| 摘要 |
PURPOSE:To detect disconnection always stably without depending on the source voltage of a battery by connecting a current detector and the constant voltage source in series to the power circuit of a lighting body with LED as light source, and performing constant voltage drive control at the time of detecting the disconnection of a light source circuit. CONSTITUTION:This lighting body 10 provided with a light source circuit formed of numerous LED elements is connected to a power circuit 11 with a battery as power source, and a current detector 12 and constant voltage source 13 are connected in series to the power circuit 11. There are also provided a first and a second PNP type transistors Tr14, 15 for separating the power from the battery passing the constant voltage source 13 from the power not passing the constant voltage source 13, and normal lighting action is performed by normally turning the Tr14 on and the Tr15 off. When disconnection is detected by the current detector 12, constant voltage driving is performed by turning the Tr14 off and the Tr15 on, and subsequent detection by the current detector 12 can be performed. |
