Electric lamp and discharge devices: systems – With automatic shunt and/or cutout
Patent
1989-12-12
1991-04-02
Pascal, Robert J.
Electric lamp and discharge devices: systems
With automatic shunt and/or cutout
315127, 315225, 315DIG7, H05B 4129
Patent
active
050049550
ABSTRACT:
An electronic ballast provides a high-frequency current-limited voltage between a first socket terminal and a second socket terminal. These socket terminals are adapted to receive and hold a rapid-start fluorescent lamp. The first terminal has a relatively low-magnitude potential with respect to ground; the second terminal has a relatively high-magnitude potential with respect to ground. A person causing in direct or indirect contact with the second terminal is apt to receive a hazardous electric shock. A self-oscillating electronic inverter is operable to provide the high-frequency voltage. To provide an output, this inverter has to be triggered into oscillation. However, if no current flows from the first terminal, the inverter will automatically become disabled within 25 milli-seconds; whereafter it will not be re-triggered for about 1.5 seconds. With no current flowing, the magnitude of the high-frequency AC voltage is high enough to permit proper starting of the rapid-start fluorescent lamp within a time span of 25 milli-seconds, but only after its cathodes have become incandescent. As soon as the lamp has started, lamp current flows from the socket terminals and through the fluorescent lamp. If lamp current flowing from the first terminal fails to materialize, or if interrupted, as for instance may happen when replacing the fluorescent lamp, the inverter becomes disabled; which means that the electric shock hazard represented by the second terminal will be removed within 25 milli-seconds.
REFERENCES:
patent: 4461980 (1984-07-01), Nilssen
patent: 4507698 (1985-03-01), Nilssen
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