design calculation of components used in (RDR-195 and AN-49)

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Hello, I am a newbie in LED drivers and I had a bit experience low power designs. Now, I am doing LED driver circuit as mentioned in (RDR-195 and AN-49). I just want to know design calculation of each and every components used in above mentioned. Thanks in advance. Best Regards, Guru

Hi Guru,


If you haven't done so, please download PI Expert Suite and use PI Expert 9 as a starting point to automatically generate a schematic and transformer spec for your design. You can also use PIXLS Designer 9 if you want to use a design spreadsheet, where you can determine various stress levels (Vdrain, Idrain, Ipk, Irms, Isp, PIVS, PIVB, etc.) that can guide you in selecting the appropriate components to be used. The spreadsheet will also tell the appropriate values of the RV resistors,  reference resistors, and feedback resistors to be used, which are pre-calculated depending on the input/output design parameters.



Hello Crumb,

                Thanks you very much for your suggestion. I already have schematics & transformers specs generated by PI Expert 9. I am attaching that file for your reference. But, I just want to calculate manually all the components values for these blocks in schematic:

·         EMI filter

·         Damper Circuit

·         Bleeder Circuit

·         Transformer specs with respect to output voltage & current.

·         In future if I want to change output voltage & current what are things in present schematic changes.  


Thanks in advance.


Best Regard,


There is no straight-forward calculation for EMI filter, damper and bleeder circuit because their actual performance and component selection will vary depending on various factors such as pcb space, pcb layout (affects emi), dimming compatibility (affects damper/bleeder circuit).


The minimum requirements in choosing these components are : voltage ratings, current ratings (make sure the emi inductors don't saturate) and thermals (in selecting R-C bleeder, the larger the C, the more energy the resistor will dissipate and it will be hotter).


Since you need to trim these components, I advise that to minimize your design and iteration time, please choose one design reference that is close to your requirements and use the values as a starting point. You need actual measurements to validate your circuit.


Transformer design can be adjusted by using PIXLS Designer which is part of PIExpert Suite.