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Class 2 transformers are small line-frequency transformers widely used for control systems requiring 24 VAC signaling, including residential and commercial HVAC systems, industrial controls, and much more. These transformers have large standby losses, low efficiencies, large weights, and high costs. In this work, we propose a power electronic alternative in the form of a low-power solid-state transformer. We design and test two 40 VA 120 VAC to 24 VAC solid state transformers, including a two-stage and a single-stage topology. Both converters provide higher efficiencies across all load ranges compared to the Class 2 line-frequency transformers, especially at light load (5 VA) with improvements of 19.6% and 29.9%, respectively. Standby losses for the two are 417 mW and 196 mW, compared to an average of 2.8 W standby loss for 40 VA Class 2 line-frequency transformers.
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Optimization of an Unregulated Low-Q Resonant Isolated DC-DC Stage for Low-Power AC-AC Converters
Low-power line-frequency transformers are common across several applications, but these transformers are found to have large standby losses, low efficiencies, large weights, and high costs. In this paper we optimize a power conversion stage for this and other applications where an unregulated, isolated converter is needed. The selected topology uses low-impedance passives to reduce their size; to address this case we analyze operation of a lower-Q resonant tank. Lastly, because of the application of low-power line-frequency transformers, we optimize around a typical usage cycle to minimize the yearly average power loss. For the application of a Class 2 line-frequency transformer, model results are accurate to simulation by within 12.1%, and optimization produced a design that was experimentally validated to achieve a yearly average power loss of 285.1 mW, a peak efficiency of 99.26% and a standby loss of 155 mW.
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- PAR ID:
- 10531576
- Publisher / Repository:
- IEEE
- Date Published:
- ISSN:
- 2151-1004
- ISBN:
- 979-8-3503-0723-8
- Page Range / eLocation ID:
- 1 to 8
- Subject(s) / Keyword(s):
- Transformers Power electronics Topology DC-DC converter unregulated DC-DC converter
- Format(s):
- Medium: X
- Location:
- Lahore, Pakistan
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/COMPEL57542.2024.10614056
