LED light drivers?

[chappy6107]

When do I need to use one and when not to. I have an old diy unit that only consist of the power supply, and the led's...had no problems so far.

[evilc66]

Well, technically, you should always use them. LEDs are current driven devices, and as a result, small changes in voltage creates large changes in current draw (0.1v increase across an LED could double or triple the current, depending on the LED). This is more of a problem with smaller strings, where changes in voltage are distributed over few LEDs, and as a result, create a larger change in current. On larger strings, the change in input voltage can be more readily absorbed by the larger number of LEDs to create a much smaller current change at each LED.

 

When you use a constant current driver, you never ever have to worry about the input voltage fluctuating. The driver regulates the output voltage based on the needs of the LEDs based on the current draw. The current is locked down and regulated tightly so that the performance is far more consistent.

 

Keeping the current under control also keeps the heat under control. As the current increases, so does the heat. This can get into a nasty situation called thermal runaway. Let's say the voltage changes slightly, and the current increases quite significantly. This adds a lot more heat to the LED. This increase in temperature leads to a drop in the effective internal resistance of the LED, which in turn increases the current, which increases the temperature, which lowers the internal resistance, which increases the current....until POOF! If you had a constant current driver, this would never happen.

 

Knowing this, should you change the setup from what you have? No. If it ain't broke, don't fix it. Just keep it in mind for the next project. DC LED drivers are dirt cheap nowadays and very reliable. They are also dimmable and have inherent built in protection from shorts and the like.

[chappy6107]

Well, technically, you should always use them. LEDs are current driven devices, and as a result, small changes in voltage creates large changes in current draw (0.1v increase across an LED could double or triple the current, depending on the LED). This is more of a problem with smaller strings, where changes in voltage are distributed over few LEDs, and as a result, create a larger change in current. On larger strings, the change in input voltage can be more readily absorbed by the larger number of LEDs to create a much smaller current change at each LED.

 

When you use a constant current driver, you never ever have to worry about the input voltage fluctuating. The driver regulates the output voltage based on the needs of the LEDs based on the current draw. The current is locked down and regulated tightly so that the performance is far more consistent.

 

Keeping the current under control also keeps the heat under control. As the current increases, so does the heat. This can get into a nasty situation called thermal runaway. Let's say the voltage changes slightly, and the current increases quite significantly. This adds a lot more heat to the LED. This increase in temperature leads to a drop in the effective internal resistance of the LED, which in turn increases the current, which increases the temperature, which lowers the internal resistance, which increases the current....until POOF! If you had a constant current driver, this would never happen.

 

Knowing this, should you change the setup from what you have? No. If it ain't broke, don't fix it. Just keep it in mind for the next project. DC LED drivers are dirt cheap nowadays and very reliable. They are also dimmable and have inherent built in protection from shorts and the like.

Thank you Evil !! this was very helpful.