LLC Resonant Converter

LLC converters use a series inductor, parallel inductor, and capacitor resonant network — often with a transformer — to achieve high efficiency through zero-voltage switching on the primary switches. They appear as isolated auxiliary supplies or intermediate stages in large dock power cabinets.

Gain varies with frequency; design the magnetizing inductance and turns ratio for the required bus and load range.

01Benefits

• ZVS on primary over a useful load range reduces switching loss.
• Low output ripple with proper secondary filter.
• Galvanic isolation for safety partitions inside the dock controller.

02Design challenges

LLC gain curve is narrow — input voltage and load spread must fit the chosen region. Transformer leakage and Lm split affect resonance. Starting into pre-biased output caps on connected vehicles requires careful sequencing.

03Relation to WPT

• Distinct from the WPT coil resonator — do not conflate two different LLC networks in one system diagram without clear labels.
• Housekeeping LLC noise must not corrupt WPT current sensing grounds.