Electric lamp and discharge devices: systems – Pulsating or a.c. supply – Induction-type discharge device load
Reexamination Certificate
2000-07-14
2001-05-01
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Pulsating or a.c. supply
Induction-type discharge device load
C330S112000, C330S282000, C330S298000, C331S1070DP, C333S017300, C333S195000
Reexamination Certificate
active
06225756
ABSTRACT:
BACKGROUND
1. Field of the Invention
The invention relates generally to a novel high power, high frequency solid state oscillator.
2. Related Art
Microwave solid state oscillators are described in various textbooks including “Microwave Solid State Circuit Design,” written by I. Bahi and P. Bhartia (Wiley-Interscience Publication, 1988, Chapters 3 and 9) and “Microwave Circuit Design Using Linear and Nonlinear Techniques,” written by George D. Vendelin, Anthony M. Pavio, and Ulrich L. Rohde (Wiley-Interscience Publication, 1990, Chapter 6). Articles on such oscillators include “Microwave Solid State Oscillator Circuits,” written by K. Kurokawa (Microwave Devices, Wiley, 1976) and “Accurate Linear Oscillator Analysis and Design,” written by J. L. Martin and F. J. Gonzales (Microwave Journal, June 1996 pp. 22-37).
Microwave oscillators utilizing solid state components and strip-line transmission lines are described in U.S. Pat. Nos. Re 32,527, 4,736,454, and 5,339,047. Solid state microwave oscillators having various feedback structures are described in U.S. Pat. Nos. 4,775,845, 4,906,946, 4,949,053, and 5,483,206.
Conventional solid state microwave oscillators produce relatively low power output, for example, ranging from a few hundred milliwatts (mW) up to a few watts (W) at most. Moreover, conventional solid-state microwave oscillators are relatively inefficient, typically less than 40%.
For higher power applications requiring a high frequency signal, the oscillator signal is typically provided to an amplifier to increase the output power. For example,
FIG. 1
is a schematic diagram of a conventional system for providing a high power, high frequency signal. An oscillator
702
provides a low power, high frequency signal to an amplifier
704
which increases the power level and outputs a high power, high frequency signal.
A radio frequency (RF) powered electrodeless light source is one example of an application which could utilize a high power, high frequency signal source. For example, U.S. Pat. No. 4,070,603 discloses an electrodeless light source which is powered by a solid state microwave power source. The microwave power source described therein has the general structure shown in FIG.
1
. Namely, the output of a relatively low power oscillator is applied to a power amplifier to provide a 40 W, 915 MHz signal, at a purported 50% direct current (DC) to RF efficiency.
SUMMARY
Various aspects, features, advantages, and applications of electrodeless lamps utilizing the novel oscillator of the present invention may be understood with reference to the parent '230 application.
An object of one aspect of the present invention is to describe an electrodeless aperture lamp which is powered by a solid state RF source in the range of several tens to several hundreds of watts.
Preferably, the lamp according to invention is extremely compact in size. Advantageously, the lamp can be conveniently packaged into a variety of configurations. For example, the bulb, RF source and DC power supply can be packaged together or each of these modules can be packaged and located separately. If separate, the bulb receives the RF energy through suitable transmission means (e.g., a coaxial cable).
Long life is a fundamental characteristic of electrodeless lamps. The elimination of all metal components in the bulb such as the filaments and electrodes, and the elimination of the accompanying glass to metal seals remove the dominant determinants of conventional lamp life times. The selection of specific bulb fills minimizes and in some cases eliminates the chemical interactions between the plasma and the bulb envelop. Such interactions can significantly affect the life time and color stability of conventional high intensity discharge lamps. Further, the lamp of the present invention is made more reliable through the use of all solid state electronics.
A novel solid-state oscillator preferably provides RF power to the lamp. One example of the oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency. Various control circuits may be employed to match the driving frequency of the oscillator to a plurality of tuning states of the lamp.
According to one aspect of the invention, an oscillator includes an amplifier having an input and an output, and an impedance transformation network connected between the input of the amplifier and the output of the amplifier, wherein the impedance transformation network is configured to provide suitable positive feedback from the output of the amplifier to the input of the amplifier to initiate and sustain an oscillating condition, and wherein the impedance transformation network is configured to protect the input of the amplifier from a destructive feedback signal. The oscillator may further include a load connected to the output of the amplifier and the impedance transformation network is configured to protect the input of the amplifier from the destructive feedback signal as the load varies from a low impedance to a high impedance. Preferably, the impedance transformation network is configured to protect the input of the amplifier from the destructive feedback signal as the load varies from a short circuit to an open circuit. Preferably, the impedance transformation network comprises only micro-strip transmission lines, stubs, and non-inductive elements. For example, the impedance transformation network may include micro-strip transmission lines, stubs, and capacitor elements. The destructive feedback signal includes, for example, a high voltage and the impedance transformation network is configured to prevent the high voltage from building up at the output of the amplifier. Preferably, the impedance transformation network is further configured to transform the high voltage on the output side of the amplifier to a high current on the input side of the amplifier. Preferably, the impedance transformation network comprises dual feedback loops. More preferably, the dual feedback loops are substantially symmetrical. The dual feedback loops may be coupled to matching stubs at the input of the amplifier.
According to another aspect of the invention, the oscillator further includes an output impedance matching circuit having a first end connected to the output of the amplifier and a high impedance end coupled to the impedance transformation network. The output of the amplifier produces an RF output voltage and wherein the output impedance matching circuit comprises stubs configured to limit a reflected voltage on the high impedance end to at most two times the RF output voltage from the output of the amplifier.
According to a preferred aspect of the invention, the amplifier comprises a single active element providing an output signal having an output power in excess of 10 watts. Preferably, the oscillator exhibits an efficiency greater than 50 percent.
According to another aspect of the invention, an oscillator includes a tuning circuit having micro-strip transmission lines connected to the input of the amplifier, wherein the output of the amplifier produces an RF output voltage having an oscillating frequency with a third harmonic thereof, and wherein a sum of the lengths of the tuning circuit transmission lines is about one-half wavelength of the third harmonic of the oscillating frequency.
The foregoing and other aspects of the invention are achieved individually and in combination. The invention should not be construed as requiring two or more of the foregoing aspects unless expressly required by the claims.
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patent: 843534 (1907-02-01), Hewitt
patent: 1854912 (1932-04-01), Spaeth
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patent: 3943404 (1976-03-01), McNeil et al.
patent: 4007392 (1977-02-01), Velfells et al.
patent: 4010400 (1977-03-01), Hollister
patent: 4016507 (1977-04-01), Havens
patent: 4021727 (1977-05-01), Fellows
patent: 4070603 (1978-01-01), Regan et al.
patent: 4127797 (1978-1
Fusion Lighting Inc.
Philogene Haissa
Steiner Paul E.
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