C-p-m Lighting, Inc.

Usi Lighting, Inc.

Ajay Maheshwari

A dimmable fluorescent lamp system embodiment of the present invention comprises a fluorescent lamp with filaments at each end that are continuously heated by independent secondary windings of a transformer. A resonating capacitor is connected in series with a resonating inductor and a pair of DC blocking capacitors are connected from each end of the fluorescent lamp to put it in parallel with the resonating capacitor. A control logic drives the primary winding with a pulse-width or frequency modulated square wave that is controlled by a feedback voltage derived from a pair of rectifiers and a dropping resistor in series with one of the DC blocking capacitors.

Electronic dimming ballast current sensing scheme

A dimmable fluorescent lamp system comprises a fluorescent lamp with filaments at each end that are continuously heated by a transformer. A resonating capacitor is connected in series with a resonating inductor and a pair of DC blocking capacitors are connected from each end of the fluorescent lamp to put it in parallel with the resonating capacitor. A control logic drives the resonating inductor with a pulse-width modulated square wave that is controlled by a feedback voltage derived from a pair of rectifiers and a dropping resistor in series with one of the DC blocking capacitors. An error amplifier with two gain settings, e.g., one for a range of 0-20% of maximum light dimming and the other for 20%-100% dimming, compares the feedback voltage to a setpoint. A threshold comparator establishes the switchover point between the two error gain ranges.

Electronic dimming ballast feedback control scheme

An electronic ballast embodiment of the present invention comprises a half-bridge parallel-loaded series resonant converter (HB-PLSRC) circuit a load is connected across a resonating capacitor with DC blocking capacitors in each of two legs and in series with a resonating inductor. The combination is connected to the junction of two switches wired in series across a DC source input such that the resonant inductor and resonant capacitor are connected across one of the switches. A coordinated manipulation of the switches is then used to charge and discharge the resonant inductor and resonant capacitor are pumped in series resonance. Alternatively, the load is connected through an isolation transformer.

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Dallas, TX, United States of America

Ajay Maheshwari