Self-voltage-buildup grid-connected circuit of aviation low-voltage direct-current generator controller

The invention discloses a self voltage buildup circuit of an aviation low-voltage direct-current generator controller. The self voltage buildup circuit comprises a step-down circuit, a switching circuit and a comparison circuit, when the direct-current generator begins to build voltage, the residual magnetism voltage is not enough to supply power to the controller, the step-down circuit has no + 5V output, the normally-closed contact of the relay U4 works, the residual magnetism voltage is directly supplied to the excitation winding, and the motor end voltage begins to climb; when the motor end voltage climbs to the working voltage of the step-down circuit, the motor end voltage is still smaller than the window voltage of the comparison circuit, the comparison circuit outputs low level, and the step-down circuit and the switching circuit start to work. By adopting the comparator with open collector output and the pull-up resistor, the end voltage of the motor is stably increased in the self voltage building p