Light emitting device and display device

Abstract

To provide a light emitting device and a display device that can reduce power consumption at low temperatures.SOLUTION: A light emitting device includes a light emitting unit having one or more semiconductor light emitting elements, a power supply unit that supplies power to the light emitting unit, a drive unit having a drive element that drives the light emitting unit, a temperature acquisition unit that acquires the temperature of the light emitting unit, and a control unit that determines the amplitude of a current flowing through the light emitting unit based on the temperature of the light emitting unit and outputs the amplitude to the drive unit, and the drive unit controls the voltage supplied by the power supply unit to one end of the light emitting unit based on the amplitude acquired from the control unit.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a light-emitting device, a display device, and the like.

Background Art

[0002] Conventionally, a light-emitting device including a light-emitting element such as an LED (Light Emitting Diode) is known. For example, Patent Document 1 discloses a light-emitting device that reduces the loss of a driving element of an LED.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The forward voltage of a light-emitting element becomes larger at low temperature than at high temperature. Therefore, in the conventional method, since the voltage supplied to the light-emitting element increases at low temperature compared to high temperature, the power consumption of the light-emitting device increases.

[0005] According to some aspects of the present disclosure, it is possible to provide a light-emitting device, a display device, and the like that can suppress power consumption at low temperature.

Means for Solving the Problems

[0006] One aspect of the present disclosure relates to a light-emitting device including a light-emitting unit having one or more semiconductor light-emitting elements, a power supply unit that supplies power to the light-emitting unit, a driving unit having a driving element that drives the light-emitting unit, a temperature acquisition unit that acquires the temperature of the light-emitting unit, and a control unit that determines the amplitude of the current flowing through the light-emitting unit based on the temperature of the light-emitting unit and outputs the amplitude to the driving unit. The driving unit controls the voltage supplied by the power supply unit to one end of the light-emitting unit based on the amplitude acquired from the control unit.

[0007] Another aspect of the present disclosure relates to a display device including the above-described light-emitting device.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6A

Figure 6B

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Figure 8

Figure 9A

Figure 9B

Figure 10A

Figure 10B

Figure 10C

Figure 11A

Figure 11B

Figure 11C

Figure 12

Embodiment for Carrying Out the Invention

[0009] Hereinafter, this embodiment will be described with reference to the drawings. For the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted. Note that the embodiment described below does not unduly limit the content described in the claims. Also, not all of the configurations described in this embodiment are essential constituent elements of the present disclosure.

[0010] 1. Example of System Configuration FIG. 1 is a diagram showing a configuration example of the light-emitting device 100 of this embodiment. The light-emitting device 100 includes a light-emitting unit 110, a driving unit 120, a power supply unit 130, a control unit 140, and a temperature acquisition unit 150. However, the configuration of the light-emitting device 100 is not limited to the example of FIG. 1, and various modifications such as omitting some configurations or adding other configurations are possible. Note that the same applies to the drawings described later, such as FIG. 2, in terms of the possibility of such modifications as omission or addition of configurations.

[0011] The light-emitting unit 110 has one or more light-emitting elements 111. The light-emitting element 111 is, for example, a semiconductor light-emitting element, and more specifically, an LED. However, the light-emitting element 111 may be a PD (Photo diode) or other light-emitting elements. Also, in the example of FIG. 1, the light-emitting unit 110 includes four light-emitting elements 111 connected in series, but the number of light-emitting elements 111 included in the light-emitting unit 110 is not limited to this.

[0012] The driving unit 120 drives the light-emitting unit 110. For example, the driving unit 120 may include a driving element 121 that drives the light-emitting unit 110. The driving unit 120 is, for example, a current driving circuit that supplies a predetermined current to the light-emitting unit 110, and the driving element 121 is an FET (Field Effect Transistor). However, other driving elements may be used as the driving element 121. The driving element 121 is connected in series with the light-emitting unit 110. In the example of FIG. 1, one end of the driving element 121, which is an FET, is connected to the cathode terminal of the light-emitting unit 110, and the other end of the driving element 121 is connected to the low-potential side power supply (e.g., ground). Also, other elements such as a resistor may be arranged between the driving element 121 and ground.

[0013] The power supply unit 130 (PSU: Power Supply Unit) supplies power to the light-emitting unit 110. Specifically, the power supply unit 130 is connected to the anode terminal of the light-emitting unit 110 and supplies a voltage VLED to the anode terminal. In the example of FIG. 1, one or more light-emitting elements 111 and the driving element 121 are connected in series between the power supply unit 130 and ground. The power supply unit 130 may control the voltage VLED based on a signal from the driving unit 120.

[0014] FIG. 2 is a diagram showing a configuration example of the driving unit 120 and showing the relationship between the driving unit 120 and the power supply unit 130. As shown in FIG. 2, the driving unit 120 may include a voltage acquisition unit 123 and a control signal output unit 125 in addition to the driving element 121.

[0015] The voltage acquisition unit 123 acquires (detects) the voltage VFET applied to the driving element 121. The control signal output unit 125 outputs a signal for determining the voltage value required for driving the light-emitting unit 110 to the power supply unit 130 based on the voltage VFET acquired by the voltage acquisition unit 123. The power supply unit 130 determines the voltage VLED to be supplied to the light-emitting unit 110 based on the output of the control signal output unit 125. Note that since known methods such as those described in Patent Document 1 can be applied to the configurations of the voltage acquisition unit 123 and the control signal output unit 125, detailed descriptions thereof are omitted. Also, since known methods such as those described in Patent Document 1 can be applied to the configuration for determining the voltage VLED based on the output of the control signal output unit 125, detailed descriptions thereof are omitted.

[0016] In this way, the driving unit 120 may control the voltage VLED supplied by the power supply unit 130 to one end (anode end) of the light-emitting unit 110 based on the second voltage (voltage VFET), which is the voltage applied to the driving element 121. By the driving unit 120 feeding back a signal based on the voltage VFET of the driving element 121 to the power supply unit 130, the power supply unit 130 can supply, as the voltage VLED, a voltage capable of driving the light-emitting element 111 included in the light-emitting unit 110.

[0017] Furthermore, the light-emitting device 100 of the present embodiment includes a control unit 140 and a temperature acquisition unit 150. The temperature acquisition unit 150 acquires the temperature of the light-emitting unit 110. The temperature acquisition unit 150 here is, for example, a thermistor that detects a resistance value that changes depending on temperature, but other configurations capable of detecting temperature may also be used. The temperature acquisition unit 150 is disposed, for example, at a position where the distance from the light-emitting unit 110 is equal to or less than a predetermined threshold value, and outputs the detected temperature as the temperature of the light-emitting unit 110. That is, in the present embodiment, the temperature acquired by the temperature acquisition unit 150 is not limited to the temperature of the light-emitting unit 110 itself (for example, the surface temperature), but broadly includes temperatures correlated with that temperature.

[0018] The control unit 140 of the present embodiment is configured by the following hardware. The hardware can include at least one of a circuit that processes digital signals and a circuit that processes analog signals. For example, the hardware can be composed of one or more circuit devices mounted on a circuit board or one or more circuit elements. The one or more circuit devices are, for example, an IC (Integrated Circuit), an FPGA (field-programmable gate array), etc. The one or more circuit elements are, for example, a resistor, a capacitor, etc.

[0019] Also, the control unit 140 may be realized by the following processor. The light-emitting device 100 of the present embodiment includes a memory that stores information and a processor that operates based on the information stored in the memory. The information is, for example, a program and various data, etc. The processor includes hardware. The processor can use various processors such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), etc. The memory may be a semiconductor memory such as an SRAM (Static Random Access Memory), a DRAM (Dynamic Random Access Memory), a flash memory, etc., or a register, or a magnetic storage device such as a hard disk drive (HDD), or an optical storage device such as an optical disk device. For example, the memory stores instructions readable by a computer, and by the processor executing the instructions, the functions of the control unit 140 are realized as processing. The instructions here may be instructions of an instruction set that constitutes a program or instructions that instruct an operation to the hardware circuit of the processor.

[0020] Based on the temperature of the light-emitting unit 110 detected by the temperature acquisition unit 150, the control unit 140 determines the amplitude of the current If flowing through the light-emitting unit 110 and outputs the amplitude to the driving unit 120.

[0021] FIG. 3 is a diagram showing a configuration example of the control unit 140. The control unit 140 includes a determination unit 141 and an amplitude setting unit 143. The determination unit 141 obtains a magnification with respect to the amplitude value of the reference current If (hereinafter referred to as the reference amplitude) based on the temperature of the light emitting unit 110 obtained from the temperature acquisition unit 150.

[0022] FIG. 4 is an example of table data showing the relationship between temperature and magnification. For example, a memory (not shown) of the light emitting device 100 may store the table data shown in FIG. 4. The determination unit 141 reads the table data from the memory and determines the amplitude magnification based on the temperature (LED temperature) of the light emitting unit 110 obtained from the temperature acquisition unit 150 and the table data. Note that the determination of the magnification is not limited to using table data, and any function may be used.

[0023] The amplitude setting unit 143 determines the amplitude value of the current If by multiplying the magnification obtained by the determination unit 141 with respect to the reference amplitude. The amplitude setting unit 143 outputs the obtained amplitude value to the driving unit 120.

[0024] The driving unit 120 drives the light emitting unit 110 as a current driving circuit based on the amplitude of the current If obtained from the amplitude setting unit 143. As can be seen from the circuit configuration of FIG. 1, the current If corresponds to the current flowing through the LED which is the light emitting element 111. When the driving element 121 drives the light emitting unit 110, feedback based on the voltage VFET is performed as described above, so that the voltage VLED supplied by the power supply unit 130 to one end of the light emitting unit 110 is controlled. That is, the driving unit 120 controls the voltage VLED supplied by the power supply unit 130 based on the amplitude obtained from the control unit 140.

[0025] According to the method of this embodiment, based on the temperature of the light-emitting unit 110, the amplitude value of the current If used by the driving element 121 (current driving circuit) to drive the light-emitting unit 110 is determined, and the voltage VLED supplied by the power supply unit 130 is also controlled by the amplitude value. Thereby, even when the temperature of the light-emitting unit 110 changes, it becomes possible to appropriately control the power consumption of the power supply unit 130. This will be specifically described below.

[0026] FIG. 5 is a diagram showing the temperature characteristics of the forward voltage Vf of the LED which is the light-emitting element 111. The vertical axis in FIG. 5 represents the forward voltage Vf, and the horizontal axis represents the temperature. As can be seen from FIG. 5, when trying to pass a current If with a certain amplitude through the light-emitting unit 110, the lower the temperature, the larger the forward voltage Vf of the light-emitting element 111.

[0027] As shown in FIG. 1, the power VLED to be supplied by the power supply unit 130 is determined by the forward voltage Vf of one or more light-emitting elements 111 and the voltage VFET of the driving element 121. For example, when four light-emitting elements 111 are connected in series as shown in FIG. 1 and one end of the driving element 121 is connected to the ground, the voltage VLED is obtained by the following formula (1). It should be easily understood by those skilled in the art that the following formula (1) can be changed according to the specific configuration. VLED = 4×Vf + VFET ···(1)

[0028] As can be seen from the above formula (1), as the value of the forward voltage Vf increases, the value of the voltage VLED that the power supply unit 130 should supply to one end of the light-emitting unit 110 also increases, and as a result, the value of the power that the power supply unit 130 should supply also increases. In the case of a conventional method that does not consider the temperature of the light-emitting unit 110, the power supply unit 130 needs to have the ability to supply a large amount of power at low temperatures, which leads to an increase in the cost of the power supply unit 130.

[0029] In this regard, in the method of this embodiment, based on the temperature of the light-emitting unit 110, the amplitude value of the current If of the driving unit 120, which is a driving circuit, is controlled. Specifically, as shown in the table data of FIG. 4, when the temperature of the light-emitting unit 110 is less than the temperature threshold, the control unit 140 performs control to reduce the amplitude compared to the case where the temperature of the light-emitting unit 110 is equal to or higher than the temperature threshold. The temperature threshold here is, for example, a temperature between 20°C and 25°C in the table data of FIG. 4, but other temperatures may be set. Also, as is clear from the table data of FIG. 4, the amplitude value is not limited to being controlled in two steps, and may be controlled in multiple steps of three or more steps. In this case, two or more temperature thresholds at which the amplitude value changes may be set. Further, the relationship between the temperature and the amplitude value may be set as a continuous function.

[0030] FIGS. 6A and 6B are diagrams showing examples of the current If. The vertical axis in FIGS. 6A and 6B represents the current value of the current If, and the horizontal axis represents time. As shown in FIGS. 6A and 6B, the driving unit 120, which is a current driving circuit, may drive the light-emitting unit 110 with a current If having a pulse-shaped waveform. FIG. 6A represents a current pulse at high temperature, and FIG. 6B represents a current pulse at low temperature. As can be seen from the comparison between FIGS. 6A and 6B, in the method of this embodiment, the amplitude value of the current If (the value on the vertical axis during the current supply period Δt) is set relatively low at low temperatures. In the examples of FIGS. 6A and 6B, the duty of the pulse is constant. The duty is the ratio of the length of the current supply period Δt to the length of one cycle of the pulse.

[0031] As shown in the temperature characteristics of FIG. 5, if the amplitude value of the current If decreases, the forward voltage Vf of the light-emitting element 111 also decreases. Therefore, in the method of this embodiment, even at low temperatures, the forward voltage Vf is suppressed from becoming excessively large, so that the maximum value of the voltage VLED that the power supply unit 130 should supply to one end of the light-emitting unit 110 can also be suppressed. As a result, since the power that the power supply unit 130 should supply is also suppressed, the specifications that the power supply unit 130 should meet can be kept low.

[0032] For example, at the start of operation of the light-emitting device 100, the light-emitting unit 110 is at a low temperature, and it is conceivable that the temperature of the light-emitting unit 110 rises as the operation continues. In this case, in the conventional method, since an attempt is made to drive the light-emitting unit 110 with a high amplitude value from the start of operation, the required voltage VLED and power increase. In this regard, in the present embodiment, since the amplitude value of the current If is suppressed at the start of operation when the light-emitting unit 110 is likely to be at a low temperature, the power at low-temperature startup can be reduced.

[0033] 2. Duty control In the above, an example has been described in which the amplitude value of the current If is relatively reduced at low temperature and the duty is set to be about the same as that at high temperature. However, the method of the present embodiment is not limited to this.

[0034] For example, the control unit 140 may determine the amplitude and duty of the current If based on the temperature of the light-emitting unit 110, and output the amplitude and duty of the current If to the driving unit 120. The driving unit 120 controls the voltage VLED supplied by the power supply unit 130 to one end of the light-emitting unit 110 based on the amplitude and duty acquired from the control unit 140. In this way, in addition to the amplitude, control of the duty becomes possible, so that it becomes possible to appropriately set the power supplied by the power supply unit 130 and the luminance of the light-emitting element 111. Details will be described below.

[0035] FIG. 7 is a diagram showing another configuration example of the control unit 140. The control unit 140 may include a determination unit 141, an amplitude setting unit 143, and a duty setting unit 145. The determination unit 141 obtains a magnification with respect to the reference amplitude and a magnification with respect to the duty of the reference current If (hereinafter referred to as the reference duty) based on the temperature of the light-emitting unit 110 acquired from the temperature acquisition unit 150.

[0036] FIG. 8 is an example of table data showing the relationship between the temperature of the light emitting unit 110 and the magnification of the current If. For example, a memory (not shown) of the light emitting device 100 may store the table data shown in FIG. 8. The determination unit 141 reads the table data from the memory, and determines the magnification of the amplitude and the duty based on the temperature (LED temperature) of the light emitting unit 110 acquired from the temperature acquisition unit 150 and the table data. As shown in FIG. 8, the determination unit 141 sets the magnification of the duty to a value greater than 1 in a temperature range where the magnification of the amplitude is less than 1. Narrowly speaking, the determination unit 141 may set the magnification of the duty to be (1 / magnification of the amplitude).

[0037] The amplitude setting unit 143 determines the amplitude value of the current If by multiplying the magnification of the amplitude obtained by the determination unit 141 with respect to the reference amplitude. The amplitude setting unit 143 outputs the obtained amplitude value to the driving unit 120.

[0038] The duty setting unit 145 determines the duty of the current If by multiplying the magnification of the duty obtained by the determination unit 141 with respect to the reference duty. The duty setting unit 145 outputs the obtained duty value to the driving unit 120.

[0039] As described above, when the temperature of the light emitting unit 110 is lower than the temperature threshold, the control unit 140 may perform control to increase the duty as compared with the case where the temperature of the light emitting unit 110 is equal to or higher than the temperature threshold. The driving unit 120 drives the light emitting unit 110 using the current If (specifically, a pulse current) having the amplitude and duty output from the control unit 140. According to the method of the present embodiment, since the amplitude is small at low temperatures, it is possible to suppress an increase in the forward voltage Vf of the light emitting element 111. Further, in the method of the present embodiment, since the duty is large at low temperatures, a decrease in the amount of current supplied to the light emitting element 111 per unit time (for example, one cycle of a pulse wave) is suppressed. For example, as described above, when each magnification is set so that the product of the magnification of the amplitude and the magnification of the duty is 1, the product of the amplitude value of the current If and the duty is maintained constant regardless of the temperature. For example, when the light emitting element 111 is an LED whose luminance is controlled by the amount of current, according to the method of the present embodiment, it is possible to maintain the luminance of the light emitting element 111 even at low temperatures.

[0040] FIGS. 9A and 9B are diagrams showing examples of the current If. The vertical axis in FIGS. 9A and 9B represents the current value of the current If, and the horizontal axis represents time. FIG. 9A represents a current pulse at high temperature, and FIG. 9B represents a current pulse at low temperature. As can be seen from a comparison between FIGS. 9A and 9B, in the method of the present embodiment, the amplitude value of the current If is set relatively low at low temperatures. Thereby, since the forward voltage Vf of the light emitting element 111 becomes small, it is possible to suppress the voltage VLED supplied by the power supply unit 130 and the power consumption.

[0041] Furthermore, in the present embodiment, the duty of the current If is set relatively high at low temperatures. Therefore, the amount of current in one cycle of the pulse wave (the area obtained by time-integrating the pulse wave) becomes larger than the case where the duty is not controlled (FIG. 6B), so that a decrease in luminance is suppressed. That is, it is possible to suppress a decrease in the brightness of the light emitting unit 110 while suppressing the specifications required for the power supply unit 130.

[0042] In the above description, an example in which the product of the amplitude value of the current If and the duty is constant regardless of the temperature has been described. However, the specific amplitude and duty values are not limited to this, and various modifications can be made. Also, the point that the amplitude and duty may be set using a function or the like instead of table data is the same as in the above-described example.

[0043] Figures 10A - 10C are diagrams summarizing the relationships between the respective parameters and the temperature in the method of this embodiment. The horizontal axis of Figures 10A - 10C represents the temperature of the light-emitting unit 110. The vertical axis of Figure 10A represents the amplitude and duty of the current If supplied to the light-emitting unit 110. As described above, when the temperature of the light-emitting unit 110 decreases, the amplitude value decreases and the duty value increases.

[0044] The vertical axis of Figure 10B represents the luminance of the light-emitting element 111. The luminance is determined, for example, based on the product of the amplitude and duty of the current If. As shown in Figure 10A, when the temperature is low, as the amplitude decreases, the duty increases. Therefore, as shown in Figure 10B, the luminance of the light-emitting element 111 is maintained constant regardless of the temperature.

[0045] The vertical axis of Figure 10C represents the voltage VLED that the power supply unit 130 supplies to one end of the light-emitting unit 110. Also, since the power is proportional to the value of the voltage VLED, Figure 10C can also be considered as a diagram showing the relationship between the power consumption and the temperature. As described above, by reducing the amplitude value of the current If at low temperatures, an increase in the forward voltage Vf of the light-emitting element 111 can be suppressed. As a result, an increase in the voltage VLED (see, for example, the above formula (1)) determined based on the forward voltage Vf can also be suppressed at low temperatures.

[0046] Figures 11A - 11C are diagrams summarizing the relationships between the respective parameters and the temperature in the comparative example of this embodiment. The values of the vertical axis and the horizontal axis in each figure are the same as in Figures 10A - 10C. Here, as a comparative example, a method that does not consider the temperature of the light-emitting unit 110 is considered.

[0047] As shown in FIG. 11A, in the comparative example, since the temperature of the light-emitting unit 110 is not considered, the amplitude and duty of the current If are constant regardless of the temperature. In this case, as shown in FIG. 11B, it is possible to maintain the brightness of the light-emitting unit 110.

[0048] However, since the amplitude of the current If is maintained, as described above with reference to FIG. 5, the forward voltage Vf of the light-emitting element 111 increases at low temperatures. As a result, in the comparative example, as shown in FIG. 11C, the voltage VLED at low temperatures becomes large, so the power consumption also increases. As can be seen from the comparison between FIG. 10C and FIG. 11C, the method of the present embodiment can achieve the effect of suppressing the voltage VLED (and power consumption) at low temperatures.

[0049] 3. Display device and area division The light-emitting device 100 of the present embodiment may include a light-emitting unit 160 having a plurality of light-emitting units 110. And the light-emitting unit 160 may be divided into a plurality of areas. Each of the plurality of areas here includes one or more light-emitting units 110.

[0050] And the temperature acquisition unit 150 may acquire the temperature of the light-emitting unit 110 for each of the plurality of areas. For example, when the light-emitting unit 160 is divided into first to Nth areas (N is an integer of 2 or more), the temperature acquisition unit 150 may include first to Nth temperature acquisition units. And the i-th temperature acquisition unit (i is an integer of 1 or more and N or less) detects the temperature of the light-emitting unit 110 included in the i-th area.

[0051] The control unit 140 determines the amplitude to be output to the driving unit 120 for each of the plurality of areas. The point that the control unit 140 may determine the duty is the same as the above-described example. That is, the control unit 140 may determine the amplitude and duty to be output to the driving unit 120 for each of the plurality of areas.

[0052] In this way, when the light-emitting device 100 includes the light-emitting unit 160 divided into a plurality of areas, it becomes possible to set the amplitude and duty of the current If for each area. As a result, the power supply unit 130 can supply, as VLED, a voltage suitable for the target area for each of the first to Nth areas. In other words, the power supply unit 130 can also vary the voltage VLED according to the area. Therefore, for example, while suppressing the power supplied to some areas, it becomes possible to appropriately operate the light-emitting unit 110 while suppressing the specifications required for the power supply unit 130, such as increasing the power supplied to other areas.

[0053] The method of this embodiment may be applied to the display device 200 including the above-described light-emitting device 100. FIG. 12 is a diagram showing an example of the external configuration of the display device 200. As shown in FIG. 12, the display device 200 includes a display 210, and the light-emitting unit 160 constitutes the display. For example, the display device 200 is a television device including a liquid crystal display, and the light-emitting unit 160 may be a backlight of the liquid crystal display. According to the method of this embodiment, it becomes possible to reduce the power consumption of the display device 200.

[0054] Also, the area set in the above-described light-emitting unit 160 may be a local dimming area. Local dimming is a method of dividing the backlight into a plurality of areas and controlling the brightness of the backlight for each area. In this way, it becomes possible to flexibly control the brightness of the light-emitting unit 110 in each local dimming area.

[0055] For example, the control unit 140 may control only the amplitude of the current If in a local dimming area where luminance is not required, and may control the amplitude and duty of the current If in a local dimming area where high luminance is required.

[0056] Further, the control unit 140 only needs to suppress the power consumption of the entire light emitting unit 160. Therefore, when there is power margin by suppressing the brightness of some local dimming areas, it is not necessary to suppress the brightness of other local dimming areas. For example, the control unit 140 may execute control to suppress the amplitude of the current If at low temperatures in some local dimming areas, and it is not necessary to execute the control in other local dimming areas. In this case, since the amplitude is not suppressed in the other local dimming areas, it becomes possible to realize the brightness (maximum brightness) that maximally exhibits the performance of the light emitting element 111. The maximum brightness here is, for example, the brightness when the amplitude and the duty are the maximum values allowed. By doing so, since the performance of the light emitting element 111 can be sufficiently exhibited even at low temperatures, it becomes possible to increase the contrast while suppressing the power consumption.

[0057] For example, the control unit 140 may acquire information on the target brightness set for each of a plurality of local dimming areas. Then, the control unit 140 counts the number of low brightness areas, which are local dimming areas where the target brightness is equal to or lower than the first brightness threshold Th1. If there are many low brightness areas, it means that there are many local dimming areas where there is no problem even if the amplitude of the current If is small, and it is considered that there is a margin in power consumption for the entire light emitting unit 160. Therefore, in this case, the control unit 140 does not execute control to suppress the amplitude of the current If even at low temperatures for high brightness areas where the target brightness is equal to or higher than the second brightness threshold Th2 (the second brightness threshold Th2 is a number equal to or higher than the first brightness threshold Th1). Note that the determination of whether there is a power margin is not limited to the above example, and various modifications such as calculating the power consumption in each local dimming area in detail are possible.

[0058] Although the present embodiment has been described in detail as above, those skilled in the art will easily understand that many modifications are possible without substantially departing from the novel matters and effects of the present embodiment. Therefore, all such modified examples are intended to be included within the scope of the present disclosure. For example, in the specification or drawings, a term that is described at least once together with a broader or synonymous different term can be replaced with that different term at any location in the specification or drawings. Also, all combinations of the present embodiment and modified examples are included within the scope of the present disclosure. Further, the configuration and operation of the light-emitting device, display device, etc. are not limited to those described in the present embodiment, and various modified implementations are possible.

Explanation of Reference Numerals

[0059] 100... Light-emitting device, 110... Light-emitting unit, 111... Light-emitting element, 120... Driving unit, 121... Driving element, 123... Voltage acquisition unit, 125... Control signal output unit, 130... Power supply unit, 140... Control unit, 141... Determination unit, 143... Amplitude setting unit, 145... Duty setting unit, 150... Temperature acquisition unit, 160... Light-emitting unit, 200... Display device, 210... Display, If... Current, Vf... Forward voltage, VFET... Voltage (voltage applied to the driving element, second voltage), VLED... Voltage (voltage supplied by the power supply unit), Δt... Current supply period

Claims

1. A light-emitting unit having one or more semiconductor light-emitting elements; A power supply unit that supplies power to the light-emitting unit; A drive unit having a drive element that drives the light-emitting unit; A temperature acquisition unit that acquires the temperature of the light-emitting unit; A control unit that determines the amplitude of the current flowing through the light-emitting unit based on the temperature of the light-emitting unit and outputs the amplitude to the drive unit; Comprising; The drive unit is; A light-emitting device that controls the voltage supplied by the power supply unit to one end of the light-emitting unit based on the amplitude acquired from the control unit.

2. In claim 1, The control unit is; When the temperature of the light-emitting unit is less than a temperature threshold, a control is performed to make the amplitude smaller than when the temperature of the light-emitting unit is greater than or equal to the temperature threshold. A light-emitting device.

3. In claim 2, The control unit is; Based on the temperature of the light-emitting unit, the amplitude and duty of the current are determined, and the amplitude and duty of the current are output to the drive unit, The drive unit is; A light-emitting device that controls the voltage supplied by the power supply unit to one end of the light-emitting unit based on the amplitude and duty acquired from the control unit.

4. In claim 3, The control unit is; When the temperature of the light-emitting unit is less than the temperature threshold, a control is performed to increase the duty compared to when the temperature of the light-emitting unit is greater than or equal to the temperature threshold. A light-emitting device.

5. In any one of claims 1 to 4, The drive unit is; A light-emitting device that controls the voltage supplied by the power supply unit to one end of the light-emitting unit based on a second voltage that is the voltage applied to the drive element.

6. In any one of claims 1 to 4, Having a plurality of the light-emitting units and including a light-emitting portion divided into a plurality of areas, The temperature acquisition unit acquires the temperature of the light-emitting unit for each of the plurality of areas, The control unit determines the amplitude to be output to the drive unit for each of the plurality of areas. A light-emitting device.

7. A display device including the light-emitting device according to any one of claims 1 to 4.

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