Drive technology is the key to high reliability and long life of LED

In the global trend of energy saving and carbon reduction, LED lighting has been looking forward to, but with the recent high brightness LED light emitting efficiency increase, the unit cost will decline, the high brightness LED application is no longer confined to small and medium size electronic products, or notebook computer, display, television and other large size LED display backlighting applications and billboards. At present, more have begun to replace the traditional incandescent lamp and other lighting products, LED has undoubtedly become the important source of generation of general lighting.

In view of the LED lighting market prospects, the extension includes the industry research institute researcher Chen Kehua estimated that in 2012 the global LED lighting output is expected to grow to $11 billion in 2015, increased to $19 billion 200 million, four years compound growth rate of nearly 20%. According to the topology analysis, consumer electronic products have a recession impact, such as the substitution effect of AMOLED display technology gradually expanded with the new LED backlight market, which rely on consumer electronics growth bottlenecks. In contrast, even if the slow growth of LED lighting, but the market outlook established within five years is expected to bring new hope for the LED industry.

In particular, the governments policy to prohibit the use of incandescent lamps will start fermentation in 2012, global more than 2/3 of the area started to ban incandescent lamp or high wattage incandescent lighting. The topology that after incandescent lamp period has come, the importance of LED in lighting applications has been highlighted, the next 4 years the layout for the LED lighting market at the critical period. Application of the market, will be the first outdoor lighting, commercial lighting, industrial lighting, automotive lighting, and finally into the home market.

High efficiency, reliability and long life, drive as the key

In various LED lighting applications in the market at the present stage, especially in the replacement market of the most popular and successful elements of the market, including high efficiency, power supply reliability and service life have enough work, according to these conditions, the LED driver played an extremely important role. For this, IR Asia Pacific Sales Vice President Pan Dawei pointed out that the solid-state lighting industry has developed rapidly, so the low cost drive electronic component demand by high brightness and grow with each passing day, thought that the high power supply of LED constant current output.

In order to meet the above requirements, IR before the date for LED lamp replacement LED lamp, lighting and other non isolated LED driver applications, launched a new high voltage buck regulator control IC - IRS2980. IRS2980 is the company's first product in the high voltage LED driver IC series, rated at 600V, and the use of hysteresis average current mode control to achieve accurate current regulation. The new LED buck driver includes a low side MOSFET driver with a high voltage internal regulator and high side current sense. The converter is compatible with electronic pulse width modulation light, current control covers 0 to 100%.

Pan David also further pointed out that, relative to other non isolated LED driver application solutions, the new IRS2980 can enhance the effectiveness of the system at a lower cost. The IRS2980 uses SO-8 package, with the integration of the latest high voltage level shift and terminal technology of the IR advanced high voltage IC process, can provide the highest level of electrical over stress protection and higher field reliability.

Digital power control method to solve many problems

Basically, the LED to replace the lamp driver, mostly using step-down switching regulator. Roma Electronics (ROHM) has pointed out that to allow the LED to light in the condition of fixed brightness, it must be installed with a constant current control LED driver IC. In general, the buck switching regulator. This is because the traditional way will cause the input voltage / output voltage change is too large, and depending on the application conditions, it may also have to re design the power module.

When the input voltage change is too large, the frequency of the AC voltage (full wave rectified: 100Hz-120Hz) will cause the input voltage ripple appears, at this time, the brightness of LED will become unstable. If you want to make the input voltage stability, it is bound to add some ingenuity in the design of power module. When the input voltage changes more, it must be based on the output voltage of the light source (LED), to change the external part of the constant, but the result of the power module to increase the style, cost of design time.

In view of the above problems, the research and development of the BD555AKFV system developed by Roma, using digital power control method, does not need to increase the external parts, as long as the detection coil current, you can solve the problem. Using the digital power supply control method, regardless of the input / output voltage value, we can achieve the goal of controlling the average LED current. This method is the coil current sampling (A/D conversion) and digital, and then based on sampling data, the peak current value, so that the average current of LED current to achieve a stable target. Then, the calculation results of the D/A conversion, and feedback to detect peak current in the comparator.

In a more cost-effective manner

Except outside the business area of Taiwan, the industry also has the Holtek semiconductor LED lighting market to introduce general isolated buck type LED lighting driving control of IC-HT7L2102 and HT7L2103, the two driver support LED protection function complete, and especially Sheng group joined the Frequency Jitter function for the inhibition of EMI, so that EMI can reduce the 5-8dB, save EMI cost.

In addition, facing a variety of load conditions and LED string and number, HT7L2102 and HT7L2103 built Green Mode power saving mode, so that the user can use a circuit design can drive different LED load string and number, but not to reduce the conversion efficiency. In the light of the support, both are built to support PWM dimming