Constant Current Source Circuit For Led

The term led power supply actually describes a constant voltage source and is used here rather colloquially.

Constant current source circuit for led.

We use also a 7805 regulator to build a constant current circuit. The input of the constant current source can be between 5v and 15v dc what is realy usefull for variable voltage sources. The circuit is a constant current source which means that it keeps the led brightness constant no matter what power supply you use or surrounding environmental conditions you subject the led s to. This controls the leds integrated in the lamp.

This is a very simple led constant current design using only 2 transistors 2 resistors and an led. From in the figure current i flowing through the value. U led u be r. In electrical engineering this circuit is often referred to as a constant current source.

It s more consistent more efficient and more flexible. 3 7805 current constant circuit. 1 we use a lm317 in its constant current mode. Each led has a slightly differing voltage drop which is normal and why we want to use a ccs.

This is better than using a resistor. The unloaded output will be the same voltage as the input 0 7v for the circuid it will regulate itself when you burden it. The t2 transistor can be bc547 if you use only usual leds the 20ma versions but it is recommended to use bd135 bd137 or bd139 because they have a higher power dissipation. Thus temperature occurs it does not affect the current flowing yet.

An led driver is an electronic circuit that generates a constant output current from the supply voltage. In this case current is 1 25 4 7 266ma. And since the temperature coefficient of transistor and led fully offset. This circuit allows you to use any voltage between 2v and 24v to drive almost any type of led with power consumption up to 5w.

Constant current circuit using led.