The system mainly adopts the adjustable LM2596T chip as the core element to carry out the dc stabilizer. When the input voltage varies from 175 V to 255 V, at the same time the load is changed from empty to full load, and the voltage adjustment rate is less than 0.2%. When the input voltage is stable at 220 V and the charging current changes from 0 to 2A, the maximum load adjustment rate is only 0.4%. Using STM32F103FC8T6 microcontroller LCD12864, real-time display shows charging voltage and charging current. The voltage ratio on both ends of the sampling resistance is realized by sampling resistance，voltage amplification is completed by low noise transport OP07. When charging voltage exceeds the range of error (customizable), charging circuit automatically will disconnect and give an alarm. The charging circuit will automatically disconnect and alarm. After power off, the value of charging voltage and current will be automatically saved and displayed after recovery.