# Tips for selecting LEDs and Drivers for a New Design

Choose between Constant Current or Constant Voltage LED Drivers

For a new design of some complexity, you will need to figure out the best combination of LED specifications and their wiring configuration to match an LED driver. This may take a little homework, as you will need to match up the LED voltages and current requirements per certain LED branches and lengths. You will need to know the voltage and current requirements of your LEDs, and the wiring configuration of the LED strip(s) and sometimes the wiring of the LEDs within the strip(s). You will want to choose the driver and LEDs simultaneously that align with the specs and wiring configuration for your lighting needs.

For example, if you have one LED rated at 3v @ 700mA per datasheet and you want to make a strip of 10 of these, you could wire these in series for a total of 30v @ 700mA. You would then choose a constant current driver that has a 700mA output and a voltage output swing that would be above and below 30v such as Vout= 20-40v as an example. The current flow through the LEDs will be constant at 700mA, and the voltage required by the LEDs are within the voltage output swing of the driver which will adjust accordingly to maintain the constant current. This is pretty basic, as it is only one series circuit.

Now, let’s say you want to use the same LEDs, but want to use quantity 1000 instead of 10. Since the total voltage would add up to 3kv in a series circuit, this does not work when the driver is running from a 120VAC input. We will have to divide the LEDs by using a series-parallel wiring configuration. Since this is not a true series configuration to the driver, the life expectancy and lighting consistency will be lowered by some margin since the current through each LED branch cannot be individually regulated unless there is some other regulating circuitry such like that in most addressable LEDs. Since there are series connections within the parallel branches, this does help the lighting consistency and reliability to some extent as some series groupings are better than none.

See Also
LED Wiring; Series Vs Parallel Vs Series-Parallel:
https://forum.digikey.com/t/led-wiring-series-vs-parallel-vs-series-parallel/1625