Patent ID: 8912731
Filing Date: 2014-12-16
Classification: H05B,Y02B

Abstract:
1. An LED backlight driving circuit comprising: a voltage converting unit having an input terminal connected to an output terminal of an external power supply and an output terminal connected to a positive electrode of an LED, wherein the voltage converting unit is for converting an output voltage of the external power supply into a driving voltage required by the LED; a driving unit having an output terminal connected to a controlled terminal of the voltage converting unit for driving the voltage converting unit to achieve a voltage conversion; a protection unit connected in series between a negative electrode of the LED and a first input terminal of the driving unit; a current detection unit connected to a second input terminal of the driving unit for connecting to the circuit protection unit through the driving unit and used for detecting a value of a current flowing through the LED, wherein a maximum allowable power of the protection unit is less than a power when the driving voltage of the LED is directly applied to the protection unit so as to form an open circuit when the positive and negative electrodes of the LED are shorted in order to cut off a connection between the LED and the driving unit; and control unit having an input terminal connected to the negative electrode of the LED and an output terminal connected to a third input terminal of the driving unit, wherein the control unit is for outputting a control signal for stopping working to the driving unit when the protection unit forms the open circuit; wherein, the driving unit comprises a controller, a first comparator, and a first switching transistor, wherein an output terminal of the controller functions as the output terminal of the driving unit and connects to the controlled terminal of the voltage converting unit, and an input terminal of the controller functions as the third input terminal of the driving unit and connects to the control unit; a positive input terminal of the first comparator is for inputting a first preset voltage, and a negative input terminal of the first comparator functions as the second input terminal of the driving unit and connects to the current detection unit; an output terminal of the first comparator connects to a control terminal of the first switching transistor, and an input terminal of the first switch functions as the first input terminal of driving unit and connects to the protection unit, and an output terminal of the first switching transistor connects to the negative input terminal of the first comparator; and the control unit is a second comparator, and a negative input terminal of the second comparator connects to the negative electrode of the LED, and a positive input terminal of the second comparator is for inputting a second preset voltage, and an output terminal of the second comparator functions as the output terminal of the control unit and connects to the third input terminal of the driving unit.