| 摘要 |
PURPOSE: A protection circuit is provided to achieve improved operation stability and reliability of a backlight driver circuit, by comparing phases and sizes of signals when two or more lamps operate. CONSTITUTION: A backlight driver circuit comprises a control unit(111), a driving unit(112), a transformer unit(113), a lamp(116), a current detection unit(114), and a protection circuit unit(115). The control unit generates a frequency for driving lamps, and outputs a control signal to the driving unit so as to control the quantity of power applied to the lamps. The driving unit converts the DC voltage applied from the control unit into an AC voltage, and supplies the AC voltage to the transformer unit. The transformer unit has a primary coil and a secondary coil. The current detection unit is connected to the secondary coil and ends of lamps connected with each other, so as to detect the quantity of current flowing along the lamps. The protection circuit unit receives signals from a cold end of a lamp and the secondary side of the transformer, compares phases and sizes of the signals, and transmits a signal to the control unit upon occurrence of abnormality.
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