A backlight driving circuit includes a constant current driving chip, a power module, and a light emitting diode (LED) lightbar coupled with the power module. The constant current driving chip includes a control module that controls switching frequency of the power module, and an adjusting module that adjusts duty cycle of effective current flowing through the LED lightbar. The control module includes a frequency pin used to set the switching frequency of the power module. An external pulse-width modulation (PWM) dimming signal is sent to the adjusting module of the constant current driving chip. The backlight driving circuit further includes a detection module that detects duty cycle of the PWM dimming signal, and a monitor module coupled with the detection module of the backlight driving circuit.