In some designs, the LEDs themselves are actually remote with relation to the driver electronic circuitry. There are advantages to keeping the heat from the LEDs away from the driver electronics. In some streetlight applications, the electronics are in the base and the LEDs are atop the pole. In these designs it may be appropriate to provide additional TVS devices to protect the LED strings from induced high voltages, since long wires from the driver circuitry to the LEDs will act as antennae (see TVS block after the DC/DC conversion, Figure 1).
Designs that utilize wire-bonded LED structures that are wired into long, high voltage series strings have an additional failure mode where heat cycles, or mechanical vibration causes the wire bond to break, resulting in an open circuit LED. The solution is to use open LED bypass devices (Figure 1) that will keep the balance of the string lit, bypassing the open LEDs. Without these devices, a single LED failing as an open circuit would extinguish the entire string. Some warranties may allow the failure of a certain percentage of the LEDs as long as the fixture maintains a specified minimum light output.