This application claims priority to and the benefit of Korean Patent Applications No. 10-2004-0026174, filed on Apr. 16, 2004, and No. 10-2004-0038275, filed on May 28, 2004, both at the Korean Patent Office, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a plasma display panel (PDP) driver, a driving method thereof, and a plasma display.
2. Description of the Related Art
The plasma display is a flat panel display that uses plasma generated via a gas discharge process to display characters or images, and tens to millions of pixels are provided thereon in a matrix format, depending on its size. Plasma displays are typically categorized as either DC plasma displays or AC plasma displays, according to supplied driving voltage waveforms and discharge cell structures.
Since DC plasma displays have electrodes exposed in the discharge space, they allow a current to flow in the discharge space while the voltage is supplied, and therefore they problematically require resistors for current restriction. On the other hand, since AC plasma displays have electrodes covered by a dielectric layer, capacitances are naturally formed to restrict current, and the electrodes are protected from ion shocks when discharging. Accordingly, they have a longer lifespan than the DC plasma displays.
In a typical AC PDP driving method a frame is divided into a plurality of subfields and includes a reset period, an address period, and a sustain period. In the reset period, the discharge cells are reset in order to stably perform an address operation. In the address period, the cells that are turned on and the cells that are not turned on are selected on the panel, and wall charges are accumulated on the cells that are turned on (i.e., the addressed cells). In the sustain period, a discharge for actually displaying pictures on the addressed cells is performed.
In order to perform these operations, a sustain discharge pulse is alternately applied to the scan electrode and sustain electrode in the sustain period, and a reset waveform and a scan waveform are applied to the scan electrode while the sustain electrode is biased with a predetermined voltage in the reset period and the address period. Typically, a scan driving board for driving the scan electrodes and a sustain driving board for driving the sustain electrodes are separately provided, which generates a problem of installing the driving boards in the chassis base and increases the cost.
Accordingly, a method for combining the two boards into a single board to provide the same to one side of the scan electrode, and extending one terminal of the sustain electrode to reach the combined board has been proposed, but the combination increases the impedance formed at the extended sustain electrode.
To solve the problem, Korean laid-open application No. 10-2003-90370 has disclosed a method for applying a sustain discharge pulse by a scan electrode driver and minimizing a sustain electrode driver.
In this instance, since very few wall charges are accumulated on the cells which are not selected in the address period when the conditions for all the discharge cells are the same, no discharge is generated between the scan electrodes and the address electrodes of the discharge cells which are not selected when the voltages Vs and −Vs are applied to the scan electrode in the sustain period.
However, a misfiring may be generated between the scan electrode and the address electrode of the non-selected cells in the address period because of unstable wall charge states between the discharge cells when the voltages Vs and −Vs are applied to the scan electrode in the sustain period.
Therefore, in order to prevent the misfiring between the address electrode and the scan electrode in the prior art, the address electrode is floated in the sustain period or an address voltage Va is applied to the address electrode when the voltage Vs is applied to the scan electrode, thereby reducing the voltage difference between the address electrode and the scan electrode.
The above-described prior art reduces the voltage difference between the scan electrode and the address electrode when positive wall charges are accumulated on the scan electrodes of discharge cells which are not selected in the address period and the voltage Vs is applied to the scan electrode in the sustain period. However, a misfiring may be generated since the voltage difference between the scan electrode and the address electrode may be greater than a firing voltage when negative wall charges are accumulated on the scan electrodes of discharge cells which are not selected in the address period and the negative voltage −Vs is applied to the scan electrode in the sustain period.
In accordance with the present invention a driving waveform of a misfiring preventing PDP with an integrated board for driving scan (Y) electrodes and sustain (X) electrodes is provided.
In one aspect of the present invention, a method is provided for dividing a frame into a plurality of subfields and driving the same in a plasma display panel including a plurality of first electrodes, second electrodes, and address (A) electrodes. In at least one subfield: (a) a reset waveform is applied to the first electrode in order to establish a discharge cell to be addressed while the second electrode is biased with a first voltage; (b) a second voltage is sequentially applied to the first electrode while the second electrode is biased with the first voltage; (c) a third voltage which is greater than the first voltage is applied to the first electrode for the purpose of a sustain discharge while the second electrode is biased with the first voltage; and (d) a fourth voltage which is less than the first voltage is applied to the first electrode for the purpose of a sustain discharge while the second electrode is biased with the first voltage. The absolute value of the difference between the first voltage and the third voltage is greater than the absolute value of the difference between the first voltage and the fourth voltage.
The voltage at the address electrode is increased to a fifth voltage in (c), and the voltage at the address electrode is maintained to be a sixth voltage which is less than the fifth voltage in (d).
The fifth voltage and the sixth voltage are applied to the address electrode respectively, and the address electrode is floated in (c) and (d).
In another aspect of the present invention, a method is provided for driving a plasma display panel including a plurality of first electrodes, second electrodes, and address electrodes. In a sustain period, a second voltage which is greater than a first voltage is applied to the first electrode while the second electrode is biased with the first voltage; and a third voltage which is less than the first voltage is applied to the first electrode while the second electrode is biased with the first voltage. A fourth voltage which is a voltage at the address electrode when the second voltage is applied to the first electrode does not correspond to a fifth voltage which is a voltage at the address electrode when the third voltage is applied to the first electrode. The absolute value of the difference between the first voltage and the second voltage is greater than the absolute value of the difference between the first voltage and the third voltage.
The fourth voltage is greater than the fifth voltage, and the address electrode is floated.
In still another aspect of the present invention, a plasma display panel having a panel and a driving circuit is provided. The panel includes a plurality of first electrodes, second electrodes, and address electrodes, and the driving circuit alternately applies a positive first voltage and a negative second voltage to the first electrode in a sustain period, and controls the voltage at the address electrode when the first voltage is applied to the first electrode to be greater than the voltage at the address electrode when the second voltage is applied to the first electrode, and an absolute value of the negative second voltage is less than an absolute value of the positive first voltage. The driving circuit maintains the voltage at the second electrode to be a ground voltage, floats the address electrode, and maintains the voltage at the second electrode to be a ground voltage in a reset period and an address period.
In still yet another aspect of the present invention, a method is provided for dividing a frame into a plurality of subfields and driving the same in a plasma display panel including a plurality of first electrodes, second electrodes, and third electrodes. In at least one subfield, a discharge cell to be turned on is selected in an address period, and a second- voltage which is greater than a first voltage and a third voltage which is less than the first voltage are alternately applied to the second electrode while the first electrode is biased with the first voltage in a sustain period. The third electrode is floated while the third voltage is applied to the second electrode in the sustain period. A fourth voltage is applied to the third electrode of the discharge cell to be turned on and a fifth voltage which is less than the fourth voltage is applied to the third electrode of the discharge cell which is not turned on in the address period, and the third electrode is decoupled from a power source for supplying the fifth voltage when the third electrode is floated.
Referring now to
The plasma panel 100 includes a plurality of address (A) electrodes A1 to Am arranged in a column direction, and a plurality of first electrodes Y1 to Yn (also referred to collectively as Y electrodes) and second electrodes X1 to Xn (also referred to collectively as X electrodes) arranged in a row direction.
The address electrode driver 200 receives an address drive control signal SA from the controller 400, and applies display data signals for selecting discharge cells to be displayed to the respective address electrodes pursuant to an image signal applied to controller 400.
The sustain scan (XY) electrode driver 320 receives an XY electrode drive signal SXY from the controller 200 and applies the signal to the X and Y electrodes. The controller 400 receives external image signals, generates the address drive control signal SA and the XY electrode drive signal SXY, and respectively transmits the signals SA and SXY to the address electrode driver 200 and the sustain scan (XY) electrode driver 320.
A PDP driving method will now be described with reference to
In the reset period, the voltage Vs is applied to the scan (Y) electrode, and a voltage which gradually rises to the voltage Vset is applied to the scan electrode. A weak discharge is generated between the scan electrode and the sustain electrode to form negative wall charges on the scan electrode and positive wall charges on the sustain electrode. The voltage at the scan electrode is reduced to the voltage Vs, and a voltage which gradually falls to the voltage −Vnf is applied to the scan electrode. A weak discharge is generated between the scan electrode and the sustain electrode to erase most of the negative wall charges formed on the scan electrode and the positive wall charges formed on the sustain electrode.
In the address period, the levels of scan voltages applied to the Y electrode are reduced by as much as the bias voltage applied to the X electrode in the address period instead of applying the bias voltage to the X electrode in order to maintain the voltages at the X and Y electrodes to be 0V and maintain the voltage difference between the X and Y electrodes.
That is, the voltage −VscL is applied to the selected scan electrode while the non-selected scan electrode is biased with the voltage −VscH, and the positive voltage Va is applied to the address (A) electrode which is passed through a discharge cell to be turned on from among discharge cells formed on the selected scan electrode. A discharge is generated between the address electrode to which the voltage Va is applied and the scan electrode to which the voltage −VscL is applied and a discharge is generated between the scan electrode and the sustain electrode so that wall charges for a sustain discharge in the sustain period are formed.
In the sustain period, pulses with the voltages of +Vs1 and −Vs2 are alternately applied to the scan electrode to generate a sustain discharge between the scan electrode and the sustain electrode, and float the address electrode in the sustain period.
In the case in which the absolute values of the voltages of +Vs1 and −Vs2 correspond to each other, a misfiring may be generated since the voltage difference between the scan electrode and the address electrode becomes greater than the firing voltage, when the negative wall charges are accumulated on the scan electrode of the discharge cell which is not selected in the address period and the negative voltage −Vs is applied to the scan electrode in the sustain period.
As shown in
Referring now to
As shown in
In this instance, the difference between the voltage Va at the address electrode and the sum of the wall voltage Vw1 at the scan electrode and the voltage +Vs1 applied to the scan electrode is reduced to be less than the firing voltage Vf between the address electrode and the scan electrode and no misfiring is accordingly generated (as illustrated in
Further, the potential at the scan electrode is reduced and the potential at the address electrode is reduced when the voltage −Vs2 is applied to the scan electrode while the output of the address electrode is floated in the sustain period. The voltage at the address electrode is clamped with 0V (as illustrated by the path (2) of
In this instance, the difference between the wall voltage Vw1 at the scan electrode and the voltage −Vs2 applied to the scan electrode is less than the firing voltage Vf between the address electrode and the scan electrode and no misfiring is accordingly generated (as illustrated in
The voltage +Vs1 is to be less than the firing voltage between the sustain electrode and the scan electrode so that no sustain discharge may be generated at the discharge cells which are not addressed in the address period. Also, the voltage −Vs2 must have a value such that the voltage −Vs2 together with the wall voltage of the addressed discharge cells may generate a discharge. In this instance, the voltages of +Vs1 and −Vs2 can be controlled within a range in which the difference between the voltages of +Vs1 and −Vs2 corresponds to the difference between the conventional voltages of +Vs and −Vs.
The address electrode is floated in the sustain period according to the first exemplary embodiment. In addition, the address electrode can be floated when the voltage pulse of +Vs1 is applied to the scan electrode in the sustain period, and differing from this, the voltage pulse of Va can be directly applied to the address electrode.
The sustain electrode is biased with 0V while the driving waveform is applied to the scan electrode in the first exemplary embodiment, and in addition, it is also possible to bias the sustain electrode with another voltage and modify the driving waveform of the scan electrode by as much as the voltage difference between the other voltage and 0V.
Further, the voltages of −Vs2 and +Vs1 have been alternately applied to the scan electrode in the sustain period in the first exemplary embodiment, and in addition, it is possible to increase the voltage at the scan electrode from the voltage −Vs2 to 0V, increase the voltage from 0V to the voltage +Vs1, reduce the voltage from the voltage +Vs1 to 0V, and reduce the voltage from 0V to the voltage −Vs2.
The voltages of −Vs2 and +Vs1 have been alternately applied to the scan electrode in the sustain period in the first exemplary embodiment, and in addition, it is possible to alternately apply the voltages of Vs and −Vs to the scan electrode in the sustain period and float the address electrode when the voltage −Vs is applied to the scan electrode.
When the voltage −Vs is applied to the scan electrode in the sustain period and the address electrode is floated as shown in
Therefore, a switch SW1 is coupled between the transistor AL and the ground voltage GND in the second exemplary embodiment.
When the voltage −Vs is applied to the scan electrode in the sustain period in the second exemplary embodiment, the voltage at the address electrode is reduced to be a negative voltage to thus decrease the voltage difference between the scan electrode and the address electrode and accordingly prevent a misfiring from being generated at the discharge cell which is not selected in the address period.
Since the driving waveform according to the second exemplary embodiment floats the address electrode when the voltage −Vs is applied to the scan electrode, the switch SW1 is repeatedly turned on and off to thus increase power consumption. Also, when the voltage Vs is applied to the scan electrode to generate a discharge, the electrons are moved to the scan electrode and the positive ions are moved to the address electrode. The address electrode is coated with a phosphor for color representation, and the positive ions collide with the phosphor surface to shorten the phosphor's lifetime.
Accordingly, a method for overcoming the problem will now be described with reference to
The voltage at the address electrode is increased according to the voltage at the scan electrode when the voltage Vs is applied to the scan electrode and the address electrode is floated. Therefore, the potential at the address electrode is increased, a large amount of positive ions are moved to the sustain (X) electrode after a sustain discharge, and hence, the phosphor covering the address electrode is protected.
When the driving waveform according to the third embodiment is generated by using the general address selecting circuit shown in
Therefore, the path of the voltage Va and the address electrode is to be intercepted in order to supply a voltage greater than the voltage Va to the address electrode in a like manner of a third exemplary embodiment.
A method for applying the driving waveform according to the third exemplary embodiment through the address selecting circuit will now be described.
When the address (A) electrode is floated and the voltage Vs is applied to the scan (Y) electrode by turning off the switches SW1 and SW2, the voltage at the address electrode is increased to be a positive voltage, and when the voltage −Vs is applied to the scan electrode, the voltage at the address electrode is reduced to be a negative voltage. In this instance, since the switches SW1 and SW2 are turned off and the address electrode is intercepted from the voltages of 0V and Va, a voltage greater than the voltage Va is applied when the voltage Vs is applied to the scan electrode, and a voltage less than the voltage 0V is applied when the voltage −Vs is applied to the scan electrode.
As described, the sustain (X) electrode driving board is eliminated by biasing the sustain electrode with a predetermined voltage, applying a driving waveform to the scan electrode, and thereby performing a reset operation, an address operation, and a sustain discharge operation. Also, the impedance on the path through which the sustain discharge pulses are applied is established to be constant since the pulses for the sustain discharge are applied to the scan electrode driving board.
The reset periods of subfields forming a frame can respectively have a rising period and a falling period as described in the first to third exemplary embodiments, and in addition, the reset periods of some subfields can respectively have a falling period.
The sustain electrode is biased with a predetermined voltage in the whole driving periods, but the present invention is not restricted to this.
According to the present invention, the sustain electrode driving board is removed since the driving waveform is applied to the scan electrode while the sustain electrode is biased with a constant voltage.
Further, the generation of misfiring at the discharge cell which is not selected in the address period is solved by controlling the absolute value of the positive voltage to be greater than the absolute value of the negative voltage in the sustain voltage pulse applied to the scan electrode (or sustain electrode) in the sustain period and thus reducing the voltage difference between the address electrode and the scan electrode (or sustain electrode).
The misfiring in the sustain period is prevented by floating the address electrode in the sustain period, adding a switch between respective power sources for supplying an address voltage and a non-address voltage applied to the address electrode in the address period and an address IC, and increasing the voltage to be greater than the address voltage or decreasing the same to be less than the address voltage when floating the address electrode in the sustain period.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
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