INVERTER SYSTEM FOR HIGH EFFICIENT COLD CATHODE RAY TUBE USING PIEZOELECTRIC TRANSFORMER

摘要

PURPOSE: An inverter system for high efficient cold cathode ray tube using a piezoelectric transformer is provided to enhance the productivity of the inverter system by controlling automatically a PWM(Pulse Width Modulation) driving frequency to a maximum efficient frequency. CONSTITUTION: An inverter system for high efficient cold cathode ray tube using a piezoelectric transformer includes a piezoelectric transformer(400), a cold cathode fluorescent lamp(500), an error amplifier(10), a PLL control portion, a PWM driving portion, and an inductor(300). The cold cathode fluorescent lamp(500) is connected to an output terminal of the piezoelectric transformer(400). The error amplifier(10) is used for extracting a voltage proportional to the output current of the cold cathode fluorescent lamp(500), comparing the voltage to the predetermined reference voltage, and outputting an error voltage to control a PWM duty ratio. The PLL control portion generates a chopping wave having an adjusted frequency. The PWM driving portion generates a PWM driving signal by comparing the chopping wave to the error voltage and outputs a PWM controlled voltage by turning on or off a switching element according to the PWM driving signal. The inductor(300) is connected between the PWM driving portion and the piezoelectric transformer(400).