Matsushita Electric Works, Ltd.

Akio Okude

Kouji Noro

Naoki Komatsu

Jun Kumagai

Tokushi Yamauchi

Kei Mitsuyasu

Naoki Ohnishi

Katsuyuki Kiyozumi

Atsushi Ueoka

Yoshifumi Kuroki

Hiromitsu Mizukawa

A discharge lamp lighting device which comprises a DC power source for generating a voltage necessary for a discharge lamp from a DC power source, a control circuit for calculating a power required by the discharge lamp to perform feedback control over the DC power source, a polarity switching circuit for switching polarities of an output of the DC power source to apply the output to the discharge lamp, an ignitor for superposing a high pulse voltage to the discharge lamp at the time of starting the discharge lamp, and a capacitor which forms a closed circuit together with the ignitor, wherein, in order to suppress excessive charging and discharging currents flowing through the capacitor when the polarities of the polarity switching circuit are switched, the control circuit controls the polarity switching circuit to be operated at a low frequency and simultaneously be chopper-operated at a high frequency. Thereby the excessive current flowing through switching elements at the time of switching the polarities can be suppressed and stresses imposed on the switching elements can be sufficiently prevented.

Discharge lamp lighting device

A discharge lamp lighting device include an inverter circuit section supplying a square wave AC power from a DC power source to a discharge lamp, and a high voltage pulse generating unit applying, upon starting, a high voltage pulse to the discharge lamp to have it started, with an arrangement for lighting the discharge lamp by the square wave AC power made to be lower in the square wave frequency upon non-loading than that upon lighting, and controlling the square wave frequency to remain as that upon the non-loading for a fixed period immediately after detection of the start of discharge of the lamp.

A discharge lamp lighting device has first switching means for converting AC power into DC power and second switching means for converting the DC power into a high frequency power, the first switching means being driven subsequently to a driving of the second switching means, and the device is arranged for intermittently applying a pulse voltage to a discharge lamp during its dimming lighting, whereby any secondary voltage can be effectively lowered and any flash apt to occur during the dimming lighting can be restrained.

A discharge lamp lighting device includes a DC power supplying means which supplies as superposed on a high frequency power fed to a low-tension, mercury-arc discharge lamp a DC power of a level capable of maintaining a discharge upon low light flux lighting, the lamp being thereby made stably lighted to an extremely low level of the flux of light.

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Kadoma, Japan

Akio Okude