JP2009169364A - Drivers, electro-optical devices, and electronic devices - Google Patents

Abstract

Power consumption of a driver for driving a data line of an electro-optical device can be reduced.
A driver 10 of an electro-optical device 400 includes a gradation voltage generation circuit 110 that generates a plurality of gradation voltages, a plurality of gradation voltages from the gradation voltage generation circuit, and gradation data. In response, the grayscale voltage generation circuit includes a plurality of data drivers 50 that drive a plurality of data lines of the electro-optical device, and the grayscale voltage generation circuit is connected in series between the first power supply VGMH and the second power supply VGML. A ladder resistor circuit 112 that has resistor circuits R0 to R32 and outputs a plurality of divided voltages divided by a plurality of resistor circuits, and a plurality of levels that sample and hold a plurality of divided voltages from the ladder resistor circuit. A sample-and-hold unit 114 that has adjustment voltage generation sample-and-hold circuits SH1 to SH32 and outputs a plurality of held divided voltages as a plurality of gradation voltages.
[Selection] Figure 2

Description

  The present invention relates to a driver, an electro-optical device, an electronic apparatus, and the like.

  In recent years, electro-optical devices such as active matrix liquid crystal panels using TFTs (Thin Film Transistors), which are becoming smaller and higher in definition, are required to display images with abundant color tone and high image quality through multi-gradation. Has been. In order to perform image display that satisfies such requirements, the drive signal of the electro-optical device is subjected to gamma correction according to the gradation characteristics of each liquid crystal panel. By performing the gamma correction, the electro-optical device outputs a gamma-corrected gradation voltage based on the gradation data for performing gradation display so as to realize a suitable transmittance of the pixel. The data line of the electro-optical device is driven based on the corrected gradation voltage.

The gamma correction is performed by a gradation voltage generated by a gamma correction circuit (gradation voltage generation circuit) having a plurality of ladder resistor circuits connected in series. Japanese Patent Application Laid-Open No. 2004-228688 discloses a gamma correction circuit that reduces power consumption flowing in a ladder resistor circuit in order to reduce power consumption of an electro-optical device. In the gamma correction circuit, a positive polarity ladder resistor circuit and a negative polarity ladder resistor circuit are provided between the first and second power supply lines to which the first and second power supply voltages are supplied. The first and second power supply lines can be electrically connected or disconnected, and each divided node and each reference voltage output node can be electrically connected or disconnected.
Japanese Patent No. 3807322

  However, in the technique disclosed in Patent Document 1, each gradation voltage output from the divided node of the ladder resistor circuit in the gamma correction circuit is driven by a data line via an operational amplifier connected with a voltage follower having a high driving capability. The data line driving circuit is supplied to the circuit and drives the data line of the electro-optical device. Therefore, even when the current is controlled to flow through the ladder resistor circuit only during the period for generating the gradation voltage, when the gradation voltage is supplied from the gamma correction circuit to the data driver during the period, the operational amplifier Excessive power is consumed for driving.

  According to some aspects of the present invention, it is possible to reduce power consumption in a driver that drives a data line of an electro-optical device.

  The present invention is a driver of an electro-optical device, and receives a grayscale voltage generation circuit that generates a plurality of grayscale voltages, a plurality of grayscale voltages from the grayscale voltage generation circuit, and grayscale data. The grayscale voltage generation circuit includes a plurality of resistance circuits connected in series between the first power supply and the second power supply, and includes a data driver that drives the plurality of data lines of the electro-optical device. A ladder resistor circuit that outputs a plurality of divided voltages divided by a plurality of resistor circuits, and a plurality of gradation voltage generation sample hold circuits that sample and hold a plurality of divided voltages from the ladder resistor circuit And a sample hold unit that outputs a plurality of held divided voltages as a plurality of gradation voltages.

  According to the driver of the present invention, the gradation voltage generation circuit samples and holds the plurality of divided voltages from the ladder resistor circuit by the plurality of gradation voltage generation sample hold circuits, and the plurality of divided voltages thus held are held. Output as a plurality of gradation voltages. Therefore, the gradation voltage can be supplied from the gradation voltage generation circuit to the data driver at a desired timing.

  In this case, according to the present invention, the ladder resistor circuit includes a first ladder resistor circuit having a plurality of resistor circuits connected in series between the first power source and the second power source, the first power source, and the first power source. A first power connection switch element provided between one end of the ladder resistance circuit and a second power connection switch provided between the second power supply and the other end of the first ladder resistance circuit. A plurality of first ladder resistor switching elements provided between the element, a plurality of first ladder resistor side divided nodes divided by a plurality of resistor circuits, and a plurality of gradation voltage generating sample hold circuits; A second ladder resistor circuit having a plurality of resistor circuits connected in series between the first power source and the second power source; and between the second power source and one end of the second ladder resistor circuit. Third switch element for connecting power supply provided, and first power supply A fourth power supply connecting switch element provided between the other end of the second ladder resistor circuit, a plurality of second ladder resistor side divided nodes divided by a plurality of resistor circuits, and a plurality of gradation voltages A plurality of second ladder resistance switch elements provided between the generation sample hold circuit and the first and second power supply connection switch elements being on, the plurality of first ladders The resistance switch element is turned on, the third and fourth power supply connection switch elements and the plurality of second ladder resistance switch elements are turned off, and the first and second power supply connection switch elements are turned off. In this case, the plurality of first ladder resistance switch elements are turned off, and the third and fourth power supply connection switch elements and the plurality of second ladder resistance switch elements are turned on. Good.

  In this way, when the gradation voltage is supplied to the data driver by the first ladder resistor circuit, the current flowing through the second ladder resistor circuit is turned off, and conversely, the gradation is generated by the second ladder resistor circuit. When the voltage is supplied to the data driver, the current flowing through the first ladder resistor circuit can be turned off. That is, when the gradation voltage is supplied by one of the two ladder resistor circuits, the current flowing through the other ladder resistor circuit can be turned off.

  In the present invention, the ladder resistor circuit includes a plurality of resistor circuits connected in series between the first power source and the second power source, and a plurality of nodes divided by the resistor circuits are provided. A ladder resistor circuit connected to a plurality of gradation voltage generating sample-and-hold circuits; a first power supply switching element provided between the first power supply and one end of the ladder resistor circuit; and a second power supply A second power connection switch element provided between the other end of the ladder resistor circuit, a third power supply switch element provided between the first power source and the other end of the ladder resistor circuit, And a fourth power connection switch element provided between one power supply and one end of the ladder resistor circuit. When the first and second power connection switches are on, the third and second 4 power connection switch element is turned off, 1 and when the second power connection switch element is turned off, may be the third and fourth power connection switch element is turned on.

  In this way, since the power connection switch elements provided at both ends of the ladder resistor circuit are turned on / off, the gradation for both the positive polarity and the negative polarity can be obtained with one ladder resistor circuit. A voltage can be generated.

  In the present invention, the first to fourth power supply switching elements may be turned off during the grayscale voltage generation sleep period in which the grayscale voltage generation circuit is set to the sleep mode.

  In this way, when the grayscale voltage generation sample-and-hold circuit is set to the sleep mode, the current flowing through the ladder resistor circuit can be turned off.

  In the present invention, the gradation voltage generating sample and hold circuit may be a flip-around sample and hold circuit.

  In this way, since the so-called offset-free operation can be realized by the sample-and-hold circuit for generating the gradation voltage, when the divided voltage of the ladder resistor circuit is supplied to the data driver as the gradation voltage, a high-accuracy scale with little variation is provided. A regulated voltage can be supplied to the data driver.

  In the present invention, the grayscale voltage generation sample-hold circuit is provided between the operational amplifier, the first input terminal of the operational amplifier, and the input node of the grayscale voltage generation sample-hold circuit. A sampling capacitor in which charge corresponding to the input voltage of the input node is accumulated in the generation sampling period, and an output voltage corresponding to the charge accumulated in the sampling capacitor in the gradation voltage generation sampling period It is good also as outputting in the hold period for adjustment voltage generation.

  According to this configuration, in the grayscale voltage sampling period, the input voltage to the input node is sampled by the sampling capacitor, and the sampling capacitor is subjected to the flip-around operation, so that the voltage stored in the sampling capacitor is changed. The output voltage can be output during the hold period.

  In the present invention, the grayscale voltage generation sample-and-hold circuit includes an operational amplifier in which an analog reference power supply voltage is set to the second input terminal, the first input terminal of the operational amplifier, and the grayscale voltage generation sample. A sampling capacitor provided between an input node of the hold circuit, a sampling switch element provided between the sampling capacitor and an input node of the gradation voltage generating sample hold circuit, an output terminal of the operational amplifier, Flip-around switch provided between the feedback switch element provided between the first input terminal, the connection node between the sampling switch element and the sampling capacitor, and the output terminal of the operational amplifier It is good also as including an element.

  In this way, sampling of the input voltage to the sampling capacitor can be realized using the sampling switch element and the feedback switch element, and the flip-around operation of the sampling capacitor can be realized using the flip-around switch element. .

  In the present invention, the data driver has a data driver sample and hold circuit. When the data driver sampling period in which sampling is performed by the data driver sample and hold circuit ends, the data driver sample and hold circuit holds the data driver. The gradation voltage generation circuit may be set to the sleep mode after the data driver hold period to be performed starts.

  In this way, when the data driver sample and hold circuit starts the hold operation, the gradation voltage necessary for driving the data driver is ensured, so that it is not necessary to supply the gradation voltage from the gradation voltage generation circuit. Become. Therefore, power consumption can be reduced by setting the grayscale voltage generation circuit in the sleep mode during a period in which the grayscale voltage is unnecessary.

  In the present invention, a plurality of gradation voltage generation sample hold circuits may be set in the sleep mode in the gradation voltage generation sleep period in which the gradation voltage generation circuit is set in the sleep mode.

  In this way, during the period when the gray scale voltage is not required, the power consumption can be reduced by putting the gray scale voltage generation sample hold circuit including the operational amplifier with high power consumption into the sleep mode.

  In the present invention, the data driver receives a plurality of gradation voltages and gradation data from the gradation voltage generation circuit, and selects a gradation voltage corresponding to the gradation data from the plurality of gradation voltages. A D / A conversion circuit that selects and outputs the selected gradation voltage; and a data line driving circuit that receives the selection gradation voltage from the D / A conversion circuit and drives the data line of the electro-optical device. The data driver sample hold circuit may be provided in the data line drive circuit to sample and hold the selected gradation voltage.

  According to this configuration, the D / A conversion circuit that has received the gradation data selects the gradation voltage corresponding to the gradation data from the plurality of gradation voltages supplied from the gradation voltage generation circuit. D / A conversion of gradation data can be realized.

  In the present invention, each of the data driver sample and hold circuits may be a flip-around sample and hold circuit.

  In this way, each data driver sample-and-hold circuit can realize so-called offset-free. Therefore, when supplying the gradation voltage for driving the data driver, a highly accurate gradation voltage with little variation is supplied to the electro-optical device. Can supply.

  In the present invention, the data driver sample hold circuit may be set to the sleep mode after the data driver hold period ends.

  In this way, the data driver sample and hold circuit can be set to the sleep mode after the end of the data driver hold period, so that the power consumption of the data driver can be reduced.

  According to the present invention, each of the data driver sample and hold circuits is provided between the operational amplifier, the first input terminal of the operational amplifier, and the first input node of the data driver sample and hold circuit. A first sampling capacitor in which charges corresponding to the input voltage of the first input node are accumulated during the sampling period, a first input terminal of the operational amplifier, and a second input node of the data driver sample hold circuit; And a second sampling capacitor in which charges corresponding to the input voltage of the second input node are accumulated in the data driver sampling period, and in the data driver sampling period, The output voltage corresponding to the charge accumulated in the sampling capacitor 2 is used as the data driver ho It may be output in de period.

  According to this configuration, the input voltages to the first and second input nodes are sampled by the first and second sampling capacitors during the sampling period, and the flip-around operation of the first and second sampling capacitors is performed. As a result, an output voltage corresponding to the charge accumulated in the first and second sampling capacitors can be output in the hold period.

  Further, according to the present invention, the data driver sample and hold circuit includes an operational amplifier in which an analog reference power supply voltage is set to the second input terminal, a first input node of the data driver sample and hold circuit, and a first of the operational amplifier. A first sampling switch element and a first sampling capacitor provided between the first input terminal and the second input node of the data driver sample hold circuit and the first input terminal of the operational amplifier. A second sampling switch element and a second sampling capacitor provided therebetween, a feedback switch element provided between the output terminal and the first input terminal of the operational amplifier, and a first sampling switch A first connection node between the switch element and the first sampling capacitor and an output terminal of the operational amplifier; Between the first flip-around type switch element provided in the second connection node, the second connection node between the second sampling switch element and the second sampling capacitor, and the output terminal of the operational amplifier A second flip-around switch element provided may be included.

  In this way, sampling of the input voltage to the first and second sampling capacitors is realized using the first and second sampling switch elements and the feedback switch element, and the first and second flip-flops are realized. Using the around switch element, the flip-around operation of the first and second sampling capacitors can be realized.

  The present invention also relates to an electro-optical device including any of the drivers described above.

  According to the electro-optical device of the present invention, since the power consumption of the driver of the electro-optical device can be reduced, the power consumption when driving the data line of the electro-optical device can be reduced.

  Furthermore, the present invention relates to an electronic apparatus including the above electro-optical device.

  According to the electronic apparatus of the present invention, it is possible to reduce the power consumption when driving the data line of the electro-optical device, so that the power consumption when driving the electronic apparatus can be reduced.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are essential as means for solving the present invention. Not necessarily.

1. Driver FIG. 1 shows a circuit configuration example of a driver 10 (integrated circuit device) of the present embodiment. Note that the driver 10 according to the present embodiment is not limited to the configuration shown in FIG. 1, and various modifications such as omitting some of the components or adding other components are possible.

  The electro-optical panel 400 (electro-optical device) includes a plurality of data lines (for example, source lines), a plurality of scanning lines (for example, gate lines), and a plurality of pixels specified by the data lines and the scanning lines. Then, the display operation is realized by changing the optical characteristics of the electro-optical element (in a narrow sense, a liquid crystal element or an EL element) in each pixel region. The electro-optical panel 400 (display panel in a narrow sense) can be constituted by, for example, an active matrix type panel using a switching element such as a TFT or a TFD. The electro-optical panel may be a panel other than the active matrix system, or may be a panel using a light emitting element such as an organic EL (Electro Luminescence) or inorganic EL other than the liquid crystal panel.

  The memory 20 (display data RAM) stores image data. The memory cell array 22 includes a plurality of memory cells and stores image data (display data) for at least one frame (one screen). The row address decoder 24 (MPU / LCD row address decoder) performs a decoding process on the row address and performs a word line selection process of the memory cell array 22. The column address decoder 26 (MPU column address decoder) performs a decoding process on the column address and performs a selection process of a bit line of the memory cell array 22. The write / read circuit 28 (MPU write / read circuit) performs a process of writing image data to the memory cell array 22 and a process of reading image data from the memory cell array 22.

  The logic circuit 40 (driver logic circuit) generates a control signal for controlling display timing, a control signal for controlling data processing timing, and the like. The logic circuit 40 can be formed by automatic placement and routing such as a gate array (G / A).

  The control circuit 42 generates various control signals and controls the entire apparatus. Specifically, gradation adjustment data (γ correction data) for adjusting gradation characteristics (γ characteristics) is output to the gradation voltage generation circuit 110, or power supply voltage is supplied to the power supply circuit 90. Outputs power adjustment data for adjusting. Further, it controls the write / read processing to the memory using the row address decoder 24, the column address decoder 26, and the write / read circuit 28.

  The display timing control circuit 44 generates various control signals for controlling the display timing, and controls reading of image data from the memory 20 to the electro-optical panel side. The host (MPU) interface circuit 46 implements a host interface that accesses the memory 20 by generating an internal pulse for each access from the host. The RGB interface circuit 48 realizes an RGB interface that writes moving image RGB data to the memory 20 using a dot clock. Note that only one of the host interface circuit 46 and the RGB interface circuit 48 may be provided.

  The data driver 50 is a circuit that supplies data signals (voltage, current) for driving the data lines of the electro-optical panel 400 (electro-optical device). Specifically, the data driver 50 receives image data (grayscale data, display data) from the memory 20, and receives a plurality of (for example, 256 levels) grayscale voltages (reference voltages) from the grayscale voltage generation circuit 110. . Then, a voltage (data voltage) corresponding to the image data (gradation data) is selected from the plurality of gradation voltages, and is output to the data line of the electro-optical panel 400.

  The scanning driver 70 is a circuit that generates a scanning signal for driving the scanning lines of the electro-optical panel 400. Specifically, a signal (enable input / output signal) is sequentially shifted in a built-in shift register, and a signal obtained by level-converting the shifted signal is output to each scanning line of the electro-optical panel 400 as a scanning signal (scanning voltage). To do. The scan driver 70 includes a scan address generation circuit and an address decoder. The scan address generation circuit generates and outputs a scan address, and the address decoder performs a scan address decoding process to generate a scan signal. Also good.

  The power supply circuit 90 is a circuit that generates various power supply voltages. Specifically, boosting is performed by a charge pump method using a boosting capacitor and a boosting transistor included in a boosting circuit incorporating an input power supply voltage and an internal power supply voltage. Then, the voltage obtained by boosting is supplied to the data driver 50, the scan driver 70, the gradation voltage generation circuit 110, and the like.

  The gradation voltage generation circuit (γ correction circuit) 110 is a circuit that generates a gradation voltage and supplies it to the data driver 50. Specifically, the gradation voltage generation circuit 110 includes a ladder resistor circuit that divides a resistance between a high potential side voltage and a low potential side voltage and outputs a gradation voltage to a resistance division node. In addition, a gradation register unit in which gradation adjustment data is written, a gradation voltage setting circuit that variably sets (controls) the gradation voltage output to the resistance division node based on the written gradation adjustment data, and the like. Can be included.

  FIG. 2 shows a detailed configuration example of the driver of the present embodiment, and particularly shows a configuration example of a gradation voltage generation circuit and a data driver (source driver) included in the driver.

  The data driver 50 receives a plurality of gradation voltages V0 to V33 from the gradation voltage generation circuit 110 that generates gradation voltages. In the case of a driver with a built-in memory, for example, the gradation data GD is received from the memory 20 in FIG. Then, the plurality of data lines SL1 to SLm (m is an integer of 2 or more) of the electro-optical panel 400 (electro-optical device) are driven. Note that the number of gradations in the present embodiment is arbitrary. In the case of a driver without a memory, the gradation data GD is supplied from the outside.

  The gradation voltage generation circuit 110 generates a plurality of gradation voltages V0 to V33 (V1 to V32) to be supplied to the data driver 50. In the present embodiment, the gradation voltage generation circuit 110 includes a ladder resistor circuit 112 and a sample hold unit 114.

  The ladder resistor circuit 112 includes a high potential side power source VGMH (first power source in a broad sense) for generating gradation voltages and a low potential side power source VGML (second power source in a broad sense) for generating gradation voltages. Between. The ladder resistor circuit 112 includes a plurality of resistor circuits (variable resistors) R0 to R32 connected in series, and each voltage at the plurality of divided nodes N1 to N32 divided by the plurality of resistor circuits R0 to R32 is divided. Becomes divided voltages VD1 to VD32.

  The sample hold unit 114 samples and holds the divided voltages VD1 to VD32 at the divided nodes N1 to N32 of the ladder resistor circuit 112. In the present embodiment, the sample hold unit 114 includes gradation voltage generation sample hold circuits SH1 to SH32 corresponding to the divided voltages VD1 to VD32 at the divided nodes N1 to N32 of the ladder resistor circuit 112. In this way, the sample and hold unit 114 samples and holds the divided voltages VD1 to VD32 at the divided nodes N1 to N32 of the ladder resistor circuit 112 by the corresponding gradation voltage generating sample and hold circuits SH1 to SH32. To do. Then, the divided voltages VD1 to VD32 held by the gradation voltage generation sample and hold circuits SH1 to SH32 are output as the plurality of gradation voltages V1 to V32 generated by the gradation voltage generation circuit 110.

  On the other hand, the data driver 50 drives data lines of an electro-optical panel 400 (electro-optical device) such as a liquid crystal panel. In this embodiment, the data driver 50 includes D / A conversion circuits 52-1 to 52-m, data lines. Drive circuits 54-1 to 54-m are included. As shown in FIG. 2, one D / A conversion circuit and one data line driving circuit may be provided corresponding to each data line, and one D / A conversion circuit is provided with a plurality of data line driving circuits. For example, the data line driving circuit for one or a plurality of pixels may be shared. Further, the data line driving circuit may drive a plurality of data lines in a time division manner. Further, part or all of the data driver 50 may be integrally formed on the electro-optical panel.

  For example, the D / A conversion circuits 52-1 to 52-m receive gradation data GD (image data and display data) from the memory 20 shown in FIG. Then, a gradation voltage corresponding to the gradation data GD is selected from the gradation voltages V1 to V32, and is output to the data line driving circuits 54-1 to 54-m as the selected gradation voltages VSL1 to VSLm.

  The data line driving circuits 54-1 to 54-m include data driver sample and hold circuits DSH1 to DSHm. These sample hold circuits DSH1 to DSHm sample and hold the selected gradation voltages VSL1 to VSLm (data voltages) from the D / A conversion circuits 52-1 to 52-m. Then, the selected gradation voltages VSL1 to VSLm sampled and held are supplied to the data lines SL1 to SLm of the electro-optical panel 400, thereby driving the data lines SL1 to SLm.

2. As shown in FIG. 2, the gradation voltage generation circuit 110 includes a ladder resistor circuit 112 having a plurality of resistor circuits (variable resistors) R0 to R32 connected in series, and each of the resistor circuits R0 to R32. A sample and hold unit 114 including gradation voltage generating sample and hold circuits SH1 to SH32 that samples and holds the divided voltages VD1 to VD32 at the divided nodes N1 to N32. Each of the resistance circuits R0 to R32 constituting the ladder resistance circuit 112 includes, for example, a plurality of resistance elements and a plurality of switch elements, and is configured such that the resistance values of the resistance circuits R0 to R32 are variable. In this case, the resistance value is adjusted using, for example, an adjustment register (not shown).

  The voltages of the first to thirty-second divided nodes N1 to N32 divided by the resistance circuits R0 to R32 of the ladder resistor circuit 112 having such a configuration become the divided voltages VD1 to VD32 of the ladder resistor circuit 112. The divided voltages VD1 to VD32 are output to the gradation voltage generating sample and hold circuits SH1 to SH32 corresponding to the divided voltages VD1 to VD32, sampled, and held.

  Outputs of the gradation voltage generation sample hold circuits SH1 to SH32 of the sample hold unit 114 are output to the D / A conversion circuits 52-1 to 52-m of the data driver 50 as gradation voltages V1 to V32. That is, the gradation voltage generation circuit 110 samples and holds the plurality of divided voltages VD1 to VD32 from the ladder resistor circuit 112 by the plurality of gradation voltage generation sample hold circuits SH1 to SH32, and the plurality of divided divisions. The voltages VD1 to VD32 are output as a plurality of gradation voltages V1 to V32. In this way, in the present embodiment, the gradation voltage can be supplied from the gradation voltage generation circuit 110 to the data driver 50 at a desired timing.

2.1. First Configuration Example FIG. 3 shows a first configuration example of the gradation voltage generation circuit of the present embodiment. In the first configuration example, the ladder resistor circuit 110A includes first and second ladder resistor circuits 112AL and 112AR between the two power sources VGMH and VGML in order to generate positive and negative grayscale voltages. Are provided in parallel. Each of these ladder resistance circuits 112AL and 112AR is configured by connecting a plurality (33 in the example shown in FIG. 3) of resistance circuits RAL0 to RAL32 and RAR0 to RAR32 in series.

  The first ladder resistor circuit 112AL is provided between the power supplies VGMH and VGML. The voltages at the divided nodes (first ladder resistor side divided nodes) NAL1 to NAL32 divided by the resistance circuits RAL0 to RAL32 become the divided voltages VDAL1 to VPAL32. These divided nodes NAL1 to NAL32 are connected to the ladder resistor switch elements (first ladder resistor switch elements) SWL1 to SWL32 for switching connection on / off, and the sample hold unit 114A for generating gradation voltages of the sample hold unit 114A. Connected to circuits SHA1 to SHA32.

  In addition, one end of the first ladder resistor circuit 112AL can be switched on / off with the power source VGMH by the first power source connection switch element SWA1. On the other hand, the other end of the first ladder resistor circuit 112AL can be switched on / off with the power source VGML by the second power source connection switch element SWA2.

  On the other hand, the second ladder resistor circuit 112AR is provided between the power supplies VGML and VGMH. The voltages at the divided nodes (second ladder resistor side divided nodes) NAR1 to NAR32 divided by the resistance circuits RAR0 to RAR32 become the divided voltages VDAR1 to VDAR32. These divided nodes NAR1 to NAR32 are connected to the ladder resistance switch elements (second ladder resistance switch elements) SWR1 to SWR32 for switching connection ON / OFF, and the sample hold section 114A for sample voltage generation for gradation voltage generation is used. Connected to circuits SHA1 to SHA32.

  Further, one end of the second ladder resistor circuit 112AR can be switched on / off with the power source VGML by the third power source connecting switch element SWA3. On the other hand, the other end of the second ladder resistor circuit 112AR can be switched on / off with the power source VGMH by the fourth power source connection switch element SWA4.

  In the first configuration example, when the first and second power connection switching elements SWA1 and SWA2 are on, the first ladder resistance switch elements SWL1 to SWL32 are turned on, and the third and fourth The power connection switch elements SWA3 and SWA4 and the second ladder resistance switch elements SWR1 to SWR32 are turned off. On the contrary, when the first and second power supply connection switch elements SWA1 and SWA2 are off, the first ladder resistance switch elements SWL1 to SWL32 are off, and the third and fourth power supply connections. Switch elements SWA3 and SWA4 and second ladder resistance switch elements SWR1 to SWR32 are turned on.

  That is, when the connection between the first ladder resistor circuit 112AL and the power sources VGMH and VGML and the gradation voltage generation sample and hold circuits SHA1 to SHA32 is on, the second ladder resistor circuit 112AR and the power sources VGML and VGMH and the gradation The connection with the voltage generation sample and hold circuits SHA1 to SHA32 is switched off. In this way, a current is passed through the first ladder resistor circuit 112AL, and the divided voltages VDAL1 to VDAL32 of the first ladder resistor circuit 112AL are sampled by the gradation voltage generating sample hold circuits SHA1 to SHA32 of the sample hold unit 114A. Is held. At this time, the first ladder resistor circuit 112AL supplies the divided voltages VDAL1 to VPAL32 to the data driver 50 as, for example, positive gradation voltages V1 to V32.

  On the other hand, when the connection between the first ladder resistor circuit 112AL and the power sources VGMH and VGML and the gradation voltage generation sample-and-hold circuits SHA1 to SHA32 is off, the second ladder resistor circuit 112AR and the power sources VGML and VGMH and the floor Switching is made so that the connection with the sample-hold circuits SHA1 to SHA32 for adjusting voltage generation is turned on. In this way, a current is passed through the second ladder resistor circuit 112AR, and the divided voltages VDAR1 to VDAR32 of the second ladder resistor circuit 112AR are sampled by the gradation voltage generating sample hold circuits SHA1 to SHA32 of the sample hold unit 114A. Is held. At this time, the second ladder resistor circuit 112AR supplies the divided voltages VDAR1 to VDAR32 to the data driver 50 as, for example, negative gradation voltages V1 to V32.

  That is, in the first configuration example, when the divided voltages VDAL1 to VDAL32 of the first ladder resistor circuit 112AL are supplied to the data driver 50 as the gradation voltages V1 to V32, the current flowing through the second ladder resistor circuit 112AR is changed. Turn off. On the other hand, when the divided voltages VDAR1 to VDAR32 of the second ladder resistor circuit 112AR are supplied to the data driver 50 as the grayscale voltages V1 to V32, the current flowing through the first ladder resistor circuit 112AL is turned off. In this way, in the period in which the divided voltage of one of the two ladder resistor circuits 112AL and 112AR is supplied to the sample-and-hold unit 114, the current flowing through either one of the ladder resistor circuits is turned off to thereby reduce the level. The power consumption of the regulated voltage generation circuit 110A can be reduced.

2.2. Second Configuration Example FIG. 4 shows a second configuration example of the gradation voltage generation circuit of the present embodiment. In the second configuration example, the gradation voltage generation circuit 110B is provided with one ladder resistor circuit 112B between the two power supplies VGMH and VGML. The ladder resistor circuit 112B is configured by connecting a plurality (33 in the example shown in FIG. 4) of resistor circuits RB0 to RB32 in series.

  In the ladder resistor circuit 112B of the second configuration example, the voltages at the divided nodes NB1 to NB32 divided by the resistor circuits RB0 to RB32 become the divided voltages VDB1 to VDB32. These divided nodes NB1 to NB32 are connected to each of the gradation voltage generating sample and hold circuits SHB1 to SHB32 of the sample and hold unit 114B.

  Also, one end of the ladder resistor circuit 112B can be switched on / off with the power supply VGMH by the first power supply connection switch element SWB1. On the other hand, the other end of the ladder resistor circuit 112B can be switched on / off with the power source VGML by the second power source connecting switch element SWB2.

  Furthermore, in the second configuration example, a third power connection switch element SWB3 is provided between the other end of the ladder resistor circuit 112B and the power source VGMH, and the third power connection switch element SWB3 provides a ladder resistance. The connection between the other end of the circuit 112B and the power supply VGMH can be switched on / off. That is, the third power supply connection switch element SWB3 is provided between the node NBV1 on the power supply VGMH side and the other end of the ladder resistor circuit 112B.

  Further, a fourth power connection switch element SWB4 is provided between the other end of the ladder resistor circuit 112B and the power supply VGML, and the other end of the ladder resistor circuit 112B and the power supply are provided by the fourth power supply connection switch element SWB4. The connection with VGML can be switched on / off. In other words, the fourth power supply connection switch element SWB4 is provided between the node NBV2 on the power supply VGML side and one end of the ladder resistor circuit 112B.

  In the second configuration example, while the first and second power connection switching elements SWB1 and SWB2 are on, the third and fourth power connection switching elements SWB3 and SWB4 are off. Conversely, while the first and second power connection switching elements SWB1 and SWB2 are off, the third and fourth power connection switching elements SWB3 and SWB4 are on.

  That is, when the connection between one end of the ladder resistor circuit 112B and the power source VGMH and the other end of the ladder resistor circuit 112B and the power source VGML are ON, the other end of the ladder resistor circuit 112B and the power source VGMH and one end of the ladder resistor circuit 112B And the power supply VGML are switched so as to be turned off. When the switching elements SWB1 to SWB4 are switched as described above, the divided voltages VDB1 to VDB32 at the divided nodes NB1 to NB32 are sampled and held by the gradation voltage generating sample hold circuits SHB1 to SHB32 of the sample hold unit 114B. After that, the grayscale voltages V1 to V32 are supplied to the data driver 50. At that time, since the current flows from one end of the ladder resistor circuit 112B toward the other end, the voltage generated at the divided nodes NB1 to NB32 is divided so as to become a higher potential toward the one end side of the ladder resistor circuit 112B. Voltages VDB1 to VDB32 are generated.

  On the other hand, when the connection between the one end of the ladder resistor circuit 112B and the power source VGMH and the other end of the ladder resistor circuit 112B and the power source VGML is OFF, the one end of the ladder resistor circuit 112B and the power source VGML and the other end of the ladder resistor circuit 112B And the power source VGMH are switched so as to be turned on. When the switching elements SWB1 to SWB4 are switched as described above, the divided voltages VDB1 to VDB32 at the divided nodes NB1 to NB32 are sampled and held by the gradation voltage generating sample hold circuits SHB1 to SHB32 of the sample hold unit 114B. After that, the grayscale voltages V1 to V32 are supplied to the data driver 50. At that time, since the current flows from the other end of the ladder resistor circuit 112B toward one end, the voltage generated at the divided nodes NB1 to NB32 is set to a higher potential toward the other end side of the ladder resistor circuit 112B. Divided voltages VDB1 to VDB32 are generated.

  As described above, in the second configuration example, the gradation voltage in the opposite direction is generated by switching on / off the power connection switch elements SWB1 to SWB4 provided on both ends of the ladder resistor circuit 112B. Will be able to. That is, the gradation voltage V1 to V32 for the positive electrode and the negative electrode can be generated by one ladder resistor circuit 112B.

2.3. Grayscale voltage generation sample-hold circuit Each of the grayscale voltage generation sample-hold circuits SH1 to SH32 (SHA1 to SHA32, SHB1 to SHB32) included in the sample hold unit 114 of the grayscale voltage generation circuit 110 is a so-called flip-around sample. It can be configured by a hold circuit. Here, the flip-around sample / hold circuit is a circuit that samples the input voltage by, for example, accumulating charges corresponding to the input voltage in the sampling capacitor in the sampling period. In the hold period, the sampling capacitor performs a flip-around operation and outputs a voltage corresponding to the accumulated charge to the output node.

  In the present embodiment, as shown in FIG. 5, the grayscale voltage generation sample hold circuit includes an operational amplifier OPS1, a grayscale voltage sampling capacitor CSS1, a grayscale voltage sampling switch element SWS1, a feedback switch element SWS2, and A flip-around switch element SWS3 is included. The gradation voltage generating sample and hold circuit includes a gradation voltage sample and hold output switch element SWS4. It should be noted that modifications such as omitting some of these components or adding other components are possible. In addition, the switch elements SWS1, SWS2, SWS3, and SWS4 can be configured by, for example, CMOS transistors such as transfer gates.

  An analog reference power supply voltage AGND is set to a non-inverting input terminal (second input terminal in a broad sense) of the operational amplifier OPS1.

  The switch element SWS1 and the capacitor CSS1 are connected to the input node NSn (n is an integer of 1 to 32) of the gradation voltage generating sample and hold circuit and the inverting input terminal (first input terminal in a broad sense) of the operational amplifier OPS1. Between.

  The feedback switch element SWS2 is provided between the output terminal of the operational amplifier OPS1 and the inverting input terminal of the operational amplifier OPS1.

  The flip-around switch element SWS3 is provided between a connection node NC1 between the switch element SWS1 and the capacitor CSS1 and the output terminal of the operational amplifier OPS1.

  With reference to FIGS. 6A and 6B, the flip-around grayscale voltage generation sample hold circuit will be described in more detail.

  As shown in FIG. 6A, the capacitor CSS1 includes a divided voltage VDn (n is 1 ≦ n) of the divided nodes N1 to N32 connected to the input node NSn of the gradation voltage generating sample and hold circuit in the sampling period. Charges corresponding to ≦ 32 (integer) are accumulated.

  Further, as shown in FIG. 6A, in the sampling period, the output of the operational amplifier OPS1 is fed back to the node NEG of the inverting input terminal of the operational amplifier OPS1. On the other hand, the non-inverting input terminal (second input terminal) of the operational amplifier OPS1 is set to the analog reference power supply voltage AGND. Therefore, the node NEG to which one end of the capacitor CSS1 is connected is set to the analog reference power supply voltage AGND by the imaginary short function of the operational amplifier OPS1. As a result, charges corresponding to the divided voltage VDn are accumulated in the capacitor CSS1.

  AGND is set (adjusted) to a voltage between the high-potential-side power supply voltage VDD and the low-potential-side power supply voltage VSS (intermediate) of the operational amplifier OPS1. Specifically, for example, AGND = VSS + (VDD + VSS) / ML is set. If VSS = 0V and ML = 2, then AGND = (VDD + VSS) / 2. At this time, the coefficient ML does not necessarily need to be ML = 2, and can be appropriately adjusted according to display characteristics and the like, and it is sufficient that at least ML> 1.

  The power supply voltage VDD is, for example, a voltage supplied to the source of the high potential side P-type transistor of the operational amplifier OPS1, and the power supply voltage VSS is a voltage supplied to the source of the low potential side N-type transistor. It is. The operational amplifier OPS1 operates using these VDD and VSS as operation power supply voltages.

  As shown in FIG. 6B, in the hold period, the gradation voltage generating sample-and-hold circuit outputs the output voltage VQGn (= VS) corresponding to the charge accumulated in the capacitor CSS1 in the sampling period. Specifically, the output voltage VQGn corresponding to the charge accumulated in the CSS1 is performed by performing a flip-around type operation in which the other end of the capacitor CSS1 to which the node NEG is connected is connected to the output terminal of the operational amplifier OPS1. Is output.

  A so-called offset-free operation can be realized by configuring the gradation voltage generating sample-and-hold circuit by the flip-around sample-and-hold circuit as described above.

For example, the offset voltage generated between the inverting input terminal and the non-inverting input terminal of the operational amplifier OPS1 is set to VOF. For simplicity of explanation, AGND is set to 0V, and the input voltage in the sampling period is set to VDn = VI. Let CS be the capacitance value of the capacitor CSS1. Then, the charge Q accumulated in the sampling period is expressed by the following equation.
Q = (VI−VOF) × CS (1)

On the other hand, if the voltage of the node NEG in the hold period is VX and the output voltage is VQGn, the charge Q ′ accumulated in the hold period is expressed by the following equation.
Q ′ = (VQGn−VX) × CS (2)

Further, when the amplification factor of the operational amplifier OPS1 is A, VQGn is expressed by the following equation.
VQGn = −A × (VX−VOF) (3)

Then, since Q = Q ′ according to the law of charge conservation, the following equation is established.
(VI−VOF) × CS = (VQGn−VX) × CS (4)

Therefore, according to the above equations (3) and (4),
VQGn = VI−VOF + VX = VI−VOF + VOF−VQG / A
Is established.

For this reason, the output voltage VQG of the gradation voltage generating sample and hold circuit is expressed by the following equation.
VQGn = {1 / (1 + 1 / A)} × VI (5)

  As is clear from the above equation (5), the output voltage VQGn of the gradation voltage generating sample-and-hold circuit does not depend on the offset voltage VOF, and the offset can be canceled, so that offset free can be realized.

  For example, when a gradation voltage is supplied to a data driver via an operational amplifier connected to a voltage follower having a high driving capability, and the data driver drives a data line of the electro-optical device, the output voltage VQGn is offset. When the voltage VOF appears, the output voltage VQGn varies between the gradation voltage supply lines, and the display quality deteriorates.

  In this respect, since the offset can be canceled by using the flip-around type sample and hold circuit, when the divided voltage of the ladder resistor circuit is supplied to the data driver as the gradation voltage, the voltage variation between the gradation voltage supply lines is reduced. Can be minimized. Therefore, highly accurate gradation voltages V1 to V32 with little variation can be supplied to the data driver 50, and display quality can be improved. In addition, since DAC driving for directly driving the data line by the D / A conversion circuit is not necessary, high-speed driving and simplification of control can be realized.

  Next, with reference to FIGS. 7A and 7B, detailed operation of the grayscale voltage generation sample hold circuit according to the present embodiment will be described.

  As shown in FIG. 7A, in the sampling period, the switch element SWS1 and the feedback switch element SWS2 are turned on, and the flip-around switch element SWS3 is turned off. Thus, the input voltage sampling operation by the flip-around sample-and-hold circuit described with reference to FIG. 6A can be realized.

  On the other hand, as shown in FIG. 7B, in the hold period, the switch element SWS1 and the feedback switch element SWS2 are turned off and the flip-around switch element SWS2 is turned on. Thereby, the hold operation of the flip-around sample hold circuit described with reference to FIG. 6B can be realized.

  The output switch element SWS4 is provided between the output terminal of the operational amplifier OPS1 and the output node of the gradation voltage generating sample hold circuit. Then, as shown in FIG. 7A, the output switch element SWS4 is turned off during the sampling period. As a result, the output of the sample-and-hold circuit for generating the gradation voltage becomes a high impedance state, and it is possible to prevent an uncertain voltage during the sampling period from being transmitted to the subsequent stage.

  On the other hand, as shown in FIG. 7B, the output switch element SWS4 is turned on in the hold period. Thereby, the voltage which is the gradation voltage sampled in the sampling period can be output. In this way, by storing the charge corresponding to the input voltage in the capacitor CSS1 using the switch element SWS1 and the feedback switch element SWS2, the input voltage is sampled, and the flip-around switch element SWS3 is used. Thus, the flip-around operation of the capacitor CSS1 can be realized.

  Here, FIG. 8A and FIG. 8B show signal waveform examples for explaining the operation of the present embodiment. FIG. 8A shows an example of a signal waveform on the grayscale voltage generation circuit 110A side of the first configuration example, and FIG. 8B shows an example of a signal waveform on the data driver 50 side.

  In the first configuration example shown in FIG. 3, for example, the first ladder resistor circuit 112AL that supplies positive polarity gradation voltage (gamma correction voltage) is switched on / off (enabled / disabled). When the second power connection switch elements SWA1 and SWA2 are turned on, for example, the current flowing in the second ladder resistor circuit 112AR that supplies a negative gradation voltage (gamma correction voltage) is turned on / off. The third and fourth power supply connection switch elements SWA3 and SWA4 are turned off. Hereinafter, the power connection switch elements SWA1 and SWA2 of the first ladder resistor circuit 112AL are turned on, and the switch elements SWA3 and SWA4 of the second ladder resistor circuit 112AR are turned off, and then the switch elements SWA1 and SWA2 are turned off. The operation when the switch elements SWA3 and SWA4 are switched to the ON state will be described.

  First, as shown by A1 in FIG. 8A, the first and second power connection switch elements SWA1 and SWA2 that are the power connection switch elements of the first ladder resistor circuit 112AL are turned on. Thereafter, as indicated by A2 and A3, the sampling switch element SWS1 and the feedback switch element SWS2 of the gradation voltage generation sample-and-hold circuits SHA1 to SHA32 are turned on (see FIG. 7A). On the other hand, the flip-around switch element SWS3 is turned off at this time, as indicated by A4 (see FIG. 7A). By doing so, a current flows through the first ladder resistor circuit 112AL, and a sampling period TA1 for sampling the divided voltages VDAL1 to VPAL32 of the first ladder resistor circuit 112AL is started.

  When the sampling period TA1 of the divided voltages VDAL1 to VPAL32 of the first ladder resistor circuit 112AL is completed, the grayscale voltage sampling switch element SWS1 and the feedback switch element SWS2 are turned off as indicated by A5 and A6 ( (See FIG. 7B). Then, as indicated by A7, the flip-around switch element SWS3 is switched on, and the period shifts to the hold period TA2 (see FIG. 7B). In this way, the divided voltages VDAL1 to VDAL32 of the first ladder resistor circuit 112AL are held by the gradation voltage generating sample hold circuit. Note that, as indicated by A5 and A6 in FIG. 8A, the gradation voltage sampling switch element SWS1 is turned off after the feedback switch element SWS2 is turned off. Thus, if the switch elements SWS1 and SWS2 are switched, the adverse effect of charge injection can be minimized.

  Thereafter, as shown in A8, the flip-around switch element SWS3 is switched off, and the hold period TA2 in which the divided voltages VDAL1 to VDAL32 of the first ladder resistor circuit 112AL are held by the gradation voltage generation sample hold circuit ends. . Then, as shown at A9, the sleep signal SLP_G input to the operational amplifier OPS1 becomes active (H level), the operational amplifier OPS1 of the sample and hold circuit is set to the sleep mode, and the gradation voltage generating sample and hold The circuit enters the sleep period TA3. At that time, when the grayscale voltage generation sample-and-hold circuit shifts to the sleep period TA3, the current input to the first ladder resistor circuit 112AL is turned off in order to cut the current flowing through the first ladder resistor circuit 112AL. To. That is, when the grayscale voltage generation sample-and-hold circuit shifts to the sleep period TA3, the first and second power supply connection switch elements SWA1 and SWA2 of the first ladder resistor circuit 112AL are switched as shown in A10. Turn off. In this way, when the grayscale voltage generation sample-and-hold circuit shifts to the sleep period TA3, the power consumption of the grayscale voltage generation circuit 110 is turned off by turning off the current input to the first ladder resistor circuit 112AL. Can be reduced.

  In the present embodiment, as indicated by B8 and B9 in FIG. 8B described in detail later, after the data driver sampling period TB2 in which sampling is performed by the data driver sample hold circuits (DSH1 to DSHm), As shown in B10, the data driver hold period TB3 by the sample hold circuit starts. Then, after the start of the data driver hold period TB3, as indicated by A8 in FIG. 8A, the sleep signal SLP_G input to the operational amplifier OPS1 of the gradation voltage generation sample hold circuit (SHA1 to SHA32) is generated. It becomes active (H level), and the operational amplifier OPS1 is set to the sleep mode. In this way, the gradation voltage generating sample and hold circuit shifts to the sleep period TA3. In this way, the power consumption of the driver 10 can be reduced by putting the operational amplifier OPS1 with high power consumption in the sleep mode during the period when the grayscale voltage is not required. Note that the sleep mode is a mode in which, for example, the operational amplifier OPS1 is set to a disabled state or a low power consumption state. Specifically, the power supply for inputting a bias voltage to the operational amplifier OPS1 is turned off, Reduce the voltage.

  When the predetermined time has elapsed in the sleep mode, the third and fourth power connection switch elements SWA3 and SWA4 of the second ladder resistor circuit 112AR are turned on as indicated by A11. In this way, the divided voltages VDAR1 to VDAR32 generated by passing a current through the second ladder resistor circuit 112AR are input to the sample hold unit 114A and sampled. Thereafter, as indicated by A12, the sleep signal SLP_G input to the operational amplifier OPS1 becomes inactive (L level), and the sleep period TA3 ends. Then, after the sleep mode of the operational amplifier OPS1 is canceled, as shown in A13 and A14, the gradation voltage sampling switch element SWS1 and the feedback switch element SWS2 of the gradation voltage generation sample-hold circuit are switched on, and the sampling period Transition to TA4. In the sampling period TA4, the sample hold circuit of the gradation voltage generation circuit 110 samples the divided voltages VDAR1 to VDAR32 generated by the second ladder resistor circuit 112AR.

  Then, as indicated by A15 and A16, after the gradation voltage sampling switch element SWS1 and the feedback switch element SWS2 are turned off, the flip-around switch element SWS3 is turned on as indicated by A17. As a result, the sampling period TA4 of the divided voltages VDAR1 to VDAR32 of the second ladder resistor circuit 112AR ends, and the period shifts to the hold period TA5. In this way, the divided voltages VDAR1 to VDAR32 of the second ladder resistor circuit 112AR are held by the gradation voltage generating sample hold circuit. As described above, the gradation voltage sampling switch element SWS1 is turned off after the feedback switch element SWS2 is turned off in order to minimize the adverse effect of charge injection.

  Thereafter, as indicated by A17, the flip-around switch element SWS3 is switched off, and the hold period TA5 in which the gradation voltage generating sample-and-hold circuit holds the divided voltages VDAR1 to VDAR32 ends. Then, as shown at A18, the sleep signal SLP_G input to the operational amplifier OPS1 becomes active (H level), and the operational amplifier OPS1 of the sample hold circuit of the gradation voltage generation circuit 110 is set to the sleep mode, The grayscale voltage generation sample-and-hold circuit shifts to the sleep period TA6. At this time, when the grayscale voltage generation sample-and-hold circuit shifts to the sleep period TA6, the current input to the second ladder resistor circuit 112AR is turned off in order to cut the current flowing through the second ladder resistor circuit 112AR. To. That is, when the grayscale voltage generation sample-and-hold circuit shifts to the sleep period TA6, the third and fourth power supply connection switch elements SWA3 and SWA4 of the second ladder resistor circuit 112AR are set as shown in A19. Turn off. As described above, when the grayscale voltage generation sample-and-hold circuit shifts to the sleep period TA6, the power consumption of the grayscale voltage generation circuit 110 is turned off by turning off the current input to the second ladder resistor circuit 112AR. Can be reduced.

  8A shows the signal waveform example on the grayscale voltage generation circuit 110A side of the first configuration example, the grayscale voltage generation circuit 110B side of the second configuration example shown in FIG. The signal waveform example of the above operation also shows the same operation mode. That is, if the first to fourth power connection switch elements SWA1 to SWA4 in FIG. 8A are replaced with the first to fourth power connection switch elements SWB1 to SWB4 in the second configuration example, respectively, FIG. FIG. 9A illustrates an example of a signal waveform on the grayscale voltage generation circuit 110B side of the second configuration example.

2.4. Operational Amplifier The grayscale voltage generation sample-and-hold circuit (SH1 to SH32) of this embodiment needs to drive a data line having a large parasitic capacitance during the hold period, and the driving load becomes high. Therefore, the operational amplifier OPS1 of the sample-and-hold circuit for generating the gradation voltage is configured by an amplifier capable of class AB amplification operation.

  FIG. 9 shows a configuration example of an operational amplifier OPS1 that is an operational amplifier capable of performing a class AB amplification operation. The operational amplifier OPS1 includes a differential section (differential stage) composed of transistors TS1, TS2, TS3, TS4, and TS5, and an output section (output stage) composed of transistors TS6 and TS7.

  The operational amplifier OPS1 of FIG. 9 is provided with a switch element SE1 to which the bias voltage BS is supplied at one end and the other end is connected to the gate node NSH3 of the transistor TS7 of the output unit. The capacitor CCP2 is provided between the output node NSH1 of the differential section and the gate node NSH3 of the transistor TS7.

  The switch element SE1 is turned on in the gradation voltage sampling period. As a result, the operational amplifier OPS1 in FIG. 9 functions as an amplifier for class A amplification operation because the bias voltage BS is input to the gate of the transistor TS7 of the output section. On the other hand, the switch element SE1 is turned off during the gradation voltage hold period. As a result, the gate node NSH3 of the transistor TS7 enters a floating state, and the voltage at the node NSH2 varies according to the voltage variation at the node NSH1 due to the capacitor CCP2. Accordingly, the operational amplifier OPS1 in FIG. 9 functions as an amplifier for class AB amplification operation.

3. Data Driver Sample Hold Circuit Each of the data driver sample hold circuits DSH1 to DSHm included in the data line drive circuits 54-1 to 54-m included in the data driver 50 can be configured by a so-called flip-around sample hold circuit.

  In this embodiment, as shown in FIG. 10, the data driver sample and hold circuit includes an operational amplifier OPD1, first and second selection gradation voltage sampling capacitors CSD1 and CSD2, and first and second selection gradations. It includes voltage sampling switch elements SWD1, SWD2, feedback switch element SWD3, and first and second flip-around switch elements SA1, SA2. The data driver sample and hold circuit includes a sample and hold output switch element SQG. It should be noted that modifications such as omitting some of these components or adding other components are possible. In addition, the switch elements SWD1, SWD2, SWD3, SA1, SA2, and SQG can be configured by, for example, CMOS transistors such as transfer gates.

  An analog reference power supply voltage AGND is set to the non-inverting input terminal (second input terminal) of the operational amplifier OPD1. Note that the operational amplifier OPD1 of the present embodiment can be configured by an amplifier capable of class AB amplification operation. Specifically, the operational amplifier OPD1 has a configuration similar to that of the operational amplifier OPS1 provided in the sample / hold circuit for grayscale voltage generation shown in FIG. Become.

  The first and second selection gradation voltage sampling switch elements SWD1 and SWD2, and the first and second selection gradation voltage sampling capacitors CSD1 and CSD2 are connected to the input node of the data driver sample hold circuit and the operational amplifier OPD1. And an inverting input terminal (first input terminal).

  The feedback switch element SWD3 is provided between the output terminal of the operational amplifier OPD1 and the inverting input terminal of the operational amplifier OPD1.

  The first flip-around switch element SA1 includes a first connection node ND1 between the first selected gradation voltage sampling switch element SWD1 and the first selected gradation voltage sampling capacitor CSD1, and an operational amplifier OPD1. Between the two output terminals.

  On the other hand, the second flip-around switch element SA2 includes a second connection node ND2 between the second selected gradation voltage sampling switch element SWD2 and the second selected gradation voltage sampling capacitor CSD2, and an arithmetic operation. It is provided between the output terminals of the amplifier OPD1.

  The flip-around type data driver sample and hold circuit of the present embodiment will be described in more detail with reference to FIGS.

  The first selected gradation voltage sampling capacitor CSD1 is provided between the inverting input terminal (first input terminal) of the operational amplifier OPD1 and the first input node NDSHn1. Then, as shown in FIG. 11A, the capacitor CSD1 has an input voltage VDn1 (first gradation voltage, first selected gradation voltage) of the first input node NDSHn1 in the sampling period. Charge is accumulated.

  The second selected gradation voltage sampling capacitor CSD2 is provided between the inverting input terminal of the operational amplifier OPD1 and the second input node NDSHn2. Then, in the capacitor CSD2, charges corresponding to the input voltage VDn2 (second gradation voltage, second selected gradation voltage) of the second input node NDSHn2 are accumulated in the sampling period.

  As shown in FIG. 11A, in the sampling period, the output of the operational amplifier OPD1 is fed back to the node NEG of the inverting input terminal of the operational amplifier OPD1. The non-inverting input terminal (second input terminal) of the operational amplifier OPD1 is set to the analog reference power supply voltage AGND. Therefore, the node NEG to which one ends of the capacitors CSD1 and CSD2 are connected is set to AGND by the imaginary short function of the operational amplifier OPD1. As a result, charges corresponding to the input voltages VDn1 and VDn2 are accumulated in the capacitors CSD1 and CSD2, respectively.

  As shown in FIG. 11B, in the hold period, the data driver sample-and-hold circuit responds to the charges accumulated in the first and second selected gradation voltage sampling capacitors CSD1 and CSD2 in the sampling period. The output voltage VQG (= VS) is output to the output node NQG. Specifically, the charge accumulated in the capacitors CSD1 and CSD2 is performed by performing a flip-around operation in which the other ends of the capacitors CSD1 and CSD2 to which the node NEG is connected at one end are connected to the output terminal of the operational amplifier OPD1. The output voltage VQG corresponding to is output.

  A detailed operation of the data driver sample hold circuit using the flip-around sample hold circuit will be described with reference to FIGS.

  As shown in FIG. 12A, in the sampling period, the first and second selection gradation voltage sampling switch elements SWD1 and SWD2 and the feedback switch element SWD3 are turned on, and the first and second The flip-around switch elements SA1 and SA2 are turned off. Thereby, the sampling operation of the flip-around sample-and-hold circuit described with reference to FIG.

  On the other hand, as shown in FIG. 12B, in the hold period, the sampling switch elements SWD1, SWD2, and the feedback switch element SWD3 are turned off, and the first and second flip-around type switch elements SA1. , SA2 is turned on. Thereby, the hold operation of the flip-around sample hold circuit described with reference to FIG. 11B can be realized.

  The output switch element SQG is provided between the output terminal of the operational amplifier OPD1 and the output node NQGm of the data driver sample hold circuit. Then, as shown in FIG. 12A, the output switch element SQG is turned off in the sampling period. As a result, the output of the sample and hold circuit for the data driver becomes a high impedance state, and it is possible to prevent an uncertain voltage during the sampling period from being transmitted to the subsequent stage.

  On the other hand, as shown in FIG. 12B, the output switch element SQG is turned on in the hold period. Thereby, the voltage VQG which is the selected gradation voltage generated in the sampling period can be output.

  According to the data driver of the present embodiment described above, the data driver sample and hold circuit receives the first and second grayscale voltages (V1, V2, and V2) that are input from the D / A conversion circuit, for example, in time division. And V3, V3 and V4, etc.) can generate a gradation voltage ((V1 + V2) / 2, (V2 + V3) / 2, (V3 + V4) / 2, etc.) between the first and second gradation voltages. . For this reason, the number of gradation voltages generated by the gradation voltage generation circuit can be reduced, the number of gradation voltage lines can be reduced, and the circuit scale of the D / A conversion circuit can be reduced.

For example, when the gradation data is 6 bits and the number of gradations is 2 ⁶ = 64 gradations, the gradation voltage generation circuit needs to generate 64 gradation voltages in the conventional method. The D / A converter circuit requires a selector group for selecting a gray scale voltage corresponding to the gray scale data from these 64 gray scale voltages. Therefore, the scaled voltage generation circuit and the D / A conversion circuit are increased in scale. In addition, since the number of gradation voltage lines is 64, the occupied area of the wiring region is also increased.

  In this regard, according to the data driver of the present embodiment, the grayscale voltage between the first and second selected grayscale voltages is generated by the data driver sample and hold circuit. For example, 32 gradation voltages may be generated, and the D / A converter circuit may be provided with a selector group for selecting a voltage from among these 32 gradation voltages. Therefore, the circuit scale can be greatly reduced as compared with the conventional method, and the number of gradation voltage lines can be reduced to 32, so that the area of the wiring region can be greatly reduced. Actually, since the data driver sample and hold circuit generates a gradation voltage between the first and second selected gradation voltages, the number of gradation voltage lines is more than 32 in the above case. (For example, 33 or 34).

  Here, the operation of the data driver of this embodiment will be described in detail with reference to FIG. In this embodiment, as shown in FIG. 8B, the operational amplifier OPS1 of the gradation voltage generating sample and hold circuit is in the sampling period TA1 and the hold period TA2, and the data driver sample and hold circuit is in the sleep period TB1. It has become. That is, as indicated by B1 in FIG. 8B, the sleep signal SLP_D input to the operational amplifier OPD1 of the data driver sample-and-hold circuit becomes active (H level) and is set to the sleep mode. The sample hold circuit is in the sleep period TB1. In the data driver 50, the read signal of the RAM, which is the memory 20, is turned on as shown in B2 during TB1 during the sleep period of the data driver sample hold circuit, and the D / A conversion circuit (52-1) of the data driver 50 ˜52-m) read the gradation data GD of the RAM. Thereafter, as indicated by B3, the sleep signal SLP_D input to the operational amplifier OPD1 becomes inactive (L level), and the sleep period TB1 ends.

  When the selected gradation voltages VSL to VSLm are supplied from the D / A conversion circuit to the data line driving circuit during the sleep period TB1, as shown at B4, B5, and B6, the data driver sample hold circuit switches The elements SWD1 and SWD2 and the feedback switch element SWD3 are turned on. Thus, the sampling period TB2 in which the selected gradation voltages VSL to VSLm supplied from the D / A conversion circuit are sampled by the sample hold circuit is started (see FIG. 12A).

  After a predetermined time has elapsed since the start of the sampling period TB2, as shown in B7, B8, B9, the first and second selection gradation voltage sampling switch elements SWD1, SWD2, and the feedback switch element SWD3 Is turned off, and the sampling period TB2 ends. Then, as shown in B10, the first and second flip-around switch elements SA1 and SA2 are switched on, and the data driver sample hold circuit shifts to the hold period TB3 (see FIG. 12B). In the hold period TB3, the selected gradation voltage sampled by the data driver sample hold circuit is supplied to the data line of the electro-optical panel 400, and the data line of the electro-optical panel 400 is driven. As indicated by B8 and B9, the first selection gradation voltage sampling switch element SWD1 is turned off after the feedback switch element SWD3 is turned off. In this way, adverse effects of charge injection can be minimized.

  The input node of the first selection gradation voltage sampling switch element SWD1 and the input node of the second selection gradation voltage sampling switch element SWD2 are connected in common, and the first input terminal is connected to the commonly connected input node. The second selection gradation voltage may be input in a time division manner. That is, both the first and second selection gradation voltage sampling switch elements SWD1 and SWD2 are turned on during the period in which the first selection gradation voltage is input. During the period when the second selection gradation voltage is input, the first selection gradation voltage sampling switch element SWD1 is turned off and the second selection gradation voltage sampling switch element SWD2 is turned on. Leave. Thereafter, before the start of the hold period TB3, the second selection gradation voltage sampling switch element SWD2 is switched off, and both the first and second selection gradation voltage sampling switch elements SWD1 and SWD2 are turned off. In this way, two selected gradation voltages can be input in a time division manner in the sampling period TB2.

  Further, during the hold period TB3, as indicated by B11, the scanning signal SG_G from the scanning driver 70 becomes active, and the corresponding scanning line of the electro-optical panel 400 is selected. Thereafter, as shown in B12, the scanning signal SG_G is deactivated, and as shown in B13, the first and second flip-around switch elements SA1 and SA2 are turned off to end the hold period TB3. . After the hold period TB3 ends, as shown in B14, the sleep signal SLP_D input to the operational amplifier OPD1 is activated (H level). Then, the operational amplifier OPD1 of the data driver sample and hold circuit enters the sleep mode TB4. As described above, the power consumption of the data driver 50 can be reduced by setting the data driver sample hold circuit to the sleep mode TB4 after the data driver hold period TB3 ends. Thereafter, in the data driver sample and hold circuit, the sampling period TB5, the hold period TB6, and the sleep period TB7 are repeated in the same manner as described above.

  As described above, in this embodiment, when the grayscale voltage generation sample-and-hold circuit samples the grayscale voltage supplied from the grayscale voltage generation circuit 110 and starts holding, the data driver 50 starts the electro-optical panel 400. The gradation voltage necessary to drive the is secured. For this reason, after the necessary gradation voltage is secured, it is not necessary to supply the gradation voltage from the gradation voltage generation circuit 110, and the gradation voltage generation circuit 110 is used in a period when the gradation voltage is not necessary. By setting to the sleep mode, the power consumption of the gradation voltage generation circuit 110 can be reduced. At this time, the power consumption can be greatly reduced by setting the grayscale voltage generation sample-and-hold circuit included in the grayscale voltage generation circuit 110, particularly the operational amplifier OPS1 having a large driving power, to the sleep mode.

4). Electronic Device FIGS. 13A and 13B show a configuration example of an electronic device (electro-optical device) including the integrated circuit device (driver) 10 of this embodiment. Various modifications such as omitting some of the components shown in FIGS. 13A and 13B and adding other components (for example, a camera, an operation unit, or a power source) are possible. It is. In addition, the electronic device 500 of the present embodiment is not limited to a mobile phone, and may be a digital camera, a PDA, an electronic notebook, an electronic dictionary, a projector, a rear projection television, a portable information terminal, or the like.

  13A and 13B, the host device 410 is, for example, an MPU or a baseband engine. The host device 410 controls the integrated circuit device 10 that is a display driver. Alternatively, processing as an application engine or baseband engine, or processing as a graphic engine such as compression, decompression, or sizing can be performed. In addition, the image processing controller 420 in FIG. 13B performs processing as a graphic engine such as compression, decompression, and sizing on behalf of the host device 410.

  In the case of FIG. 13A, an integrated circuit device (driver) 10 having a built-in memory can be used. That is, in this case, the integrated circuit device 10 once writes the image data from the host device 410 into the built-in memory, reads the written image data from the built-in memory, and drives the display panel. On the other hand, in the case of FIG. 13B, an integrated circuit device 10 without a memory can be used. That is, in this case, the image data from the host device 410 is written in the built-in memory of the image processing controller 420. The integrated circuit device 10 drives the display panel 400 under the control of the image processing controller 420.

  Although the present embodiment has been described in detail as described above, it will be easily understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention. For example, in the specification or the drawings, it is described at least once together with different terms having a broader meaning or the same meaning (first input terminal, second input terminal, analog reference power supply voltage, first power supply, second power supply, etc.). The terms (inverted input terminal, non-inverted input terminal, AGND, VSS, VDD, VGMH, VGML, etc.) can be replaced with the different terms anywhere in the specification or the drawings. In addition, the configuration and operation of the data driver, D / A conversion circuit, switch circuit, data line driving circuit, gradation voltage generation sample hold circuit, data driver sample hold circuit, integrated circuit device, electronic device, and the like in this embodiment. The present invention is not limited to what has been described, and various modifications can be made.

2 is a configuration example of a driver according to the present embodiment. 3 is a detailed configuration example of a driver according to the present embodiment. 1 is a first configuration example of a gradation voltage generation circuit. 2 shows a second configuration example of a gradation voltage generation circuit. 6 is a configuration example of a sample-and-hold circuit for generating a gradation voltage. 6A and 6B are explanatory diagrams of a flip-around sample-and-hold circuit. 7A and 7B are configuration examples of a sample-and-hold circuit for generating a gradation voltage using a flip-around sample-and-hold circuit. 8A shows an example of a signal waveform on the gradation voltage generation circuit side, and FIG. 8B shows an example of a signal waveform on the data driver side. 2 is a configuration example of an operational amplifier provided in a sample-and-hold circuit for generating a gradation voltage. 2 is a configuration example of a sample driver circuit for a data driver. 11A and 11B are explanatory diagrams of a flip-around sample-and-hold circuit. FIGS. 12A and 12B are configuration examples of a data driver sample hold circuit using a flip-around sample hold circuit. FIGS. 13A and 13B are configuration examples of electronic devices.

Explanation of symbols

V1 to V32 gradation voltage, VD1 to VD32 divided voltage,
VSL1 to VSLm select gradation voltage, OPS1, OPD1 operational amplifier,
SL1 to SLm data lines, SWA1 to SWA4 switch elements,
SWS1, SWD1, SWD2 sampling switch elements,
CSS1, CSD1, CSD2 sampling capacitors,
SHA1 to SHA32, SHB1 to SHB32 Sample hold circuits DSH1 to DSHm Sample hold circuits SWS2 and SWD3 for data drivers Feedback switch elements,
SWS3, SA1, SA2 flip-around switch element,
SWS4, SQG output switch element,
10 integrated circuit device, 20 memory, 22 memory cell array,
24 row address decoder, 26 column address decoder,
28 write / read circuit, 40 logic circuit, 42 control circuit,
44 display timing control circuit, 46 host interface circuit,
48 RGB interface circuit, 50 data driver,
52-1 to 52-m D / A conversion circuit, 54-1 to 54-m data line driving circuit,
70 scan driver, 90 power supply circuit, 110 gradation voltage generation circuit,
400 display panel, 410 host device, 420 image processing controller,
500 Electronic equipment

Claims (16)

A driver of an electro-optical device,
A gradation voltage generation circuit for generating a plurality of gradation voltages;
A data driver that receives the plurality of gradation voltages and the gradation data from the gradation voltage generation circuit and drives the plurality of data lines of the electro-optical device;
The gradation voltage generation circuit includes:
A ladder resistor circuit having a plurality of resistor circuits connected in series between a first power source and a second power source, and outputting a plurality of divided voltages divided by the plurality of resistor circuits;
A sample having a plurality of gradation voltage generation sample-and-hold circuits for sampling and holding the plurality of divided voltages from the ladder resistor circuit, and outputting the plurality of held divided voltages as the plurality of gradation voltages A hold section;
The driver characterized by including. In claim 1,
The ladder resistor circuit is
A first ladder resistor circuit having a plurality of resistor circuits connected in series between the first power source and the second power source;
A first power connection switch element provided between the first power source and one end of the first ladder resistor circuit;
A second power connection switch element provided between the second power source and the other end of the first ladder resistor circuit;
A plurality of first ladder resistor switching elements provided between a plurality of first ladder resistor side divided nodes divided by the plurality of resistor circuits and the plurality of gradation voltage generating sample hold circuits;
A second ladder resistor circuit having a plurality of resistor circuits connected in series between the first power source and the second power source;
A third power connection switch element provided between the second power source and one end of the second ladder resistor circuit;
A fourth power connection switch element provided between the first power source and the other end of the second ladder resistor circuit;
A plurality of second ladder resistor switching elements provided between a plurality of second ladder resistor side divided nodes divided by the plurality of resistor circuits and the plurality of gradation voltage generating sample hold circuits; Including
When the first and second power connection switch elements are on, the plurality of first ladder resistance switch elements are turned on, and the third and fourth power connection switch elements And the plurality of second ladder resistor switch elements are turned off,
When the first and second power supply connection switch elements are off, the plurality of first ladder resistance switch elements are turned off, and the third and fourth power supply connection switch elements are turned off. And the plurality of second ladder resistance switch elements are turned on. In claim 1,
The ladder resistor circuit is
A plurality of resistor circuits connected in series between the first power source and the second power source, and a plurality of nodes divided by the plurality of resistor circuits for generating the plurality of gradation voltages; A ladder resistor circuit connected to the sample hold circuit;
A first power connection switch element provided between the first power source and one end of the ladder resistor circuit;
A second power connection switch element provided between the second power source and the other end of the ladder resistor circuit;
A third power supply connection switch element provided between the first power supply and the other end of the ladder resistor circuit;
A fourth power connection switch element provided between the second power source and one end of the ladder resistor circuit,
When the first and second power connection switch elements are on, the third and fourth power connection switch elements are off,
When the first and second power supply connection switch elements are off, the third and fourth power supply connection switch elements are turned on. In claim 2 or claim 3,
The driver, wherein the first to fourth power supply connection switch elements are turned off during a grayscale voltage generation sleep period in which the grayscale voltage generation circuit is set to the sleep mode. In any one of Claims 1 thru | or 4,
2. The driver according to claim 1, wherein each of the plurality of gradation voltage generation sample-hold circuits is a flip-around sample-hold circuit. In claim 5,
Each of the gradation voltage generation sample hold circuits,
An operational amplifier;
Provided between the first input terminal of the operational amplifier and the input node of each of the gradation voltage generating sample and hold circuits, charges corresponding to the input voltage of the input node are accumulated in the gradation voltage generating sampling period. A sampling capacitor
A driver characterized in that an output voltage corresponding to the charge accumulated in the sampling capacitor in the gradation voltage generation sampling period is output in the gradation voltage generation hold period. In claim 5,
Each of the gradation voltage generation sample hold circuits,
An operational amplifier having an analog reference power supply voltage set at its second input terminal;
A sampling capacitor provided between a first input terminal of the operational amplifier and an input node of each of the gradation voltage generating sample and hold circuits;
A sampling switch element provided between the sampling capacitor and the input node of each of the gradation voltage generation sample hold circuits;
A feedback switch element provided between an output terminal of the operational amplifier and the first input terminal;
And a flip-around switch element provided between a connection node between the sampling switch element and the sampling capacitor and the output terminal of the operational amplifier. In any one of Claims 1 thru | or 7,
The data driver is
It has a sample and hold circuit for the data driver,
After the data driver sampling period in which sampling is performed by the data driver sample and hold circuit and after the data driver hold period in which holding is performed by the data driver sample and hold circuit starts, the gradation voltage generation circuit Is set to the sleep mode. In claim 8,
The driver, wherein the plurality of gradation voltage generation sample-hold circuits are set to a sleep mode in a gradation voltage generation sleep period in which the gradation voltage generation circuit is set to the sleep mode. In claim 8 or claim 9,
The data driver is
In response to the plurality of gradation voltages and the gradation data from the gradation voltage generation circuit, the gradation voltage corresponding to the gradation data is selected from the plurality of gradation voltages and selected. A D / A conversion circuit for outputting as a gradation voltage;
A data line driving circuit that receives the selected gradation voltage from the D / A conversion circuit and drives each data line of the plurality of data lines of the electro-optical device;
The data driver sample and hold circuit comprises:
A driver provided in the data line driving circuit, which samples and holds the selected gradation voltage. In any one of Claims 8 thru | or 10.
The data driver sample and hold circuit is a flip-around sample and hold circuit. In claim 11,
The data driver sample and hold circuit comprises:
The driver is set to a sleep mode after the data driver hold period ends. In claim 11 or claim 12,
The data driver sample and hold circuit comprises:
An operational amplifier;
Charge provided between the first input terminal of the operational amplifier and the first input node of the data driver sample and hold circuit, and according to the input voltage of the first input node in the data driver sampling period A first sampling capacitor in which is stored;
Provided between the first input terminal of the operational amplifier and the second input node of the data driver sample and hold circuit, and according to the input voltage of the second input node in the data driver sampling period A second sampling capacitor in which charge is stored,
In the data driver sampling period, an output voltage corresponding to the electric charge accumulated in the first and second sampling capacitors is output in the data driver hold period. In claim 11 or claim 12,
The data driver sample and hold circuit comprises:
An operational amplifier having an analog reference power supply voltage set at its second input terminal;
A first sampling switch element and a first sampling capacitor provided between a first input node of the data driver sample and hold circuit and a first input terminal of the operational amplifier;
A second sampling switch element and a second sampling capacitor provided between a second input node of the data driver sample and hold circuit and the first input terminal of the operational amplifier;
A feedback switch element provided between an output terminal of the operational amplifier and the first input terminal;
A first flip-around switch element provided between a first connection node between the first sampling switch element and the first sampling capacitor and the output terminal of the operational amplifier; ,
A second flip-around switch element provided between a second connection node between the second sampling switch element and the second sampling capacitor and the output terminal of the operational amplifier; A driver characterized by including.   An electro-optical device comprising the driver according to claim 1.   An electronic apparatus comprising the electro-optical device according to claim 15.

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