Alexander Cook

A novel resonant converter topology and its application

This paper describes a secondary side resonant converter with particular suitability to step up and high power applications. A description of the basic circuit is followed by a detailed description and some important developments building upon the basic circuit, including inversion and bi-directional configurations. Efficiency is very good (/spl ap/94%) as a result of the zero voltage switching and zero current switching operation, and this is demonstrated with test data for two prototype configurations from 1 kW to 6 kW.

Design and Implementation of a Bidirectional Isolated Ćuk Converter for Low-Voltage and High-Current Automotive DC Source Applications

This paper presents the design guideline of a bidirectional isolated Ćuk converter with an active-snubber circuit, which is used as a cell level tester for multiple automotive dc energy storage devices (ESDs), such as ultracapacitors, Li-ion batteries, and NiMH batteries. The converter interfaces those automotive dc ESD cells with 24-V dc systems, and it realizes bidirectional power flow with two main switches. Based on the ratings of those dc ESD cells, the designed converter operates at a very low voltage range, i.e., from 1.5 to 6 V, with current as high as 300 A. The detailed operation principle and major features, such as soft switching and energy recovery, are analyzed under continuous current mode. Based on the analysis, the design guideline of the dc-dc converter is presented. A 1.2-kW laboratory prototype has been built and tested with full power rating. Both simulation and experimental results are presented to verify the analysis.

A high boost ratio bidirectional isolated DC-DC converter for wide range low voltage high current applications

This paper introduces a high boost ratio, bidirectional, isolated, dc/dc converter designed as an interface between low voltage, high current dc sources and 24 V dc systems. This converter realizes bidirectional power flow with two main switches and operates under a wide input voltage range, from 1.5 V to 12 V, with an input current as high as 300 A. An active snubber circuit is utilized to recycle the energy stored in the leakage inductor of transformer and realize zero voltage switching (ZVS) off for one main switch. The zero current switching (ZCS) on of this switch is achieved by using transformer leakage inductor, thus no additional components are needed. Furthermore, the power loss of another main switch is minimized by operating it in the Synchronous Rectification mode. Complete circuit description and operation principles are provided in this paper. A 1.2 kW lab prototype has been built and tested with full power rating. Both simulation results and experimental results are presented to verify proposed functions.

Achieving a wide input voltage and output power load range step-down DC-DC conversion with good full range efficiency at 4kW

This paper describes an original topology for a step-down DC-DC converter. This converter is a resonant converter with zero voltage switching and zero current switching. Regulation of the converter is done by PWM and variable frequency; this provides good regulation, from no load to full load. A prototype was built for an output power of 4kW, an input voltage range of 280VDC to 440VDC, and an output voltage of 14VDC. The prototype converter has an efficiency of 92-94%, is cost effective, and a good fit for high power and high current applications. The authors suggest that the presented topology is a better alternative to a typical phase-shift topology, with an additional advantage of being bi-directional.

Passive soft-switching snubber circuit with energy recovery

This paper describes a passive snubber circuit with energy recovery to the source. This circuit uses only passive components and can work with a full-leg power conversion topology, i.e., using standard IGBT modules. The circuit provides soft-switching, that is ZVS turn off, reduces slew rate, and increases efficiency around 1% under full load conditions (tested on a DC-AC inverter at 12 kW load and 120 VAC output). The authors suggest that this passive snubber circuit can work with many types of converters.

Cost effective resonant DC-DC converter for hi-power and wide load range operation

This paper describes an original topology for a stepdown DC-DC converter. This converter is a resonant converter with zero voltage switching and zero current switching. Regulation of the converter is done by PWM and variable frequency; this provides good regulation, from no load to full load. A prototype was built for an output power of 4 kW, an input voltage range of 280 VDC to 440 VDC, and an output voltage of 14 VDC. The prototype converter has an efficiency of 92-94%, is cost effective, and a good fit for high power and high current applications. The authors suggest that the presented topology is a better alternative to a typical phase-shift topology, with an additional advantage of being bi-directional

Step-up DC-DC converter for automotive application

Electrification of vehicle accessories often requires the application of low voltage high current step up DC-DC converter with a high voltage gain ratio qualified for use in an automotive environment. The proposed topology provides step-up on low voltage side that reduces the transformer turns ratio, leading to a simplified transformer design with reduced cost and increased efficiency which is especially important with low input voltage (10-20VDC) at 2-4kW or more. Fundamental operation of the topology has been and verified by simulation in NL-5. An experimental prototype has been built, which verifies the performance and high efficiency of the circuit topology. High efficiency DC-DC (94%, 3kW and 94.5%, 10kW) prototypes have been built. This topology is a better solution for higher power at low input voltage than parallel input stages. It was compared with other topologies by cost and performance.

Philosophy of Topology and Components Selection for Cost and Performance in Automotive Converters.

This presentation will show the relationship between power converter topology, for a rating of 2kW or more, and their cost in contemporary environmental and practical situations and propose how to achieve a robust and cost effective design for automotive industry. The discussion involves a comparison of different topologies and major power stage components and focuses on the application of the converter in hybrid and other vehicles. All this will be based on the authors 30 years of international development experience in the automotive industry.