Backlight driving circuit and liquid crystal display

A liquid crystal display, comprising a light source and a backlight driving circuit, and the backlight driving circuit being connected to the light source, wherein the backlight driving circuit comprises a voltage conversion circuit, a PWM controller, a zener diode, a first electrical switch, an optocoupler unit, a boost switch and a light source drive assembly, and the voltage conversion circuit is used to connect an input voltage end to receive an input voltage and to conduct a voltage conversion of the input voltage, and the voltage conversion circuit is also connected to the optocoupler unit, the PWM controller, the boost switch and the light source of the liquid crystal display to output a converted voltage to the optocoupler unit, the PWM controller, the boost switch, and the light source, and the PWM controller is used to control an output of the voltage conversion circuit, and the light source drive assembly is connected to the boost switch and the light source to control on and off of the boost switch according to a light source condition, and a cathode of the zener diode is connected to the optocoupler unit, and an anode of the zener diode is connected to a control end of the first electric switch, and a first end of the first electrical switch is connected to the PWM controller, and a second end of the first electrical switch is grounded;

• as the boost switch is short, a current outputted by the voltage conversion circuit increases, and a voltage of the optocoupler unit fed back to the zener diode is larger than a breakdown voltage, and the zener diode is on and then, the first electric switch is on, and the PWM controller stops working to turn off the boost switch.