Sharp Kabushiki Kaisha Corporation

Sharp Display Technology Corporation

Adnan Heganovic

Tong Lu

Michael James Brownlow

Kohhei Tanaka

Ryo Yonebayashi

Masahito Sano

Kaoru Yamamoto

When a current-driven display device with an internal compensation method operates in a pause driving mode, a non-light emission period according to a light emission duty is provided in both a refresh frame period and a non-refresh frame period, and an on-bias applying period for applying on-bias to a drive transistor in a pixel circuit is provided in both the non-light emission periods. In the non-light emission period in the refresh frame period, an on-bias applying period is provided in a period from when data writing with threshold compensation is performed to when the light emission period starts. Thus, even when the light emission duty is low, the difference in the stress state of the drive transistor between the refresh frame period and the non-refresh frame period is reduced.

Display device and method for driving same

A pixel circuit for a display device minimizes the one horizontal time while maintaining accurate compensation of the threshold voltage of the drive transistor, by extending the compensation phase beyond the data programming phase. The pixel circuit includes a drive transistor configured to control an amount of current to a light-emitting device during an emission phase and a storage capacitor connected between the gate of the drive transistor and the light-emitting device for compensating a threshold voltage of the drive transistor. During a combined data programming and threshold compensation phase, data is programmed and the threshold voltage of the drive transistor is partially compensated, with the data voltage being stored by the internal capacitance of the light-emitting device. The data voltage remains stored during an extended compensation phase in which the drive transistor is further compensated. The pixel circuit includes switch transistors that control the application of supply voltages to the drive transistor, storage capacitor, and light-emitting device during the different phases of operation.

Fast 1H OLED pixel circuit applying data to anode

A pixel circuit operates to output a high drive current for high-current display applications by operating the drive transistor in the triode region. To maintain operation of the drive transistor in the triode region in a stable manner, the source-drain voltage dependence of the output current of the drive transistor is compensated with a bias transistor, which keeps the drain voltage of the drive transistor constant at a target drain voltage. The bias transistor is controlled by an operational amplifier (Opamp) running a negative feedback loop to ensure a fixed target voltage occurs at the drain of the drive transistor. To configure the negative feedback loop, the Opamp output terminal is connected to the gate of the bias transistor, with the negative terminal being connected to the drain of the drive transistor and the positive terminal being connected to a voltage supply line that supplies the target voltage.

High current active matrix pixel architecture

A pixel circuit includes a drive transistor configured to control an amount of current to a light emitting device during an emission phase depending upon a voltage applied to a control terminal of the drive transistor, the drive transistor having a first terminal and a second terminal. During a first phase, an anode of the light emitting device is set to a reference voltage and the first terminal of the drive transistor is set to a fixed data voltage such that the drive transistor is stressed with a fixed source-to-gate voltage to prevent a drift of a threshold voltage in the drive transistor thereby preventing a drift in screen brightness. During a second phase, the anode of the light emitting device is set to the reference voltage and the first terminal of the drive transistor is set to a voltage of the first power supply.

Light emitting device driving circuit and related method

A pixel circuit that drives a light-emitting device employs a diode-connection compensation scheme that compensates for threshold variations of the diode connecting switch that diode connects the drive transistor during a threshold compensation phase. The pixel circuit operates to reduce the impact of threshold voltage variations of the diode connecting switch to improve brightness uniformity and picture quality. The pixel circuit includes two compensation capacitors in addition to the storage capacitor for data programming to control the flow and magnitude of a rebalancing current through the diode connecting switch in such a way to cancel excess or deficit of charge caused by threshold voltage variations of the diode connecting switch due to capacitive coupling between the gate node of the switch and the storage capacitor. Therefore, the circuit configuration employs a triple-capacitor structure to significantly improve compensation performance and reliability.

Pixel circuit with reduced sensitivity to threshold variations of the diode connecting switch

A pixel circuit for driving a light-emitting device for a display device is operable in an initialization phase, a compensation phase, a data programming phase, and an emission phase. The one horizontal time is minimized while maintaining accurate compensation of the threshold voltage of the drive transistor, and the pixel circuit further employs a varactor to compensate for variations in the threshold voltage of the drive transistor and for parasitic capacitances that arise within the pixel circuit. A capacitance of the varactor varies with a voltage at a node Nconstituting an electrical connection during the compensation phase of the drive transistor, the light-emitting device, a storage capacitor, and the varactor. The use of the capacitance variation of the varactor accounts for a variation in the threshold voltage of the drive transistor and for parasitic capacitances in the pixel circuit. The varactor may be implemented as a thin film transistor that operates as a variable capacitor.

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Oxford, United Kingdom

Adnan Heganovic