US 6,188,179 B1Granted

Induction circuits for lighting

AssigneeAuckland Uniservices Limited

InventorsJohn Talbot Boys, Andrew William Green

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Abstract

Disclosed is inductive coupling of power to devices having negative resistances, such as gas-filled discharge lamps (fluorescent tubes, neon signs, and the like) from a primary inductive loop, using resonant conditioning of the power provided to the device. A “C” shaped inductor (202) around the loop and a resonating capacitor (406) in parallel with the inductor provide a current source to the lamp (403) from across the capacitor. The circuit is capable of first igniting a lamp using a higher voltage available when the Q of the unloaded circuit is high, then running the lamp or other device at a controlled current. The lamp current is substantially proportional to the primary inductive loop flux, and substantially independent of the lamp resistance. A second inductor (404) in series with the first though not itself a collector of flux acts as a current limit. Applications include lighting, displays (optionally isolated and dimmable), and production of ultraviolet radiation.

Claims6

Dependent claims

A circuit for collecting inductively transferred electric power and supplying the power to a load having a negative resistance, the circuit comprising:

(a) at least one first inductor having a core oriented so that it is capable of intercepting, in a loosely coupled fashion, the magnetic flux radiating from a powered primary conductor, thereby causing a voltage to be induced in the windings of the at least one first inductor,
(b) at least one second inductor in series with the at least one first inductor, the second inductor having a core substantially incapable of intercepting the magnetic flux radiating from the primary conductor,
(c) at least one capacitor connected in parallel across at least one of the series of inductors, thereby forming in combination with the series of inductors a circuit capable of resonance at or about a supply frequency,
(d) an output from across the at least one capacitor,
(e) the second inductor being saturated by the current therethrough at a predetermined value of said current and thereby detuning the resonant circuit, so that in use the circuit provides
i) when not under load, an alternating output at a high voltage—and then
ii) when under load, a source of the constant-current type, supplying a current substantially proportional to the magnetic flux about the primary conductor yet substantially independent of the resistance of the load, and having an upper current level limited by the second inductor.

4 more elements

Dependencies are inferred from the claim text.