Circuit arrangement for controlling backlight source and operation method thereof

• US 10,665,177 B2
• Filed: 10/18/2018
• Issued: 05/26/2020
• Est. Priority Date: 11/30/2017
• Status: Active Grant

• Current Assignee: Novatek Microelectronics Corporation (Novatek Microelectronics Corp Limited)
• Original Assignee: Novatek Microelectronics Corporation (Novatek Microelectronics Corp Limited)
• Inventors: Wu, Chung-Wen, Lin, Wen-Chi, Lin, Jiun-Yi
• Primary Examiner(s): Mengistu, Amare
• Assistant Examiner(s): Mathews, Crystal
• Application Number:
  US16/163,593
• Publication Number:
  US 20190164507A1
• Time in Patent Office: 586 Days
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/10 Special adaptations of display systems for operation with variable images
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/36 using liquid crystals

Abstract

A circuit arrangement for controlling a backlight source and an operation method are provided. The circuit arrangement includes a generator. The generator receives a sync signal and generates a pulse width modulation signal synchronous with the sync signal to control the backlight source. The sync signal indicates a frequency of a video including a series of image frames. The sync signal includes a sync period corresponding to a frame of the video. The pulse width modulation signal includes a first waveform pattern in a first sub-period of the sync period and a second waveform pattern in a second sub-period of the sync period. Each of the first waveform pattern and the second waveform pattern includes at least one active pulse. The first waveform pattern is substantially identical to the second waveform pattern.

Claims

1. A circuit arrangement for controlling a backlight source, comprising:

a generator, configured to receive a sync signal and generate a pulse width modulation signal synchronous with the sync signal to control the backlight source, wherein the sync signal indicates a frequency of a video comprising a series of image frames, wherein

the sync signal comprises a sync period corresponding to a frame of the video,

the pulse width modulation signal comprises a first waveform pattern in a first sub-period of the sync period and a second waveform pattern in a second sub-period of the sync period,

each of the first waveform pattern and the second waveform pattern respectively comprises at least one active pulse, and

the first waveform pattern is substantially identical to the second waveform pattern.

2. The circuit arrangement according to claim 1, wherein the generator comprises:

a pulse width modulation control circuit, configured to receive the sync signal from a video processing circuit, wherein the pulse width modulation control circuit checks a frequency of the sync signal, the pulse width modulation control circuit multiplies the frequency of the sync signal to generate a multiplied sync signal when the frequency of the sync signal is lower than a threshold frequency, the pulse width modulation control circuit serves the sync signal as the multiplied sync signal when the frequency of the sync signal is higher than the threshold frequency, and the pulse width modulation control circuit generates the pulse width modulation signal according to the multiplied sync signal; and

a backlight driving circuit, coupled to the pulse width modulation control circuit to receive the pulse width modulation signal, and configured to drive the backlight source of a display panel according to the pulse width modulation signal.

3. The circuit arrangement according to claim 2, wherein the video processing circuit comprises a scaler circuit, and the sync signal comprises a vertical sync signal.

4. The circuit arrangement according to claim 2, wherein the pulse width modulation control circuit checks a time length of the sync period, the pulse width modulation control circuit at least divides the sync period into the first sub-period and the second sub-period when the time length of the sync period exceeds a rated time length, and a duty ratio of the pulse width modulation signal in the first sub-period is equal to a duty ratio of the pulse width modulation signal in the second sub-period.

5. The circuit arrangement according to claim 4, wherein a frequency of the pulse width modulation signal in the first sub-period is equal to a frequency of the pulse width modulation signal in the second sub-period.

6. The circuit arrangement according to claim 2, wherein the pulse width modulation control circuit comprises:

a frequency checking circuit, configured to receive the sync signal from the video processing circuit and check the frequency of the sync signal, wherein the frequency checking circuit multiplies the frequency of the sync signal to generate the multiplied sync signal when the frequency of the sync signal is lower than the threshold frequency, and the frequency checking circuit serves the sync signal as the multiplied sync signal when the frequency of the sync signal is higher than the threshold frequency; and

a pulse width modulation signal generating circuit, coupled to the frequency checking circuit to receive the multiplied sync signal, and configured to generate the pulse width modulation signal to the backlight driving circuit according to the multiplied sync signal and determine a duty ratio of the pulse width modulation signal according to a duty ratio parameter.

7. The circuit arrangement according to claim 2, wherein the pulse width modulation control circuit at least divides the first sub-period into a third sub-period and a fourth sub-period according to the multiplied sync signal.

8. The circuit arrangement according to claim 7, wherein the pulse width modulation signal has a pulses respectively in an initiate period and an end period in the third sub-period, and the pulse width modulation signal has no pulse in a middle period in the third sub-period.

9. The circuit arrangement according to claim 7, wherein the pulse width modulation control circuit comprises:

a frequency checking circuit, configured to receive the sync signal from the video processing circuit and check the frequency of the sync signal, wherein the frequency checking circuit multiplies the frequency of the sync signal to generate the multiplied sync signal when the frequency of the sync signal is lower than the threshold frequency, and the frequency checking circuit serves the sync signal as the multiplied sync signal when the frequency of the sync signal is higher than the threshold frequency;

a period defining circuit, coupled to the frequency checking circuit to receive the multiplied sync signal, and configured to generate a first enablement signal and a second enablement signal according to a timing of the multiplied sync signal, wherein the third sub-period is defined by the first enablement signal, and the fourth sub-period is defined by the second enablement signal;

a first pulse width modulation signal generating circuit, coupled to the period defining circuit to receive the first enablement signal, and configured to generate a first pulse width modulation signal in the third sub-period according to the first enablement signal and determine a duty ratio of the first pulse width modulation signal in the third sub-period according to a duty ratio parameter;

a second pulse width modulation signal generating circuit, coupled to the period defining circuit to receive the second enablement signal, and configured to generate a second pulse width modulation signal in the fourth sub-period according to the second enablement signal and determine a duty ratio of the second pulse width modulation signal in the fourth sub-period according to the duty ratio parameter, wherein a frequency of the second pulse width modulation signal is different from a frequency of the first pulse width modulation signal; and

a superimposing circuit, coupled to the first pulse width modulation signal generating circuit to receive the first pulse width modulation signal, coupled to the second pulse width modulation signal generating circuit to receive the second pulse width modulation signal, and configured to superimpose the first pulse width modulation signal and the second pulse width modulation signal to obtain the pulse width modulation signal.

10. The circuit arrangement according to claim 9, wherein the first pulse width modulation signal generating circuit further determines a phase of the first pulse width modulation signal in the third sub-period according to a delay parameter.

11. An operation method of a circuit arrangement for controlling a backlight source, comprising:

receiving, by a generator, a sync signal indicating a frequency of a video comprising a series of image frames; and

generating, by the generator, a pulse width modulation signal synchronous with the sync signal to control the backlight source, wherein

the sync signal comprises a sync period corresponding to a frame of the video,

the pulse width modulation signal comprises a first waveform pattern in a first sub-period of the sync period and a second waveform pattern in a second sub-period of the sync period,

each of the first waveform pattern and the second waveform pattern respectively comprises at least one active pulse, and

the first waveform pattern is substantially identical to the second waveform pattern.

12. The operation method according to claim 11, wherein the step of generating the pulse width modulation signal comprises:

checking a frequency of the sync signal;

multiplying the frequency of the sync signal to generate a multiplied sync signal when the frequency of the sync signal is lower than a threshold frequency;

serving the sync signal as the multiplied sync signal when the frequency of the sync signal is higher than the threshold frequency;

generating the pulse width modulation signal according to the multiplied sync signal; and

driving, by a backlight driving circuit, the backlight source of a display panel according to the pulse width modulation signal.

13. The operation method according to claim 12, wherein the sync signal comprises a vertical sync signal.

14. The operation method according to claim 12, wherein the step of checking the frequency of the sync signal comprises:

checking a time length of the sync period; and

at least dividing the sync period into the first sub-period and the second sub-period when the time length of the sync period exceeds a rated time length, wherein a duty ratio of the pulse width modulation signal in the first sub-period is equal to a duty ratio of the pulse width modulation signal in the second sub-period.

15. The operation method according to claim 14, wherein a frequency of the pulse width modulation signal in the first sub-period is equal to a frequency of the pulse width modulation signal in the second sub-period.

16. The operation method according to claim 12, wherein the step of generating the pulse width modulation signal comprises:

generating, by a pulse width modulation signal generating circuit, the pulse width modulation signal to the backlight driving circuit according to the multiplied sync signal; and

determining, by the pulse width modulation signal generating circuit, a duty ratio of the pulse width modulation signal according to a duty ratio parameter.

17. The operation method according to claim 12, further comprising:

at least dividing the first sub-period into a third sub-period and a fourth sub-period according to the multiplied sync signal.

18. The operation method according to claim 17, wherein the pulse width modulation signal has pulses respectively in an initiate period and an end period in the third sub-period, and the pulse width modulation signal has no pulse in a middle period in the third sub-period.

19. The operation method according to claim 17, wherein the step of generating the pulse width modulation signal comprises:

generating, by a period defining circuit, a first enablement signal and a second enablement signal according to a timing of the multiplied sync signal, wherein the third sub-period is defined by the first enablement signal, and the fourth sub-period is defined by the second enablement signal;

generating a first pulse width modulation signal in the third sub-period according to the first enablement signal and determining a duty ratio of the first pulse width modulation signal in the third sub-period according to a duty ratio parameter by a first pulse width modulation signal generating circuit;

generating a second pulse width modulation signal in the fourth sub-period according to the second enablement signal and determining a duty ratio of the second pulse width modulation signal in the fourth sub-period according to the duty ratio parameter by a second pulse width modulation signal generating circuit, wherein a frequency of the second pulse width modulation signal is different from a frequency of the first pulse width modulation signal; and

superimposing, by a superimposing circuit, the first pulse width modulation signal and the second pulse width modulation signal to obtain the pulse width modulation signal.

20. The operation method according to claim 19, wherein a phase of the first pulse width modulation signal in the third sub-period is further determined according to a delay parameter by the first pulse width modulation signal generating circuit.

21. A circuit arrangement for controlling a backlight source, comprising:

a generator, configured to receive a sync signal and generate a pulse width modulation signal synchronous with the sync signal to control the backlight source, wherein the sync signal indicates a frequency of a video comprising a series of image frames, wherein

the sync signal comprises a sync period corresponding to a frame of the video,

the pulse width modulation signal comprises a plurality of repeated waveform patterns in a first sub-period and a second sub-period of the sync period, and

each of the repeated waveform patterns comprises at least one active pulse.

22. A circuit arrangement for controlling a backlight source, comprising:

a generator, configured to receive a sync signal and generate a pulse width modulation signal synchronous with the sync signal to control the backlight source, wherein the sync signal indicates a frequency of a video comprising a series of image frames, wherein

the sync signal comprises a sync period corresponding to a frame of the video,

the generator at least divides the sync period into a first sub-period and a second sub-period,

the pulse width modulation signal comprises a first waveform pattern in the first sub-period of the sync period and a second waveform pattern in the second sub-period of the sync period, and

each of the first waveform pattern and the second waveform pattern comprises at least one active pulse.

23. A circuit arrangement for controlling a backlight source, comprising:

a generator, configured to receive a sync signal and generate a pulse width modulation signal synchronous with the sync signal to control the backlight source, wherein the sync signal indicates a frequency of a video comprising a series of image frames, wherein

the sync signal comprises a first sync period corresponding to a first frame of the video and a second sync period corresponding to a second frame of the video;

the first sync period is longer in time than the second sync period;

the pulse width modulation signal comprises a first waveform pattern in a first sub-period of the first sync period, a second waveform pattern in a second sub-period of the first sync period and a third waveform pattern in the second sync period;

each of the first waveform pattern, the second waveform pattern and the third waveform pattern respectively comprises at least one active pulse; and

the first waveform pattern is substantially identical to the second waveform pattern.