Plasma display panel unit

The plasma display panel (PDP) unit of the present invention comprises a PDP drive circuit for supplying drive power to a display panel and a control portion for controlling the drive power. The control portion includes a power correction value generating circuit for generating a power correction value and the PDP drive circuit contains a voltage adjusting circuit for outputting the drive power based on the power correction value.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to technology relating to matrix type plasma display panel (PDP) and more particularly to technology relating to plasma display panel whose drive power supply is automatically adjusted.

2. Description of the Related Art

Conventionally, the drive voltage for a sustain driver and a scan driver has been adjusted by adjusting variable resistance upon shipment so as to secure an amount of margin corresponding to an influence upon the PDP by a change in temperature upon operation, a change of the PDP itself by time passage and the like. More specifically, a voltage adjusting circuit shown inFIG. 6is inserted during a supply of electric power to the aforementioned driver and the variable resistor R63is adjusted so as to correct the voltage of an input to an amplifier60thereby adjusting the driving voltage.

Conventional technology about the driving circuit of the PDP unit has been disclosed in Japanese Patent Application Laid-Open No. 2000-293135.

However, it takes skill for adjustment of this PDP and therefore there is a limit in reduction of adjustment cost. Further, there is a room in which human error may be induced.

The intensity of illumination is changed by a change in temperature at the time of startup and after long-hour use and this intensity of illumination is changed by a change with time passage of the PDP itself also. However, the change in the intensity of illumination in the PDP cannot be eliminated completely by adjustment of a single time before shipment.

In the above-mentioned Japanese Patent Application Laid-Open No. 2000-293135, the power supply is described only a symbol of the DC power supply inFIG. 3, is not described about a voltage adjusting function.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a PDP unit capable of eliminating human error upon adjustment of the PDP drive power and reducing cost.

The above object of the present invention can be achieved by a plasma display panel unit provided with: a panel driving device which supplies drive power to a display panel and a power control device which controls the drive power, wherein the power control device has a power correction value generating device which generates power correction value; and the panel driving device has a drive power changing device which changes and outputs the drive power based on the power correction value.

As a result, the drive power is changed based on the power correction value and outputted to the driver. Therefore, the drive power of the driver can be adjusted.

According to the present invention, automatic adjustment of the drive voltage is enabled. Thus, it is possible to omit voltage adjustment by skilled persons to eliminate human error completely and reduce cost.

The above object of the present invention can be achieved by a plasma display panel unit provided with a panel driving device which supplies drive power to a display panel and a voltage control device which control the voltage of the drive power, wherein the voltage control device has a voltage correction value generating device which generates voltage correction value; and the panel driving device has a drive voltage changing device which changes and outputs the drive voltage based on the voltage correction value.

Because the drive voltage is changed based on the voltage correction value and outputted to the driver, the drive voltage of the driver can be adjusted.

In one aspect of the plasma display panel unit of the present invention, the plasma display panel unit is further provided with at least any one of a temperature detecting device which detects the temperature of the display panel and a usage time computing device which computes usage time of the display panel, wherein the voltage correction value generating device generates the voltage correction value based on at least any one of a detected panel temperature and a measured usage time.

Because the control portion outputs the voltage correction value considering usage time or temperature of the panel, the drive voltage can be automatically adjusted corresponding to an influence by a change in the PDP temperature upon operation, changes in the PDP itself with time passage and the like.

Because the control portion can automatically output the voltage correction value and adjust the drive voltage considering panel usage time and panel temperature, it is possible to eliminate an influence by the temperature change in the PDP, an influence by the PDP itself with time passage and the like.

In another aspect of the plasma display panel unit of the present invention, the plasma display panel unit is further provided with an external control signal receiving device which receives an external control signal from outside, wherein the voltage correction value generating device generates the voltage correction value based on the external control signal.

Consequently, the control portion can receive the control signal from the remote controller, personal computer and the like and output the voltage correction value so as to adjust the drive voltage.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of a plasma display panel (PDP) unit of the present invention will be described with reference to the accompanied drawings.

FIG. 1is a block diagram showing an outline of the PDP unit.

The PDP unit comprises an input terminal21, an A/D converter22, a display data generating portion23, a frame memory24, a control portion5, and a D/A converter6. A PDP drive circuit acting as a panel driving device includes an address driver2, an X electrode driver3, and a Y electrode driver4. Further, a PDP display unit includes a temperature detector7which works as a temperature detecting device for the display panel, a usage time counting circuit9which works as a usage time counting device for the display panel, and an external control signal receiver8which works as an external control signal receiving device.

A video signal inputted from the input terminal21is converted to digital video data by the A/D converter22, processed to display data by the display data generating portion23, and then supplied to the frame memory24. The display data generating portion23computes emission time corresponding to the intensity of illumination of video data and corrects the data by reallocation so as to generate display data. The frame memory24is composed of, for example, a VRAM, which accumulates display data of a screen sent from the display data generating portion23and supplies it to the address driver2following synchronous signal from a control portion5which will be described later. The address driver2is composed of a driving circuit having a DC power supply and switching device, and generates pixel data pulse to each discharge cell on the display panel based on the display data inputted from a frame memory24and applies this to a column electrode Dj for every display line.

The control portion5is composed of, for example, CPU, which outputs synchronous signal to the A/D converter22, the display data generating portion23and the frame memory24. Further, the control portion5, which works as a voltage control device, includes a voltage correction value generating circuit, which works as a voltage correction value generating device, so as to output a voltage correction value to adjust the PDP driving voltage. The D/A converter6converts the voltage correction value that the control portion5outputs in the form of digital value into an voltage correction value which is an analog signal and outputs it to an X-electrode driver3and a Y-electrode driver4. As shown inFIG. 3, each of the X-electrode driver3and the Y-electrode driver4is constituted of a driving circuit containing a DC power supply and switching devices. Based on synchronous signal from the control portion5, the X-electrode driver3applies sustain discharge pulse IPx to the electrode Xj and the Y-electrode driver4applies sustain discharge pulse IPy to the electrode Yj.

The temperature detector7of the display panel detects the temperature of a display panel and outputs the result of detection to the control portion5. The usage time computing circuit9of the display panel computes a time in which the power of the display panel is turned ON and is part of the control portion5. The external control signal receiver8receives a control signal from outside, for example, a remote controller or personal computer and outputs its content to the control portion5.

The operation of the PDP unit having such a structure will be described below.

A video signal inputted from the input terminal21as an analog signal is converted to digital video data by the A/D converter22, processed to display data by the display data generating portion23, and supplied to the frame memory24. The frame memory24accumulates display data sent from the display data generating portion23and supplies it to the address driver2following synchronous signal from the control portion5.

A synchronous signal is separated from the video signal inputted from the input terminal21by a sync separation circuit (not shown), and then the control portion5outputs the synchronous signal to the A/D converter22, the display data generating portion23and the frame memory24on the basis of this separated synchronous signal. The control portion5drives the PDP by controlling ON/OFF of a switching device of the PDP driving circuit1, which is a panel driving device shown in FIG.3. Additionally, the control portion5outputs an appropriate voltage correction value by computing a drive voltage of the PDP according to the result of temperature detection on the display panel and usage time of the display panel. Further, the control portion5receives a control signal from outside, for example, a remote controller or a personal computer, and computes a voltage correction value depending upon its content, and outputs. At this time, the D/A converter6converts the voltage correction value to be outputted by the control portion5as digital value to analog value and outputs the result to the X electrode driver3or the Y electrode driver4. Therefore, the control portion5facilitates adjustment of the driver voltage by means of a voltage adjusting circuit, which will be described later.

The drive sequence of the PDP unit will be described with reference to FIG.2.

FIG. 2is a schematic diagram showing the drive sequence of the PDP according to an embodiment of the present invention.

A set of a sub-field (1SF) has a reset period, an address period, and a sustain period. A set of a field, which is a drive sequence of the PDP, has several sub-fields, repeated N times, and thereafter a main erase process for resetting to a condition in which wall charge is erased by applying erase pulse respectively to all cells.

In the reset period, all the discharge cells of the PDP unit are gotten into luminous discharge cell condition. In the subsequent address period, the address driver2forms wall charge selectively to each discharge cell based on video signal so as to generate pixel data pulse which sets up luminous discharge cell or non-luminous discharge cell and apply this pulse to a column electrode of every display line. In the sustain period, sustain discharge pulse IPxand sustain discharge pulse IPyare generated alternately and applied to the column electrode X and column electrode Y alternately. As a result, in a luminous discharge cell in which the above-described wall charge remains, discharge light emission is repeated and then that light emission is sustained.

The PDP unit of this embodiment adjusts the voltage of the X electrode driver3or the Y electrode driver4in the address period and the sustain period.

FIG. 3is a conceptual diagram showing the structure of the PDP drive circuit1of this embodiment.

The PDP drive circuit1, which works as a panel drive device, is comprised of the address driver2, the X electrode driver3, and the Y electrode driver4. The X electrode driver3includes a reset pulse driver portion and a first sustain driver portion. The Y electrode driver4includes a reset pulse driver portion, a scan driver portion, and a second sustain driver portion.

The reset pulse driver portion applies a reset pulse respectively to all the column electrodes X1-Xn, Y1-Ynat the same time in the reset period. Consequently, all the discharge cells in the PDP unit are simultaneously discharged and excited to generate charged particles. After this discharge is stopped, a predetermined quantity of wall charges are accumulated on a dielectric layer of the discharge cells, so that luminous discharge cell condition is attained.

The scan driver portion applies a scan pulse SP to the electrode Yjin the address period so as to set the electrode Yjto a predetermined positive potential (Vh−Voff). This application is carried out synchronously with application of pixel data pulse DPjfrom the address driver2. As a result, of the cells of the column electrode on which the scan pulse SP is applied, discharge occurs in only a cell onto which pixel data pulse of positive voltage is applied at the same time.

The first sustain driver portion and the second sustain driver portion generate sustain discharge pulse IPxand sustain discharge pulse IPyalternately in the sustain period and apply it to the column electrodes X1-Xnand the column electrodes Y1-Ynalternately. Consequently, discharge light emission is repeated in the light emission discharge cell in which the wall charge remains, and the light emission is sustained.

The operation of the PDP drive circuit1having the above described structure will be described below.

The column electrode Xjis an electrode at the column j (one electrode composing the j display line) in the column electrodes X1-Xnand the column electrode Yjis an electrode at the column j (the other electrode composing the j display line) in the column electrodes Y1-Yn. The display panel cell is located between the column electrode Xjand Yjwhich form a pair and acts as a capacitor Co. A power supply B1outputs sustain voltage Vs1and the voltage changes depending on an input of the voltage correction value from the control portion5. A power supply B2outputs a reset voltage Vr1.

The power supply B3outputs the sustain voltage Vs1and the voltage changes depending on input of the voltage correction value from the control portion5. The power supply B4outputs the reset voltage Vr1. The power supply B5generates the voltage Voffand the power supply B6generates the scan pulse voltage Vhincluding the analog voltage correction value.

Because the voltage correction value can be inputted to the power supplies B1, B3, the sustain voltage can be adjusted and because the voltage correction value can be inputted to the power supply B6, the scan pulse voltage can be adjusted.

A voltage adjusting circuit for use in the sustain driver power supplies B1, B3and the scan driver power supply B6in the PDP drive circuit1having such a structure will be described below.

FIG. 4is an outline diagram of the voltage adjusting circuit of this embodiment.

The voltage adjusting circuit of this embodiment is a drive voltage changing device and includes a loop circuit comprised of an amplifier, a transistor Tr and resistor R41as shown in FIG.4. Hereinafter, a loop gain is as A for describing.

Hereinafter, the operation of the voltage adjusting circuit having the above-described structure will be described.

If analog voltage V0±α containing ±α analog voltage correction value in its original input voltage V0is inputted into the voltage adjusting circuit shown inFIG. 4from the control portion, an increase/decrease amount ΔV1=±A·α is added to the original output voltage V1because the loop gain is A, so that the output voltage V1±ΔV1is applied to the driver. Thus, the voltage correction value ±ΔV1acts on the driver so as to enable adjustment of the driver drive voltage.

The voltage adjusting circuit having such a structure is disposed at power supplies B1, B3, B6of the PDP drive circuit1and the voltage correction value outputted from the control portion5is inputted as analog voltage correction value through the D/A converter6. Thus, the sustain voltage can be adjusted at the power supplies B1and B3. The scan pulse voltage can be adjusted at the power supply B6.

The operation of the PDP drive circuit1having such a structure will be described with reference to a time chart shown in FIG.5. The drive sequence of this PDP describes the operation in a single sub-field. Subsequently, the reset period, address period, and sustain period will be described separately.

First, in the reset period, a switching device S8of the X electrode driver3is turned ON, and at the same time, switching devices S16and S22of the Y electrode driver4are turned ON. The other switching devices are kept OFF. When the switching device S8is turned ON, current flows from the electrode Xjto a negative terminal of the power supply B2through a resistor R1and a switching device S8. When the switching device S16is turned ON, current flows into the electrode Yjfrom a positive terminal of a power supply B4through a switching device S16, a resistor R1, and a switching device S22. The potential of the electrode Xjis decreased gradually depending upon time constant of a capacitor Coand the resistor R1so that a reset pulse RPXis generated. The potential of the electrode Yjis increased gradually depending on time constant of the capacitor Coand the resistor R1so that a reset pulse RPyis generated. Then, the potential of the reset pulse RPxis saturated to the voltage level −Vr1and the potential of the reset pulse RPyis saturated to the voltage level Vr1. This reset pulse RPxis applied to all the column electrodes X1-Xnat the same time and the reset pulse RPyis applied to all the column electrodes Y1-Ynsimultaneously.

When these reset pulses RPx, RPyare applied at the same time, all discharge cells of the PDP are discharged and excited at the same time so as to generate charged particles. After this discharge is stopped, a predetermined quantity of wall charge is accumulated on dielectric layers of all discharge cells, so that luminous discharge cell condition is attained. When the reset pulses RPxand RPyare saturated after a predetermined time interval elapses, the switching device S8and the switching device S16are turned OFF before the reset period is terminated. At the same time, the switching devices S4, S14and S15are turned ON and the electrodes Xj, Yjare grounded. The reset period is terminated.

Next, in the address period, the address driver2forms wall charge selectively to each discharge cell based on display data outputted by the display data generating portion23, pixel data pulses DP1-DPmgenerate and the pulses set the cells the luminous discharge cells or non-luminous discharge cells. This process is applied to the column electrodes D1-Dmfor every display line. Pixel data pulses DPj, DPj+1are applied to the electrodes Yj, Yj+1. When the address period is started, the switching devices S14and S15are turned OFF, and the switching devices S17and S21are turned ON, and simultaneously the switching device S22is turned OFF. If the switching devices S17and S21are turned ON, positive potential (Vh-Voff) is applied to the electrode Yj. Because as described above, the power supply B6generates scan pulse voltage Vhcontaining analog voltage correction value, the positive potential (Vh-Voff), which is applied to the electrode Yjat this time, also contains voltage correction value.

The switching device S21is turned OFF synchronously with application of the pixel data pulse DPjfrom the address driver2and then switching device S22is turned ON. Consequently, a negative potential indicating the voltage −Voffat a negative terminal of the power supply B5is applied to as a scan pulse SP the electrode Yjthrough the switching device S22. Then, the switching device S21is turned ON synchronously with termination of the pixel data pulse DPjfrom the address driver2, and the switching device S22is turned OFF, so that a predetermined positive potential (Vh-Voff) is applied to the electrode Yj. After that, the scan pulse SP is applied to the electrode Yj+1also synchronously with application of the pixel data pulse DPj+1from the address driver2like the case of the electrode Yj.

In the discharge cell belonging to the column electrode onto which the scan pulse SP is applied, discharge occurs only in a discharge cell onto which pixel data pulse of positive voltage is applied at the same time, so that wall charge of the cell erases. On the other hand, no discharge occurs in a discharge cell on which pixel data pulse of positive voltage is not applied at the same time although the scan pulse is applied and therefore, wall charge of the cell remains. In this case, the discharge cell in which the wall charge remains turns to a luminous discharge cell, while a discharge cell in which the wall charge is erased turns to a non-luminous discharge cell. When the address period is switched over to the sustain period, the switching devices S17and S21are turned OFF and at the same time, the switching devices S14, S15and S22are turned ON. The switching device S4is kept ON.

Finally, the sustain period begins, the switching device S4is turned OFF while the switching device S1is turned ON. Consequently, current, whose origin is an electric charge accumulated in the capacitor C1, flows to the electrode Xjthrough a coil L1, a diode D1, and the switching device S1to charge the capacitor Co. At this time, the potential of the electrode Xjis raised gradually depending on time constant of the coil L1and capacitor Co. When half cycle of resonance cycle by the coil L1and capacitor Coelapses, the switching device S1is turned OFF while the switching device S3is turned ON. Consequently, the potential of the electrode Xjturns to an equal potential to the sustain voltage Vs1containing the voltage correction value of the power supply B1.

After a predetermined time elapses, the switching device S3is turned OFF while the switching device S2is turned ON. As a result, current flows to the capacitor C1through a coil L2, a diode D2and the switching device S2based on charge accumulated in the capacitor Coso as to charge the capacitor C1. At this time, the potential of the electrode Xjlowers gradually depending on time constant of the coil L2and capacitor CoWhen half cycle of resonance cycle by the coil L2and capacitor Coelapses (when the potential of the electrode Xjreaches 0V), the switching device S2is turned OFF while the switching device S4is turned ON.

By such operation, the X electrode driver3applies sustain discharge pulse IPxto the electrode Xj. At the same time when the switching device S4for erasing the sustain discharge pulse IPxis turned ON, the Y electrode driver4turns ON the switching device S11and turns OFF the switching device S14. When the switching device S14is turned ON, the potential of the electrode Yjis at grounding potential of 0V. When the switching device S11is turned ON while the switching device S14is turned OFF, current flows to the electrode Yjthrough a coil L3, a diode D3, the switching device S11, a switching device S15and a diode D6based on electric charge accumulated on the capacitor C2so that the capacitor Cois charged. At this time, the potential at the electrode Yjrises gradually depending upon time constant of the coil L3and the capacitor C0.

When the half cycle of resonance cycle by the coil L3and the capacitor Coelapses, the switching device S11is turned OFF while the switching device S13is turned ON. As a result, the potential of the electrode Yjturns to an equal potential to the sustain voltage Vs1containing the voltage correction value of the power supply B3. If, after a predetermined time elapses, the switching device S13is turned OFF while the switching device S12is turned ON, current flows to the capacitor C2through a switching device S22, a switching device S15, a coil L4, a diode D4and the switching device12based on electric charge accumulated in the capacitor Coso as to charge the capacitor C2.

At this time, the potential of the electrode Yjdrops gradually depending upon time constant of the coil L4and capacitor Co. When the half cycle of resonance cycle by the coil L4and the capacitor Coelapses (when the potential of the electrode Yjreaches 0V), the switching device S12is turned OFF while the switching device S14is turned ON.

By such operation, the Y electrode driver4applies sustain discharge pulse IPyof positive voltage to the electrode Yj. In the sustain period, the sustain discharge pulse IPxand the sustain discharge pulse IPyare generated alternately and applied to the column electrode X1-Xnand the column electrodes Y1-Ynalternately. As a result, the luminous discharge cell in which the wall charge remains repeats discharge light emission so as to sustain its light emission.

As shown inFIG. 1, the temperature detector7detects the temperature of the display panel, and the control portion5outputs a voltage correction value from that value. Because the drive voltage is adjusted through the D/A converter6, automatic adjustment of the power voltage is enabled based on the panel temperature.

Further, because the control portion5is provided with the usage time computing circuit9for the display panel, it can output a voltage correction value corresponding to a passage time from the startup of the PDP unit, and can compute and output the voltage correction value by integrating PDP usage time and considering deterioration of brightness due to a change of the PDP with time passage. Because the analog voltage correction value is applied to the PDP drive circuit through the D/A converter6, automatic adjustment of the drive voltage corresponding to the change of the PDP with time passage is enabled.

Further, by providing with the external control signal receiver8for receiving an external control signal from a remote controller, a personal computer or the like, the control portion5can output the voltage correction value corresponding to the external control signal so as to adjust the drive voltage. Consequently, the voltage can be adjusted by remote control or through the personal computer without removing a cover of the PDP main body.

The entire disclosure of Japanese Patent Application No. 2001-197990 filed on Jun. 29, 2001 including the specification, claims, drawings and summary is incorporated herein by reference in its entirety.