Northrop Grumman Systems Corporation

United Technologies Corporation

US Government As Represented by the Secretary of the Army

Norhtrop Grumman Corporation

Mohan L Kapoor

Thomas J Rebeschi

Edward L Young

Russell A Budzilek

Dominic L Monarchie

Daniel J Toffolo

Peter O Shanaghan

Pixel luminance of an electroluminescent display panel is controlled by a row driver applying a voltage equal to the panel's threshold voltage, and column drivers applying the voltage value above the threshold voltage to bring the pixel to the desired luminance. Each column driver independently samples a stepped ramp voltage signal at its own predetermined time selected as a function of the desired luminance. Each column driver then holds the sampled voltage value, and applies to its corresponding column electrode at the appropriate time a voltage equal to the sampled voltage value. The voltage rate of change of each individual step of the stepped ramped voltage signal can be controlled to vary the luminance levels, and to uniformly separate each of the luminance levels.

Gray-scale stepped ramp generator with individual step correction

A method and apparatus for providing a driver circuit for an electroluminescent display panel comprising a row driver including positive row drive elements and negative row drive elements, a first power lead with a first predetermined voltage V.sub.neg connected in series through a first switch connection to a first node, the first node connected to a first current limiter to the negative row drive elements, a second current limiter operably connected between a first fixed potential to a second node, the second node connected to the positive row drive elements, a third current limiter connected between the negative row drive element and the second fixed potential, a second power lead with a second predetermined voltage V.sub.pos connected in parallel to the first node through a second switch connection and a power storage device connected between the first and second nodes, wherein the voltage across the positive and negative row drive elements is selectable, via predetermined operation of the first and second switch connections, between a) V.sub.neg and b) the difference between V.sub.pos and V.sub.neg.

Symmetric row drive for an electroluminescent display

A thin film electroluminescent display panel is driven with either a symmetric or asymmetric drive scheme which includes at least one equalizing voltage pulse per write cycle to remove carriers trapped at the interfaces of dielectric layers and phosphor layer in order to stabilize the charge of each display panel pixel. The present invention reduces the smearing, latent image and pseudo persistence problems caused by carriers being retained and accumulated at the dielectric and phosphor layer interfaces.

Increased brightness drive system for an electroluminescent display panel

A power supply for providing a symmetric drive for an AC electroluminescent (EL) display panel includes a single power supply which provides two voltage signal values of opposite polarity V.sub.pos,V.sub.neg to the panel's row drivers. The supply also corrects the difference between the two voltage signal values V.sub.pos,V.sub.neg as a function of the difference between the maximum column driver voltage value V.sub.col and its nominal value to reduce latent images on the display panel. By utilizing a single switching regulator to generate the opposite polarity row voltages V.sub.pos,V.sub.neg the circuit complexity and cost associated with providing a symmetric drive for an EL panel is reduced.

Symmetric drive for an electroluminscent display panel

A simplified row driver switching circuit for display panels and the like, including particularly electroluminescent (EL) panels, as well as plasma panels, using inductance coupling between the power supply and the row electrodes. The circuit limits energy transfer to each row electrode of the EL panel through the inductance coupling, minimizing the effects of destructive arcing caused by inter-electrode shorts. The circuit is energy conservative and eliminates the need for, for example, -160 V and +220 V power supplies. Two row driver circuits are disclosed (FIGS. 4 & 6), the latter allowing the row electrodes to be driven to negative, as well as positive, voltages. Inductor(s) (L of FIG. 4; L.sub.1 & L.sub.2 of FIG. 6) are used to store and transfer energy to the row electrode load (C.sub.panel) and then back to the power source (V.sub.in), as various switches are pulsed 'on' and released. The same power supply can be used for both the row driver and the column driver (FIG. 7).

Row driver for EL panels and the like with inductance coupling

A simplified row driver switching circuit for display panels and the like, including particularly electroluminescent (EL) panels, as well as plasma panels, using transformer coupling between the power supply and the row electrodes. The circuit limits energy transfer to each row electrode of the EL panel to minimize the effects of destructive arcing caused by inter-electrode shorts. The circuit is energy conservative and eliminates the need for, for example, -160V and +220V power supplies, and provides reduced stress levels for many components through transformer coupling, and all active switches are driven from ground potential. Two row driver circuits are disclosed (FIGS. 4 & 6), the latter, using a split primary coil and double sets of paired switches, allows the row electrodes to be driven to negative, as well as positive, voltages. The primary and secondary windings on the transformer (T.sub.1 of FIGS. 4 & 6) are used to store and transfer energy to the essentially capacitive row electrode load (C.sub.panel) and then back to the power source (V.sub.in), as various associated switches are pulsed 'on' and released. The same power supply can be used for both the row driver and the column driver (FIG. 8).

Row driver for EL panels and the like with transformer coupling

Circuitry for selectively sustaining a gaseous discharge display panel to splay selected information which circuitry permits the use of a single power supply.

Growing community of inventors

Orange, CT, United States of America

Mohan L Kapoor