Micro-LED amplitude control system
A control system for an LED array relies on defining a first and a second group of separately addressed LED pixels, with the first group including pixels with an average current no less than the current at a Q point and a second group including pixels with an average current less than the current at a Q point. An amplitude signal provided to the first group of separately addressed LED pixels is selectively modulated, while providing a DC mode 100% duty cycle. An amplitude signal provided to the second group of separately addressed LED pixels is fixed, and a modulated duty cycle is provided.
1. A control method for a light emitting diode (LED) array, comprising:
defining a first and a second group of separately addressed LED pixels, with the first group including pixels with an average current no less than the current at a Q point and a second group including pixels with an average current less than the current at the Q point, wherein the Q point is at a maximum external quantum efficiency (EQE) of an EQE versus current density curve for the LED array, the average current defined by an image to be provided by the LED array;
selectively modulating, by a digital to analog converter (DAC), an amplitude of a first signal provided to LED pixels of the first group, the first signal further including a fixed duty cycle pulse width; and
fixing, by a pulse width modulator (PWM), an amplitude of a second signal provided to LED pixels of the second group, the second signal further including a modulated duty cycle.
2. The control method for an LED array of claim 1 , wherein the first signal is a direct current (DC) mode 100% duty cycle signal.
3. The control method for an LED array of claim 1 , wherein the amplitude of the first signal is set at Iampi*D i , where Iampi is a current amplitude defined by the image and D i is the fixed duty cycle.
4. The control method for an LED array of claim 1 , wherein the amplitude of the second signal is set at the Q point for the LED and the duty cycle is set at D i *Iampi/IQ, where Iampi is a current amplitude defined by the image, D i is a pixel duty cycle, and IQ is the current at the Q point of the EQE versus current density curve.
5. The control method for an LED array of claim 1 , wherein additional groups of separately addressed LED pixels are determined, each group having a defined range of image amplitudes.
6. The control method for an LED array of claim 1 , wherein the individually addressed LED pixels present the image provided by an image processing unit.
7. A control system for a light emitting diode (LED) array, comprising:
first and second groups of individually addressed LED pixels, the first group including pixels with an average current no less than the current at a Q point of the individual LED and a second group including pixels with an average current less than the current at a Q point of the individual LED, the Q point is the maximum external quantum efficiency (EQE) of an EQE versus current curve for the individual LED, the average current defined by an image to be provided by the LED array;
a digital to analog controller (DAC) module able to selectively adjust amplitude of signals; and
a pulse width modulator acting with the DAC module to supply the first group of LED pixels with a first signal including a fixed duty cycle and a modulated amplitude, and the second group of LED pixels with a second signal with a fixed amplitude with the DAC and a modulated duty cycle.
8. The control system for an LED array of claim 7 , wherein the first signal is a direct current (DC) mode 100% duty cycle signal.
9. The control system for an LED array of claim 7 , wherein the DAC module further comprises multiple DAC units.
10. The control system for an LED array of claim 7 , wherein the individually addressed LED pixels present the image provided by an image processing unit.
11. The control system for an LED array of claim 7 , further comprising more than two groups of separately addressed LED pixels; and
wherein the DAC module is able to selectively adjust an amplitude of a respective signal provided to each of the multiple groups of separately addressed LED pixels.
12. The control system for an LED array of claim 7 , wherein the amplitude of the second signal is less than the amplitude of the first signal.
13. The control system for an LED array of claim 7 , wherein the second signal has amplitude fixed to approach peak external quantum efficiency (EQE) and lower overall system power usage.
14. A control method for a light emitting diode (LED) array, comprising:
providing a first and a second group of individually addressed LED pixels with the first group including pixels with an average current no less than the current at a Q point and a second group including pixels with an average current less than the current at the Q point, wherein the Q point is at a maximum external quantum efficiency (EQE) of an EQE versus current density curve for the LED array, the average current defined by an image to be provided by the LED array;
supplying, by a pulse width modulator, the first group with a first signal that includes a fixed duty cycle and a modulated amplitude; and
supplying, by a digital to analog converter, the second group with a second signal that includes a modulated duty cycle and a fixed amplitude signal.
15. The control method for an LED array of claim 14 , wherein the first signal is a direct current (DC) mode 100% duty cycle signal.
16. The control method for an LED array of claim 14 , wherein the individually addressed LED pixels present an image provided by an image processing unit.
17. The control method for an LED array of claim 14 , wherein the second signal has amplitude decreased and duty cycle increased with respect to the first signal.
18. The control method for an LED array of claim 14 , wherein the second signal has amplitude decreased and duty cycle increased with respect to the first signal to approach peak external quantum efficiency (EQE) and lower overall system power usage.
19. The control method for an LED array of claim 14 , wherein additional groups of separately addressed LED pixels are determined, each group having a defined, different signal amplitude.