A power circuit, control method, power system, and package structure of power circuit are disclosed. The power circuit includes a quasi-cascade power unit. The quasi-cascade power unit includes a normally-on switch, normally-off switch, control unit, first switch unit and second switch unit. The normally-off switch is electrically connected to the normally-on switch in series. The first end and the third end of the control unit are electrically connected to the control end of the normally-off switch and the control end of the normally-on switch, respectively. The first end and the second end of the first switch unit are electrically connected to the control end of the normally-on switch and the second end of the normally-off switch, respectively. The first end and the control end of the second switch unit are electrically connected to the second end of the control unit and the second end of the normally-on switch, respectively.