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US 8,476,846 B1Granted
Stochastic signal density modulation for optical transducer control
AssigneeCypress Semiconductor Corporation
InventorsDavid Van Ess, Patrick N. Prendergast
Life of this patent
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Abstract
A controller for optical transducers uses stochastic signal density modulation to reduce electromagnetic interference.
Claims16
A method of controlling one or more light emitting diodes (LEDs), comprising:
- generating a stochastic signal density modulation signal;
- controlling a light intensity output from the one or more LEDs by modulating a controllable current with the stochastic signal density modulation signal having a frequency greater than a uniform frequency modulation and free of spectral peaks, wherein the stochastic signal density modulation signal has a reduced electromagnetic interference content relative to the uniform frequency modulation;
- and
- comparing a stochastic value to a programmed number to generate the stochastic signal density modulation signal.
1 more element
An apparatus, comprising:
- a stochastic signal density modulation circuit adapted to generate a stochastic signal density modulation signal;
- a current control circuit adapted to control a light intensity output from one or more light emitting diodes by modulating a controllable current with the stochastic signal density modulation signal having a frequency greater than a uniform frequency modulation and free of spectral peaks, wherein the stochastic signal density modulation signal has a reduced electromagnetic interference content relative to the uniform frequency modulation;
- and
- a comparator adapted to compare a state of a stochastic state machine to a programmed number to generate the stochastic signal density modulation signal.
1 more element
A processing device, comprising:
- a controllable current supply coupled to a light-emitting diode;
- and
- a stochastic signal density modulator (SSDM) circuit coupled to the controllable current supply, wherein the SSDM circuit is configured to provide a stochastic control signal to the controllable current supply to control a light intensity output of the light-emitting diode and to reduce electromagnetic interference, and wherein the stochastic control signal comprises a signal density corresponding to a stored signal density value;
- and
- a comparator adapted to compare a state of a stochastic state machine to a programmed number to provide the stochastic control signal.
2 more elements
Dependencies are inferred from the claim text.