North American Philips Corporation

Robert A Erhardt

Mark W Fellows

John M Wong

Edmond Toy

James A Thomsen, Jr

Allan E Brown

An electronic controller for fluorescent lamps includes a DC to AC converter which supplies high frequency current to the lamps and a preconditioner stage which includes a switched mode power supply connected to accept line power and produce a DC input for the DC to AC converter. The switched mode power supply and the DC to AC converter are synchronized to operate in a fixed phase relationship and/or at the same frequency.

Fluorescent lamp controllers

A controller operates in pre-ignition and ignition phases to obtain stable and reliable control of operation of a half-bridge DC-AC converter in a frequency range which is offset from a resonant frequency of an output circuit which includes a transformer and capacitors and which couples the converter to a fluorescent lamp load. The converter is supplied with a DC voltage from a switched-mode DC-DC supply of a pre-conditioner circuit which responds to a full-wave rectified AC voltage and which is supplied with pulse-width modulated gating pulses from the controller, preferably at a frequency which is the same as that of the converter. The controller monitors signals from the output circuit and pre-conditioner circuits and exercises control to reliable starting and highly efficient lamp operation and to obtain an in-phase proportional relationship of input voltage and current wave forms.

An improved power supply for one or more electric discharge lamps includes a high frequency oscillator-inverter circuit coupled to the output of a full-wave rectifier circuit via a transformer primary winding (25). The rectifier circuit is energized from a low frequency source of AC voltage. The oscillator-inverter circuit supplies high frequency oscillations to the lamp via a frequency-dependent ballast coupling circuit. A regenerative power supply is coupled to the transformer primary winding by means of a secondary winding (62) of the transformer thereby to charge a capacitor (49) operative as a switchable auxiliary supply voltage for the oscillator-inverter circuit. Improved start-up operation is achieved by winding the transformer (25, 62) so as to provide a polarity inversion for the supply of electric energy to the regenerative power supply.

High frequency oscillator-inverter with improved regenerative power

A ballast control apparatus for an electric discharge lamp comprises a first series circuit including a first winding of an AC supply voltage transformer, a first winding of a ballast transformer, a lamp current sensing resistor and the lamp. A current sensing transformer has a first winding parallel to the resistor. A second winding of the supply voltage transformer, the ballast transformer and the current sensing transformer are connected in a second series circuit. A signal voltage proportional to lamp power is derived by adding together the voltages induced in the three series-connected second windings. A second signal voltage proportional to lamp voltage is derived across the series combination of the second windings of the ballast transformer and the supply voltage transformer. The voltage induced in the second winding of the current sensing transformer is proportional to lamp current. A signal voltage indicative of the condition of the lamp load can be derived across the second winding of the ballast transformer. These three signal voltages are used to control a DC/AC inverter that energizes the lamp via the supply voltage transformer.

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Chicago, IL, United States of America

Robert A Erhardt