Driver technology is the key to LED high efficiency, reliability and long life

　　Under the global trend of energy conservation and carbon reduction, LED lighting is highly anticipated. As the luminous efficiency of high-brightness LEDs has continued to improve in recent years, the unit cost has also declined, prompting the application of high-brightness LEDs to no longer be limited to small and medium-sized electronic products, or larger-sized backlight applications such as notebook computers, monitors, and TVs, and LED display billboards. It has now begun to replace traditional incandescent lamps and other lighting products. LED has undoubtedly become an important light source for next-generation general lighting.

　　Regarding the market prospects of LED lighting , industry insiders pointed out that the global LED lighting output value is expected to grow to US$11 billion in 2012 and increase to US$19.2 billion in 2015, with a four-year compound annual growth rate of nearly 20%. Industry insiders analyzed that consumer electronics products were hit by the poor economic situation, and the substitution effect of new display technologies such as AMOLED gradually expanded, making the LED backlight market that relies on consumer electronics products face a bottleneck. On the other hand, even if LED lighting grows slowly, the market prospects are established and it is expected to bring new hope to the LED industry within five years.

　　In particular, the policies of governments around the world to ban incandescent lamps will begin to take effect in 2012. More than two-thirds of the world's regions will begin to ban incandescent lamps or high-wattage incandescent lamps. The post-incandescent lamp era has arrived, and the importance of LED in lighting applications has been highlighted. The next four years will be the last critical period for LED to layout the lighting market. In terms of application markets, outdoor lighting will be the priority, followed by commercial lighting, industrial lighting, and automotive lighting, and finally penetrate into the home market.

　　High efficiency, reliability and long life, the driver is the key

　　Among all LED lighting application markets, the market for replacing lamp tubes is the most popular at this stage. The success factors of this market include high efficiency, sufficient working reliability and life of the driving power supply, etc. For these conditions, LED drivers play an extremely important role. In response to this, Pan Dawei, vice president of sales for IR Asia Pacific, pointed out that the solid-state lighting industry is developing rapidly, so the demand for low-cost driver electronic components is increasing day by day to supply constant current output for high-brightness and high-power LEDs.

　　To meet the above needs, IR recently launched a new high-voltage buck regulator control IC, IRS2980, for LED bulb replacement, LED tube lighting and other non-isolated LED driver applications. IRS2980 is the company's first product in the high-voltage LED driver IC series, rated at 600V, and uses hysteresis average current mode control to achieve precise current regulation. The new LED buck driver includes a low-side MOSFET driver with a high-voltage internal regulator and high-side current sensing. The converter is compatible with electronic pulse width modulation dimming, and the current control covers 0 to 100%.

　　Pan Dawei further pointed out that compared with other solutions designed for non-isolated LED driver applications, the new IRS2980 can improve performance at a lower system cost. The IRS2980, which uses SO-8 packaging, provides top-level electrical overstress protection and higher field reliability by integrating IR's advanced high-voltage IC process with the latest high-voltage level shifting and terminal technology. 　　Digital power control method solves many problems

　　Basically, the drivers of LED replacement lamps are mostly implemented by buck-type switching regulators. ROHM Electronics pointed out that in order to make LEDs light up under fixed brightness conditions, it is necessary to install LED driver ICs that can perform constant current control. Generally speaking, buck-type switching regulators are usually used. This is because the traditional method will cause excessive changes in input voltage/output voltage, and depending on the application conditions, it may be necessary to redesign the power module.

　　When the input voltage changes too much, the frequency of the AC voltage (after full-wave rectification: 100Hz-120Hz) will cause ripples in the input voltage. At this time, the brightness of the LED will become unstable. If you want to stabilize the input voltage, you must add some ingenuity to the design of the power module. When the input voltage changes more, you must change the constant of the external parts according to the output voltage of the light source (the number of LEDs), which results in an increase in the style of the power module and a waste of design time.

　　In response to the above problems, the BD555AKFV developed by Rohm uses digital power control method. It does not require the addition of external parts. It can solve the above problems by detecting the coil current. After using the digital power control method, the goal of controlling the average value of the LED current can be achieved regardless of the input/output voltage value. This method is to sample the coil current (A/D conversion) and digitize it, and then calculate the peak current value based on the sampled data so that the average current of the LED current can achieve the goal of stability. Then, the calculation result is D/A converted and fed back to the comparator used to detect the peak current.

　　More cost-effective way to curb

　　In addition to foreign companies, Taiwan-based Holtek Semiconductor has also launched universal isolated buck LED lighting driver control ICs - HT7L2102 and HT7L2103 for the LED lighting market. Both drivers support complete LED protection functions. Holtek has also added a Frequency Jitter function specifically for EMI suppression, which can reduce EMI by 5-8dB and save EMI costs.

　　In addition, in the face of diverse LED load conditions and serial and parallel numbers, the HT7L2102 and HT7L2103 have built-in GreenMode power saving mode, allowing users to drive different serial and parallel numbers of LED loads with only one circuit design without reducing conversion efficiency. In terms of dimming support, both have built-in support for PWM dimming interface. The HT7L2102 is designed for T8/T9 tube applications, while the HT7L2103 is designed for E26/E27 bulb applications. Holtek Semiconductor emphasizes that due to the small space of the E26/E27 bulb structure, the HT7L2103 integrates more functions, allowing isolated AC-DC power drive functions to be achieved in a limited space.

　　High-quality LED drivers drive the LED lighting market

　　According to forecasts, the LED driver IC market revenue will increase from nearly US$2 billion in 2010 to nearly US$3.5 billion in 2015. The lighting LED driver IC market growth rate is expected to reach 40% between 2010 and 2015.

　　Since LED driver ICs are responsible for controlling the light quality of LEDs in electronic products, the quality and stability of the chip are very important. In comparison, international manufacturers have better design capabilities, higher brand awareness and quality assurance, so they still have a larger share in the market. However, it is worth noting that in recent years, Taiwan's LED driver IC companies have actively invested in the field of LED replacement lamps, and also provided the market with options other than foreign companies.

　　In general, LED light sources are low-voltage, high-current driven devices, and their luminous intensity is determined by the current flowing through the LED. Excessive current will cause LED light attenuation, and too little current will affect the luminous intensity of the LED. Therefore, the LED driver needs to provide a constant current power supply to ensure the safety of high-power LED use while achieving the ideal luminous intensity. In the field of LED lighting, in order to reflect the energy-saving and long life characteristics of LED lamps, it is very important to correctly select the LED driver IC. Only by choosing a good match of the driver IC can the advantages of LED lighting be highlighted, thereby promoting the accelerated popularization of LED lighting.