AC-DC LED Driver Modules - cui.com · 2. Introduction. Purpose. To provide an overview of the VLED15 AC-DC LED power supply and its advantages. Objectives • Identify the market
To provide an overview of the VLED15 AC-DC LED power supply and its advantages
Objectives
• Identify the market opportunity for LEDs
• Discuss why TRIAC dimming is important
• Describe the key specifications of the VLED15 series
Content: 11 pages
Learning Time: 7 minutes
Presenter
Presentation Notes
In this presentation, we will present an overview of CUI Inc’s VLED15 AC-DC power supply designed for the LED market, TRIAC dimming, and why being capable of TRIAC dimming is important in supporting existing installations.
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LED Market Opportunity
• Increased global government regulations to improve lighting efficiency levels
• US Federal Regulations requiring efficiency levels significantly higher than current incandescent bulbs
• Declining pricing for LED lamps
Presenter
Presentation Notes
The enormous growth of LED lighting is being driven by a number of factors. One of the more important drivers are the numerous government regulations mandating improvement of lighting efficiency. Many governments have gone even further and passed measures to completely eliminate the use of incandescent bulbs altogether. Governments around the world, including those in the European Union, Australia, and Brazil, have begun phasing out incandescent bulbs for general lighting and this trend is expected to continue. This is significant as incandescent bulbs are the primary light source used globally and their ubiquity has created an enormous potential opportunity for alternative lighting sources. Current incandescent bulb technology is unable to achieve the required mandated limits. Couple this with superior efficiency and declining prices for LED lamps and the market opportunity for LED lighting is immense.
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Applications for LED Lighting
Residential Lighting• Accent lighting• Downlights• Cabinet lighting• Pendant lighting
Commercial Lighting• Fluorescent lamp
replacement• Downlights• Showcase lights
Presenter
Presentation Notes
There are a number of different residential and commercial lighting applications for LEDs. These markets essentially replicate current markets for incandescent lighting. They include recessed lighting, shelf lighting, cabinet lighting, down lights, and fluorescent lamp replacements.
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Driving LEDs
• Simple two terminal devices
• Constant current
• Typically driven in series
• Must consider how to dim
Presenter
Presentation Notes
LEDs by definition are simple two terminal devices. When current flows from the anode to the cathode, the movement of electrons releases photons which result in light. To increase the brightness, either more current is run through the LEDs or more LEDs are strung together. Although they can be driven either in series or parallel, most are driven in series or a combination of series arrays to better address brightness variations that may exist from LED to LED. Because ambient conditions may vary, dimming a light source is important and this is no different for LEDs. Dimming LEDs is fairly straightforward when operated with a constant current DC power source. One needs to merely vary the duty cycle of a pulse width modulated square wave. Care must be taken to avoid visible flicker but the design challenge is minimal.
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Typical Existing Installations
TRIAC Dimmer
VLED15
TRIAC Dimmer
Presenter
Presentation Notes
A much bigger challenge arises if the source is AC and the power supply must convert the AC line voltage to DC. Additional concerns like power factoring come into play that affect LEDs in ways that do not affect incandescent lamps. In many existing installations, phase cut dimmers have already been installed to control the light output of the incandescent light sources. Dimmers, such as TRIAC type dimmers, do not work seamlessly with LED lamps and require additional, more complex circuitry to function correctly.
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TRIAC Dimming
• Leading edge, phase cut dimmers
• Reduces the amount of energy delivered to the light source
• Most TRIAC dimmers have a minimum load required to operate properly
AC POWER
-120 4 6 8 12 1410
0
-0.5
0.5
1
-120 4 6 8 12 1410
0
-0.5
0.5
1
Presenter
Presentation Notes
TRIAC is an acronym for Triode for Alternating Current. It is equivalent to two rectifiers in reverse parallel which functions as a bidirectional electronic switch. It can thus handle current flowing in either direction. TRIAC dimmers have been used for decades as the main type of dimming control. There are therefore millions of installed TRIAC dimmers in use around the world. They operate by reducing the amount of energy delivered to the light source by blocking the leading edge of the AC waveform at different points of the AC cycle. They are inexpensive and reliable. These dimmers are designed to function with resistive loads and work very well with incandescent lamps. TRIAC dimmers also require a minimum load in order to ensure proper operation. This may vary from 40W to 60W and can easily be met by a standard incandescent lamp.
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Challenges for High Bright LEDs
• LEDs are driven differently than incandescent lamps
• Light output is managed by controlling the forward current going through the LEDs
• LED lamps don’t act as purely resistive loads
• Standard switch mode power supplies have regulated outputs
• Minimum loading must be considered when used with TRIACs
Presenter
Presentation Notes
Although the market potential is large, the widespread utilization of LEDs is not without its challenges. Incandescent bulbs have been in use for over a century and can be driven by any simple voltage source. Dimming the bulbs is fairly straightforward with the installed base of TRIAC dimmers. LEDs on the other hand are driven quite differently from these incandescent lamps. Their light output is managed by controlling the forward current going through the diode and hence do not resemble the simple resistive load of its lighting counterpart. The difference in the apparent loading create challenges for existing installations which use TRIAC dimming. Unfortunately, it is not easy to translate the TRIAC dimmer output to a current that is usable for LEDs to operate. Some level of input voltage sensing is needed to smoothly control the dimming from maximum brightness to lower settings. Standard switch mode power supplies utilize regulated outputs so some type of control loop is necessary to emulate a resistive load. Additionally, LEDs are much more efficient than their incandescent light bulb predecessors. The minimum loading needs that were so easy to achieve using inefficient incandescent bulbs now create potential obstacles when transitioning over to LEDs. In the vast majority of existing installations using TRIAC dimmers, multiple light sources will be involved and the minimum loading concerns will be easily addressed.
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LED Lighting Power Needs
• Dimming capable
• Backward compatible
• Simple to use
• Inexpensive
Presenter
Presentation Notes
The lighting industry has long relied on the incandescent light bulb as the primary lighting technology. This has created an infrastructure of existing installations that must be taken into consideration for implementation of all new technologies. Backward compatibility in working with these installations will be important for quicker adoptions and market penetration. This includes seamless interfacing with all dimming technologies, including TRIAC type dimmers. The power supplies must be simple to use and inexpensive so users can focus on installations and mounting and not spend time on trying to design circuitry to interface with existing infrastructures.
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VLED15 Series – Truly TRIAC Dimmable
• Integrated TRIAC dimming support
• Operates with industry standard dimmers
Presenter
Presentation Notes
CUI’s new VLED15 LED drivers are ideally suited to expand LED lighting acceptance. The VLED15 series has integrated TRIAC dimming support, operating seamlessly with today’s industry standard dimmers. This transparent functionality allows for immediate use in retrofitting existing installations that use TRIAC dimmers. Being TRIAC dimmable is only the starting point for seamless operation. The current installation environment is relatively undefined. In some instances, the AC power cables may extend well over 100 feet from the source TRIAC. In other instances, the source TRIAC dimmer may be positioned very close to the driver module. The number of driver modules connected to the TRIAC dimmer can also vary greatly depending on the installation environment. In certain applications, the TRIAC may only be asked to drive a few modules, while in other applications, up to 30 modules may be connected to a single TRIAC dimmer. These varying installation scenarios inevitably lead to line instability and line noise, causing many LED drivers to improperly dim under TRIAC control and result in “flickering” during the dimming cycle. The highest incidents of “flicker” normally occur at either the highest current point or when the conduction angle is approaching its lowest point. The VLED15 series is one of the first TRIAC dimmable drivers to operate in most installation environments without “flicker” related problems. To overcome these stability issues in installations, the VLED series uses a complex input filter to clean and isolate the AC line from the internal operation of the driver. This results in very stable dimming in most installations with approved TRIAC dimmers.
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VLED15 Models
• AC-DC operation eliminating the need for DC-DC constant current LED drivers
Another benefit of the VLED15 LED drivers is that the units directly accept AC line voltage, eliminating the need for downstream DC-DC current sources. These constant current devices incorporate active power factor correction and can drive up to 1500 mA of current. They also are offered in specific models tailored to line voltages of 120 Vac or 230 Vac.
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Summary
• The potential for LEDs in replacing incandescent lamps is enormous
• Being able to transparently interface with existing TRIAC dimmer installations will accelerate adoption
• CUI’s VLED15 series offers a truly TRIAC-dimmable solution
Presenter
Presentation Notes
The potential for LEDs in replacing the installed base of incandescent light bulbs is enormous. Government regulations increasing the minimum efficiency levels of lighting sources and in many cases, mandating complete phase out of incandescent bulbs altogether, has created a global opportunity for alternative solutions. These solutions must be compatible with the existing installed systems to accelerate adoption around the world. One of the bigger hurdles that must be considered relates to LEDs interfacing with TRIAC dimmers. The inherent differences between operation of a LED and incandescent creates a technical challenge that CUI’s VLED series transparently overcomes.
