Drive circuit, display apparatus, and information display apparatus

• US 20040066357A1
• Filed: 08/29/2003
• Published: 04/08/2004
• Est. Priority Date: 09/02/2002
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Kawasaki, Somei
• Granted Patent: US 7,212,195 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0417 Special arrangements specific to the use of low carrier mobility technology
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/0254 Control of polarity reversal in general, other than for liquid crystal displays
• CPC Class Codes: G09G 2310/066 Waveforms comprising a gently increasing or decreasing portion, e.g. ramp
• CPC Class Codes: G09G 2320/02 Improving the quality of display appearance
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/325 the data current flowing through the driving transistor during a setting phase, e.g. by using a switch for connecting the driving transistor to the data driver
• CPC Class Codes: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements

Abstract

The present invention relates to a configuration utilizing a driven element that is driven by a current. Specifically, there is provided a pixel circuit having a driven element and a current-drive transistor for supplying a current for driving the driven element to a current injection terminal of the driven element, a voltage buffer, a current signal line for supplying a current signal to the pixel circuit, and a wiring for connecting an output of the voltage buffer and a gate electrode of the current drive transistor. The pixel circuit has a switch for controlling connection between the voltage buffer and the gate electrode of the current-drive transistor, and an input terminal of the voltage buffer is connected to the current signal line.

Claims

1. A drive circuit comprising:

a pixel circuit having a driven clement and a current-drive transistor for supplying a current for driving the driven element to a current injection terminal of the driven element;

a voltage buffer;

a current signal line for supplying a current signal to the pixel circuit; and

a wiring for connecting an output of the voltage buffer and a gate electrode of the current-drive transistor, wherein

the pixel circuit has a switch for controlling the connection between the voltage buffer and the gate electrode of the current-drive transistor; and

an input terminal of the voltage buffer is connected to the current signal line.

2. A drive circuit according to claim 1, wherein the voltage buffer has a source-follower circuit.

3. A drive circuit according to claim 1, wherein the voltage buffer is a feedback type voltage buffer.

4. A drive circuit according to claim 1, wherein the voltage buffer has a current source and wherein a current value of the current source corresponds to a current supplied to the current signal line during a predetermined period.

5. A drive circuit according to claim 1, wherein the pixel circuit further has a switch for controlling connection between an electrode of the current-drive transistor other than the gate electrode and the current signal line.

6. A drive circuit according to claim 1, wherein the pixel circuit further has a switch for controlling connection between an electrode of the current-drive transistor for passing a current through the driven element and the driven element.

7. A drive circuit according to claim 1, wherein the pixel circuit further has:

a first switch for controlling connection between an electrode of the current-drive transistor other than the gate electrode and the current signal line; and

a second switch for controlling connection between an electrode of the current-drive transistor for passing a current through the driven element and the driven element.

8. A drive circuit according to claim 7, wherein the first switch and the second switch are controlled

such that there is a period in which the first switch keeps the current signal line and the current-drive transistor connected to each other and the second switch keeps the current-drive transistor and the driven element disconnected from each other and

such that there is a period in which the first switch keeps the current signal line and the current-drive transistor disconnected from each other and the second switch keeps the current-drive transistor and the driven element connected to each other.

9. A drive circuit according to claim 1, further comprising a switch for controlling connection between a current supply circuit and the current signal line.

10. A drive circuit according to claim 9, wherein the current supply circuit and the current signal line are connected for a predetermined period before a gate potential of the current-drive transistor is determined according to the current signal and are disconnected from each other after the predetermined period passes.

12. A drive circuit according to claim 1, wherein the driven element is an electroluminescent element.

14. A display apparatus utilizing a drive circuit according to claim 1, wherein a plurality of the pixel circuits is arranged in the form of a matrix.

16. An information display apparatus for performing display in accordance with information inputted thereto, having an information input part and a display apparatus according to claim 14 that performs display in accordance with information inputted to the information input part.

11. A drive circuit comprising:

a plurality of pixel circuits each including a driven element which is driven by passing a current therethrough and a current-drive transistor for passing a current through the driven element;

a current signal line for sequentially supplying a current signal to each of the plurality of pixel circuits; and

a current path line to serve as a current path for sequentially passing a current for determining a gate potential of the current-drive transistor of each of the plurality of pixel circuits, wherein

the gate potential of the current-drive transistor is set such that a current corresponding to the current signal is made to flow between a source electrode and a drain electrode of the current-drive transistor by the flow of the current signal through the current signal line and the flow of the current for changing the gate potential of the current-drive transistor through the current path line and wherein the current flowing through the current-drive transistor is thereafter supplied to the driven element while maintaining the gate potential.

13. A drive circuit according to claim 11, wherein the driven element is an electroluminescent element.

15. A display apparatus utilizing a drive circuit according to claim 11, wherein a plurality of the pixel circuits is arranged in the form of a matrix.

17. An information display apparatus for performing display in accordance with information inputted thereto, having an information input part and a display apparatus according to claim 15 that performs display in accordance with information inputted to the information input part.