Dimming Function – Pulse-width Modulation (PWM) Presented by: Illuminating Asia SG

What is Pulse-width Modulation(PWM)? Lesser used method of low voltage dimmers out of all (Eg: 0- 10V, DALI, DSI, DMX and PWM) Relationship between forward current and lumen output is effectively linear at lower forward current levels and becomes nonlinear as forward current increases Source efficacy (lumens per watt) begins to decrease in the nonlinear segment of the range because an increasing percentage of output power is converted to heat Commonly used for both static and dynamic dimming Dimming of the LED is approximately proportional to the amount of on time to the amount of off time Length of duty cycle determines the ultimate voltage of low-voltage signal delivered to ballast Control signal is inverse to the dimming (The more the voltage is on, the dimmer the lamp appears) https://learn.sparkfun.com/tutorials/pulse-width-modulation http://mzltg.com/wp-content/uploads/2015/07/dimming-technologies.pdf http://lumenhub.com/pwm-signal/

Demonstration of 8RGB LED Diodes with PWM dimming

Duty Cycle of PWM LED are turned on and off very quickly. At full light output, LED is turned on and never turns off At 50% of light output, LED is on half the time and off half the time To dim the light at any given level, simply change the ratio of time on and time off If the speed of switching on and off (frequency) is high enough, human eye won’t see the switching http://www.xicato.com/technology/dimming-technology

Pros and Cons of PWM Dimming Smooth dimming capability More precise output levels Better consistency in color over various levels Relatively more expensive Flicker perceived in peripheral vision if the driver is run below 100Hz frequency Stroboscopic effect evident in fast moving environments when driver frequency is low Electromagnetic Interference (EMI) issues due to rise and fall of the current in PWM dimming Performance issues arise when the driver is mounted remotely from the light source http://www.lighting.philips.com/main/support/support/faqs/dimming-with-leds/relative-advantages-of-PWM-dimming http://www.lighting.philips.com/main/support/support/faqs/dimming-with-leds/disadvantages-of-pwm

Differences between 0-10V, PWM, Triac Dimmable 0-10V Dimming PWM Dimming Triac Dimming How the dimming works Control signal is a DC voltage that varies between 0 to 10V Average value of voltage (and current) fed to the load is controlled by turning the switch between supply and load on and off at a fast pace Conduct current in either direction when it is triggered (turned on) Voltage Patterns http://www.cgledlighting.com/news/59-1-10v-dimming-pwm-dimming-triac-dimmable-dali-dimmable.pdf