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: 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 ballast for a low pressure gas discharge lamp, preferably of the heated-filament type, includes an on-off indicator for a lamp. The ballast includes a load circuit with a lamp, and a driver for supplying AC load current to the lamp. Such driver includes circuitry for shutting off the load current in the presence of a lamp fault condition. The ballast also includes a pair of nodes having voltage across them when the lamp operates normally, and having substantially no voltage across them when the lamp is off. An on-off lamp indicator circuit includes a light-emitting device and is coupled to the pair of nodes for causing the light-emitting device to emit light when the driver supplies load current to the lamp and for causing the light-emitting device to cease to emit light when the driver no longer supplies load current to the lamp.

Abstract: A resonant fluorescent lamp ballast includes an IC driver for a half-bridge arrangement that supplies AC current to a lamp. The IC creates a frequency sweep from a pre-heat frequency, through a resonant frequency, to a still lower operating frequency. A pre-heat pin in the IC triggers a re-start or the frequency sweep when a first signal exceeds a first threshold level. A shut-down pin in the IC associated with an internal shut-down latch shuts down the driver when a second signal exceeds a second threshold level. Pre-heat trigger circuitry detects a current spike through half-bridge switches when the lamp has not yet started, supplying the pre-heat pin with a first signal exceeding the first threshold level. End-of-life circuitry provides to the shut-down pin a second signal exceeding the second threshold level if lamp current fails to reach a substantial portion of its normal level within a predetermined time.