| 摘要 |
PURPOSE:To reduce the number of control circuits, and to reduce cost by dividing one unit into several blocks comprising a plurality of lamps, and by arranging a control circuit for each block. CONSTITUTION:Bulbs 11-19 of a lighting circuit for which one unit is formed by the bulbs 11-19 being connected to one another in series, are divided into three blocks, and control circuits 21-23 are connected thereto in series, respectively. When power is supplied from a commercial power source for one unit, the bulbs 11-19 are lighted at a rated voltage value. When one of the bulbs 11-19 is in an non-lighted condition due to filament disconnection, the interterminal voltage of the block to which the disconnected bulb belongs, is increased, while a time limit capacitor 3 is rapidly charged, and a diod AC switch (DIAC) 2 is conducted between each halfwave phase of the supply power source. A triode AC switch (TRIAC) 1 is conducted thereby, and a shortcircuited circuit between each terminal of the block is formed, and a voltage close to a normal value is applied to the bulbs in the remainder of the blocks. The number of the control circuits is reduced, and the cost is thus reduced. |
