Capacitive lamp out detector
AssigneeEnergy Savings, Inc.
InventorsPeter W. Shackle, Randy G. Russell, Kent E. Crouse
Life of this patent
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Abstract
An electronic ballast includes a boost circuit, a low voltage control circuit, and a driven inverter in a half-bridge, push-pull, series resonant, parallel loaded configuration. The boost circuit includes a low voltage output for powering the control circuit. In the event of a fault, the control circuit shuts off the boost circuit and the inverter. A sense capacitor is in series with the lamps and the voltage across the capacitor prevents a timer in the control circuit from shutting off the ballast. The timer circuit waits a period longer than the time it takes for the lamps to start normally. The sense capacitor is either in series with the lamp across the resonant capacitor or is in series with the resonant capacitor.
Claims17
An electronic ballast for a gas discharge lamp, said ballast comprising:
- a series resonant, parallel loaded, half-bridge inverter for producing a high frequency pulses from direct current;
- said inverter including a half-bridge capacitor for shifting the level of said pulses to produce alternating current;
- wherein a first DC voltage occurs across said half-bridge capacitor during normal operation and a second DC voltage occurs across said half-bridge capacitor when no lamp is attached to the ballast, said first DC voltage being greater than said second DC voltage;
- and
- a control circuit coupled to said half-bridge capacitor for sensing the DC voltage across said half-bridge capacitor and for turning off said inverter when said second DC voltage occurs.
An electronic ballast for a gas discharge lamp, said ballast comprising:
- an AC input circuit for receiving alternating current from a power line and producing a direct current;
- an inverter coupled to said AC input circuit and having a first output terminal and a second output terminal, said inverter converting direct current into high frequency pulses;
- a capacitor coupled to one of said output terminals for shifting the level of said pulses to produce alternating current at said first output terminal and at said second output terminal, wherein there is a high DC voltage across said capacitor when a lamp is connected to said output terminals and is operating normally, otherwise there is a low DC voltage across said capacitor;
- and
- a control circuit coupled to said inverter and to said capacitor for sensing the DC voltage across said capacitor and for reducing said high frequency alternating current when the voltage across said capacitor is low.
Dependencies are inferred from the claim text.