Driving circuit of current-driven active matrix organic light emitting diode pixel

• US 8,502,754 B2
• Filed: 02/16/2004
• Issued: 08/06/2013
• Est. Priority Date: 03/12/2003
• Status: Active Grant

• Current Assignee: AU Optronics Corporation
• Original Assignee: AU Optronics Corporation
• Inventors: Lin, Chiao-Ju
• Primary Examiner(s): Mengistu, Amare
• Assistant Examiner(s): PATEL, PREMAL R
• Application Number:
  US10/708,198
• Publication Number:
  US 20040178407A1
• Time in Patent Office: 3,459 Days
• Field of Search: 345/55, 345/63, 345 67- 69, 345 76- 83, 345 90- 92, 345 94- 96, 345/98, 345/99, 345/204, 345/205, 345/208, 345/210, 345/690, 315/169.1, 315/169.3, 257/88
• US Class Current: 345/82
• 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 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

A method and a driving circuit for driving a current-driven active matrix organic light emitting diode (AMOLED) pixel are provided. A driving power source is used to pre-charge the capacitor before a current source charges/discharges a capacitor connected to a driving thin film transistor of the pixel. Therefore, an insufficient brightness problem during displaying a low gray can be solved.

Claims

1. A current-driven active matrix organic light emitting diode pixel (AMOLED pixel), comprising:

an organic light emitting diode (OLED) having an anode and a cathode directly connected to a negative power source;

a driving thin film transistor;

a capacitor having a first end directly connected to a gate of the driving thin film transistor and a second end directly connected to a positive power source;

a first switch having a first end directly connected to the anode of the OLED, a second end directly connected to a drain of the driving thin film transistor, and a control end directly receiving a first control signal;

a second switch having a first end directly connected to a current source, a second end directly connected to the drain of the driving thin film transistor and the second end of the first switch, and a control end directly receiving a second control signal;

a third switch having a first end directly connected to the drain of the driving thin film transistor and the second end of the first switch, a second end directly connected to the gate of the driving thin film transistor and the first end of the capacitor, and a control end directly connected to the control end of the second switch for directly receiving the second control signal; and

a pre-charge switch having a first end directly receiving a driving power source, a second end directly connected to the gate of the driving thin film transistor, the first end of the capacitor and the second end of the third switch, and a control end directly receiving a third control signal,

wherein the pre-charge switch is first turned on by the third control signal so as to make the driving power source pre-charge the capacitor to a pre-charge voltage level before the current source charges or discharges the capacitor, and thus making the driving thin film transistor have turned on when the current source charges or discharges the capacitor,

the second and the third switches are turned on by the second control signal after the pre-charge switch is turned off by the third control signal, and

the first switch is turned on by the first control signal after the second and the third switches are turned off by the second control signal.

2. The current-driven AMOLED pixel of claim 1, wherein each of the first switch, the second switch, the third switch, the driving thin film transistor, and the pre-charge switch is a P-channel thin film transistor.

3. The current-driven AMOLED pixel of claim 1, wherein each of the first switch, the second switch, the third switch, the driving thin film transistor, and the pre-charge switch is an N-channel thin film transistor.

4. The current-driven AMOLED pixel of claim 1, wherein the driving power source is a negative power source.

5. The current-driven AMOLED pixel of claim 1, wherein the driving power source comprises two different voltage levels.

6. A current-driven active matrix organic light emitting diode pixel (AMOLED pixel), comprising:

an organic light emitting diode (OLED) having an anode and a cathode directly connected to a negative power source;

a driving thin film transistor;

a capacitor having a first end directly connected to a gate of the driving thin film transistor and a second end directly connected to a positive power source;

a first switch having a first end directly connected to the anode of the OLED, a second end directly connected to a drain of the driving thin film transistor, and a control end directly receiving a first control signal;

a second switch having a first end directly connected to a current source, a second end directly connected to the drain of the driving thin film transistor and the second end of the first switch, and a control end directly receiving a second control signal;

a third switch having a first end directly connected to the drain of the driving thin film transistor and the second end of the first switch, a second end directly connected to the gate of the driving thin film transistor and the first end of the capacitor, and a control end directly connected to the control end of the second switch for directly receiving the second control signal; and

a pre-charge switch having a first end directly receiving a driving power source, a second end directly connected to the gate of the driving thin film transistor, the first end of the capacitor and the second end of the third switch, and a control end directly receiving a third control signal.