Method and apparatus for 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
Claims13
A system for measuring output from a photodetector comprising:
- a) a photodetector operable to generate a photodetector output signal;
- b) a ramp generator operable to generate a ramp signal;
- and
- c) a comparator operable to compare the ramp signal with the photodetector output signal and generate an output signal resulting in a pulse width of length proportional to the time it takes the ramp signal to exceed the photodetector output signal.
A system for generating a ramp voltage signal comprising:
- a) a capacitor operable to generate a ramp signal, wherein the ramp voltage signal has a low voltage level;
- and
- b) a voltage divider operable to set the low voltage level of the ramp voltage.
A method of converting a varying voltage level to a varying width pulse, the method comprising:
- a) generating a ramp signal for use as an input to a comparator;
- b) providing a photodetector output signal as an input to the comparator;
- c) producing an output signal of the comparator having a crossover point;
- and
- d) 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.