Ushio Denki Kabushiki Kaisha

Tetsu Okamoto

Tetsuji Hirao

Hiroyuki Ishii

Takashi Yamashita

Minoru Fukuda

Tomoyoshi Arimoto

Shoichi Terada

Kentaro Fujita

Keiichi Matsumoto

Teppei Kagata

A high pressure discharge lamp lighting apparatus includes a high pressure discharge lamp and a power supply apparatus, wherein in a steady state lighting operation, an alternating current of a steady state lighting frequency and alternating current of a low frequency are supplied by turns to the high pressure discharge lamp, and wherein in a small electric power lighting in which electric power to be applied is smaller than that of the steady state lighting, alternating current of a small electric power lighting frequency and direct current are supplied by turns to the high pressure discharge lamp.

High pressure discharge lamp lighting apparatus

To stabilize the arc bright point position of a discharge lamp and suppress deformation of an electrode when an ultrahigh-pressure discharge lamp is operated with extremely low electric power, the lamp is operated by supplying power from a power supply device having a step-down chopper circuit and a full bridge circuit, a rectangular wave alternating current being supplied when it is operated with rated power or dimmed power (about 60 to 80% of rated power), a DC current being supplied during standby power operation of at most 0.5&#xd7;P (W) with respect to the maximum operating power P (W). Moreover, the high-pressure discharge lamp light source device may be mounted on a projector for projecting images and the mode being changed to standby power operation when there is no change in an image signal, for example, for a prescribed period of time.

High-pressure discharge lamp light source device having a power supply device with a switching state for switching from a direct current drive in a standby state to an alternating current drive in an operating state and projector

A discharge lamp lighting apparatus includes a discharge container, a pair of electrodes and a power supply apparatus. An alternating current of a frequency, which is lower than stationary frequency, is inserted periodically into the alternating current of stationary frequency. When a lighting current value of the discharge lamp is smaller than a predetermined lower limit, the frequency is set as predetermined minimum frequency. When the lighting current value of a discharge lamp is larger than a predetermined maximum value, the frequency is set as predetermined maximum frequency. When a lighting current value of the discharge lamp is between the lower limit and the maximum value, the frequency is set as a selected frequency corresponding to the lighting current value. The selected frequency increases according to an increase of frequency change as a lighting current value increases.

An ultra-high pressure mercury lamp in which the tungsten comprising the electrodes is prevented from spraying during starting and operation, and blackening on the inside wall of the arc tube is prevented is achieved in that at least one of the electrodes has an axial part which is made essentially of tungsten and a starting part which is made essentially of tungsten, at least one of the axial part and of the starting part containing an electron emission material with a smaller work function than tungsten such that the value of S/A in mm/% by weight is in the range 1&#x2266;S/A&#x2266;1&#xd7;10, S in mmdesignating the surface area of the part of the electrode projecting into the arc tube containing the electron emission material and A in % by weight indicating the concentration of the electron emission material in this part.

Growing community of inventors

Himeji, Japan

Tetsu Okamoto