DC/DC Converter Drives Lumileds White LEDs


Posted on May 20, 2012

Powered from two alkaline cells, the circuit in Figure 2 can illuminate a 1W LXHL-BW02 LumiledsTM white LED with a constant 320mA current at 85% efficiency. The forward voltage of the 1W LED, 3.6V typical, requires a boosted voltage from the 2-cell input. In order to turn off the LED, an input disconnect switch is required. Typically in handheld lighting applications, this is a simple pushbutton or switch. Without input disconnect, the shutdown pin would only prevent the IC from switching, still providing a direct path of current from the input to the output through the inductor and catch diode.






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