High pressure discharge lamp ballast with adaptive filament heating control based on lamp age

A method of adaptive control for a high pressure discharge lamp ballast, the ballast comprising an inverter, a lamp parameter detection circuit, and a control circuit effective to control a power output from the inverter to a high pressure discharge lamp, the method comprising:

• reading a cumulative lamp parameter from the lamp parameter detection circuit, the lamp parameter comprising either a cumulative lighting time for the lamp or a cumulative lamp ignition count;
• setting a power output parameter for the power converter based on the cumulative lamp parameter;
• controlling the power converter to provide an output power to the lamp corresponding to the power output parameter during a filament heating period which begins after dielectric breakdown of the lamp;
• terminating the filament heating period and entering a steady-state period, wherein the control circuit controls the power converter to decrease an operating frequency and maintain a stable light output from the lamp.

An illumination system comprising:

• one or more illumination fixtures, each illumination fixture comprising
• a ballast housing,
• a high pressure discharge lamp ballast positioned within the ballast housing,
• a lamp housing mechanically coupled to the ballast housing and electrically coupled to the discharge lamp ballast, and containing a high pressure discharge lamp, and
• a control device for controlling each of the one or more illumination fixtures;
• the lamp ballast further comprising
• a DC-AC power converter,
• a lamp parameter detection circuit, and
• a control circuit effective to control the power converter, the control circuit configured to determine a power output parameter to the high pressure discharge lamp in a filament heating period after dielectric breakdown of the lamp;
• and
• wherein the power output parameter is determined in accordance with one or more lamp parameters detected by the lamp status detection circuit.