KR20170019304A - Luminous element driving system - Google Patents

Abstract

A luminous device driving system comprises: an electrochemiluminescence device emitting light by an oxidation and reduction reaction; an optical sensor configured to measure a change in brightness of the electrochemiluminescence device, and to output a brightness value corresponding to the measured change in the brightness; a controller configured to control a driving frequency of each of a plurality of alternating current voltage signals that are applied to the electrochemiluminescence device, according to a comparison result of the brightness value and a reference value; and a driving circuit configured to apply the alternating current voltage signals having a controlled driving frequency to the electrochemiluminescence device according to control of the controller. The controller reduces the driving frequency when the brightness value is less than the reference value, and increases the driving frequency when the brightness value is greater than or equal to the reference value.

Description

[0001] LUMINOUS ELEMENT DRIVING SYSTEM [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to a light emitting device driving system, and more particularly, to a display device including an electrochemiluminescence (hereinafter referred to as an ECL) device.

With the development of the information communication industry, the use of display devices is increasing. In recent years, a display device that satisfies the conditions of low power, light weight, thin shape, and high resolution has been demanded. Organic light emitting display devices or ECL devices using organic light emitting characteristics have been developed in response to these demands.

An organic light emitting display device is a next-generation display device having self-emission characteristics. However, in an organic light emitting display device, impurities may be accumulated in an electrode by a direct current driving method. As a result, the organic light emitting display has a low stability, and it is necessary to improve the charge transfer problem in the multi-layer hybrid structure.

An ECL device is a light emitting device that combines the features of electroluminescence (EL) and chemiluminescence (CL) devices. Since the ECL element can be driven at a low voltage, it can have an improved lifetime as compared with the EL element. Further, the ECL element can be driven by an AC voltage. The ECL device can emit light through an oxidation and reduction reaction according to the application of an AC voltage.

It is an object of the present invention to provide a light emitting device driving system capable of adjusting a driving frequency of an AC voltage applied to two electrodes of an ECL device.

The light emitting device driving system according to the embodiment of the present invention measures the brightness change of the electrochemical light emitting device and the electrochemical light emitting device that emits light by the oxidation and reduction reaction and outputs a brightness value corresponding to the change in brightness to the measured temperature A controller configured to adjust a driving frequency of each of a plurality of AC voltage signals applied to the electrochemical light emitting device according to a result of comparison between the brightness value and the reference value; And a driving circuit configured to apply a plurality of AC voltage signals having the adjusted driving frequency to the electrochemical light emitting device under the control of the controller, wherein the controller decreases the driving frequency when the brightness value is smaller than the reference value , And if the brightness value is equal to or greater than the reference value, the driving frequency is increased.

According to the embodiments of the present invention as described above, an ECL device capable of maintaining a constant brightness without being affected by changes in the external environment can be provided. Thus, the power consumption efficiency of the ECL element can be improved and the lifetime can be increased.

1 is a block diagram illustrating a light emitting device driving system according to an embodiment of the present invention.
2 is a circuit diagram showing a method of driving an ECL element.
FIG. 3 is a graph illustrating a relationship between a driving frequency and brightness of an ECL device in the light emitting device driving system shown in FIG. 1. Referring to FIG.
4 is a block diagram illustrating a method of driving an ECL device according to an embodiment of the present invention.
5 is a timing diagram for an AC voltage signal having a period of a first time T1.
6 is a timing chart for an AC voltage signal applied at a period of a second time T2.
7 is a flowchart illustrating a method of driving a pixel according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing. In the accompanying drawings, the dimensions of the structures are enlarged from the actual size in order to clarify the present invention. The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by terms. Terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. The singular expressions include plural expressions unless the context clearly dictates otherwise.

In this application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a part or a combination thereof is described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Also, where a section such as a layer, a film, an area, a plate, or the like is referred to as being "on" another section, it includes not only the case where it is "directly on" another part but also the case where there is another part in between. On the contrary, where a section such as a layer, a film, an area, a plate, etc. is referred to as being "under" another section, this includes not only the case where the section is "directly underneath"

1 is a block diagram illustrating a light emitting device driving system according to an embodiment of the present invention. 1, the light emitting device driving system 100 may include an optical sensor 110, a controller 120, a driving circuit 130, and an electrochemiluminescence (ECL) device 140 .

The optical sensor 110 according to the embodiment of the present invention can measure a change in brightness of the ECL device 140. FIG. The optical sensor 110 may output a brightness value corresponding to the brightness of the measured ECL element 140. [ In some embodiments, the optical sensor 110 may be included in at least one of the controller 120, the driver circuit 130, and the display panel 140.

The controller 120 may receive the brightness value from the optical sensor 110. Based on the received brightness value, the controller 120 can control the operation of the driving circuit 130. [ Illustratively, the controller 120 may output a control signal CNTL for controlling the operation of the driving circuit 130 in accordance with the brightness value. The controller 120 can control the driving frequency of the driving signal output from the driving circuit 130 according to the brightness value. Illustratively, the controller 120 may compare the brightness value received from the optical sensor 110 with a reference brightness value and output a control signal CNTL. The control method of the controller 120 will be described in detail with reference to the drawings.

The driving circuit 130 may be connected to the ECL element 140 via a line L. [ In some embodiments,

The driving circuit 130 can output a driving signal for driving the ECL element 140. [ The drive signal may be an AC voltage signal. The driving circuit 130 can drive the ECL element 140 in response to the control signal CNTL of the controller 120. [ Illustratively, the driving circuit 130 can adjust the driving frequency of the driving signal in response to the control signal CNTL. This will be described in detail with the drawings below.

 The ECL element 140 may be connected to the driving circuit 130 via a line L. [ The ECL element 140 can be driven by a driving signal applied from the driving circuit 130. The ECL element 140 can be driven in the light emission mode, and the driving method of the ECL element 140 will be described in detail with reference to Fig. In some embodiments, the ECL element 140 may be used as a unit pixel constituting a display device. The ECL element 140 can be used as a light emitting element of the illumination device.

The light emitting element driving system 100 shown in FIG. 1 can drive the ECL element 140 using an AC voltage signal. The display device 100 can sense a temperature change of the display panel 140. [ The display apparatus 100 can adjust the driving frequency of the AC voltage signal according to the temperature change.

)은 수학식 1과 같은 방법으로 나타낼 수 있다.2 is a circuit diagram showing a method of driving an ECL element. 1 and 2, an AC voltage AC may be applied to the first substrate 143 and the second substrate 144 of the ECL device 140, respectively. The ECL element 140 can be driven by an AC voltage (AC). When a negative voltage is applied to each of the first substrate 143 and the second substrate 144, a plurality of molecules R may be reduced to a plurality of anions R- through a reduction reaction. When a positive voltage is applied to each of the first substrate 143 and the second substrate 144, a plurality of molecules R may be oxidized to a plurality of positive ions R + through an oxidation reaction. When a negative voltage and a positive voltage are alternately applied to the first substrate 143 and the second substrate 144 by the AC voltage AC, Anion (R-) and a plurality of cations (R +) can be bonded. A plurality of anions (R-) and a plurality of cations (R +) are bonded, so that a plurality of molecules (R *) in an excited state can be generated. The molecules R * of a plurality of excited states can emit light and the ECL element 140 can realize a light emitting mode through the emission of the molecules R * of a plurality of excited states. The ECL efficiency (which is the light emitting performance index of the ECL element 140)

) Can be expressed in the same manner as in Equation (1).

)은 ECL 소자(140)의 전체 전자의 수(number of faradaic electrons)에 대한 광자의 개수(number of emitted photons)의 비율로 나타낼 수 있다. 전체 전자의 수 대비 광자(R*)의 개수가 많을수록, ECL 소자(140)의 ECL 효율(

)은 증가할 수 있다. ECL 소자(140)는 외부 환경의 변화에 의해 ECL 효율(

)에 영향을 받을 수 있다. 예시적으로, ECL 소자(140)는 외부 온도에 의해 영향을 받을 수 있다. 외부 온도의 변화에 따른 ECL 소자(140)의 구동 방법은 도 3 내지 도 6을 통해 설명된다. Referring to Equation (1), the ECL efficiency

Can be expressed as a ratio of the number of emitted photons to the number of farad electrons of the ECL device 140. [ The greater the number of photons (R *) versus the total number of electrons, the greater the ECL efficiency of the ECL device 140

) Can be increased. The ECL element 140 may have ECL efficiency (< RTI ID = 0.0 >

). ≪ / RTI > Illustratively, the ECL device 140 may be affected by the external temperature. The driving method of the ECL device 140 according to the change of the external temperature will be described with reference to Figs.

FIG. 3 is a graph illustrating a relationship between a driving frequency and brightness of an ECL device in the light emitting device driving system shown in FIG. 1. Referring to FIG. Referring to FIGS. 1 and 2, the abscissa of the graph may represent an inverse value of temperature. The vertical axis of the graph can indicate the brightness of the ECL element 140. [

Illustratively, the reference brightness Ref of the ECL element 140 is determined based on the reference temperature value T0 of the graph and the reference driving frequency f0. Illustratively, the reference brightness Ref may be a brightness that can convey the correct color, brightness and saturation of the image information to the user.

Referring to FIG. 3, if the temperature of the display panel 140 has a first temperature value T1 higher than the reference temperature value T0, the brightness of the ECL device 140 can be reduced. In order to increase the brightness of the ECL element 140, the driving circuit 130 may increase the magnitude of the power applied to the ECL element 140. However, if the magnitude of the applied power is increased, the power efficiency of the light emitting element drive system 100 can be reduced. Therefore, instead of increasing the magnitude of the power applied to the ECL device 140, the controller 120 can adjust the driving frequency of the driving signal to the first driving frequency f1. The first drive frequency f1 is a drive frequency lower than the reference drive frequency f0. When the driving frequency is lowered, the brightness of the ECL element 140 can be increased without increasing the magnitude of the power.

Illustratively, if the temperature of the display panel 140 has a second temperature value T2 lower than the reference temperature value T0, the brightness of the ECL element 140 may increase. If the brightness of the ECL element 140 becomes higher than the reference brightness Ref, accurate image information can not be delivered to the user. Therefore, in order to reduce the brightness of the ECL element 140 to the reference brightness Ref, the controller 120 may adjust the driving frequency of the driving signal to the second driving frequency f2. The second driving frequency f2 is a driving frequency higher than the reference driving frequency f0. When the driving frequency becomes high, since the ECL element 140 can be reduced to the reference brightness Ref, accurate image information can be delivered to the user.

Referring to FIG. 3, the magnitude of the power applied to the ECL device 140 may not be adjusted by adjusting the driving frequency according to the change of the temperature value. Therefore, the power efficiency of the display apparatus 100 can be kept constant. Therefore, the light emitting element driving system 100 can consume a constant power, and the lifetime of the ECL element 140 can be increased.

4 is a block diagram illustrating a method of driving an ECL device according to an embodiment of the present invention. Referring to Figures 1 and 3, a method of driving the ECL device 140 is described. The ECL device 140 includes a first substrate 141, a second substrate 142, a first electrode 143, a second electrode 144, spacers 145, and a luminous element layer 146 . The first and second substrates 141 and 142 may be formed of glass or a transparent plastic substrate. The first substrate 141 may provide image information and light to the user in a first direction D1.

The first and second electrodes 143 and 144 may be transparent electrodes. The first electrode 143 may be formed under the first substrate 141. The second electrode 144 may be formed on the second substrate 142. The first and second electrodes 143 and 144 may be formed of at least one of a metal, a non-metal, and an oxide. Illustratively, the first and second electrodes 143 and 144 may be formed of indium tin oxide (ITO), indium zinc oxide (IZO), or transparent conductive oxide (TCO) . For example, the light transmittance of the first and second electrodes 143 and 144 may be 70% or more.

The spacers 250 may support between the first and second electrodes 143 and 144. When the ECL element 140 is fabricated, the length of the spacers 145 can be determined. Depending on the length of the spacers 145, the spacing between the first and second electrodes 143 and 144 may be determined.

The light emitting element layer 146 may be formed of a material that emits light through an electrochemical oxidation or reduction reaction. The light emitting device layer 146 may be formed of an electrochemiluminescent (ECL) material. The light emitting element layer 146 may be formed of at least one material selected from polycyclic aromatic compounds, heteroaromatic compounds, and organometallic compounds. The light emitting element layer 146 is oxidized or reduced by a driving signal supplied through the first and second electrodes 143 and 144. The light emitting element layer 146 can emit light by an oxidation or reduction reaction.

The driving circuit 130 may include a power supply terminal 131, a switch SW, an oscillator 132, a first buffer 133, and a second buffer 134. The power supply terminal 131 may supply the power voltage to the first and second electrodes 143 and 144 of the pixel PXnm. A switch SW may be connected between the power terminal 131 and the first electrode 143.

When the switch SW is connected, a power voltage may be applied to the first and second electrodes 143 and 144. The optical sensor 110 may measure a change in brightness of the ECL element 140 and transmit the brightness value according to the brightness change to the controller 120. [ The controller 120 may receive the brightness value from the optical sensor 110. According to the brightness value, the controller 120 may output a control signal CNTL for adjusting the driving frequency of the driving signal. The controller 120 may be coupled to an oscillator 132 of the drive circuit 130. Illustratively, if the temperature value is greater than the reference temperature value, the controller 120 may control the oscillator 132 such that the drive frequency of the drive signal decreases. When the temperature value becomes smaller than the reference temperature value, the controller 120 can control the oscillator 132 so that the driving frequency of the driving signal increases.

The oscillator 132 can output a drive signal having a specific frequency. The oscillator 132 may be connected between the switch SW and the first electrode 143. [ When the switch SW is connected, the oscillator 132 can receive the power supply voltage. The oscillator 132 can adjust the driving frequency according to the control signal CNTL. The oscillator 132 can output a driving signal having a regulated driving frequency.

The first buffer 133 may be connected between the oscillator 132 and the first electrode 143. The first buffer 133 may include an amplifier. The first buffer 133 may receive a drive signal having an adjusted drive frequency from the oscillator 132. [ The first buffer 133 can amplify and output the driving signal. The amplified driving signal may be transmitted to the first electrode 143 and the second buffer 134, respectively.

The second buffer 134 may receive the amplified drive signal. The second buffer 134 may include at least one of an inverter and a phase delay buffer. When the second buffer 134 is an inverter, the second buffer 134 may invert the phase of the amplified drive signal and output a signal having an inverted phase. When the second buffer 134 is a phase delay buffer, the second buffer 134 may delay the phase of the amplified driving signal by 180 ° and output a signal having a delayed phase. The signal output from the second buffer 134 may be applied to the second electrode 144. [ The ECL element 140 can emit light by a driving signal and can output image information.

5 is a timing chart for showing an AC voltage signal applied to the ECL element of FIG. 4 when the brightness value of the ECL element is larger than the reference value. 6 is a timing chart for showing an AC voltage signal applied to the pixel of FIG. 3 when the brightness value of the ECL element is smaller than a reference value.

5 is a timing diagram for an AC voltage signal having a period of a first time T1. 5 is a timing chart for a driving signal applied to the first electrode 143. FIG. Referring to FIGS. 4 and 5, the first driving signal Vecl1 and the second driving signal Vecl2 may be applied to the first electrode 143, respectively. Specifically, the first driving signal Vecll may be applied to the first electrode 143 during a part of the first time T1. The second driving signal Vecl2 may be applied to the first electrode 143 during the remaining period of the first time T1. In some embodiments, the first drive signal Vecll may be a positive voltage. The second driving signal Vecl2 may be a negative voltage.

A driving signal having a phase opposite to that shown in Fig. 5 may be applied to the second electrode 144. [ In addition, a driving signal having a phase delayed by 180 DEG from the phase of the signal shown in Fig. 5 may be applied to the second electrode 144. Fig. Accordingly, when the first driving signal Vecl1 is applied to the first electrode 143, the second driving signal Vecl2 may be applied to the second electrode 144. [ When the second driving signal Vecl2 is applied to the first electrode 143, the first driving signal Vecl1 may be applied to the second electrode 144. [

When the first driving signal Vecl1 is applied to the first electrode 143, the electrons injected into the material of the light emitting element layer 146 may move to the first electrode 143. [ As the electrons are moved, an oxidation reaction may occur in the first electrode 143. Radical cations can be generated in the phosphors of the light-emitting element layer 146 by the oxidation reaction.

When the second driving signal Vecl2 is applied to the second electrode 144, electrons are injected into the material of the light emitting element layer 146, and a reduction reaction may occur. By the reduction reaction, a radical anion can be generated in the phosphor for coloring at least one of green, blue, and white in the light emitting element layer 146.

When the first driving signal Vecl1 is applied to the second electrode 144, electrons injected into the material of the light emitting element layer 146 may move to the second electrode 144. [ As the electrons are moved, an oxidation reaction may occur in the second electrode 144. Radical cations can be generated in the phosphors of the light-emitting element layer 146 by the oxidation reaction.

When the second driving signal Vecl2 is applied to the first electrode 143, electrons are injected into the material of the light emitting element layer 146, and a reduction reaction may occur. By the reduction reaction, a radical anion can be generated in the phosphor for coloring at least one of green, blue, and white in the light emitting element layer 146. As such, the first and second driving signals Vecl1 and Vecl2 may be alternately applied to the first and second electrodes 143 and 144, respectively.

The radical cations and the radical anions generated in the light emitting element layer 146 by the first and second driving signals Vecl1 and Vecl2 can recombine while colliding with each other. At this time, the recombination energy generated by the recombination can turn the phosphor of the light emitting element layer 146 into an excited state. The phosphor of the light emitting element layer 146 in the excited state can emit light.

6 is a timing chart for an AC voltage signal applied at a period of a second time T2. When an AC voltage signal is applied to the ECL element 140 as shown in Fig. 6, it may be driven in the same manner as described with reference to Fig. 5 or the like. However, the second time T2 is longer than the first time T1. As shown in FIGS. 5 and 6, the controller 120 can adjust the frequency of each of the first and second driving signals Vecl1 and Vecl2.

An AC voltage may be applied to the ECL device 140 in the manner described with reference to FIGS. Depending on the brightness change of the ECL element 140, a frequency-regulated alternating voltage may be applied to the ECL element 140. Therefore, the brightness of the ECL element 140 can be kept constant, and the lifetime can be improved.

7 is a flowchart illustrating a method of driving a pixel according to an embodiment of the present invention. Referring to FIGS. 1 and 7, the optical sensor 110 may measure a change in brightness of the ECL device 140 (S110). The brightness of the ECL element 140 may vary depending on the external environment. Illustratively, the ambient temperature may be the light sensor 110 outputting the brightness value based on the measured brightness change.

The controller 120 may compare the brightness value received from the optical sensor 110 with a reference value (S120). If the temperature value is smaller than the reference value, step S130 may be performed. If the brightness value is equal to or greater than the reference value, step S140 may be performed.

If the brightness value is smaller than the reference value, the controller 120 may reduce the driving frequency of the driving signal (S130). If the brightness value is equal to or greater than the reference value, the controller 120 can increase the driving frequency of the driving signal (S140).

The ECL element 140 may be driven by a drive signal having an adjusted drive frequency. The ECL element 140 can display image information (S150).

As described with reference to the figures according to embodiments of the present invention, the ECL device 140 may be driven by an alternating voltage signal having a regulated drive frequency. By adjusting the driving frequency of the AC voltage signal, the ECL device 140 can be driven while maintaining a constant efficiency. The ECL element 140 can consume a constant power, so that the life can be improved.

As described above, an optimal embodiment has been disclosed in the drawings and specification. Although specific terms have been employed herein, they are used for purposes of illustration only and are not intended to limit the scope of the invention as defined in the claims or the claims. Therefore, those skilled in the art will appreciate that various modifications and equivalent embodiments are possible without departing from the scope of the present invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

100: display device
110: Light sensor
130: driving circuit
140: Display panel

Claims (1)

An electrochemical light-emitting device which emits light by an oxidation and reduction reaction;
An optical sensor configured to measure a brightness change of the electrochemical light emitting device and output a brightness value corresponding to the brightness change to the measured temperature;
A controller configured to adjust a driving frequency of each of a plurality of AC voltage signals applied to the electrochemical light emitting device according to the comparison result of the brightness value and the reference value; And
And a driving circuit configured to apply the plurality of AC voltage signals having the adjusted driving frequency to the electrochemical light emitting device under the control of the controller,
Wherein the controller decreases the driving frequency when the brightness value is smaller than the reference value and increases the driving frequency when the brightness value is equal to or greater than the reference value.

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