Lighting emitting display, pixel circuit and driving method thereof

• US 7,903,059 B2
• Filed: 03/13/2007
• Issued: 03/08/2011
• Est. Priority Date: 03/13/2006
• Status: Expired due to Fees

• Current Assignee: Himax Technologies Ltd. (Himax Technologies Incorporated)
• Original Assignee: Himax Technologies Ltd. (Himax Technologies Incorporated)
• Inventors: Chiou, Yu-Wen, Chang, Chin-Tien, Guo, Hong-Ru
• Primary Examiner(s): Nguyen; Chanh
• Assistant Examiner(s): PARKER, JEFFREY ALAN
• Application Number:
  US11/717,104
• Publication Number:
  US 20070210998A1
• Time in Patent Office: 1,456 Days
• Field of Search: 345/76, 345/77, 345/78, 345/82, 345/83
• US Class Current: 345/82
• 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 2310/0262 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 2320/043 Preventing or counteracting the effects of ageing
• 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 lighting emitting display, a pixel circuit and a driving method thereof. The pixel circuit includes a driving transistor, a capacitor and a LED. The capacitor receives a first supply voltage and is coupled to a gate of the driving transistor. A cathode of the LED receives a second supply voltage. During a pre-charge period, the gate and the drain of the driving transistor are coupled to an anode of the LED, the source of the driving transistor is coupled to a charging voltage. The source of the driving transistor receives a data signal and the drain and gate of the driving transistor are coupled to each other during a programming period. The source of the driving transistor is coupled to receive the first supply voltage and the drain of the driving transistor is coupled to the anode of the LED during a display period.

Claims

1. A pixel circuit, comprising:

a driving transistor;

a capacitor having one end coupled to receive a first supply voltage and the other end coupled to a gate of the driving transistor;

a light emitting diode having a cathode coupled to receive a second supply voltage and having an anode directly coupled to the drain of the driving transistor;

a first switch coupled between the source of the driving transistor and the first supply voltage;

a second switch coupled between the source of the driving transistor and the data signal; and

a third switch coupled between the gate of the driving transistor and the drain of the driving transistor;

wherein the gate and a drain of the driving transistor are commonly coupled to an anode of the light emitting diode, and a source of the driving transistor is coupled to receive a charging voltage during a pre-charge period, the source of the driving transistor is coupled to receive a data signal and the drain and gate of the driving transistor are coupled to each other during a programming period, and the source of the driving transistor is coupled to receive the first supply voltage during a display period;

wherein the second supply voltage is independent of pixel data indicated by the data signal;

the second supply voltage has a first voltage level during the pre-charge period;

the second supply voltage has a second voltage level during the display period and the second supply voltage has a third voltage level during the display period, wherein the third voltage level is between the first and the second voltage levels.

2. The pixel circuit according to claim 1,

wherein the first switch is turned on, the second switch is turned off and the third switch is turned on during the pre-charge period, the first switch is turned off, the second switch is turned on and the third switch is turned on during the programming period, and the first switch is turned on, the second switch is turned off and the third switch is turned off during the display period.

3. The pixel circuit according to claim 2, wherein the charging voltage is provided by the first supply voltage during the pre-charge period.

4. The pixel circuit according to claim 1,

wherein the first switch is turned off, the second switch is turned on and the third switch is turned on during the pre-charge period, the first switch is turned off, the second switch is turned on and the third switch is turned on during the programming period, and the first switch is turned on, the second switch is turned off and the third switch is turned off during the display period.

5. The pixel circuit according to claim 4, wherein the charging voltage is provided by the data signal during the pre-charge period.

6. The pixel circuit according to claim 1, wherein the driving transistor is a PMOS transistor and the second voltage level is higher than the first voltage level.

7. The pixel circuit according to claim 6, wherein the magnitude of the second supply voltage is substantially equal to the magnitude of the charging voltage during the programming period.