| 摘要 |
PURPOSE: To prevent the unnecessary and dangerous high voltage and high current generated during the lighting preparation period in a ballast circuit for the lamp load including a fluorescent lamp, and provide a compact ballast circuit of high efficiency with the low cost, by setting the fundamental sine wave frequency to be lower than that of a resonance frequency of a series L-C circuit. CONSTITUTION: When a ballast circuit 20 is built up first, the input voltage is made to be a rectangular wave voltage having the peak-peak voltage of about 390V, before the voltage is boosted by a pre-conditioner 80, the voltage is applied to a primary winding TP of a transformer T1 , and the voltage between the peaks at both edges of a secondary winding TS is elevated to about 570V. During the time, a cathode of an electric lamp is heated, the conditioner 80 is started after about 0.5 seconds, the adjusted DC voltage of about 480 V is applied to a boost converter 40, and the voltage at the both edges of the winding TS is elevated to about 700V. Thereby the voltage enought for lighting the lamp load LL can be obtained, and a value of an inductor L7 is adjusted to be a value corresponding to the necessary lighting current in a stationary condition. |
