Whenever a lighting application, such as street lighting for example, requires an elevated number of LEDs, there are basically two solutions: the first is to connect all the diodes in series in a single "string"; the second is to place several strings in parallel with fewer elements in each one.
This evaluation board is designed around an L6902D-based DC-DC converter with dimming interface. The board implements both of two well known dimming methods: - Analog current control - Average current control by PWM
The ZXLD1350 is a continuous mode inductive step-down converter, designed for driving single or multiple series connected LEDs efficiently from a voltage source higher than the LED voltage. The device operates from an input supply between 7V and 30V and provides an externally adjustable output current of up to 350mA.
The CAT4201 is a high efficiency step-down LED driver from Catalyst Semiconductor. This device is designed to drive high brightness LEDs up to 350mA from a power supply up to 28V. The LED brightness is controlled by a single resistor from the RSET pin to GND. Analog dimming and idle mode control are available through the CTRL input. An external circuit is provided on the CAT4201AEVB for PWM dimmin…
The L6920D is used in this flashlight application as it is a high efficiency step-up controller that realizes the conversion from battery voltage to the selected output voltage with only three external components.
* The eval board must be modified for 350mA output. The Transformer/Dual inductor and sense resistor(s). This circuit is intended for driving high power LEDs, such as the Cree XLAMP™ series, Lumileds Luxeon™ Rebel and K2 and OSRAM, Golden and Platinum Dragon™ as well as the OSTAR™.
The evaluation board is designed to display the full functionality of L5973D as a LED driver to drive one to three 1W, 3W as well as 5W LEDs at 12Vac input. The components selected for the demo board are optimized for 5W LED driver application.
The LM3402 circuit and BOM have been designed to provide a constant forward current of 350 mA to a single LED with a forward voltage of approximately 3.5V. (Typical of white, blue, and green LEDs using InGaN technology.)