LIQUID CRYSTAL DISPLAY DEVICE AND CONTROL METHOD USED IN SAME

Abstract

A liquid crystal display device employing an AC driving method is provided which is capable of minimizing a period of time during which a difference in magnitude between a positive voltage and a negative voltage relative to an intermediate potential occurs in gray-level reference voltages making up AC driving voltages when AC voltages are changed during operations of the liquid crystal display device by selecting an optimized order of outputting the gray-level reference voltages generated by a sequential switching method. An output switching control section is provided in a gray-level reference voltage generating section which outputs, at a time of changing the gray-level reference voltages during operations of the device, the gray-level reference voltage to a source driver in an order being different from an order of having received the gray-level reference voltage input from a same output voltage setting section after being sequentially switched.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, advantages, and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a block diagram showing an entire configuration of an LCD device according to a first embodiment of the present invention;

FIG. 2 is a diagram showing a concrete configuration of a gray-level reference voltage generating section in the LCD device of FIG. 1;

FIG. 3 is a timing chart showing changes of a gray-level reference voltage of the LCD device of FIG. 1;

FIG. 4 is a block diagram showing an entire configuration of an LCD device according to a second embodiment of the present invention;

FIG. 5 is a block diagram showing an entire configuration of an LCD device according to a third embodiment of the present invention;

FIG. 6 is a block diagram showing an entire configuration of an LCD device according to a fourth embodiment of the present invention;

FIG. 7 is a block diagram showing concrete configurations of a gray-level reference voltage generating section in the LCD device of a fifth embodiment of the present invention;

FIG. 8 is a diagram showing basic configurations of a conventional LCD device;

FIG. 9 is a diagram showing one example of configurations of circuits to be used when all outputs of gray-level reference voltages are generated by using each of different D/A converters;

FIG. 10 is a diagram showing one example of configurations of circuits to be used when a plurality of gray-level reference voltages is generated by sequentially switching voltage outputs one by one by using the same circuit and

FIG. 11 is a timing chart explaining changes of gray-level reference voltages applied when a plurality of gray-level reference voltages is generated by sequentially switching voltage outputs one by one by using the same circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Best modes of carrying out the present invention will be described in further detail using various embodiments with reference to the accompanying drawings. In the AC-driving-method type LCD device of the present invention, a gray-level reference voltage generating section is provided which has an output switching control section to supply a gray-level reference voltage to a source driver in an outputting order being different from the order in which the gray-level reference voltages have been sequentially input from the same output voltage setting section after being sequentially switched and to exerts control so as to minimize, when the gray-level reference voltage making up the AC driving voltage to be input to the source driver is changed during operations of the LCD device, a period of time during which a difference in magnitude between the positive voltage and negative voltage relative to the optimized intermediate voltage occurs in the gray-level reference voltages making up the AC driving voltage to be input to the source driver.

First Embodiment

FIG. 1 is a block diagram showing an entire configuration of an LCD device according to a first embodiment of the present invention. FIG. 2 is a diagram showing a concrete configuration of a gray-level reference voltage generating section in the LCD device of FIG. 1. FIG. 3 is a timing chart explaining changes of a gray-level reference voltage of the LCD device of FIG. 1. The LCD device of the first embodiment chiefly includes, as shown in FIG. 1, an LCD panel 1, a source driver IC 2, a gate driver IC 3, a gray-level reference voltage generating section 4A, a power supply section 5, and a control section 6. Out of these, the configurations of the LCD panel 1, source driver IC 2, gate driver IC 3, power supply section 5, and control section 6 are the same as those of the conventional LCD device shown in FIG. 7 and their detailed descriptions are omitted accordingly.

FIG. 2 shows a concrete configuration of the gray-level reference voltage generating section 4A of the LCD device of the first embodiment. The gray-level reference voltage generating section 4A is made up of an output voltage setting section 7 and an output switching control section 11 and is configured to generate a gray-level reference voltage according to external control signals and then output the generated voltage to the source driver IC 2. The configurations of the output voltage setting section 7 are the same as those shown in FIG. 10. The output voltage setting section 7 operates according to external control signals and sequentially sets gray-level reference voltages V₀, V₁, . . . , V_n, V_n+1, . . . , V_x−1, V_x to be output to each pixel on pixel strings in the source driver IC 2.

The output switching control section 11 includes a switching unit 8A and a switching unit control section 12. The switching unit control section 12 operates according to external control signals and controls switching order of the switching unit 8A on a specified sequence. The output voltage setting section 7 includes a gray-level voltage setting section 9 and a digital-analog converter 10. The switching unit 8A is configured to change the order of outputting gray-level reference voltages output from the digital-analog converter 10 of the output voltage setting section 7 to the order controlled by the switching unit control section 12 and output the voltage in the switched order.

FIG. 3 is a timing chart explaining operations of the gray-level reference voltage generating section 4A shown in FIG. 2. The control section 6 shown in FIG. 1 outputs set data to be written in each pixel of pixel strings according to input video signals. The source driver IC 2 outputs a drain voltage generated from a gray-level reference voltage based on set data to each pixel driving transistor through a corresponding data line.

With configuration shown in FIG. 2, the switching unit 8A changes, under the control of the switching unit control section 12, the order of outputting the gray-level reference voltages V₀→V₁, . . . , V_n→V_n+1, . . . , V_x−1→V_x to be sequentially output from the output voltage setting section 7, on a specified sequence and outputs the gray-level reference voltages in the changed order. By this operation, the order of having received the gray-level reference voltages to the source driver IC 2 is changed to the order being, for example, V₀→V_x, . . . , V₁→V_x−1, V_n→V_n+1.

When each of the gray-level reference voltages is changed from VA₀ to VB₀, from VA₁ to VB₁, VA_n to VB_n, from VA_n+1 to VB_n+1, from VA_x−1 to VA_x−1 to VB_x−1, presuming that an AC driving voltage made up of VA₀ and VA_x is referred to a voltage “A” and an AC voltage driving voltage made up of VB₀ and VB_x is referred to a voltage “G”, during the period “T1” from a time when transition from VA₀ to VB₀ starts to a time when transition from VA_x to VB_x ends, an AC driving voltage “D” made up of VB₀ and VA_x is applied to the source driver IC 2. Also, when an AC driving voltage made up of VA₁ and VA_x−1 is referred to as a voltage “B” and an AC driving voltage made up of VB₁ and VB_x−1 is referred to as a voltage “H”, during the period “T2” from the time when transition from VA₁ to VB₁ to the time starts to the time when transition from VA_x−1 to VB_x−1 ends, an AC driving voltage “E” made up of VB₁ and VA_x−1 is applied to the source driver IC 2. Similarly, when an AC driving voltage made up of VA_n and VA_n+1 is referred to as a voltage “C” and an AC driving voltage made up of VB_n and VB_n+1 is referred to as a voltage “I”, during the period “T3” from the time when transition from VA_n to VB_n starts to the time when transition from VA_n+1 to VB_n+1 ends, an AC driving voltage “F” made up of VB_n and VA_n+1 is applied to the source driver IC 2.

In the LCD device shown in FIG. 1, as shown in FIG. 3, when a state in which the AC driving voltages “A”, “B”, and “C” are output is changed to be a state in which the AC driving voltages “G”, “H”, and “I”, by changing the order of outputting the gray-level reference voltages sequentially input from the same output voltage setting section 7, it is made possible to minimize the periods of time “T1”, “T2”, and “T3” during which non-uniformity in magnitude of the gray-level reference voltages making up the AC driving voltage occurs relative to an intermediate voltage (Vcom). Thus, according to the LCD device shown in FIG. 1, the period of time during which a voltage being non-uniform relative to an optimized intermediate potential (Vcom) is applied can be minimized and, therefore, the occurrence of an afterimage, flicker phenomenon, luminance change phenomenon, or a like, or the degradation of display quality can be suppressed.

Second Embodiment

FIG. 4 is a block diagram showing an entire configuration of an LCD device according to a second embodiment of the present invention. The LCD device of the second embodiment chiefly includes, as shown in FIG. 4, an LCD panel 1, a source driver IC 2, a gate driver IC 3, a power supply section 5, a control section 6, an output voltage setting section 7, and an output switching control section 13. Out of these, configurations of the LCD panel 1, source driver IC 2, gate driver IC 3, power supply section 5, control section 6, and output voltage setting section 7 are the same as those shown in FIG. 1.

The output switching control section 13 is provided between the output voltage setting section 7 and the source driver IC 2 and, though not shown, has a switching unit control section and a switching unit. The output switching control section 13 is also configured to operate by supply power for operations fed from the power supply section 5 and to change the order of outputting the gray-level reference voltages V₀→V₁, . . . , V_n→V_n+1, . . . , V_x−1→V_x sequentially input from the output voltage setting section 7 and to be output to the source driver on a specified sequence and, therefore, to be able to change the order of outputting the gray-level reference voltage input from the output voltage setting section 7 to be output to the source driver IC 2 from the above order being V₀→V₁, . . . , V_n→V_n+1, . . . , V_x−1→V_x to the order being, for example, V₀→V_x, . . . , V₁→V_x−1, V_n→V_n+1, or a like.

According to the LCD device shown in FIG. 4, as in the case of the first embodiment, when a state of outputting of the AC driving voltage is changed, by changing the order of outputting the AC driving voltage sequentially input from the same output voltage setting section 7, the period of time during which non-uniformity occurs in magnitude of the gray-level reference voltages making up the AC driving voltage relative to an intermediate potential (Vcom) can be minimized. Thus, according to the LCD device shown in FIG. 4, the period of time during which a voltage being non-uniform relative to the optimized intermediate potential (Vcom) is applied can be minimized and, therefore, the occurrence of an afterimage, flicker phenomena, luminance change phenomenon, or a like, or the degradation of display quality can be suppressed.

Third Embodiment

FIG. 5 is a block diagram showing an entire configuration of an LCD device according to a third embodiment of the present invention. The LCD device of the third embodiment chiefly includes an LCD panel 1, a source driver IC 2, a gate driver IC 3, a gray-level reference voltage generating section 4B, a power supply section 5, a control section 6, and a power supply voltage monitoring circuit 14. Out of these, configurations of the LCD panel 1, source driver IC 2, gate driver IC 3, power supply section 5, and control section 6 are the same as those shown in FIG. 1.

The gray-level reference voltage generating section 4B is made up of an output voltage setting section 7 and an output switching control section 11A. Out of these, configurations of the output voltage setting section 7 are the same as those in FIG. 1. The output switching control section 11A is so configured as to operate on a sequence on which the order of outputting gray-level reference voltages is switched based on states of supply power voltages to be applied at the starting times of operations of the LCD device and to be applied at the driving times of operations in a manner to correspond to change in supply power voltage to be applied to the gate driver IC 3.

The output switching control section 11A is configured to operate, according to control of the supply power monitoring circuit 14, on either a sequence to be applied at the starting time of operations of the LCD device during which the order of outputting gray-level reference voltage is not changed or on a sequence of the present invention to be applied at the driving time of the device during which the time when a difference is made large in magnitude of the gray-level reference voltages making up an AC driving voltage relative to an intermediate voltage (Vcom) at the time of changing the order of outputting the gray-level reference voltages is minimized. Here, the “starting time of operations of the device” denotes a state in which displaying is going to be started directly after the application of input supply power to the LCD device (and in which neither a drain voltage nor a gate voltage is fed from the power supply section to each pixel driving transistor, while the “driving time of the device” denotes a state in which displaying by the LCD device is being continued (and in which a logic voltage is being fed from the power supply section to the source driver IC and both the drain voltage and gate voltage are being fed to each pixel driving transistor). A precondition for operations of the supply power monitoring circuit 14 is that the logic voltage has already been applied to the source driver IC. The supply power monitoring circuit 14 judges whether the logic voltage has been turned ON or OFF and, if the logic voltage has not been placed yet, does not output control information to the output switching control section 11A and, therefore, the gray-level reference voltage output from the output switching control section 11A is fed on the sequence to be applied at the starting time of operations of the device when the order of outputting is not changed. On the other hand, the supply power monitoring circuit 14 outputs control information to the output switching control section if the logic voltage has been placed and, therefore, the gray-level reference voltage output from the output switching control section 11A is fed on the sequence to be applied at the driving time of the LCD device when the order of outputting is changed.

Moreover, by changing the setting, the output switching control section in the output switching control section 13 shown in FIG. 4 can be configured to operate, as in the case in FIG. 5, on a sequence on which the order of outputting the gray-level reference voltage sequentially generated by the output voltage setting section 7 is changed or not changed according to control information fed from the supply power monitoring circuit 14.

According to the LCD device of the third embodiment in FIG. 5, when the order of outputting gray-level reference voltages is not changed at the starting time of operations of the LCD device and the order of outputting the gray-level reference voltages is changed at the driving time of the LCD device according to information of results from monitoring supply voltages, the period of time during which a voltage being nonuniform relative to an optimized intermediate potential (Vcom) is applied can be minimized by changing the order of outputting the gray-level reference voltages sequentially input from the same output voltage setting section and, therefore, the occurrence of an afterimage, flicker, luminance change, or a like can be prevented, or the degradation of display quality can be suppressed.

Fourth Embodiment

FIG. 6 is a block diagram showing an entire configuration of an LCD device according to a fourth embodiment of the present invention. The LCD device of the fourth embodiment, as shown in FIG. 6, chiefly includes an LCD panel 1, a source driver IC 2, a gate driver IC 3, a gray-level reference voltage generating section 4C, a power supply section 5, a control section 6, and a driving time detecting circuit 15. Out of these, the LCD panel 1, the source driver IC 2, the gate driver IC 3, the power supply section 5, and the control section 6 are the same as shown in FIG. 1.

The gray-level reference voltage generating section 4C is made up of an output voltage setting section 7 and an output switching control section 11B. Out of these, the output voltage setting section 7 is the same as shown in FIG. 1. The output switching control section 11B is so configured to operate on a sequence on which the order of outputting gray-level reference voltages is switched based on states of device supply power that changes with elapsed time after the start of operations of the LCD device in a manner to correspond to change in supply power to be applied to the gate driver IC 3.

The output switching control section 11B is configured to operate, according to control of the driving time detecting circuit 15, on either a sequence to be applied at the starting time of operations of the LCD device during which the order of outputting gray-level reference voltages is not changed or on a sequence of the present invention to be applied at the driving time of the device when the period of time during which a difference is made large in magnitude of the gray-level reference voltages relative to an intermediate voltage (Vcom) at the time of making up an AC driving voltage at the time of changing the order of outputting the gray-level reference voltages is minimized. Here, the states of the “starting time of operations of the device” and of the “driving time of the device” are the same as those described when the operation of the output switching control section 11A in FIG. 5 was explained. A precondition for operations of the driving time detecting circuit 15 is that the logic voltage has already been placed. The driving time detecting circuit 15 judges whether the logic voltage has been turned ON or OFF and, if the logic voltage has not been placed, does not output control information to the output switching control section 11B and, therefore, the gray-level reference voltage output from the output switching control section 11B is fed on the sequence to be applied at the starting time of operations of the LCD device when the order of outputting is not changed. On the other hand, the driving time detecting circuit 15 outputs control information to the output switching control section 11B if the logic voltage has been placed and, therefore, the gray-level reference voltage output from the output switching control section 11B is fed on the sequence to be applied at the driving time of the LCD device when the order of outputting is changed. However, for the time period required for changing the order of outputting video signals to the source driver IC 2 which are input after the LCD device is powered on before displaying is started or for the idle time period required for the stabilization of clock synchronization, no displaying occurs even if a logic voltage is placed and, therefore, these time periods are not considered as “the period of time during which the LCD device is in operation”.

Moreover, a switching unit control section in an output switching control section 13 shown in FIG. 4, as in the case in FIG. 6, is also allowed to operate on a sequence of changing, according to control information fed from the driving time detecting circuit 15, the order of gray-level reference voltage sequentially generated by the output voltage setting section 7 or on a sequence of not changing the gray-level reference voltage.

According to the LCD device of the fourth embodiment in FIG. 6, when the order of outputting the gray-level reference voltage is not changed at the starting time of the LCD device and the state of outputting the AC driving voltage is changed after the LCD device is in a driving state according to information obtained during elapsed time after the start of its operations, by changing the order of outputting the gray-level reference voltage sequentially input from the same output voltage setting section 7, the period of time during which a voltage being non-uniform relative to the optimized intermediate potential (Vcom) is applied can be minimized, thus suppressing an occurrence of an afterimage, flicker, luminance change, or a like, or a degradation of display quality.

Fifth Embodiment

FIG. 7 is a block diagram showing concrete configurations of a gray-level reference voltage generating section in the LCD device of a fifth embodiment of the present invention. The gray-level reference voltage generating section 4D of the fifth embodiment, as shown in FIG. 7, includes an output voltage setting section 7 and an output switching control section 11C. Out of these, configurations of the output voltage setting section 7 are the same as shown in FIG. 2. The output switching control section 11C is made up of a switching unit 8A, switching unit control section 12A, and an external storage medium 16. Out of these, configurations of the switching unit 8A are the same as those shown in FIG. 2.

The switching unit control section 12A controls the order of switching the switching unit 8A on a sequence read from the external storage medium 16 according to external control signals. The external storage medium 16 is configured to output sequence data to change the order of outputting gray-level reference voltages in the switching unit 8A according to information of a result from monitoring of supply power fed from the supply power monitoring circuit 14 or not to change the above order.

As a result, the switching unit 8A does not change the order of outputting gray-level reference voltages fed from the output voltage setting section 7 on a sequence to be applied at the driving time of the device while the AC driving voltage is applied at the driving time of the device and, in the driving state of the LCD device, according to information of a result from monitoring the supply voltage or to information obtained during elapsed time after the start of operations of the LCD device, the order of outputting the gray-level reference voltage fed from the output voltage setting section 7 is changed according to a sequence on which the order of outputting the gray-level reference voltage at the time of application of the AC driving voltage is changed.

Moreover, the switching unit in the output switching control section 13 shown in FIG. 4, as in the case in FIG. 7, is also allowed to set the order of outputting gray-level reference voltages sequentially input from the output voltage setting section 7 on a sequence set by the external storage medium 16 according to changes in device supply power at the starting time of operations fed from the supply power monitoring circuit 15 or according to information obtained during elapsed time after driving of the device fed from the driving time detecting circuit 15.

According to the LCD device of the fifth embodiment shown in FIG. 7, the output switching control section 11A (FIG. 5) or the output switching control section 11B (FIG. 6), even if sequence data on changing the order of outputting the gray-level reference voltage is not set thereto, decides not to change the order of outputting the gray-level voltage, according to information of results from monitoring the supply power being fed or according to information obtained during elapsed time after operations of the LCD device is started, or decides to change, when the state of outputting the AC driving voltage is changed after the LCD device is in a driving state, the order of outputting the gray-level reference voltage sequentially input from the same output voltage setting section 7 and, as a result, the period of time during which a voltage being non-uniform relative to the optimized intermediate potential (Vcom) is applied can be minimized, thus suppressing the occurrence of an afterimage, flicker, luminance change, or a like, or the degradation of display quality.

It is apparent that the present invention is not limited to the above embodiments but may be changed and modified without departing from the scope and spirit of the invention. For example, the driving method of the LCD panel in the LCD device is not limited to the AC driving method in which the polarity of voltages for an entire frame in one frame period is inverted and may includes a line-inversion AC driving method in which a polarity is alternately inverted in every one line in a screen and the polarity of each line is alternately inverted in every one frame and a dot-inversion AC driving method in which a polarity is inverted in every dot (pixel) in a screen and the polarity of each dot is alternately inverted in every frame period.

Furthermore, the LCD device and method of driving the LCD device can be used to suppress the occurrence of an afterimage, flicker, luminance change, or a like, and to prevent the degradation of display quality in the LCD section of such as a liquid crystal television set, personal computer, car navigation system, personal digital assistant (PDA), or a like.

Claims

1. A liquid crystal display device employing an AC driving method comprising: an output switching control section provided in a gray-level reference voltage generating unit to output a gray-level reference voltage to a source driver in an order being different from an order of having received said gray-level reference voltage from a same output voltage setting section after being sequentially switched, wherein said output switching control section exerts control, at a time of changing an order of outputting said gray-level reference voltage during operations of said liquid crystal display device, so as to minimize a period of time during which a difference in magnitude between a positive voltage and a negative voltage relative to an optimized intermediate potential occurs in said gray-level reference voltage making up an AC driving voltage to be input to said source driver.

2. The liquid crystal display device according to claim 1, wherein said output switching control section comprises a switching unit control section to control so that said gray-level reference voltage is output in a specified sequence in an order being different from an order in which said gray-level reference voltage has been input and a switching unit to make a gray-level reference voltage fed from said output voltage setting unit be output to said source driver according to control of said output switching control section in an order being different from an order in which said gray-level reference voltage has been input.

3. The liquid crystal display device according to claim 1, further comprising a supply power monitoring circuit to monitor a state of supply power to be fed to said liquid crystal display device and to output control information when said liquid crystal display device is driven and wherein said output switching control section is configured not to change, at a starting time of operations of said liquid crystal display device, an order of outputting a gray-level reference voltage fed from said output voltage setting unit and to output, at a driving time of said liquid crystal display device, according to said control information, said gray-level reference voltage fed from said output voltage setting unit in an order being different from an order of having received the gray-level reference voltages to said source driver.

4. The liquid crystal display device according to claim 3, wherein said supply power monitoring circuit is configured to output said control information when judging that a logic voltage is being applied to said source driver.

5. The liquid crystal display device according to claim 1, further comprising a driving time detecting circuit to detect elapsed time after the start of operations of the liquid crystal display device and to output control information only at the time of driving said liquid crystal display device and wherein said output switching control section is configured not to change, at the starting time of operations of said liquid crystal display device, an order of outputting a gray-level reference voltage fed from said output voltage setting unit and to output, at the driving time of said crystal display device, according to said control information, said gray-level reference voltage fed from said output voltage setting unit in an order being different from an order of having received said gray-level reference voltage to said source driver.

6. The liquid crystal display device according to claim 5, wherein said driving time detecting circuit is configured to output said control information when judging that said liquid crystal display device is in operation based on a lapse of specified time in a state in which a logic voltage is being fed to said source driver.

7. The liquid crystal display device according to claim 3, still further comprising an external storage medium to store sequence data to be used by said output switching control section and, according to said sequence data stored in said external storage medium, said output switching control section is allowed to change its operations.

8. The liquid crystal display device according to claim 3, wherein, by reading sequence data to be used by said output switching control section from said storage medium according to control information fed from said supply power monitoring circuit or control information fed from said driving time detecting circuit and by supplying the read sequence data to said switching unit control section provided in said output switching control section, said switching unit control section exerts control of the order of switching by using said switching unit.

9. A liquid crystal display device employing an AC driving method comprising: an output switching control section provided between an output voltage setting section and a source driver, wherein said output switching control section exerts control so as to supply a gray-level reference voltage input after being sequentially switched to a source driver in an order being different from an order of having received said gray-level reference voltage and so as to minimize, at a time of changing an order of outputting said gray-level reference voltage during operations of said liquid crystal display device, a period of time during which a difference in magnitude between a positive voltage and a negative voltage relative to an optimized intermediate potential occurs in said gray-level reference voltage making up an AC driving voltage to be input to said source driver.

10. The liquid crystal display device according to claim 9, wherein said output switching control section comprises a switching unit control section to exert control so that said gray-level reference voltage is output in a specified sequence in an order being different from an order in which said gray-level reference voltage has been input and a switching unit to make a gray-level reference voltage fed from said output voltage setting unit be output to said source driver according to control of said output switching control section in an order being different from an order in which said gray-level reference voltage has been input.

11. The liquid crystal display device according to claim 9, further comprising a supply power monitoring circuit to monitor a state of supply power to be fed to said liquid crystal display device and to output control information when said liquid crystal display device is driven and wherein said output switching control section is configured not to change, at a starting time of operations of said liquid crystal display device, an order of outputting a gray-level reference voltage fed from said output voltage setting unit and to output, at a driving time of said liquid crystal display device, according to said control information, said gray-level reference voltage fed from said output voltage setting unit in an order being different from an order of having received the gray-level reference voltages to a source driver.

12. The liquid crystal display device according to claim 11, wherein said supply power monitoring circuit is configured to output said control information when judging that a logic voltage is being applied to a source driver.

13. The liquid crystal display device according to claim 9, further comprising a driving time detecting circuit to detect elapsed time after the start of operations of the liquid crystal display device and to output control information only at the time of driving said liquid crystal display device and wherein said output switching control section is configured not to change, at the starting time of operations of said liquid crystal display device, an order of outputting a gray-level reference voltage fed from said output voltage setting unit and to output, at the driving time of said crystal display device, according to said control information, said gray-level reference voltage fed from said output voltage setting unit in an order being different from an order of having received said gray-level reference voltage to a source driver.

14. The liquid crystal display device according to claim 13, wherein said driving time detecting circuit is configured to output said control information when judging that said liquid crystal display device is in operation based on a lapse of specified time in a state in which a logic voltage is being fed to said source driver.

15. The liquid crystal display device according to claim 11, still further comprising an external storage medium to store sequence data to be used by said output switching control section and, according to said sequence data stored in said external storage medium, said output switching control section is allowed to change its operations.

16. The liquid crystal display device according to claim 11, wherein, by reading sequence data to be used by said output switching control section from said storage medium according to control information fed from said supply power monitoring circuit or control information fed from said driving time detecting circuit and by supplying the read sequence data to said switching unit control section provided in said output switching control section, said switching unit control section exerts control of the order of switching by using said switching unit.

17. A control method of a liquid crystal display device employing an AC driving method comprising: outputting, by using an output switching control section provided in a gray-level reference voltage generating unit, a gray-level reference voltage to a source driver in an order being different from an order of having received said gray-level reference voltage from a same output voltage setting section after being sequentially switched; andexerting control, by using said output switching control section at a time of changing an order of outputting said gray-level reference voltage during operations of said liquid crystal display device, so as to minimize a period of time during which a difference in magnitude between a positive voltage and a negative voltage relative to an optimized intermediate potential occurs in said gray-level reference voltage making up an AC driving voltage to be input to said source driver.

18. The control method of the liquid crystal display device according to claim 17, wherein said output switching control section comprises a switching unit control section to exert control so that said gray-level reference voltage is output in a specified sequence in an order being different from an order in which said gray-level reference voltage has been input and a switching unit to make a gray-level reference voltage fed from said output voltage setting unit be output to said source driver according to control of said output switching control section in an order being different from an order in which said gray-level reference voltage has been input.

19. The control method of the liquid crystal display device according to claim 17, further comprising: monitoring, by using a supply power monitoring circuit, a state of supply power to be fed to said liquid crystal display device and outputting control information when said liquid crystal display device has been driven and;configuring said output switching control section so as not to change, at a starting time of operations of said liquid crystal display device, an order of outputting a gray-level reference voltage fed from said output voltage setting unit and to output, at a driving time of said crystal display device, according to said control information, said gray-level reference voltage fed from said output voltage setting unit in an order being different from an order of having received said gray-level reference voltage to said source driver.

20. The control method of the liquid crystal display device according to claim 19, wherein said supply power monitoring circuit is configured to output said control information when judging that a logic voltage is being applied to a source driver.

21. The control method of the liquid crystal display device according to claim 17, still further comprising: detecting, by using a driving time detecting circuit, elapsed time after the start of operations of said liquid crystal display device and to output control information only at the time of driving said liquid crystal display device; andconfiguring said output switching control section not to change, at the starting time of operations of said liquid crystal display device, an order of outputting a gray-level reference voltage fed from said output voltage setting unit and to output, at the driving time of said crystal display device, according to said control information, said gray-level reference voltage fed from said output voltage setting unit in an order being different from an order of having received said gray-level reference voltages to said source driver.

22. The control method of the liquid crystal display device according to claim 21, wherein said driving time detecting circuit is configured to output said control information when judging that said liquid crystal display device is in operation based on a lapse of specified time in a state in which a logic voltage is being fed to said source driver.

23. The control method of the liquid crystal display device according to claim 19, still further comprising: storing, by using an external storage medium, sequence data to be used by said output switching control section and, according to said sequence data stored in said external storage medium, said output switching control section is allowed to change its operations.

24. The control method of the liquid crystal display device according to claim 23: wherein, by reading said sequence data to be used by said output switching control section from said storage medium according to control information fed from said supply power monitoring circuit or control information fed from said driving time detecting circuit and by supplying the read sequence data to said switching unit control section provided in said output switching control section, said switching unit control section exerts control of the order of switching of said switching unit.

25. A control method of a liquid crystal display device employing an AC driving method comprising: supplying, by using an output switching control section provided between an output voltage setting section and a source driver, a gray-level reference voltage input after being sequentially switched to a source driver in an order being different from an order of having received said gray-level reference voltage; andminimizing, at a time of changing an order of outputting said gray-level reference voltage during operations of said liquid crystal display device, a period of time during which a difference in magnitude between a positive voltage and a negative voltage relative to an optimized intermediate potential occurs in said gray-level reference voltage making up an AC driving voltage to be input to said source driver.

26. The control method of the liquid crystal display device according to claim 25, further comprising: controlling, by using said output switching control section with a switching unit control section, so that said gray-level reference voltage is output in a specified sequence in an order being different from an order in which said gray-level reference voltage has been input; andmaking, by using a switching unit, a gray-level reference voltage fed from said output voltage setting unit be output to said source driver according to control of said output switching control section in an order being different from an order in which said gray-level reference voltage has been input.

27. The control method of the liquid crystal display device according to claim 25, further comprising: monitoring, by using a supply power monitoring circuit, a state of supply power to be fed to said liquid crystal display device and outputting control information when said liquid crystal display device has been driven and;configuring said output switching control section so as not to change, at a starting time of operations of said liquid crystal display device, an order of outputting a gray-level reference voltage fed from said output voltage setting unit and to output, at a driving time of said crystal display device, according to said control information, said gray-level reference voltage fed from said output voltage setting unit in an order being different from an order of having received said gray-level reference voltage to said source driver.

28. The control method of the liquid crystal display device according to claim 27, wherein said supply power monitoring circuit is configured to output said control information when judging that a logic voltage is being applied to a source driver.

29. The control method of the liquid crystal display device according to claim 25, still further comprising: detecting, by using a driving time detecting circuit, elapsed time after the start of operations of said liquid crystal display device and to output control information only at the time of driving said liquid crystal display device; andconfiguring said output switching control section not to change, at the starting time of operations of said liquid crystal display device, an order of outputting a gray-level reference voltage fed from said output voltage setting unit and to output, at the driving time of said crystal display device, according to said control information, said gray-level reference voltage fed from said output voltage setting unit in an order being different from an order of having received said gray-level reference voltages to said source driver.

30. The control method of the liquid crystal display device according to claim 29, wherein said driving time detecting circuit is configured to output said control information when judging that said liquid crystal display device is in operation based on a lapse of specified time in a state in which a logic voltage is being fed to said source driver.

31. The control method of the liquid crystal display device according to claim 27, still further comprising: storing, by using an external storage medium, sequence data to be used by said output switching control section and, according to said sequence data stored in said external storage medium, said output switching control section is allowed to change its operations.

32. The control method of the liquid crystal display device according to claim 31: wherein, by reading said sequence data to be used by said output switching control section from said storage medium according to control information fed from said supply power monitoring circuit or control information fed from said driving time detecting circuit and by supplying the read sequence data to said switching unit control section provided in said output switching control section, said switching unit control section exerts control of the order of switching of said switching unit.