DEMOBCR60260VICTRLTOBO1 Infineon

AN 2007 PL39 2009 125229 Tunable white LED drivers with BCR601 and BCR602 How to design cost effective, highly efficient LED drivers of highest light quality About this document Scope and purpose LED lighting has become a mature technology, with stringent requirements for light quality. The requirements regarding input power and light quality can be fulfilled most easily by two-stage topologies. A combination of high power factor flyback as the first stage with a buck as the second stage has turned out to offer flexibility and high performance. This application note shows that the buck on the secondary can be replaced with a linear regulator with active headroom control (AHC) without sacrificing efficiency. At the same time the linear regulator leads to the highest possible light quality with a very cost effective approach. The cost advantage compared to buck topology becomes most obvious in tunable white and multichannel drivers. Intended audience LED driver design engineers, field application engineers. Table of contents About this document ....................................................................................................................... 1 Table of contents ............................................................................................................................ 1 1 Linear constant current regulators in LED drivers ...................................................................... 3 1.1 Linear regulator with active headroom control ..................................................................................... 3 1.2 LED current setting and dimming circuit ............................................................................................... 5 1.3 Efficiency optimization ........................................................................................................................... 6 1.4 Setting V for best efficiency .................................................................................................................. 8 HR 1.5 MOSFET and BJT selection ..................................................................................................................... 9 1.6 Overvoltage protection ......................................................................................................................... 10 1.7 Overtemperature and hot-plug protection .......................................................................................... 10 1.8 Output short-circuit protection ............................................................................................................ 11 2 Multichannel LED driver with BCR601 plus BCR602 ................................................................... 14 2.1 Setting V in multichannel drivers ....................................................................................................... 17 HR 2.2 Dimming, overvoltage, short-circuit and hot-plug protection in multichannel drivers ..................... 17 3 Tunable white reference design with BCR601 and BCR602 ......................................................... 18 3.1 Board setup ........................................................................................................................................... 18 3.2 Board specifications .............................................................................................................................. 18 3.3 Schematics and circuit description ...................................................................................................... 19 3.4 Electrical performance .......................................................................................................................... 23 3.4.1 Light quality ...................................................................................................................................... 23 3.5 LED current stability and regulator efficiency ...................................................................................... 23 Application Note Please read the Important Notice and Warnings at the end of this document V 1.0 www.infineon.com/ref-tw-bcr601-55v-0.5a page 1 of 32 2021-01-29 Tunable white LED drivers with BCR601 and BCR602 How to design cost effective, highly efficient LED drivers of highest light quality Linear constant current regulators in LED drivers 3.6 Light quality ........................................................................................................................................... 24 3.7 System performance ............................................................................................................................. 26 3.8 Bill of materials ...................................................................................................................................... 28 4 References ........................................................................................................................... 30 Revision history............................................................................................................................. 31 Application Note 2 of 32 V 1.0 2021-01-29