Patent ID: 7889061

Claim:
A power-line communication device, comprising: a switching power supply including a DC voltage generating circuit, a transformer in which one end of a primary winding of the transformer is connected to the DC voltage generating circuit, a switching element connected between another end of the primary winding and the DC voltage generating circuit, and a rectifying-and-smoothing circuit connected to a secondary winding of the transformer; a communication unit provided on a power line connecting a unit to which power is supplied from the switching power supply; a control unit that generates a control signal to be transmitted to the unit; and a switching noise detection unit that monitors an output from the switching power supply, detects a switching noise present in the output from the switching power supply, wherein the communication unit superimposes the control signal on the power line in synchronization with the switching noise detected by the switching detection unit such that the control signal does not cross a boundary between an ON period and an OFF period of the switching power supply.