Research And Development Of Lithium Battery Charging And Discharging Device Based On Bi-directional Flyback Converter

Nowadays as power lithium battery has been widely used, battery formation manufactures have also mushroomed. C urrently, the existing formation equipment has been discovered with many problems: Consuming extensive power; Low efficiency in charging and discharging and a serious waste of the energy;Small amount of controlled formation lithium battery with large bulks of equipment, leading to high cost and not meeting the standard of quantitative production; Large ripples in voltage and current during formation leading to less accuracy.Considering this and also taking the promising application prospect of the small and medium-power lithium, this paper puts forward a Bi-directional flyback topology digital control power supply. Adopting DSP chip as the controller, this system mainly studies:1. Adopting low-cost, small-size Bi-directional flyback structure, this research then designed the transformer, snubber circuit, filter circuit and sampling circuit and it go ne on to build system SIMULINK simulation model to test the effectiveness of the topology. In the meantime in order to further lower the cost this research integrated four single- input and single-output flyback current supply into one circuit board, controlled only by one major chip to complete the design of a four-channel battery formation system.2. Designed the ideal small signal mathematic model with the transformer being under the CCM mode. Analyzed and compared the two strategies then test them by means of SIMULINK. Finally, conducted equivalent analysis in light of the double loop switch system.3. The design of the digital compensator. Taking key parameters(ADC resolution ratio, zero-order-hold, delay et.) of the digital control system in to consideration, adopt direct digital method to design the controller for discrete z area inside the SISOTOOL tool. Designed different control strategies regarding various working modes and stud ied the relationship between dynamic response and bandwidth. This research has conduct simulation experiments with different controllers to select the best strategy.4. The improvement of the lithium battery charging and discharging algorithm. Based on the two-stage charging method, this research attempted to resolve the current pattern peak problem in constant voltage mode and rea lized the non- impact pattern concerning constant current transforming into constant voltage.This paper designed a 40 W four-channel Bi-directional flyback topology machine.Realized voltage 0~5v, current 0~10A range digital control and t here is no impact while cc mode transforms into cv mode. The result finds that the accuracy of voltage under constant state is1%, that the accuracy of current under constant state is 2%. This result has proven the anticipated effectiveness of the hardware design and the controlling method.