Eliminating flicker in LED-based display systems
AssigneeMaxim Integrated Products, Inc.
InventorsGianluca Mariano, Suresh Hariharan
Life of this patent
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Abstract
A system includes a driver circuit, a modulator circuit, and a reset circuit. The driver circuit drives a plurality of light emitting diodes via a switch. The switch is controlled by a first signal having a first frequency. The driver circuit controls brightness of the light emitting diodes based on a second signal including a plurality of pulses. The modulator circuit modulates the first signal using a direct sequence spread spectrum modulation. The direct sequence spread spectrum modulation uses a sequence generated based on the first signal. The reset circuit resets the modulator circuit at each of the plurality of pulses of the second signal. The modulator circuit repeats the sequence at each of the plurality of pulses of the second signal.
Claims12
A system comprising:
- a driver circuit that drives a plurality of light emitting diodes via a switch, wherein the switch is controlled by a first signal having a first frequency, wherein the driver circuit controls brightness of the light emitting diodes based on a second signal including a plurality of pulses, wherein the plurality of pulses of the second signal has a second frequency, wherein the first signal is different than the second signal, and wherein the first frequency is different than the second frequency;
- a modulator circuit that modulates the first signal using a direct sequence spread spectrum modulation, wherein the direct sequence spread spectrum modulation uses a sequence generated based on the first signal;
- and
- a reset circuit that resets the modulator circuit at each of the plurality of pulses of the second signal,
- wherein the modulator circuit repeats the sequence generated based on the first signal at each of the plurality of pulses of the second signal and eliminates flicker in the light emitting diodes by eliminating harmonics having frequencies less than the second frequency by repeating the sequence generated based on the first signal at each of the plurality of pulses of the second signal.
A method comprising:
- driving a plurality of light emitting diodes via a switch;
- controlling the switch by a first signal having a first frequency;
- modulating the first signal using a direct sequence spread spectrum modulation, wherein the direct sequence spread spectrum modulation uses a sequence generated based on the first signal;
- controlling brightness of the light emitting diodes based on a second signal including a plurality of pulses, wherein the plurality of pulses of the second signal has a second frequency, wherein the first signal is different than the second signal, and wherein the first frequency is different than the second frequency;
- repeating the sequence generated based on the first signal at each of the plurality of pulses of the second signal;
- and
- eliminating flicker in the light emitting diodes by eliminating harmonics having frequencies less than the second frequency by repeating the sequence generated based on the first signal at each of the plurality of pulses of the second signal.
Dependencies are inferred from the claim text.