JP2011145447A - Display element drive circuit, electro-optical device, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate a voltage required for driving a display element while lowering the voltage of a data signal than the breakdown voltage of a switching element. <P>SOLUTION: The display element drive circuit 1 includes: a first switching means connected to a data line 101; a plurality of energy storage elements 10, 11 electrically connected to the first switching means; a second switching means including a plurality of switching elements 21, 22, 23 for switching connection of the plurality of energy storage elements; and a pixel electrode 50. After the first switching means blocks the data signal, the second switching means switches the connections of the plurality of energy storage elements, from parallel connection into direct connection and thus generates a higher voltage than the voltage of the data signal for supplying it to the pixel electrode 50; and at this time, the connection of the pixel electrode 50 with the first switching means is disconnected. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a display element driving circuit that can be used as, for example, a pixel circuit used in a display device, and an electro-optical device and an electronic apparatus using the display element driving circuit.

  A display device using an active matrix system is widely used as a display unit of a TV or a portable device. These display devices include a display element that exhibits an electro-optic response, a display element driving circuit in which an active element is provided for each pixel, and a peripheral driving circuit that supplies a signal to the display element driving circuit.

  Examples of display elements that exhibit an electro-optic response include liquid crystals and electrophoretic elements. In the case of a liquid crystal, the light transmittance changes with respect to the voltage, and in the case of an electrophoretic element, the light reflectance changes with respect to the voltage.

  A driving circuit of a display device using these display elements must generate voltages necessary for driving the display elements and have a withstand voltage against these voltages. However, it is desirable for the display device to have low power consumption, and for this purpose, it is desirable to operate the drive circuit at a low voltage.

  For example, Patent Document 1 discloses a circuit that generates a high voltage in a pixel using a boosting capacitor after a video signal is written to the pixel electrode at a low voltage.

JP 2009-109600 A

  In the pixel circuit disclosed in Patent Document 1, one of the terminals supplying the video signal of the switching element is connected to the video signal line, and the other end is connected to the pixel electrode to which the boosted high voltage is supplied. Yes.

  High and low voltages are supplied to the video signal lines in accordance with display contents. For example, when the voltage of the video signal line is set to 0V to 5V and the boosted voltage is set to 0V to 10V, a maximum voltage of 10V is applied to both ends of the switching element. Therefore, the switching element is required to have a breakdown voltage that is about the same as the maximum voltage supplied to the pixel electrode.

  If the voltage necessary for driving the display element is higher than the breakdown voltage of the switching element, the display element cannot be driven sufficiently. Alternatively, a high voltage exceeding the breakdown voltage of the switching element must be generated.

  That is, the pixel circuit of Patent Document 1 has a problem that the boosted high voltage may exceed the withstand voltage of the switching element.

  The present invention is realized as the following forms or application examples so as to solve at least a part of the problems described above.

  [Application Example 1] A first switching unit that is constructed for each pixel of a display element having a plurality of pixels, is connected to a data line and switches a data signal, and a plurality of units that are electrically connected to the first switching unit. A second switching means comprising an energy storage element, a plurality of switching elements for switching the connection of the plurality of energy storage elements, a pixel electrode connected to the first switching means via the second switching means, And after the first switching means shuts off the data signal, the second switching means switches the connection of the plurality of energy storage elements from parallel connection to series connection, and is higher than the voltage of the data signal. A display element driving circuit that generates a voltage of the voltage and supplies the generated voltage to the display element, and disconnects the connection between the pixel electrode and the first switching unit when the voltage is supplied.

  According to such a configuration, a voltage higher than the voltage of the data signal is generated and applied to the pixel electrode. However, since the pixel electrode is electrically connected to the other switching means via the switching means, the switching means It is possible to make the voltage applied to the lower than the generated high voltage.

  Application Example 2 In the application example described above, the plurality of energy storage elements are display element drive circuits including two capacitors.

  Application Example 3 In the application example described above, the second switching unit is a display element driving circuit including three field effect transistors.

  According to this configuration, the connection of the two capacitors can be switched between the parallel supply and the series connection by the three field effect transistors.

  Application Example 4 In the application example described above, the second switching unit is a display element driving circuit including a complementary field effect transistor.

  According to such a configuration, the first switch means and the second switch means can be controlled by the common control line.

  Application Example 5 In the application example described above, the display element driving circuit in which the plurality of energy storage elements have the same capacitance.

  According to such a configuration, after a voltage higher than the data signal voltage is generated, the voltage applied to the first switch means and the second switch means is the voltage of the data signal supplied to the data line. Be the same. Therefore, the withstand voltage required for the first switch means and the second switch means can be suppressed to the same level as the maximum voltage of the data signal.

  Application Example 6 An electro-optical device including the display element driving circuit according to the application example described above.

  According to the electro-optical device having such a configuration, for example, an electro-optical device using a display element in which the voltage required for driving is higher than the withstand voltage of the switch means is provided by including any of the characteristics of the display element driving circuit. And so on.

  Application Example 7 Electronic equipment including the electro-optical device according to the application example described above.

  According to the electronic device having such a configuration, it is possible to configure an electronic device using a display element that requires a high voltage for driving, for example, by including the characteristics of any of the display element driving circuits described above. Become.

  Application Example 7 A plurality of pixels provided corresponding to a plurality of data lines, a plurality of scanning lines intersecting with the plurality of data lines, and intersections of the plurality of data lines and the plurality of scanning lines A display element driving circuit constructed for each pixel of the display element, the pixel electrode, a booster circuit connected to the pixel electrode, and the scan line, the data line, and the booster circuit And a first switching element for controlling connection between the data line and the booster circuit, wherein the booster circuit has a first signal voltage from the data line larger than the first signal voltage. Boosting to a second signal voltage and supplying the boosted voltage to the pixel electrode, the boosting circuit includes a second switching element disposed between the pixel electrode and the first switching element, and The switching element is the boost circuit There display element drive circuit, characterized in that the off state when supplying the second signal voltage to the pixel electrode.

The circuit diagram which shows the structural example of a display element drive circuit. The wave form diagram of each part at the time of operation | movement of a display element drive circuit. The wave form diagram of each part at the time of operation | movement of a display element drive circuit. The wave form diagram of each part at the time of operation | movement of a display element drive circuit. The circuit diagram which shows the structural example of a display element drive circuit. The wave form diagram of each part at the time of operation | movement of a display element drive circuit. FIG. 3 is a block diagram illustrating a configuration of an electro-optical device. The perspective view of the television provided with the electro-optical apparatus. The perspective view of the personal computer provided with the electro-optical apparatus.

  Embodiments according to the present invention will be specifically described with reference to the drawings. However, the embodiment described below is merely an example of the present invention. That is, the present invention is not limited to the configurations and operations illustrated in the following embodiments, and can be arbitrarily modified within the scope of the gist of the present invention. In the drawings, the same components are denoted by the same reference numerals.

The terms used in this specification are defined as follows.
“Node”: refers to a predetermined location in a circuit. In addition, the potential at the node may be indicated using the same reference numeral. For example, the potential X refers to the potential of the node X.
“First electrode, second electrode”: The switching means includes a source electrode, a drain electrode, and a control electrode (gate electrode) that controls electrical conduction between the source electrode and the drain electrode. It may not be necessary to distinguish clearly from electrodes. In this specification, one of the drain electrode and the source electrode in the switching means may be referred to as a “first electrode”, and the other may be referred to as a “second electrode”. Similarly, one terminal of the energy storage element may be referred to as a “first electrode”, and the other terminal may be referred to as a “second electrode”.
“On state, off state”: A state in which the first electrode and the second electrode of the switching unit are electrically connected is referred to as an on state, and a state in which the first electrode is not conductive is referred to as an off state.

(First embodiment)
FIG. 1 is a circuit diagram illustrating a configuration example of the display element driving circuit 1. In the present embodiment, the switching element 20 corresponds to the first switching means, and the portion constituted by the switching elements 21, 22, 23 corresponds to the second switching means. As shown in FIG. 1, the display element driving circuit 1 includes a switching element 20, a switching element 21, a switching element 22, a switching element 23, an energy storage element 10, and an energy storage element 11. The switching element 20 corresponds to the first switching element, and the switching element 21 corresponds to the second switching element. The switching elements 21, 22, 23 and the energy storage elements 10, 11 constitute a booster circuit.

  The switching element 20 has a first electrode connected to the data line 101, and a second electrode connected to the first electrode of the energy storage element 10, the first electrode of the switching element 21, and the first electrode of the switching element 22. The control electrode is connected to the scanning line 100. The switching element 21 has a second electrode connected to the first electrode of the energy storage element 11 and the pixel electrode 50, and a control electrode connected to the scanning line 100. The switching element 22 has a second electrode connected to the second electrode of the energy storage element 11 and the second electrode of the switching element 23, and a control electrode connected to the boost control line 102. The first electrode of the switching element 23 is connected to the reference potential line 103, and the control electrode is connected to the scanning line 100. The second electrode of the energy storage element 10 is connected to the reference potential line 103.

  Next, the operation of the display element driving circuit 1 will be described with reference to FIG. FIG. 2 is a potential waveform diagram of each part during the operation of the display element driving circuit 1. The waveform diagram of FIG. 2 is, in order from the top, the reference potential line 103, the scanning line 100, the data line 101, the boost control line 102, and the node. The time change of each potential waveform at 300, node 301, and node 302 is shown. In FIG. 2, T1 to T4 indicate predetermined timings (time).

  The switching elements 20, 21, 22, and 23 are turned on when the potentials of the scanning line 100 and the boost control line 102 are at a high level, and are turned off when the potential is at a low level.

  First, at T1, a high-level control signal voltage is supplied to the scanning line 100. Thereby, the switching element 20, the switching element 21, and the switching element 23 connected to the scanning line 100 are turned on. Note that in this specification, when a potential is supplied to, applied to, or held in an element or a node, the voltage is supplied, applied, or held using a voltage corresponding to the potential difference between the reference potential and the potential. May be expressed.

  At this time, since the switching element 23 is turned on, the potential of the node 302 becomes the same as the potential of the reference potential line 103. Here, the potential of the reference potential line 103 is at the GND level, and the potential of the node 302 is at the GND level.

  The first electrodes of the energy storage elements 10 and 11 are electrically connected to the node 301, and the second electrodes are both electrically connected to the reference potential line 103. That is, the energy storage element 10 and the energy storage element 11 are connected in parallel.

  Next, at T2, the signal voltage Vsig (first signal voltage) is supplied to the data line 101. Since the switching element 20 and the switching element 21 are on, the potentials of the node 300 and the node 301 become the signal voltage Vsig. Further, the first electrode of the energy storage element 10 and the first electrode of the energy storage element 11 hold the potential of the node 301.

  Next, at T3, the potential of the scanning line 100 becomes a low level, and the switching element 20, the switching element 21, and the switching element 23 are turned off.

  Next, at T4, the boost control line 102 becomes High level, and the switching element 22 is turned on. At this time, the first electrode of the energy storage element 10 is electrically connected to the second electrode of the energy storage element 11, and the energy storage elements 10 and 11 are connected in series.

  Since both of the energy storage elements 10 and 11 held the voltage of Vsig, when the energy storage elements 10 and 11 are connected in series, the energy storage elements 10 and 11 have twice the Vsig between the second electrode of the energy storage element 10 and the first electrode of the energy storage element. The voltage of 2Vsig is held. At this time, the potential of the first electrode (node 301) of the energy storage element 11 is 2 Vsig. Therefore, a voltage higher than the signal voltage supplied to the data line can be generated. The voltage 2Vsig generated here corresponds to the second signal voltage.

  At this time, the switching element in the off state is interposed between the pixel electrode 50 to which the high voltage (2 Vsig) is supplied and the switching element 20 to which the data line 101 to which the high and low signal voltage is supplied is connected to the first electrode. 21 is present and the electrical connection is interrupted. A node 300 to which the second electrode of the switching element 20 and the first electrode of the switching element 21 are connected holds the signal voltage supplied from the data line 101. For this reason, the generated high voltage is not directly applied between the first electrode and the second electrode of the switching element 20.

  Here, when the capacity of the energy storage element 10 is C0 and the capacity of the energy storage element 11 is C1, the potentials of the node 300 and the node 302 are 2 Vsig (C1 / (C0 + C1)).

  Next, FIGS. 2 to 4 show the relationship between the magnitude relationship between C0 and C1 and potential changes at the nodes 300 and 302. FIG. FIG. 2 shows a case where C0 = C1, and the potential difference between the node 300 and the node 302 is Vsig. Therefore, the potential difference between the first electrode and the second electrode of the switching element 20 and the switching element 21 is Vsig. Therefore, the breakdown voltage required for the switching element 20 and the switching element 21 is Vsig.

  FIG. 3 shows a case where C0 <C1, and the potential difference between the node 300 and the node 302 becomes higher than Vsig at T4. Therefore, when the potential of the data line 101 is low, the potential difference between the first electrode and the second electrode of the switching element 20 may be larger than Vsig, and the switching element 20 needs to have a breakdown voltage larger than Vsig.

  FIG. 4 shows a case where C0> C1, and the potential difference between the node 300 and the node 302 becomes lower than Vsig at T4. Therefore, the potential difference between the first electrode and the second electrode of the switching element 21 becomes larger than Vsig, and the switching element 21 needs to have a breakdown voltage larger than Vsig.

  From the above, it is preferable to make C0 equal to C1 because the withstand voltage required for the switching element 20 and the switching element 21 is suppressed to Vsig only when C0 = C1.

(Second Embodiment)
FIG. 5 is a circuit diagram showing a configuration example of the display element driving circuit 2 according to the second embodiment. The display element driving circuit 2 includes a complementary field effect transistor, thereby controlling the first switching means and the second switching means only by the scanning lines, and is the same as the display element driving circuit 1 according to the first embodiment. In addition, the data signal voltage can be lowered and the high voltage can be generated. Below, it demonstrates centering on difference with the display element drive circuit 1 which concerns on 1st Embodiment. Other points are the same as those of the display element driving circuit 1 according to the first embodiment.

  In the present embodiment, the switching element 20 corresponds to the first switching means, and the portion composed of the switching elements 21, 23, 24 corresponds to the second switching means. The switching element 20, the switching element 21, and the switching element 23 of FIG. 3 are turned on when the potential of the control electrode is at a high level, and the switching element 24 is turned on when the potential of the control electrode is at a low level. To do. As an example, the switching elements 20, 21, and 23 can be composed of N-channel thin film transistors, and the switching element 24 can be composed of P-channel thin film transistors.

  The switching element 24 has a first electrode connected to the second electrode of the switching element 20, a first electrode of the switching element 21, and a first electrode of the energy storage element 10, and a second electrode connected to the second electrode of the switching element 23 and energy storage. The control electrode is connected to the scanning line 100 and is connected to the second electrode of the element 11.

  The operation of the display element driving circuit 2 will be described with reference to FIG. FIG. 6 is a potential waveform diagram of each part during the operation of the display element driving circuit 1. The waveform diagrams are in order from the top, the reference potential line 103, the scanning line 100, the data line 101, the node 300, the node 301, and the node 302. Shows the time variation of each potential waveform. In FIG. 6, T1 to T4 indicate predetermined timings (time).

  First, at T1, a high-level control signal voltage is supplied to the scanning line 100. Thereby, the switching element 20, the switching element 21, and the switching element 23 connected to the scanning line 100 are turned on, and the switching element 24 is turned off.

  At this time, the first electrodes of the energy storage element 10 and the energy storage element 11 are electrically connected to the node 301, and the second electrodes of the energy storage element 10 and the energy storage element 11 are both electrically connected to the reference potential line 103. Are connected in parallel.

  Next, at T2, the signal voltage Vsig is supplied to the data line 101. Since the switching element 20 and the switching element 21 are in the on state, the potential difference between the node 300 and the node 301 becomes the signal voltage Vsig. Further, the first electrode of the energy storage element 10 and the first electrode of the energy storage element 11 hold the potential of the node 301.

  Next, at T3, the potential of the scanning line 100 becomes a low level, the switching element 20, the switching element 21, and the switching element 23 are turned off, and the switching element 24 is turned on. At this time, the first electrode of the energy storage element 10 is electrically connected to the second electrode of the energy storage element 11, and the energy storage elements 10 and 11 are connected in series.

  Since both of the energy storage elements 10 and 11 held the potential difference of Vsig, the potential of the first electrode (node 301) of the energy storage element 11 is twice Vsig and 2Vsig due to the series connection. Therefore, it is possible to switch the parallel connection and the serial connection of the energy storage elements 10 and 11 by controlling only the scanning line 100 and generate a voltage higher than the signal voltage supplied to the data line 101.

  FIG. 7 is a block diagram illustrating a configuration of an electro-optical device which is an application example of the display element driving circuit according to the above-described embodiment. The electro-optical device 3 includes a display unit 30 and a peripheral circuit unit 31. The peripheral circuit unit 31 is provided with, for example, a scanning driver 33, a data driver 34, and a control circuit 32 for controlling them.

  The scan driver 33 is configured to supply a scan line signal to the scan lines of the pixel circuits included in the display unit 30 so that the potential of the scan lines can be changed. The data driver 34 is configured to supply a data line signal to a data line of a pixel circuit included in the display unit 30 so that the potential of the data line signal can be changed. The control circuit 32 is configured to determine a signal to be supplied from the scan driver 33 and the data driver 34 to the display unit 30 and to instruct the scan driver 33 and the data driver 34.

  As the display element driving circuit included in the display unit 30, the display element driving circuit described in the above embodiment is used. As a result, the voltage of the data signal can be lowered as compared with the voltage necessary for driving the display element, so that the burden on the data driver 34 can be reduced.

  Note that examples of the electro-optical device include display devices such as an electrophoretic device, an organic EL device, and a liquid crystal device.

  Next, specific examples of an electronic apparatus including the electro-optical device 200 will be described with reference to FIGS. FIG. 8 shows an application example to a television. A television 550 includes the electro-optical device 200 and an audio output unit 551. FIG. 9 shows a personal computer. The personal computer includes a main body 561 provided with a keyboard 560 and a display unit 562 using the electro-optical device.

  The electronic device is not limited to the above example, and can be applied to various electronic devices having a display function, for example. In addition to the above, a fax machine with a display function, a finder for a digital camera, a monitor for a video camera, a portable TV, an electronic notebook, an electric bulletin board, a display for advertising, and the like are also included.

  According to the electronic device having such a configuration, for example, an electronic device using a display element that requires a high voltage for driving can be configured by including the characteristics of any one of the display element driving circuits described above. . In addition, since the driving load is small, it is possible to reduce power consumption.

  DESCRIPTION OF SYMBOLS 1 ... Display element drive circuit, 10, 11 ... Energy storage element, 20, 21, 22, 23, 24 ... Switch means, 30 ... Display part, 31 ... Peripheral circuit part, 32 ... Control circuit, 33 ... Scan driver, 34 DESCRIPTION OF SYMBOLS ... Data driver, 50 ... Pixel electrode, 100 ... Scan line, 101 ... Data line, 102 ... Boost control line, 103 ... Reference potential line, 200 ... Electro-optical device, 300, 301, 302 ... Node, 550 ... Television set, 551 ... Audio output unit, 560 ... Keyboard, 561 ... Main unit, 562 ... Display unit.

Claims (7)

A display driving circuit constructed for each pixel of a display element having a plurality of pixels,
First switching means connected to the data line and switching data signals;
A plurality of energy storage elements electrically connected to the first switching means;
A second switching means comprising a plurality of switching elements for switching the connection of the plurality of energy storage elements;
A pixel electrode connected to the first switching means via the second switching means,
After the first switching means shuts off the data signal,
The second switching means switches the connection of the plurality of energy storage elements from parallel connection to series connection,
A voltage higher than the voltage of the data signal is generated and supplied to the display element, and at the time of supply, the connection between the pixel electrode and the first switching unit is cut off;
A display element driving circuit. The plurality of energy storage elements include two capacitors;
The display element driving circuit according to claim 1. The second switching means includes three field effect transistors.
The display element driving circuit according to claim 1, wherein the display element driving circuit is a display element driving circuit. The second switching means includes a complementary field effect transistor,
The display element driving circuit according to claim 1, wherein the display element driving circuit is a display element driving circuit. The plurality of energy storage elements are formed of energy storage elements having the same capacity.
The display element driving circuit according to claim 1, wherein the display element driving circuit is a display element driving circuit. The display element driving circuit according to claim 1 is provided.
An electro-optical device.   An electronic apparatus comprising the electro-optical device according to claim 6.

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