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A Bright Future for Lighting

Ali Husain, Corporate Marketing & Strategy, ON Semiconductor

Let there be (electric) light! But who was the bright spark responsible?

Lighting
Figure 1: Can we use a visually-attractive stock image of lighting, such as this one from https://www.onsemi.com/pub/ Collateral/BRD8034-D.PDF

There are many competing claims to be the inventor of electric light, with multiple developments in the mid-19th century paving the way for the world to get that little bit brighter.

We may not be able to pinpoint the exact Eureka! moment of invention, but what we do know is that, in 1879, Thomas Edison patented the first commercially-successful electric light bulb, with a carbonized bamboo filament. Apart from minor improvements in filament materials, including a shift from carbon to tungsten in the early 20th century, we’ve basically used Edison’s age old technology ever since, until recently.

Incandescent light bulbs quickly became ubiquitous, offering low cost and high quality light. But over the last decade or two, there’s been a fundamental shift in lighting technology, with LEDs replacing traditional incandescent lights in most residential and commercial installations.

LEDs take over

LED lights have been around since the 1960s, but it’s only the invention of the blue LED in the 1990s that enabled white LED light bulbs to be created. Since then, they have become the dominant technology in many markets, as its price has steadily dropped to compete with traditional light bulbs.

In worldwide residential sales, LEDs have also overtaken fluorescent lamps, reaching a 40% market share by 2018 . Today, an LED light bulb might retail for something like US$2 to US$5 in many countries, with even lower prices in some regions. For example, in India, the government has successfully driven the adoption of LED lighting through tax and tariff reductions for local manufacturers.

LEDs offer multiple advantages over incandescent bulbs: they last much longer, generate less heat, and use less power, thus reducing lifetime costs, and their lower electricity consumption makes them greener. LEDs also use less power than most fluorescent lamps, and have the advantage of reaching full brightness immediately when switched on.

Going green

Lighting accounts for a significant amount of global electricity consumption, which is estimated at around 15% by the European Commission . In the USA, lighting in the residential and industrial/commercial sectors uses 7% of the total energy (not just electricity) that is consumed .

With the climate crisis upon us, we need to reduce the power consumption of lighting – and substantial cuts are needed to enable countries signed up to the Paris Agreement meet their greenhouse gas reduction targets.

LEDs can help make this happen: residential LED lights typically offer efficiencies of more than 90 lumens of light for each Watt of power they consume (lm/W), while vendors claim figures of 200 lm/W or more for some new models . For comparison, a traditional light bulb might achieve something like 15 lm/W, a halogen light 25 lm/W, and an ‘energy saving’ fluorescent bulb typically around 55-60 lm/W.

For businesses, the light source of choice has often been fluorescent lighting, which is relatively efficient at around 100 lm/W. But the quality of light it produces is harsh, and the warmer light produced by LEDs is typically preferred by most people – a win/win when the newer LEDs offer the same amount of light for half the electricity used by a fluorescent tube.

Lower power consumption also creates new opportunities to make electric light possible where it wasn’t previously available – and specifically, to power lights from solar energy where there is no mains electricity grid. For example, 130 million solar-based lights were deployed between 2010-17, mainly in Africa and Asia. With clean, safe lighting available after sunset, this can dramatically improve people’s quality of life, and their children’s ability to study at home.

Government regulations have accelerated the move to LEDs in some areas. For example, in the EU there are minimum efficiency standards for LED lights, and other less efficient lamps are no longer permitted to be sold.

Driving efficiencies

For residential and commercial lighting, we need to power our LEDs from the high-voltage alternating current (AC) mains supply. But LEDs need a much lower voltage, and direct current (DC). To convert AC to DC at the correct voltage, we need appropriate drivers and other power management devices – these inevitably introduce some inefficiency, which we obviously want to minimize.

Depending on the current and color, the forward voltage of the LED might vary from less than 2 V, up to 4.5 V. Companies such as ON Semiconductor have been enablers of LED adoption, by using their expertise in power management to develop the required devices to drive LEDs, reliably and efficiently.

For example, the NCL30082 from ON Semiconductor® is an LED driver designed for use with AC input power. It includes a PWM current mode controller that provides high efficiency, and a novel control method reduces the number of external components required. The driver also supports dimming of the LED. An input bridge rectifier and a superjunction MOSFET, also available from ON Semiconductor, complete the power conversion circuit to drive the LED.

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Figure 2: NCL30082 internal circuit architecture [source: https://www.onsemi.com/pub/Collateral/NCL30082-D.PDF]

As well as the LED drivers, lighting applications need other components to create a full system. This includes sensors, for example to detect the ambient light level so the LED brightness can be automatically adjusted, or to turn a light on when the presence of a person is detected in an office.

Another component required in some applications is an LED bypass shunt, such as the NUD4700 from ON Semiconductor. This ensures that if one LED fails, the shunt allows current to flow around the failed LED, so the remainder of the LED string remains lit.

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Figure 3: LED bypass shunt minimizes impact of failed LEDs (source: https://www.onsemi.com/pub/Collateral/BRD8034-D.PDF)

Looking ahead: lighting gets smarter ‘

Smart’ or ‘connected’ lighting is another growing trend, not least because it provides an opportunity for LED light vendors to differentiate their products, and to increase margins. More importantly, it enables further power savings, beyond just using LEDs, through automation and user control – for example, to automatically adjust lighting conditions during specific times of the day, such as turning office lights off at the weekend.

Light fixtures can be controlled using powerline networking, such as the industry-standard KNX® network, or wireless technologies, such as Zigbee® technology and Bluetooth® technology. As well as the fall in prices of LEDs themselves, these networking products have dramatically decreased in cost over recent years, so that smart LED light bulbs are becoming increasingly affordable for residential use.

Connected lighting has now become the area of highest potential growth in the smart homes and buildings sectors. As more consumers start to add smart home technology to their houses, including voice-controlled assistants such as Amazon® Alexa®voice-controlled assistant, the smart lighting market is likely to grow rapidly over the next few years. LEDs can be dimmed and their color varied, enabling new developments in home lighting that responds to ambient light, time of day, or even the output of a TV. The Connected Lighting Platform by ON Semiconductor is a modular kit that allows an engineer to test various LED power solutions paired with Bluetooth technology, Zigbee technology or other wireless technologies.

While LED technology has come a long way, further reductions in power consumption are expected over the next few years, and economies of scale will continue to drive prices down.

Vendors, such as ON Semiconductor, are continually striving to improve the efficiency and capabilities of the electronics needed for LED lighting, across residential, commercial and automotive applications. Whatever they’re used for, innovation in LED lights means that the future is bright.

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