Electric lamp and discharge devices: systems – Pulsating or a.c. supply – Induction-type discharge device load
Reexamination Certificate
2001-02-06
2002-07-23
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Pulsating or a.c. supply
Induction-type discharge device load
C315S246000
Reexamination Certificate
active
06424099
ABSTRACT:
BACKGROUND
1. Field of the Invention
The various aspects of the invention relate generally to discharge lamps, and more specifically to inductively coupled electrodeless lamps. The invention also relates to novel lamp configurations, coupling circuits, bulbs, heat dissipating lamp head assemblies, RF sources (oscillators), directional couplers, aperture structures, and excitation coils for inductively coupled electrodeless lamps. Another aspect of the invention also relates to an improved electrodeless aperture lamp, and to methods of making and using an electrodeless aperture lamp. The invention also relates generally to a novel high power, high frequency solid state oscillator. The invention further relates to a novel control circuit and method for operating an electrodeless lamp. Another aspect of the invention relates generally to RF driven loads with changing impedance characteristics.
2. Related Art
In general, the various aspects of the invention relate to the type of lamps disclosed in U.S. Pat. Nos. 5,404,076 and 5,903,091 and PCT Publication No. WO 99/36940, each of which is herein incorporated by reference in its entirety.
Electrodeless discharges are generally classified as either E discharges, microwave discharges, travelling wave discharges, or H discharges. Most examples of the invention relates to those discharges preponderantly characterized as H discharges.
FIG. 1
is a schematic diagram of a conventional electrodeless lamp which produces an E discharge. A power source
1
provides power to a capacitor
2
. A gas-filled vessel
3
is placed between the plates of the capacitor
2
. E discharges in electrodeless lamps are similar to arc discharges in an electroded lamp, except that current is usually much less in an electroded arc discharge. Once breakdown of the gas to its ionized or plasma state is achieved, current flows through the capacitance of the vessels walls between the plates of the capacitor
2
, thereby producing a discharge current in the plasma.
FIG. 2
is a schematic diagram of a conventional electrodeless lamp which produces a microwave discharge. A microwave power source
4
provides microwave energy which is directed by a waveguide
5
to a microwave cavity
6
which houses a gas-filled bulb
7
. The microwave energy excites the fill in the bulb
7
and produces a plasma discharge. In a microwave discharge, the wavelength of the electromagnetic field is comparable to the dimensions of the exciting structure, and the discharge is excited by both E and H components of the field.
FIG. 3
is a schematic diagram of a conventional electrodeless lamp which produces a travelling wave discharge. A power source
8
provides power to a launcher
9
. A gas-filled vessel
10
is disposed in the launcher
9
. The gap between the electrodes of the launcher
9
provides an E field which launches a surface wave discharge. The plasma in the vessel
10
is the structure along which the wave is then propagated.
FIG. 4
is a schematic diagram of a conventional electrodeless lamp which produces an H discharge. Electrodeless lamps which produce an H discharge are also referred to as inductively coupled lamps. As shown in
FIG. 4
, one example for a conventional inductively coupled lamp includes a low frequency power source
11
providing power to a coil
12
which is wound around a gas-filled vessel
13
. The alternating current in the coil
12
causes a changing magnetic field, which induces an electric field which drives a current in the plasma. In effect, the plasma can be analyzed as a single turn secondary to the coil
12
. An H discharge is characterized by a closed electrical field, which in many examples forms a visible donut-shaped plasma discharge.
A number of parameters characterize highly useful sources of light. These include spectrum, efficiency, brightness, economy, durability (working life), and others. For example, a highly efficient, low wattage light source with a long working life, particularly a light source with high brightness, represents a highly desirable combination of operating features. Electrodeless lamps have the potential to provide a much longer working life than electroded lamps.
SUMMARY
One aspect of the invention is to provide an ultra bright, low wattage electrodeless lamp which has many practical applications. Specifically, an aspect of the invention is to provide an electrodeless aperture lamp which is powered by a solid state RF source in the range of several tens to several hundreds of watts. Various aspects of the invention may be adapted to provide an excellent light source for such diverse applications as projection display, automotive headlamps and general illumination including office environments, schools, factories, shops, homes, and virtually anywhere which requires or benefits from artificial lighting.
According to one aspect of the invention, an inductively coupled electrodeless lamp includes an excitation coil; a capacitor structure connected to the excitation coil, the capacitor structure and excitation coil together forming a resonant lamp circuit; an electrodeless lamp bulb positioned proximate to the excitation coil, the bulb containing a fill which emits light when excited by RF energy; and an RF source connected to the resonant lamp circuit and adapted to provide RF energy for exciting the fill, wherein the capacitor structure is adapted to inhibit arcing during operation of the lamp. For example, the excitation coil comprises a wedding ring shaped excitation coil having an axial lead on one end and a radial lead on the other end, and wherein the capacitor structure comprises a capacitor stack connected to the axial lead of the wedding ring coil. The capacitor stack may include a material having a low dielectric constant for the high voltage capacitor an may further include a conformal coating covering at least a portion or substantially all of the capacitor stack and optionally a portion of the axial lead of the wedding ring coil. The capacitor stack may have a circular high voltage plate, which may include an edge radius which is larger than one half of the plate thickness. In some examples, the lamp may include a heat transfer structure providing a thermal conduction path from the capacitor structure to a heat dissipating structure.
According to another aspect of the invention, the capacitor structure comprises a coaxial capacitor circuit, including a first capacitor comprising a first cylindrical sleeve; a second capacitor comprising a second cylindrical sleeve disposed at least partially inside the first cylindrical sleeve of the first capacitor; and insulators disposed in between the first and second sleeves, wherein the first and second capacitors are connected in series with a center conductor being connected at a junction of the series connection.
According to another aspect of the invention, the lamp includes an enclosure housing the resonant lamp circuit, the enclosure comprising thermally conductive structures for transferring heat from the lamp circuit, and the enclosure comprises substantially flat outer surfaces for interfacing with further heat dissipating structures. The excitation coil may be made from copper. In some examples, the enclosure comprises a base portion and a cover, and a thermal gasket is disposed between the cover and the base. The coil and capacitor structure may be integrated in a single assembly, with the capacitor structure including a multi-layer printed circuit board adapted to form a capacitor stack.
According to yet another aspect of the invention, an inductively coupled electrodeless lamp includes an excitation coil; a capacitor structure connected to the excitation coil, the capacitor structure and excitation coil together forming a resonant lamp circuit; an electrodeless lamp bulb positioned proximate to the excitation coil, the bulb containing a fill which emits light when excited by RF energy; an RF source connected to the resonant lamp circuit and adapted to provide RF energy for exciting the fill; and a structure encasing the bulb except for a light emitting ap
Bass Gary K.
Copsey Jesse F.
Garber, Jr. William E.
Kirkpatrick Douglas A.
Kwong Vincent H.
Fusion Lighting Inc.
Lee Wilson
Steiner Paul E.
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