NEC Rolls out LED Controllers

New controllers provide ‘fine-grained control' of light-emitting diodes

Charles J. Murray, Senior Technical Editor -- Design News, March 18, 2009

NEC Electronics Corp. has ramped up its LED (light-emitting diode) control lineup, rolling out a family of 8-bit microcontrollers for lighting applications. The introduction of the new 14-device family follows on the heels of NEC's mid-2008 unveiling of a microcontroller (MCU) with a constant high-current driver for LEDs.
Known as the 78KO/Ix2, the new family is targeted at both fluorescent and LED applications. NEC engineers say the devices in the lineup are created with two 16-bit timers that can do power factor correction, making them well-suited for LED applications in which AC power is used. Along with the power factor correction, the new devices also enable users to drive LEDs at constant current.

"By combining those two features into one device, this lineup fits well in applications where you use AC voltage and you want to bring it down to DC voltage and light up an LED," says Lance Zheng, applications manager for NEC's Multi-Purpose MCU Group.

NEC says the new MCUs provide an energy conservation boost because they make it easier for users to switch from incandescent to fluorescent lighting or to LED lighting. By employing an MCU rather than a dedicated IC to do inverter control and dimming functions, lighting manufacturers can control illumination at "a fine-grained level" and do remote control of illumination.

NEC's announcement follows its 2008 introduction of the µPD78F8024, an 8-bit all-Flash MCU with a four-channel high-current driver for LEDs. At the time of the introduction last May, NEC said the µPD78F8024 was the world's first microcontroller to offer a constant high-current driver. NEC engineers say that's important for users who want to control the level of light intensity.

"If you want to deliver constant light, you have to drive the LED at constant current," Zheng says.

Multiple-channel design is also said to be important for users who want to maintain independent control over groups of lights. In the four-channel arrangement, when one string (or channel) of LEDs fails, the other three channels remain intact, the company says.

NEC engineers expect the use of advanced LED controllers to grow in the next few years, especially as LED prices continue to drop. "Often times, when you drive an LED, you need intelligence," Zheng says. "To have quality lighting, you have to have intelligent control."