Method and apparatus for a phototransistor pulse width converter
AssigneeIntel Corporation
InventorPhilip W. Doberenz
Life of this patent
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Abstract
A system for measuring output voltage from a photodetector. The system includes a photodetector that generates a photodetector output signal, a ramp generator that generates a ramp signal and a comparator that outputs a signal level based on which of the two signals is larger. The voltage level of the output of the phototransistor determines how long it will take for the ramp voltage to catch up and cross over the phototransistor voltage. The crossover time determines the width of an output signal and is directly proportional to the voltage level. A microcontroller can then determine the pulse width by multiple samplings and therefore determine photodetector voltage.
Claims8
A system for measuring output from a photodetector comprising:
- a photodetector to generate a photodetector output signal;
- a ramp generator to generate a ramp signal;
- and
- a comparator to:
- compare the ramp signal with the photodetector output signal;
- and
- generate an output signal having a pulse width of length proportional to a time period during which the ramp signal reaches a level at which it exceeds the photodetector output signal, the output signal combined with the photodetector output signal as feedback.
A method of converting a varying voltage level to a varying width pulse, the method comprising:
- generating a ramp signal for use as an input to a comparator;
- providing a photodetector output signal as an input to the comparator;
- producing an output signal of the comparator having a crossover point;
- and
- sampling the output signal of the comparator to produce a digital pulse of a width proportional to the varying voltage level.
Dependencies are inferred from the claim text.