LED backlight driving circuit for LCD panels

A drive circuit, for driving a light-emitting diode (LED) string, comprising:

• an output transistor, being an NPN bipolar transistor, wherein a collector of the output transistor is connected to a cathode of the LED string;
• a current control resistor, disposed between an emitter of the output transistor and a fixed voltage terminal that is stabilized at a specific potential;
• a first error amplifier, wherein an output terminal of the first error amplifier is connected to a base of the output transistor, a first input terminal of the first error amplifier is connected to a connection point of the output transistor and the current control resistor, and a reference voltage is applied to a second input terminal of the first error amplifier, and a source current of the first error amplifier emitted from the output terminal is supplied from the cathode of the LED string;
• a switch power supply, providing an output voltage to an anode of the LED string and inputting a feedback voltage based on the output voltage to a feedback terminal;
• a second error amplifier, amplifying an error between a base voltage of the output transistor and a second reference voltage and generating an error voltage according to the error;
• a transistor, wherein a first terminal of the transistor is connected to the error voltage;
• and
• a feedback voltage control resistor having a first end connected to a second terminal of the transistor and a second end connected to the feedback terminal, and the error voltage being output through the transistor and the feedback voltage control resistor and being input to the feedback terminal.