| 摘要 |
PROBLEM TO BE SOLVED: To correctly detect circuit abnormality even when at least one cold-cathode tube is lit eve if the circuit abnormality occurs, in an inverter circuit for controlling the lighting of two cold-cathode tubes. SOLUTION: Respective balances of positive currents and negative currents of the two cold-cathode tubes 6 and 7 are detected by diodes 8, 9, 11 and 12 and resistors 10, 13, 18 and 22. The balance detection outputs are inputted to a capacitor 28 through diodes 25 and 26, and the current balance is detected by the voltage between both ends of the capacitor 28. For instance, when a terminal 5-3 of a connector 5 is grounded, although a current flows through the cold-cathode tube 6 to light it, current balance is collapsed in the current balance detection circuit of the cold-cathode tubes 6 and 7 so that it is detected and abnormality can be detected. When a terminal 5-2 of the connector 5 is grounded, since only the cold-cathode tube 7 is lit, the current balance is collapsed and it is detected, whereby the abnormality can be detected. COPYRIGHT: (C)2005,JPO&NCIPI |
