Design of Solar Charger Tang XX (XX Class XX, XXXXXXXX College, XX University) Abstract: According to the theory of independent photovoltaic power generation system, a solar charger is designed. The solar charger converts light energy into electric energy through polysilicon solar cells, and then converts it into stable DC output through Buck converter, and uses lithium-ion batteries as energy storage units. The control and management system of charging circuit is designed by using AT89S52 single chip microcomputer, and the output of the circuit is controlled by adjusting the duty ratio of PWM waveform. Keywords: solar cell; AT89S52 single chip microcomputer; Intelligent charging; Due to the increasingly tense energy problem, people are keen on the application of solar energy. At present, the products composed of solar cells, charge and discharge controllers and storage batteries are relatively mature, and many experts at home and abroad are also doing in-depth research in this field. The application prospect of solar energy is broad. Based on the professional basic theory, combined with the knowledge of other related disciplines and predecessors' research results in this field, this paper studies and determines a solar charger scheme based on AT89S52 single chip microcomputer, analyzes the charging mode of solar cells, the functional requirements and practical application of the controller, completes the hardware circuit design, algorithm research and software writing, and realizes the scientificity of the battery. The front stage of independent photovoltaic power generation system consists of photovoltaic cells, DC-DC converters and storage batteries. [1] In this design, the polysilicon solar panel converts solar energy into electric energy, which is processed by the voltage stabilizing circuit and the Buck converter respectively to supply power for the control module and the charging circuit. After a detailed analysis of the charging and discharging process of lithium-ion battery and various factors affecting the service life of lithium-ion battery, the method of starting constant current fast charging and automatically switching to constant voltage charging when the battery voltage rises to the limit value is adopted. In the process of charging, AT89S52 single-chip microcomputer is used to simulate the PWM output to control the on-off of the switch tube, so as to realize the charging control of the lithium-ion battery by the circuit. Overcurrent and overvoltage protection is designed in the system to avoid battery damage due to overcharge.