| 摘要 |
PURPOSE: A fault operation preventive circuit for a backlight inverter is provided to sense immediately a fault operation which makes a transformer operate unstably and then make the operation of the inverter stop when sensing the fault operation, thereby improving the protective function of the lamp and an inverter set. CONSTITUTION: A transformer(24) supplies LCD(Liquid Crystal Display) lamps(L21,L22) with a driving current. Feedback circuit units(25a,25b) check the driving voltage of the LCD lamps(L21,L22). A PWM oscillating unit(26) supplies a PWM signal corresponding to the driving current of the LCD lamps(L21,L22). A duty ratio control unit(27) controls a duty ratio of the PWM signal of the PWM oscillating unit(26) according to a difference voltage between the voltage checked by the feedback circuit units(25a,25b) and the predetermined voltage. A transformer fault sensing device(31) senses a fault of the transformer and then provides a fault sensing signal(S2) according to a voltage(S1) of a connection point(PZ) of the transformer(24). A shutdown protective device(32) provides a shutdown signal(S3) when the fault sensing signal(S2) is inputted from the transformer fault sensing device(31). An output driving device(33) provides a PWM driving signal(S51) according to the PWM signal(S4) of the duty ration control unit(27) and an output stop signal(S51) according to the shutdown signal(S3) of the shutdown protective device(32). A driving switch(21) performs a voltage on/off switching according to the PWM driving signal(S51) by the output driving device(33) and stops the output of the lamp driving signal according to the output stop signal(S52) by the output driving device(33). |
