KR19980014827A - Liquid crystal display device having power-off discharge circuit - Google Patents

Abstract

The present invention relates to a liquid crystal display (LCD) having a power-off discharge circuit,

A voltage generator which is implemented as a printed circuit board and generates 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; A discharge circuit for discharging at least one of the remaining voltages by current bypass when the power supply voltage generated by the voltage generator is cut off due to interruption of supply of the external power supply, And a drive circuit for generating a display signal necessary for a display operation, wherein the discharge circuit and the drive circuit are formed as an integrated circuit; And a liquid crystal panel for providing an intended image according to a display signal generated in the driving integrated circuit,

The discharge circuit is fabricated as an integrated circuit together with the driving circuit, thereby reducing the mounting area and manufacturing cost as compared with the conventional printed circuit board.

Description

Liquid crystal display device having power-off discharge circuit

The present invention relates to a liquid crystal display (LCD) having a power-off discharge circuit, and more particularly to a liquid crystal display having a discharge circuit provided so as to save manufacturing cost and a mounting area And a liquid crystal display device.

In general, there are two types of voltages used in a liquid crystal display device, one being a voltage substantially applied to a liquid crystal panel and the other being a peripheral circuit such as a source driving circuit, a gate driving circuit, an interface circuit, (peripheral circuit).

The voltages actually applied to the liquid crystal panel include a Von voltage for turning on the switching elements in the panel, a Voff voltage for turning off the switching elements, a gradation voltage for displaying operation of the pixels, And an electrode voltage Vcom. The voltages for the peripheral circuits include a power supply voltage VCC, a ground voltage GND, and a DC / DC converter output voltage used in the voltage generator as the case may be.

Such a liquid crystal display device is provided with a discharge circuit for rapidly discharging a voltage applied to the liquid crystal panel at the time of power-off at which the power source voltage is cut off. Without such a discharge circuit, the voltage finally applied to the liquid crystal panel has a bad influence on the pixels in the panel.

Hereinafter, a liquid crystal display device 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,

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

1, a conventional liquid crystal display device includes a voltage generating circuit 1, a driver IC 2, and a liquid crystal panel 3, and the voltage generating circuit 1 comprises a voltage generator 11 and a discharge circuit 12. Although there are more components than those described above in the liquid crystal display, only the parts related to the discharge circuit 12 are shown in Fig.

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

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

Fig. 2 shows an example of mounting the liquid crystal display device described in Fig.

The voltage generating 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 implemented with a large-scale integrated circuit is mounted on the tape by a tap automated bonding (TAP) process. The tape is flexible, so that the printed circuit board can be folded back to the back surface 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 generating circuit and the voltage generating circuit is implemented on the printed circuit board, the mounting area is large and the manufacturing cost is increased.

It is an object of the present invention to provide a liquid crystal display device capable of avoiding an increase in a mounting area and an increase in manufacturing cost by allowing a discharge circuit to be incorporated in a driving integrated circuit.

1 is a configuration 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 the liquid crystal display device shown in FIG. 1; FIG.

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.

FIG. 4 is a circuit diagram showing an example of the discharge circuit shown in FIG. 3; FIG.

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

According to an aspect of the present invention, there is provided a liquid crystal display device comprising:

A voltage generator for 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;

A discharge circuit for discharging at least one of the remaining voltages by current bypass when the power supply voltage generated by the voltage generator is cut off due to interruption of supply of the external power supply, And a drive circuit for generating a display signal necessary for a display operation, wherein the discharge circuit and the drive circuit are formed as an integrated circuit; And

And a liquid crystal panel for providing an intended image according to a 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 built in the drive integrated circuit and is integrated with the drive circuit in an integrated circuit, the mounting area of the circuit can be greatly reduced. In addition, the manufacturing cost is reduced because the portion manufactured by the integrated circuit is increased as compared with the conventional one.

Hereinafter, preferred 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,

FIG. 4 is a circuit diagram showing an example of the discharge circuit shown in FIG. 3,

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

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

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. Fig. The liquid crystal display device of the present invention further includes other components in addition to those shown in FIG. 3, but FIG. 3 shows only the components related to the discharge circuit. The voltage generator 4 is implemented as a printed circuit board, and the discharge circuit and the drive circuit are implemented as an integrated circuit.

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

The voltage generated by the voltage generator 4 is provided to the driving integrated circuit 5 and the discharging circuit provided in the driving integrated circuit 5 supplies the power voltage VCC The at least one output voltage of the voltage generator (4) is discharged by current bypass. The discharging process of the discharging circuit will be described later with reference to Fig. 4 and Figs. 5A to 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 by using the voltages generated in the voltage generator 4. [ The generated display signals OUT1 to OUTn are provided to the liquid crystal panel 6, and the liquid crystal panel 6 performs a display operation intended by the signals.

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

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

The power supply voltage VCC is cut off by the capacitor C and the gate-source voltage of the transistor P is approximately 0.7 V which is the threshold voltage of the diode D . At this time, since the transistor P has a negative threshold voltage because it is a PMOS transistor, 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 directly transmitted to the driving circuit.

In the power-off state, the power source voltage VCC falls to the ground state. At this time, since the capacitor C is charged with a voltage of a certain magnitude, the gate of the transistor P is provided with a negative voltage smaller than the threshold voltage. Therefore, 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, Current flows. As a result, the turn-off voltage Voff at the time of power-off of the power source voltage VCC can be rapidly discharged.

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

5A to 5D illustrate another example of the discharge circuit shown in FIG. 3, and are discharge circuits using a resistor.

5A is a discharge circuit for the turn-on voltage Von and the common electrode voltage Vcom, and the resistor R is connected between the turn-on voltage Von terminal and the common electrode voltage Vcom. 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 through the resistor R, and the external power is mostly applied to the load. In the power-off state, the supply of the external power is interrupted, Is discharged through the current path provided by the resistor (R). The current at this time is referred to as a leakage current, and the resistance value of the resistor R is adjusted so as to be a value usually within 1 mA.

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, ), A common electrode voltage (Vcom), and a turn-off voltage (Voff).

The operation of the discharge circuit shown in Figs. 5B to 5D is also 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 device of the present invention described above includes a driving integrated circuit having a built-in discharge circuit. Since the discharge circuit is manufactured as an integrated circuit together with the driving circuit, the mounting area is reduced and the manufacturing cost is reduced. In other words, the above-described effect can be achieved by embodying an integrated circuit in which a printed circuit board is embodied.

Claims (4)

A voltage generator for 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; A discharge circuit for discharging at least one of the remaining voltages by current bypass when the power supply voltage generated by the voltage generator is cut off due to interruption of supply of the external power supply, And a drive circuit for generating a display signal necessary for a display operation, wherein the discharge circuit and the drive circuit are formed as an integrated circuit; And And a liquid crystal panel for providing an intended image in accordance with a display signal generated in said drive integrated circuit. A liquid crystal display device having a power-off discharge circuit. The plasma display apparatus according to claim 1, wherein the discharge circuit A transistor having a source connected to a ground voltage, a gate coupled to a power supply voltage, and a drain coupled to receive one of the output voltages of the voltage generator, the transistor being turned off when the power voltage is in a power- A power-on state in which the power source voltage is in a power-off state, A liquid crystal display device having a power-off discharge circuit. 3. The plasma display panel of claim 2, wherein the discharge circuit includes at least one transistor, and a drain of each transistor is applied with a voltage output from the voltage generator. A liquid crystal display device having a power-off discharge circuit. The plasma display apparatus according to claim 1, wherein the discharge circuit And 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.