| 摘要 |
PURPOSE:To detect the end of life of a lamp and to reduce the power consumption, by detecting the voltage generated across a current limiting element and counting the voltage in a digital way to detect the change of the voltage. CONSTITUTION:In the normal state, a lamp 97 glows after the application of a power supply 99, and the collector voltage of a transistor 18 of a voltage detecting circuit 1 kept at H level. A counter 2 does not count plural numbers, and a lift detecting circuit 3 delivers nothing with no working of a relay 5. Thus the lamp 97 is kept glowing. In case the lamp 97 is at the end of its life, the collector voltage of the transistor 18 repeats L and H levels. At the same time, the counter 2 counts up its value. When the count value of the counter 2 reaches a prescribed level, the circuit 3 detects this. Then the signal is fed to a relay 5 to cut off the circuit 3. In such a way, the useless consumption of electric power can be previously prevented in the half-wave glowing mode. |
