US 3,942,069 AGranted

Discharge lamp lighting apparatus and method

AssigneeNEC Sylvania Corporation

InventorIsao Kaneda

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Abstract

A discharge lamp lighting apparatus includes three oscillation circuits. The first comprises a linear inductor and a capacitor connected in series to a power source. The second oscillation circuit is connected across the capacitor and includes a bounce or backswing booster inductor and a voltage responsive switching element connected in series. The third oscillation circuit comprises the bounce inductor and its distributed capacity. The bounce booster inductor has a magnetic core with a shape and of a material providing an abrupt saturation characteristic. The core factor K of the core is small and may have a ratio of the cross sections of the wound to the unwound parts thereof of less than one half. Alternatively, the ratio of the wound part of the core to the unwound part thereof is less than one fourth and a conventional core material may be employed for the core. Further, the peak temperature characteristic such as the first peak of the initial permeability of the core material may be selected in the range of -40.degree.C to +5.degree.C. The core is provided with a small gap to improve lamp starting operation at high temperatures, the gap having conventional as opposed to mirror polished faces.

In a discharge lamp lighting apparatus including a first oscillation circuit adapted to be connected to a power source and including a linear inductor and a capacitor connected in series, a second oscillation circuit connected across said capacitor and having a bounce booster saturable inductor and a voltage responsive switching element connected in series, and a third oscillation circuit including said bounce booster saturable inductor and its distributed capacity, whereby a discharge lamp may be connected across said capacitor, said switching element having a breakdown voltage within a range of from above a virtual voltage across said discharge lamp, as lighted, to below the maximum instantaneous voltage of said power source, whereby said first, second and third oscillation circuits generate a high oscillation voltage across said capacitor for starting said discharge lamp;

the improvement wherein said bounce booster saturable inductor comprises a magnetic core and a coil, said core having a coiled portion around which said coil is wound, and a non-coiled portion free of said coil, said core having a core factor K defined by the relationship:
K = K.sub.1 + K.sub.2
where K.sub.1 is the core factor of said coiled portion and K.sub.2 is the core factor of said non-coiled portion of said core, said core factors K.sub.1, K.sub.2 having the relationship:
K.sub.1 .sub." K.sub.2
the cross sectional area of said coiled core portion being less than one half of the cross sectional area of said non-coiled portion, the magnetic path length of said coiled portion being less than one quarter of the overall magnetic path length of said core, whereby when said discharge lamp remains lighted the equivalent inductance of said bounce booster saturable inductor increases to block a peak value of a voltage across said discharge lamp to avoid actuation of said second oscillation circuit and to avoid repetitive unoscillating operation of said discharge lamp.

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Abstract

Claims14