To prevent the flickering effect and also because reverse voltage acceptable by a LED is relatively weak, the LED is powered with direct current. This file is dedicated to power supply of LEDs and to their mounting in series or in parallel.
Voltages and intensities, characteristic powers The technical characteristics are given by the product documentation:
Vf or forward voltage: this is the diode's operating voltage. The technical sheets generally give the minimum voltage, a typical voltage for a given current and a maximum voltage. The typical voltage for the nominal current allows getting the desired optical characterstics.
If maximum: maximum current intensity.
If maximum intensity of the pulsed current (greater than If).
Vr Reverse voltage: maximum voltage acceptable in reverse polarisation.
The operating and storage voltages.
The standard diodes are traversed by 6 to 20mA for a 3V voltage depending on the semi-conductor used, that is, from 0.18 to 0.60mW.
High performance white LEDs (0.5 to 5W)
High performance LEDs are surface components. In fact, in the diode to be inserted only the connection cathode and anode take the semi-conductor heat towards the outside (epoxy is not heat conductor), this is insufficient when the power and thereby the heat to be dissipated increase.
The LED mounted on surface is provides with a heat dissipation chip under its semi-conductor. This chip shall be pasted on the electrical circuit.
If an increase in ambient temperature is combined with the heat contribution of the LED and other components of the circuit the maximum temperature of the junction may be exceeded (variable based on the products but generally around 120 degree, the circuit shall be provided with a radiator or even a radiator along with a fan.