Electric lamp and discharge devices: systems – Periodic switch in the supply circuit – Periodic switch cut-out
Patent
1996-07-24
1998-03-17
Pascal, Robert
Electric lamp and discharge devices: systems
Periodic switch in the supply circuit
Periodic switch cut-out
315DIG7, 315307, 315209R, H05B 3702
Patent
active
057290962
ABSTRACT:
A protection method (10) and protection circuit (500) for protecting an inverter (300) in an electronic preheat ballast (100) for powering at least one fluorescent lamp (902). The inverter (300) includes a first inverter switch (306), a second inverter switch (310), an output circuit (800), and an inverter driver circuit (400) having a drive frequency. The protection circuit (500) comprises a frequency shift circuit (600), a latch circuit (700), a current source network (520), a current sensing circuit (510), and a DC supply capacitance (502). The protection method (10) includes the steps of (a) providing a filament preheat period by initially setting the drive frequency at a first frequency, (b) shifting the drive frequency to a second frequency for igniting and operating the lamps, (c) changing the drive frequency back to the first frequency in response to a lamp fault, and (d) providing, upon correction of the lamp fault, a filament preheat period prior to attempting to ignite and operate the lamps.
REFERENCES:
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patent: 5220247 (1993-06-01), Moisin
patent: 5387846 (1995-02-01), So
patent: 5404083 (1995-04-01), Nilssen
patent: 5436529 (1995-07-01), Bobel
patent: 5500576 (1996-03-01), Russell et al.
patent: 5635799 (1997-06-01), Hesterman
Liu Guang
Upadhyay Anand K.
Cunningham Gary J.
Labudda Kenneth D.
Motorola Inc.
Pascal Robert
Shingleton Michael B.
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