With LED lights getting more advanced in technology, there is a need for maximum integration with LED drivers to make these more cost effective and compact in size
By EB Bureau
Wednesday, October 10, 2012: As the lighting industry is moving towards energy efficient solutions like light emitting diodes (LEDs), many key players are launching LED products for the Indian market. According to Frost & Sullivan, the overall Indian LED lighting market is expected to reach US$ 399.2 million by 2015, at an estimated annual growth rate of 41.5 per cent till 2014. This, in turn, has given a boost to the market for components like LED drivers, which have a tremendous potential to grow in various sectors such as general lighting, automotive lighting and industrial lighting.
An LED driver is an essential part of LED lighting, and it controls the amount of current and voltage supplied to the LEDs. With an increasing market size, LED driver technology is also getting more advanced. Most LED drivers are used in backlights for LCD displays, such as in mobile phones and TVs. LED drivers are also used in DVD and MP3 players.
What’s the latest?
With LED lights getting more advanced with respect to technology, there is a need for maximum integration with LED drivers to make these more cost effective and compact in size. Customers look for facilities like power factor correction (PFC), triodes for alternating current (TRIAC), dimming, etc.
There are many different types of LED drivers—white LED drivers, LED PWM drivers, RGB LED drivers, constant current LED drivers, and 7 segment LED drivers. A white LED driver provides white light for backlighting and offers very low noise, with efficiencies as high as 90 per cent. An LED PWM driver can be programmed through an I2C compatible interface for applications that require colour, pattern and intensity programmability control. In an RGB LED driver, all the functions are controlled by software through an SPI interface and internal registers. A constant current LED driver features internal circuitry that monitors the loop current of each LED and automatically adjusts the DC voltage generated to the minimum value required to produce the highest forward voltage. A 7 segment LED driver uses a combinational logic circuit, which accepts a 4-bit BCD input and generates seven output signals to control seven individual display segments.
The dimmable feature: Today, LED drivers come with a dimming capability, which can dim the LED light output from 100 per cent to zero per cent. During dimming, LEDs still operate at the same voltage and current as during full light output. In addition, lamp life is not affected by dimming, as is sometimes the case with frequently dimmed fluorescent lighting. These LED drivers come in a wide power range from 2 W to 150 W. Highly efficient DC input LED drivers in the buck and buck boost topology are also available.
ON Semiconductor has introduced two new LED drivers to help designers optimise their solutions for automotive, industrial and general lighting applications. The new power factor corrected offline LED driver (NCL30051) when combined with the new NCL30160—a dimmable constant current step-down LED driver—provides a good solution for high brightness LED driver applications where space is limited and high efficiency is important. The NCL30051 is capable of delivering a constant voltage to a step down DC-DC converter/LED driver. The device, which combines a critical conduction
mode (CrM), a PFC controller and a half bridge resonant controller with a built-in 600 volt (V) driver, is optimised for offline power supply applications. NCL30160, a switching regulator for high power LEDs, takes the constant voltage delivered by the NCL30051 enabled power supply and steps down the voltage to provide a constant current across the LED string. Solutions with up to 98 per cent efficiency are achieved by utilising the low 55 milliohm (mΩ) internal MOSFET and the ability to operate at a 100 per cent duty cycle.
Buck boost LED drivers: RECOM Asia Pte Ltd has just launched its RBD LED drivers, which are highly efficient 3-20 W DC/DC constant current LED drivers in a buck boost topology. These LED drivers allow the user to drive high power LEDs even from a battery source, making them a perfect solution for solar applications.
The RECOM RBD 12 series, which the company claims to be the only buck boost module solution in the market, is ideal for solar and battery driven LED systems for transport and traffic applications like e-cars, streetlights, traffic signals, etc, as well as for use in marine and air traffic lighting.
The latest that Texas Instruments (TI) offers is a broad range of LED drivers for solar based LED lighting solutions (TPS61165, LM3401, and TPS40211). TI also offers the latest LED drivers for LED bulbs, tube lights, downlighters (TPS92310/1), and for high wattage products like TPS92210, TPS92020, LM3464.
TPS92210 is a natural power factor correction (PFC) lighting driver controller with advanced energy features to provide high efficiency control for LED lighting applications. It offers a predictable maximum power threshold and a timed response to an overload, allowing safe handling of surge power requirements. TPS92020 is a high performance resonant switching LED driver controller. It is designed for use in higher power LED lighting systems and uses resonant switching in an LLC topology to achieve a very high efficiency compared to traditional half bridge converters. LM3464/64A is a 4 channel high voltage current regulator that provides a simple solution for LED lighting applications. It provides four individual current regulator channels and works in conjunction with external N-channel MOSFETs and sense resistors to give accurate driving current for every LED string.
Early this year, Linear Technology launched LT3791, a synchronous buck boost DC-DC LED driver and voltage controller, which can deliver over 100 W of LED power. Its 4.7 V to 60 V input voltage range makes it ideal for a wide variety of applications, including automotive, industrial and architectural lighting. Similarly, its output voltage can be set from 0 V to 60 V, enabling the LT3791 to drive a wide range of LEDs in a single string. Its internal 4-switch buck boost controller operates from input voltages above, below or equal to the output voltage—making it ideal for applications in the automotive sector, where the input voltage can vary dramatically during stopping or starting, cold cranking and load dumping. LT3791’s unique design utilises three control loops to monitor input current, LED current and output voltage to deliver optimal performance and reliability.
Power Integrations has recently launched the DER-323, a reference design for an 18W, 88 per cent efficient, non-isolated A19 LED driver based on LNK460VG, a low profile IC from the company’s LinkSwitch PL family. The design is suitable
for a 100 W incandescent bulb replacement and is optimised for low line (90 VAC to 135 VAC) operation. The DER-323 utilises a simple buck boost converter topology that fits easily inside the A19 bulb. The design is EN61000-3-2 (C) compliant and has a high power factor of over 0.98, easily satisfying commercial and consumer compliance requirements.
Colour changing: LED drivers can also be used to enable colour changing or sequencing. This can be achieved by dimming a mix of coloured LEDs in an array to change colours. Another option is that the driver can work with a colour sequencer, which receives the 10 V or 24 V LED driver output and converts it into 3-channel output—usually red, blue and green—that can be mixed to create a wide, dynamic range of colours.
Resistant to voltage fluctuations: Today, LED drivers are more flexible in handling voltage fluctuations and can
even resist these fluctuations. GlacialTech’s new series of higher input-output voltage LED drivers gives more flexibility to the LED lighting designers. With this new range of LED drivers, designers can use as many LEDs in a series as the design requires. Even if the output voltage ranges from 100 V to 425 V and the input voltage ranges from 90 V to 425 V, these LED drivers can control any voltage fluctuation and can resist it. These drivers are very compact in size, which makes LED lighting installations even easier, when compared to the bulkier drivers. Earlier, LED drivers lacked flexibility, but now they are being designed according to the needs of the Indian market as the voltage conditions in India are very tough.
Flyback and LLC topology: GlacialTech has also recently launched an LED driver in the flyback topology, which is comparatively compact and cheap. The flyback driver can be used in both AC-DC and DC-DC conversion with galvanic isolation between input and output. These drivers use the flyback converter, which is a buck boost converter with an inductor split to form a transformer. This helps to multiply voltage ratios with an additional advantage of isolation.
Now LED drivers come with line level control (LLC) resonant topology, which gives high efficiency but is also comparatively higher in cost. LLC resonant topology allows zero voltage switching of the main switches, thereby lowering energy loss and boosting efficiency. With LLC resonant converters, an efficiency of 93-96 per cent can be achieved.
High power LED drivers: Early this year, Mornsun launched a new LED driver series, the KC24H-R, which is a high power step down constant current LED driver source. Its key features include high efficiency of up to 95 per cent, a wide input range of 5.5-46 VDC, low ripple and noise (<100mV), PWM dimming and analogue dimming, continuous short circuit protection, large capacitive loads (1000μF), etc. KC24H-R can be used in backlights and in 12 V, 24 V and 36 V automotive lighting, landscape lighting, special lighting controls, commercial lighting, street lighting, home lighting, etc.
Compact LED drivers: Recently, GlacialTech launched a series of compact LED drivers with high power efficiency—GP-LS50PH-142C, GP-LS70PH-100C, GP-LS100PH-142C and GP-LS100PH-71C. With the compact dimensions of 177×57×37 mm (LxWxH), these four LED drivers make LED lighting installations even easier compared to bulkier drivers. Even while being small, this series has a high power conversion efficiency rate of 91 per cent ensuring low power consumption. These four fully integrated AC/DC LED driver micro-modules incorporate the active PFC circuitry to deliver up to 99.4 W of power to the LED with a high power factor. With the current trend for higher output voltage requirements, due to more and more applications using LEDs in a series, this series provides output voltage up to 142 V DC. GlacialTech’s R&D team has developed the LED driver to eliminate the need for an electronic transformer, aiming to provide more energy saving and environmentally friendly LED products.
AC/DC constant current driver: Texas Instruments has also launched TPS92310 AC/DC constant current driver this year. This new driver with PFC reduces costs and shrinks to fit into high power LED retrofit bulbs, including A19, PAR30/38 and GU10. Its key features are: the AC input voltage supports all common line voltages (100V, 120V, 230V, 240V and 277V); true primary side sensing and regulation provides accurate LED current regulation, eliminating the need for the opto-coupler, secondary error amplifier and associated passive components; adaptive constant-on-time (COT) provides inherent PFC with no external components; and PFC reduces the EMI signature to ensure regulatory approval.
Smart digital control (SDC) technology: Recently, NXP Semiconductors introduced SSL2110, the first in a new family of GreenChip LED driver ICs featuring smart digital control (SDC) technology. Incorporating intelligent digital control within a compact analogue design, SSL21101 delivers better, more accurate system performance while reducing the bill of materials, providing a good solution for non-dimmable, high performance LED applications up to 15 W.
MOSFET technology: Fairchild Semiconductor has expanded its LED lighting driver solutions portfolio to include optimised low power offerings—FLS0116, FLS3217 and FLS3247. These come with integrated MOSFETs and PFCs. They are optimally designed for low power LED applications. With the addition of the integrated power MOSFET, these devices help to minimise board space and the overall component count while decreasing design time. Equipped with cycle by cycle current limiting and integrated protection features such as over temperature protection (OTP) and under voltage lockout (UVLO), these devices help to significantly improve LED lamp system reliability.
Tips to choose appropriate LED drivers
Customers need to know a few important things before choosing an LED driver. They should check the input/output voltage, current flowing through the LEDs, wattage, whether the driver has the dimming feature, whether it is PFC or non-PFC based, and its efficiency.
Selecting LED drivers requires an analysis of performance specifications and special features. Therefore, a buyer must take a close look at the data sheet of the product.
A very important factor to check is whether the product is tested to meet certain important certification standards like Underwriters Laboratories (UL), CE, Federal Communications Commission (FCC), Certified Performance Technologist (CPT), CB and IP67. These certifications are a must, since they assure that the drivers are well protected from water, dust and moisture, and are quality products.
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