Display device and method of driving the same

This application claims priority from Korean Patent Application No. 2006-82360, filed on Aug. 29, 2006, the contents of which are incorporated herein by reference in its entirety.

1. Field of the Invention

The present invention relates to a display device and a method of driving the same. More particularly, the present invention relates to a display device for providing a charge discharged from data lines to a battery and a method of driving the same.

2. Description of the Related Art

A display device displays a certain image, and especially an organic electroluminescent device is a self light emitting device.

FIG. 1 is a view illustrating a common display device.

In FIG. 1 , the display device includes a panel 100 , a controller 102 , a first scan driving circuit 104 , a second scan driving circuit 106 , a discharging circuit 108 , a precharging circuit 110 , a data driving circuit 112 , a battery 114 and a DC-DC circuit 116 .

The panel 100 includes a plurality of pixels E 11 to E 44 formed in cross areas of data lines D 1 to D 4 and scan lines S 1 to S 4 .

The controller 102 receives display data from an outside apparatus (not shown), and controls the scan driving circuits 104 and 106 , the precharging circuit 110 , and the data driving circuit 112 by using the received display data.

The first scan driving circuit 104 transmits first scan signals to some of the scan lines S 1 to S 4 , e.g. S 1 and S 3 under control of the controller 102 .

The second scan driving circuit 106 transmits second scan signals to the other scan lines S 2 and S 4 under control of the controller 102 . As a result, the scan lines S 1 to S 4 are connected in sequence to a ground.

The discharging circuit 108 has switches SW 1 to SW 4 and a zener diode ZD, and discharges the data lines D 1 to D 4 up to the voltage of the zener diode ZD during a discharge time.

The precharging circuit 110 provides precharge currents corresponding to the display data to the data lines D 1 to D 4 under control of the controller 102 , thereby precharging the data lines D 1 to D 4 .

The data driving circuit 112 includes a plurality of current sources IS 1 to IS 4 , and provides data currents corresponding to the display data and outputted from the current sources IS 1 to IS 4 to the data lines D 1 to D 4 under control of the controller 102 . As a result, the pixels E 11 to E 44 emit light.

The DC-DC circuit 116 boosts a battery voltage outputted from the battery 114 up to a driving voltage Vcc, and then outputs the boosted battery voltage.

FIG. 2A and FIG. 2B are views illustrating the process of driving the display device of FIG. 1 . FIG. 2C is a timing diagram illustrating the process of driving the display device.

In FIG. 2A and FIG. 2C , the switches SW 1 to SW 4 are turned on, and the scan lines S 1 to S 4 are connected to a non-luminescent source having the same voltage V 2 as the driving voltage Vcc. As a result, the data lines D 1 to D 4 are discharged up to the voltage of the zener diode ZD during a first discharge time dcha 1 .

Subsequently, the precharge circuit 110 provides precharge currents to the data lines D 1 to D 4 during a first precharge time pcha 1 , thereby precharging the discharged data lines D 1 to D 4 .

Then, the first scan line S 1 is connected to the ground as shown in FIG. 2A , and the other scan lines S 2 to S 4 are connected to the non-luminescent source. In addition, the switches SW 1 to SW 4 are turned off.

Subsequently, the data driving circuit 112 provides data currents I 11 to I 41 corresponding to first display data to the precharged data lines D 1 to D 4 during a first luminescent time t 1 . In this case, the data currents I 11 to I 41 are passed to the ground through the data lines D 1 to D 4 , the pixels E 11 to E 41 , and the first scan line S 1 . As a result, the pixels E 11 to E 41 related to the first scan line S 1 emit light.

Then, the switches SW 1 to SW 4 are turned on during a second discharge time dcha 2 , and the scan lines S 1 to S 4 are connected to the non-luminescent source. As a result, the data lines D 1 to D 4 are discharged to the voltage of the zener diode ZD.

Subsequently, the precharging circuit 110 provides precharge currents to the discharged data lines D 1 to D 4 during a second precharge time pcha 2 , thereby precharging the discharged data lines D 1 to D 4 .

Then, a second scan line S 2 is connected to the ground, and the other scan lines S 1 , S 3 and S 4 are connected to the non-luminescent source. Additionally, the switches SW 1 to SW 4 are turned off.

Then, the data driving circuit 112 provides data currents I 12 to I 42 corresponding to second display data to the precharged data lines D 1 to D 4 during a second luminescent time t 2 as shown in FIG. 2B , wherein the second display data is inputted to the controller 102 after the first display data is inputted to the controller 102 . In this case, the data currents I 12 to I 42 are passed to the ground through the data lines D 1 to D 4 , the pixels E 12 to E 42 , and the second scan line S 2 . As a result, the pixels E 12 to E 42 related to the second scan line S 2 emit light.

Pixels E 13 to E 43 corresponding to a third scan line S 3 emit light through the method described above, and then pixels E 14 to E 44 corresponding to a fourth scan line S 4 emit light. Subsequently, the above process of emitting light in the pixels E 11 to E 44 is repeated as one unit of the scan lines S 1 to S 4 , i.e. a frame.

As described above, the data lines D 1 to D 4 are discharged up to a certain discharging voltage during a discharge time, i.e. electric charges charged to the data lines D 1 to D 4 are discharged and consumed. Thus, the battery 114 is consumed a lot, and accordingly, the power consumption of the display device becomes high.

The above and other features and advantages of the present invention will become readily apparent by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a view illustrating a common display device;

FIG. 2A and FIG. 2B are views illustrating the process of driving the display device of FIG. 1 ;

FIG. 2C is a timing diagram illustrating the process of driving the display device;

FIG. 3 is a view illustrating a display device according to a first embodiment of the present invention;

FIG. 4A and FIG. 4B are views illustrating the process of driving the display device in FIG. 3 ;

FIG. 4C is a timing diagram illustrating the process of driving the display device;

FIG. 5 is a view illustrating the voltage adjusting circuit in FIG. 3 according to one embodiment of the present invention; and

FIG. 6 is a view illustrating a display device according to a second embodiment of the present invention.

Hereinafter, the preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings.

FIG. 3 is a view illustrating a display device according to a first embodiment of the present invention.

In FIG. 3 , the display device of the present embodiment includes a panel 300 , a controller 302 , a first scan driving circuit 304 , a second scan driving circuit 306 , a discharging circuit 308 , a precharging circuit 310 , a data driving circuit 312 , a battery 314 , a voltage adjusting circuit 316 and a feedback circuit 318 .

The display device according to one embodiment of the present invention includes an organic electroluminescent device, a plasma display panel, a liquid crystal display, and others. Hereinafter, the organic electroluminescent device will be described as an example of the display device for the convenience of description.

The panel 300 includes a plurality of pixels E 11 to E 44 formed in cross areas of data lines D 1 to D 4 and scan lines S 1 to S 4 .

In case that the display device is organic electroluminescent device, each of the pixels E 11 to E 44 has a first electrode layer, an organic layer made up of organic material, and a second electrode layer formed in sequence on a substrate.

One of the first electrode layer and the second electrode layer is positive electrode, and the other layer is negative electrode.

When certain voltages are applied to the first electrode layer and the second electrode layer, holes generated from the positive electrode and electrons generated from the negative electrode are combined in the organic layer to form excitons. Then, the excitons are decomposed, and so a light having a certain wavelength is emitted from the organic layer in the decomposition process.

The controller 302 receives display data from an outside apparatus (not shown), and controls the scan driving circuits 304 and 306 , a precharging circuit 310 , and the data driving circuit 312 by using the received display data. Here, the controller 302 may store the received display data.

The first scan driving circuit 304 provides first scan signals to some of the scan lines S 1 to S 4 , e.g. S 1 and S 3 under control of the controller 302 .

The second scan driving circuit 306 provides second scan signals to the other scan lines S 2 and S 4 under control of the controller 302 . As a result, the scan lines S 1 to S 4 are coupled in sequence to a luminescent source, e.g. ground.

The discharging circuit 308 includes switches SW 1 to SW 4 , SW 6 and a zener diode ZD, and discharges the data lines D 1 to D 4 up to the voltage of the zener diode ZD. Hereinafter, this discharging process will be described in detail with reference to the accompanying drawings.

The precharging circuit 310 provides precharge currents corresponding to the display data to the data lines D 1 to D 4 under control of the controller 302 , thereby precharging the data lines D 1 to D 4 .

The data driving circuit 312 includes a plurality of current sources IS 1 to IS 4 , and provides data signals, e.g. data currents corresponding to the display data and outputted from the current sources IS 1 to IS 4 , to the data lines D 1 to D 4 under control of the controller 302 . As a result, the pixels E 11 to E 44 emit light. Here, the data signals have a level of not higher than the driving voltage Vcc, and are synchronized with the scan signals.

The voltage adjusting circuit 316 boosts a battery voltage outputted from the battery 314 up to the driving voltage Vcc, and generates the driving voltage Vcc. For example, the voltage adjusting circuit 316 is DC-DC circuit.

The feedback circuit 318 feeds electric charges discharged from the data lines D 1 to D 4 back to the battery 314 , and includes a charge storing circuit 320 , a comparing circuit 322 and a switch SW 7 . Hereinafter, the function of the feedback circuit 318 will be described in detail with reference to the accompanying drawings.

As described above, unlike the display device in the Related Art which consumes electric charges discharged from the data lines D 1 to D 4 , the display device of the present invention feeds electric charges discharged from the data lines D 1 to D 4 back to the battery 314 . Accordingly, the power consumption of the display device of the present invention is reduced, compared with the display device in the Related Art, and so the life of the battery 314 may be increased.

FIG. 4A and FIG. 4B are views illustrating the process of driving the display device in FIG. 3 . FIG. 4C is a timing diagram illustrating the process of driving the display device.

In FIG. 4A and FIG. 4C , the switches SW 1 to SW 5 are turned on during a first sub-discharge time of a first discharge time dcha 1 , and the scan lines S 1 to S 4 are coupled to a non-luminescent source having the same magnitude V 2 as the driving voltage Vcc. As a result, electric charges charged to the data lines D 1 to D 4 are stored in a capacitor C included in the charge storing circuit 320 during the first sub-discharge time T 1 of a first discharge time t 1 .

Subsequently, the switches SW 1 to SW 4 maintain the ‘turn-on’ condition during a second sub-discharge time T 2 of the first discharge time dcha 1 , the switch SW 5 is turned off, and the switch SW 6 is turned on. As a result, the data lines D 1 to D 4 are discharged up to the voltage of the zener diode ZD. In this case, a switching circuit SW 7 may be turned on or off.

Hereinafter, the function of the switching circuit SW 7 will be described in detail.

The comparing circuit 322 compares the battery voltage outputted from the batter 314 with a charging voltage Vc corresponding to electric charges stored in the capacitor C. For instance, the comparing circuit 322 compares the battery voltage with the charging voltage Vc by using OP amplifier.

In case that the charging voltage Vc is more than the battery voltage, the switching circuit SW 7 is turned on. As a result, the electric charges stored in the capacitor C are moved into the battery 314 during the second sub-discharge time T 2 , and so the moved charges are charged to the battery 314 .

However, in case that the charging voltage Vc is lower than the battery voltage, the switching circuit SW 7 is turned off. That is, in case that the switching circuit SW 7 is turned on, electric charges charged in the battery 314 are moved into the capacitor C since the battery voltage is higher than the charging voltage Vc. Then, the power consumption of the display device is increased, contrary to the object of the present invention. Generally, this phenomenon may be occurred when pixels related to the data lines D 1 to D 4 emit light having low brightness. Accordingly, if the charging voltage Vc is higher than the battery voltage though the pixels emit light having low brightness, the display device may not include the comparing circuit 322 .

Hereinafter, the process of driving the display device of the present embodiment will be described.

The precharging circuit 310 provides precharge currents to the discharged data lines D 1 to D 4 during a first precharge time pcha 1 , thereby precharging the discharged data lines D 1 to D 4 .

Then, the first scan line S 1 is coupled to a luminescent source, e.g. ground, the other scan lines S 2 to S 4 are coupled to the non-luminescent source, and the switches SW 1 to SW 4 are turned off.

Subsequently, the data driving circuit 312 provides data currents I 11 to I 41 corresponding to first display data to the precharged data lines D 1 to D 4 during a first luminescent time t 1 . These data currents I 11 to I 41 are passed to the luminescent source through data lines D 1 to D 4 , the pixels E 11 to E 14 , and the first scan line S 1 . As a result, each of the pixels E 11 to E 41 related to the first scan line S 1 emits light having brightness corresponding to the difference of its anode voltage VA 11 to VA 41 and its cathode voltage VC 11 to VC 41 . Here, the data currents I 11 to I 41 are synchronized with a scan signal SP 1 , e.g. the data currents I 11 to I 41 are provided to the data lines D 1 to D 4 during low logic area of the scan signal SP 1 .

Then, the switches SW 1 to SW 5 are turned on during a first sub-discharge time T 3 during a second discharge time dcha 2 , and the scan lines S 1 to S 4 are coupled to the non-luminescent source. As a result, electric charges charged to the data lines D 1 to D 4 are stored in the capacitor C included in the charge storing circuit 320 during the first sub-discharge time T 3 .

Subsequently, the switches SW 1 to SW 4 maintain the ‘turn-on’ condition during a second sub-discharge time T 4 of the second discharge time dcha 2 , the switch SW 5 is turned off, and the switch SW 6 is turned on.

Consequently, the data lines D 1 to D 4 are discharged up to the voltage of the zener diode ZD. In this case, the comparing circuit 322 compares the battery voltage outputted from the battery 314 with a charging voltage Vc corresponding to the electric charges stored in the capacitor C. In case that the charging voltage Vc is more than the battery voltage in accordance with the comparison result, the switching circuit SW 7 is turned on. Accordingly, the electric charges in the capacitor C are moved into the battery 314 during the second sub-discharge time T 4 , and so the moved electric charges are charged into the battery 314 .

Subsequently, the precharging circuit 310 provides precharge currents to the discharged data lines D 1 to D 4 during a second precharge time pcha 2 , thereby precharging the discharged data lines D 1 to D 4 .

Then, the second scan line S 2 is connected to the ground, the other scan lines S 1 , S 3 and S 4 are connected to the non-luminescent source, and the switches SW 1 to SW 4 are turned off.

Subsequently, the data driving circuit 312 provides data currents I 12 to I 42 corresponding to second display data to the precharged data lines D 1 to D 4 during a second luminescent time t 2 as shown in FIG. 4B , wherein the second display data is inputted to the controller 302 after the first display data is inputted. These data currents I 12 to I 42 are passed to the luminescent source through the data lines D 1 to D 4 , the pixels E 12 to E 42 , and the second scan line S 2 . As a result, each of the pixels E 12 to E 42 related to the second scan line S 2 emits light having brightness corresponding to the difference of its anode voltage VA 12 to VA 42 and its cathode voltage VC 12 to VC 42 . Here, the data currents I 12 to I 42 are synchronized with a scan signal SP 2 , e.g. the data currents I 12 to I 42 are provided to the data lines D 1 to D 4 during low logic area of the scan signal SP 2 .

Pixels E 13 to E 43 corresponding to a third scan line S 3 emit light in a similar method to the above. Then, pixels E 14 to E 44 corresponding to a fourth scan line S 4 emit light. Subsequently, the above process of emitting light in the pixels E 11 to E 44 is repeated as one unit of the scan lines S 1 to S 4 , i.e. frame unit. That is, the pixels E 11 to E 44 emit light as frame unit corresponding to one screen image of the display device, and so a certain image is displayed on a panel 300 .

FIG. 5 is a view illustrating the voltage adjusting circuit in FIG. 3 according to one embodiment of the present invention.

In FIG. 5 , the voltage adjusting circuit 316 includes a boosting circuit 330 and a boosted voltage detecting circuit 332 .

The boosting circuit 330 has an inductor ID and a boosting integrated circuit chip 334 coupled to both terminals of the inductor ID.

The boosting integrated circuit chip 334 has a switch SW, and boosts the battery voltage outputted from the battery 314 by switching the switch SW Here, since the boosting integrated circuit chip 334 is employed generally as boosting device, any further description concerning the elements of the boosting integrated circuit chip 334 except the switch SW will be omitted.

The boosted voltage detecting circuit 332 has resistors R 1 and R 2 coupled in series.

Hereinafter, the process of driving the voltage adjusting circuit 316 will be described in detail.

The switch SW is turned off, and so the battery voltage outputted from the battery 314 is stored in the inductor ID.

Subsequently, the switch SW is turned on, and so electric charges in the inductor ID are outputted to a second node.

Then, the switch SW is turned off, and so the battery voltage is stored in the inductor ID.

In other words, the switch SW repeats the turn-on/off, and so the battery voltage is boosted. Consequently, the second node has the boosted battery voltage. Here, the turn-on/off rate of the switch SW means the duty rate.

Subsequently, when the boosted battery voltage is more than the threshold voltage of a diode D, the booted battery voltage is passed to a third node through the diode D. As a result, the third node has the boosted battery voltage.

Then, the boosted voltage detecting circuit 332 detects the boosted battery voltage, i.e. the voltage of the third node.

Below, it is assumed that the voltage adjusting circuit 316 boosts the battery voltage, e.g. 3.7V, outputted from the battery 314 up to 18V, and a fourth node has 9V when the boosted battery voltage is 18V

For example, in case that the battery voltage boosted by the boosting circuit 330 is 16V, the boosted voltage detecting circuit 332 detects that the fourth node has 8V.

Subsequently, the boosted voltage detecting circuit 332 provides the information concerning the detected voltage of the fourth node to a FB terminal of the boosting integrated circuit chip 334 . In this case, the boosting integrated circuit chip 334 detects that the battery voltage is not boosted up to the desired voltage 18V through the provided information. Thus, the boosting integrated circuit chip 334 adjusts the duty rate of the switch SW to make the boosted battery voltage 18V.

The voltage adjusting circuit 316 boosts the battery voltage up to a desired voltage through the above described method, and outputs the boosted battery voltage, i.e. driving voltage Vcc.

FIG. 6 is a view illustrating a display device according to a second embodiment of the present invention.

In FIG. 6 , the display device of the present embodiment includes a panel 600 , a controller 602 , a scan driving circuit 604 , a discharging circuit 606 , a precharging circuit 608 , a data driving circuit 610 , a battery 612 , a voltage adjusting circuit 614 and a feedback circuit 616 .

Since the elements of the present embodiment except the scan driving circuit 604 are the same as in the first embodiment, any further description concerning the same elements will be omitted.

Unlike the scan driving circuit 304 and 306 in the first embodiment which is disposed in both directions of the panel 300 , the scan driving circuit 604 in the second embodiment disposed in one direction of the panel 600 is as shown in FIG. 6 .

An embodiment may be achieved in whole or in part by the display device comprising: data lines disposed in a first direction; scan lines disposed in a second direction different from the first direction; a plurality of pixels formed in cross areas of data lines and scan lines, and configured to drive on the basis of a driving voltage; a charge storing circuit connected to at least one data line during a first sub-discharge time of a discharge time, and configured to store charges discharged from the data line during the first sub-discharge time, wherein the discharge time includes at least two sub-discharge times; and a discharging circuit connected to the data line during a second sub-discharge time of the discharge time, and configured to discharge the data line up to a certain discharge voltage during the second sub-discharge time.

Another embodiment may be achieved in whole or in part by a circuit driving device for driving a panel having a plurality of pixels formed in cross areas of data lines and scan lines comprising: a charge storing circuit configured to store charges discharged from at least one of the data lines during a first sub-discharge time of a discharge time, wherein the discharge time includes at least two sub-discharge times; and a discharging circuit configured to discharge the data line up to a certain discharge voltage during a second sub-discharge time of the discharge time.

Still another embodiment may be achieved in whole or in part by a method of driving a display device having a plurality of pixels formed in cross areas of data lines and scan lines comprising: storing charges discharged from at least one of data lines during a first sub-discharge time of a discharge time, wherein the discharge time includes at least two sub-discharge times; and discharging the data line up to a certain discharge voltage during a second sub-discharge time of the discharge time.

As described above, the display device and the method of driving the same feed electric chares discharged from the data line back to the battery in discharging, and so the power consumption of the display device may be reduced.

Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to affect such feature, structure, or characteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.