LEVEL SHIFTER FOR GATE DRIVER

• US 20080186058A1
• Filed: 02/01/2008
• Published: 08/07/2008
• Est. Priority Date: 02/02/2007
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Chen, Ming-Daw, Kung, Chen-Pang, Chen, Hung-Chun, Chiang, Ko-Yu
• Granted Patent: US 7,598,771 B2
• Time in Patent Office: Days
• US Class Current: 326/80
• CPC Class Codes: H03K 19/018521 of complementary type, e.g. CMOS

Abstract

A level shifter for a gate driver has a driving transistor, a reset transistor, a charge/discharge circuit, a threshold voltage detector, and a memory capacitor. An initial threshold voltage of the driving transistor is detected by the threshold voltage detector, and then memorized in the memory capacitor. The charge/discharge circuit charges or discharges the capacitor, and receives a control signal to actuate the level shifter. The reset transistor receives an output signal of a next stage level shifter as a reset signal, so as to restore the initial status of the level shifter. In this way, the driving current output from the level shifter is irrelevant to the threshold voltage of the driving transistor.

Claims

1. A level shifter, wherein multiple stages of the level shifters are suitable to be serially-connected into a gate drive circuit, and each stage comprising an output end coupled to an input end of a next stage level shifter, and a reset end for receiving an output signal of the next stage level shifter, the level shifter comprising:

a first node and a second node;

a driving transistor, provided with a gate, a source, and a drain, wherein the gate is coupled to the first node, the drain is coupled to a clock signal, and the source functioning as the output end outputs an output signal;

a reset transistor, provided with a gate, a source, and a drain, wherein the gate receives the output signal of the next stage level shifter as a reset signal, the source is coupled to a first low-potential voltage, and the drain is coupled to the first node;

a charge/discharge circuit, for receiving an input signal and a control signal, and coupled to the second node;

a threshold voltage detector, for receiving the control signal, and coupled to the first node and the source of the driving transistor; and

a memory capacitor, provided with a first end and a second end respectively coupled to the first node and the second node, for memorizing a threshold voltage of the driving transistor.

2. The level shifter according to claim 1, wherein the charge/discharge circuit further comprises:

a first transistor, provided with a gate, a source, and a drain, wherein the gate is coupled to the input signal, the drain is coupled to a high-potential voltage, and the source is coupled to the second node; and

a second transistor, provided with a gate, a source, and a drain, wherein the gate is coupled to the control signal, the drain is coupled to the second node, and the source is coupled to a second low-potential voltage.

3. The level shifter according to claim 2, wherein the gate and the drain of the first transistor are coupled, for receiving the input signal.

4. The level shifter according to claim 2, wherein the first low-potential voltage is different from the second low-potential voltage.

5. The level shifter according to claim 2, wherein the first low-potential voltage is the same as the second low-potential voltage.

6. The level shifter according to claim 1, wherein the memory capacitor is a transistor-based capacitor or a metal-insulator-metal capacitor.

7. A level shifter, wherein multiple stages of the level shifters are suitable to be serially-connected into a gate drive circuit, each stage comprising an output end coupled to an input end of a next stage level shifter, and a reset end for receiving an output signal of the next stage level shifter, the level shifter comprising:

a first node and a second node;

a driving transistor, provided with a gate, a source, and a drain, wherein the gate is coupled to the first node, the drain is coupled to a clock signal, and the source is coupled to an output signal;

a reset transistor, provided with a gate, a source, and a drain, wherein the gate receives the output signal of the next stage level shifter as a reset signal, the source is coupled to a first low-potential voltage, and the drain is coupled to the second node;

a charge/discharge circuit, for receiving an input signal and a control signal, and coupled to a high-potential voltage, a second low-potential voltage, and the second node;

a threshold voltage detector, for receiving the control signal, and coupled to the first node and the source of the driving transistor; and

a memory capacitor, provided with a first end and a second end respectively coupled to the first node and the second node, for memorizing a threshold voltage of the driving transistor.

8. The level shifter according to claim 7, wherein the charge/discharge circuit further comprises:

a first transistor, provided with a gate, a source, and a drain, wherein the gate is coupled to the input signal, the drain is coupled to the high-potential voltage, and the source is coupled to the second node; and

a second transistor, provided with a gate, a source, and a drain, wherein the gate is coupled to the control signal, the drain is coupled to the second node, and the source is coupled to the second low-potential voltage.

9. The level shifter according to claim 8, wherein the gate and the drain of the first transistor are coupled, and the input signal functions as a high-potential voltage level.

10. The level shifter according to claim 7, wherein the first low-potential voltage is different from the second low-potential voltage.

11. The level shifter according to claim 7, wherein the first low-potential voltage is the same as the second low-potential voltage.

12. The level shifter according to claim 7, wherein the memory capacitor is a transistor-based capacitor or a metal-insulator-metal capacitor.

13. A level shifter, wherein multiple stages of the level shifters are suitable to be serially-connected into a gate drive circuit, each comprising an output end coupled to an input end of a next stage level shifter, and a reset end for receiving an output signal of the next stage level shifter, the level shifter comprising:

a first node and a second node;

a driving transistor, provided with a gate, a source, and a drain, wherein the gate is coupled to the first node, the drain is coupled to a clock signal, and the source functioning as the output end outputs an output signal;

a reset transistor, provided with a gate, a source, and a drain, wherein the gate receives the output signal of the next stage level shifter as a reset signal, the source is coupled to a first low-potential voltage, and the drain is coupled to the first node;

a charge/discharge circuit, used for receiving an input signal, a first control signal, and a second control signal, and coupled to a second low-potential voltage and the second node;

a threshold voltage detector, used for receiving the first control signal and the second control signal, and coupled to the first node and the source of the driving transistor; and

a memory capacitor, provided with a first end and a second end respectively coupled to the first node and the second node, for memorizing a threshold voltage of the driving transistor.

14. The level shifter according to claim 13, wherein the charge/discharge circuit further comprises:

a first transistor, provided with a gate, a source, and a drain, wherein the gate is coupled to the drain for receiving the input signal, and the source is coupled to the second node;

a second transistor, provided with a gate, a source, and a drain, wherein the gate is coupled to the first control signal, and the drain is coupled to the second node; and

a third transistor, provided with a gate, a source, and a drain, wherein the gate is coupled to the second control signal, and the drain is coupled to the second node.

15. The level shifter according to claim 14, wherein the sources of the second transistor and the third transistor are coupled to the same low-potential voltage.

16. The level shifter according to claim 14, wherein the sources of the second transistor and the third transistor are coupled to different low-potential voltages.

17. The level shifter according to claim 13, wherein the threshold voltage detector further comprises:

a fourth transistor, provided with a gate, a source, and a drain, wherein the gate is coupled to the first control signal, the drain is coupled to a high-potential voltage, and the source is coupled to the first node;

a fifth transistor, provided with a gate, a source, and a drain, wherein the gate is coupled to the second control signal, and the source is coupled to the first node; and

a sixth transistor, provided with a gate, a source, and a drain, wherein the gate is coupled to the first node and the gate of the driving transistor, the drain is coupled to the drain of the fifth transistor, and the source is coupled to the source of the driving transistor.

18. The level shifter according to claim 13, wherein the gate and the drain of the fourth transistor are further coupled together, for receiving the first control signal.

19. The level shifter according to claim 13, further comprising a seventh transistor provided with a gate, a source, and a drain, wherein the gate and the drain are both coupled to the source of the driving transistor, and the source is connected to a third low-potential voltage.

20. The level shifter according to claim 13, further comprising an eighth transistor provided with a gate, a source, and a drain, wherein the gate is coupled to the gate of the driving transistor, the drain is coupled to the clock signal, and the source is coupled to a pixel end.

21. The level shifter according to claim 13, wherein the memory capacitor is a transistor-based capacitor or a metal-insulator-metal capacitor.

22. The level shifter according to claim 13, wherein the first low-potential voltage is different from the second low-potential voltage.

23. The level shifter according to claim 13, wherein the first low-potential voltage is the same as the second low-potential voltage.

24. A level shifter, wherein multiple stages of the level shifters are suitable to be serially-connected into a gate drive circuit, each stage comprising an output end coupled to an input end of a next stage level shifter, and a reset end for receiving an output signal of the next stage level shifter, the level shifter comprising:

a first node and a second node;

a driving transistor, provided with a gate, a source, and a drain, wherein the gate is coupled to the first node, the drain is coupled to a clock signal, and the source functioning as the output end outputs an output signal;

a reset transistor, provided with a gate, a source, and a drain, wherein the gate receives the output signal of the next stage level shifter as a reset signal, the source is coupled to a low-potential voltage, and the drain is, coupled to the first node;

a charge circuit, for receiving an input signal, and coupled to the second node;

a threshold voltage detector, for receiving the control signal, and coupled to the first node, the second node, and the source of the driving transistor; and

a memory capacitor, provided with a first end and a second end respectively coupled to the first node and the second node, for memorizing a threshold voltage of the driving transistor.

25. The level shifter according to claim 24, wherein the charge circuit is a first transistor provided with a gate, a source, and a drain, the gate is coupled to the input signal, the drain is coupled to a high-potential voltage, and the source is coupled to the second node.

26. The level shifter according to claim 25, wherein the gate and the drain of the first transistor are coupled, for receiving the input signal.

27. The level shifter according to claim 24, wherein the memory capacitor is a transistor-based capacitor or a metal-insulator-metal capacitor.