Sources driver circuit for active matrix electroluminescent display and driving method thereof
AssigneeElectronics and Telecommunications Research Institute
InventorsYil Suk Yang, Jong Dae Kim, Dae Woo Lee, Tae Moon Roh, Il Yong Park, Sung Ku Kwon, Byoung Gon Yu
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Abstract
Provided is a source driver circuit for an active matrix electroluminescent (EL) display including a digital-to-analog converter/ramp circuit for converting a digital signal into an analog signal, and generating a ramp signal in this process, simultaneously, whereby high degree of integration would be possible since a conventional complicated circuit is not required and gray scale with the high characteristic can be implanted, regardless of a change of a temperature or a threshold voltage.
Claims7
A source driver circuit for an active matrix electroluminescent (EL) display, comprising:
- a shift register circuit for receiving a main clock signal and generating an enable signal for sequentially storing a digital data;
- a line latch circuit for sequentially storing the data by the enable signal, and outputting the stored digital data, in parallel;
- a digital-to-analog converter/ramp circuit for converting the digital signal, which is outputted from the line latch circuit, to an analog signal, and at this time, generating a ramp signal, simultaneously, the digital-to-analog converter/ramp circuit further comprising:
- a resistor-string comprising a plurality of nodes between power supply terminals, a given voltage difference existing therebetween;
- a digital-to-analog converter (DAC) switch unit in which each of DAC switches is connected to each of the nodes in the resistor-string;
- a digital decoder arranged to receive the digital data and generate a signal that controls each of the switches;
- and
- a ramp switch unit in which each of ramp switches is connected to each of the nodes in the resistor-string;
- an output buffer circuit for inputting the converted analog data;
- and
- a ramp signal that is independent of a change of temperature or a threshold voltage;
- wherein each of the ramp switches is a MOS device;
- and
- wherein each MOS device has its gate driven by a separate ramp switch control signal;
- each MOS device source input is connected to a different node of the resistor-string;
- and drains of the MOS device are connected together to generate the ramp signal.
A driving method of a source for an active matrix EL display, comprising the steps of:
- receiving a main clock signal and generating an enable signal for sequentially storing a digital data;
- sequentially storing the digital data by the enable signal and outputting the stored digital data in parallel;
- converting the outputted digital signal into an analog signal using output nodes of a resistor string to generate a ramp signal to be used as a reference voltage during the digital to analog conversion;
- and
- outputting the converted analog data and the ramp signal;
- wherein each output node of the resistor string is connected to a gate input of a separate MOS device and drains of the MOS device are connected together to generate the ramp signal;
- and
- wherein the generated ramp signal is independent of a change of temperature or a threshold voltage.
Dependencies are inferred from the claim text.