Research On Control Model Of Ni-MH Battery Charging Power Supply

Along with the development of battery technology, charging technology is also constantly updating,which not only meets the charging requirements of the new battery but also improves the quality of the charger and extends battery life. Since the advent of Ni-MH battery, due to the restriction of technical conditions, the traditional method of charging fails to comply with the internal physical and chemical laws of the battery. So that the whole process of charging has the serious problems of gas separating and over charging that shorten the battery life. In this paper, the control mode of Ni-MH battery charging is analyzed thoroughly and a Ni-MH battery charging system based on PWM technology is proposed, which consists of hardware and software design.Firstly, the paper analyses of the physical and chemical mechanisms of Ni-MH battery charging process in detail and the unique bimodal effect during the process is indicated. The polarization phenomena in the process of Ni-MH battery charging are discussed based on the electrochemical theory, and its causes are analyzed and the corresponding countermeasures are proposed.Secondly, the power circuit, detection circuit and control circuit of the charging supply circuit are designed, and main devices are selected and the parameters of transformers are calculated. In order to optimize control strategy design, the open-loop model of power circuit is established and the power circuit simulation is analyzed. The micro-control unit is used as the controller in control loop. Ni-MH battery voltage, current and temperature are sampled to MCU by sampling circuit. The PWM output duty cycle control is achieved through digital PID algorithm.In this paper, the Ni-MH battery control strategy and rapid charging strategy are deeply researched. Based on analysis of the various control modes, we select the negative voltage increment as the main method of judging the termination of fast charge control mode to the requirements of the system. After analyzing the design requirements of software, the paper completes the system software design and gives the design processes of the whole software and the various stages.Finally, this paper completes the Ni-MH battery charging systems experiments and the charge and discharge pulses current, amplitude, discharge width and the idle time parameters are determined based on the experiments. In accordance with the parameters, the experimental results indicate that the system can wipe off the polarization effect of the battery charging process, and improve the Ni-MH battery charging efficiency. The charging process is safe and reliable, and the recharging time is shortened. The practicality and feasibility of the design ways and means are verified.