TW200535773A - Discharge device and discharge method and liquid crystal display using thereof - Google Patents

Abstract

A discharge device and discharge method for a LCD is provided. The discharge device includes a first discharge circuit connected to a first capacitor, a second discharge circuit connected to a second capacitor, and a switch circuit connected to the first and the second capacitor. When the power of the LCD driver is turned off suddenly, a discharge signal is provided to activate the switch circuit, thus the switch circuit is open, then the first capacitor is discharged by the first discharge circuit, and the second capacitor is discharged by the second discharge circuit. When the power of the LCD driver is turned on, the switch circuit is inactivated and closed, thus the first and the second capacitor are short. Accordingly, when the power of LCD driver is turned off suddenly, the charge stored in any one of the scan lines of the LCD can be discharged rapidly, and the black line phenomenon can be avoided.

Description

200535773 V. Description of the invention (1) Technical field to which the invention belongs The present invention relates to liquid crystal display and electric circuits and the prior art. In recent years, screens, televisions, etc. (Cathode has light weight, a ruler, and no radiation. It can meet the weight. Traditionally, it will hide a certain voltage of the line because it does not operate. However, at a certain potential voltage, the panel voltage is generally accumulated. It is related to the discharge circuit and method, and especially there is Regarding the panel 0 (Liquid Crystal Display, LCDπ) display method 0, used for the display of electronic equipment, there have been significant developments. Phase Ray Tube, "CRT1 丨), thin, area can be large or small, wire and other advantages In recent years, portable electronic business opportunity screens, personal digital assistants, n PDAn) display screens, etc., light, thin, small area, etc.? A liquid crystal display panel in its integrated circuit (Integrated has its X The scan line of the COM terminal scan bar of the direction still remains because the LCD display panel voltage, which makes this COM terminal or SEG hold for a long time. Wait until the root-mean-square (Root device, such as a computer screen, for traditional cathode ray) is low due to leakage or a certain period of time during which the residual voltage is maintained. It is the mainstream of display panels because of its low operating voltage and power saving. , Such as notebook computers (Personal Digital is only required for LCD screens can be portable. When the power is suddenly turned off, C ircuit, π IC π) has been scanned in line or Υ direction SEG end-scan LCD display panel The voltage stabilizing capacitor still remains on the scanning line of the terminal basically 'this liquid crystal display will not disappear until the discharge path. (Mean Square on the LCD panel, n RMS π)

11549twf.ptd Page 8 200535773 V. Description of the invention (2) The phenomenon of black line that can be observed due to voltage. Please refer to FIG. 1A and FIG. 1B, which are schematic diagrams of black lines generated by a residual voltage on a conventional liquid crystal display panel. In order to solve the above problem, a conventional liquid crystal display panel needs to be added with a discharge circuit. When the power is turned off, the electric charge on the capacitor in the liquid crystal display panel can be quickly discharged, and the phenomenon of the black line can be eliminated. Please refer to Fig. 2, which shows a circuit diagram of a conventional discharge circuit of a liquid crystal display panel. Among them, an LCD driver 1C 203 includes a switching transistor 206 and a resistor 208. The switching transistor 2 0 6 is connected to all capacitors in a liquid crystal display panel 2 0 1 through a driving switch 2 0 4. In addition, the switching transistor 2 0 6 is further connected to an external capacitor 4 2 1 0. The liquid crystal display panel 2 0 1 is connected to this external capacitor 2 1 0 'for the purpose of stabilizing the sweep voltage of the cat line COM and SEG'. Therefore, the capacitance of the external capacitor is usually quite large, basically all are liquid crystal display panels. The capacitance in 201 is more than 1000 times. When the power of the liquid crystal display west panel 2 1 in Figure 2 is turned off, the switching transistor 2 0 6 is turned on and the liquid crystal display panel 2 0 1 and the external capacitor 2 1 0 are connected to the resistor 2 0 8 to connect the liquid crystal. The capacitors in the display panel 201 and the charges on the external capacitor 210 are discharged to eliminate the phenomenon of the black lines. However, because the discharge current can not be too large and needs to be limited, and because the capacitance value of the external capacitor is quite large, the time required for this discharge process will be long, so that the phenomenon of the above black line cannot be quickly affected. eliminate. Therefore, a device and method that can shorten the discharge time and quickly eliminate black lines are necessary.

11549twf.ptd Page 9 200535773 V. Description of the Invention (3) Summary of the Invention In view of the limitation of the above-mentioned conventional technology, the first object of the present invention is to propose a discharge circuit and a discharge method that can shorten the discharge time and eliminate black lines. A second object of the present invention is to provide a discharge circuit and method for a liquid crystal display panel, which can shorten the discharge time of the liquid crystal display panel and eliminate the occurrence of black lines. Therefore, in order to achieve a part of the above purpose, the present invention proposes a discharge circuit including a first discharge circuit connected to a first capacitor; a second discharge circuit connected to a second capacitor; a switching circuit connected to The first capacitor and the second capacitor; and a discharge signal < for activating or disabling the discharge circuit; wherein when the discharge signal activates the discharge circuit, the switching circuit is opened to start the first discharge circuit So that the first capacitor is discharged through the first discharge circuit, and the second discharge circuit is activated, so that the second capacitor is discharged through the second discharge circuit; when the discharge circuit is closed, the switching circuit is closed, and closed The first discharge circuit and the second discharge circuit make the first capacitor and the second capacitor short-circuited together. The discharge circuit as described above, more preferably, 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. The present invention provides a discharge method including generating a discharge signal 0 for a first capacitor and a second capacitor; and when the discharge signal is an active signal, the first capacitor and the first capacitor Two capacitors

11549twf.ptd Page 10 200535773 V. Description of the Invention (4) Electricity; and when the discharge signal is an off (i n a c t i v e) signal, short the first capacitor and the second capacitor together. In order to achieve a part of the above object, the present invention provides a discharge circuit of a liquid crystal display panel, which includes a liquid crystal display panel with a first capacitor; a first discharge circuit connected to the first capacitor in the liquid crystal display panel; A second discharge circuit connected to a second capacitor; a switching device connected to the first capacitor and the second capacitor; and a discharge signal for enabling or disabling the discharge circuit; wherein when the discharge signal starts the When the circuit is discharged, the switching circuit is opened, the first discharge circuit is started, so that the first capacitor is discharged through the first discharge circuit, and the second discharge circuit is started, so that the second capacitor is discharged through the second discharge The circuit discharges; when the discharge circuit is closed, the switching circuit is closed, and the first discharge circuit and the second discharge circuit are closed, so that the first capacitor and the second capacitor are short-circuited together. As described above, the discharge circuit of the liquid crystal display panel is more preferably, wherein the first capacitor includes at least one of a parasitic capacitor or an external capacitor of the liquid crystal display panel. The discharge circuit of the liquid crystal display panel as described above, more preferably, further includes a set of power detection devices for detecting a power supply of the liquid crystal display panel. When the power supply changes, the discharge signal is generated. The discharge circuit of the liquid crystal display panel described above is 'better', 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 One second resistor.

11549twf.ptd Page 11 200535773 V. Description of the invention (5) In order to achieve a part of the above purpose, the present invention proposes a method for discharging a liquid crystal display panel, which includes generating a discharge signal for a liquid crystal display having a first capacitor. Panel and a second capacitor; when the discharge signal is an enable signal, discharge the first capacitor and the second capacitor; and when the discharge signal is a shutdown signal, connect the first capacitor and the second capacitor Shorted together. In summary, the discharge circuit and method provided by the present invention and the discharge circuit and method of a liquid crystal display panel can provide a discharge circuit when one of the power sources of the liquid crystal display panel is suddenly turned off to shorten the discharge time of the liquid crystal display panel. And eliminate the generation of black lines. In order to make the above and other objects, features, and advantages of the present invention more obvious and understandable, a preferred embodiment is given below in conjunction with the accompanying drawings to make a detailed description as follows: The embodiment is as follows, FIG. 3A It is a circuit diagram showing a discharge circuit according to a preferred embodiment of the present invention. Referring to FIG. 3A, a discharge circuit 302 is provided, which includes a first discharge circuit 310 connected to a first capacitor 312, a second discharge circuit 320, connected to a second capacitor 322, and A switch circuit 330 is connected to the first capacitor 312 and the second capacitor 322. In FIG. 3A, a discharge signal is provided for activating (a c t i v e) or inactive the discharge circuit 302. The switching circuit 330 includes a main switching element (ac t i v e) or a passive switching element (p a s s i v e). In one embodiment of the present invention, it is more preferred, as shown in FIG. 3A.

11549twf.ptd Page 12 200535773 V. Discharge circuit 302 described in the description of the invention (6), wherein 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 The switching circuit 324 and a second resistor 326. The first switching circuit 3 1 4 includes an active switching element or a passive switching element. The second switching circuit 3 2 4 includes an active switching element or a passive switching element. More preferably, the switching circuit 3 3 0, the first switching circuit 314, and the second switching circuit 3 2 4 may include a metal oxide semiconductor (Metal Oxide).

Semiconductor, nM0Sn), and bipolar junction transistor (Bipolar Junction Transistor, BJT "), etc. Figure 3B is a circuit diagram showing a discharge circuit, according to another embodiment of the present invention. 3B is different from FIG. 3A in that in your first discharge circuit 3 10, the first switching circuit 3 14 is located between the first resistor 316 and the ground terminal, and in the second discharge circuit 320, the first The second switching circuit 324 is located between the second resistor 326 and the ground terminal. The circuit configurations of FIG. 3B and FIG. 3A are different, but both can achieve the results of the present invention. In addition, in one embodiment of the present invention In FIG. 3B or FIG. 3A, the first resistor 316 or a second resistor 326 may be, for example, a parasitic resistor in a circuit or a resistor that is actually configured. ° Below, FIGS. 4A and 4B are The operation diagram of the discharge circuit in Figure 3A is based on a preferred embodiment of the present invention. The operation of the discharge circuit in Figure 3 β can also refer to the description of Figures 4A and 4B ^. 礓 | Please refer to 4 A picture, when the discharge signal is to start the discharge circuit 3 〇 2 When the switching circuit 3 3 0 is switched to an open circuit (〇 p e n), and the first discharge circuit is turned on

11549twf.ptd Page 13 200535773 V. Description of the invention (7) 310, that is, the first switching circuit 314 in the first discharge circuit 310 is closed, so it is connected to the first resistor 316, so that the charge in the first capacitor 312 passes through The first discharge circuit 3 10 is discharged. And the second discharge circuit 320 ′ is turned on, that is, the second switching circuit 324 in the second discharge circuit 320 is closed, so it is connected to the second resistor 326, so that the charge in the second capacitor 322 is discharged through the second discharge circuit 3 2 0 . Referring to FIG. 4B, when the discharge signal is to close the discharge circuit 3 02, the switching circuit 330 is switched to a closed circuit, so that the first capacitor and the second capacitor are short-circuited together. The first discharge circuit 310 and the second discharge circuit 320 are closed, that is, the first switching circuit 314 in the first discharging circuit 31o is opened, and the second switching circuit 324 in the second discharging circuit 320 is opened. In summary, according to a preferred embodiment of the present invention, the present invention provides a discharging method, which includes firstly generating a discharge signal for a first capacitor 312 and a second capacitor 322. When the discharge signal is an active signal, the first capacitor 312 and the second capacitor 322 are discharged. When the discharge signal is an off (i n a c t i v e) signal, the first capacitor 312 and the second capacitor 322 are shorted together. Hereinafter, FIG. 5A and FIG. 5B are schematic diagrams of the operation of a discharge circuit applied to a liquid crystal display panel according to a preferred embodiment of the present invention. Referring to FIG. 5A, the present invention provides a discharge circuit 502, which is suitable for an LCD driver 1C 503. The discharge circuit 502 includes a first discharge circuit 510, a second discharge circuit 520, and a switching circuit 530. The first discharge circuit 5 10 is connected to a liquid crystal display through a driving switch 504.

11549twf.ptd Page 14 200535773 V. Description of the invention (8) All the capacitors in the display panel 501 and the drive switch 504. In Figure 5A, one of these capacitors is summed as a first capacitor. 512 means it. The second discharge circuit 520 is connected to a second capacitor 522. The purpose of connecting the liquid crystal display panel 5 0 1 to this second capacitor 5 2 2 is to stabilize the scanning voltages of the scan lines COM and SEG. Therefore, usually the capacitance of the second capacitor 522 is quite large, basically all are The capacitance of the liquid crystal display panel 501 is more than 100 times. In FIG. 5A, a discharge signal is provided, which is used for activating (active) or inactive (502) the discharge circuit. The switching circuit 530 includes an active switching element or a passive (p a s s i v e) switching element. In an embodiment of the present invention, it is more preferable that the discharge circuit 502 is as shown in FIG. 5A, wherein the first discharge circuit 510 includes a first switching circuit 514 and a first resistor 516, and a second The discharge circuit 520 includes a second switching circuit 5 2 4 and a second resistor 5 2 6. The first switching circuit 5 1 4 includes an active switching element or a passive switching element. The second switching circuit 5 2 4 includes an active switching element or a passive switching element. More preferably, the switching circuit 530, the first switching circuit 514, and the second switching circuit 524 may include a metal oxide semiconductor ("M0Sn") and a bipolar junction transistor (Bipolar Junction). Transistor, " BJTn) etc. Figure 5C is a schematic diagram of the operation of a discharge circuit applied to a liquid crystal display panel, according to an embodiment of the present invention. In Figure 5C, what is different from Figure 5A is that In the first discharge circuit 510, the first switching circuit 5 1 4 is located between the first resistor 5 1 6 and the ground terminal, and the second discharge circuit

11549twf.ptd Page 15 200535773 V. Description of the Invention (9) In the circuit 520, the second switching circuit 524 is located between the second resistor 526 and the ground terminal. The circuit configuration of Fig. 5C is different from that of Fig. 5A, but both can achieve the results of the present invention. In addition, in one embodiment of the present invention, the first resistor 516 or a second resistor 526 in FIGS. 5A to 5C may be, for example, a parasitic resistor in a circuit or an actually configured resistor. Below, Figures 5A and 5B are schematic diagrams of the operation of a discharge circuit. The operation of the discharge circuit in Figure 5C can also refer to the descriptions in Figures 5A and 5B. Please refer to FIG. 5A. When the discharge signal is to start the discharge circuit 502, the switching circuit 5 30 will switch to open and open the first discharge circuit # 510, which is the first discharge circuit 510. The first switching circuit 514 is closed, so it is connected to the first resistor 516, so that the charge in the first capacitor 512 is discharged through the first discharging circuit 5 10. And the second discharge circuit 520 is turned on, that is, the second switching circuit 524 in the second discharge circuit 520 is closed, so it is connected to the second resistor 526, so that the charge in the second capacitor 522 is discharged through the second discharge circuit 520. Please refer to FIG. 5B. When the discharge signal is to close the discharge circuit 502, the switching circuit 5 30 will switch to a closed circuit (c 1 〇se), so that the first capacitor and the second capacitor are short-circuited. together. The first discharge circuit 510 and the second discharge circuit 520 are turned off, that is, the first switching circuit 514 in the first discharge circuit 510 is opened, and the second switching circuit 324 in the second discharge circuit 520 is opened. At this time, the liquid crystal display panel 5 0 1 is connected to the second capacitor 5 2 2 through the driving switch 5 0 4 and the switching switch 5 3 0 to make the scanning line

11549twf.ptd Page 16 200535773 V. Description of Invention (ί) The scanning voltage of COM and SEG can be stabilized by the second capacitor 522. This FIG. 5B shows the state of the liquid crystal display panel 501 under normal operation. In one embodiment of the present invention, it is more preferable that the above-mentioned discharge circuit 50 2 of the liquid crystal display panel 5 0 1 further includes a set of power detection devices 5 4 0 for detecting the liquid crystal display panel 5 A power source of 0 1 is generated when the power source is changed or interrupted. The discharge signal is generated as shown in Figure 5A. More preferably, in the discharge circuit 502 of the liquid crystal display panel 501, the first capacitor 512 further includes at least one of a parasitic capacitor or an external capacitor of the liquid crystal display panel 501. In summary, according to a preferred embodiment of the present invention, the present invention provides a method for discharging a liquid crystal display panel, which includes, first, generating a discharge signal for a liquid crystal display panel having a first capacitor. With a second capacitor. When the discharge signal is an enable signal, the first capacitor and the second capacitor are discharged. And when the discharge signal is a close signal, the first capacitor and the second capacitor are short-circuited together. In summary, the discharge circuit and method provided by the present invention and the discharge circuit and method of a liquid crystal display panel can be used to provide a discharge circuit 50 2 when one of the power sources of the liquid crystal display panel 51 is suddenly turned off, so that The scanning line in the liquid crystal display panel 501 or the capacitance of other parts, that is, the first capacitance 5 1 2 can be discharged quickly without generating black lines. Although the above-mentioned second capacitor 522, that is, an external capacitor, has a large capacitance value and cannot be discharged quickly, it is because the discharge circuit of the external capacitor 5 2 0 And LCD panel 5 0 1 points

11549twf.ptd Page 17 200535773 V. Description of the invention (11) On, so it will not affect the LCD panel 501 to produce black lines. In summary, the discharge circuit and method provided by the present invention and the discharge circuit and method of a liquid crystal display panel can provide a discharge circuit when one of the power sources of the liquid crystal display panel is suddenly turned off to shorten the discharge time of the liquid crystal display panel. And eliminate the generation of black lines. Although the present invention has been disclosed as above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some changes and retouch without departing from the spirit and scope of the present invention. The scope of protection of the invention shall be determined by the scope of the attached patent application.

11549twf.ptd Page 18 200535773 The diagram briefly illustrates Figures 1 A and 1 B, showing a schematic diagram of a black line generated by residual voltage on a conventional liquid crystal display panel; Figure 2 is a circuit diagram showing a The conventional discharge circuit of a liquid crystal display panel; FIG. 3A is a circuit diagram showing a discharge circuit according to a preferred embodiment of the present invention; FIG. 3B is a circuit diagram showing a discharge circuit, based on Another embodiment of the present invention; FIG. 4A and FIG. 4B are schematic diagrams of the operation of a discharge circuit, according to a preferred embodiment of the present invention; and FIGS. 5A and 5B are a discharge circuit applied to a liquid crystal display The operation diagram of the surface φ plate is according to a preferred embodiment of the present invention; and FIG. 5C is an operation diagram of a discharge circuit applied to a liquid crystal display panel, according to an embodiment of the present invention. The drawings are clear: 2 0 1, 5 0 1 · LCD display panel 203, 503: LCD drive 1C 2 0 4, 5 0 4 · • Drive switch 2 0 6: Switch transistor 2 0 8 , 3 1 6 ^ 3 2 6, 51 6 > 5 2 6: f resistance 210, 312, 322, 512, 522: t capacity 3 0 2, 5 0 2: discharge line ❶ 310, 320, 510, 520: Discharge circuits 314 > 324, 330, 514 > 524, 530: switching circuits

11549twf.ptd page 19 200535773 Schematic description COM, SEG: Scan line «11549twf.ptd page 20 111 ·!»

Claims (1)

200535773 VI. Application for patent scope 1. A discharge circuit comprising: a first discharge circuit connected to a first capacitor; a second discharge circuit connected to a second capacitor; a switch circuit connected to the The first capacitor and the second capacitor; and a discharge signal for activating or inactive the discharge circuit; wherein when the discharge signal activates the discharge circuit, the switching circuit is opened to start The first discharge circuit causes the first capacitor to be discharged through the first discharge circuit, and activates the second discharge circuit so that the second capacitor is discharged through the second discharge circuit; when the discharge circuit is closed, the The switching circuit is closed (c 1 0se), and the first discharge circuit and the second discharge circuit are closed, so that the first capacitor and the second capacitor are shorted together. 2. The discharge circuit as described in item 1 of the scope of patent application, which further includes a set of power detection devices to generate the discharge signal when a power source changes. 3. The discharge circuit according to item 1 of the scope of patent application, wherein the switching circuit includes one of an active switching element and a passive switching element. 4. The discharge circuit according to item 1 of the scope of patent application, wherein the switching circuit, wherein the switching circuit comprises one of a metal oxide semiconductor (MOS) and a ○ bi-junction transistor (BJT). 5. The discharge circuit described in item 1 of the scope of patent application, wherein 11549twf.ptd Page 21 200535773 6. Scope of patent application 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 item 5 of the scope of patent application, wherein the first resistor or the second resistor includes a parasitic resistor of the discharge circuit or a resistor of an actual configuration. 7. The discharge circuit according to item 5 of the scope of patent application, wherein the first switching circuit includes one of an active switching element and a passive switching element, and the second switching circuit includes an active switching element, With one of the passive switching elements. 8. The discharge circuit as described in item 7 of the scope of patent application, wherein the first switching circuit includes one of a metal oxide semiconductor (M0S), an electric f-crystal (BJT) connected to a double-carrier, and the second switching The circuit includes one of a metal-oxide-semiconductor (MOS) and a bipolar junction transistor (BJT). 9. A discharging method, comprising: generating a discharge signal for a first capacitor and a second capacitor; and when the discharge signal is an active signal, discharging the first capacitor and the second capacitor; And when the discharge signal is an inactive signal, the first capacitor and the second capacitor are shorted together. 10. A discharge circuit of a liquid crystal display panel, comprising: a liquid crystal display panel having a first capacitor; a first discharge circuit connected to the first capacitor of the liquid crystal display panel; a second discharge circuit, Connected to a second capacitor; 11549twf.ptd Page 22 200535773 VI. Patent application scope a switch device connected to the first capacitor and the second capacitor; and a discharge signal for activating or inactive the discharge circuit Wherein, when the discharge signal activates the discharge circuit, the switching circuit is opened, the first discharge circuit is activated, so that the first capacitor is discharged through the first discharge circuit, and the second discharge circuit is activated, so that The second capacitor is discharged through the second discharge circuit; when the discharge circuit is closed, the switching circuit is closed (c 1 0se), and the first discharge circuit and the second discharge circuit are closed, so that the first capacitor Short with the second capacitor. Peak 11. The discharge circuit of the liquid crystal display panel as described in item 10 of the patent application scope, wherein the first capacitor includes at least one of a parasitic capacitor or an external capacitor of the liquid crystal display panel. 12. The discharge circuit of the liquid crystal display panel as described in item 10 of the scope of patent application, which further includes a set of power detection devices for detecting a power supply of the liquid crystal display panel. When the power supply changes, it generates The discharge signal. 13. The discharge circuit of the liquid crystal display panel according to item 10 of the patent application scope, wherein the switching circuit includes one of an active switching element and a passive switching element. 14. The discharge circuit of the liquid crystal display panel as described in Item 13 of the scope of patent application, wherein the switching circuit, wherein the switching circuit includes a metal oxide semiconductor (M0S), connected to a bipolar transistor (BJT). one. 11549twf.ptd Page 23 200535773 6. Application for patent scope 15. The discharge circuit of the liquid crystal display panel described in item 10 of the scope of patent application, 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 the liquid crystal display panel according to item 15 of the scope of the patent application, wherein the first resistor or the second resistor includes a parasitic resistor of the discharge circuit or a resistor configured actually. 17. The discharge circuit of the liquid crystal display panel according to item 15 of the scope of patent application, wherein the first switching circuit includes one of an active switching element and a passive switching element, and the second switching circuit includes An active switching element and one of the passive switching elements. 〇18. The discharge circuit of the liquid crystal display panel described in item 17 of the scope of patent application, wherein the first switching circuit includes a metal oxide semiconductor (MOS), and One of the BJTs, and the second switching circuit includes a metal oxide semiconductor (MOS), and one of the BJTs. 19. A method for discharging a liquid crystal display panel, comprising: generating a discharge signal for a liquid crystal display panel having a first capacitor and a second capacitor; and when the discharge signal is an active signal, The first capacitor and the second capacitor are discharged; and when the discharge signal is an inactive signal, the first capacitor and the second capacitor are short-circuited together. 11549twf.ptd Page 24 200535773 6. Application for patent scope 20. The method for discharging a liquid crystal display panel as described in item 19 of the scope of patent application, wherein the first capacitor includes at least one parasitic capacitor of the liquid crystal display panel or an external One of the capacitors. 2 1. The method for discharging a liquid crystal display panel as described in item 19 of the scope of patent application, further including a set of power detection devices 'for detecting a power supply of the liquid crystal display panel when the power supply changes' This discharge signal is generated. 11549twf.ptd Page 25