Electric lamp and discharge devices: systems – Pulsating or a.c. supply – Induction-type discharge device load
Reexamination Certificate
2001-09-25
2004-03-02
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Pulsating or a.c. supply
Induction-type discharge device load
C315S161000, C315S283000
Reexamination Certificate
active
06700332
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electrodeless discharge lamp system, more particularly, to an electrodeless discharge lamp system which is used for a tunnel lighting, a bridge lighting, and a photochemical processing device for a sewage bactericidal processing.
BACKGROUND OF THE INVENTION
An electrodeless discharge lamp has a spherical or ellipsoidal glass bulb filled therein with rare earth discharge gas and metal vapor such as mercury vapor. Moreover, an excitation coil is placed near the discharge lamp. By using a high frequency power source the excitation coil induces a magnetic field alternating At 13.56 MHz. The discharge lamp is operated by the electric filed induced by the magnetic field.
A conventional electrodeless discharge lamp system is comprised of, e.g., an electrodeless discharge lamp with spherical glass bulb filled therein discharge gases such as inert gases or metal vapor and coated with either transparent or fluorescent substance on its inner surface, an excitation coil placed in proximity of the periphery of the electrodeless discharge lamp for inducing a high-frequency electromagnetic field, a high frequency power source for supplying a high frequency power to the excitation coil connected thereto, and a matching circuit for matching the excitation coil and the high frequency power source with each other so as to effectively supply the high frequency power to the electrodeless discharge lamp without line reflection.
It is known that the high frequency power source is comprised of a high frequency oscillator for supplying the high frequency power source into the excitation coil, and a DC power source for converting an AC voltage from an AC power source such as a commercial-frequency power source into a DC power voltage for driving the high frequency oscillator
A high frequency magnetic field is induced by feeding the excitation coil with a high frequency current at a several MHz to a several hundred MHz from the high frequency power source. Then, a high frequency plasma current is induced inside the electrodeless discharge lamp, and the ultraviolet ray or the visible light is emitted
On the other hand, in the conventional electrodeless discharge lamp, impedances of the excitation coil and the electrodeless discharge lamp vary from moment to moment in a while in a transient period from a start of operation till reaching a stable operation. Therefore, according to the change of these impedances, it is necessary to match the impedance of the high frequency power source to that of the excitation coil by adjusting at least the output impedance of the high frequency power source.
For this reason, as an electrodeless discharge lamp system which is capable of transmitting a high frequency power with a high degree of efficiency even though a load condition in tho electrodeless discharge lamp varies, there is proposed an electrodeless discharge lamp system comprised of, e.g., a high frequency power excitation coil coupled across the output terminals of the high frequency power source, an electrodeless discharge lamp filled with discharge gases such as inert gases and metal vapor in its glass bulb, placed in proximity of the high frequency power excitation coil, a first matching circuit connected between the high frequency power source and the high frequency power excitation coil, a coaxial cable connecting the high frequency power source and the first matching circuit, and a second matching circuit connecting the coaxial cable and the high frequency power source in the Japan Unexamined Patent Publication (Kokai) H6-310291.
In the electrodeless discharge lamp system with the above configuration, the coaxial cable is used in matching with the characteristic impedance of the lamp system. As a consequence, the coaxial cable advantageously exerts a high efficiency of power transmission. Moreover, the Japan Unexamined Patent Publication (Kokai) H6-310291 shows a configuration for adjusting operating conditions of the high frequency power source by varying driving DC brass of switching elements of the high frequency power source on and after starting the operation of the electrodeless discharge lamp.
On the other hand, the conventional electrodeless discharge lamp system can be modified to have multiple parallel-connected high frequency power sources, i.e., DC-RF power converters and combine their outputs for transmitting them to its load, i.e., an electrodeless discharge lamp via a transmission line. According to the configuration, it is able to achieve the operation and effect an described above, and it is also able to use power converters with a relatively small power capacity. Therefore, the development of the system becomes easy and be reduced its duration, as well as reduced its manufacturing cost.
However, matters to be considered for changing operating conditions differ between a configuration where only one high frequency power source is subjected for the change of operating conditions like the conventional electrodeless discharge lamp system and a configuration where multiple parallel-connected high frequency power sources of supplying a combined power to a load, i.e., an electrodeless discharge lamp are subjected for the change of operating conditions, as described above. For instance, in the configuration of operating multiple parallel-connected power sources, the operation power increases in proportion to the number of power sources. When these power sources operate in asynchronization with each other, there arises a drawback of upsizing the combiner. That is, such a configuration of combining powers of multiple parallel-connected high frequency power source (DC-RF power converting circuit) is able to improve the power conversion efficiency at a low cost much more than the configuration of supplying a bulk power from only one high frequency power source. However, since it is necessary to deal with a bulk power in a single matching circuit like the conventional device, there arises a drawback that the circuit efficiency and cost efficiency reduce in the matching circuit.
To solve the above drawbacks, inventors have developed an electrodeless discharge lamp system which is comprised of an electrodeless discharge lamp, an excitation coil placed in the proximity along the electrodeless discharge lamp, a resonance circuit for supplying an appropriate power to the excitation coil, a high frequency power source for supplying a combined output of multiple parallel-connected power sources to the resonance circuit, and a driver of the high frequency power source, as a result of several researches and studies The inventors have ascertain that in such an electrodeless discharge lamp system since a combined output of the multiple parallel-connected power sources may be achieved by driven in synchronization or approximately in synchronization with each other, a magnetic flux induced by one power output may be counteracted by other magnetic flux induced by the other power output in the combiner. Therefore, the inventors have also ascertained that since the magnetic fluxes inside a magnetic core utilized in a combiner may counteract each other, and thus core-losses may be reduced in the combiner, the combiner may be miniaturized at a low cost.
Here, as described above, since the operation power of the driver which works as a switching element in the parallel-connected high frequency power sources increases in proportion to the number of an amplifier comprising the power source, the rise in the number of the amplifier without the change of threshold for turning on and off the switching element causes drawback of decreasing a operating voltage of the switching element. So, the inventors have ascertained that if the DC voltage is superposed on the output of the driver for the switching element, the parallel-connected power sources may be driven in a relatively small driver.
On the other hand, the inventors have also ascertained that in case of operating multiple parallel-connected DC-RF power converters in synchronization or approximately in synchroni
Doi Hiroyuki
Kawamura Masaaki
Suzuki Ioshiya
Terai Takashi
Yokozeki Ichiro
Toshiba Lighting & Technology Corporation
Tran Thuy Vinh
Wong Don
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