High-Brightness LED-Driver

This is a high-brightness LED-driver circuit. To provide a constant-voltage output we usually use DC/DC regulators. But constant-current output is the one that is needed in LED application. To provide a constant-current output, we can use this circuit. Here is the schematic diagram of high-brightness LED-driver circuit :

This circuit uses R1 to sense the LED current. The TPS40211 is used to minimize the losses in R1 due to its low 250-mV reference voltage. To protect against output overvoltage in the event of an LED-string open circuit, this circuit uses D1. The brightness can be programmed by the current injection into the FB pin, by the PWM dimming or by varying the value of R1. [Source: Texas Instruments Application Notes]