Techniques for duplex communication and power transfer across an isolator are provided. In an example, a first transceiver coupled to a firs-t side of an isolator can include a transmit modulator configured to receive first data and timing signals, to provide control signals to oscillate an output of the transceiver to transmit power and to order each half-cycle of an oscillation cycle of the output to transmit the first data. A second transceiver coupled to a second side of the isolator can include a receive detection circuit configured to compare a received oscillation cycle with a plurality of thresholds and to provide a plurality of comparator outputs indicative of reception of the positive half-cycle and the negative half-cycle, and a receive decoder configured to identify the order of half-cycles and to provide an output indicative of logic level of the first data.

Instead of the method of performing the power disconnection in the existing phase angle control AC power line communication, using relays or various power semiconductor devices, if communication is executed through data mapping on a pattern where polarity switching (in the case of AC, phase-shifting by 180) occurs at a differential voltage level of a power line, no power disconnection occurs and high voltage interval is utilized so that the power line communication is strongly resistant to external noise and provides high communication speed, while transmitting several bits in one period of AC voltage waveform. This solves the disadvantages the existing classical condenser coupling type power line communication and the phase angle control AC power line communication for long distance have had. Even though the power line communication is utilized for DC power line communication, many advantages are obtained and high power transmission efficiency is achieved through the relays.

In one embodiment, a method includes transmitting pulse power on two wire pairs, the pulse power comprising a plurality of high voltage pulses with the high voltage pulses on the wire pairs offset between the wire pairs to provide continuous power, performing low voltage fault detection on each of the wire pairs between the high voltage pulses, and transmitting data on at least one of the wire pairs during transmittal of the high voltage pulses. Data transmittal is suspended during the low voltage fault detection.

Systems and methods for relative phase detection and zero crossing detection for power line communications (PLC) are described. In some embodiments, both transmit and receive PLC devices detect a zero crossing on an AC mains phase. The devices start a phase detection counter (PDC) by generating a zero crossing pulse within 5% of the actual zero crossing time. When a frame is transmitted, the transmitting device includes a PDC value in the frame control header (FCH). The PDC value corresponds to the start time of the FCH. When the frame is received at the receive PLC device, the receive PLC device measures a local PDC value between the zero crossing and the start of the FCH. The receive device compares the local PDC value to the PDC value in the FCH of the received frame and determines if the devices are on the same phase.

The invention relates to a device adapted to transmit baseband signals with a power line of an AC power source. The invention uses both of the power line and a signal line for data transmission, rather than directly loading the signals onto the power line. Specifically, the device includes a rectification and energy storage circuit for continuously converting the AC power source into a current source with a common reference potential, ensuring uninterrupted communication for continuous data transmission. Moreover, the invention addresses the problem of noise interference by using the signal line for data transmission.