Electroluminescent display device
First Claim
1. An electroluminescent (EL) display device comprisingan array of display pixels,each display pixel comprisingan EL display element anda driving circuit that is configured to drive the EL display element based on a data signal and a supply voltage anda mode controller that is configured to control the supply voltage to each display pixel,wherein:
- each pixel is operable in first and second modes, wherein;
in the first mode, the mode controller is configured to provide a first value of the supply voltage to place a driving transistor in the driving circuit in a linear mode, so that an analogue current is supplied to the EL display element by the driving circuit in dependence on the data signal supplied to the pixel, andin the second mode, to provide a second value of the supply voltage to place the driving transistor in a switching mode, so that one of two voltages is provided across the EL display element by the driving circuit in dependence on the data signal supplied to the pixel;
the first value of the supply voltage is configured to provide a first voltage drop across the driving transistor;
the second value of the supply voltage is configured to provide a second voltage drop across the driving transistor; and
the second voltage drop is substantially less than the first voltage drop.
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Accused Products
Abstract
An EL display device is operable in analogue and digital modes. In the analogue mode a current is supplied to the EL display elements (2) in dependence on a data signal (6) 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.
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Citations
24 Claims
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1. An electroluminescent (EL) display device comprising
an array of display pixels, each display pixel comprising an EL display element and a driving circuit that is configured to drive the EL display element based on a data signal and a supply voltage and a mode controller that is configured to control the supply voltage to each display pixel, wherein: -
each pixel is operable in first and second modes, wherein; in the first mode, the mode controller is configured to provide a first value of the supply voltage to place a driving transistor in the driving circuit in a linear mode, so that an analogue current is supplied to the EL display element by the driving circuit in dependence on the data signal supplied to the pixel, and in the second mode, to provide a second value of the supply voltage to place the driving transistor in a switching mode, so that one of two voltages is provided across the EL display element by the driving circuit in dependence on the data signal supplied to the pixel; the first value of the supply voltage is configured to provide a first voltage drop across the driving transistor; the second value of the supply voltage is configured to provide a second voltage drop across the driving transistor; and the second voltage drop is substantially less than the first voltage drop. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of driving an electroluminescent (EL) display device comprising an array of pixels, each pixel comprising an electroluminescent (EL) display element and a drive circuit, the method comprising, for each pixel of the display:
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selecting an analogue or a digital drive mode; when the analogue mode is selected, providing a first set of voltages to the drive circuit to place the drive circuit in a linear mode, and supplying a data signal to the pixel thereby resulting in an analogue current being supplied to the EL display element; when the digital mode is selected, providing a second set of voltages to the drive circuit to place the drive circuit in a switching mode, and supplying a data signal to the pixel thereby driving the EL display element to one of two states, wherein the first set of voltages are configured to provide a first voltage drop across a driving element of the drive circuit, the second set of voltages are configured to provide a second voltage drop across the driving element, and the second voltage drop is substantially less than the first voltage drop. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification