Current sensing circuit and organic light emitting diode display including the same

Patent metadata

Field	Value
Publication number	US-2016163261-A1
Application number	US-201514962815-A
Country	US
Kind code	A1
Filing date	Dec 8, 2015
Priority date	Dec 9, 2014
Publication date	Jun 9, 2016
Grant date	—

Abstract

Discussed are a current sensing circuit capable of compensating for degradation of an organic light emitting diode by sensing a current of the organic light emitting diode, and an organic light emitting diode display having the same. The current sensing circuit according to an embodiment includes a plurality of sensing modules configured to sense a pixel current from a display panel having an organic light emitting diode on each of a plurality of pixels, and to output a sensing voltage according to a sensing result; and an analogue-digital converter configured to convert the sensing voltage into an analogue-digital voltage, and to output sensing data.

First claim

What is claimed is:

1 . A current sensing circuit, comprising:
a plurality of sensing modules configured to sense a pixel current from a display panel having an organic light emitting diode on each of a plurality of pixels, and to output a sensing voltage according to a sensing result; and an analogue-digital converter configured to convert the sensing voltage into an analogue-digital voltage, and to output sensing data, wherein each of the plurality of sensing modules includes: a current buffer configured to generate a sensing current by sensing the pixel current from an anode electrode of the organic light emitting diode; and a current integrator configured to output the sensing voltage by receiving the sensing current as a voltage.

2 . The current sensing circuit of claim 1 , wherein the current buffer includes:
an operational amplifier composed of a first input terminal connected to the anode electrode of the organic light emitting diode, a second input terminal connected to the current integrator, and an output terminal; a first resistor connected between the first input terminal and the output terminal; and a second resistor connected between the second input terminal and the output terminal.

3 . The current sensing circuit of claim 2 , wherein the current buffer controls a level of the sensing current by controlling a ratio between sizes of the first and second resistors.

4 . The current sensing circuit of claim 1 , wherein the current buffer includes:
a first switching device having a gate electrode and a drain electrode connected to an anode electrode of the pixel; and a second switching device having a gate electrode connected to the gate electrode of the first switching device, and having a drain electrode connected to the current integrator, and wherein source electrodes of the first and second switching devices are commonly connected to a ground.

5 . The current sensing circuit of claim 4 , wherein the current buffer controls a level of the sensing current by controlling a ratio between sizes of the first and second switching devices.

6 . The current sensing circuit of claim 1 , further comprising a reference current source configured to provide a reference current by being connected to the current buffer.

7 . The current sensing circuit of claim 1 , wherein the current buffer is a current mirror circuit.

8 . The current sensing circuit of claim 1 , wherein the current integrator includes:
a resistor connected to the current buffer; an operational amplifier composed of a first input terminal to which a voltage by the sensing current is input through the resistor, a second input terminal to which a reference voltage is input, and an output terminal from which the sensing voltage is output; and a capacitor connected between the first input terminal and the output terminal.

9 . The current sensing circuit of claim 1 , further comprising a switch disposed between the current buffer and the organic light emitting diode,
wherein as the switch is turned on for a compensation driving period of the display panel, the sensing voltage is output through the current integrator.

10 . An organic light emitting diode display, comprising:
a display panel having a plurality of pixels, each pixel including an organic light emitting diode; a data driving unit having a current sensing circuit for outputting sensing data by sensing a pixel current from each of the plurality of pixels; and a timing controller configured to generate compensation image data by compensating for image data based on the sensing data, and to output the compensation image data to the data driving unit, wherein the current sensing circuit includes:
a plurality of sensing modules configured to sense the pixel currents by being connected to anode electrodes of the organic light emitting diodes disposed at the plurality of pixels, and to output a sensing voltage according to a sensing result; and
an analogue-digital converter configured to convert the sensing voltage into an analogue-digital voltage, and to output the sensing data,
wherein each of the plurality of sensing modules includes:
a current buffer configured to generate a sensing current by sensing the pixel current from the anode electrode of the organic light emitting diode; and
a current integrator configured to output the sensing voltage by receiving the sensing current as a voltage.

11 . The organic light emitting diode display of claim 10 , wherein the current sensing circuit is operated at a compensation driving period of the display panel.

Assignees

• Lg Display Co Ltd

Inventors

• Kim Sangyun
• Yang Junhyeok

Classifications

• G09G3/3225 Primary

  using an active matrix · CPC title

• G09G3/3233 Primary

  with pixel circuitry controlling the current through the light-emitting element · CPC title

• G09G2300/0426

  Layout of electrodes and connections · CPC title

• G09G2310/08

  Details of timing specific for flat panels, other than clock recovery · CPC title

• G09G2330/12

  Test circuits or failure detection circuits included in a display system, as permanent part thereof · CPC title