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All   >>  LED Lighting   >>   General Lighting Applications   >>   Questions
 

I want to understand when isolation is required in LED lighting driver applications. I understand that Underwriters Laboratories (UL) has standards for safety certification that sometimes require isolation and sometimes do not, but I do not understand when it is required and when it is not.\n\nPreviously I had believed that isolation is always required when designing a driver that powers an LED from an AC mains voltage (off-line application). And I had understood that flyback transformer designs were used largely because they provide this isolation. However as I read more about the topic it seems there are some off-line applications where isolation is not required.\n\nIs there a wattage or voltage limit that defines when isolation is required? Or does it depend on the type of application? For example, is isolation required by UL when designing a driver that would operate inside a closed mechanical structure such as an LED retrofit light bulb? What if the driver is mechanically separated from the LED element and connected by wires?

There is no black and white answer especially when LED bulbs fit in, at the end the end product must be safe and comply with UL requirements but there are several ways to solve this problem based not only on the driver but the mechanical design. The spec applies to the end product product.\n\nNow if a customer was design an LED power supply like UL1310 Class 2 then that dictates specific requirements and in those cases it would be isolated but that is the exception.\nThank you. Answered by:
ON Semiconductor
2011-09-25 15:23:26.0