ELECTRONIC BALLAST AND HIGH FREQUENCY SUPPLY SYSTEM FOR GAS DISCHARGE LAMPS

摘要

The invention pertains to an electronic ballast for gas discharge lamps, particularly fluorescent tubes, which supplies them with high frequency AC at proper voltage from a supply of DC, such as a battery, solar cell or rectifier adapted to be connected, if necessary through a transformer, to a commercial source of AC of any voltage, frequency and phase. The ballast is adapted to be used in combination with an electrical system, e.g., the electrical system of a building, with many electrical connecting means such as fixtures for holding the fluorescent tubes, commercial frequency distribution means for AC at voltage suitable for appliances, small motors, etc., and the high frequency AC distribution system connecting the source of DC to one or more ballasts to supply the tubes to be used in the fixtures. The ballast includes inverting means comprising a symmetrical class B, push-pull, current limited, dual feedback oscillator and preferably also not only a high frequency transformer to deliver the output of the oscillator to the building wiring system but also a further transformer, e.g., an autotransformer, having its primary winding placed across the terminals of a lamp and having at least one secondary winding for supplying heating current for the filaments of the fluorescent tubes. This arrangement provides high enough voltage rapidly to heat the filaments and to start the arc in a tube but as soon as the arc strikes the voltage immediately falls to a lower value and the filament current is reduced to a lower level, thereby effecting great economy in operation. Means for dimming the lights may also be incorporated in the system. A particularly efficient rectifier utilizes a transformer having a delta-connected primary winding and a six-winding star-connected secondary with diodes connected to the outer end of each secondary winding to conduct positive and negative current, respectively, to DC terminals, and the central connection of the secondary windings may provide a grounded neutral. for a three wire DC distribution system.