The present invention discloses a backlight driving board for driving a backlight source, comprising a microprocessor and a constant current driver chip. The microprocessor receives a display mode switching signal and a synchronization signal from a liquid crystal driving board, and generating a first pulse width modulation signal corresponding to the backlight source according to the display mode switching signal and the synchronization signal. The constant current driver chip controls an operation state of the backlight source according to the first pulse width modulation signal. The present invention can reduce the signal lines between the backlight driving board and the liquid crystal driving board in order to avoid the backlight driving board from external interference because of too many signal lines, and thus be able to enhance the stability of the LCD device when operating.
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