10.1.2 Zero-Crossing Detection

The PL460 implements a zero-crossing detection stage. An external circuit is required to adapt the AC signal to VZC input requirements of the PL460. Once adapted, the zero-crossing detection stage measures rising and falling edges by hardware and then a PLL software algorithm is applied. The center of the low-level pulse input must be aligned with the peak of the mains wave, although some adjustment can be made on the application to correct the delay between pulse and wave.

Figure 10-2. Zero-Crossing Signal

The achieved precision meets the standard requirements to track 50 Hz or 60 Hz ±10% mains.

A simple external circuit is required to adapt the mains signal to VZC input. A typical application circuit for unidirectional topologies is shown in the figure below.

Figure 10-3. Typical Circuit, Using a Unidirectional Optocoupler