Color control for dynamic scanning backlight

• US 7,548,030 B2
• Filed: 03/17/2008
• Issued: 06/16/2009
• Est. Priority Date: 03/29/2007
• Status: Active Grant

• Current Assignee: Polaris PowerLED Technologies, LLC (Microchip Technology Incorporated)
• Original Assignee: Microsemi Corp. - Analog Mixed Signal Group, Ltd. (Microchip Technology Incorporated)
• Inventors: Ferentz, Alon, Korcharz, Dror, Peker, Arkadiy, Langer, Tamir
• Primary Examiner(s): Vu; David Hung
• Assistant Examiner(s): Le; Tung X
• Application Number:
  US12/049,410
• Publication Number:
  US 20080238341A1
• Time in Patent Office: 456 Days
• Field of Search: 315/149, 315/155, 315/185.R, 315/224, 315246-247, 315/291, 315/294, 315/297, 315/299, 315/307, 315/308, 315/312, 315/360, 345 83- 84, 345 87- 88, 345/99, 345/102, 345/204, 345/213, 345/214, 362/227, 362/612, 362/800
• US Class Current: 315/307
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2320/08 Arrangements within a display terminal for setting, manually or automatically, display parameters of the display terminal
• CPC Class Codes: G09G 2360/147 the originated light output being determined for each pixel
• CPC Class Codes: G09G 3/2092 Details of a display terminals using a flat panel, the details relating to the control arrangement of the display terminal and to the interfaces thereto suitable for both CRT and flat panel G09G5/003; specific for a CRT G09G1/165
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A method of controlling the output of a luminaire by receiving a first target signal associated with a first frame; generating a first light output control signal for an on time portion of the first frame, the light output control signal responsive to the received first target signal; sampling a light output during the on time portion of the first frame, the light output being responsive to the first light output control signal; receiving a second target signal associated with a second frame, the second frame following the first frame; comparing the received second target signal with the sampled light output of the on time portion of the first frame; and generating an error signal responsive to the comparing.

Claims

1. A method of controlling the output of a luminaire comprising:

receiving a first target signal associated with a first frame;

generating a first light control signal for an on time portion of said first frame, said light control signal responsive to said received first target signal;

sampling a light output during said on time portion of said first frame, the light output being responsive to said first light control signal;

receiving a second target signal associated with a second frame, said second frame following said first frame;

comparing said received second target signal associated with said second frame with said sampled light output of said on time portion of said first frame; and

generating an error signal responsive to said comparing.

2. A method according to claim 1, further comprising:

generating a second light control signal for an on time portion of said second frame, said generated second light control signal responsive to said generated error signal.

3. A method according to claim 1, wherein said generating said first light control signal comprises generating a pulse width modulated signal exhibiting a period and a duty cycle, and wherein said sampling the light output comprises:

repeatedly sampling the light output during said on time portion of said first frame; and

averaging said repeated samplings to generate an average per said period.

4. A method according to claim 3, wherein said sampled light output of said first frame being compared with said received second target signal is said average of said repeated samplings of a last period of said on time of said first frame.

5. A method according to claim 1, further comprising adjusting said first light control signal during said on time portion of said first frame responsive to said sampled light output of said on time portion of said first frame.

6. A method according to claim 5, wherein said generating said first light control signal comprises generating a pulse width modulated signal exhibiting a period and a duty cycle, and

wherein said adjusting said first light control signal comprises adjusting said duty cycle.

7. A method according to claim 5, further comprising generating a pulse width modulated light control signal for an on time portion of said second frame exhibiting said period and a duty cycle responsive to said generated error signal.

8. A method according to claim 1, wherein said generating said first light control signal for said on time portion of said first frame comprises:

enabling a pulse width modulation exhibiting a duty cycle and a period;

enabling a feedback controller associated with said pulse width modulation; and

adjusting, responsive to said enabled feedback controller, said duty cycle of said first light control signal during said on time portion of said first frame responsive to said sampled light output of said on time portion of said first frame.

9. A method according to claim 1, further comprising:

receiving a synchronizing signal;

waiting a first period; and

enabling said first light control signal for said on time portion of said first frame at the expiration of said first period.

10. A method according to claim 9, wherein said first period is a function of the zone associated with the luminaire.

11. A method of controlling the output of a luminaire comprising a plurality of LED strings, the method comprising:

receiving a first target signal associated with a first frame;

generating a plurality of pulse width modulated first light control signals for a portion of said first frame responsive to said received first target signal, said pulse width modulated first light output signals exhibiting a period and a respective first duty cycle for each of the plurality of LED strings;

sampling a light output of the plurality of LED strings at discrete intervals during said portion of said first frame, the light output being responsive to said pulse width modulated first light control signals;

averaging said samples of said first frame over at least one of said period;

adjusting, during said first frame, said first duty cycle of at least one of said plurality of pulse width modulated first light control signals responsive to said averaging;

receiving a second target signal associated with a second frame, said second frame following said first frame;

comparing said received second target signal with a least one of said averages; and

generating a plurality of pulse width modulated second light control signals for a portion of said second frame exhibiting said period and a respective second duty cycle for each of the plurality of LED strings, said second duty cycles being responsive to said comparing.

12. A backlight luminaire controller for a frame by frame changing target signal, the backlight luminaire controller comprising:

a synchronizing controller;

a difference circuit;

a feedback controller responsive to said synchronizing controller and said difference circuit;

a pulse width modulation (PWM) functionality exhibiting a duty cycle and a period, said duty cycle being responsive to said feedback controller; and

an averager responsive to said feedback controller and operative to generate at least one average over an integer multiple of said period,

said feedback controller operative responsive to said synchronizing controller to generate a duty cycle for the next frame responsive to at least one of said generated at least one average of the current frame and a received target signal of said next frame.

13. A backlight system comprising:

a backlight luminaire controller according to claim 12;

a luminaire arranged to produce light responsive to said PWM functionality, said produced light exhibiting a luminance and a color balance;

a sensor arranged to receive a portion of said produced light;

a low pass filter arranged to receive the output of said sensor; and

an analog to digital converter in communication with said low pass filter,

wherein said averager is in communication with said analog to digital converter, said integer is one, and said averager is operative to output an indication of said luminance and said color balance of said produced light for at least one particular period of said pulse width modulation functionality.

14. A backlight system according to claim 13, wherein said low pass filter exhibits a cutoff frequency on the order of 1/10 of the frequency of said pulse width modulation period.

15. A backlight system according to claim 14, wherein said pulse width modulation functionality exhibits an n-bit division of said period, and said analog to digital converter exhibits a sampling rate less than the frequency associated with said n-bit division of said period.

16. A backlight system according to claim 13, further comprising a calibration matrix coupled to said averager and operative to convert said at least one average indication to a system consonant with the frame by frame changing target signal.

17. A backlight system according to claim 13, wherein said feedback controller is operative in a single cycle mode.

18. A backlight system according claim 17, wherein said synchronizing controller is operative to operate said feedback controller in said single cycle mode for a single cycle prior to producing light of said next frame from said luminaire.

19. An apparatus for controlling a luminaire responsive to a target signal with a value changing on a frame by frame basis, the apparatus comprising:

a feedback controller;

a signal generator, responsive to said feedback controller and operative to generate a light control signal for an on time portion of a first frame responsive to a first frame target signal value;

a sampler operative to sample a light output during said on time portion of the first frame, said light output being responsive to said generated light control signal of the first frame; and

a difference circuit arranged to compare a second frame target signal value with said sampled light output of said on time portion of the first frame and generate an error signal responsive to said comparison,

wherein said feedback controller is operative to control said signal generator to generate a light control signal for an on time portion of the second frame responsive to said error signal.

20. An apparatus according to claim 19, wherein said feedback controller is further operative to control said signal generator so as to adjust said light control signal during said on time portion of the first frame responsive to said sampled light output.

21. An apparatus according to claim 20, wherein said signal generator comprises a pulse width modulated functionality exhibiting a period and a duty cycle, and wherein said sampler is operative to:

repeatedly sample said light output during said on time portion of the first frame; and

average said repeated samplings to generate an average per said period,

wherein said control of said signal generator by said feedback controller is responsive to said average of said repeated samplings.

22. An apparatus according to claim 21, wherein said sampled light output of said first frame being compared with said second frame target signal value is said average of said repeated samplings of a last period of said on time of the first frame.

23. An apparatus according to claim 21, wherein said adjusting of said feedback controller comprises adjusting said duty cycle.

24. An apparatus according to claim 21, wherein said signal generator is further operative to generate a pulse width modulated signal for an on time portion of the second frame exhibiting said period and a duty cycle responsive to said feedback controller.

25. An apparatus according to claim 19, wherein said signal generator comprises a pulse width modulation functionality, and wherein said generating said light control signal for said on time portion of the first frame comprises:

enable said pulse width modulation exhibiting a duty cycle and a period; and

enable said feedback controller.