3.3.4 Zero-Crossing Detector Circuit

The phase identification is an important feature of the devices that are connected to Smart Grid networks, such as smart meters. A typical use of the zero-cross detection is to measure 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.

Important: The phase identification feature is mandatory for G3-PLC and PRIME1.4, but not for PRIME1.3.

The Figure 3-14 shows the Zero-Crossing Detection circuit used in the PL460-EK board, which features detection of rising edges of the mains voltage. The output signal of the detection circuit “Zero-crossing Detector” is connected to the pin VZC of the PL460, and a synchronization algorithm is applied to obtain an accurate measurement of the time between the reception of a PLC frame and the zero-crossing event.

Figure 3-14. Zero-Crossing Detection Circuit

Note: If using an external zero-crossing signal source, it must be made available through the Xplained PRO connector at pin 14/TXD by soldering R57 and removing R29.

Tip: Designs that do not require galvanic isolation can use a simpler Zero-Crossing Detector circuit, such as a Zener diode, instead of the previous circuit.