Power device including parallel power conversion modules and cascaded power conversion units

A power device for receiving a bus voltage and providing an output voltage to a load, the power device comprising:

• a first conversion module comprising an input terminal, an output terminal and at least a first conversion unit, wherein the first conversion unit receives a first divided voltage of the bus voltage;
• and
• a second conversion module comprising an input terminal, an output terminal and a cascade conversion circuit with at least one second conversion unit and at least one third conversion unit;
• wherein the input terminal of the second conversion module and the input terminal of the first conversion module are connected with each other in series, the input terminal of the second conversion module receives a second divided voltage of the bus voltage, and the output terminal of the second conversion module and the output terminal of the first conversion module are electrically connected with each other in parallel so as to provide the output voltage to the load, wherein the third conversion unit detects the output voltage in real time to control the output voltage stable, wherein a first voltage is converted into a second voltage by the second conversion unit, wherein a second ratio of a input voltage to a output voltage of the first conversion unit is fixed, wherein the bus voltage comprises plural intervals, each of the plural intervals has a start voltage and a terminal voltage, the start voltage of each of the plural intervals is equal to the terminal voltage of a previous interval of the plural intervals, wherein a first ratio of the first voltage to the second voltage is adjustable discontinuously between two adjacent intervals of the plural intervals, the first ratio of the first voltage to the second voltage is different between the two adjacent intervals of the plural intervals through increasing of the bus voltage, a first magnitude of each of the plural intervals is greater than a second magnitude of the previous interval of the plural intervals through increasing of the bus voltage.