Exploiting power line communications
Power Line Communication (PLC) uses existing power lines to send and receive data. Electrical power companies use PLC to transmit operational data relating to the power grid over many miles of electrical cable to a central location. PLC can be exploited by engineers to provide a communication link for a LED-based lighting system by connecting it over the same lines that power the application. This eliminates the need for a dedicated cable to act as a communication link.
Rather than implement the full PLC standard, developers can employ a low data rate PLC implementation such as Texas Instruments' PLC-lite, a simple, flexible standard that is particularly applicable for low-cost applications requiring a robust communications link e.g. simple light bulbs or wall switches within a home network.
Compared with more complex PLC types (i.e. G3 or PRIME), there is a considerably lower cost per link, owing to the lower data rate and reduced protocol overhead. The flexibility of PLC-Lite allows developers to implement specific channel characteristics that improve link robustness in situations where line interference may be a problem.
Radio frequency (RF) technology can also be utilized to wirelessly connect devices. The modular architecture allows the connectivity technology to be employed that is most applicable to the end user. Data is transmitted to the microcontroller over a standard I2C or SPI port for both PLC- or Wi-Fi-based links.
Intelligent digital solution - the Piccolo microcontroller platform
Texas Instruments' C2000 Piccolo platform of microcontrollers (Figure 3
) is designed to support a wide range of lighting applications. Piccolo microcontrollers have a high-performance, highly integrated architecture, providing flexible digital power control to support a variety of power topologies. Integrated I2C, SPI, UART, USB and CAN peripherals are available with production-ready firmware drivers to meet the connectivity needs of all applications. The advanced PWM generation (Table 3
) and 12-bit high-resolution analog-to-digital converter (ADC) modules (with fast sampling and conversion speeds; 4.6 Mega samples/second) enable the creation of a tight feedback loop to react rapidly to shifting operating conditions.
Figure 3: The Piccolo platform of microcontrollers
Tab 3: Piccolo PWM capabilities
The Piccolo platform of microcontrollers can support a range of applications from entry-level devices to complex, multi-string systems with PLC. The 32-bit TMS320C28x core
can implement power stage calculations, LED string control and lighting protocols such as DMX512. The Piccolo microcontrollers possess programmable flexibility, optimized math operation, and real-time control (via a responsive, interrupt-driven architecture).
Piccolo microcontrollers even offer dual core architecture configurations. Alongside the CX28x core
, Piccolo F2803x devices
have a separate independently running Control Law Accelerator (CLA) core that provides parallel processing. The lighting system functions and communications can be separately partitioned between the C28x core (digital power conversion and LED string control) and the CLA core (PLC algorithms). For advanced/higher bandwidth PLC applications, Piccolo F2806x microcontrollers
are available with an additional integrated Viterbi Complex Math Unit (VCU) to speed up PLC processing.
Piccolo microcontrollers are available to support a wide range of intelligent lighting systems:
Piccolo F2802x microcontrollers for low-cost systems: sufficient performance to reduce system component count, real-time digital power technology, supports DALI, DMX512, and KNX Piccolo F2803x microcontrollers for entry-level PLC remote connectivity: supports PLC-Lite, with additional LED channels and performance than the F2802x Piccolo F2806x microcontrollers for high-performance systems: supports advanced PLC and USB, with additional LED channels and processing capabilities.
In some lighting systems, however, the presence of high and low voltages dictates that an isolation boundary is needed to separate PFC and DC/DC conversion. In this case, it may be simpler to use two Piccolo microcontrollers that communicate via an I2C or SPI interface, owing to the difficulty crossing the boundary (Figure 4
). It can, however, be more cost effective to implement PFC and DC/DC conversion on a single microcontroller if the design is non-isolated.
Figure 4: LED-based lighting system with isolation boundary
In order to help support LED-based lighting design engineers create new systems, a range of development hardware and software is available for all applications from low voltage to remotely connected full-AC mains powered systems. Tools offered by Texas Instruments include the:
TMS320C2000 AC LED Lighting and Communications Developer's Kit for AC mains-powered, intelligent lighting products (Figure 5
) DC/DC LED Lighting Developer's Kit Multi-DC/DC Color LED Kit Power Line Communications (PLC) Add-on Kit LED BoosterPack with the C2000 LaunchPad
or MSP430 LaunchPad
, supported by the C2000 controlSUITE software.
Figure 5: The TMS320C2000 AC LED Lighting and Communications Developer’s Kit with high operating efficiency (around 90 percent), remote connectivity and lighting communication protocol support (e.g. DALI, DMX512, KNX and PLC)
For more information, visit http://www.ti.com/ww/en/lighting/products.htm
About the author:
Patrick Carner is the C2000™ microcontrollers and lighting applications marketing manager at Texas Instruments. He is responsible for product definition and positioning, customer design engagements, business development, and customer support for the C2000 product line. Carner received a B.S. in EECS from the University of California at Berkeley.
Courtesy of EETimes Europe
See related links:
White LEDs printed on paper
Controlling multiple LED strings with C2000 MCUs
Infrared LEDs for camera systems
LED - Design archive
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