JP2009128524A - Drive circuit, display device, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive circuit capable of reducing power consumption by making a drive voltage for making a light-emitting element emit light and a scanner drive voltage for driving a drive scanner independent from each other, and to provide a display device and an electronic device. <P>SOLUTION: The drive circuit applies a drive signal to a display part where pixels are arranged in a matrix, the pixels each comprising: a light-emitting element; and a transistor which is connected at a second terminal to the light-emitting element and which applies a light-emitting current according to the voltage signal based on a voltage signal to be applied to a control terminal and the drive signal applied to a first terminal. The drive circuit includes: a first power supply which supplies a voltage of a first level, and a voltage of a second level lower in the voltage level than the voltage of the first level; a second power supply which supplies the voltage of a third level higher in the voltage level than the voltage of the second level; and a buffer which is supplied with the voltage of the first level, the voltage of the second level and the voltage of the third level and selectively outputs the voltage of the second level or the voltage of the third level as the drive signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a drive circuit, a display device, and an electronic device.

  In recent years, as a display device replacing a CRT display (Cathode Ray Tube display), an organic EL display (Organic Light Emitting Diode display) or FED (Field Emission Display) is used. Various display devices such as LCD (Liquid Crystal Display), PDP (Plasma Display Panel), and projectors have been developed.

  Among the various display devices as described above, the organic EL display is a self-luminous display device using an electroluminescence phenomenon (ElectroLuminescence), and is compared with a display device that requires a separate light source such as an LCD. Then, since it has excellent moving image characteristics, viewing angle characteristics, color reproducibility, and the like, it is particularly attracting attention as a next-generation display device. Here, the electroluminescence phenomenon means that the electronic state of a substance (organic EL element) is changed from a ground state to an excited state by an electric field, and from an unstable excited state to a stable ground state. This is a phenomenon in which the energy of the difference is emitted as light when returning.

  Under such circumstances, various technologies relating to self-luminous display devices have been developed. As a technique related to a pixel circuit to which a compensation function for a characteristic variation of a light emitting element and a threshold voltage variation of a transistor is added, for example, Patent Document 1 is cited.

JP 2005-345722 A

  In the related art related to the pixel circuit to which a compensation function for the characteristic variation of the light emitting element and the threshold voltage variation of the transistor is added, a power source for applying a driving voltage for driving the light emitting element is provided. A transistor serving as a switch for connecting the power source to the light emitting element is provided. Further, the pixel circuit according to the related art has a configuration in which the control terminal of the transistor is connected to a power supply line, and a high / low level drive signal output from the drive scanner is applied to the power supply line. However, the configuration of the pixel circuit is not limited to the above, and for example, a configuration in which the drive voltage applied from the power supply and the drive signal output from the drive scanner are integrated, and the switches (transistors) are further reduced, that is, A configuration in which the number of transistors included in the pixel circuit is reduced can also be adopted.

  When the pixel circuit is configured as described above, for example, when the light emission drive voltage of the light emitting element becomes low due to a change in material or the like, the magnitude of the voltage of the high level drive signal output from the drive scanner is emitted. From the viewpoint of reducing power consumption, it is effective to reduce the voltage in accordance with the light emission driving voltage of the element. However, since the high level drive signal is also a scanner drive voltage of the scanner circuit constituting the drive scanner, if the magnitude of the voltage of the high level drive signal is reduced in accordance with the light emission drive voltage of the light emitting element, the drive scanner The scanner driving capability (response speed, etc.) may be reduced, and the drive scanner may stop functioning.

  The present invention has been made in view of the above problems, and an object of the present invention is to make the drive voltage for causing the light emitting element to emit light and the scanner drive voltage for driving the drive scanner independent of each other, It is an object of the present invention to provide a new and improved drive circuit, display device, and electronic device that can reduce power consumption.

  In order to achieve the above object, according to a first aspect of the present invention, a light emitting element that emits light according to the amount of current, a voltage signal that is applied to a control terminal with a second terminal connected to the light emitting element, and Each of the pixels of the display unit in which pixels including a transistor that applies a light emission current corresponding to the voltage signal to the light emitting element based on a drive signal applied to the first terminal is arranged in a matrix form is driven. A driving circuit for applying a signal, a first power supply for supplying a first level voltage and a second level voltage lower than the first level voltage; and a second level voltage A second power source for supplying a third level voltage having a high voltage level, the first level voltage, the second level voltage, and the third level voltage, and the first level voltage and Second above Driven by the voltage of the bell, the drive circuit comprising a buffer for selectively outputting the voltage of the second level voltage or the third level as the drive signal is provided.

  The first level voltage and the second level voltage can be used as, for example, a scanner driving voltage for driving a buffer constituting a drive scanner, and the third level voltage is, for example, It can be used as a driving voltage for driving a light emitting element included in each pixel. With this configuration, the drive voltage for driving the light emitting element (third level voltage) and the scanner drive voltage for driving the drive scanner (first level voltage, second level voltage) are consumed independently of each other. Electric power can be reduced.

  The buffer has a first terminal connected to the second power source, and selectively selects the third level voltage according to the first level voltage or the second level voltage applied to the control terminal. The first buffer transistor output from the second terminal is opposite in conductivity type to the first buffer transistor, the second level voltage is applied to the first terminal, and the first level is applied to the control terminal. And a second buffer transistor that selectively outputs the second level voltage from the second terminal according to the voltage or the second level voltage.

  With this configuration, the second level voltage or the third level voltage can be selectively output as a drive signal.

  In order to achieve the above object, according to a second aspect of the present invention, a light emitting element that emits light according to the amount of current, and a voltage that is applied to the control terminal by connecting the second terminal to the light emitting element. A display unit in which pixels each including a transistor that applies a light-emitting current corresponding to the voltage signal to the light-emitting element based on the signal and the drive signal applied to the first terminal are arranged in a matrix; and a first level And a first power supply for supplying a second level voltage lower than the first level voltage, and a third level voltage higher than the second level voltage. The display unit is supplied with a second power source, the first level voltage, the second level voltage, and the third level voltage, and is driven by the first level voltage and the second level voltage. The above pixel it Display device comprising the voltage of the second level voltage or the third level and the driving signal applying unit for selectively applying as the drive signal is provided to the LES.

  The drive signal application unit can function as, for example, a drive scanner that applies a drive signal to each pixel of the display unit in the display device. The first level voltage and the second level voltage can be used as a scanner driving voltage for driving a drive scanner (drive signal applying unit), for example, and the third level voltage is For example, it can be used as a driving voltage for driving a light emitting element included in each pixel of the display portion. With this configuration, it is possible to reduce power consumption by making the drive voltage for causing the light emitting element to emit light and the scanner drive voltage for driving the drive scanner independent of each other.

  In order to achieve the above object, according to a third aspect of the present invention, a light emitting element that emits light according to the amount of current and a voltage that is applied to the control terminal by connecting the second terminal to the light emitting element. A display unit in which pixels each including a transistor that applies a light-emitting current corresponding to the voltage signal to the light-emitting element based on the signal and the drive signal applied to the first terminal are arranged in a matrix; and a first level A first power source that supplies a second level voltage that is lower than the first level voltage, and a second power source that supplies a third level voltage that is higher than the second level. The power source is supplied with the first level voltage, the second level voltage, and the third level voltage, and is driven by the first level voltage and the second level voltage. For each pixel Electronic device and a driving signal applying unit the serial second level voltage or the voltage of the third level selectively applied as the drive signal.

  The drive signal applying unit can function as, for example, a drive scanner that applies a drive signal to each pixel of the display unit in an electronic device. The first level voltage and the second level voltage can be used as a scanner driving voltage for driving a drive scanner (drive signal applying unit), for example, and the third level voltage is For example, it can be used as a driving voltage for driving a light emitting element included in each pixel of the display portion. With this configuration, it is possible to reduce power consumption by making the drive voltage for causing the light emitting element to emit light and the scanner drive voltage for driving the drive scanner independent of each other.

  According to the present invention, it is possible to reduce power consumption by making the drive voltage for causing the light emitting element to emit light and the scanner drive voltage for driving the drive scanner independent of each other.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

(Conventional display device)
Before describing a display device according to an embodiment of the present invention, a configuration of a conventional display device and problems thereof will be described.

  FIG. 1 is an explanatory diagram showing a conventional display device 10 and shows a display panel portion that displays an image corresponding to an input image signal.

  Referring to FIG. 1, the display device 10 includes a display unit 12, a horizontal selector 14, a write scanner 16, a drive scanner 18, and a common power supply 20.

  The display device 10 includes, for example, a control unit (not shown) configured by an MPU (Micro Processing Unit) or the like that can control the entire display device 10, programs used by the control unit, calculation parameters, and the like. Image signal transmitted from a ROM (Read Only Memory; not shown) in which control data is recorded, a RAM (Random Access Memory; not shown) that primarily stores a program executed by the control unit, a broadcasting station, and the like May include a receiving unit (not shown) for receiving a signal, an operation unit (not shown) that can be operated by the user, a communication unit (not shown) for communicating with an external device (not shown), and the like. . The display device 10 connects the above-described constituent elements by, for example, a bus as a data transmission path.

  In the display unit 12, pixels are arranged in a matrix (matrix) of m × n (m and n are natural numbers of 2 or more). In each pixel, a signal line DTLp (p is a positive integer equal to or less than n) to which a voltage signal corresponding to an image signal is applied, and a scanning line WSLq (to which a selection signal output from the write scanner 16 is applied. q is a positive integer less than or equal to m.), and a power supply line DSLq to which a drive signal output from the drive scanner 18 is applied is connected. Each pixel includes a light-emitting element that emits light according to the amount of current, and a transistor having a first terminal connected to the power supply line DSLq and a second terminal connected to the light-emitting element. Each pixel emits light when a light emitting current of an amount corresponding to a voltage signal applied to the control terminal of the transistor is applied to the light emitting element. Here, in FIG. 1, the pixels 30 </ b> A to 30 </ b> F are illustrated as the pixels included in the display unit 12.

  The horizontal selector 14 selectively outputs a voltage signal corresponding to the image signal to the signal line DTLp based on the input image signal.

  The write scanner 16 selectively outputs a selection signal for selecting a pixel to which a voltage signal corresponding to the image signal is applied to the scanning line WSLq.

  The drive scanner 18 selectively outputs a drive signal for causing the light emitting element included in each pixel to emit light to the power supply line DSLq. Here, the configuration of the drive scanner 18 will be described later.

  The common power source 20 is a power supply unit included in the display device 10 and supplies power to, for example, the horizontal selector 14, the light scanner 16, the drive scanner 18, and a control unit (not shown). Here, the common power supply 20 controls, for example, voltages supplied to the horizontal selector 14, the light scanner 16, and the drive scanner 18 in accordance with a command from a control unit (not shown).

  With the configuration shown in FIG. 1, the display device 10 selectively causes the light emitting elements included in each pixel to emit light according to an input image signal.

[Configuration Example of Drive Scanner 18 Provided in Conventional Display Device 10]
FIG. 2 is an explanatory diagram showing a configuration example of the drive scanner 18 provided in the conventional display device 10. In FIG. 2, in addition to the drive scanner 18, the pixels 30 </ b> A,...

  FIG. 2 shows a partial configuration of the pixel circuit only for the pixel 30A among the pixels connected to the power supply line DSL1. Here, the pixel 30A includes a light-emitting element D and an N-channel transistor Tr whose drain is connected to the power supply voltage line DSL1 and whose source is connected to the light-emitting element D. The pixel 30A has the potential of the gate, source, and drain of the transistor Tr. Depending on the state, a light emission current is applied to the light emitting element D, and the light emitting element D emits light.

  Referring to FIG. 2, the drive scanner 18 includes a shift register 40, a waveform adjustment circuit 42, and buffers 44A, 44B,..., 44C respectively corresponding to the power supply lines DSLq.

  The shift register 40 sequentially outputs a high level or low level voltage signal supplied from the common power supply 20 with a delay in accordance with a clock signal (not shown). Here, the clock signal can be generated by, for example, a clock generation unit (not shown) including a crystal and an oscillator.

  The waveform adjustment circuit 42 adjusts the voltage signal sequentially output from the shift register 40 according to a broadcast standard such as a PAL (Phase Alternating Line) standard.

  The buffers 44 </ b> A,..., 44 </ b> C output a drive signal by selectively outputting a high level voltage or a low level voltage based on the voltage signal output from the waveform adjustment circuit 42.

[Configuration Example of Buffer Provided in Conventional Display Device 10]
FIG. 3 is an explanatory diagram illustrating a configuration example of a buffer included in the conventional display device 10, and illustrates a buffer 44A. In FIG. 3, only the elements related to the power supply line DSL1 are shown, but the other power supply lines DSLq are the same, and thus the description thereof is omitted.

  Referring to FIG. 3, the buffer 44 </ b> A includes a P-channel type transistor P <b> 11 and a transistor P <b> 12 whose first terminals are connected to a wiring to which a high level voltage Vcc_H supplied from the common power supply 20 is applied, and the common power supply 20. An N-channel transistor N11 and a transistor N12 having a first terminal connected to a wiring to which a low-level voltage Vcc_L to be supplied is applied (hereinafter referred to as a transistor P11, a transistor P12, a transistor N11, and a transistor N12, respectively). . The second terminal of the transistor P11 and the second terminal of the transistor N11 are connected to selectively output the voltage Vcc_H or the voltage Vcc_L based on a high level or low level voltage signal input to the respective control terminals. Further, the second terminal of the transistor P12 and the second terminal of the transistor N12 are connected, and based on the voltage Vcc_H or the voltage Vcc_L inputted to the respective control terminals, the voltage Vcc_H or the voltage Vcc_L is selectively supplied as a drive signal. Output to the supply line DSL1.

  Here, the high-level voltage Vcc_H output from the buffer 44A is used as a drive voltage for causing the light emitting element D included in each pixel connected to the power supply line DSL1 to emit light. More specifically, referring to the pixel 30A in FIG. 3, when the voltage Vcc_H is output from the buffer 44A, the transistor Tr connected to the DSL1 is turned on, so that the light emitting element D side is changed from the DSL1 side. A current flows, and the light emitting element D emits light according to the amount of the current.

  The conventional display device 10 includes the drive scanner 18 as shown in FIGS. 2 and 3, so that a drive signal can be applied to each pixel connected to the power supply line DSLq.

[Problems of the conventional display device 10]
The light-emitting element included in each pixel has a different light-emitting element driving voltage required for light emission depending on a material to be configured. That is, for example, the light emitting element driving voltage of the light emitting element may be further reduced by changing the material of the light emitting element included in each pixel. When the light emitting element driving voltage of the light emitting element is small, each pixel can emit light with a smaller driving voltage. Therefore, from the viewpoint of reducing the power consumption consumed by each pixel, the light emission provided for each pixel. It is effective to reduce the magnitude of the driving voltage output from the drive scanner 18, that is, the high-level voltage Vcc_H in accordance with the light emitting element driving voltage of the element.

  However, the voltage Vcc_H is also a voltage (scanner drive voltage) for driving the transistors P11 and P12, the transistor N11, and the transistor N12, as shown in FIG. Therefore, if the voltage Vcc_H is lowered in accordance with the light emitting element driving voltage of the light emitting element, for example, the following problems (1) and (2) may occur.

(1) Decrease in drive capability of drive scanner 18 By reducing the voltage Vcc_H, there is an increased possibility that the drive capability of drive scanner 18 will be reduced, for example, a reduction in response speed.

(2) Stopping the function of the drive scanner 18 As a result of reducing the voltage Vcc_H, the P-channel transistor stops functioning when the following equation 1 is satisfied in the buffer, and the N-channel type when the following equation 2 is satisfied in the buffer The transistor stops functioning. Therefore, since the drive scanner 18 cannot selectively output the voltage Vcc_H or the voltage Vcc_L, the function of the drive scanner 18 is stopped. Here, pVth shown in Formula 1 is a threshold voltage between the control terminal and the first terminal in the P-channel transistor, and nVth shown in Formula 2 is the control terminal and the first terminal in the N-channel transistor. The threshold voltage between

Vcc_L> Vcc_H-pVth
... (Formula 1)
Vcc_H <Vcc_L + nVth
... (Formula 2)

  As described above, the conventional display device 10 has a function of the drive scanner 18 when the magnitude of the high level voltage Vcc_H output from the drive scanner 18 is reduced in accordance with the light emitting element driving voltage of the light emitting element. May cause problems. Therefore, the conventional display device 10 cannot achieve both reduction of power consumption in each pixel and normal function of the drive scanner 18.

(Display device according to an embodiment of the present invention)
Therefore, next, a display according to an embodiment of the present invention that can achieve both reduction of power consumption in each pixel and normal operation of the drive scanner (maintenance or improvement of drive capability of the drive scanner). The apparatus will be described. Hereinafter, an organic EL display, which is a self-luminous display device that emits light according to a current flowing through a light emitting element, will be described as an example of the display device according to the embodiment of the present invention. The display device according to the embodiment of the present invention is not limited to an organic EL display, and can be applied to a display device that can emit light according to a current flowing through a light emitting element such as an LCD.

[Problem Solving Method for Display Device According to Embodiment of Present Invention]
In order to achieve both the reduction of power consumption in each pixel and the functioning of the drive scanner normally, the display device according to the embodiment of the present invention includes a driving voltage for driving the light emitting element included in each pixel. The drive voltage for driving the drive scanner is independent from each other. More specifically, the display device according to the embodiment of the present invention includes a first power source that supplies a first level voltage and a second level voltage lower than the first level to the drive scanner as a scanner driving voltage. And a second power supply that supplies a third level voltage, which is higher than the second level, to the drive scanner as a drive voltage. The drive scanner selectively outputs a second level voltage supplied from the first power supply or a third level voltage supplied from the second power supply. Here, the second level voltage or the third level voltage output from the drive scanner corresponds to the drive signal.

  Even if the display device according to the embodiment of the present invention has the above-described configuration, even if the third-level voltage (drive voltage) is reduced in accordance with the light-emitting element drive voltage of the light-emitting element included in each pixel, The drive scanner can be driven by a first level voltage or a second level voltage supplied from a first power source. Therefore, the display device according to the embodiment of the present invention can reduce power consumption in each pixel while maintaining the drive capability of the drive scanner.

  Further, the display device according to the embodiment of the present invention is configured to increase the first level voltage supplied from the first power supply, in order to further increase the drive capability of the drive scanner, by adopting the above configuration. However, the third level voltage supplied from the second power source is not affected at all. Therefore, the display device according to the embodiment of the present invention drives the drive while maintaining the level of the third level voltage supplied from the second power source (that is, without requiring an increase in power consumption). The drive capability of the scanner can be improved.

[Configuration Example of Display Device According to Embodiment of Present Invention]
The configuration of the display device according to the embodiment of the present invention will be described below. FIG. 4 is an explanatory diagram showing the display device 100 according to the embodiment of the present invention.

  Referring to FIG. 4, the display device 100 includes a display unit 102, a horizontal selector 104, a write scanner 106, a drive scanner 108, a common power source 110 (first power source), and a second power source 112.

  In addition, the display device 100 includes, for example, a control unit (not shown) configured by an MPU or the like and capable of controlling the entire display device 100, and control data such as programs and calculation parameters used by the control unit. ROM (not shown), a RAM (not shown) that primarily stores programs executed by the control unit, a receiving unit (not shown) that receives image signals transmitted from a broadcasting station, etc., a video file Storage unit (not shown) that can store image files and the like, an operation unit (not shown) that can be operated by the user, a communication unit (not shown) for communicating with an external device (not shown), etc. May be provided. The display device 100 connects the above-described constituent elements by, for example, a bus as a data transmission path.

  Here, as the storage unit (not shown), for example, a magnetic recording medium such as a hard disk, an EEPROM (Electronically Erasable and Programmable Read Only Memory), a flash memory, a MRAM (Magnetoresistive Random Access) Non-volatile memory such as Memory (RAM), FeRAM (Ferroelectric Random Access Memory), PRAM (Phase change Random Access Memory), and the like, but is not limited thereto. The operation unit (not shown) includes, for example, an operation input device such as a keyboard and a mouse, a rotary selector such as a button, a direction key, and a jog dial, or a combination thereof. However, it is not limited to the above.

  The display device 100 and an external device (not shown) include, for example, a USB (Universal Serial Bus) terminal, an IEEE 1394 standard terminal, a DVI (Digital Visual Interface) terminal, or an HDMI (High-Definition Multimedia Interface) terminal. It may be physically connected via a wireless LAN, or may be connected wirelessly using WUSB (Wireless Universal Serial Bus), IEEE 802.11, or the like. Furthermore, the display device 100 and an external device (not shown) can be connected via a network, for example. As the network, for example, a wired network such as a LAN (Local Area Network) or a WAN (Wide Area Network), a wireless network such as a WLAN (Wireless Local Area Network) using MIMO (Multiple-Input Multiple-Output), or a TCP The Internet using a communication protocol such as / IP (Transmission Control Protocol / Internet Protocol) may be mentioned, but is not limited thereto. Therefore, the communication unit (not shown) has an interface corresponding to the connection form with the external device (not shown).

  The display unit 102 includes a plurality of pixels arranged in a matrix (matrix). For example, a display unit that displays an SD (Standard Definition) resolution video (moving image / still image) has at least 640 × 480 = 307200 (row × column) pixels, and the pixel is red for color display. In the case of (Red), green (Blue), and blue (Blue) sub-pixels, it has 640 × 480 × 3 = 921600 (rows × columns × number of sub-pixels) sub-pixels. Similarly, for example, a display unit that displays an HD (High Definition) resolution image has 1920 × 1080 pixels, and has 1920 × 1080 × 3 sub-pixels for color display. Here, in FIG. 4, the pixels 120 </ b> A to 120 </ b> F are illustrated as pixels included in the display unit 102. Hereinafter, a configuration in which each pixel includes one light emitting element will be described as an example.

[Application example of light emitting element: organic EL element]
When the light emitting element constituting each pixel is an organic EL element, the IL characteristic (current-light emission amount characteristic) is linear, and light is emitted according to the amount of current applied to the light emitting element. Therefore, when an organic EL display is applied as the display device 100 according to the embodiment of the present invention, the display device 100 emits light from the light amount of the subject indicated by the input image signal and the light emitting element of the display device. Since the relationship with the light emission amount can be made linear, video and images faithful to the image signal can be displayed.

  Each pixel has a signal line DTLp to which a voltage signal corresponding to an image signal is applied, a scanning line WSLq to which a selection signal output from the write scanner 106 is applied, and a drive signal output from the drive scanner 108. Is connected to the power supply line DSLq.

[Configuration of Pixel According to Embodiment of Present Invention]
[1] Configuration Example of Pixel According to Embodiment of Present Invention Here, an example of a circuit configuration of a pixel according to the embodiment of the present invention is shown. FIG. 5 is an explanatory diagram illustrating a circuit configuration example of the pixel according to the embodiment of the present invention. In FIG. 5, only the pixel 120A is shown, but other pixels can have the same configuration.

  Referring to FIG. 5, the pixel 120A includes a transistor 1A, a transistor 1B, a capacitor 1C, and a light emitting element 1D. The transistors 1A and 1B are composed of, for example, thin film transistors. Here, FIG. 5 shows an example in which the transistors 1A and 1B are N-channel transistors, but the pixel according to the embodiment of the present invention is not limited to the above configuration. For example, each of the transistors 1A and 1B can be a P-channel transistor, or one of them can be an N-channel transistor and the other can be a P-channel transistor.

  The transistor 1A has a gate (control terminal) connected to the scanning line WSL1. The drain (first terminal) of the transistor 1A is connected to the signal line DTL1, and the source (second terminal) is connected to the gate of the transistor 1B.

  The transistor 1A is turned ON / OFF according to the scanning signal applied to the scanning line, and applies a voltage signal applied to the signal line to the gate (control terminal) of the transistor 1B based on the scanning signal. That is, the transistor 1A functions as a switch.

  The gate of the transistor 1B is connected to the source of the transistor 1A. The drain (first terminal) of the transistor 1B is connected to the power supply line DSL1, and the source (second terminal) is connected to the anode of the light emitting element 1D.

The transistor 1B applies a light-emitting current Ids for causing the light-emitting element 1D to emit light according to the potential states of the gate, the source, and the drain. Here, the transistor 1B is driven so that the light emission current Ids flows according to the following Equation 3 in the light emitting state in which the light emitting element 1D emits light. In Equation 3, each term indicates the following.
μ: Effective mobility Vgs: Gate-source potential difference Vth: Threshold voltage k: (1/2) · (W / L) · Cox
L: channel length W: channel width Cox: (relative permittivity of gate insulating layer) · (dielectric constant of vacuum) / (thickness of gate insulating layer)

Ids = k · μ · (Vgs−Vth) ²
... (Formula 3)

  The capacitor 1C serves to compensate for the threshold voltage Vth between the gate and the source of the transistor 1B, mobility, and the like.

  The light emitting element 1D has an anode connected to the source of the transistor 1B and a cathode connected to the common power supply line 1H, and emits light according to the amount of light emission current Ids applied from the transistor 1B. FIG. 5 shows an example in which the cathode of the light emitting element 1D is connected to the common power supply line 1H, but is not limited thereto. For example, the pixel according to the embodiment of the present invention can be configured such that the cathode of the light emitting element 1D is connected to the ground.

  The pixel 120A includes, for example, the pixel circuit illustrated in FIG. 5, and thus is based on a voltage signal applied to the signal line DTL1, a scanning signal applied to the scanning line WSL1, and a driving signal applied to the power supply line DSL1. The light emitting element 1D can emit light.

[2] Example of Driving Pixel According to Embodiment of the Present Invention Next, an example of driving the pixel 120A will be described. FIG. 6 is a first explanatory diagram for explaining the driving of the pixel according to the embodiment of the present invention. FIG. 7A and FIG. 7B are second and third explanatory views for explaining the driving of the pixel according to the embodiment of the present invention, respectively. Here, FIG. 6A shows the scanning line potential, and FIG. 6B shows the power supply line potential. Similarly, FIG. 6C to FIG. 6E show the signal line potential, the transistor 1B gate potential, and the transistor 1B source potential, respectively. Further, a shown in FIG. 6 corresponds to FIG. 7A (a), and e shown in FIG. 6 corresponds to FIG. 7B (e). Similarly, b to d and f to h shown in FIG. 6 correspond to FIGS. 7A (b) to (d) and FIGS. 7B (f) to (h), respectively. 7A and 7B, the transistor 1A is represented as a switch, and the parasitic capacitance 1I of the light emitting element 1D is illustrated.

[2-1] Periods a and b in FIG.
FIG. 7A (a) shows a light emission state in which the light emission current Ids is applied to the light emitting element 1D to emit light. When the drive signal is applied to the power supply line DSL1, the potential of the power supply line DSL1 changes from the high potential Vcc_P shown in FIG. 7A (a) to the potential Vcc_L shown in FIG. 7A (b), so that the source potential of the transistor 1B Vs is approximately equal to Vcc_L. Note that the potential Vcc_L is a potential sufficiently lower than the reference potential Vo of the signal line DTL1. More specifically, the potential Vcc_L is set such that the gate-source voltage Vgs of the transistor 1B is equal to or higher than the threshold voltage Vth of the transistor 1B. Here, the gate-source voltage Vgs corresponds to a potential difference between the gate potential Vg and the source potential Vs.

  Here, Vcc_P corresponds to the third level voltage supplied from the second power supply 112, Vcc_L corresponds to the second level voltage supplied from the common power supply 110, and Vcc_P and VCC_L are output from the drive scanner 108, respectively. Configure the drive signal. In the drive signal output from the drive scanner 108, Vcc_P corresponds to a high level signal and Vcc_L corresponds to a low level signal.

[2-2] Period c in FIG.
As the potential of the scanning line WSL1 transitions to the high potential side (a high level scanning signal is applied from the write scanner 106), the transistor 1A is turned on as shown in FIG. 7A (c). Therefore, the gate potential Vg of the transistor 1B becomes the reference potential Vo of the signal line DTL1. Further, along with the gate potential Vg, the source potential Vs of the transistor 1B becomes a potential Vcc_L that is sufficiently lower than the reference potential Vo of the signal line DTL1.

[2-3] Period d in FIG.
When the drive signal is applied to the power supply line DSL1, the potential of the power supply line DSL1 transitions from the potential Vcc_L shown in FIG. 7A (c) to the potential Vcc_P shown in FIG. 7A (d), so that the source potential Vs of the transistor 1B. Starts to rise, and the gate-source voltage Vgs of the transistor 1B eventually becomes the threshold voltage Vth. When the gate-source voltage Vgs becomes the threshold voltage Vth, the light emission current Ids does not flow through the transistor 1B as shown in Equation 3, and the transistor 1B is turned off. Here, the potential of the common power supply line 1H is set so that the light emitting element 1D is cut off, and the light emission current Ids hardly flows through the light emitting element 1D.

  By setting the gate-source voltage Vgs of the transistor 1B to the threshold voltage Vth, the threshold voltage Vth is held in the capacitor 1C. By holding the threshold voltage Vth of the pixel 120A in the capacitor 1C, variations in the threshold voltage of each pixel included in the display unit 102 can be compensated, and higher image quality can be achieved.

[2-4] Periods e and f in FIG.
When the potential of the scanning line WSL1 transitions to the low potential side (a low level scanning signal is applied from the write scanner 106), the transistor 1A is turned off as shown in FIG. 7B (e). At this time, the gate of the transistor 1B is in a floating state, but since the gate-source voltage Vgs is the threshold voltage Vth, the light emission current Ids does not flow through the transistor 1B as shown in Equation 3. Thereafter, as shown in FIG. 7B (f), the voltage signal is applied from the horizontal selector 104, whereby the potential of the signal line DTL1 changes from the reference potential Vo to the sampling potential Vsig. Here, the sampling potential Vsig corresponds to the image signal input to the display device 100.

[2-5] Period g in FIG.
When the potential of the scanning line WSL1 transitions to the high potential side (a high level scanning signal is applied from the write scanner 106), the transistor 1A is turned on as shown in FIG. 7B (g). At this time, the gate potential Vg of the transistor 1B rises, but the source potential Vs of the transistor 1B also rises due to the coupling between the capacitor 1C and the parasitic capacitance 1I of the light emitting element 1D. More specifically, since the light emitting element 1D is in the cut-off state (high impedance), the light emission current Ids (drain-source current) flowing through the transistor 1B flows through the parasitic capacitance 1I, and the parasitic capacitance 1I is charged. As a result, the source potential Vs of the transistor 1B rises. The gate-source voltage Vgs of the transistor 1B is “Vsig + Vth−ΔV”. Here, ΔV is a mobility correction term for correcting the mobility of the transistor 1B in the pixel 120A.

  By setting the gate-source voltage Vgs of the transistor 1B to Vsig + Vth−ΔV, Vsig + Vth−ΔV reflecting the correction of the threshold and the correction of the mobility is held in the capacitor 1C. Since Vsig + Vth−ΔV is held in the capacitor 1 </ b> C, variation in threshold voltage and mobility in each pixel included in the display unit 102 can be compensated, so that higher image quality can be achieved.

  Here, the effects of threshold correction and mobility correction according to the embodiment of the present invention will be described. FIG. 8 is an explanatory diagram for explaining the effect of correction in the pixel according to the embodiment of the present invention. The pixel 120A and the pixel 120D are taken as examples and correspond to the transistor 1B in FIG. 5 of each pixel. A relationship between a sampling potential Vsig and a light emission current Ids in a transistor (hereinafter, a transistor corresponding to the transistor 1B in each pixel is referred to as a “driving transistor”) is shown.

  FIG. 8A shows a state in which threshold correction and mobility correction are not performed. Referring to FIG. 8A, it can be seen that the light emission current Ids differs between the pixel 120A and the pixel 120D even when the gate potential Vg of the driving transistor is the sampling potential Vsig having the same magnitude. In the state of FIG. 8A, since the light emission amount of the light emitting element of the pixel 120A and the light emitting element of the pixel 120D are different, the image displayed on the display unit 102 has an unintended luminance difference and the image quality is improved. It will decline. This occurs because of a variation in threshold voltage and / or mobility between the drive transistor that forms the pixel circuit of the pixel 120A and the drive transistor that forms the pixel circuit of the pixel 120D.

  FIG. 8B shows a state in which threshold correction has been performed. Referring to FIG. 8B, the value of the sampling potential Vsig at which the light emission current Ids flows through the drive transistor of the pixel 120A and the drive transistor of the pixel 120D by correcting the threshold voltage of the drive transistor that forms the pixel circuit. Can be seen to match.

  Further, FIG. 8C shows a state in which threshold correction and mobility correction are performed. By further correcting the mobility in addition to the threshold correction, the pixel 120A and the pixel 120C have substantially the same Vsig-Ids characteristics.

  Therefore, the threshold value correction and the mobility correction are performed in each pixel according to the embodiment of the present invention, so that no matter what gradation the image signal input to the display device 100 is, the display unit When an image is displayed on the display 102, there is no luminance variation and the image quality can be improved.

  Referring to FIGS. 6 to 7B again, an example of driving the pixel according to the embodiment of the present invention will be described.

[2-6]
When the potential of the scanning line WSL1 transitions to the low potential side (a low level scanning signal is applied from the write scanner 106), the transistor 1A is turned off as shown in FIG. 7B (h). At this time, a light emission current Ids flows through the light emitting element 1D to emit light, and the anode potential of the light emitting element 1D rises according to the light emission current. Here, the increase in the anode potential of the light emitting element 1D corresponds to the increase in the source potential Vs of the transistor 1B.

  Further, when the source potential Vs of the transistor 1B increases, the gate potential Vg of the transistor 1B also increases due to the boost trap operation of the capacitor 1C. Here, the increase amount of the gate potential Vg of the transistor 1B is equal to the increase amount of the source potential Vs. Therefore, the gate-source voltage Vgs of the transistor 1B is maintained at Vsig + Vth−ΔV reflecting the correction of the threshold and the correction of the mobility.

  Each pixel according to the embodiment of the present invention can display the display unit 102 regardless of the gradation of the image signal input to the display device 100 by the operation as illustrated in FIGS. When displaying an image on the screen, there is no variation in luminance and the like, and high image quality can be achieved.

  With reference to FIG. 4 again, the components of the display device 100 will be described. The horizontal selector 104 selectively outputs a voltage signal corresponding to the image signal to the signal line DTLp based on the input image signal.

  The write scanner 106 selectively outputs a selection signal for selecting a pixel to which a voltage signal corresponding to the image signal is applied to the scanning line WSLq. By outputting the selection signal to the scanning line WSLq, a transistor (for example, the transistor 1A shown in FIG. 5) serving as a switch of each pixel is turned on / off.

  The drive scanner 108 is supplied with the first level voltage and the second level voltage from the common power source 110, and is supplied with the third level voltage from the second power source 112. The drive scanner 108 is driven using the first level voltage and the second level voltage, and selectively outputs the second level voltage or the third level voltage to the power supply line DSLq as a drive signal. . Here, the configuration of the drive scanner 108 will be described later.

  The common power supply 110 is a power supply unit included in the display device 100, and supplies power to, for example, the horizontal selector 104, the light scanner 106, the drive scanner 108, a control unit (not shown), and the like. For example, the common power supply 110 supplies the drive scanner 108 with a first level voltage and a second level voltage that is lower than the first level. The common power supply 110 controls the voltages supplied to the horizontal selector 104, the write scanner 106, and the drive scanner 108, for example, according to a command from a control unit (not shown). Here, the common power source 110 corresponds to the first power source described above.

  The second power supply 112 is another power supply unit included in the display device 100 and supplies a third level voltage to the drive scanner 108. Here, the voltage of the third level can be set together with the light emission driving voltage of the light emitting element of each pixel included in the display unit 102.

  With the configuration shown in FIG. 4, the display device 100 can selectively cause the light emitting elements included in each pixel to emit light in accordance with an input image signal and display an image indicated by the image signal on the display unit 102. .

  Further, the drive scanner 108 of the display device 100 is driven using the first level voltage and the second level voltage supplied from the common power supply 110, and the second level voltage or the third level voltage is used as a drive signal. It selectively outputs to the power supply line DSLq. Therefore, even if the display device 100 reduces the third level voltage in accordance with the light emitting element driving voltage of the light emitting element included in each pixel, the drive scanner 108 is supplied with the first level voltage supplied from the common power supply 110. Alternatively, it can be driven by a second level voltage. Therefore, the display device 100 can reduce power consumption in each pixel while maintaining the drive capability of the drive scanner.

  Furthermore, even if the display device 100 increases the first level voltage supplied from the common power source 110 in order to further improve the drive capability of the drive scanner, the display device 100 can operate at the third level supplied from the second power source 112. It has no effect on the voltage. Therefore, the display device 100 can improve the drive capability of the drive scanner while maintaining the third level voltage supplied from the second power supply 112.

  Hereinafter, the configuration of the drive scanner 108 according to the embodiment of the present invention will be described more specifically.

[Configuration Example of Drive Scanner 108 Provided in Display Device 100]
FIG. 9 is an explanatory diagram showing a configuration example of the drive scanner 108 included in the display device 100 according to the embodiment of the present invention. In FIG. 9, in addition to the drive scanner 108, the pixels 120A,..., The common power supply 110, and the second power supply 112 are shown together. Here, the drive scanner 108, the common power supply 110, and the second power supply 112 shown in FIG. 9 can constitute a drive circuit that applies a drive signal to each pixel.

  Referring to FIG. 9, the drive scanner 108 includes a shift register 130, a waveform adjustment circuit 132, and buffers 134A, 134B,..., 134C corresponding to the power supply lines DSLq, respectively.

  The shift register 130 sequentially delays a high level (first level voltage) or low level (second level voltage) voltage signal supplied from the common power supply 110 in accordance with a clock signal (not shown). Output. Here, the clock signal can be generated by, for example, a clock generation unit (not shown) including a crystal and an oscillator.

  The waveform adjustment circuit 132 adjusts the voltage signals sequentially output from the shift register 130 according to a broadcast standard such as the PAL standard. 9 shows a configuration in which the drive scanner 108 includes the waveform adjustment circuit 132. However, the drive scanner according to the embodiment of the present invention is not limited to the above. For example, the drive scanner 108 does not include the waveform adjustment circuit 132. You can also.

  Based on the voltage signal output from the waveform adjustment circuit 132, the buffers 134A,..., 134C selectively select the second level voltage or the third level voltage supplied from the second power supply 112 to the power supply line DSLq. Output to. Here, the second level voltage or the third level voltage selectively output from each of the buffers 134 </ b> A,..., 134 </ b> C corresponds to a drive signal applied to each pixel of the display unit 102. Therefore, each of the buffers 134A,..., 134C serves as a drive signal applying unit. The configuration of the buffer according to the embodiment of the present invention will be described below.

[Configuration Example of Buffer Provided in Display Device 100]
FIG. 10 is an explanatory diagram illustrating a configuration example of a buffer included in the display device 100 according to the embodiment of the present invention, and illustrates the buffer 134A. In FIG. 10, only elements related to the power supply line DSL1 are shown, but the other power supply lines DSLq are the same, and thus the description thereof is omitted.

  Hereinafter, the first level voltage output from the common power source 110 is referred to as voltage Vcc_H, the second level voltage is referred to as Vcc_L, and the third level voltage output from the second power source 112 is referred to as voltage Vcc_P. In addition, the first level voltage and the third level voltage are set higher than the second level voltage, respectively. Therefore, when the second level voltage is a low level voltage, the first level voltage and the third level voltage can be high level voltages, respectively. The first level voltage is set to a value that does not satisfy the conditions of Formulas 1 and 2, for example, and the third level voltage is set to a value that satisfies Formula 4 below, for example. This is because the scanner function of the drive scanner 108 is not deteriorated or stopped. Here, trVth in Expression 4 is a threshold voltage between the control terminal and the first terminal in the transistor to which the voltage Vcc_P is applied (in FIG. 10, a P-channel transistor P2).

Vcc_P> trVth + Vcc_L
... (Formula 4)

  In addition, the first level voltage and the third level voltage are independently supplied from separate power sources, and as described above, the respective uses of the first level voltage and the third level voltage are mutually different. Different. Therefore, the relationship between the first level voltage and the third level voltage is not a problem.

  Referring to FIG. 10, the buffer 134 </ b> A is supplied from the common power supply 110 and the P-channel transistor P <b> 1 whose first terminal is connected to the wiring to which the high level voltage Vcc_H supplied from the common power supply 110 is applied. An N-channel transistor N1 and a transistor N2 (second buffer transistor) whose first terminals are connected to a wiring to which a low-level voltage Vcc_L is applied, and a high-level voltage Vcc_P supplied from the second power supply 112 are applied And a P-channel transistor P2 (first buffer transistor) having a first terminal connected to the wiring (hereinafter referred to as a transistor P1, a transistor P2, a transistor N1, and a transistor N2, respectively).

  The second terminal of the transistor P1 and the second terminal of the transistor N1 are connected, and the transistor P1 and the transistor N1 receive the voltage Vcc_H or the voltage Vcc_L based on the high level or low level voltage signal input to the respective control terminals. Selectively output. The second terminal of the transistor P2 and the second terminal of the transistor N2 are connected, and the voltage Vcc_H or the voltage Vcc_L output from the transistor P1 or the transistor N1 is input to each control terminal. The transistors P2 and N2 selectively output the voltage Vcc_P or the voltage Vcc_L to the power supply line DSL1 based on the voltage Vcc_H or the voltage Vcc_L input to the respective control terminals.

  The display device 100 includes the drive scanner 108 as shown in FIGS. 9 and 10, so that the second level voltage (Vcc_L) and the third level voltage (for each pixel connected to the power supply line DSLq ( Vcc_P; drive voltage) can be selectively applied. Therefore, a second level voltage or a third level voltage is applied to each pixel included in the display unit 102 as a drive signal from the power supply line DSLq, and the light emitting element is driven as illustrated in FIGS. 6 to 7B. By emitting light, an image corresponding to the image signal input to the display device 100 can be displayed.

  As described above, the display device 100 according to the embodiment of the present invention includes the drive scanner 108 that applies a drive signal to each pixel of the display unit 102 via the power supply line DSLq. The drive scanner 108 is supplied with the first level voltage and the second level voltage from the common power source 110 (first power source), and is supplied with the third level voltage from the second power source 112. Here, each of the voltage of the first level and the voltage of the third level is set higher than the voltage of the second level. The drive scanner 108 is driven using the first level voltage and the second level voltage as the scanner drive voltage, and outputs the second level voltage and the third level voltage as drive signals. Here, the third level voltage constituting the driving signal is used as a driving voltage for driving the light emitting element included in each pixel of the display unit 102, and is set to a value corresponding to the light emitting driving voltage of the light emitting element. Can do. Therefore, the display device 100 can reduce power consumption consumed by each pixel of the display unit 102.

  The display device 100 also includes a driving voltage (third level voltage) for driving the light emitting elements included in each pixel of the display unit 102 and a scanner driving voltage (first level voltage) for driving the drive scanner 108. , The second level voltage). Therefore, even if the display device 100 sets the third level voltage (drive voltage) to be small in accordance with the light emitting element driving voltage of the light emitting element included in each pixel of the display unit 102, the drive scanner 108 uses the common power source 110. It can be driven by a first level voltage or a second level voltage supplied from (first power supply). Therefore, the display device 100 can reduce power consumption in each pixel while maintaining the drive capability of the drive scanner 108.

  Furthermore, since the display device 100 supplies the first level voltage and the third level voltage to the drive scanner 108 independently, the first level voltage is used to increase the drive capability of the drive scanner 108. Even if it is made larger, the third level voltage is not affected at all. Therefore, the display device 100 maintains the magnitude of the third level voltage supplied from the second power supply 112 (that is, without requiring an increase in power consumption), and the drive capability of the drive scanner 108. Can be improved.

[Modification of Display Device According to Embodiment of Present Invention]
[1] First Modification In the display device 100 shown in FIG. 10, the configuration in which the source (second terminal) of the transistor 1B (driving transistor) is connected to the anode of the light emitting element 1D in the pixel 120A is shown. However, the configuration of the pixel circuit of the pixel according to the embodiment of the present invention is not limited to the above. For example, the source of the driving transistor is connected to the cathode of the light emitting element 1D, and the anode of the light emitting element 1D corresponds to the light emitting element driving voltage. It is also possible to adopt a configuration in which a voltage is applied.

  When the pixel has the above-described configuration, the display device according to the first modification example of the present invention uses the high level voltage Vcc_H (first level voltage) shown in FIG. 10 for each buffer included in the drive scanner. A low level voltage Vcc_L (second level voltage) is supplied in reverse. The display device according to the first modification of the present invention has a low level lower than the voltage Vcc_H from the second power supply to the buffer instead of the high level voltage Vcc_P (third level voltage). A voltage Vcc_P ′ (fourth level voltage) is supplied. That is, the high level voltage Vcc_H (first level voltage) and the low level voltage Vcc_P ′ (fourth level voltage) are drive signals from the buffers of the display device according to the first modification of the present invention. Is output as

  Here, in the pixel of the display device according to the first modified example of the present invention, the source of the driving transistor is connected to the cathode of the light emitting element 1D, and a voltage corresponding to the light emitting element driving voltage is applied to the anode. Therefore, in the display device according to the first modification of the present invention, the low level voltage Vcc_P ′ (fourth level voltage) serves as a drive signal for causing the light emitting element to emit light.

  Therefore, the display device according to the first modification example of the present invention includes a driving voltage (fourth level voltage) for driving the light emitting element included in each pixel of the display unit and a scanner for driving the drive scanner 108. Since the driving voltages (the first level voltage and the second level voltage) can be made independent of each other, the same effects as those of the display device 100 described above can be obtained.

[2] Second Modification Also, in the display device 100 shown in FIG. 5, the configuration in which the display device 100 includes the common power source 110 and the second power source 112 is shown. However, the display device according to the embodiment of the present invention is described above. Not limited to. For example, the display device according to the embodiment of the present invention does not include the common power source and / or the second power source, and the first level voltage, the second level voltage, and / or the power supply device as an external device is supplied to the drive scanner. Alternatively, a third level voltage may be supplied. Even with the above configuration, the display device according to the second modification example of the present invention includes a drive voltage (third level voltage) for driving the light emitting element included in each pixel of the display unit, and a drive scanner. Since the scanner driving voltages (first level voltage and second level voltage) for driving can be made independent of each other, the same effects as those of the display device 100 described above can be obtained.

[3] Third Modification A display device according to a third modification of the present invention may be configured by combining the first modification and the second modification described above. Even if it is said structure, the display apparatus which concerns on the 3rd modification of this invention can have an effect similar to the display apparatus 100 mentioned above.

  As described above, in the embodiment of the present invention, the display device 100 has been described. However, the embodiment of the present invention is not limited to such a form, and for example, a light emitting element that emits light according to the amount of current, such as an organic EL display or an LCD. It can apply to a display apparatus provided with.

  The embodiment of the present invention is applied to a receiving device that receives a television broadcast, a portable communication device such as a mobile phone, and an electronic device such as a computer such as a PC (Personal Computer) or a server (Server). be able to.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, in the display device 100 illustrated in FIG. 4, the configuration including the common power source 110 and the second power source 112 is illustrated, but the embodiment of the present invention is not limited to such a configuration. For example, the display device according to the embodiment of the present invention can include a common power source and a second power source as an integrated power source.

  The configuration described above shows an example of the embodiment of the present invention, and naturally belongs to the technical scope of the present invention.

It is explanatory drawing which shows the conventional display apparatus. It is explanatory drawing which shows the structural example of the drive scanner with which the conventional display apparatus is provided. It is explanatory drawing which shows the structural example of the buffer with which the conventional display apparatus is provided. It is explanatory drawing which shows the display apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the circuit structural example of the pixel which concerns on embodiment of this invention. FIG. 3 is a first explanatory diagram for explaining driving of a pixel according to the embodiment of the present invention. It is the 2nd explanatory view for explaining the drive of the pixel concerning the embodiment of the present invention. It is a 3rd explanatory view for explaining the drive of the pixel concerning the embodiment of the present invention. It is explanatory drawing for demonstrating the effect of the correction | amendment in the pixel which concerns on embodiment of this invention. It is explanatory drawing which shows the structural example of the drive scanner with which the display apparatus which concerns on embodiment of this invention is provided. It is explanatory drawing which shows the structural example of the buffer with which the display apparatus which concerns on embodiment of this invention is provided.

Explanation of symbols

10, 100 Display device 12, 102 Display unit 14, 104 Horizontal selector 16, 106 Write scanner 18, 108 Drive scanner 20, 110 Common power supply 112 Second power supply

Claims (4)

A light-emitting element that emits light according to the amount of current, a voltage corresponding to the voltage signal based on a voltage signal applied to the control terminal with the second terminal connected to the light-emitting element and a drive signal applied to the first terminal A driving circuit that applies the driving signal to each of the pixels of the display unit in which pixels each having a light emitting current applied to the light emitting element are arranged in a matrix.
A first power supply for supplying a first level voltage and a second level voltage lower than the first level voltage;
A second power supply for supplying a third level voltage that is higher than the second level voltage;
The first level voltage, the second level voltage, and the third level voltage are supplied, driven by the first level voltage and the second level voltage, and the second level voltage or the A buffer that selectively outputs a third level voltage as the drive signal;
A drive circuit comprising: The buffer is
The first terminal is connected to the second power source, and the third level voltage is selectively output from the second terminal according to the first level voltage or the second level voltage applied to the control terminal. A first buffer transistor that;
The first buffer transistor is of a reverse conductivity type, the second level voltage is applied to a first terminal, and the first level voltage or the second level voltage applied to a control terminal, A second buffer transistor for selectively outputting a second level voltage from the second terminal;
The drive circuit according to claim 1, comprising: A light-emitting element that emits light according to the amount of current, a voltage corresponding to the voltage signal based on a voltage signal applied to the control terminal with the second terminal connected to the light-emitting element and a drive signal applied to the first terminal A display unit in which pixels each including a transistor for applying a light emitting current of 1 to the light emitting element are arranged in a matrix;
A first power supply for supplying a first level voltage and a second level voltage lower than the first level voltage;
A second power supply for supplying a third level voltage that is higher than the second level voltage;
The first level voltage, the second level voltage, and the third level voltage are supplied, driven by the first level voltage and the second level voltage, and applied to each of the pixels of the display unit. A drive signal applying unit that selectively applies the second level voltage or the third level voltage as the drive signal;
A display device comprising: A light-emitting element that emits light according to the amount of current, a voltage corresponding to the voltage signal based on a voltage signal applied to the control terminal with the second terminal connected to the light-emitting element and a drive signal applied to the first terminal A display unit in which pixels each including a transistor for applying a light emitting current of 1 to the light emitting element are arranged in a matrix;
A first power supply for supplying a first level voltage and a second level voltage lower than the first level voltage;
A second power supply for supplying a third level voltage having a voltage level higher than the second level;
The first level voltage, the second level voltage, and the third level voltage are supplied, driven by the first level voltage and the second level voltage, and applied to each of the pixels of the display unit. A drive signal applying unit that selectively applies the second level voltage or the third level voltage as the drive signal;
An electronic device comprising:

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