Patent Publication Number: US-8982030-B2

Title: Gate output control method and corresponding gate pulse modulator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Taiwan Patent Application No. 098134665, filed Oct. 13, 2009, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to the display field, and more particularly to a gate output control method and a corresponding gate pulse modulator. 
     2. Description of the Related Art 
     Flat display (such as, liquid crystal display) has many advantages, such as high image quality, little size, light weight and wide application range, etc., thus it is widely applied into various consumption, such as mobile phone, notebook computer, desktop computer and television, etc. Therefore, the flat display has gradually substituted conventional cathode ray tube (CRT) display to be a main trend of the display. 
     Refer to  FIG. 1 , which is a schematic view of a conventional flat display. As shown in  FIG. 1 , the flat display  100  includes a substrate  110 , a printed circuit board (PCB)  120  and a plurality of fixable circuit boards (FCB)  130 . The substrate  110  has a plurality of gate drive integrated circuits (IC) GD 1  and GD 2 , a plurality of source drive integrated circuits (not shown), and display blocks  111  and  112 . The gate drive integrated circuits GD 1  and GD 2  are configured for controlling the display blocks  111  and  112  respectively and are coupled with each other in series through wire-on-array (WOA) technique. The printed circuit board  120  is electrically coupled to the substrate  110  through the flexible circuit boards  130 , and has a timing controller  140  and a gate pulse modulator  150  disposed thereon. The timing controller  140  is configured for providing gate output enable signals YOE_Y 1  and YOE_Y 2  to the gate drive integrated circuits GD 1  and GD 2  respectively, and providing a gate control signal VGH 1  and an oblique control signal to the gate pulse modulator  150  such that the gate pulse modulator  150  outputs a modulated gate control signal VGH to the gate drive integrated circuits GD 1  and GD 2 . Then the modulated gate control signal VGH is cooperated with the gate output enable signals YOE_Y 1  and YOE_Y 2  to generate corresponding gate drive signals Gate Pulse_Y 1  and Gate Pulse_Y 2 . 
     Refer to  FIG. 2 , which is a schematic view of a conventional gate pulse modulator. As shown in  FIG. 2 , the gate pulse modulator  150  is a pulse-width modulation integrated circuit, which includes a gate control signal terminal  151 , an oblique control signal terminal  152 , a discharge circuit  153  and an output terminal  154 . The gate control signal terminal  151  is configured for receiving the gate control signal VGH 1 , the oblique control signal terminal  152  is configured for receiving the oblique control signal YV 1 C, and the gate pulse modulator  150  determines whether employing the discharge circuit  153  to discharge the gate control signal VGH 1  for generating the modulated gate control signal VGH and employing the output terminal  154  to output the modulated gate control signal VGH to the gate drive integrated circuits GD 1  and GD 2  according to the oblique control signal YV 1 C. 
     Refer to  FIG. 3 , which is a timing chart of the gate control signal VGH 1 , the oblique control signal YV 1 C and the modulated gate control signal VGH of the gate pulse modulator as shown in  FIG. 2 , and the gate output enable signals YOE_Y 1  and YOE_Y 2 , the gate drive signals Gate Pulse_Y 1  and Gate Pulse_Y 2  as shown in  FIG. 1 . As shown in  FIG. 3 , the modulated gate control signal VGH output from the gate pulse modulator  150  is a gate control signal with oblique, which falls to a certain voltage in a slope, and then changes in a vertical mode. In addition, since the resistance of the WOA is large, the modulated gate control signal VGH and the gate output enable signals YOE_Y 1  and YOE_Y 2  attenuate to generate wave-change in a process when they are transmitted to the gate drive integrated circuits GD 1  and GD 2 , such that oblique cutoff voltages V 1  and V 2  of the gate drive signals Gate Pulse_Y 1  and Gate Pulse_Y 2  configured for driving the gate drive integrated circuits GD 1  and GD 2  have a voltage difference ΔV 0  therebetween. Therefore, luminance of the display blocks  111  and  112  are different to generate a horizontal slight boundary. That is, the luminance is non-uniform in the perpendicular direction. 
     BRIEF SUMMARY 
     The present invention relates to a gate output control method which can effectually solve the problem of the conventional art having a non-uniform luminance in a perpendicular direction. 
     The present invention also relates to a gate pulse modulator which can effectually solve the problem of the conventional art having a non-uniform luminance in a perpendicular direction. 
     A gate output control method of the present invention is adapted into a flat display. The flat display comprises a first gate drive integrated circuit and a gate drive integrated circuit. The gate output control method comprises: providing a gate control signal; providing a oblique control signal to oblique modulate the gate control signal for generating a gate control signal with oblique; modulating the gate control signal with oblique to obtain a modulated gate control signal; and outputting the modulated gate control signal to the first gate drive integrated circuit and the second gate drive integrated circuit to control the first gate drive integrated circuit and the second gate drive integrated circuit in sequence. A falling edge of the modulated gate control signal comprises a oblique-varying period and a vertical-varying period. In the vertical-varying period, the modulated gate control signal firstly changes to a predetermined voltage in a first slope, and then changes in a second slope until the vertical-varying period. The modulated gate control signal changes vertically or nearly vertically in the vertical-varying period. 
     In an exemplary embodiment of the present invention, the step of providing the oblique control signal to oblique modulate the gate control signal for generating the gate control signal with oblique, comprises: determining whether employing a discharge circuit to discharge the gate control signal according to the oblique control signal. 
     In an exemplary embodiment of the present invention, the second slope of the modulated gate control signal is approximate 0 to make the modulated gate control signal continuously kept close to the predetermined voltage. 
     In an exemplary embodiment of the present invention, the step of modulating the gate control signal with oblique to obtain the modulated gate control signal is performed by a oblique constant-voltage circuit. The step comprise: employing a predetermined voltage power to provide the predetermined voltage; in the oblique-varying period, regarding the predetermined voltage provided by the predetermined voltage power as the modulated gate control signal when the gate control signal with oblique is less than the predetermined voltage. 
     In an exemplary embodiment of the present invention, the step of modulating the gate control signal with oblique to obtain the modulated gate control signal may also comprises: determining whether employing a second discharge circuit to further discharge the gate control signal with oblique according to a control signal, such that in the oblique-varying period the second slope of the modulated gate control signal is approximately 0 to make the modulated gate control signal continuously kept close to the predetermined voltage. When the second discharge circuit further discharges the gate control signal with oblique, the first discharge circuit continuously discharges. Alternatively, when the second discharge circuit further discharges the gate control signal with oblique, the first discharge circuit stops discharging. 
     In an exemplary embodiment of the present invention, the gate output control method further comprises: outputting a first enable signal and a second enable signal to the first gate drive integrated circuit and the second gate drive integrated circuit respectively to be cooperated with the modulated gate control signal for generating a first gate drive signal and a second gate drive signal. Furthermore, the first gate drive signal has an oblique cutoff voltage same to that of the second gate drive signal. 
     A gate pulse modulator of the present invention is adapted into a flat display. The flat display comprises a first gate drive integrated circuit and a second gate drive integrated circuit. The gate pulse modulator comprises a gate control signal terminal, an oblique control signal terminal, a first discharge circuit, an oblique output terminal, an oblique constant-voltage circuit and an output terminal. The gate control signal terminal is configured for receiving a gate control signal, the oblique control signal terminal is configured for receiving an oblique control signal, the oblique output terminal is configured for outputting a gate control signal with oblique, and the output terminal is configured for outputting a modulated gate control signal to the first gate drive integrated circuit and a second gate drive integrated circuit. The gate pulse modulator determines whether employing the first discharge circuit to discharge the gate control signal according to the oblique control signal for generating the gate control signal with oblique, and employs the oblique constant-voltage circuit to modulate the gate control signal with oblique to obtain the modulated gate control signal. A falling edge of the modulated gate control signal comprises an oblique-varying period and a vertical-varying period. In the oblique-varying period, the modulated gate control signal firstly changes to a predetermined voltage in a first slope, and then changes in a second slope until the vertical-varying period. The modulated gate control signal changes vertically or nearly vertically in the vertical-varying period. 
     In an exemplary embodiment of the present invention, the oblique constant-voltage circuit comprises a predetermined voltage power and a diode. The predetermined voltage power provides the predetermined voltage. A positive terminal of the diode is electrically coupled to the predetermined voltage, and a negative terminal thereof is electrically coupled to the oblique output terminal to receive the gate control signal with oblique. In the oblique-varying period, the predetermined voltage provided by the predetermined voltage power is regarded as the modulated gate control signal when the gate control signal with oblique is less than the predetermined voltage. 
     In an exemplary embodiment of the present invention, the oblique constant-voltage circuit may also comprise a switch and a second discharge circuit. The switch is configured for receiving a control signal, and the second discharge circuit is electrically coupled to the switch. The gate pulse modulator determines whether employing the second discharge circuit to further discharge the gate control signal with oblique according to the control signal, such that in the oblique-varying period, the second slope of the modulated gate control signal is approximately 0 to make the modulated gate control signal continuously kept close to the predetermined voltage. 
     The present invention employs the modulated gate control signal continuously kept close to the predetermined voltage after falling down to the predetermined voltage in the oblique-varying period, such that the gate drive signals configured for controlling the different gate drive integrated circuits have the same oblique cutoff voltages, and there are no any voltage difference among the gate drive signals configured for controlling the different gate drive integrated circuits. Therefore, the present invention can effectually solve the problem of the conventional art having a non-uniform luminance in a perpendicular direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which: 
         FIG. 1  is a structure block view of a conventional flat display. 
         FIG. 2  is a schematic view of a conventional gate pulse modulator. 
         FIG. 3  is a timing chart of a gate control signal, an oblique control signal and a modulated gate control signal as shown in  FIG. 2 , and gate output enable signals and gate drive signals as shown in  FIG. 1 . 
         FIG. 4  is a schematic view of a gate pulse modulator in accordance with an exemplary embodiment of the present invention. 
         FIG. 5  is a timing chart of various signals of a gate output control method in accordance with an exemplary embodiment of the present invention. 
         FIG. 6  is a schematic view of a gate pulse modulator in accordance with another exemplary embodiment of the present invention. 
         FIG. 7  is a timing chart of various signals of a gate output control method in accordance with another exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to the drawings to describe exemplary embodiments of the present gate output control method and corresponding gate pulse modulator in detail. The following description is given by way of example, and not limitation. 
     The following describes a gate pulse modulator and a corresponding gate output control method in accordance with an exemplary embodiment of the present invention in detail cooperating with  FIGS. 1 ,  4  and  5 .  FIG. 4  is a schematic view of the gate pulse modulator of the exemplary embodiment of the present invention, and  FIG. 5  is a timing chart of various signals in the gate output control method of the exemplary embodiment of the present invention. The gate pulse modulator  200  disclosed in the exemplary embodiment is adapted into the flat display  100  having the gate drive integrated circuits GD 1  and GD 2 , and the structure of the flat display  100  is described in the above description and not described in following. As shown in  FIG. 4 , the gate pulse modulator  200  of the exemplary embodiment includes a gate control signal terminal  210 , an oblique control signal terminal  220 , an oblique output terminal  230 , a discharge circuit  240 , an oblique constant-voltage circuit  250  and an output terminal  260 . 
     Referring to FIGS.  1  and  4 - 5 , the gate control signal terminal  210  receives a gate control signal VGH 1 , the oblique control signal terminal  220  receives an oblique control signal YV 1 C, and the gate pulse modulator  200  determines whether employing the discharge circuit  240  to discharge the gate control signal VGH 1  according to the oblique control signal YV 1 C for generating a gate control signal VGH 2  with oblique at the oblique output terminal  230 . The discharge circuit  240  includes a resistor  2401  electrically coupled between a discharge terminal  2402  and ground. The gate control signal VGH 2  with oblique is same to the modulated gate control signal VGH as shown in  FIGS. 2 and 3 , thus it is obvious for persons skilled in the art and not described in following. 
     The oblique constant-voltage circuit  250  is configured for modulating the gate control signal VGH 2  with oblique to obtain a modulated gate control signal VGH. A falling edge of the modulated gate control signal VGH includes a oblique-varying period  280  and a vertical-varying period  290 . In the oblique-varying period  280 , the modulated gate control signal VGH firstly changes to a predetermined voltage Vfix in a first slope  281 , and then changes in a second slope  282  until the vertical-varying period  290 . Furthermore, in the vertical-varying period  290 , the modulated gate control signal VGH changes the voltage vertically or nearly vertically. 
     In this exemplary embodiment, the second slope of the modulated gate control signal VGH is 0 such that the modulated gate control signal VGH is kept in the predetermined voltage Vfix. In detail, the oblique constant-voltage circuit  250  of the exemplary embodiment includes a diode  251  and a constant-voltage source  252 . A positive terminal of the diode  251  is electrically coupled to the constant-voltage source  252  to receive the predetermined voltage Vfix provided by the constant-voltage source  252 , and a negative terminal of the diode  252  is electrically coupled to the oblique output terminal  240  to receive the gate control signal VGH 2  with oblique. In the oblique-varying period  280 , when the gate control signal VGH 2  with oblique is larger than the predetermined voltage Vfix, the diode  251  turns off, such that the output terminal  260  of the gate pulse modulator  200  outputs the gate control signal VGH 2  with oblique as the modulated gate control signal VGH. When the gate control signal VGH 2  with oblique is less than the predetermined voltage Vfix, the diode  251  turns on, such that the output terminal  260  of the gate pulse modulator  200  outputs the predetermined voltage Vfix as the modulated gate control signal VGH. Therefore, the oblique constant-voltage circuit  250  can make the second slope of the modulated gate control signal VGH be 0 such that the modulated gate control signal VGH is continuously kept in the predetermined voltage Vfix. 
     Then the modulated gate control signal VGH is output to the gate drive integrated circuits GD 1  and GD 2  of the flat display  100  as shown in  FIG. 1 , and is cooperated with the enable signals YOE_Y 1  and YOE_Y 2  output to the gate drive integrated circuits GD 1  and GD 2  respectively, to generate corresponding gate drive signals Gate Pulse_Y 1  and Gate Pulse_Y 2 . As shown in  FIG. 5 , since the modulated gate control signal VGH is continuously kept in the predetermined voltage Vfix in a mode of the second slope being 0 after falling down to the predetermined voltage Vfix in the oblique-varying period  280 , oblique cutoff voltages V 1  and V 2  of the gate drive signals Gate Pulse_Y 1  and Gate Pulse_Y 2  are same, and are both kept in the predetermined voltage Vfix, that is, V 1 =V 2 =Vfix. Therefore, there is not a voltage difference between the oblique cutoff voltages V 1  and V 2  of the gate drive signals Gate Pulse_Y 1  and Gate Pulse_Y 2 , that is, V 1 −V 2 =ΔV=0. 
     Refer to  FIGS. 6 and 7 , which are schematic views of a gate pulse modulator and a corresponding gate output control method thereof in accordance with another exemplary embodiment of the present invention. As shown in  FIGS. 6 and 7 , the gate pulse modulator  300  of the exemplary embodiment is similar with the gate pulse modulator  200  as shown in  FIG. 4 , except that the oblique constant-voltage circuit  350  of the gate pulse modulator  300  of the exemplary embodiment includes a switch  351  and a discharge circuit  352  electrically coupled to the switch  351 . The switch  351  receives a control signal YV 1 C 2 , and determines whether employing the discharge circuit  352  to further discharge the gate control signal VGH 2  with oblique according to the control signal YV 1 C 2 , such that in the oblique-varying period  380 , the modulated gate control signal VGH changes in the second slope  382  until the vertical-varying period  390 . The discharge circuit  352  includes a resistor  3521  electrically coupled between the switch  351  and ground. The second slope can change by adjusting the resistance value of the resistor  3521 . In this exemplary embodiment, the resistance value of the resistor  3521  may be designed to make the second slope be approximately 0, such that the modulated gate control signal is continuously kept close to the predetermined voltage Vfix. That is, the gate pulse modulator  300  of the exemplary embodiment employs the discharge circuits  340  and  350  to perform two discharge operations, such that the modulated gate control signal VGH changes in the first slope  381 , and then changes in the second slope  382  toward 0 to make the modulated gate control signal VGH continuously be kept close to the predetermined voltage Vfix. 
     In addition, as shown in  FIG. 7 , in the exemplary embodiment, when the discharge circuit  352  discharges the gate control signal VGH 2  with oblique, at this moment the discharge circuit  340  continuously discharges the gate control signal VGH 2  with oblique. Of course, it is obvious for persons skilled in the art that when the discharge circuit  352  discharges the gate control signal VGH 2  with oblique, the discharge circuit  340  stops discharging and only the discharge circuit  352  performs the discharge operation. 
     Furthermore, the gate drive integrated circuits GD 1  and GD 2  of the present invention are not limited to be electrically coupled in series with each other. Alternatively, they may be electrically coupled in parallel with each other through the WOA. It should be noted that, the gate output control method and the gate pulse modulator of the present invention is not limited to be applied into the flat display including two gate drive integrated circuits, and they may be applied into the flat display including a plurality of (such as three or more than three) gate drive integrated circuits. The present invention makes the modulated gate control signal VGH continuously kept close to the predetermined voltage Vfix after falling down to the predetermined voltage Vfix such that there are no any voltage difference among the gate drive signals output to the plurality of gate drive integrated circuits. 
     In summary, the present invention makes the modulated gate control signals continuously kept close to the predetermined voltage after falling down to the predetermined voltage in the oblique-varying period, such that the gate drive signals configured for controlling the different gate drive integrated circuits have the same oblique cutoff voltages, and there are no any voltage difference among the gate drive signals configured for controlling the different gate drive integrated circuits. Therefore, the present invention can solve the problem of the conventional art having the non-uniform luminance in the perpendicular direction. 
     The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein, including configurations ways of the recessed portions and materials and/or designs of the attaching structures. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments.