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18W Non-isolated Led Driver with LYT5218

Posted by: senthilkumar03 on 04/27/2016


We design the 18W LED Driver with LYT5218. 

I have two queries,

1. How can i select the SHUNT Resistor

2. The Driver is Working, But i have an issue when i put it into aluminium enclosure. LED Driver wattage will increase 2Watts with Aluminium enclosure. Why this is happening and How can i rectify it.

Please Help Me...

For your Referance here i attached the PCB, SCH and Transformer Specification.



Submitted by PI-Crumb on 04/28/2016


I am not sure what resistor are you referring to as shunt. Please specify.

Did you use PIExpert Online to do the design? If not, please go here-

Make sure that the values match the PIXLS.

But then your problem is when you put the unit in aluminum enclosure. It could layout-related. I briefly checked your layout and here's my comment:

1. The position of R11 and C6 are a little far from the pin.

2. The trace from C8- to LYT5 source is very thin.

Please check DER-515 layout for reference.

I also suggest to increase Bias voltage to about 25V in case the transformer gets affected with aluminum enclosure.

You can measure the bias voltage with and without enclosure and if it changes, then it's the one causing the problem.