Improved Dynamic Behavior for the Series-Resonant Converter Using Bidirectional Charge Control

A new control method for the bidirectional series-resonant converter is presented that optimizes dynamic behavior. The series-resonant converter is a frequently used converter type due to its inherent zero-voltage switching property for switching frequencies above the resonance frequency. However, a method to control the series-resonant converter dynamically while facilitating bidirectional power flow and zero-voltage switching of all switches is not yet presented. This article presents bidirectional charge control, a control method that realizes dynamic, bidirectional operation of the series-resonant converter. It targets a net amount of charge displacement through the controlled port between two consecutive zero-current crossings, by describing all switching events as a function of the charge difference across the resonant capacitor. As a result, bidirectional charge control facilitates ZVS operation of all switches, regardless of the operating conditions, while minimizing the reactive currents through the connected voltage sources. This article describes the theoretical analysis regarding bidirectional charge control as well as an experimental verification, including nonidealities and the corresponding implementation to guarantee the desired control of the series-resonant converter. Bidirectional charge control realizes dynamic, bidirectional operation of the series-resonant converter while guaranteeing zero-voltage switching of all switches.