Research On Multi-step Constant-current /Constant-voltage Charging Device Based On DSP Control

The Battery charging technique is a subject which has been concerned widely in the battery application fields, it is the key factor which affects the battery life. But because of the complex charging process, and the simple charging methods in practical application greatly decrease battery life, a reasonable slection of charging methods is very important; and at some particular situation, various voltage-levels battery are needed, for charging conveniently and reasonably, the charging devices must be rationality and generality. This paper described a charging device which is suitable for the battery of voltage-level under 24V, the charging method is two-stage charging strategy.At first, this paper described some widely used charging methods, and determined constant-current and constant-voltage charing as this charing device's charing methods. Then according to the accepted charing current, this device selected a two-stage charing, that're constant-current/constant-current and constant-voltage/constant-voltage strategy, it is suitable for the charing requirements of ni-cd alkaline battery and lead-acid battery.This charging device is powered by three-phase AC, in order to decrease the current harmonic caused by rectifier, lower conducted interference to AC power grid, this part uses 12 pulse rectifier with autotransformer. And in order to reduce the switching loss, the phase-shifted ZVS full bridge cell was used. IGBT was selected as the switch that was drivered by 2SD106AI-17 module. The charging control system was based on DSP chip (TMS320LF240). Using this topology, higher frequency could be gained,switching loss was much redused and control system was telligent and so on.The control principles of charging device were time,voltage and mixed principle. This paper also presented a design method of the PI algorithm of integral separation and variable parameter. At last, the experimental results from the prototype indicate that the software works properly, and constant-current and constant-voltage charging are realized.