KR100825411B1 - Ambient light sensor circuit and flat panel device having it - Google Patents

Abstract

An ambient light sensing circuit and a flat panel display having the same are provided to improve visibility of the display by regulating output voltage level according to the ambient brightness. A transistor(T1) is connected to a first voltage source. A first capacitor(C1) is electrically connected between the transistor and a reference voltage source. A second capacitor(C2) is connected between the first voltage source and the reference voltage source and between the transistor and the reference voltage source. A photo detector(PD) is electrically connected to the reference voltage source and generates a current according to the ambient brightness. The photo detector adjusts the voltage of the first capacitor according to coupling between the first and second capacitors. A first switch(S1) is connected to the transistor and outputs a current from the first voltage source through the transistor.

Description

AMBIENT LIGHT SENSOR CIRCUIT AND FLAT PANEL DEVICE HAVING IT}

1A and 1B are circuit diagrams illustrating an ambient light sensing circuit according to the present invention.

2 is a timing diagram of an ambient light sensing circuit in accordance with the present invention.

Figure 3 shows the current flow during the initialization period by the ambient light sensing circuit of the present invention.

Figure 4 shows the current flow during the ambient light sensing period by the ambient light sensing circuit of the present invention.

5 shows the current flow during the sampling period by the ambient light sensing circuit of the present invention.

6A to 6C are graphs simulating changes in output current according to changes in ambient light of the ambient light sensing circuit according to the present invention.

7 is a block diagram illustrating a state in which an ambient light control processor is further connected to an ambient light sensing circuit according to the present invention.

8 is a block diagram illustrating a configuration of a flat panel display device having an ambient light sensing circuit according to the present invention.

FIG. 9A is a circuit diagram illustrating an example of a pixel circuit in an organic EL panel of the flat panel display, and FIG. 9B is a timing diagram thereof.

Fig. 10A is a block diagram showing the configuration of a flat panel display device having another ambient light sensing circuit according to the present invention, and Fig. 10B is a timing diagram thereof.

Fig. 11A is a block diagram showing the configuration of a flat panel display device having another ambient light sensing circuit according to the present invention, and Fig. 11B is a timing diagram thereof.

12 is a block diagram illustrating a configuration of a flat panel display device having another ambient light sensing circuit according to the present invention.

FIG. 13 is a block diagram specifically illustrating an example of the inverter illustrated in FIG. 12.

<Description of Symbols for Main Parts of Drawings>

100; Ambient light sensing circuit T1; transistor

C1; First capacitive element C2; Second capacitive element

C3; Third capacitive element PD; Light receiving element

S1; First switch S2; Second switch

S3; Third switch S4; 4th switch

S5; Fifth switch S6; 6th switch

110; Current load 120; Output load

200; Ambient light control processor 210; Analog to digital converter

220; First memory 230; Control

240; Second memory 300; Timing control

310; Brightness selector 320; Lookup table

400; A data driver 500; Organic electroluminescent panels

600; Scan driver 700; Light emission control driver

800; Power control unit

910; Inverter 911; PWM control

912; Converter 913; Current detector

920; Backlight 930; Gate driver

940; A data driver 950; Liquid crystal display panel

The present invention relates to an ambient light sensing circuit and a flat panel display device having the same, and more particularly, to accurately detect the ambient brightness, and to automatically adjust the screen brightness according to the ambient brightness by using the same. The present invention relates to an ambient light sensing circuit that can be implemented and a flat panel display having the same.

In general, a flat panel display means an organic light emitting display, a liquid crystal display, a plasma display, a field emission display, or the like. Such flat panel displays are not only thin, light in weight, but also increasingly small in power consumption, rapidly replacing conventional display devices made of Cathode Ray Tubes (CRTs). In addition, among the flat panel display devices, the organic light emitting display device and the liquid crystal display device can be easily manufactured in a small size, and can be used for a long time with a battery, and thus are widely used as display devices of portable electronic devices.

By the way, such a flat panel display device such as an organic light emitting display device or a liquid crystal display device can artificially adjust the screen brightness by a user's operation, but is generally designed to display the screen at a constant brightness regardless of the ambient brightness. For example, a conventional flat panel display is designed to have an optimal screen brightness in a room where ambient brightness is not bright. Therefore, the brightness of the screen is relatively too bright in a dark place, the brightness of the screen is relatively too small under sunlight, there is a problem in visibility.

In addition, since the brightness of the screen is set to be constant as described above, the conventional flat panel display has a problem in that the screen brightness is unnecessarily bright for a long time in a place where the surrounding brightness is relatively dark, thereby increasing the power consumption rate.

In addition, in the conventional flat panel display device, when manufacturing the ambient light sensing circuit for sensing the ambient brightness, a sensor, a substrate, and a processing circuit should be formed on a substrate separate from the main substrate on which the flat panel display panel is formed. By connecting, the size and thickness of the flat panel display device are increased, and power consumption is also increased.

The present invention is to overcome the above-mentioned conventional problems, an object of the present invention to provide an ambient light sensing circuit that can accurately detect the ambient brightness.

Another object of the present invention is to provide a flat panel display that can automatically adjust the brightness of the screen according to the ambient brightness.

Another object of the present invention is to provide an ambient light sensing circuit and a flat panel display having the same, which can implement an ambient light sensing circuit and a signal processing circuit as a low temperature crystallized polysilicon thin film transistor on a substrate on which a pixel circuit is formed.

In order to achieve the above object, the ambient light sensing circuit according to the present invention includes a transistor electrically connected to a first power source, a first capacitive element electrically connected between the transistor and a reference power source, the first power source and the transistor. And a second capacitive element electrically connected between the reference power source, and a second capacitive element electrically connected to the reference power source and flowing a current in response to ambient light. A light receiving element that adjusts the voltage of the first capacitive element through coupling; and electrically connected to the transistor, a current from the first power supply is output through the transistor according to the voltage of the first capacitive element. And a first switch to enable.

A second switch for applying a reference voltage from a reference power source may be further electrically connected to the first capacitive element and the second capacitive element.

A third switch may be further electrically connected between the control electrode of the transistor and the first switch.

The first switch may be further electrically connected to a fourth switch for allowing current through the first power source, transistor, first switch, and third switch to be consumed through the current load.

A fifth switch may be electrically connected to the first switch to allow the transistor to flow a constant current from the first power source to an output load in response to the voltage of the first capacitive element.

A third capacitive element may be further electrically connected to the light receiving element in order to increase the reverse bias capacity of the light receiving element.

A sixth switch may be further provided between the light receiving element and the third capacitive element to electrically connect them.

The light receiving device may be any one selected from a PIN diode, a PN diode, and a photo coupler.

The light receiving device may be any one selected from a PIN diode, a PN diode, and a photo coupler.

An ambient light control processor may be further electrically connected to the fifth switch.

The ambient light control processor is electrically connected to the output load, and converts the analog current value of the output load into a digital value, and is electrically connected to the analog and digital converter, the digital according to the current ambient light condition A first memory for storing a value, a controller electrically connected to the first memory to calculate and output a brightness of the current ambient light, a digital value electrically connected to the controller, and stored in advance from the ambient light having various brightnesses; The second memory may include.

In addition, to achieve the above object, a flat panel display device according to the present invention includes a transistor electrically connected to a first power source, a first capacitive element electrically connected between the transistor and a reference power source, the first power source, and the A second capacitive element electrically connected between a transistor and the reference power source, and a first capacitive element and the second capacitive element electrically connected to the reference power source and flowing current in response to ambient light. A light-receiving element for regulating the voltage of the first capacitive element through a coupling of and electrically connected to the transistor, and a current from the first power source through the transistor according to the voltage of the first capacitive element Ambient light sensing circuit comprising a first switch for outputting, and an analog output signal of the ambient light sensing circuit as an input signal A peripheral light control processor for calculating the current ambient light and outputting the digital value as a digital value, a timing controller for outputting a control signal suitable for the current ambient light using the output signal of the ambient light control processor as an input signal, and the timing controller. A data driver for outputting a data signal suitable for current ambient light by using an output signal of? And an organic electroluminescent panel that emits light with a brightness suitable for current ambient light using a data signal of the data driver as an input signal; Include.

The timing controller compares a lookup table storing data suitable for the current lighting and data obtained from the ambient light control processor with data stored in the lookup table, and selects a control signal suitable for the current lighting to select the data driver. It includes a brightness selection unit for outputting.

The data driver outputs a data voltage to output light proportional to the ambient light obtained from the ambient light sensing circuit.

In addition, to achieve the above object, a flat panel display device according to the present invention includes a transistor electrically connected to a first power source, a first capacitive element electrically connected between the transistor and a reference power source, the first power source, and the A second capacitive element electrically connected between a transistor and the reference power source, and a first capacitive element and the second capacitive element electrically connected to the reference power source and flowing current in response to ambient light. A light-receiving element for regulating the voltage of the first capacitive element through a coupling of and electrically connected to the transistor, and a current from the first power source through the transistor according to the voltage of the first capacitive element Ambient light sensing circuit comprising a first switch for outputting, and an analog output signal of the ambient light sensing circuit as an input signal An ambient light control processor for calculating current ambient light and outputting it as a digital value, a timing controller for outputting a control signal suitable for the current ambient light using an output signal of the ambient light control processor as an input signal, and A light emission control driver for outputting a light emission control signal suitable for the current ambient light by using the output signal as an input signal, and an organic electric field that emits light at a brightness suitable for the current ambient light using the light emission control signal of the light emission control driver as an input signal. It includes a light emitting panel.

The timing controller compares the lookup table storing data suitable for the current lighting and the data obtained from the ambient light control processing with the data stored in the lookup table, and selects a control signal suitable for the current lighting to emit the light. And a brightness selector output to the control driver.

The light emission control driver outputs a light emission control signal having a time proportional to the ambient light obtained from the ambient light sensing circuit.

In addition, to achieve the above object, a flat panel display device according to the present invention includes a transistor electrically connected to a first power source, a first capacitive element electrically connected between the transistor and a reference power source, the first power source, and the A second capacitive element electrically connected between a transistor and the reference power source, and a first capacitive element and the second capacitive element electrically connected to the reference power source and flowing current in response to ambient light. A light-receiving element for regulating the voltage of the first capacitive element through a coupling of and electrically connected to the transistor, and a current from the first power source through the transistor according to the voltage of the first capacitive element Ambient light sensing circuit comprising a first switch for outputting, and an analog output signal of the ambient light sensing circuit as an input signal An ambient light control processor for calculating current ambient light and outputting it as a digital value, a timing controller for outputting a control signal suitable for the current ambient light using an output signal of the ambient light control processor as an input signal, and A power supply control unit for outputting a power supply voltage suitable for current ambient light using the output signal as an input signal, and an organic electroluminescent panel for self-luminous by using the power supply voltage of the power supply control unit as an input signal.

The timing controller compares a lookup table storing data suitable for the current lighting and data obtained from the ambient light control processor with data stored in the lookup table, and selects a control signal suitable for the current lighting to control the power control unit. It includes a brightness selection unit for outputting.

The power control unit outputs a power supply voltage proportional to the ambient light obtained from the ambient light sensing circuit.

In addition, to achieve the above object, a flat panel display device according to the present invention includes a transistor electrically connected to a first power source, a first capacitive element electrically connected between the transistor and a reference power source, the first power source, and the A second capacitive element electrically connected between a transistor and the reference power source, and a first capacitive element and the second capacitive element electrically connected to the reference power source and flowing current in response to ambient light. A light-receiving element for regulating the voltage of the first capacitive element through a coupling of and electrically connected to the transistor, and a current from the first power source through the transistor according to the voltage of the first capacitive element Ambient light sensing circuit comprising a first switch for outputting, and an analog output signal of the ambient light sensing circuit as an input signal An ambient light control processor for calculating current ambient light and outputting it as a digital value, a timing controller for outputting a control signal suitable for the current ambient light using an output signal of the ambient light control processor as an input signal, and An inverter that boosts and outputs a power supply voltage according to current ambient light using an output signal as an input signal, a backlight that is lit by a voltage supplied from the inverter, and a liquid crystal display panel that displays a screen by the backlight. .

The timing controller compares a lookup table storing data suitable for the current lighting and data obtained from the ambient light control processing unit with data stored in the lookup table, and selects a control signal suitable for the current lighting to the inverter. It includes a brightness selection unit for outputting.

The inverter outputs a boosted voltage proportional to the ambient light obtained from the ambient light sensing circuit.

When the control signal is input from the timing controller, the inverter outputs a PWM control signal suitable for the control signal, and the output signal of the PWM controller is an input signal. And a current sensing unit for sensing a current through the backlight and feeding it back to the PWM controller.

As described above, the ambient light sensing circuit and the flat panel display having the same according to the present invention obtain various levels of output current according to the ambient light, and accordingly, automatically adjust the brightness of the screen through the display device, so that it is bright or dark. In all places, the visibility of a flat panel display device becomes excellent.

In addition, as described above, the flat panel display having the ambient light sensing circuit according to the present invention automatically adjusts the power consumption according to the ambient light, thereby maintaining the optimum power consumption, and thus the usable time of the portable flat panel display. This will be longer.

In addition, as described above, the ambient light sensing circuit and the flat panel display having the same according to the present invention may include an ambient light sensing circuit, an ambient light control processing unit, a timing controller, and an organic electroluminescent panel (or liquid crystal display panel) all on one common substrate. The silicon thin film transistor can be formed using a silicon thin film transistor process, thereby making the thickness of the flat panel display device even thinner.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings such that those skilled in the art may easily implement the present invention.

Here, the same reference numerals are attached to parts having similar configurations and operations throughout the specification. In addition, when a part is electrically connected to another part, this includes not only the case where it is directly connected but also the case where another element is connected in between.

1A and 1B are circuit diagrams illustrating an ambient light sensing circuit according to the present invention.

First, as shown in FIG. 1A, the ambient light sensing circuit 100 according to the present invention includes a transistor T1, a first capacitive element C1, a second capacitive element C2, and a third capacitive element C3. ), The light receiving element PD, the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, and the sixth switch S6. Include.

The transistor T1 includes a first electrode (source or drain), a second electrode (drain or source), and a control electrode (gate electrode). The transistor T1 may be any one selected from a polysilicon thin film transistor, an amorphous silicon thin film transistor, an organic thin film transistor, and an equivalent thereof, but is not limited to the type or material of the transistor T1.

In addition, when the transistor T1 is a polysilicon thin film transistor, it may be formed by a low temperature crystallization method such as a laser crystallization method, a metal induced crystallization method, or a high pressure crystallization method, but here, the method of manufacturing the polysilicon thin film transistor is limited. It is not.

For reference, the laser crystallization method is a method of crystallizing amorphous silicon, for example by irradiating an excimer laser, the metal-induced crystallization method is applied to the metal by applying a relatively high temperature with a metal, for example on the amorphous silicon Crystallization is started from the above, and the high-pressure crystallization method is a method of crystallizing amorphous silicon by applying a relatively high pressure, for example. In addition, the transistor T1 may be any one selected from a P-channel transistor, an N-channel transistor, and an equivalent thereof, but is not limited thereto. In the following description, it is assumed that the transistor T1 is a P-channel transistor.

The first capacitive element C1 may be electrically connected to the transistor T1. More specifically, in the first capacitive element C1, a first electrode is electrically connected to the light receiving element PD, that is, the first node N1, and the second electrode is a control electrode of the transistor T1. It may be electrically connected to the second node N2. The first capacitive element C1 is coupled with the second capacitive element C2, and serves to apply a voltage changed by the coupling to the control electrode of the transistor T1.

The second capacitive element C2 increases its reverse bias capacitance to the light receiving element PD so that the signal holding characteristic is improved. In the second capacitive element C2, a first electrode is electrically connected to a cathode of the light receiving element PD, that is, a fifth node N5, and the second electrode is an anode of the light receiving element PD, that is, a first electrode. It may be electrically connected to one node N1.

The third capacitive element C3 also increases the reverse bias capacitance of the light receiving element PD so that the signal holding characteristic is improved. In the third capacitive element C3, a first electrode may be electrically connected to the cathode of the light receiving element PD, and the second electrode may be electrically connected to a sixth switch S6 to be described below.

The light receiving element PD may be electrically connected between the first power source VDD, the first capacitive element C1, and the second capacitive element C2, that is, the first node N1. In the light receiving device PD, a cathode is electrically connected to the first power supply VDD, and an anode is connected to the first capacitive element C1 and the second capacitive element C2, It may be electrically connected to the first node N1. In addition, the light receiving element PD may be any one selected from a PIN diode, a PN diode, a photo coupler, and an equivalent thereof, but the type of the light receiving element PD is not limited thereto. The light receiving element PD serves to charge the second capacitive element C2 by flowing a current from the first power source VDD in response to ambient light.

In the first switch S1, a first electrode is electrically connected to the second electrode of the transistor T1, and the second electrode is a contact point of the fourth switch S4 and the fifth switch S5, that is, the third electrode. It may be electrically connected to the node N3. In addition, a first control signal may be applied to the control electrode of the first switch S1. The first switch S1 may be formed of any one selected from P-channel low temperature crystallized polysilicon and its equivalents, but is not limited thereto. The first switch S1 initializes the first capacitive element C1 to a constant voltage or is changed through coupling of the first capacitive element C1 and the second capacitive element C2. In response to the voltage of the first capacitive element C1, a predetermined amount of current flows from the first power supply VDD to the output load 120 through the transistor T1.

The second switch S2 is electrically connected between the reference power supply V _REF and the first node N1 to provide a reference voltage to the first capacitive element C1 and the second capacitive element C1. It serves to supply (V _REF ). That is, the second switch S2 has a first electrode electrically connected to the reference power supply V _REF , a second electrode electrically connected to the first node N1, and a second control to a control electrode. A signal can be applied. In addition, the second switch S2 may be any one selected from P-channel low-temperature crystallized polysilicon and its equivalents, but is not limited thereto. The reference power source and the reference voltage are denoted by the same reference numerals for convenience of description.

The third switch S3 is electrically connected between the first capacitive element C1 and the transistor T1 so that the first capacitive element C1 is initialized. That is, in the third switch S3, a first electrode is electrically connected to a second electrode of the first capacitive element C1, that is, the second node N2, and the second electrode is formed of the transistor T1. The second control signal may be electrically connected to two electrodes, that is, the fourth node N4, and the above-described second control signal may be applied to the control electrode. The third switch S3 may be any one selected from P-channel low-temperature crystallized polysilicon and its equivalents, but is not limited thereto.

The fourth switch S4 is electrically connected between the first switch S1 and the current load 110 so that the first capacitive element C1 and the first capacitive element C1 are initialized when the first capacitive element C1 is initialized. The current from the first power source VDD serves to flow toward the current load 110. In the fourth switch S4, the first electrode is electrically connected to the second electrode of the first switch S1, that is, the third node N3, and the second electrode is electrically connected to the current load 110. The third control signal may be applied to the control electrode. The fourth switch S4 may be any one selected from P-channel low-temperature crystallized polysilicon and its equivalents, but is not limited thereto.

The fifth switch S5 is electrically connected between the first switch S1 and the output load 120, and a constant current is output from the first power source VDD through the transistor T1. To flow). In the fifth switch S5, a first electrode is electrically connected to a second electrode of the first switch S1, that is, a third node N3, and a second electrode is electrically connected to the output load 120. The fourth control signal may be applied to the control electrode. The fifth switch S5 may be any one selected from P-channel low temperature crystallized polysilicon and its equivalents, but is not limited thereto.

The sixth switch S6 is electrically connected between the light receiving element PD and the third capacitive element C3 so that the third capacitive element C3 is connected in parallel to the light receiving element PD. Be sure to In the sixth switch S6, a first electrode is electrically connected to the second electrode of the third capacitive element C3, and the second electrode is an anode of the light receiving element PD, that is, the first node N1. The fifth control signal may be electrically connected to the control electrode. In addition, the sixth switch S6 may be any one selected from P-channel low-temperature crystallized polysilicon and its equivalents, but is not limited thereto.

Meanwhile, as illustrated in FIG. 1B, another ambient light sensing circuit 101 of the present invention may have a connection position of the light receiving device PD different from the circuit 100 described above. That is, as illustrated in FIG. 1B, the light receiving device PD may have a cathode electrically connected to the first node N1, and an anode electrically connected to the ground terminal GND. Therefore, in the circuit 100, when the reverse current flows through the light receiving element PD, the second capacitive element C2 is charged, but in the circuit 101 shown in FIG. 1B, the light receiving element PD is shown. When the reverse current flows through the second capacitive element C2, the second capacitor C2 is discharged. Therefore, in the circuit 100 shown in FIG. 1A, as the reverse current through the light receiving element PD increases, the voltage of the first capacitive element is relatively decreased due to the coupling of the first capacitive element and the second capacitive element. In the circuit 101 shown in FIG. 1B, the voltage of the first capacitive element is increased by coupling of the first capacitive element and the second capacitive element as the reverse current through the light receiving element PD increases. This becomes relatively small. Of course, the reference voltage V _REF is relatively higher than the ground voltage GND in the circuit 101 shown in FIG. 1B for this operation.

2 is a timing diagram of an ambient light sensing circuit in accordance with the present invention.

As shown, the ambient light sensing circuit 100 according to the present invention operates with one frame that the flat panel display outputs one screen, that is, a period of approximately 16.7 ms. Therefore, the flat panel display using the ambient light sensing circuit according to the present invention automatically adjusts the screen brightness in response to the ambient brightness.

The periphery sensing circuit 100 according to the present invention performs the initialization process T1 of the circuit for about 500 mW, performs the ambient light sensing process T2 for about 15 mW, and the sampling process T3 for about 500 mW. Do this. Of course, four control signals, that is, a first control signal, a second control signal, a third control signal, and a fourth control signal, are applied to the ambient light sensing circuit 100.

As described above, the present invention allows the ambient light sensing circuit 100 to perform the ambient light sensing process T2 for the longest time, thereby improving the ambient light sensing efficiency.

In addition, in the present invention, when the ambient light is relatively bright, the fifth control signal is further applied to the ambient light sensing circuit 100, but the timing diagram for the fifth control signal is omitted. However, the operation of the sixth switch S6 by the fifth control signal will be described in detail below.

The operation of the present invention will be described with reference to FIGS. 2 and 3 to 5.

3 is a circuit diagram showing the current flow during the initialization process (T1) by the ambient light sensing circuit 100 of the present invention.

As shown in FIGS. 2 and 3, in the initialization process T1, a low level first control signal is applied to the first switch S1, and a low level second control signal is applied to the second switch S2 and the second level. The third switch S3 is applied to the third switch S3, and a low level third control signal is applied to the fourth switch S4. Therefore, only the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 are turned on. Of course, the fifth switch S5 and the sixth switch S6 maintain the turn-off state.

Accordingly, the voltage V _REF of the reference power source is applied to the first electrode of the first capacitive element C1 through the second switch S2. In addition, a current path between the transistor T1, the first switch S1, the fourth switch S4, and the current load 110 connected in the form of a diode by the first power supply VDD and the third switch S3. Is formed. Therefore, a predetermined voltage V _A is applied to the second electrode of the first capacitive element C1. In other words, during the initialization period T1, the first capacitive element C1 is initialized while the voltage of V _REF -V _A is charged.

In addition, assuming that the potential of the first power supply VDD is relatively higher than the potential of the reference power supply V _REF , the second capacitive element C2 is charged with a voltage corresponding to the difference between VDD and V _REF . It is initialized.

4 is a circuit diagram illustrating the current flow during the ambient light detection process by the ambient light detection circuit of the present invention.

2 and 4, in the ambient light sensing process T2, a first control signal, a second control signal, a third control signal, and a fourth control signal of a high level are applied to the first switch S1. ), The second switch S2, the third switch S3, the fourth switch S4, and the fifth switch S5 are turned off.

Accordingly, the voltage VDD by the first power source VDD is applied to the contacts of the first capacitive element C1 and the second capacitive element C2 through the light receiving element PD. Of course, the reverse current through the light receiving element PD depends on the brightness of the ambient light. For example, when the ambient light is relatively bright, the amount of current through the light receiving element PD is large, and when the ambient light is relatively dark, the amount of current through the light receiving element PD is small. Here, the first power source and the voltage thereof will be denoted by the same reference numeral for convenience of description.

In this manner, a voltage of V _REF + ΔV is applied to the contacts of the first capacitive element C1 and the second capacitive element C2, and thus also to the second electrode of the first capacitive element C1. _A voltage of V _A + ΔV is applied. Of course, the ΔV is directly proportional to the ambient light brightness. Here, the charging speed of the second capacitive element C2 is fast when the ambient light is relatively bright and slow when the ambient light is relatively dark.

5 is a circuit diagram illustrating a current flow during a sampling process by the ambient light sensing circuit of the present invention.

2 and 5, in the sampling process T3, a low level first control signal is applied to the first switch S1, and a low level fourth control signal is applied to the fifth switch S5. Is applied to. Therefore, only the first switch S1 and the fifth switch S5 are turned on. Of course, the second switch S2 to the fourth switch S4 and the sixth switch S6 maintain the turn-off state.

Accordingly, a current path is formed through the first power source VDD, the transistor T1, the first switch S1, the fifth switch S5, and the output load 120. Of course, the currents I _{REF -ΔI} through the transistor T1 are connected to the first capacitive element C1 through coupling of the first capacitive element C1 and the second capacitive element C2. It flows in response to the voltage. That is, since the voltage of the first capacitive element C1 becomes the control electrode voltage of the transistor T1, when the voltage of the first capacitive element C1 is small, a relatively large current flows, and the first When the voltage of the single capacitive element C1 is large, a relatively small current flows. In this way, the transistor T1 transmits a predetermined amount of current I _REF -ΔI from the first power source VDD to the output load 120 through the first switch S1 and the fifth switch S5. Let it flow Here, ΔI becomes large when the voltage of the first capacitive element C1 is relatively large, and becomes small when the voltage is relatively small.

As a result, when dark light is incident on the light receiving element PD, the current flowing through the light receiving element PD is relatively small, and thus the first capacitive element C1 and the second capacitive element ( The coupling voltage by C2) is relatively small. Then, the current I _REF -ΔI of the first power source VDD flowing through the transistor T1 becomes relatively large. In addition, when bright light is incident on the light receiving element PD, a current flowing through the light receiving element PD is relatively large, and thus, the first capacitive element C1 and the second capacitive element C2 are relatively high. Coupling voltage is relatively large. Then, the currents I _REF -ΔI of the first power source VDD flowing through the transistor T1 are relatively small.

Of course, the current output through the output load 120 is output to, for example, an analog to digital converter (not shown) through the output terminal.

Meanwhile, the operation of the third capacitive element C3 by the fifth control signal will be described.

When a lot of light suddenly enters the light receiving element PD, the second capacitive element C2 is rapidly charged through it. That is, since the second capacitive element C2 is charged too quickly, it is difficult to secure a reliable output voltage from the transistor T1, and thus accurate ambient light sensing operation is impossible.

In order to prevent this phenomenon, the present invention uses the fifth control signal as a feedback signal when the output current through the output terminal (for example, the current input to the analog-to-digital converter) continues to fall below the threshold for a predetermined time. 6 is applied to the control electrode of the switch S6.

Then, the third capacitive element C3 is connected to the light receiving element PD together with the second capacitive element C2 in parallel.

Therefore, since the second capacitive element C2 and the third capacitive element C3 are connected in parallel to the light receiving element PD, the reverse bias capacitance is further increased. Accordingly, it is possible to send a current through the light receiving element PD for a time sufficient to sense ambient light. Of course, the second capacitive element C2 and the third capacitive element C3 affect the coupling voltage with the first capacitive element C1, and this coupling voltage is again used as the transistor T1. Will contribute to the operation.

Therefore, the transistor T1 operates in a reliable operation section, and thus the output voltage is stabilized. In other words, the ambient light is detected smoothly.

6A to 6C are simulation graphs of changes in output current according to changes in ambient light of the ambient light sensing circuit according to the present invention.

In this graph, the X axis represents time (ms), and the Y axis represents output voltage (Vout) and output current (Iout). In the graph _{, VG, T1 (fast)} represents a fast transistor having ΔV _TH of −1V and Δmobility of + 20%, and VG _{, T1 (normal)} represents ΔV _TH of 0V, Normal transistor with 0% mobility, V _{G, T1 (slow)} means _slow transistor with _{ΔV TH} + 1V and Δmobility -20%. .

First, as shown in FIG. 6A, the ambient light sensing circuit 100 according to the present invention has an output current Iout through the output terminal when the current I _PIN flowing through the light receiving element PD is 25 pA, for example. Is output with a deviation of 2.622∼2.659㎂.

In addition, as shown in FIG. 6B, the ambient light sensing circuit 100 according to the present invention has an output current Iout through the output terminal when the current I _PIN flowing through the light receiving element PD is 120 pA, for example. ) Is output with deviation of 1.702 ~ 1.802㎂.

In addition, as shown in FIG. 6C, the ambient light sensing circuit 100 according to the present invention has an output current through the output terminal when the current I _PIN flowing through the light receiving element PD is 567 pA, for example. It is output with deviation of ~ 32㎁.

Here, the ambient light sensing circuit 100 according to the present invention, even if a significant difference in the control electrode voltage of the transistor T1 due to the threshold voltage variation or the difference in mobility, as shown in the above-described graph, the output current ( Iout) is outputted with a deviation within a predetermined range, so that it is possible to reliably detect ambient light.

In addition, humans are generally known to recognize ambient light in log scale units. In other words, it is easy to recognize a slight change in ambient light in a small ambient light (for example, a dark room), but a small change in ambient light in a relatively large state (for example, under sunlight) is not easily sensed. can not do it.

Therefore, as in the present invention, it is preferable that an output current having a small deviation is output in a state where the ambient light is relatively small. In addition, even in the state where the ambient light is relatively large, even if the output current having a relatively large deviation is output, it can be seen that there is no big problem in using the output current anyway because humans do not feel this well.

7 is a block diagram illustrating a state in which an ambient light control processor is further connected to an ambient light sensing circuit according to the present invention.

As shown, the present invention may further include an ambient light control processor 200 for signal processing from the ambient light sensing circuit 100. The ambient light control processor 200 includes an analog-digital converter 210, a first memory 220, a controller 230, and a second memory 240.

The analog-to-digital converter 210 is electrically connected through the fifth switch S5. Of course, the output load 120 and the load capacitive element CL are incorporated in the analog-to-digital converter 210. Substantially, the output load is an internal load of the analog-to-digital converter, and the load capacitive element CL may be a capacitive component formed in the wiring. The analog-to-digital converter 210 serves to convert the analog output current value into a digital value and output the digital value.

The first memory 220 is electrically connected to the analog-to-digital converter 210, which temporarily stores a digital value according to a currently detected ambient light state.

The controller 230 is electrically connected to the first memory 220 to calculate and output the brightness of the currently detected ambient light.

The second memory 240 is electrically connected to the controller 230 to store digital values obtained from ambient light having various brightnesses in advance.

With this configuration, the present invention compares the sensed ambient light data input from the first memory 220 and the ambient light data of various brightness stored in the second memory 240 to calculate the current ambient light brightness. .

Meanwhile, in the drawing, the first switch S1 is formed in the ambient light sensing circuit 100, and the fourth switch S4 and the fifth switch S5 are shown in the ambient light control processor 200. However, the present invention is not limited to this configuration. That is, all of the above components may be formed in the ambient light sensing circuit 100 or in the ambient light control processor 200.

Substantially, the ambient light sensing circuit 100 is formed on a substrate such as an organic electroluminescent panel, whereas the ambient light control processing unit 200 may be separately formed as a one chip form. Of course, the one-chip form of the ambient light control processing unit 200 is not limited, and it may be formed on a substrate such as an organic electroluminescent panel.

Here, the fourth switch (S4), the fifth switch (S5) and the current load 110, etc. are formed in the ambient light control processing unit 200 in the form of a one-chip for convenience of design, or the ambient light sensing formed on the substrate It can be formed in the circuit 100.

8 is a block diagram illustrating a configuration of a flat panel display device having an ambient light sensing circuit according to the present invention.

Here, the ambient light sensing circuit 100 and the ambient light control processing unit 200 are shown in a block diagram for convenience of description.

As illustrated, the flat panel display according to the present invention includes the timing controller 300, the data driver 400, the organic electroluminescent panel 500, in addition to the above-described ambient light sensing circuit 100 and the ambient light control processor 200. The scan driver 600 and the emission control driver 700 may be further included. Of course, since the configuration and operation of the ambient light sensing circuit 100 and the ambient light control processor 200 have been described in detail above, the description thereof will be minimized. In addition, the organic electroluminescent panel 500 includes a circuit unit and an organic emission layer forming one pixel, and the pixels are arranged in a matrix to display a still image or a moving image. That is, the organic electroluminescent panel 500 has a plurality of data lines D1 to Dm extending from the data driver 400, and a plurality of scan lines S1 to Sn extending from the scan driver 600. And a plurality of emission control lines E1 to En extending from the emission control driver 700. In addition, a predetermined pixel is formed in an intersection area of the data line, the scan line, and the emission control line.

The timing controller 300 includes a brightness selector 310 and a lookup table 320. The timing controller 300 compares the digital value input from the ambient light control processor 200 with the value stored in the pre-formed lookup table 320 by the brightness selector 310, and outputs a data control signal suitable for the data control signal. Output to the data driver 400. Of course, the look-up table 320 is stored in advance the optimum brightness data control signal matching the digital value input from the ambient light control processing unit 200 for each of R, G, B.

Then, the data driver 400 outputs an appropriate data signal according to external ambient light to the organic light emitting diode. For example, when the detected ambient light is relatively bright, a relatively bright screen is output through the organic light emitting panel 500 by outputting a data voltage (| V |) that outputs a relatively large amount of light. do. In addition, when the detected ambient light is relatively dark, a relatively low amount of light outputs a data voltage (| V |), so that the screen of weak brightness is displayed through the organic EL panel 500.

In this manner, the present invention provides a display device in which the brightness of a screen is automatically adjusted according to external ambient light. The scan driver 600 outputs a scan signal to the organic electroluminescent panel 500 so that the organic electroluminescent panel 500 can select a pixel to be turned on and a pixel to be turned off. The control driver 700 outputs an emission time signal corresponding to the turn-on time of each pixel to the organic EL panel 500. Since the scan driver 600 and the emission control driver 700 are well known to those skilled in the art, detailed descriptions thereof will be omitted.

Meanwhile, the ambient light sensing circuit 100, the ambient light control processor 200, the timing controller 300, the data driver 400, the organic electroluminescent panel 500, the scan driver 600, and the light emission control described above. Naturally, the driving part 700 may be formed on one common substrate through a semiconductor process and a thick film process. Of course, the present invention is at least one of the ambient light sensing circuit 100, the ambient light control processor 200, the timing controller 300, the data driver 400, the scan driver 600 and the light emission control driver 700. The organic electroluminescent panel 500 may be formed on a substrate different from the substrate on which the organic electroluminescent panel 500 is formed, and the position of forming each of the components is not limited.

FIG. 9A is a circuit diagram illustrating an example of a pixel circuit in an organic EL panel of a flat panel display, and FIG. 9B is a timing diagram thereof.

As shown in FIG. 9A, the pixel circuit supplies a scan line Sn for supplying a scan signal, a data line Dm for supplying a data voltage, a first power line VDD for supplying a first voltage, and a second voltage. The second power line VSS, the auto zero line An for supplying the auto zero signal, the light emission control line En for supplying the light emission control signal, and the first to fourth transistors T1, T2, T3, and T4. ), First and second capacitive elements C1 and C2, and an organic electroluminescent element OLED. Here, the voltage of the first power line VDD is relatively higher than the voltage of the second power line VSS.

As illustrated in FIG. 9B, when the low level control signal is supplied from the auto zero line An to the control electrode of the third transistor T3, the third transistor T3 is turned on. Subsequently, when the high level control signal is supplied to the control electrode of the fourth transistor T4 from the emission control line En, the fourth transistor T4 is turned off. Then, while the first transistor T1 is connected in the form of a diode, the threshold voltage of the first transistor T1 is stored in the first capacitive element C1. When the auto zero signal becomes a high level again, and then a data voltage having a predetermined level suitable for ambient light is applied from the data line Dm, the first and second capacitive elements C1 and C2 A data voltage of which the threshold voltage is compensated by the ratio is supplied to the control electrode of the first transistor T1. (Data writing operation) When the light emission control signal becomes low level, the fourth transistor T4 ) Is turned on so that a predetermined current flows to the organic light emitting diode OLED to emit light.

According to such a pixel circuit, the current flowing through the organic EL device flows only in response to the data voltage supplied from the data line, regardless of the threshold voltage of the first transistor. That is, according to the pixel circuit, since the deviation of the threshold voltage of the first transistor is compensated for, it is possible to implement a high gradation organic light emitting display device.

Meanwhile, in the present invention, the brightness of the screen is automatically adjusted according to the ambient brightness as described above. That is, according to the present invention, the data voltage through the data line Dm in the pixel circuit is adjusted, so that the coupling voltages of the first capacitive element C1 and the second capacitive element C2 are adjusted. Current through the first transistor T1 to the organic light emitting diode OLED is changed. Therefore, the current through the organic light emitting diode OLED is changed, thereby finally adjusting the brightness of the organic electroluminescent panel.

Fig. 10A is a block diagram showing the configuration of a flat panel display device having another ambient light sensing circuit according to the present invention, and Fig. 10B is a timing diagram thereof.

As shown in FIG. 10A, in the flat panel display having the other ambient light sensing circuit of the present invention, the brightness control signal output from the timing controller 300 is not the data driver 400 but the light emission control driver different from that shown in FIG. 8. Entered at 700.

Accordingly, the emission control driver 700 outputs an appropriate emission control signal according to external ambient light to the organic light emitting panel 500. For example, when the detected ambient light is relatively bright, a light emission control signal of a relatively long time is output, so that a screen having a strong brightness is displayed through the organic EL panel 500. In addition, when the detected ambient light is relatively dark, a light emission control signal of a relatively short time is output, so that a screen having a weak brightness is displayed through the organic EL panel 500.

In this manner, the present invention provides a display device in which the brightness of a screen is automatically adjusted according to external ambient light.

In more detail, as illustrated in FIG. 10B, the light emission time of the organic light emitting diode OLED is controlled by adjusting the length of the time T of the light emission control signal En. For example, when the ambient brightness is dark, a light emission control time T of a relatively short time is supplied, so that the light emission time of the organic light emitting diode OLED is relatively short, thereby displaying a dark screen. In addition, when the ambient brightness is bright, the light emission control time T of a relatively long time is supplied, so that the light emission time of the organic light emitting diode OLED is relatively long, thereby displaying a bright screen.

Fig. 11A is a block diagram showing the configuration of a flat panel display device having another ambient light sensing circuit according to the present invention, and Fig. 11B is a timing diagram thereof.

As shown in FIG. 11A, the flat panel display having the other ambient light sensing circuit of the present invention is different from that shown in FIG. 10A in which the brightness control signal output from the timing controller 300 is not the light emission control driver 700 but the power control unit. Is entered at 800.

As described above, the power control unit 800 supplies the organic EL panel 500 with a suitable power voltage according to external ambient light. For example, when the detected ambient light is relatively bright, a relatively high power supply voltage is supplied to display a screen having a strong brightness through the organic EL panel 500. In addition, when the detected ambient light is relatively dark, a relatively low power supply voltage is supplied so that a screen having a weak brightness is displayed through the organic EL panel 500. In the drawings, reference numeral PL denotes a power line formed in the organic EL panel.

In this manner, the present invention provides a display device in which the brightness of a screen is automatically adjusted according to external ambient light.

That is, the present invention adjusts the brightness of the organic light emitting diode OLED by adjusting the voltage of the first power source VDD (indicated by reference numeral V in the drawing) as shown in FIG. 11B. For example, when the ambient brightness is dark, by supplying a relatively small power supply voltage, the brightness of the organic light emitting diode OLED is relatively small so that a dark screen is displayed. In addition, when the ambient brightness is bright, by supplying a relatively high power supply voltage, the brightness of the organic light emitting diode OLED is relatively increased so that a bright screen is displayed.

12 is a block diagram illustrating a configuration of a flat panel display device having another ambient light sensing circuit according to the present invention.

As shown, another flat panel display according to the present invention includes the ambient light sensing circuit 100, the ambient light control processor 200, the timing controller 300, the inverter 910, the backlight 920, and the gate driver 930. And a data driver 940 and a liquid crystal display panel 950. Of course, since the configuration and operation of the ambient light sensing circuit 100, the ambient light control processor 200, and the timing controller 300 have been described in detail above, the description thereof will be minimized.

The timing controller 300 outputs a brightness control signal to the inverter 910.

Then, the inverter 910 supplies a boost voltage suitable for external ambient light to the backlight 920. For example, when the detected ambient light is relatively bright, the inverter 910 supplies a relatively high boost voltage to the backlight 920 so that a screen having a strong brightness is displayed through the liquid crystal display panel 950. . In addition, when the detected ambient light is relatively dark, the inverter 910 supplies a relatively small boosted voltage to the backlight 920 so that a screen having a weak brightness is displayed through the liquid crystal display panel 950.

In this manner, the present invention provides a display device in which the brightness of a screen is automatically adjusted according to external ambient light.

In the liquid crystal display panel 950, a circuit unit and a color filter form one pixel P, and the pixels are arranged in a matrix to display a still image or a moving image. Of course, the circuit unit and the color filter serve as a kind of camera shutter, and a backlight 920 such as a cold cathode fluorescent lamp (CCFL) is positioned on the rear surface of the liquid crystal display panel 950, and is output from the backlight 920. An image of a predetermined brightness is displayed by light. In addition, a plurality of scan lines S1 -Sn extending from the gate driver 930 are formed in the liquid crystal display panel 950, and a plurality of data lines D1 -Dm extending from the data driver 940 are formed. Can be.

Here, the gate driver 930 supplies a scan signal to the liquid crystal display panel 950, and the data driver 940 serves to supply a data voltage from the liquid crystal display panel 950. Since the gate driver 930 and the data driver 940 are well known to those skilled in the art, a detailed description thereof will be omitted.

Meanwhile, the ambient light sensing circuit 100, the ambient light control processor 200, the timing controller 300, the inverter 910, the gate driver 930, the data driver 940, and the liquid crystal display panel 950 described so far. Of course, all may be formed on a common substrate through a semiconductor process, a thick film process, and the like. Of course, at least one of the ambient light sensing circuit 100, the ambient light control processing unit 200, the timing control unit 300, the inverter 910, the gate driver 930, the data driver 940 is the The liquid crystal display panel 950 may be formed on a different substrate or chip than the substrate on which the liquid crystal display panel 950 is formed, and the position of forming each of the components is not limited.

13 is a block diagram illustrating an example of an inverter in the flat panel display device according to the present invention.

As shown, the inverter 910 is a PWM control unit 911 for outputting a pulse width modulation (PWM) control signal suitable for the control signal when the control signal related to the brightness is input from the timing control unit 300, Using the output signal of the PWM control unit 911 as an input signal, the converter 912 for boosting the power supply voltage VDD to a predetermined level and supplying it to the backlight 920, and detecting current through the backlight 920. It may include a current sensing unit 913 that feeds back to the PWM control unit 911. Of course, the configuration of the inverter 910 is only an example, it should be noted that there are other inverters of various configurations.

As described above, the PWM control unit 911 may receive a control signal related to brightness from the timing controller 300.

Then, the PWM controller 911 outputs a PWM control signal matching the control signal described above to the converter 912. That is, if the current ambient light is dark output a PWM control signal to relatively lower the boost voltage, and if the current ambient light is bright output a PWM control signal to relatively increase the boost voltage.

Then, the converter 912 receives the power supply voltage VDD and then boosts it to a predetermined voltage in response to the PWM control signal to supply the backlight 920. Of course, the backlight 920 is turned on at a predetermined brightness. Here, the backlight 920 lowers the brightness when the boost voltage is low, and increases the brightness when the boost voltage is high.

Meanwhile, the current detector 913 including a plurality of resistors, diodes, and capacitive elements lowers the current through the backlight 920 to a predetermined level and feeds it back to the PWM controller 911. Therefore, the PWM controller 911 can efficiently control the backlight 920 to suit the target brightness.

In this way, in the present invention, when the ambient light is dark, the backlight 920 is relatively dark, so that the brightness of the screen through the liquid crystal display panel 950 is relatively dark. In addition, according to the present invention, when the ambient light is bright, the backlight 490 is relatively brightly lit, so that the brightness of the screen through the liquid crystal display panel 950 is relatively bright. That is, in the flat panel display according to the present invention, the brightness of the screen is automatically adjusted in response to the ambient light.

As described above, the ambient light sensing circuit and the flat panel display having the same according to the present invention obtain output voltages of various levels according to the ambient light, and automatically adjust the brightness of the screen through the display device. In all places, the visibility of a flat panel display device becomes excellent.

In addition, as described above, the flat panel display having the ambient light sensing circuit according to the present invention automatically adjusts the power consumption according to the ambient light, thereby maintaining the optimum power consumption, and thus the usable time of the portable flat panel display. This will be longer.

In addition, as described above, the ambient light sensing circuit and the flat panel display apparatus having the same according to the present invention may include an ambient light sensing circuit, an ambient light control processor, a timing controller, a data driver, a scan driver, a light emission control driver, and an organic electroluminescent panel (or The liquid crystal display panel) can be formed on a single common substrate by using a low temperature crystallized silicon thin film transistor process, whereby the thickness of the flat panel display device can be further reduced.

What has been described above is only one embodiment for implementing the ambient light sensing circuit and the flat panel display device having the same according to the present invention, and the present invention is not limited to the above-described embodiment, which is claimed in the following claims. As will be apparent to those skilled in the art to which the present invention pertains without departing from the gist of the present invention, the technical spirit of the present invention may be changed to the extent that various modifications can be made.

Claims (24)

A transistor electrically connected to the first power source; A first capacitive element electrically connected between the transistor and a reference power source; A second capacitive element electrically connected between the first power supply, the transistor, and the reference power supply; A light receiving device electrically connected to the reference power supply and configured to flow a current in response to ambient light, thereby adjusting a voltage of the first capacitive element through coupling of the first capacitive element and the second capacitive element; device; And a first switch electrically connected to the transistor, the first switch configured to output a current from the first power supply through the transistor according to the voltage of the first capacitive element. The ambient light sensing circuit according to claim 1, wherein the first capacitive element and the second capacitive element are further electrically connected to a second switch for applying a reference voltage from a reference power source. The ambient light sensing circuit according to claim 2, wherein a third switch is further electrically connected between the control electrode of the transistor and the first switch. 4. The ambient light of claim 3, wherein a fourth switch is further electrically connected to the first switch so that current through the first power source, transistor, first switch, and third switch is consumed through a current load. Sensing circuit. The method of claim 1, wherein the first switch is electrically connected to a fifth switch for causing the transistor to flow a constant current from the first power source to the output load in response to the voltage of the first capacitive element. Ambient light sensing circuit. The ambient light sensing circuit according to claim 1, wherein a third capacitive element is further electrically connected to the second capacitive element to increase the reverse bias capacitance of the light receiving element. 7. The ambient light sensing circuit according to claim 6, wherein a sixth switch is further provided between the second capacitive element and the third capacitive element to electrically connect them. The ambient light sensing circuit of claim 1, wherein the light receiving element is any one selected from a PIN diode, a PN diode, and a photo coupler, the anode of which is electrically connected to a reference power source, and the cathode of which is electrically connected to a first power source. . The ambient light sensing circuit of claim 1, wherein the light receiving element is any one selected from a PIN diode, a PN diode, and a photo coupler, the cathode of which is electrically connected to a reference power source, and the anode of which is electrically connected to a ground terminal. The ambient light sensing circuit of claim 5, wherein an ambient light control processor is further electrically connected to the fifth switch. The method of claim 10, wherein the ambient light control processing unit An analog-digital converter electrically connected to the output load and converting an analog current value of the output load into a digital value; A first memory electrically connected to the analog to digital converter to store a digital value according to a current ambient light condition; A controller electrically connected to the first memory to calculate and output brightness of current ambient light; And, And a second memory electrically connected to the control unit to store digital values obtained from ambient light having various brightnesses in advance. A transistor electrically connected to a first power source, a first capacitive element electrically connected between the transistor and a reference power source, a second capacitive element electrically connected between the first power source, the transistor, and the reference power source; A light receiving device electrically connected to the reference power supply and configured to flow a current in response to ambient light, thereby adjusting a voltage of the first capacitive element through coupling of the first capacitive element and the second capacitive element; An ambient light sensing circuit electrically connected to the device, the first switch configured to output a current from the first power supply through the transistor according to the voltage of the first capacitive device; An ambient light control processor configured to calculate a current ambient light and output a digital value using the analog output signal of the ambient light sensing circuit as an input signal; A timing controller configured to output a control signal suitable for current ambient light by using the output signal of the ambient light control unit as an input signal; A data driver which outputs a data signal suitable for current ambient light by using the output signal of the timing controller as an input signal; And, And an organic electroluminescent panel which emits light at a brightness suitable for current ambient light using the data signal of the data driver as an input signal. The method of claim 12, wherein the timing controller A lookup table storing data suitable for the current lighting; And, And a brightness selector which compares data obtained from the ambient light control processor with data stored in the lookup table to select a control signal suitable for current lighting and output the control signal to the data driver. The flat panel display of claim 12, wherein the data driver outputs a data voltage to output light proportional to the ambient light obtained from the ambient light sensing circuit. A transistor electrically connected to a first power source, a first capacitive element electrically connected between the transistor and a reference power source, a second capacitive element electrically connected between the first power source, the transistor, and the reference power source; A light receiving device electrically connected to the reference power supply and configured to flow a current in response to ambient light, thereby adjusting a voltage of the first capacitive element through coupling of the first capacitive element and the second capacitive element; An ambient light sensing circuit electrically connected to the device, the first switch configured to output a current from the first power supply through the transistor according to the voltage of the first capacitive device; An ambient light control processor configured to calculate a current ambient light and output a digital value using the analog output signal of the ambient light sensing circuit as an input signal; A timing controller configured to output a control signal suitable for current ambient light by using the output signal of the ambient light control unit as an input signal; An emission control driver for outputting an emission control signal suitable for current ambient light using the output signal of the timing controller as an input signal; And, And an organic electroluminescent panel which self-emits light at a brightness suitable for current ambient light, using the light emission control signal of the light emission control driver as an input signal. The method of claim 15, wherein the timing controller A lookup table storing data suitable for the current lighting; And, And a brightness selector which compares data obtained from the ambient light control processor with data stored in the lookup table to select a control signal suitable for current illumination and output the control signal to the light emission control driver. The flat panel display of claim 15, wherein the emission control driver outputs an emission control signal having a time proportional to the ambient light obtained from the ambient light sensing circuit. A transistor electrically connected to a first power source, a first capacitive element electrically connected between the transistor and a reference power source, a second capacitive element electrically connected between the first power source, the transistor, and the reference power source; A light receiving device electrically connected to the reference power supply and configured to flow a current in response to ambient light, thereby adjusting a voltage of the first capacitive element through coupling of the first capacitive element and the second capacitive element; An ambient light sensing circuit electrically connected to the device, the first switch configured to output a current from the first power supply through the transistor according to the voltage of the first capacitive device; An ambient light control processor configured to calculate a current ambient light and output a digital value using the analog output signal of the ambient light sensing circuit as an input signal; A timing controller configured to output a control signal suitable for current ambient light by using the output signal of the ambient light control unit as an input signal; A power control unit outputting a power supply voltage suitable for current ambient light by using the output signal of the timing control unit as an input signal; And, And an organic electroluminescent panel which emits light by using the power voltage of the power control unit as an input signal. 19. The apparatus of claim 18, wherein the timing controller A lookup table storing data suitable for the current lighting; And, And a brightness selector which compares data obtained from the ambient light control processor with data stored in the lookup table to select a control signal suitable for current lighting and output the selected control signal to the power control unit. The flat panel display of claim 18, wherein the power control unit outputs a power voltage proportional to an ambient light obtained from the ambient light sensing circuit. A transistor electrically connected to a first power source, a first capacitive element electrically connected between the transistor and a reference power source, a second capacitive element electrically connected between the first power source, the transistor, and the reference power source; A light receiving device electrically connected to the reference power supply and configured to flow a current in response to ambient light, thereby adjusting a voltage of the first capacitive element through coupling of the first capacitive element and the second capacitive element; An ambient light sensing circuit electrically connected to the device, the first switch configured to output a current from the first power supply through the transistor according to the voltage of the first capacitive device; An ambient light control processor configured to calculate a current ambient light and output a digital value using the analog output signal of the ambient light sensing circuit as an input signal; A timing controller configured to output a control signal suitable for current ambient light by using the output signal of the ambient light control unit as an input signal; An inverter for boosting and outputting a power supply voltage appropriate to current ambient light by using the output signal of the timing controller as an input signal; A backlight that is turned on by a voltage supplied from the inverter; And, And a liquid crystal display panel for displaying a screen by the backlight. The method of claim 21, wherein the timing controller A lookup table storing data suitable for the current lighting; And, And a brightness selector configured to compare data obtained from the ambient light control processor with data stored in the lookup table to select a control signal suitable for current illumination and output the same to the inverter. The flat panel display of claim 21, wherein the inverter outputs a boosted voltage proportional to an ambient light obtained from the ambient light sensing circuit. The method of claim 21, wherein the inverter A PWM controller for outputting a PWM control signal suitable for the control signal when a control signal is input from the timing controller; A converter for boosting a power supply voltage to a predetermined level using the output signal of the PWM controller as an input signal and supplying the backlight to the backlight; And, And a current sensing unit configured to sense a current through the backlight and feed it back to the PWM controller.

Images