Method and circuit arrangement for the ageing compensation of an organic light-emitting diode and circuit arrangement
First Claim
1. Method for the ageing compensation of an organic light-emitting diode (OLED) which is fed from a supply voltage and is switched by means of a driver transistor operated in saturation operation, by means of a driving of the light-emitting diode, the method comprising the following steps of:
- storing at least one desired current-voltage value pair of a desired current-voltage characteristic curve of the light-emitting diode,transferring the driver transistor from saturation operation to linear operation during a measurement cycle,measuring a current value for the current through the light-emitting diode by means of a current measuring circuit in the measurement cycle,determining at least one present current-voltage value pair of a present current-voltage characteristic curve of the light-emitting diode by means of the measured current value,comparing the at least one present current-voltage value pair of the light-emitting diode with the desired current-voltage value pair of the light-emitting diode,generating driving parameters for driving the light-emitting diode in a manner dependent on the result of the comparison,characterized in that the ageing compensation is implemented in a display having a multiplicity of display elements which are formed by a circuit, comprising an OLED, driver transistor, and driving transistor wherein a supply voltage VDD is reduced to an extent such that the driver transistors of the plurality of light-emitting diodes are transferred from saturation operation to linear operation,wherein all of the plurality of light-emitting diodes are switched off before one of the plurality of light-emitting diodes which is to be measured is switched on and for an associated driver transistor of the light-emitting diode which is to be measured the source-drain current IDonlinear through the display supply line is measured,the source-drain voltage of the associated driver transistor for the light-emitting diode which is to be measured is determined by means of the characteristic curve of the associated driver transistor, the gate voltage and the measured source-drain current,a forward voltage value for the light-emitting diode which is to be measured is calculated from the difference between the supply voltage and the calculated source-drain voltage, anda characteristic curve alteration is determined from the comparison of the desired current-voltage value pair with the present current-voltage value pair for the light-emitting diode which is to be measured.
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Abstract
The invention relates to a method and a circuit arrangement for the ageing compensation of an organic light-emitting diode (OLED) which is fed from a supply voltage and is switched by means of a driver transistor operated in saturation operation, by means of a driving of the light-emitting diode. The method comprises the following steps of: storing at least one desired current-voltage value pair of a desired current-voltage characteristic curve of the light-emitting diode; transferring the driver transistor from saturation operation to linear operation during a measurement cycle; measuring a current value for the current through the light-emitting diode by means of a current measuring circuit in the measurement cycle; determining at least one present current-voltage value pair of a present current-voltage characteristic curve of the light-emitting diode by means of the measured current value; comparing the at least one present current-voltage value pair of the light-emitting diode with the desired current-voltage value pair of the light-emitting diode; and generating driving parameters for driving the light-emitting diode in a manner dependent on the result of the comparison.
140 Citations
14 Claims
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1. Method for the ageing compensation of an organic light-emitting diode (OLED) which is fed from a supply voltage and is switched by means of a driver transistor operated in saturation operation, by means of a driving of the light-emitting diode, the method comprising the following steps of:
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storing at least one desired current-voltage value pair of a desired current-voltage characteristic curve of the light-emitting diode, transferring the driver transistor from saturation operation to linear operation during a measurement cycle, measuring a current value for the current through the light-emitting diode by means of a current measuring circuit in the measurement cycle, determining at least one present current-voltage value pair of a present current-voltage characteristic curve of the light-emitting diode by means of the measured current value, comparing the at least one present current-voltage value pair of the light-emitting diode with the desired current-voltage value pair of the light-emitting diode, generating driving parameters for driving the light-emitting diode in a manner dependent on the result of the comparison, characterized in that the ageing compensation is implemented in a display having a multiplicity of display elements which are formed by a circuit, comprising an OLED, driver transistor, and driving transistor wherein a supply voltage VDD is reduced to an extent such that the driver transistors of the plurality of light-emitting diodes are transferred from saturation operation to linear operation, wherein all of the plurality of light-emitting diodes are switched off before one of the plurality of light-emitting diodes which is to be measured is switched on and for an associated driver transistor of the light-emitting diode which is to be measured the source-drain current IDonlinear through the display supply line is measured, the source-drain voltage of the associated driver transistor for the light-emitting diode which is to be measured is determined by means of the characteristic curve of the associated driver transistor, the gate voltage and the measured source-drain current, a forward voltage value for the light-emitting diode which is to be measured is calculated from the difference between the supply voltage and the calculated source-drain voltage, and a characteristic curve alteration is determined from the comparison of the desired current-voltage value pair with the present current-voltage value pair for the light-emitting diode which is to be measured. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification