There are numerous types of drivers within the market to choose from for LED light fixtures. However, while LEDs are considered constant current driven devices, why do manufacturers offer both constant voltage and constant-current drivers for LEDs and what is the difference?
Constant Current LED Driver vs. Constant Voltage LED Driver
First, let us discuss what exactly a constant current driver is versus a constant voltage driver. A constant current power supply varies the voltage across an electronic circuit allowing the device to maintain a constant electric current. This thus ensures that, no matter the variation in voltage, the current delivered to LEDs does not change. In contrast to constant current power supplies, constant voltage drivers have a fixed voltage of 12VDC or 24VDC supplied to the circuit. Knowing these differences, however, and the fact that LEDs are considered constant current driven devices, how does one then decided between a constant current driver and a constant voltage driver for one’s application?
Constant Current LED Power Supply
For many LED applications, it is desirable to utilize constant current drivers. Constant current LED drivers are ideal in that they offer designers more control for applications, providing them with the ability to design displays with almost no variation in brightness across the display.
Constant Voltage LED Power Supply
Most LEDs, however, are constructed by connecting a number of LEDs in series or parallel to form cluster or string configurations. In this case, if strings of LEDs are connected in parallel, there may be an issue in terms of trying to match the current in all the strings. Thus, an external constant-voltage driver is required. Constant voltage led power supplies are, consequently, most often used for signs for which it is not known, prior to their installation, how many LED loads there will be. Constant voltage drivers are also used in rectilinear architectural signage and designs where there are multiple LED modules connected together. While utilizing a constant voltage driver may result in a slightly less efficient overall number of lumens per watt, it enables the user to have full flexibility, for it ensures that a consistent and identical current flows through LED strings that are in parallel.
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