System and methods for power conservation for AMOLED pixel drivers
A system is provided for conserving energy in an AMOLED display having pixels that include a drive transistor and an organic light emitting device, and an adjustable source of a supply voltage for the drive transistor. The system monitors the content of a selected segment of the display, sets the supply voltage to the minimum supply voltage required for the current content of the selected segment of the display, determines whether the number of pixels requiring a supply voltage larger than the set value is greater than a predetermined threshold number, and, when the answer is negative, reduces the supply voltage by a predetermined step amount.
1. A method of conserving energy in an AMOLED display having pixels that include a drive transistor and an organic light emitting device, and an adjustable source of a supply voltage for the drive transistor, the method comprising
monitoring the content of a selected segment of the display,
setting the supply voltage to the minimum supply voltage required for the current content of said selected segment of the display, and
determining whether the number of pixels in said selected segment that require a supply voltage larger than the set value, is greater than a predetermined threshold number and, when the answer is negative, reducing the supply voltage by a predetermined step amount.
2. The method of claim 1 in which said monitoring of said content of said selected segment of the display comprises monitoring the voltage supplied to the gate input of said drive transistor input.
3. An active matrix organic light emitting device display, comprising:
an adjustable supply voltage source;
a plurality of pixels, each coupled to the adjustable supply voltage source, each pixel including:
an organic light emitting device;
a drive transistor having a source and a drain, one of which is coupled to the organic light emitting device and the other of which is coupled to the adjustable supply voltage source;
a plurality of programming voltage inputs coupled to the gates of the drive transistors of the plurality of pixels, the programming voltage inputs providing a programming voltage indicative of a desired brightness of each of the plurality of pixels; and
a supply voltage controller coupled to the adjustable voltage source to regulate the level of a supply voltage supplied to each of the drive transistors, the supply voltage controller
monitoring the content of a selected segment of the display,
setting the supply voltage to the minimum supply voltage required for the current content of said selected segment of the display, and
reducing the supply voltage by a predetermined step amount when the number of pixels in the selected segment that require a supply voltage larger than the set value, is greater than a predetermined threshold number.
4. The active matrix organic light emitting device display of claim 3 in which said content of said selected segment of the display is monitored by monitoring the voltage supplied to the gate input of said drive transistor input.