A current-type driver for organic light emitting diode displays

摘要

An OLED Driver circuit decreases capacitance charging time in the driver circuit by providing a high current signal to the circuit during a sample phase which rapidly charges the capacitances. A lower current signal is then provided during a hold phase to drive the corresponding OLED. The current levels are produced by operating the current driver of the circuit in the sub-threshold region where the output current is exponentially proportional to a reference voltage. The reference voltage may be controlled to provide a difference in reference voltage that produces the desired output current reduction. The driver circuit also includes a voltage driver that pre-charges the current driver gate to reduce settling time. The pre-charge level is provided during an initial portion of a sample phase to reduce the time it takes for the voltage at a current driver gate of the circuit to reach the desired signal level. The pre-set voltage is either selected by reference to the input signal level or by reference to a global level. In one implementation the global level is the black-level voltage for the corresponding display.