Display driver circuits
First Claim
1. A display driver for a passive organic electroluminescent display, the display driver comprising:
- a controllable current generator to provide a variable current drive output to the display, the current generator comprising at least one bipolar transistor in series with the current drive output;
whereby the display brightness is adjustable by controlling the current generator to vary the current drive to the display.
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Accused Products
Abstract
Display driver circuits are described for driving organic light emitting diode displays, particularly passive matrix displays, with greater efficiency. The display drivers comprise a controllable current generator to provide a variable current drive output to an OLED display, the current generator comprising at least one bipolar transistor in series with the current drive output. The display brightness is adjustable by controlling the current generator to vary the current drive to the display. Preferably the bipolar transistor has an emitter terminal substantially directly connected to a power supply line of the driver to reduce losses in the driver. A corresponding method is also described. By employing a bipolar transistor current drive and varying display brightness by controlling the current an efficient driver-display combination is obtained.
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Citations
22 Claims
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1. A display driver for a passive organic electroluminescent display, the display driver comprising:
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a controllable current generator to provide a variable current drive output to the display, the current generator comprising at least one bipolar transistor in series with the current drive output;
whereby the display brightness is adjustable by controlling the current generator to vary the current drive to the display. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. Display driver circuitry for an organic electroluminescent display, the display comprising a plurality of organic electroluminescent pixels, each pixel being addressed by one of each of a first plurality and a second plurality of driving electrodes, the display driver circuitry comprising:
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a power supply connection;
a plurality of electrode driver outputs for driving a plurality of said display driving electrodes;
a plurality of variable current driver circuits, each having a control input and providing a variable current drive for a said electrode driver output, and each comprising a bipolar current drive transistor having an emitter terminal substantially directly connected to said power supply connection and a collector terminal coupled to a said electrode driver output; and
control circuitry coupled to the control inputs of said driver circuits and configured to provide an analog signal to each said control input for controlling the variable current drive provided by each said driver circuit;
whereby the brightness of each pixel is adjustable. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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- 16. A column electrode display driver for a passive organic light-emitting diode (OLED) display, the display comprising a matrix of OLEDs and a plurality of row and column electrodes, each OLED having an anode coupled to a column electrode and a cathode coupled to a row electrode, the display driver comprising a plurality of independently adjustable, high compliance bipolar column current drivers each having an analog input for providing a variable column current drive to the display.
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20. Display driver circuitry for an organic electrolmninescent display, the display comprising a plurality of organic electroluminescent pixels, each pixel being addressed by one of each of a first plurality and a second plurality of driving electrodes, the display driver circuitry comprising:
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a power supply connection;
a plurality of electrode driver outputs for driving a plurality of said display driving electrodes;
a plurality of current driver circuits for each driving electrode for providing a plurality of current drives for a said electrode driver output, each having a control input and each comprising a bipolar current drive transistor having an emitter terminal substantially directly connected to said power supply connection and a collector terminal coupled to a said electrode driver output; and
control circuitry coupled to the control inputs of said driver circuits and configured to provide a signal to each said control input for controlling the current drive provided to a said electrode driver output;
whereby the brightness of each pixel is adjustable.
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21. A method of increasing the efficiency of a current driver for an organic electroluminescent display, the method comprising:
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providing a current drive for the display using a bipolar transistor with an emitter terminal substantially directly connected to a power line; and
using a voltage for the power line such that when the organic electroluminescent display is at substantially a maximum desired brightness the bipolar transistor current drive is operating substantially at-its limit of compliance. - View Dependent Claims (22)
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Specification