Digital lighting control chip in a high-efficiency street lighting design

February 13, 2014 // By Graham Prophet
ST Microelectronics offers a design around its STLUX385A digital controller for lighting and power-conversion applications, which it says enables “Jump-start[ing] municipal savings by accelerating street-light conversions.... new possibilities for high-power/street-lighting LED applications pave the way to smart cities.” The design helps optimise LED lamp efficiency at any dimming level and minimise power in idle conditions.

The complete and configurable solution allows designers to develop and efficiently control a dimmable, high-brightness LED string (up to 100W) for street-lighting applications. Based on ST’s STLUX385A digital power controller, the street-lighting plug-and-play design highlights the device’s ability to optimise LED efficiency at any dimming level and minimise power in idle conditions.

The reference design includes full schematics, bill of materials and firmware, enabling you to rapidly develop digital power controllers for 100W LED lamps using ST’s universal digital controller for lighting and power-conversion applications. The STLUX385A device handles a primary-side regulated power-conversion stage, as well as all the supported communication links. The power-conversion stage consists of a PFC regulator followed by a Zero Voltage Switching (ZVS) LC-resonant stage. High-precision dimming is controlled using a primary-side regulation (PSR) control technique.

The demonstration board provides all the key physical-communication interfaces such as DALI (Digital Addressable Lighting Interface), insulated 0-10 and UART, with all the communication managed by the STLUX385A device. The board also connects to other interfaces such as Wi-Fi, power-line modems, Bluetooth and ZigBee.

The demonstration board is available now at $140.

Many cities around the world, ST says, have started to convert their existing streetlamps to use LED technology and even more are drawing up plans to do so. In the USA, for example, Boston, Massachusetts had converted 40% of its 64,000 electric streetlamps to LEDs by the end of 2012 and was already realising $2.8 million savings annually in electricity costs, about 35% of that expense.

Replacing incandescent, low-pressure sodium and high-intensity discharge streetlights with LEDs is widely seen as the most promising way to reduce the huge amount of energy that the world uses to light the streets of its cities, towns and villages. LEDs are inherently more efficient than earlier lamp technologies and, more important, they are dimmable. This means that, in conjunction with a smart power supply, their light output can be rapidly adjusted to