Design and Implementation of High Power Density Assisting Step-Up Converter With Integrated Battery Balancing Feature

This paper presents a novel step-up power converter architecture for portable applications with multicell battery packs that integrates battery cell balancing function. Compared to conventionally used boost converter, which is not providing cell balancing, the new architecture has smaller overall volume and approximately the same power processing efficiency. The step-up function is obtained using the assisting concept, where the flyback output is placed at the top of the battery pack and, therefore, is only processing a portion of the output power. As a result, high-power processing efficiency and small converter volume are achieved. The operation of the system is regulated by a digital controller that provides the two functions at the same time. Experimental results obtained with an 8-to-12 V, 20 W, 500 kHz prototype demonstrates that the assisting flyback simultaneously provide output voltage regulation and cell balancing. Operation of the converter during charging and discharging is demonstrated. Also, a conventional boost converter that has the same input-output specifications is built and tested for comparison. The results show that, compared to the equivalent boost which is the most commonly used converter in the targeted applications, the prototype has about 23% smaller overall volume and a comparable power processing efficiency curve with a peak efficiency of a 93.4%.