Electric lamp and discharge devices: systems – Current and/or voltage regulation
Reexamination Certificate
1999-12-03
2001-09-04
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Current and/or voltage regulation
C315S224000, C315S307000, C315S360000, C315S2090SC, C315SDIG005
Reexamination Certificate
active
06285138
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for lighting fluorescent lamp, particularly to a bulb-type fluorescent lamp, that is, a fluorescent lamp having a shape of electric bulb.
In recent years, in view of energy conservation and the like, bulb-type fluorescent lamps have been used instead of incandescent lamps. In a conventional bulb-type fluorescent lamp, a light-emitting tube, a starter and a stabilizer are integrated and accommodated in the screw base portion thereof, making the base portion large and heavy.
FIG. 47
is a circuit diagram of a conventional bulb-type fluorescent lamp. The circuit configuration of the bulb-type fluorescent lamp will be described below referring to FIG.
47
.
An AC power source
101
is connected to the AC input terminals of a full-wave rectifier
104
via a filter circuit comprising an inductor
103
and a capacitor
102
. A smoothing capacitor
105
is connected across the DC output terminals of the full-wave rectifier
104
. To the smoothing capacitor
105
, two switching devices
111
and
112
are connected in a half-bridge configuration. A transformer
114
for generating a resonance voltage has inductors
115
,
116
and
117
. One of the terminals of the inductor
115
of the transformer
114
is connected to the connection point (hereinafter simply referred to as the connection point between the switching devices) of the first switching device
111
and the second switching device
112
. A starting resistor
200
and a capacitor
201
are connected in parallel between the connection point between the switching devices and the smoothing capacitor
105
. The parallel arrangement of a capacitor
204
and zener diodes
206
and
207
is connected between the gate terminal of the first switching device
111
and the connection point between the switching devices. The cathodes of the two zener diodes
206
and
207
are connected to each other in series. An inductor
202
is connected between the other terminal of the inductor
115
of the transformer
114
and the gate terminal of the first switching device
111
.
An inductor
203
is connected between one of the terminals of the inductor
116
of the transformer
114
and the gate terminal of the second switching device
112
. In addition, a smoothing capacitor
205
is connected between the other terminal of the inductor
116
and the gate terminal of the second switching device
112
. Furthermore, two zener diodes
208
and
209
are directly connected between the other terminal of the inductor
116
and the gate terminal of the second switching terminal
112
in parallel with the smoothing capacitor
205
. The cathodes of these two zener diodes
208
and
209
are connected to each other. A resistor
210
is connected between the connection point of the two zener diodes
208
and
209
and the other terminal of the second switching device
112
. Moreover, the other terminal of the second switching terminal
112
is connected to the smoothing capacitor
205
via a capacitor
213
.
One of the terminals of the inductor
117
of the transformer
114
is connected to the connection point between the switching devices, and a pair of filament terminals in a light-emitting tube
135
and a capacitor
134
are connected in series between the other terminal of this inductor
117
and a capacitor
133
.
Next, the operation of the conventional bulb-type fluorescent lamp configured as described above will be described.
The starter of the conventional bulb-type fluorescent lamp shown in
FIG. 47
includes the two switching devices
111
and
112
, the inductor
117
used as the secondary winding of the transformer
114
and the capacitors
133
and
134
connected to the light-emitting tube
135
. The two switching devices
111
and
112
turn on and off alternatively at high speed, thereby converting the DC voltage across the smoothing capacitor
105
into a high-frequency signal. As a result, the light-emitting tube
135
is set in a lighting state by the high-frequency signal. The capacitor
134
inserted and connected across the pair of filament electrodes of the light-emitting tube
135
forms the current path of the preheating current for filaments of the light-emitting tube
135
, and is also used as a resonance capacitor in combination with the inductor
117
.
The capacitor
133
is a coupling capacitor used to cut DC components in the power source. To alternatively switch the two switching devices
111
and
112
, the inductors
115
and
116
of the transformer
114
detect the timing of on/off operation, and the inductors
202
and
203
carry out driving.
The starting resistor
200
turns on the first switching device
111
at the time of power-on to start the starter. In this way, until the starter is started by power-on and the light-emitting tube
135
is lit, resonance is caused at the inductor
117
and the capacitor
134
constituting a resonance circuit by the two switching devices
111
and
112
, thereby generating a high voltage and lighting the light-emitting tube
135
.
After the light-emitting tube
135
is lit, the impedance across the light-emitting tube
135
becomes low. As a result, the resonance capacitor
134
becomes nearly short-circuited. For this reason, self-oscillation occurs at the low resonance frequency determined by the capacitor
133
and the inductor
117
, whereby the light-emitting tube
135
can continue high-frequency lighting operation at high efficiency.
However, in the above-mentioned conventional bulb-type fluorescent lamp, a high voltage is generated for lighting at the resonance frequency determined by the inductor
117
and the capacitor
134
, immediately when and after the power is turned on. Therefore, at the time of lighting, the above-mentioned lighting operation is carried out while the external tube of the light-emitting tube is still cool, without sufficiently heating the filaments. Therefore, stress is applied to the filaments of the light-emitting tube, thereby causing a problem of shortening the service life of the light-emitting tube.
Furthermore, in the conventional bulb-type fluorescent lamp, the preheating time for the filaments cannot be taken sufficiently, thereby causing a problem of making the luminous flux small because the temperature of the external tube is low immediately after lighting, and making the luminous flux larger as the temperature of the external tube rises.
BRIEF SUMMARY OF THE INVENTION
In order to solve the above-mentioned problems, the present invention provides an apparatus for lighting fluorescent lamp, that is a fluorescent lamp lighting apparatus, configured to sufficiently provide a preheating time at the time of lighting and capable of carrying out control at a level not applying stress to the filaments of the light-emitting tube thereof. In addition, the present invention is intended to provide a fluorescent lamp lighting apparatus having a smaller mounting area by significantly reducing the number of components by using a one-chip monolithic IC accommodating an oscillator, and capable of maintaining a constant luminous flux immediately after lighting.
In order to attain the above-mentioned objects, a fluorescent lamp lighting apparatus in accordance with the present invention comprises:
a DC-voltage generation circuit for generating a DC voltage,
a drive-signal generation circuit for generating and outputting desired high-voltage-side and low-voltage-side pulse signals by using the DC voltage from the above-mentioned DC-voltage generation circuit, and
a drive control circuit having switching means driven by the pulse signals input from the above-mentioned drive-signal generation circuit to output a drive signal across the output terminals thereof, wherein a resonance circuit and the filament electrodes of a fluorescent lamp light-emitting tube are connected across the output terminals of the above-mentioned switching means.
In accordance with the present invention configured as described above, the power source circuit portion has the DC-voltage generation circuit,
Kataoka Shinichiro
Matsunaga Hiroki
Nakagawa Yo
Yamanaka Masanori
Matsushita Electric - Industrial Co., Ltd.
Sheridan & Ross P.C.
Vo Tuyet T.
Wong Don
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