Electric lamp and discharge devices: systems – Pulsating or a.c. supply – Induction-type discharge device load
Reexamination Certificate
2001-02-06
2002-09-24
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Pulsating or a.c. supply
Induction-type discharge device load
C315S246000, C315S291000
Reexamination Certificate
active
06456015
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to fluorescent illuminating devices, and, more particularly, to an inductive-resistive fluorescent apparatus and method.
Fluorescent lamps are well known in the prior art. There are three basic types of such lamps. These are the preheat lamp, the instant-start lamp, and the rapid-start lamp. In each type of lamp, a glass tube is provided which has a coating of phosphor powder on the inside of the tube. Electrodes are disposed at opposite ends of the tube. The tube is filled with an inert gas, such as argon, and a small amount of mercury. Electrons emitted from the electrodes strike mercury atoms contained within the tube, causing the mercury atoms to emit ultraviolet radiation. The ultraviolet radiation is absorbed by the phosphor powder, which in turn emits visible light via a fluorescent process.
The differences between the three lamp types generally relate to the manner in which the lamp is initially started. Referring now to
FIG. 1
, in a preheat lamp circuit, designated generally as
10
, a starter bulb
12
is included. Preheat lamp
14
includes first and second electrodes
16
and
18
, each of which has two terminals
20
. During initial start-up of the preheat lamp, starter bulb
12
, which acts as a switch, is closed, thus shorting electrodes
16
and
18
together. Current therefore passes through electrode
16
and then through electrode
18
. This current serves to preheat the electrodes, making them more susceptible to emission of electrons. After a suitable time period has elapsed, during which the electrodes
16
and
18
have warmed up, the starter bulb
12
opens, and thus, an electric potential is now applied between electrodes
16
and
18
, resulting in electron emission between the two electrodes, with subsequent operation of the lamp.
A relatively high voltage is applied initially for starting purposes. A lower voltage is used during normal operation. A reactance is placed in series with the lamp to absorb any difference between the applied and operating voltages, in order to prevent damage to the lamp. The reactance, suitable transformers, capacitors, and other required starting and operating components are contained within a device known as a ballast (designated generally as
22
). Ballasts are relatively large, heavy and expensive, with inherent efficiency limitations and difficulties in operating at low temperatures. The components within ballasts are typically potted with a thermally conductive, electrically insulating compound, in an effort to dissipate the heat generated by the components of the ballast. Difficulties in heat dissipation are yet another disadvantage of conventional ballasts.
Referring now to
FIG. 2
, an instant-start lamp circuit, designated generally as
24
, is shown. Instant-start lamp
26
includes first and second electrodes
28
and
30
.
Electrodes
28
and
30
each only have a single terminal designated as
32
. In operation of the instant-start lamp, no preheating of the electrodes is required. Rather, an extremely high starting voltage is typically applied in order to induce current flow without preheating of the electrodes. The high starting voltage is supplied by a special instant-start ballast, designated generally as
34
. Instant-start type ballasts suffer from similar disadvantages to those of the preheat type. Further, because of the danger of the high starting voltage from the instant-start ballast
34
, a special disconnect lamp holder
36
must be employed in order to disconnect the ballast when the lamp
26
is not properly secured in position.
Referring now to
FIG. 3
, a rapid-start lamp circuit, designated generally as
38
, is shown. Rapid start lamp
40
includes first and second electrodes
42
and
44
, each of which has two terminals
46
, similar to the preheat lamp
14
, discussed above. The rapid-start ballast, designated generally as
48
, contains transformer windings, which continuously provide the appropriate voltage and current for heating of the electrodes
42
and
44
. Rapid heating of electrodes
42
and
44
permits relatively fast development of an arc from electrode
42
to electrode
44
using only the applied voltage from the secondary windings present in ballast
48
. The rapid start ballast
48
permits relatively quick lamp starting, with smaller ballasts than those required for instant-start lamps, and without flicker which may be associated with preheat lamps. Further, no starter bulb is required. However, ballast
48
is still relatively large, heavy, inefficient, and unsuitable to low ambient-temperature operation. Dimming and flashing of rapid-start lamps are possible, albeit with the use of special ballasts and circuits.
It will be appreciated that operation of the prior art lamps described above is dependent on heating of the electrodes and/or application of a high voltage between the electrodes in order to start the operation of the lamp. This necessitates the use of ballasts and associated control circuitry, having the undesirable attributes discussed above. Recently, there has been interest in employing other physical phenomena to enable efficient starting and operation of fluorescent lamps. For example, EPO Publication Number 0 593 312 A2 discloses a fluorescent light source illuminated by means of an RF (radio frequency) electromagnetic field. However, the device of the '312 publication still suffers from numerous disadvantages, including the complex circuitry required to generate the RF field and the potential for RF interference.
In the parent international Application No. PCT/US97/18650, a ballast-free drive circuit is disclosed which, in one embodiment, employs a direct current (DC) or pulsed DC source (see FIG.
25
). It has been found, however, that operating a fluorescent lamp with a DC or pulsed DC source can lead to mercury migration in the lamp and an associated reduction of light output over time. This mercury migration problem may, therefore, substantially shorten the usable life of the fluorescent lamp.
Through experimentation, it was additionally observed that the fluorescent lamp drive circuit disclosed in the parent International Application exhibited unreliable starting of the fluorescent lamp, particularly when used with certain types of fluorescent lamps (e.g., T
8
lamps). This starting problem was found to be related, at least in part, to an insufficient voltage being generated across the output capacitors in the drive circuit. In such instances, the capacitors were not always fully charged to an appropriate voltage level necessary to form the arc in the fluorescent medium.
There is, therefore, a need in the prior art for an inductive-resistive fluorescent apparatus which permits simple, economical and reliable starting and operation of fluorescent lamps with low-cost, light weight, low-volume components which are capable of efficiently operating the lamp, even at relatively low ambient temperatures, which afford efficient heat dissipation and which are capable of operating at ordinary household AC frequencies. It is desirable to adapt such an inductive-resistive fluorescent apparatus to substantially eliminate mercury migration in the fluorescent lamp. It is additionally desirable to provide a fluorescent apparatus having the flexibility for enhanced features, including the ability to remotely control the fluorescent apparatus via a proportional industrial controller (PIC) or similar building controller. Furthermore, it is desirable to adapt such an inductive-resistive apparatus to direct “plug-in” replacement of incandescent bulbs.
SUMMARY OF THE INVENTION
The present invention, which addresses the needs of the prior art, provides an inductive-resistive fluorescent apparatus and method. The apparatus includes a translucent housing having a chamber for supporting a fluorescent medium, and having electrical connections configured to provide an electrical potential across the chamber. A fluorescent medium is supported within the chamber. An inductive-resistive structure is fi
Brooks Sheldon B.
Duhon Edward
Geiger Dana
Lovell Walter C.
Hoffmann & Baron , LLP
Lee Wilson
Tapeswitch Corporation
Vu David
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