Title:
DISCHARGE LAMP LIGHTING DEVICE
Document Type and Number:
Japanese Patent JPH1167484
Kind Code:
A
Abstract:
PROBLEM TO BE SOLVED: To suppress over increase of d.c. power source voltage and lower the cost of parts by decreasing the withstand voltage of elements. SOLUTION: The impedance (a load impedance) of a load circuit Z including a high voltage discharge lamp is detected by a computing circuit part 4 from detected values of an output electric current-detecting part 2 and an output voltage-detecting part 3. A control circuit 1 controls ON/OFF of respective switching elements Q1-A4 as to operate these elements in a first operation mode in a low region (a low impedance region) where the load impedance is low just like that at the time of starting lighting of the high voltage discharge lamp contained in the load circuit Z and as to operate these elements in a second operation mode in a region (a rated impedance region) where the load impedance becomes an impedance at the time of lighting the high voltage discharge lamp at the rated voltage. While over increase of voltage between both terminals of a smoothing capacitor CO in relation to a load just like a high voltage discharge lamp which changes the value of the load impedance in a wide range is suppressed, the input electric current strain can be improved.
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Inventors:
HIZUMA SHINJI
Application Number:
JP22993897A
Publication Date:
March 09, 1999
Filing Date:
August 26, 1997
Export Citation:
Assignee:
MATSUSHITA ELECTRIC WORKS LTD
International Classes:
H05B41/282; (IPC1-7): H05B41/29
Attorney, Agent or Firm:
Keisei Nishikawa (1 person outside)