3.3.3.3 PLC Coupling Circuit

The PLC coupling circuit connects the PLC signal directly to the mains grid or even to the DC power rails without requiring any hardware adaptation.

The main purpose of the circuit is to block the mains voltage of the grid to/from which the signal is injected or received. This is carried out in PL460-EK (see Figure 3-13) by a high-voltage capacitor, C1. The R10, R11, and R12 resistors allow the high-voltage capacitor to discharge after disconnection from mains.

CAUTION: The PLC coupling components are designed for a maximum voltage of 250 VAC or 325 VDC.

The TR1 transformer (with turn ratio 1:1) provides safety isolation from the L-N connection.

Varistor, fuse, and TVS diodes protect the board against overvoltages and high-transient voltages (surges and spikes) from mains. For additional information about TVS diode, SMAJ12CAE3 (D3), refer to the SMAJ12CAE3 product web page.

Figure 3-13. Isolated Coupling Schematic