Bidirectional Switches Permit ZVS Operation In Single-Ended Forward Converters

Focus:

Hard switching in the single-ended forward converter topology limits the switching frequency and restricts its usage up to a few hundred watts. Meanwhile, soft switching increases circuit complexity, making other topologies with zero voltage switching (ZVS) more popular at higher power levels. However, recent developments in SiC MOSFET and bidirectional GaN switch technologies have created new opportunities for forward converter design, simplifying implementation of ZVS and making the forward converter competitive above 1 kW. This article studies opportunities and application benefits of employing such devices in the forward converter. The topology described here uses a bidirectional switch in place of the secondary-side rectifier diode and the buffer inductor. The operation of this ZVS single-ended forward topology is explained and equations for key operating parameters are presented. Configurations with multiple outputs and synchronous rectification are also described.

What you’ll learn:

• How to simplify implementation of zero voltage switching in the single-ended forward topology
• How to extend use of the single-ended forward converter topology to 1 kW or more
• How to implement ZVS in a forward converter at a fixed frequency through the use of a bidirectional switch

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Author & Publication:

Viktor Vogman, Power Conversion Consulting, Olympia, Wash., How2Power Today, Jun 15 2021

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