
LLC Design Approach
- Ideally want ZVS/ZCS, therefore conduction loss is the main loss mechanism in the LLC.
- Therefore RMS currents as well as component resistances should be minimized.
- Buck mode reduces RMS currents compared to Boost mode, highest efficiency is near resonance:
- Pick a transformer turns ratio that minimizes DCM operation, and places resonance near the minimum Vin (operating condition which normally results in the lowest efficiency).
- Minimize transformer flux (core loss) as it contributes across the load range.