventional technique, a control signal dedicated to turning on / off the liquid crystal system power supply is required in order to remove a line of strong contrast remaining in the liquid crystal, and this signal is controlled by software. There is a problem of having to do it. In addition, if all the power supply systems are turned off when the display is turned off regardless of the display quality, there is a problem that the liquid crystal controller must be initialized again during operation. If this is avoided and the liquid crystal system power is not turned off when the display is turned off, useless power is consumed in the field of liquid crystal modules that require low power consumption. An object of the present invention is to provide a liquid crystal module in which low power consumption is realized without newly providing a control signal dedicated to the liquid crystal system power supply and the display quality of the liquid crystal module is improved.

[0004]

In the liquid crystal module of the present invention, paying attention to the display enable signal output from the liquid crystal controller, the display enable signal is used as an ON / OFF dedicated control signal for the liquid crystal system power supply, and the display enable signal is used. Is not directly used as a control signal for the liquid crystal system power supply, but is used as a control signal via a delay circuit.

[0005]

In the liquid crystal module according to the present invention, the liquid crystal system power is turned on without newly providing a dedicated control signal.
It becomes possible to control off. Further, through the delay circuit, it is possible to perform an operation of logic system on-liquid crystal system on for the liquid crystal driver IC having two kinds of power supply systems, that is, logic system power supply and liquid crystal system power supply. When the display is turned off, the liquid crystal system power supply is turned off after all the voltages applied to the liquid crystal panel reach the non-selection level. It is possible to reduce power consumption as much as possible, and it is possible to prevent the phenomenon that lines with strong contrast remain on the liquid crystal panel when the power is turned on and off.

[0006]

1 is a block diagram of a liquid crystal module according to an embodiment of the present invention. The liquid crystal controller 1 controls the operation of the entire liquid crystal module. The display enable signal, which is an output signal, is connected to the liquid crystal driver 2 and the liquid crystal drive power source 4. When the display is off, this display enable signal is disabled. LCD driver 2
The control signal from the liquid crystal controller 1 gives the liquid crystal panel 3 a selection waveform and a non-selection waveform generated by the liquid crystal system power supply. When the display enable signal is disabled, the output signal to the liquid crystal panel 3 is forcibly set to the non-selection level. The liquid crystal drive power supply 4 supplies the liquid crystal system power supply of the liquid crystal driver 2. 1 is different from the conventional circuit configuration in that the display enable signal output from the liquid crystal controller 1 is used as an on / off control signal of the liquid crystal drive power supply 4. Since the liquid crystal controller 1 disables the display enable signal when the display is off, the liquid crystal drive power supply is turned off and the liquid crystal system power supply to the liquid crystal driver 2 is cut off.

FIG. 2 shows another embodiment of the present invention in which a delay circuit 5 is added to a display enable signal which is an output signal of the liquid crystal controller 1 and is used as an ON / OFF control signal for the liquid crystal drive power source 4. The liquid crystal driver 2 is directly connected.

FIG. 3 is a circuit diagram of the delay circuit 5 used in this example. FIG. 4 shows an input signal waveform by the delay circuit of FIG.
The waveforms of the input and output signals to the Schmitt trigger input IC are shown.

The delay circuit in FIG. 3 comprises a resistor R, a capacitor C, and a Schmitt trigger input IC. The bar (INH) signal that is the input of this circuit is the display enable signal that is output from the liquid crystal controller, and the bar (POFF) signal that is the output is connected to the liquid crystal drive power supply as the on / off control signal of the liquid crystal drive power supply. There is.

In FIG. 4, when the logic system power of the liquid crystal module is turned on, the input bar (INH) at time t0
Since the signal is at a low level (disabled state), the output bar (POFF) signal is also at a low level and the liquid crystal drive power supply is turned off. At time t1, when the operating state or the display state is entered, the input bar (INH) signal becomes high level. A charging current flows through the resistor R and the capacitor C, and the capacitor C starts to be charged. Although the potential at the point A gradually begins to rise, the output bar (POFF) signal remains low until the potential reaches the MIN level of the high level input voltage of the Schmitt trigger input IC. The liquid crystal drive power supply remains off, and the liquid crystal driver power supply to the liquid crystal system power supply is cut off. This charging continues until the electric charge reaches the electrostatic capacity of the capacitor C, t2
The potential at point A is the Schmitt trigger input IC
When the high level input voltage level of
F) The signal becomes high level and the LCD drive power is turned on.
The logic system on-liquid crystal system on operation was performed on the power supply system of the liquid crystal driver, and the liquid crystal system power supply is turned on while the logic system power supply is stable. There is no unexpected display of. When the display is turned off, the liquid crystal controller sets the display enable signal to a low level after a lapse of 1 to 2 frames. At the time of t3, the input bar (I
When the (NH) signal goes low, the capacitor C
The electric charge stored in the battery begins to be released. Although the voltage level at the point A gradually begins to drop, the output bar (POFF) signal remains high level until the potential reaches the MAX level of the low level input voltage of the Schmitt trigger input IC. This discharge continues until all the charge is discharged, t
At time point 4, the potential at point A is the Schmitt trigger input I
When the low level input voltage level of C is reached, the output bar (P
OFF) signal goes low, so the liquid crystal drive power is turned off. At this point, the LCD driver has already applied the non-selection level voltage to the LCD panel.
Even when the liquid crystal driving power is turned off in this state, unpredictable display does not remain as in the case where the liquid crystal system power is turned on. Next, until the operating state or the display-on state, the liquid crystal driving power supply having a relatively large steady current is turned off, so that the power consumption of the liquid crystal module is saved.

[0011]

As described above, according to the present invention, the liquid crystal system power supply can be controlled in the liquid crystal module without newly providing a control signal dedicated to the liquid crystal system power supply. Further, the liquid crystal system power supply of the liquid crystal driver is turned on and off while the logic system power supply is in a stable state, and a liquid crystal module with low power consumption and high display quality can be realized.

[Brief description of drawings]

FIG. 1 is an example of the present invention. Liquid crystal module block diagram.

FIG. 2 is another embodiment of the present invention. Liquid crystal module block diagram.

FIG. 3 is a delay circuit diagram.

FIG. 4 is an input / output waveform diagram of the delay circuit.

FIG. 5 shows a conventional example. Liquid crystal module block diagram.

[Explanation of symbols]

 1 ... Liquid crystal controller 2 ... Liquid crystal driver 3 ... Liquid crystal panel 4 ... Liquid crystal driving power supply 5 ... Delay circuit R ... Fixed resistance C ... Capacitor IC ... Schmidt trigger input IC

Claims (2)

[Claims] 1. A liquid crystal module characterized by using a display enable signal output from a liquid crystal controller to a liquid crystal driver, and turning off a liquid crystal drive power supply in a disabled state. 2. A liquid crystal module characterized in that a display enable signal output from a liquid crystal controller to a liquid crystal driver is used, a delay circuit is added to the signal, and a liquid crystal driving power supply is turned off in a disabled state.