Electric lamp and discharge devices: systems – Periodic switch in the supply circuit – Periodic switch in the primary circuit of the supply...
Patent
1994-07-11
2000-08-22
Shingleton, Michael B
Electric lamp and discharge devices: systems
Periodic switch in the supply circuit
Periodic switch in the primary circuit of the supply...
315244, 315307, 315DIG4, 315DIG5, 315DIG7, H05B 3702
Patent
active
061077496
ABSTRACT:
In a power-line-operated high-frequency electronic ballast, a half-bridge inverter is powered from a DC supply voltage and a fluorescent lamp is connected with the inverter's more-or-less asymmetrical squarewave output voltage by way of a of a series-resonant L-C circuit. The amount of power supplied by the inverter to the series-resonant L-C circuit and/or to the fluorescent lamp at any given moment depends on four significant factors: (i) the instantaneous magnitude of the DC supply voltage, (ii) the instantaneous frequency of the inverter's squarewave output voltage, (iii) the symmetry of the inverter's squarewave output voltage (which determines the effective magnitude of of its fundamental frequency voltage component), and (iv) the instantaneous operational characteristics of the fluorescent lamp. Arrangements are provided whereby the symmetry, and thereby the effective magnitude, of the inverter's output voltage is automatically adjusted so as to prevent inverter overload in case the fluorescent lamp is non-present or inoperative. The half-bridge inverter includes a bipolar transistor series-connected with a FET. The bipolar transistor operates with a substantially constant per-cycle ON-time, whereas the FET operates with a per-cycle ON-time of controllable duration.
REFERENCES:
patent: 4346332 (1982-08-01), Walden
patent: 4471269 (1984-09-01), Ganser et al.
patent: 4698553 (1987-10-01), Nilssen
patent: 4719390 (1988-01-01), Sairanen
patent: 4933605 (1990-06-01), Quazi et al.
patent: 4983887 (1991-01-01), Nilssen
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