Electric lamp and discharge devices: systems – Periodic switch in the supply circuit – Periodic switch cut-out
Reexamination Certificate
1995-12-13
2001-04-03
Kinkead, Arnold (Department: 2817)
Electric lamp and discharge devices: systems
Periodic switch in the supply circuit
Periodic switch cut-out
C315S311000, C315S284000, C315S205000, C315S225000
Reexamination Certificate
active
06211625
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to electronic ballasts for rapid-start fluorescent lamps, particularly where the lamps are powered via a series-resonant LC circuit.
2. Description of Prior Art
For a description of pertinent prior art, reference is made to U.S. Pat. No. 4,677,345 to Nilssen; which patent issued from a Division of application Ser. No. 06/178,107 filed Aug. 14, 1980; which application is the original progenitor of instant application.
Otherwise, reference is made to the following U.S. patents: No. 3,263,122 to Genuit; No. 3,320,510 to Locklair; No. 3,996,493 to Davenport et el.; No. 4,100,476 to Ghiringhelli; No. 4,262,327 to Kovacik et al.; No. 4,370,600 to Zansky; No. 4,634,932 to Nilssen; and No. 4,857,806 to Nilssen.
SUMMARY OF THE INVENTION
Objects of the Invention
An object of the present invention is that of providing for a cost-effective electronic ballast.
This as well as other objects, features and advantages of the present invention will become apparent from the following description and claims.
Brief Description
The present invention is directed to providing improved inverter circuits for powering and controlling gas discharge lamps. The inverter circuits according to the present invention are highly efficient, can be compactly constructed and are ideally suited for energizing gas discharge lamps, particularly “instant-start” and “self-ballasted” fluorescent lamps.
According to one form of the present invention, a series-connected combination of an inductor and a capacitor is provided in circuit with the inverter transistors to be energized upon periodic transistor conduction. Transistor drive current is preferably provided through the use of at least one saturable inductor to control the transistor inversion frequency to be equal to or greater than the natural resonant frequency of the inductor and capacitor combination. The high voltages efficiently developed by loading the inverter with the inductor and capacitor are ideally suited for energizing external loads such as gas discharge lamps. In such an application, the use of an adjustable inductor permits control of the inverter output as a means of adjusting the level of lamp illumination.
According to another important form of the present invention, reliable and highly efficient half-bridge inverters include a saturable inductor in a current feedback circuit to drive the transistors for alternate conduction. The inverters also include a load having an inductance sufficient to effect periodic energy storage for self-sustained transistor inversion. Importantly, improved reliability is achieved because of the relatively low and transient-free voltages across the transistors in these half-bridge inverters.
Further, according to another feature of the present invention, novel and economical power supplies particularly useful with the disclosed inverter circuits convert conventional AC input voltages to DC for supplying to the inverters.
Yet further, according to still another feature of the invention, a rapid-start fluorescent lamp is powered by way of a series-resonant LC circuit; while heating power for the lamp's cathodes is provided via loosely-coupled auxiliary windings on the tank inductor of the LC circuit. Alternatively, cathode heating power is provided from tightly-coupled windings on the tank inductor; in which case output current-limiting is provided via a non-linear resistance means, such as an incandescent filament in a light bulb, connected in series with the output of each winding.
REFERENCES:
patent: 3733541 (1973-05-01), Elms
patent: 4005335 (1977-01-01), Perper
patent: 4045711 (1977-08-01), Pitel
patent: 4244013 (1981-01-01), Wotowiec
patent: 4270071 (1981-05-01), Morton
patent: 4298822 (1981-11-01), Fukuda
patent: 4337414 (1982-06-01), Young
“Conversion of Incandescent Lamp Sockets to Flourescent in the Home Market” by E.A. Dale et al., Lighting & Design Appl., Mar. 1976, pp. 18-23.
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