A modified average current-mode controller for converter-based optimal battery charging

This paper presents an average current mode controller with a feedback clamp circuit for converter based optimal battery chargers. Similar to conventional controllers, the proposed implementation enables the converter to work as a current source when the battery state-of-charge (SOC) is below a predefined reference level and automatically reverts to voltage source when the battery SOC exceeds the predefined reference level. However, the proposed implementation avoids the use of separate voltage and current loops and extra switching circuits to achieve current and voltage source property of the converter. As the current clamping in the proposed implementation is not based on saturation of the error amplifier, it is always feedback controlled and the transition between constant current to constant voltage mode is fast. The proposed implementation adapts well to pulse charging technique. Experimental and simulation results verify the application of the proposed circuit in a synchronous buck converter and boost-buck converter with coupled inductor of 10 W and 250 W, respectively.