Electronic ballast with controlled operating voltage

Details Electronic ballast with controlled operating voltage Electronic ballast with controlled operating voltage

1993-02-10

1995-06-27

Pascal, Robert J.

Electric lamp and discharge devices: systems

With automatic shunt and/or cutout

Supply circuit current and/or potential actuated switch

315125, 315119, 315225, 315242, 315243, 315244, 315284, 315DIG7, H05B 3702

Patent

active

054282640

ABSTRACT:
In a fluorescent lamp ballast, a high-frequency AC voltage is applied directly across a tuned L-C circuit. The fluorescent lamp is connected in parallel with the capacitor of the L-C circuit and a voltage-limiting means prevents the series-resonating L-C circuit from overloading the source of AC voltage during any period when the lamp is not effective in providing circuit loading. When power is initially applied to the L-C circuit, a control means provides a short circuit across the capacitor; and, by way of a first current transformer, the resulting short circuit current is used for pre-heating the fluorescent lamp cathodes. After about 1.5 second, the control means provides for removal of the short circuit for a period of about 25 milli-seconds, thereby permitting the voltage across the capacitor to grow to a magnitude sufficient to ignite and operate the lamp, while at the same time removing the cathode voltage. If the lamp ignites, the resulting lamp current is then used, by way of a second current transformer, to prevent the control means from re-providing the short circuit. If lamp current does not flow, or if it at any time ceases to flow, the control means will re-provide the short circuit within about 25 milli-second. Thereafter, until power is removed or until an operable lamp is connected, the control means will continuously repeat the cycle of 1.5 second short circuit and 25 milli-seconds open circuit.

REFERENCES:
patent: 3662216 (1972-05-01), Hildebrant
patent: 4370600 (1983-01-01), Zansky
patent: 4612478 (1986-09-01), Payne

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