Patent ID: 8384291

Claim:
A backlight protection circuit comprising: a driving circuit; a first lamp, comprising a high voltage end connected to the driving circuit and a low voltage end; a second lamp, comprising a high voltage end connected to the driving circuit and a low voltage end; a pulse modulator to control operation of the driving circuit, the pulse modulator comprising a voltage sampling end; an over-voltage feedback circuit electrically connecting the low voltage end of the first lamp to the voltage sampling end of the pulse modulator, and electrically connecting the low voltage end of the second lamp to the voltage sampling end of the pulse modulator; a first diode connected between the low voltage end of the first lamp and the over-voltage feedback circuit; and a second diode connected between the low voltage end of the second lamp and the over-voltage feedback circuit; and a pulse feedback circuit connected to the low voltage end of the first lamp, the low voltage end of the second lamp, and the pulse modulator, wherein the pulse feedback circuit comprises: a first voltage dividing resistor connected to the low voltage end of the first lamp; a second voltage dividing resistor connected between the low voltage end of the second lamp and the first voltage dividing resistor; a third voltage dividing resistor having a first end connected to the first voltage dividing resistor and the second voltage dividing resistor, and a second end grounded; a coupling capacitor having a first end connected to the first, second and third voltage dividing resistors, and a second end; a third diode connected between the pulse modulator and the second end of the coupling capacitor; and a fourth diode connected between the second end of the coupling capacitor and ground, wherein when a voltage of the low voltage end of the first or second lamp exceeds a first reference voltage, the pulse modulator directs the driving circuit to stop operation.