Light emitting display device
AssigneeSamsung Display Co., Ltd.
InventorsSung-Cheon Park, Choon-Yul Oh
Life of this patent
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Abstract
A light emitting display includes: a pixel portion including a plurality of pixels; a scan driver adapted to supply a scan signal to scan lines connected to the pixels; a DC/DC converter adapted to supply a first voltage and a second voltage to the plurality of pixels; and a synchronizer adapted to maintain a ripple voltage of the first voltage at a predetermined level when the scan signals are converted into a turn off voltage. With this configuration, since the ripple voltage of the first voltage is always kept constant when the scan signal is turned off, a uniform brightness in a horizontal line and a frame can be displayed.
Claims16
A light emitting display device, comprising:
- a pixel portion including a plurality of pixels, each pixel comprising a second transistor and an organic light emitting diode (OLED), with one of source and drain electrodes of the second transistor being connected to an anode of the OLED;
- a scan driver adapted to supply scan signals to scan lines connected to a gate electrode of a first transistor included in each of the plurality of pixels and to supply at least one scan signal to a synchronizer;
- a data driver adapted to supply data signals to data lines connected to the plurality of pixels;
- a DC/DC converter adapted to supply a first voltage different from the scan and data signals directly to another one of source and drain electrodes of the second transistor included in each of the plurality of pixels and to supply a second voltage to a cathode of the OLED included in each of the plurality of pixels;
- and
- the synchronizer adapted to, when the scan signals are converted into a turn off voltage, maintain a ripple voltage of the first voltage at a predetermined level.
A DC/DC converter, comprising:
- a first switching device and a second switching device physically distinct from the first switching device;
- an oscillator adapted to generate a pulse signal having a predetermined frequency;
- a synchronizer adapted to synchronize the pulse signal with an externally supplied scan signal;
- a switching controller adapted to alternately turn on and turn off the first switching device and the second switching device in response to the pulse signal synchronized by the synchronizer within one cycle of the pulse signal;
- a first voltage generator adapted to generate a first voltage corresponding to a turn on and turn off period of the first switching device, with the first voltage being different from the scan signal;
- a second voltage generator adapted to generate a second voltage corresponding to a turn on and turn off period of the second switching device, with the second voltage being different from the scan signal;
- and
- the first switching device controlling the generation of the first voltage by the first voltage generator independently of the control of the generation of the second voltage by the second voltage generator, and the second switching device controlling the generation of the second voltage by the second voltage generator independently of the control of the generation of the first voltage by the first voltage generator.
A method of driving a light emitting display device, the method comprising:
- connecting one of source and drain electrodes of a first transistor included in each of a plurality of pixels to an anode of an organic light emitting diode (OLED) included in each of the plurality of pixels;
- connecting a gate electrode of a second transistor included in each of a plurality of pixels to a scan line to receive a scan signal;
- connecting the plurality of pixels to a data line to receive a data signal;
- driving an oscillator to generate a first pulse signal having a predetermined frequency;
- generating a second pulse signal by synchronizing the first pulse signal with the scan signal;
- generating a first voltage different from the scan and data signals and a second voltage using the second pulse signal;
- and
- supplying the first voltage directly to another one of source and drain electrodes of the first transistor included in each of the plurality of pixels and supplying the second voltage to a cathode of the OLED included in each of the plurality of pixels,
- wherein the second pulse signal is generated by synchronizing a rising edge or a falling edge of the first pulse signal at a time when the scan signal is converted into a turn off voltage.
Dependencies are inferred from the claim text.