Patent ID: 6133697
Filing Date: 2000-10-17
Classification: H05B,Y10S

Abstract:
A dimming apparatus of a fluorescent lamp, comprising:a fluorescent lamp;a high frequency power supply for supplying high frequency power to said fluorescent lamp;a control unit for controlling an output frequency of said high frequency power supply in response to an inputted light dimming signal; anda coil provided between said high frequency power supply and said fluorescent lamp, for limiting a current which flows from said high frequency power supply to said fluorescent lamp; wherein:said dimming apparatus is further comprised of a lamp voltage detecting circuit for detecting a discharge voltage of said fluorescent lamp; andsaid control unit intermittently controls the output frequency of said high frequency power supply in such a manner that said output frequency becomes higher than a dimming frequency based on said dimming signal so as to periodically change a current supplied to said fluorescent lamp into a low current; and when the output frequency of said high frequency power supply becomes higher than said dimming frequency, said control unit sets a lower limit dimming set value based upon a detection voltage of said lamp voltage detecting circuit in order that the output frequency of said high frequency power supply is controlled to become lower than, or equal to a upper limit frequency in accordance with said lower limit dimming set value.