Light emitting device with cross-talk preventing circuit and method of driving the same

1. Field of the Invention

The present invention relates to a light emitting device and a method of driving the same, particularly relates to a light emitting device without cross-talk phenomenon and a method of driving such light emitting device.

2. Description of the Related Art

An organic electroluminescent device is a light emitting device, which emits light with a certain applied voltage thereto.

FIG. 1A is a block diagram illustrating an organic electroluminescent device; and FIG. 1B is an equivalent circuit diagram of some of the pixels of FIG. 1A .

Referring to FIG. 1A , an organic electroluminescent device is comprised of a panel 100 , a scan driving circuit 102 , a data driving circuit 106 and a controller 104 .

The panel 100 includes a plurality of pixels E 11 to E 44 that are defined as overlying areas of data lines D 1 to D 4 and scan lines S 1 to S 4 .

For example, the pixels E 11 to E 44 of the panel will emit light in the case that a voltage 20V is applied to the data lines D 1 to D 4 and a voltage 0V is applied to the scan lines S 1 to S 4 .

In this case, some of the pixels E 11 to E 44 may not emit light for various reasons. For example, when some of the pixels E 33 to E 43 located on a third scan line S 3 are set not to generate light at a certain time, the total current value passing through the third scan line S 3 becomes less than the total current value passing through the other scan lines S 1 , S 2 and S 4 .

Conventionally, the organic electroluminescent device provides the scan lines S 1 to S 4 with scan signals of the same low logic value, for example 0V, in sequence. Thus, it is appreciated that the same voltage, e.g. 20V is applied between the cathode and the anode of each pixel if the electroluminescent device normally operates.

However, in reality, different voltages are applied to the cathodes of the luminescent (luminescent) pixels because of the combined effect of the line resistance (for example 160Ω) of the scan lines and some non-luminescent pixels E 33 and E 43 .

As a result, the voltages applied between the cathode and the anode of the pixels may be different from each other, and thus the pixels emit light at different luminance even though they are predetermined to have the same luminance value. Such phenomenon is referred to as cross-talk.

For example, let's assume that the total current passing through the first scan line S 1 is 14 mA, and that of the third scan line S 3 is 10 mA because of the non-luminescent pixels E 33 and E 34 . Here, the first pixel E 11 and the third pixel E 13 are preset to emit light at the same luminance in a normal state.

In this case, since the line resistance of each scan line S 1 to S 4 is 160 Ω, the voltage difference between the cathode and the anode of the first pixel E 11 on the first scan line S 1 is 20V(Vcc)−0V(the voltage of the first scan signal)−2.24V(14 mA×160Ω, the voltage of the first scan line S 1 )=17.76V. In comparison, the voltage difference between those of the third pixel E 13 on the third scan line S 3 is 20V(Vcc)−0V(the voltage of the third scan signal)−1.6V(10 mA×160Ω, the voltage of the third scan line S 3 )=18.4V.

Namely, the voltage difference between the cathode and the anode of the luminescent pixels on the third scan line S 3 is larger than the voltage difference of the pixels on the other scan lines S 1 , S 2 and S 4 which are preset to emit light at the same luminance. As a result, the luminescent pixels on the third scan line S 3 emit light with higher luminance than the pixels on the other scan lines S 1 , S 2 and S 4 do.

In short, such luminance variation occurs adversely to the designer's intention between the pixels due to the above described cross-talk phenomenon.

Although the organic electroluminescent device is taken as an example in the foregoing description, the cross-talk is a common phenomenon encountered in other light emitting devices. Therefore, there is a need to develop a light emitting device and method of driving the same where such cross-talk problem may be solved.

The object of the present invention is to provide a light emitting device and a method of driving the same that can prevent the occurrence of cross-talk phenomenon.

In one aspect of the present invention, the present invention provides a light emitting device comprising a display panel including a plurality of scan lines disposed in a first direction; a plurality of data lines disposed in a second direction, wherein the second direction is different from the first direction; and a plurality of pixels that are defined as overlying areas of the plurality of scan lines and the plurality of data lines; and a cross-talk preventing circuit configured to provide the plurality of scan lines with compensating currents according to display data provided by an outside device.

In another aspect of the present invention, the present invention provides a light emitting device comprising a display panel including a plurality of scan lines including a plurality of first scan lines extending in a first direction; and a plurality of second scan lines extending in a second direction; a plurality of data lines disposed to cross with the plurality of scan lines; and a plurality of pixels that are defined as crossing areas of the plurality of scan lines and the plurality of data lines; and a cross-talk preventing circuit configured to provide the plurality of scan lines with compensating currents according to display data provided by an outside device, the cross-talk preventing circuit including a first cross-talk preventing circuit electrically coupled to the plurality of first scan lines and configured to provide the plurality of first scan lines with the compensating currents; and a second cross-talk preventing circuit electrically coupled to the plurality of second scan lines and configured to provide the plurality of second scan lines with the compensating currents.

In further another aspect of the present invention, the present invention provides a method of driving a light emitting device including a plurality of pixels that are defined as overlying areas of the plurality of scan lines and the plurality of data lines, the method comprising the steps of (a) receiving display data provided by an outside device; and (b) providing the plurality of scan lines with compensating currents according to the received display data.

In further another aspect of the present invention, the present invention provides a method of driving a light emitting device including a plurality of pixels that are defined as overlying areas of the plurality of scan lines including first scan lines and second scan lines and the plurality of data lines, the method comprising the steps of (a) receiving display data provided by an outside device; (b) providing the first scan lines with compensating currents according to the received display data; and (c) providing the second scan lines with compensating currents according to the received display data.

According to the present invention, the total current values passing through the scan lines all are made equal with the aid of the compensating currents that the cross-talk preventing circuits provide so that the cross-talk problem may be solved.

These and other features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:

FIG. 1A is a block diagram illustrating an organic electroluminescent device;

FIG. 1B is an equivalent circuit diagram of some of the pixels of FIG. 1A ;

FIG. 2 is a block diagram illustrating an electroluminescent device according to one embodiment of the present invention;

FIG. 3 is a flow chart illustrating a method of driving the electroluminescent device of FIG. 2 ;

FIG. 4 is a block diagram illustrating an electroluminescent device according to another embodiment of the present invention; and

FIG. 5 is a flow chart illustrating a method of driving the electroluminescent device of FIG. 4 .

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Hereinafter, the preferred embodiments of the present will be described in detail with reference to the accompanying drawings. In the following embodiments, the organic electroluminescent device is provided as an example of the light emitting device. It is, however, obvious that the teaching of the present invention is not limited to the organic electroluminescent device.

FIG. 2 is a block diagram illustrating an electroluminescent device according to one embodiment of the present invention.

Referring to FIG. 2 , the electroluminescent device of one embodiment of the present invention comprises a panel 200 , a san driving circuit 202 , a data driving circuit 206 , a controller 204 and a cross-talk preventing circuit 208 .

The panel 200 includes a plurality of pixels E 11 to E 44 that are defined as overlying areas of data lines D 1 to D 4 and scan lines S 1 to S 4 .

Here, the scan lines S 1 to S 4 are extended in one direction. In other words, all scan lines S 1 to S 4 are connected to one scan driving circuit 202 at one side thereof, i.e. the left side in FIG. 2 .

The scan driving circuit 202 transmits a plurality of scan signals to the scan lines S 1 to S 4 in sequence.

The data driving circuit 206 transmits to the data lines D 1 to D 4 data signals corresponding to display data provided through the controller 204 .

When the data signals are transmitted to the data lines D 1 to D 4 , and the scan signals are transmitted to the scan lines S 1 to S 4 , the pixels E 11 to E 44 emit light.

The controller 204 receives the display data transmitted from an outside device (not shown) to provide the display data to the data driving circuit 206 and the cross-talk preventing circuit 208 , and also control the operation of the scan driving circuit 202 , the data driving circuit 206 and the cross-talk preventing circuit 208 .

The cross-talk preventing circuit 208 includes a current controlling circuit 210 and a current providing circuit 212 .

The current controlling circuit 210 is provided with the display data from the controller 204 , and then provides the current providing circuit 212 with control signals corresponding to the display data.

The current providing circuit 212 provides the scan lines S 1 to S 4 with compensating currents according to the control signals transmitted from the current controlling circuit 210 .

As a result, the same amounts of the total current passes through each scan line S 1 to S 4 .

In another embodiment, the current providing circuit 212 includes just one current source which provides the scan lines S 1 to S 4 with currents according to the control signals.

Hereinafter, the method of driving the electroluminescent device of the present invention will be described in detail by presenting an example. Here, it is assumed that the line resistance of each scan line S 1 to S 4 is 160Ω.

Firstly, the controller 204 receives the display data from the outside device and transmits the received display data to the data driving circuit 206 .

Subsequently, the data driving circuit 206 provides the data lines D 1 to D 4 with first data signals, i.e. first data currents according to first display data transmitted through the controller 204 .

As a result, for example, the first data current of 1 mA passes through the first data line D 1 ; the first data current of 1 mA passes through the second data line D 2 ; the first data current of 3 mA passes through the third data line D 3 ; and the first data current of 6 mA passes through the fourth data line D 4 .

In this case, the cross-talk preventing circuit 208 recognizes in advance from the first display data transmitted from the controller 204 that the current of total 11 mA will pass through the data lines D 1 to D 4 .

Here, the cross-talk preventing circuit 208 can also recognize in advance that the current of 11 mA will pass through the first scan line S 1 since the first data currents passing through the data lines D 1 to D 4 will flow along the first scan line S 1 through the pixels E 11 to E 41 .

After that, the cross-talk preventing circuit 208 provides the first scan line S 1 with the compensating current of 9 mA. As a result, total 20 mA of current may flow through the first scan line S 1 .

Next, the data driving circuit 206 provides the data lines D 1 to D 4 with second data signals, i.e. second data currents according to second display data transmitted through the controller 204 .

As a result, for example, the second data current of 2 mA passes through the first data line D 1 ; the second data current of 3 mA passes through the second data line D 2 ; the second data current of 3 mA passes through the third data line D 3 ; and the second data current of 6 mA passes through the fourth data line D 4 .

In this case, the cross-talk preventing circuit 208 recognizes in advance that the sum of the second data currents, 14 mA of current will flow through the second scan line S 2 .

After that, the cross-talk preventing circuit 208 provides the second scan line S 2 with the compensating current of 6 mA. As a result, total 20 mA of current flows through the second scan line S 2 .

Namely, in such way as described above, the present invention make it possible that the same amount of current passes through each scan line S 1 to S 4 . As a result, the cathodes of the pixels E 11 to E 44 have a voltage of 3.2V.

In summary, in the electroluminescent device of the present, the same voltage is applied to the cathode of the pixels E 11 to E 44 unlike the conventional electroluminescent device where the cathodes of the pixels do not have the same voltage value.

Therefore, in the electroluminescent device of the present invention, the cross-talk problem can be overcome.

FIG. 3 is a flow chart illustrating a method of driving the electroluminescent device of FIG. 2 .

Referring to FIG. 3 , the scan driving circuit 202 provides the scan lines S 1 to S 4 with the scan signals in sequence (S 300 ).

Next, the controller 204 receives the display data transmitted from the outside device (S 302 ).

Subsequently, the cross-talk preventing circuit 208 provides each scan line S 1 to S 4 with the currents corresponding to the display data (S 304 ).

As a result, the total current passing through each scan line S 1 to S 4 becomes of the same value.

Next, the data driving circuit 206 provides the data lines D 1 to D 4 with the data signals corresponding to the display data transmitted from the controller 204 (S 306 ).

As a result, the pixels E 11 to E 44 come to emit light at a desired luminance without the cross-talk phenomenon.

FIG. 4 is a bock diagram illustrating an electroluminescent device according to another embodiment of the present invention.

Referring to FIG. 4 , the electroluminescent device of another embodiment of the present invention comprises a panel 300 , a first san driving circuit 302 , a second san driving circuit 304 , a controller 306 , a data driving circuit 308 , a first cross-talk preventing circuit 310 , a second cross-talk preventing circuit 312 , a first switching circuit 322 and a second switching circuit 324 .

The panel 300 includes a plurality of pixels E 11 to E 44 that are defined as overlying areas of data lines D 1 to D 4 and scan lines S 1 to S 4 .

Here, the scan lines S 1 to S 4 are extended in two directions. In other words, the scan lines S 1 to S 4 include first scan lines S 1 and S 3 extended in first direction, and second scan lines S 2 and S 4 extended in second direction. Furthermore, the first scan lines S 1 and S 3 are connected to the first scan driving circuit 302 , and the second scan lines S 2 and S 4 are connected to the second scan driving circuit 304 .

The first scan driving circuit 302 transmits a plurality of first scan signals to the first scan lines S 1 and S 3 in sequence.

The scan driving circuit 304 transmits a plurality of second scan signals to the scan lines S 2 to S 4 in sequence.

The data driving circuit 308 transmits to the data lines D 1 to D 4 data signals corresponding to display data provided through the controller 306 .

When the data signals are transmitted to the data lines D 1 to D 4 with the scan signals being provided to the scan lines S 1 to S 4 , the pixels E 11 to E 44 emit light.

The controller 306 receives the display data transmitted from an outside device (not shown) to provide the display data to the data driving circuit 308 , the first and the second cross-talk preventing circuits 310 and 312 , and also control the operation of the first and second scan driving circuits 302 and 304 , the data driving circuit 308 and the first and the second cross-talk preventing circuits 310 and 312 .

The first cross-talk preventing circuit 310 includes a first current controlling circuit 314 and a first current providing circuit 316 .

The first current controlling circuit 314 is provided with the display data from the controller 306 , and then provides the first current providing circuit 316 with first control signals corresponding to the display data.

The first current providing circuit 316 provides the scan lines S 1 and S 3 respectively with the compensating currents upon receiving the first control signals transmitted from the first current controlling circuit 314 .

The second cross-talk preventing circuit 312 includes a second current controlling circuit 318 and a second current providing circuit 320 .

The second current controlling circuit 318 is provided with the display data from the controller 306 , and then provides the first current providing circuit 320 with second control signals corresponding to the display data.

The second current providing circuit 320 provides the second scan lines S 2 and S 4 respectively with the compensating currents upon receiving the second control signals transmitted from the second current controlling circuit 318 .

As a result, the total current of each scan line S 1 to S 4 can become of the same value.

In another embodiment, the current providing circuits 316 and 320 include just one current source, which provides the scan lines S 1 to S 4 respectively with currents according to the control signals.

The first switching circuit 322 switches the connection between the first cross-talk preventing circuit 310 and the first scan lines S 1 and S 3 .

The second switching circuit 324 switches the connection between the second cross-talk preventing circuit 312 and the second scan lines S 2 and S 4 .

For example, in order for the first cross-talk preventing circuit 310 to provide the scan line S 1 with the compensating current, the first switch SW 1 of the first switching circuit 322 is turned on, in which case the other switches SW 2 to SW 4 are turned off

And, in order for the second cross-talk preventing circuit 312 to provide the scan line S 2 with the compensating current, the third switch SW 3 of the second switching circuit 324 is turned on, in which case the other switches SW 1 , SW 2 and SW 4 are turned off.

Hereinafter, the method of driving the electroluminescent device of the present invention will be described in detail by presenting an example. Here, it is assumed that the line resistance of each scan line S 1 to S 4 is 160Ω.

Firstly, the controller 306 receives first display data from the outside device and transmits the received display data to the data driving circuit 308 .

Subsequently, the data driving circuit 308 provides the data lines D 1 to D 4 with first data signals, i.e. first data currents according to the first display data transmitted through the controller 308 .

As a result, for example, the first data current of 1 mA passes through the first data line D 1 ; the first data current of 1 mA passes through the second data line D 2 ; the first data current of 3 mA passes through the third data line D 3 ; and the first data current of 6 mA passes through the fourth data line D 4 .

In this case, the first cross-talk preventing circuit 310 recognizes in advance from the first display data transmitted from the controller 306 that total 11 mA of current will pass through the data lines D 1 to D 4 .

Here, the first cross-talk preventing circuit 310 also recognizes in advance that the total 11 mA of current will pass through the scan line S 1 since the first data currents passing through the data lines D 1 to D 4 will flow along the scan line S 1 through the pixels E 11 to E 41 .

After that, the first cross-talk preventing circuit 310 provides the scan line S 1 with the compensating current of 9 mA. As a result, a total 20 mA of current comes to passé through the scan line S 1 .

Subsequently, the controller 306 receives second display data from the outside device and transmits the received second display data to the data driving circuit 308 .

Then, the data driving circuit 308 provides the data lines D 1 to D 4 with second data signals, i.e. second data currents according to the second display data transmitted through the controller 308 .

As a result, for example, the second data current of 2 mA passes through the first data line D 1 ; the second data current of 3 mA passes through the second data line D 2 ; the second data current of 3 mA passes through the third data line D 3 ; and the second data current of 6 mA passes through the fourth data line D 4 .

In this case, the second cross-talk preventing circuit 312 recognizes in advance that a total 14 mA of current will pass through the scan line S 2 .

After that, the second cross-talk preventing circuit 312 provides the scan line S 2 with the compensating current of 9 mA. As a result, a total 20 mA of current comes to pass through the scan line S 2 .

Namely, in such way as described above, the present invention make it possible that the same current passes through each scan line S 1 to S 4 . As a result, the cathodes of the pixels E 11 to E 44 have a voltage of 3.2V.

In summary, in the electroluminescent device of the present invention, the same voltage is applied to the cathode of the pixels E 11 to E 44 unlike in the conventional electroluminescent device where the cathodes of the pixels do not have the same voltage value.

Therefore, in the electroluminescent device of the present invention, the cross-talk problem can be overcome.

FIG. 5 is a flow chart illustrating a method of driving the electroluminescent device of FIG. 4 .

Referring to FIG. 5 , the first and second scan driving circuits 302 and 304 provide the scan lines S 1 to S 4 with the first and second scan signals in sequence (S 400 ).

Next, the controller 306 receives the display data transmitted from the outside device (S 402 ).

Subsequently, the first and second cross-talk preventing circuits 310 and 312 provide each scan line S 1 to S 4 with the compensating currents corresponding to the display data (S 404 ).

As a result, the total current passing through each scan line S 1 to S 4 becomes of the same value.

Next, the data driving circuit 308 provides the data lines D 1 to D 4 with the data signals corresponding to the display data transmitted from the controller 306 (S 406 ).

As a result, the pixels E 11 to E 44 come to emit light at a desired luminance without the cross-talk phenomenon.