Optoelectronics
Figure 3: Demonstration of high frequency 100 per cent flicker input voltage at 50 per cent dim position and flicker free output of LED driver in LTF’s Sunlight2 MR16 bulbs.
help validate the performance of flicker reduction techniques.
By addressing these challenges and implementing appropriate solutions, LED driver designers can achieve flicker-free dimming enhancing visual comfort and ensuring a superior lighting experience. Continued research and development in this field will lead to further advancements in flicker reduction techniques, resulting in even better performance and user satisfaction.
ranging from 2W to 300W, accommodating different LED load conditions with constant current output and constant voltage models. We also offer the compact DL series for low voltage input drivers with 12 VAC/DC and 24 VAC/DC input, catering to COBs or low-power LED array loads, all with constant current output.
Advantages of this approach in engineering terms
There are several advantages of this approach in engineering terms, including: wide range of options for constant current output drivers with ripple remover for low flickering; multi- stage converters for DL series drivers to lower or remove output current ripples; flexible dimming methods, including leading-edge, trailing-edge, 0-10V dimming, and wireless dimming; high efficiency, high power factor, low input current THD (total harmonic distortion); and low EMI (electromagnetic interference).
Scope graph images such as Figure 1 illustrate the low flicker percentage <1 per cent flicker of the LTF Technology DA series LED driver both with and without a dimmer connected.
LTF Quantum Lux light engines can directly be driven by input line voltage and dimmed by Triac or ELV dimmer, easily integrated into lighting system without external LED driver. They have higher PF, low THD and EMI, and providing one of the lowest flicker rates in the marketplace.
Overview of dimming range and low
Achieving a wide dimming range without introducing flicker poses a challenge. As the duty cycle approaches 0 per cent or 100 per cent, the flicker amplitude tends to increase. In most cases there are several approaches
www.cieonline.co.uk
that a design engineer can take advantage of depending on product application and other requirements. 1. High frequency PWM: Increasing the PWM frequency helps reduce flicker perception by shifting it outside the range of human visual sensitivity. A higher frequency, typically above 1 kHz, minimises the perception of flicker and improves visual comfort. 2. Hybrid dimming: Combining PWM dimming with other methods, such as analogue or digital control, can mitigate flicker issues. Transitioning to another dimming method at lower light levels effectively reduces or eliminates flicker. 3. Flicker-free algorithm: Implementing intelligent algorithms in LED drivers can dynamically adjust the PWM duty cycle to minimise flicker. These algorithms monitor the human eye response and optimise the dimming profile for flicker-free operation. 4. Adaptive control: Adaptive control techniques adjust the PWM parameters based on real-time feedback. By continuously monitoring the flicker level and user preferences, the system can dynamically optimise the dimming parameters for flicker reduction. 5. Synchronisation: Synchronising the PWM dimming frequency with the AC line frequency helps reduce perceptible flicker. This synchronisation minimises interference between the LED driver and the power grid, resulting in smoother dimming operation. 6. Calibration and testing: Rigorous calibration and testing processes are crucial to ensure flicker-free operation. Measurement and analysis of flicker metrics, such as flicker index and modulation depth,
According to the Illuminating Engineering Society, modulation depth (MD) is a metric used to quantify the degree of variation in light output during pulse width modulation (PWM) dimming of LEDs. It measures the difference in brightness between the on and off states of the LED. Modulation depth is typically expressed as a percentage and is calculated by dividing the difference between the maximum and minimum light intensities by the maximum intensity.
MD = (I max – I min) / Imax where: I max is the maximum light intensity during the on state of the PWM signal. I min is the minimum light intensity during the off state of the PWM signal.
Figure 4: Flicker Index defined by Illuminating Engineering Society (IES).
depth indicate a smaller difference and reduced flicker.
In flicker-free LED dimming, it is desirable to minimise the modulation depth to ensure a smooth and continuous dimming experience without perceptible flicker. This can be achieved by optimising the PWM duty cycle, frequency, and control algorithms to create a gradual transition between brightness levels. Accurate measurement and control of modulation depth are crucial for evaluating the quality of dimming performance in LED lighting systems. It helps assess the effectiveness of flicker reduction techniques and ensures that the LED driver operates within acceptable visual comfort limits. By considering modulation depth as part of the design and testing process, LED manufacturers and lighting designers can deliver flicker-free dimming solutions that provide a high-quality and visually comfortable lighting experience for users.
In conclusion, flicker-free LED lighting products play a crucial role in promoting healthier lighting environments. LTF Technology, with its extensive expertise in LED driver design and engineering, offers a range of reliable, high-performance products that address the challenges of light flickering. With continuous innovation and design enhancements, LTF Technology delivers flicker-
Modulation depth directly affects the perceptibility of flicker. Higher values of modulation depth indicate a larger difference in light intensity between on and off states, resulting in more noticeable flicker. Conversely, lower values of modulation
References (1)
(2)
free LED drivers, light engines, and Sunlight2 LED lamps that enhance visual comfort, offer greater user satisfaction, and contribute to improvements to overall well-being in illuminated spaces.
https://ltftechnology.com/ Dr. G.W. Brundrett (1974), Human sensitivity to flicker. Dr. Arnold Wilkins, 2017, The scientific reason you don’t like LED bulbs. Components in Electronics June 2025 47
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56
