Photosensor device with dark current cancellation
AssigneeLuxsentek Microelectronics Corp.
InventorsChih-Wei Lin, Chen-Hua Hsi
Life of this patent
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Abstract
The present invention provides a photosensor device, which can cancel a dark current in 1-2 milliseconds. This photosensor device utilizes a small capacitor to quickly accumulate and transform the dark current to a dark-current voltage. Based on the dark-current voltage and an environment temperature, a calibration voltage can be obtained. By cancelling the calibration voltage from the sensed voltage to get a light voltage, which can be amplified to a lux signal. The process is very quick and sensitive, so the photosensor device can be used in an environment under a low luminance.
Claims12
A photosensor device, comprising:
- a first photodiode without being illuminated connected to a first switch-cap circuit comprising a first amplifier, a first switch unit, and a first capacitor, wherein the first photodiode is configured to measure a dark current and the first switch-cap circuit is used to convert the dark current to a first voltage;
- at least one second photodiode with being illuminated connected to a second switch-cap circuit comprising a second amplifier, a second switch unit, and a second capacitor, wherein the second photodiode is configured to sense a light to generate a sensing current, and the second switch-cap circuit is used to convert the sensing current to a second voltage;
- a programmable gain amplifier electrically connected to the first switch-cap circuit and the second switch-cap circuit;
- a temperature tracking table unit for storing a dark current temperature gain table;
- and
- a micro-processing unit connected to the temperature tracking table unit, the first switch-cap circuit, and the second switch-cap circuit, wherein the micro-processing unit generates a control signal used to control switching of the first switch unit and the second switch unit to generate an output voltage (VOUT) according to the temperature tracking unit, and both of the first capacitor and the second capacitor are small capacitors, which are saturated within 1-2 milliseconds.
Dependencies are inferred from the claim text.