Chip manufacturers are always coming up with ever more sophisticated constant current driver chips for LEDs. We have included this design for those of you who prefer a more cheap and cheerful solution.
Regulating LED Current: Achieving Stable Illumination
Within this circuit, the LEDs’ current flow results in a voltage drop across resistor R1. As the current increases to yield a 0.6 V voltage drop across R1, T2 becomes conductive, diverting T1’s gate voltage to the ground. This action maintains a consistent current (I = 0.6 V/R1) flowing through the LEDs, ensuring their stable illumination.
Flexible Control Input: Tailoring LED Brightness
Facilitating versatile LED control, the input can activate the LEDs by applying voltages ranging from 5 V to approximately 12 V. Conversely, switching off the LEDs is achieved by applying a 0 V voltage. When modulated using a pulse width modulation signal, this input enables precise adjustment of LED brightness, providing a dynamic range of illumination possibilities.
Optimizing Supply Voltage: Maximizing LED Performance
For the series-connected LEDs, the supply voltage can be set at the highest practical level, ensuring optimal illumination. The key consideration lies in not surpassing T2’s maximum drain-source rating. The choice of T2 and the requirement for a heat sink hinges on the power dissipated within the device, a value that can be computed using a specific formula.
(Supply voltage minus the voltage drop across the LEDs) × ILED
Types Of Resistors
- Varistor Resistors.
- Photo Resistor or LDR (Light Dependent Resistors)
- Surface Mount Resistors.