COLOR CONTROL OF A DISCHARGE LAMP DURING DIMMING

• Main Authors: LI JIANWU, CHALMERS ALAN G
• Format: Patent
• Language: English
• Published: 13.08.2009
• Subjects: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS,e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USERAPPLICATIONS; ELECTRIC HEATING; ELECTRIC LIGHTING NOT OTHERWISE PROVIDED FOR; ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR; ELECTRICITY; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS; TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINSTCLIMATE CHANGE

A ballast circuit is suitable for driving a high intensity discharge lamp in at least two power modes including a nominal power mode for driving the high intensity discharge lamp at a nominal power and a reduced power dimming mode for driving the lamp at less than the nominal power. The lamp ballast circuit generates a first alternating current waveform during the nominal power mode and generates a background alternating current waveform in the reduced power mode which is perturbed at intervals by a high intensity pulse which helps to reduce the change in correlated color temperature which would otherwise occur in the dimming mode.