The use of LEDs in lighting systems brings many benefits from energy savings to durability and longer life. However the adoption and growth of LED lighting is dependent on the ability to connect to existing lighting infrastructures. Besides the physical issues related to fitting into different light sockets, LED lights need to support various communications and control requirements. For example, in a residential environment, LED lights need to operate with TRIAC dimmers (Fig. 1). In an office or theatrical lighting application, LED lights need to communicate with DALI (Fig. 2) or DMX512 (Fig. 3) networking protocols respectively. And in street lighting, support for fault-detection correction is important. Using an intelligent microcontroller with integrated specialized hardware makes these requirements easier to achieve.
To meet these design needs, NEC Electronics offers two microcontroller lines, the 78K0/Ix2 MCUs (uPD78F074s/75x) and HCD/LED MCUs (uPD78F9024/25), with specialized hardware to drive LEDs, improve light quality and handle communication functions (Fig. 4). The K0/Ix2 MCU has interlinking ADCs and high frequency PWM timers. When these interlinked peripherals are programmed, they can run independently from the microcontroller. The HCD/LED MCU has an integrated 4-channel constant current driver (CCD) and each of the four channels can drive up to 10 HB LEDs in a series. The high-current CCD can operate at high switching frequency and high voltage giving it the flexibility to perform in either boost or buck mode.
With dedicated peripherals and hardware, these microcontrollers have extra bandwidth to support existing infrastructures in various applications. For example, ADCs and comparators in the 78K0/Ix2 MCU can be used to detect phase cut from a residential TRIAC dimmer, enabling the MCU to compute and adjust the PWM timers proportionally to dim the LED lights. For industrial lighting in offices and theaters, both the 78K0/Ix2 and the HCD/LED MCUs have enough memory and processing power to run DALI and DMX512 protocols to control networked lighting. In street lights, where multiple channels of LEDs are often used, these MCUs can use their ADCs to detect a blown LED channel. When a fault is detected, the microcontroller can increase the intensity of the other channels for compensation, and at the same time, relay a fault message back to the central office.
Visit www.SemiconductorStore.com for an NEC Electronics lighting-control development kit and more information about NEC Electronics products for lighting applications. For questions about pricing, availability, or product features related to NEC Electronics microcontrollers, power management, or memory products, contact Symmetry Electronics at (866) 506-8829.