Technical Support

In the global trend of energy saving and carbon reduction, LED lighting is highly anticipated, and with the continuous improvement of high-brightness LED luminous efficiency in recent years, the unit cost has also declined, prompting high-brightness LED applications are no longer limited to small and medium-sized electronic products, or laptops, monitors, TVs and other larger size backlight applications and LED display billboards, and has begun to replace traditional incandescent lighting products. LED has undoubtedly become an important light source for the next generation of general lighting.

For the market prospects of LED lighting, Topology Research Institute Chen Kehua predicted that the global LED lighting output value is expected to grow to $11 billion in 2012 and increase to $19.2 billion in 2015, with a compound annual growth rate of nearly 20% in four years. According to Topology's analysis, consumer electronics products are affected by the poor economy, coupled with the gradual expansion of new display technologies such as AMOLED replacement effect, making the growth of LED backlight market relying on consumer electronics products is facing a bottleneck. On the contrary, even if the growth of LED lighting is slow, but the market outlook is established, within five years is expected to bring new hope for the LED industry.

Especially governments to ban incandescent policy will begin to ferment in 2012, more than 2/3 of the world began to ban incandescent lamps or high wattage incandescent lighting. Topology believes that the post-incandescent period has come, the importance of LED in lighting applications has been highlighted, the next four years for the final critical period of LED layout lighting market. Application market part, will take priority to outdoor lighting, commercial lighting, industrial lighting, automotive lighting second, and finally penetrate into the home market.

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

In various LED lighting applications market, especially at this stage to replace the lamp market has attracted the most attention, and the success factors of this market include high efficiency, drive power supply has sufficient working reliability and life, etc., for these conditions, LED drivers play an extremely important role. In response, IR Asia Pacific Vice President of Sales David Pan pointed out that the solid-state lighting industry is growing rapidly, so the demand for low-cost driver electronic components is increasing, by supplying constant current output for high brightness and high power LEDs.

IR for LED replacement lamp lighting launched a new high-voltage buck regulator control IC.

To meet these needs, IR has introduced the IRS2980, a new high-voltage step-down regulator control IC for LED bulb replacement, LED tube lighting and other non-isolated LED driver applications. The IRS2980 is the first in the company's family of high-voltage LED driver ICs, rated at 600V, and utilizes hysteresis-averaged 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 converters are compatible with electronic pulse width modulation dimming, and current control covers 0 to 100%.

David Pan further pointed out that the new IRS2980 can improve performance at a lower system cost than other solutions designed for non-isolated LED driver applications. The IRS2980 in SO-8 package provides top electrical overstress protection and higher field efficiency reliability with IR's advanced high voltage IC process that integrates the latest high voltage level shifting and termination technologies.

Digital power control method to solve many challenges

Basically, the drivers for LED replacement lamps are mostly implemented by means of step-down switching regulators. ROHM Electronics (ROHM) pointed out that, in order for the LED to be able to light up under the condition of fixed brightness, it is necessary to install the LED driver IC that can perform constant current control. This is because the traditional method will cause the input voltage / output voltage changes too much, and depending on the application conditions, may also have to redesign the power supply module.

When the input voltage varies too much, the frequency of the AC voltage (after full-wave rectification: 100Hz-120Hz) will cause the input voltage to ripple, and at this time, the brightness of the LED will become unstable. If the input voltage is to be stable, it is inevitable to add some ingenuity to the power module design. When the input voltage changes more, it must be based on the output voltage of the light source (the number of LEDs), change the constant of the external parts, but the result causes the power supply module style increased, costly design time.

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