Koninklijke Philips Corporation N.V.

U.S. Philips Corporation

Chi Mei Optoelectronics Corporation

Iain M Hunter

Mark Thomas Johnson

Adrianus Sempel

Edward Willem Albert Young

Martin John Edwards

Steven Charles Deane

Mark Johnathan Childs

Nigel David Young

Alan G Knapp

Neil C Bird

An EL display device is operable in analogue and digital modes. In the analogue mode a current is supplied to the EL display elements () in dependence on a data signal () supplied to the pixel, and in the digital mode one of two voltages is provided across the EL display elements in dependence on the data signal supplied to the pixel. This enables the display to have a low power standby mode in which a digital drive scheme is implemented. This is particularly appropriate for static images and preferably for images without grey scales. The first mode is the normal current addressing mode.

Electroluminescent display device

A display device, for example a liquid crystal display device (), and driving method are provided that avoid the need to provide the display device with display data (e.g. video) containing individual display settings for each pixel. The display device comprises an array of pixels (---) and an array of processing elements (---), each processing element being associated with a respective pixel or group of pixels. The processing elements (---) perform processing of compressed input display data at pixel level. The processing elements (---) decompress the input data to determine individual pixel settings for their associated pixel or pixels. The processing elements (---) then drive the pixels (---) at the individual settings. A processing element may interpolate pixel settings from input data allocated to itself and one or more neighbouring processing elements. Alternatively, the processing elements may have knowledge of the pixel locations of pixels associated with it, and use this information to determine whether one or more of its pixels needs to be driven in response to common input data received by the plural processing elements.

Display devices and driving method therefor

An active matrix electroluminescent display device has an array of pixels (), each pixel having a plurality of current-driven display elements (), for example comprising organic electroluminescent material, connected in a series arrangement with one another and with drive means () operable to control the current through the respective series arrangement. By sub-dividing each pixel in this way, the high voltage drops, that can occur along power supply lines, are reduced thus improving the uniformity of the light outputs from the display elements across the display area.

Active matrix electroluminescent display device

Grey scale linearity and power efficiency in active matrix (O) LEDs are enhanced by storing the grey value in a memory circuit, coupled to an adjusting circuit, preferably via a current mirror.

Display device

A reset driving scheme for addressing a switching mirror display enables current to flow in two directions through the switching elements. The display is forced into a predefined state and drives the display into the other optical states by using an addressable TFT providing a continous current.

Light switching device with reset

A display device has current-addressed pixels, with the currents being supplied by driver circuitry which comprises a transistor ( ) for applying a charging voltage to a switched capacitor arrangement (Ci, S , S ) arranged to selectively charge and discharge the capacitor (Ci) at a predetermined rate to a charging voltage. A transistor control voltage (Vref) is applied to a control terminal of the transistor which is adjusted depending on the transistor threshold voltage to ensure that the capacitor (Ci) is charged to the charging voltage irrespectively of the value of the threshold voltage. This enables an accurately controllable current to be provided which is used to drive the current-addressed pixels.

Display device having current-addressed pixels

Grey scale linearity and power efficiency in active matrix (O) LEDs are enhanced by operating the display in a switched mode.

An active matrix electroluminescent display device comprises an array of display pixels ( ) which each include a current-driven electroluminescent display element ( ) connected to a driving device ( ) controlling the current flowing through the display element in a drive period according to a voltage stored on a capacitance ( ) and determined by a data signal applied in a preceding address period. In order to compensate for ageing effects in the display element, electro-optic devices ( ) are included in the pixel for adjusting the voltage stored on the capacitance in dependence on the light output of its display element during the address period.

In an active matrix electroluminescent display device the drive current through an EL display element ( ) in each pixel ( ) in a drive period is controlled by a driving device ( ) based on a drive signal applied to the pixel in preceding address period and stored as a voltage on an associated storage capacitor ( ). In order to counteract the effects of display element ageing through which the light output of an element for a given drive signal level diminishes over time, the pixel includes a feedback circuit ( ) which is responsive to the potential difference across the display element in an initial part of the drive period indicative of the extent of ageing and which is arranged to adjust the voltage stored on the storage capacitance accordingly.

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Brighton, United Kingdom

Iain M Hunter