Importance

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Abstract

The high pressure discharge lamp ballast of the present invention includes: power supply means for supplying an AC current to a lamp; and control means for cyclically changing a current value of the AC current to be supplied and a time interval between polarity inversions. The AC current has a cycle of a time period TL and a time period TS, and the power supply means is controlled by the control means to apply a half cycle of a first low frequency current and, immediately after that, apply one cycle of a high frequency current in the time period TL, the high frequency current in only the second half of the cycle or the entire cycle having a peak current value that is higher than a current value of the first low frequency current, and to repeat cycles of only a second low frequency current in the time period

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First Claim