DISCHARGE TUBE LIGHTING DEVICE

PROBLEM TO BE SOLVED: To obtain a discharge tube lighting device which has an arrangement of controlling multiple discharge tubes at once with a lighting circuit, and can stop controlling multiple discharge tubes if any of them fails. SOLUTION: A discharge tube malfunction detecting circuit 51 receives a voltage (a detection voltage) which is a DC voltage converted from a tube current flowing through cold cathode tubes 7 and 8 as voltages dividing from bases of NPN bipolar transistors 28 and 29. The transistors 28 and 29 are arranged so that they turn on, and collector potential becomes 0 V if the cold-cathode tubes 7 and 8 lights normally, while they turn off and collector potential becomes Vcc if malfunction occurs. NPN bipolar transistors 30 and 31 which receive collector potentials of the transistors 28 and 29 from bases are prepared to make the collector potential of the transistor 30 or 31 0 V if the cold-cathode tube 7 or 8 fails. COPYRIGHT: (C)2008,JPO&INPIT