Electric lamp and discharge devices: systems – Periodic switch in the supply circuit – Impedance or current regulator in the supply circuit
Reexamination Certificate
2000-03-09
2001-09-25
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Periodic switch in the supply circuit
Impedance or current regulator in the supply circuit
C315S219000, C315SDIG005, C310S316020, C310S359000
Reexamination Certificate
active
06294881
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a discharging tube and a discharging method thereof, in particular, to a cold cathode fluorescent tube.
2. Description of the Related Art
In recent years, portable information terminal units such as note type personal computers and palm top type personal computers have been widely used.
For display units of these portable information terminal units, liquid crystal display units have been used because of small size, light weight, and low power consumption. For the light source of the back-light of the liquid crystal display unit, a cold cathode tube has been used. To cause the cold cathode tube to emit light, a high AC voltage is required. Thus, with an electromagnetic converting type AC inverter transformer, a high AC voltage is generated and thereby the cold cathode tube emits light.
FIG. 1
is a schematic diagram showing a driving method of a conventional cold cathode tube.
In
FIG. 1
, a DC voltage of around 10 to 15V is supplied from a DC power supply
271
to an inverter circuit
272
. The inverter circuit
272
converts the DC voltage supplied from the DC power supply
271
to a high AC voltage of around 1200V/50 kHz. The resultant high AC voltage is supplied to a cold cathode tube
273
. When the high AC voltage is supplied, from the inverter circuit
272
to the cold cathode tube
273
, the cold cathode tube
273
discharges electricity and emits light.
However, in the conventional driving method of a cold cathode tube, a high voltage wiring line should be connected from the inverter circuit
272
to the cold cathode tube
273
. Thus, the voltage supplied from the inverter circuit
272
leaks out through the static stray capacitance of the high voltage wiring line. Thus, the power consumption for driving the cold cathode tube increases. Consequently, when the cold cathode tube is used for the back-light of a portable information terminal unit, the service life of the battery of the portable information terminal unit becomes short.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a discharging tube that is effectively operated.
A discharging tube according to the present invention comprises a transforming unit, a discharging unit, a cathode, an anode, a piezoelectric transformer, a holding unit, a piezoelectric substrate, a primary electrode, a secondary electrode, a driving unit, an outputting unit, and a driving unit.
In a first aspect of the present invention, the piezoelectric unit transforms a voltage that is supplied to the discharging tube. The discharging unit discharges electricity corresponding to the voltage transformed by the transforming unit.
In a second aspect of the present invention, the cathode and the anode are disposed opposite to each other. The piezoelectric transformer transforms the voltage supplied to the anode or the cathode. The holding unit holds the piezoelectric transformer.
In a third aspect of the present invention, the piezoelectric substrate has a first region and a second region. The first region is polarized in the direction of the thickness of the piezoelectric substrate. The second region is polarized in the direction of the length of the piezoelectric substrate. The primary electrodes are disposed on an upper surface and a lower surface of the first region of the piezoelectric substrate. The secondary electrode is disposed on an end surface of the second region of the piezoelectric substrate. In the discharging unit, the secondary electrode is used for the cathode or the anode.
In a fourth aspect of the present invention, the driving unit generates an AC voltage. The transforming unit transforms the AC voltage in the discharging tube. The outputting unit outputs the transformed AC voltage to the cathode or the anode of the discharging tube.
In a fifth aspect of the present invention, the driving circuit generates an AC voltage. The length of the piezoelectric substrate is nearly the same as the length of the discharging tube that has the first region polarized in the direction of the thickness thereof and the second area polarized in the direction of the length thereof. The primary electrodes are disposed on an upper electrode and a lower surface of the first region of the piezoelectric substrate to which the AC voltage is supplied. The secondary electrode is disposed on an end surface of the second region of the piezoelectric substrate.
In a sixth aspect of the present invention, the driving circuit generates an AC voltage. The piezoelectric substrate has a first region and a second region. The first region is polarized in the direction of the thickness of the piezoelectric substrate. The second region is polarized in the direction of the length of the piezoelectric substrate. The section perpendicular to the direction of the length of the piezoelectric substrate is formed in a U-letter shape. The primary electrodes are disposed on an inner surface and an outer surface of the first region of the voltage substrate to which AC voltage is input. The secondary electrode is disposed on an end surface of the second area of the piezoelectric substrate.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of best mode embodiments thereof, as illustrated in the accompanying drawings.
REFERENCES:
patent: 5424620 (1995-06-01), Cheon et al.
patent: 5548189 (1996-08-01), Williams
patent: 5705879 (1998-01-01), Abe et al.
patent: 5929554 (1999-07-01), Kanayama et al.
patent: 7-220888 (1995-08-01), None
patent: 7-335386 (1995-12-01), None
Miyazaki Shingo
Shimeki Yoshio
Sotokawa Akio
Fujitsu Limited
Staas & Halsey , LLP
Vu David
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