RSS
 

Archive for the ‘Design & customized’ Category

Inside LED Home Lighting Possibilities And What To Consider

14 Oct

It could be a hassle attempting to determine the most effective LED home lighting alternative for the residence. In current years, the number of choices for how to light up your home has improved dramatically. All these choices can make it a problem to choose the proper 1. Would you favor track LED home lighting or fluorescent bulbs? Have you regarded as using halogens or would you favor fluorescent bulbs? To locate the very best option to your house, you ought to study the different alternatives accessible. Use the following inquiries to help guide you in your study.

Consider some time to research the distinct LED home lighting kinds that you can select from. A few concentrate on overhead LED home lighting. Or region lamps and gentle light up also have a good touch. A well-liked choice for kitchens is turning into track LED home lighting. Fluorescent bulbs are an older choices but are gradually turning into obsolete. The general appear and really feel of one’s area is impacted by which lights you select. Lamps will carry a various appear than monitor LED home lighting for instance. What type of space do you require to light up up? Big rooms require much more light than little rooms. Rooms that are 10×10, for instance, only need a single or two lamps. A larger area will normally will need much more than a single source of light up, particularly in the event you want to make certain that the entire area could be observed. If your primary concern is only a little area, you can use a focal light. Should you need to light up the complete area, you might opt for overhead lights or some really good ground lamps.

Once you are figuring out your inside LED home lighting options, don’t overlook about the relaxation of the home’s adorning scheme. It will probably be simpler for you personally to determine in between all with the distinct LED home lighting alternatives if you keep towards the decorating scheme that you have currently chosen for that rest of the house. A house which is filled with tiny pockets of various sorts of focus like office corners and studying chairs won’t be very properly served if you only use diffuse lights. It’s better to make use of small lamps in these areas to assist concentrate your and other people’s attentions. Adhering to your adorning scheme can even help you pick lights for difficult rooms like your cooking area. Huge fluorescent bulbs will not do well in a kitchen that is in a residence that’s embellished with softer tones (observe LED home lighting is better)!!!

Once you determine to light up your home, there are lots of inside LED home lighting alternatives accessible. Don’t limit your choices by only searching at simple overhead lights or aspect table lamps. Take into consideration the elegance of LED home lighting too as its perform capability. Selecting LED home lighting should be enjoyable and your personality ought to shine through those choices. Keep in mind to perform your study and in no time you can light your residence, creatively and affordably.

 

Brighter LEDs Can Simplify Driver Designs

29 Sep

LED vendors are producing components that can operate at higher drive currents and produce more lumens, and system designers can move to a simpler two-stage driver as the number of LEDs in a fixture is reduced, explains BERNIE WEIR.

Much attention in the LED lighting world has focused on two applications that are at polar extremes; low-power incandescent bulb replacement and high-power street lights. While these applications are ubiquitous and iconic, there is also a range of area-lighting applications – such as parking garages, park lighting, stairway lighting – and outdoor commercial lighting – such as wall packs, wall washers, and security, flood, gas-station canopy and pathway lighting – which are hiding in plain sight. These medium- to high-power applications are ideal candidates for solid-state lighting (SSL), and new LEDs that operate at higher drive currents and produce more lumens are a good match. Designing a luminaire with fewer brighter LEDs can also simplify the driver electronics and ease the task of adding adaptive controls.

The applications mentioned above are a good match with LEDs, because they consume large amounts of power, have high hours of annual use, and are used in public spaces that may not be occupied for many hours, thus opening the door for adaptive controls and dimming that can significantly reduce energy consumption. Beyond energy cost, a driving factor of LED lighting is long life and reducing the maintenance cost of bulb replacement.

Traditionally, the aforementioned medium-power applications have used high-pressure-sodium (HPS) and metal-halide (MH) light sources. HPS light sources are actually very efficient but generate a decidedly yellow/orange light that has very poor color rendering since the light source is nearly monochromatic.

MH sources display better optical characteristics but have slightly lower initial lumen output, shorter lifetime, and higher lumen degradation over the useful life. MH lifetime (measured to 50% failure point of the population) is in the 10-20,000 hour range depending on the bulb design and construction, whereas HPS has typical lifetimes of 24,000 hours.

HPS and MH sources are also limited in terms of adaptive controls and dimming. And most of these area-lighting applications require directional light. Although HPS and MH bulbs have high lumen output, 40-60% of the generated light can be lost in the fixture.

LED life and controls

High-brightness white-LED light sources address many of the limitations of the legacy lighting technologies as they are inherently directional in nature, have very long operating lifetimes, provide white light with good color rendering and, given their instant-on characteristics, are easy to dim across a wide range of light levels.


FIG. 1

Moreover LED performance has been rapidly improving in terms of lumen output and efficacy (lm/W) and over the last few years has been making in-roads into these traditional area-lighting applications.

When white HB-LEDs came on the market, the most common configuration was called a “1W” LED because when it was driven with 350 mA, it typically dissipated around 1.2W given a nominal forward voltage of 3.3-3.5V. Today, widely-available 1W LEDs can generate more than 100 lumens at an efficacy of over 100 lm/W. To generate 5000 delivered lumens a fixture needs on the order of 50 LEDs whereas 18-24 months ago the same application may have required 80-100 LEDs.

To power such a large number of LEDs from the AC line, drivers have typically used a three-stage power-conversion architecture as illustrated in Fig 1. A two-stage constant-voltage power supply implements power-factor correction (PFC) in the first stage, followed by a high-voltage DC-DC converter that generates a safe isolated voltage rail typically in the range of 28-60 VDC.

The fixed-voltage output rail supplies multiple strings of LEDs. A third-stage, a dedicated buck DC-DC LED driver, provides regulated current to each string. Depending on the output of the second stage and the forward voltage of the LEDs, each string might include 8-12 LEDs.

Brighter LEDs

Some LED manufacturers have developed advanced processes and improved LED chip designs that deliver more lumens at higher drive currents while maintaining the same forward voltage. For example, the Cree XM-L is rated for up to 3A drive current and has a very low typical forward voltage of 3.1V at 1500 mA drive current. At 1500 mA and 85°C junction temperature, in cool white, each LED generates 440-475 lm. A fixture that uses just 12 such LEDs would have an output in the range of 5200-5700 lm with a typical load power of around 53W, delivering over 100 lm/W efficacy.

Going from 50 LEDs in the previous example to 12 simplifies the optics but it has a more sweeping impact on the driver architecture. Now all the LEDs can be safely driven in a single string, eliminating the need for multiple parallel DC-DC LED buck drivers. This also improves light uniformity as all LEDs are driven at the same exact current.

To eliminate the third stage, the two-stage constant-voltage LED power supply is replaced with a constant-current LED driver. This provides two fundamental advantages. The overall system efficiency is improved as one power-conversion stage is completely eliminated, and the cost and design complexity of multiple DC-DC converters is eliminated. It also simplifies adding intelligent control as the dimming function can now be integrated in the current-control loop of the constant-current LED driver.

Adaptive controls have been used in indoor lighting for a number of years and involve combining sensors with networked or autonomous microprocessor-based controls to optimize the lighting level to the needs of the environment. Simple examples include adding an occupancy-sensor lighting control to turn off a light source when there is no activity for a prescribed time.

Control scenarios

In area lighting, controls have been mostly limited to on and off at dusk and dawn. But dimming LED light sources is very straightforward compared to HPS and MH light sources that have long turn-on and restart times. LED light sources can be dimmed across a wide range and can rapidly turn on to 100% brightness based on activity or occupancy. In an outdoor park-lighting scene, for example, this means the light along the running path or walkway can be turned down significantly when no activity is detected and instantaneously turned to full brightness if a jogger runs down the trail in the middle of the night.

Fig. 2 illustrates a possible dimming profile through the course of a typical evening. The gray area represents timer-based control and the blue areas indicate those times that the light source is increased to 100% when activity is detected. The energy savings can be substantial since most of the operating hours are at the reduced energy-consumption levels.


FIG. 2

Application trials for such bi-level control performed by the California Lighting Technology Center at the University of California-Davis indicate these control schemes can yield energy savings of as much as 70-90% over traditional HID approaches.

Let’s consider an example of how new high-lumen packaged LEDs can simply the luminaire system architecture and efficiently convert AC power into a regulated current in the 1-3A range (Fig. 3). Such an LED driver design can also incorporate support functions to enable adaptive controls. The addition of a low-cost microcontroller (MCU) opens the door to more-sophisticated control schemes that can monitor ambient light, occupancy/activity sensors, time of day, and day of week to provide appropriate light in a variety of situations while maximizing energy savings.

MCUs and networks add functionality

For centralized control, these smart luminaires can be networked, for example using a power-line-communications (PLC) modem block (Fig. 3). Alternatively, a system can use a wireless interface like Zigbee, a traditional wired interface such as Ethernet, or existing lighting and building controls.


FIG. 3

The block diagram illustrates an AC-DC driver based on a high-efficiency PFC and half-bridge-resonant (HBR) isolated DC/DC step-down controller integrated in the NCL30051 from ON Semiconductor. The basic current-control loop consists of a simple analog circuit which monitors the output current and provides feedback across the isolation barrier via an opto-coupler to the primary-side control IC. The circuit also monitors the maximum output voltage, preventing driver damage in the event the LED string is accidentally opened.

The MCU monitors sensor feedback and network communications to control the light level. Moreover the MCU generates a PWM signal that is used to turn on and off the half-bridge driver, thereby controlling the light level. The PFC block implements a critical conduction mode (CCM) control scheme which achieves high power factor (>0.98 typical) with low harmonic content and is suitable for applications up to 200W.

Efficiency and power factor

This driver architecture can support a wide range of power levels. Fig. 4 illustrates the typical efficiency and power-factor curve of an example driver design based on the NCL30051 driving 2A with a nominal LED load of 55W. Across the 115-240 VAC line-voltage range, the efficiency exceeds 88% and the power factor is greater than 0.94.


FIG. 4

The Cree XM-L LED is ideally suited for this range of current. At 700 mA, it generates 260-280 lm (neutral/cool white). A string of 9 LEDs driven at 2A outputs more than 5000 lm. This lumen level can easily address a range of area-lighting applications such as wall packs and wall washers. Depending on the drive current and LED configuration, this type of driver approach can exceed 90% wall-plug efficiency, as well as supporting a range of dimming methods required for intelligent control.

New LEDs that have high source-lumen capability can greatly simplify the LED driver architecture by reducing power-conversion stages and increasing overall power-conversion efficiency. Adding smart controls can yield further energy savings and opens the door to new capabilities such as constant-lumen-output operation modes. Here, the driver can control the LED current to maintain constant lumen output over lifetime to combat lumen depreciation. Smart dimming-control techniques have an additional benefit of extending the operating lifetime of the LEDs as well as the driver electronics by reducing the average operating temperature.

 

Peru’s Stadium Façade Lighting Responds to Football Fever

13 Sep

Cinimod Studio and an international design team developed an interactive LED lighting system for the Peru National Stadium that captures the audio levels of the stadium crowd and depicts it visually on a dynamic façade.

Cinimod Studio, a London, UK-based architecture and lighting design firm, has delivered an interactive lighting-control system for the Peru National Stadium in Lima. The system gathers the crowd’s noise levels in real-time and translates the audible signal into a visual map that is depicted on the façade’s lighting display.


LED-lit façade

Cinimod Studio worked as part of an international design and delivery team including lighting designer CAM and software designer ArquiLEDS, both of Lima, Peru; e:cue, a lighting control company based in Paderborn, Germany; and Traxon Technologies, a lighting designer based in Hong Kong.

The façade-lighting system begins with a network of customized microphones deployed along the stadium’s roof line. This data is then processed by Cinimod’s custom processing hardware and software located in the stadium’s main communications room. The audible data is analyzed using mathematic calculations and self-calibrating algorithms. The software then communicates a “mood state” to the e:cue lighting controller, which transmits the relevant DMX control signal to the lighting fixtures on the building’s facade.

The external lighting scheme is designed to integrate seamlessly within the architectural framework of the building. The majority of the lights are laid out as fans of flames that wrap upwards around the form of the structure. The façade’s patterns vary in color, speed, brightness and scale.

The software runs perpetually, constantly evaluating the mood, which varies between celebration at one end of the spectrum to disappointed at the other.


The façade’s patterns

The main mood states include: 1) Boring, a neutral mood; 2) Excitement, accompanying a surge in crowd noise and pitch; 3) Celebration, typically triggered by a goal and followed by a further rise in noise level; and 4) Disappointed, triggered by an excited state followed by a rapid decline in noise level.

The scale of the stadium façade necessitated a very large array of color- and pixel-addressable fittings. The lighting controller provides 62 universes of DMX lighting control output.

 

Cree Announces Blue LED and Remote-phosphor Licensing Program

10 Aug

Royal Blue XLamp XT-E LED targets remote-phosphor SSL applications, and Cree is offering licenses for its remote phosphor-technology for ready usage by lamp and luminaire vendors.

Cree announced the new XLamp XT-E Royal Blue LED that delivers 525 mW of radiant flux, and targets remote-phosphor solid-state-lighting (SSL) applications. The company will match that LED with a remote-phosphor patent licensing program that will allow lamp and luminaire designers to accelerate the SSL design cycle.

Cree says that the new LED offers “category-leading brightness” along with 2.5-nm bins that it asserts are the industry’s tightest. Mike Watson, Cree senior director of marketing, LED components, said, “The new Cree XLamp XT-E Royal Blue LED outperforms the competition in both elements enabling our customers to design high-performance and low-cost systems.”


Cree royal-blue LED

The LED is based on Cree’s Direct Attach packaging technology that relies on bond pads on the bottom side of the emitter and what the company calls a “eutectic die-attach process” that eliminates bond wires and uses a chemical compound for the bond. That design yields the 525 mW of flux at 350-mA drive current and 85° C operating temperature.

Remote-phosphor technology

Remote-phosphor SSL designs typically utilize a blue emitter — generally considered to be the color that delivers maximum efficacy. The phosphor that generates the white light is coated on a secondary optic or diffuser. Proponents believe such designs deliver better efficacy than do phosphor-converted LEDs. Phosphor-specialist Intematix, for one example, maintains that its remote-phosphor technology can deliver a 30% efficiency advantage.

There are certainly notable examples of remote-phosphor products that achieve superior efficacy. For example, the Philips lamp that was announced as the US Department of Energy (DOE) L Prize winner last week uses a remote phosphor.


Royal Blue XLamp XT-E LED side view

Patent licensing

Cree hopes to help design teams working on remote-phosphor lamps and systems via the patent licensing program. Cree says that a license will allow access to patents that are fundamental to the combination of a blue emitter and a phosphor-coated optical element.

Early this year, Cree announced what is essentially a reference design of a 60W-equivalent LED-based lamp that uses remote-phosphor technology and that according to Cree would meet Energy Star requirements. At the time of that announcement, Cree said that the design relied on patented remote-phosphor technology. It’s not clear if that same technology is included in the new licensing program.


Cree A-lamp reference design

Other royal-blue LEDs

Cree is not the first company to announce a royal-blue LED targeted at remote-phosphor lamps and luminaires. Philips made a similar announcement back in May of a royal-blue LED in the Luxeon ES family of components.

Coincidentally, or not, both the Cree and Philips announcements were lacking a measurement of light output in the more traditional units of lumens (lm). Cree chose to specify its product in the wattage unit that defines the radiometric power or radiant flux of the output.

Originally Philips simply provided a specification of wall plug efficiency for its LED. Subsequently the company has published a data sheet with a rating of 500 mW at 350 mA.

 

LED Drivers And Light Sensors Enable Compelling Displays

06 Jul

TAOS has released light and proximity sensors while Supertex and iWatt have launched new drivers to enable compelling LED-backlit displays.

LED-based display backlighting continues to be the largest market for high-brightness LEDs despite the fact that the general-illumination application gets more notice. New LED driver and sensor products from Texas Advanced Optoelectronic Solutions (Taos), Supertex and iWatt promise to enable displays with the latest solid-state-lighting (SSL) technology for optimal image quality and minimal power consumption.

Indeed light and proximity sensing is needed in devices based on LCDs to set the appropriate backlight level for maximum display quality without wasting power when ambient light is sufficient or when no one is present to view the display. Taos is targeting mobile devices such as smartphones and tablets with its new TSL2×72 family, although the company also expects the sensors to be used in computer-display and HDTV applications.


Taos dual-diode sensor

The new products include the TSL2572 family for digital ambient light sensing (ALS), the TSL2672 family for proximity detection, and the TSL2772 family that includes both light and proximity sensors.

To serve in mobile applications, the sensors must work in very bright environments and the new Taos products are designed for use in full sunlight at levels to 60,000 lx and beyond. “Mobile device vendors are continually striving to deliver more compelling products with an improved user experience; therefore, they demand ALS and proximity detection solutions capable of operating in a very wide range of lighting conditions,” said Jerry Koontz, TAOS Director of Marketing.

Taos uses programmable signal-gain modes, including a reduced-gain mode, to boost the dynamic range of the light sensors. Meanwhile the company boosted the signal-to-noise performance and added crosstalk-compensation technology to deliver more-accurate proximity detection. Both sensor types can be used sporadically while remaining in sleep mode much of the time to minimize power consumption – especially important in any battery-powered application.

The sensors work with any type of light source including fluorescent and at virtually any lighting level. Moreover the dual-diode architecture can provide accurate results even when mounted behind glass that can distort the spectrum.

Supertex driver handles six strings

Supertex is also targeting battery-powered, mobile devices with its new six-channel HV9957 LED driver. Moreover, the driver offers fault protection features for over-temperature, over current, and over- and under-voltage conditions.


Supertex 6-channel driver

“By providing superior fault protection, HV9957 offers manufacturers a precise LED driver that can handle difficult fault conditions in individual LED strings,” states Stephen Lin, Supertex Vice President of Marketing. “HV9957 also features sophisticated digital circuitry to provide frequency control, fault protection, and phased dimming that is controllable to very low duty cycles for high dynamic range in today’s LED backlighting drivers.”

The HV9957 integrates a switch-mode boost converter and six individual linear low-dropout (LDO) regulators for precise control of each LED string. The driver circuit can supply 30 mA to each LED string, a level typical of battery-powered designs.

iWatt targets TVs with 32-string driver

iWatt, meanwhile, is targeting both edge- and direct-lit HDTV designs with its iW7032 driver that can handle 32 LED strings. The driver uses what iWatt calls adaptive-switching technology to both reduce power consumption and component temperature. Gyan Tiwary, Senior Vice President at iWatt, said, “By overcoming the thermal problems of driving large numbers of LEDs together, our engineers have made a large contribution towards cutting costs for the dynamic backlighting industry.”

The adaptive-switching technology senses the mismatch of the forward voltage of the different LED strings, and adapts that drive current individually for each. The company says that the technique reduces the driver power consumption by 2-5W relative to competitors. The technique both saves power and reduces the heat generated by the driver that in turns extends LED component life.

A single iW7032 driver can power a total of 480 LEDs with stack voltages as high as 56V. The driver also integrates the MOSFETs required to handle the output current to each string. The IC supports three different pulse-width modulation (PWM) schemes with 10-bit granularity for brightness control.

Strategies Unlimited projects driver market

The LED driver market is certainly a significant one as Strategies Unlimited details in a new report on the LED driver market segment. The research firm (like LEDs Magazine a PennWell business unit) projects that driver sales will grow to $3.5 billion by 2015 from $2 billion in 2010.

Strategies Unlimited confirms that display-backlight applications will dominate the market through 2015. But the firm expects general-lighting to be the next major market mover for LEDs and associated technology such as drivers.

 
 
LED Blog