Abstract: The present invention discloses a high step-down modular DC power supply, belonging to the field of power electronics technology, and the high step-down modular DC power supply includes an upper modular cascade circuit string, a lower modular cascade circuit string, a load, and an input source, where the upper modular cascade circuit string includes i upper sub-module circuits, and the lower modular cascade circuit string includes j lower sub-module circuits. A combination manner of module circuits includes: upper module string cascading, lower module string cascading, and hybrid cascading of the upper module string and the lower module string. The power supply is formed to be a high voltage step-down ratio power supply with high voltage direct current input and low voltage direct current output through modular cascading.

Abstract: Disclosed is a back-type expanding and opening foldable sunshade apparatus. The back-type expanding and opening foldable sunshade apparatus can be used directly on the back of a person or used together with a backpack by placing in the backpack, can adjust the opening extent and position of the shade in a lockable manner, and the width of the shade is expanded transversely when opening, thereby shading more effectively; and during use, the shade can be quickly opened, and when being not in use, the shade can be easily folded into a small device on the back or concealed in an interlayer of a backpack, thus being convenient and attractive.

Abstract: Disclosed is a back-type expanding and opening foldable sunshade apparatus. The back-type expanding and opening foldable sunshade apparatus can be used directly on the back of a person or used together with a backpack by placing in the backpack, can adjust the opening extent and position of the shade in a lockable manner, and the width of the shade is expanded transversely when opening, thereby shading more effectively; and during use, the shade can be quickly opened, and when being not in use, the shade can be easily folded into a small device on the back or concealed in an interlayer of a backpack, thus being convenient and attractive.