| 摘要 |
PROBLEM TO BE SOLVED: To suppress the transient voltage generated when switching from a dimming state to a lighting state to reduce the stress on an element and to suppress going out when switching from the lighting state to the dimming state in a backlight device for a liquid crystal display to cause a high frequency lighting while switching a fluorescent lamp of a hot-cathode type between the lighting state and the dimming state. SOLUTION: The backlight device for the liquid crystal display is equipped with an inverter circuit 1 which flows a lamp current of a high frequency of the fluorescent lamp La of the hot-cathode type, a preheating circuit 2 which flows a preheating current to a pair of filaments of the fluorescent lamp La, and a control circuit 3 which controls the operating frequency of the inverter circuit 1. The control circuit 3 continuously changes the operating frequency of the inverter circuit 1 as time passes by between the first frequency f1 at which the lamp current is not zero and the frequency f2 at which the lamp current turns to high output when the circuit receives a dimming signal Sd to switch the lamp current to high/low in compliance with the display update period of the liquid crystal panel and switches the lamp current. COPYRIGHT: (C)2007,JPO&INPIT |
