Patent Publication Number: US-10332468-B2

Title: Gate driving circuit and driving method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the priority of Chinese patent application CN 201710580980.0, entitled “Gate driving circuit and driving method thereof” and filed on Jul. 17, 2017, the entirety of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present disclosure relates to the technical field of display control, and in particular, to a gate driving circuit and a driving method thereof. 
     BACKGROUND OF THE INVENTION 
     As flat panel display technology develops, it has become a trend to develop flat display panels with a high resolution, a high contrast, a high refresh rate, a narrow bezel, and a thin body. At present, liquid crystal display (LCD) panels are still a mainstream product of panel display. In order to realize narrow-bezel, thin, and cost-effective LCD panels, development and application of GOA (Gate Driver On Array) technology have become relatively mature. 
     In the prior art, generally speaking, reset of Q(n) node in a GOA circuit of a display panel can be realized only by means of a high-level scanning signal outputted by a gate driving circuit in a G(n+2) th  stage. If the G(n+2) th -stage gate driving circuit does not output the scanning signal normally, Q(n) node in an n th  stage of the GOA circuit cannot be reset, which affects normal display of a next frame. Sometimes, the abnormality can also make a gate output a multiple-pulse waveform, which will then activate an over-current protection function and lead to an automatic shutdown of the device. 
     SUMMARY OF THE INVENTION 
     To solve the above problem, the present disclosure provides a gate driving circuit and a driving method thereof, so that abnormality of a control signal of a GOA circuit will not affect normal driving of a panel. 
     According to one aspect of the present disclosure, a gate driving circuit is provided. The gate driving circuit comprises a pull-up control module, a pull-up module, a pull-down module, and a pull-down maintaining module. 
     The pull-up control module is used to input a scanning signal of a second-previous-stage gate driving circuit under the control of a scanning-starting signal of the second-previous-stage gate driving circuit. 
     The pull-up module is used to input a clock signal under the control of the scanning signal of the second-previous-stage gate driving circuit which is outputted by the pull-up control module, so as to generate a scanning signal of a current-stage gate driving circuit. 
     The pull-down module is used to pull down level of an output terminal of the pull-up control module and level of the scanning signal of the current-stage gate driving circuit, under the control of a clock signal of a second-succeeding-stage gate driving circuit. 
     The pull-down maintaining module is used to maintain the level of the output terminal of the pull-up control module and the level of the scanning signal of the current-stage gate driving circuit both at a predetermined low level, under the control of the level of the output terminal of the pull-up control module and an external signal. 
     According to one embodiment of the present disclosure, the pull-up control module comprises a first transistor. A gate of the first transistor is used to input the scanning-starting signal of the second-previous-stage gate driving circuit, a source thereof is used to input the scanning signal of the second-previous-stage gate driving circuit, and a drain thereof is connected with the pull-up module. 
     According to one embodiment of the present disclosure, the pull-up module comprises a second transistor. A gate of the second transistor is connected with the drain of the first transistor, a source thereof is used to input a clock signal, and a drain thereof is used to output the scanning signal of the current-stage gate driving circuit. 
     According to one embodiment of the present disclosure, the pull-down module comprises a third transistor and a fourth transistor. 
     A gate of the third transistor is used to input the clock signal of the second-succeeding-stage gate driving circuit, a source thereof is connected with the drain of the second transistor, and a drain thereof is connected with the predetermined low level. 
     A gate of the fourth transistor is used to input the clock signal of the second-succeeding-stage gate driving circuit, a source thereof is connected with the gate of the second transistor, and a drain thereof is connected with the predetermined low level. 
     According to one embodiment of the present disclosure, the pull-down maintaining module comprises a first pull-down maintaining sub-module. The first pull-down maintaining sub-module comprises a fifth transistor, a sixth transistor, a seventh transistor, an eighth transistor, a ninth transistor, and a tenth transistor. 
     A gate of the fifth transistor is used to input a first external signal and a source thereof is connected with its gate. 
     A gate of the sixth transistor is connected with the output terminal of the pull-up control module, a source thereof is connected with the drain of the fifth transistor, and a drain thereof is connected with the predetermined low level. 
     A gate of the seventh transistor is connected with the drain of the fifth transistor and a source thereof is connected with the source of the fifth transistor. A gate of the eighth transistor is connected with the output terminal of the pull-up control module, a source thereof is connected with the drain of the seventh transistor, and a drain thereof is connected with the predetermined low level. 
     A gate of the ninth transistor is connected with the drain of the seventh transistor, a source thereof is connected with the output terminal of the pull-up control module, and a drain thereof is connected with the predetermined low level. 
     A gate of the tenth transistor is connected with the drain of the seventh transistor, a source thereof is connected with the output terminal of the pull-up module and connected with the output terminal of the pull-up control module by means of a coupling capacitor, and a drain thereof is connected with the predetermined low level. 
     According to one embodiment of the present disclosure, the pull-down maintaining module further comprises a second pull-down maintaining sub-module. 
     The second pull-down maintaining sub-module comprises an eleventh transistor, a twelfth transistor, a thirteenth transistor, a fourteenth transistor, a fifteenth transistor, and a sixteenth transistor. 
     A gate of the eleventh transistor is used to input a second external signal and a source thereof is connected with its gate. The second external control signal and the first external control signal are configured to alternately drive a corresponding pull-down maintaining module to work. 
     A gate of the twelfth transistor is connected with the output terminal of the pull-up control module, a source thereof is connected with the drain of the eleventh transistor, and a drain thereof is connected with the predetermined low level. 
     A gate of the thirteenth transistor is connected with the drain of the eleventh transistor and a source thereof is connected with the source of the eleventh transistor. 
     A gate of the fourteenth transistor is connected with the output terminal of the pull-up control module, a source thereof is connected with the drain of the thirteenth transistor, and a drain thereof is connected with the predetermined low level. 
     A gate of the fifteenth transistor is connected with the drain of the thirteenth transistor, a source thereof is connected with the output terminal of the pull-up control module, and a drain thereof is connected with the predetermined low level. 
     A gate of the sixteenth transistor is connected with the drain of the thirteenth transistor, a source thereof is connected with the output terminal of the pull-up module and connected with the output terminal of the pull-up control module by means of a coupling capacitor, and a drain thereof is connected with the predetermined low level. 
     According to one embodiment of the present disclosure, the circuit further comprises a reset module which comprises a seventeenth transistor. 
     A gate of the seventeenth transistor is used to input a reset signal, a source thereof is connected with the output terminal of the pull-up control module, and a drain thereof is connected with the predetermined low level. 
     According to one embodiment of the present disclosure, the circuit further comprises a scanning-starting signal generation module which comprises an eighteenth transistor. 
     A gate of the eighteenth transistor is connected with the output terminal of the pull-up control module, a source thereof is used to input the clock signal, and a drain thereof is used to generate the scanning-starting signal of the current-stage gate driving circuit. 
     According to one embodiment of the present disclosure, the clock signal comprises 8 square wave clock sub-signals which have a duty ratio of 1/4 and are out of phase with each other sequentially by 1/8 clock cycle. 
     According to another aspect of the present disclosure, a driving method of a gate driving circuit is also provided. The method comprises the following steps. 
     A scanning-starting signal of a second-previous-stage gate driving circuit is applied to a pull-up control module, so that a scanning signal of the second-previous-stage gate driving circuit is outputted by the pull-up control module. 
     A clock signal is outputted by the pull-up module under the control of the scanning signal of the second-previous-stage gate driving circuit outputted by the pull-up control module, so as to generate a scanning signal of the current-stage gate driving circuit. 
     A clock signal of a second-succeeding-stage gate driving circuit is applied to a pull-down module, so that level of an output terminal of the pull-up control module and level of the scanning signal of the current-stage gate driving circuit are pulled down to a predetermined low level. 
     An external signal is applied to a pull-down maintaining module, and in presence of the predetermined low level of the output terminal of the pull-up control module, level of the output terminal of the pull-up control module and level of the scanning signal of the current-stage gate driving circuit are both maintained at the predetermined low level. 
     The present disclosure achieves the following beneficial effects. 
     The present disclosure uses a clock signal CK, rather than a scanning signal, to pull down level of Q(n) node, so that abnormality of a control signal of a GOA circuit will not affect normal driving of a panel. 
     Other advantages, objectives, and features of the present disclosure will be further explained in the following description, and partially become self-evident therefrom, or be understood through the embodiments of the present disclosure. The objectives and advantages of the present disclosure will be achieved through the structure specifically pointed out in the description, claims, and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings provide further understandings of the present disclosure or the prior art, and constitute one part of the description. The drawings are used for interpreting the present disclosure together with the embodiments, not for limiting the present disclosure. In the drawings: 
         FIG. 1  schematically shows a structure of a gate driving circuit in one embodiment of the present disclosure: 
         FIG. 2  schematically shows a timing sequence of output of the gate driving circuit in  FIG. 1 ; and 
         FIG. 3  schematically shows a flow diagram of a method of driving the circuit in  FIG. 1  in one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present disclosure will be explained in details with reference to the embodiments and the accompanying drawings, whereby it can be fully understood how to solve the technical problem by the technical means according to the present disclosure and achieve the technical effects thereof, and thus the technical solution according to the present disclosure can be implemented. It should be noted that, as long as there is no conflict, all the technical features mentioned in all the embodiments may be combined together in any manner, and the technical solutions obtained in this manner all fall within the scope of the present disclosure. 
     The present disclosure provides a gate driving circuit, which uses a clock signal to pull down level of Q(n) node, so that abnormality of a scanning signal will not affect normal driving of a panel.  FIG. 1  schematically shows a structure of a gate driving circuit in a G(n) th  stage in one embodiment of the present disclosure. The present disclosure will be explained in details with reference to  FIG. 1 . Adjacent gate driving circuits in a G(n−2) th  stage, in a G(n) th  stage, and in a G(n+2) th  stage are taken as an example. The gate driving circuits in the G(n−2) th  stage, in the G(n) th  stage, in the G(n+2) th  stage, . . . , are used to drive gate lines in odd rows or in even rows, and each gate driving circuit outputs a corresponding scanning signal. Gate driving circuits in a G(n−1) th  stage, in a G(n+1) th  stage, in a G(n+3) th  stage, . . . , are used to drive gate lines in even rows or in odd rows, and each gate driving circuit outputs a corresponding scanning signal. 
     As shown in  FIG. 1 , each gate driving circuit comprises a pull-up control module  11 , a pull-up module  12 , a pull-down module  13 , and a pull-down maintaining module  14 . 
     The pull-up control module  11  is used to input a scanning signal G(n−2) of a second-previous-stage gate driving circuit (i.e. a gate driving circuit before a previous-stage gate driving circuit), under the control of a scanning-starting signal ST(n−2) of the second-previous-stage gate driving circuit. In other words, the G(n) th -stage gate driving circuit is configured to start working under the control of the G(n−2) th -stage gate driving circuit. An output terminal of the pull-up control module  11  is generally marked as a Q(n) node, and the pull-up control module  11  is mainly used to output the scanning signal G(n−2) of the second-previous-stage gate driving circuit to the Q(n) node under the control of the signal ST(n−2). 
     The pull-up module  12  is configured to input a clock signal CK under the control of the scanning signal G(n−2) of the second-previous-stage gate driving circuit which is outputted by the pull-up control module  11  to the Q(n) node, so as to generate a scanning signal G(n) of a current-stage gate driving circuit. 
     The pull-down module  13  is used to pull down level of the output terminal of the pull-up control module  11  and level of the scanning signal G(n) of the current-stage gate driving circuit, under the control of a clock signal CK (n+2) of a second-succeeding-stage gate driving circuit (i.e. a gate driving circuit following a next-stage gate driving circuit). As shown in  FIG. 3 , while outputting the scanning signal G(n), the pull-up module  12  inputs a clock signal CK 1 . At that time, the pull-down module  13  is controlled by a clock signal CK 3 . While the pull-up module  12  inputs a clock signal CK 2 , the pull-down module  13  is controlled by a clock signal CK 4 . Likewise, the rest goes in the same manner. While the pull-up module  12  inputs a clock signal CK 7  and a clock signal CK 8 , go back to the starting, that is, the pull-down module  13  is controlled by the clock signal CK 1  and a clock signal CK 2 . 
     The pull-down maintaining module  14  is used to maintain the level of the output terminal of the pull-up control module  11  and the level of the scanning signal G(n) of the current-stage gate driving circuit both at a predetermined low level Vss, under the control of the level of the output terminal of the pull-up control module  11  and an external signal LC. In other words, after the pull-down module  13  pulls down the level of the output terminal of the pull-up control module  11  and the level of the scanning signal of the current-stage gate driving circuit to the predetermined low level Vss, the pull-down maintaining module  14  maintains the level of the output terminal of the pull-up control module  11  and the level of the scanning signal of the current-stage gate driving circuit both at the predetermined low level Vss, under the control of the level of the output terminal of the pull-up control module  11  and the external signal LC. 
     In the present disclosure, the pull-down module  13  of the gate driving circuit is controlled by the clock signal CK (n+2) of the second-succeeding-stage gate driving circuit, instead of the signal G(n+2), so that when output of the signal G(n+2) is abnormal, the level of Q(n) node is pulled down by the clock signal CK. Even if the signal G(n+2) is abnormal, the gate driving circuit can still work normally when a next frame refreshes. 
     In one embodiment of the present disclosure, the pull-up control module  11  comprises a first transistor T 11 . A gate of the first transistor T 11  is used to input a scanning-starting signal CK(n−2) of the second-previous-stage gate driving circuit, a source thereof is used to input the scanning signal G(n−2) of the second-previous-stage gate driving circuit, and a drain thereof is connected with the pull-up module  12 . During working, the scanning-starting signal ST(n−2) outputted by the G(n−2) th -stage gate driving circuit turns on the first transistor T 11  and the scanning signal G(n−2) outputted by the G(n−2) th -stage gate driving circuit arrives at the pull-up module through the first transistor T 11 , so as to control the pull-up module  12  to generate the scanning signal G(n) of the current-stage gate driving circuit. 
     In one embodiment of the present disclosure, the pull-up module  12  comprises a second transistor T 21 . A gate of the second transistor T 21  is connected with the drain of the first transistor T 11 , a source thereof is used to input the clock signal CK, and a drain thereof is used to output the scanning signal G(n) of the current-stage gate driving circuit. During working, the scanning-starting signal ST(n−2) outputted by the pull-up control module  11  turns on the second transistor T 21  and the clock signal CK is outputted by the source of the second transistor T 21  to the drain, so as to generate the scanning signal G(n) of the current-stage gate driving circuit. 
     In one embodiment of the present disclosure, the pull-down module  13  comprises a third transistor T 31  and a fourth transistor T 41 . A gate of the third transistor T 31  is used to input the clock signal CK of the second-succeeding-stage gate driving circuit, a source thereof is connected with the drain of the second transistor T 21 , and a drain thereof is connected with the predetermined low level Vss. 
     A gate of the fourth transistor T 41  is used to input the clock signal CK of the second-succeeding-stage gate driving circuit, a source thereof is connected with the gate of the second transistor T 21 , and a drain thereof is connected with the predetermined low level Vss. During working, while the clock signal CK of the second-succeeding-stage gate driving circuit is at a high level, the third transistor T 31  and the fourth transistor T 41  are both turned on. The predetermined low level Vss is in communication with the output terminal of the pull-up control module  11  through the third transistor T 31  and in communication with the output terminal of the pull-up module  12  through the fourth transistor T 41 , so that the level of Q(n) node and the level of the scanning signal G(n) are pulled down to the predetermined low level Vss. 
     The clock signal CK of the second-succeeding-stage gate driving circuit is at a high level only when the current-stage gate driving circuit is outputting a scanning signal; at other times, the clock signal CK is at a low level. To ensure that the level of Q(n) node and the level of the scanning signal G(n) are maintained at the predetermined low level while the current-stage gate driving circuit is not outputting a scanning signal, a pull-down maintaining module is required. In one embodiment of the present disclosure, the pull-down maintaining module  14  comprises a first pull-down maintaining sub-module  141 . The first pull-down maintaining sub-module  141  comprises a fifth transistor T 51 , a sixth transistor T 52 , a seventh transistor T 53 , an eighth transistor T 54 , a ninth transistor T 42 , and a tenth transistor T 32 . A gate of the fifth transistor T 51  is used to input a first external signal LC 1  and a source thereof is connected with its gate. A gate of the sixth transistor T 52  is connected with the output terminal of the pull-up control module  11 , a source thereof is connected with the drain of the fifth transistor T 51 , and a drain thereof is connected with the predetermined low level Vss. A gate of the seventh transistor T 53  is connected with the drain of the fifth transistor T 51  and a source thereof is connected with the source of the fifth transistor T 51 . A gate of the eighth transistor T 54  is connected with the output terminal of the pull-up control module  11 , a source thereof is connected with the drain of the seventh transistor T 53 , and a drain thereof is connected with the predetermined low level Vss. A gate of the ninth transistor T 42  is connected with the drain of the seventh transistor T 53 , a source thereof is connected with the output terminal of the pull-up control module  11 , and a drain thereof is connected with the predetermined low level Vss. A gate of the tenth transistor T 32  is connected with the drain of the seventh transistor T 53 , a source thereof is connected with the output terminal of the pull-up module  12  and connected with the output terminal of the pull-up control module  11  by means of a coupling capacitor Cb, and a drain thereof is connected with the predetermined low level Vss. 
     Specifically, while the scanning signal G( 3 ) is being outputted, the high-level scanning signal G( 3 ) pulls down the level of Q( 1 ) node and the level of G( 1 ) node to Vss. At that moment, the sixth transistor T 52  and the eighth transistor T 54  are turned off. The high-level first external signal LC 1  is applied and the fifth transistor T 51  and the seventh transistor T 53  are turned on. Then the ninth transistor T 42  is turned on and Q( 1 ) node is connected to the predetermined low level Vss; the tenth transistor T 32  is turned on and G( 1 ) node is connected to the predetermined low level Vss. By way of this, Q( 1 ) node and G( 1 ) node can be maintained at the predetermined low level, until a high-level scanning signal G( 1 ) is outputted. In addition, while the high-level scanning signal G( 1 ) is outputted, the sixth transistor T 52  and the eighth transistor T 54  are turned on, so that the ninth transistor T 42  and the tenth transistor T 32  are turned off and the first pull-down maintaining sub-module  141  is not able to work. 
     In one embodiment of the present disclosure, the pull-down maintaining module  14  comprises a second pull-down maintaining sub-module  142 . The second pull-down maintaining sub-module  142  comprises an eleventh transistor T 61 , a twelfth transistor T 62 , a thirteenth transistor T 63 , a fourteenth transistor T 64 , a fifteenth transistor T 43 , and a sixteenth transistor T 33 . A gate of the eleventh transistor T 61  is used to input a second external signal LC 2 , and a source thereof is connected with its gate. The second external signal LC 2  and the first external signal LC 1  alternately drive a corresponding pull-down maintaining module to work. A gate of the twelfth transistor T 62  is connected with the output terminal of the pull-up control module  11 , a source thereof is connected with the drain of the eleventh transistor T 51 , and a drain thereof is connected with the predetermined low level Vss. A gate of the thirteenth transistor T 63  is connected with the drain of the eleventh transistor T 51  and a source thereof is connected with the source of the eleventh transistor T 51 . A gate of the fourteenth transistor T 64  is connected with the output terminal of the pull-up control module  12 , a source thereof is connected with the drain of the thirteenth transistor T 63 , and a drain thereof is connected with the predetermined low level Vss. A gate of the fifteenth transistor T 43  is connected with the drain of the thirteenth transistor T 63 , a source thereof is connected with the output terminal of the pull-up control module  11 , and a drain thereof is connected with the predetermined low level Vss. A gate of the sixteenth transistor T 33  is connected with the drain of the thirteenth transistor T 63 , a source thereof is connected with the output terminal of the pull-up module  12  and connected with the output terminal of the pull-up control module  11  by means of a coupling capacitor Cb, and a drain thereof is connected with the predetermined low level Vss. The first external signal LC 1  and the second external signal LC 2  are low-frequency signals with a period that is 200 times a length of a frame period and a duty ratio of 1/2 . The first external signal LC 1  and the second external signal LC 2  are out of phase by 1/2 period. The first external signal LC 1  drives the first pull-down maintaining sub-module  141  and the second external signal LC 2  drives the second pull-down maintaining sub-module  142 . The first pull-down maintaining sub-module  141  and the second pull-down maintaining sub-module  142  work alternatively. The second pull-down maintaining sub-module  142  works in the same way as the first pull-down maintaining sub-module  141  and thus its course of work will not be elaborated here. 
     In one embodiment of the present disclosure, the gate driving circuit further comprises a reset module  15 . The reset module  15  comprises a seventeenth transistor T 71 . A gate of the seventeenth transistor T 71  is used to input a reset signal, a source thereof is connected with the output terminal of the pull-up control module  11 , and a drain thereof is connected with the predetermined low level Vss. The seventeenth transistor T 71  is used to reset level of Q(n) node when an external control signal Reset is applied. 
     In one embodiment of the present disclosure, the gate driving circuit further comprises a scanning-starting signal generation module  16 . The scanning-starting signal generation module  16  comprises an eighteenth transistor T 22 . A gate of the eighteenth transistor T 22  is connected with the output terminal of the pull-up control module  11 , a source thereof is used to input the clock signal CK, and a drain thereof is used to output the scanning-starting signal ST(n) of the current-stage gate driving circuit. 
     In the prior art, a gate driving circuit generally adopts 4 square wave clock sub-signals with a duty ratio of 1/2 . In the present disclosure, a gate driving circuit adopts a clock signal comprising 8 square wave clock sub-signals that have a duty ratio of 1/4 and are out of phase with each other sequentially by 1/8 clock period, as shown in  FIG. 2 . By way of this, the load of each CK line and risks of wrong charge can be reduced. In the meanwhile, choosing a square wave signal to pull down can increase dependence of a thin-film transistor in the pull-down module and lengthen its working life. In addition, choosing a square wave signal CK to pull down the level of Q(n) node can increase the anti-jamming ability of signals, so that a next frame will not be affected by abnormal output of one signal at one moment. 
     According to another aspect of the present disclosure, a driving method of the gate driving circuit is provided. The method comprises the following steps, as shown in  FIG. 3 . Its corresponding time sequence diagram is as shown in  FIG. 2 . 
     Firstly, in step S 110 , a scanning-starting signal of a second-previous-stage gate driving circuit is applied to a pull-up control module  11 , so that a scanning signal of the second-previous-stage gate driving circuit is outputted by the pull-up control module  11 . As for a G 1 ( 1 ) th -stage gate driving circuit, since there is no scanning-starting signal of the second-previous-stage gate driving circuit, a starting signal STV is usually applied to start the G 1 ( 1 ) th -stage gate driving circuit. 
     Then, in step S 120 , a pull-up module  12 , under the control of the scanning signal of the second-previous-stage gate driving circuit outputted by the pull-up control module  11 , outputs a clock signal, so that a scanning signal of a current-stage gate driving circuit is generated. 
     Next, in step S 130 , a clock signal of a second-succeeding-stage gate driving circuit is applied to a pull-down module  13 , so that level of an output terminal of the pull-up control module and level of the scanning signal of the current-stage gate driving circuit are pulled down to a predetermined low level. 
     Lastly, in step S 140 , an external signal is applied to a pull-down maintaining module  14  and in presence of the predetermined low level of the output terminal of the pull-up control module  11 , level of the output terminal of the pull-up control module  22  and level of the scanning signal of the current-stage gate driving circuit are both maintained at the predetermined low level. 
     The above embodiments are described only for better understanding, rather than restricting, the present disclosure. Any person skilled in the art can make amendments to the implementing forms or details without departing from the spirit and scope of the present disclosure. The protection scope of the present disclosure shall be determined by the scope as defined in the claims.