Dimmable instant start ballast

Details Dimmable instant start ballast Dimmable instant start ballast

2008-02-29

2010-10-19

Owens, Douglas W (Department: 2821)

Electric lamp and discharge devices: systems

Periodic switch in the supply circuit

Impedance or current regulator in the supply circuit

C315S276000, C315S284000

Reexamination Certificate

active

07816872

ABSTRACT:
In an instant start ballast, dimming control is provided over a range of operation in which lamps driven by the ballast do not require external cathode heating. An interface circuit (92) includes a winding (90) that is inductively coupled to windings (68, 70) of an inverter circuit (12). The interface circuit (92) also includes a variable impedance in parallel with the winding (90) where the variable impedance includes a transistor (96) and a Zener diode (98). By varying an input voltage across control leads (94), the apparent inductance of the winding (90) is varied. This variance affects the switching frequency of the inverter circuit (12) affecting the frequency of a drive signal provided to the lamps. Thus the instant start ballast can be dimmed without use of multiple ballasts and/or external cathode heating.

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PCT/US2009/032170 International Search Report, mailed Apr. 1, 2009.

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