| 1. |
- Bakar, Muhammad Abu, 1969-, et al.
(författare)
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A 2x3 Reconfigurable Modes Wide Input Wide Output Range DC-DC Power Converter
- 2021
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Ingår i: IEEE Access. - 2169-3536. ; 9, s. 44292-44303
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Tidskriftsartikel (refereegranskat)abstract
- There is an increasing demand for efficient and low-profile power converters in almost all industrial applications. Some require stable performance over a wide range of input voltages, whereas others require converters with a stable performance over a wide range of output voltages. In this regard, little work has been done to combine both requirements into one solution. This work suggests a unique solution that addresses both requirements at once. A power converter with 2x3 reconfigurable modes has been presented, able to operate with DC gains of 1, 2 and 4, which can be further extended to 8. The converter shows stable performance for the extended range of both input and output voltage. The flexible reconfigurable feature of the proposal can be applied in a variety of applications. Two reconfigurable modes on the input side can be configured following the variation in the line voltage to maintain a stable performance, and three reconfigurable modes for the output voltage, which raises the output voltage from 24V to 48V and 96V. The proposal is applied in an example application of a phase shifted full bridge converter. The converter is characterized for Vin = 100-400Vdc, Pout = 1kW. CCBY
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| 2. |
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| 3. |
- Bakar, Muhammad Abu, 1969-, et al.
(författare)
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Characterization of phase shifted full bridge converter along with GaN devices and series-connected hybrid transformers for medium power applications
- 2020
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Konferensbidrag (refereegranskat)abstract
- Compact power converters are the major concern of today’s power industry. This article proposes GaN devices based isolated dc-dc phase shifted full bridge converter along with the configuration of four series-connected hybrid transformers. The series connection of transformers reduces the applied volt-second on each transformer which reduces the proportional losses and simplify thermal management. This configuration also reduces the required turn’s ratio as well as bringing down the stress on the secondary devices and filters. The converter is characterized in a compact prototype up to the load power of 2.2 kW for Vout=48 Vdc at Vin=400 Vdc. The converter reports satisfactory performance with a maximum efficiency of 96%.
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| 4. |
- Bakar, Muhammad Abu, 1969-, et al.
(författare)
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Dual-mode stable performance Phase-Shifted Full-Bridge converter for wide-input and medium power applications
- 2021
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Ingår i: IEEE transactions on power electronics. - 0885-8993 .- 1941-0107. ; 36:6, s. 6375-6388
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Tidskriftsartikel (refereegranskat)abstract
- Power converters with an extended range of line voltage are the main requirement in today's industrial applications like photovoltaic and supercapacitors based energy systems. The variation in the line voltage severely degrades the performance of power converters, because of the extended freewheeling interval, more circulation current, narrow range of zero voltage switching and increased EMI. This work suggests a modified Phase-Shifted Full-Bridge converter that cuts the freewheeling interval and minimizes these problems. It extends the input voltage range by keeping the operational duty cycle of the converter high over the wide range of input voltage while maintaining the performance stable. The proposed converter consists of four low profile transformers having reconfigurable interconnection structure. There are two distinct reconfigurable modes, a series mode and a parallel mode, which can be configured with changes in the operational conditions. The operation of the proposed converter with high switching frequency improves power density. Additionally, the use of multiple transformers minimizes heat management efforts and reduces the overall volume of the converter. The proposed work is validated in hardware characterization for a wide range of input voltage 100-400Vdc and up to the load power of 1kW. The measured energy efficiency of the proposed converter remains stable over the complete range input voltage 100-400Vdc.
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| 5. |
- Bakar, Muhammad Abu, 1969-, et al.
(författare)
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Modeling and Characterization of Series Connected Hybrid Transformers for Low-Profile Power Converters
- 2020
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Ingår i: IEEE Access. - : IEEE. - 2169-3536. ; 8, s. 53293-53306
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Tidskriftsartikel (refereegranskat)abstract
- Compact and low profile power converters are the main business of today's power industry. A significant volume of a power converter is occupied by the power transformer. This article proposes a unique solution that would make the power converters low profile. Instead of designing a power converter by using a single bulky transformer, the solution proposed is to split the main bulky transformer into a number of low profile transformers. This not only reduces the total weight and volume of the converter but also the total transformer losses. The use of more than one transformer in series reduces the applied voltage on the transformers, which minimizes the required turns ratio and decreases the stress on the secondary rectifiers and filter elements. Moreover, the decrease in the applied voltage reduces the proportional loss per transformer and makes it possible to design a hybrid transformer by combining Litz wire and traces of a printed circuit board. The reduced copper loss and lower heat dissipation per transformer simplify thermal management. An analytical comparison is made between the utilization of a single transformer or a number of transformers. The procedure of splitting a volume of a single transformer into a number of small transformers has been comprehensively discussed. The idea is investigated both experimentally and in computer simulation for an example application of a phase shifted full bridge dc-dc converter. The converter is characterized up to a load power of 2.2 kW at Vin = 400 Vdc and Vout = 48 Vdc. To make the approach more practical, the transformers are modeled using the traditional analytical method. The design of the example application using the split transformer approach reduces the total transformer weight by 45%, compared to the traditional approachwith a single transformer. The converter also shows good performance with a maximum efficiency of 96%.
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| 6. |
- Bakar, Muhammad Abu, 1969-, et al.
(författare)
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Reconfigurable three state dc-dc power converter for the wide output range applications
- 2019
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Ingår i: IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society. - Lisbon : IEEE. - 9781728148786 ; , s. 4911-4916
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Konferensbidrag (refereegranskat)abstract
- Improving the dc voltage gain of power converters has been the primary focus of the current and past research in the area of power electronics. This work presents another solution to widen the range of the output voltage. It proposes three reconfigurable steps for the output voltage. The range of theoutput voltage varies up to four times the base level. These configurations together vary the output voltage from 15 to 96 volts. A soft switched dc-dc power converter is built with the traditional topology of phase shifted full bridge converter along with improved characteristics. For better management of thetransformer loss, a configuration of four transformers has been employed. The proportional gate drive approach is implemented to obtain four similar isolated blocks of the output voltage. This makes it possible to either configure these blocks all in series,parallel or in series/ parallel combination of two. The concept is verified in a low-profile prototype. The hardware is characterized up to the load power of 1kW for the input voltage of 400Vdc. The converter reports better efficiency over the complete range of output voltage.
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| 7. |
- Bakar, Muhammad Abu, 1969-, et al.
(författare)
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A Modified Higher Operational Duty Phase Shifted Full Bridge Converter for Reduced Circulation Current
- 2020
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Ingår i: IEEE Open Journal of the Industrial Electronics Society. - 2644-1284. ; 1, s. 82-96
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Tidskriftsartikel (refereegranskat)abstract
- Besides many advantages, the reduction in the operational duty of traditional phase shifted full converter limits its scope in applications where a wide range of input voltage is the main requirement. Operation with low duty cycle extends freewheeling interval, which results in degraded performance such as more circulation current, increased conduction loss in power devices, narrow range of zero voltage switching and increased EMI. To overcome these drawbacks, this work suggests a modified phase shifted full bridge converter that keeps the operational duty of the converter high for a wide range of input voltage. This cuts the freewheeling interval and improves performance. The proposed converter consists of four low profile transformers having reconfigurable interconnection structure. There are two distinct reconfigurable modes, a low gain mode and a high gain mode, which can be adopted in accordance with the variation in line voltage. The proposed work is validated in LTspice simulation and hardware characterization for a wide range of input voltage 100-400Vdc/12Vout and up to the load power of 1.2kW.
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| 8. |
- Bakar, Muhammad Abu, 1969-, et al.
(författare)
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An improved modelling and construction of power transformer for controlled leakage inductance
- 2016
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Ingår i: Environment and Electrical Engineering (EEEIC), 2016 IEEE 16th International Conference on. - : IEEE. - 9781509023202 - 9781509023196
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Konferensbidrag (refereegranskat)abstract
- In this work, a transformer with increased leakage inductance for the soft switched power applications is presented as a practical solution by constructing a transformer with good control over the leakage inductance. An analytical reluctance based model is presented, which accurately predicts the leakage inductance. With the presented approach, a transformer is designed with a leakage inductance varying between 3-7μH. Increasing the efficiency and improving the power density has been the main focus of power electronics researchers in the recent years. In this regards, transformers with increased leakage inductance are becoming more popular in order to accomplish different soft switching concepts and for improving the power density.
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| 9. |
- Bakar, Muhammad Abu, 1969-, et al.
(författare)
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Contribution of Leakage Flux to the total Losses in Transformers with Magnetic Shunt
- 2021
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Ingår i: International journal of electronics (Print). - London : Taylor & Francis Group. - 0020-7217 .- 1362-3060. ; 108:4, s. 558-573
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Tidskriftsartikel (refereegranskat)abstract
- To execute soft switching methods in resonant power converters, transformers with larger leakage inductance are getting more attention. Many papers have constructed various concepts in this regard. However, a discussion about, how the transformer efficiency is affected is lacking in the literature. This paper analyses the effects of the increased leakage inductance on the performance of the transformer. A transformer for increased leakage inductance is modelled and constructed to investigate the losses. The model discusses the effects of increased leakage inductance either by increasing the inter-winding spacing or by integrating the magnetic shunt within the transformer. The investigations show that increasing the leakage inductance by inserting a magnetic shunt can have severe degrading effects on the performance of the transformer, if not designed adequately. Additional losses are also calculated and the effects are verified by the experiments.
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| 10. |
- Bakar, Muhammad Abu, 1969-, et al.
(författare)
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High frequency (MHz) soft switched flyback dc-dc converter using GaN switches and six-layered PCB transformer
- 2016
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Ingår i: IET Conference Publications. - UK : Institution of Engineering and Technology. - 9781785611889 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- The increased switching losses with increasing switching frequency are the biggest concerns in designing high power density converters. This paper presents the investigation of an energy efficient DC-DC flyback converter in combination with six layered printed circuit board transformer. The recorded efficiency of the low profile transformer for the frequency range of 1-5MHz is 98% at power density of 770W/in3. The proposed converter is characterized for frequencies up to 4MHz by using possible soft switching techniques such as Boundary Mode and Quasi Resonant Mode. The emerging Gallium Nitride (GaN FET) devices are used as power switch. The control is incorporated with Digital Signal Processor (dsPIC) for both the Boundary and Quasi Resonant Modes of operations. The proposed flyback DC-DC converter is tested on a prototype Printed Circuit Board (PCB). The performance of the proposed converter is investigated for the telecom input voltage range of 36-72Vdc. The maximum obtained energy efficiency of the converter is about 94%. According to the authors' knowledge, this is the maximum efficiency ever achieved in flyback converters switching in MHz frequency range. The results are very encouraging for the development of high frequency, high power density and low cost isolated power converters.
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