Wide Input-Voltage Range High-Power LED Driver
This is a wide input-voltage range high-power LED driver circuit. This circuit based on a buck/boost converter controller regulates current to a white LED. This circuit can be used to replace incandescent bulbs, it efficiently match the LEDs to available power sources such as electrical systems car, batteries, etc. It also can used to control and regulate the LED output despite variations in output voltage from the power source. Following figure shows the schematic diagram of the circuit, the current regulation for 0.5A and 1A output currents and the corresponding efficiencies :
This circuit requires the input voltage range from 2.7V minimum to to 16.5V maximum. For a current-regulation loop, this circuit uses buck-boost converter controller (IC1) with external MOSFET power switch and a 0.1O current-sense resistor in series with the power LED.
From the second figure, the dotted line break is current regulation for 0.5A and the black line is current regulation for 1 A. From the third figure, we can see 0.5 A operation is more efficient than 1 A operation. The efficiency for 0.5 A operation is almost 80%, and the efficiency for 1 A operation is about 75%. [Source: maxim-ic.com]