KR100440540B1 - Lcd with power-off discharging circuit incorporated in driving ic - Google Patents

Abstract

PURPOSE: An LCD with a power-off discharging circuit in a driving IC is provided to form the circuit with the IC, thereby reducing the mounting space thereof and fabrication cost. CONSTITUTION: An LCD includes a voltage generator(4), a driving IC(5), and an LCD panel(6). The driving IC includes a discharging circuit and a driving circuit integrated together. The discharging circuit discharges, by a current bypass, at least one or more power voltages generated by the voltage generator and remaining after power supply failure. The driving circuit generates display signals required for displaying operation by using respective voltages generated by the voltage generator.

Description

Liquid Crystal Display with Power-Off Discharge Circuit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display (LCD) having a power-off discharging circuit. More specifically, the present invention relates to a liquid crystal display (LCD) having a discharge circuit installed to save manufacturing cost and mounting area. It relates to a liquid crystal display device.

In general, there are two types of voltages used in liquid crystal display devices, one of which is a voltage substantially applied to the liquid crystal panel, and the other is a peripheral circuit such as a source driving circuit, a gate driving circuit, an interface circuit, and various voltage generators. This is the voltage required for the operation of the (peripheral circuit).

The voltage actually applied to the liquid crystal panel includes a Von voltage for turning on the switching element in the panel, a Voff voltage for turning off the switching element, a gradation voltage for the display operation of the pixel, and providing a reference voltage to each pixel in the panel. There is an electrode voltage Vcom. In addition, the voltages for the peripheral circuits include a power supply voltage VCC, a ground voltage GND, and optionally a DC / DC converter output voltage used in the voltage generator.

However, such a liquid crystal display device includes a discharge circuit for rapidly discharging the voltage applied in the liquid crystal panel when the power-off voltage is cut off. Without such a discharge circuit, the voltage applied to the liquid crystal panel finally affects the pixels in the panel.

Hereinafter, a liquid crystal display having a conventional discharge circuit will be described with reference to the accompanying drawings.

1 is a configuration diagram of a liquid crystal display device having a conventional power-off discharge circuit,

FIG. 2 is a side view illustrating an example of mounting the liquid crystal display shown in FIG. 1.

As shown in FIG. 1, a conventional liquid crystal display device includes a voltage generator circuit 1, a driver IC 2, and a liquid crystal panel 3, and the voltage generator circuit 1) is composed of a voltage generator 11 and a discharge circuit 12. In addition to the above described, more components exist in the liquid crystal display device, but only parts related to the discharge circuit 12 are shown in FIG.

The voltage generator 11 of the voltage generator circuit 1 uses the external power sources VCC, GND and control signals to supply the voltages VCC, Von, Voff, Vcom, GND required for the operation of the liquid crystal panel 3 described above. Create The voltage generator 11 may be implemented as a commercial circuit such as a DC / DC converter and a voltage regulator. The discharge circuit 12 discharges the voltage applied to the driving integrated circuit 2 when the power supply voltage VCC is cut off.

The driving integrated circuit 2 generates predetermined driving voltages OUT1 to OUTn by using the voltage signal provided from the voltage generating circuit 1 and applies it to the liquid crystal panel 3. Accordingly, the intended display operation can be performed in the liquid crystal panel 3.

2 illustrates an example of mounting the liquid crystal display described with reference to FIG. 1.

The voltage generation circuit 1 shown in FIG. 1 is implemented on a printed circuit board (PCB) of FIG. 2, and the printed circuit board and the liquid crystal panel are connected by a tape. The drive integrated circuit 2, which is realized as a large scale integrated circuit, is installed on the tape by a tape automated bonding (TAP) process. The tape is flexible so that the printed circuit board can be folded to the back side of the liquid crystal panel, thereby reducing the surface area of the liquid crystal display device.

However, in the conventional liquid crystal display device, since the discharge circuit is located inside the voltage generation circuit and the voltage generation circuit is implemented on the printed circuit board, it takes up a large mounting area and increases manufacturing costs.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described technical problems, and to provide a liquid crystal display device capable of avoiding an increase in mounting area and an increase in manufacturing cost by allowing a discharge circuit to be incorporated in a driving integrated circuit.

1 is a block diagram of a liquid crystal display device having a conventional power-off discharge circuit.

FIG. 2 is a side view showing an example of mounting of the liquid crystal display shown in FIG.

3 is a configuration diagram of a liquid crystal display device having a power-off discharge circuit according to the embodiment of the present invention.

4 is a circuit diagram showing an example of the discharge circuit shown in FIG.

5A to 5D are circuit diagrams showing another example of the discharge circuit shown in FIG.

The liquid crystal display device of the present invention for achieving the above object,

A voltage generator embodied on a printed circuit board, the voltage generator generating a power supply voltage, a gate line turn-on voltage, a gate line turn-off voltage, a common electrode voltage, and a ground voltage using a power supply voltage, a ground voltage and a control signal;

When the power supply voltage generated by the voltage generator is cut off due to the interruption of the external power supply, a discharge circuit for discharging at least one of the remaining voltages by current bypass, and each voltage generated by the voltage generator A driving integrated circuit configured to generate a display signal required for a display operation, wherein the discharge circuit and the driving circuit comprise an integrated circuit; And

And a liquid crystal panel for providing an intended image according to the display signal generated in the driving integrated circuit.

According to the liquid crystal display of the present invention described above, since the discharge circuit is embedded in the driving integrated circuit and manufactured as an integrated circuit while being integrated with the driving circuit, the mounting area of the circuit can be greatly reduced. In addition, since the parts made of integrated circuits increase in comparison with the related art, manufacturing costs are reduced.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a configuration diagram of a liquid crystal display device having a power-off discharge circuit according to an embodiment of the present invention;

4 is a circuit diagram showing an example of the discharge circuit shown in FIG.

5A to 5D are circuit diagrams showing another example of the discharge circuit shown in FIG.

First, a configuration of a liquid crystal display according to an exemplary embodiment of the present invention will be described with reference to FIG. 3.

As shown in Fig. 3, the liquid crystal display device according to the embodiment of the present invention includes a voltage generator 4, a drive integrated circuit 5 composed of a discharge circuit and a drive circuit, and a liquid crystal panel 6. The liquid crystal display of the present invention further includes other components in addition to those shown in FIG. 3, but only components related to the discharge circuit are shown in FIG. The voltage generator 4 is embodied on a printed circuit board, and the discharge and drive circuits are embodied in integrated circuits.

A power supply voltage VCC, a control signal CTR, and a ground voltage GND are input to the voltage generator 4, and the voltage generator 4 uses the input voltage to control the display operation of the liquid crystal panel 6. The required power supply voltage VCC, the gate line turn-on voltage Von, the gate line turn-off voltage Voff, the common electrode voltage Vcom, and the ground voltage GND are generated.

The voltage generated by the voltage generator 4 is provided to the driving integrated circuit 5, and the discharge circuit provided in the driving integrated circuit 5 has the power supply voltage VCC due to the cutoff of the external power supply. When interrupted, at least one of the voltage generator 4 output voltages is discharged by current bypass. The discharge process of the discharge circuit will be described later with reference to FIGS. 4 and 5A-5D.

The driving circuit provided in the driving integrated circuit 5 generates display signals OUT1 to OUTn for the display operation of the liquid crystal panel 6 using the respective voltages generated by the voltage generator 4. The generated display signals OUT1 to OUTn are provided to the liquid crystal panel 6, and the intended display operation is performed by the signal in the liquid crystal panel 6.

4 shows an example of the discharge circuit, which is a discharge circuit for the gate line turn-off voltage Voff using a transistor.

As shown in FIG. 4, a capacitor C is connected to a gate of the PMOS transistor P, and a power supply voltage VCC is applied to the capacitor C. As shown in FIG. A ground voltage GND is applied to a source of the transistor P, a diode D having an anode facing the gate is connected between the source and the gate, and a power supply voltage Voff is connected to the drain of the transistor P. Is authorized.

In the power-on state in which power is normally supplied, the power supply voltage VCC is cut off by the capacitor C, and the gate-source voltage of the transistor P is approximately 0.7V, which is the threshold voltage of the diode D. Keep it. At this time, since the transistor P has a negative threshold voltage because it is a PMOS, the transistor P is turned off. That is, no current flows between the source and the drain of the transistor P, and the turn-off voltage Voff is transmitted to the driving circuit as it is.

In the power-off state, the power supply voltage VCC drops to the ground state. At this time, since the capacitor C is charged with a voltage having a constant magnitude, a negative voltage smaller than the threshold voltage is provided to the gate of the transistor P. Accordingly, since the transistor P is turned on and the voltage of the source to which the ground voltage GND is applied is smaller than the drain to which the turn-off voltage Voff is applied, the transistor P is turned toward the source from the drain of the transistor P. Current flows As a result, the turn-off voltage Voff may be rapidly discharged at the power-off of the power supply voltage VCC.

The discharge circuit shown in FIG. 3 includes at least one circuit structure shown in FIG.

5A to 5D show another example of the discharge circuit shown in FIG. 3, which is a discharge circuit using a resistor.

5A illustrates a discharge circuit for the turn-on voltage Von and the common electrode voltage Vcom, and a resistor R is connected between the turn-on voltage Von terminal and the common electrode voltage Vcom terminal. The resistance value of the resistor R is designed to be much larger than the value of a load (not shown) connected to the two terminals. Therefore, in the power-on state, no current flows to the resistor R, and the external power is almost applied to the load, and in the power-off state, the supply of the external power is cut off, so that the voltage charged by a component such as a capacitor in the load This is discharged through the current path provided by the resistor R. The current at this time is referred to as leakage current, and the resistance value of the resistor R is adjusted to be within 1 mA.

FIG. 5B is a discharge circuit for the common electrode voltage Vcom and the turn-off voltage Voff, FIG. 5C is a discharge circuit for the ground voltage GND and the turn-off voltage Voff, and FIG. 5D is a turn-on voltage Von. ), A discharge circuit for the common electrode voltage Vcom and the turn-off voltage Voff.

The operation of the discharge circuit shown in Figs. 5B to 5D is similar to that shown in Fig. 5A, and each resistor R is designed to have a resistance value much larger than the load connected to each voltage terminal.

The liquid crystal display of the present invention described above includes a drive integrated circuit with a built-in discharge circuit, and the discharge circuit is manufactured as an integrated circuit together with the drive circuit, thereby reducing the mounting area and lowering the manufacturing cost. That is, in the related art, the above effects may be achieved by implementing a printed circuit board on an integrated circuit.

Claims (4)

A voltage generator embodied on a printed circuit board, the voltage generator generating a power supply voltage, a gate line turn-on voltage, a gate line turn-off voltage, a common electrode voltage, and a ground voltage using a power supply voltage, a ground voltage and a control signal; When the power supply voltage generated by the voltage generator is cut off due to the interruption of the external power supply, a discharge circuit for discharging at least one of the remaining voltages by current bypass, and each voltage generated by the voltage generator A driving integrated circuit configured to generate a display signal required for a display operation, wherein the discharge circuit and the driving circuit comprise an integrated circuit; And A liquid crystal panel for providing an intended image according to a display signal generated in the driving integrated circuit; A liquid crystal display device having a power-off discharge circuit. The method of claim 1, wherein the discharge circuit is A source voltage applied to a source, a power supply voltage to a gate, and a drain connected to one of the output voltages of the voltage generator, the transistor being turned off when the power supply voltage is in a power-on state. When the power supply voltage is turned off, A liquid crystal display device having a power-off discharge circuit. The discharge circuit of claim 2, wherein the discharge circuit includes at least one transistor, and any one of voltages output from the voltage generator is applied to a drain of each transistor. A liquid crystal display device having a power-off discharge circuit. The method of claim 1, wherein the discharge circuit is At least one resistor connected between at least two voltage terminals output from the voltage generator, A liquid crystal display device having a power-off discharge circuit.