A high voltage gain power converter includes: a main switch element; an assistant switch element; a first inductive element, a first switch element, and a first capacitive element; and a second inductive element, a second switch element, and a second capacitive element. The first inductive element is connected between an input node and first switch element. The first capacitive element, connected between the first switch element and ground, provides a first boost output voltage. The second inductive element is connected between the main switch element and first capacitive element. The second switch element is connected to a common node of the second inductive element and main switch element. The second capacitive element, connecting the second switch element to a first node, provides a second boost output voltage. The assistant switch element is connected between the first inductive element and common node of the second inductive element and main switch element.