Lutron, a leading provider of wireless lighting controls and home automation systems, has filed a patent application for delivering two-way communications over a building’s existing powerlines – so-called powerline-carrier (PLC) technology popularized by X10 in the 1990s.
The patent application (#20160295670), “Digital load control system providing power and communication via existing power wiring,” is a follow-up to a 2013 patent Lutron filed on PLC technology.
Lutron points to other PLC inventions in the filing, noting that most others require a neutral wire to deliver data over the same wires that power a load. Lutron’s technology does not require a neutral.
Much of the discussion in the patent application refers to the ease of replacing a non-dimmable lighting ballast with a dimmable model, without having to run additional wires for control.
 Despite decades of attempts to develop practical power line carrier lighting control systems, there continues to be a need for apparatus that can reliably communicate data over a single power line between a dimmer switch and an electronic dimming ballast in a low-cost lighting control system. There also continues to be a need for low cost apparatus that can reliably and selectively control a plurality of fluorescent or light-emitting diode (LED) lighting fixtures connected to a single controller by a single power line. In addition, there continues to be a need for low cost PLC apparatus that is suitable for upgrading a simple, non-dim lighting system to a dimmed lighting system without the need for additional wiring or a complex commissioning process.
Beyond lighting ballasts, however, the technology has other implications for home automation.
The application mentions smart bulbs, thermostats, pool pumps, motorized shades, audio systems and other devices that could be controlled via the powerlines.
Here’s more on the technology:
 Rather than modulating high-frequency digital messages or pulses onto the AC mains line voltage to communicate with the power devices, the controller generates a phase-control voltage having a variable timing edge (i.e., phase angle). Specifically, the controller transmits “forward” digital messages to the power devices by modulating the timing edges of the phase-control voltage relative to a reference edge, i.e., digital information is encoded in the timing between the edges. The timing of the edges of the phase-control voltage can be controlled precisely by the controller and detected reliably by each power device, which does not require a zero-crossing detector to detect the timing edges of the phase-control voltage. Each power device is operable to transmit a “reverse” digital message to the controller and the other power devices of the load control system in response to receiving a forward digital message. Specifically, the power device is operable to modify the phase-control voltage generated by the controller to transmit reverse digital messages.
 Since the controller generates a phase-control voltage for communicating digital information to the power device, the electrical hardware of the controller is very similar to that of a standard dimmer switch. In addition, the controller is able to “swallow” the phase-control signal, such that the phase-control signal only exists on the power wiring between the controller and the power device, and does not generate noise that interferes with other control devices coupled to the power wiring. In other words, the phase-control signal only travels downstream from the controller to the power device, and not upstream from the controller to the AC power source. Since the controller and the power devices do not modulate high-frequency digital messages onto the AC mains line voltage, large reactive elements coupled across the AC power source do not degrade the quality of the digital messages transmitted by the controller to the power device.
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