ILLUMINANCE SENSOR AND LIGHT CONTROL APPARATUS

• US 20080179498A1
• Filed: 01/29/2008
• Published: 07/31/2008
• Est. Priority Date: 01/31/2007
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Shimizu, Takayuki
• Granted Patent: US 7,554,065 B2
• Time in Patent Office: Days
• US Class Current: 250/214AL
• CPC Class Codes: H05B 31/50 specially adapted for ac
• CPC Class Codes: H05B 45/12 using optical feedback
• CPC Class Codes: H05B 45/38 using boost topology

Abstract

The following members are included: a light receiving element which outputs an electric signal corresponding to ambient light; an A/D converter which converts the electric signal output from the light receiving element into a digital signal; a register which stores the digital signal output from the A/D converter and determines the duty ratio of a PWM signal based on the digital signal; and a PWM controller which outputs the PWM signal based on the duty ratio output from the register.

Claims

1. An illuminance sensor, comprising:

light receiving means for outputting an electric signal corresponding to ambient brightness;

A/D conversion means for converting the electric signal output from the light receiving means into a digital signal;

duty ratio determination means including;

an illuminance register storing the digital signal output from the A/D conversion means; and

duty ratio registers each storing a duty ratio which is output based on a value of the illuminance register, the duty ratio determination means determining the duty ratio of a PWM signal based on the digital signal output from the A/D conversion means; and

PWM signal output means for outputting the PWM signal based on the duty ratio output from the duty ratio determination means.

2. The illuminance sensor as defined in claim 1,

wherein, the light receiving means, the A/D conversion means, the duty ratio determination means, and the PWM signal output means are integrated so as to constitute a single semiconductor device.

3. The illuminance sensor as defined in claim 1, further comprising:

temperature compensation means having same temperature characteristics as the light receiving means;

light receiving signal logarithmic compression means for logarithmic-compressing the electric signal which is output from the light receiving means and outputting the electric signal as a voltage;

temperature correction signal logarithmic compression means for logarithmic-compressing the electric signal which is output from the temperature compensation means and outputting the electric signal as a voltage;

potential difference output means for outputting, as an analog signal, a difference between electric potentials output which are from the light receiving signal logarithmic compression means and the temperature correction signal logarithmic compression means, respectively;

D/A conversion means being included in the A/D conversion means and re-converting the digital signal which is output from the A/D conversion means into an analog signal; and

analog signal comparison means for comparing (i) a magnitude of the analog signal which is output from the potential difference output means with (ii) a magnitude of the analog signal which is output from the D/A conversion means, and outputting a digital signal control signal for controlling the digital signal output from the A/D conversion means in such a way as to equalize the magnitudes of the analog signals,

the A/D conversion means increasing or decreasing a value of the digital signal which is output therefrom, based on the digital signal control signal.

4. The illuminance sensor as defined in claim 1,

wherein, the duty ratio determination means further includes register information input means, and

the register information input means inputs the duty ratio to the duty ratio registers from register information output means which is provided outside of the illuminance sensor.

5. The illuminance sensor as defined in claim 1,

wherein, the duty ratio determination means further includes a duty ratio variation speed adjustment register,

the duty ratio variation speed adjustment register stores a time variation ratio for a case where the duty ratio increases and another time variation ratio for a case where the duty ratio decreases, and

when the duty ratio increases or decreases, the PWM signal output means varies the duty ratio of the PWM signal over time, based on the corresponding time variation ratio stored in the duty ratio variation speed adjustment register.

6. The illuminance sensor as defined in claim 2,

wherein, the duty ratio determination means further includes a duty ratio variation speed adjustment register,

the duty ratio variation speed adjustment register stores a time variation ratio for a case where the duty ratio increases and another time variation ratio for a case where the duty ratio decreases, and

when the duty ratio increases or decreases, the PWM signal output means varies the duty ratio of the PWM signal over time, based on the corresponding time variation ratio stored in the duty ratio variation speed adjustment register.

7. The illuminance sensor as defined in claim 3,

wherein, the duty ratio determination means further includes a duty ratio variation speed adjustment register,

the duty ratio variation speed adjustment register stores a time variation ratio for a case where the duty ratio increases and another time variation ratio for a case where the duty ratio decreases, and

when the duty ratio increases or decreases, the PWM signal output means varies the duty ratio of the PWM signal over time, based on the corresponding time variation ratio stored in the duty ratio variation speed adjustment register.

8. The illuminance sensor as defined in claim 4,

wherein, the duty ratio determination means further includes a duty ratio variation speed adjustment register,

the duty ratio variation speed adjustment register stores a time variation ratio for a case where the duty ratio increases and another time variation ratio for a case where the duty ratio decreases, and

when the duty ratio increases or decreases, the PWM signal output means varies the duty ratio of the PWM signal over time, based on the corresponding time variation ratio stored in the duty ratio variation speed adjustment register.

9. The illuminance sensor as defined in claim 5,

wherein, the time variation ratios of the duty ratio are set so as to be lower than 1/400.

10. The illuminance sensor as defined in claim 6,

wherein, the time variation ratios of the duty ratio are set so as to be lower than 1/400.

11. The illuminance sensor as defined in claim 7,

wherein, the time variation ratios of the duty ratio are set so as to be lower than 1/400.

12. The illuminance sensor as defined in claim 8,

wherein, the time variation ratios of the duty ratio are set so as to be lower than 1/400.

13. A light control apparatus, comprising the illuminance sensor defined in claim 1.

14. A light control apparatus, comprising the illuminance sensor defined in claim 2.

15. A light control apparatus, comprising the illuminance sensor defined in claim 3.

16. A light control apparatus, comprising the illuminance sensor defined in claim 4.

17. A light control apparatus, comprising the illuminance sensor defined in claim 5.

18. A light control apparatus, comprising the illuminance sensor defined in claim 6.

19. A light control apparatus, comprising the illuminance sensor defined in claim 7.

20. A light control apparatus, comprising the illuminance sensor defined in claim 8.

21. A light control apparatus, comprising the illuminance sensor defined in claim 9.

22. A light control apparatus, comprising the illuminance sensor defined in claim 10.

23. A light control apparatus, comprising the illuminance sensor defined in claim 11.

24. A light control apparatus, comprising the illuminance sensor defined in claim 12.