Driving apparatus and method for light emitting diode display
The present invention provides a driving apparatus, method and system for a light emitting device, suitable for use in an active matrix organic light emitting diode (AMOLED) display, which has an adjustable reference voltage, so as to compensate for degradation in brightness due to LED materials decay.
1. A driving apparatus for a light emitting device, which has an adjustable input reference voltage, the driving apparatus comprising:
a driving transistor, having a gate connected to a first node;
the light emitting device, serially connected to the driving transistor at a second node, so as to constitute a light emitting path, wherein, the light emitting path is connected in between a system high voltage and a system low voltage, such that when the driving transistor is activated, the system high voltage drives the light emitting device to make it emit the light;
a maintain capacitor, connected to the first node and to the system high voltage, a first transistor, having a gate connected to a scanning line, a source connected to a data line, and a drain connected to a third node;
a second transistor, having a gate connected to the scanning line, a source connected to the third node, and a drain connected to the first node;
a third transistor, having a gate connected to the second node, a source connected to an adjustable reference voltage, and a drain connected to the third node.
2. The driving apparatus of claim 1 , wherein, when the resistance of the LED increases, the voltage at the third node decreases toward a value approaching that of the reference voltage, so as to cause the current through the driving transistor and the light emitting device to increase, and thus for the LED to maintain its original brightness value.
3. The driving apparatus of claim 2 , wherein the system high voltage level is a first predetermined voltage, the system low voltage level is a second predetermined voltage, the scanning line voltage is a third predetermined voltage, the data line voltage is a fourth predetermined voltage, and the reference voltage is a fifth predetermined voltage.
4. The driving apparatus of claim 3 , wherein when the driving transistor is P-type, the reference voltage is set less than the data line voltage.
5. The driving apparatus of claim 3 , wherein when the driving transistor is N-type, the reference voltage is set greater than the data line voltage.
6. The driving apparatus of claim 2 , wherein the light emitting device comprises an organic light emitting diode.