Details of a selfdesigned small DC uninterruptible power charger for automatic weather stations are described. It is based on the UC3906 chip design, in conjunction with LM2576 chip to constitute an integrated buck switching regulator circuit, triggered by high and low levels to control the charging process of the different states. It has functions of not only high efficiency precision charging, but also accessing and cutting off standby power, so to enable the power supply management of small automatic weather stations. In addition, the charger is also designed to measure sunshine duration, which is calculated based on the change rate of level outputs of the solar panel. Compared with conventional singlechip chargers, the charger improves the charging efficiency and lifetime of the system, so to make full use of solar energy. The practical application indicates that it performs well and has certain potential of promotion.