Matsushita Electric Works, Ltd.

Shozo Kataoka

Masahito Ohnishi

Kazuo Yoshida

Takashi Kanda

Fumio Ueno

Ichirou Oota

Takashi Yamasaki

Noriaki Hara

Ikko Harada

A light source power supply circuit includes a DC power source and an energy accumulating capacitor connected in parallel through a charging switching element to the DC power source. A polarity inverting circuit is connected across the energy accumulating capacitor for applying the capacitor voltage across a light source with the polarity alternately inverted. A starting high voltage generating circuit applies a high voltage to the light source a high voltage for starting the light source. A control circuit controls a polarity inverting circuit so that the inverting frequency is above a critical fusion frequency for the light source.

Light source lighting device

A power converter has two switched capacitor circuits each including at least a plurality of sets of capacitors and switching elements, first of which circuits is provided for supplying a DC power to a load while second of which accumulates a power in a period receiving a higher input voltage, and the first switched capacitor circuit being made to receive, in a period receiving a lower input voltage, a power supplied from a DC power source and also the power supplied from the second switched capacitor circuit for supplying to the load the DC power of a constant voltage, in which an input current collectively taken up by the two switched capacitor circuits is made similar in the waveform to the input voltage to eliminate any harmonics distortion of the current drawn from the source, for attaining the supply of the DC power of the constant voltage to the load, whereby the power converter is rendered not to require any large inductor to be capable of being minimized in size and restraining any noise radiation from occurring.

Power converter

An apparatus for operating discharge lamps with a stable electric current supply and minimal dimensional area requirements. The apparatus includes an input power source coupled across a capacitor, establishing a first loop circuit. A discharge lamp may also be connected across the capacitor, thereby forming a second loop circuit. A first switch repeatedly turns ON and OFF, making and breaking the first loop circuit at a first frequency, and thereby charges the capacitor. A second switch repeatedly turns ON and OFF, making and breaking the second loop circuit at a second frequency, and thereby discharges the capacitor through the discharge lamp. A control mechanism controls the first and second switches for supplying a predetermined current to the discharge lamp for flickerless operation.

Apparatus for operating discharge lamps

A discharge lamp lighting device employs first and second series circuits, each series circuit including two switching elements and a connecting point located therebetween. The first and second series circuits are both connected in parallel across a DC voltage source. A load circuit, including a discharge lamp, is connected between the two connecting points in the first and second series circuits. ON/OFF timing of the switching elements in the first series circuit varies between in-phase and 180 degrees out-of-phase from ON/OFF timing of the switching elements in the second series circuit. The ON period ratio of the switching elements is different in at least one of the first and second series circuits. The device allows dimming of the discharge lamp over a wide range, and lighting of the discharge lamp with a small supplied power.

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Hirakata, Japan

Shozo Kataoka