This application provides an interface circuit of a vehicle-mounted control unit comprising an H-bridge circuit, an input branch, and a pull-up network. An input end of the H-bridge circuit is connected to a controller 240, and an output end of the H-bridge circuit is connected to an interface port IO of the interface circuit. A first end of the input branch is connected to the interface port IO, and a second end of the input branch is connected to the controller.