| 摘要 |
PROBLEM TO BE SOLVED: To improve performance and function for substituting a filament type bulb. SOLUTION: This LED signal bulb is provided with an attaching and detaching part 10 having a base 12 interchangeable with a railway signal lamp and a connecting contact part 11, an LED light emitting part 70 having plural LEDs 71, 72, and a rectifying circuit 30 interposed in a power feeding path extending from the connecting contact part 11 to the light emitting part 70. This bulb is provided with a smoothing circuit 40 interposed between the rectifying circuit 30 and the light emitting part 70, a driving circuit 50 for detecting the supply current to the light emitting part 70 and controlling the same constant, a detecting means 60 for detecting the existence/absence of the supply current, and a current application amount switching means 20 for switching the current application amount of the connecting contact part 11 between a large value and a small value according the above detection result. The LED 72 is reverse to the LED 71. Thus, even if the input power supply voltage varies, the light intensity is kept constant so that it can be applied to a signal in which when two lamps are used in series, and one is extinguished due to disconnection trouble, the other lamp is also extinguished to need back light. |
