Panasonic Corporation

Matsushita Electric Works, Ltd.

Naokage Kishimoto

Shigeru Ido

Yoshinobu Murakami

Toshiya Kanja

Joji Oyama

A electronic ballast according includes a DC power source circuit for generating a DC voltage from an AC power source, a pair of switching elements, an LC series resonance circuit, an inverter circuit for converting the DC voltage into a high frequency voltage to supply to a fluorescent lamp FL, and means such as a current transformer for detecting a current flowing into the fluorescent lamp FL, wherein oscillation of the inverter circuit is stopped when a value of a current flowing into the fluorescent lamp exceeds a predetermined value.

Dimming electronic ballast with lamp end of life detection

A discharge lamp driving device capable of detecting a lamp life end reliably in a high or low temperature environment for circuit protection, yet preventing the occurrence of the cataphoresis phenomenon. Impedance elements Z and Z are inserted respectively between one filament ends of individual discharge lamps La and La and a node (the ground) having no high frequency amplitude in order to detect a difference between AC components of individual lamp voltages VLa and VLa in closed loops of the discharge lamps La and La and the impedance elements Z and Z in order to judge whether or not the depletion of the emitter occurs. Thus, it is possible to reliably judge the presence of abnormality even when the amplitudes of the lamp voltages VLa and VLa varies in a range of low to high temperature. Also, since there is no need to provide a DC blocking capacitor to a secondary winding N of a leakage transformer LT the discharge lamps La and La can be free from the DC component so as to be prevented from causing the cataphoresis phenomenon.

Growing community of inventors

Hirakata, Japan

Naokage Kishimoto