Shift register unit, gate driving circuit and display apparatus

Patent metadata

Field	Value
Publication number	US-10417983-B2
Application number	US-201515122265-A
Country	US
Kind code	B2
Filing date	Aug 31, 2015
Priority date	Feb 6, 2015
Publication date	Sep 17, 2019
Grant date	Sep 17, 2019

Abstract

The embodiments of the present disclosure provide a shift register unit, a gate driving circuit with bi-directional scan, and a display apparatus. The shift register unit comprises: an input module configured to provide a first input signal to a first node; a first control module configured to provide a pull-up output based on the first input signal and the third clock signal, and then provide a pull-down output; and a second control module configured to maintain a level at the output node at the source voltage based on a fourth clock signal. The first control module comprises a first transistor that remains on after the pull-up output to provide the pull-down output, and the second control module comprises a second transistor that maintains the level at the output node. The shift register unit according to the embodiment of the present disclosure achieves bi-directional scan with a simple design, which is beneficial for wiring in display panels with narrow rims and high resolutions. Further, since the second transistor is provided only for pull-down maintenance, a transistor of a small size can be used to further reduce the size of the circuit.

First claim

What is claimed is:

1. A shift register unit, comprising:
an input circuit configured to provide a first input signal to a first node based on a first clock signal;
a first control circuit connected to the input circuit at the first node and configured to provide a pull-up output by providing a third clock signal to an output node of the shift register unit based on the first input signal and the third clock signal, and then provide a pull-down output by providing a source voltage to the output node based on a second input signal that is provided by the input circuit to the first node based on a second clock signal; and
a second control circuit configured to maintain a level at the output node at the source voltage based on a fourth clock signal,
wherein the first control circuit comprises a first transistor that remains on after the pull-up output to provide the pull-down output, and wherein the second control circuit comprises a second transistor that maintains the level at the output node; and
wherein the second transistor has its gate connected to a second node, its drain connected to the source voltage and its source connected to the output node;
wherein the second control circuit further comprises: a fifth transistor having its gate and drain connected to the fourth clock signal and its source connected to the second node; and a sixth transistor having its gate connected to the second node, its source connected to the first node and its drain connected to the source voltage.

2. The shift register unit of claim 1 , wherein a ratio of a size of the first transistor to that of the second transistor is 30:1˜1:1.

3. The shift register unit of claim 2 , wherein the ratio of the size of the first transistor to that of the second transistor is 6:1˜3:1.

4. The shift register unit of claim 1 , wherein the first transistor has its gate connected to the first node, its source connected to the third clock signal and its drain connected to the output node, and wherein a first capacitance is provided between the gate and the drain of the first transistor, as a voltage maintenance capacitance for the first node;
wherein the first control circuit further comprises a seventh transistor having its gate connected to the first node, its source connected to a first terminal of a second capacitance at the second node, and its drain connected to the source voltage;
wherein the second capacitance has a second terminal connected to the source voltage and serves as a voltage maintenance capacitance for the second node.

5. The shift register unit of claim 4 , wherein the first and second capacitances are provided by inherent parasitic capacitances or additional capacitors between the transistors.

6. The shift register unit of claim 1 , wherein the second control circuit further comprises: an eighth transistor having its gate and drain connected to the second clock signal and its source connected to the second node; and a ninth transistor having its gate connected to the first clock signal, its source connected to the second node and its drain connected to a second source voltage having an opposite polarity to that of the source voltage.

7. The shift register unit of claim 6 , wherein the input circuit comprises:
a third transistor having its gate connected to the first clock signal, its source connected to the first input signal and its drain connected to the first node; and
a fourth transistor having its gate connected to the fourth clock signal, its drain connected to the second input signal and its source connected to the first node.

8. The shift register unit of claim 6 , wherein the input circuit comprises:
a third transistor having its gate connected to the first input signal, its source connected to the first clock signal and its drain connected to the first node; and
a fourth transistor having its gate connected to the second input signal, its drain connected to the fourth clock signal and its source connected to the first node.

9. The shift register unit of claim 1 , wherein the input circuit comprises:
a third transistor having its gate connected to the first clock signal, its source connected to the first input signal and its drain connected to the first node; and
a fourth transistor having its gate connected to the fourth clock signal, its drain connected to the second input signal and its source connected to the first node.

10. The shift register unit of claim 9 , wherein each of the first transistor, the second transistor, the third transistor, the fourth transistor, the fifth transistor, and the sixth transistor is an NMOS transistor, the source voltage is negative.

11. The shift register unit of claim 1 , wherein the input circuit comprises:
a third transistor having its gate connected to the first input signal, its source connected to the first clock signal and its drain connected to the first node; and
a fourth transistor having its gate connected to the second input signal, its drain connected to the fourth clock signal and its source connected to the first node.

12. The shift register unit of claim 11 , wherein each of the first transistor, the second transistor, the third transistor, the fourth transistor, the fifth transistor, and the sixth transistor is a PMOS transistor, the source voltage is positive.

13. A gate driving circuit, comprising the shift register unit according to claim 1 .

14. The gate driving circuit of claim 13 , wherein the gate driving circuit consists of N cascaded shift register units, where N is an integer larger than 1, and
each of the shift register units, except the one at the first stage, has its first input terminal connected to the output node of the shift register unit at the previous stage, and the shift register unit at the first stage has its first input terminal connected to a first enabling signal,
each of the shift register units, except the one at the last stage, has its second input terminal connected to the output node of the shift register unit at the next stage, and the shift register unit at the last stage has its second input terminal connected to a second enabling signal,
when each shift register unit shifts forward, a high level pulse of the first clock signal occurs prior to that of the third clock signal, and the first clock signal has a waveform identical to that of a voltage at the output node of the shift register unit at the previous stage, and
when each shift register unit shifts reversely, a high level pulse of the second clock signal occurs prior to that of the third clock signal, and the second clock signal has a waveform identical to that of a voltage at the output node of the shift register unit at the next stage.

15. A display apparatus comprising the gate driving circuit according to claim 13 .

16. A display apparatus comprising the gate driving circuit according to claim 14 .

Assignees

• Boe Technology Group Co Ltd
• Chengdu Boe Optoelect Tech Co

Inventors

• Hu Like
• Qi Xiaojing

Classifications

• G09G2310/0267

  Details of drivers for scan electrodes, other than drivers for liquid crystal, plasma or OLED displays · CPC title

• G11C19/28

  using semiconductor elements (G11C19/14, G11C19/36 take precedence) · CPC title

• G09G3/36

  using liquid crystals · CPC title

• G09G3/20 Primary

  for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix {no fixed position being assigned to or needed to be assigned to the individual characters or partial characters} · CPC title

• G09G2310/08

  Details of timing specific for flat panels, other than clock recovery · CPC title