Gokhan Sen

Analysis and Design of Fully Integrated Planar Magnetics for Primary–Parallel Isolated Boost Converter

A high efficient planar integrated magnetics (PIM) design approach for primary parallel isolated boost converters is presented. All magnetic components in the converter including two input inductors and two transformers with primary-parallel and secondary-series windings are integrated into an E-I-E core geometry. Due to a low reluctance path provided by the shared I-core, the two transformers as well as the two input inductors can be integrated independently, reducing the total ferrite volume and core loss. AC losses in the windings and the leakage inductance of the transformer are kept low by interleaving the primary and secondary turns of the transformers. To verify the validity of the design approach, a 1-kW prototype converter with two primary power stages is implemented for a fuel cell fed battery charger application with 20–40 V input and 170–230 V output. An efficiency of 96% can be achieved during nominal operating conditions. Also experimental comparisons between the PIM module and two separate cases have been done in order to illustrate the advantages of the proposed method.

Fully integrated planar magnetics for primary-parallel isolated boost converter

A high efficient planar integrated magnetics (PIM) design approach for primary parallel isolated boost converters is presented. All magnetic components in the converter including two input inductors and two transformers with primary-parallel and secondary-series windings are integrated into an E-I-E core geometry. Due to a low reluctance path provided by the shared I-core, the two transformers as well as the two input inductors can be integrated independently, reducing the total ferrite volume and core loss. AC losses in the windings and the leakage inductance of the transformer are kept low by interleaving the primary and secondary turns of the transformers. To verify the validity of the design approach, a 1-kW prototype converter with two primary power stages is implemented for a fuel cell fed battery charger application with 20–40 V input and 170–230 V output. An efficiency of 96% can be achieved during nominal operating conditions. Also experimental comparisons between the PIM module and two separate cases have been done in order to illustrate the advantages of the proposed method.

A new method for start-up of isolated boost converters using magnetic- and winding-integration

A new solution to the start-up and low output voltage operation of isolated boost family converters is presented. By the use of integrated magnetics and winding integration, the transformer secondary winding is re-used during start-up as a flyback winding coupled to the boost inductor. The traditional added flyback winding coupled to the boost inductor is thus eliminated from the circuit, bringing substantial cost savings, increased efficiency and simplified design. Each subinterval of the converter operation is described through electrical and magnetic circuit diagrams, and the concept is extended to other isolated boost family topologies. The principle of operation is demonstrated with a 800W isolated boost prototype, and a 1600W primary parallel series secondary isolated boost converter. Efficiency measurements of both prototypes are presented, including measurements during both start-up and normal boost operation.

A high efficient integrated planar transformer for primary-parallel isolated boost converters

A simple, easy to manufacture and high efficient integrated planar transformer design approach for primary parallel isolated boost converters is presented. Utilizing the same phase flux flow, transformers are integrated, reducing the total ferrite volume and core loss for the same peak flux density. Number of turns is minimized for easy manufacturing by cascade placement of planar cores increasing the effective cross-sectional area. AC losses in the windings as well as the leakage inductance of the transformer are kept low by extensive interleaving of the primary and secondary turns. The idea of transformer integration is further extended to multiple primary power stages using modular geometry of the planar core, further reducing the core loss and allowing a higher power density. To verify the validity of the design approach, a 4-kW prototype converter with two primary power stages is implemented for a fuel cell fed battery charger application with 50–110 V input and 65–105 V output. Input inductors are coupled for current sharing, eliminating the use of current sharing transformers. An efficiency of 94% is achieved during nominal operating condition where the input is 70-V and the output is 84-V.

Modeling and control of primary parallel isolated boost converter

In this paper state space modeling and closed loop controlled operation have been presented for primary parallel isolated boost converter (PPIBC) topology as a battery charging unit. Parasitic resistances have been included to have an accurate dynamic model. The accuracy of the model has been tested by comparing the calculated and measured loop gains. The designed controller has been implemented in a DSP based control circuit and stable operation of the converter has been achieved.

Comparison of current balancing configurations for Primary Parallel Isolated Boost Converter

Different current balancing configurations have been investigated for Primary Parallel Isolated Boost Converter (PPIBC). It has been shown that parallel branch current balancing is possible with several configurations of coupled/uncoupled inductors. Analytical expressions for branch currents have been derived for different cases of gate signal mismatch causing current imbalance. It has been observed that turn-on and turn-off delays in parallel power stages of the PPIBC have different effects in the branch currents deviating from ideal. It has also been observed that in some configurations inductance differences due to core tolerances play an important role in current imbalance. Analytical and simulation results have shown that another side effect of the gate signal delay and inductor value difference is additional voltage stress over the switches during the mismatch times. Advantages of each configuration in terms of effective current balancing, efficiency and manufacturing simplicity have been highlighted. Simulations with ideal components for each case have been carried out to confirm the analytical derivations. Experimental results have also been included to show the performances of different configurations where component non-idealities like transformer leakage inductances also become effective.

Isolated Boost Converter with Bidirectional Operation for Supercapacitor Applications

This paper presents an isolated bidirectional dc/dc converter based on primary parallel isolated boost converter (PPIBC). This topology is an efficient solution in low voltage high power applications due to its ability to handle high currents in the low voltage side. In this paper, the converter has been modeled using non-ideal components and operated without any additional circuitry for startup using a digital soft-start procedure. Simulated and measured loop gains have been compared for the validity of the model. On-the-fly current direction change has been achieved with a prototype interconnecting two battery banks. A second prototype has been constructed and tested for supercapacitor operation in constant power charge mode.

Primary parallel isolated boost converter with bidirectional operation

This paper presents a bidirectional dc/dc converter operated with batteries both in the input and output. Primary parallel isolated boost converter (PPIBC) with transformer series connection on the high voltage side is preferred due to its ability to handle high currents in the low voltage side. The converter has been modeled using non-ideal components and operated without any additional circuitry for startup using a digital soft-start procedure. Simulated and measured loop gains have been compared for the validity of the model. On-the-fly current direction change has been achieved between input and output battery banks with a defined ramp.