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Why do LEDs need PWM?
As I am sure you are aware, dimming in this case, is the process by which we vary the light output of an LED. We utilize this process to save energy, increase the lifecycle of the LED, afford other functionality, or even to set the ambiance in some cases. LEDs rely on PWM for maintaining their voltage.
Why do LEDs have different voltage drops?
The circuit must provide sufficient current to light the LED at the required brightness, but must limit the current to prevent damaging the LED. The voltage drop across an LED is approximately constant over a wide range of operating current; therefore, a small increase in applied voltage greatly increases the current.
What is Pulse LED?
LEDs can be used to make continuous light, keeping constant the current flowing through the device. On the other hand, LEDs can be easily driven in a pulsed (on/off) regime and can be switched on and off in sequence, turning them on only when necessary.
How fast can your pulse an LED?
Special purpose LEDs are available, whose junction and bond-wire geometries are designed specifically to permit 800 picosecond to 2 nanosecond pulses. For even shorter pulses, special purpose laser diodes, in many ways operationally similar to LEDs, work all the way down to 50 picosecond pulses.
Why are my LED lights flickering?
What makes LED lights flicker? Well… put simply, LEDs flicker when their light output fluctuates. This fluctuation happens because your dimmable light-emitting diodes are designed to switch on and off at very high speed.
How does PWM dimming affect LED light output?
Analog dimming changes LED light output by simply adjusting the DC current in the string, while PWM dimming achieves the same effect by varying the duty cycle of a constant current in the string to effectively change the average current in the string.
Can a constant current led be used as a dimmer?
Although both constant-current and constant-voltage drivers can be made with a dimming feature, not all LEDs are dimmable — and the ones that are capable of dimming must be used with the proper dimming technology (e.g., PWM or CCR). Be sure to review the LED’s datasheet and/or specifications for determining which dimming technology is required.
How does constant current reduction work on LEDs?
Constant current reduction, also referred to as analog dimming, is the relatively simple method of controlling the amount of current supplied to the LED (s). Full LED brightness occurs when the maximum amount of allotted current is provided to the LED (s), and dimming occurs when the current is reduced.
How is the voltage of a led not fixed?
The voltage accross the LED is not fixed. Even though the LED is a diode, the voltage will still increase a bit with increased current. Therefore, the LED will be less efficient (power out / power in) at high currents, even if the light output stays proportional to current. Light output is not totally proportional to current.