Analog to digital conversion device, illuminance sensor device, and electronic apparatus comprising the illuminance sensor device

Patent metadata

Field	Value
Publication number	US-9893736-B2
Application number	US-201314389922-A
Country	US
Kind code	B2
Filing date	Mar 28, 2013
Priority date	Apr 9, 2012
Publication date	Feb 13, 2018
Grant date	Feb 13, 2018

Abstract

An analog to digital conversion device has a plurality of, two, for example, analog to digital converters, and a reference charge quantity interchange section arranged and configured to interchange, among the plurality of analog to digital converters, reference quantities of electric charge (e.g., reference currents or reference capacitances) to be used therein during an analog to digital conversion period.

First claim

The invention claimed is:

1. An analog to digital conversion device comprising:
a plurality of analog to digital converters; and
a reference charge quantity interchange section arranged and configured to interchange among the plurality of analog to digital converters reference quantities of electric charge to be used therein during an analog to digital conversion period,
wherein the analog to digital converters consist of n analog to digital converters, where n is an integer of two or more,
the analog to digital conversion device comprising a reference current source to supply each of the n analog to digital converters with n reference currents used as the reference quantities of electric charge, wherein the reference charge quantity interchange section interchanges the reference currents among the n analog to digital converters every one-nth (1/n) of the analog to digital conversion period such that each of the n analog to digital converters uses the n reference currents by time-division scheme.

2. An analog to digital conversion device comprising:
a plurality of analog to digital converters; and
a reference charge quantity interchange section arranged and configured to interchange among the plurality of analog to digital converters reference quantities of electric charge to be used therein during an analog to digital conversion period,
wherein the analog to digital converters consist of n analog to digital converters, where n is an integer of two or more,
the analog to digital conversion device comprising n reference capacitors providing each of the n analog to digital converters with reference capacitances used as the reference quantities of electric charge, wherein the reference charge quantity interchange section interchanges the reference capacitors among the n analog to digital converters every one-nth (l/n) of the analog to digital conversion period such that each of the n analog to digital converters uses the reference capacitances of the n reference capacitors by time-division scheme.

3. An analog to digital conversion device comprising:
a plurality of analog to digital converters; and
a reference charge quantity interchange section arranged and configured to interchange among the plurality of analog to digital converters reference quantities of electric charge to be used therein during an analog to digital conversion period,
wherein each analog to digital converter comprises:
a charge circuit having a capacitor for storing electric charge corresponding to an input current to the analog to digital converter;
a discharge circuit configured to discharge the electric charge stored in the capacitor of the charge circuit;
a reference voltage source configured to supply a reference voltage;
a comparator configured to compare an output voltage output from the charge circuit with the reference voltage output from the reference voltage source;
a switch configured to connect an output of the reference voltage source to an output of the charge circuit to charge the output of the charge circuit up to the reference voltage; and
a control circuit controlling the discharge circuit, the control circuit being configured to count a number of discharges by the discharge circuit, based on outputs of the comparator, and output a digital value corresponding to the number of discharges.

4. An illuminance sensor device comprising:
the analog to digital conversion device according to claim 1 ;
a first photodiode having spectral characteristics of an infrared region; and
a second photodiode having spectral characteristics of from a visible to an infrared region,
wherein the analog to digital conversion device has two analog to digital converters, one of which is supplied with an input current from the first photodiode and the other of which is supplied with an input current from the second photodiode.

5. An illuminance sensor device comprising:
the analog to digital conversion device according to claim 1 ;
a first photodiode provided with a filter transmitting light in a red region;
a second photodiode provided with a filter transmitting light in a green region;
a third photodiode provided with a filter transmitting light in a blue region; and
a fourth photodiode having spectral characteristics of from a visible to an infrared region,
the analog to digital conversion device having four analog to digital converters, which are first to fourth analog to digital converters, wherein
the first analog to digital converter is supplied with an input current from the first photodiode,
the second analog to digital converter is supplied with an input current from the second photodiode,
the third analog to digital converter being supplied with an input current from the third photodiode, and
the fourth analog to digital converter being supplied with an input current from the fourth photodiode.

6. Electronic apparatus comprising:
a liquid crystal panel configured to display a screen;
a backlight device configured to illuminate the liquid crystal panel;
a backlight control unit configured to control luminance of light of the backlight device; and
the illuminance sensor device according to claim 4 ,
the backlight control unit controlling the luminance of light of the backlight device based on digital signals output from the analog to digital converters of the illuminance sensor device.

7. The illuminance sensor device according to claim 4 , wherein the analog to digital converters of the analog to digital conversion device consist of n analog to digital converters, where n is an integer of two or more, and
the analog to digital conversion device comprises a reference current source to supply each of the n analog to digital converters with n reference currents used as the reference quantities of electric charge, wherein the reference charge quantity interchange section interchanges the reference currents among the n analog to digital converters every one-nth (1/n) of the analog to digital conversion period such that each of the n analog to digital converters uses the n reference currents by time-division scheme.

8. The illuminance sensor device according to claim 4 , wherein the analog to digital converters of the analog to digital conversion device consist of n analog to digital converters, where n is an integer of two or more, and
the analog to digital conversion device comprises n reference capacitors providing each of the n analog to digital converters with reference capacitances used as the reference quantities of electric charge, wherein the reference charge quantity interchange section interchanges the reference capacitors among the n analog to digital converters every one-nth (1/n) of the analog to digital conversion period such that each of the n analog to digital converters uses the reference capacitances of the n reference capacitors by time-division scheme.

9. The illuminance sensor device according to claim 4 , wherein each analog to digital converter of the analog to digital conversion device comprises:
a charge circuit having a capacitor for storing electric charge corresponding to an input current to the analog to digital converter;
a discharge circuit configured to discharge the electric charge stored in the capacitor of the charge circuit;
a reference voltage source configured to supply a reference voltage;
a comparator configured to compare an output voltage output from the charge circuit with the reference voltage output from the reference voltage source;
a switch configured to connect an output of the reference voltage source to an output of the charge circuit to charge the output of the charge circuit up to the reference voltage; and
a control circuit controlling the discharge circuit, the

Assignees

• Sharp Kk

Inventors

• Sato Hideki
• Inoue Takahiro

Classifications

• G09G3/3406

  Control of illumination source (illumination devices structurally associated with liquid crystal cells G02F1/1336) · CPC title

• H03M1/0634

  by averaging out the errors, e.g. using sliding scale · CPC title

• G02F1/13318

  Circuits comprising a photodetector · CPC title

• H03M1/123

  Simultaneous, i.e. using one converter per channel but with common control or reference circuits for multiple converters · CPC title

• G01J2001/444

  Compensating; Calibrating, e.g. dark current, temperature drift, noise reduction or baseline correction; Adjusting · CPC title