Matsushita Electric Works, Ltd.

Kazuhiro Hori

Masahiro Naruo

Takashi Kanda

Masahito Ohnishi

Kazuo Yoshida

A power source device includes a control circuit which controls switching elements in full-bridge arrangement so as, in decreasing an output to a load, to substantially equalize ON timing of one of two switching elements at diagonal position to the other of them with ON period of the one switching element shortened, that is, with ON duty ratio of the one switching element decreased. Switching operation of the elements in this event is not made to be in the hard switching operation, and a range in which the output to load can be controlled without increasing any stress or noise is thereby broadened, whereby it is enabled to minimize varying width of switching frequency and to attain a wide range control of the output to load without causing any one of the switching elements to be in the hard switching operation.

Power source device

A discharge lamp lighting device includes a rectifier, a first diode connected at the anode in forward direction to a positive polarity output terminal of the rectifier, a smoothing capacitor connected between the cathode of the first diode and a negative polarity output terminal of the rectifier, a second diode connected at the anode in forward direction to the cathod of the first diode, a pair of switching elements connected in series between the cathode of the second diode and the negative polarity output terminal of the rectifier, a first capacitor connected in parallel to one of the first diode and the rectifier, a second capacitor connected in parallel to the second diode, and a control circuit for controlling ON/OFF operation of these switching elements, and a transformer having a primary winding n,connected between a junction point of the pair of switching elements and one of output terminals of the rectifier and a secondary winding connected to a load circuit including a discharge lamp, and their arrangement can reduce peak factor of currents flowing to the load circuit and any loss occurring at the switching elements.

Discharge lamp lighting device

An electronic ballast for discharge lamps comprises a main resonance circuit for applying a voltage necessary for operating of a discharge lamp having filaments to both ends of the discharge lamp and a filament resonance circuit for supplying a filament current to the filaments, wherein the main resonance circuit and filament resonance circuit have resonance circuits having different resonance characteristics in an output path leading to the discharge lamp and also change their outputs depending on an operating frequency of switching elements. Thereby a filament current and a voltage across the discharge lamp can be set at suitable one of respective operational modes of the discharge lamp according to an operational state of the discharge lamp.

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Kadoma, Japan

Kazuhiro Hori