An LED Driver Is Like A Resistor

LEDs have a very nonlinear current-voltage characteristic. If a LED was connected to a constant voltage source, the current and hence the power drawn by the LED would be very difficult to predict. Furthermore the current would depend strongly on the temperature. It is possible for thermal runaway to occur where the power drawn by the LED causes heating of the LED P-N junction causing the current draw to increase and the light output to decrease - a vicious circle leading to the destruction of the LED.

A LED driver is a constant current device, designed to operate with an output voltage in the expected range for the LED. Since the LED is supplied with a constant current, thermal runaway cannot occur and the LED power is constrained within narrow limits. A LED driver can supply the optimum current to the LED so that the light output is maximised subject to keeping the LED within its safe operating envelope.

Basically, an LED driver is like a resistor that limits the current flowing through an LED. Since LEDs are very fragile they need something that will protect them from excessive current.

So in low power LEDs, we usually use a resistor to limit the current. However, in high-power LEDs, the current required by the LED to operate normally is very high.

So as the current flowing through the series resistor increases, more power is being dissipated by the resistor and that would be very inefficient. That’s why there is an LED driver, which is an optimized circuit that can be used to drive high-power LEDs efficiently.