JP4687070B2 - Display drive device, display device, and drive control method for display drive device - Google Patents

Description

The present invention relates to a display drive device, a display device, and a drive control method for a display drive device that apply a display signal voltage corresponding to a display signal to each signal line of the display panel to control driving of the display panel.

  A liquid crystal display device that displays an image by driving a liquid crystal is known. Such a liquid crystal display device includes an active matrix type in which a plurality of scanning lines and a plurality of signal lines are arranged orthogonally on a liquid crystal display panel, and liquid crystal pixels are arranged in the vicinity of each intersection. In this active matrix type liquid crystal display device, a pixel electrode (display pixel) connected to a signal line via a switching element (for example, a thin film transistor (TFT)) is disposed to face the pixel electrode. Liquid crystal is filled between the common electrode and an electric field is formed between the two electrodes, thereby driving the liquid crystal.

  FIG. 9 is a configuration diagram of a main part of the liquid crystal display device. FIG. 10 is an equivalent circuit of a display pixel. As shown in FIG. 9, the liquid crystal display device includes a liquid crystal display panel 10, a signal driver 120, a scanning driver 30, and the like.

  The liquid crystal display panel 10 includes a plurality of scanning lines G arranged in the row direction and a plurality of signal lines S arranged in the column direction, and each of the intersections of the scanning lines G and the signal lines S is shown in FIG. The display pixel shown is provided.

  As shown in FIG. 10, each display pixel includes a pixel electrode 92 connected to the scanning line G and the signal line S via a thin film transistor (TFT) 91, and a counter electrode 93 disposed at a position facing the pixel electrode 92. A pixel capacitor 94 in which liquid crystal is filled between the pixel electrode 92 and the counter electrode 93, and an auxiliary capacitor 31 that is connected in parallel with the pixel capacitor 94 and holds a voltage applied to the pixel capacitor 94. Image display is realized by changing the alignment of the liquid crystal due to the electric field formed between the electrode 92 and the counter electrode 93.

  A scanning line G is connected to the scanning driver 30, and a scanning pixel is sequentially applied to each scanning line G based on an input vertical control signal so as to be in a selected state, and a display pixel at a position crossing the signal line S ( The gradation voltage supplied from the signal driver 120 via the signal line S is applied to the pixel electrode).

  A signal line S is connected to the signal driver 120, and display data input based on input horizontal control signals (clock signal CLK, shift register signal STR, latch operation control signal STB, output enable signal OE, etc.). Are stored in units of one row, and gradation voltages corresponding to the display data are sequentially supplied to the signal lines S.

  Specifically, the signal driver 120 includes a shift register 21, a data register 22, a latch circuit 23, a selection circuit 24, a gradation voltage generation circuit 127, an output buffer 25, and the like. The shift register 21 receives the clock signal CLK and the shift register signal STR, and the shift register signal STR is sequentially shifted by the clock signal CLK.

  The data register 22 receives a-bit display data corresponding to the RGB color video signals, and the display data is sequentially taken in at the timing of the output signal from the shift register 21.

  A latch operation control signal STB is input to the latch circuit 23, and display data fetched into the data register 22 is held in the latch circuit 23 and is output to the selection circuit 24.

  The selection circuit 24 decodes the display data input from the latch circuit 23, and selects a gradation voltage corresponding to the gradation level of the display data from the plurality of gradation voltages input from the gradation voltage generation circuit 127. And output.

  An output enable signal OE is input to the output buffer 25, and the gradation voltage output from the selection circuit 24 is applied to each signal line S of the liquid crystal display panel 10 as display data.

Here, for example, as disclosed in Patent Document 1 and Patent Document 2, the gradation voltage is generated by dividing a predetermined voltage with a resistor, and the divided voltage is a gradation amplifier having a voltage follower circuit. A method of outputting via a circuit is generally known. FIG. 11 is a diagram showing an example of the circuit configuration of the selection circuit and the gradation voltage generation circuit. The gradation voltage generation circuit 127 first divides the voltage between a predetermined positive voltage VS and GND by a plurality of resistors R corresponding to the number of gradations of display data (n = 2 ^a ). A predetermined bias current is supplied from the amplifier power supply control circuit 1271 to the gradation amplifiers AMP1, AMP2,..., AMPn (hereinafter collectively referred to as “gradation amplifier AMP”), and the divided voltage is supplied to the gradation amplifier AMP1, AMP2,. The grayscale voltage application lines AL1, AL2,..., ALn (hereinafter collectively referred to as “grayscale voltage application line AL”) are applied as the regulated voltages.

  The selection circuit 24 is a gradation voltage output line SLR1, SLG1, SLB1,..., SLRm, SLGm, SLBm (hereinafter collectively referred to as “gradation voltage output line SL”) corresponding to each signal line S. The gradation voltage application lines AL connected to the output terminals of the gradation amplifier AMP are arranged in a matrix, and select switches SWR11,..., SWRnm, SWG11, ..., SWGnm, SWB11, .. SWBnm (hereinafter collectively referred to as “selection switch SW”) is connected.

Decoders 841R-1, 841G-1, 841B-1,..., 841R-m, 841G-m, and 841B-m (hereinafter collectively referred to as “decoder 841”) are held in the latch circuit 23. The display data is decoded and a gradation level signal corresponding to the number of gradations of each RGB pixel is output. Each of the selection switches SWR11,..., SWBnm is controlled to be turned on / off based on the gradation level signal output from the decoder 841. At the time of ON, the gradation voltage application line AL and the gradation voltage output line SL are conducted, and the gradation voltage applied to the gradation voltage application line AL is applied to the gradation voltage output line SL. That is, the gradation voltage of the selected gradation voltage application line AL is output to the gradation voltage output line SL to the gradation voltage output line SL.
JP 2003-122325 A JP 2004-21163 A

  By the way, the current drive capability of each of the gradation amplifiers AMP1,. The gradation voltage is set to a certain value so that each gradation voltage can be stably supplied according to the capacity 94 and the like. That is, the current driving capability is set so as to stably supply the maximum voltage level of the gradation voltage that requires the highest current driving capability. However, when the voltage level of the gradation voltage relative to the gradation level of the display data is relatively low, the current driving capability required for the gradation amplifier AMP may be lower than when the voltage level of the gradation voltage is high. That is, when the voltage level of the gradation voltage is low, an excessive current driving capability more than necessary is set in the gradation amplifier AMP. Therefore, power is wasted due to this excessive current driving capability.

  The present invention has been made in consideration of the above points, and an object of the present invention is to provide a display drive device, a display device, and a drive control method for the display drive device with reduced power consumption.

In order to solve the above problem, the invention according to claim 1, by dividing a predetermined voltage into a plurality of voltages, generates a voltage corresponding to the gradation level for each gradation level, and A display driving device in which an amplifier circuit corresponding to the gradation level is provided for each level, wherein each of the voltages simultaneously applied to the signal lines of the display panel is higher than a voltage corresponding to a predetermined gradation level. When the bias current is small, the bias current supplied to each of the amplifier circuits is equal to each other at a predetermined current value, and the voltage applied simultaneously to each signal line of the display panel is The value of the bias current supplied to each of the amplifier circuits is larger than the predetermined current value when any one is larger than the voltage corresponding to the predetermined gradation level. Characterized in that it comprises a means for supplying the bias current to be equal to each other at a current value.

According to the second aspect of the present invention, a voltage corresponding to the gradation level is generated for each gradation level by dividing the predetermined voltage into a plurality of voltages, and the gradation level is supported for each gradation level. The display driving device provided with the above-described amplifier circuit, wherein when the total value of the gradation levels corresponding to the voltages simultaneously applied to the respective signal lines of the display panel is smaller than a predetermined threshold, the amplifier The bias current is supplied so that the bias current values supplied to each of the circuits are equal to each other at a predetermined current value, and supplied to each of the amplifier circuits when the total value is larger than the predetermined threshold value The bias current is supplied so that the bias current values are equal to each other at a current value larger than the predetermined current value .

According to the third aspect of the present invention, a plurality of signal lines are provided on the display panel, and an amplifier circuit corresponding to the gradation level is provided for each gradation level, and the predetermined voltage is divided into the plurality of voltages. The display device generates a voltage corresponding to the gradation level for each gradation level, and each of the voltages simultaneously applied to the signal lines of the display panel is based on a voltage corresponding to a predetermined gradation level. Voltage is applied to the signal lines of the display panel at the same time so that the bias currents supplied to the amplifier circuits are equal to each other at a predetermined current value. Is greater than the voltage corresponding to the predetermined gradation level, the value of the bias current supplied to each of the amplifier circuits is the predetermined current value. Characterized in that it comprises a means for supplying the bias current to be equal to each other at even higher current value Ri.

According to a fourth aspect of the present invention, a plurality of signal lines are provided on the display panel, and an amplifier circuit corresponding to the gradation level is provided for each gradation level, and the predetermined voltage is divided into the plurality of voltages. The display device generates a voltage corresponding to the gradation level for each gradation level, and a total value of the gradation levels corresponding to each of the voltages simultaneously applied to the signal lines of the display panel is predetermined. The bias current is supplied so that the bias current values supplied to the respective amplifier circuits are equal to each other at a predetermined current value when the threshold value is smaller than the threshold value, and the total value is larger than the predetermined threshold value. Sometimes, the bias current is supplied so that the values of the bias current supplied to each of the amplifier circuits are equal to each other at a current value larger than the predetermined current value. Characterized in that it comprises means that.

The invention according to claim 5 generates a voltage corresponding to the gradation level for each gradation level by dividing a predetermined voltage into a plurality of voltages, and corresponds to the gradation level for each gradation level. A drive control method for a display driving device provided with the amplifier circuit, wherein each of the voltages applied simultaneously to each signal line of the display panel is smaller than a voltage corresponding to a predetermined gradation level, The bias current is supplied so that the values of the bias current supplied to each of the amplifier circuits are equal to each other at a predetermined current value, and any one of the voltages simultaneously applied to the signal lines of the display panel is the predetermined voltage. When the voltage is higher than the voltage corresponding to the gradation level, the values of the bias currents supplied to the amplifier circuits are mutually greater than the predetermined current value. Characterized in that to be equal to supply the bias current.

According to the sixth aspect of the present invention, a voltage corresponding to the gradation level is generated for each gradation level by dividing the predetermined voltage into a plurality of voltages, and the gradation level is supported for each gradation level. Drive control method for a display driving device provided with the above-described amplifier circuit, wherein the total value of the gradation levels corresponding to each of the voltages simultaneously applied to the signal lines of the display panel is smaller than a predetermined threshold value When the bias current is supplied so that the values of the bias current supplied to each of the amplifier circuits are equal to each other at a predetermined current value, and the total value is larger than the predetermined threshold, the amplifier circuit The bias currents are supplied so that the values of the bias currents supplied to the respective currents are equal to each other at a current value larger than the predetermined current value .

According to the present invention, power consumption can be reduced.

[First Embodiment]
Hereinafter, an embodiment in which the present invention is applied to a liquid crystal display device will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of a liquid crystal display device according to the present embodiment. In addition, about the function and structure equivalent to the structure in the background art mentioned above, the same code | symbol is attached | subjected and the description is simplified or abbreviate | omitted. The liquid crystal display device 1 includes a liquid crystal display panel 10, a signal driver (signal side driving means) 20, a scanning driver (scanning side driving means) 30, an RGB decoder 40, a memory (storage means) 60, a drive amplifier 70, an LCD controller 80, A voltage generation circuit 90 and the like are provided.

  The liquid crystal display panel 10 includes a plurality of scanning lines G arranged in the row direction and a plurality of signal lines S arranged in the column direction, and each of the intersections of the scanning lines G and the signal lines S is shown in FIG. The display pixel shown is provided.

  A signal line S is connected to the signal driver 20, and horizontal control signals (clock signal CLK, shift register signal STR, latch operation control signal STB, output enable signal OE, reference signal REF, etc.) output from an LCD controller 80 described later. ), The display data of each color of R (red), G (green), and B (blue) supplied from the memory 60 is stored in units of one row, and the display signal based on the display data is stored in the gradation voltage. Are sequentially supplied to each signal line S. Details will be described later.

  A scanning line G is connected to the scanning driver 30, and based on a vertical control signal output from the LCD controller 80, a scanning signal is sequentially applied to each scanning line G to be in a selected state, and a position that intersects the signal line S The gradation voltage supplied from the signal driver 20 via the signal line S is applied to the display pixel (pixel electrode).

  For example, the RGB decoder 40 extracts the horizontal synchronization signal H, the vertical synchronization signal V, and the composite synchronization signal CSY from a video signal (composite video signal) supplied from the outside of the liquid crystal display device 1 and supplies the extracted signal to the LCD controller 80. At the same time, R, G, and B color signals (RGB signal: display signal) included in the video signal are extracted and output to the memory 60.

  The memory 60 is composed of a RAM or the like, for example, temporarily stores RGB signals (display signals) for one frame (one screen), and stores the stored RGB signals as a-bit display data in the signal driver 20. Output.

  The drive amplifier 70 generates a common signal voltage VCOM applied to the auxiliary capacitance line (common line) C and the counter electrode 93 connected to the auxiliary capacitance 31 of each display pixel, and outputs a polarity control signal output from the LCD controller 80. The polarity of the common signal voltage VCOM is inverted according to POL and output.

  The LCD controller 80 generates a polarity control signal POL and the like based on the horizontal synchronization signal H, the vertical synchronization signal V, and the composite synchronization signal CSY supplied from the RGB decoder 40, outputs them to the drive amplifier 70, and performs horizontal control. By generating signals and vertical control signals and outputting them to the signal driver 20 and the scanning driver 30, respectively, a gradation voltage is applied to each display pixel at a predetermined timing, and a predetermined voltage based on display data is applied to the liquid crystal display panel 10. Control to display the image information.

  The voltage generation circuit 90 generates and supplies a plurality of voltages necessary for each circuit constituting the liquid crystal display device 9. For example, an internal power supply voltage VDD of each circuit, a voltage VS for generating a gradation voltage, and the like are generated, and the voltage VS is supplied to the signal driver 20.

  FIG. 2 is a main part configuration diagram of the signal driver in the present embodiment. In the background art, the same components as those of the signal driver 120 described with reference to FIG. 9 are denoted by the same reference numerals, and description thereof is omitted or simplified. The signal driver 20 includes a shift register 21, a data register 22, a latch circuit 23, a selection circuit 24, a comparison circuit 26, a gradation voltage generation circuit 27, an output buffer 25, and the like.

  The comparison circuit 26 compares the display data held and output by the latch circuit 23 with the reference signal REF input from the LCD controller 80, and outputs the comparison result to the gradation voltage generation circuit 27 as a signal A.

The gradation voltage generation circuit 27 divides the voltage VS and GND by a plurality of resistors R corresponding to the number of gradations (n = 2 ^a ) of the display data, and the divided voltage is supplied via the gradation amplifier AMP. Output as gradation voltage. Further, for example, the gradation voltage is inverted (not shown) according to the polarity control signal POL output from the LCD controller 80. Here, the gradation amplifier circuit AMP has a voltage follower circuit. The current drive capability of each of the gradation amplifiers AMP1,... AMPn constituting the gradation voltage generation circuit 27 is set by the amplifier power supply control circuit 271, and in this embodiment, as will be described later, The current drive capability is controlled to be changed based on the comparison result signal A input from the comparison circuit 26.

  FIG. 3 is a diagram illustrating circuit configurations of the selection circuit, the comparison circuit, and the gradation voltage generation circuit in the present embodiment. The comparison circuit 26 compares comparators 121R-1, 121G-1, 121B-1,..., 121R-m, 121G-m that compare the display data for each signal line held in the latch circuit 23 with the reference signal REF. , 121B-m (hereinafter collectively referred to as “comparator 121”). The comparator 121 compares the gradation level (gradation value) of the input display data with the reference gradation level (reference gradation value) indicated by the reference signal REF. The comparison result output from each comparator 121 is input to the OR circuit 261. The signal A output from the OR circuit 261 is input to the amplifier power supply control circuit 271 of the gradation voltage generation circuit 27.

  When the liquid crystal display panel 10 is in a normally white mode and the gradation level of the display data is low, the gradation voltage is high (black display), and when the gradation level is high, the gradation voltage is low ( White display), for example, the display data is 6 bits (64 gradations), the reference gradation level indicated by the reference signal REF is an intermediate 32 gradations, and the gradation level of the display data is 16 In the case of gradation, the comparator 121 compares the gradation level indicated by the input display data with the reference gradation level (32 gradations) indicated by the reference signal REF, and the gradation level of the display data is the reference gradation. It is determined that it is lower than the level, and “1” is output as the comparison result. On the other hand, when the gradation level of the display data is 48 gradations, the comparator 121 determines that the gradation level of the display data is higher than the reference gradation level, and outputs “0” as the comparison result. Thus, the comparator 121 outputs “1” as the comparison result when the gradation level of the input display data is equal to or lower than the reference gradation level, and as the comparison result when it is higher than the reference gradation level. Outputs “0”.

  The OR circuit 261 outputs “1” as the comparison result signal A when any of the comparison results output from the comparators 121R-1,..., 121B-m is “1”. When all the comparison results output from 121R-1,..., 121B-m are “0”, “0” is output as the comparison result signal A.

  The amplifier power supply control circuit 271 in the gradation voltage generation circuit 27 has a function of changing and controlling the set value of the current drive capability of the gradation amplifier AMP in accordance with the comparison result signal A output from the OR circuit 261. The OR circuit When “0” is input as the comparison result signal A from H.261, the amplifier power supply control circuit 271 lowers the set value of the current drive capability of the gradation amplifier AMP, and “1” is input as the comparison result signal A. If it is, the current drive capability of the gradation amplifier AMP is controlled to be higher than the set value when “0” is input as the comparison result signal A. The gradation amplifier AMP outputs the divided voltage as a gradation voltage to the gradation voltage application line AL in accordance with the current drive capability set by the amplifier power supply control circuit 271. That is, when “0” is input as the comparison result signal A, the gradation level of the display data is higher than the reference gradation level of the reference signal REF and the gradation voltage is relatively low. The current drive capability required for the AMP is in a relatively low state, and the current drive capability of the gradation amplifier AMP is set to be relatively low. On the other hand, when “1” is input as the comparison result signal A, the gradation level of the display data is lower than the reference gradation level of the reference signal REF, and the gradation voltage is relatively high. This is a state where the AMP requires a relatively high current driving capability, and the current driving capability of the gradation amplifier AMP is set to be relatively high. Note that switching of the current drive capability of the gradation amplifier AMP is performed, for example, by changing the current value of the bias current supplied from the power supply of the gradation amplifier AMP.

  As described above, in the present embodiment, the reference gradation level of the reference signal REF is compared with the gradation level of the display data, and the setting value of the current drive capability of the gradation amplifier AMP is changed and controlled based on the comparison result. When the gradation voltage corresponding to the gradation level of the display data is relatively low, the setting value of the current driving capability of the gradation amplifier AMP is lowered, and the gradation voltage corresponding to the gradation level of the display data is relatively high. In some cases, the current driving capability of the gradation amplifier AMP can be set to a level corresponding to the gradation level of the display data by increasing the set value of the current driving capability of the gradation amplifier AMP. As a result, it is possible to suppress a situation in which the gradation amplifier AMP has an excessive current driving capability and consumes power unnecessarily, and power consumption can be reduced.

The liquid crystal display device 1 according to the present embodiment includes the memory 60 that temporarily stores RGB signals. However, the present invention is not limited to this, and the RGB decoder 40 is not provided with the memory 60. The RGB signal (display data) may be directly output from the signal driver 20 to the signal driver 20.
<Modification>

  The application of the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit of the present invention. FIG. 4 is a circuit configuration diagram showing a modification of the selection circuit, the comparison circuit, and the gradation voltage generation circuit in the present embodiment. For example, in the above description, the gradation level of the display data for each signal line is compared with the reference gradation level of the reference signal REF. However, as shown in FIG. An adder 281 for adding the gradation levels of the display data for each signal line is provided, and the sum of the gradation levels of the display data for one line added by the adder 281 and the reference gradation level of the reference signal REF ′ It is good also as comparing. Here, the value of the reference gradation level of the reference signal REF ′ is, for example, a reference total value (reference total value) obtained by summing up the reference signal REF for one line.

  In FIG. 4, the comparator 282 outputs “1” as the comparison result signal A ′ when the total value input from the adder 281 is equal to or less than the reference total value indicated by the reference signal REF ′. When the total value input from 281 is larger than the reference total value indicated by the reference signal REF ′, “0” is output as the comparison result signal A ′. Similarly to the case of FIG. 3, the amplifier power supply control circuit 271 reduces the current drive capability of the gradation amplifier AMP when the comparison result signal A ′ is inputted from the comparator 282, and the comparison result When “1” is input as the signal A ′, switching is performed so as to increase the current drive capability of the gradation amplifier AMP. In this case, one comparator can be provided, and the circuit scale of the comparison circuit 28 can be reduced.

  In the above description, the total gradation level of the display data for one line is compared with the reference gradation level, but the average value of the gradation levels of the display data for one line is calculated. The average value may be compared with the reference gradation level. In this case, the reference gradation level of the reference signal is a reference average value (reference average value).

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the first embodiment described above, the display data for one line is compared with the reference signal REF. However, in the second embodiment of the present invention, each gradation level signal output from the decoder 841 is used. Is configured to control the operation / stop of the corresponding gradation amplifier AMP to reduce power consumption. The liquid crystal display device 1 according to the second embodiment is substantially the same as the liquid crystal display device 1 described with reference to FIG. 1 in the first embodiment, and only the configuration of the signal driver 20 is different.

  FIG. 5 is a configuration diagram of a main part of the signal driver in the present embodiment. In addition, about the function and structure equivalent to the structure in 1st Embodiment mentioned above, the same code | symbol is attached | subjected and the description is simplified or abbreviate | omitted. The signal driver 20A includes a shift register 21, a data register 22, a latch circuit 23, a selection circuit 24A, a comparison circuit 26A, a gradation voltage generation circuit 27A, an output buffer 25, and the like.

  The comparison circuit 26A outputs a signal for setting the operation / stop of each gradation amplifier AMP included in the gradation voltage generation circuit 27A based on each gradation level signal output from the decoder 841 of the selection circuit 24. Details will be described later.

  The gradation voltage generation circuit 27A divides between the voltages VS and GND by a plurality of resistors R corresponding to the number of gradations of display data, and the divided voltages are converted into a plurality of gradation voltages via the gradation amplifier AMP. Output.

  FIG. 6 is a diagram illustrating an example of the circuit configuration of the selection circuit, the comparison circuit, and the gradation voltage generation circuit in this embodiment. The comparison circuit 26A includes OR circuits 521, 522,..., 52n (hereinafter collectively referred to as “OR circuits 52”) to which the gradation level signal output from the decoder 841 is input. A gradation level signal for selecting the same gradation reference voltage of each pixel is input to the circuits 521, 522,. Signals B1, B2,..., Bn (hereinafter collectively referred to as “signal B”) output from the OR circuit 52 are output to the gradation voltage generation circuit 27A.

  In the gradation voltage generation circuit 27A, the amplifier power supply control circuit 271A supplies a predetermined bias current for setting the current drive capability of the gradation amplifier AMP to a predetermined level. Also provided are switches SW1, SW2,..., SWn (hereinafter collectively referred to as “switch SW”) for intermittently supplying the bias current output from the amplifier power supply control circuit 271A. Here, the switches SW1,..., SWn are normally turned off, and on / off switching is controlled by the signal B output from the OR circuit 52 of the comparison circuit 26A.

  For example, when n gradation level signals input to the OR circuit 521 in the OR circuit 52 are all “0”, the signal B1 output from the OR circuit 521 is “0”, and the switch SW1 is in the off state. Maintained. Accordingly, the bias current supplied from the amplifier power supply control circuit 271A is cut off, and the operation of the gradation amplifier AMP1 is stopped. On the other hand, when any one of the n gradation level signals input to the OR circuit 521 is “1”, the signal B1 output from the OR circuit 521 is “1”, and the corresponding switch SW1 is turned on. Then, the gradation amplifier AMP1 is activated.

  That is, in each gradation voltage output from the gradation voltage generation circuit 27A, the gradation level signal is “0” in any gradation voltage output line SLR1,..., SLBm and is connected to the gradation voltage application line AL. When all the selected switches SW are turned off, it is not necessary to apply the gradation voltage to the gradation voltage application line AL, so that the operation of the corresponding gradation amplifier AMP is stopped. Further, when any of the gradation level signals of the gradation voltage output lines SLR1,..., SLBm is “1” and any of the selection switches SW connected to the gradation voltage application line AL is turned on. Then, the gradation amplifier AMP having the corresponding gradation voltage is operated.

  As described above, in this embodiment, by controlling the operation / stop of the corresponding gradation amplifier AMP based on each gradation level signal, generation of gradation voltages that do not require output is stopped, and the liquid crystal display device Power consumption can be reduced.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. The third embodiment has a configuration in which the first embodiment and the second embodiment described above are combined. FIG. 7 is a main part configuration diagram of the signal driver in the present embodiment. In addition, about the function and structure equivalent to the structure in 1st Embodiment mentioned above and 2nd Embodiment, the same code | symbol is attached | subjected and the description is simplified or abbreviate | omitted. The signal driver 20B includes a shift register 21, a data register 22, a latch circuit 23, a selection circuit 24A, an output buffer 25, a first comparison circuit 26B, a second comparison circuit 28B, a gradation voltage generation circuit 27B, and the like.

  The first comparison circuit 26B is the same as the comparison circuit 26 in the first embodiment, and compares the display data for each pixel held in the latch circuit 23 with the reference signal REF input from the LCD controller 80. The comparison result is output to the gradation voltage generation circuit 27B.

  The selection circuit 24A has the same configuration as the selection circuit 24A in the second embodiment. The second comparison circuit 28B has a configuration similar to that of the comparison circuit 26A in the second embodiment, and the gradation voltage generation circuit 27B is configured based on each gradation level signal output from the decoder 841 of the selection circuit 24B. A signal for setting operation / stop of the gradation amplifier AMP provided is output.

  The gradation voltage generation circuit 27B divides the voltage VS and GND by a plurality of resistors R corresponding to the number of gradations of display data, and the divided voltages are converted into a plurality of gradation voltages via the gradation amplifier AMP. Output. The current drive capability of the gradation amplifier AMP constituting the gradation voltage generation circuit 27B is controlled based on the comparison result input from the first comparison circuit 26B, and the operation / stop of the gradation amplifier AMP is controlled by the second comparison circuit 28B. It is controlled on the basis of a more input signal.

  FIG. 8 is a diagram illustrating an example of the circuit configuration of the selection circuit, the first comparison circuit, the second comparison circuit, and the gradation voltage generation circuit in this embodiment. First, the comparator 121 of the first comparison circuit 26B compares the gradation level of the display data for each signal line with the reference gradation level of the reference signal REF. The comparison results output from the respective comparators 121R-1,..., 121B-m are input to the OR circuit 261. The comparison result signal A output from the OR circuit 261 is input to the amplifier power supply control circuit 271 of the gradation voltage generation circuit 27B.

  The current drive capability of the gradation amplifier AMP is set by the amplifier power supply control circuit 271, and switching control of the current drive capability of the gradation amplifier AMP is performed based on the comparison result signal A output from the OR circuit 261.

  Further, each of the OR circuits 521, 522,..., 52n of the second comparison circuit 28B receives a gradation level signal for selecting the same gradation voltage, and the signal B output from the OR circuit 52 is the gradation voltage. Based on the signal B output to the generation circuit 27A, the on / off of the switch SW is controlled.

  As a result, the grayscale amplifier AMP has an excessive current driving capability and suppresses a state where wasteful power is consumed, and generation of a grayscale voltage that does not require output is stopped, thereby further reducing power consumption. Can be reduced.

1 is a block diagram illustrating a configuration of a liquid crystal display device according to a first embodiment. The principal part block diagram of the signal driver in 1st Embodiment. FIG. 3 is a circuit configuration diagram of a selection circuit, a comparison circuit, and a gradation voltage generation circuit in the first embodiment. FIG. 6 is a circuit configuration diagram showing a modification of the selection circuit, the comparison circuit, and the gradation voltage generation circuit in the first embodiment. The principal part block diagram of the signal driver in 2nd Embodiment. The circuit block diagram of the selection circuit in the 2nd Embodiment, a comparison circuit, and a gradation voltage generation circuit. The principal part block diagram of the signal driver in 3rd Embodiment. The circuit block diagram of the selection circuit in the 3rd Embodiment, a comparison circuit, and a gradation voltage generation circuit. The principal part block diagram of the conventional liquid crystal display device. The principal part block diagram of the conventional signal driver. The circuit block diagram of the conventional selection circuit, a comparison circuit, and a gradation voltage generation circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 10 Liquid crystal display panel 20 Signal driver 21 Shift register 22 Data register 23 Latch circuit 24, 24A, 24B Selection circuit 25 Output buffer 26, 26A Comparison circuit 26B First comparison circuit 28B Second comparison circuits 27, 27A, 27B Grayscale voltage generation circuit 30 Scan driver 40 RGB decoder

60 Memory 70 Drive amplifier 80 LCD controller 90 Voltage generation circuit

Claims (6)

A voltage corresponding to the gradation level is generated for each gradation level by dividing the predetermined voltage into a plurality of voltages, and an amplifier circuit corresponding to the gradation level is provided for each gradation level. A driving device comprising:
When each of the voltages simultaneously applied to the signal lines of the display panel is smaller than a voltage corresponding to a predetermined gradation level, the values of the bias currents supplied to the amplifier circuits are mutually equal at a predetermined current value. Supplying the bias current to be equal,
When any one of the voltages simultaneously applied to the signal lines of the display panel is higher than a voltage corresponding to the predetermined gradation level, the value of the bias current supplied to each of the amplifier circuits is A display driving apparatus comprising means for supplying the bias current so as to be equal to each other at a current value larger than a predetermined current value . A voltage corresponding to the gradation level is generated for each gradation level by dividing the predetermined voltage into a plurality of voltages, and an amplifier circuit corresponding to the gradation level is provided for each gradation level. A driving device comprising:
When the total value of the gradation levels corresponding to each of the voltages applied simultaneously to each signal line of the display panel is smaller than a predetermined threshold, the value of the bias current supplied to each of the amplifier circuits is a predetermined current Supplying the bias current to be equal to each other in value,
When the total value is larger than the predetermined threshold value, the bias current is supplied so that the bias current values supplied to the amplifier circuits are equal to each other at a current value larger than the predetermined current value. A display driving device characterized by comprising: A plurality of signal lines are provided on the display panel, and an amplifier circuit corresponding to the gradation level is provided for each gradation level.
A display device that generates a voltage corresponding to each gradation level by dividing a predetermined voltage into a plurality of voltages,
When each voltage applied simultaneously to each signal line of the display panel is smaller than a voltage corresponding to a predetermined gradation level, the value of the bias current supplied to each of the amplifier circuits is a predetermined current value. Supplying the bias currents to be equal to each other;
When any one of the voltages simultaneously applied to the signal lines of the display panel is higher than a voltage corresponding to the predetermined gradation level, the value of the bias current supplied to each of the amplifier circuits is A display device comprising means for supplying the bias current so as to be equal to each other at a current value larger than a predetermined current value. A plurality of signal lines are provided on the display panel, and an amplifier circuit corresponding to the gradation level is provided for each gradation level.
A display device that generates a voltage corresponding to each gradation level by dividing a predetermined voltage into a plurality of voltages,
When the total value of the gradation levels corresponding to each of the voltages simultaneously applied to the signal lines of the display panel is smaller than a predetermined threshold, the value of the bias current supplied to each of the amplifier circuits is a predetermined value. Supplying the bias current so that the current values are equal to each other;
When the total value is larger than the predetermined threshold value, the bias current is supplied so that the bias current values supplied to the amplifier circuits are equal to each other at a current value larger than the predetermined current value. A display device comprising means for performing A voltage corresponding to the gradation level is generated for each gradation level by dividing the predetermined voltage into a plurality of voltages, and an amplifier circuit corresponding to the gradation level is provided for each gradation level. A drive control method for a drive device, comprising:
When each of the voltages simultaneously applied to the signal lines of the display panel is smaller than a voltage corresponding to a predetermined gradation level, the values of the bias currents supplied to the amplifier circuits are mutually equal at a predetermined current value. Supplying the bias current to be equal,
When any one of the voltages simultaneously applied to the signal lines of the display panel is higher than a voltage corresponding to the predetermined gradation level, the value of the bias current supplied to each of the amplifier circuits is A drive control method for a display drive device, characterized in that the bias currents are supplied so as to be equal to each other at a current value larger than a predetermined current value. A voltage corresponding to the gradation level is generated for each gradation level by dividing the predetermined voltage into a plurality of voltages, and an amplifier circuit corresponding to the gradation level is provided for each gradation level. A drive control method for a drive device, comprising:
When the total value of the gradation levels corresponding to each of the voltages applied simultaneously to each signal line of the display panel is smaller than a predetermined threshold, the value of the bias current supplied to each of the amplifier circuits is a predetermined current Supplying the bias current to be equal to each other in value,
When the total value is larger than the predetermined threshold value, the bias current is supplied so that the bias current values supplied to the amplifier circuits are equal to each other at a current value larger than the predetermined current value. A drive control method for a display drive device.

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