Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2001-05-31
2003-09-09
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C345S080000, C345S092000, C345S204000
Reexamination Certificate
active
06617796
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority under 35USC §119 to Japanese Patent Application No.2000-162780, filed May 31, 2000 and No.2001-4163, filed Jan. 11, 2001; the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flat panel display device in which a pixel portion and a driving circuit for driving the pixel portion are integrally formed on the same substrate, and to a pumping circuit used for the flat panel display device.
2. Description of the Related Art
In recent years, an active matrix type liquid crystal display device in which a TFT (a thin film transistor) is disposed for each pixel as a switching element has come to a mainstream of a flat panel display device. Development of a liquid crystal display device has been lately progressed, in which a driving circuit and a power source circuit are integrally formed on an array substrate having a pixel portion formed thereon.
In the liquid crystal display device of such a kind, various kinds of clock signals and a power source voltage are supplied from an external control circuit to the driving circuit and the power source circuit on the array substrate. At present, in order to make the external control circuit in a compact size, it has been investigated to arrange a pumping circuit, which is included in the external control circuit, on the array substrate. However, since a capacitor having a large capacitance, which is necessary for the pumping circuit, cannot be formed on the array substrate in present fabrication processes, the external control circuit cannot be made in a more compact size. Furthermore, if the pumping circuit can be fabricated in the same fabrication processes as those for fabricating the pixel portion and the driving circuit, the pumping circuit can be fabricated in cost lower than a case where the pumping circuit is mounted on the external control circuit. Nevertheless, as described above, since the pumping circuit cannot be formed on the array substrate, it is impossible to fabricate the pumping circuit in low cost.
On the other hand, an operation to form a TFT on a glass plate like an array substrate makes fabrication processes difficult, and transistor characteristic are made to be unstable in many cases. Accordingly, when the pumping circuit is formed on the array substrate, the characteristics of the TFT constituting the circuit are expected to become unstable. In this case, a problem that variations in a threshold occur and an output voltage from the pumping circuit becomes unstable is caused.
Furthermore, when the TFT on the array substrate is formed of polycrystalline Si, performance of the TFT formed of the polycrystalline Si is inferior to that formed of a single crystal Si. When a gate length of the TFT formed of the polycrystalline Si is made to be longer to compensate the inferiority to the TFT formed of the single crystal Si, an area required to a circuit arrangement becomes large. Accordingly, in the case where the pumping circuit arranged on the array substrate is constituted of the TFT, a problem that a fringe region around the pixel portion becomes large is caused.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a flat panel display device, which achieves a compact sized and low cost external control circuit.
Another object of the present invention is to provide a pumping circuit capable of stabilizing an output voltage therefrom without being influenced by TFT fabrication processes.
Still another object of the present invention is to provide a flat panel display device capable of arranging a pumping circuit on an array substrate without enlarging a fringe region thereof.
To achieve the above-described objects of the present invention, a first aspect of the present invention is a flat panel display device which comprises: a first substrate including a plurality of scanning lines, and a plurality of signal lines intersecting the scanning lines, a switching element arranged on an intersection point of each of the scanning lines and the signal lines, a pixel electrode connected to the switching element; a second substrate including an opposite electrode opposite to the pixel electrode; a display layer held between said first and second substrates; a data driver which supplies a data signal to each of the signal lines; and a scan driver which supplies a scanning signal to each of the scanning lines, wherein a control signal and a power source voltage are supplied from an external control circuit to the data driver and the scan driver, and wherein a control signal and a power source voltage from an external control circuit are supplied to the data driver and the scan driver, and wherein at least one pumping circuit included in the external control circuit is arranged on the first substrate, and a first capacitor connected to a clock input portion of the pumping circuit and a second capacitor connected between an output portion and the ground are arranged outside the first substrate.
To achieve another object of the present invention, a second aspect of the present invention is a pumping circuit which comprises a first transistor having a first electrode region and a third electrode region supplied with a power source voltage and a second electrode region connected to a potential of a first intermediate node; a second transistor having a first electrode region supplied with the power source voltage, a second electrode region connected to a potential of a second intermediate node and a third electrode region connected to the potential of the first intermediate node; and a third transistor having a first electrode region connected to the potential of the second intermediate node, a second electrode region connected to an output portion together with a third capacitor, and a third electrode region connected to the potential of the first intermediate node, wherein a first clock input portion for receiving a first clock signal through a first capacitor is connected to the first intermediate node, and a second input portion for receiving a second clock signal through a second capacitor is connected to the second intermediate node.
To achieve another object of the present invention, a third aspect of the present invention is a pumping circuit, wherein a first transistor of a first conductivity type and a second transistor of a second conductivity type are connected in series, and two transistor pairs, each being composed of the first and second transistor, are connected in series.
To achieve another object of the present invention, a fourth aspect of the present invention is a pumping circuit, wherein a first transistor of a first conductivity type and a second transistor of a second conductivity type are connected in parallel, and two transistor pairs, each being composed of the first and second transistors, are in series.
To achieve another object of the present invention, a fifth aspect of the present invention is a pumping circuit comprises: a first pumping circuit in which a first transistor of a first conductivity type and a second transistor of a second conductivity type are connected in series, and two transistor pairs, each being composed of the first and second transistors, are in series connected; a second pumping circuit in which a first transistor of the second conductivity type and a second transistor of the first conductivity type are connected in series, and two transistor pairs, each being composed of the first and second transistors, are in series connected; and an operational amplifier which receives an output from the first pumping circuit as a positive polarity power source and an output from the second pumping circuit as a negative polarity power source.
To achieve still another object of the present invention, a sixth aspect of the present invention is a flat panel display device which comprises: a first substrate including a plurality of scanning lines, and a plurality of signal line
Hanazawa Yasuyuki
Hirai Hoko
Miyatake Masaki
Sasaki Yasushi
Sato Hajime
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tran Thuy Vinh
Wong Don
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