COLD-CATHODE TUBE LIGHTING DEVICE

摘要

A cold-cathode tube lighting device which uniformly lights up a plurality of cold-cathode tubes with a common power supply to uniformly keep their luminances with high accuracy in the length directions of respective cold-cathode tubes. A first block (1) converts a dc voltage (Vi) into a pair of ac voltages (VA, VB). The low leakage impedance of step-up transformers (5A, 5B) allows the first block (1) to function as a pair of low-impedance power supplies. Second blocks (2) have cold-cathode tubes (20) that are connected one to one. A ballast inductor (LB), when resonated with a matching capacitor (CM), stabilizes a tube current when a cold-cathode tube (20) is lighted. For each cold-cathode tube (20), a synthetic impedance of a matching capacitor (CM) and a surrounding floating capacitance matches the impedance of the ballast inductor (LB). Since a delay circuit (7) allows the phases of two pulse waves (P1, P2) to deviate from each other, the phase difference between ac voltages (VA, VB) is deviated from 180°.