| 摘要 |
PURPOSE:To eliminate the danger of a resonant circuit becoming inoperative by connecting a rectification means of avalanche type or the like in inverse parallel with a first transistor, the rectification means breaking down when the voltage value between the terminals of a smoothing capacitor is above a certain level. CONSTITUTION:A series connection of first 30 and second 31 switching elements is connected in parallel with a smoothing capacitor 34 between the output terminals (a), (b) of a rectifier circuit 22 and the elements 30, 31 are alternately turned on and off to keep' a fluorescent lamp 40 turned on. When the element 30 is inoperative for some reason, the charging voltage of the capacitor 34 rises abnormally; an avalanche or Zener type rectification means 32 is connected in inverse parallel with the element 30 which, together with a resonant capacitor 38 and a resonant inductor 37, constitutes a resonant circuit, and thereby the means 32 prevents abnormal accumulation of charge in place of the capacitor 34, so that the danger of the capacitor 34 being burst can be eliminated easily at low cost. |
