LED Drivers


LED power supplies (LED-driver), constant voltage and constant current

LEDs require special power supply technology so that the luminaires can be operated for a corresponding length of time. Inappropriate power supplies quickly lead to heat death of the LED chips. Depending on the design, the LED luminaires and LED lamps are operated with constant voltage or constant current. Under no circumstances may e.g. LED luminaires designed for constant current be operated on power supplies with constant voltage and vice versa.
To explain the technical differences:
Constant voltage:
This is the much better known version of power supplies, which have also been used before, e.g. for halogen lamps. Up to the power limit such power supplies deliver a constant voltage e.g. 12 VDC, 24 VDC, 36 VDC with varying output current. Advantage: Many luminaires can be operated in parallel on one power supply unit. It is important that the LED luminaires are explicitly designed for constant voltage, e.g. LED strips or LED lamps.

Constant current:
Such power supplies are used particularly in modern LED technology, in luminaires without integrated constant current control (usually for cost reasons). Such power supplies deliver a constant output current (e.g. 300 mA) up to the power limit, whereby the output voltage varies. The range of such power supplies is enormous. When selecting the power supply units, attention must be paid not only to the output current but also to the appropriate voltage range. However, this depends on the internal wiring of the LED luminaires, which is usually not published in the technical data. There can therefore be no general recommendation which power supply can be used as a replacement if the technical data of the previously used power supply are no longer available.
To calculate the correct values, you need the type of LEDs and their arrangement on the PCB: how many LEDs are connected in series, how many series are connected in parallel. Advantage: Such power supplies are more efficient and can usually also be supplied in dimmable versions (0-10 V, DALI, etc.). Disadvantage: Each lamp must be powered by its own power supply unit.