Introduction: LED Lighting for Sustainability and Style
LED lighting offers many advantages over earlier technologies, from saving carbon and hazardous waste to new styling opportunities for product designers, as well as improved user experiences.
Compared to incandescent lighting, with typical bulb ratings such as 40W, 60W, or 100W, replacement LED lamps deliver comparable illumination at less than one-tenth the power. This dramatic increase in efficacy, delivering many more lumens per Watt, aligns with the global cultural shift towards improving living conditions while also preserving Earth’s resources. Lighting is estimated to account for 15% of global power consumption and 5% of global carbon emissions[1]. Switching to LED lighting could save as much as 6 tons of CO2 emissions annually for every 100 households.
At the same time, LED lighting brings new design opportunities. The light sources are smaller than preceding technologies, making new shapes and new types of products possible. Electronically driven RGB combinations allow flexible features like color tuning and color changing. This creates opportunities to produce entertaining effects or create different moods in spaces such as offices or retail areas. On the other hand, selectively boosting red and blue wavelengths enhances plant growth in horticultural lighting applications.
Such flexible controls can be achieved more easily and at more affordable prices than has been possible with earlier digital interfaces for AC-powered lighting. Moreover, combining easy, direct controllability with sensors and networking technologies provides the foundation for smart lighting, automating functions like on/off switching, dimming, custom scenes, and others.
Technical Requirements
The new LED lighting opportunities and commercial/industrial building lighting compliance and regulation bring new challenges for designers because the engineering disciplines for lighting design shift from an electrical to electronic base. These include ensuring the voltage and driving current supplied to strings of LEDs are stable, smooth, and consistent to prevent flickering, which can be noticeable to the human eye. This requires designing low-pass filters to remove flickering by minimizing output current ripples.
In addition, the standby power of the control circuitry must be considered to minimize the total energy consumed when the lights are turned off. This is needed to ensure a greater net saving in energy/CO2 compared to older technologies.
In commercial and industrial applications, the power factor of the lighting electrical system is also extremely important. If a building contains many lighting loads with a low power factor that will increase currents, the real power demand may exceed the rating of circuit breakers and reduce their life span. High power-factor correction is needed, therefore, to prevent early wear-out. It also avoids adverse effects on the wider power grid and prolongs system life span.
When activated from a standby or off state, some LED lighting systems may experience a delay before reaching full brightness. This can negatively impact the user experience. To sharpen the system response to provide immediate illumination when required, for a superior user experience, the driver and control circuitry can be optimized for rapid start-up times.
Regulations and Eco-Design
It is also important to bear in mind local regulations and standards in force in the target market. Increasingly, building standards are seeking to drive improvements in environmental performance, in addition to specifications aimed at ensuring quality and safety. In India, the Bureau of Indian Standards (BIS) is the national standards body that specifies the standards for LED lighting. Additionally, the Bureau of Energy Efficiency (BEE) plays a crucial role in promoting energy-efficient products through its labeling programs.
Eco-design standards worldwide often influence and build upon one another, as governments and regulatory bodies adopt policies that have been seen to be successful in other regions and adapt them to local contexts. Energy-saving product requirements around the world are continuously being shaped by adopting and iterating upon each other’s specifications.
Among the toughest eco-oriented frameworks, the Title 24 building regulations in force in California have strict rules for lighting that are conceived to ensure fixtures and systems are both energy-efficient and cost-effective. There are stringent requirements for vacancy sensors and shutoff controls, as well as demands for separately controlled display and decorative lighting, for users to light only those areas that require illumination.
Some rules also promote the use of daylight, including placement of windows, and electric lighting must be reduced to 65% when the daylight is more than 1.5 times the lighting system’s design maximum. Compliant lighting products must be Energy Star® compliant. Further specific performance requirements include maximum standby power of 200mW, power factor greater than 0.9, and maximum limits on output current ripple and total harmonic distortion (THD). These are imposed to avoid flicker.
Design for Compliant Lighting
By adhering to high standards such as Title 24, manufacturers can quickly gain the approvals needed to sell their lighting systems in multiple markets. Designers must consider all these aspects when creating new LED lighting products. On the other hand, designers must ensure that the end product can be competitively priced. Achieving a fast time to market is also critical.
A wide variety of ICs is on offer, from various manufacturers, that provide the underlying building blocks of the lighting control system. However, the diverse options on offer challenge designers to select components that will provide all the desired features and fulfill mandatory performance requirements. Essential functions of a suitable control circuit include the LED driver, ripple suppression to provide stable current and voltage, and power-factor correction. To support smart functionalities, the driver should provide capabilities such as dimming and a suitable network technology such as Wi-Fi™, Bluetooth®, Zigbee®, or Matter® needs to be integrated.
For applications up to 30W, a single-stage LED driver is a common choice. The advantages of the single-stage design include its relative simplicity and cost-effectiveness, as well as greater efficiency. On the other hand, careful design is needed to ensure performance meets the requirements of building standards. It can be challenging to achieve a wide dimming range, high power factor, and low THD.
To help designers tackle these challenges and quickly realize a design that fulfills all requirements, Diodes Incorporated has built a reference design for a single-stage LED driver aimed at commercial lighting applications. The design is based on a chipset, curated from the portfolio of drivers and dimming-control ICs. Together, these devices help to minimize the bill of materials while meeting or exceeding regulatory performance demands. The dimming range of 1-100%, using either analog or PWM control, exceeds Title 24 requirements, while power factor exceeds 0.9 and THD is below 20%. LED current line and load regulation is within ±2%. In addition, by including the AL5822 ripple current suppressor, this chipset solution ensures a current ripple of just 1~3% for flicker-free operation.
Figure 1 presents a functional block diagram of the driver. The high-voltage buck regulator powering the smart communication subsystem, either the AL17051 or AL17052, is specially designed for IoT connectivity applications. With a no-load power consumption of less than 10mW and ultra-fast startup time within 8ms, the regulator includes fault protection with auto-restart and integrates a 700V MOSFET to permit a low component-count buck topology.
The AL1665/AL1666/AL1666A high-performance single-stage flyback isolated or buck-boost non-isolated AC to DC constant current controllers keep high power factor and support analog/PWM dimming modes. The AL8116 is a flexible dimming signal interface controller that can convert the three different inputs of dimmer type, including 0 to 10V DC linear dimming, 0 to 100% duty cycle pulse width modulation (PWM) signal, and a simple resistive potentiometer to an output PWM signal.
For applications above 30W, a two-stage driver is typically preferred. While typical approaches to two-stage designs permit inherently high power factor with low THD, designers must handle other challenges, including greater complexity and increased physical size, relative to a single-stage design.
Figure 2 proposes a two-stage design from Diodes that includes the AL1783 3-channel dimmable driver that delivers LED output current of up to 250mA per channel with an accuracy greater than ±4%. The AL8866 is a multi-mode constant current DC switching LED controller that supports buck-boost, boost, buck, and SEPIC isolated designs and drives an external MOSFET for high-power LED lighting applications. The AL8862 and AL8863 are 60V hysteresis buck LED driver and controller devices while the AL8891 is a 65V synchronous buck LED driver that provides hybrid analog and PWM dimming down to 0.01%. The AL6562A and AL1788 are AC/DC voltage controllers for primary side control. Both of these controllers offer high power factor (>0.9) and low THD (< 20%).
Here, the chipset approach streamlines the design. There are only three main components, resulting in low bill of materials (BOM) costs and compact circuit size.
Conclusion
Low-energy LED lighting, currently being adopted worldwide, is an important tool in the battle to combine sustainability with comfort and safety both indoors and outdoors. As building code requirements increasingly prioritise environmental performance for efficiency and energy savings, solutions such as Diodes’ chipset-based reference designs can help designers of industrial and commercial lighting products ensure an affordable BOM and a compact form factor, as well as accelerate time to market while exceeding the requirements of today’s most stringent building codes.
[1] www.alliedmarketresearch.com/industrial-commercial-led-lighting-market
