Lighting device for display device and display device

1. A lighting device for a display device comprising:

a light source; and

a light source control device arranged to generate a pulse signal as a light source control signal to control the light source; wherein

the light source control signal is an aperiodic signal that includes pulses each having different shapes from each other;

the light source control device includes a periodic signal generating circuit, an aperiodic signal generating circuit, and a mixing circuit including an arithmetic logic circuit arranged to perform a logical operation on a plurality of signals;

the mixing circuit is arranged to generate the light source control signal by performing the logical operation on respective pulses of a periodic signal generated by the periodic signal generating circuit and an aperiodic signal generated by the aperiodic signal generating circuit and to superimpose the pulses of the aperiodic signal on the pulses of the periodic signal to generate the light source control signal;

the periodic signal generating circuit is arranged to generate a pulse signal defining the periodic signal including pulses provided at constant intervals and having a same shape; and

the aperiodic signal generating circuit is arranged to generate a pulse signal defining the aperiodic signal including pulses having a different shape, and a number of the pulses of the aperiodic signal is equal to a number of the pulses of the periodic signal in one vertical period.

2. A lighting device for a display device as in claim 1 , wherein:

said periodic signal generating circuit includes at least three periodic signal generating circuits arranged to generate signals individually at different frequencies; and

said arithmetic logic circuit is arranged to generate said light source control signal by performing the logical operation on at least two periodic signals which are randomly selected for each time period from periodic signals generated from said periodic signal generating circuits.

3. A lighting device for a display device as in claim 1 , further comprising:

a correction circuit provided between said light source and said light source control device, and

arranged to control said light source control signal generated by said light source control device so as to provide a constant time ratio between a light-on period and a light-off period in one vertical period.

4. A lighting device for a display device as in claim 3 , wherein

said correction circuit includes:

an input section arranged to receive the periodic signal generated by said periodic signal generating circuit as a reference signal;

a detection section arranged to compare the light source control signal and the reference signal and to detect, as a phase difference, a difference in a ratio of a light-on period in one vertical period between said reference signal and said light source control signal; and an output section arranged to output a corrected light source control signal that is corrected based on said phase difference.

5. A lighting device for a display device as in claim 4 , wherein:

the difference in the ratio that is detected by the detection section is an error component indicating the light-on period difference between the light source control signal and the reference signal; and

the correction circuit further includes a correction signal generating section arranged to generate a correction signal based on the error component.

6. A lighting device for a display device as in claim 5 , wherein:

the correction circuit further includes a correction section arranged to correct the light source control signal based on the correction signal so that a ratio of light-on periods of the light source control signal in one vertical period coincides with a corresponding ratio provided by the reference signal of light on-periods of the reference signal in one vertical period.

7. A lighting device for a display device as in claim 3 , wherein said correction circuit includes:

an input section arranged to receive, as a reference signal, a previous light source control signal that has been generated as said light source control signal;

a detection section arranged to detect, as a phase difference, a difference between said reference signal and a subsequent light source control signal in a ratio of light-on period in one vertical period; and

an output section arranged to output a corrected light source control signal as a result of correcting said subsequent light source control signal by said phase difference.

8. A lighting device for a display device as in claim 1 , wherein the periodic signal generating circuit generates a Pulse Width Modulation signal that regularly repeats on-and-off operations of the light source as the periodic pulse signal and the aperiodic signal generating circuit generates a current-controlled dimming signal as the aperiodic pulse signal.

9. A display device comprising:

a lighting device for a display device according to claim 1 ; and

a display panel arranged to perform display by use of light from said lighting device for a display device.

10. A display device as in claim 9 , wherein said display panel is a liquid crystal panel including liquid crystal material.