Voltage-comparator, solid-state, current-switch starter for fluorescent lamp
First Claim
1. A starter for use with a fluorescent lamp having cathodes connected in a series circuit with a ballast and energized by an alternating (AC) power source, said starter lighting the lamp by igniting a plasma which a voltage from each half cycle of the AC power thereafter sustains, said starter adapted to be connected to the cathodes, said starter comprising:
- a conduction initiation circuit to selectively conduct current from the AC power source through the ballast and the cathodes commencing during one half cycle of applied AC current; and
a conduction termination circuit to cease conducting current substantially instantaneously at a predetermined time during the one half cycle when the current is of a predetermined level to establish a sufficiently great change in current per change in time (di/dt) to generate a starting voltage pulse from the ballast between the cathodes sufficient to ignite the plasma, the predetermined time at which the di/dt creates the starting pulse being a time when the voltage of the AC power across the cathodes exceeds a predetermined ignition voltage of the plasma;
the conduction initiation circuit further comprising;
a sensing circuit adapted to be connected to the cathodes and operative to develop a first signal related to the voltage between the cathodes;
a reference circuit to supply a second signal related to a predetermined voltage at which the plasma ignites; and
a trigger circuit including a comparator responsive to the first and second signals to control application of a trigger signal to initiate current conduction by the conduction initiation circuit and to terminate current conduction by the conduction termination circuit upon the first signal obtaining a predetermined relationship compared to the second signal.
1 Assignment
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Accused Products
Abstract
A starter for a fluorescent lamp selectively conducts current from an AC power source through a ballast and cathodes of the lamp during one half cycle of conducted current from the AC power source. Thereafter and during the same on half cycle of current the starter ceases conducting current substantially instantaneously when the current is of a predetermined level. The resulting di/dt generates a starting voltage pulse from the ballast sufficient to ignite the plasma. The starting pulse occurs when the AC voltage across the cathodes exceeds an ignition voltage of the plasma. Preferably the starter employs a thyristor which has a predetermined holding current at least equal to the predetermined level to allow the inherent commutation of the thyristor to create the di/dt. The current conducted by the thyristor heats the cathodes prior to igniting the plasma. A voltage sensing capability associated with the starter triggers the thyristor into conduction only when the voltage across the cathodes exceeds the ignition voltage of the plasma, which occurs when the fluorescent lamp is not lighted, and therefore automatically starts the lamp. Lamp dimming and programmable turn on and turn off conditions are easily effected by timing an ignition and extinguishing sequence.
65 Citations
26 Claims
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1. A starter for use with a fluorescent lamp having cathodes connected in a series circuit with a ballast and energized by an alternating (AC) power source, said starter lighting the lamp by igniting a plasma which a voltage from each half cycle of the AC power thereafter sustains, said starter adapted to be connected to the cathodes, said starter comprising:
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a conduction initiation circuit to selectively conduct current from the AC power source through the ballast and the cathodes commencing during one half cycle of applied AC current; and a conduction termination circuit to cease conducting current substantially instantaneously at a predetermined time during the one half cycle when the current is of a predetermined level to establish a sufficiently great change in current per change in time (di/dt) to generate a starting voltage pulse from the ballast between the cathodes sufficient to ignite the plasma, the predetermined time at which the di/dt creates the starting pulse being a time when the voltage of the AC power across the cathodes exceeds a predetermined ignition voltage of the plasma; the conduction initiation circuit further comprising; a sensing circuit adapted to be connected to the cathodes and operative to develop a first signal related to the voltage between the cathodes; a reference circuit to supply a second signal related to a predetermined voltage at which the plasma ignites; and a trigger circuit including a comparator responsive to the first and second signals to control application of a trigger signal to initiate current conduction by the conduction initiation circuit and to terminate current conduction by the conduction termination circuit upon the first signal obtaining a predetermined relationship compared to the second signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A starter for use with a fluorescent lamp having cathodes connected to a ballast in a circuit energized by an alternating (AC) power source, said starter lighting the lamp by igniting a plasma which a voltage from each half cycle of the AC power thereafter sustains, said starter comprising:
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a pair of terminals adapted to connect to the cathodes; a controllable semiconductor switch connected between the terminals and operative in response to a trigger signal to begin conducting current from the AC power source between the terminals and through the cathodes and to end conducting current substantially immediately when the current conducted by the switch decreases to a predetermined level; a sensing circuit connected to the terminals and operative to develop a first signal related to the voltage applied between the terminals; a reference circuit to supply a second signal related to the ignition voltage of the plasma within the lamp; a trigger circuit responsive to the first and second signals to supply a trigger signal to the controllable switch when the voltage of the AC power applied between the cathodes exceeds the ignition voltage; the substantially immediate end of current conduction occurs at a time when the current flow through the ballast from the AC power source nears a zero crossing point and the voltage across the cathodes from the applied AC power is in excess of the ignition voltage; and the predetermined level of current at which the switch ends conducting is sufficiently great and the substantially immediate time for the switch to cease conducting current is sufficiently small to establish a change in current per change in time characteristic (di/dt) which creates a voltage from the ballast between the cathodes sufficient to ignite a plasma in the lamp between the cathodes. - View Dependent Claims (22, 23, 24, 25, 26)
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Specification