US Patent 11689194 Power supply device for protective relay

The present disclosure relates to a power supply device for a protective relay. The power supply device comprises a power circuit for supplying a power to the control circuit, wherein the power circuit includes: a semiconductor switch element having an input terminal connected to a first node for receiving a direct current, and an output terminal connected to a reference node, wherein the reference node has a voltage lower than a voltage of the first node; and a first voltage drop element disposed between the first node and a second node, wherein the second node is connected to a switching terminal of the semiconductor switch element.