Method of driving an emitter array
Methods and apparatus for driving an emitter array are described. A method includes determining a thermal environment profile for a plurality of emitters of the emitter array, computing a current pulse profile for at least one of the plurality of emitters based on the thermal environment profile, and applying a current pulse with the computed current pulse profile to the at least one of plurality of emitters.
1. A display comprising:
an emitter comprising a matrix of light emitting diodes;
a thermal environment module configured to determine a thermal environment profile of the light emitting diodes, the thermal environment profile including thermal responses of each light emitting diode affected by others of the light emitting diodes;
a current profile computation module configured to compute, for each light emitting diode based on the thermal environment profile, a current pulse profile tailored to a respective one of the light emitting diodes; and
a driver configured to apply, to each light emitting diode, a current pulse with the computed current pulse profile for the respective light emitting diode to produce substantially uniform light output from the respective light emitting diode over a time interval of the current pulse even though a temperature of the respective light emitting diode changes during the current pulse.
2. The display according to claim 1 , wherein a shape of the current pulse is substantially rectangular in which the current pulse monotonically increases from a start of the time interval to a later point of the time interval.
3. The display according to claim 2 , wherein the current pulse monotonically increases from the start of the time interval to an end of the time interval.
4. The display according to claim 2 , wherein the current pulse monotonically increases from the start of the time interval to a point at which the current pulse remains constant until an end of the time interval.
5. The display according to claim 1 , wherein an increase of the current pulse varies with position of the respective light emitting diode within the matrix.
6. The display according to claim 1 , wherein the current profile computation module is configured to use at least one previous pulse event to compute the current pulse profile.
7. The display according to claim 1 , wherein the current pulse applied to at least two different light emitting diodes in the matrix have different pulse shapes.
8. The display according to claim 1 , wherein a pulse shape of the current pulse reflects an increase in current over a time period of the current pulse.
9. The display according to claim 1 , wherein the thermal environment module is configured to consider a thermal time constant of a sub mount or printed circuit board (PCB) on which the light emitting diodes are disposed to determine the thermal environment profile.
10. The display according to claim 1 , further comprising a forward voltage measuring module coupled to the thermal environment module, the forward voltage measuring module configured to measure forward voltages of the light emitting diodes and provide the forward voltages to the thermal environment module, the thermal environment module configured to estimate actual temperatures of the light emitting diodes based on the forward voltages to predict a temperature behavior of the light emitting diodes.
11. The display according to claim 1 , further comprising a split current module configured to deploy a split current algorithm that combines information from a light emitting diode color table with information from a specification source to divide available current into current pulse sets for two emitters, the light emitting diode color table to be compiled using information provided by the thermal environment module to determine a ratio of a first emitter color to a second emitter color during the current pulse to achieve a uniform color temperature distribution.
12. The display according to claim 1 , wherein the light emitting diodes are micro-light emitting diodes.
13. A method of driving an emitter array in a display, the method comprising:
determining a thermal environment profile of light emitting diodes in the emitter array, the thermal environment profile including thermal responses of each light emitting diode affected by others of the light emitting diodes;
computing, for each light emitting diode based on the thermal environment profile, a current pulse profile tailored to a respective one of the light emitting diodes; and
applying, to each light emitting diode, a current pulse with the computed current pulse profile for a respective one of the light emitting diodes to produce uniform light output from the respective light emitting diode over a time interval of the current pulse even in response to a change in a temperature of the respective light emitting diode changes during the current pulse.
14. The method according to claim 13 , wherein a shape of the current pulse is substantially rectangular in which the current pulse monotonically increases from a start of the time interval to a later point of the time interval.
15. The method according to claim 13 , wherein an increase of the current pulse varies with position of the respective light emitting diode within the array.
16. The method according to claim 13 , further comprising using at least one previous pulse event to compute the current pulse profile.
17. The method according to claim 13 , further comprising considering a thermal time constant of a sub mount or printed circuit board (PCB) on which the light emitting diodes are disposed to determine the thermal environment profile.
18. The method according to claim 13 , further comprising:
measuring forward voltages of the light emitting diodes; and
estimating actual temperatures of the light emitting diodes based the forward voltages to predict a temperature behavior of the light emitting diodes.
19. A display comprising:
a printed circuit board (PCB), the PCB comprising:
an emitter comprising a matrix of light emitting diodes disposed on the PCB;
a thermal environment module configured to determine a thermal environment profile of the light emitting diodes, thermal responses of each light emitting diode affected by a thermal time constant of the PCB and others of the light emitting diodes determined to form the thermal environment profile;
a current profile computation module configured to compute, for each light emitting diode based on the thermal environment profile, a current pulse profile tailored to a respective one of the light emitting diodes; and
a driver configured to apply, to each light emitting diode, a current pulse with the computed current pulse profile for the respective light emitting diode to produce uniform light output from the respective light emitting diode over an entire time interval of the current pulse even in response to a change in a temperature of the respective light emitting diode changes during the current pulse.
20. The display according to claim 19 , wherein the PCB further comprises a forward voltage measuring module coupled to the thermal environment module, the forward voltage measuring module configured to measure forward voltages of the light emitting diodes and provide the forward voltages to the thermal environment module, the thermal environment module configured to estimate actual temperatures of the light emitting diodes based the forward voltages to predict a temperature behavior of the light emitting diodes.