Phase identification is an important feature of devices that are connected to a Smart Grid network, such as smart meters. A typical implementation is based on measuring the time difference between a specific PLC frame reception and the last zero crossing event of the mains single-phase to which the device is connected.
Zero-Crossing Detection Circuit shows the Zero-Crossing Detection circuit used in PL360MB board, which features detection of rising and falling edges of the mains voltage. The output signal of the detection circuit “VZ CROSS” is connected to VZ pin of PL360 and a synchronization algorithm is applied in order to obtain an accurate measurement of the time between PLC frame reception and zero crossing events.
The “VZ CROSS” signal is also connected to a GPIO pin of the SAM4CMS16C in order to also have information about zero crossing events on the microcontroller side.
It is important to note that for designs that do not require galvanic isolation, a simpler Zero-Crossing Detector such as a Zener diode can be used instead of the circuit previously shown.