Constant Current LED Drivers

LED

LED Drivers

LED has enjoyed undisturbed rise to popularity in the recent past. Missing from this limelight though, are LED drives. LED drives may not be as popular as the LED but it is critical for its operation and just like the LED modules, LED drivers are available in a broad array of quality and technical properties. This makes it hard to understand them.
LEDs are primarily designed to run on low voltage. Unfortunately, the most available power supplied in many places is the AC current. The LED driver, therefore, rectifies the AC to DC. The drives also protect the LEDs from the fluctuation of current or voltage. A fluctuation of the voltage supplied could case current supplied to also vary. This will consequently cause light output to vary or degrade fast due to elevated temperatures since the current is directly proportional to the light output. LED drives are primarily divided into two types;
  • Constant current
  • Constant voltage
In this article, we will feature the constant current LED drivers

Constant current LED driver

Constant current LED drivers are designed to produce a designated range of output voltages while maintaining a constant current output. It offers a constant current output over a range of voltage levels. This enables it to protect itself from thermal runaway. Thermal runaway refers to a situation whereby an LED draws more current than it is rated for resulting in lower LED life-spans and premature burnouts as a result of elevated temperatures. It is ideal for driving high power LEDs since it maintains a consistent brightness across all LEDs in series.

How constant current LED driver work

We will use the figure below to illustrate how constant current LED driver work.
If the voltage exceeds 2V then more current flows through the collector of T2 and hence the current of T1 increases as well as driving the transistor to a conduction state. At the same time, the collector potential of T1 becomes more negative. The same also happens to the base of T2 making it to “close” hence going against the initial growth of current. As such a stabilizing effect is achieved hence providing a constant current through the LED.

Advantages of constant current LED drive

Constant current LEDs avoid violating maximum current specified for LEDs this avoiding thermal runaway
They offer an easy means to control application and helps create light with more consistent brightness.

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