Design and Implementation of a PI-Controlled Lithium Ion Battery Charger with Protection and Monitoring

The importance of power electronics has been growing in recent decades and nowadays it is playing an undeniable important role in our everyday life. One of the most common application of power electronics is switching mode power supply. Those chargers for mobile phones and laptops, power supply for desktop computers, and uninterruptable power supplies are few examples of such converters. In this thesis work, a design and implementation of a PI controller for a switching power supply, that is specifically a Lithium-Ion battery charger, is presented. A brief review of rechargeable batteries and DC-DC converter is provided. Different control techniques for charging the Lithium-Ion battery is studied and constant-current/constant-voltage interpretation is employed in this study. Different topologies for DC-DC power conversion are compared and a half-bridge converter is designed and implemented as a prototype. A comprehensive description of protective mechanism and safety systems is provided. Moreover, a brief description for all the components that are used in this thesis is presented. The design of the control loop and PI compensator are investigated in details. The results of the stability analysis in form of step response and Bode plot are presented in simulations and experimental tests. In the conclusion it is indicated that the proposed digital controller can effectively eliminate the steady-state error with an excellent gain margin and phase margin improvements. Keywords: Battery Charger, Half-bridge converter, PI controller, Digital Controller.