ON Semiconductor’s energy-efficient and smarter LED driver solutions that match the general lighting trend

Electricity for lighting is an important source of global energy consumption. According to calculations, China’s electricity consumption for lighting accounts for about 12% of the total electricity consumption of the whole society. Among various lighting fixtures, incandescent lamps with a long history but low energy efficiency are still widely used. If the use of low-energy-efficiency light sources is restricted, and more energy-efficient and environmentally friendly light sources are vigorously promoted and applied, it will be conducive to energy saving.

Therefore, many countries in the world, including China, have formulated policies to phase out incandescent light bulbs. For example, China plans to phase out all incandescent bulbs for general lighting above 60W in 2015. Fluorescent lamps and compact fluorescent lamps (CFL) have higher energy efficiency than incandescent lamps and have been used in the market for many years. However, fluorescent lamps contain highly toxic mercury, which has caused more and more environmental concerns.

In comparison, the performance of LEDs in various aspects such as luminous efficiency has been continuously improved, as well as environmental protection and long-life characteristics, and more and more attention has been paid. In fact, LED downlights and modified bulbs already have higher energy efficiency than current lighting technologies such as incandescent lamps, halogen lamps or CFLs. In terms of cost, the study found that compared with 2010, the price of LED has accelerated (decreased by 13% to 24% per year), and it is expected to continue to decline in the next few years, which will help reduce the cost of LED bulbs and lamps.

Therefore, countries all over the world are optimistic about and promote the development of the LED lighting industry. For example, the National Development and Reform Commission of China issued the “semiconductor Lighting Energy-saving Industry Plan”, which plans to achieve a market share of more than 20% of LED functional lighting products by 2015 and an annual growth of about 30% in the output value of the LED lighting energy-saving industry. In 2015, the output value reached 450 billion yuan ( (Equivalent to 72 billion U.S. dollars).

LED general lighting applications and development prospects

In addition to being widely used in mobile devices, large and medium-sized liquid crystal Display (LCD) backlights and LED signs, LEDs are now increasingly used in LED automotive interior/exterior lighting, such as headlights, fog lights, and tail lights. , Parking lights, dashboard backlights, roof lights, reading lights and ambient lights, etc., as well as LED general lighting such as residential lighting and building decorative lighting.

LED general lighting applications cover a wide range of power, as low as 3 W to 15 W LED residential lighting, medium power such as 15 W to 75 W commercial and architectural decorative lighting, as high as 75 W to 250 W outdoor and infrastructure Lighting, typical lighting products include MR16/GU10 lamps, E27/A19 bulbs, ballasts, downlights, T8 tubes, street lights, etc.

Figure 1: Typical LED general lighting applications

LED general lighting applications have great development prospects. Among various LED general lighting fixtures, in the near future, the development momentum of LED bulbs (such as A19 LED bulbs) is amazing. According to statistics, global LED bulb shipments reached 735 million in 2012, and it is expected to grow to 1.225 billion in 2013; it is expected that the tipping point of the LED bulb market will be ushered in by 2014, when the price of LED bulbs will drop to $10. Below, shipments are expected to increase by about 85% compared to 2013, reaching 2.27 billion; and by 2015, shipments will further increase to 3.9 billion.

Energy-efficient drivers are the focus of LED general lighting

To maximize the energy-saving function of LED lighting, energy-efficient LED drivers are needed. Let’s take LED bulbs as an example. A typical LED bulb includes major components such as LED array, drive circuit, diffuser, heat sink, and spiral lamp holder, as shown in the left half of Figure 2. As far as the drive circuit is concerned, high-efficiency LED driver ICs are undoubtedly the focus. The right half of Figure 2 shows a typical LED bulb drive circuit, which uses a typical stand-alone LED driver.

Figure 2: a) Cross-sectional view of a typical LED bulb (left picture); b) a typical LED bulb drive circuit (right picture)

To take advantage of the high energy efficiency of LED general lighting, LED drivers have multiple challenges. The first is that energy efficiency is of the utmost importance. Take LED bulbs as an example. They have a fixed shape and limited heat dissipation. The use of high-efficiency LED drivers can help convert more electrical energy into light energy and help dissipate heat. Secondly, LED bulbs have limited space and require a larger heat sink area, especially for larger power bulbs. In addition, LEDs are changing rapidly, offering a variety of options, which poses a challenge to the choice of LED drivers. Due to the limited space of LED bulbs, it is necessary to reduce the size of the driving Electronic circuit to increase the remaining space and cooperate with heat dissipation. LED general lighting covers different power levels, so LED driver selection must be optimized to meet different lighting and power requirements. Due to factors such as safety regulations and LED selection, designers must also consider whether to use an isolated or non-isolated topology, which also affects the choice of LED drivers.

ON Semiconductor’s driver solution for LED general lighting

ON Semiconductor actively promotes energy-efficient innovations, including LED lighting, high-efficiency electronic innovations, involving many market segments of LED lighting, such as the aforementioned mobile devices, LCD backlights, LED signs, automobiles and general lighting. Among them, LED general lighting is now the focus of ON Semiconductor in the lighting market. In the LED general lighting market, ON Semiconductor’s strategy is to make full use of the company’s broad lineup of analog power ICs, discrete devices, and advanced micro-packages to provide unique and energy-efficient LED driver solutions.

ON Semiconductor provides LED driver solutions covering a wide range of power and different topologies. The drivers that ON Semiconductor can use for low-power LED general lighting applications include NCL30000, NCL30002, and NCL3008x series. Among them, NCL30000 is a single-stage power factor correction (PFC) LED driver that supports TRIAC dimming. It adopts a secondary-side controller and supports topologies such as flyback/buck/buck-boost. NCL30002 is also a single-stage power factor correction LED driver, supports step-down topology, and provides a current tolerance of ±3%. The NCL3008x series currently includes devices such as NCL30080, NCL30081, NCL30082 and NCL30083, which are newly launched high-efficiency quasi-resonant controllers for low-power LED lighting applications.

It is worth mentioning that the NCL3008x series adopts a novel control method called Primary Side Regulation (Primary Side Regulation) technology (also known as primary side control or primary side control), eliminating the need for secondary side control circuits and optocouplers, which can be accurate The ground conducts constant current and steady flow of the LED current from the primary side to help simplify PCB wiring, save board space, improve energy efficiency, and simplify safety analysis (see Figure 3, left). In addition, it also has many advantages such as high current stability accuracy, wide forward voltage drop (Vf) range, low electromagnetic interference (EMI) and integrated strong protection features. This series of devices provide a power factor of 0.8 to 0.9, which meets the requirements of the US “Energy Star” for the power factor of LED bulbs with a power greater than 5 W (PF>0.7).

Figure 3: a) NCL3008x novel primary-side control technology (left);
b) A19 bulb reference design based on NCL3008x (right)

ON Semiconductor has also developed a reference design for the compact A19 LED bulb based on NCL30082 (see the right side of Figure 2). This reference design is optimized for isolated flyback or non-isolated buck-boost topology and optimized for 10 W LED lighting applications. It uses valley-filled PFC to meet the requirement of “Energy Star” power factor higher than 0.7. The size target of PCB and components is 22 x 60 mm cylinder. Tests have shown that this reference design provides high energy efficiency, high power factor and high steady current accuracy.

In terms of medium-power and high-power LED lighting, ON Semiconductor also provides a rich product portfolio to meet the needs of customers for different applications. It includes both single-stage and combined controllers, as well as traditional two-stage (PFC section + DC-DC section) controllers, covering a wide power range from 15 W to 400 W, as shown in Figure 4.

Figure 4: ON Semiconductor’s driver for medium and high power LED general lighting

It can be seen from Figure 4 that in medium-power LED general lighting applications, single-segment power factor correction LED controllers such as NCL30000 and NCL30001 can be used; and in more powerful applications, NCL30051 and NCP1910 can be used. Energy-efficient combination controller. Take NCL30051 as an example. This is a power factor correction (PFC) and resonant half-bridge combination controller, optimized for offline LED lighting applications, and can provide constant voltage for step-down DC-DC converters/LED drivers. This device integrates a critical conduction mode (CrM) PFC controller and a half-bridge resonant controller, and a built-in 600 V driver. It is optimized for offline power applications and has all the necessary energy efficiency and small form factor designs. characteristic.

In addition to the above-mentioned single-stage scheme, designers can also choose the traditional two-stage (PFC section + DC-DC conversion section) scheme according to application requirements. Specifically, the available controllers for the PFC section include NCP1653, NCP1631, NCP1611/NCP1612, and NCP1608. Among them, NCP1611/2 is an enhanced high-efficiency PFC controller, based on the innovative current control frequency reverse (CCFF) architecture, when the PFC Inductor current exceeds the set value, the circuit usually works in critical conduction mode (CrM), and when When the current is lower than the preset value, the switching frequency is linearly reduced to about 20 kHz, and the current is zero at this time. The CCFF architecture also maximizes rated load working energy efficiency and light load energy efficiency, especially to minimize standby loss. Typical applications include flat-screen TVs, all-in-one computers and high-power power adapters, as well as LED lighting power supplies and drivers. Ballasts for dimming fluorescent lamps, etc.

In the DC-DC segment, the available devices include NCP1398, NCP1380, NCP1288 and NCL30105. In addition to these devices, ON Semiconductor is also developing more new products to meet the wider application needs of customers.

Advantages and development forecast of smart LED lighting

The emerging LED smart lighting is another focus of the LED general lighting market and an important development direction. The so-called “smart lighting” often combines smart dimmable LED drivers, wireless receivers, infrared receivers, ambient light sensors and passive infrared occupancy sensors.

Figure 5: Smart LED lighting integrates a variety of new functions

LED smart lighting will make LEDs easier to control and dimming. A variety of new functions will be enhanced in the LED intelligent lighting electronic circuit, such as combining occupancy sensors or ambient light sensors to coordinate dimming control and power saving. For example, the built-in occupancy sensor can be used to detect and determine whether there are people in the lighting area. It is generally used at the entrance or exit of the room, and can be used for safe lighting control and power saving. Most of these sensors use passive infrared (Ir) sensors, and other sensor options include ultrasonic and motion sensors.

In addition, silicon photoelectric sensors are used in electronic circuits, which can be used for different applications, such as measuring ambient light to collect sunlight, and sensing light output of lamps for LED lighting control. Typical ambient light sensors include ON Semiconductor NOA1211/2 with linear output and NOA1305 with dual output. The ambient light sensor cooperates with outdoor (dusk/dawn) and indoor (daylight harvesting) dimming, thus saving energy. Through closed-loop control of the LED light source, the specific light output under different temperature and time conditions can be adjusted. In addition, constant light output adjustment with LED output light feedback can save and extend the life of the driver.

Figure 6: ON Semiconductor NOA1211/2 and NOA1305 ambient light sensors can cooperate with LED smart lighting applications

Smart lighting will also be more flexible and can use low-energy wireless interfaces, such as IrDA infrared, Zigbee and Bluetooth low energy (Bluetooth LE), without the need to change switches or cables. But this requires wireless control standards such as Zigbee Light Link™ to be in place.

For LED driver ICs to cooperate with LED “smart” lighting, their design must be able to easily cooperate with analog and digital (ie, PWM) dimming. For example, ON Semiconductor’s NCL30082 LED controller with intelligent dimming interface can perform analog dimming, digital dimming, or simultaneous analog and digital dimming with a single control pin, providing 0 to 100% wide dimming Scope. This device is easy to connect to analog sensors or microcontrollers (MCU) general-purpose input/output ports (GPIO), which enhances design flexibility.

With the cooperation of these technologies, smart LED bulbs and LED modules are about to appear. By combining standardized wireless control technology, Ethernet and the Internet, people are expected to use smart phones to remotely control LED bulbs. The new solution can also solve thermal management, optics, and modularity/replacement issues. The commercial/industrial market segment is expected to lead the adoption of smart lighting solutions.

summary

Driven by the tide of environmental protection and various policies and regulations, LED lighting is developing rapidly. To make full use of the high energy efficiency advantages of LED general lighting, the use of energy efficient LED drivers is essential. This article introduces the challenges faced by general lighting LED drivers and the LED driver solutions that ON Semiconductor overcomes these challenges and applies to different LED general lighting applications. ON Semiconductor provides a broad lineup and complementary solutions, including LED drivers and related sensors with smart dimming, to help promote and welcome the advent of the LED smart lighting era.