Light-emitting device, driving method for light-emitting device, and electronic device

Abstract

A luminescent device according to an embodiment of the present disclosure comprises a pixel circuit including a light-emitting part and a tone control unit for controlling a tone. The pixel circuit comprises a light-emitting time control unit for controlling the light-emitting time of the light-emitting part and an amplitude modulation unit including an output transistor connected in series with the light-emitting part. The tone control unit performs, via the light-emitting time control unit, on / off control on the output transistor of the amplitude modulation unit and tone control by modulation control.

Description

[Technical Field]

[0001] The present disclosure relates to a light-emitting device, a method for driving a light-emitting device, and an electronic device. [Background technology]

[0002] A light-emitting device (so-called planar light-emitting device) having light-emitting portions arranged in a matrix (two-dimensional matrix) in the row and column directions can be used as a self-luminous display device, a backlight device for a liquid crystal display device, etc. Examples of light-emitting portions of a light-emitting device include self-luminous elements such as light-emitting diodes (LEDs) and organic electroluminescence (EL) elements. Of these self-luminous elements, light-emitting diodes in particular are attracting attention as light-emitting elements for next-generation displays because of their low element degradation and high efficiency.

[0003] Light-emitting diodes have the characteristic that their spectrum shifts toward the blue side depending on the current (light-emitting current) flowing through the element, and as a result, it is known that chromaticity varies depending on the value of the light-emitting current and that there is a large variation in brightness in the low current range. Therefore, when configuring a light-emitting device using light-emitting diodes, if the brightness is controlled by changing the light-emitting current through current modulation or voltage modulation, problems arise such as an inability to accurately express colors depending on the brightness and the occurrence of brightness unevenness at low brightness.

[0004] To solve such problems, in LED display devices that use, for example, light-emitting diodes as light-emitting sections, known methods include PWM (Pulse Width Modulation) driving, which performs modulation by changing the duty ratio of the light-emitting section, and subfield driving, which divides one field into multiple subfields for driving.Patent Document 1 (JP 2007-333768 A) discloses a technique that uses PWM driving and a technique that uses subfield driving to drive light-emitting sections. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-333768 Summary of the Invention

[0006] However, high-resolution PWM drive is vulnerable to noise and various fluctuations, and its implementation requires a large-scale circuit configuration. Also, although there are many display devices that use passive matrix PWM drive, they have problems such as low brightness because the light-emitting duty cannot be made large, and the number of drivers increases as resolution increases, resulting in high costs.

[0007] On the other hand, subfield driving does not require a large circuit scale compared to PWM driving. However, subfield driving has problems such as a linear gamma characteristic, which results in insufficient resolution, especially at low gradations. Furthermore, subfield driving has the problem of false contours in moving images caused by the light emitted in the subfields.

[0008] The above has explained the problems associated with LED display devices that use light-emitting diodes as their light-emitting elements, but the above-mentioned issues are not limited to LED display devices that use light-emitting diodes as their light-emitting elements, but apply to all light-emitting devices that are made up of self-luminous elements arranged in a two-dimensional matrix.

[0009] It is desirable to provide a light-emitting device with a simple circuit configuration, which is resistant to noise and various fluctuations, which minimizes the use of the low current region that is particularly problematic when driving light-emitting diodes, and which has high gradation performance and little change in chromaticity, a method for driving the light-emitting device, and electronic equipment having the light-emitting device.

[0010] A light emitting device according to an embodiment of the present disclosure includes: a pixel circuit including a light-emitting portion; and a gradation control unit that performs gradation control; Equipped with The pixel circuit is a light emitting time control unit for controlling the light emitting time of the light emitting unit; an amplitude modulation unit including an output transistor connected in series to the light emitting unit; and The gradation control section performs gradation control by controlling the on / off of the output transistor of the amplitude modulation section and controlling modulation of the amplitude modulation section via the light emission time control section.

[0011] A method for driving a light emitting device according to an embodiment of the present disclosure includes: a pixel circuit including a light-emitting portion; and a gradation control unit that performs gradation control; Equipped with The pixel circuit is a light emitting time control unit for controlling the light emitting time of the light emitting unit; an amplitude modulation unit including an output transistor connected in series to the light emitting unit; In a light emitting device having Under the control of the gradation control section, the output transistor of the amplitude modulation section is controlled to be on / off, and the amplitude modulation section is also controlled to be modulated, thereby performing gradation control.

[0012] An electronic device according to an embodiment of the present disclosure includes: a gradation control unit that performs gradation control; Equipped with The pixel circuit is a light emitting time control unit for controlling the light emitting time of the light emitting unit; an amplitude modulation unit including an output transistor connected in series to the light emitting unit; and The gradation control unit performs gradation control by controlling the on / off of the output transistor of the amplitude modulation unit and controlling modulation of the amplitude modulation unit via the light emission time control unit. It has a light emitting device. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a conceptual diagram of a circuit constituting a light emitting device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a waveform diagram showing a stepped sawtooth wave signal SAW. [Figure 3] FIG. 3 is a circuit diagram illustrating an example of a circuit configuration of a pixel circuit according to the first embodiment. [Figure 4] FIG. 4A is a circuit diagram showing an example of a circuit of a light emitting time control section according to a reference example, and FIG. 4B is a waveform diagram for explaining an example of operation of the light emitting time control section according to the reference example. [Figure 5] FIG. 5A is a circuit diagram illustrating an example of a circuit of a light emitting time control unit according to the second embodiment, and FIG. 5B is a waveform diagram illustrating an example of an operation of the light emitting time control unit according to the second embodiment. [Figure 6] 6A to 6D are diagrams showing how the light emission time is discretely controlled under the driving method according to the third embodiment. [Figure 7] FIG. 7 is a characteristic diagram showing the curve characteristics of current versus luminance when discrete control of light emission duty is performed. [Figure 8] FIG. 8 is a diagram for explaining generation of a gamma curve for luminance gradation. [Figure 9] FIG. 9A is a characteristic diagram of logarithmic luminance gamma characteristics, and FIG. 9B is a characteristic diagram of luminance gamma characteristics of an arbitrary curve. [Figure 10] FIG. 10A is a diagram illustrating the luminance vs. chromaticity characteristics when no chromaticity correction is performed using the driving method according to Example 4, and FIG. 10B is a diagram illustrating the luminance vs. chromaticity characteristics when chromaticity correction is performed using the driving method according to Example 4. [Figure 11] FIG. 11 is a diagram illustrating chromaticity correction by the driving method according to the fourth embodiment. [Figure 12] FIG. 12 is a circuit diagram illustrating a specific circuit example of the current modulation unit according to the fifth embodiment. [Figure 13] FIG. 13A is a block diagram illustrating a specific circuit example of the sawtooth wave generating unit according to the sixth embodiment, and FIGS. 13B and 13C are waveform diagrams illustrating example operating waveforms of the sawtooth wave generating unit according to the sixth embodiment. [Figure 14] FIG. 14A is a waveform diagram of a sawtooth wave signal SAW when there is an extreme change in light emission duty between certain gradations, and FIG. 14B is a waveform diagram of a sawtooth wave signal SAW for realizing a driving method according to Example 7. [Figure 15] FIG. 15A is a diagram showing an image obtained by scrolling a rectangular shape when there is a discrete change in light emission duty, and FIG. 15B is a diagram showing an image obtained by scrolling a lamp image when there is no discrete change in light emission duty. [Figure 16] FIG. 16A is a diagram showing an image obtained by scrolling a rectangular shape with discrete changes in light emission duty, and FIG. 16B is a diagram showing an image obtained by scrolling a rectangular shape without discrete changes in light emission duty. [Figure 17] FIG. 17A is a diagram illustrating the operation in the normal mode, and FIG. 17B is a diagram illustrating the operation in the re-capture mode according to the eighth embodiment. [Figure 18] FIG. 18 is a timing waveform diagram showing the relationship between the exposure time of the rolling shutter and light emission in the normal mode and the re-capture mode. [Figure 19] FIG. 19 is a circuit diagram illustrating an example of a circuit configuration of a pixel circuit according to a ninth embodiment. [Figure 20] FIG. 20 is a circuit diagram illustrating a specific circuit example of a voltage modulation unit in a pixel circuit according to Example 9. As shown in FIG. [Figure 21] FIG. 21 is a schematic diagram illustrating a tiling display according to a first specific example of an electronic device of the present disclosure. [Figure 22] FIG. 22 is an exploded perspective view that schematically shows a liquid crystal display device according to a second specific example of the electronic device of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a mode for carrying out the technology of the present disclosure (hereinafter referred to as "embodiment") will be described in detail with reference to the drawings. The technology of the present disclosure is not limited to the embodiment. In the following description, the same elements or elements having the same functions will be designated by the same reference numerals, and duplicated description will be omitted. The description will be given in the following order. 1. General Description of the Light-Emitting Device, the Method for Driving the Light-Emitting Device, and the Electronic Device of the Present Disclosure 2. Light-emitting device according to an embodiment of the present disclosure 2-1. Example 1 (Circuit example of pixel circuit in case of current modulation) 2-2. Reference example (Example of placing a switch element in the current path of the light-emitting part) 2-3. Example 2 (Circuit example and operation example of the light emitting time control unit in the pixel circuit according to Example 1) 2-4. Example 3 (Example of a driving method for performing gradation control using the pixel circuit according to Example 1) 2-5. Example 4 (Example of a driving method for performing chromaticity correction in the current range used for gradation control) 2-6. Example 5 (Specific circuit example of the current modulation section in the pixel circuit according to Example 1) 2-7. Example 6 (Example of a specific circuit and operating waveform of the sawtooth wave generating unit) 2-8. Example 7 (Example of a driving method for maintaining good moving image characteristics when varying the light emission duty discretely) 2-9. Example 8 (Example with re-shooting mode) 2-10. Example 9 (Circuit example of pixel circuit in case of voltage modulation) 3. Variations 4. Electronic Device of the Present Disclosure 4-1. First Example (Tiling Display Example) 4-2. Second Example (Example of a backlight device for a liquid crystal display device) 5. Configurations that the present disclosure can take

[0015] <General Description of Light-Emitting Device, Light-Emitting Device Driving Method, and Electronic Device of the Present Disclosure> In the light-emitting device, the method for driving the light-emitting device, and the electronic device of the present disclosure, the light-emitting time control unit can be configured to discretely control the light-emitting time of the light-emitting unit by controlling the on / off of the output transistor of the amplitude modulation unit under the control of the gradation control unit, and the amplitude modulation unit can be configured to control the value of the current flowing through the light-emitting unit or the value of the voltage applied to the light-emitting unit according to the light-emitting time of the light-emitting unit under the control of the gradation control unit. Furthermore, the amplitude modulation unit can be configured as a current modulation unit that controls the value of the current flowing through the light-emitting unit or a voltage modulation unit that controls the value of the voltage applied to the light-emitting unit.

[0016] In the light-emitting device, the method for driving the light-emitting device, and the electronic device according to the present disclosure, which include the above-described preferred configurations, when a sawtooth wave generation unit that generates a stepped sawtooth wave signal is provided, the light-emission time control unit can be configured to control the light-emission time of the light-emitting unit based on the stepped sawtooth wave signal generated by the sawtooth wave generation unit. The sawtooth wave generation unit can be configured to generate a stepped sawtooth wave signal for each pixel row of a pixel array unit in which pixel circuits are arranged in a matrix, and the light-emission time control unit can be configured to control the light-emission time of the light-emitting unit for each pixel row based on the stepped sawtooth wave signal generated by the sawtooth wave generation unit. Furthermore, the sawtooth wave generation unit can be configured to generate the stepped sawtooth wave signal using a sample-and-hold circuit.

[0017] Furthermore, in the light-emitting device, the driving method of the light-emitting device, and the electronic device according to the present disclosure, including the preferred configurations described above, the gradation control unit may be configured to discretely decrease the light-emitting time of the light-emitting unit at a constant ratio. Furthermore, the gradation control unit may be configured to control the light-emitting time of the light-emitting unit and the value of the current flowing through the light-emitting unit so that the current-to-luminance characteristic approaches a logarithmic gamma characteristic. Furthermore, when α is a number smaller than 1 and the luminance of the light-emitting unit is increased by α times from the maximum value, the gradation control unit may be configured to increase the light-emitting duty by α at a gradation at which the luminance is increased by α times for an arbitrary gamma curve, and to vary the amplitude gradation step interval so as to allocate the step interval according to this gradation interval, and vary the amplitude gradation so that it is increased by α times at this interval.

[0018] Furthermore, in the light-emitting device, the method for driving the light-emitting device, and the electronic device of the present disclosure, which include the above-described preferred configuration, the gradation control unit can be configured to set the rate of change of the light-emitting duty per light emission during the light-emitting period in one frame to a predetermined rate or less when discretely controlling the light-emitting time of the light-emitting unit.

[0019] Furthermore, in the light-emitting device, the driving method for the light-emitting device, and the electronic device according to the present disclosure, which include the above-described preferred configurations, the gradation control unit may be configured to use only a specific light-emitting current range of the light-emitting unit outside the minimum light-emitting time width of the light-emitting unit, and to perform monochromatic chromaticity correction within the specific current range of the light-emitting unit. Furthermore, the gradation control unit may be configured to perform monochromatic chromaticity correction using an interpolation technique, and to perform monochromatic chromaticity correction by interpolating two or more current values.

[0020] Furthermore, the light emitting device, the driving method of the light emitting device, and the electronic device according to the present disclosure, including the above-described preferred configuration, may be configured to have a re-shooting mode in which light emission in one frame period is divided into multiple times and the light emitting duty is not changed periodically. Also, the light emitting element of the light emitting unit may be configured to be a light emitting diode.

[0021] Furthermore, in the light-emitting device, the method for driving the light-emitting device, and the electronic device according to the present disclosure, which include the above-described preferred configuration, the light-emitting element of the light-emitting unit may be a light-emitting diode. The light-emitting diode may be a light-emitting diode having a well-known configuration and structure. That is, a light-emitting diode having an optimal configuration and structure and made of appropriate materials may be selected depending on the light-emitting color of the light-emitting diode.

[0022] In a light-emitting device that uses light-emitting diodes as its light-emitting portions, a light-emitting portion made up of a red light-emitting diode functions as a red-emitting sub-pixel, a light-emitting portion made up of a green light-emitting diode functions as a green-emitting sub-pixel, and a light-emitting portion made up of a blue light-emitting diode functions as a blue-emitting sub-pixel. These three types of sub-pixels form one pixel, which is a unit for forming a color image. In other words, a color image can be displayed depending on the light-emitting states of these three types of sub-pixels. Note that "one pixel" in this disclosure corresponds to "one sub-pixel" in such a light-emitting device, and therefore "one sub-pixel" in such a light-emitting device can be read as "one pixel."

[0023] <Light-emitting device according to an embodiment of the present disclosure> 1 is a conceptual diagram of a circuit constituting a light-emitting device according to an embodiment of the present disclosure. The light-emitting device according to an embodiment of the present disclosure (hereinafter sometimes referred to as "the present embodiment") has a pixel array section 20 in which a plurality of pixel circuits 10 including light-emitting sections constituting pixels (more specifically, sub-pixels, the same applies hereinafter) are arranged in a matrix (two-dimensional matrix) in the row and column directions.

[0024] The light emitting device of this embodiment further includes peripheral driving units arranged around the pixel array unit 20 for driving the plurality of pixel circuits 10, such as a scanning unit (scanning line driving unit) 30, a gradation control unit 40, and a sawtooth wave generating unit 50.

[0025] The scanning unit 30 has scanning lines 611 to 612 arranged for each pixel row in a pixel array of m rows and n columns arranged in a two-dimensional matrix. m A plurality of pixel circuits 10 are driven through the

[0026] The gradation control unit 40 has two control lines 621-622 wired for each pixel column in a pixel array of m rows and n columns. m and control lines 631 to 63 m Modulation signals (I-Sig / V-Sig) and light emission time control signals (D-Sig) are supplied to the plurality of pixel circuits 10 through the LCD panel 10, and gradation control is performed for each pixel.

[0027] The sawtooth wave generating unit 50 generates a sawtooth wave signal SAW having the waveform shown in FIG. 2, i.e., a sawtooth wave signal whose level changes in a stepped manner (hereinafter referred to as a "stepped sawtooth wave signal") . Assuming that this light-emitting device is used as a display device for displaying images, many display devices write signals for each line (pixel row) and then start emitting light for that scan line before moving on to writing signals for the next line. Accordingly, in accordance with this operation, the sawtooth wave generating unit 50 supplies the generated stepped sawtooth wave signal SAW to each pixel circuit 10 in the pixel array unit 20 for each pixel row. However, depending on the circuit configuration, the sawtooth wave signal having the waveform shown in FIG. 2 may be upside down.

[0028] With regard to peripheral driving units such as the scanning unit (scanning line driving unit) 30, the gradation control unit 40, and the sawtooth wave generating unit 50, some or all of them may be provided on the same substrate as the pixel array unit 20, or may be provided outside the substrate.

[0029] The light-emitting device according to the embodiment of the present disclosure having the above configuration can be used as an LED display device in which the light-emitting portion of the pixel circuit is made up of a light-emitting diode, or as an organic EL display device in which the light-emitting portion of the pixel circuit is made up of an organic EL element.

[0030] Specific examples of circuits constituting a light-emitting device according to an embodiment of the present disclosure will be described below. Current modulation and voltage modulation are possible examples of amplitude modulation that controls brightness by changing the light-emitting current of the light-emitting portion of a pixel (sub-pixel). In the case of current modulation, a current modulation portion is used as an amplitude modulation portion, and in the case of voltage modulation, a voltage modulation portion is used as an amplitude modulation portion.

[0031] [Example 1] Example 1 is a circuit example of the pixel circuit 10 in the case of current modulation. An example of the circuit configuration of the pixel circuit 10 according to Example 1 is shown in FIG.

[0032] In the case of current modulation, the pixel circuit 10 has a circuit configuration including a light emitting unit 11, a current modulation unit 12, and a light emitting time control unit 13. The light emitting element of the light emitting unit 11 can be a self-luminous element such as a light emitting diode (LED) or an organic EL element.

[0033] In the pixel circuit 10 according to the first embodiment, a light-emitting diode (LED) is used as the light-emitting element of the light-emitting section 11. The light-emitting element of the light-emitting section 11, i.e., the anode electrode of the light-emitting diode, is connected to a power supply voltage V DD It is known that light-emitting diodes have a blue shift in their spectrum, which occurs depending on the current (light-emitting current) flowing through the element, and that the chromaticity varies depending on the value of the light-emitting current, and that there is a large variation in brightness in the low current range.

[0034] The current modulation unit 12 includes an output transistor TR out and controls the value of the current flowing through the light emitting unit 11 in accordance with the light emitting time of the light emitting unit 11. out is made up of, for example, an N-channel field effect transistor, with its drain electrode connected to the anode electrode of the light emitting section 11 and its source electrode connected to a reference potential node (for example, ground).

[0035] The current modulation unit 12 receives the scanning line 61 (611 to 61 m ) is applied to the current modulation section 12 via the control lines 62 (621 to 622) from the gradation control section 40. m ) according to a current modulation signal I-Sig given as a modulation signal, the value of the current flowing through the light emitting unit 11, that is, the current value of the light emitting current of the light emitting diode, is controlled.

[0036] The light emission time control unit 13 receives the scanning lines 61 (611 to 61 m ) from the gradation control unit 40 to the control line 63 (631 to 63 m ), a light emission time control signal D-Sig is input from the scanning signal Gate, and a stepped sawtooth wave signal SAW is input from the sawtooth wave generating unit 50. The light emission time control unit 13 becomes operative in response to the scanning signal Gate, and controls the light emission time of the light emitting unit 11 based on the stepped sawtooth wave signal SAW and the light emission time control signal D-Sig. By controlling the light emission time, the proportion of the light emission time in the period of one frame (one display frame), which is the display unit for displaying one image, i.e., the light emission duty, is controlled.

[0037] Further, the light emission time control unit 13 controls the output transistor TR of the current modulation unit 12 under the control of the gradation control unit 40. out Under the control of the light emission time control unit 13, the output transistor TR outThe current modulator 12 selectively blocks the current flowing through the light emitting unit 11. That is, the current modulator 12 has a mechanism for selectively blocking the current flowing through the light emitting unit 11.

[0038] For the pixel circuit 10 configured as described above, the gradation control unit 40 performs gradation control (grayscale expression) by controlling the current modulation unit 12 and the light emission time control unit 13. Specifically, the gradation control unit 40 controls the output transistor TR of the current modulation unit 12 by the light emission time control unit 13. out The light emitting time of the light emitting unit 11 is reduced discretely (in stages) at a constant ratio by the on / off control, and the gradation is expressed by controlling the current value flowing to the light emitting unit 11 by the current modulation unit 12 according to the light emitting time of the light emitting unit 11.

[0039] As described above, the pixel circuit 10 according to the first embodiment includes the output transistor TR out In the pixel circuit 10 according to the first embodiment, the light emission time is discretely determined for each pixel by controlling the on / off of the output transistor TR out The light emission time is changed stepwise and roughly by the on / off control of the output transistor TR out According to the light emission time determined by the on / off control, the current is minutely modulated under the control of the gradation control unit 40, and driving using only a specific range of current values ​​can be realized.

[0040] If the light-emitting time of the light-emitting unit 11 can be varied discretely in this way, it becomes possible to control the light-emitting time with high precision even with a simple circuit configuration, for example, by using a stepped sawtooth wave signal SAW as shown in Figure 2 and setting the steps of the stepped waveform to be larger than the noise level. The noise referred to here refers to potential fluctuations and the like caused by power supply fluctuations when the light-emitting unit 11 emits light, and the noise level differs depending on the circuit configuration of the pixel circuit 10.

[0041] [Comparative Example] Incidentally, a pixel circuit that controls detailed gradations by current modulation while discretely controlling the light-emitting time can also be realized by arranging a switch element in the current path of the light-emitting section 11 and configuring the switch element to perform switching control and the current modulation section 12 to perform modulation control under the control of the gradation control section 40. Hereinafter, a pixel circuit configured to arrange a switch element in the current path of the light-emitting section 11 will be described as a pixel circuit according to a reference example.

[0042] The pixel circuit according to the reference example introduces a discrete time amplitude modulation that can be varied only within a predetermined time width, thereby resolving the problems of PWM circuit variations and vulnerability to noise, while limiting the current range used in most sections, thereby avoiding changes in emitted color due to the current value of the light-emitting current and variations in the low current range.

[0043] However, in the pixel circuit according to the reference example, since the light-emitting current flows through the switch element that cuts off the current, the power supply voltage rises due to the voltage across the switch element, which causes a corresponding increase in power consumption. Furthermore, if the switch element is configured using a field-effect transistor or the like in order to suppress the rise in power supply voltage, the element size must be increased, which is a circuit configuration that is disadvantageous from the perspective of reducing the circuit scale.

[0044] However, in LED display devices using TFTs (Thin Film Transistors), which cannot use complex and large-scale circuits, micro LED display devices using CMOS backplanes, and backlight devices for liquid crystal display devices in which micro LED elements are driven by TFTs or small CMOS elements, problems such as brightness variations in the low current range and chromaticity changes due to light-emitting current become an issue. In these environments, there are many use cases in which a very large light-emitting current is controlled relative to the element size, and a reduction in circuit scale is desirable. Therefore, from the perspective of reducing circuit scale, it is not desirable to use the pixel circuit according to the reference example.

[0045] In contrast, the pixel circuit 10 according to the first embodiment can configure a small-scale circuit for small signals without using a switch element, which would otherwise be relatively large in size to pass the light-emitting current, and can solve the problem of the pixel circuit according to the reference example, in which the power supply voltage rises and power consumption increases due to the inclusion of a switch element in the path of the large light-emitting current.

[0046] [Reference example] Here, let us consider a specific circuit configuration of the light emission time control unit 13. The light emission time control unit 13 generates a signal that controls the start and end of light emission of the light emission unit 11 based on the light emission time control signal D-Sig sent from the gradation control unit 40, and sends this signal to the current modulation unit 12, thereby controlling the light emission time of the light emission unit 11. Various circuit configurations are possible for the light emission time control unit 13, but a simple example is a circuit configuration that generates a light emission period pulse that rises when light emission starts and falls when light emission ends. This light emission period pulse signal may be generated multiple times during one frame period.

[0047] This light emission period pulse signal can be generated, for example, by counting an integer value sent from the gradation control unit 40 using a counter circuit. This circuit is inherently complex simply because a counter is used, but to simplify the circuit as much as possible, it is possible to slow down the clock and reduce the number of counts. The resulting time width will be roughly discrete.

[0048] Here, a simple circuit configuration shown in Fig. 4A is illustrated as a reference example of the light emission time control unit 13 that generates the light emission period pulse signal. Fig. 4A shows an example of the circuit of the light emission time control unit 13 according to the reference example, and Fig. 4B shows a waveform diagram for explaining an example of the operation of the light emission time control unit 13 according to the reference example.

[0049] 4A, the light emission time control unit 13 according to the reference example illustrated here has a circuit configuration including a comparator 131, an N-channel field effect transistor 132, and a capacitance element 133. In the light emission time control unit 13 according to this reference example, the comparator 131 compares a sawtooth wave signal whose level changes linearly (hereinafter referred to as a "linear sawtooth wave signal") with a DC signal, and outputs a pulse in the section where the linear sawtooth wave signal is clipped by the DC signal as a light emission period pulse signal, as shown in FIG.

[0050] However, light emission time control unit 13 according to the reference example of the circuit configuration described above is very susceptible to noise and various fluctuations, and the light emission period pulse signal fluctuates even when noise is superimposed on the linear sawtooth wave signal, or when slight temperature characteristics or variations in comparator 131 occur. For this reason, pixel circuit 10 needs to stabilize the waveform by lowering the impedance of the wiring for the linear sawtooth wave signal, or use a comparator 131 with small variations, resulting in a large, complex, and expensive circuit.

[0051] [Example 2] Example 2 shows a circuit example and an operation example of a light emission time control unit that can avoid the defects of the light emission time control unit according to the reference example. An example of a circuit of the light emission time control unit 13 according to Example 2 is shown in Fig. 5A, and a waveform diagram for explaining an operation example of the light emission time control unit 13 according to Example 2 is shown in Fig. 5B.

[0052] The light emission time control unit 13 according to the second embodiment has a comparator 131, an N-channel field effect transistor 132, and a capacitance element 133, and the basic circuit configuration is the same as that of the light emission time control unit according to the reference example, but differs in the following respect: In the light emission time control unit according to the reference example, the comparator 131 compares a linear sawtooth wave signal with a DC signal, whereas in the light emission time control unit 13 according to the second embodiment, the comparator 131 compares a stepped sawtooth wave signal shown in FIG.

[0053] As described above, the light emission time control unit 13 according to the second embodiment uses a stepped sawtooth wave signal instead of a linear sawtooth wave signal as the sawtooth wave signal, and limits the possible light emission width in advance. This makes it difficult for noise up to the height of the stepped waveform of the stepped sawtooth wave signal to affect the light emission width.

[0054] [Example 3] Example 3 is an example of a driving method (i.e., a driving method for a light emitting device) for performing gradation control in the pixel circuit according to Example 1 using a stepped sawtooth wave signal. The gradation control by the driving method according to Example 3 is performed in the pixel circuit 10 according to Example 1 by controlling the current value of the light emitting unit 11 by the current modulation unit 12 and controlling the current of the output transistor TR of the current modulation unit 12 by the light emitting time control unit 13 under the control of the gradation control unit 40. out This is done by on / off control.

[0055] Here, using the pixel circuit 10 according to the first embodiment, for example, a change in gradation when the luminance is reduced from a state of a maximum light-emitting current value at a maximum light-emitting duty will be considered.

[0056] As described above, the gradation control unit 40 performs control to discretely reduce the light-emitting time of the light-emitting unit 11 at a constant rate. Specifically, when the current is reduced until the brightness of the light-emitting unit 11 becomes a multiple α, which is a multiple smaller than 1, of the maximum value, the light-emitting duty is multiplied by α for the next gradation, and the current is returned to the maximum value. The current is reduced again while maintaining this light-emitting duty, and when the brightness becomes α times the maximum value, the light-emitting duty is again multiplied by α, and returned to the maximum value. By repeating this operation, the brightness can be reduced without changing the variable range of the current, and the greatest number of gradations can be obtained.

[0057] On the other hand, if the light emitting duty is set to a value greater than α when the current is reduced until the brightness is increased by a factor of α, the current will not return to its maximum value when the next gradation is determined. Conversely, the previous gradation can also be expressed with a new light emitting duty, resulting in a gradation intersection between discrete light emitting duties. Alternating between these intersections for each frame can be used to mitigate false contours and chromaticity differences between light emitting duties.

[0058] As described above, the manner in which the light emission time is discretely controlled is shown in Figs. 6A to 6D. By performing such discrete control of the light emission time, the current vs. luminance characteristic can be made into a curve characteristic as shown in Fig. 7. In the characteristic diagram shown in Fig. 7, luminance ranges A to D correspond to the light emission times of Figs. 6A to 6D, respectively. The characteristic diagram shown in Fig. 7 exemplifies the case of 2 bits and 4 steps. Here, luminance L(I0) is the maximum light emission current value I max When the light-emitting current at which the brightness is increased by α is I0, it is given by the following equation: L(I0)=α L(I max )

[0059] By using the driving method according to Example 3 in the pixel circuit 10 according to Example 1, as shown in the characteristic diagram of FIG. 7, it is possible to express many luminance gradations using only a limited current range X. In other words, it is possible to express many luminance gradations by using only a specific light-emitting current range X outside the minimum light-emitting time width of the light-emitting unit 11. This makes it possible to minimize the influence of changes in chromaticity of the light-emitting unit 11 due to the light-emitting current. Furthermore, if the minimum light-emitting time can be shortened to a certain extent, it is possible to express gradations below that time using error diffusion, which is a dithering technique. Therefore, it is possible to express all gradations without using a low-current region with large luminance variations.

[0060] As described above, when the brightness is multiplied by α by reducing the current, and the light-emitting duty is multiplied by α at the next gradation to return the current to its maximum value, a table of current control register values ​​is created to define amplitude gradations that control the current in a slightly downward convex or approximately linear manner. By arranging these in the direction of lower gradations while multiplying the light-emitting duty by α, as shown in Figure 8, a gamma curve for the brightness gradation can be generated.

[0061] If these amplitude gradations are arranged in the direction of lower gradations while multiplying the light emitting duty by α, it is possible to realize a luminance gamma characteristic in the form of a logarithmic curve, i.e., a logarithmic luminance gamma characteristic, as shown in Fig. 9A. In other words, the gradation control unit 40 controls the light emitting duty of the light emitting unit 11 and the value of the current flowing through the light emitting unit 11 so that the current vs. luminance characteristic approaches a logarithmic gamma characteristic.

[0062] Furthermore, when the luminance of the light-emitting unit 11 is multiplied by α times a multiple that is smaller than 1 from the maximum value, for any gamma curve that is desired to be realized, the light-emitting duty is multiplied by α at the gradation at which the luminance is multiplied by α, and the step interval of the amplitude gradation is varied so as to be allocated according to this gradation interval, and the amplitude gradation is varied so as to be multiplied by α at this interval, thereby making it possible to realize the luminance gamma characteristic of any gamma curve as shown in Figure 9B.

[0063] The logarithmic luminance gamma characteristic shown in Figure 9A is a particularly advantageous characteristic when configuring a tiling display, which will be described later. A tiling display is a display device formed by arranging multiple display units (unit panels) in a tiled pattern. In this tiling display, if adjacent display units do not have similar gamma characteristics, brightness differences will occur, degrading image quality, and therefore fine brightness adjustment is required.

[0064] Therefore, by using the above-mentioned display device with a logarithmic gamma curve for the current-to-luminance characteristic as the display unit in a tiling display, it becomes possible to control the luminance at a constant, small rate of change over the entire range of the light-emitting current. If the luminance can be adjusted to a luminance ratio of, for example, about 1.8%, this will be below the luminance difference that the human eye can distinguish, making it possible to configure a tiling display with excellent image quality and no luminance step between adjacent display units.

[0065] It is known that the blue shift in brightness of the light-emitting diodes (LEDs) used as the light-emitting unit 11 is greater in the lower current range. For this reason, as in the driving method according to Example 3, a minimum value for the light-emitting current is determined and the current value is lowered at frequencies other than the minimum light-emitting duty, and gradations lower than the minimum current at the minimum light-emitting duty are expressed using error diffusion or the like, while the current value is adjusted to a current value equal to or greater than the minimum value, which is very meaningful in terms of chromaticity change. While red light-emitting diodes exhibit little chromaticity change due to the characteristics of their materials, green and blue light-emitting diodes exhibit greater chromaticity change. Therefore, by controlling the current value so that it does not fall below the minimum current value in the low-current range, chromaticity change can be minimized.

[0066] Incidentally, when light-emitting diodes are used as light-emitting elements in a display device that uses a backplane, such as a TFT circuit, which makes it difficult to use a large number of elements, problems arise such as variations in brightness in the low current region and changes in chromaticity due to the light-emitting current. In contrast, the driving method according to Example 3 has a simple circuit configuration that is resistant to noise and various fluctuations, and can achieve driving with high gradation performance and no changes in chromaticity while minimizing the use of the low current region, which is problematic when driving light-emitting diodes.

[0067] [Example 4] The fourth embodiment is an example of a driving method for performing chromaticity correction in the current range used for gradation control.

[0068] As described above, the driving method according to the third embodiment can realize gradation control using only a limited current range (current range X shown in FIG. 7). However, although the color difference in the repeatedly used current range is smaller than the color difference in the low current range, the light-emitting unit 11, particularly the light-emitting diode, is not free from the influence of the blue shift in the spectrum due to the light-emitting current. When the chromaticity of the maximum current used is used as a reference, the chromaticity difference (color difference) at each gradation according to the driving method according to the third embodiment changes jaggedly due to the repeatedly used current range, as shown in FIG. 10A.

[0069] In display devices for strict applications, changes in chromaticity due to light-emitting current can cause problems such as banding (stripes of light and dark), so it is desirable to be able to completely correct changes in chromaticity due to light-emitting current at each gray level.

[0070] Therefore, in the driving method according to the fourth embodiment, monochromatic chromaticity correction is performed under the control of the gradation control unit 40 in a specific current range X used for gradation control. Specifically, as shown in FIG. 11 , matrix chromaticity correction is performed using other colors, R (red), G (green), and B (blue), at two or more current values, namely, the maximum current value and the minimum current value in the repetitive use range, in the current range X used for gradation control. In this way, in the region between the maximum current value and the minimum repetitive use current value, matrix linear chromaticity correction is performed by linearly interpolating the two matrix values. As shown in the luminance vs. chromaticity difference characteristic diagram in FIG. 10B , chromaticity changes due to the light-emitting current at each gradation can be suppressed. That is, as is clear from the comparison between FIG. 10A and FIG. 10B , the driving method according to the fourth embodiment enables nearly precise chromaticity correction.

[0071] [Example 5] Example 5 is a specific circuit example of the current modulation section 12 in the pixel circuit 10 according to Example 1. A specific circuit example of the current modulation section 12 according to Example 5 is shown in FIG.

[0072] The current modulation unit 12 according to the fifth embodiment includes an output transistor TR outIn addition, the circuit has an N-channel field effect transistor 121, a capacitance element 122, and a CMOS inverter consisting of an N-channel field effect transistor 123 and a P-channel field effect transistor .

[0073] In the current modulation section 12 having the above circuit configuration, when a scanning signal Gate is applied to the gate electrode, the N-channel field effect transistor 121 is turned on, writes the current modulation signal I-Sig, and holds it in the capacitance element 122. When a light emission period pulse signal is input, the light emission period pulse signal drives the output transistor TR out On / off control will be performed.

[0074] [Example 6] Example 6 shows a specific circuit example and operational waveform examples of the sawtooth wave generating section 50. Fig. 13A shows a specific circuit example of the sawtooth wave generating section 50 according to Example 6, and Figs. 13B and 13C show operational waveform examples.

[0075] As described above, the sawtooth wave generating unit 50 needs to generate a sawtooth wave signal SAW for each scanning line, and therefore, a circuit portion for generating the sawtooth wave signal SAW is provided for each scanning line, and it is therefore desirable to realize this with a simple circuit.

[0076] The circuit shown in Fig. 13A is a circuit portion provided for each scan line of the sawtooth wave generating unit 50. The sawtooth wave signal SAW to be generated by the sawtooth wave generating unit 50 has a stepped waveform as shown in Fig. 2, and therefore can be realized by a sample and hold circuit 51 that samples and holds a voltage. The sample and hold circuit 51 is configured by, for example, two operational amplifiers 511, 512, an N-channel field effect transistor 513, a P-channel field effect transistor 514, and two capacitance elements 515, 516.

[0077] The write signal shown in Fig. 13B and the variable voltage shown by the dashed line in Fig. 13C are input to the sample and hold circuit 51. The sample and hold circuit 51 samples and holds the variable voltage in synchronization with the write signal, thereby generating the sawtooth wave signal SAW shown by the solid line in Fig. 13C. The variable voltage can be easily realized by using a source driver or the like used in organic EL display devices.

[0078] [Example 7] The seventh embodiment is an example of a driving method that maintains good moving image characteristics when the light emission duty is varied discretely.

[0079] It is generally known that light emission duty has a significant effect on video blur (video distortion). For example, sudden changes in light emission duty can cause false contours to appear in scrolling videos of still objects, and the amount of blur in a video can vary greatly depending on the brightness, making it look unnatural.

[0080] To prevent this, it is preferable to keep the rate of change of the light emission duty per light emission below a certain percentage (for example, 75%). In the video response of the eye, when multiple lights are emitted within one frame, the light emission duty can be considered to be from the first light emission to the last light emission, so one possible method is to divide the stepped waveform into multiple parts and vary the light emission duty.

[0081] Therefore, in the driving method according to the seventh embodiment, the light emission is divided into parts, and while maintaining the total light emission duty, the rate of change in the light emission duty for one light emission during the light emission period in one frame is suppressed to a predetermined rate (75%, for example) or less. In other words, the change in time from the start of light emission to the end of light emission is reduced so as not to cause an extreme change in the light emission duty.

[0082] Fig. 14A shows a waveform diagram of the sawtooth wave signal SAW when there is an extreme change in light emission duty between certain gradations. The waveform in Fig. 14A corresponds to the stepped waveform of the sawtooth wave signal SAW shown in Fig. 2. Fig. 14B shows a waveform diagram of the sawtooth wave signal SAW for realizing the driving method according to Example 7. Both Fig. 14A and Fig. 14B show the waveform of the sawtooth wave signal SAW when the light emission duty changes in increments of 0.5.

[0083] 15A and 15B, and 16A and 16B show the results of a moving image simulation of a 10-pixel / frame scrolling image of a horizontal luminance ramp and a vertical bar-shaped vertical luminance ramp, in the case where the light emission duty changes in increments of 0.5 and where there is an extreme change in light emission duty between certain gradations (using one sawtooth wave signal SAW) and where there is no extreme change in light emission duty (the sawtooth wave signal SAW is divided into two). The moving image simulation results in Fig. 15A and 16A are the results of a simulation for the case of Fig. 14A, in which there is one sawtooth wave signal SAW, i.e., where there is a discrete change in light emission duty, and it can be seen that false contours are visible in the horizontal ramp image and the amount of blur changes in stages in the vertical bar-shaped vertical ramp image.

[0084] The moving image simulation results in Figures 15B and 16B are simulation results for the case of Figure 14B in which the sawtooth wave signal SAW is divided into two under driving by the driving method of Example 7, i.e., a case in which there is no discrete change in the light emission duty. It can be seen that, with the driving method of Example 7, the false contours are greatly improved and the amount of blur is more natural compared to the case in which there is a discrete change in the light emission duty.

[0085] If further improvement is desired, one possible method is to subtly change the switching points of the steps of the sawtooth wave signal SAW for each frame, thereby scattering the switching points of the light emission duty for each frame, thereby blurring the density of the pseudo contours and the switching points of the moving image blur.

[0086] In the driving method according to the seventh embodiment, the change in time from the start of light emission to the end of light emission in a light emission period within one frame is reduced, and the light emission duty is narrowed, which means inserting black. The black insertion can reduce the effect on moving image blur (moving image distortion).

[0087] [Example 8] Example 8 is an example having a re-shooting mode that realizes strong light emission in re-shooting. "Re-shooting" means, for example, capturing an image displayed on a display device such as a large screen using an imaging device such as a CMOS image sensor.

[0088] Many imaging devices, such as CMOS image sensors, use a rolling shutter, which exposes each scan line, so when an image displayed on a display device is photographed (or re-photographed), if the display device does not emit light during this exposure, that part will not be exposed and black bands may appear in the photograph.To prevent this with PWM drive, the display device's light emission can be made to flash repeatedly at short, equal intervals.

[0089] The display device according to Example 8 has a normal mode in which the light-emitting duty is controlled to be changed discretely, and also has a re-shooting mode in which light emission is resistant to re-shooting. In the normal mode, as shown in Fig. 17A, one frame period is divided into a writing section and a light-emitting section, and the light-emitting duty is changed discretely in the light-emitting section. In contrast, in the re-shooting mode, as shown in Fig. 17B, light emission in one frame period is divided into multiple times, and the light-emitting duty is not changed periodically.

[0090] In the normal mode, there are intervals in which the light-emitting unit 11 does not emit light, and black is displayed during those intervals, and when re-capture is performed, the image appears as black streaks, resulting in degradation of the image quality of the captured image. In contrast, according to the re-capture mode of the display device according to the eighth embodiment, the light-emitting unit 11 is constantly emitting light, so that it is possible to achieve light emission that is strong in re-capture and to prevent the occurrence of the moving image problem described in the fourth embodiment.

[0091] The relationship between the exposure time of the rolling shutter and the light emission in the normal mode and the re-shooting mode is shown in Fig. 18. In Fig. 18, the light emission in the normal mode relative to the exposure time of the rolling shutter is shown by shading.

[0092] [Example 9] Example 9 is a circuit example of the pixel circuit 10 in the case of voltage modulation. An example of the circuit configuration of the pixel circuit 10 according to Example 9 is shown in FIG.

[0093] In the case of voltage modulation, the pixel circuit 10 has a circuit configuration including a light emitting unit 11, a voltage modulation unit 14, and a light emitting time control unit 13. In the case of voltage modulation, as in the case of current modulation, a self-luminous element such as a light emitting diode (LED) or an organic EL element can be used as the light emitting element of the light emitting unit 11.

[0094] 20 shows a specific circuit example of the voltage modulation unit 14. The voltage modulation unit 14 according to this circuit example includes an N-channel field effect transistor 141, a capacitance element 142, a CMOS inverter consisting of an N-channel field effect transistor 143 and a P-channel field effect transistor 144, and an operational amplifier 145.

[0095] In the voltage modulation section 14 having the above circuit configuration, the output transistor (not shown) of the operational amplifier 145 is connected in series to the light-emitting section 11. When a scanning signal Gate is applied to the gate electrode of the N-channel field-effect transistor 141, the N-channel field-effect transistor 141 is turned on, writes the voltage modulation signal V-Sig supplied from the gradation control section 40, and holds it in the capacitance element 142. When a light-emitting period pulse signal is input, the light-emitting period pulse signal controls the activation / deactivation of the operational amplifier 145, including the output transistor connected in series to the light-emitting section 11.

[0096] As described above, pixel circuit 10 according to Example 9 is configured to discretely determine the light emission time for each pixel by controlling the activation / deactivation of operational amplifier 145 of voltage modulation unit 14. Pixel circuit 10 according to Example 9 having this configuration, i.e., voltage-modulated pixel circuit 10, can also achieve the same functions and effects as current-modulated pixel circuit 10. That is, by roughly changing the light emission time in stages by controlling the activation / deactivation of operational amplifier 145, and then performing fine voltage modulation under the control of gradation control unit 40 in accordance with the light emission time determined by controlling the activation / deactivation of operational amplifier 145, and performing driving using only a specific range of current values, it is possible to control the light emission time with high precision even with a simple circuit configuration.

[0097] <Modification> Although the technology of the present disclosure has been described above based on a preferred embodiment, the technology of the present disclosure is not limited to this embodiment. The configuration and structure of the display device described in the above embodiment are examples and can be modified as appropriate. For example, in the pixel circuit according to Example 1, the connection relationship between the light emitting unit 11 and the current modulation unit 12 is such that the light emitting unit 11 is connected to the current modulation unit 12 via a power supply voltage V DD However, the present invention is not limited to this connection relationship. In other words, the same effects can be obtained even with a circuit configuration in which the light-emitting unit 11 is disposed on the reference potential node (for example, ground) side.

[0098] Electronic Device of the Present Disclosure The display device of the present disclosure described above can be used as a display unit (display device) for electronic devices in a variety of fields, which displays a video signal input to the electronic device or a video signal generated within the electronic device as an image or video. Examples of electronic devices of the present disclosure include television sets, notebook personal computers, digital still cameras, mobile terminal devices such as mobile phones, tiling displays, etc. However, the present disclosure is not limited to these.

[0099] [First specific example] A first specific example of an electronic device using a display device according to the present disclosure is an example of a tiling display. Fig. 21 is a schematic diagram showing a tiling display according to one specific example of an electronic device according to the present disclosure.

[0100] The tiling display 100 according to the first specific example is a display device formed by arranging, for example, a total of nine display units (unit panels) 101 in a tiled pattern of 3 x 3. Here, the number of display units 101 is set to 9 (3 x 3), but the number of display units 101 is arbitrary.

[0101] In a tiling display 100, if adjacent display units 101 do not have similar gamma characteristics, brightness gaps will occur, resulting in poor image quality, and therefore fine brightness adjustment is required. Therefore, in the tiling display 100 according to the first specific example, the light-emitting device according to the embodiment described above, which has a logarithmic gamma characteristic of current versus brightness, is used as the display unit 101. This makes it possible to control brightness at a constant, small rate of change across the entire range of light-emitting current. Furthermore, if brightness can be adjusted with a brightness ratio of, for example, about 1.8%, this is below the brightness difference that the human eye can distinguish, making it possible to provide a tiling display with no brightness gaps between adjacent display units 101 and excellent image quality.

[0102] [Second specific example] A second specific example of an electronic device using a display device according to the present disclosure is an example of a backlight device for a liquid crystal display device. Fig. 22 is an exploded perspective view schematically showing a liquid crystal display device according to the second specific example of the electronic device according to the present disclosure.

[0103] The liquid crystal display device 200 according to the second specific example has a so-called direct-type LED partial drive configuration in which a backlight device 300 using light-emitting diodes (LEDs) as light-emitting units is disposed on the back surface. The light-emitting device according to the above-described embodiment can be used as the backlight device 300 of this direct-type LED partial drive liquid crystal display device 200. Then, by performing partial drive in the backlight device 300, in which only the light-emitting units (LEDs) are lit for bright scenes and the light-emitting units (LEDs) are not lit for dark scenes, it is possible to provide a liquid crystal display device with excellent image quality.

[0104] <Configurations that the present disclosure can take> The present disclosure may also be configured as follows.

[0105] <A. Light-emitting device> [A-01] A pixel circuit including a light-emitting portion, and a gradation control unit that performs gradation control; Equipped with The pixel circuit is a light emitting time control unit for controlling the light emitting time of the light emitting unit; an amplitude modulation unit including an output transistor connected in series to the light emitting unit; and The gradation control unit performs gradation control by controlling the on / off of the output transistor of the amplitude modulation unit and controlling modulation of the amplitude modulation unit via the light emission time control unit. Light-emitting device. [A-02] The light emitting time control section controls the light emitting time of the light emitting section discretely by controlling the on / off of the output transistor of the amplitude modulation section under the control of the gradation control section; The amplitude modulation unit controls the value of a current flowing through the light-emitting unit or the value of a voltage applied to the light-emitting unit according to the light-emitting time of the light-emitting unit under the control of the gradation control unit. The light emitting device according to [A-01] above. [A-03] The amplitude modulation unit is a current modulation unit that controls the value of the current flowing in the light-emitting unit, or a voltage modulation unit that controls the value of the voltage applied to the light-emitting unit. The light-emitting device according to [A-02] above. [A-04] A sawtooth wave generating unit that generates a stepped sawtooth wave signal, the light emission time control unit controls the light emission time of the light emitting unit based on the stepped sawtooth wave signal generated by the sawtooth wave generating unit; The light emitting device according to any one of [A-01] to [A-03] above. [A-05] The sawtooth wave generating unit generates a stepped sawtooth wave signal for each pixel row of a pixel array unit in which pixel circuits are arranged in a matrix, the light emitting time control unit controls the light emitting time of the light emitting unit for each pixel row based on the stepped sawtooth wave signal generated by the sawtooth wave generating unit; The light-emitting device according to [A-04] above. [A-06] The sawtooth wave generating unit generates a stepped sawtooth wave signal using a sample-and-hold circuit. The light-emitting device according to [A-04] or [A-05] above. [A-07] The gradation control unit discretely reduces the light emitting time of the light emitting unit at a constant ratio. The light emitting device according to any one of [A-01] to [A-06] above. [A-08] The gradation control unit controls the light-emitting time of the light-emitting unit and the value of the current flowing through the light-emitting unit so that the current-to-luminance characteristic approaches the gamma characteristic of a logarithmic curve. The light-emitting device according to [A-07] above. [A-09] When α is a number smaller than 1 and the brightness of the light-emitting part is set to α times the maximum value, The gradation control unit multiplies the light emitting duty by α at a gradation where the luminance is multiplied by α for an arbitrary gamma curve, and varies the step interval of the amplitude gradation so as to allocate it according to this gradation interval, and varies the amplitude gradation so as to be multiplied by α at this interval. The light-emitting device according to [A-07] above. [A-10] The gradation control unit, when discretely controlling the light emitting time of the light emitting unit, sets the rate of change of one light emission of the light emitting duty in the light emitting period within one frame to a predetermined rate or less. The light emitting device according to any one of [A-02] to [A-09] above. [A-11] The gradation control unit uses only a specific light-emitting current range of the light-emitting unit except for the minimum light-emitting time width of the light-emitting unit. The light emitting device according to any one of [A-02] to [A-10] above. [A-12] The gradation control unit performs monochromatic chromaticity correction in a section of a specific current range of the light emitting unit, The light emitting device according to [A-11] above. [A-13] The gradation control unit performs chromaticity correction for a single color using an interpolation processing technique. The light emitting device according to [A-12] above. [A-14] The gradation control unit performs chromaticity correction for a single color by interpolating two or more current values. The light emitting device according to [A-13] above. [A-15] A re-shooting mode is provided in which light emission in one frame period is divided into multiple times and the light emission duty is not periodically changed. The light emitting device according to any one of [A-01] to [A-14] above. [A-16] The light-emitting element of the light-emitting unit is a light-emitting diode. The light emitting device according to any one of [A-01] to [A-15] above.

[0106] B. Method for driving the light-emitting device [B-01] A pixel circuit including a light-emitting portion, and a gradation control unit that performs gradation control; Equipped with The pixel circuit is a light emitting time control unit for controlling the light emitting time of the light emitting unit; an amplitude modulation unit including an output transistor connected in series to the light emitting unit; When driving a light emitting device having Under the control of the gradation control unit, the output transistor of the amplitude modulation unit is controlled to be turned on / off, and the gradation control is performed by controlling the modulation of the amplitude modulation unit. A method for driving a light emitting device. [B-02] Controlling the light-emitting time of the light-emitting unit based on a stepped sawtooth wave signal. The light emitting device according to [B-01] above. [B-03] Controlling the light-emitting time of the light-emitting section for each pixel row based on a stepped sawtooth wave signal. The light-emitting device according to [B-02] above. [B-04] The light-emitting time of the light-emitting part is discretely reduced at a constant rate. The light emitting device according to any one of [B-01] to [B-03] above. [B-05] The light-emitting time of the light-emitting unit and the value of the current flowing through the light-emitting unit are controlled so that the current-to-luminance characteristic approaches the gamma characteristic of a logarithmic curve. The light-emitting device according to [B-04] above. [B-06] When α is a number smaller than 1 and the brightness of the light-emitting part is α times the maximum value, For an arbitrary gamma curve, the light emission duty is multiplied by α at a gradation where the brightness is multiplied by α, and the step interval of the amplitude gradation is varied so as to be allocated according to this gradation interval, and the amplitude gradation is varied so as to be multiplied by α at this interval. The light-emitting device according to [B-06] above. [B-07] When discretely controlling the light-emitting time of the light-emitting unit, the rate of change of the light-emitting duty per light-emitting in the light-emitting period within one frame is set to a predetermined rate or less. The light emitting device according to any one of [B-01] to [B-06] above. [B-08] Except for the minimum light emitting time width of the light emitting unit, only the specific light emitting current range of the light emitting unit is used. The light emitting device according to any one of [B-02] to [B-07] above. [B-09] Perform chromaticity correction for a single color in a specific current range of the light-emitting section. The light-emitting device according to [B-08] above. [B-10] Monochromatic chromaticity correction is performed using interpolation processing technology. The light-emitting device according to [B-09] above. [B-11] Monochromatic chromaticity correction is performed by interpolating two or more current values. The light emitting device according to [B-10] above. [B-12] The light emission in one frame period is divided into multiple times, and a re-shooting mode is provided in which the light emission duty is not periodically changed. The light emitting device according to any one of [B-01] to [B-11] above. [B-13] The light-emitting element of the light-emitting unit is a light-emitting diode. The light emitting device according to any one of [B-01] to [B-12] above.

[0107] ≪C.Electronic equipment≫ [C-01] A pixel circuit including a light-emitting portion, and a gradation control unit that performs gradation control; Equipped with The pixel circuit is a light emitting time control unit for controlling the light emitting time of the light emitting unit; an amplitude modulation unit including an output transistor connected in series to the light emitting unit; and The gradation control unit performs gradation control by controlling the on / off of the output transistor of the amplitude modulation unit and controlling modulation of the amplitude modulation unit via the light emission time control unit. An electronic device having a light-emitting device. [C-02] The light emitting time control unit controls the light emitting time of the light emitting unit discretely by controlling the on / off of the output transistor of the amplitude modulation unit under the control of the gradation control unit; The amplitude modulation unit controls the value of a current flowing through the light-emitting unit or the value of a voltage applied to the light-emitting unit according to the light-emitting time of the light-emitting unit under the control of the gradation control unit. The electronic device described in [C-01] above. [C-03] The amplitude modulation unit is a current modulation unit that controls the value of the current flowing in the light-emitting unit, or a voltage modulation unit that controls the value of the voltage applied to the light-emitting unit. The electronic device described in [C-02] above. [C-04] A sawtooth wave generating unit that generates a stepped sawtooth wave signal, the light emission time control unit controls the light emission time of the light emitting unit based on the stepped sawtooth wave signal generated by the sawtooth wave generating unit; The electronic device according to any one of [C-01] to [C-03] above. [C-05] The sawtooth wave generating unit generates a stepped sawtooth wave signal for each pixel row of a pixel array unit in which pixel circuits are arranged in a matrix, the light emitting time control unit controls the light emitting time of the light emitting unit for each pixel row based on the stepped sawtooth wave signal generated by the sawtooth wave generating unit; The electronic device described in [C-04] above. [C-06] The sawtooth wave generating unit generates a stepped sawtooth wave signal using a sample-and-hold circuit. The electronic device according to [C-04] or [C-05] above. [C-07] The gradation control unit discretely reduces the light-emitting time of the light-emitting unit at a constant rate. The electronic device according to any one of [C-01] to [C-06] above. [C-08] The gradation control unit controls the light-emitting time of the light-emitting unit and the value of the current flowing through the light-emitting unit so that the current-to-luminance characteristic approaches the gamma characteristic of a logarithmic curve. The electronic device described in [C-07] above. [C-09] When α is a number smaller than 1 and the brightness of the light-emitting part is increased by α times from the maximum value, The gradation control unit multiplies the light emitting duty by α at a gradation where the luminance is multiplied by α for an arbitrary gamma curve, and varies the step interval of the amplitude gradation so as to allocate it according to this gradation interval, and varies the amplitude gradation so as to be multiplied by α at this interval. The electronic device described in [C-07] above. [C-10] The gradation control unit, when discretely controlling the light emitting time of the light emitting unit, sets the rate of change of one light emission of the light emitting duty in the light emitting period within one frame to a predetermined rate or less. The electronic device according to any one of [C-02] to [C-09] above. [C-11] The gradation control unit uses only a specific light-emitting current range of the light-emitting unit except for the minimum light-emitting time width of the light-emitting unit. The electronic device according to any one of [C-02] to [C-10] above. [C-12] The gradation control unit performs monochromatic chromaticity correction in a specific current range of the light emitting unit. The electronic device according to [C-11] above. [C-13] The gradation control unit performs chromaticity correction for a single color using an interpolation processing technique. The electronic device according to [C-12] above. [C-14] The gradation control unit performs chromaticity correction for a single color by interpolating two or more current values. The electronic device according to [C-13] above. [C-15] A re-shooting mode is provided in which the light emission in one frame period is divided into multiple times and the light emission duty is not periodically changed. The electronic device according to any one of [C-01] to [C-14] above. [C-16] The light-emitting element of the light-emitting unit is a light-emitting diode. The electronic device according to any one of [C-01] to [C-15] above.

[0108] This application claims priority based on Japanese Patent Application No. 2020-187090, filed on November 10, 2020, in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0109] Those skilled in the art will recognize that various modifications, combinations, subcombinations, and variations may occur depending on design requirements and other factors, and are intended to be within the scope of the appended claims and their equivalents.

Claims

1. a pixel circuit including a light-emitting portion; and a gradation control unit that performs gradation control; Equipped with The pixel circuit is a light emitting time control unit for controlling the light emitting time of the light emitting unit; an amplitude modulation unit including an output transistor connected in series to the light emitting unit; and the gradation control unit performs gradation control by controlling the on / off of the output transistor of the amplitude modulation unit and controlling modulation of the amplitude modulation unit via the light emission time control unit; the light emitting time control section, under the control of the gradation control section, controls the on / off of the output transistor of the amplitude modulation section to discretely control the light emitting time of the light emitting section; the amplitude modulation unit controls a current value flowing through the light-emitting unit or a voltage value applied to the light-emitting unit according to a light-emitting time of the light-emitting unit under the control of the gradation control unit; the gradation control unit, when discretely controlling the light emitting time of the light emitting unit so that the light emitting unit emits light n times within one frame, sets a change rate of one light emission of the light emitting duty during the light emitting period within one frame (where a represents the light emitting time of the (a+1)th light emission relative to the light emitting time of the ath light emission (a is a natural number between 1 and n-1)) to 75% or less; Light-emitting device.

2. The amplitude modulation unit is a current modulation unit that controls the value of a current flowing through the light-emitting unit, or a voltage modulation unit that controls the value of a voltage applied to the light-emitting unit. The light emitting device according to claim 1 .

3. a sawtooth wave generating unit that generates a stepped sawtooth wave signal; the light emission time control unit controls the light emission time of the light emitting unit based on the stepped sawtooth wave signal generated by the sawtooth wave generating unit; The light emitting device according to claim 1 .

4. the sawtooth wave generating unit generates a stepped sawtooth wave signal for each pixel row of a pixel array unit in which pixel circuits are arranged in a matrix; the light emitting time control unit controls the light emitting time of the light emitting unit for each pixel row based on the stepped sawtooth wave signal generated by the sawtooth wave generating unit; The light emitting device according to claim 3 .

5. The sawtooth wave generating unit generates a stepped sawtooth wave signal using a sample-and-hold circuit. The light emitting device according to claim 3 .

6. The gradation control unit discretely reduces the light emitting time of the light emitting unit at a constant ratio. The light emitting device according to claim 1 .

7. the gradation control unit controls the light emitting time of the light emitting unit and the value of the current flowing through the light emitting unit so that the current vs. luminance characteristic approaches the gamma characteristic of a logarithmic curve; The light emitting device according to claim 6 .

8. The gradation control unit uses only a specific light-emitting current range of the light-emitting unit except for the minimum light-emitting time width of the light-emitting unit. The light emitting device according to claim 1 .

9. A re-shooting mode is provided in which light emission in one frame period is divided into multiple times and the light emission duty is not periodically changed. The light emitting device according to claim 1 .

10. The light-emitting element of the light-emitting unit is a light-emitting diode. The light emitting device according to claim 1 .

11. a pixel circuit including a light-emitting portion; and a gradation control unit that performs gradation control; Equipped with The pixel circuit is a light emitting time control unit for controlling the light emitting time of the light emitting unit; an amplitude modulation unit including an output transistor connected in series to the light emitting unit; When driving a light emitting device having Under the control of the gradation control unit, the output transistor of the amplitude modulation unit is controlled to be turned on / off, and the gradation control is performed by controlling the modulation of the amplitude modulation unit; Under the control of the gradation control unit, a current value flowing through the light-emitting unit or a voltage value applied to the light-emitting unit is controlled in accordance with the light-emitting time of the light-emitting unit; When the light emitting time of the light emitting unit is discretely controlled so that the light emitting unit emits light n times within one frame, the rate of change of the light emitting duty for one light emission during the light emitting period within one frame (where a represents the light emitting time of the (a+1)th light emission relative to the light emitting time of the ath light emission (a is a natural number between 1 and n-1)) is set to 75% or less. A method for driving a light emitting device.

12. a pixel circuit including a light-emitting portion; and a gradation control unit that performs gradation control; Equipped with The pixel circuit is a light emitting time control unit for controlling the light emitting time of the light emitting unit; an amplitude modulation unit including an output transistor connected in series to the light emitting unit; and the gradation control unit performs gradation control by controlling the on / off of the output transistor of the amplitude modulation unit and controlling modulation of the amplitude modulation unit via the light emission time control unit; the light emitting time control section, under the control of the gradation control section, controls the on / off of the output transistor of the amplitude modulation section to discretely control the light emitting time of the light emitting section; the amplitude modulation unit controls a current value flowing through the light-emitting unit or a voltage value applied to the light-emitting unit according to a light-emitting time of the light-emitting unit under the control of the gradation control unit; the gradation control unit, when discretely controlling the light emitting time of the light emitting unit so that the light emitting unit emits light n times within one frame, sets a change rate of one light emission of the light emitting duty during the light emitting period within one frame (where a represents the light emitting time of the (a+1)th light emission relative to the light emitting time of the ath light emission (a is a natural number between 1 and n-1)) to 75% or less; An electronic device having a light-emitting device.

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