Patent ID: 6954364

Claim:
A backlight inverter for an LCD panel comprising: a switch for switching a direct current (DC) operating voltage in response to a pulse width modulation (PWM) drive signal; a rectifier for rectifying an output voltage from said switch; a transformer driver for converting an output voltage from said rectifier into an alternating current (AC) voltage; a plurality of transformers for boosting the AC voltage outputted from said transformer driver to levels of a lamp operating voltage and a complementary lamp operating voltage, said transformers being connected in parallel to said transformer driver and driven in pairs; a plurality of lamps each being operated by a corresponding one of said transformers; an operation stop control for detecting a voltage at a midpoint of secondary windings of each of said transformer pairs, determining from the detected voltage whether a fault exists in said transformers and outputting an operation stop signal upon determining that the fault exists in said transformers; an output driver for supplying said PWM drive signal to said switch in normal operation and a switch-off signal to said switch upon receiving said operation stop signal from said operation stop control; a reference signal generator for generating a sawtooth-wave reference signal based on said output voltage from said rectifier and a DC input voltage; an over-voltage detector for detecting said output voltage from said rectifier; a lamp voltage detector for detecting a voltage corresponding to a current flowing through each of said lamps; a voltage selector for selecting a higher one of the voltage detected by said over-voltage detector and the voltage detected by said lamp voltage detector; a first comparator for comparing the voltage selected by said voltage selector with an internal reference voltage for over-voltage detection and, based on a result of said comparing, outputting a signal indicative of whether an over-voltage condition has been detected; a second comparator for comparing the signal outputted from said first comparator with said sawtooth-wave reference signal from said reference signal generator and providing a duty cycle adjustment signal in response to the signal outputted from said first comparator; and a logical operation unit for ORing an inverted version of said duty cycle adjustment signal from said second comparator and said operation stop signal from said operation stop control and providing the ORed result to said output driver.