Shift register

• US 7,792,237 B2
• Filed: 11/07/2008
• Issued: 09/07/2010
• Est. Priority Date: 01/09/2008
• Status: Active Grant

• Current Assignee: AU Optronics Corporation
• Original Assignee: AU Optronics Corporation
• Inventors: Chen, Chung-chun, Pai, Cheng-chiu, Chiou, Hung-yu
• Primary Examiner(s): Lam; Tuan
• Application Number:
  US12/267,053
• Publication Number:
  US 20090175405A1
• Time in Patent Office: 669 Days
• Field of Search: 377/64, 377 68- 75, 377 77- 81
• US Class Current: 377/64
• CPC Class Codes: G11C 19/184 with field-effect transistors, e.g. MOS-FET
• CPC Class Codes: G11C 19/28 using semiconductor elements G11C19/14, G11C19/36 take precedence

Abstract

A shift register is used for outputting an output pulse at output end in response to a delay of an input pulse received at an input end. The shift register includes a controller, a pre-charging switch, a level shifting switch, and an output generator. The controller is used for generating a level switching signal. The pre-charging switch is used for conducting a first supply voltage to a level shifting node in response to the input pulse. The level shifting switch turns on in response to the level switching signal. The output generator is used for generating the output pulse at the output end, when the level shifting switch turns on.

Claims

1. A shift register for outputting an output pulse at an output end in response to a delay of an input pulse received at an input end, comprising:

a first voltage supply end for providing a first supply voltage;

a second voltage supply end for providing a second supply voltage;

a controller electrically coupled to the input end, for generating a level switching signal in response to the input pulse, a first clock signal, and a second clock signal complementary to the first clock signal;

a pre-charging switch electrically coupled to the first voltage supply end and the input end, for conducting the first supply voltage to a level shifting node in response to the input pulse;

a level shifting switch electrically coupled to the controller and the level shifting node, turning on in response to the level switching signal, wherein the level shifting switch is a first transistor, and a gate, a first electrode, and a second electrode of the first transistor are respectively electrically coupled to the level switching signal from the controller, the output end, and the level shifting node; and

an output generator electrically coupled to the output end and the level shifting node, for generating the output pulse at the output end in response to the second clock signal and voltage on the level shifting node, when the level shifting switch turns on.

2. The shift register of claim 1, wherein the output generator comprises a second transistor and a third transistor, a gate, a first electrode, and a second electrode of the second transistor being respectively electrically coupled to the level shifting node, the output end, and the second clock signal, and a gate, a first electrode, and a second electrode of the third transistor being respectively electrically coupled to the level switching signal from the controller, the second voltage supply end, and the output end.

3. The shift register of claim 1, wherein the pre-charging switch is a second transistor, and a gate, a first electrode, and a second electrode of the second transistor are respectively electrically coupled to the input end, the first voltage supply end, and the level shifting node.

4. The shift register of claim 3, further comprising a level compensating capacitor electrically coupled between the gate and the second electrode of the second transistor.

5. The shift register of claim 4, wherein the level compensating capacitor is a third transistor of which a gate is electrically coupled to the input end, and both a first electrode and a second electrode are electrically coupled to the level shifting node.

6. The shift register of claim 1, wherein the controller comprises:

an inverter electrically coupled to the input end to receive the input pulse, for inverting the input pulse;

a sampling switch electrically coupled to the inverter and controlled by the second clock signal, for outputting the inverted input pulse; and

a clock level shifter electrically coupled to the input end and the sampling switch, for delivering the level switching signal based on the inverted input pulse from the sampling signal.

7. The shift register of claim 6, wherein the inverter comprises:

a second transistor, comprising a gate electrically coupled to the first clock signal, and a second electrode electrically coupled to the first voltage supply end; and

a third transistor, comprising a gate electrically coupled to the input end, and a first electrode coupling to the second voltage supply end.

8. The shift register of claim 7, wherein the sampling switch is an fourth transistor having a gate electrically coupled to the second clock signal.

9. The shift register of claim 8, wherein the clock level shifter comprises:

a fifth transistor, comprising a gate electrically coupled to the fourth transistor, and a first electrode electrically coupled to the first voltage supply end;

a sixth transistor, comprising a gate electrically coupled to the input end, and a first electrode electrically coupled to the second voltage supply end; and

an seventh transistor, comprising a gate electrically coupled to the output end, a first electrode electrically coupled to the second voltage supply end, and a second electrode electrically coupled to the level switching signal.

10. The shift register of claim 1, further comprising

a first rest switch electrically coupled to the level shifting node, for resetting the shift register in response to a reset signal.

11. The shift register of claim 10, wherein the first reset switch is a second transistor comprising a gate electrically coupled to the reset signal, a first electrode electrically coupled to the level shifting node, and a second electrode electrically coupled to the second voltage supply end.

12. The shift register of claim 10, further comprising a second reset switch electrically coupled to input end, for resetting the shift register in response to the reset signal.

13. The shift register of claim 12, wherein the second reset switch is a third transistor comprising a gate electrically coupled to the reset signal, a first electrode electrically coupled to the second voltage supply end, and a second electrode electrically coupled to the input end.