CONTROL CIRCUIT FOR STARTING, SUSTAINING AND OPERATING ARC LAMPS
First Claim
1. A control circuit for starting, sustaining and operating an arc lamp from a source of alternating current comprising, in combination, a ballast transformer having input means for connection to said source of alternating current and output means for connecting said arc lamp in a lamp operating circuit loop, differentiating circuit means coupled across the output means of said ballast transformer for detecting a voltage transition in said lamp operating circuit loop and generating a trigger signal in response thereto, and means coupled to said lamp operating circuit loop and responsive to said trigger signal for introducing a voltage pulse of sufficient energy to ignite said arc lamp.
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Abstract
A control circuit for starting, sustaining and operating metal halide arc lamps comprising a bridged air gap ballast transformer having AC input terminals and output terminals for connection to an arc lamp. A differentiating circuit is connected across the output terminals for detecting voltage transitions in the lamp circuit and generating trigger signals in response thereto. Serially connected across the AC input terminals are a pulse winding magnetically coupled to the secondary winding of the ballast transformer, a capacitor, and a switch for discharging the capacitor through the pulse winding in response to the trigger signal from the differentiating circuit to thereby supply a voltage pulse of sufficient energy to ignite the arc lamp.
28 Citations
13 Claims
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1. A control circuit for starting, sustaining and operating an arc lamp from a source of alternating current comprising, in combination, a ballast transformer having input means for connection to said source of alternating current and output means for connecting said arc lamp in a lamp operating circuit loop, differentiating circuit means coupled across the output means of said ballast transformer for detecting a voltage transition in said lamp operating circuit loop and generating a trigger signal in response thereto, and means coupled to said lamp operating circuit loop and responsive to said trigger signal for introducing a voltage pulse of sufficient energy to ignite said arc lamp.
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2. A control circuit in accordance with claim 1 wherein said differentiating circuit means includes a normally closed switching means operative to provide an open circuit after a predetermined period of operation of said control circuit.
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3. A control circuit in accordance with claim 1 wherein said differentiating circuit means comprises a capacitor and an autotransformer serially connected across the output means of said ballast transformer, said trigger signal being available at a tap on said autotransformer.
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4. A control circuit for starting, sustaining and operating an arc lamp from a source of alternating current comprising, in combination:
- a ballast transformer having input means for connection to said source of alternating current and output means for connecting said arc lamp in a lamp operating circuit loop;
means for detecting a voltage transition in said lamp operating circuit loop and generating a trigger signal in response thereto; and
means coUpled to said lamp operating circuit loop and response to said trigger signal for introducing a voltage pulse of sufficient energy to ignite said arc lamp;
said means for detecting a voltage transition comprising a pickoff winding magnetically coupled to the output means of said ballast transformer, a high pass filter connected to the output of said pick-off winding, and a differentiating capacitor connected at the output of said filter for providing said trigger signal.
- a ballast transformer having input means for connection to said source of alternating current and output means for connecting said arc lamp in a lamp operating circuit loop;
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5. A control circuit for starting, sustaining and operating an arc lamp from a source of alternating current comprising, in combination:
- a ballast transformer comprising a first magnetic core, closed except for an air gap, a second magnetic core, closed except for at least one bridged air gap, a portion of one core being close to but spaced from a portion of said other core, a primary winding encircling each of said portions of said cores and overlying the air gap in said first magnetic core, and a secondary winding encircling a portion of said second magnetic core only and overlying a bridged air gap therein, said secondary winding being connected in series with at least a portion of said primary winding to form an autotransformer;
input means for connection to said source of alternating current comprising an input terminal connected to one end of said primary winding and a common terminal connected to the other end of said primary winding;
ballast output means for connecting said arc lamp in a lamp operating circuit loop comprising said common terminal, said secondary winding, and an output terminal coupled to one end of said secondary winding;
means for detecting a voltage transition in said lamp operating circuit loop and generating a trigger signal in response thereto; and
means coupled to said lamp operating circuit loop and responsive to said trigger signal for introducing a voltage pulse of sufficient energy to ignite said arc lamp.
- a ballast transformer comprising a first magnetic core, closed except for an air gap, a second magnetic core, closed except for at least one bridged air gap, a portion of one core being close to but spaced from a portion of said other core, a primary winding encircling each of said portions of said cores and overlying the air gap in said first magnetic core, and a secondary winding encircling a portion of said second magnetic core only and overlying a bridged air gap therein, said secondary winding being connected in series with at least a portion of said primary winding to form an autotransformer;
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6. A control circuit in accordance with claim 5 wherein said means for introducing a voltage pulse to ignite the arc lamp comprises a pulse winding magnetically coupled to the secondary winding of said ballast transformer, a capacitor, and switching means for discharging said capacitor through said pulse winding in response to said trigger signal, said pulse winding, capacitor and switching means being serially connected in that order between said input terminal and said common terminal.
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7. A control circuit in accordance with claim 5 wherein said means for introducing a voltage pulse to ignite the arc lamp comprises a pulse winding magnetically coupled to the secondary winding of said ballast transformer, a capacitor, and switching means for discharging said capacitor through said pulse winding in response to said trigger signal, said switching means, capacitor and pulse winding being serially connected in that order between said common terminal and the interconnection of said ballast transformer primary and secondary windings, said pulse winding thereby being connected in series with the secondary winding of said ballast transformer to form an autotransformer.
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8. A control circuit in accordance with claim 5 wherein said means for introducing a voltage pulse to ignite the arc lamp comprises a pulse transformer having primary and secondary windings, a capacitor, and switching means for discharging said capacitor through the primary winding of said pulse transformer in response to said trigger signal, said pulse transformer primary winding, capacitor, and switching means being serially connected in that order between said input terminal and said common terminal, and said pulse transformer secondary winding being serially connected in said lamp operating circuit loop between said ballast transformer secondary winding and said output terminal.
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9. A control circuit in accordance with claim 5 wherein said means for detecting a voltage transition comprises a pick-off winding magnetically coupled to the secondary winding of said ballast transformer, a high pass filter coNnected to the output of said pick-off winding, and a differentiating capacitor connected at the output of said filter for providing said trigger signal.
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10. A control circuit in accordance with claim 5 wherein said means for detecting a voltage transition comprises differentiating circuit means coupled between said output terminal and said common terminal.
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11. A control circuit in accordance with claim 10 wherein said differentiating circuit means comprises a capacitor and a step-down autotransformer serially connected between said output terminal and said common terminal, said trigger signal being available at a tap on said step-down autotransformer.
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12. A control circuit in accordance with claim 11 wherein said means for introducing a voltage pulse to ignite the arc lamp comprises a pulse winding magnetically coupled to said ballast transformer secondary winding, a capacitor, and a switching means serially connected in that order between said input terminal and said common terminal, said switching means having a trigger input terminal connected to the tap on said step-down autotransformer.
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13. A control circuit in accordance with claim 11 wherein said differentiating circuit means further includes a thermal relay having normally closed switch contacts serially connected between said capacitor and said step-down autotransformer.
Specification