Filament cut-back circuit
AssigneeKoninklijke Philips Electronics N.V.
InventorsRamakrishnan Venkatraman, Michael Y. Zhang
Life of this patent
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Abstract
A filament cut-back circuit comprises an impedance circuit coupled in series between either an AC voltage source and a primary filament winding, or a secondary filament winding and a filament. In response to an alternating voltage from the AC voltage source when coupled in series thereto or an alternating voltage from the secondary filament winding when coupled in series thereto, the impedance circuit operates as a short circuit when the alternating voltage is at a preheat frequency and operates as an open circuit when the alternating voltage is at an operating frequency.
Claims31
A filament cut-back circuit, comprising:
- a filament winding;
- an impedance circuit in electrical communication with said filament winding,
- wherein said impedance circuit operates as a short circuit in response to a reception of an alternating voltage at a preheat frequency, and
- wherein said impedance circuit operates as an open circuit when the alternating voltage is at an operating frequency.
A filament cut-back circuit comprising:
- a filament winding;
- an impedance circuit in electrical communication with said filament winding,
- wherein said impedance circuit operates as a short circuit in response to a reception of an alternating voltage at a preheat frequency, and
- wherein said impedance circuit operates as an open circuit when the alternating voltage is at an operating frequency, wherein said impedance circuit includes:
- a first inductor (L1);
- a capacitor (C) coupled in parallel to said first inductor (L1);
- and
- a second inductor (L2) coupled in series to the parallel coupling of said first inductor (L1) and said capacitor (C).
A filament cut-back circuit, comprising
- a filament winding;
- and
- an impedance circuit in electrical communication with said filament winding, said impedance circuit including
- a first inductor (L1),
- a capacitor (C) coupled in parallel to said first inductor (L1) to constitute a parallel coupling of said first inductor (L1) and said capacitor (C), and
- a second inductor (L2) coupled in series to the parallel coupling of said first inductor (L1) and said capacitor (C).
A method of operating a filament cut-back circuit including an impedance circuit, said method comprising:
- operating the filament cut-back circuit to provide an alternating voltage at a preheat frequency;
- operating the impedance circuit as a short circuit in response to the alternating voltage being at the preheat frequency;
- operating the filament cut-back circuit to provide the alternating voltage at an operating frequency subsequent to the alternating voltage being at the preheat frequency;
- and
- operating the impedance circuit as an open circuit in response to the alternating voltage being at the operating frequency.
A method of operating an impedance circuit employed within a filament cut-back circuit, the impedance circuit including a capacitor (C), a first inductor (L1) and a second inductor (L2), said method comprising:
- operating the impedance circuit as a short circuit in response to reception of an alternating voltage being at a preheat frequency;
- and
- subsequently operating the impedance circuit as an open circuit in response to the alternating voltage being at an operating frequency.
A filament cut-back circuit for operation with a discharge lamp having a filament, the filament cut-back circuit comprising:
- filament winding means,
- an impedance circuit electrically coupled to the filament winding means, and
- means for applying an alternating voltage to the impedance circuit at a preheat frequency prior to lamp ignition and at an operating frequency after ignition of the discharge lamp,
- wherein said impedance circuit operates as a short circuit in response to the alternating voltage at the preheat frequency, and
- wherein said impedance circuit operates as an open circuit when the alternating voltage is at the operating frequency.
Dependencies are inferred from the claim text.