Lamp protective, electronic ballast
AssigneeEnergy Savings, Inc., a Delaware Corporation
InventorsRonald J. Bezdon, Randy G. Russell, Peter W. Shackle
Life of this patent
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Abstract
A lamp protective, electronic ballast includes a lamp voltage detector having a capacitor and resistor series connected across a discharge lamp. The junction of the resistor and capacitor is coupled to a voltage sensitive switch for detecting DC offset on the lamp and excessive AC voltage on the lamp. The switch is more sensitive to DC offset than to excessive AC voltage and is disabled while the lamp is started.
Claims9
A lamp protective, electronic ballast for powering a gas discharge lamp, said ballast comprising:
- an inverter for producing high frequency pulses and having an output for coupling the pulses to said lamp;
- a control circuit coupled to said inverter and including means for shutting off said inverter;
- a lamp voltage detector coupled to said lamp and to control circuit for detecting, as a first condition, when the magnitude of the DC offset across said lamp exceeds a first predetermined voltage and for detecting, as a second condition, when the magnitude of the AC voltage across said lamp exceeds a second predetermined voltage, said lamp voltage detector causing said control circuit to shut off said inverter when either condition is met.
A lamp protective, electronic ballast for powering a gas discharge lamp from an AC input voltage, said ballast comprising:
- a converter for converting said AC input voltage into direct current at a high voltage;
- a half-bridge inverter powered by said converter, said inverter producing high frequency pulses and having a series resonant, direct coupled output for connection to said lamp;
- a control circuit coupled to said inverter for driving said inverter at a predetermined frequency, said control circuitry including means for increasing the frequency of said pulses;
- a lamp voltage detector including
- a first capacitor,
- a first resistor coupled between said output and said capacitor, and
- a voltage sensitive switch coupled between said first capacitor and said control circuit, said voltage sensitive switch means causing said control circuit to increase the frequency of said pulses when the AC voltage across said lamp exceeds a first predetermined voltage or when the absolute value of the DC offset across said lamp exceeds a second predetermined voltage.
Dependencies are inferred from the claim text.