Patent Publication Number: US-9886889-B2

Title: Shift register unit, gate driving circuit and display device

Description:
TECHNICAL FIELD 
     The present disclosure relates to a shift register unit, a gate driving circuit and a display device. 
     BACKGROUND 
     A liquid crystal panel adopts a progressive scanning matrix of M×N dot arrangement to display. A thin film transistor-liquid crystal display (TFT-LCD) driver comprises mainly a gate driver and a data driver, wherein the gate driver makes the input clock signal converted by the shift register and then applies the converted input clock signal to a gate line of the liquid crystal display panel. 
     The shift register is used generally in the gate driver of the liquid crystal display panel. Each of gate lines is correspondingly connected to a stage of circuit unit of the shift register. A gate input signal is output through the gate driving circuit to progressively scan respective pixels. The gate driving circuit can be disposed in the display panel by means of an encapsulation mode of chip on array (COA) technique on a flexible substrate or chip on glass (COG) technique on a glass substrate, or can be formed in the display panel through composing an integrated circuit unit by TFTs. For the liquid crystal display panel, the design that the gate driver is integrated on the gate on array (GOA) can reduce the product cost and also subtracts a process therefrom, so as to raise the productivity. 
     The patent application number 200510106997.X discloses a shift register unit, but the gate driving circuit composed of the shift register unit has high power consumption, and is easy to produce noise. 
     SUMMARY 
     According to one aspect of the present disclosure, there is provided a shift register unit, comprising: 
     an input module connected to a first input signal terminal, a first direct current signal terminal, a second input signal terminal and a second direct current signal terminal respectively, and configured to provide a first input signal received by the first input signal terminal to a pulling-up node according to a first direct current signal received by the first direct current signal terminal, and provide a second input signal received by the second input signal terminal to the pulling-up node according to a second direct current signal received by the second direct current signal terminal; 
     an output module connected to a first clock signal terminal and configured to provide a first clock signal received by the first clock signal terminal to an output terminal according to a voltage signal of the pulling-up node; 
     a pulling-down driving module connected to the first clock signal terminal, a second clock signal terminal and a low voltage signal terminal, and configured to provide a second clock signal received by the second clock signal terminal to a pulling-down node according to the first clock signal received by the first clock signal terminal and the second clock signal, and provide a low voltage signal received by the low voltage signal terminal to the pulling-down node according to the voltage signal of the pulling-up node; 
     a pulling-down module connected to the low voltage signal terminal and configured to provide the low voltage signal received by the low voltage signal terminal to the pulling-up node and the output terminal according to the voltage signal of the pulling-down node; 
     a resetting module connected to the second clock signal terminal and the low voltage signal terminal respectively, and configured to provide the low voltage signal received by the low voltage signal terminal to the output terminal according to the second clock signal received by the second clock signal terminal, 
     wherein the pulling-up node is a connecting point of the input module and the output module, and the pulling-down driving module is connected to the pulling-down module through the pulling-down node. 
     Alternatively, the input module comprises a first transistor, a second transistor, a third transistor and a fourth transistor. A gate and a source of the first transistor are connected to the first input signal terminal. A drain of the second transistor is connected to the source of the first transistor, a gate thereof is connected to the first direct current signal terminal, and a source thereof is connected to the pulling-up node. A gate and a source of the third transistor are connected to the second input signal terminal, and a drain thereof is connected to the pulling-up node. A source of the fourth transistor is connected to the drain of the third transistor, a gate thereof is connected to the second direct current signal terminal, and a drain thereof is connected to the pulling-up node. 
     Alternatively, the output module comprises a fifth transistor and a first capacitor. A gate of the fifth transistor is connected to the pulling-up node, a drain thereof is connected to the first clock signal terminal, and a source thereof is connected to the output terminal. One terminal of the first capacitor is connected to the pulling-up node, and another terminal of the first capacitor is connected to the low voltage signal terminal or the output terminal. 
     Alternatively, the pulling-down driving module comprises a sixth transistor, a seventh transistor, an eighth transistor, a ninth transistor and a second capacitor. A gate and a drain of the seventh transistor are connected to the first clock signal terminal, and a source thereof is connected to a gate of the ninth transistor. A drain of the ninth transistor is connected to the second clock signal terminal, and a source thereof is connected to a source of the eighth transistor. A gate of the eighth transistor is connected to the second clock signal terminal, and the drain thereof is connected to the pulling-down node. A gate of the sixth transistor is connected to the pulling-up node, a drain thereof is connected to the pulling-down node, and a source thereof is connected to the low voltage signal terminal. One terminal of the second capacitor is connected to the low voltage signal terminal, and another terminal thereof is connected to the source of the seventh transistor. 
     Alternatively, the pulling-down module comprises a tenth transistor and an eleventh transistor. A drain of the tenth transistor is connected to the low voltage signal terminal, a source thereof is connected to the pulling-up node, and a gate thereof is connected to the pulling-down node. A gate of the eleventh transistor is connected to the pulling-down node, a source thereof is connected to the low voltage signal terminal, and a drain thereof is connected to the output terminal. 
     Alternatively, the resetting unit comprises a twelfth transistor. A gate of the twelfth transistor is connected to the second clock signal terminal, a drain thereof is connected to the low voltage signal terminal, and a source thereof is connected to the output terminal. 
     Alternatively, the first direct current signal has a phase opposite to that of the second direct current signal. 
     Alternatively, the first clock signal has a phase opposite to that of the second clock signal. 
     According to another aspect of the present disclosure, there is provided a gate driving circuit comprising multiple stages of shift register units described above. Except for a first stage of shift register unit and a last stage of shift register unit, a first input signal of each stage of shift register is connected to an output terminal of an adjacent previous stage of shift register unit, a second input signal of each sage of shift register unit is connected to an output terminal of an adjacent next shift register unit, and an output terminal of each stage of shift register unit is connected to a second input signal terminal of the adjacent previous stage of shift register unit and a first input signal terminal of the adjacent next stage of shift register unit. 
     According to another aspect of the present disclosure, there is further provided a display device comprising the gate driving circuit described above. 
     The present disclosure pulls down a potential at the pulling-up node through the pulling-down module. The pulling-down module keeps in an operation state before the next frame starts, thereby effectively avoiding the pulling-up node in a non-operation state from producing noise. The present disclosure pulls down the potential at the output terminal in the non-operation state through the pulling-down module and the resetting module, thereby effectively avoiding noise of the output terminal. The present disclosure enables each high level signal of the second clock signal to pull up the potential at the pulling-down node through the pulling-down driving mode, thereby reducing power consumption of the whole circuit and avoiding the pulling-down node from producing noise. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a shift register unit provided in an implementation of the present disclosure; 
         FIG. 2  is a schematic diagram of another shift register unit provided in an implementation of the present disclosure; 
         FIG. 3  is a schematic diagram of a structure of a gate driving circuit provided in an implementation of the present disclosure; 
         FIG. 4  is a timing diagram of a shift register unit provide in an implementation of the present disclosure; 
         FIG. 5  is a schematic diagram of output waveforms of respective shift register units in a gate driving circuit provided in an implementation of the present disclosure; 
         FIG. 6  is a timing diagram of another shift register unit provided in an implementation of the present disclosure; 
         FIG. 7  is a schematic diagram of output waveforms of respective shift register units in another gate driving circuit provided in an implementation of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Specific implementations of the present disclosure will be further described in detail by combining with the accompanying figures and embodiments. The following embodiments are used for describing the present disclosure, but not for limiting the scope of the present disclosure. 
       FIG. 1  is a schematic diagram of a shift register unit provided in an implementation of the present disclosure, comprising an input module  101 , an output module  102 , a pulling-down driving module  103 , a pulling-down module  104  and a resetting module  105 . 
     As shown in  FIG. 1 , the input module  101  is connected to a first input signal terminal INPUT 1 , a first direct current signal terminal CN, a second input signal terminal INPUT 2  and a second direct current signal terminal CNB respectively, and is configured to provide a first input signal received by the first input signal terminal INPUT 1  to a pulling-up node PU according to a first direct current signal received by the first direct current signal terminal CN, and provide a second input signal received by the second input signal terminal INPUT 2  to the pulling-up node PU according to a second direct current signal received by the second direct current signal terminal INPUT 2 . The pulling-up node PU is a connecting point of the input module  101  and the output module  102 . 
     The output module  102  is connected to a first clock signal terminal CK, and configured to provide a first clock signal received by the first clock signal terminal CK to an output terminal OUTPUT according to a voltage signal of the pulling-up node PU. 
     The pulling-down driving module  103  is connected to the first clock signal terminal CK, a second clock signal terminal CKB and a low voltage signal terminal Vg 1 , and configured to provide a second clock signal received by the second clock signal terminal CKB to a pulling-down node PD according to the first clock signal received by the first clock signal terminal CK and the second clock signal, and provide a low voltage signal received by the low voltage signal terminal Vg 1  to the pulling-down node PD according to the voltage signal of the pulling-up node PU. The pulling-down driving module  103  is connected to the pulling-down module  104  through the pulling-down node PD. 
     The pulling-down module  104  is connected to the low voltage signal terminal Vg 1 , and configured to provide the low voltage signal received by the low voltage signal terminal Vg 1  to the pulling-up node PU and the output terminal OUTPUT according to the voltage signal of the pulling-down node PD. 
     The resetting module  105  is connected to the second clock signal terminal CKB and the low voltage signal terminal Vg 1  respectively, and configured to provide the low voltage signal received by the low voltage signal terminal Vg 1  to the output terminal OUTPUT according to the second clock signal received by the second clock signal terminal CKB. 
       FIG. 2  is a schematic diagram of another shift register unit provided in an implementation of the present disclosure. Referring to  FIG. 2 , the input module  101  comprises a first transistor M 1 , a second transistor M 2 , a third transistor M 3  and a fourth transistor M 4 . 
     A gate and a source of the first transistor M 1  are connected to the first input signal terminal INPUT 1 . A drain of the second transistor M 2  is connected to the drain of the first transistor M 1 , a gate thereof is connected to the first direct current signal terminal CN, and a source thereof is connected to the pulling-up node PU. A gate and a source of the third transistor M 3  are connected to the second input signal terminal INPUT 2 , and a drain thereof is connected to the pulling-up node PU. A source of the fourth transistor M 4  is connected to the drain of the third transistor M 3 , a gate thereof is connected to the second direct current signal terminal CNB, and a drain thereof is connected to the pulling-up node PU. 
     In  FIG. 2 , the output module  102  comprises a fifth transistor M 5  and a first capacitor C 1 . 
     A gate of the fifth transistor M 5  is connected to the pulling-up node PU, a drain thereof is connected to the first clock signal terminal CK, and a source thereof is connected to the output terminal OUTPUT. One terminal of the first capacitor C 1  is connected to the pulling-up node PU, and another terminal of the first capacitor C 1  is connected to the low voltage signal terminal Vg 1  or the output terminal OUTPUT (not shown). 
     Further, the pulling-down driving module  103  comprises a sixth transistor M 6 , a seventh transistor M 7 , an eighth transistor M 8 , a ninth transistor M 9  and a second capacitor C 2 . 
     A gate and a drain of the seventh transistor M 7  are connected to the first clock signal terminal CK, and a source of the seventh transistor M 7  is connected to a gate of the ninth transistor M 9 . A drain of the ninth transistor M 9  is connected to the second clock signal terminal CKB, and a source of the ninth transistor M 9  is connected to a source of the eighth transistor M 8 . A gate of the eighth transistor M 8  is connected to the second clock signal terminal CKB, and the drain thereof is connected to the pulling-down node PD. A gate of the sixth transistor M 6  is connected to the pulling-up node PU, a drain thereof is connected to the pulling-down node PD, and a source thereof is connected to the low voltage signal terminal Vg 1 . One terminal of the second capacitor C 2  is connected to the low voltage signal terminal Vg 1 , and another terminal thereof is connected to the source of the seventh transistor M 7 . 
     It needs to note that the structure of the pulling-down driving module is just an embodiment, and is not used to limit the specific structure of the pulling-down driving module. Also, the pulling-down driving module may not comprise the second capacitor C 2 . 
     As shown in  FIG. 2 , the pulling-down module  104  comprises a tenth transistor M 10  and an eleventh transistor M 11 . 
     A drain of the tenth transistor M 10  is connected to the low voltage signal terminal Vg 1 , a source thereof is connected to the pulling-up node PU, and a gate thereof is connected to the pulling-down node PD. 
     A gate of the eleventh transistor M 11  is connected to the pulling-down node PD, a source thereof is connected to the low voltage signal terminal Vg 1 , and a drain thereof is connected to the output terminal OUTPUT. 
     Further, the resetting unit  105  comprises a twelfth transistor M 12 . A gate of the twelfth transistor M 12  is connected to the second clock signal terminal CKB, a drain thereof is connected to the low voltage signal terminal Vg 1 , and a source thereof is connected to the output terminal OUTPUT 
     Further, it needs to note that for transistors in the liquid crystal display field, there is no specific distinction between drains and sources. Therefore, the sources of transistors mentioned in the embodiments of the present disclosure can be drains of the transistors, and the drains of the transistors can also be the sources of the transistors. 
     Alternatively, the first direct current signal has a phase opposite to the second direct current signal. 
     Alternatively, the first clock signal has a phase opposite to the second clock signal. For example, if the first clock signal is CK, then the second clock signal is CKB; if the first clock signal is CKB, then the second clock signal is CK. 
     The shift register unit provided in the implementation of the present disclosure pulls down a potential at the pulling-up node through the pulling-down module. The pulling-down module keeps in an operation state before the next frame starts, thereby effectively avoiding the pulling-up node in a non-operation state from producing the noise. The shift register unit pulls down the potential at the output terminal in the non-operation state through the pulling-down module and the resetting module, thereby effectively avoiding the output terminal from producing the noise. The shift register unit enables each high level signal of the second clock signal to pull up the potential at the pulling-down node through the pulling-down driving module, thereby reducing the power consumption of the whole circuit and avoiding pulling-down node from producing the noise. 
     In addition,  FIG. 3  is a schematic diagram of a structure of a gate driving circuit provided in an implementation of the present disclosure. Referring to  FIG. 3 , the gate driving circuit comprises multiple stages of any shift register units described above. Except for a first stage of shift register unit and a last stage of shift register unit, a first input signal of each stage of shift register is connected to an output terminal of an adjacent previous stage of shift register unit, a second input signal of each sage of shift register unit is connected to an output terminal of an adjacent next shift register unit, and an output terminal of each stage of shift register unit is connected to a second input signal terminal of the adjacent previous stage of shift register unit and a first input signal terminal of the adjacent next stage of shift register unit. Herein, when forward scanning, a first input terminal INPUT 1  of the first stage of shift register unit inputs a start signal STV, and a second input terminal INPUT 2  of the last stage of shift register unit separately inputs a resetting signal or adds a virtual shift register unit to reset the last stage of shift register unit. When backward scanning, the second input terminal INPUT 2  of the last stage of shift register unit inputs the start signal STV, the first input terminal INPUT 1  of the first stage of shift register unit separately inputs a resetting signal or adds a virtual shift register unit to reset the first stage of shift register unit. 
     For example, the gate driving circuit can comprise N stages of shift register units, wherein an output terminal of the (N−1)-th stage can be connected to a first input signal terminal of the N-th stage, and the output terminal of the N-th stage can be connected to a first input signal terminal of the (N−1)-th stage, where N is related to resolution of products. For the two adjacent shift register units, phases of clock signals received by the first clock signal terminal are opposite. For example, if a first clock signal received by a first clock signal terminal of a second stage of shift register is CKB, and a second clock signal received by a second clock signal terminal thereof is CK, then a first clock signal received by a first clock signal terminal of a third stage of shift register is CK, and a second clock signal received by the second clock signal terminal thereof is CKB. 
     In order to further describe the shift register unit provided in the implementation of the present disclosure, an operation principle of the N-th stage of shift register unit in the gate diving circuit provided in the implementation of the present disclosure will be described by combining with a timing diagram as shown in  FIG. 4 .  FIG. 4  is a timing diagram of the N-th stage of shift register unit in the gate driving unit. 
     When forward scanning, referring to  FIG. 4 , in a first phase S 1 , the first direct current signal terminal CN, the first input signal terminal INPUT 1  and the second clock signal terminal CKB are at the high level, and thus the first transistor M 1  and the second transistor M 2  are turned on, the potential at the pulling-up node PU rises, C 1  is charged, the sixth transistor M 6  is turned on, and the potential at the pulling-down node PD is pulled down. Since the first clock signal terminal CK outputs a low level and M 12  is in a turn-on state, the output terminal OUTPUT_N outputs a low level; 
     In a second phase S 2 , the first clock signal terminal CK is at the high level, transistors M 7  and M 9  are turned on, and C 2  is charged. Due to the effect of C 1 , the potential at the pulling-up node PU continuously rises, so that M 6  and M 5  continue to be in the turn-on state and the potential at the node PD is continuously pulled down. The potential at the node PD is related to M 6 , M 8  and M 9 , and an adjustment of size proportion of M 6  and M 8 , M 9  will influence voltage at the step of the node PD. At this time, the output terminal OUTPUT_N of the N-th stage of shift register unit outputs the high level; 
     In a third phase S 3 , the second clock signal terminal CKB is at the high level, and thus M 8  is turned on. Due to the effect of the capacitor C 2 , M 9  is turned on, and thus the potential at the node PD rises, M 10  is turned on, and the potential at the node PU is pulled down. Since M 11  and M 12  are turned on, OUTPUT_N outputs the low level. 
     Herein, before a frame starts, since each high level signal at the second clock signal terminal CKB pulls up the potential at the node PD, M 10  and M 11  keep in the turn-on state and signals at the node PU and OUTPUT_N are pulled down, so as to effectively avoid noise from producing. 
     When forward scanning, output waveforms of respective shift register units in the gate driving circuit are as shown in  FIG. 5 . 
     When backward scanning, referring to  FIG. 6 ,  FIG. 6  is a timing diagram of the N-th stage of shift register unit in the gate driving circuit. 
     In the first phase, the second direct current signal terminal CNB, the second input signal terminal INPUT 2 , and the second clock signal terminal CKB are at the high level, and thus M 3  and M 4  are turned on, the voltage at the node PU rises, C 1  is charged, M 6  is turned on, and the potential at the node PD is pulled down. Since CK outputs the low level and M 12  is in the turn-on state, OUTPUT_N outputs the low level. 
     In the second phase, the first clock signal terminal CK is at the high level, and thus M 7  and M 9  are turned on, and C 2  is charged. Due to the effect of C 1 , the potential at the node PU continuously rises, so that M 6  and M 5  continues to be in the turn-on state, and the potential at the node PD continues to be pulled down. The potential at the node PD is related to M 6 , M 8  and M 9 , and an adjustment of size proportion of M 6  and M 8 , M 9  will influence the voltage at the step of node PD. At this time, OUTPUT_N outputs the high level; 
     In the third phase, the second clock signal terminal CKB is at the high level, and thus M 8  is turned on. Due to the effect of C 2 , M 9  is turned on, and thus the potential at the node PD rises, M 10  is turned on, the potential at the node PU is pulled down, and M 6  and m 5  are turned off. Since M 11  and M 12  are turned on, OUTPUT_N outputs the low level. 
     Herein, before a frame starts, each high level signal at CKB pulls up the potential at the node PD, so that M 10  and M 12  keep in the turn-on state, and signals at the node PU and OUTPUT_N are always pulled down, so as to effectively avoid noise from producing. 
     When backward scanning, output waveforms of respective shift register units in the gate driving circuit are as shown in  FIG. 7 . 
     The gate driving circuit provided in the implementation of the present disclosure enables the gate driving circuit to have the function of bilateral scanning through the third transistor M 3 , the fourth transistor M 4  and the second transistor M 2 , which satisfies the requirement of customers better. The gate driving circuit pulls down the potential at the pulling-up node PU through the tenth transistor M 10  and the eleventh transistor M 11 , and before the next frame starts, the tenth transistor M 10  and the eleventh transistor M 11  keep in the turn-on state, which effectively avoid the noise at the node PU from producing in the non-operation state. The gate driving circuit pulls down the potential at the output terminal in the non-operation state through the eleventh transistor M 11  and twelfth transistor M 12 , which effectively avoids the noise of the output terminal. The gate driving circuit enables each high level signal of the second clock signal CKB to pull up the potential at the node PD through the design of the second capacitor C 2 , which reduces the power consumption of the entire circuit and avoids the noise at the pulling-down PD from producing. At the same time, in the gate driving circuit, through an arrangement of a whole device and a flexible combination of signals, it realizes that the entire gate driving circuit adopts the same shift register unit, thus greatly reducing the difficulty in the gate driving circuit layout (GOA layout). 
     In addition, the embodiment of the present disclosure further provides a display device comprising the gate driving circuit described above. The display device may be any produce or means having a display function, such as a liquid crystal panel, an electronic paper, a cell phone, a tablet computer, a TV set, a display, a notebook computer, a digital photo frame, a navigator and so on. 
     The above implementations are just used for describing the present disclosure but not for limiting the present disclosure. Those skilled in the related art can make various alternations and modifications without departing the spirit and scope of the present disclosure. Therefore, all equivalent technical solution also fall into the scope of the present disclosure. The patent protection scope of the present disclosure shall be defined by the claims. 
     The present application claims the priority of Chinese Patent Application No. 201310749863.4 filed on Dec. 31, 2013, the full text of which is incorporated herein as part of the present disclosure by reference.