Electric lamp and discharge devices: systems – Condenser in the supply circuit – Inductance in the condenser circuit
Patent
1983-06-03
1985-08-27
Moore, David K.
Electric lamp and discharge devices: systems
Condenser in the supply circuit
Inductance in the condenser circuit
315225, 315DIG7, H05B 3700
Patent
active
045380953
ABSTRACT:
Subject invention relates to an inverter-type electronic fluorescent lamp ballast wherein a series-resonant LC circuit connected across the inverter's output is used for matching the inverter's operating characteristics to those of the fluorescent lamp--the fluorescent lamp being connected in parallel with the tank-capacitor of this LC circuit. In particular, the invention relates to the use of a Varistor coupled in parallel with this tank-capacitor, thereby limiting the voltage developed thereacross to a magnitude suitable for proper lamp starting. Moreover, by providing for means whereby the inverter shuts itself off in case current flows through this Varistor for more than about one second or so (which is the maximum length of time that it should normally take for a fluorescent lamp to start), inverter as well as Varistor overload protection is obtained. Without such overload protection the inverter and/or the Varistor would self-destruct in case the fluorescent lamp failed to start or if it were removed from the circuit. Also, to mitigate the possibility of electric shock hazard for persons servicing fluorescent lighting fixtures using ballasts based on subject invention--as might occur if someone were to touch a terminal at one end of a fluorescent lamp while inserting the other end into its socket--the inverter will shut itself off immediately in case there is flow of current directly from one of the ballast terminals and to earth ground.
REFERENCES:
patent: 4370600 (1983-01-01), Zansky
patent: 4378514 (1983-03-01), Collins
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