"Constant current LED driver circuit"

 LED Control:

A constant current LED driver is an LED power supply that regulates the current flowing through an LED array so as to maintain a desired level of light output. Conventional power supplies provide an output that is regulated to deliver a constant voltage.

Circuit Diagram:


Description:

This circuit is used to light up an LED with a precise amount of current.



When an LED is forward biased, a precise voltage develops across it, called Vf, which is an intrinsic parameter of the device. The difference between Vcc and Vf gives the voltage drop across the resistor., so you can find the current by dividing it by R.


Question:

1)What is used to control LED current?

Answer: Active control of LED forward current requires an active power supply. The topologies normally used for powering LEDs are the buck and the boost Switch Mode Power Supply (SMPS). Both actively control the current to the LED, and both benefit from the intelligence of a DSC.

2)Why do LED need constant current?

Answer: A constant-current driver is used to regulate the amount of current that is supplied to an LED or LED array to maximize LED lifetime.

3)Are LEDs current or voltage driven?

Answer: CURRENT DRIVEN

A LED is described as a CURRENT DRIVEN DEVICE. This means the illumination is determined by the amount of current flowing through it. This is the way to see what we mean: Place a LED and 100R resistor in series and connect it to a variable power supply.

4)How are LEDs controlled?

Answer: High-current LEDs will require specially designed driver boards or MOSFETs for control, in addition to any microcontroller you may use. Another option to take control of the brightness is to use Pulse Width Modulation (PWM), which requires a microcontroller.

5)Do all LEDs need a resistor?

Answer: Resistors in Light Emitting Diode (LED) Circuits

Such a resistor is often called a ballast resistor. The ballast resistor is used to limit the current through the LED and to prevent excess current that can burn out the LED. If the voltage source is equal to the voltage drop of the LED, no resistor is required.

6)Why do LEDs need current limiting resistors?

Answer: In the case of LED strips or commercial lighting, current limiting resistors are installed to minimize the effects of variation in the voltage source.

7)Do LEDs have a resistance?

Answer: LEDs do not have a linear relationship between current and voltage so they cannot be modeled as simply as a resistor using Ohm's Law, V = IR . We can, however, make a simplification and model them over a range of currents as a combination of a resistor and a voltage source.

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