JP2005309428A - Discharge circuit, its method, discharge circuit for liquid crystal display, and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge circuit and its method by which the discharging time of a liquid crystal display can be shortened by quickly discharging residual charge in the liquid crystal display when a power supply for the liquid crystal display suddenly stops and the generation of black lines can be removed. <P>SOLUTION: In the discharge circuit and its method, the liquid crystal display comprises a first discharge circuit connected to a first capacitor, a second discharge circuit connected to a second capacitor and a switching circuit connected to the first and second capacitors to provide a discharge signal for starting or stopping the discharge circuits. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

          The present invention relates to a discharge circuit and a method thereof, and more particularly, to a discharge circuit and a method of a liquid crystal display (LCD).

          In recent years, display devices used for electronic equipment such as computer monitors and televisions have been greatly developed. Compared with the conventional cathode ray tube (Cathode Ray Tube, CRT), the liquid crystal display is light and thin, can be large or small in area, has a low operating voltage, saves power, does not emit radiation, etc. In recent years, liquid crystal displays have become mainstream. For portable electronic products such as notebook computer monitors, mobile phone monitors, and PDA (Personal Digital Assistance) monitors that have been popular in recent years, only liquid crystal monitors meet the requirements for portable devices such as lightweight, thin, and compact. Can be satisfied.

          In the conventional liquid crystal display, since the internal integrated circuit (IC) does not operate when the power supply suddenly stops, the scan line has one COM line in the X direction or one scan line in the Y direction. The scan voltage of the liquid crystal display is held. However, since the voltage stabilizing capacitor of the liquid crystal display maintains a certain voltage, the voltage remaining on the scan line at the COM end or the SEG end is maintained for a considerably long time. Basically, the voltage of the liquid crystal display disappears due to electric leakage or via a discharge path. In general, a sufficient root mean square (RMS) voltage is already accumulated in the liquid crystal display during the time when the residual voltage is maintained, and a phenomenon in which a visible black line is generated. Arise. 1a and 1b are schematic diagrams showing black lines where residual voltage is generated on a known liquid crystal display.

          FIG. 2 is a circuit diagram showing a discharge circuit of a known liquid crystal display. The LCD driving IC 203 includes a switch transistor 206 and a resistor 208. The switch transistor 206 passes through the drive switch 204 and is connected to all capacitors of the liquid crystal display 201. The switch transistor 206 is further connected to the external capacitor 210. The purpose of connecting the liquid crystal display 201 to the external capacitor 210 is to stabilize the scan voltage of the scan lines COM and SEG. Usually, the capacity of the external capacitor is very large. 1000 times or more.

          In FIG. 2, when the power source of the liquid crystal display 201 is stopped, the switch transistor 206 is turned on, the liquid crystal display 201 and the external capacitor 210 are connected to the resistor 208, and the charge of the capacitor of the liquid crystal display 201 and the external capacitor 210 is discharged. This eliminates the phenomenon of black lines.

However, in the prior art as described above, the discharged current cannot basically be so large and needs to be limited. Furthermore, since the capacitance of the external capacitor is quite large, it is necessary for this discharge process. The long time is very long, and the phenomenon that the black line is generated cannot be quickly removed. Therefore, there is a need for an apparatus and method that can shorten the discharge time and quickly remove black lines.
In order to solve the above problems, it is necessary to add a discharge circuit to the conventional liquid crystal display, and when the power is turned off, the charge of the capacitor of the liquid crystal display can be discharged at a high speed. The phenomenon that occurs can be removed.

          The first object of the present invention is to provide a discharge circuit and a discharge method capable of shortening the discharge time and eliminating the occurrence of black lines, against the limitations of the prior art described above.

          A second object of the present invention is to provide a discharge circuit and method for a liquid crystal display capable of reducing the discharge time of the liquid crystal display and eliminating the occurrence of black lines.

          Therefore, to achieve one of the above objects, the present invention provides a first discharge circuit connected to a first capacitor, a second discharge circuit connected to a second capacitor, the first capacitor, and the second capacitor. A switching circuit connected to the capacitor; and a discharge signal for starting or stopping the discharge circuit. When the discharge signal starts the discharge circuit, the first capacitor is discharged via the first discharge circuit. Thus, the switching circuit is opened to start the first discharge circuit, and the second discharge circuit is started to discharge the second discharge capacitor through the second discharge circuit. Further, when the discharge circuit is stopped, the switching circuit is closed, and the first discharge circuit and the second discharge circuit are stopped so that the first capacitor and the second capacitor are short-circuited together. For example, in the above discharge circuit, it is preferable that the first discharge circuit includes a first switching circuit and a first resistor, and the second discharge circuit includes a second switching circuit and a second resistor.

          The discharge method provided by the present invention generates a discharge signal to be provided to the first capacitor and the second capacitor, and when the discharge signal is an active signal, the first capacitor and the second capacitor are discharged. When the discharge signal is an inactive signal, both the first capacitor and the second capacitor are short-circuited.

          In order to achieve one of the above objects, a discharge circuit for a liquid crystal display provided by the present invention includes a liquid crystal display including a first capacitor, a first discharge circuit connected to the first capacitor of the liquid crystal display, A second discharge circuit connected to two capacitors, a switching device connected to the first capacitor and the second capacitor, and a discharge signal for starting or stopping the discharge circuit, wherein the discharge signal is When the discharge circuit is activated, the switching circuit is opened to activate the first discharge circuit so that the first capacitor is discharged via the first discharge circuit, and the first discharge circuit is activated via the second discharge circuit. The second discharge circuit is activated so that the second discharge capacitor is discharged. Further, when the discharge circuit is stopped, the switching circuit is closed, and the first discharge circuit and the second discharge circuit are stopped so that the first capacitor and the second capacitor are short-circuited together.

          In the discharge circuit of the liquid crystal display, the first capacitor preferably includes at least one of a parasitic capacitor or an external capacitor of the liquid crystal display.

          The discharge circuit of the liquid crystal display preferably includes a power supply detection device that detects a power supply of the liquid crystal display, and generates the discharge signal when the power supply changes.

          In the liquid crystal display discharge circuit, the first discharge circuit preferably includes a first switching circuit and a first resistor, and the second discharge circuit preferably includes a second switching circuit and a second resistor.

          In order to achieve one of the above objects, a discharge circuit for a liquid crystal display provided by the present invention generates a discharge signal to be provided to a liquid crystal display having a first capacitor and a second capacitor, and the discharge signal is an activation signal. At the time, the first capacitor and the second capacitor are discharged, and when the discharge signal is a stop signal, both the first capacitor and the second capacitor are short-circuited.

          According to the present invention, the discharge circuit and method thereof provided by the present invention, and the discharge circuit and method of a liquid crystal display provide a discharge circuit when the power supply of the liquid crystal display suddenly stops, and the scan line of the liquid crystal display is provided. Or other parts of the capacitor, that is, the first capacitor is discharged at a high speed, so that no black line is generated. The capacitance of the second capacitor, i.e., the external capacitor, is large and cannot be discharged at high speed. However, after the power supply of the liquid crystal display is stopped, the discharge circuit of the external capacitor is already separated from the liquid crystal display. There is no effect of generating black lines on the display. In summary, the discharge circuit and method thereof provided by the present invention, and the discharge circuit and method of a liquid crystal display provide a discharge circuit when the power of the liquid crystal display suddenly stops, thereby increasing the discharge time of the liquid crystal display. As a result, the generation of black lines can be eliminated.

          BRIEF DESCRIPTION OF THE DRAWINGS To clearly understand the above and other objects, features and advantages of the present invention, the best mode for carrying out the invention will now be described in detail with reference to several preferred embodiments illustrated in the accompanying drawings. explain.

          FIG. 3a is a circuit diagram showing a discharge circuit according to a more preferred embodiment of the present invention.

          Referring to FIG. 3 a, a discharge circuit 302 includes a first discharge circuit 310 connected to a first capacitor 312, a second discharge circuit 320 connected to a second capacitor 322, a first capacitor 312 and a second capacitor 322. And a switching circuit 330 connected to the. In FIG. 3a, the discharge circuit 302 is configured to be activated and deactivated. The switching circuit 330 includes an active switch element or a passive switch element.

          3A, the first discharge circuit 310 includes a first switching circuit 314 and a first resistor 316, and the second discharge circuit 320 includes a second switching circuit 324 and a second resistor 326. Is preferably included. The first switching circuit 314 includes an active switch element or a passive switch element. The second switching circuit 324 includes an active switch element or a passive switch element. Furthermore, the switching circuit 330, the first switching circuit 314, and the second switching circuit 324 preferably include a metal oxide semiconductor (MOS), a bipolar junction transistor (BJT), and the like.

          FIG. 3b is a circuit diagram showing a discharge circuit constructed according to another embodiment of the present invention. 3b is different from FIG. 3a in that the first switching circuit 314 of the first discharge circuit 310 is installed between the first resistor 316 and the ground terminal, and in the second discharge circuit 320, and the second switching circuit 324 is different. Is installed between the second resistor 326 and the ground end. Although the circuit arrangements of FIG. 3b and FIG. 3a are different, both can achieve the object of the present invention.

          In addition, in the embodiment according to the present invention, the first resistor 316 or the second resistor 326 in FIGS. 3B and 3A is, for example, a parasitic resistor in the circuit or an actually formed resistor.

          4a and 4b are schematic diagrams showing the operation of the discharge circuit of FIG. 3a based on a more preferred embodiment according to the present invention.

          Referring to FIG. 4a, when the discharge signal activates the discharge circuit 302, the switching circuit 330 switches to open and activates the first discharge circuit 310, that is, the first switching circuit 314 in the first discharge circuit 310 is closed. To do. Therefore, the charge of the first capacitor 312 is discharged through the first discharge circuit 310 by connecting to the first resistor 316. Then, the second discharge circuit 320 is activated, that is, the second switching circuit 324 in the second discharge circuit 320 is closed. Therefore, the second capacitor 322 is discharged through the second discharge circuit 320 by connecting to the second resistor 326.

          Referring to FIG. 4b, when the discharge signal stops the discharge circuit 302, the switching circuit 330 is switched to close, and both the first capacitor 312 and the second capacitor 322 are short-circuited. Then, the first discharge circuit 310 and the second discharge circuit 320 are stopped, that is, the first switching circuit 314 of the first discharge circuit 310 is opened and the second switching circuit 324 of the second discharge circuit 320 is opened.

          In summary, based on a more preferred embodiment of the present invention, the discharge method provided by the present invention first generates a discharge signal to be provided to the first capacitor 312 and the second capacitor 322. When the discharge signal is a start signal, the first capacitor 312 and the second capacitor 322 are discharged. When the discharge signal is a stop signal, both the first capacitor 312 and the second capacitor 322 are short-circuited.

          5a and 5b are schematic diagrams showing the operation of a discharge circuit operated in a liquid crystal display based on a more preferred embodiment according to the present invention.

          Referring to FIG. 5 a, the discharge circuit 502 provided by the present invention is applied in the LCD driving IC 503. Discharge circuit 502 includes a first discharge circuit 510, a second discharge circuit 520, and a switching circuit 530. The first discharge circuit 510 passes through the drive switch 504 and is connected to all the capacitors in the liquid crystal display 501 and the drive switch 504. The total of the capacitors is displayed by the first capacitor 512 in FIG. The second discharge circuit 520 is connected to the second capacitor 522. The purpose of circumscribing the liquid crystal display 501 to the second capacitor 522 is to stabilize scan voltages such as the scan lines COM and SEG. Therefore, normally, the capacitance of the capacitor of the second capacitor 522 is very large, and is basically 100 times or more of the capacitor of the liquid crystal display 501. In FIG. 5a, a discharge signal is provided to activate or deactivate the discharge circuit 502. The switching circuit 530 includes an active switch element or a passive switch element.

          5A, the first discharge circuit 510 includes a first switching circuit 514 and a first resistor 516, and the second discharge circuit 520 includes a second switching circuit 524 and a second resistor. 526 is preferably included. The first switching circuit 514 includes an active switch element or a passive switch element. The second switching circuit 524 includes an active switch element or a passive switch element. Furthermore, switching circuit 530, first switching circuit 514, and second switching circuit 524 preferably include a metal oxide semiconductor (MOS), a bipolar junction transistor (BJT), and the like.

          FIG. 5c is a schematic diagram showing the operation of the discharge circuit operated in the liquid crystal display. 5c is different from FIG. 5a in the first discharge circuit 510, in which the first switching circuit 514 is installed between the first resistor 516 and the ground terminal and in the second discharge circuit 520. 524 is installed between the second resistor 526 and the ground end. Although the circuit arrangements of FIG. 5c and FIG. 5a are different, both can reach the results of the present invention.

          In addition, in the embodiment according to the present invention, the first resistor 516 or the second resistor 526 in FIGS. 5a and 5c is a parasitic resistance in the circuit or an actually formed resistance.

          5a and 5b are schematic diagrams showing the operation of the discharge circuit. The operation status of the discharge circuit of FIG. 5c can be referred to the description of FIGS. 5a and 5b.

          Referring to FIG. 5a, when the discharge signal activates the discharge signal 502, the switching circuit 530 is switched to open to activate the first discharge circuit 510, that is, the first switching circuit 514 of the first discharge circuit 510 is closed. Therefore, the first capacitor 512 is connected to the first resistor 516 and the first capacitor 512 is discharged through the first discharge circuit 510. Then, the second discharge circuit 520 is activated, that is, the second switching circuit 524 of the second discharge circuit 520 is closed. Therefore, the second discharge circuit 520 is connected to the second resistor 526, and the second capacitor 522 is connected via the second discharge circuit 520. The electric charge is discharged.

          Referring to FIG. 5b, when the discharge signal stops the discharge circuit 502, the switching circuit 530 is switched to close and shorts the first capacitor 512 and the second capacitor 522 together. Then, the first discharge circuit 510 and the second discharge circuit 520 are stopped, that is, the first switching circuit 514 of the first discharge circuit 510 is opened and the second switching circuit 524 of the second discharge circuit 520 is opened. At this time, the liquid crystal display 501 passes through the drive switch 504 and the switching circuit 530, is connected to the second capacitor 522, and stabilizes scan voltages such as the scan lines COM and SEG via the second capacitor 522. FIG. 5b illustrates a state in which the liquid crystal display 501 is operating normally.

          In an embodiment of the present invention, the discharge circuit 502 of the liquid crystal display 501 includes a power search device 540 that detects the power of the liquid crystal display 501 and generates a discharge signal when the power changes or is interrupted. The operation shown in FIG. 5a is preferably performed.

          Further, in the discharge circuit 502 of the liquid crystal display 501, the first capacitor 512 preferably includes at least one of a parasitic capacitor or an external capacitor of the liquid crystal display 501.

          In summary, based on a more preferred embodiment of the present invention, a liquid crystal display discharging method provided by the present invention first generates a liquid crystal display having a first capacitor and a discharge signal provided to the second capacitor. . When the discharge signal is a start signal, the first capacitor and the second capacitor are discharged. When the discharge signal is a stop signal, both the first capacitor and the second capacitor are short-circuited.

          In summary, the discharge circuit and method of the present invention and the discharge circuit and method of the liquid crystal display provide a discharge circuit when the power supply of the liquid crystal display 501 is suddenly stopped. And the generation of black lines can be eliminated.

        As described above, the present invention has been disclosed by the preferred embodiments. However, these embodiments are not intended to limit the present invention, and the techniques of the present invention can be easily understood by those skilled in the art. Since appropriate changes and modifications can be naturally made within the scope of the idea, the scope of the present invention should be defined on the basis of the scope of claims and a scope equivalent thereto.

Schematic which showed the black line which the residual voltage produced | generated in the well-known liquid crystal display. FIG. 1b is a schematic diagram showing a black line in which a residual voltage is generated in a known liquid crystal display as in FIG. The circuit diagram which showed the discharge circuit of the well-known liquid crystal display. The circuit diagram which showed the discharge circuit based on the more preferable Example based on this invention. The circuit diagram which showed the discharge circuit based on another preferable Example which concerns on this invention. The circuit diagram which showed the discharge circuit based on the more preferable Example based on this invention. The circuit diagram which showed the discharge circuit based on the more preferable Example based on this invention similarly to FIG. 4a. It is the schematic which shows operation | movement of the discharge circuit operated in a liquid crystal display based on the more preferable Example which concerns on this invention. FIG. 6B is a schematic diagram showing the operation of the discharge circuit operated in the liquid crystal display based on a more preferred embodiment according to the present invention, similar to FIG. 5a. The schematic which shows operation | movement of the discharge circuit operated in a liquid crystal display based on the Example which concerns on this invention.

Explanation of symbols

201, 501 LCD 203, 503 LCD driver IC
204, 504 Drive switch 206 Switch transistor 208 Resistor 316, 516 First resistor 326, 526 Second resistor 210 Capacitor 312, 512 First capacitor 322, 522 Second capacitor 302, 502 Discharge circuit 310, 510 First discharge circuit 320, 520 Second discharge circuit 330, 530 Switching circuit 314, 514 First switching circuit 324, 524 Second switching circuit 540 Power supply search device COM, SEG Scan line

Claims (21)

A first discharge circuit connected to the first capacitor;
A second discharge circuit connected to the second capacitor;
A switching circuit connected to the first capacitor and the second capacitor;
A discharge signal for starting or stopping the discharge circuit,
When the discharge signal activates the discharge circuit, the switching circuit is opened to activate the first discharge circuit so that the first capacitor is discharged via the first discharge circuit, and the second discharge is activated. Activating the second discharge circuit to discharge the second discharge capacitor through the circuit;
When the discharge circuit is stopped, the switching circuit is closed, and the first discharge circuit and the second discharge circuit are stopped so that the first capacitor and the second capacitor are short-circuited together. Discharge circuit.           The discharge circuit according to claim 1, further comprising a power supply detection device that generates the discharge signal when the power supply changes.           The discharge circuit according to claim 1, comprising one of an active switch element and a passive switch element.           2. The discharge circuit according to claim 1, wherein the switching circuit includes one of a metal oxide semiconductor (MOS) and a bipolar junction transistor (BJT).           2. The discharge circuit according to claim 1, wherein the first discharge circuit includes a first switching circuit and a first resistor, and the second discharge circuit includes a second switching circuit and a second resistor.           6. The discharge circuit according to claim 5, wherein the first resistor or the second resistor includes a parasitic resistor in the circuit or an actually formed resistor.           The first switching circuit includes one of an active switching element and a passive switching element, and the second switching circuit includes one of an active switching element and a passive switching element. 5. The discharge circuit according to 5.           The first switching circuit includes one of a metal oxide semiconductor (MOS) and a bipolar junction transistor (BJT), and the second switching circuit includes a metal oxide semiconductor (MOS) and a bipolar junction transistor (BJT). 8. The discharge circuit according to claim 7, comprising one of (BJT). Generating a discharge signal to be provided to the first capacitor and the second capacitor;
When the discharge signal is a start signal, the first capacitor and the second capacitor are discharged,
When the discharge signal is a stop signal, both the first capacitor and the second capacitor are short-circuited. A liquid crystal display comprising a first capacitor;
A first discharge circuit connected to the first capacitor of the liquid crystal display;
A second discharge circuit connected to the second capacitor;
A switching device connected to the first capacitor and the second capacitor;
A discharge signal for starting or stopping the discharge circuit,
When the discharge signal activates the discharge circuit, the switching circuit is opened to activate the first discharge circuit so that the first capacitor is discharged via the first discharge circuit, and the second discharge Activating the second discharge circuit so that the second discharge capacitor discharges through the circuit;
When the discharge circuit is stopped, the switching circuit is closed, and the first discharge circuit and the second discharge circuit are stopped so that the first capacitor and the second capacitor are short-circuited together. A discharge circuit for a liquid crystal display.           11. The discharge circuit of the liquid crystal display according to claim 10, wherein the first capacitor includes at least one of a parasitic capacitor or an external capacitor of the liquid crystal display.           11. The discharge circuit of a liquid crystal display according to claim 10, further comprising a power supply detection device for detecting a power supply of the liquid crystal display, wherein the discharge signal is generated when the power supply changes.           11. The discharge circuit of a liquid crystal display according to claim 10, wherein the switching circuit includes one of an active switch element and a passive switch element.           The discharge circuit of the liquid crystal display according to claim 13, wherein the switching circuit includes one of a metal oxide semiconductor (MOS) and a bipolar junction transistor (BJT).           11. The discharge circuit of a liquid crystal display according to claim 10, wherein the first discharge circuit includes a first switching circuit and a first resistor, and the second discharge circuit includes a second switching circuit and a second resistor.           16. The discharge circuit of a liquid crystal display according to claim 15, wherein the first resistance or the second resistance includes a parasitic resistance in the circuit or an actually formed resistance.           The first switching circuit includes one of an active switching element or a passive switching element, and the second switching circuit includes one of an active switching element or a passive switching element. Item 16. A discharge circuit for a liquid crystal display according to Item 15.           The first switching circuit includes one of a metal oxide semiconductor (MOS) and a bipolar junction transistor (BJT), and the second switching circuit includes a metal oxide semiconductor (MOS) and a bipolar junction transistor. The discharge circuit of a liquid crystal display according to claim 17, comprising one of (BJT). Generating a discharge signal to be provided to the first capacitor and the second capacitor;
When the discharge signal is a start signal, the first capacitor and the second capacitor are discharged,
The method according to claim 1, wherein when the discharge signal is a stop signal, the first capacitor and the second capacitor are short-circuited together.           The method of claim 19, wherein the first capacitor includes at least one of a parasitic capacitor or an external capacitor of the liquid crystal display. 20. The method of discharging a liquid crystal display according to claim 19, further comprising a power detection device that detects a power source of the liquid crystal display, and generating the discharge signal when the power source changes.

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