If a LED module is operated using a constant voltage source without current limitation, the current will increase up to the thermal destruction of the LED. To avoid this effect, LED modules for operation with constant voltage are fitted with integrated current control.
When operating a LED using a constant current source, the LED is operated at a constant current, with current control being integrated in the driver. Constant current sources can feature either transistors or integrated circuits. The use of a constant current source is more efficient.
Tolerance values for output currents constitute a qualitative criterion.
A value of ± 5% is typical for high-quality devices, while a value of ± 10% is characteristic of low-cost devices.