LIGHT REGULATION CIRCUIT

摘要

PROBLEM TO BE SOLVED: To improve the light regulation rate for a liquid crystal display device, using a cold-cathode tube as a backlight. SOLUTION: A current, flowing through the cold-cathode tube 7, is reduced by lowering the output voltage of a variable power circuit 3, in addition to light regulation by the blinking of the cold-cathode tube 7 by the switching of a switch circuit 4 by a control circuit 2 receiving brightness signal from a light detector 1. This circuit is provided with the control circuit 2 connected to the light detector 1 for generating a voltage control signal and a pulse signal according to the brightness signal; and the variable power circuit 3 for generating a power voltage obtained by controlling its output voltage by the voltage control signal from the control circuit 2 to output it to the switch circuit 4. The switching circuit 4 supplies the controlled power voltage from the variable power circuit 3 to an oscillation circuit 5.