Matrix element voltage sensing for precharge
AssigneeClare Micronix Integrated Systems, Inc.
InventorJames Everitt
Life of this patent
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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.
Claims25
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, the calibration time being based on a comparison between a plurality of display conduction voltage samples;
- 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.
A method of calibrating a display device having at least one electroluminescent element and a display driver, the method comprising:
- (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.
A calibration circuit for a display device, comprising:
- 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 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.
A calibration circuit for a display device, comprising:
- 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.
Dependencies are inferred from the claim text.