One of the most commonly used methods of dimming LEDs is by modulating the driving current and voltage of the LEDs attached to the driver. Pulse Width Modulation (PWM) is such a technique, but this type of modulation scheme has significant drawbacks from a healthy lighting perspective, including:
• The flicker index is always set at a maximum 100% because the forward current is switched between 100% and 0% for some point in time, which places PWM drivers in the danger zone
• The frequency of the flicker is usually limited to a few hundred Hertz.
• If the application requires high quality dimming, which does not have steps at the low intensity levels, then the flicker frequency has to be reduced further in order to increase the dimming resolution making it difficult to achieve high quality healthy lighting
The best way to combat flicker is to avoid the use of PWM type dimming drivers and specify:
• Two stage, high frequency LED drivers
• LED drivers which dim using either DC or Constant Current Reduction
• LED drivers which dim using Pulse Amplitude Modulation (PAM)