Two drivers in parallel provide twice as much current and split power loss into two locations, which makes for easier heat dissipation.

A power-limit circuit can be added to the circuit in Fig. 1 to limit the overall power when there is a large voltage variation for parallel strings of LEDs, with the result shown in Fig. 2.

Resistors (Ω) oppose current, are color-coded, and connect in series (Rt = ΣR) or parallel. Current-limiting resistors protect LEDs.