JP2009009432A - Semiconductor device and display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device with a display driving circuit having a multifunction property and versatility, and to provide a display apparatus. <P>SOLUTION: On a display panel, a plurality of selection lines, a plurality of signal lines and a plurality of pixels formed on their intersections are arranged. The plurality of pixels on the display panel are successively selected by successively selecting the selection lines by a selection circuit. A display driving circuit forms a display voltage corresponding to the selection timing of the selection line by the selection circuit and supplies the display voltage to the selected pixel on the display panel. The display driving circuit comprises an output MOSFET for forming the display voltage, a sense MOSFET of which the gate and source are connected to the output MOSFET, and a current sense circuit for extracting a difference between a drain current of the sense MOSFET and a prescribed current. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor device and a display device. For example, the present invention is applied to a semiconductor device having a display drive circuit for supplying a gradation display voltage corresponding to display data indicating gradation to a TFT liquid crystal display panel and the like and a display device using the same. And effective technology.

As an example of a touch sense device incorporated in a display panel such as a liquid crystal, there is JP-A-7-307657. A digital touch panel is formed by forming an ITO film, which is a resistance film, on a glass or film in a strip shape so as to be orthogonal to the XY shape, and the upper and lower resistance films are touched by touching the surface. To do.
JP-A-7-307657

  FIG. 9 shows a circuit diagram of the display device and the touch panel studied by the inventors of the present application. The digital touch panel is formed in a strip shape so that the ITO film, which is a resistance film, is orthogonal to the XY shape as shown by the dotted line in the figure, and each has a pull-up resistor, an X comparator, and a pull-down resistor. A Y comparator is provided. In such a digital touch panel, the reading position can be accurately set, but X and Y comparators and resistors are required corresponding to the strip-shaped electrodes, respectively, the number of parts is large, and the connection terminals to the display panel are also provided. Become more.

  A source amplifier that inputs display data to the display panel is composed of a semiconductor device and needs to be able to drive various display panels having different sizes. However, the required current varies depending on the size of the display panel and the like. If the current supply capability of the source amplifier is large with respect to the current required for the display operation, a current flows unnecessarily even after the amplifier output is stabilized. On the other hand, if the current supply capability of the amplifier is small with respect to the required load current, the response is delayed in the middle of the change of the display voltage, so that a correct display voltage cannot be transmitted to the pixel. The load current of the display panel varies and can vary depending on the display panel. If the gradation voltage to be output is different, the amplitude changes, so the same thing as described above occurs. Therefore, it has been considered to realize a multi-function and versatility of a semiconductor device in which a display drive circuit is mounted by adding a current sense function to the source amplifier and a display device using the semiconductor device.

  An object of the present invention is to provide a semiconductor device and a display device having a display drive circuit that realizes multi-function and versatility. The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  One embodiment disclosed in the present application is as follows. The semiconductor device includes a plurality of display drive circuits that supply a plurality of display voltages to the display device. The display driving circuit includes an output MOSFET that forms the display voltage, a sense MOSFET in which a gate and a source are connected to the output MOSFET, and a current sense circuit that extracts a difference between a drain current of the sense MOSFET and a predetermined reference current And have.

  One of the other embodiments disclosed in the present application is as follows. The display panel includes a plurality of selection lines, a plurality of signal lines, and a plurality of pixels provided at respective intersections. In the display panel, the selection lines are sequentially selected by a selection circuit. The display driving circuit generates a display voltage corresponding to the selection timing of the selection line by the selection circuit and supplies it to the selected pixel of the display panel. The display driving circuit includes an output MOSFET that forms the display voltage, a sense MOSFET in which a gate and a source are connected to the output MOSFET, and a current sense circuit that extracts a difference between a drain current of the sense MOSFET and a predetermined reference current And have.

  A semiconductor having a display drive circuit that realizes multi-functionality and versatility by providing a comparator function of a digital touch panel provided on the display panel by the current sense circuit and forming a drive current suitable for the display panel A device and a display device can be realized.

  FIG. 1 shows a schematic circuit diagram of an embodiment of a display device according to the present invention. In the figure, a display panel provided with a digital touch panel, a source amplifier for driving a signal line (source line) of the display panel, a gate driver for sequentially selecting a selection line of the display panel, and a Y comparator are shown. The source amplifier is a display driving circuit that supplies a display voltage supplied to the pixels of the display panel, and has an X comparator function of the digital touch panel. In the drawing, three signal lines (source lines) S1 to S3 and four scanning lines (gate lines) G1 to G4 are exemplarily shown.

  One pixel of the display panel has a source-drain path connected between a signal line (source line S1) and a pixel electrode (Cpx) as exemplarily shown in FIG. (G4) includes a TFT transistor Qs having a gate connected thereto, and a capacitor Cpx including the pixel electrode. The capacitor Cpx holds the display voltage supplied from the source amplifier. The liquid crystal provided between the common electrode and the pixel electrode of the liquid crystal panel functions as a dielectric film of the capacitor Cpx.

  The touch panel includes a first electrode that extends along the signal lines S1 to S3 and a second electrode that extends along the scanning lines G1 to G4. The first electrode is connected to the output terminal of the source amplifier together with the corresponding source lines S1 to S3. The second electrode is connected to a Y comparator via terminals y1 to y4. As shown by way of example for the Y comparator corresponding to the terminal y1, P-channel MOSFETs Q8 and Q9 in the form of current mirror and an N-channel as a constant current source for supplying a reference current Ir to the current mirror circuit It consists of MOSFETQ10. The comparator output is a connection node between the MOSFETs Q9 and Q10. The MOSFET Q10 is formed in a current mirror form with a diode-shaped N-channel MOSFET Q7 in which the reference current Ir flows, and the reference current Ir flows. The Y comparators corresponding to the other terminals y2 to y4 are also composed of MOSFETs in the same manner as described above.

  The source amplifier has an output circuit composed of an N-channel output MOSFET Q2 and a P-channel MOSFET Q1 as current source load means, as exemplarily shown corresponding to the source line S1. The output circuit is supplied with an output signal of a differential circuit as will be described later. The gradation voltage Vpx1 is supplied to one input terminal (+) of the differential circuit. The output signal is fed back to the feedback terminal (−) of the differential circuit to form a voltage follower circuit. Therefore, a display voltage corresponding to the gradation voltage Vpx1 is supplied to the source line S1.

  MOSFETs Q3 to Q6 are added to give the source amplifier a current sensing function. That is, the output MOSFET Q2 is provided with an N-channel type sense MOSFET Q3 having a common source and gate. The drain current of the MOSFET Q3 is supplied to a current mirror circuit composed of P-channel MOSFETs Q5 and Q6. The drain of the output MOSFET Q6 of this current mirror circuit is provided with an N-channel type MOSFET Q4 through which the reference current Ir flows. The MOSFET Q4 is in the form of a current mirror with the MOSFET Q7 so that the reference current Ir flows. These MOSFETs Q3 to Q6 are used as an X comparator of the touch panel. The same applies to the source amplifiers and X comparators corresponding to the other source lines S2 and S3.

  The operation of the touch panel of this embodiment is as follows. When contact is made between the first electrode corresponding to the source line S1 and the second electrode corresponding to the scanning line G1 (switch) like a touch indicated by an arrow in FIG. A current path is formed between the second electrode and the first electrode corresponding to the source line S1, and a current path such as the MOSFET Q8 of the Y comparator—the terminal y1—the second electrode—the first electrode—the output MOSFET Q2 of the source amplifier. Causes Δi to flow. This current Δi is set to be larger than the reference current Ir. The other switches composed of the first electrode and the second electrode are in the OFF state, and no current path is formed. The reference current Ir may be constant, but if the current Δi changes depending on the contact strength, the contact strength can be known by changing the reference current Ir stepwise. If the current Δi changes with time, it may be changed for correction.

  In the liquid crystal display device or the like, the pixel can be regarded as the capacitor Cpx as described above. Therefore, when the display voltage is written to the capacitor Cpx, no current flows through the output MOSFET Q2. In such a state, if a current path such as the MOSFET Q8 of the Y comparator—the terminal y1—the second electrode—the first electrode—the output MOSFET Q2 of the source amplifier is formed by the touch as described above, the terminal y1 In the corresponding Y comparator, the current Δi flowing through the MOSFET Q9 is larger than the reference current Ir flowing through the MOSFET Q10, and the output signal Y1 is set to the high level.

  In the X comparator corresponding to the source line S1, the same current Δi flows through the sense MOSFET Q3 whose gate and source are commonly connected to the output MOSFET Q2. This current Δi also flows through the current mirror MOSFETs Q5 and Q6. Similarly to the above, in the X comparator corresponding to the source line S1, the current Δi flowing through the MOSFET Q6 is larger than the reference current Ir flowing through the MOSFET Q4, and the output signal X1 is set to the high level. The outputs Y2 to Y4, X2, and X3 of the other comparators are set to the low level by the MOSFETs corresponding to the MOSFETs Q10 and Q4 through which the reference current Ir flows because the current path (the switch is off) is not formed.

  As described above, when the display voltage corresponding to the predetermined gradation voltages Vpx1 to Vpx3 is charged to the pixel and no current flows from the source amplifier, the outputs of the X and Y comparators are enabled. Thus, X1 and Y1 that are set to the high level in response to the touch of the digital touch panel as described above can be obtained.

  In this embodiment, by adding a current sense function to the source amplifier, a terminal for connecting to the X comparator provided in the display panel can be made unnecessary, and the X comparator has four MOSFETs, Y The comparator can be realized by a simple circuit like the three MOSFETs as described above. That is, for the display device employing the digital touch panel as shown in FIG. 9, the number of terminals connected to the display device and the circuit elements constituting the comparator and the like can be greatly reduced.

  FIG. 2 shows a schematic circuit diagram of another embodiment of the display device according to the present invention. In this embodiment, the simplification of the Y comparator and the number of terminals to which it is connected are reduced. That is, in this embodiment, switching elements such as MOSFETs Q11 to Q14 that are switch-controlled by selection signals of the scanning lines G1 to G4 are provided on the second electrode. The second electrode is commonly connected via these switch elements Q11 to Q14 and connected to the terminal y. The one comparator (Q8 to Q10) is provided at the terminal y. The source amplifier and the X comparator are the same as those in the embodiment of FIG.

  When contact is made between the first electrode corresponding to the source line S1 and the second electrode corresponding to the scanning line G1 (switch) like a touch indicated by an arrow in FIG. A current path is formed between the second electrode and the first electrode corresponding to the source line S1, and the MOSFET Q8 of the Y comparator—the terminal y—the common electrode—the MOSFET Q11—the second electrode—the first electrode—the output MOSFET Q2 of the source amplifier. Δi similar to the above is caused to flow by the current path as described above. Thereby, in the X converter, the output signal X1 is set to the high level. The Y comparator determines that the high level of the output signal Y and the input signal of the gate driver at that time are output signals. That is, the input signal of the gate driver that sets the scanning line G1 to the high level is determined as the output signal Y1 of the Y comparator. In this embodiment, compared to the embodiment of FIG. 1, the Y comparator and the terminals to which it is connected can be greatly reduced.

  FIG. 3 is a schematic circuit diagram of still another embodiment of the display device according to the present invention. This embodiment is a modification of the embodiment of FIG. 2, and is a unidirectional element that prevents current Δi from flowing backward when two switches are simultaneously turned on on the digital touch panel. Diode-type MOSFETs Q15 to Q17 are provided. For example, there is a difference voltage between the grayscale voltage Vpx1 output to the source line S1 and the grayscale voltage Vpx2 output to the source line S2, and a first electrode corresponding to the source lines S1 and S2 and a first electrode orthogonal thereto. When two switches composed of two electrodes are turned on at the same time, a current corresponding to the difference voltage flows between the source lines S1 and S2 and affects the display operation. Therefore, diode-type MOSFETs Q15 to Q17 are provided so that the above-described reverse current does not flow. These MOSFETs Q15 to Q17 may be any one-way element such as a diode.

  In the embodiment of FIG. 3, the conductivity types of the MOSFETs Q1 to Q10 are opposite to those shown in FIGS. That is, the load MOSFET Q1 is an N-channel MOSFET, and the output MOSFET Q2 is a P-channel MOSFET. Correspondingly, the MOSFETs Q3 and Q4 of the X comparator are P-channel MOSFETs, and the MOSFETs Q5 and Q6 are N-channel MOSFETs. The MOSFET Q7 that flows the reference current Ir to form the bias voltage VPSBI is a P-channel MOSFET. The MOSFET Q10 of the Y comparator is composed of a P channel MOSFET, and the MOSFETs Q8 and Q9 are composed of N channel MOSFETs. Corresponding to the reverse of the conductivity type of the MOSFET, a current Δi flows from the first electrode to the second electrode in the touch panel.

  Also in the embodiment of FIG. 1 or FIG. 2, a unidirectional element may be added to prevent current flowing between source lines by simultaneously turning on a plurality of switches of the touch panel as shown in FIG. . In this case, since the flowing current is reversed as described above, the direction of the unidirectional element is reversed from that shown in FIG.

  FIG. 4 shows a configuration diagram of an embodiment of the touch panel used in the present invention. FIG. 4A shows a cross-sectional portion, and FIG. 4B shows a perspective view of two electrodes assembled. The strip-shaped 1st electrode 7 extended in the horizontal direction is provided on the surface of glass or the film 6 in the same figure. Glass or film 6 constitutes a lower fixed substrate, and the first electrode is formed of an ITO film which is a resistance film (transparent conductive film). A strip-shaped second electrode 3 extending in a direction orthogonal to the first electrode 7 is provided on the lower surface (back surface) side of the film 1. The film 1 constitutes the touch surface of the movable substrate, and the second electrode 3 is formed of an ITO film as described above. The first electrode 7 and the second electrode 3 are bonded together via a bonding material 4 as a spacer so as to face each other. On the surface of the glass or film 6, dot spacers 5 are provided along the first electrodes 7 and separated into individual switches.

  When the surface of the film 1 is touched with a finger or a pen 2 as shown in FIG. 4A, the upper and lower chastity resistance films (second electrode 3 and first electrode 7) come into contact, and the switch is turned on. Thus, the intersection points X1, Y1, etc. are input points. The resolution is determined by the number (number of lines) of the first electrode 7 and the second electrode 3. Since the number of the first electrodes 7 and the second electrodes 3 is determined according to the required resolution, the first electrodes 7 and the second electrodes 3 are connected to the source lines (signals) of the display device as shown in FIGS. Lines) and scanning lines (gate lines) are not provided in one-to-one correspondence. The pixels of the display device are small for high-definition display, whereas one intersection (switch) necessary for the touch panel is set large corresponding to the fingertip 2 and the like. Accordingly, the first electrode 7 and the second electrode 3 of the touch panel are actually provided at a ratio of one to a plurality of source lines or gate lines of the display panel. Therefore, it should be understood that FIGS. 1 to 3 illustrate source lines S1 to S3 and gate lines G1 to G4 corresponding to the first electrode 7 and the second electrode 3 of the touch panel.

  FIG. 5 shows a circuit diagram of an embodiment of a source amplifier according to the present invention. Since the liquid crystal display device deteriorates when a DC voltage is applied to the liquid crystal, it is AC driven so that the voltage of each pixel changes between a negative gradation voltage and a positive gradation voltage. Therefore, in this embodiment, a source amplifier SAP corresponding to the positive gradation voltage Vpxp and a source amplifier SAN corresponding to the negative gradation voltage Vpxn are provided.

  The source amplifier SAP is composed of a single-ended differential circuit and an output circuit. The differential circuit includes N-channel type differential MOSFETs Q20 and Q21, an N-channel MOSFET Q23 provided on the common source side for flowing an operating current, and a P-channel in a current mirror form provided on the drain side as an active load circuit. It is composed of MOSFETs Q24 and Q25. The gate of the differential MOSFET Q20 is supplied with the positive gradation voltage Vpxp as an input terminal. The gate of the differential MOSFET Q21 is used as a feedback terminal, and the output signal of the output circuit is fed back to form a voltage follower circuit. The output circuit includes a P-channel output MOSFET Q26 to which the inverted output signal of the differential circuit is supplied to the gate, and an N-channel load MOSFET Q27 provided on the drain side.

  Similarly to the above, the source amplifier SAN is also composed of a differential circuit composed of MOSFETs Q40 to Q45 and an output circuit composed of MOSFETs Q46 and Q47. However, the conductivity type of the MOSFET is reversed from that of the source amplifier SAP. That is, the differential MOSFETs Q40 and Q41 and the current source MOSFET Q43 are constituted by P-channel MOSFETs, and the load MOSFETs Q45 and 46 are constituted by N-channel MOSFETs. Correspondingly, in the output circuit, the output MOSFET Q46 is constituted by an N-channel MOSFET, and the load MOSFET Q47 is constituted by a P-channel MOSFET.

  A switch SW1 is provided between the output terminals of the two source amplifiers SAP and SAN and the source line of the liquid crystal panel. When the polarity of the display voltage of the liquid crystal panel is reversed, the switch SW1 is switched. Corresponding to the switching of the switch SW1, the source line (pixel) of the liquid crystal panel changes at high speed from the negative gradation voltage Vpxn to the positive gradation voltage Vpxp or from the positive gradation voltage Vpxp to the negative gradation voltage Vpxn. It is necessary to let In order to speed up this voltage change, it is necessary to temporarily increase the operating current of the source amplifier to increase the response speed.

  In this embodiment, in the source amplifier SAP, the bias voltage VN supplied to the gates of the MOSFETs Q23 and Q27 as the current source is switched by the switch SW2. That is, when inverting the polarity, the bias voltage VPBH, which is set to a large voltage so as to allow a large current to flow temporarily by the switch SW2, is supplied, and then switched to the bias voltage VPBL. In the source amplifier SAN, the bias voltage VP supplied to the gates of the MOSFETs Q43 and Q47 as the current source is similarly switched by the switch SW3. When inverting the polarity, the bias voltage VNBH, which is set to a large voltage so that a large current is temporarily passed by the switch SW3, is supplied and then switched to the bias voltage VNBL. Since the MOSFETs Q43 and Q47 are P-channel type, the bias voltage VNBH is set to a voltage (a voltage larger in the negative direction) than the bias voltage VNBL with reference to the power supply voltage.

  For example, when switching from the negative gradation voltage Vpxn to the positive gradation voltage Vpxp, if the high-speed operation period TBIH is set to a certain period as shown in FIG. 10, a liquid crystal display panel with a small source line load capacity (small capacity) In, a large current continues to flow even after the output voltage of the source amplifier SAP is stabilized at the positive gradation voltage Vpxp, and the current is increased unnecessarily. Conversely, in a liquid crystal display panel (large capacity) with a large source line load capacity, the output voltage of the source amplifier SAP does not reach the positive gray scale voltage Vpxp, and the response occurs after the high-speed operation period TBIH has passed. Becomes slower and the source voltage deviates from the positive gradation voltage Vpxp. That is, if the high-speed operation period TBIH is set assuming a certain load capacity (medium capacity), a problem occurs in the display operation of a liquid crystal display panel having a smaller load capacity or a larger load capacity. The load capacity of the source line differs depending on the screen size, the number of pixels, or manufacturing variations, and the same problem arises because the amplitude changes if the gradation voltage at the time of the positive-negative mutual switching is different.

  In this embodiment, the sense MOSFET is used to optimize the high-speed operation period TBIH. That is, the source amplifier SAP will be described. A sense MOSFET Q28 having a common gate and source is provided in the output MOSFET Q26. The drain current of the MOSFET Q28 corresponding to the output current Ino flowing through the output MOSFET Q26 is input to a current mirror circuit composed of N-channel MOSFETs Q30 and Q31. A P-channel MOSFET Q29 is connected in series to the drain of the MOSFET Q31. The diode-shaped P-channel MOSFET Q32 and the P-channel MOSFET Q29 in which the reference current Ir is allowed to flow are formed in a current mirror shape so that the reference current Ir flows. Therefore, the drain voltages of the MOSFETs Q29 and Q31 are set to high level (H) / low level (L) corresponding to the magnitude relationship between the reference current Ir and the output current Ino. If Ino> Ir, the output signal is set to a low level (L), and if Ino <Ir, the output signal is set to a high level (H).

  As described above, when switching from the negative gradation voltage Vpxn to the positive gradation voltage Vpxp, the switch SW2 selects the bias voltage VPBH and operates at the high-speed operation current. At this time, Ino> Ir, the supply of the bias voltage VPBH is continued. When the voltage of the source line increases and the output current Ino gradually decreases, and when Ino <Ir, the output signal changes from the low level to the high level, the switch SW2 switches to the bias voltage VPBL, and the high-speed operation period TBIH End. The source amplifier SAN is also provided with MOSFETs Q48 to Q52 similar to the source amplifier SAP. However, the conductivity types of these MOSFETs are reversed from the corresponding MOSFETs Q28 to Q32 of the source amplifier SAP. Similarly to the above, when switching from the positive gradation voltage Vpxp to the negative gradation voltage Vpxn, the switch SW3 is switched by these MOSFETs Q48 to Q52 to determine the high speed operation period TBIH.

  FIG. 6 is a waveform diagram for explaining an example of the operation of the source amplifier of FIG. For example, when switching from the negative gradation voltage Vpxn to the positive gradation voltage Vpxp, the switch SW2 selects the bias voltage VPBH. As a result, the gate voltage VN of the MOSFETs Q23 and Q27 increases to form a large operating current Ins. That is, the source amplifier SAP operates with a large operating current Ins, and changes the source line from the negative gradation voltage Vpxn to the positive gradation voltage Vpxp at high speed. When the voltage transmitted to the source line becomes smaller, the voltage difference between the positive gradation voltage Vpxp, the voltage between the gate and the source of the output MOSFET Q26 correspondingly decreases, and the current value of the output current Ino decreases. When Ino <Ir, the switch SW2 is switched, the gate voltage VN of the MOSFETs Q23 and Q27 becomes small like the bias voltage VPBL, the operating current current Ins becomes small, and the high-speed operating period TBIH ends.

  FIG. 7 is a waveform diagram for explaining another example of the operation of the source amplifier of FIG. In the figure, an example in which the load capacity of the source line is smaller than in the case of FIG. 6 is shown. Thus, when the load capacitance of the source line is small, the potential change of the source line is fast, and Ino <Ir in a short time (TBIH). Correspondingly, the switch SW2 is switched, and the gate voltage VN of the MOSFETs Q23 and Q27 becomes small like the bias voltage VPBL, so that the operating current current Ins becomes small and wasteful current consumption is suppressed.

  FIG. 8 is a waveform diagram for explaining another example of the operation of the source amplifier of FIG. In the drawing, an example in which the load capacity of the source line is larger than that in the case of FIG. 6 is shown. Thus, when the load capacitance of the source line is large, the potential change of the source line is slow, so that the high speed operation period TBIH becomes longer than that in FIG. 5, and the source line is set to the desired gradation voltage Vpxp within a short time as a whole. be able to. As a result, a high-quality display operation can be realized, and an undesired DC voltage can be prevented from being applied to the liquid crystal.

  In the liquid crystal panel on which the touch panel as described above is mounted, the output current Ino flows corresponding to the ON position of the switch at the time of touch. In order to distinguish between the touch current Ino and the output current Ino when the gradation voltage Vpxp including the polarity switching is changed, the end timing of the high-speed operation period TBIH is used. A maximum signal MSK which is delayed by a predetermined period tDL of the end timing of the high-speed operation period TBIH and is set to a high level for a predetermined period is formed. The touch output X of the touch panel is validated only when the mask signal MSK is at a high level. The mask period MSK for taking out the touch output can be stably set regardless of the load capacity of the source line of the liquid crystal display panel by using the end timing of the high-speed operation period TBIH.

  The comparator that sets the high-speed operation period TBIH and the X comparator of the touch panel may be shared, or may be configured to perform an optimum detection operation with different reference currents Ir. Good. In order to prevent the comparator setting the high-speed operation period TBIH from responding to the detection current Δi generated by touching the touch panel and switching the switch SW2 from the H side to the L side, for example, the output signal of the comparator is supplied to the latch circuit. Capture, thereby forming a control signal for the switch SW2. For this reason, the latch circuit may be reset every time the gradation voltage including polarity inversion is written. Thus, the comparator that sets the high-speed operation period TBIH and the X comparator of the touch panel can be shared by making the same circuit operate at different timings. Each reference current may be different in accordance with this timing.

  The source amplifiers shown in FIGS. 1 and 2 use the source amplifier SAN, and the source amplifier shown in FIG. 3 uses the source amplifier SAP. For example, display voltage is written 60 times per second to one pixel of the liquid crystal panel. Since the positive polarity and the negative polarity need to have the same gradation voltage, 30 images are updated per second. Therefore, the X comparator used for the touch panel can perform touch sensing 30 times per second even if one of the two source amplifiers SAP and SAN is used. There is no problem.

  In this embodiment, it is possible to reduce the number of connection terminals and the number of parts by using the current sense function of the source amplifier for the comparator of the touch panel. By making the high-speed operation period TBIH of the source amplifier variable by the current sense function, current consumption and response speed can be made appropriate, and power consumption image quality can be optimized. In this manner, by adding a current sense function to the source amplifier, a semiconductor device and a display device having a display driver circuit that realizes multi-function and versatility can be obtained.

  The invention made by the inventor has been specifically described based on the embodiments. However, the present invention is not limited to the embodiments, and various modifications can be made without departing from the scope of the invention. Not too long. For example, the specific configuration of the touch panel can take various embodiments. In other words, not only physical contact but also current generated by a photosensor such as input using a light pen may be read. In the source amplifier, a plurality of current source MOSFETs may be provided, and the operating current Ins may be switched by changing the number of operating MOSFETs. 2 and FIG. 3, MOSFETs Q11 to Q14 and Q15 to Q17 provided on the touch panel may use TFT transistors formed on a glass substrate, and MOSFETs Q15 to Q17 may be diode elements. The gate driver may be constituted by a semiconductor device constituted by a MOSFET as well as a source amplifier other than those incorporated in a liquid crystal panel. The present invention can be widely used for a semiconductor device having a display driving circuit and a display device.

1 is a schematic circuit diagram of an embodiment of a display device according to the present invention. FIG. 6 is a schematic circuit diagram of another embodiment of the display device according to the present invention. FIG. 6 is a schematic circuit diagram of still another embodiment of the display device according to the present invention. It is a block diagram of one Example of the touchscreen used for this invention. 1 is a circuit diagram of an embodiment of a source amplifier according to the present invention. FIG. FIG. 6 is a waveform diagram for explaining an example of the operation of the source amplifier of FIG. 5. FIG. 6 is a waveform diagram for explaining another example of the operation of the source amplifier of FIG. 5. FIG. 6 is a waveform diagram for explaining another example of the operation of the source amplifier of FIG. 5. It is the circuit diagram of the display apparatus and touch panel which were examined by this inventor. FIG. 6 is a waveform diagram for explaining the source amplifier of FIG. 5.

Explanation of symbols

Q1-Q52 ... MOSFET, Qs ... TFT transistor, Cpx ... pixel (electrode), S1-S3 ... signal line (source line), G1-G4 ... scan line (gate line), SAP, SAN ... source amplifier,
DESCRIPTION OF SYMBOLS 1 ... Film, 2 ... Finger or pen, 3 ... 2nd electrode, 4 ... Laminating material, 5 ... Dot spacer, 6 ... Glass substrate or film, 7 ... 1st electrode,

Claims (13)

A plurality of display drive circuits for supplying a plurality of display voltages to the display device;
The display drive circuit is
An output MOSFET for forming the display voltage;
A sense MOSFET having a gate and a source connected to the output MOSFET;
A semiconductor device having a current sense circuit for extracting a difference between a drain current of the sense MOSFET and a predetermined reference current. In claim 1,
The display drive circuit is
A differential circuit having an input terminal and a feedback terminal;
In the output MOSFET, the output signal of the differential circuit is supplied to the gate, the current source load means is provided in the drain,
A semiconductor device in which an output voltage of the output MOSFET is fed back to the feedback terminal. A display panel having a plurality of selection lines, a plurality of signal lines, and a plurality of pixels provided at respective intersections;
A selection circuit for sequentially selecting the selection lines;
A display driving circuit that forms a display voltage corresponding to the selection timing of the selection line by the selection circuit and supplies the display voltage to a selected pixel of the display panel;
The display drive circuit is
An output MOSFET for forming the display voltage;
A sense MOSFET having a gate and a source connected to the output MOSFET;
A display device having a current sense circuit for extracting a difference between a drain current of the sense MOSFET and a predetermined reference current. In claim 3,
The display drive circuit is
A differential circuit having an input terminal and a feedback terminal;
In the output MOSFET, the output signal of the differential circuit is supplied to the gate, the current source load means is provided in the drain,
A display device in which an output voltage of the output MOSFET is fed back to the feedback terminal. In claim 4,
The display panel has a digital touch panel on the surface,
The touch panel
A plurality of first electrodes provided along the selection line;
A plurality of second electrodes provided along the signal line,
The plurality of first electrodes are provided with a current detection circuit of a predetermined current,
The plurality of second electrodes are connected to corresponding output terminals of the display drive circuit,
A display device in which an output signal of the current detection circuit and an output signal of the sense circuit of the display drive circuit are paired to form an output signal of the touch panel. In claim 5,
The current detection circuit is
A first MOSFET in the form of a diode for supplying a current to the first electrode;
A first MOSFET and a second MOSFET in the form of a current mirror;
The second MOSFET and a third MOSFET configured to flow a reference current in a DC form;
A display device using the current difference between the second MOSFET and the third MOSFET as an output signal. In claim 5,
The current detection circuit is
A switch element that is turned on by a selection level of the selection line;
A current source for supplying a predetermined current to the first electrode via the switch element;
A display device in which the selection timing of the selection line is decoded and used as an output signal of the current detection circuit. In claim 5,
A display device in which a unidirectional element for supplying the predetermined current is provided between an output terminal of the display drive circuit and a second electrode corresponding to the output terminal. In claim 4,
The display drive circuit is
A first display driving circuit for outputting a positive display voltage;
A second display drive circuit that outputs a negative display voltage;
The differential circuits constituting the first display drive circuit and the second display drive circuit are:
A first operating state in which a first operating current is passed;
A second operating state in which a second current having a current value larger than the first operating current is passed;
It is operated in the second operation state at the timing of switching the display voltage between the positive polarity and the negative polarity, and is switched from the second operation state to the first operation state in response to the inversion operation of the output signal of the sense circuit. Display device. In claim 9,
In the first operating state, a first voltage is supplied to the gate of the MOSFET,
The display device in which the second operation state is switched to a second voltage that is larger in absolute value than the first voltage. In claim 10,
The display panel further includes a digital touch panel on the surface,
The touch panel
A plurality of first electrodes provided along the selection line;
The plurality of first electrodes are provided with a supply detection circuit for a predetermined current,
A plurality of second electrodes provided along the signal line;
The plurality of second electrodes are connected to the corresponding output terminal of the display drive circuit. In claim 11,
A display device in which an output signal from the touch panel is valid for a certain period after a lapse of a certain time from the inversion timing of the output signal of the sense circuit. In claim 12,
The display voltage is a gradation voltage,
The display device is a TFT liquid crystal panel.

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