What is the difference between constant current and constant voltage?

posted in: Drivers Products Constant current


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First of all, when Semper Fi Power Supply uses the term "LED Driver", we are referring to a Constant Current Driver.

A Constant Voltage device is not an LED driver because LEDs are current driven components.  Therefore, the LED fixture must incorporate additional components to regulate the amperage through the LED.

The amperage through the LED is one of the most important variables in determining LED performance and reliability.

When you are instructed to wire an LED fixture to 120 VAC, 12 VDC or some other Voltage, then the fixture already has integral components on board that regulate the amperage through the LED.  If an LED was wired to a nominal voltage source without these ballasting components, then the LED would be destroyed on start-up. 

It is possible to use a voltage source (like a battery) to power LEDs directly, but it is more difficult to provide consistent and repeatable performance - when using battery or renewable energy solutions, we recommend the use of our RPK-LV Constant current drivers to provide optimal results every time.

The Forward Voltage on the circuit accumulates with every LED wired in Series.  The conversion from line to low voltage is one step and another converts AC to DC.  The end result is that all LEDs are current driven, but the powering solution to achieve this result may be different every time and each involves trade offs.  One powering solution may be superior in one application, but not in another.

Brief overview below