OLED DISPLAY PANEL WITH PWM CONTROL

• US 20110084993A1
• Filed: 03/17/2009
• Published: 04/14/2011
• Est. Priority Date: 03/19/2008
• Status: Abandoned Application

• Current Assignee: Global OLED Technology LLC (LG Display Co., Ltd.)
• Original Assignee: Global OLED Technology LLC (LG Display Co., Ltd.)
• Inventors: Kawabe, Kazuyoshi
• Application Number:
  US12/922,660
• Publication Number:
  US 20110084993A1
• Time in Patent Office: Days
• US Class Current: 345/691
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than 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 2300/0876 Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• CPC Class Codes: G09G 2310/066 Waveforms comprising a gently increasing or decreasing portion, e.g. ramp
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes

Abstract

A display panel which applies a PWM drive to a drive transistor (2) is provided. A drive transistor supplies current in accordance with its gate voltage, and the current is supplied to a light-emitting element (1) to illuminate the light emitting element. One end of a storage capacitor (6) is connected to the gate of the drive transistor, while the other end thereof is connected to a sweep line (12). A triangular wave which alternately repeats an up phase and a down phase is supplied to the sweep line in order to control an on period of the drive transistor in accordance with the gate voltage, to thereby control light emission of the light-emitting element.

Claims

1. A display panel having pixels arranged in a matrix, each pixel comprising:

a drive transistor which supplies current in accordance with a gate voltage;

a light-emitting element which emits light by current supplied from the drive transistor;

a storage capacitor having one end connected to a gate of the drive transistor and another end connected to a sweep line; and

means for applying a triangular wave which alternately repeats an up phase and a down phase to the sweep line to control an on period of the drive transistor in accordance with the gate voltage to thereby control light emission of each pixel.

2. A display panel having pixels arranged in a matrix, each pixel comprising:

a coupling capacitor having one end connected to a data line;

a selection transistor having one end connected to another end of the coupling capacitor and a gate connected to a selection line;

a drive transistor, having a gate connected to another end of the selection transistor, which supplies current in accordance with a gate voltage;

a light-emitting element which is connected to a drain of the drive transistor and emits light by the current supplied from the drive transistor;

a reset transistor having one end connected to a connecting point of the drive transistor and the light-emitting element, another end connected to a connecting point of the coupling capacitor and the selection transistor, and a gate connected to a reset line;

a storage capacitor having one end connected to a gate of the drive transistor and another end connected to a sweep line;

means for turning on the reset transistor and the selection transistor are turned on, the drive transistor is diode-connected so that current flows and a voltage corresponding to a characteristic of the drive transistor is written into the coupling capacitor, and then, in a state that turns off the reset transistor, the selection transistor is turned on and a voltage of the data line is written into the storage capacitor via the coupling capacitor; and

means for applying a triangular wave which alternately repeats an up phase and a down phase to the sweep line i to control an on period of the drive transistor in accordance with the gate voltage to thereby control light emission.

3. The display panel according to claim 2, wherein

a light emission control transistor is arranged between the connecting point of the drain of the drive transistor and the reset transistor, and the light-emitting element, and

when the reset transistor is turned on, the light-emission control transistor is turned off.