Mahmoud Shousha

Assisting converter based integrated battery management system for low power applications

This paper introduces a new battery management system for portable electronics applications based on the flyback converter. This new architecture integrates the voltage step-up and balancing functions inside a single converter. The step-up function is obtained using an assisting concept, where the flyback output is placed at the top of the battery pack and is therefore 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 voltage regulation and charge balancing of the battery cells at the same time. Experimental results obtained with 8-to-12V, 20W, 250 KHz prototype demonstrate a peak efficiency of 93.4% and show that the assisting flyback requires about 9 times smaller output capacitor than the conventional boost while maintaining approximately the same inductor volume.

A transformerless dual active half-bridge DC-DC converter for point-of-load power supplies

Point-of-load (POL) power supplies contribute significantly to the overall volume, weight, and cost of many electronic devices. This is mainly due to the fairly large inductor of the buck converter commonly used in these applications, which causes it to have a relatively low power density. The goal of this paper is to propose an alternative converter for POL applications which uses a much smaller inductor. The proposed converter, referred to as a transformerless dual active half-bridge (DAHB), uses an ac-link to transfer power, instead of the more conventional dc-link. Not only does the transformerless DAHB offer a significant reduction in the volume of the bulky inductor, but it also allows soft switching and 50% duty cycle operation of all active devices. The advantages of the proposed converter have been verified with a 12 V to 3.3 V, 10 A, 0.3 MHz to 1 MHz experimental prototype. The results demonstrate a reduction of approximately 50% in the volume of reactive components, while maintaining high power processing efficiency.

On-chip high performance magnetics for point-of-load high-frequency DC-DC converters

This paper presents the design, fabrication, and characterization of on silicon integrated micro-transformers for high frequency power applications. The microtransformer device is used and tested in DC-DC converter application at high switching frequency. This device has stable L vs. f characteristic up to 50 MHz. The design is improved regarding to the electrical resistance and current capability. The microtransformer shows an inductivity of about 60 nH, resistance of 350 mΩ and can be applied for current up to 1.5 A.

Design and Implementation of Assisting Converter-Based Integrated Battery Management System for Electromobility Applications

This paper presents a high power density battery management system for electromobility applications that integrates voltage step-up and cell balancing functions inside a single converter topology. The presented system is based on assisting conversion concept, implemented with multiple dual-active bridge (DAB) converter modules. The assisting conversion, where the converter is only processing a portion of the output power proportional to the voltage difference between the battery pack and the output of the converter, allows for the use of a smaller converter than those of conventional systems. Also, at the system level, this type of conversion results in a higher power processing efficiency. The modular structure of the converter provides multiple connections to battery cells and allows on-line cell balancing during standstill, charging, and discharging of the battery pack. The operation of the system is regulated by a practical digital controller that performs cell balancing and, at the same time, regulates the output voltage. Experimental results obtained with a 24–48 V, 200-W, 100-KHz converter for small scooters demonstrate that the assisting converter is capable of providing the two previously mentioned functions while having a smaller volume and better power processing efficiency than both the conventional DAB and boost-based solutions. The assisting DAB converter runs at a peak efficiency of a 95.4% and processes only a maximum of a 66% of the output power.

Portable rotational electromagnetic energy harvester with a maximum energy tracking power management system

This paper presents a development and fabrication of a rotational electromagnetic energy harvesting (EH) system. The electromagnetic harvester is driven mechanically by pushing a button. The energy harvester converts the linear translation of the button into rotation with a rotational speed of about 1000r/min. The electromagnetic part of the harvester consists of a multilayer planar coils embedded into PCB and of multipole NdFeB permanent magnets. The energy harvester device generates maximal energy of about 20mJ. The maximal open circuit voltage up to 4V is achieved. Also, the Power Management System (PMS) used with the EH is discussed and shown. The PMS is based on a dual phase buck-boost topology that converts ac-to-dc voltage in a single stage. Moreover, the PMS combines a maximum energy tracking feature, based on resistive impedance tracking, without adding additional components. Experimental results show the ability of the PMS to convert from ac-to-dc voltage while providing a maximum energy tracking feature.