Electric lamp and discharge devices: systems – With cathode or cathode heater supply circuit – Delayed application of the discharge potential
Patent
1990-02-20
1991-06-25
Mis, David
Electric lamp and discharge devices: systems
With cathode or cathode heater supply circuit
Delayed application of the discharge potential
315106, 315200R, 315DIG7, H05B 4104
Patent
active
050270320
ABSTRACT:
A magnetic-type ballast powers two series-connected fluorescent lamps from a 277 Volt power line. Except when the lamps are loading the ballast, an electronic control circuit provides an intermittently interrupted short circuit across the two lamps: providing for socket voltages high enough to permit lamp ignition for a period of about 25 milli-seconds every two seconds or so, but keeping the average socket voltages low enough to satisfy safety requirements.
When initially connecting power to the lamp-ballast combination, the control circuit enters its short circuit state and remains there for two seconds. Then, after two seconds, the control circuit switches into an open circuit, thereby permitting the voltage across the lamps to become high enough to cause lamp starting within a few milli-seconds. If the lamps fail to start, the electronic circuit reverts back to a short circuit within 25 milli-seconds.
Normally the lamps do start, thereby causing a reduction in the voltage across the lamps compared with pre-starting. Due to this voltage reduction, the electronic circuit changes its mode into a continuous open circuit state.
The electronic control circuit comprises a bridge rectifier and a push-pull inverter that can be triggered into and out of self-oscillation. When the inverter oscillates, it acts as an short circuit, while also providing heating power for all lamp cathodes. When not oscillating, it acts as an open circuit.
REFERENCES:
patent: 3818312 (1974-06-01), Luursema et al.
patent: 4256992 (1981-03-01), Luursema
patent: 4523131 (1985-06-01), Zansky
patent: 4588924 (1986-05-01), Luursema et al.
patent: 4613934 (1986-09-01), Pacholok
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