Koninklijke Philips Corporation N.v.

Tpo Displays Corporation

William A Steer

David Andrew Fish

Franciscus P M Budzelaar

An active matrix electroluminescent display has means for interrupting the drive of current through the display element. Row driver circuitry for the display has a shift register and logic arrangement () for generating the drive voltage for the interrupting means, and which includes a pulse having a duration which can be varied up to substantially the full field period less the address period. The signal or signals propagated through the shift register arrangement () control the pulse duration. This arrangement provides reduced driver complexity to allow control for the row by row addressing of the pixels with control of the overall light emission period of each row. The control enables a scrolling addressing scheme to be implemented.

Electroluminescent display device with scrolling addressing

An active matrix electroluminescent display device uses a stepped voltage waveform to the input of the pixel, the stepped voltage waveform being voltage-shifted by a previously stored pixel drive voltage before application to the gate of a drive transistor. The level of the voltage shift determines the duty cycle with which the display element is driven, and thereby controls the grey level output. The height of the steps in the stepped voltage waveform is greater than the voltage width of linear operating region of the drive transistor, so that a selected step of the stepped waveform defines a transition from the drive transistor between fully on and fully off. In this way, the drive transistor is never driven in the linear region.

Active matrix organic electroluminescent display device

An active matrix electroluminescent display device comprises an array of display pixels. In each pixel, a first switch connects power from a power supply line to the display element and a second switch routes current from a current-measurement supply line to the display element. The gate voltage applied to a drive transistor is controlled by a feedback system, such that control voltage is controlled in closed loop manner to achieve the desired current. The control voltage can then be used for subsequent addressing of the pixel.

Electroluminescent display devices

An active matrix electroluminescent display device has a current sampling resistor within each pixel in series with the display element. A feedback signal represents the voltage drop across the current sampling resistor and the pixel drive signals are modified in dependence on the feedback signal to control the current driven through the display element. In this way, threshold compensation is provided, whilst enabling a single voltage-driven drive transistor to be employed.

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Stanmore, United Kingdom

William A Steer