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Linear vs. Switching HBLED Drivers

by Administrator Administrator on ‎06-23-2009 04:09 PM (2,793 Views)

Written by: M. Burns, Avnet Field Application Engineer

 

Most HBLED Driver applications in the market today take advantage of the major switching topologies: buck, boost, or buck-boost depending on the power source driving the HBLEDs.  These constant-current HBLED drivers can switch the drive FETs anywhere between a few hundred kilohertz to a few megahertz.  In general, the higher the switching frequency, the lower the required inductor value.  This can lead to smaller PCB areas needed for the design. However, one complication of this approach can be radiated EMI noise.

 

One approach to eliminate or greatly reduce the EMI noise that results from the switching FET is to use a linear HBLED driver.  This may not be applicable in all situations, but for HBLEDs with low to medium current needs (ILED < 2.5A), this may be a good approach to use.

 

A good solution along these lines is Infineon’s BCR400 series of low-cost linear HBLED drivers.  At first glance, these may seem like good solutions for ILED < 100mA.  However, several Ap Notes from Infineon show how you can drive higher currents linearly. These products also allow for HBLED dimming via a PWM signal from a MCU.

 

Some Ap Notes to look at:

 

AN097Using BCR402R/BCR402U at High Supply Voltages

 

AN101 - Using Infineon‘s BCR400 Family of Constant-Current, Linear-Mode LED Drivers for Lighting Applications from 10 mA - 700 mA

 

AN105 - LED Driver IC BCR450, using OSRAM Platinum Dragon LW_W5SN

 

More information about these parts can be found here.