How PCLC Works

A building’s AC line voltage is always varying by small amounts as loads are switched on and off in the building and the neighborhood. Lighting loads are designed to handle small voltage variations without flicker.

PCLC uses very brief, small, reductions of the line voltage for signaling only when the user commands a change to the lighting level. This signaling just commands lighting changes as is done in DALI, rather than making large reductions in voltage delivered to the load like low voltage transformers and TRIAC / Phase Cut dimming.

PCLC signaling is AC power and thus the building wiring and loads are designed to be compatible with it and will not try to filter it out as happens to competing high frequency PLC systems. Competing PLC signaling is essentially RF and shares with RF many of the same problems of noise from other devices occurring in the same frequency band, mutual interference between systems, the need for networking, and system failures as new devices are added to the environment.

Ordinary line voltage fluctuations and PCLC don’t cause electrical or RF noise or interference and always reach the lighting load because they don’t have range limits like RF or competing PLC. Voltage fluctuations and PCLC don’t noticeably degrade power quality.

TRIAC dimmers are by far the most popular form of dimmable lighting controls. We believe this is due to the low cost of products and installation consisting of just replacing the light switch with a dimmer and installing a light source compatible with the dimming signal. There is no need to set up a network, everything powered through the dimmer will be dimmed and nothing else will be. These features are also true of PCLC. Unlike PCLC, TRIAC dimmers cause unacceptable power quality that prevents widespread deployment in commercial buildings and can cause flicker in LEDs.