Abstract: The present invention provides, in one embodiment, a gas discharge lamp ballast with an integral shutdown timer. The ballast includes a circuit for receiving AC power, a converter circuit for converting the AC power to DC power and a square wave oscillator powered from the DC power. A resonant circuit powered by the square wave oscillator supplies power to at least one gas discharge lamp. A time-delay circuit disables the square wave oscillator, without interrupting the DC power supplied to the oscillator, upon the passage of a predetermined period of time from power-up of the AC power. The ballast can be realized with only a marginal increase in cost and size of the ballast.

Abstract: A hybrid ballast apparatus for starting and operating a plurality of series-connected discharge lamps and which provides protection against electric shock. The ballast apparatus includes first and second bidirectional thyristors connected in parallel with first and second ones of said lamps, respectively, and a trigger control circuit for simultaneously triggering the thyristors into conduction. Each lamp has two filaments and means are provided for connecting an L-C ballast device, the lamp filaments and the first and second thyristors in a series circuit across the AC supply voltage terminals. If one end of a lamp is removed from its socket, the series circuit is opened so that the maximum voltage at any lamp electrodes is limited to the AC supply voltage.

Abstract: A ballast circuit for starting and operating a preheat type circular fluorescent lamp, which replaces a multiple wattage incandescent lamp in a three-way incandescent lamp socket, so that the fluorescent lamp can be ignited to function at three different operating wattages. A lamination stacked core structure mounts first and second coils. A passive circuit element, such as positive temperature coefficient resistor also known as a thermistor, is connected in the circuit, which includes a three-way incandescent lamp screw base, for current switching functions to achieve the desired ignition and operating currents for the fluorescent lamp at its different operating wattages.

Abstract: A two-lamp rapid start fluorescent lamp circuit in which the lamps are ignited in sequence and then operated in series. The circuit being energized from a low voltage a.c. source through the use of a substantially conventional ballast which utilizes a transformer having a primary winding and a secondary winding connected in autotransformer relationship. The circuit includes a disconnect socket and a conventional two contact socket for mounting each lamp. The disconnect sockets in one circuit are arranged in one example to open the connections between the filament windings and a filament of each lamp. In another circuit one disconnect socket is arranged to open a connection to a filament winding and the other disconnect socket is arranged to open one of the connections to the line.

Abstract: A discharge lamp ballast circuit comprises at least one discharge lamp connected in series circuit with a ballast capacitor and inductor across a pair of input terminals for a source of A.C. supply voltage. A controlled semiconductor switching element is coupled across the lamp electrodes and a control circuit for the switching element is coupled to the input terminals and to a control electrode of the switching element. A voltage dependent non-linear impedance device is connected in shunt with the capacitor so as to limit the capacitor voltage to a predetermined value. The voltage dependent impedance device prevents the occurrence of hazardous voltage levels in the circuit and improves the stability during the warm up phase.

Abstract: A circuit for protecting a ballast in a high pressure metal vapor, such as sodium, lamp system which includes means for interrupting the power supply to the ballast in the event that no current is flowing through the lamp, once the system has been energized. The circuit has automatic compensation for short interruptions and for the time which it normally requires for the lamp to ignite. The absence of current flow through the lamp is sensed and this information used to provide the protection.