| 摘要 |
PURPOSE:To allow the high-density packaging of circuits by introducing the surge voltage generated in a power supply line via diodes to one Zener diode. CONSTITUTION:The voltage impressed to the power supply source does not attain the Zener voltage of the Zener diode ZD thereof in the state in which the surge voltage is not generated and an ordinary operation is executed in light control circuits 1 to 3 and, therefore, the ordinary light control operation is carried out. On the other hand, the current by the surge voltage is introduced via the diodes D1 to D3 connected to this power supply line to the Zener diode ZD and the impression of an overvoltage on the light control circuits C1 to C3 is obviated when the surge voltage is generated in the power supply line. Namely, the Zener diode ZD is larger than the diodes and the panel mounting of this diode is difficult, but just one Zener diode ZD is necessitated. The high- density packaging is possible in this way. |
