Patent ID: 9153955
Filing Date: 2015-10-06
Classification: H02H,H04L

Abstract:
1. A communication line isolator that is configured with an isolation transformer including a primary winding connected to a communication line and a secondary winding connected to a protection target device that performs communication with the communication line, and blocks a lightning surge voltage entering from the communication line to protect the protection target device, wherein: the protection target device has a pulse transformer and an inner circuit to transmit/receive a pulse signal to/from the communication line via the pulse transformer and perform the communication, the pulse transformer includes a primary winding connected to a side of the secondary winding of the isolation transformer and a secondary winding connected to the inner circuit side of the protection target device, and a medium tap in the primary winding of the pulse transformer is grounded through an inner capacitance of the protection target device; and a parasitic capacitance caused between the primary winding and the secondary winding in the isolation transformer and the inner capacitance are connected in series such that the lightning surge voltage is divided by the parasitic capacitance and the inner capacitance, and a capacitance value of the parasitic capacitance is set such that a divided voltage of the inner capacitance is equal to or below a predetermined value.