APPARATUS FOR ADJUSTING BRIGHTNESS

摘要

PURPOSE: An apparatus for controlling brightness is provided to increase the adjustment width of brightness by controlling an amount of a current that flows in a lighting apparatus. CONSTITUTION: One power line of a fluorescent lamp(10) is connected to a secondary coil of a step-up transformer(13). A current sensing circuit(21) senses an amount of a current of the fluorescent lamp(10) to convert the amount of a current sensed into a corresponding voltage signal. The voltage signal is inputted to a comparator(22). The comparator(22) compares the voltage signal with a brightness adjusting voltage to generate a pulse width adjusting signal. The pulse width adjusting signal is inputted to a PWM(Pulse Width Modulation) signal generating circuit(24). The PWM signal generating circuit(24) generates a PWM signal to output to a switching circuit(25). The switching circuit(25), in response to the PWM signal, controls an amount of a current that flows in the fluorescent lamp(10).