Efficiency and Connectivity
Exploiting the benefits of LED technology advances, Smart Lighting designs are adding more efficiency and intelligence to their devices. Analog IC vendors are keeping pace with LED drivers, development kits and other solutions.
Encompassing advances ranging from LED technology to IoT-based intelligent city lamp posts, Smart Lighting has become both a consumer electronics phenomenon and a smart city infrastructure challenge. System developers are considering energy savings, lighting controls, lighting sensors and IoT connectivity. Even LED lights for the automotive space are part of the Smart Lighting puzzle.
In lighting technology, the engineering issues encompass the entire “luminaire.” In the jargon of the lighting industry, a luminaire refers to the complete lighting unit, comprising one or more lamps—bulbs or tubes that emit light—as well as the socket and other parts that hold the lamps in place and the wiring that connect to power and reflecting sources that direct the light.
Over the past couple years, analog IC vendors, lighting solution specialists and even standards groups have been rolling out Smart Lighting solutions—both individually and in partnerships with one another.
LEDs AND SMART STREETLAMPS
At the forefront of Smart Lighting, in the context of smart cites, is the smart streetlamp. A report from the IoT analyst firm Berg Insight says that the installed base of smart street lights was 10.4 million units worldwide at the end of 2018. Growing at a compound annual growth rate (CAGR) of 24.5%, the installed base will reach 31.2 million units in 2023 (Figure 1). Europe is the leading smart street lighting market accounting for nearly 40% of the installed base says the report. Characterized by a higher degree of utility ownership of street lighting assets, the North American market has seen a more scattered uptake of smart street lighting but is nevertheless home to several of the world’s largest deployments. North America accounted for around 30%.
Providing a solution for LED streetlamp development, STMicroelectronics (ST) offers its EVL150W-HVSL LED-driver evaluation board and reference design. It is designed to accelerate the creation of LED streetlamps and other medium- to high-power lighting applications, and integrates features that ensure high performance and save bill-of-materials (BOM) costs (Figure 2).
As a 150W, 1A mains-input driver, the EVL150W-HVSL achieves full-load efficiency above 91% to maximize utility-cost savings for streetlamp operators. Electromagnetic interference (EMI) is within relevant EN55022 limits and input-current total harmonic distortion (THD) less than 10% at 230V AC from 30% to 100% of full load meets European EN61000-3-2 Class-C and Japanese JEITA-MITI Class-C norms for lighting equipment. The EVL150W-HVSL has a universal 90V-264V AC input and meets IEC 60950-1 and 62368-1 safety standards. The board supports analog, resistive and PWM (pulse width modulation) dimming modes, with flicker-free PWM dimming down to 1% at any frequency.
In addition, the board contains ST’s STCMB1 integrated power-factor correction (PFC) controller and high-voltage resonant half-bridge controller working with the LCC topology, which can deliver constant current independently of the output voltage and is therefore well suited to LED driving. Proprietary features of this device, such as the constant on-time PFC control, timeshift control of the resonant half-bridge and hard-switching prevention, save external components and ensure superior dynamic performance and ripple rejection.
The PFC and half bridge are synchronized when in burst mode, reducing light-load input power consumption to less than 0.5W. The compact 20-pin STCMB1 also integrates 800V startup circuitry as well as X-capacitor discharge and power-sequencing circuitry. No auxiliary power supply is needed. Lights powered by the EVL150W-HVSL benefit from comprehensive protection including output-overload, output short-circuit, and open-loop protection, each with auto-restart capability to satisfy street-lighting application requirements.
Smart Lighting involves an intersection of multiple facets of the lighting industry. Therefore, it’s no surprise to see multiple consortiums collaborating on Smart Lighting standards and certifications.
Zhaga is a global association of lighting companies that is standardizing interfaces of components of LED luminaires, including LED light engines, LED modules, LED arrays, holders, electronic control gear (LED drivers) and connectivity fit systems. Meanwhile, The DALI Alliance is an open, global consortium of lighting companies that drives the growth of lighting-control solutions based on internationally-standardized Digital Addressable Lighting Interface (DALI) technology.
In June, the two groups announced that the world’s first Zhaga-D4i RF Node, which allows control and monitoring of public lighting, was certified by the Zhaga Consortium and the DALI Alliance.
This Tridonic controller enables Zhaga-D4i certified luminaries to connect with IoT/Smart City platforms for intelligent use cases and energy savings (Figure 3). The ecosystem of Zhaga-D4i certified products for road lighting now includes DALI-based control devices with Zhaga connectors, as well as luminaires.
The joint Zhaga-D4i certification program from the DALI Alliance and the Zhaga Consortium has already qualified 100 product families of Zhaga Book 18 outdoor luminaires with Zhaga receptacles and D4i components. “Up to now, it has been very difficult to match the long lifetime of outdoor lighting infrastructure with the dynamic developments in digital communication and sensor technology,” said Dee Denteneer, Secretary General of the Zhaga Consortium. “This has led to an underutilization of the lighting infrastructure for smart applications. Now, luminaires can be upgraded in the field and thereby keep pace with rapid developments in digital networking technology.”
The ecosystem of Zhaga-D4i certified products for road lighting consists of Zhaga-D4i luminaires with a powered Zhaga receptacle, which can accommodate a D4i-certified sensor or communication node with a corresponding Zhaga baseplate. Zhaga-D4i luminaires use LED drivers meeting the D4i requirements, including the availability of DALI luminaire, energy and diagnostics data. D4i enables DALI in intelligent, IoT-ready luminaires. By taking care of control, power and mechanical requirements, D4i and Zhaga Book 18 make it much easier to mount sensors and communication devices on luminaires.
SMART LIGHTING SOLUTION FOR IoT
IoT connectivity is a key piece of today’s Smart Lighting design efforts. Feeding those needs, Qorvo partnered with lighting company Leedarson to create a family of smart home lighting products that operate concurrently with Zigbee 3.0 and Bluetooth Low Energy (BLE) 5.0 protocols. The first of these solutions was a Leedarson smart light bulb and light switch that integrates Qorvo’s QPG6095 SoC, a multi-protocol/multichannel smart home communications controller for ultra-low-power wireless applications.
Qorvo says its QPG6095 SoC advances the state of smart home networking by supporting different connectivity standards, including IEEE 802.15.4, Zigbee 3.0, Thread and BLE 5.0, for sensors and actuators throughout the home. This enables easy integration of multi-protocol use cases in IoT smart home devices, supporting simultaneous interactions with a BLE-enabled smartphone and the Zigbee network. The QPG6095 is BLE 5.0 and Zigbee 3.0 platform and product certified, and Zigbee certified for Touchlink, for lighting applications. It also provides Green Power energy efficiency, extended range and battery life, and robust interference mitigation.
Leedarson says that Qorvo’s QPG6095 enabled it to develop solutions that support multiple IoT protocols, enabling new use cases and applications in the lighting market. Its Green Power feature enables coin cell battery operation, offering a longer battery life of 10 years for light switches and smart home sensors. This greatly reduces cost and time spent by users replacing batteries.
The QPG6095 features a radio transceiver, integrated real-time Medium Access Control and BLE controller, integrated Arm Cortex-M4 microcontroller (MCU), RAM and flash memory, security engine, event scheduler and an extensive set of peripherals including analog signal monitors and comparators. The QPG6095 integrated RF baluns and filters reduce the product’s RF design complexity enabling very low-cost single layer applications using simple PCB antennas requiring no shielding and a minimum number of external components. The flash memory allows for software upgrade over the air.
The QPG6095 is capable of running the full stack and applications for Zigbee 3.0, Thread and BLE devices, including the OpenThread open-source implementation of the Thread networking protocols. Integrated multistack, multi-protocol support enables stacks to operate concurrently, and on different channels, enabling innovative new applications combining Zigbee, Thread and BLE in one product.
The QPG6095 Development Kit enables complete product emulation (Figure 4). It has successfully passed Zigbee 3.0 Color Dimmable Light and Door/Window sensor Combined Interface product certifications. OpenThread running on the QPG6095 has passed Thread specification compliance and interoperability testing. These certifications reduce risk of implementation and time to market for products integrating the QPG6095.
SMART LED LIGHT BULBS
Focusing on the consumer space, earlier this year Silicon Labs collaborated with Yeelight, a Smart Lighting company, on a smart LED light bulb to support Seamless Setup in the Google Home app. The Yeelight Smart LED Bulb M2 multi-color light bulb is designed with Silicon Labs’ Bluetooth BG21 SoC (Figure 5). The SoC enables reliable wireless connectivity and allows users to connect and control smart home devices in the Google Home app without requiring other applications.
Silicon Labs says that Yeelight is one of the first brands to deliver a smart lighting integration with Google Seamless. The Yeelight M2 Bulb allows for multi-colored effects, adjustable color temperature, and increased luminance of up to 1000 lumens (lm)—bright enough for daily illumination. Seamless Setup allows users to quickly and easily set up smart home devices in the Google Home app in just a few steps. No additional apps are required, and the Google Nest device can act as a hub to connect smart home devices to the web.
Connected by Silicon Labs’ BG21 solution, the Yeelight M2 bulb offers off-premise access to Google Assistant-enabled devices, as well as higher reliability. Users can ask Google to turn on/off, dim or change colors of the lights simply by using their voice. The M2 pairs directly with Google Assistant, resulting in an improved response time from Google Assistant-enabled speakers or displays. Users are also able to set up Google Assistant Routines in the Google Home app to automatically control lighting in certain settings using simple voice commands.
Smart Lighting is all about adding intelligence to connected lighting devices. Along those lines, in June ON Semiconductor announced two new devices designed to enhance the performance of connected lighting systems. The NCL31000 and the NCL31001 LED drivers allow manufacturers to develop LED luminaires with light-based positioning technology and visible light communication (Figure 6). By adding data intelligence and accurate positioning (up to 30cm), these solutions will enhance lighting in a variety of spaces including supermarkets, warehouses, hospitals and airports, says ON Semiconductor.
The NCL31000 is part of an extensive LED driver family and is designed specifically for luminaire applications. At the heart of the device is a highly energy efficient buck LED driver that supports both high-bandwidth analog dimming and PWM dimming down to zero current. The driver includes an integrated 3V3 fixed DC-DC converter and a further adjustable DC-DC (2.5V to 24V), which can be used to power system components such as sensing devices and the MCU. Integrating these power solutions in the driver dramatically simplifies system design while boosting efficiency.
The accurate linear dimming enables visible light communication (VLC), allowing for the development of indoor light-based positioning systems that can be safely implemented in many locations where RF-based solutions cannot be used. Example systems include hazardous spaces such as mines or RF sensitive areas such as in hospitals or on-board aircrafts. The ability to dim to true dark with an accuracy of 0.1% ensures that there is no ghost light at the lowest dim settings.
Highly accurate diagnostics further reduce system complexity by integrating a 10-bit analog-to-digital converter (ADC). The ADC measures system voltages, currents and temperature to monitor LED and overall system efficiency, and detect any anomalies. A serial (I2C / SPI) interface makes all diagnostic data available to an external MCU that can monitor and control the intelligent lighting system. The architecture of the NCL31000 ensures excellent EMI performance. In tests it has been shown to be greater than 14dB below the requirements of CISPR15 / EN55015.
ON Semiconductor announced the availability of the NCL31001 as a companion driver to the NCL31000. The addition of the NCL31001 creates a solution that supports multi-string lighting applications, including those with color control. The NCL31001 offers the same features as the NCL31000 except for the DC-DC converters to avoid unnecessary duplication. The new LED drivers are part of a comprehensive portfolio of connected lighting solutions from ON Semiconductor including the Connected Lighting Platform, which features multiple connectivity options—BLE and Power over Ethernet (PoE)—for smart LED control.
FLYBACK LED CONTROLLERS
LED driver technology continues to advance, serving the needs of Smart Lighting device developers. In July, Infineon Technologies introduced the ICL8800, ICL8810 and ICL8820 single-stage flyback LED controllers for constant output voltages (Figure 7). Cost-effective dimmable and intelligent LED systems are expected to increase the market share disproportionately in the coming years, says the company. With their unique features, the ICs meet the necessary performance requirements for LED lighting applications, such as LED drivers and luminaires up to 125W, Smart Lighting, and emergency luminaire. Outside this market segment, adapters and chargers, flat TVs, all-in-one PCs and monitors up to 125W profit from the ICL88xx family.
All three variants offer benchmarking performance for power factor correction and THD at full-load and low-load conditions, thus enabling platform design and window drivers. They are optimized as secondary-side regulated (SSR) constant voltage (CV) output flyback controllers and are also well suited for primary-side regulation (PSR). To achieve optimum efficiency and low electromagnetic EMI without compromising light quality, they are featuring critical conduction mode (CCM) and quasi-resonant mode (QRM) with smart valley hopping.
The ICL88xx family offers an external start-up circuit control signal for more flexibility and a cost-optimized bottom-up platform design for many applications. It has a comprehensive set of protection features, including a power limitation and secondary side over-voltage protection. In addition, the devices require a minimum number of external components, leading to outstanding cost-effectiveness compared to existing solutions. The gate driver current enables designs up to 125W with state-of-the-art MOSFETs. The system performance and efficiency can be further optimized using Infineon’s CoolMOS P7 power MOSFETs.
ICL8800 is the basic variant providing all of the above features. ICL8810 is an advanced variant with an integrated burst mode that allows a very low standby power consumption of less than 100mW and flicker-free deep dimming down to 0.1%. This feature makes ICL8810 ideally suited for smart lighting applications in connection with microcontrollers. Finally, ICL8820 is the fully-featured variant, additionally equipped with an integrated DC-input jitter function. The latter improves EMI performance and supports the fulfillment of EMI requirements in DC operation. ICL8820 eases EMI certification in the design of emergency lighting LED driver applications without additional circuitry, minimizing cost and effort. ICL8800, ICL8810 and ICL8820 single-stage flyback LED controller variants are available in PG-DSO-8 packages and can be ordered now.
ALL-LED LIGHTING IN CARS
According to Analog Devices (ADI), as the automotive industry accelerates its transition to all-LED lighting, designers face new challenges in improving efficiency, simplifying designs and reducing system costs, while passing strict EMI requirements. Traditionally, designers had to employ multiple components in their systems in order to pass EMI specifications. To achieve performance gains, they would often have to compromise on space and system efficiency while also addressing thermal issues and high costs.
To address those challenges, in July ADI (formerly Maxim Integrated) announced the MAX25610A and MAX25610B LED drivers. The synchronous buck, buck-boost LED drivers/DC-DC converters offer a complete solution that features high EMI performance, without compromising on efficiency and size (Figure 8). These ICs drive up to eight HBLEDs directly from the automotive battery and integrate many external components to save on BOM costs and space, making them excellent solutions for automotive lighting systems as well as industrial and commercial lighting applications, says ADI.
The MAX25610A/B LED drivers combine solution size, high efficiency and EMI performance into a single package. These ICs meet the wide range of voltage requirements and can decrease design complexity, lower BOM costs and improve power efficiency. They offer a wide input voltage range from 5V to 36V in buck-boost LED driver applications with up to 90% efficiency in buck-boost mode.
These LED drivers have an internal current sense option and integrated high- and low-side switching MOSFETs to reduce solution space and cost. They offer programmable on-chip PWM dimming, which allows for fine dimming control without having to use a separate microcontroller. Additionally, the MAX25610B features a 2.2MHz switching frequency option allowing for an even more compact solution. The device integrates two MOSFETs (high- and low-side switching) and is available in a 5mm × 5mm TQFN package.
INTERIOR CAR LIGHTING WITH LED TECHNOLOGY
Automotive interior lighting is an interesting subset of the Smart Lighting world. Serving those needs, Melexis provides the MLX81116, a multichannel RGB-LED driver. The MLX81116 supports the MeLiBu high speed communication IP to enable intelligent animated automotive lighting concepts (Figure 9). The technology is already being leveraged by leading global manufacturers to enhance the safety features of their latest models, says the company.
An increasing number of car manufacturers are looking to introduce animated lighting into the cabin, as a way of conveying important driver-assistance prompts and vehicle-status information. Current design thinking envisions using an RGB-LED lightbar to communicate to the driver, through color coding, color changing and blinking sequences, says Melexis.
There are engineering challenges to maintaining consistent color across all the LEDs in the lightbar, and ensuring they all change together, at the same time. The MLX81116 addresses this through its unique high-speed communication interface IP, MeLiBu. The MeLiBu controls all individual LEDs separately in the lightbar to produce the lighting effects commanded by the vehicle. The intelligent RGB-LED controller also provides real-time compensation of any LED color drift caused by environmental changes.
The MeLiBu communication interface leverages the proven CAN-FD physical layer, which ensures robustness, reliability and high speed (up to 2Mb)—features that are key requirements for today’s car manufacturers. Support for dedicated optical parameters allows color-mixing accuracy with a delta UV of 1% to ensure no distinguishable differences between individual LEDs in the lightbar. In addition, intelligent high resolution for temperature-related color drift helps maintain a consistent and non-distracting user experience under all operating conditions.
The MLX81116 driver IC has an extremely wide dimming range that allows optimal brightness adjustment for daytime and night driving. Meeting automotive ISO 26262 functional safety requirements up to safety integrity level B (ASIL B), the MLX81116 also features low EMI emission and high immunity, thanks to the use of the CAN-FD physical layer, which eases compliance with applicable EMC regulations.
AUTOMOTIVE SEQUENTIAL LED LIGHTING
Another automotive LED solution is the MAX25605 sequential LED controller from ADI. The device enables easy and cost-effective addition of automotive sequential LED lighting features, says the company (Figure 10). It saves development time and reduces design complexity by eliminating the need for an MCU or software.
In addition, the MAX25605 reduces design space by up to 50% and slashes BOM costs by up to 25% compared to the closest competing solution, according to ADI.
Sequential LED lighting features used to be exclusive to high-end vehicle model segments due to complexity in design and cost constraints. The MAX25605 simplifies designs, allowing more mid-range and economy models to adopt their own animation signatures. It controls LED current up to 750mA versus 100mA for competing solutions, thus providing more flexibility in the lighting design.
The MAX25605 integrates six switches, manages up to three LEDs per switch and can be daisy-chained up to 16 devices without the need for an MCU or software. With this comprehensive solution, designers can accurately program sequence timing, direction and linear or log dimming, while also easily detecting fault conditions. This component reduction cuts BOM costs and saves time and effort by eliminating the need for software.
Analog Devices | www.analog.com
Berg Insight | www.berginsight.com
The DALI Alliance | www.dali-alliance.org
Infineon Technologies | www.infineon.com
Melexis | www.melexis.com
Maxim Integrated | www.maximintegrated.com
ON Semiconductor | www.onsemi.com
Qorvo | www.qorvo.com
Renesas Electronics | www.renesas.com
Silicon Labs | www.silabs.com
STMicroelectronics | www.st.com
Zhaga | www.zhagastandard.org
PUBLISHED IN CIRCUIT CELLAR MAGAZINE • NOVEMBER 2021 #376 – Get a PDF of the issueSponsor this Article
Jeff served as Editor-in-Chief for both LinuxGizmos.com and its sister publication, Circuit Cellar magazine 6/2017—3/2022. In nearly three decades of covering the embedded electronics and computing industry, Jeff has also held senior editorial positions at EE Times, Computer Design, Electronic Design, Embedded Systems Development, and COTS Journal. His knowledge spans a broad range of electronics and computing topics, including CPUs, MCUs, memory, storage, graphics, power supplies, software development, and real-time OSes.