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US 10,764,975 B2Granted
Pulse-width-modulation control of micro light emitting diode
AssigneeFacebook Technologies, LLC
InventorGareth John Valentine
Life of this patent
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Abstract
Embodiments relate to a light-emitting-diode (LED) cell that includes a LED and a controller. The controller receives a brightness data signal and generates a driving signal corresponding to the brightness data signal. The controller includes a comparator that receives the brightness data signal and a control waveform signal. The controller is coupled to a switched current source that generates a driving current based on the driving signal.
Claims20
A light-emitting-diode (LED) display device comprising:
- a LED disposed within a cell of the LED display device, the LED configured to emit light;
- and
- a controller disposed within the cell of the LED display device, the controller receiving an analog brightness control data signal corresponding to a desired brightness of the LED, and generating a driving signal having a fixed amplitude and a varying duration corresponding to an amplitude of the analog brightness control data signal, the controller comprising:
- a sample and hold circuit configured to receive the analog brightness control data signal, and store the analog brightness control data signal as a frame brightness signal in a storing element responsive to receiving a select signal having a predetermined value, wherein the received analog brightness control data signal is not based on a voltage at a terminal of the LED, and
- a comparator circuit having an input coupled to an output of the sample and hold circuit, the comparator circuit configured to receive the frame brightness signal and a control waveform signal, and generate the driving signal based on a comparison between a voltage level of the frame brightness signal and a voltage level of the control waveform signal, wherein the control waveform signal is a periodic signal that changes from a first value to a second value within each display frame;
- and
- a switched current source configured to receive the driving signal and generate a driving current based on the driving signal for driving the LED, the driving current having a fixed amplitude and a varying duration corresponding to the amplitude of the analog brightness control data signal.
4 more elements
A light emitting diode (LED) driver circuit comprising:
- a controller receiving a brightness data signal corresponding to a desired brightness of the LED, and generating a driving signal corresponding to the brightness data signal, the controller comprising:
- a sample and hold circuit configured to receive the brightness data signal, and store the brightness data signal as a frame brightness signal in a storing element responsive to receiving a select signal having a predetermined value, wherein the received brightness data signal is not based on a voltage at a terminal of the LED, and
- a comparator circuit having an input coupled to an output of the sample and hold circuit, the comparator circuit configured to receive the frame brightness signal and a control waveform signal, and generate the driving signal based on a comparison between a voltage level of the frame brightness signal and a voltage level of the control waveform signal, wherein the control waveform signal is a periodic signal that changes from a first value to a second value within each display frame;
- and
- a switched current source configured to receive the driving signal and generate a driving current based on the driving signal for driving the LED.
2 more elements
A method for operating a light-emitting-diode (LED) of an LED display device, the LED display device displaying images in display frames, comprising:
- receiving a digital brightness data signal corresponding to a desired brightness of the LED in a subsequent display frame;
- converting the digital brightness data signal to an analog brightness data signal;
- storing the analog brightness data signal as a frame brightness signal responsive to receiving a select signal having a predetermined value, wherein the stored analog brightness data signal is not based on a voltage at a terminal of the LED;
- receiving a sawtooth pulse signal;
- generating a control signal by comparing the stored frame brightness signal and the sawtooth pulse signal, wherein the sawtooth pulse signal is a periodic signal that changes from a first value to a second value within each display frame;
- generating a driving current having a fixed amplitude and a varying duration based on the generated control signal, the duration of the generated driving current corresponding to an amplitude of the analog brightness data signal;
- and
- driving the LED using the generated control signal.
5 more elements
Dependencies are inferred from the claim text.