Display signal processing device and display device

1. A display signal processing device comprising:

a reference gradation voltage generating circuit that generates a first predetermined number of reference gradation voltages;

a source drive comprising a digital-to-analog converting circuit that converts a display signal to a pixel voltage by selectively using the first predetermined number of reference gradation voltages from said reference gradation voltage generating circuit; and

a control section that controls said source drive and said reference gradation voltage generating circuit, wherein

said reference gradation voltage generating circuit includes a resistance circuit comprising a plurality of resistors connected in series, and a second predetermined number of variable voltage generating sections connected to both ends of said resistance circuit and to a predetermined connecting section of connecting sections of the plurality of resistors, the second predetermined number being less than the first predetermined number,

said second predetermined number of variable voltage generating sections comprises a digital-to-analog converter that converts a plurality of numeral data supplied from said control section into output voltages which are each varied for gamma correction, and supplies the output voltages to said resistance circuit, and

difference voltages between output terminals of said variable voltage generating sections are divided by said resistance circuit and the first predetermined number of reference gradation voltages are derived.

2. The display signal processing device according to claim 1 , wherein said reference gradation voltage generating circuit includes a protection circuit that protects said digital-to-analog converting circuit by detecting abnormality in output voltage occurring in any one of said second predetermined number of variable voltage generating sections, and switching output voltages of all the variable voltage generating sections to a specified voltage.

3. The display signal processing device according to claim 1 , wherein said control section includes an output section that serially outputs items of numeral data, which are to be converted by said digital-to-analog converter, in an order beginning with one with a longest conversion period.

4. The display signal processing device according to claim 1 , further comprising:

a correction circuit that is disposed on an output side of said variable voltage generating sections, the correction circuit selectively correcting the first predetermined number of reference gradation voltages to eliminate a difference in the gradations for at least one of the vicinity of the minimum luminance and the vicinity of the maximum luminance, and delivers the corrected reference gradation voltage to said digital-to-analog converting circuit.

5. The display signal processing device according to claim 1 , wherein said control section includes a correction circuit that corrects the display signal to eliminate a difference in the gradations for at least one of the vicinity of the minimum luminance and the vicinity of the maximum luminance, and delivers the corrected display signal to said digital-to-analog converting circuit.

6. The display device according to claim 1 , wherein the control section is configured to execute a control of setting the first predetermined number of reference gradation voltages at a predetermined identical level prior to turning off of power.