Control circuit for starting, sustaining and operating arc lamps

Claim 2

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.

Claim 3

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.

Claim 4

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.

Claim 5

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.

Claim 6

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.

Claim 7

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.

Claim 8

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.

Claim 9

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.

Claim 10

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.

Claim 11

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.

Claim 12

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.

Claim 13

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.

Claim 14

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.

Claim 15

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.

Claim 16

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.