Light monitor

• US 20060097136A1
• Filed: 06/16/2005
• Published: 05/11/2006
• Est. Priority Date: 11/11/2004
• Status: Active Application

• Current Assignee: STMicroelectronics Limited (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Limited (STMicroelectronics NV)
• Inventors: Raynor, Jeffrey, Baxter, Patrick
• Granted Patent: US 7,265,332 B2
• Time in Patent Office: Days
• US Class Current: 250/214.0AL
• CPC Class Codes: G01J 1/32 adapted for automatic variation of the measured or reference value regulation of light intensity G05D25/00
• CPC Class Codes: G01J 1/46 using a capacitor

Abstract

A light monitor includes a single semiconductor substrate. A light to frequency (LTF) converter is on the single semiconductor substrate, a threshold comparator is on the single semiconductor substrate and coupled to an output of the light to frequency converter, and a light intensity calculator is on the single semiconductor substrate and coupled to an output of the threshold comparator.

Claims

1-24. -24. (canceled)

25. A light monitor comprising:

a single semiconductor substrate;

a light to frequency (LTF) converter on said single semiconductor substrate;

a threshold comparator on said single semiconductor substrate and coupled to an output of said LTF converter; and

a light intensity calculator on said single semiconductor substrate and coupled to an output of said threshold comparator.

26. A light monitor according to claim 25, wherein said light intensity calculator comprises:

a counter; and

a clock signal generator for providing a clock signal to said counter, and comprising

a current source, and

a charge sensing amplifier circuit coupled to said current source and comprising a first feedback capacitor.

27. A light monitor according to claim 25, wherein said light intensity calculator scales a signal generated by said LTF converter in accordance with the clock signal, and accumulates a resulting scaled signal in said counter for calculating a scaled measurement variable.

28. A light monitor according to claim 25, wherein said light intensity calculator comprises:

a counter;

a reference signal generator; and

a crystal oscillator whose output provides a clock signal to said counter;

said counter accumulating a reference signal generated by said reference signal generator for calculating a reference variable.

29. A light monitor according to claim 28, wherein said counter comprises a gain adjustment calculator for calculating a gain adjustment that includes deviation between the reference variable and an expected value of the reference variable.

30. A light monitor according to claim 29, wherein said counter accumulates a signal from said LTF converter for calculating a measurement variable.

31. A light monitor according to claim 30, wherein said counter adjusts the measurement variable in accordance with the gain adjustment for calculating a scaled measurement variable.

32. A light monitor according to claim 27, wherein said threshold comparator comprises at least one register for containing a value of a first limit variable, and compares a value of the scaled measurement variable from said light intensity calculator with a value of the first limit variable.

33. A light monitor according to claim 32, wherein said threshold comparator outputs to an external system an indicator of whether the value of the scaled measurement variable exceeds the value of the first limit variable.

34. A light monitor according to claim 33, wherein said threshold comparator comprises a single output pin for outputting the indicator to the external system.

35. A light monitor according to claim 27, wherein said threshold comparator comprises a plurality of registers for containing a value of a first limit variable and a second limit variable, said threshold comparator comparing a value of the scaled measurement variable with a value of the first limit variable and the second limit variable.

36. A light monitor according to claim 35, wherein said threshold comparator outputs to an external system an indicator of whether the value of the scaled measurement variable

exceeds the value of the first limit variable;

is less than the value of the second limit variable;

or

is between the values of the first limit variable and the second limit variable.

37. A light monitor according to claim 35, wherein said threshold comparator comprises outputs coupled to a bi-directional interface.

38. A light monitor according to claim 37, wherein the bi-directional interface comprises at least one of an I2C interface, an SPI interface and a CAN interface.

39. A light monitor according to claim 37, wherein the bi-directional interface comprises a wireless interface.

40. A light monitor according to claim 39, wherein the wireless interface comprises a Zigbee interface.

41. A light monitor according to claim 39, wherein said threshold comparator outputs the values of the first and second limit variables to said plurality of registers through said bi-directional interface.

42. An electronic device comprising:

a light source for generating light;

a light monitor providing a signal representing an intensity of ambient light, and comprising

a single semiconductor substrate,

a light to frequency (LTF) converter on said single semiconductor substrate,

a threshold comparator on said single semiconductor substrate and coupled to an output of said LTF converter, and

a light intensity calculator on said single semiconductor substrate and coupled to an output of said threshold comparator; and

a controller having an input for receiving the signal representing the intensity of ambient light from said light monitor, and providing a control signal to said light source in response thereto;

said light source altering the generated light based upon the control signal.

43. An electronic device according to claim 42, wherein said light intensity calculator comprises:

a counter; and

a clock signal generator for providing a clock signal to said counter, and comprising

a current source, and

a charge sensing amplifier circuit coupled to said current source and comprising a first feedback capacitor.

44. An electronic device according to claim 42, wherein said light intensity calculator scales a signal generated by said LTF converter in accordance with the clock signal, and accumulates a resulting scaled signal in said counter for calculating a scaled measurement variable.

45. An electronic device according to claim 42, wherein said light intensity calculator comprises:

a counter;

a reference signal generator; and

a crystal oscillator whose output provides a clock signal to said counter;

said counter accumulating a reference signal generated by said reference signal generator for calculating a reference variable.

46. An electronic device according to claim 44, wherein said threshold comparator comprises at least one register for containing a value of a first limit variable, and compares a value of the scaled measurement variable from said light intensity calculator with a value of the first limit variable.

47. An electronic device according to claim 44, wherein said threshold comparator comprises a plurality of registers for containing a value of a first limit variable and a second limit variable, said threshold comparator comparing a value of the scaled measurement variable with a value of the first limit variable and the second limit variable.

48. An electronic device according to claim 42, wherein said light source, said light monitor and said controller define a lighting control system for at least one of a portable computing device back-light control system, a mobile telecommunications device back-light control system, a street lighting control system, and an automotive lighting control system.

49. A method for making a light monitor comprising:

forming on a single semiconductor substrate a light to frequency (LTF) converter, a threshold comparator coupled to an output of the LTF converter, and a light intensity calculator coupled to an output of the threshold comparator.

50. A method according to claim 49, wherein forming the light intensity calculator comprises forming a counter, and a clock signal generator for providing a clock signal to the counter, the clock signal generator comprising a current source, and a charge sensing amplifier circuit coupled to the current source and comprising a first feedback capacitor.

51. A method according to claim 49, wherein the light intensity calculator scales a signal generated by the LTF converter in accordance with the clock signal, and accumulates a resulting scaled signal in the counter for calculating a scaled measurement variable.

52. A method according to claim 49, wherein forming the light intensity calculator comprises forming a counter, a reference signal generator, and a crystal oscillator whose output provides a clock signal to the counter, and wherein the counter accumulates a reference signal generated by the reference signal generator for calculating a reference variable.

53. A method according to claim 51, wherein forming the threshold comparator comprises forming at least one register for containing a value of a first limit variable, said threshold comparator for comparing a value of the scaled measurement variable from the light intensity calculator with a value of the first limit variable.

54. A method according to claim 51, wherein forming the threshold comparator comprises forming a plurality of registers for containing a value of a first limit variable and a second limit variable, the threshold comparator for comparing a value of the scaled measurement variable with a value of the first limit variable and the second limit variable.