I’ve recently been trying to figure out an LED driver circuit for my 32V, 0.7A CoB emitter.
I settled on the TPS40211, since it ticked all the boxed in terms of input voltage range, output, etc.
I followed the datasheet design process and also made use of WEBENCH to determine a lot of the component values. However, after more reading I found an application schematic on page 32 of the datasheet (figure 36) that demonstrated a way to drive almost exactly what I need (aside from the input voltage being a little off)
I noticed a few major changes in this topology from the previous straightforward Boost converter schematics. Surprisingly for a TI datasheet, it offered no explanation as to how the driver functioned and what purpose these changes served.
For example, what’s the purpose of D2 in reverse bias to the ISNS pin? How does the PWM dimming work with D3, R15 and C14? R6, R23 and R13 also weren’t on the other schematics. How is R23 and R13 worked out and what’s “loop response injection” for?
I’m really pretty perplexed at this point, but the documentation seems almost too extensive in some areas and totally lacking in others…