Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2002-05-21
2003-07-22
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169100, C315S169400, C345S060000
Reexamination Certificate
active
06597122
ABSTRACT:
This application incorporates by reference Taiwanese application Serial No. 090112560, filed May 24, 2001.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to a driving apparatus and a method thereof, and in particular, to the apparatus for driving the address electrode of the plasma display panel and the method thereof.
2. Description of the Related Art
With the rapid developments in the fabrication technology of the audio/video (A/V) device, it can be foreseen that people in the future will enjoy the audio and video service with much higher performance than now. Taking the display device as an example, the conventional cathode ray tube (CRT) display device has the disadvantages of large volume, serious radiation issue, and serious image contortion and distortion at the brim region of the screen. Therefore, the conventional CRT display device certainly cannot satisfy the people who desire to enjoy the audio and video service with higher performance. When the high definition digital television (HDTV) system starts to operate and broadcast in the near future, the conventional CRT display device designed in the analog manner will gradually be obsolete. Instead, the plasma display panel (PDP), which has at least the advantages of low radiation, low power consumption, and large display area with small volume, can be a very promising product to replace the CRT display device.
FIG. 1
shows the diagram of the discharge unit of the tri-electrode alternating current plasma display panel (AC PDP). A plasma display panel includes n Y electrodes Y
1
~Yn, n X electrodes coupled to each other, and m address electrodes A
1
~Am. Each Y electrode is parallel to each X electrode respectively. A pair of the X electrode and the Y electrode is orthogonal to an address electrode to form a discharge unit, as shown in FIG.
1
. Therefore, the plasma display panel includes n×m discharge units. Each discharge unit can be lighted independently.
FIG. 2
shows the cross-sectional view of one discharge unit of the tri-electrode alternating current plasma display panel (AC PDP). Each discharge unit includes an X electrode, a Y electrode and an address electrode A. The X electrode and the Y electrode are set on the front glass substrate
202
in parallel and covered by the dielectric layer
204
. The dielectric layer
204
is used for accumulating wall charges. The dielectric layer
204
is covered by the protective layer
206
. The protective layer
206
is used for protecting the X electrode, the Y electrode, and the dielectric layer
204
. The address electrode A is set on the back glass substrate
208
opposite to the front glass substrate
202
, and is orthogonal to the X electrode and the Y electrode respectively. The address electrode A is covered by the fluorescence layer
210
. The rib
212
is formed along the sides of the address electrode A. The space between the protective layer
206
and the fluorescence layer
210
is the discharge space
214
. The discharge space
214
is filled with the discharge gas which comprises Ne and Xe.
The disadvantages of the plasma display panel are that the power loss is huge and the electromagnetic interference (EMI) problem is serious when switching the voltage of the address electrode by the address electrode driving apparatus. There are three kinds of conventional address electrode driving apparatus called the address electrode driving apparatus, the hard switching apparatus, and the bootstrap driving apparatus respectively. Each of them will be described in the following article.
FIG. 3
shows the diagram of the conventional address electrode driving apparatus for driving the address electrode of the plasma display panel
300
. The conventional address electrode driving apparatus
300
comprises four switches (M
1
, M
2
, M
3
, and M
4
), two diodes (D
1
and D
2
), a capacitor (Cs), and an inductance (L), as shown in FIG.
3
. An external power source is coupled to the conventional address electrode driving apparatus
300
for applying the driving voltage Vd. A signal control apparatus
302
is coupled to the conventional address electrode driving apparatus
300
at the node a. The plasma display panel
304
is coupled to the signal control apparatus
302
. The plasma display panel is represented in the form of the equivalent circuit
304
in FIG.
3
. The equivalent circuit of the plasma display panel
304
includes the equivalent capacitor between the X electrode and the address electrode Cx, the equivalent capacitor between the Y electrode and the address electrode Cy, and the equivalent capacitor between the X electrode and the Y electrode Cxy, as shown in FIG.
3
.
FIG. 4
shows the timing chart of the gate to the source voltage (Vgs) of M
1
(V
g1
), M
2
(V
g2
), M
3
(V
g3
), and M
4
(V
g4
), respectively, and the voltage of the node a (Va). When applying the gate to the source voltage Vgs to the gate electrode of the switch, the switch can be turned on. And when the gate to the source voltage Vgs does not apply anymore, the switch can be turned off. The operation of the conventional address electrode driving apparatus
300
can be controlled by controlling the ON and the OFF stages of the switches M
1
, M
2
, M
3
, and M
4
periodically. The operation of the conventional address electrode driving apparatus
300
can be divided in 5 stages according to the stage of the switches M
1
, M
2
, M
3
, and M
4
in one period. Each stage will be described in the following article.
When 0≦
t≦t
1
: 1.
When t=0, the switch M
2
can be turned on and the other switches are turned off. The node a is coupled to the ground when the switch M
2
is turned on. Therefore, the node a voltage Va is 0. After t=0, the switch M
2
is turned off, and the voltage of node a remains 0.
When
t
1
≦
t≦t
2
: 2.
When t=t
1
, the switch M
3
can be turned on and the other switches are turned off.
FIG. 5
a
shows the equivalent circuit of the conventional address electrode driving apparatus
300
when the switch M
3
is turned on and the switches M
1
, M
2
, and M
4
are turned off. The equivalent circuit of the plasma display panel
304
can be represented in the form of an equivalent capacitor Cp in
FIGS. 5
a
and
5
b
. The capacitor voltage of the capacitor Cs is Vs. The capacitance of the capacitor Cs is much larger than the capacitance of the equivalent capacitor Cp. Therefore, the capacitor Cs can be regarded as a voltage source with a voltage Vs. When the switch M
3
is turned on, a current I
1
can flow from the capacitor Cs to the capacitor Cp through the inductance L. The capacitor Cp is charged by the current I
1
and the node a voltage Va can be raised when the switch M
3
is turned on, as shown in FIG.
4
.
When
t
2
≦
t≦t
3
: 3.
When t=t
2
, the voltage of node a is Vd and the switch M
1
can be turned on. When the switch M
1
is turned on, the node a is coupled to the external power source directly. Because the magnitude of the node a voltage and the applying voltage of the external power source is equaled when the switch M
1
is turned on, there is no current between the external power source and the node a. Therefore, the voltage of node a is still Vd.
When
t
3
≦
t≦t
4
: 4.
When t=t
3
, the switch M
4
can be turned on and the other switches are turned off.
FIG. 5
b
shows the equivalent circuit of the conventional address electrode driving apparatus
300
when the switch M
4
is turned on and the switches M
1
, M
2
, and M
3
are turned off. When the switch M
4
is turned on, the capacitor Cp will be discharged and a current I
2
will flow from the capacitor Cp to the capacitor Cs through the inductance L. The capacitor Cp can be in resonance with the inductance L. Therefore, the node a voltage can be lowered. When switching the voltage of the address electrode, the power is stored by the resonance between the capacitor and the inductance. In this manner, the power loss of the plasma display panel can be decr
Huang Yi-Min
Lee Kun-Ming
AU Optronics Corp.
Rabin & Berdo P.C.
Vu Jimmy T.
Wong Don
LandOfFree
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