Electric lamp and discharge devices: systems – Pulsating or a.c. supply – With power factor control device
Patent
1992-07-13
1995-07-18
Pascal, Robert J.
Electric lamp and discharge devices: systems
Pulsating or a.c. supply
With power factor control device
315244, 315209R, 315224, H05B 4116
Patent
active
054344816
ABSTRACT:
An electronic ballast draws current from the power line with power factor over 90% and total harmonic distortion under 20%, and powers two series-connected 48"/T-12 fluorescent lamps with a 30 kHz current having crest-factor better than 1.7. The ballast includes a power-factor-correcting up-converter and a half-bridge inverter providing a 30 kHz squarewave voltage across a series-resonant high-Q L-C circuit. When the L-C circuit is not loaded, the magnitude of the 30 kHz voltage developing across its tank capacitor is clamped by non-dissipative means to a peak-to-peak magnitude equal to the magnitude of the inverter's DC supply voltage. The ballast output voltage consists of the sum of two components: (i) the 30 kHz voltage across the tank capacitor, and (ii) a 30 kHz voltage obtained from an auxiliary winding on the tank inductor. The ballast output voltage is non-pulsing and is provided at a pair of ballast output terminals across which are series-connected the two 48"/T-12 fluorescent lamps. When the fluorescent lamps are non-connected, the amount of power drawn by the ballast from the power line is less than 10 Watt. Shock hazard mitigation is attained by making the ballast output voltage balanced about ground and by making the magnitude of this 30 kHz ballast output voltage as measured between ground and either one of the ballast output terminals lower than what is required to ignite one of the fluorescent lamps. Control of the magnitude of the inverter's DC supply voltage is attained in a "bang-bang" manner in that the up-converter is disabled whenever the magnitude of the DC supply voltage increases above a certain level and it is re-enabled whenever this magnitude decreases below a certain lower level.
REFERENCES:
patent: 4463287 (1984-07-01), Pitel
patent: 4700111 (1987-10-01), Folwell et al.
patent: 5057748 (1991-10-01), Doss
Pascal Robert J.
Ratliff Reginald A.
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