Using Dim-to-Warm to Offer More Comfortable LED Lighting, Affordably

Transcription

1 Using Dim-to-Warm to Offer More Comfortable LED Lighting, Affordably Daryl Kistenmacher, Mario Falcone, Steve Klinger, Greg Goltz SMT Engineering LLC, Lighting Team When LED lighting first began, its light color and intensity were far from appealing. Technology has greatly improved the LED industry s offerings, and today one particular technology is gaining traction: dim to warm. This LED lighting technology offers more comfortable lighting options, but your design options can vary greatly depending on your desired output. In its most basic form, dim to warm works just as it sounds: as you dim bright, cool lights to cool white, the color spectrum transitions to a dimmer, warmer and less harsh light (technically speaking, from >5,000 K cool or daylight to 3,000 K 5,000 K cool white to 2,700 K 1,800 K warm color). Dim to warm goes beyond the existing LED concept of tunable white, where you transition from a cool white to a warmer white without dimming. By adding dimming to the equation you add a whole new axis 1

2 to the capability of the system, one that enables you to have even more control over your environment. This is commonly referred to as mood lighting. Dim to warm can go beyond just mood lighting to using specific color temperatures in very specific sequences to mimic the sun, which has shown benefits when used in both the early mornings and evenings. [3,6] as you dim bright, cool lights to cool white, the color spectrum transitions to a dimmer, warmer and less harsh light Benefits of dim-to-warm LED technology There are several reasons to use dim to warm technology in your LED lighting application. First, it more closely follows the dimming characteristics of traditional incandescent light bulbs. This is very desirable in the hospitality industry, especially hotel/conference centers and high end restaurants [4]. The whole concept of mood lighting is very important in the hospitality industry. Imagine if your candlelight dinner was under a blinding 4,000 K fluorescent lamp not very romantic, is it? On the other hand, it would be very uncomfortable holding a business lunch under a dimly lit, 1,800 K E12 bulb. With dim to warm LED lighting, a restaurant manager or host can easily adjust the lighting to the most appropriate level and color temperature for the situation. This application holds true for hotels, entertainment venues, homes and many other locations that can benefit from the adjustability of a dimto warm LED application. Second, though manufacturers are not yet touting the health benefits of the dim to warm features on their LED products, studies have shown that dim to warm lighting technology can have a positive impact. Most theorize that lighting systems that more closely replicate the cycle of the sun help regulate our circadian rhythms, leading to both higher energy during the day and better sleep at night. [2,5,6] A dim to warm LED bulb can mimic this pattern. For example, in a large business office with minimal windows the dim to warm controller could simply adjust the light intensity and color automatically throughout the day to mimic the natural sunlight occurring outside, which has been shown to improve overall productivity in the work place. [1] Similarly, when evening approaches our bodies need to produce melatonin to aid in our sleep, but the harsh blue lights in many LEDs, televisions and other consumer electronics actually reduce melatonin production in the body causing poor sleep conditions later at night. A properly timed dim to warm LED bulb can help avoid this. [6] Design Solutions There are multiple ways to design a dim to warm solution, ranging from self contained Chip On Board (COB) modules to custom programmable dimming profiles. The examples below provide a brief 2

3 overview of multiple approaches and their associated benefits and shortcomings. Surely, new approaches will emerge as applications in the various market segments foster their growth. AC Retrofit Design Certain LED manufacturers are providing solutions that directly replace incandescent lamps that are controlled by a dimmer in an AC application. The AC LED module contains the necessary circuitry to allow a 120/277 VAC input to power the on board dim to warm LEDs. Power can be applied to the LEDs in a triac splicing fashion or through typical rectification and constant current drivers. Depending on the approach, dimming may suffer from flickers or excessive heat dissipation. Typically the AC retrofit requires a larger luminaire design to account for various design factors. Advantage: Directly replaces existing incandescent design Disadvantage: Lighting quality and larger size On board Regulation and Driver Components: Current driver/switcher MPS MP100L, Microchip HV9961, ON Semi NCL30100 Bridge Rectifier Fairchild DF08S2, Vishay DF06S Mosfet Vishay VN2460N8 Inductor Bourns SRR Standard Dimmer: Lutron Lumea LECL 153PH 3

4 Passive Design An approach that relies on off the shelf (OTS) LED drivers to power the COB is becoming more popular. The COB contains the necessary passive components to effectively manage the current consumption of each of the two color temperature LED strings as the power to the COB is dimming. Manufacturers are developing various combinations of white and warm color temperatures for multiple consumer applications. Designs using the passive approach should pay special attention to the pulse width modulation used in drivers at low dimming levels and the noticeable flickering affect and stalling of color temperature. This benefits from this approach include the ability to retrofit the OTS drivers and the design simplicity. Advantage: Retrofits existing OTS Drivers, design simplicity and readily available OTS Drivers Disadvantage: May exhibit noticeable flickering affect and stalling of color temperature LED Driver: AMER90 AZ, AMEPR60 AZ, AMEOR60 AZ Control: Leviton IP710 LFZ, Lutron Diva or Maestro Dim to warm COB: Sharp Mini Zenigata, Luxtech Warm Dim, Citizen CLC0x0 Custom Driver Design One step away from a passive COB solution is the custom driver approach. This type of design starts from scratch in LED driver design and utilizes a standard dimming control input signal that is then customized to provide the needed dimming profiles. The LES is a custom design as well, and requires independent LED power for each color temperature string. This design has the advantage of being 4

5 programmable for custom dimming profiles. Because of the very custom nature of this design, it is more complex and therefore requires a larger product development commitment. Advantage: Programmable (flexible) Disadvantage: Complex design, cost Custom D2W Driver Components: MCU Microchip PIC16F1778 LED Driver/Controller TI LM3409HVMY Mosfets Vishay VN2460N8, Fairchild BSS123L Switch mode controller ST Microcontroller Viper 50 Inductors Bourns SRR Control: Leviton IP710 LFZ, Lutron Diva or Maestro LEDs: Osram GW PSLR31.CM Custom Controller Design An alternate custom approach is to design a control module that sits between the dimming control and the dual LED driver. In this approach the custom controller manages the dimming signal and provides the corrected input into the dual LED driver to independently control each color temperature string. The benefit is being able to use an OTS driver and programmable dimming profiles. Liabilities of this 5

6 approach include the additional LES power lines and the addition of a custom controller to design and mount. Advantage: Off the shelf drivers and programmability Disadvantage: Complexity (cost), extra wiring LED Driver: AMER90 AZ, AMEPR60 AZ, AMEOR60 AZ Control: Leviton IP710 LFZ, Lutron Diva or Maestro D2W Custom Control Board Components: MCU Microchip PIC16F1778 Bridge Rectifier Fairchild DF08S2, Vishay DF06S Inductors Bourns SRR Op Amp ST Microelectronics LMV321ILT LEDs: Osram GW PSLR31.CM In line Controller Design Many designers use in line controllers to attempt to maintain retrofit capabilities while using programmable dimming profiles in standard luminaries. When an OTS LED driver is used, a custom inline controller is mounted near the LES to monitor the dimming power and provide color temperature LED dimming profile control. This approach is straightforward from an installation standpoint but its 6

7 complexity must be carefully considered during the design phases. Though standard OTS LED drivers can be used there is the need to right size the power to allow the overhead of operating the in line controller. Advantage: Programmability of custom dimming profiles Disadvantage: Higher wattage LED driver needed to support MCU overhead LED Driver: AMER90 AZ, AMEPR60 AZ, AMEOR60 AZ Control: Leviton IP710 LFZ, Lutron Diva or Maestro MCU D2W Profile Components: MCU Microchip PIC16F1778 LED Driver/Controller TI LM3409HVMY Mosfets Vishay VN2460N8, Fairchild BSS123L Inductors Bourns SRR LEDs: Osram GW PSLR31.CM 7

8 Light color and intensity can create a mood, bright blue lighting improves attention and focus, and warmer yellows create a welcoming environment. Understanding how a room s lighting can improve the atmosphere helps frame the importance of dimto warm in some applications. Light color and intensity can create a mood, bright blue lighting improves attention and focus, and warmer yellows create a welcoming environment. Beyond the comfort and usefulness of mood lighting in commercial and residential applications, studies have shown a significant connection between light and circadian rhythms. Lighting can have an impact on productivity, mood, energy and alertness for example nearly 68% of employees say that issues with lighting in their place of work cause stress and unproductivity [1]. Dim to warm is a feature rich LED technology that can enable you to offer more comfortable lighting options. Still, your design options can vary greatly depending on your desired output. While fully programmable options may seem like the best route to take, you must remember to consider your total costs. 1. Greenberg, Molly (2017, Feb 22) Flick of a Switch: How Lighting Affects Productivity and Mood of a switch how lighting affects productivity and mood/ ( of a switch how lighting affects productivity and mood/) 2. Lighting Research Center, Light and Health: Researching How Light can be Used to Promote Health and Wellbeing ( 3. Jeanne F. Duffy ( term=duffy%20jf%5bauthor%5d&cauthor=true&cauthor_uid= ), M.B.A., Ph.D.a,* and Charles A. Czeisler ( term=czeisler%20ca%5bauthor%5d&cauthor=true&cauthor_uid= ), Ph.D., M.D.b,c Effect of Light on Human Circadian Physiology,National Center for Biotechnology Information, US National Library of Medicine, ( 4. Brandon Melton, 3 Pitfalls to Avoid in Restaurant Lighting, Lighting Insight Blog, 12/8/ pitfalls to avoid in restaurant lighting 5. Harvard Health Letter, Blue Light has a Dark Side, September 2, healthy/blue light has a dark side ( healthy/blue light has a dark side) 6. Hyman, Mark MD, How a Light Bulb Can Help You Sleep Better, THE BLOG, 11/08/ mark hyman/light sleep_b_ html 8

9 Daryl Kistenmacher, Mario Falcone, Steve Klinger, Greg Goltz The team has a combined 62 years of industry experience and 10 years of LED Lighting experience. 9