Matrix element voltage sensing for precharge
First Claim
1. A method of determining a precharge voltage for current-driven devices in a matrix, the method comprising:
- driving a selected current through a target device;
determining a calibration time for a steady-state voltage developed by the target device conducting the selected current;
sampling a calibration display conduction voltage at the calibration time;
producing a calibration value representing the calibration voltage; and
storing the calibration value for later use during normal operation.
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Accused Products
Abstract
A method and apparatus to calibrate an LED matrix display such that a driver will provide a proper precharge voltage to LED elements within the display during a scan period. A current is driven through a calibration element, and a voltage reflecting the steady-state element voltage is measured and stored as a calibration value. A processor controls whether to precharge during the calibration cycle, and determines when the calibration cycle is completed. During subsequent normal scans, a driver applies a voltage based on the stored calibration value to rapidly precharge parasitic capacitance associated with a display element to a proper value, and also drives a selected current through the device.
58 Citations
39 Claims
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1. A method of determining a precharge voltage for current-driven devices in a matrix, the method comprising:
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driving a selected current through a target device;
determining a calibration time for a steady-state voltage developed by the target device conducting the selected current;
sampling a calibration display conduction voltage at the calibration time;
producing a calibration value representing the calibration voltage; and
storing the calibration value for later use during normal operation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An apparatus for driving current in a display device having at least one display element which includes first and second terminal regions, the apparatus comprising:
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a first current driver circuit connected to the first terminal region of the display element and configured to generate a first current;
a second driver circuit configured to connect the second terminal region of the display element to a known voltage source to accept the first current;
a display conduction voltage sensing circuit configured to generate a representation of a display conduction voltage created when the display device conducts a known current; and
a precharge circuit configured to output a precharge voltage to the display element based upon the representation of the display conduction voltage. - View Dependent Claims (12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 39)
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16. A method of calibrating a display device having at least one electroluminescent element and a display driver, the method comprising:
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(i) predetermining a measurement period of time;
(ii) applying a first current to the element from a current start time;
(iii) continuing the current for the predetermined period of time;
(iv) measuring a display device voltage reflecting a voltage of the electroluminescent element at the end of the predetermined period; and
(v) storing a representation of the measured voltage in a memory as a calibration value for later retrieval during a non-calibration mode of the display device.
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27. A calibration circuit for a display device, comprising:
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a current source configured to provide a known current to the display device beginning at a calibration current start time;
a measurement circuit configured to sample display device voltages at directed sample times and create representations of the sampled voltages;
a controller configured toselect a steady-state sample time corresponding to a steady-state response to the known current, direct the measurement circuit to sample the display device voltage at the steady-state sample time to create a corresponding steady-state voltage representation, coordinate transfer to memory of the steady-state voltage representation, and direct retrieval of the steady-state voltage representation during a non-calibration mode of operation; and
a memory configured to store the steady-state voltage representation for retrieval during the non-calibration mode of operation.
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38. A calibration circuit for a display device, comprising:
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a means for providing a known current to the display device beginning at a calibration current start time;
a means for measuring display device sampled voltages at directed sample times to create representations of the sampled voltages;
a controller configured to select a steady-state sample time corresponding to a steady-state response to the known current, direct the measurement circuit to sample the display device voltage at the steady-state sample time to create a corresponding steady-state voltage representation, coordinate transfer to memory of the steady-state voltage representation, and direct retrieval of the steady-state voltage representation during a non-calibration mode of operation; and
a memory configured to store the steady-state voltage representation for retrieval during the non-calibration mode of operation.
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Specification