JP2015094814A - Light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make luminance of respective light-emitting sections uniform in all luminance when the significantly wide range of luminance is required for a light-emitting device.SOLUTION: A light-emitting device 10 includes a plurality of light-emitting regions 110 and a controller 120. The controller 120 applies a pulse current to each of the plurality of light-emitting regions 110 to control luminance thereof by controlling the electrical signal of the pulse current. The controller 120 controls a first period where a voltage rises and a second period where the voltage becomes a constant value in the electrical signal.

Description

  The present invention relates to a light emitting device.

  There is a light-emitting device having a plurality of light-emitting portions, such as a segment-type display device. In this light emitting device, it may be desired to align the luminance of the plurality of light emitting units. For example, in Patent Document 1, in a segment type display device, light is emitted by inputting a pulse voltage (electric signal) to each segment, and the peak value of a constant current supplied to each segment is emitted from the segment. It is described that the value is proportional to the area.

  Patent Document 2 describes that light is emitted by inputting a pulse current to each segment, and that the pulse width of the pulse current supplied to each segment is set to a value proportional to the area of the segment. .

JP 2003-15576 A JP 2000-47637 A

As a result of examination by the present inventors, the light emitting device has a plurality of light emitting portions, and the luminance range required for the light emitting device is very wide (for example, from about 1 cd / m ² to 1000 cd / m ² or more). In this case, it has been found that it is difficult to make the brightness of each light emitting unit uniform in all the brightnesses.

  As an example of the problem to be solved by the present invention, in a case where the range of luminance required for the light emitting device is very wide, it is possible to provide an example in which the luminance of each light emitting unit can be made uniform at all luminances.

The invention according to claim 1 includes a plurality of light emitting regions,
A control unit that controls the luminance of the plurality of light emitting regions by applying a pulse current to each of the plurality of light emitting regions and controlling an electric signal for generating the pulse current;
With
The control unit is a light emitting device that controls, for each light emitting region, a first period in which a forward voltage rises and a second period in which the forward voltage becomes a constant value in the electrical signal.

It is a block diagram which shows the function structure of the light-emitting device which concerns on embodiment. It is a figure which shows an example of the electric power which a control part outputs to a light emission area | region. It is a figure explaining the drive signal in the area | region enclosed by S of FIG. It is a figure explaining the drive signal in the area | region enclosed by S of FIG. It is a graph which shows the change of the relative value of the brightness | luminance of two light emission area | regions. It is a figure which shows the modification of FIG. It is a figure which shows the modification of FIG. It is a figure which shows the structure of the light-emitting device which concerns on an Example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

  In the following description, the control unit 120 is not a hardware unit configuration but a functional unit block. The control unit 120 is realized by an arbitrary arithmetic device, a memory, a program loaded in the memory, a storage medium such as a hard disk for storing the program, and an arbitrary combination of hardware and software centering on a network connection interface. . There are various modifications of the implementation method and apparatus.

(Embodiment)
FIG. 1 is a block diagram illustrating a functional configuration of a light emitting device 10 according to the embodiment. The light emitting device 10 according to the present embodiment includes a plurality of light emitting regions 110 and a control unit 120. The control unit 120 controls the luminance of the plurality of light emitting regions 110 by applying a pulse current to each of the plurality of light emitting regions 110 and controlling the pulse (electric signal) of the pulse current. Then, in the above-described pulse (electric signal), the control unit 120 includes a first period in which the forward voltage (luminance) for each light emitting region 110 rises, and a second period in which the forward voltage (luminance) becomes a constant value. The period is controlled for each light emitting region 110. Details will be described below.

  The light emitting region 110 has at least one light emitting element. The light emitting element is, for example, an organic EL (Organic Electroluminescence) element or an LED (Light Emitting Diode), but may be other types of light emitting elements. The light emitting area 110 is, for example, a segment in a segment type display device. In the example shown in this figure, the light emitting region 110a has a relatively large area, and the light emitting region 110b has a relatively small area. However, when the light emitting element of the light emitting region 110 is an organic EL element or LED, the plurality of light emitting regions 110 have substantially the same structure except for the area and the material and thickness of the organic layer.

  When the light emitting region 110 is represented by an equivalent circuit, a diode and a resistor are connected in series, and a capacitance is connected in parallel to the diode and the resistor. Then, depending on the length of the wiring from the control unit 120 to the light emitting element in the light emitting region 110 (that is, the magnitude of the resistance of the lead wiring) and the area of the light emitting element (that is, the magnitude of the parasitic resistance), Are different among the plurality of light emitting regions 110. In addition, the above-described capacitance varies among the plurality of light emitting regions 110 depending on the area of the light emitting element. Due to the size of these resistors and capacitors, the period in which the forward voltage rises differs for each light emitting region 110, and the luminance (voltage) rising characteristics of the light emitting region 110 differ.

  The light emitting area 110 may be a light emitting panel. In this case, the plurality of light emitting regions 110 have the same structure, but the lengths of the wirings from the control unit 120 to the light emitting region 110 are different from each other. For this reason, the rising characteristics of the luminance (voltage) of the light emitting region 110 are different due to the length of the wiring.

  The control unit 120 includes a control circuit that generates a control signal and a current control circuit that controls a current input to the light emitting region 110 based on the control signal. The control circuit and the current control circuit are formed, for example, on different semiconductor chips. The control circuit controls the luminance of the light emitting region 110 by, for example, a PWM (pulse width modulation) method. Further, the control circuit varies the shape and width of the pulse constituting the electric signal for each of the plurality of light emitting regions 110. The frequency of this electrical signal is, for example, 60 Hz or more and 500 Hz or less.

  Note that the set value of the luminance of the light emitting region 110 is input to the control unit 120 from the user of the light emitting device 10 via the input unit, for example. Then, the control unit 120 controls the shape and width of the pulse of the electric signal input to the plurality of light emitting areas 110 so that the luminance of the plurality of light emitting areas 110 becomes the set value that is input.

  FIG. 2 is a diagram illustrating an example of power output from the control unit 120 to the light emitting region 110. As described above, the control unit 120 applies pulsed power (electric signal) to the light emitting region 110. The luminance of the light emitting region 110 is controlled by adjusting the width and shape of the pulse. The width and shape of the pulse of the electrical signal are determined based on the resistance value and the capacity of the light emitting region 110.

  3 and 4 are diagrams for explaining the drive signals in the region surrounded by S in FIG. In each figure, (a) uses current values on the vertical axis, and (b) uses voltage (luminance) on the vertical axis. The electric signal shown in FIG. 3 is used to control the luminance of the light emitting region 110 having a relatively large area (for example, the light emitting region 110a in FIG. 1), and the electric signal shown in FIG. 4 has a relatively small area. This is used to control the luminance of the light emitting area 110 (for example, the light emitting area 110b in FIG. 1).

Specifically, as shown in FIG. 3, the control unit 120 inputs the same current value to the light emitting region 110a during both the first period when the voltage rises and the second period when the voltage is constant. (I ₁ = I ₂ ).

On the other hand, as shown in FIG. 4, the control unit 120, the light emitting region 110b, a current value _{I 1} of the first period, to be larger than the current value _{I 2} of the second period.

That is, in the example shown in FIGS. 3 and 4, the control unit 120 makes I ₁ / I ₂ different between the light emitting region 110a and the light emitting region 110b. Specifically, I ₁ / I ₂ (first relative value) in the light emitting region 110a is made smaller than I ₁ / I ₂ (second relative value) in the light emitting region 110b. In addition, I ₁ / I ₂ in the light emitting region 110a is 1, and I ₁ / I ₂ in the light emitting region 110b is larger than 1. Here, in any case of FIGS. 3 and 4, the current value I _{2 in} the second period is the same in each of the plurality of light emitting regions 110 so that the luminance is equal to each other while the current value I ₂ is flowing. Is set. Note that the length of the first period is preferably common to all the light emitting regions 110.

The electrical signal shown in FIG. 3 is used when controlling the luminance of the light emitting region 110 having a relatively small lead wire resistance, and the electrical signal shown in FIG. 4 is a light emission having a relatively large lead wire resistance. It may be used when controlling the luminance of the area 110. Therefore, _{I 2} in the light emitting region 110a is larger than _{I 2} in the light emitting region 110b.

  3 is used when controlling the luminance of the light emitting region 110 having relatively high light emission efficiency (ie, low parasitic resistance), and the electric signal shown in FIG. 4 is relatively high in light emission efficiency. May be used when controlling the luminance of the light emitting region 110 having a low (ie, high parasitic resistance).

FIG. 5 is a graph showing a change in the relative value of the luminance of the light emitting areas 110a and 110b. The x axis is the luminance of the light emitting region 110b, and the y axis is the luminance of the light emitting region 110a. In the example shown in the figure, the control unit 120 performs general PWM control on the light emitting areas 110a and 110b. Therefore, light emission in both the regions 110a and the light emitting region 110b, the current value of the first period _{I 1} that same value is used for the current value _{I 2} of the second period _{(I 1 /} I 2 = 1). In addition, the control unit 120 controls the light emitting areas 110a and 110b to have the same luminance at any luminance.

  As a result of studies by the present inventors, the following has been found. First, when the light emitting region 110b emits light with a certain luminance (hereinafter referred to as luminance c), the luminance of the light emitting region 110a has the same value as the luminance of the light emitting region 110b. On the other hand, when the light emitting regions 110a and 110b are controlled to have a luminance smaller than the luminance c, the luminance of the light emitting region 110a is higher than the luminance of the light emitting region 110b (y is larger than the graph of x = y). On the other hand, when the light emitting areas 110a and 110b are controlled to a brightness higher than the brightness c, the brightness of the light emitting area 110a is lower than the brightness of the light emitting area 110b (y is smaller than the graph of x = y). Such a tendency is caused when the area of the light emitting region 110a is larger than the area of the light emitting region 110b, when the resistance of the lead wiring of the light emitting region 110a is smaller than the resistance of the lead wiring of the light emitting region 110b, or Appears when the luminous efficiency is higher than the luminous efficiency of the light emitting region 110b.

On the other hand, when the luminance of the light emitting region 110 is controlled by the pulse width of the electric signal, when the luminance of the light emitting region 110 is lowered, the second period is shortened (or becomes 0), so that the magnitude of I ₁ is 110 brightness is greatly affected. On the other hand, when the luminance of the light emitting region 110 is increased, the second period becomes longer, and thus the magnitude of I ₂ greatly affects the luminance of the light emitting region 110. For this reason, as in this embodiment, I ₁ / I ₂ (first relative value) in the light emitting region 110a is made different (eg, made smaller) than I ₁ / I ₂ (second relative value) in the light emitting region 110b. ) And lowering the luminance of the light emitting region 110a when the luminance is low, and increasing the luminance of the light emitting region 110a when the luminance is high. Therefore, it is possible to suppress the luminance of the light emitting areas 110a and 110b from being different from each other in a wide luminance range. In particular, when the luminance range of the light emitting region 110 is large (for example, when the maximum luminance value is 1000 times or more the minimum luminance value), the luminance uniformity according to the present embodiment becomes remarkable.

  Further, when the luminance of the light emitting region 110 is low and is equal to or lower than the reference value, the pulse output from the control unit 120 to the light emitting region 110 is only part or all of the first period. Even in such a low luminance case, according to the present embodiment, the luminance uniformity of the plurality of light emitting regions 110 is increased. The reference value described above varies depending on the structure of the light emitting device 10.

6 and 7, in the light emitting region 110b, the same current value is input in both the first period and the second period (I ₁ = I ₂ ), and then the light emitting region in 110a, a current value _{I 1} of the first period may be smaller than the current value _{I 2} of the second period.

  FIG. 8 is a diagram illustrating a configuration of the light emitting device 10 according to the embodiment. In the example shown in the figure, the light emitting device 10 has light emitting regions 110a, 110b, and 110c. The light emitting area increases in the order of the light emitting regions 110c, 110a, and 110b. In addition, the lead wire 130a that connects the control unit 120 and the light emitting region 110a is shorter than the lead wire 130b that connects the light emitting region 110b and the control unit 120, and is longer than the lead wire 130c that connects the light emitting region 110c and the control unit 120. .

Then, the control unit 120, the _I 1 / _{I 2} in the light emitting region 110a, and less than _I 1 / _{I 2} in the light emitting region 110b, and is made larger than _I 1 / _{I 2} in the light emitting region 110c. For this reason, also in this embodiment, the luminance of the light emitting regions 110a, 110b, and 110c can be made uniform over a wide luminance range.

  As mentioned above, although embodiment and the Example were described with reference to drawings, these are illustrations of this invention and can also employ | adopt various structures other than the above.

DESCRIPTION OF SYMBOLS 10 Light-emitting device 110 Light-emitting area 120 Control part 130a, 130b, 130c Lead wiring

Claims (7)

Multiple light emitting areas;
A control unit that controls the luminance of the plurality of light emitting regions by applying a pulse current to each of the plurality of light emitting regions and controlling an electric signal for generating the pulse current;
With
In the electrical signal, the control unit controls, for each light emitting region, a first period in which a forward voltage rises and a second period in which the forward voltage becomes a constant value. The light-emitting device according to claim 1.
The first relative value, which is the ratio of the current value of the first period to the current value of the second period in the first light emitting region, is the current value of the second period in the second light emitting region. A light emitting device having a value different from a second relative value that is a ratio of current values in the first period. The light-emitting device according to claim 2.
The area of the first light emitting region is larger than the area of the second light emitting region,
The light emitting device, wherein the first relative value is smaller than the second relative value. The light-emitting device according to claim 2.
The resistance of the lead wiring of the first light emitting region is smaller than the resistance of the lead wiring of the second light emitting region,
The light emitting device, wherein the first relative value is smaller than the second relative value. The light-emitting device according to claim 2.
The luminous efficiency of the first light emitting region is higher than the luminous efficiency of the second light emitting region,
The light emitting device, wherein the first relative value is smaller than the second relative value. The light emitting device according to claim 3.
The light emitting device, wherein the second relative value is greater than 1. The light-emitting device according to claim 6.
The control unit is a light-emitting device in which, when the luminance is equal to or less than a reference value, the electrical signal is only part or all of the first period.

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