Patent Publication Number: US-11049469-B2

Title: Data signal line drive circuit and liquid crystal display device provided with same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to U.S. Provisional Application No. 62/937,291 filed on Nov. 19, 2019. The entire contents of the above-identified application are hereby incorporated by reference. 
    
    
     BACKGROUND 
     Technical Field 
     The following disclosure relates to a data signal line drive circuit of a liquid crystal display device, and particularly relates to a data signal line drive circuit of a liquid crystal display device including memory circuits in pixel circuits. 
     In recent years, liquid crystal display devices provided with memory circuits in pixel circuits have been developed in order to reduce power consumption. Such a liquid crystal display device is referred to as “memory liquid crystal” or the like. In general, in the memory liquid crystal, one bit of data can be held for each pixel, and in a case where an image of the same content or an image with a little change is displayed for a long period of time, image display is performed by using the data held in the memory circuit. In the memory liquid crystal, once the data is written to the memory circuit, the contents of the data written to the memory circuit are then held until rewritten. Thus, little power is consumed in periods other than the periods before and after the contents of the image change. Therefore, low power consumption can be achieved by the memory liquid crystal. 
     Incidentally, a circuit that supplies a data signal to a pixel circuit in the memory liquid crystal is referred to as a “binary driver”.  FIG. 26  is a circuit block diagram illustrating a configuration of a portion of a known binary driver. Note that, it is also assumed here that there are 1600 source bus lines (data signal lines) that are driven for every 16 lines. It is also assumed that binary data is written to each of the source bus lines. A portion corresponding to the source bus lines from the (16z−15)-th line to the 16z-th line is referred to as a “z-th stage” with z as an integer greater than or equal to 1 and smaller than or equal to 100. For example, a portion corresponding to the source bus lines from the 33-th line to the 48-th line is referred to as a “third stage”. A reference sign, for example, SL &lt;1:16&gt;, such as in  FIG. 26  denotes a data signal output to the source bus lines from the first line to the 16-th line. 
     The binary driver is constituted with a shift register  910  including 100 unit circuits  91  ( 1 ) to  91  ( 100 ), a first latch portion  920  constituted with 100 first latch circuits  92  ( 1 ) to  92  ( 100 ), and a second latch portion  930  constituted with 100 second latch circuits  93  ( 1 ) to  93  ( 100 ). Note that  FIG. 26  illustrates constituent elements from the first stage to the fourth stage. 
     Each of the first latch circuits  92  includes 16 unit latch circuits corresponding to the 16 source bus lines, respectively. Similarly, each of the second latch circuits  93  includes 16 unit latch circuits corresponding to the 16 source bus lines, respectively. The unit latch circuits employ D latch circuits, referred to as “pass-through latches”, “gated D latches” and the like. The unit latch circuit captures a data signal, based on an enable signal EN and outputs the captured data signal. Note that, hereinafter, a signal provided as an enable signal EN to the first latch circuit  92  is referred to as a “first latch signal”, and a signal provided as an enable signal EN to the second latch circuit  93  is referred to as a “second latch signal”. 
     Each of the unit circuits  91  in the shift register  910  operates based on a binary start pulse signal BSP and two-phased binary clock signals BCK and BCKB. The output signal LTEN from each of the unit circuits  91  is provided as a set signal S to the unit circuit  91  at the next stage, and is provided as the first latch signal described above to the corresponding first latch circuit  92 . Each of the first latch circuits  92  captures a data signal DATA transmitted from the outside, based on the first latch signal, and outputs the captured data signal. Each of the second latch circuits  93  captures the data signal output from the corresponding first latch circuit  92 , based on the second latch signal and outputs the captured data signal to a corresponding source bus line. Note that, as can be understood from  FIG. 26 , all of the second latch circuits  93  ( 1 ) to  93  ( 100 ) are given the same signal EN 2  as the second latch signal. 
       FIG. 27  is a signal waveform diagram for describing the operation of the known binary driver. Note that numerical values listed in a column of the data signal DATA &lt;1:16&gt; indicates in what stage the data is. Here, data corresponding to a value greater than or equal to 1 or smaller than or equal to 100 is valid data. The numerical values listed in the columns of the binary clock signals BCK and BCKB represent of what stage of data the pulse contribute to the capturing. 
     After the pulse generation of the binary start pulse signal BSP, in a case where the binary clock signal BCK rises first, the output signal LTEN ( 1 ) from the unit circuit  91  ( 1 ) at the first stage is set to the high level. As a result, the first latch circuit  92  ( 1 ) at the first stage captures the data signal DATA transmitted from the outside. Next, in a case where the binary clock signal BCKB rises, the output signal LTEN ( 2 ) from the unit circuit  91  ( 2 ) at the second stage is set to the high level. As a result, the first latch circuit  92  ( 2 ) at the second stage captures the data signal DATA transmitted from the outside. In this way, in each of the first latch circuits  92 , the data signal DATA is captured based on the output signal LIEN from the corresponding unit circuit  91 . Then, in a case where the output signal LTEN ( 100 ) from the unit circuit  91  ( 100 ) at the 100-th stage is set to the high level, the data signal DATA has been captured by all of the first latch circuits  92  ( 1 ) to  92  ( 100 ). In such a state, the second latch signal EN 2  is set to the high level at the time point tx. As described above, this second latch signal EN 2  is provided in common to all of the second latch circuits  93  ( 1 ) to  93  ( 100 ). In this way, the capturing of the data signal in all of the second latch circuits  93  ( 1 ) to  93  ( 100 ) is performed in unison. Then, the data signal SL is output in unison to all of the source bus lines. In this regard, the source bus lines are connected to the pixel circuits and the wiring line capacity is large, and a number of source bus lines are disposed in a display portion. Thus, by the data signals being output in unison to all the source bus lines, a large current flows, resulting in a voltage drop (drop in power supply voltage) (see a section labeled with the reference signs  98  and  99  in  FIG. 27 ). Such a voltage drop may have an undesirable effect on the operation of the internal circuit and may be a factor of malfunction. Driving at a low voltage (e.g., 3 V) is often performed in the memory liquid crystal, and thus the memory liquid crystal is particularly susceptible to voltage drop. 
     A technique for reducing the effect of voltage drop as described above is disclosed in JP 2010-122509 A. Specifically, it is described that a delay circuit (see FIG. 3 and FIG. 5 of JP 2010-122509 A) is provided so as to generate time differences in the data capturing timing between a plurality of second latch groups in a case where data is captured by the plurality of second latch groups. However, it is difficult to generate a large time difference in data capturing timing by this technique. Thus, before the power supply returns from a voltage drop occurred due to capturing of data in a certain second latch group, capturing of data in a next second latch group may be performed in some cases. In this case, the voltage drop will occur again before the power supply returns, so the effect of reducing the effect of the voltage drop is less effective. Although it is possible to increase the time difference in data capturing timing by increasing the number of inverters that constitute the delay circuit, the increase in the number of inverters causes an increase in circuit size. As the number of inverters increases, the effect of process variation increases, which makes control difficult. 
     SUMMARY 
     Therefore, an object of the following disclosure is to realize a binary driver (data signal line drive circuit) that can effectively reduce the effect of voltage drop while suppressing an increase in circuit size. 
     (1) A data signal line drive circuit according to some embodiments of the disclosure is a data signal line drive circuit including: 
     a shift register including a plurality of unit circuits connected in series; 
     a first latch portion including a plurality of first latch circuits configured to operate based on two power supply voltages; and 
     a second latch portion including a plurality of second latch circuits configured to operate based on two power supply voltages, the data signal line drive circuit being configured to output data signals to a plurality of data signal lines, 
     wherein each of the plurality of first latch circuits captures a data signal transmitted from outside, based on a first latch signal, and outputs the captured data signal, 
     each of the plurality of second latch circuits captures a data signal output from a corresponding first latch circuit, based on a second latch signal, and outputs the captured data signal to a corresponding data signal line, 
     each of the plurality of first latch circuits is provided with a shift pulse output from a corresponding unit circuit as the first latch signal, and 
     first latch signals provided to (k+1)-th and subsequent first latch circuits are given as the second latch signal to a k-th second latch circuit, as capturing of data signals at the second latch portion is split into two or more timings, with k as a natural number. 
     According to such a configuration, the capturing of the data signals (data signals output from the first latch portion) in the second latch portion is performed by dividing into two or more timings instead of being performed in unison. In other words, the output timings of the data signals to the plurality of data signal lines are distributed. As a result, the size of the voltage drop caused by the output of the data signals to the data signal lines is significantly smaller than in the related art. Because no delay circuit is provided in the data signal line drive circuit, the time difference of the capturing timings of the data signals can be increased without increasing the circuit size. In the configuration described above, a data signal line drive circuit is realized that can effectively reduce the effect of voltage drop while suppressing an increase in circuit size. 
     (2) A data signal line drive circuit according to some embodiments of the disclosure includes the configuration of (1) described above, 
     wherein a first latch signal provided to a (k+p)-th first latch circuit is provided as the second latch signal to the k-th second latch circuit, with p as a particular natural number. 
     (3) A data signal line drive circuit according to some embodiments of the disclosure includes the configuration of (1) described above, 
     wherein a same signal is provided as the second latch signal to continuous q second latch circuits, with q as an integer greater than or equal to 2. 
     (4) A data signal line drive circuit according to some embodiments of the disclosure includes the configuration of (1) described above, 
     wherein the data signals represent binary data. 
     (5) A liquid crystal display device according to some embodiments of the disclosure includes: 
     a plurality of pixel circuits including memory circuits configure to hold data, based on the data signals; 
     a plurality of data signal lines configured to supply the data signals to the plurality of pixel circuits; and 
     a data signal line drive circuit according to any configuration of (1) to (4) described above. 
     These and other objects, features, aspects, and advantages of the disclosure will become more apparent from the following detailed description of the disclosure with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The disclosure will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a circuit block diagram illustrating a configuration of a portion of a binary driver according to a first embodiment. 
         FIG. 2  is a block diagram illustrating an overall configuration of a liquid crystal display device according to the first embodiment. 
         FIG. 3  is a diagram for describing a configuration of a display portion according to the first embodiment. 
         FIG. 4  is a circuit diagram illustrating a detailed configuration of a pixel circuit in the display portion according to the first embodiment. 
         FIG. 5  is a signal waveform diagram for describing the operation of the pixel circuit according to the first embodiment. 
         FIG. 6  is a block diagram illustrating a schematic configuration of the binary driver according to the first embodiment. 
         FIG. 7  is a circuit block diagram for describing a configuration of one stage of the binary driver according to the first embodiment. 
         FIG. 8  is a circuit diagram illustrating a configuration of one stage of a shift register (configuration of a unit circuit) according to the first embodiment. 
         FIG. 9  is a circuit diagram illustrating a detailed configuration of a unit latch circuit according to the first embodiment. 
         FIG. 10  is a signal waveform diagram for describing the operation of the binary driver according to the first embodiment. 
         FIG. 11  is a signal waveform diagram for describing the first latch signal provided to the first latch circuit and the second latch signal provided to the second latch circuit according to the first embodiment. 
         FIG. 12  is a diagram for describing reference signs used in  FIG. 11 . 
         FIG. 13  is a circuit block diagram illustrating a configuration of a portion of a binary driver according to a second embodiment. 
         FIG. 14  is a signal waveform diagram for describing the operation of the binary driver according to the second embodiment. 
         FIG. 15  is a signal waveform diagram for describing the first latch signal provided to the first latch circuit and the second latch signal provided to the second latch circuit according to the second embodiment. 
         FIG. 16  is a circuit block diagram illustrating a configuration of a portion of a binary driver according to a third embodiment. 
         FIG. 17  is a signal waveform diagram for describing the operation of the binary driver according to the third embodiment. 
         FIG. 18  is a signal waveform diagram for describing the first latch signal provided to the first latch circuit and the second latch signal provided to the second latch circuit according to the third embodiment. 
         FIG. 19  is a circuit block diagram illustrating a configuration of a portion of a binary driver according to a fourth embodiment. 
         FIG. 20  is a signal waveform diagram for describing the operation of the binary driver according to the fourth embodiment. 
         FIG. 21  is a signal waveform diagram for describing the first latch signal provided to the first latch circuit and the second latch signal provided to the second latch circuit according to the fourth embodiment. 
         FIG. 22  is a circuit block diagram illustrating a configuration of a portion of a binary driver according to a fifth embodiment. 
         FIG. 23  is a circuit block diagram illustrating a configuration of a portion (final stage side) of the binary driver according to the fifth embodiment. 
         FIG. 24  is a signal waveform diagram for describing the operation of the binary driver according to the fifth embodiment. 
         FIG. 25  is a signal waveform diagram for describing the first latch signal provided to the first latch circuit and the second latch signal provided to the second latch circuit according to the fifth embodiment. 
         FIG. 26  is a circuit block diagram illustrating a configuration of a portion of a known binary driver. 
         FIG. 27  is a signal waveform diagram for describing the operation of the known binary driver. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments will be described below with reference to the accompanying drawings. The liquid crystal display device described in each of the following embodiments is a liquid crystal display device called the “memory liquid crystal” described above. 
     1. First Embodiment 
     1.1 Overall Configuration and Schematic Operation 
       FIG. 2  is a block diagram illustrating an overall configuration of a liquid crystal display device  1  according to a first embodiment. 
     As illustrated in  FIG. 2 , the liquid crystal display device  1  includes a display portion  10 , a gate driver (scanning signal line drive circuit)  20 , and a binary driver (data signal line drive circuit)  30 . In the display portion  10 , as illustrated in  FIG. 3 , a plurality of (i) gate bus lines (scanning signal lines) GL ( 1 ) to GL (i), a plurality of (j) source bus lines (data signal lines) SL ( 1 ) to SL (j), and a plurality of (i*j) pixel circuits  100  each provided corresponding to the intersections of the plurality of gate bus lines GL ( 1 ) to GL (i) and the plurality of source bus lines SL ( 1 ) to SL (j) are formed. Note that a detailed configuration of the pixel circuits  100  will be described later. 
     The gate driver  20  drives the gate bus lines GL ( 1 ) to GL (i), based on a gate control signal GCTL transmitted from the outside. The gate control signal GCTL includes a gate start pulse signal and a gate clock signal. The operation of the gate driver  20  typically applies active scanning signals sequentially one at a time to the i gate bus lines GL, in each vertical scanning period. The binary driver  30  receives a binary control signal BCTL and a data signal DATA transmitted from the outside, and applies the data signal to the j source bus lines SL ( 1 ) to SL (j). The detailed configuration and operation of the binary driver  30  will be described later. Note that the gate control signal GCTL and the binary control signal BCTL may be generated by a timing generator in the liquid crystal display device  1 . 
     As described above, by the data signal being applied to each of the source bus lines SL ( 1 ) to SL (j), and the scanning signal being applied to each of the gate bus lines GL ( 1 ) to GL (i), an image is displayed to the display portion  10 . Note that in the following, the data signal applied to the source bus lines is also denoted by the reference sign SL, and the scanning signal applied to the gate bus lines is also denoted by reference sign GL. 
     1.2 Pixel Circuit 
       FIG. 4  is a circuit diagram illustrating a detailed configuration of one pixel circuit  100  in the display portion  10 . Note that the configuration illustrated in  FIG. 4  is merely an example, and no such limitation is intended. As illustrated in  FIG. 4 , the pixel circuit  100  in the present embodiment includes a switch  110 , a memory circuit  120 , a liquid crystal drive voltage application circuit  130 , and a display element portion  140 . The pixel circuit  100  is supplied with the scanning signal GL, the data signal SL, the high-level power source voltage VDD, the low-level power source voltage VSS, the white display voltage VA, and the black display voltage VB. 
     The switch  110  is a n-channel type transistor. The switch  110  is in the on state in a case where the scanning signal GL is at the high level. In a case where the switch  110  is in the on state, the source bus line SL and the node  125  in the memory circuit  120  are electrically connected via the switch  110 . In the configuration described above, in a case where the scanning signal GL is at the high level, the potential of the data signal SL is provided to the node  125 . 
     The memory circuit  120  is constituted by a CMOS inverter  120   a  including a p-channel type transistor  121  and an re-channel type transistor  122 , and a CMOS inverter  120   b  including a p-channel type transistor  123  and an n-channel type transistor  124 . For the CMOS inverter  120   a , the input terminal is connected to the node  126 , and the output terminal is connected to the node  125 . For the CMOS inverter  120   b , the input terminal is connected to the node  125 , and the output terminal is connected to the node  126 . In the configuration described above, the memory circuit  120  functions to hold a value (logic value) based on the potential provided to the node  125  in a case where the switch  110  is in the on state until the next time the switch  110  is in the on state. 
     The liquid crystal drive voltage application circuit  130  is constituted by a CMOS switch  130   a  including a p-channel type transistor  131  and an n-channel type transistor  132 , and a CMOS switch  130   b  including an n-channel type transistor  133  and a p-channel type transistor  134 . The CMOS switch  130   a  is in the on state in a case where the potential of the node  125  is at the high level and the potential of the node  126  is at the low level. In a case where the CMOS switch  130   a  is in the on state, a white display voltage VA is provided to the pixel electrode  142 . The CMOS switch  130   b  is in the on state in a case where the potential of the node  125  is at the low level and the potential of the node  126  is at the high level. In a case where the CMOS switch  130   b  is in the on state, a black display voltage VB is provided to the pixel electrode  142 . 
     The display element portion  140  is constituted by a liquid crystal  141 , a pixel electrode  142 , and a common electrode  143 . A voltage is applied to the liquid crystal, based on the voltage applied to the pixel electrode  142  and the voltage applied to the common electrode  143 , and the liquid crystal application voltage is reflected in the display state of the pixel. 
     According to the pixel circuit  100  configured as described above, in a case where the scanning signal GL applied to the corresponding gate bus line is at the high level, the binary data is held in the memory circuit  120 , based on the potential of the data signal SL that is being applied to the corresponding source bus line (see  FIG. 5 ). In the liquid crystal drive voltage application circuit  130 , the display voltage to be applied to the pixel electrode  142  (either the white display voltage VA or the black display voltage VB) is selected based on the binary data held in the memory circuit  120 . Then, the selected display voltage is applied to the pixel electrode  142  (see the waveform of the reference sign PIX in  FIG. 5 ), and the display state of the pixel becomes a white display or a black display. 
     Note that a CMOS switch including a p-channel type transistor and an n-channel type transistor may be provided instead of an n-channel type transistor as the switch  110 . An n-channel type transistor may be provided instead of the CMOS switch  130   a , and an n-channel type transistor may be provided instead of the CMOS switch  130   b.    
     1.3 Configuration of Binary Driver 
       FIG. 6  is a block diagram illustrating a schematic configuration of the binary driver  30 . As illustrated in  FIG. 6 , the binary driver  30  includes a shift register  310 , a first latch portion  320 , and a second latch portion  330 . The shift register  310  is provided with a binary start pulse signal BSP and binary clock signals BCK and BCKB from the outside as the binary control signal BCTL. The first latch portion  320  is provided with a data signal DATA from the outside. Note that in the present embodiment, the data signal DATA is composed of 16 pieces of data of 1 bit. 
       FIG. 1  is a circuit block diagram illustrating a configuration of a portion of the binary driver  30  according to the present embodiment. Note that  FIG. 1  illustrates constituent elements from the first stage to the fourth stage. It is also assumed here that there are 1600 source bus lines that are driven for every 16 lines. The binary driver  30  is constituted with the shift register  310  constituted with 104 unit circuits  31  ( 1 ) to  31  ( 104 ), for example, connected in series, the first latch portion  320  constituted with 100 first latch circuits  32  ( 1 ) to  32  ( 100 ), and the second latch portion  330  constituted with 100 second latch circuits  33  ( 1 ) to  33  ( 100 ). 
     Here, a configuration of one stage of the shift register  310  (the configuration of the unit circuit  31 ) will be described with reference to  FIG. 8 . Note that the configuration described hereinafter is merely an example, and no such limitation is intended. As illustrated in  FIG. 8 , the unit circuit  31  includes: a CMOS inverter  510  constituted with a p-channel type transistor  511  and an n-channel type transistor  512 ; a CMOS inverter  520  constituted with a p-channel type transistor  521  and an n-channel type transistor  522 ; a switch (n-channel type transistor)  530 ; a clocked inverter  540  constituted with a p-channel type transistor  541 , a p-channel type transistor  542 , an n-channel type transistor  543 , and an n-channel type transistor  544 ; a CMOS inverter  550  constituted with a p-channel type transistor  551  and an n-channel type transistor  552 ; a NAND circuit  560 ; a NOR circuit  570 ; an inverter  580 ; and an inverter  590 . 
     As can be seen from  FIG. 1  and  FIG. 8 , to each of the unit circuits  31 , one of the binary clock signal BCK and the binary clock signal BCKB is input as a clock CK, the other of the binary clock signal BCK and the binary clock signal BCKB is input as a clock CKB, the output signal LIEN from the unit circuit  31  at one stage before is given as a set signal S, and the output signal LIEN from the unit circuit  31  at one stage later is given as a reset signal R. However, the binary start pulse signal BSP is given as the set signal S to the unit circuit  31  ( 1 ) at the first stage. 
     In the unit circuit  31 , in a case where the set signal S is set to the high level while the reset signal R is maintained at the low level, the potential of the node  515  is set to the low level while the switch  530  is off. As a result, the potential of the node  525  is set to the high level. Here, for the clocked inverter  540 , the input terminal is connected to the node  546 , and the output terminal is connected to the node  547 . For the CMOS inverter  550 , the input terminal is connected to the node  547 , and the output terminal is connected to the node  546 . In the configuration described above, during the period in which the reset signal R is maintained at the low level, the potential of the node  525  is held by the clocked inverter  540  and the CMOS inverter  550 . In a case where the clock CK is at the high level in this state, the output signal from the NAND circuit  560  is set to the low level. At this time, the clock CKB is at the low level, and the output signal from the NOR circuit  570  is at the high level. Then, the output signal from the inverter  580  is set to the low level, and the output signal from the inverter  590  is set to the high level. In this way, the output signal OUT from the unit circuit  31  is set to the high level. 
     In the unit circuit  31 , in a case where the reset signal R is set to the high level while the set signal S is maintained at the low level, the n-channel type transistors  522  and  530  are in the on state and the p-channel type transistor  521  is in the off state, so the potential of the node  525  is set to the low level. At this time, because the potential of the node  547  is also set to the low level, the output signal from the NAND circuit  560  is set to the high level regardless of whether the clock CK is at the high level or the low level. As a result, the output signal from the NOR circuit  570  is set to the low level regardless of whether the clock CKB is at the high level or the low level. Then, the output signal from the inverter  580  is set to the high level, and the output signal from the inverter  590  is set to the low level. In this way, the output signal OUT from the unit circuit  31  is set to the low level. 
     In the configuration described above, in each of the unit circuits  31 , after the set signal S is set to the high level, the output signal LTEN is set to the high level, based on the clocks CK and CKB (i.e., the shift pulse is outputted). Then, the output signal LTEN is set to the low level by the reset signal R being at the high level. 
     Since the unit circuit  31  operates as described above, the output signal LTEN from the unit circuit  31  is set to the high level stage by stage, based on the binary clock signals BCK and BCKB, after the generation of the pulse of the binary start pulse signal BSP. That is, the high-level output signal LTEN output from each of the unit circuits  31  is sequentially transferred as a shift pulse from the first stage to the final stage. The output signal LTEN from each of the unit circuits  31  is provided to the unit circuits  31  at the next stage and the previous stage, is provided as a first latch signal to the corresponding first latch circuit  32 , and is provided as a second latch signal to the second latch circuit  33  in two prior stages. In this way, the first latch circuit  32  as well as the second latch circuit  33  are operated based on the output signal LTEN from the unit circuit  31  constituting the shift register  310 . 
     With respect to the constituent elements illustrated in  FIG. 1 , each of the first latch circuits  32  captures the data signal DATA transmitted from the outside, based on the first latch signal (output signal LTEN from the corresponding unit circuit  31 ) and outputs the captured data signal. Each of the second latch circuits  33  captures the data signal output from the corresponding first latch circuit  32 , based on the second latch signal (output signal LTEN from the unit circuit  31  of two stages later), and outputs the captured data signal to the corresponding source bus line SL. 
     Incidentally, the portion denoted by reference sign  4  in  FIG. 1  is actually configured as illustrated in  FIG. 7 . That is, each of the first latch circuits  32  includes 16 unit latch circuits  60  corresponding to each of the 16 source bus lines SL. Similarly, each of the second latch circuits  33  includes 16 unit latch circuits  60  corresponding to each of the 16 source bus lines SL. The unit latch circuits employ D latch circuits, referred to as “pass-through latches”, “gated D latches” and the like. 
       FIG. 9  is a circuit diagram illustrating a detailed configuration of a unit latch circuit  60 . Note that the configuration described hereinafter is merely an example, and no such limitation is intended. The unit latch circuit  60  includes: a CMOS inverter  610  constituted with a p-channel type transistor  611  and an n-channel type transistor  612 ; a CMOS switch  620  constituted with an n-channel type transistor  621  and a p-channel type transistor  622 ; a clocked inverter  630  constituted with a p-channel type transistor  631 , a p-channel type transistor  632 , a n-channel type transistor  633 , and an n-channel type transistor  634 ; a CMOS inverter  640  constituted with a p-channel type transistor  641  and an re-channel type transistor  642 ; and a CMOS inverter  650  constituted with a p-channel type transistor  651  and an re-channel type transistor  652 . 
     The unit latch circuit  60  in the first latch circuit  32  is provided with a data signal DATA transmitted from the outside as an input signal IN, and is provided with a first latch signal as an enable signal EN. The unit latch circuit  60  in the second latch circuit  33  is provided with a data signal output from the corresponding unit latch circuit  60  in the first latch circuit  32  as an input signal IN, and is provided with a second latch signal as an enable signal EN. Note that the input signal IN to the unit latch circuit  60  is one bit of data (i.e., binary data). 
     The enable signal EN input to the unit latch circuit  60  is provided to the gate terminal of the n-channel type transistor  621 . As illustrated in  FIG. 9 , the CMOS inverter  610  is provided so that an inverted enable signal ENB is provided to the gate terminal of the p-channel type transistor  622 . In the configuration described above, in a case where the enable signal EN is at the high level, both the n-channel type transistor  621  and the p-channel type transistor  622  are set to the on state, so the input signal IN is provided to the clocked inverter  630 . On the other hand, in a case where the enable signal EN is at the low level, both the n-channel type transistor  621  and the p-channel type transistor  622  are set to the off state, so the input signal IN is not provided to the clocked inverter  630 . 
     For the clocked inverter  630 , the input terminal is connected to the node  662 , and the output terminal is connected to the node  661 . For the CMOS inverter  640 , the input terminal is connected to the node  661 , and the output terminal is connected to the node  662 . In a case where the enable signal EN is at the low level, both the p-channel type transistor  631  and the n-channel type transistor  634  are set to the on state, and in a case where the enable signal EN is at the high level, both the p-channel type transistor  631  and the n-channel type transistor  634  are set to the off state. In the configuration described above, the value of the input signal IN input to the unit latch circuit  60  in a case where the enable signal EN is at the high level is then held by the clocked inverter  630  and the CMOS inverter  640  over a period until the next time the enable signal EN is set to the high level. Incidentally, in a case where the input signal IN is at the high level, the potential of the node  661  is set to the high level, and the output signal OUT is also set to the high level. On the other hand, in a case where the input signal IN is at the low level, the potential of the node  661  is set to the low level, and the output signal OUT is also set to the low level. 
     Because the unit latch circuit  60  operates as described above, the first latch circuit  32  captures and outputs the data signal, based on the first latch signal, and the second latch circuit  33  captures and outputs the data signal, based on the second latch signal. 
     1.4 Operation of Binary Driver 
       FIG. 10  is a signal waveform diagram for describing the operation of the binary driver  30  according to the present embodiment.  FIG. 11  is a signal waveform diagram for describing the first latch signal provided to the first latch circuit  32  and the second latch signal provided to the second latch circuit  33 .  FIG. 12  is a diagram for describing reference signs used in  FIG. 11 . As illustrated in  FIG. 12 , in  FIG. 11 , the first latch signal provided to the first latch circuit  32  ( k ) at the k stage is denoted by the reference sign L 1  ( k ) in, and the second latch signal provided to the second latch circuit  33  ( k ) at the k stage is denoted by the reference sign L 2  ( k ) in (the same applies to  FIG. 15 ,  FIG. 18 ,  FIG. 21 , and  FIG. 25 ). 
     After the pulse generation of the binary start pulse signal BSP, in a case where the binary clock signal BCK rises first, the output signal LIEN ( 1 ) from the unit circuit  31  ( 1 ) at the first stage is set to the high level. The output signal LIEN ( 1 ) is provided to the first latch circuit  32  ( 1 ) at the first stage as the first latch signal L 1  ( 1 ) in. As a result, the first latch circuit  32  ( 1 ) at the first stage captures the data signal DATA transmitted from the outside. Next, in a case where the binary clock signal BCKB rises, the output signal LIEN ( 2 ) from the unit circuit  31  ( 2 ) at the second stage is set to the high level. The output signal LIEN ( 2 ) is provided to the first latch circuit  32  ( 2 ) at the second stage as the first latch signal L 1  ( 2 ) in. As a result, the first latch circuit  32  ( 2 ) at the second stage captures the data signal DATA transmitted from the outside. Next, in a case where the binary clock signal BCK rises, the output signal LIEN ( 3 ) from the unit circuit  31  ( 3 ) at the third stage is set to the high level. The output signal LIEN ( 3 ) is provided to the first latch circuit  32  ( 3 ) at the third stage as the first latch signal L 1  ( 3 ) in. As a result, the first latch circuit  32  ( 3 ) at the third stage captures the data signal DATA transmitted from the outside. 
     Incidentally, the output signal LIEN ( 3 ) is provided as the second latch signal L 2  ( 1 ) in to the second latch circuit  33  ( 1 ) at the first stage. Thus, at the time point t 01  (see  FIG. 10 ), the second latch circuit  33  ( 1 ) at the first stage captures the data signal output from the first latch circuit  32  ( 1 ) at the first stage. Then, the data signal captured in the second latch circuit  33  ( 1 ) at the first stage is output to the 1 to 16 column source bus lines. Thereafter, each time the binary clock signal BCK or the binary clock signal BCKB rises, the capturing of the data signal in the first latch circuit  32  and the capturing of the data signal in the second latch circuit  33  are performed. Note that in a case where the output signal LIEN (N) from the unit circuit  31  (N) at the N-th stage is set to the high level as N is an integer equal to or greater than 3, the first latch signal L 1  (N) in provided to the first latch circuit  32  (N) at the N-th stage and the second latch signal L 2  (N−2) in provided to the second latch circuit  33  (N−2) at the (N−2)-th stage are set to the high level, and the data signal DATA transmitted from the outside is captured by the first latch circuit  32  (N) at the N-th stage, while the data signal output from the first latch circuit  32  (N−2) at the (N−2)-th stage is capture by the second latch circuit  33  (N−2) at the (N−2)-th stage (see  FIG. 11 ). 
     At the time point t 02  (see  FIG. 10 ), the output signal LIEN ( 102 ) from the unit circuit  31  ( 102 ) at the 102-th stage is set to the high level, and the data signal output from the first latch circuit  32  ( 100 ) at the 100-th stage is captured by the second latch circuit  33  ( 100 ) at the 100-th stage. The data signal captured in the second latch circuit  33  ( 100 ) at the 100-th stage is output to the 1585 to 1600 column source bus lines. 
     1.5 Effect 
     According to the present embodiment, as k is a natural number, the second latch circuit  33  ( k ) at the k-th stage is given the output signal LIEN (k+2) from the unit circuit  31  (k+2) at the (k+2)-th stage (in other words, the first latch signal provided to the first latch circuit  32  (k+2) at the (k+2)-th stage) as the second latch signal. For this reason, the capturing of the data signal in the second latch portion  330  is not performed in unison, but is performed sequentially stage by stage. In other words, the output of the data signal to the source bus lines is performed sequentially for every 16 lines. Since the output timing of the data signal to the source bus lines is distributed in this manner, the size of the voltage drop caused by the output of the data signal to the source bus lines becomes significantly smaller than in the related art (see portions with the reference signs  71  and  72  in  FIG. 10 ). Unlike the technique disclosed in JP 2010-122509 A, the time difference of the capturing timing of the data signal can be increased without increasing the circuit size. As described above, according to the present embodiment, a binary driver  30  can be realized in which a voltage drop effect can be effectively reduced while suppressing an increase in circuit size. 
     2. Second Embodiment 
     Hereinafter, aspects different from the first embodiment will be mainly described. 
     2.1 Configuration of Binary Driver 
       FIG. 13  is a circuit block diagram illustrating a configuration of a portion of the binary driver  30  according to the present embodiment. In the present embodiment, as k is a natural number, the second latch circuit  33  ( k ) at the k-th stage is provided with the first latch signal provided to the first latch circuit  32  (k+1) at the (k+1)-th stage as the second latch signal. In other words, the second latch circuit  33  ( k ) at the k-th stage is provided with the output signal LIEN (k+1) from the unit circuit  31  (k+1) at the (k+1)-th stage as the second latch signal. For example, the second latch circuit  33  ( 3 ) at the third stage is provided with the output signal LIEN ( 4 ) from the unit circuit  31  ( 4 ) at the fourth stage as the second latch signal. 
     2.2 Operation of Binary Driver 
       FIG. 14  is a signal waveform diagram for describing the operation of the binary driver  30  according to the present embodiment.  FIG. 15  is a signal waveform diagram for describing the first latch signal provided to the first latch circuit  32  and the second latch signal provided to the second latch circuit  33 . 
     After the pulse of the binary start pulse signal BSP is generated, in a case where the binary clock signal BCK rises first, the output signal LIEN ( 1 ) is set to the high level, and as in the first embodiment, the data signal DATA transmitted from the outside is captured by the first latch circuit  32  ( 1 ) at the first stage. Next, in a case where the binary clock signal BCKB rises, the output signal LIEN ( 2 ) is set to the high level, and as in the first embodiment, the data signal DATA transmitted from the outside is captured by the first latch circuit  32  ( 2 ) at the second stage. 
     In the present embodiment, the output signal LIEN ( 2 ) is provided as the second latch signal L 2  ( 1 ) in to the second latch circuit  33  ( 1 ) at the first stage (see  FIG. 15 ). Thus, at the time point t 11  (see  FIG. 14 ), the second latch circuit  33  ( 1 ) at the first stage captures the data signal output from the first latch circuit  32  ( 1 ) at the first stage. Then, the data signal captured in the second latch circuit  33  ( 1 ) at the first stage is output to the 1 to 16 column source bus lines. Thereafter, each time the binary clock signal BCK or the binary clock signal BCKB rises, the capturing of the data signal in the first latch circuit  32  and the capturing of the data signal in the second latch circuit  33  are performed. Note that in a case where the output signal LIEN (N) from the unit circuit  31  (N) at the N-th stage is set to the high level as N is an integer equal to or greater than 2, the first latch signal L 1  (N) in provided to the first latch circuit  32  (N) at the N-th stage and the second latch signal L 2  (N−1) in provided to the second latch circuit  33  (N−1) at the (N−1)-th stage are set to the high level, and the data signal DATA transmitted from the outside is captured by the first latch circuit  32  (N) at the N-th stage, while the data signal output from the first latch circuit  32  (N−1) at the (N−1)-th stage is capture by the second latch circuit  33  (N−1) at the (N−1)-th stage (see  FIG. 15 ). 
     At the time point t 12  (see  FIG. 14 ), the output signal LIEN ( 101 ) from the unit circuit  31  ( 101 ) at the 101-th stage is set to the high level, and the data signal output from the first latch circuit  32  ( 100 ) at the 100-th stage is captured by the second latch circuit  33  ( 100 ) at the 100-th stage. The data signal captured in the second latch circuit  33  ( 100 ) at the 100-th stage is output to the 1585 to 1600 column source bus lines. 
     2.3 Effects 
     In the present embodiment as well, similar to the first embodiment, a binary driver  30  can be realized in which a voltage drop effect can be effectively reduced while suppressing an increase in circuit size. 
     3. Third Embodiment 
     3.1 Configuration of Binary Driver 
       FIG. 16  is a circuit block diagram illustrating a configuration of a portion of the binary driver  30  according to the present embodiment. In the present embodiment, as k is a natural number, the second latch circuit  33  ( k ) at the k-th stage is provided with the first latch signal provided to the first latch circuit  32  (k+3) at the (k+3)-th stage as the second latch signal. In other words, the second latch circuit  33  ( k ) at the k-th stage is provided with the output signal LTEN (k+3) from the unit circuit  31  (k+3) at the (k+3)-th stage as the second latch signal. For example, the second latch circuit  33  ( 1 ) at the first stage is provided with the output signal LTEN ( 4 ) from the unit circuit  31  ( 4 ) at the fourth stage as the second latch signal. Note that the first latch signal provided to the first latch circuit  32  after the (k+4)-th stage may be provided as the second latch signal to the second latch circuit  33  ( k ) at the k-th stage. 
     3.2 Operation of Binary Driver 
       FIG. 17  is a signal waveform diagram for describing the operation of the binary driver  30  according to the present embodiment.  FIG. 18  is a signal waveform diagram for describing the first latch signal provided to the first latch circuit  32  and the second latch signal provided to the second latch circuit  33 . 
     In the present embodiment, the second latch circuit  33  ( 1 ) at the first stage is provided with the output signal LIEN ( 4 ) from the unit circuit  31  ( 4 ) at the fourth stage as the second latch signal. Therefore, by the output signal LTEN ( 4 ) being set to the high level at the time point t 21  (see  FIG. 17 ), the data signal output from the first latch circuit  32  ( 1 ) at the first stage is captured in the second latch circuit  33  ( 1 ) at the first stage. Then, the data signal captured in the second latch circuit  33  ( 1 ) at the first stage is output to the 1 to 16 column source bus lines. Thereafter, each time the binary clock signal BCK or the binary clock signal BCKB rises, the capturing of the data signal in the first latch circuit  32  and the capturing of the data signal in the second latch circuit  33  are performed. Note that in a case where the output signal LTEN (N) from the unit circuit  31  (N) at the N-th stage is set to the high level as N is an integer equal to or greater than 4, the first latch signal L 1  (N) in provided to the first latch circuit  32  (N) at the N-th stage and the second latch signal L 2  (N−3) in provided to the second latch circuit  33  (N−3) at the (N−3)-th stage are set to the high level, and the data signal DATA transmitted from the outside is captured by the first latch circuit  32  (N) at the N-th stage, while the data signal output from the first latch circuit  32  (N−3) at the (N−3)-th stage is capture by the second latch circuit  33  (N−3) at the (N−3)-th stage (see  FIG. 18 ). 
     At the time point t 22  (see  FIG. 17 ), the output signal LTEN ( 103 ) from the unit circuit  31  ( 103 ) at the 103-th stage is set to the high level, and the data signal output from the first latch circuit  32  ( 100 ) at the 100-th stage is captured by the second latch circuit  33  ( 100 ) at the 100-th stage. The data signal captured in the second latch circuit  33  ( 100 ) at the 100-th stage is output to the 1585 to 1600 column source bus lines. 
     3.3 Effects 
     In the present embodiment as well, similar to the first embodiment, a binary driver  30  can be realized in which a voltage drop effect can be effectively reduced while suppressing an increase in circuit size. 
     4. Fourth Embodiment 
     4.1 Configuration of Binary Driver 
       FIG. 19  is a circuit block diagram illustrating a configuration of a portion of the binary driver  30  according to the present embodiment. In the first to third embodiments, the output signal LIEN from each of the unit circuits  31  constituting the shift register  310  is provided only to one second latch circuit  33  as the second latch signal. In contrast, in the present embodiment, the output signals LIEN from the unit circuits  31  at the even-numbered stages are not provided to any second latch circuit  33  as the second latch signal, but the output signals LIEN from the unit circuits  31  at the odd-numbered stages are provided to two second latch circuits  33  that are continuous as the second latch signal. Specifically, as N is an odd number equal to or greater than 3, the output signal LIEN (N) from the unit circuit  31  (N) at the N-th stage is given to the second latch circuit  33  (N−2) at the (N−2)-th stage and the second latch circuit  33  (N−1) at the (N−1)-th stage as the second latch signal. For example, the output signal LIEN ( 3 ) from the unit circuit  31  ( 3 ) at the third stage is provided to the second latch circuit  33  ( 1 ) at the first stage and the second latch circuit  33  ( 2 ) at the second stage as the second latch signal. As described above, the two continuous second latch circuits  33  are given the same signal as the second latch signal. 
     4.2 Operation of Binary Driver 
       FIG. 20  is a signal waveform diagram for describing the operation of the binary driver  30  according to the present embodiment.  FIG. 21  is a signal waveform diagram for describing the first latch signal provided to the first latch circuit  32  and the second latch signal provided to the second latch circuit  33 . Focusing on the second latch signal in  FIG. 21 , it is understood that the output signal LIEN ( 3 ) from the unit circuit  31  ( 3 ) at the third stage is provided as the second latch signals L 2  ( 1 ) in to L 2  ( 2 ) in to the second latch circuits  33  ( 1 ) to  33  ( 2 ) at the first to second stages, and it is understood that the output signal LIEN ( 5 ) from the unit circuit  31  ( 5 ) at the fifth stage is provided as the second latch signals L 2  ( 3 ) in to L 2  ( 4 ) in to the second latch circuits  33  ( 3 ) to  33  ( 4 ) at the third to fourth stages. 
     After the pulse of the binary start pulse signal BSP is generated, in a case where the binary clock signal BCK rises first, the output signal LIEN ( 1 ) is set to the high level, and as in the first embodiment, the data signal DATA transmitted from the outside is captured by the first latch circuit  32  ( 1 ) at the first stage. Next, in a case where the binary clock signal BCKB rises, the output signal LIEN ( 2 ) is set to the high level, and as in the first embodiment, the data signal DATA transmitted from the outside is captured by the first latch circuit  32  ( 2 ) at the second stage. Next, in a case where the binary clock signal BCK rises, the output signal LIEN ( 3 ) is set to the high level, and as in the first embodiment, the data signal DATA transmitted from the outside is captured by the first latch circuit  32  ( 3 ) at the third stage. 
     In the present embodiment, the output signal LIEN ( 3 ) is provided as the second latch signal L 2  ( 1 ) in to the second latch circuit  33  ( 1 ) at the first stage and as the second latch signal L 2  ( 2 ) in to the second latch circuit  33  ( 2 ) at the second stage. Thus, at the time point t 31  (see  FIG. 20 ), the data signal output from the first latch circuit  32  ( 1 ) at the first stage is captured by the second latch circuit  33  ( 1 ) at the first stage, and the data signal output from the first latch circuit  32  ( 2 ) at the second stage is captured by the second latch circuit  33  ( 2 ) at the second stage. Then, the data signal captured by the second latch circuit  33  ( 1 ) at the first stage and the second latch circuit  33  ( 2 ) at the second stage is output to the 1 to 32 column source bus lines. Thereafter, each time the binary clock signal BCK or the binary clock signal BCKB rises, the data signal is captured in the first latch circuit  32 , and each time the binary clock signal BCK rises, the data signal is captured in the two second latch circuits  33 . Note that, as N is an odd number equal to or greater than 3, in a case where the output signal LIEN (N) from the unit circuit  31  (N) at the N-th stage is set to the high level, in addition to the first latch signal L 1  (N) in provided to the first latch circuit  32  (N) at the N-th stage being set to the high level, the second latch signal L 2  (N−2) in provided to the second latch circuit  33  (N−2) at the (N−2)-th stage and the second latch signal L 2  (N−1) in provided to the second latch circuit  33  (N−1) at the (N−1)-th stage are set to the high level (see  FIG. 21 ). Accordingly, in a case where the output signal LIEN (N) is set to the high level, the capturing of the data signal output from the first latch circuit  32  is performed by the second latch circuit  33  (N−2) at the (N−2)-th stage and the second latch circuits  33  (N−1) at the stage (N−1). 
     At the time point t 32  (see  FIG. 20 ), the output signal LIEN ( 101 ) from the unit circuit  31  ( 101 ) at the 101-th stage is set to the high level, the data signal output from the first latch circuit  32  ( 99 ) at the 99-th stage is captured by the second latch circuit  33  ( 99 ) at the 99-th stage, and the data signal output from the first latch circuit  32  ( 100 ) at the 100-th stage is captured by the second latch circuit  33  ( 100 ) at the 100-th stage. The data signal captured by the first latch circuit  32  ( 99 ) at the 99-th stage and the second latch circuit  33  ( 100 ) at the 100-th stage are output to the 1569 to 1600 column source bus lines. 
     4.3 Effects 
     In the present embodiment as well, similar to the first embodiment, a binary driver  30  can be realized in which a voltage drop effect can be effectively reduced while suppressing an increase in circuit size. 
     5. Fifth Embodiment 
     5.1 Configuration of Binary Driver 
       FIG. 22  is a circuit block diagram illustrating a configuration of a portion of the binary driver  30  according to the present embodiment. In the fourth embodiment, the same signal is provided as the second latch signal to two continuous second latch circuits  33  (see  FIG. 19 ). In contrast, in the present embodiment, the same signal is provided as the second latch signal to three continuous second latch circuits  33 . For example, the second latch circuits  33  ( 1 ) to  33  ( 3 ) at the first to third stages are provided with the output signal LIEN ( 4 ) from the unit circuit  31  ( 4 ) at the fourth stage as the second latch signal. Note that the same signal may be provided as the second latch signal to four or more continuous second latch circuits  33 . 
     Incidentally, in the present embodiment, the grouping is performed for every three second latch circuits  33  in a configuration in which 100 second latch circuits  33  are present, the second latch circuit  33  ( 100 ) at the 100-th stage is not grouped. In other words, as illustrated in  FIG. 23 , the output signal LIEN ( 101 ) provided as the second latch signal to the second latch circuit  33  ( 100 ) at the 100-th stage is not provided as the second latch signal to the second latch circuits  33  other than that at the 100-th stage. 
     5.2 Operation of Binary Driver 
       FIG. 24  is a signal waveform diagram for describing the operation of the binary driver  30  according to the present embodiment.  FIG. 25  is a signal waveform diagram for describing the first latch signal provided to the first latch circuit  32  and the second latch signal provided to the second latch circuit  33 . Focusing on the second latch signal in  FIG. 25 , it is understood that the output signal LIEN ( 4 ) from the unit circuit  31  ( 4 ) at the fourth stage is provided as the second latch signals L 2  ( 1 ) in to L 2  ( 3 ) in to the second latch circuits  33  ( 1 ) to  33  ( 3 ) at the first to third stages, and it is understood that the output signal LIEN ( 7 ) from the unit circuit  31  ( 7 ) at the seventh stage is provided as the second latch signals L 2  ( 4 ) in to L 2  ( 6 ) in to the second latch circuits  33  ( 4 ) to  33  ( 6 ) at the fourth to sixth stages. 
     In the present embodiment, as described above, the output signal LIEN ( 4 ) from the unit circuit  31  ( 4 ) at the fourth stage is provided as the second latch signal to the second latch circuits  33  ( 1 ) to  33  ( 3 ) at the first to third stages. Therefore, by the output signal LIEN ( 4 ) being set to the high level at the time point t 41  (see  FIG. 24 ), the data signal output from the first latch circuits  32  ( 1 ) to  32  ( 3 ) at the first to third stages are captured in the second latch circuits  33  ( 1 ) to  33  ( 3 ) at the first to third stages. Then, the data signal captured by the second latch circuits  33  ( 1 ) to  33  ( 3 ) at the first to third stages is output to the first to 48-th column source bus lines. Thereafter, the data signal is captured in three second latch circuits  33  each time the binary clock signal BCK and the binary clock signal BCKB rise three times together. 
     At the time point t 42  (see  FIG. 24 ), the output signal LIEN ( 101 ) from the unit circuit  31  ( 101 ) at the 101-th stage is set to the high level, and the data signal output from the first latch circuit  32  ( 100 ) at the 100-th stage is captured by the second latch circuit  33  ( 100 ) at the 100-th stage. The data signal captured in the second latch circuit  33  ( 100 ) at the 100-th stage is output to the 1585 to 1600 column source bus lines. 
     5.3 Effect 
     In the present embodiment as well, similar to the first embodiment, a binary driver  30  can be realized in which a voltage drop effect can be effectively reduced while suppressing an increase in circuit size. 
     6. Other Matters 
     Although the disclosure has been described in detail above, the above description is exemplary in all respects and is not limiting. It is understood that numerous other modifications or variations can be made without departing from the scope of the disclosure. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.