Active matrix type display apparatus and driving method thereof

• US 8,354,981 B2
• Filed: 06/30/2008
• Issued: 01/15/2013
• Est. Priority Date: 07/02/2007
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kawasaki, Somei, Goden, Tatsuhito
• Primary Examiner(s): Awad, Amr
• Assistant Examiner(s): WILLIS, RANDAL L
• Application Number:
  US12/164,542
• Publication Number:
  US 20090015571A1
• Time in Patent Office: 1,660 Days
• Field of Search: 345/204, 345/76, 345/77
• US Class Current: 345/77
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• 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

Abstract

In an active matrix type display apparatus, during a first selection period, a second main conductive terminal of a drive transistor and a display element are isolated, and at the same time, a control terminal of the drive transistor and the second main conductive terminal and a signal line are connected, and the signal line is supplied with a first current capable of conducting the drive transistor. The first current does not correspond to a signal current corresponding to a current injected to the display element. During a second selection period, a connection of the second main conductive terminal of the drive transistor and the signal line is broken, and the signal line is supplied with a second current. The second current corresponds to a signal current corresponding to the current injected to the display element. During a non-selection period, the second main conductive terminal of the drive transistor and the display element are connected, and the drive current of the drive transistor corresponding to voltage between both terminals of a capacitive element is supplied to the display element.

Claims

1. An active matrix type display apparatus configured by disposing a pixel circuit for supplying a current to a display element disposed at a position where a signal line and a scanning line intersect the pixel circuit, comprising:

a drive transistor having a first main conductive terminal connected to a constant voltage source, a second main conductive terminal for injecting the current to the display element, and a control terminal; and

a capacitive element connected between the control terminal of the drive transistor and the first main conductive terminal,

the pixel circuit being connected to the signal line during a selection period, and isolated from the signal line during a non-selection period,

wherein the selection period includes a first period and a second period, and

during the first period, the second main conductive terminal of the drive transistor and the display element are isolated, the control terminal and the second main conductive terminal of the drive transistor are connected to the signal line, and the signal line is supplied with a first current capable of conducting the drive transistor, with the first current not corresponding to a signal current corresponding to the current injected to the display element,

during the second period, the second main conductive terminal of the drive transistor is disconnected from the signal line, and the signal line is supplied with a second current corresponding to a signal current for controlling a display image, in a direction reverse to the first current, and

during the non-selection period, the second main conductive terminal of the drive transistor and the display element are connected, and a drive current according to the voltage between both terminals of the capacitive element is supplied from the drive transistor to the display element.

2. The active matrix type display apparatus according to claim 1, wherein, after the first period and before the second period, the control terminal of the drive transistor is disconnected from the signal line.

3. The active matrix type display apparatus according to claim 1, wherein a connection with the second main conductive terminal of the drive transistor and the display element is broken within the non-selection period, so that the display element is turned off.

4. The active matrix type display apparatus according to claim 1, wherein the pixel circuit further includes a first switch, a second switch and a third switch including transistors whose on-and-off operations are controlled by the control signal of the scanning line, and

the first switch is disposed between the control terminal of the drive transistor and the signal line,

the second switch is disposed between the second main conductive terminal of the drive transistor and the signal line, and

the third switch is disposed between the second main conductive terminal of the drive transistor and one terminal of the display element.

5. The active matrix type display apparatus according to claim 4, wherein the scanning line comprises a first scanning line, a second scanning line and a third scanning line,

the first scanning line is connected to a control terminal of the first switch,

the second scanning line is connected to a control terminal of the second switch, and

the third scanning line is connected to a control terminal of the third switch.

6. The active matrix type display apparatus according to claim 4, wherein any of the drive transistor, the first switch, the second switch and the third switch includes a TFT.

7. The active matrix type display apparatus according to claim 6, wherein the drive transistor includes a p-type TFT, and any of the first switch, second switch and third switch includes an n-type TFT.

8. A driving method of an active matrix type display apparatus disposed with a pixel circuit to which a signal line and a scanning line are connected for supplying a current to a display element two dimensionally arranged, with the pixel circuit comprising a drive transistor having a first main conductive terminal connected to a constant voltage source, a second main conductive terminal for injecting the current to the display element, and a control terminal, and a capacitive element connected between the control terminal of the drive transistor and the first main conductive terminal, the pixel circuit being connected to the signal line during a selection period and isolated from the signal line during a non-selection period, wherein the selection period includes a first period and a second period, the driving method comprising:

during the first period, the second main conductive terminal of the drive transistor and the display element are isolated, the control terminal and the second main conductive terminal of the drive transistor are connected to the signal line, the step of supplying the signal line with a first current capable of conducting the drive transistor, with the first current not corresponding to a signal current corresponding to the current injected to the display element;

during the second period, the second main conductive terminal of the drive transistor is disconnected from the signal line, the step of supplying the signal line with a second current corresponding to a signal current for controlling a display image, in a direction reverse to the first current; and

during the non-selection period, the second main conductive terminal of the drive transistor and the display element are connected, the step of supplying a drive current according to the voltage between both terminals of the capacitive element from the drive transistor to the display element.