Dimmable self-ballasted fluorescent lamp and discharge lamp...

Details Dimmable self-ballasted fluorescent lamp and discharge lamp... Dimmable self-ballasted fluorescent lamp and discharge lamp...

2002-03-20

2003-12-09

Wong, Don (Department: 2821)

Electric lamp and discharge devices: systems

Current and/or voltage regulation

C315S2090SC, C315SDIG005

Reexamination Certificate

active

06661185

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a discharge lamp operating apparatus for operating a discharge lamp (in particular, fluorescent lamp). The present invention also relates to a dimmable self-ballasted fluorescent lamp.
Fluorescent lamps are characterized by a higher efficiency and a longer life than those of incandescent lamps, and have been used in a wide range of application such as for household illumination. In particular, self-ballasted fluorescent lamps that hardly have flickers and are capable of starting to operate instantly and in which a high frequency inverter ballast and a fluorescent lamp are formed as one unit can be mounted on a socket for incandescent lamps as they are, so that there is an increasing demand for the self-ballasted fluorescent lamps in view of energy saving and natural resources saving.
FIG. 4
shows an example of the structure of a self-ballasted fluorescent lamp. The self-ballasted fluorescent lamp shown in
FIG. 4
includes a fluorescent lamp
101
, a lamp base
102
such as E26 type for incandescent lamps, and a circuit substrate
103
. In the circuit substrate
103
, wiring for a high frequency inverter ballast is formed, and circuit components
106
are provided. The circuit substrate
103
is accommodated in a case
104
, and the lamp base
102
is provided in one end of the case
104
. A translucent globe
105
is provided below the case
104
so as to enclose the periphery of the fluorescent lamp
101
.
The fluorescent lamp
101
has a structure, for example, shown in FIG.
5
.
FIG. 5A
schematically shows the upper surface of the fluorescent lamp
101
, and
FIG. 5B
schematically shows the side face of the fluorescent lamp
101
.
The fluorescent lamp
101
shown in
FIG. 5
includes a glass bulb
107
whose inner face is coated with a phosphor, and both ends of the glass bulb
107
are sealed with filament electrodes
108
and
109
. Electrode lead wires
110
and
111
are electrically connected to the filament electrodes
108
and
109
. Four U-shaped glass bulbs
107
are arranged to form a square shape when viewed from the upper face, and connected to adjacent bulbs with a bridge
112
. Mercury and rare gas such as argon are enclosed in the glass bulb
107
. In addition, amalgam
113
is enclosed to control the vapor pressure of mercury during operation.
The high frequency inverter ballast has a structure, for example, as shown in FIG.
6
. The high frequency inverter ballast shown in
FIG. 6
includes a line filter
115
connected to an AC power
114
, a rectifying circuit
116
, a smoothing capacitor
117
, a driving circuit
118
, and FETs
119
and
120
, which are switching elements, a chalk coil
121
, and capacitors
122
and
123
. Coils
124
are secondary windings of the chalk coil
121
.
The line filter
115
prevents high frequency noise from flowing out to the AC power
114
, and the rectifying circuit
116
and the smoothing capacitor
117
convert an AC voltage to a DC voltage. The FETs
119
and
120
turn on and off in response to a signal from the driving circuit
118
, and thus the DC voltage from the smoothing capacitor
117
is converted to a high frequency AC voltage. The frequency of the high frequency AC voltage depends on the frequency at which the FETs
119
and
120
turn on and off, and generally it is set to about 50 to 80 kHz. The chalk coil
121
, the capacitors
122
and
123
, and the fluorescent lamp
101
form a load circuit that supplies the high frequency power to the fluorescent
101
, and the lamp current that is to flow through the fluorescent lamp
101
is limited by the chalk coil
121
, which is a current limiting element. The secondary windings
124
supply a preheating current to the filament electrodes
108
and
109
of the fluorescent lamp
101
by an induced voltage generated by the current flowing through the chalk coil
121
.
In the circuit substrate
103
as shown in
FIG. 4
, multiple circuit components
106
are provided, but in the drawing, only typical components are shown. The fluorescent lamp
101
and the circuit substrate
103
in
FIG. 4
are electrically connected to each other through connection pins provided on the circuit substrate
103
by for example, the approach of wrapping with the electrode lead wires
110
and
111
shown in FIG.
5
B. The lamp base
102
and the circuit substrate
103
are electrically connected, and power is supplied by threading the lamp base
102
into a socket for incandescent lamps to operate the fluorescent lamp
101
.
The self-ballasted fluorescent lamp shown in
FIG. 4
can be exchangeable directly with an incandescent lamp, so that the self-ballasted fluorescent lamp has been widely used for the same applications as for incandescent lamps. As it has been used increasingly in a wide range, the needs for dimming in the self-ballasted fluorescent lamp as in the incandescent lamps have emerged. Unlike the incandescent lamps that can be dimmed simply by adjusting the amount of power, it was technically very difficult to dim self-ballasted fluorescent lamps, which are discharge lamps. However, in recent years, a dimmable self-ballasted fluorescent lamp has been developed (e.g., see Japanese Laid-Open Patent Publication No. 11-111486), and the needs as described above have come to be met.
However, for dimmable self-ballasted fluorescent lamps, a member having a dimming function has to be further provided in a compact self-ballasted fluorescent lamp, so that it is more difficult to produce the dimmable self-ballasted fluorescent lamp than a self-ballasted fluorescent lamp without a dimming function. It goes without saying that it is more difficult to produce the self-ballasted fluorescent lamp than an ordinary discharge operating apparatus that can be provided with a discrete ballast.
When the inventors of the present invention investigated self-ballasted fluorescent lamps that were found to be defects during production, it was turned out that the defects were generated by the following defect factor. Referring to
FIG. 5
, in the process of assembling the fluorescent lamp
101
, the lamp base
102
, the circuit substrate
103
, the case
104
, and the globe
105
into one unit, the electrode lead wires
110
a
and
110
b
or
111
a
and
111
b
may be brought into contact with each other.
Since the electrode lead wire
110
and
111
have to be electrically connected to the connection pins on the circuit substrate
103
, these electrode lead wires are generally not subjected to a treatment for insulating coating or the like. Therefore, when these electrode leads wires are brought into contact with each other, the electrode lead wire
110
and
111
are provided with a contact resistance at the contact point. The contact resistance value changes depending on the state in which the electrode lead wire
110
and
111
are brought into contact. When the electrode lead wires
110
and
111
are brought into contact, the current output from the secondary windings
124
depends on the contact resistance value.
When the contact state of the electrode lead wires
110
and
111
is a complete short-circuit, that is, the contact resistance value is substantially 0&OHgr;, a large current of several tens A flows from the secondary windings
124
, so that the chalk coil
121
and the secondary windings
124
fail substantially instantly and the ballast stops (hereinafter, referred to as “large current failure mode”). When the contact resistance value is such that a current of about 3 A flows through the secondary winding
124
, the fluorescent lamp
101
is operated while consuming about several W of power at the contact point and the ballast continues to be operated. Meanwhile, the temperature at the contact point reaches several hundred ° C., and the adjacent circuit substrate
103
, the case
104
and the like may be excessively heated (hereinafter, referred to as “small current failure mode”).
With respect to these problems, the inventors of the present invention found that if the electrode lead wires
110
a,
110
b,
111

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