Analog dimming consists of changing the constant current through the LED by adjusting the sense voltage. – Quiet, does not generate additional noise in the system. – The dominant wavelength varies with LED current however, so the color will change using this method. Analog Dimming – Why Not? Analog Dimming
• CCT provides the basis for “cool” white (more blue) and “warm” white (more red) - CCT shifts with IF as well
• Most white LEDs are made off blue LEDs with yellowish phosphor coating
• CCT shifts are much easier to see than with colored LEDs (more yellow at low IF and more blue at high IF) 1616 8
• PWM dimming consists of setting a desired LED current and turning the LED on and off at speeds faster than the human eye can detect. – Noisier.
The input supply must be filtered properly to accommodate the high input current transients. – The dominant wavelength does not change so color can be well controlled. This is usually the preferred method of dimming high current LEDs.